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Hank Levi

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Regular Bostwick Consistometer vs. Long Bostwick Consistometer

By Hank Levi on Thu, Apr 27, 2017 @ 01:22 PM

Many of us have used the CSC Bostwick Bostwick Consistometer.pngConsistometer and are familiar with it's operation.  Pressing down the gate and loading the trigger is step one.  Pouring in your sample and scraping off the top to a clean and even surface is important to getting repeatable results.  With a stopwatch in one hand, "popping" the trigger and letting the sample flow out and down the trough comes next.  Some tests are designed to see how far a sample will flow in say, 10 seconds.  Another testing approach might be to time the movement of the sample until it reaches a pre-determined point (bostwick).  If you have ever noticed in the bottom of the tray there are lines with numbers ranging from 0 to 24 (you really can't see a number 24 because the tray stops exactly at what would be 24).  Over the years these lines with numbers have affectionatly become to be known as "bostwicks". 

Most recently we have had requests to extend the length of the Bostwick Consistometer to accommodate samples that require more time and distance.  Not every sample flows the same way so this seemed like a good idea.  So to meet these needs we have now just started to offer a longer version of the Bostwick Consistometer!  Don't worry we still have the regular length Bostwick Consistometer available.

Bostwick Consistometers.jpg

  • The long version of the Bostwick Consistometer (part# 24925-000L) now extends from 0 to 32.  
  • The regular length Bostwick Consistometer (part#  24925-000) has a range of 0 to 24.  





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What is water activity?

By Hank Levi on Mon, Nov 14, 2016 @ 03:16 PM

There is sometimes confusion about water activity and how it relates to water content.  Water content is how much.  Water activity (aw) tells us about the energy of the water.  Both are measurable.  

Water Content

We know a lot about water content and how to measure it using various popular methods including loss on drying, Karl Fischer titration, capacitance and more.  Water content is typically expressed in % or Parts Per Million (PPM).

Water Activity

Water Activity is the amount of unbound water in a sample.  Water that is not bound to the ingredients themselves can be used by unwanted microorganisms which could lead to one of the contributing factors for food spoilage.  Water activity is a vaporpressure.pngthermodynamic measure of water expressed as the vapor pressure of water in a sample divided by vapor pressure of pure water at a given temperature.  

Water Activity is based on a scale from 0.0 to 1.0 


The more unbound water we have the more likelihood we have for microbial spoilage. Water Activity (aw) Meters measure the unbound water vapor pressures to determine microbial spoilage, chemical and physical stability. 


Well documented and scientifically established guidelines that are also supported by FDA regulations outline these thresholds of microbial limits using a water activity (aw) range or scale.  This water activity (aw) range provides the lowest rating for inhibition of microorganism and other degradative chemical and physical reactions that effect shelf life in foods (see chart below).  

                                     Get more Water Activity information

Water Activity & Growth of Microorganisms in Food

Range of aw Microorganisms generally inhibited by lowest aw in the range Foods generally with this range
1.00-0.95 Pseudomonas,Escherichia,Proteus,Shigella,Klebsiella,Bacillus,Clostridium perfringens, some yeasts Highly perishable foods and canned fruits, vegetables, meat, fish, milk, and beverages
0.95-0.91 Salmonella, Salmonella, Vibrio parahaemolyticus, C. botulinum, Serratia, Lactobacillus, Pediococcus, some molds, yeasts (Rhodotorula, Pichia) Some cheeses (Cheddar, Swiss,Muenster, Provolone), cured meat (ham), bread, tortillas
0.91-0.87 Many yeasts (Candida, Torulopsis, Hansenula), Micrococcus Fermented sausage (salami),
sponge cakes, dry cheeses,
0.87-0.80 Most molds (mycotoxigenic penicillia), Staphyloccocus aureus, most Saccharomyces (bailii) spp., Debaryomyces Most fruit juice concentrates,
sweetened condensed milk,
syrups, jams, jellies, soft pet food
0.80-0.75 Most halophilic bacteria, mycotoxigenic aspergilli Marmalade, marzipan, glacé fruits, beef jerky
0.75-0.65 Xerophilic molds (Aspergillus chevalieri, A. candidus, Wallemia sebi), Saccharomyces bisporus Molasses, raw cane sugar, some dried fruits, nuts, snack bars, snack cakes
0.65-0.60 Osmophilic yeasts (Saccharomyces rouxii), few molds (Aspergillus echinulatus, Monascus bisporus) Dried fruits containing 15-20% moisture; some toffees and caramels; honey, candies
0.60-0.50 No microbial proliferation Dry pasta, spices, rice, confections, wheat
0.50-0.40 No microbial proliferation Whole egg powder, chewing
gum, flour, dry beans
0.40-0.30 No microbial proliferation  Cookies, crackers, bread crusts, breakfast cereals, dry pet food, peanut butter
 0.30-0.20  No microbial proliferation  Whole milk powder, dried
vegetables, freeze dried corn

*Adapted from L.R. Beuchat, Cereal Foods World, 26:345 (1981) 

Pure water that is unencumbered has more energy and therefore can be available and used to do bad things by microorganisms.  As water comes in contact with a material substance the water's energy and water activity (aw) decrease. Water reacts differently with different material substances and can have a higher or lower water activity rating* (aw).  A water activity (aw) number closer to the top of the chart closer to 1.00 has a higher water activity while those lower have less.

Understanding and documenting how water activity is effected by different material substances provides valuable information.   Using this information provides a way for us to take proactive measures to lower water activity as we seek to improve microbial, chemical and structure stability of foods, pharmaceuticals, and other materials. 


Packaging to improve shelf life






Equilibrium of ingredients to make foods last longer


Explore multi-ingredient products where water activity in each ingredient will seek to equilibrate and change the overall water activity (aw) result of the product.  This can trick people who only look at water content of each ingredient and or even the water activity individually.

      CONTACT US ABOUT------>   Water Activity (aw) 

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How to find Bromine number and index with a Karl Fischer Titrator

By Hank Levi on Sun, Apr 10, 2016 @ 08:47 AM


The degree of unsaturated hydrogen carbide (Hydrocarbon) in oil and petroleum products is indicated by Bromine number or index. Hydrocarbons containing between 6 and 10 carbon molecules are the primary components of most fuels where the process of burning them produces energy. Saturated hydrocarbons are defined by molecular structure and are defined as Alkanes.  Alkanes are the basis for petroleum fuels.  Unsaturated hydrocarbons are also defined by their molecular structure and produce less energy when burned than do saturated hydrocarbons.  Mathematically it therefore requires a greater quantity of unsaturated hydrocarbons to be burned to equal the same amount of energy produced by burning the same amount of saturated hydrocarbons.  An un-friendly environmental side effect of burning hydrocarbons is the creation of carbon dioxide.  So from an environmental standpoint you could say we prefer the lesser of two evils and prefer to burn saturated hydrocarbons vs. unsaturated hydrocarbons. For these reasons alone it would make sense that we would want to measure and quantify these hydrocarbons. 



Methane Fuel in electrical generation
Ethane Chemical applications
Propane Heating and cooking
Butane lighters and aerosol
Pentane Lab & production of polystyrene
Hexane Glue
Heptane & Octane Major contributor to gasoline

Diesel fuel


Jet fuel, gasoline and diesel


Although the test method ASTM2710 describes the use of an automatic potentiometric titrator the coulometric Karl Fischer method is easier to perform (see ASTMD1492-08e1).  


Bromine number :The amount of bromine (unit: g/100) consumed in 100g sample.

Bromine index :The amount of bromine (unit: mg/100) consumed in 100g sample.



The unsaturated hydrogen carbon reacts with bromine as follows: R-CH=CH-R+Br2R-CHBr-CHBr-R- (Eq. #1)

In coulometric titration, bromine is generated by electrolysis of anolyte containing bromine ion:  2Br-Br2+2e- (Eq. #2)


When generated bromine is consumed according to Eq. (#1), the electrode detects bromine consumption, and continues generating bromine according to Eq. (#2).

Such bromine is generated in proportion to the electricity determined by Faraday’s Law. From Eq. (#1), Bromine reacts with coupled C=C evenly (1:1). ==>Thus, one mol of bromine(159.8g) is equivalent to 2 96500 coulomb, which means 1.2 coulomb/1mgBr2.

Based on the above principle, the electricity consumed in electrolysis is converted to the exiting bromine.


Special notes to obtain correct measurement results:

  1. Replace anolyte and catholyte reagent often (daily).
  2. When anolyte turns to white color replace it with new anolyte.
  3. Over use of anolyte and catholyte and not replacing it can cause results to be higher than expected.
  4. Do not share Bromine titration cell with a moisture titration cell

 Download a copy of this method

Step 1: Preparation of Reagents

Prepare the reagents and samples for measurement of bromine number and bromine index.

Use the following reagent for measurement of bromine number or index:

Anolyte Reagent: Mixture of Acetic acid (high grade) 600mL; Methanol (high grade) 260mL; 1M-Potassium bromide solution 140mL. Blend it well and use 100mL each time.

Catholyte Reagent: 0.2M-Potassium chloride solution. Use 5mL each time.

Check Solution:  0.05Wt-Cyclohexene toluene mixture (Approx. 93 ~ 102mgBr2/100g). Theoretical value is calculated by the below formula:



Step 2: Prepare Reagent for testing

Refer to the below chart for sample size:

Bromine index (mg/100g)  Sample Size (g) 

 Below 10

10 ~ 50

50 ~100

100 ~ 200

More than 200

 10 ~ 15

5 ~ 10

3 ~ 5

1 ~ 3

~ 1

For bromine number, a sample is diluted with toluene to Bromine number 0.2 (g/100g), and approximately 1g is used for measurement. Calculate the toluene to be used for diluting to Bromine number 0.2 (g/100g) with the following equation:


Obtain the dilution coefficient in advance according to the following equation:



Step 3: Measurement Procedure

Measure Bromine Number and Bromine Index

  1. Discharge 20 100μL check solution into the electrolysis cell, and press [Pre-titr.*] key.

  2. After pre-titration is finished, press [Sample*] key to enter sample name, its ID and size, and enter the dilution coefficient (D) .
    Press [MENU/HOME*] to Main display.

  3. Press [Start] key, and discharge the sample into the cell. Again press [Start*] key for titration to start.

  4. After titration is over, the measurement results appear on display with printout when a printer is connected.

*Note that different Karl Fischer Titrator Models will have different button commands.  The MKC-710 series coulometric Karl Fischer titrators come standard with pre-programmed setup for running Bromine and follow the above button commands.

We hope this information helps you get started.  If you have any questions or would like some help please contact us by clicking on the button below.

Download a copy of this method 



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How to Clean Karl Fischer Titrator Electrodes

By Hank Levi on Wed, Mar 30, 2016 @ 03:31 PM

How to Clean Karl Fischer Electrodes:

A Karl Fischer Titrator uses two electrodes.  The Inner burette (aka Generator Electrode) and the Detector Electrode.  We hope this infromation is helpful in giving some guidance on cleaing and caring for these Karl Fischer Titrator electrodes.


Twin platinum reference "Karl Fischer Detector Electrode" K103-M713/ K103-M714 or any other model

If the electrode is heavily stained and the potential is unstable and measurement reading fluctuates clean with nitric acid. After cleaning use methanol and wipe off with clean gauze.


Single or Dual Inner burette K443-0006/ K103-0002 or any other model (aka Generator Electrode)

Periodic cleaning of the inner burette is recommended if the inner burette is stained and the electrolysis reaction will not run smoothly.  A faulty Inner Burette may cause a longer length of time in the measuring process with measurement results being recorded at higher than theoretical values.


Cleaning with alcohol: general method

  1. Turn off all power
  2. Disconnect the electrodes from their ports.
  3. Take out both anolyte and catholyte.
  4. Wipe off grease around sliding area with methanol.
  5. Rinse the inner burette with methanol, and fill it with approximately 10mL of methanol and then put it in a beaker. Fill the beaker with methanol up to the level of methanol inside the inner burette, and leave it for about 30 minutes.
  6. After the above 5), dry the inner burette.


Cleaning with nitric acid (boiling): If the color of inner burette or diaphragm does not disappear

When there is a deposition of iodine on the diaphragm or the electrode surface, clean with 1mol nitric acid (boiling):

  1. Immerse the diaphragm or the electrode surface in nitric acid, and boil with a hot stirrer.
  2. Drain out the chromate inside the cell, and rinse it with pure water for 2 to 3 times until yellowish color disappears.
  3. Clean the inner burette with methanol or with alcohol.
  4. Repeat the above steps several times when dirt does not come off.



Cleaning with chromic acid mixture : When dirt does not come off

If foreign objects are observed on diaphragm and platinum surface, use chromic acid mixture instead of methanol for cleaning.

Chromic acid mixture:  1.5g approx. potassium dichromate dissolved in 100mL of concentrated sulfuric acid






  1. Follow the same steps as above for methanol.
  2. Drain out the chromate inside the cell, and rinse it with pure water for 5 to 6 times until yellowish color disappears.
  3. Clean the inner burette with methanol or with alcohol.



How to dry the inner burette and diaphragm

Dry it in a decompression dryer for more than 2 hours.  Below sketch shows an example of commercially sold drying under reduced pressure.



NOTE:  Dry the inner burette itself only after removed from the titration cell in order to avoid possible breakage of inside ceramic diaphragm.

SUGGESTION: Use a hair dryer if a compression dryer is not available. With a hair dryer, dry the inner burette well enough as long as for more than 10 minutes, especially dry the diaphragm until it is really dried. Any residue of moisture will cause high drift level.

CAUTION: Set the temperature of the constant temperature drying oven at 65°C or below.  When drying with a hair dryer, make sure not to overheat its cable and connector. Overheating may result in malfunction.


Find more Coulometric Karl Fischer Titrator information

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Electrode Shower Cleaning for Auto Titrator Sample Changers

By Hank Levi on Thu, Feb 25, 2016 @ 12:04 PM


Sample changers that are connected with automatic titrators generally are there for a reason.  Efficiency. From an operators point of view getting multiple tests done quickly while being able to take on other tasks in the lab is a key productivity booster.  Sample changers offer various sizes ranging from as few as 6 positions for samples up to some of the largest exceeding 50 sample positions.  Sample changers either have rotating carousels or an arm that moves electrodes and nozzles from sample to sample.  Each time a sample test is completed the electrode must be cleaned before moving on to the next test.  Many sample changers offer as standard a dip rinse between sample testing and as the name suggests it's really nothing more then dipping the electrode in clean water or solution.  For some samples this process is sufficent but for others it is not enough to effectively clean the electrode before the next test.  Luckily most manufacturers of sample changers offer additional cleaning power with the use of a shower rinse system.   Below is a video showing how a shower rinse process works.   Water is stored in a container and then is flushd and rinsed in one of the sample positions designated as the cleaning station.  Water is evacuated via tubes to a drain or sink.  



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Automatic Tensiometer vs. Manual Tensiometer

By Hank Levi on Mon, Jan 11, 2016 @ 11:56 AM

Ever wonder what a tensiometer looked like?   

There are MANUAL TENSIOMETERS that look like this:



  • >Great for hands-on learning
  • >Can use virtually anywhere (does not require electricity)
  • >Easy to learn how to use
  • >Less expensive


  • >It's manual.  You have to twist the dials by hand
  • >There is a technique to getting repeatable results
  • >Human error potential is higher
  • >Need to record results by hand




There are AUTOMATIC TENSIOMETERS that look like this.



  • >Easy to operate.  Press a button and walk away
  • >Run more tests quickly with high repeatability
  • >Ability to record and report data results (store historical data too)
  • >Dynamic testing features including time tests and Lamella length and more
  • >Most handle both DuNouy Ring and Wilhelmy Plate


  • >More Expensive
  • >Some models require a computer (some don't)



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.


                        Created on 09/22/11 at 12:43:16

Click here to go to the platinum page


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How to measure salt in potato chips using an automatic titrator

By Hank Levi on Mon, Oct 12, 2015 @ 04:22 PM

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


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)


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.


Ask for more information  


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How to test for moisture in Jet Fuel Oil using a Karl Fischer titrator

By Hank Levi on Mon, Sep 21, 2015 @ 03:15 PM

From start to finish watch this short video to see how a sample of Jet Fuel Oil is tested for water content using a karl Fischer Titrator. For this training video we use:

  1. The Aquapal III coulometric Karl Fischer Titrator (setup as a dual reagent configuration)
  2. Reagents; Anolyte is coulomat AG and the catholyte is coulomat CG
  3. A 4-place analytical balance SA-80
  4. And a disposable syringe and disposable needle

In this video you will see the steps for running a test successfully including how to:

  1. Extract your sample into the syringe
  2. How to weigh your sample and tare the balance
  3. How to inject a sample properly
  4. How to input the sample weight and obtain a final result


HubSpot Video

Find out more about the Aquapal III

We hope you found the video helpful and informative!  If you think a colleague could benefit from this please share it with them!  Click on the twitter button to automatically share this video!

Tweet: How to test for moisture in Jet Fuel Oil using a Karl Fischer Titrator http://bit.ly/1NJ8If4"How to test for moisture in Jet Fuel Oil using a Karl Fischer titrator"


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Karl Fischer Glassware and reagents 101

By Hank Levi on Mon, Sep 21, 2015 @ 01:53 PM

Many people use coulometric Karl Fischer Titrators to measure low level moisture at the part per million (PPM) level.  When it's time to start testing it's critical to have an understanding of how to:

  1. Properly identify the glassware components
  2. Assemble the glassware
  3. Identify the reagents  (anolytes and catholytes)
  4. Introduce the reagents required by the instrument and the sample being tested 

Once you have these concepts down you will have a strong working knowledge of how a Karl Fischer Titrator works and how to trouble shoot future problems.  Watch this short training video to learn more.

Find out more about the Aquapal III

If you found this information helpful please share this with your colleagues!  Just click on the tweet this button.

 Tweet: Karl Fischer glassware & reagents 101: properly identify glassware components, assemble glassware & identify reagents http://bit.ly/1Qvwv1v "Karl Fischer Glassware and reagents 101: Properly identify the glassware components, Assemble the glassware and Identify the reagents"

We hope you find the training video helpful!
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Karl Fischer Glassware and Reagents 101: How to setup.

By Hank Levi on Wed, Jun 17, 2015 @ 10:53 PM

Karl Fischer Glassware and Reagents 101:  How to setup.


It seems sometimes we overlook the obvious and forget to explain some of the most basic concepts.  Sorry about that.  So we thought it might be a good idea to show how Karl Fischer Glassware is setup and how we introduce or "charge" the vessel with reagents.  We hope you enjoy this short video tutorial!


 Find out more about the Aquapal III

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