314 Biological Stains 



Molecular weight 792.832 



Hydrogen equivalents per mol of dye 2. 



ml. of N/10 TiCla per gram of dye 25.226 



Samples of this stain should contain not less than 70% anhydrous dye. 



Biological Tests: Light green is tested by the same procedure as fast green. 



Basic Fuchsin, C. I. No. 677 



Identification: Stains marketed under the name of basic fuchsin may be either the 

 chloride or acetate of pure* pararosanilin, or mixtures of it with the higher homo- 

 logs. Rosanilin (the base) is triaminodiphenyltolylcarbinol. Its chloride has the 

 formula, C20H20N3CI, its acetate is C2oH2oN3- C2H3O2. Pararosanilin (the base) is 

 triaminotriphenylcarbinol. Its chloride has the formula, CigHigNsCl, and its acetate 

 is Ci9Hi8N3"C2H302. The method of identification is: Dissolve 50 mg. of the sample 

 in 125 ml. of 95% alcohol and then dilute to 250 ml. with distilled water. Dilute 

 3 ml. of this solution to 200 ml. with 50% alcohol. Read in Beckman spectropho- 

 tometer. Absorption maxima; pararosanilin 545-546 m/i; rosanilin 549-550 mfi; 

 ratio P— 15/P+15 for pararosanilin is 1.26 to 1.34, for rosanilin 1.16 to 1.35. To 

 test for acetate, add 1 ml. of 6iV H2SO4 to 2.0 g. of the dye dissolved in 5 ml. of 

 distilled water, and heat. The odor of acetic acid escaping from the hot mixture 

 indicates the presence of acetate in the original sample; if not present the sample 

 can be assumed to be the chloride. 



Decolor ization Test: Dissolve 0.5 g. of the dye in 100 ml. of boiling distilled water, 

 cool to 50° C, filter into a small flask and add 10 ml. of N hydrochloric acid to the 

 filtrate. Add 0.5 g. of potassium metabisulfite, K2S2O5, shake until dissolved, 

 stopper tightly and allow to stand in the dark for 12-18 hours. The solution is color- 

 less, or not more than pale yellow. (A yellowish orange, yellowish brown or brown 

 solution, especially in the presence of a dark sediment, indicates the poorer grades 

 of fuschin.) 



Method of Analysis: Spectrophotometric. Percent dye (pararosanilin acetate) = 

 D-peak X 129. Percent dye (rosanilin chloride) = D-peak X 122. D-peak (color 

 density at peak) measured on dye solution described under "Identification". The 

 following data are used in calculating the percentage of anhydrous dye in the 

 original sample. 



Rosanilin: Chloride Acetate 



Molecular weight 337.841 361.428 



Hydrogen equivalents per mol of dye 2. 2. 



ml. of N/10 TiCla per gram of dye 59.200 55.336 



Pararosanilin: Chloride Acetate 



Molecular weight 323.815 347.402 



Hydrogen equivalents per mol of dye 2. 2. 



ml. of N/10 TiCla per gram of dye 61.673 57.670 



*"Pure" is used here in the sense of freedom from homologous dyes, and not in 

 the sense of freedom from such impurities as inorganic salts, colorless organic sub- 

 stances, and sometimes subsidiary dyes. 



