REAGENTS AND SOLUTIONS 6oi 



hydroxide in about 200 c.c. of ammonia-free water. Mix 15 grams of 

 mercuric iodide and 10 grams of potassium iodide and dissolve in about 

 15 c.c. of water. Transfer with the aid of the alkali to a 500 c.c. volu- 

 metric flask and make up to 500 c.c. with ammonia-free water. Trans- 

 fer to an Erlenmeyer flask and let stand 24 hours to settle. 



Giinzberg's Reagent. 1 Dissolve 2 grams of phloroglucinol and i 

 gram of vanillin in 100 c.c. of 95 per cent alcohol. 



Haines' Solution. 2 This solution may be prepared by dissolving 

 8.314 grams of copper sulphate in 400 c.c. of water adding 40 c.c. of 

 glycerol and 500 c.c. of 5 per cent potassium hydroxide solution. 



Hammarsten's Reagent. 3 Mix i volume of 25 per cent nitric 

 acid and 19 volumes of 25 per cent hydrochloric acid and add i volume 

 of this acid mixture to 4 volumes of 95 per cent alcohol. It is prefer- 

 able that the acid mixture be prepared in advance and allowed to stand 

 until yellow in color before adding it to the alcohol. 



Hayem's Solution. This solution has the following formula: 



Mercuric chloride o. 25 grams. 



Sodium chloride 0.5 grams. 



Sodium sulphate 2.5 grams. 



Distilled water ....'... 100 . o grams. 



Hopkins-Cole Reagent. 4 To i liter of a saturated solution of 

 oxalic acid add 60 grams of sodium amalgam and allow the mixture 

 to stand until the evolution of gas ceases. Filter and dilute with 2-3 

 volumes of water. 



Hopkins-Cole Reagent (Benedict's Modification). Ten grams 

 of powdered magnesium are placed in a large Erlenmeyer flask and 

 shaken up with enough distilled water to liberally cover the magnesium. 

 Two hundred and fifty c.c. of a cold, saturated solution of oxalic acid is 

 now added slowly. The reaction proceeds very rapidly and with the 

 liberation of much heat, so that the flask should be cooled under running 

 water during the addition of the acid. The contents of the flask are 

 shaken after the addition of the last portion of the acid and then poured 

 upon a filter, to remove the insoluble magnesium oxalate. A little 

 wash water is poured through the filter, the filtrate acidified with 

 acetic acid to prevent the partial precipitation of the magnesium on long 

 standing, and made up to a liter with distilled water. This solution 

 contains only the magnesium salt of glyoxylic acid. 



Hypobromite Solution. 5 The ingredients of this solution should 



1 Test for free acid, p. 154. 

 2 Haines' test, p. 419. 



3 Hammarsten's reaction, pp. 207 and 433. 



4 Hopkins-Cole reaction, p. 98. 



5 Methods for determination of urea, p. 496. 



