At one end of the spectrum of the moisture world is the classic Speedy Moisture Tester where you use the reaction of water with calcium carbide to cause a mini explosion resulting in a moisture measurement reading. This method is used frequently for soils, concrete, and other like materials.
Many accessing our web site ask questions such as:
“How does water content affect water activity?”
"How is water activity different from water content?”
”Can I convert from moisture to water activity?”
I previously commented on water activity and now hope to clarify the differences between water activity and moisture content. Given that both of these measurements deal with water connected to a material, we must first understand of water content in a product.
Loss-On-Drying moisture analysis seemed like a simple process until, in a state of naïve bliss, I promised to look at evaporation, vapor pressure and bound water. While I was otherwise occupied with hese realities, I offered to enter the world of witchcraft and folklore; water activity.
When our customers tell me about the different places where CENCO and CSC Digital Moisture balances are used it always interests me.
As usual when we pose a question, like:
Should you use Coulometric or Volumetric Karl Fischer to measure moisture in your product?
We often get a the reaction, “So Who Cares?” We'll try to answer both questions.
The most popular was to measure include:
- Drying the material and measure the weight loss
- Using a calibration and electronic instrument
- Using a titration method such as Karl Fischer
When using these processes, we take for granted that the results will be the product's actual moisture.
Topics: Coulometric Karl Fischer, Moisture Analysis, Moisture Testing, Karl Fischer Oven, Karl Fischer, Karl Fischer Titration, Loss-On-Drying, Moisture, interfacial tension, moisture content, moisture measurement
What seems like a million words ago, I began this journey explaining the simplest approach to measuring or determining moisture: Loss-on Drying. Little did I know how involved and esoteric it would become.
This voyage has taken me down mysterious paths through spooky theories, back to age-old chemistry concepts and into the vagaries of thermodynamics related to evaporation, vapor pressure, bound water and water activity. I have come full-circle; back to explaining Loss-on Drying -- a form of drying that I had assumed would be the simplest of all.
I thought the first four topics [evaporation, vapor pressure, bound moisture, water activity] were tough, complex, confounding and less-than-obvious. Drying -- defined as “the mass-transfer process of removing water (or other solute) by evaporation from a solid, semi solid or liquid” -- seemed easy.
As is often the case, reality makes “easy” a non-operative word. Such has turned out to be so with respect to the issue of drying.
In my previous missive about Loss-On drying, we discussed Vapor Pressure -- because logically it was next. As we continue to explore moisture, we learn how vital vapor pressure is when regarding the quirky issues of free and bound water.
Topics: Evaporation, Bound Moisture, Free Moisture, Moisture Analysis, Moisture Testing, Karl Fischer Titration, Praxis Moisture Balance, Loss-On-Drying, Moisture, karl fischer moisture, water content measurement