1908-9.] Life and Chemical Work of Archibald S. Oouper. 223 
by distilling under ordinary pressure gives, with water, salicylic acid 
and monochlorobenzoic acid, and was therefore regarded as a mixture of 
the acichlorides of these acids. 
The puzzling thing was, what had become of the phosphorus oxy- 
chloride which must have been formed by the reaction of the hydroxyl 
of the salicylic acid with the phosphorus pentachloride ? The production 
of chlorbenzoyl chloride from the supposed salicyl chloride was also unin- 
telligible. Besides, most of the conclusions lacked the support of analysis. 
The problem had, therefore, attractiveness enough to lead a sharp- 
sighted investigator like Couper to attack it again. 
I use, for reference in the meantime, only Couper ’s first paper, that 
in the Gomptes rendus * in which he contented himself with the use of 
empirical molecular formulae, as we should now call them, using the 
atomic weights C = 6 and 0 = 8. He describes his method and the course 
of the reaction thus :■ — He added gaultheria oil in small quantities at a 
time to the phosphorus pentachloride, in the proportion of one equivalent 
of the former to two of the latter. After the reaction (which ran exactly 
the same course when salicylic acid was used) was finished, he distilled 
the product under ordinary pressure. When the trace of phosphorus oxy- 
chloride and the excess of the pentachloride had been driven off, there 
passed over, between 285° and 295°, a colourless liquid, which he named 
“ trichlorophosphate de salicyle, C 14 H 4 Cl 3 Ph0 6 ,” formed according to the 
equations : 
C 16 H 8 0 6 + PhCl 5 = HC1 + 0 2 H 3 C1 + C 14 H 4 Cl 3 Ph0 6 ; 
gaultheria oil 
C 14 H 6 0 6 + PhCl 5 = 2HC1 + C 14 H 4 Cl 3 Pli0 6 .” 
salicylic acid 
The “ trichlorophosphate de salicyle ” is instantly decomposed by hot 
water, giving hydrochloric, phosphoric, and salicylic acids ; according to 
the equation : 
C 14 H 4 Cl 3 Pli0 6 + 8HO = PhH 3 0 8 + 3HC1 + C 14 H 6 0 6 . 
If the “trichlorophosphate de salicyle” is quickly distilled, it partially 
decomposes with abundant evolution of hydrochloric acid. Above 300° 
there passes over a liquid which, when sealed up in a glass tube, deposits 
large crystals of “ monochlorophosphate de salicyle, C 14 H 4 0 8 ClPh.” Both 
the trichlorophosphate and the monochlorophosphate take up moisture from 
the air and give rise to a new acid, “ acide phosphosalicylique, C 14 H 7 Ph0 12 .” 
This is formed in accordance with the equations : 
C 14 H 4 Cl 3 Ph0 6 + 6HO = 3HC1 + C 14 H 7 Ph0 12 ; 
C 14 H 4 C1PH0 8 + 4H0 = HC1 + C 14 H 7 Ph0 12 . 
* xlvi. 1107 - 1110 . 
