REAGENTS AND SOLUTIONS 605 



Phenolphthalein. 1 Dissolve i gram of phenolphthalein in 100 c.c. 

 of 95 per cent alcohol. 



Permanganate Solution (Alkaline) for Van Slyke Method. 2 The 

 alkaline permanganate solution contains 50 grams of potassium per- 

 manganate and 25 grams of potassium hydroxide per liter. 



Potassium Permanganate Standard (N/io) Solution. Dissolve 

 3.162 grams of pure potassium permanganate in a liter of distilled 

 water, allow to stand a few days, and filter through glass wool. Stand- 

 ardize against N/io oxalic acid solution or against pure dry sodium or 

 potassium oxalate. One c.c. of N/io permanganate is equivalent to 

 7.0 mg. of sodium oxaiate. 



Phenylhydrazine Mixture. 3 This mixture is prepared by com- 

 bining i part of phenylhydrazine-hydrochloride and 2 parts of sodium 

 acetate by weight. These are thoroughly mixed in a mortar. 



Phenylhydrazine -Acetate Solution. 4 This solution is prepared by 

 mixing i volume of glacial acetic acid, i volume of water, and 2 volumes 

 of phenylhydrazine (the base) . 



Picramic Acid. Permanent Standard for Lewis-Benedict Blood Sugar 

 Method.' A solution of picramic acid makes a very satisfactory 

 permanent standard. The color is identical in quality with that formed 

 in the method and its solution keeps perfectly. The formula of the 

 permanent standard is: 



Picramic acid o . 064 gram. 



Sodium carbonate (anhydrous) o. 100 gram. 



Water to make 1000.0 c.c. 



Dissolve the picramic acid with the aid of heat in 25-50 c.c. of distilled 

 water which has been made alkaline with sodium carbonate. Cool and 

 dilute to i liter. This solution has the same intensity of color as that 

 obtained by the proposed method with 0.64 mg. of sugar when the 

 final volume of the reaction fluid is made 10 c.c. The solution should 

 be standardized against pure glucose. A satisfactory preparation of 

 picramic acid may be obtained from the J. T. Baker Chemical Co., 

 Phillipsburg, N. J. 



Roberts' Reagent. 6 Mix i volume of concentrated nitric acid and 

 5 volumes of a saturated solution of magnesium sulphate. 



Rosenheim's lodo-Potassium Iodide Solution. 7 Dissolve 2 grams 

 of iodine and 6 grams of potassium iodide in 100 c.c. of water. 



1 Topfer's method, p. 174. 



2 Determination of amino-acid nitrogen p. 88. 



3 Phenylhydrazine reaction, pp. 22 and 413. 



4 Phenylhydrazine reaction, pp. 22 and 413. 



5 Determination of sugar in blood, p. 279. 



6 Roberts' ring test, pp. 104 and 424. 



7 Rosenheim's periodide test, p. 273. 



