ABSTRACT
Commercial calibration gases are presently prepared by several specialty gas producers. The quality and technical support of these gases varies with the supplier. All calibration gases must meet three minimum requirements to assure the user of their quality. Calibration gases must be homogeneous, stable and accurate. There are two basic types of calibration gases. These gases are usually refered to as primary and certified. The determination of which type of preparation method used is based on the accuracy requirements of the calibration gas. In an effort to supply the industry with a more reliable calibration gas, a combination of these two techniques has been developed. This combined technique is called the UniPhase calibration mixtures, which is a trademark of Big Three Industries, Inc. Primary calibration gases are prepared gravimetrically, using high load, high sensitivity balances. Certified calibration gases are prepared either gravimetrically or volumetrically.
