ohn, My Hawley's says the same as your Merck. But ACGIH has two CAS # and so do many other references. I'm going to take a suggestion from Lynn Knudtson and contact CAS directly. I have to wait two days to do it because if I don't attend a family gathering in the Hamptons Wednesday and Thursday, I'll be busy responding to a divorce petition.
Monona
In a message dated 8/16/2011 3:08:30 PM Eastern Daylight Time, dura_chemiker**At_Symbol_Here**YAHOO.COM writes:
Monona,
I read your E-mail inquiry regarding various allotropes of phosphorous and immediately opened my Merck Index. According to the Merck, there is only one CAS number for phosphorous [7723-14-0]. They do not provide individual CAS numbers for the different allotropes. It also states that there are three main allotropic forms: white, black and red. White is sometimes refered to as yellow as a result of impurities, while red is sometimes refered to as violet. I also checked the CRC Handbook of Chemistry and Physics just for confirmation. The Merck Index provides some health and safety information.
John D. Turner