600 PHYSIOLOGICAL CHEMISTRY 



greater delicacy is secured by mixing the solutions in the proportion 

 1:100. The sodium nitrite deteriorates upon standing and becomes 

 unfit for use in the course of a few weeks. 



Esbach's Reagent. 1 Dissolve 10 grams of picric acid and 20 grams 

 of citric acid in i liter of water. 



Fehling's Solution. 2j Fehling's solution is composed of two definite 

 solutions a copper sulphate solution and an alkaline tartrate solution, 

 which may be prepared as follows: 



Copper sulphate solution = 34.65 grams of copper sulphate dissolved 

 in water and made up to 500 c.c. 



Alkaline tartrate solution =125 grams of potassium hydroxide and 

 173 grams of Rochelle salt dissolved in water and made up to 500 c.c. 



These solutions should be preserved separately in rubber-stoppered 

 bottles and mixed in equal volumes when needed for use. This is done 

 to prevent deterioration. 



Ferric Alum Solution. 3 A cold saturated solution. 



Folin-Shaffer Reagent. 4 This reagent consists of 500 grams of am- 

 monium sulphate, 5 grams of uranium acetate, and 60 c.c. of 10 per 

 cent acetic acid in 650 c.c. of distilled water. 



Formalin Solution (Neutral). 5 To 50 c.c. of commercial formalde- 

 hyde solution (30-40 per cent) add i c.c. of phenolphthalein solution 

 and then standard alkali solution until the mixture assumes a faint 

 red color. The solution should be freshly prepared for each set of 

 determinations. 



Furfural Solution. 6 Add i c.c. of furfural to 1000 c.c. of distilled 

 water. 



Gallic Acid Solution. 7 A saturated alcoholic solution. 



Guaiac Solution. 8 Dissolve 0.5 gram of guaiac resin in 30 c.c. of 

 95 per cent alcohol. 



Gulick's Acid Oxidizing Mixture. 9 To 125 c.c. of ammonia free 

 water add 40 c.c. of sulphuric acid, 5 c.c. of a saturated solution of 

 mercuric chloride, and 20 grams of potassium sulphate. Then make up 

 to 200 c.c. with ammonia-free water. 



Gulick's Modified Winkler Solution. 10 Dissolve 40 grams of sodium 



1 Esbach's method, p. 532. 



2 Fehling's method, p. 523. Fehling's test, pp. 26 and 416. 



3 Volhard-Arnold method, p. 556. 



4 Folin-Shaffer method, p. 511. 



5 Formol titration procedure, p. 502. 



6 Mylius's modification of Pettenkofer's test, pp. 208 and 434/v. Udransky's test, pp. 

 208 and 434. 



7 Gallic acid test, p. 32 3. 



8 Guaiac test, pp. 15, 235, 262, and 432. 



9 Determination of total nitrogen, p. 490. 



10 Determination of total nitrogen, p. 490. 



