1908-9.] Life and Chemical Work of Archibald S. Couper. 267 
APPENDIX IV b. 
Researches on Salicylic Acid. By Archibald S. Couper.* 
Conflicting opinions being entertained among chemists respecting the constitution 
and basicity of salicylic acid, in order, if possible, to throw some additional light 
upon this question, I have been induced to undertake the investigation of the action 
of two equivalents of pentachloride of phosphorus upon the salicylate of methyl. 
When these two bodies are brought into contact, the reaction which ensues is 
exceedingly violent, and it is necessary to add very gradually the one equivalent of 
oil of gaultheria to the two equivalents of perchloride of phosphorus. Vapour of 
hydrochloric acid, mingled with that of the chloride of methyl, is disengaged during 
the whole course of the operation. 
The residue of this reaction is submitted to distillation. A trace of oxychloride 
passes over, and is followed by something approaching to an equivalent of the 
perchloride of phosphorus. 
The temperature having now risen to about 160°, the residue has darkened in 
colour. Submitted to a further distillation, a colourless or slightly yellow liquid 
passes over, while the temperature rises rapidly to about 285° and 295° Cent. The 
portion passing between these temperatures is collected apart. It constitutes the 
larger part of the product of distillation. There remains a pitchy residue, which 
solidifies on cooling. The liquid collected, as described, on being submitted to 
analysis, furnished the following results : — 
1. 0*41 grms. of substance gave 0*464 grms. of carbonic acid, and 0*0585 grms. of 
water. 
2. 049 grms. of substance gave 0*528 grms. of carbonic acid, and 0*0705 grms. of 
water. 
3. 0*515 grms. of substance gave 0*565 grms. carbonic acid, and 0*071 grms. 
of water. 
1. 0*438 grms. of substance gave 0*7595 grms. of chloride of silver. 
2. 0*34 grms. of substance gave 0*563 grms. of chloride of silver. 
1. 0*651 grms. of substance gave 0*283 grms. of the pyrophosphate of magnesia. 
These analyses lead to the crude formula, — 
C 7 H 4 C1 3 P0 6 . 
Found. Calculated. 
I. II. III. 
Carbon . 
30*86 
29*4 
29*9 
30*65 
Hydrogen 
1*58 
1*59 
1*51 
1*46 
Chlorine 
41*01 
41*05 
38*86 
Phosphorus . 
12*2 
11*5 
Edinburgh New Philosophical Journal . 
New series, 
vol. viii., July to October 1858, 
213-217. 
