36 ANALYTICAL PROCESSES. 



but the error so introduced is not great and may usual- 

 ly be disregarded. 



SUGAR. 



The following method due to Soxhlet, employs a 

 Fehling's solution, made as required, by mixing equal 

 parts of the following solutions : 



Copper Sulfate Solution. 34.64 grams of pure crys- 

 tallized copper sulfate are dissolved in distilled water 

 and made up to 500 c c. 



Alkaline Tartrate Solution. \J ^ grams of pure sodium 

 potassium tartrate, and 5 I grams of sodium hydroxid 

 of good quality, are dissolved and made up to 500 c. c. 



100 c. c. of the mixed nitrate from the precipitated 

 proteids are brought to boiling, in a beaker, 50 c. c. of 

 boiling Fehling's solution added, and the boiling con- 

 tinued for six minutes. The precipitate is allowed to 

 settle for a short time, and the supernatant liquid pour- 

 ed through a filter. About 50 c. c. of boiling water are 

 added to the residue, and the heating continued for a 

 minute or two. The precipitate is then conveyed to 

 the filter, washed with boiling water, with alcohol and 

 finally with a small quantity of ether. The filter and 

 contents are dried in the water oven, the precipitate re- 

 moved to a tared porcelain crucible, the filter held over 

 the crucible and burnt to ash, which is added to the 

 precipitate, and the cuprous oxid converted into cupric 

 oxid by strong ignition for five or ten minutes over the 

 Bunsen burner. 



The amount of copper reduced under the conditions 

 detailed above is not directly proportional to the milk 



