§ 70. ACETIC ACID. 101 



in the quantity of substance taken. Then from the pro- 

 portion, 



m : 0.18 = W : X, 

 we may learn how much oxalic anhydride, C^Og, was con- 

 tained in the substance analyzed. 



h. Oxalic acid may be estimated in any substance con- 

 taining it and free from carbonic acid, by converting it 

 into carbonic acid with the aid of manganic oxide and 

 concentrated sulphuric acid, and determining this car- 

 bonic acid. Weigh the substance in the flask A, Fig. 1, 

 § 60, add about the same weight of manganic oxide free 

 from carbonic acid, fill B with concentrated sulphuric 

 acid, weigh the whole apparatus, and proceed further as 

 in the estimation of carbonic acid with this form of ap- 

 paratus (§ 60, d). Each equivalent of oxalic anhydride, 

 C^Og, yields two equivalents of carbonic anhydride, COg. 



ACETIC ACID. HC2H3O2. 60. 



70 • All acetates are soluble in water. 



Reactions. — Acetates are blackened when quickly heat- 

 ed to a high temperature, carbon being set free. 



If a neutral acetate is mixed with a solution of ferric 

 chloride, a deep red liquid is produced ; on boiling the 

 mixture a red precipitate is formed. 



If an acetate is heated with concentrated sulphuric acid 

 and alcohol in about equal volumes, acetic ether is disen- 

 gaged, the pleasant aromatic odor of which is best distin- 

 guished from that of common ether, which may be 

 formed from sulphuric acid and alcohol alone, after the 

 liquid has become quite cold. 



Quantitative estimation.— Free acetic acid may be es- 

 timated by a volumetric process, with the aid of the 

 standard sodic solution. 



Since neutral sodic acetate has a slightly alkaline re- 

 action, it is best to ascertain first, the relation between 



