228 
Proceedings of the Royal Society of Edinburgh. [Sess. 
connection with the formation of glycollic acid from monochloracetic acid, 
tried to convert monochlorobenzoic acid into salicylic acid. He prepared 
the chlorobenzoic acid from its chloride, which he obtained, according to 
Chiozza’s directions, by distilling the product of the reaction of phosphorus 
pentachloride on salicylic acid. His attempts to pass from the sodium 
salt of chlorobenzoic acid to salicylic acid, as he * and Reinhold Hoffmann f 
had obtained glycollic acid from chloracetic acid, convinced Kekule of 
the small reactive power of the chlorine in chlorobenzoic acid. He could 
as little replace it by hydroxyl as Couper could the bromine in brom- 
benzene and dibrombenzene. This communication of Kekule, “ Bildung 
von Glykolsaure aus Essigsaure,” which closes with the experiments as to 
salicylic acid, was sent to the editors of Liebig s Annalen on the 25th 
December 1857. Couper’s paper on salicylic acid appeared in the first 
June number of the Comptes rendus,\ so that Kekule could not have 
known anything of this work of Couper. But, after the appearance of 
Couper’s paper, Kekule, who had in the meantime moved from Heidelberg 
to Ghent, applied himself with the greatest zeal to the continuation of his 
work on salicylic acid. In his communication laid before the Belgian 
Academy on the 4th August 1860,§ entitled, “Faits pour completer l’histoire 
de 1’acide salicylique et de l’acide benzoique,” which appeared in the 
number of Liebig s Annalen || published 4th February 1861, under the 
title, “ Beitrage zur Kenntniss der Salicylsaure und der Benzoesaure,” 
Kekule minutely discusses Couper’s work. 
Kekule gives salicylic acid the formula 
H r 
The phosphorus compound, C 7 H 4 C1 3 P0 3 , described by Couper, is regarded 
by Kekule as an indirect combination of phosphorus oxychloride with the 
anhydride of salicylic acid, or as a compound of the radicals salicyl and 
phosphoryl, belonging to a mixed type, according to the formula 
H3CI3 
H 2 0 
- H 2 0 + 3HC1. 
He cannot confirm Couper’s statements as to the products of the action 
of phosphorus pentachloride on salicylic acid or on its methyl ether. He 
writes, in the Annalen : — “ Ich habe diesen Versuch mehr als 20mal 
* Liebig's Annalen , cv. 286-292 (Heft iii. issued 27th Maerz 1858). 
t Ibid., cii. 12. f xlvi. 1107-1110. 
§ Bull. Acad. Roy. Belg. (2), x. 337-350. || cxvii. 145-164. 
