Commerically available 'pure' Azure dyes - caveat emptor.

Conclusion Of the batches of dye examined only one (Azure B, Merck number YE 132) can be regarded as being of acceptable quality. This material retails at $6.60/g for a 250 g lot, and may be considered to be reasonably priced. The quality of all Serva's pure dyes is alarmingly poor and leaves much to be desired. In view of the fact that these dyes retail at $700.00/g, the purchaser should expect to obtain analytically pure material. It is hoped that this note may persuade users of commercially available pure Azure dyes to check the purity of any samples they might possess: manufacturers' claims should not be accepted at face value.