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. 50 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. 



