You may be saying to yourself, "Wait a minute! Last time you wrote about salt testing you said there were really only 2 popular methods being used.  What's going on and what is this 3rd method all about?"

Well, you are right.  Historically we have written about and discussed 2 popular methods where operators used either conductivity meters and, or, titration for testing salt in food products.  But recently we have seen a new development for testing salt levels in food products and thought it should be shared with you.  Before we do, let's review.

A quick overview on Salt:

When we talk about salt we need to agree on the terminology. 

Table salt or "salt" that we think about in our foods is known as sodium chloride (NaCl).  Although you cannot find NaCl on the periodic table of elements shown below, you can see both sodium (Na) and chlorine (Cl).   What's the deal with chlorine you say?  Well, chlorine under standard conditions is actually a yellow-green gas but when chlorine atoms gain one electron they become a chloride ion (Cl-).  Since an ion cannot remain in a free state all by itself it must combine with another element(s) to form a compound.  Chloride (Cl-) is therefore a by-product of the reaction between chlorine (Cl) and an electrolyte such as sodium (Na).  Hence, sodium chloride (NaCl) is known as an Ionic Compound.  There are other "related" chlorides (Ionic Compounds) but not as common and they are; calcium chloride, magnesium chloride and potassium chloride (we will save a discussion about these chlorides for another blog post).

Sodium chloride (NaCl) is naturally occurring in much of the earth's crust and can be found in places like the Great Salt Lake Basin in Utah.  A gift to this earth, nature, and our bodies!  You see, the human body needs both sodium and chloride to function properly although it's worth mentioning that there is still debate about the effects of chloride levels in the body as compared with the more well known negative effects we associate with sodium (Na) and high blood pressure. 

So, when we talk about measuring and monitoring salt levels we generally are saying that we want to know how much sodium (Na) is present.  Since table salt is Na+Cl- (NaCl) then, we approach our testing for NaCl accordingly based on the ratios of each elements atomic weight and mass percent:

[NaCl = 39.3372% Na + 60.6628% Cl]

These numbers are significant because if we look for (Cl) then we can determine (Na) and or (NaCl) by doing simple math, e.g. if you can find (Cl) then you can back into (NaCl) or determine (Na).

So that's it for the salt review, lets move on to the testing methods.

Method #1 - A review of the Conductivity Method:

"Conductivity meters" are based on the conductivity of water and is a measure of the waters ability to pass an electrical current.  Water with more ions present will conduct more electrical current.  Seawater has more ions and is more conductive than fresh water.  In our example for testing salt (NaCl) the chloride (Cl) readily dissolves in water.  The fact that chloride (Cl) dissolves in water is key.  The more chlorides (Cl) that dissolve, the greater the number of conductive ions that will be present and therefore increase the conductivity of the water, and vice versa for lesser amounts.  The conductivity levels measured then are compared with known standards and tables like seawater.  These numbers can then be reported in micro Siemens per centimeter or other conversion scales.

The conductivity method is an indirect measurement but it is easy and fast (several seconds).  It tends to be less accurate than other methods and has some limitations with the range of measurement.

Method #2 - A review of the popular titration method (mohr's method):

Titration can be performed manually or by using an automatic titrator.  This popular titration method determines the chloride ion concentration.  Silver nitrate is used as the indicator and is added until all of the chloride ions are precipitated.  So, this method also measures the amount of chloride (Cl) and uses the mass percent weights to determine sodium chloride (NaCl) and or sodium (Na).

This method for measuring salt is more involved, takes a little more time (3 to 6 minutes usually), but is very accurate to the parts per million (PPM) level.  The titration method does require the use of a silver electrode/ph electrode (or combined silver electrode), silver nitrate, and someone who understands how to run the method (manual or via automatic titrator).

Method #3 - A new method?  Nuclear Magnetic Resonance (NMR):

Nuclear Magnetic Resonance (NMR)?  Huh?  Nuclear Magnetic Resonance (NMR) has been around since 1938 and has benefited the field of chemistry and medicine in important ways, helping researchers and chemist to identify and measure certain elements found on the periodic table.

It's only now that technology has allowed for the miniaturization of the components (magnets, etc) necessary for making a benchtop NMR device.  This greater access and ease of use with NMR technology has the potential not only for researchers and chemist but for main-stream industry to find new and useful applications for testing materials with NMR. 

So, if you can see where this is going then, YES, you guessed it.  NMR can identify and measure sodium (Na) directly with part per million (PPM) accuracy.  I will say it again, this method measures total sodium (Na) directly with part per million (PPM) accuracy.  (NaCl) and (Cl) can be determined also as we know the mass percentages for these elements.  

Although it's a new concept for the food industry this new approach for measuring sodium could prove promising because it is easy, accurate to the part per million (PPM) level, and quick too (about 30 seconds per test).  

Certain types of Karl Fischer vessels require the use of Karl Fischer grease. Vessels with smooth port openings need a thin layer of the grease applied to plugs, electrodes, dessicant tubes, bubbler tubes and injection port plugs to help form a snug fit.  Decreasing or limiting "ambient moisture" from getting into the vessel - otherwise known as "drift" - is the key benefit of using Karl Fischer grease.  Another benefit of Karl Fischer grease is that it also helps prevent chipping of glass on glass fittings.  Watch this short video to see how Karl Fischer Grease should be applied.

If you find this information helpful please consider subscribing to our blog.  Once you subscribe you will get notified when we post a new article.

Measuring moisture using a karl Fischer Titrator is a common and popular choice among operators.  Karl Fischer titration provides excellent accuracy at the part-per-million (PPM) level and is widely accepted and trusted as a reliable method for measuring moisture.  Ketones and Aldehydes however are two organic compounds that can cause problems and lead to errors with measured results if they are present in a sample during testing.  The presence of these organic compounds can create an unwanted side-effect inside the titration vessel.

 What are the side-effects?  

The effects are side-reactions that can either falsley increase your moisture results or falsley reduce your moisture results.  Depending on whether your dealing with ketones or aldehydes or both you will want to know how to deal with them.  

How do you solve the problem?

Once you have identified the problem you need to take stock in your equipment and the chemical reagents you are using.  The equipment setup and reagent choices you make can help you to suppress these side reactions and obtain accurate results.

Watch this short 3 minute video to learn about the preferred equipment setup and your chemical reagent choices.

 On a sidenote who knew that Ketones have an impact on the human body? Check out this cool review

Just thought it was interesting and wanted to share.

If your reading this post you probably already have an understanding of a few basic concepts.  For those who missed it here they are for review.

Basic Concepts

• A dyne per centimeter is a unit of force
• A dyne is defined as the force required to accelerate a mass of one gram at a rate of one centimeter per second squared
• A dyne per centimeter is the unit traditionally used to measure surface tension and interfacial tension
• Surface tension is a measurement taken on a liquid and Interfacial tension is a measurement taken between/among liquids.
• Surface tension and Interfacial tension are both measured using an instrument called a tensiometer

I suppose it's worth mentioning why we decided to write this particular post about tensiometers and their surface tension and interfacial tension measuring limitations.   The simple explanation being that people have continued to ask us the question!  In fact, one time we had someone ask if we could recommend a tensiometer that could measure up to and above 500 dynes per centimeter! ...and we simply said "why?" and scratched our heads.

I guess you could say we finally received enough inquiries about this to force us into action and write about it.

Tensiometer readout design

If you have ever looked at a manual tensiometer guage like this one you will notice the dial only goes to 90 (90 dynes per centimeter).  

Compare this to some of the automatic tensiometers that use sensitive electronic balances and software and you will notice they have for the most part (various models) a range up to around 100 (100 dynes per centimeter).  See the red arrows below;

Why not make them with larger ranges?

Up to this point you have seen a couple of examples of the range capabilities for a manual and an automatic tensiometer. The truth of the matter is that the dial on the manual tensiometer could be re-etched to include additional numbers going up much higher than 90.  And the automatic tensiometers using the electronic balances could be configured and the software re-written to go as high as 1,000! 

So why haven't the engineers who make these tensiometers made the range on their tensiometers as big as they can?  Wouldn't that make the tensiometer that much more appealing?  A bigger range would mean you could measure more samples right? 

Well maybe...but not on this planet or in this universe. 

Liquids and fluidic metals?

You see, the answer is not really about the tensiometer.  In general, except for fluidic metals there are no known liquids that will indicate a surface or interfacial tension above 90/100 dynes per centimeter.  Surface tension of Mercury for example is generally reported around 480 dynes per centimeter but it does not wet to either the Wilhelmy Plate or Du Nouy Ring and cannot be measured by a traditional tensiometer.  Other fluidic metals need high temperatures and special atmoshperic conditions and are also unsuitable for traditional tensiometers.  With the exception of fluidic metals just mentioned solutions including metal ions but excluding surfactants (e.g. plating solutions) indicate comparatively high surface tension readings of 80 to 90 dynes per centimeter at most.  One of the highest surface tension liquids except Mercury is Sodium Chloride 6.0mol/20°C at 82.55 dynes per centimeter (mN/m).

In summary then, we can conclude that all of the liquids we will encounter while measuring surface tension or interfacial tension with a traditional tenstiometer will fall in the range not to exceed 100 dynes per centimeter.  Therefore restating the obvious you don't need a tensiometer that can measure surface tension above 100 dynes per centimeter.

Make sense?

There are many ASTM methods companies follow.  Here are a few of the more popular ASTM methods relating to surface and interfacial tension:

• ASTM D971; Interfacial tension of oil against water: This standard is used to evaluate hydrocarbon fluids and possible contamination levels.  Evaluating hydrocarbon fluid contamination levels is important in numerous industries including transformer oil testing and most Fuels.  Our heavy use of petroleum products and the effects of hydrocarbon fluid contamination makes for an almost limitless list of applications that require testing.

• ASTM D1331; Solutions of surface-active agents:  This standard applies to detergents and soaps but also includes emulsifiers and surfactants.  The test method determines the surface tension of popular substances including diswasher detergents and laundrey soap mixtures in water.
  ASTM D1331 is broken into two separate sections based on the liquid mixture being tested. ASTM D1331 method A applies to aqueous solutions containing surface-active agents. It includes water with two or more surfactants added. ASTM D1331 states that it "is also applicable to nonaqueous solutions and mixed solvent solutions." This includes electrolytes. ASTM D1331 applies to two-phase mixtures. Two-phase mixtures include a water and surfactant mixture containing air in the form of foam or bubbles. Two-phase mixtures include solid particles with the aqueous mixture. ASTM D1331 states "more than one solute component may be present, including solute components that are not in themselves surface-active." This allows for the surface tension testing of soaps when it includes artificial colorings, scents or skin conditioners. Surface tension testing methods do not change when multiple surfactants are included in the mixture.
  
  Read more: ASTM D1331 Methods | eHow.com http://www.ehow.com/info_8694874_astm-d1331-methods.html#ixzz2DivCVGeX
   This method applies to both aqueous and non-aqueous solutions
  
  ASTM D1331 is broken into two separate sections based on the liquid mixture being tested. ASTM D1331 method A applies to aqueous solutions containing surface-active agents. It includes water with two or more surfactants added. ASTM D1331 states that it "is also applicable to nonaqueous solutions and mixed solvent solutions." This includes electrolytes. ASTM D1331 applies to two-phase mixtures. Two-phase mixtures include a water and surfactant mixture containing air in the form of foam or bubbles. Two-phase mixtures include solid particles with the aqueous mixture. ASTM D1331 states "more than one solute component may be present, including solute components that are not in themselves surface-active." This allows for the surface tension testing of soaps when it includes artificial colorings, scents or skin conditioners. Surface tension testing methods do not change when multiple surfactants are included in the mixture.
  
  Read more: ASTM D1331 Methods | eHow.com http://www.ehow.com/info_8694874_astm-d1331-methods.html#ixzz2DivCVGeX
  
  
  Read more: ASTM D1331 Methods | eHow.com http://www.ehow.com/info_8694874_astm-d1331-methods.html#ixzz2DivCVGeX

• ASTM D1590; Surface tension of industrial water and Industrial waste water

The popularity of these ASTM methods require users to perform many of these tests day-to-day and in the process find themselves in situations where they either need to have their tensiometer ring repaired or replaced.  These platinum wire accessories while possessing a very high and durable melt-point can be damaged easily due to mishandling.  Damaged tensiometer rings can effect results so examine the rings routinely and handle with care at all times.

If you do find yourself in a situation where you need a quick repair for your Du Nouy Ring or need to find a replacement let us know.

The AT-700 automatic titrator provides operators a variety of choices including the use of an integrated mini sample changer.  The mini sample changer can hold up to 6 samples.  The design utilizes a rotating arm that holds the electrode(s), dispensing nozzle(s), and propeller stirrer above each sample and maneuvers from sample to sample.  The compact design allows a small footprint on the bench because the titrator sits on top of the sample changer.  Watch the short demo video to learn more about this titration system.

The AT-700 automatic titrator is a new compact potentiometric titrator.  The unit is ideal for conducting basic end-point titrations all the way up to more complex configurations that can include a sample changer, an additional permanent burette, to a chain of 8 automatic piston burettes (APBs).  The titrator can work stand alone or pair with advanced computer controlled software. 

Watch the video to learn and see more: https://youtu.be/CymMenF1fqA

Scientificgear LLC provides several targeted areas of service including:

• Karl Fischer Moisture Titration
• Titration
• Surface Tension (Tensiometers and Du Nouy Rings)
• Contact Angle Analyzers for surface analysis
• Thermal instruments (WBGT, Conductivity, Heat Flow)
• Liquid Density Instruments (Benchtop and handheld)
• Refractometers, Brix Meters

We support companies and organizations in select industries by providing:

• Technical Support
• Sales of Instruments
• In-house and field repair service on select instruments
• Calibration Service
• Training and Installation
• Some in-house testing
• Manufacture and repair of Du Nouy Rings

Don’t know whether you need to run a Bromine Number or Bromine Index?  Not sure what the difference is between Electrometric or Coulometric?  And just how many approved ASTM methods are there, anyway? 

Well, a good place to start is to check out the comparison table below and evaluate your sample(s) with respect to the scope & limits of products listed for each method.

If you’re trying to decide which of the last two Bromine Index methods to use, remember that the D1492 Coulometric method is most often employed for materials having very low expected values ( > ~20).

Be careful about converting back and forth between the two using that factor of 1000.  You can safely convert a Bromine Index to a Bromine Number by dividing it by 1000, but it’s not OK to derive a Bromine Index from a Bromine Number by multiplying the Number by 1000.

Need to run Bromine Number or Bromine Index with an AUTOMATIC TITRATOR?

OR

Interested in getting more detailed information on how to do Bromine using your KARL FISCHER TITRATOR? 

Most of us know about the Heat Index (HI) and might have even seen a sling psychrometer used by a coach or trainer.   How heat measurements were taken before tended to limit the amount of measurements taken due to the separate actions required to determine humidity levels and related temperature readings along with other factors. A confusing process.  In many cases measurements were done before and after a practice session - and that was it.

Trying to determine how hot it is and how dangerous the environmental factors are has been a concern for a long time. As with most things we find improved ways of accomplishing tasks that were previosuly cumbersome or difficult.  What we are seeing now is the emerging use of a different method.  The WBGT or Wet Bulb Globe Temperature.  This method while not new has some benefits. 

The WBGT meter can be deployed continuously measuring the environmental conditions non-stop, during a practice for example.  If conditions become dangerous during practice actions can be taken.  In particular, the WBGT Meter HD32 is a reliable hand-held wbgt meter that uses replaceable sensors.This is a very nice feature because in the past most people had to send in their entire instrument if they wanted it calibrated.  A costly and timely process.  We believe the removable sensors will  change the way calibrations are viewed.  Users will now be able to replace just the sensors and even have back ups available for use. 

You can watch the video below that shows the WBGT Meter HD32 and how it is unpacked and assembled.  The video also describes and shows some of the other features of the WBGT HD32.

This video demonstrates how to unpack and assemble the WBGT HD32.2. It also discusses some of the key features of this hand-held WBGT Meter.

We have all seen it.  We’re running a test to see how much moisture is in our sample when inexplicably the liquid inside the Karl Fischer vessel starts to turn from a normal light-yellow color to a dark burnt-red looking color.  Sometimes the titrator screen will inform us of the problem with a digital readout stating the dreaded

“OVER-TITRATION!” 

Sometimes the digital readout says nothing at all.  In either case the operator knows something has gone wrong because the Karl Fischer Titrator is no longer giving moisture results.  A panic to figure out the problem and get testing underway again becomes the immediate priority. 

But where do you start?  

As it turns out “over-titration” is probably one of the top 2 or 3 complaints or issues we hear about from operators.    So what is causing this problem to occur?  How can we determine the source of this problem, fix it, and more importantly how can we avoid it?

 
This is a critical question for operators and managers working in a production or QC environment who are concerned with keeping their Karl Fischer Titrator 100% “in-service”, day-in and day-out.   Having the ability to identify the problem correctly so appropriate measures can be taken quickly is very important.

 
So how do we approach the problem of “over-titration”?   By knowing the facts.  Having a clear understanding of the process can help operators correct the problem faster when time is of the essence.  

Important facts you should know about over-titration:  

1. Over-titration is a state where there is more iodine present in the vessel than water (general definition).
2. When over-titration occurs the vessel will become very dark as a result of the abundance of iodine present inside the vessel.
3. The reagent inside the vessel should normally have a light-yellow color absent a very dark sample such as oil.
4. The Karl Fischer Titrator always attempts to maintain an equilibrium where only enough iodine is introduced to counter and neutralize the water present inside the vessel.
5. During a single titration test there should only be enough iodine introduced to counter and neutralize the amount of water present inside the titration vessel during that test – no more, no less.
6. Any incident that interferes with the final amount of iodine introduced during the titration test can lead to dis-equilibrium and result in more iodine being introduced than necessary.

    Important facts you should know about Karl Fischer Titrator Glassware:  

1. The Karl Fischer Vessel and Glassware is composed of the following
   1. Vessel (coulometric and volumetric)
   2. Generator Electrode (coulometric only) - The Generator Electrode is a precision electrode designed to deliver an electrical current inside the vessel to the reagent – causing the reagent to produce iodine
   3. Titration nozzle (volumetric only) - The titration nozzle delivers precise amounts of iodine (composite or titrant) via a burette driven mechanism using a piston
   4. Detector Electrode (coulometric and volumetric) - The detector electrode has a sole purpose and probably the most important role in continuously monitoring and determining the conductivity levels within the titration vessel.

  So what are the causes that can lead to over-titration? 

✓ A damaged Detector Electrode

✓ A "Tricked" or "Fooled" Detector Electrode (no joke)

Since coulometric and volumetric Karl Fischer Titrators handle the delivery of iodine differently it’s worth describing the two methods separately.  

A Word About Coulometric Karl Fischer Titration:

In a coulometric system the reagent is a complete system where it is designed to release iodine when the generator electrode delivers an electrical current to it.  So what causes the generator electrode to deliver too much current causing the over production of iodine?  Another way to say it is, “who or what” is telling the generator electrode to continue to generate a current when it’s not needed?  

   
The detector electrode!  So why would the detector electrode do this?  
Without getting into too much of the electronics the detector electrode is designed to “detect” conductivity in the vessel.  Depending on the amount of conductivity detected the detector electrode will send a message to the titrator telling it to continue producing a current - enough to release the appropriate amount of iodine to counter and neutralize the water present in the vessel.  As long as this process is working during a titration an eventual endpoint will be found and a result will be produced.  

So it’s really a problem of misinformation. If the Karl Fischer Titrator is not getting the right information from the detector electrode then over-titration is possible. 

The problems we see that can effect the proper functioning of the detector electrode include:  

1. The electrode cable.  If the cable becomes cracked or breaks it can cause a situation where the message to the titrator is to continue producing a current – continually.  In this case the vessel will become very dark and in most cases the titrator will not even know it is in an over-titration state.  The generator electrode will simply continue to produce a current, turning the vessel very dark.  There will be no other warning or notice from the titrator for the operator to see.
2. Cracked electrode.  Sometimes mishandling or even a stirrer bar bouncing around inside the vessel can cause a tiny crack near the bottom of the detector electrode that cannot be seen with the naked eye.  These cracks can allow small amounts of reagent inside the electrode enough where errors in detection will begin to occur.  What ensues is an unstable drift that jumps around giving the titrator a misreading. The jumping around and unstable drift may be picked up by the titrator and an error stating “OVER TITRATION” may be seen on the screen of the titrator.
3. Cable connectors.  Sometimes the connectors on the titrator itself can become dirty, wet and corroded.  Also, some electrodes use multi-plug designs that can also become dirty, wet and corroded.   These connectors if not clean and dry can lead to a similar misreading similar to a cracked electrode where the drift begins to jump around and become unstable.  The titrator may also state that there is “OVER TITRATION” when this occurs.

A "Tricked" or "Fooled" Detector Electrode you say?

If it’s determined that the problem is not the detector electrode then we need to look at the stirring action inside the vessel.  If the iodine being released is not mixing well because the stirrer is off or set too low, then the detector electrode will not realize there is iodine already released inside the vessel.  This will cause the detector electrode to continue telling the titrator to produce more current via the generator electrode up to the point where the detector electrode senses a reduction in the conductivity level inside the vessel.  Conductivity only reduces as the iodine interacts with the water.  So it is important for the detector electrode to sense the true and most accurate “mix or state” of iodine and water during the titration process.  If it does not know the true state of the mix it will be fooled into telling the titrator to keep going – causing OVER TITRATION.        

A Word About Volumetric Karl Fischer Titration:

   
In a volumetric system the reagent setup is different where a composite or titrant is introduced via a burette piston through a titration nozzle.  The amount of composite or titrant delivered is based upon the commands of the titrator.  The command from the titrator to the burette and piston that push out the “iodine” through the titration nozzle is, yes, given by the detector electrode.  For the purposes of this discussion the difference between the coulometric and volumetric setup is that the delivery of iodine is different.   But the same problem can occur where the iodine does not mix well and therefore trick the detector electrode in to thinking there is not enough iodine present inside the vessel to counter and neutralize the water.  Since both coulometric and volumetric Karl Fischer Titrators use detector electrodes the problems mentioned earlier about the detector electrode will hold true with volumetric titrators also.  

 7 Thoughts (DOs and DON'Ts) on Problem Solving and Prevention:  

1.  Don’t abuse the detector electrode!  Be very careful with the detector electrode and do not handle it unnecessarily.  Small bumps (clanks) here and there can lead to a crack.   Do you really need to remove the detector electrode from the vessel all the time?
2.  Don’t turn up the titrator’s stirrer speed to high.  This will only cause the stirrer bar to bounce around uncontrollably and possibly hit and damage the detector electrode (crack).
3.  Do inspect all connections and connectors on the detector electrode cable and Karl Fischer Titrator to ensure they are dry and clean.
4.  Do be careful with the detector electrode cable.  Try not to bend it unnecessarily.
5.  Do make sure there is enough stirring action inside the vessel to mix the iodine around effectively.  A small vortex should be visible.  But not too fast to cause the stir bar to bounce around.
6.  Do introduce some moisture - Sometimes when you are in an over-titration situation and the vessel is already very dark you can introduce a little moisture to bring the vessel back to equilibrium.  This sometimes works and immediately the vessel turns from a dark burnt-red color to a light-yellow.
7.  Do have a spare detector electrode on hand.  This little electrode seems to get over looked but plays a huge role inside the Karl Fischer Titrator vessel.

Hi, this is Hank Levi, and I wanted to take a minute to tell you about what we're doing to provide repair service and replacement of new Du Nouy Rings.  We have been supporting operators working with popular manual and automatic tensiometers for about 10 years.  It may have been a result of the day-in and day-out working with these tensiometers that led us to where we are today...but it all started about 3 1/2 years ago when we started repairing Du Nouy Rings as part of our service.  About a year later we began providing New replacement Du Nouy Rings also.

Since then we have found customers who have needed help with Du Nouy Rings from other tensiometer manufacturers as well.  Last year Fisher Scientific stopped selling and servicing their tensiometers and with it their ability to provide Du Nouy Ring service.  We also discovered that customers of other manufacturers including Kruss, KSV, Kyowa, CSC, SEO and a few others might have a need for our du Nouy Ring service support too.

Well, the good news is that we are in the Du Nouy Ring business.  We can repair or provide replacement rings for any brand of Du Nouy Ring on the market.  This includes Du Nouy Rings for the popular Fischer Scientific Tensiomat, CSC Scientific, Kruss, KSV, Kyowa, SEO and more.

Do you have a need to have a ring repaired?  Or maybe you just need a new one.  Or maybe both.  Well we can help.  Just submit your contact information so we have a way to reach you and tell us what type rings you have.   We'll have someone contact you to review the details and if needed arrange to have your damaged rings sent in for service.
If you know of another person or organization that could benefit from our service please don't hesitate to forward this information to them.

Have you ever wondered about how surface tension is measured?  Without getting into the details relating to things like, "What's a dyne per centimeter?", "Du Nouy Ring vs. Wilhelmy Plate", "the effects and force of gravity", "viscosity of liquid", or "temperature",  we decided to put together this short video tutorial to help explain the main components of a popular manual tensiometer (70545000) and how the instrument works.  We think seeing how a basic manual tensiometer measures surface tension is helpful in gaining a better understanding of the big picture.

CSC Tensiometer Model 70545 Interfacial from Scientificgear on Vimeo.

SOME QUICK FACTS ABOUT SURFACE TENSION AND HOW TENSIOMETERS HELP

APPLICATIONS OF SURFACE AND INTERFACIAL TENSIONS: Surface and Interfacial tension measurements are extremely important in the control and improvement of:

• absorption
• emulsification
• osmotic pressure
• cataphoresis
• evaporation
• solubility
• condenstion
• miscibility

Industries using dye solutions, producing detergents, clarifying liquids, or sparating ores by the flotation process can obtain greater uniformity and efficiency through close control of surface tension of the process liquid.  A close relationship exists between interfacial tensions of oil-liquid systems and the lubricating value of the oil.  Another major use is determining the sludging condition within a transformer, thereby eliminating costly repairs.

Although the CSC Scientific Interfacial Tensiometer is fundamentally very straight forward, it is helpful to have a basic understanding of the operational features and components of the tensiometer.  There are dials, clamps, Du Nouy Rings, and Verniers to consider. 

In this video we show you how to check your calibration using a given weight. 

To conduct this calibration check we assume the tensiometer's tension wire is secure and the unit has the ability to provide a stable reading for your given samples.  Take a look at this short video and let us know if you have questions about the process.

Most everyone working with Karl Fischer Titration at some point ends up wanting to check their instrument for accuracy and overall operational readiness.  Karl Fischer Water Standards were made to assist operators with making these operational checks.  Sometimes however we find there is some confusion about the choice of water standards available and what the numbers mean.

Karl Fischer Titration Water Standard Video from Scientificgear on Vimeo.

Hydranal water standards provide a few popular choices for both coulometric and volumetric Karl Fischer Titrators:

• Hydranal 0.1 (100PPM ±10% error acceptance)
• Hydranal 1.0 (1,000PPM ±3% error acceptance)
• Hydranal 10.0 (10,000PPM)

So what do the numbers mean?  0.1, 1.0, 10.0?

Simply put, these numbers tell us the amount of moisture (H2O) that is present in 1 gram of the water standard.  The amount of moisture (H2O) is expressed as milligrams on the packaging.  Using the Hydranal 1.0 for example we say there is 1.0 milligram of moisture (H2O) in 1 gram of the water standard.  Did you know there are 1,000 micrograms per 1.0 milligram?  Yes there is.  So instead of thinking in terms of 1 milligram per 1 gram of water standard, think in terms of 1,000 micrograms per 1 gram of water standard.  Why?

Karl Fischer Titrators count moisture in micrograms!

Since Karl Fischer Titrators count moisture in micrograms it's easier to think about the water standards in terms of micrograms.  Why?

We evaluate our water standard test in PPM

For the Hydyanal 1.0 we are looking for results within ±3% of 1,000PPM (970PPM to 1030PPM).  For the Hydranal 0.1 we are looking for results within ±10% of 100PPM (90PPM to 110PPM).

Don't forget this formula!:

PPM = WATER DETECTED IN MICROGRAMS/SAMPLE SIZE IN GRAMS

(For those who don't know PPM stands for Parts Per Million)

We hope this information has been helpful.

If your operating a dual-reagent Karl Fisher Titrator and your getting lower than expected moisture results you may want to check a few things.  First, make sure your analytical balance or specific gravity (if you use it) calculation is not the problem. Next, focus your attention on the reagents.

Reagents can cause problems if they are not being replaced often enough.

With a dual-reagent setup the operator places anolyte into the main vessel (75mL to 150mL of anolyte solution depending on the vessel size) and catholyte into the generator electrode (5mL of catholyte solution).

Now for some reason, most operators focus their attention primarily on the anolyte reagent and take great care in monitoring the condition and level of the anolyte. Unfortunately their is a tendency to forget about the catholyte. I say unfortunately because it is this oversight that can cause the problem.

Before I tell you the reason for the problem it’s helpful to know some useful information about the reagents ability to measure moisture. A typical vessel can hold 100mL of anolyte. 100mL of anolyte (Coulomat A, Coulomat AG, Coulomat AG-H) can measure 1,000,000 micro grams of water. Yes, 1 million micrograms of water!. Conversely, the pre-measured 5mL ampules of catholyte solution (Coulomat CG) that goes into the generator electrode has the ability to only measure 300,000 micro grams of water per 5mL charge. Do you see it?  Do you see the connection?

There is a 3 to 1 relationship of the catholyte to anolyte!

Yes, you should be replacing the catholyte 3 times per 1 charge of the vessel. Or put another way, change the catholyte 3 times as often as you change the anolyte.

Now, back to the problem and the answer. If your not replacing the catholyte often enough, the catholyte will actually begin to convert and form a salt by-product. This “salt by-product” can then form and become deposited down around the frit at the bottom of the generator electrode (AKA inner buret) and clog the receptors. When this happens the generator electrode does not work as effectively and can contribute to low recovery on expected moisture levels.

What's the fix?

1. Make sure to change the catholyte more often as required.
2. Soak your generator electrode in methanol or even a light acid over night to clean out some of those salty deposits. That should help.

(Note: Coulomat AK anolyte and Coulomat CG-K catholyte are used in combination for samples with Keytones and have a 1 to 1 relationship and can measure 100,000 micrograms of water. Also, the popular Coulomat Oil anolyte has a smaller amount of moisture measuring capability as compared with the other mentioned anolytes above and has a capacity to measure 300,000 micrograms of moisture. eg. If your using Coulomat oil anolyte and Coulomat CG both have the capacity to measure 300,000 micro grams of water and have a 1 to 1 relationship.)

Hope this helps.

Titration

So you need to measure the amount of sodium chloride in your food products. While we have written about this topic previously in other posts and addressed some of the approaches used to test for % sodium chloride (including the use of hand-held salt meters) we have found that it is a more common practice to use an automatic titrator to accomplish this task.  In fact we think it is the preferred instrument and method of choice.  To be sure there are pros and cons to using different methods but we still find that titration is accepted as the primary method for getting the most accurate results.

How it's used

Although salt meters using the conductive method are faster (3 seconds vs. 2 to 3 mintues) and can be employed quickly in a production line process, titrators can also be implemented in the same testing environment with modest effort.  Additionally and regardless of how the tests were performed on the production line, titrators are generally put to work in the Quality Control/Quality Assurance Lab as a final check against periodic production line testing.

Supporting the use of titration as an accepted method includes some well known documented techniques including Mohr's and Volhard's methods making titration a recognized and trusted approach.

What's next...

Once you have made the decsion to use titration as the testing method it's just a matter of knowing:

• What items you need

• How to prep your sample

• How to setup the titrator

Luckily we have already thought about this and put together a list of 8 items your going to need.  We also created an application-note providing step-by-step instructions for you to follow to conduct a titration.

Many companies produce the foods we eat.  Do you ever wonder why or how they test for salt during the production process?

Salt which is made up of 40% sodium and 60% Chloride is an important ingredient found in food.  While salt can make food taste better, control color, and maintain food texture, it is also considered a health-risk factor (mostly due to the sodium).  Measuring and controlling the levels of salt between the extremes is a constant battle.  Producers of processed foods generally have the biggest need for identifying and controlling salt levels to address not only the taste, color, and texture of foods but also to address some of the healthier eating lifestyles more and more consumers are demanding.

For these reasons it is paramount that salt is measured accurately.  So how do we do that?

Food comes in a variety of forms.  Solid, Liquids, pastes, creams, pieces, chunks, wafers, crackers, gooey, sauces, liquids with chunks in them...let's see what else..Anyway, you get the idea.  There are a lot of ways food can be produced and consumed!

So what device or devices can we use to measure the salt found in these numerous forms of processed foods?

Well, there are a number of "salt meters" out there that can measure salt.  However, not all salt meters can measure the particular salt you are looking for in the same way.  In fact some "salt meters" can only measure salt under certain conditions and or in certain substances like water or sea water.  For this reason it is important to first consider what your going to be testing.  For example, If your food sample includes "food stuff particles" that you can grind into a paste form, then you can probably use a salt meter that utilizes the conductivity method.  On the other hand if you have a brine that you immerse food into and your only concerned with the liquid then perhaps a different salt meter will work.  

The point is this.  The form of the food at the instant you are going to perform the test is key.  Many types of foods can be formed into pastes and diluted with water.  If the food you need to test is like this then a simple salt meter utilizing the conductivity method may be able to perform the test to your satisfaction.  I say may because % salt levels and other accuracy factors may require that you use an entirely different method of titration known as silver nitrate titration instead.

Salt Meter vs. Titration?

A brief explanation and description of the two measurement approaches:

The Mohr method, also known as a silver nitrate titration method, utilizes the characteristics of silver nitrate that reacts with chloride ions to measure the salinity %. 

Conversley, some of the more popular salt meters emloy the electric conductivity method.  Both methods measure the salinity but operate on different measurement principles.  However, by creating a conversion table between the two testing methods, correlation between the set of results can be seen.

Aside from the measurement capabilities of each approach there are pros and cons to each.

While each method has benefits we have recently found through some informal surveying that some food processors are choosing to use both methods.  These companies are finding that it is easier to use the hand held devices and perform quick spot checks on the production line.  If any problems are identified on the production line then further verification and testing can be performed using the titration approach.  Some think using this collaborative approach is ideal.

ALSO READ OUR MOST RECENT UPDATES TO THIS BLOG POST : Salt related posts

Tensiometers are instruments used for conducting surface analysis on liquid substances.  Typical applications Tensiometers perform include measuring surface tension, interfacial tension as well as liquid density and Lamella Length on some Tensiometer models.  Some models can also perform other tasks including powder wettability and dynamic contact angle of a solid substrate.  Depending on the types of information the operator is seeking to find one model may be more appropriate than the other.

To help prospective users evaluate and compare the different types of models available in the market we have prepared a reference document we call the:

"Tensiometer Selection Matrix"

This matrix is not necessarily brand specific as it was designed to help those seeking to compare capabilities and prices among popular manual Tensiometer models vs. popular Automatic or "digital" Tensiometer models.

We hope you find the Tensiometer Selection Matrix helpful in your search and evaluation of Tensiometers.

YES IT CAN!

You can measure moisture in solid samples including plastics, powders, ores, gooey substances that are thick and viscous, greases, and many more.  The key is sample preparation to ensure that a uniform material will be tested.  Once those details are worked out the pattern for testing is the same every time. 

You hear a lot about people running traditional Karl Fischer titration using direct injection with a syringe and needle. That’s pretty easy. 

So how do you test for moisture in solids?

For more awkward samples like a solid or solid-like substance we can evaluate the moisture using a Karl Fischer Titrator with an Evaporator Oven.

Believe it or not that’s pretty easy too. I guess that’s why we wrote this post. We wanted to let readers know that the process for running a Karl Fischer moisture test using an evaporator oven is not that difficult.  As mentioned already the most difficult part is probably working with your sample. To help show how the process works we created this short 7 minute video detailing the steps along the way. Please make note that the instruments used for this demonstration are the Karl Fischer Titrator (MKC-610DT) and the Evaporator Oven (ADP-611).

Hope you enjoy.

In the video below we show the 600 series Karl Fischer Titrator.  Today we have additional models like the MKC-710 series that work with the ADP-611 solids evaporator.

We work with numerous titrator models and encounter many of the day-to-day problems associated with broken electrodes.  In many instances some of the electrodes are destroyed beyond repair but in other circumstances we find that some are in fact capable of being repaired. 

Most of our success with repairing or refurbishing electrodes is with Karl Fischer Generator Electrodes (also known as Inner Burettes). 

However, we do try to evaluate and determine whether other types of electrodes can be repaired also.  Generally we will ask for a photo or other description of the damaged electrode to determine if a repair is possible.  An example of how we examine a typical Karl Fischer Generator Electrode can be viewed in the following short video.  Take a look and let us know if we can help you.

On July 5th, 2008, a workplace rule designed to protect workers from outdoor heat exposure took effect in Washington State. This rule was passed on June 4 after six public hearings were conducted on heat stress and its causes. The hearings confirmed what officials already knew: working outside in hot weather is a health hazard.  The three requirements for employers with employees who work outside are to:

·  Train employees and supervisors to recognize heat-related illness and what to do if someone has symptoms.

·  On days when temperatures require preventive measures, increase the volume of water available to employees.

·  Have the ability to appropriately respond to any employee with symptoms of illness.

It's now 3 years later...would a handheld WBGT Meter be a helpful tool?...

The Wet Bulb Globe Temperature (WBGT Handheld meter) is a tool perfectly suited to helping Washington State employers comply with this new law. This hand-held tool is used to estimate the effect of temperature, humidity, and solar radiation on humans and determine appropriate exposure levels to high temperatures. A WBGT index is commonly used as a guide for environmental heat stress to prevent heat stroke during physical exercise or while at work. Based on the index shown, employers can estimate the probability that a heat-related illness with occur and provide the appropriate amount of water available for the current weather conditions. See a video demonstrating the use of the WBGT103 below.

For more information on the new Washington State law, go to: http://www.lni.wa.gov/safety/topics/atoz/heatstress/default.asp

Most operators who measure moisture using a Volumetric Karl Fischer Titrator tend to have difficulty in 3 areas.   Unlike Coulometric Karl Fischer Titrators where the equipment setup and reagents are fairly straight forward, Volumetric Karl Fischer Titrators differ greatly.  Understanding how a Volumetric Karl Fischer Titrator differs and how the equipment functions is not only paramount in terms of knowing how to operate the instrument it is critical if you want to obtain accurate and repeatable results.

8 out of 10 questions we receive usually fall into one of these 3 problem areas:

1. What REAGENTS should I use for testing my samples?  Titrants, Composites, Solvents?

2. "TITER VALUE" ..Who, What, Where, Why and How?

3. "SAMPLE SIZE" ..How much do I need or should I use? 

Although these 3 areas at first may seem problematic and unrelated they are not.  In this 9-minute presentation we will explain why the burette size matters, how to calculate a correct sample size and explain how the volumetric titrator reagent strengths work.  Tying all three areas together will hopefully not only clear up some of the mysteries surrounding Volumetric Karl Fischer Titration but also empower operators with choices for conducting tests under varied conditions.  And, oh yes, obtain accurate and repeatable results every time.    Important note:1 ppm = 0.001 mg/g; 1 mg/g = 1000 ppm.

In this presentation we discuss the basic Karl Fischer Water Standards and talk about some of their uses for both Coulometric and Volumetric Karl Fischer Titration.  We also describe some of the related problems that can be identified and overcome by using Karl Fischer Water Standards.

• Karl Fischer Water Standards
• Why we use them
• Coulometric Karl Fischer
• Volumetric Karl Fischer 

As a service provider of Karl Fisher testing apparatus, we see different moisture testing issues that many operators, managers, and even companies face. We have come to realize that helping operators become more knowledgeable about "the little things" can help boost confidence, improve performance and efficiency, and ensure accurate testing. 

Are you new to Karl Fisher Titration and just beginning to learn about moisture testing or has it just been a while since you had to pull the Karl Fisher Titrator out to run some tests?  Regardless of your reason we know how important it is to get up to speed quickly so you can be running tests and providing moisture test results to those who need them.

To help with this we have compiled a list of the 20 most critical questions to help operators navigate through the learning curve and gain a better understanding of Karl Fisher Titration.

Some examples of issues you will discover include:

1.  "Our Karl Fisher says 'OVER TITRATION' and the reagent is turning really dark. Why?”

2.  “Why won’t the instrument go into “Ready mode”?”

3.  “Results seem "all over the place", what should I do?”

4.  "We use a solids evaporator and we are getting ZERO moisture results. Why?"

5.  "How many tests can I run and when should I change out my reagents?"

Avoid unnecessary surprises by getting a copy of the complete list of questions and learn what the issues are and why they are important.

Simply put, drift is background moisture that the Karl Fisher titrator is detecting.  What is background moisture?  Well, it is moisture that the Karl Fisher titrator (specifically the detector electrode) is detecting inside the vessel -that’s not coming from your sample.  Drift or "background moisture" can be the result of having the titration vessel sitting idle for some time where moisture has slowly infiltrated and accumulated inside the vessel, or it may be the result of a leak that is allowing a small amount of moisture to enter the vessel continually.  Although we might like to think that the Karl Fisher titrator vessel is air-tight/moisture-tight, it is not.  Depending on how well the vessel is sealed there may be a little or there may be a lot of background moisture interference.  All Karl Fisher titrators deal with the drift issue.  Unfortunately drift cannot be completely eliminated but the good news is that it can be reduced, measured, isolated, and discarded from your test results.

Before a single test is run on a Karl Fisher titrator it must go into a “ready” mode.   But before the titrator can go into a “ready” mode it most likely will go through a “pre-titration” mode.  During the “pre-titration” mode excess drift (moisture) is detected and removed by the reagent inside the vessel.  A “ready” mode ideally will occur when the drift being measured is low and steady/stable – usually below .1 micro grams per second.  Once the drift becomes low and stable the Karl Fisher Titrator records the drift level and goes into a “ready” mode and will allow the operator to introduce a sample into the vessel.  Upon completion of the test the Karl Fisher titrator adds up all of the moisture detected over the duration of the test and subtracts out the known drift level that was also measured during the test.  This process of knowing what the drift was before the test allows the Karl Fisher Titrator to then determine and backout the drift -leaving only the moisture detected from the sample as your result.

There are multiple methods of moisture determination, including loss on drying, Karl Fischer titration, piezoelectric sorption, spectroscopy, and chilled mirrors among others. However, it is advantageous to use Karl Fischer (KF) titration in moisture analysis for the following reasons:

1. It is highly accurate and precise (Part Per Million Accuracy).
2. KF is specific to water determination. This specification is different from the other popular moisture analysis method, loss on drying (LOD), because LOD can detect the loss of any volatile substance. However, this specification is advantageous because it allows KF titration to work independent from volatile substances present in the sample
3. The process does not require large samples, which is typically truer with Loss on Drying where more sample is required to achieve higher accuracy and repeatability - which introduces another entirely different problem.
4. It does not require much time to perform an analysis since the samples are easy to prepare and the analysis itself is short in duration.
5. The method has a nearly unlimited measurement range (from 1ppm to 100%).
6. Karl Fischer titration can determine the moisture content of a sample in any state, whether it is a solid, liquid, or gas.

We hope the above advantages show some of the benefits that Karl Fischer titrators can provide.  Even today with technological advancements Karl Fisher Titration remains very popular not only because of the advantages we mention, but also because it is widely accepted as a standard for moisture detection and measurement.  

Measuring interfacial tension is effective in understanding how two or more immiscible liquids are, or can be - emulsified.

Immiscible liquids by definition are liquids incapable of being mixed to form a homogeneous substance.  Oil and water are immiscible.  We can act upon these immiscible liquids by emulsifying them into a single homogeneous substance referred to as an  emulsion.  Emulsifying two liquids that ordinarily do not mix well -such as oil and water- causes tiny droplets from one liquid to be suspended in the other liquid - forming an emulsion.

We refer to a liquid as a phase.  Where one phase meets another phase (liquid to liquid - oil to water for example) a boundary forms between them and an imbalance of forces occur.  The amount of the imbalance can attribute to an energy at the point where the two phases meet.  We refer to this energy as surface free energy where a measure of energy/area or interfacial tension as force/length can be observed.  Increasing the interface area by dispersing one liquid phase into another by emulsification or the use of a surfactant for example will result in a lower interfacial tension.  The Interfacial Tension is measured in Dynes per Centimeter using an instrument known as a tensiometer.

Understanding these relationships exist and measuring them under different testing conditions is important to understanding how many liquid products interact. Knowing the interfacial tension becomes more important for researchers on how best to pursue future R&D as well as for production managers to maintain quality control for existing products used every day.  Some examples of industry where effectively measuring and monitoring emulsifications is important include:

• Food Products
• Beverages
• Dairy Products
• Cosmetics
• Chemicals
• Pharmaceuticals

This is a popular question for most operators using a coulometric Karl Fischer titrator.  So let's get started.  There are two things to consider.  First, you have the chemical limitations of the reagents themselves.  Second, you have the user/operator variable. Sometimes changing the reagent has more to do with the condition of the reagent sitting in the vessel.  How full is the vessel after running numerous test? How long has the reagent been sitting in the vessel? How messy is the reagent and sample residue inside the vessel? Sometimes the user may simply want to replace the reagents because they look dirty/messy or their vessel is too full from adding samples during previous tests.

Setting aside those factors just mentioned, if we look at the reagents themselves and their capacity to measure moisture, we can come up with a general guideline as follows:

Note:  This example describes a Coulometric Karl Fischer Titrator with dual reagent setup (using Anolyte and Catholyte)

1.  In general and with regard to reagent brand, 100mL of Anolyte (AKA Anode- the reagent used in the vessel) reagent analyzes up to 1gram (1 million micro grams) of water.  20mL of Catholyte (AKA Cathode- the reagent used in the generator electrode/inner buret) reagent analyzes up to 1gram (1 million micro grams) of water.  The relationship according to the amount of water each reagent can analyze has a relationship of 100mL Anolyte to 20mL Catholyte – a 20% relationship of catholyte to anolyte.

2.  Anolyte is commonly purchased in 500ml bottles, Catholyte is commonly purchased in10x5mL ampules.

3.  A typical coulometric Karl Fischer titrator Vessel is charged with 75mL of anolyte and 1ea 5mL catholyte ampule.  Based on the 20% relationship it says that 3x5mL catholyte ampules would be used with each 75mL vessel charge of Anolyte.

4.  A 500mL bottle of Anolyte can charge the Coulometric Karl Fischer titrator vessel 6.6 times (round to 6 times to account for spillage).  3x5mL Catholyte ampules per charge of the vessel times 6 charges of the vessel = 18x5mL catholyte ampules.

Typically users do not expire the entire useful life of the reagents moisture measuring capability because of some of the factors I mentioned initially.  Another factor that I have to mention is that ambient moisture will require the coulometric Karl Fischer Titrator to maintain a dry vessel.  This process of keeping or getting the vessel in a ready to go mode can use some of the reagents useful life.  e.g. it’s not counting the moisture in your samples but that of the outside ambient moisture – for the most part this should be a small amount, but something to keep in mind and know about.

So, with all of this information, the question you may have is how long will my reagents last?  Well, that depends.  But, if you want to continue using the math we have already discussed, then, 1 charge of the vessel (75mL of anolyte with 3x5mL catholyte ampules) can measure 750,000 micro grams of water.

And, for those of you who think in Parts Per Million (PPM) you can translate into the  following:

PPM = micro grams of H2O detected / Your Sample Size (in grams)

A simple method is to run a water standard through the Karl Fischer Titrator like a normal direct injection test. Depending on the water standard you use, the result should equal a pre-determined level of moisture plus or minus a margin for error. These water standards are certified by the manufacturer (a certificate is included) to equal a precise level of moisture.

We use Hydranal water standards. There are two kinds we typically use for coulometric Karl Fischer Titrators.

1) 0.1 normal

2) 1.0 normal.

The 0.1 normal administered at about 1mL should result in 100ppm (Parts Per Million) of moisture when measured. The acceptable result for this standard for the Karl Fischer titrator is +/- 10%. So your Karl Fischer Titrator should produce a reading between 90ppm and 110ppm to be in the acceptable range. If it is, you know your Karl Fischer Titrator is performing correctly.

For the 1.0 normal everything is the same except the standard should result in 1,000ppm and your acceptable range is smaller at +/-3%. So your Karl Fischer Titrator should produce a reading between 970ppm and 1,030ppm.

We get this question a lot.  "How do you go about testing for moisture if the sample is in liquid form?..What about solid form?"

Well basically, moisture testing using the karl fischer method is a standard in the industry that measures down to the Parts per million (PPM) level.  The theoretical accuracy is down to 1 part per million level.  I say theoretical because usually any variance is due to atmospheric conditions and operator repeatability.  Specifically, and for this example, “coulometric” Karl Ficsher is best when you are using a small sample and expect and are trying to measure less than 1% (1%moisture =10,000PPM) of water (moisture/humidity) in your sample.  [Note: there is a volumetric Karl Fischer method vs. coulometric Karl Fisher method but for this discussion I am speaking from the coulometric Karl Fischer standpoint]

With this in mind,

A. If you are testing a liquid sample you only have to use the karl fischer titrator and directly inject the liquid sample with a syringe (usually around 1mL) into the vessel.

B. If you are testing a solid sample (that cannot be “broken down sufficiently with solvents like Xylene for example) you will use both the karl Fischer AND an evaporator oven.  The evaporator oven heats up the sample (usually the sample size is less than 1gram…we typically might use 1/10th of a gram..but then again we might use 3 grams -it really depends on how much moisture you expect to find). The evaporator is connected with a nitrogen gas source that is used to deliver the moisture via a heater tube on the evaporator into the titration vessel.

To see an actual demonstration of the Karl Fischer Titrator and the evaporator oven during an actual test please view the video below and watch the short 2 to 3 minute video.

To be sure there are many more things I could mention but this is a high level summary of the two approaches.

Hope this helps.

Here it is!  The new AT-700 Potentiometric Titrator with integrated sample changer, CHA-700, is coming out soon.  Manufactured by Kyoto Electronics Manufacturing (KEM) this will mark their 7th generation of industrial grade, high quality, titration instrumentation.  We have not yet received all of the details on this amazing looking, newly designed potentiometric titrator but can tell you that it incorporates a carousel design sample changer that handles eight samples.  From the photo you can see how the sample changer's compact design revolves around the Potentiometric Titrator.  There are a few key design features on the new potentiometric titrator:

• No need to read measurement parameters
• New burette system
• All-in-one compact design

We're told this new design will make significant improvements with the measurement of Mercaptans down to 1PPM (ASTMD3227,UOP163,IP272).

*Advantages include a special sealing cell and electrodes to avoid oxidization of mercaptan sulfer under atmospheric conditions.

*Application: Determination of mercaptan sulfer and hydrogen sulfide in fuels and liquid petroleum gases (LPG) is one of the important applications in petroleum and gas analysis.

We anticipate this newly designed Potentiometric Titrator will serve many other titration applications and provide operators with a compact yet fully automated functioning titrator.

As we receive more information on this new titration system we will let you know.

A Word About Karl Fischer Water Standards

Some operators use Karl Fischer water standards daily while others do so sparingly. Regardless of the type of operator you are, there still seems to be some confusion about what Karl Fischer water standards are supposed to accomplish and/or why we use them.

Water standards for Coulometric Karl Fischer Titrators verify “recovery” of a known amount of water. We say “recovery” because we are seeking to recover or measure water that was introduced during a test. When introducing a water standard with a known amount of water using a syringe and needle — known as the direct injection method — we should expect to recover all of that water. If we do not recover it all, there could be a problem.

Water standards can also be used to verify recovery for Volumetric Karl Fischer Titrators, but they can also be used to help calculate the titer value associated with Volumetric Titration. Additionally, if a solids evaporator oven is being utilized in conjunction with a Karl Fischer Titrator, we can use a water standard in powder form to verify moisture delivery from the evaporator to the titrator.

We offer a line of Karl Fischer Water Standards covering a range of moisture content for both direct injection tests as well as evaporator powder standards.

Typically, the high range standard known as “10.0” is used with the Volumetric Karl Fischer Titrators. The other lower range water standards including the “1.0”, “0.1” and “Water Standard Oil”, are used with the Coulometric Karl Fischer Titrators. You can see a breakdown of the water standards as follows:

· “10.0” contains 10.0mg (10,000 micro grams) of H20 per gram (1g = 1mL)
· “1.0” contains 1.0mg (1,000 micro grams) of H20 per gram (1g=1mL)
· “0.1” contains 0.1mg (100 micro grams) of H20 per gram (1g=1.16mL*)
· “Water standard oil” contains a target PPM result (by LOT) of 6.0PPM
· “Water standard KF oven” (230°-240° C) approximate 5.55% result
· “Water standard KF oven” (140°-160° C) approximate 5.0% result

Note that a water standard with a specific gravity of 1.0 means that 1gram (mass) is equal to 1 milliliter (volume). You will notice that the “0.1” water standard has a specific gravity of less than 1.0 because it contains some xylene (we will cover specific gravity in more detail later).

To actually run a direct injection water standard test the operator will typically fill their syringe with 4 mL of water standard (water standards are generally sold in convenient 4mL ampules) and dispose of 1 mL to clean and prep the needle prior to conducting a direct injection water standard check. Utilizing the 3 mL remaining inside the syringe, three separate tests can be performed by injecting 1mL for each subsequent test. If the operator finds the results to be inconsistent, a larger amount of water standard can be used for each injection to improve accuracy and repeatability.

Hopefully this information will help with some of the challenges many operators encounter daily as well as improve performance and reliability of moisture testing results. 

We will cover more regarding Karl Fischer Titration including using specific gravity, trouble shooting problems, volumetric reagents and calculating sample sizes to name a few. Until then, we hope you will continue to read, enjoy and share our posts regarding the interesting and sometimes confusing topic of Karl Fischer Titration.

Thanks for reading and, as always, feedback is welcome.

Hank Levi

We all know that surface tension affects our daily lives thru everyday applications like the ink you use in a pen, detergents for washing clothes, soap to clean your hands, paint for the house, just to name a few.  But Surface tension is more involved in your life than you may think.

Tap water is usually around 72 to 73 dynes/cm.  This can vary by temperature and other variables but for the sake of this blog post we will assume 73 dynes/cm.  Now this is where it gets interesting.  At 73 dynes/cm water will hydrate you.  Or does it?  You see, It is known that on a cellular level your body has to convert fluids to 45 dynes/cm to allow the water to penetrate the human cells.  Once water penetrates the cells it can hydrate and remove toxins from the cells.   If water cannot effectively penetrate human cells an accumulation can build up and over time cause the cells to die.  Amazingly, I have seen places around the world where people claim to have special water.  They claim their water has a lower surface tension and less colloidal minerals.  You knew this was coming..Yes, these same people have demonstrated good health as they easily live to be 100 years old!  And yes, they attribute this to their water.

Not surprisingly, I see web sites now that sell supplements to lower the surface tension of  water to improve your health.

Fact or Fiction you ask?
I think I am going to order some of these supplements and check it myself with a digital tensiometer!  As they say the proof is in the pudding. Or in this case the surface tension!

Stay tuned.  I will update my findings and how I did.

Thank You,
Gus

Most people know about Karl Fisher as a method for determining moisture content.  After that there seems to be confusion when the words “Coulometric” and “Volumetric” are mentioned.  It goes something like this:

Novice: “Hi, I need to test for moisture and I need a Karl Fisher Titrator.  Can you tell me how much it costs?”

Expert: “O.K., do you need a Coulometric or Volumetric Karl Fisher Titrator?”

Novice: “uh what?”

Expert: “Well you see there are two kinds of Karl Fisher Titrators.  Depending on your sample size and the amount of moisture you expect to find -it may not only be advantageous but necessary to use a Coulometric vs. a Volumetric..and or vice versa.”

Novice: “I see.”  So how do I know what kind of Karl Fisher I need?

Expert: “Generally speaking, if you are working with small samples (0 to a few grams) AND the expected moisture is low (around 1% or less) you probably want to use a Coulometric Karl Fisher.  On the other hand, if your sample size is larger AND you expect to find a lot of moisture in the 2%+ range then you probably should consider a Volumetric Karl Fisher Titrator.”

Novice: “Do they both report moisture results the same way? You know, accuracy, resolution, repeatability?”

Expert: “Yes they do.  Both Volumetric and Coulometric Karl Fisher Titrators report moisture results in either Parts Per Million (PPM) or %.

Novice: “So then what makes them different?”

Expert: “Coulomeric Karl Fisher Titrators use a reagent called an Anolyte.  This Anolyte is 100% self contained and requires only an electrical current to cause a reaction where the Anolyte releases iodine.  It is this “iodine” that “neutralizes” the moisture inside the vessel.  A typical Coulometric Karl Fisher Titration Vessel can hold about 75mL of Anolyte.  The amount of Anolyte inside the vessel can only “release” so much iodine and therefore can only neutralize and measure a finite amount of moisture.  In this case using the 75mL as the example the reagent can only neutralize and measure 750,000 micro grams of moisture (water/H2O).  Now compare this to a Volumetric Karl Fisher and the game changes.  The Volumetric Karl Fisher method does not use a single self-contained Anolyte reagent that reacts to an electrical current.  Instead, the Volumetric titration is performed by “dripping” in IODINE at an precise amount into the titration vessel where there is a SOLVENT solution present in the vessel.

Novice: “How does the Volumetric Titrator “Drip in” IODINE into the vessel where the SOLVENT is located?”

Expert:”Good question.  It uses a buret that has a piston that moves up and down pulling The IODINE solution from a source bottle into and filling the buret and then pushing it out through tubing and into the vessel. ”

Novice: “Is there another name for this “IODINE solution”?  How do I get it?

Expert: “Another good question.  “This IODINE solution” is what makes the volumetric method so versatile when measuring larger amounts of moisture via Karl Fisher Titration.  The Iodine solution can come in two forms and with differing strengths.”

Novice:” Two forms?  Different strengths? Huh?

Expert: ” Yes, the two forms are referred to as “One-Component” and “Two-Component”.”

Expert: “The “One-Component” Iodine solution is referred to as Composite or Titer.  The Composite can come in 3 strengths; 1 (1mL of composition can consume 1mg or 1,000micro grams of water), 2 (1mL of composition can consume 2mg or 2,000micro grams of water) and 5 (1mL of composition can consume 5mg or 5,000micro grams of water).  We refer to these compositions as Composition-1 (aka Comp1), Composition-2 (aka Comp2), and Composition-5 (aka Comp5).

Novice: Differing Strengths.  Hmmm.  So for every 1mL you “drip in” it will consume, neutralize and measure the corresponding amount of moisture depending on the Composition strength.

Expert: “That’s right.  So for example if you use a Volumetric Karl Fisher Titrator with a 20mL buret you could conceivably introduce in one push of the piston that’s inside the buret, 20mLs of Composition.  If your using Comp5 you would be able to consume, neutralize and measure 20mL x 5,000 micro grams =100,000 micro grams of water.   Most Composition are sold in 500mL bottles.  So each bottle has the capacity to consume, neutralize and measure 2,500,000 micro grams of water.

Novice: “That’s a lot of water measuring capability!”

Expert: “Yes it is.”

This is a simple example and there are other factors to be considered for sure.  We thought this brief example would help those just getting started and trying to understand the basic comparison between Coulometic Karl Fisher and Volumetric Karl Fisher.