188 METHODS FOR THE ANALYSIS OF BLOOD 



water. A solution containing 3 gms. of bismuth nitrate is added. 

 (It is well to keep on hand a 60 per cent solution of the crystallized 

 salt in 2 N HNOa.) If a precipitate forms (due to excessive 

 alkalinity of the KNO2), dilute nitric acid is added carefully until 

 it redissolves. A strong solution containing 1.6 gm. of CsNOs 

 and 1 c.c. of 2 N HNO 3 is added. The solution is diluted to 100 

 c.c. and dilute nitric acid is used to remove any turbidity which 

 may form. At this stage the reagent should be a clear orange- 

 yellow. If sodium salts were present in any of the chemicals as 

 impurity, the insoluble precipitate which has formed at the end 

 of twenty-four hours is filtered off. The reagent is kept under 

 illuminating gas in the cold room. 



2. Acetone. Redistilled and kept ready for use at 1 C. 



3. A 50 per cent solution of acetone saturated at 1 C. with 

 sodium cesium bismuth nitrite. 



For Volumetric Procedure. 1. Permanganate 0.1 N or 0.05 N. 



2. Oxalic acid, 0.1 N or 0.05 N. 



3. Hi&Oi concentrated acid diluted with equal volume of water. 

 For Colorimetric Procedure. 1. Alkaline tartrate. Equal 



volumes of KOH (10 per cent) and tartaric acid (10 per cent) 

 are mixed. 



2. Sulfanilic acid, 0.8 per cent in 5 N acetic acid. 



3. a-Naphthylamine, 0.5 per cent in 5 N acetic acid. 



4. Nitrite standard. Made by recrystallizing AgNC>2 from 

 hot water until free from nitrate. Add NaCl equivalent to the 

 AgNOo and filter off silver chloride. Determine nitrite nitrogen 

 by Devarda's method and dilute so that 5 c.c. = 0.01 mg. N. 



Method of Devarda for Nitrite Nitrogen l 



An amount of this solution which is equivalent to 0.5 gm. 

 nitrite is placed in an Erlenmeyer flask of 600 to 800 c.c. capacity 

 to which are added 60 c.c. water, 5 c.c. alcohol and 50 c.c. of 

 KOH of sp. gr. 1.3. To this solution 2.5 gms. of a powdered 

 amalgam formed from 45 parts of aluminum, 50 parts copper 

 and 5 parts zinc are added; the flask is immediately connected with 

 a distilling apparatus and the resulting ammonia caught in a 

 standard acid. 



1 Devarda: Z. anal. Chem., 1894, 33, 113. 



