March 25, 1992

Mr. Thomas G. Grumbles
Manager Environmental Affairs
Vistal Chemical Company
900 Threadneedle
Houston, Texas 77079-2990

Dear Mr. Grumbles:

This is in response to your letter of March 2, requesting a clarification on the listing of Hydrogen Chloride in Appendix A of the Process Safety Standard which was promulgated by the Occupational Safety and Health Administration (OSHA) on February 24, 1992 (57FR 6356).

Specifically, you asked why Hydrogen Chloride and Hydrochloric Acid, anhydrous were both listed in Appendix A and both had the same CAS number (CAS #7647-01-0).

The Appendix A list is referring to Hydrogen Chloride gas and its liquid form. If hydrogen chloride gas is liquefied, it is sometimes referred to as Hydrogen Chloride, Anhydrous or Hydrochloric acid, anhydrous. However, it is still the same substance. Consequently, the Agency listed the substance both ways, but with the same CAS number, to indicate that they are both the same substance.

I hope this information will be of assistance to you and have clarified your question.

Sincerely,

Thomas H. Seymour
Deputy Director, Directorate
of Safety Standards Programs