this stain commonly found in the literature it should be suspected that the trouble 

 might be due to the greater concentration of pyronins now available and the tests 

 should be made by the following formula calling for a suialler proportion of pyronin : 



Methyl green 100 gm. 



Pyronin 25 gm. 



Alcohol o. cc. 



Glycerin 20 cc. 



,2 per cent carbolized water 100 cc. 



SPECIFICATIONS FOR EOSIN Y 



1 . vSamples of eosin Y must be of the type represented by Colour Index No. 768. 

 They must, furthermore, be the dibasic sodium salt of tetra-brom fluorescein 

 having an absorption maximum at approximately 516^;* as determined in a .002 

 per cent solution in a layer 1 cc. thick in a spectrophotometer. They should be 

 readily soluble in water and alcohol (insoluble material not over 0.5 per cent) . 



2. Eosin samples to be certified by the Commission must contain at least 85 

 per cent total color as determined when reduced by titanous chloride in an atmos- 

 phere of carbon dioxide. 



3. Eosin samples must yield a satisfactory Wright's stain in combination with 

 methylene blue by the formula given in Mallory and Wright (1924) page 470. 

 The quality of the resulting compound d\'e must be judged by someone skilled in 

 its use for staining blood. 



4. The samples must prove satisfactory for counterstaining against basic dyes 

 in histological technic, their performance to be judged by experts in the staining 

 procedures involved. 



5. Eosin should prove satisfactory with methylene blue in the Levine eosin- 

 methylene-blue medium for the differentiation of certain organisms of the colon 

 typhoid group. In making this test the method should be followed wliich is 

 published by Levine (1921) p. ()2-4. 



SPECIFICATIONS FOR ORANGE G 



1. Samples of orange G submitted for certification must be of the t^^pe listed in 

 the Colour Index as No. 27 and must be characterized by an absorption maximum 

 at approximately 485/A/i as determined in a .004 per cent solution in a layer 1 cc. 

 thick in a spectrophotometer. 



2. The total dye content of the samples must be at least 80 per cent as de- 

 termined by reduction of titanous chloride in an atmosphere of carbon dioxide. 



3. The samples must prove satisfactory for counterstaining in histology and 

 cytology, giving a clear orange shade and in a brown tone to the cytoplasmic bodies. 

 They shall also be satisfactory for the Flemming triple stain, in which this dye is 

 used in contrast to safranin and crystal violet. Its performance in these procedures 

 shall be judged only by ones skilled in the technic in question. 



SPECIFICATIONS FOR HAEMATOXYLIN 



1. A sample of haematoxylin to be considered for certification must consist of 

 well defined crystals showing sandy or light brown color and shall contain less than 

 0.1 per cent ash. With NaOH it shall yield a purple solution turning brown on 



1S6 



