Formation of Iodobenzoic, Iodotoluylic, and Iodoanisic Acids. 227 



groups C 14 (H 4 N' 2 ) 4 and C u ( H 5 H 2 N) 4 , in the first of which 

 the two equivalents of monatomic nitrogen are replaced by hydro- 

 chloric acid, producing C 14 (H 5 C1)0 4 , while the second simply com- 

 bines with hydrochloric acid, producing hydrochlorate of benzamic 

 acid. It deserves to be mentioned that the acid C 28 H u N 3 8 may 

 be derived also from two equivalents of hydrated oxide of ammo- 

 nium, when its formula assumes the following shape : — 

 [(C u H 4 3 ) a »Ni"HNJ»-l 



Further experiments are necessary to decide which of these two 

 formulae deserves the preference. 



Iodobenzoic Acid, C 14 ](H 5 "I)0 4 . 

 This substance is produced by a process similar to that which 

 furnishes the chlorobenzoic acid, viz. by the action of hydriodic 

 acid on the acid C 28 H u N 3 8 , — beautiful white plates resembling 

 benzoic acid, easily soluble in alcohol and in ether and difficultly 

 soluble in water. Iodobenzoic acid is remarkable for its great 

 stability ; even fuming nitric acid fails to expel the iodine, and 

 transforms the substance simply into nitro-iodobenzoic acid. The 

 silver salt of iodobenzoic acid is a white amorphous precipitate con- 

 taining C 14 (H 4 1 Ag)0 4 . 



Iodotoluic Acid, C 16 (H 7 1)0 4 . 



This acid is formed from the analogous nitrogenous acid in the 

 toluic series, according to the equation 



C 32 H ls N 3 8 + 2HI=C 16 (H,I)0 1 +C 16 (H,H a N)0 1 ,HI + N 2 . 

 It crystallizes in white plates of a pearly lustre, which in their che- 

 mical and physical properties are very similar to iodobenzoic acid. 



Iodanisic Acid, C i6 (H 7 1) O e 

 is obtained by the action of hydriodic acid upon the nitrogenous 

 acidC 32 H 15 N 3 12 , 



C 32 H, 5 N 3 12 + H 2 I 2 =C 16 (H 7 1) 6 + C 16 (H 7 H 2 N) 6 , HI + N 2 . 

 Exceedingly small, nearly white needles, almost insoluble in boiling 

 water, very soluble in alcohol and in ether. 



The new method of substitution, by which the described products 

 were obtained, although less direct than the ordinary processes, 

 promises nevertheless to adapt itself to several cases of special interest. 

 I am at present engaged in pursuing these experiments, with the view 

 of producing fluo- and cyano-benzoic acids and their homologues, 

 which have never been obtained. 



The experiments which I have described were performed in Pro- 

 fessor Hofmann's laboratory. 



Feb. 16. — Sir Benjamin C. Brodie, Bart., President, in the Chair. 



The following communications were read : — 



" Description of an Instrument combining in one a Maximum and 

 Minimum Mercurial Thermometer, invented by Mr. James Hicks." 

 By Balfour Stewart, Esq. 



About a fortnight since, Mr. James Hicks, the intelligent foreman 



