The Scientific*gear Blog

In this short 30 minute webinar we dive into understanding the common titration application known as TAN or "total acid number", also known as,  ASTM D664.  As part of our titration webinar series we have a fun and uncomplicated talk about this titration application known as "total acid number".  

In this short but informative webinar we explore:

• What is TAN, total acid number, ASTM D664?
• Why do we test for it?
• How do we test for it?
• How do you set up the titration application?
• What are common problems you need to avoid?
• Best practices you should know about and try to follow

It only takes a few seconds to register for this highly interactive webinar (recorded).  You will be able to watch, send us emails with questions, download various application resources including the application notes, electrode prep tips, and more.

This is a valuable tool for seasoned experts and first timers.

There are still many who test salt content by hand and so the thought of using an automatic titrator might sound intimidating.  It's not. Really.  So we thought it would help if we made some videos to explain some of the basic steps involved and show for those who have never seen one what a titrator looks like.  To be sure there are many capable titrators that can do the job so don't get completely caught up in which one is best but think more about the benefits of automating a test that is repeated many times daily.  

In the following videos we provide a step by step look at how a sample (potato chips) would be prepared and tested using an automatic titrator with the help of a 6 position sample changer.  

VIDEO DEMONSTRATION:  Testing Salt in Potato Chips with Titrator

WHAT YOUR GOING TO NEED IN ADDITION TO THE TITRATOR:

1. Silver Nitrate; 1.0 or 0.1 normal strength (This is the titrant that you will use)

2. Combined silver electrode (it's a silver and pH electrode combined)

THINGS YOU SHOULD KNOW:

1.  How do you currently prep your sample.  This process should not really change.  Sample prep is important though and should be considered.

2. Know the ingredients of your sample.  You should have a pretty good idea about the types of chlorides and sodium that may be found in your sample.

Get More Information on Salt Testing Equipment.  Click here

We get this question a lot.  So, we decided to try and figure it out the best we can.  In this analysis, we are only going to examine and include the per-unit cost of the titrator (automatic) and the reagents (silver nitrate - AgNO3).  It seems we could include other factors including human resources and electrical power requirements but these can vary greatly so we will leave them out of this analysis.  Additional ancillary costs can always be added later.

Let's start off by assuming we purchase a basic automatic titrator for $8,500.00  

Next, let's examine our most required consumable.  Silver Nitrate- AgNO3.

We performed a salt titration on this food product (soy sauce).  On the label, we can see that the amount of sodium is 590mg of sodium per serving.  For this titration (see below), you can see we used 15.8ml of silver nitrate @ (0.1N mol).   

Note that silver nitrate can come in different strengths so there is a little math we need to consider when deciding on which strength of silver nitrate we should use.

Let's consider using a different strength silver nitrate.  Let's look at using 0.5N mol instead of the 0.1N mol we used in our test.  Initially, we used 0.1N for our titration.  So dividing 15.8mL by 5 helps us see that using a bit stronger silver nitrate will reduce our consumption of silver nitrate.  In this case,  around 3mL per test.   But it's not that simple.  Conversely, we can change the strength of the silver nitrate and make it stronger as long as you don't have other samples that have a lot less sodium.  Otherwise, it would be too strong for the other samples with less sodium and it would not be ideal in those situations (You probably would not find the endpoint).  Bottom line, if you are working with only one burette (doses the silver nitrate), then you are going to need to pick a silver nitrate strength that can be used for all of your samples.  The only alternative would be to refill the burette each time with different strength silver nitrate, or, have a swappable burette on hand.  Having a swappable burette means you can have preloaded burettes with different strength silver nitrate and you can then easily swap them on and off the titrator when needed.  Even better, some titrators can be configured to have two or more onboard burettes which would alleviate the need for manually swapping burettes. 

Let's ignore this for the moment and continue to focus on our cost analysis assuming a single burette.

To give you an idea about pricing for silver nitrate. 

•  We recently purchased some 0.1N mol Silver Nitrate (strength).  A 1 Liter bottle cost approximately $75.00.  Divide $75.00 by 1,000 and the per mL cost is $0.075 per mL of 0.1N mol silver nitrate.   Assume 15.8mL of 0.1N mol silver nitrate per test => 15.8x$0.075=$1.19 per test.

• Assume 0.5N mol Silver Nitrate (strength). => 15.8mL divided by 5 = 3.2mL of silver nitrate per test. (e.g. you will use less with stronger).  Some recent pricing for 0.5N mol; $170.00 / 500mL => $0.34 per mL, or Bulk pricing if you buy a larger bottle $1,000.00 / 4L (4,000mL) => $0.25 per mL ~ 3.2mL per test x $0.34 per mL = $1.09 per test or 3.2mL x $.25 per mL = $0.80 per test.

So if you can purchase silver nitrate in bulk you can drive down your per test cost.

When you decide to test for salt (NaCl) using a titrator you are going to have that initial outlay to pay for the titrator.  After that, it's really a question of what strength of silver nitrate you are using and the amount you are using.   Hopefully, from this example, you can see how the price per test can range from about $0.80 per test to almost $1.20 per test.  So if we do some estimating you could say on average it costs about $1.00 per test.  If you are testing 200 samples per day your daily cost for silver nitrate will cost you about $200.00.

Now let's assume depreciation of the titrator using the straight-line method with the useful life of the titrator equal to 5 years (I think this is what a tax accountant would assume for tax purposes).  $8,500 / 5 = $1,700.00 per year.  Let's assume 251 working days per year ==> $1,700 / 251 = $6.73 per working day in depreciation expense.  In this case, divide that by 200 tests today, and that = $0.03 per test.  

I think these numbers (for the most part) provide a good working basis for determining daily operating costs.  They're probably not perfect but they show you how to go about figuring this out. As always we hope you find this information helpful!

This article is not intended to explain a manual titration process but rather how you can configure an automatic titration system to run both acid and salt titrations independently and or as a combined method.

Performing acid and salt titrations is a popular requirement in the food industry.  Some foods like tomatoes for example tend to have naturally occurring acidic properties but also take on a salt component when processed into other intermediary products like pizza sauce or spaghetti sauce.  

Although sodium (Na) is an important element to measure and report on food labels, salt (NaCl) content is also important in measuring to ensure the taste is good and repeatable during the production process.

Performing titrations whether manually or with the use of an automatic titrator involves a burette where specific amounts of titrant are delivered to evaluate the potential and or content of what is being measured. Results are usually reported in % for both acidity and salt content.

Here is an example of how you might set up a titration for testing both acidity and salt.  Below we have 2 scenarios.  The first scenario is configured so that the titration for both acidity and salt can be performed using a single sample.  To accomplish this you will need 3 burettes.  We will first perform the acidity titration using burette #1 with NaOH (Sodium Hydroxide) as our titrant.  In our example, during the acidity titration, the pH will rise to about 8.2.  At the end of the acidity titration, the pH level will be too high for us to run the salt titration so we will need to lower the pH.  We accomplish this task by dosing HNO3 (Nitric Acid) into the sample using the burette on the Automatic Piston Burette (APB ~ we will call this burette #3).  We will dose HNO3 to reduce the pH down to about 4.1.  Once the pH level is reduced the salt titration can begin.  The second burette (burette #2) located on the titrator then performs the salt titration using silver nitrate (AgNO3) as the titrant.  It is worth noting that silver nitrate comes in various strengths and so depending on your sample and the amount of "salt" you expect to find, you may need to adjust the strength (1.0N vs. 0.5N vs 0.1N, etc).

What the setup will look like

Electrodes we will use:

• pH glass electrode (noted as H171 in the diagram)
• combined silver electrode (noted as C373 in the diagram)

When running the titration using only one sample to obtain both the acidity % and the salt %, we will use both electrodes as the combined silver electrode will act as a reference electrode for the pH electrode. 

When running a single titration on two different samples in two different beakers, leave both electrodes and nozzles in the samples ensuring to clean the nozzles and electrodes between tests of each sample.  In this scenario, the combined silver electrode (C373) will also work as a reference electrode for the pH electrode (H171) while running the acidity titration.

• Silver Nitrate (AgNO3) titrant for salt titrations
• Sodium Hydroxide (NaOH) titrant for acidity titrations
• Nitric Acid (HNO3) buffer if combining methods
• Combined Silver Electrode (C373) for salt titrations
• pH glass electrode (H171) for acidity titrations

In the video below we show the titration setup described above.

We hope you find this information useful!

Hello!  Please meet our new Web Helpers!  Moisture Elle, Karl Fischer, Shaker Sam, Terri Tenso, and Vivian Visco!  Each of our helpers will provide technical information ranging from general topics to more in-depth discussion pertaining to; Moisture testing, Karl Fischer Titration, Particle Size Analysis, Surface Tension, and Viscosity.

Watch this video to learn more about the very capable DA-130N Portable Density Meter.

Evaporators configured for use with Karl Fischer moisture testers can provide added benefit when testing for moisture in samples that are not easily solubilized in the titration cell.  In some cases even if it's possible to solubilize the sample in the titration cell you may find that it is better to use an evaporator to improve repeat testing by keeping the cell clean.  While traditonal Karl Fischer moistutre testing is performed using a direct injection method where a syringe and needle is used to introduce the liquid sample into the titration cell, the use of evaporators follow a different approach. 

Within the evaporator family there are SOLIDS EVAPORATORS that can range from 0 to 300 degree C as well as high heat solids evaporators that can range from 0 to 1,000 degree C. 

A typical OIL EVAPORATOR will have a range from 0 to 300 degree C. 

Solids evaporators will typically be used to measure moisture in these types of samples:

• plastic pellets (pte, etc)
• plastic parts (you can cut into smaller pieces with a pair of scissors)
• paper material (transformers)
• thick grease samples
• thick petroleum based samples like heavy paints, etc
• and the list goes on

Oil evaporators will generally be used when working with heavy crude oil samples with high turnover testing (keeping the cell clean).

In this video we will discuss and show how the oil evaporator works with a Karl Fischer Titrator.

Talking points include:

• Karl Fischer Titrator
• Oil Evaporator
• Base Oil
• Bubbler Tube
• Nitrogen Gas Source
• Regulator
• Thermocouple

This is a quick guide to getting started and running your first test.  We thought it would be helpful for those getting started and checking their first calibration before running tests with actual samples.  We will also continue to explore and share more information about calibration options, general maintenance, and data export methods using the DA-130N portable density meter.

O.K.  Let's install three 'AAA' batteries to get started.

And then attach the sampling nozzle.  

A few words about precautions when taking test measurements.

When measuring a sample make sure to hold the instrument so that the sampling nozzle is vertical to the ground.  When laying down the instrument between or after measurements make sure to drain the remaining sample from the built-in syring (the built-in syringe is located inside the meter right above the sampling nozzle).

Now let's run a preliminary test using water.  

Calibration of the measuring cell using pure water

Set calibration mode to OFF.  Press the [esc] key 2 times to return to the main menu.  Sample pure water making sure no air bubbles are visible.  The measuring cell with pure water can be calibrated automatically with the key entries as follows:  Press [cal.] key for more than 2 seconds to show CALIB(Water) (inversed colo on the display) showing calibration with pure water in progress.

After calibration is over the deviation from the theoretical value will be shown so that you can check if the calibration has been successfully completed.

Note: if after attempting re-calibration of the measuring cell and results are still not within specifications it is possible the measuring cell itself is contaminated.  In this case ensure to carefully clean the measuring cell and then re-calibrate again.

Note 1: You can also calibrate with a standard liquid that has a known density.  Sometimes calibrating with a liquid that has a similar density to your test samples will help improve precision.

Note 2: You can also calibrate with air.

General maintenance - How to clean and dry the measuring cell and replace the built-in syringe

Step 1: Clean the measuring cell

You can thoroughly clean the measuring cell with just pure water.  You can also improve the cleaning of the measuring cell by using Ethyl Alcohol.  Ethyl Alcohol gets rid of dirt that cannot be removed with pure water and also reduces the amount of time to dry the measuring cell.

• Estimate 5 to 10 minutes for the measuring cell to dry after cleaning with pure water
• Estimate 3 to 5 minutes for the measuring cell to dry after cleaning with Ethyl Alcoho

Step 2: Purge air to dry the cell thoroughly and completely 

option using an air pump:

OR use the optional manual pump to dry the cell:

When using the optional manual pump to dry the cell make sure to clean the cell first and then press the sample discharging lever all the way down, and push the sample intake lever upward to lock it.  With the adapter for the syringe attached connect the kit as illustrated above and feed air forcefully using the manual bulb.

How to replace the built-in syringe.

• Press down the sample discharging lever all the way and remove the syringe cover by pulling it toward you as illustrated.
• Turn the syringe 45degrees counter clockwise to release it from the o-ring.
• Slightly pull the sample drain-out lever toward you to pull out the syringe from the o-ring.
• Remove the syringe from the drain rack and replace it with a new one.
• Pull down the drain rack and insert the o-ring  and turn it back clockwise until it stops.
• Place the syringe cover back on the unit.

Data Processing and Storage

The maximum number of data which can be stored in the DA-130N memory is 1,100 samples.  Data can be set to be saved automatically or manually after each test.  You can recall stored measurement data on the DA-130N display again or output the data to a printer or PC.

Exporting data to a PC via Infrared:

Exporting data to a PC via RS-232

Sending data to a printer:

Example printout of data:

We hope this information about this particula density meter is helpful.  If you need other capabilities beyond a traditional portable density meters refer to other bench top density meter models for increased accuracy. 

Sometimes pressing a button and hearing a beep just drives you crazy.  We know.  Below we received some video of a problem where the operator could not move the piston burette up or down on their automatic titrator.  We decided to replicate the problem and then show how to take corrective action.  We hope you find the video informative even though it is raw footage.  Send us your questions too.  Video, audio, pictures, etc.  We can use any format.