130 TURPENTINE AS A SOLVENT FOR CAOUTCHOUC. 
length of time employed. The essential oil, obtained by 
distillation from tar, has a disagreeable smell, from which 
it is so difficult to free the fabrics, that I determined to find, 
x f possible, another solvent. 
From the first I thought of a natural carburetted hydrogen 
(essence of turpentine,) which it is well known acts as a 
solvent of caoutchouc ; I hoped that by modifying it by 
heat its solvent properties might be augmented — I was con- 
firmed in this idea by experience. By distilling this essence 
openly, once or twice, a solvent is obtained which gives 
satisfactory results. I also remarked, that by effecting this 
distillation upon fire-brick, the essence being submitted to 
a higher temperature, a liquid was obtained which was 
very little inferior, as a solvent, to the pyrogenous oil of 
caoutchouc. 
The manufacturer who had consulted me hastened to 
profit by the results which I had obtained, and having re- 
served the right of publishing them, I made them known 
in my treatise upon the productsof distillation of caoutchouc, 
inserted in vol. 23 of the Journal die Pharmacie. Since 
that time, the essence of turpentine, modified by one or two 
open distillations, has been the solvent for caoutchouc em- 
ployed by manufacturers of waterproof fabrics in both 
France and England. 
The following are the physical properties possessed by 
essence of turpentine, obtained by open distillation upon 
fire-brick. Its colour is yellowish: its smell partakes of 
that of thyme, oil of naphtha, and essence of turpentine ; it 
is lighter than the essence from which it was made, in the 
proportion of 0.8726 to 0.S420. Its boiling point is 185° 
F. ; but the temperature rises immediately afterwards to 
310°, and remains stationary at that point. I have inquired 
whether it was not possible to isolate the former more 
volatile portions ; but, notwithstanding great care and the 
best refrigerating mixtures, I have only been able to sepa- 
rate a very small portion, insufficient for useful examina- 
