226 HALE AND SEIDELL: SUPRARENAL GLAND 



Permanent color standards. It was found that the color ob- 

 tained in the reaction just described consisted of a mixture of 

 red and yellow and its tint could be accurately matched by a 

 mixture of about 3 parts of a 1.2 per cent cobalt chloride solution 

 strongly acidified with HC1 and 1 part of similarly acidified 0.2 

 per cent potassium platinic chloride solution. (These solutions 

 are described by the Committee on Standard Methods of Water 

 Analysis.) The intensity of this permanent color standard was 

 then adjusted to correspond exactly with that obtained by mix- 

 ing 5 cc. of a 1 :50,000 solution of the ash free active principle of 

 the suprarenal, with 5 cc. of a 0.2 per cent KI0 3 solution (yielding 

 therefore 0.1 mg. active principle per 10 cc), heating just to the 

 boiling point and after 15 minutes comparing with the color stand- 

 ard in a suitable colorimeter. After standardization, a series 

 of test tubes were prepared with dilutions of the permanent color 

 standard, corresponding to 0.01, 0.02, 0.03, 0.04, 0.06, 0.08 and 

 0.10 mg. active principle per 10 cc. of solution. 



The determination of the per cent of active principle in a given 

 sample of desiccated suprarenal is made as follows: 0.01 gm. is 

 placed in a test-tube with 5 cc. of dilute HC1 (2.5 cc. 0.1 n HC1 

 diluted to 100 cc. with H 2 0) and 5 cc. of 0.2 per cent aqueous 

 KI0 3 solution, and the mixture heated just to the boiling point, 

 allowed to stand 10 minutes and filtered; the color obtained is 

 compared with the series of standards and its position determined. 

 There may be a slight difference in the tint of the unknown solu- 

 tion due to yellow coloring matter extracted from the desiccated 

 glands, but this difference has so far not been sufficient to inter- 

 fere with the accurate determination of the position in the series 

 of standards. 



Determinations were made upon nine samples of desiccated 

 suprarenal glands obtained from two firms and one sample of 

 1 :1000 solution of the active principle which had been in the 

 laboratory some time. The physiological activity of these same 

 samples was determined by the blood pressure method, using as 

 a basis for the determination the same sample of pure base which 

 had been used to standardize the permanent color tubes required 

 in the colorimetric method. The results are as follows. 



