644 PHYSIOLOGICAL CHEMISTRY 



Erlenmeyer flask, add i gram of potassium iodide dissolved in a 

 little water, and a few cubic centimeters of dilute hydrochloric acid. 

 Titrate immediately with the thiosulphate solution. When the solution 

 becomes pale yellow add a few cubic centimeters of i per cent solu- 

 tion of soluble starch and titrate to loss of blue color. 



Sodium Tungstate Solution. 1 A 10 per cent solution of sodium 

 tungstate in water. Some sodium tungstates though labeled c.p. are 

 not serviceable for this work. They usually contain too much sodium 

 carbonate. The c.p. sodium tungstate made by the Primes Chemical 

 Co., Primos, Pa., is satisfactory. 



Solera's Test Paper. 2 Saturate a good quality of filter paper with 

 0.5 per cent starch paste to which has been added sufficient iodic acid 

 to make a i per cent solution of iodic acid and allow the paper to dry 

 in the air. Cut it in strips of suitable size and preserve for use. 



Spiegler's Reagent. 3 This reagent has the following composition: 



Tartaric acid 20 grams. 



Mercuric chloride 40 grams. 



Sodium chloride 50 grams. 



Glycerol 100 grams. 



Distilled water. 1000 grams. 



Starch Iodide Solution. 4 Mix o.i gram of starch powder with 

 cold water in a mortar and pour the suspended starch granules into 75- 

 100 c.c. of boiling water, stirring continuously. Cool the starch paste, 

 add 20-25 grams of potassium iodide and dilute the mixture to 250 c.c. 

 This solution deteriorates upon standing, and therefore must be freshly 

 prepared as needed. 



Starch Paste.' Grind 2 grams of starch powder in a mortar with a 

 small amount of water. Bring 200 c.c. of water to the boiling-point and 

 add the starch mixture from the mortar with continuous stirring. Bring 

 again to the boiling-point and allow it to cool. This makes an approxi- 

 mate i per cent starch paste which is a very satisfactory strength for 

 general use. 



Stokes' Reagent. 5 A solution containing 2 per cent ferrous sulphate 

 and 3 per cent tartaric acid. When needed for use a small amount 

 should be placed in a test-tube and ammonium hydroxide added until 

 the precipitate which forms on the first addition of the hydroxide has 

 entirely dissolved. This produces ammonium ferrotartrate, which is a 

 reducing agent. 



1 Preparation of protein-free blood filtrate, p. 276. 



2 Solera's reaction, p. 58. 



3 Spiegler's ring test, pp. 103 and 440. 



4 Fehling's method, p. 542. 



5 Hemoglobin, p. 301. Hemochromogen, p. 302 



