640 PHYSIOLOGICAL CHEMISTRY 



material to water and settle in a few seconds. It may be used more 

 than once by washing first with water, then with 2 per cent acetic acid 

 and finally with water again. 



Peters' Sugar Reagents. 1 (a) Copper Solution. Dissolve 34.639 

 grams of highest purity crystallized copper sulphate (such as Kahl- 

 baum's "zur analyse mit garantieschein ") in water to make 500 c.c. 



(b) Alkaline Tartrate Solution. Dissolve 173 grams of sodium 

 potassium tartrate and 125 grams of potassium hydroxide in water to 

 make 500 c.c. 



(c) N/$ Sodium Thiosulphate. Dissolve about 50 grams of ordinary 

 c.p. sodium thiosulphate or exactly 49.66 grams of the, pure, dry, 

 recrystallized salt, in enough boiled out distilled water to make a 

 liter. Allow to stand for several days. The solution should be stand- 

 ardized against the copper solution prepared as above. For this 

 purpose introduce 20 c.c. of the copper solution into a 200 c.c. Erlen- 

 meyer flask, add 20 c.c. of strong acetic acid (30 per cent) and 40 c.c. of 

 water. Add about 7 grams of a saturated solution of KI and titrate 

 with the thiosulphate using starch as an indicator. Calculate the 

 equivalent of i c.c. of thiosulphate in Cu. One c.c. of the copper 

 sulphates solution contains 17.647 mg. of Cu. The thiosulphate remains 

 constant for some months. It should be kept in a dark bottle. 



Phenolphthalein. 2 Dissolve i gram of phenolphthalein in 100 c.c. 

 of 95 per cent alcohol. 



Permanganate Solution (Alkaline) for Van Slyke Method. 3 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 oxalate. 



Phenylhydrazine Mixture. 4 This mixture is prepared by com- 

 bining 2 parts of phenylhydrazine-hydrochloride and 3 parts of sodium 

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



Phenylhydrazine-Acetate Solution. 5 This solution is prepared by 

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

 of phenylhydrazine (the base.) 



1 Determination of sugar, p. 543. 

 9 Topfer's method, p. 177. 



3 Determination of ammo-acid nitrogen, p. 87. 



4 Phenylhydrazine reaction, pp. 22 and 431. 



5 Phenylhydrazine reaction, pp. 22 and 431. 



