Hydrogen Ion Concentration. 



127 



pure ammonium salt gives a better color in the absence Na 2 C0 3 

 and sulphite lessens the color markedly, facts which explain why 

 Wu apparently did not recognize that his salt under proper con- 

 ditions gave more color than Folin's original solution. Our 

 method is simpler and yields more usable material than Wu's 

 method would if used for the same purpose. 



The actual method of blood analysis is somewhat modified. 

 No sodium carbonate is used, the cyanide furnishing the requisite 

 alkalinity. Benedict's standard must be used. The cyanide 

 must be measured to an accuracy of 0.1 c.c. 



Abstracts of the Communications, 

 Pacific Coast Branch. 

 Twenty-seventh meeting. 



San Francisco, California, January 12, 1Q21. 

 61 (1643) 



Colorimetric determination of hydrogen ion concentration by 

 means of a double-wedge comparator. 



By G. D. BARNETT and C. W. BARNETT. 



[From the Laboratories of the Division of Medicine, Stanford 

 University Medical School.] 



In a former paper 2 a method was outlined for determining 

 hydrogen ion concentration colorimetrically without the use of 

 buffer solutions, and data for making such determinations for P H 

 values between 6.7 and 8.1 were given, using phenolsulphone- 

 phthalein as an indicator. The method consisted in the partition 

 of a constant amount of indicator solution between pairs of test 

 tubes of equal caliber, one tube of each pair containing 5 c.c. of 

 weak acid, and the other tube 5 c.c. of weak base. When such 

 pairs of tubes are viewed by transmitted light in the comparator 

 of Hurwitz, Meyer and Ostenberg a series of colors is observed 



2 Barnett, G. D. and Chapman, H. S., 1918, "Colorimetric determination of 

 reaction of bacteriologic mediums and other fluids," Jour. Amer. Med. Assoc., lxx, 

 1062. 



