CSC Scientific Blog
Sometimes we encounter a product that is so simple and rugged that it would be tempting to deem it indestructible. Consider a stainless steel trough with a gate and etched numbers on the bottom. Seems simple and the stainless would make it tough, right? That is not the case, but it has survived nearly unchanged for more than 85 years.
- Is your concrete going to be strong enough?
Will you chocolates taste right?
Will your washing powder flow and dissolve as advertised?
Is there dangerous residue in your pill stock?
Will the “frack sand” keep the fractures open?
Is my salt of the correct grade?
If these are not correct, serious consequences could result (e.g. spoiled product, returned batches, rework or scrap).
“Why are my Moisture Test results inconsistent?”
That is an issue for many of you who test for moisture. We discussed the complexities and multiplicity of issues involved with moisture content determination in our “Loss-on Drying Moisture Analysis and other Moisture Mysteries” series.
In addition to intrinsic properties of test samples that may adversely affect moisture testing systems, automatic equipment parameter set-up, operator oversights and sample handling contribute to seemingly intractable moisture test result inaccuracies.
Within the catalog of questions we are asked is a category related to Calibrating duNouy Ring Tensiometers. The subject matter ranges from how, why and what is proven?
I guess the immediate and wise-assed answers are:
When People are first introduced to the Karl Fischer Moisture Determination Method, eyes glaze over and we can perceive a mental “Why did I ask?”
If you have any history with moisture analysis, you will have found, that for some applications, the Karl Fischer Titration Method is the best and sometimes the only way to get an accurate moisture measurement.
In April, we published an article in "Powder-Bulk Solids" comparing certification process veracity with a sieve calibration process using calibrated glass microspheres (or beads). The certification process merely indicates that a sieve mesh conforms to a standard that has a wide tolerance regarding mesh openings. It is performed on a small number of openings. On the other hand, calibration using the calibrated beads results in a number representing the mean opening -- a result generated by actually performing a test encompassing at least 80% of the mesh openings.
Just over six months 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.
Customers want Bostwick Consistometer Calibrations.
When told that CSC Scientific does not calibrate Bostwick Consistometers, people ask . “Then how can I calibrate my consistometer and where can I get a calibration standard?”.
This ramble is about changes in the Surface Tension Equipment landscape.
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 these realities, I offered to enter the world of witchcraft and folklore; water activity.
The primary purpose of a sieve shaker is to provide motion to a sample in a test sieve.
An effective sieve shaker creates a motion that presents all the particles to all of the sieve openings and assists particles in passing through. This requires both rotary and vertical motion.
This process seems simple enough, but let's not be taken in.
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.
You may recall that I promised to offer my interpretation as to how Surface Tension is related to Viscosity.
To begin with, liquid surface tension and viscosity share a common trait: they both involve properties of fluids. After that, things start to get murky.