46 ANALYTICAL PROCESSES. 



may be advantageously substituted for lime in this pro- 

 cess, the details of the modification being given in The 

 Analyst for August, 1891. 



Salicylic Acid. — 5.0 c. c. of the sample are treated 

 with acid mercuric nitrate for the removal of the fat 

 and proteids, as described in connection with the deter- 

 mination of milk sugar, and the liquid filtered. The 

 filtrate is shaken violently with about one half its vol- 

 ume of a mixture of equal parts of ether and petroleum 

 ether. The ethereal liquid is evaporated and a drop of 

 neutral solution of ferric chlorid added to the residue. 

 If salicylic acid be present, a characteristic violet color 

 is developed. The reaction is very delicate. 



