In order to determine the stability, reactivity and compatibility of two or more materials, such as explosives, paints or adhesives, it is necessary to monitor the change of pressure of these materials over an extended period of time.
Current standard techniques employed to monitor such change of pressure utilize a mercury manometer connected to a sample tube. The materials are placed in a test tube which is fitted with a ground glass ball joint. A manometer tube is attached thereto via a mating ground glass ball joint. The reservoir on the other end of the manometer is filled with mercury. A vacuum source is attached to the tip of the manometer to permit evacuation of the interior of the assembly. After evacuation, the assembly is placed in a holding fixture with the test tube immersed in a heated bath at a preferred temperature of 100 degrees Centigrade.
The distance from the top of the mercury in the reservoir to the top of the column in the manometer capillary is measured and recorded, along with the ambient temperature and ambient pressure. At the end of a specified time, usually 40 hours, the mercury column height and ambient temperature and pressure are measured and recorded again. The change in internal gas volume is then calculated, corrected for standard temperature and pressure.
The data obtained by this technique provides only the change in internal gas volume over the duration of the test. The fragility of the manometer makes it a practical impossibility to measure the column height with any frequency. Moreover, the technique requires the handling of mercury in large quantities. Precision calibrated glassware needs to be repeatedly handled, including cleansing of melted energetic materials adhering to the test tube. Operating costs are high due to repeated cleaning requirements, the high cost of replacing breakable precision glassware, and the need to perform extensive and complicated calibration procedures on new glassware components.