orders both dahlia and Hoffman violet. His dealer, who is prob- 

 ably quite unacquainted with dyes, will very likely send him a 

 bottle bearing each name, and the purchaser has no easy way of 

 discovering that the two are identical; so he may continue for years 

 to use the two stains for different purposes, misled by their labels 

 and thinking them distinct. The manufacturers and dealers in 

 stains have sometimes encouraged this confusion by their practice 

 of taking care to have the label on the bottle agree with the name 

 used in the customer's order, regardless as to what the usual name 

 for the dve mav be. 



An attempt to relieve this confusion has been made by the Com- 

 mission on Standardization of Biological Stains (1923f) by publish- 

 ing a list of biological stains with their best known synonyms. In 

 each case one of the names is listed as a preferred designation. 

 Sometimes general usage made it easy to select one name as the 

 preferred one; but in other instances the selection was more or less 

 arbitrary. This same list, with a few revisions in the way of ad- 

 ditions and corrections, is given in the appendix of this book (p. 

 106). The preferred designations in this list are the same as in the 

 earlier, except in the one case of methylene azure. For this stain 

 Azure I was preferred in the earlier list; but as it was merely a 

 trade name of somewhat uncertain application methylene azure 

 seems preferable. The list of synonyms has been revised more 

 extensively, largely to omit names that are obsolete and have no 

 present meaning. 



DYE INDEXES 



Inasmuch as the dye industry originated in Germany and until 

 the war was almost a monopoly of that country, it is natural that 

 the first serious efforts to index the dyes should have been under- 

 taken in that country. Until recently the only important index of 

 dyes was Schultz's Farbstofftabellen, which is now in its sixth 

 edition (1923). This index lists all of the important textile dyes, 

 giving their synonymy, their chemical composition, methods of 

 preparation, and distinctive characteristics. As these descriptions 

 are concise, it seemed well to refer to the Schultz number of all the 

 stains listed in the article on stain nomenclature above mentioned 

 (Commission, 1923f), wherever such could be given. 



More recently another dye index has been published in England 

 by the Society of Dyers and Colourists (1923). This publication, 

 known as the Colour Index, is more complete than even the sixth 

 edition of Schultz, and lists even such dyes as narcein, thionin and 

 iodine green, which are no longer of use in the textile industry and 

 have been omitted from recent editions of Schultz. The synonymy 

 is more complete and up-to-date than that in Schultz, and many 

 more chemical formulae are given. Accordingly in the following 

 pages the stains are denoted by their Colour Index number (ab- 

 breviated C. I. No.) instead of by their Schultz number, as in the 



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