190 PROCEEDINGS OP THE AMERICAN ACADEMY 



was divided into difluorbenzoic acid and benzoic acid, as proved by 

 analyses of the barium salt. We are convinced, therefore, that no 

 monofluorbenzoic acid is formed by the action of chromic super- 

 fluoride on benzoic acid, but the products of the reaction are only 

 difluorbenzoic acid and chromic fluoride with a little chromic anhy- 

 dride as an impurity. 



Dlflxiorbenzoic Acid, C^HgFgCOOH. 



The acid prepared and jiurified, as described above, appears when 

 sublimed in white flattened needles looking very much like benzoic 

 acid, when crystallized from alcohol or benzol in short fine needles ; it 

 sublimes at a temperature far below its melting-point, 232" (uncor.), 

 but with much more difficulty than benzoic acid, and burns with a 

 strongly green-bordered flame. It is essentially insoluble in cold 

 water, and only slightly soluble in hot, the boiling solution depositing 

 a few crystalline flocks of the acid on cooling; not very freely soluble 

 in cold alcohol or benzol, but freely in either of these solvents when 

 hot, very soluble in ether or glacial acetic acid, less so in methyl 

 alcohol, and almost insoluble in ligroine, or carbonic disulphide. Ben- 

 zol is the best solvent for purifying it by crystallization. 



Its composition was established by the following combustions : — 



I. 0.2549 gr. of substance burnt with plumbic chromate in a closed 

 tube* gave 0.49G4 gr. of carbonic dioxide and 0.0982 gr. of 

 water. 

 II. 0.1595 gr. gave 0.3131 gr. of carbonic dioxide and 0.0506 gr. 

 of water. 



Calculated for Found. 



C H F . I. I^' 



Carbon 53.16 53.13 53.52 



Hydrogen 2.53 4.28 3.53 



The ammouic difluorbenzoate is decomposed by evaporating its so- 

 lution to dryness ; but a solution freed from ammonia by boiling gave 

 white precipitates with plumbic acetate, and mercurous, mercuric, and 

 argentic nitrates, and a bluish white precipitate with cupric sulphate. 



Baric Difluorbenzoate, Ba(CyH3F202)2' ™ade by boiling the acid 

 with baric carbonate and water, crystallizes in white scales, and con- 

 tains no water of crystallization even when only air-dried. 



* We found it impossible to obtain agreeing results when the combustion 

 was performed in the ordinary way with oxygen. 



