ANALYTICAL GUIDE. 



Acetic acid, C 2 H 4 2 . 1. Extraction from animal sub- 

 stances. Extract the substance with boiling water ; 

 neutralise by soda if acid, and if dilute, evaporate to a 

 reasonable bulk. Distil with dilute sulphuric or phos- 

 phoric acid; neutralise the distillate with soda, and 

 evaporate to the consistence of an extract. Treat 

 this like the extract of urine, now to be described. 



2. Extraction from urine. Evaporate fresh urine to 

 an extract, and decant from crystals of sodium chloride 

 and other deposited matters. Mix with a sufficient 

 quantity of sulphuric acid to decompose nearly all the 

 urea, and distil the mixture from a retort. Neutralise 

 the distillate with sodium carbonate, and evaporate to 

 a low bulk. Add excess of somewhat dilute sulphuric 

 acid; allow benzoic acid to crystallise and filter. 

 Neutralise the filtrate again with soda and evaporate to 

 a low bulk ; and if you desire to prove the presence of 

 and extract formic acid, proceed as stated under that 

 head. Then evaporate the soda salt to dryness, and 

 heat in a retort with excess of concentrated sulphuric 

 acid. The f ormiate will be destroyed, yielding carbonic 



