# CSC Scientific Blog

## Art Gatenby

Manufacturer of test equipment. The Company specialized in the measurement of Moisture, Particle Size and Surface Tension. In these areas CSC Scientific serves the Food, Chemical, Pharmaceutical, Petroleum, Waste Water, Mining, Power and similar industries.
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### Recent Posts

Regularly I’m asked the question; “How accurate is this moisture balance?”

The questioner asks for the answer in terms of percent (%) moisture. When I answer “it depends”, I always get the unspoken response, “Why did I ask this stupid idiot?

# Absolute Measurement

When you ask about the accuracy of something like weight or temperature the answers are straight forward and relate to the instruments' precision. For example 25 grams or 50 degrees plus or minus (+/-) 0.1 gram or 1/2 degree.

# Percent is Relative

When you ask the question of how accurate is my percentage reading, the answer becomes complicated. It’s complicated because percentage (%) is a relative term. For example, the answer for the result of a Loss on Drying (LOD) moisture test, is based on the size of the sample you use.

Using the example of a LOD moisture test we can understand the concept. The result of this type of test is calculated by subtracting the weight of the sample at the end of the test from the weight of the sample at the beginning of the test. This difference is divided by the initial weight of the sample. This procedure produces a % moisture result.

# Sample Size

In the following analysis, the implication s of sample size and instrument precision will be illustrated. This will be based on a sample that has 23.5% moisture and an electronic LOD moisture balance that has a sensitivity of 0.001 grams and repeatability of ± .005 grams.

# Sample Analysis

In past ramblings on particle size analysis we have touched on shakers, ASTM standards, sieve checking, separating small particles, inhibitors like static charges and how to get sieve tests done.  A couple of things that we rarely addressed.

The first recorded application of density measurement was for fraud detection. The density measurement concept then expanded to encompass determination of material composition and assessment of product quality.

When tempted to think I know all there is about surface tension measurement, further information brings me back to earth. I’m conversant with the principal applications: surfactant analysis, plating, detecting contaminants, development of ink and the like. I have assisted customers to set up and calibrate duNouy Ring tensiometers for most applications -- all the while taking for granted that the Ring technique was the method of choice -- with only infrequent questions arising about Wilhelmy Plate tensiometers.

# Do You Re-Certify? Compare with a Master Stack? Check with Calibration Samples?

### What Does Recertification Give?

The ASTM E-11 committee has done a great job of establishing three levels of testing. These levels show the probability of a sieve’s mesh to be within the permissible variations. These variations relate to the size of openings in wire-cloth used for test sieves.

We’ve all heard of Density since general science class in middle school. "The weight of a 12 ounce Coke." That’s pretty simple.

The first question is, "What are Liquid Properties?" Are they some kind of underwater real estate?

Loss on Drying (LOD) Moisture Balance analysis is based on drying a sample and comparing the difference in weight before and after drying.

Quiet Sieve Shakers

Recently in a quiet, reflective moment, I recalled my first work with sieve shakers. Horizontal motion with tapping was the basic shaker design. The Ro-Tap® was King, and there were few alternatives. Different shakers for special applications, such as the Mary Jane and one that was hung from the ceiling, were the exception.