XXVlll STANDARDIZATION OF STAINS 



concerning the nature of dyes as related to their use in microscopic technique ; 

 secondly, by working with the manufacturers and dealers it endeavors to see 

 that the supply of available stains in America is of the highest possible quality 

 as judged by their performance in actual laboratory use. The first of these 

 purposes has inspired a useful book on "Biological Stains" by Conn, now in its 

 fifth (1946) edition, and at the same time has led to the pubhcation by the 

 Commission of a quarterly, "Stain Technology." The second object is being 

 brought about by the certifying of stains. 



The certification plan has been adopted because of the great difficulty of 

 drawing up any chemical or physical standards to determine which stains are 

 satisfactory'- and which are not. If such standards were formulated, it would 

 be possible to prepare specifications with which manufacturers of stains ^^■ould 

 be expected to comply. In the early work of the Stain Commission an attempt 

 was made to draw up such specifications and they were published, in provisional 

 form, for a few stains in the first edition of "Biological Stains." Full specifica- 

 tions are given in the current edition and in the National Formulary. 



Instead of drawing up specifications, therefore, the Stain Commission instructs 

 the manufacturers of stains to submit samples to it of every batch manufactured 

 of any of the stains that are on the certification basis. The Commission submits 

 these samples to certain definite tests which have now been formulated and 

 published (see Conn, pp. 246-276). The methods in question include chemical, 

 spectrophotometric, and biological tests, and only those dyes are certified which 

 are satisfactory in all these tests. Such dyes the manufacturers are allowed to 

 sell with a special label on the package indicating approval by the Stain Com- 

 mission. 



The certification label on any bottle of stain means, therefore, that: (1) a 

 sample of the batch bearing the label has been submitted to the Commission for 

 testing and a portion of the sample is permanently on file in the chairman's 

 oflBce; (2) the sample proves true to type, as judged by spectrophotometric tests; 



(3) its dye content is up to specification and is correctly indicated on the label; 



(4) it has been tested by experts in the procedures named on the label and has 

 been found satisfactory by them ; and lastly, (5) no other batch can be sold under 

 the same certification number except by such a flagrant breach of confidence on 

 the part of the company as to risk losing the good will of the Commission. At 

 present (1950) the following stains have been placed on the certified list. In 

 descriptions of their use the names should be followed by C.C., indicating that 

 the products were Commission Certified, for instance, alizarin red S (C.C.). 



Eight companies in the United States are now submitting their stains to the 

 Commission for certification before putting them on the market. It must be 

 realized, however, that no one of these concerns necessarily manufactures all 

 the stains which it thus submits ; but in the case of any stain which is manufac- 

 tured elsewhere, the company takes responsibility for its performance as a bio- 

 logical stain, on the basis of tests made to show its adequacy, and in many in- 

 stances carries out a certain degree of purification or other processing before 



