80 THE BENZOIC ACID GROUP. 



Hydrated benzoic acid C 14 H 6 O 4 -2CO 2 =C 12 H 6 = Benzole or Benzin 

 Hydrated cumic acid C 20 H 12 O 4 2CO 2 =C ls H 12 =Cumole or Cumin 

 Hydrated toluylic acid C 16 H 8 O 4 -2CO 2 =C 14 H 8 =Toluole or Toluin 



In these carbo-hydrogens we may again replace 1 equivalent 

 of hydrogen by 1 equivalent of chlorine, bromine, iodine, or 

 hyponitric acid (HO 4 ) ; and in this way there are formed, for 

 instance, chlorobenzide, C 12 H 5 C1, bromocumide, C 18 H n Br, iodo- 

 toluide, C 14 H 7 I, and nitrobenzide, nitrocumide, and nitrotoluide, 

 C I2 H 5 .N0 4 ,C 18 H U .N0 4 and C I4 H,.NO 4 . 



These last-named nitrogenous compounds form yellow, oleagi- 

 nous bodies, from which, by the action of sulphuretted hydrogen, 

 we obtain the organic, non-oxygenous, volatile bases, benzidine, 

 C 12 H 7 N, cumidine, C 18 H 13 N, and toluidine, C 14 H 9 N (according 

 to the equation C 14 H 7 .NO 4 + 6HS=4HO + 6S + C 14 H 9 N). 



BENZOIC ACID. C 14 H 5 O 3 .HO. 



Chemical Relations. 



Properties. In its sublimed state this acid occurs in colourless, 

 delicate needles ; in the moist way it crystallises in scales, or small 

 prisms, or six-sided needles (the primary form of the right 

 rhombic prism) ; it fuses at a temperature exceeding 120, boils 

 at 239, and then becomes converted into a thick, irritating vapour ; 

 it is not decomposed either by nitric or by sulphuric acid ; in other 

 respects it has the general properties of the acids of this group. 



Composition. In accordance with the above formula, it con- 

 sists of: 



Carbon Hatoms .... 68*853 



Hydrogen 5 .... 4*098 



Oxygen 3 .... 19*672 



Water . 1 .... 7'377 



-^ 



100-000 



The atomic weight of the hypothetical anhydrous acid = 1412*5, 

 and its saturating capacity = 7*079. 



Combinations. Most of the benzoates are soluble in water ; the 

 alkaline and magnesian salts are very soluble, but do not readily 

 crystallise; the combinations of benzoic acid with the oxides of the 

 heavy metals are for the most part difficult of solution, but are 

 taken up more freely by hot than by cold water 



