ACETIC ACID. 51 



ACETIC ACID. C 4 H 3 O 3 . HO. 



Chemical Relations. 



Properties. Acetic acid has the general characters of the acids 

 of this group. In its most concentrated state, as first hydrate, it 

 forms a crystalline mass below + 16; above this temperature it 

 is fluid, has a specific gravity of 1*080, and boils at 117*3; its 

 second hydrate, containing 2 atoms of water, has a specific gravity of 

 1-078 and boils at 140. 



We shall notice only the most important points regarding acetic 

 acid and its compounds, and those having an especial bearing on 

 animal chemistry ; the other compounds of acetic acid pertaining 

 to pure rather than to physiological chemistry. 



Composition. According to the above formula, acetic acid con- 

 sists of: 



Carbon 4 atoms 40*000 



Hydrogen 3 .... 5-000 



Oxygen 3 .... 40'000 



Water 1 15-000 



100-000 



The atomic weight of the hypothetical anhydrous acid =637*5 ; 

 its saturating capacity = 15 '686. Kolbe's hypothesis that acetic acid 

 is oxalic acid conjugated with methyl = C 2 H 3 . C 2 O 3 . HO, was an- 

 ticipated by Berzelius. Till then it was assumed that the radical 

 C 4 H 3 existed in acetic acid, and aldehyde and aldehydic acid were 

 regarded as lower stages of oxidation of the same radical. 



Combinations. The only acid acetate with which we are 

 acquainted is a potash-salt ; with the oxides of the heavy metals 

 it has a strong tendency to form basic salts. 



Acetamide, H 2 N. C 4 H 3 O 2 =C 4 H 5 NO 2 , is prepared from acetic 

 ether and ammonia ; it forms a white, crystalline, diffluent mass, 

 which fuses at 78 and boils at 228 ; it has a sweetish, cooling 

 taste ; by anhydrous phosphoric acid it is converted into cyanide 

 of methyl ; hence it has been considered as hydrocyanate of wood- 

 spirit (C 4 H 5 N0 2 =C 2 H 3 + HC 2 N + HO). 



By dry distillation of the acetates with strong bases, we obtain 

 acetone or hydrated oxide of cenyl, C 6 H 5 O.HO, which presents 

 much similarity with the alcohols of the haloid bases. 



On heating equal parts of acetate of potash and arsenious acid 

 in a retort, we obtain alkarsin or oxide of kakodyl, C 4 H 6 As 5 O, 

 which is distinguished by its very specific odour. 



E 2 



