Physical Property Testing
Our services includes the following tests (see below for more info on each service):
- Heat of Combustion (BTU, HHV)
- Thermogravimetric Analysis/Differential Scanning Calorimetry (TGA/DSC)
- Freezing Points
- Melting points
- Flash Points
- Boiling Points
- Density/Specific Gravity
- Refractive Index
- Polarimetry/Optical Rotation/Specific Rotation
Heat of Combustion
This test gives 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 is requested. Methodology: ASTM D5865, modified to apply to most organic substances. Click below to view Galbraith’s Internal Method Summary:
Thermogravimetric Analysis/Differential Scanning Calorimetry (TGA/DSC)
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. The test gives a thermogram that indicates mass loss as a function of temperature. Differential scanning calorimetry gives the change in heat flow into (or out of) a sample over the range of temperature. Both of these services are reported by providing a copy of the thermogram. For more information on TGA/DSC, please click here.
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. Methodology is given in ASTM, USP and EP tests.
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 technician watches for a phase change. Once observed, the technician indicates the temperature. The beginning of melt, middle of melt and end of melt temperatures are recorded and reported. Common methodology for this test is given: Galbraith Internal Method S-105 and USP <741> Method 1A. Click here to view the USP (must have USP login)
Click below to view the Method Summary:
Flash point tests are commonly performed for publication on Safety Data Sheets (SDS). This test is performed in a closed or open container that is heated slowly. An ignition source is held close to the top of the sample and the technician watches for evidence of a flash as the sample temperature increases. For closed containers, the technician periodically opens a shutter on the top of the container to allow vapor to contact the flame. When a flash is observed, the technician records the temperature of the fluid and that value is reported. We offer testing in Pensky Martens (ASTM D93) and Tag Closed Cup (ASTM D56) flash point testers.
Boiling points are measured by heating a sample and recording the temperature of the boiling fluid. We report the temperature of the fluid at the beginning of the boil, 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. Methodology for this test is given in ASTM procedures.
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. Galbraith can provide this test according to our internal method, USP <841> Method I, or by an ASTM standard. To determine specific gravity, the density value is compared to the mass of the same volume of water. Specific gravity measurements are conducted at a specific temperature and do not have units.
The refractive index value (n) is commonly performed on oils or 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. We can only test fluids for refractive index value.
Polarimetry/Optical Rotation/Specific Rotation
Polarimetry is the measurement of a solutions’ property to rotate polarized light. This property is common in liquids or solutions containing dissolved compounds that contain an asymmetric center. This analysis is commonly performed using the sodium D line (589.0 nm and 589.6 nm), though the analysis may be conducted using other wavelengths of light. Results are reported as as the specific rotation value at a specific temperature and wavelength. Methodology for this test is given in USP <781>. Angular rotation is also provided.
Physical Property Testing