Physical Property Testing
This test generally involves freezing the sample and then allowing it to warm slowly while making temperature observations at a fixed frequency. The temperatures are plotted and the freezing point determined from the chart.
Boiling points are measured by heating a sample and recording the temperature of the boiling fluid. The temperature of the fluid at the beginning of the boil is reported, at the point when approximately 75% of the fluid remains, at the point when approximately 50% of the fluid remains, at the point when approximately 25% of the fluid remains, and at the end of the boil.
This test is performed using a melting point apparatus. It requires a small sample size (several mg) of crystalline product to be placed in a capillary tube and heated slowly while the material is observed for phase changes. Once observed, the temperature is recorded. The beginning of melt, middle of melt and end of melt temperatures are typically reported.
Flash point tests are commonly performed for publication on Safety Data Sheets (SDS). This test is performed in a closed container that is heated slowly. An ignition source is held close to the top of the sample, and the container is periodically opened to allow vapor to contact the flame. The sample vapor is observed for evidence of a flash as the temperature increases. When a flash is observed, the temperature of the fluid is recorded and that value is reported. We offer testing in Pensky Martens (ASTM D93) and Tag Closed Cup (ASTM D56) flash point testers.
A refractive index determination is commonly performed on oils and other fluids. It is a measurement of the ratio of light speed in air versus light speed in the substance. This test is performed on a refractometer that has a small cell on which a drop or two of the sample is placed. The instrument automatically measures the refractive index of the fluid at a specific temperature using the sodium D line (589.0 nm and 589.6 nm). Results are reported as the reading at a specific temperature. Since refractive index values are ratios, they do not have units.
Polarimetry, the measurement of optical rotation, is the measurement of a solution’s property to rotate polarized light. There are many substances that have the ability to rotate a plane of polarized light so that the transmitted light emerges at a measurable angle, expressed in degrees, from the plane. These substances are known as “optically active”. Generally, the reason the light is rotated is due to the presence of one or more asymmetric compound centers, usually a carbon atom with four different substituents. Optical rotation is positive for dextrorotatory substances, and negative for levorotatory substances. Polarimetry is commonly used for identity and purity purposes in the pharmaceutical, flavor, fragrance, essential oil, food industry, and chemical industries.
Heat of Combustion
This test provides a measurement of the energy released during combustion of a sample in an oxygen atmosphere. Sample is combusted within a Parr Bomb that is submerged in a measured volume of water. The increase in temperature of the water after combustion is used to calculate the BTU value of the sample. Results are reported in BTU/lb, unless an alternate unit is requested.
Thermogravimetric Analysis & Differential Thermal Analysis (TGA/DTA)
A thermogravimetric analysis is conducted by heating a sample at a constant rate over a range of temperature while the sample is on a balance. TGA results in a plot of mass loss as a function of temperature. Differential Thermal Analysis (DTA) provides information about dynamic temperature changes as the sample is heated. DTA, with calibration, can also be used to create Differential Scanning Calorimetry (DSC) data for heat-flow measurements, melting enthalpies, and more. TGA/DTA services are reported by providing a copy of the thermogram.
Density & Specific Gravity
Density measurements are conducted using pycnometers. A known volume of sample is placed into the pycnometer and is then weighed on an analytical balance. The result is reported in g/mL at a specific temperature. To determine specific gravity, the density value is compared to the mass of the same volume of water.
Viscosity measurements are performed using the Brookfield and Kinematic techniques. With Brookfield Viscosity, a spindle is inserted into a liquid sample at a specific temperature. The torque required to rotate the spindle is directly proportional to the viscosity of the liquid. Kinematic viscosity is a measure of a fluid’s resistance to flow under gravitational forces. It is determined by measuring the amount of time required for a known quantity of liquid to flow a known distance through a capillary viscometer at a specific temperature.