jVIE. c. geeville williams on isopeene and caoutchine. 
253 
Corresponding sufficiently with the formula 
C 18 (H^Ag^O®). 
I intend to try the alternate action of bromine and sodium upon other isomers 
of turpentine, with a view to their conversion into cymole, or hydrocarbons isomeric 
with it. 
On the Action of Sulphuric Acid on Caoutchine. 
On adding slowly caoutchine to sulphuiic acid (sp. gr. 1’845) in great excess, the 
latter becomes warm and the greater part of the hydrocarbon dissolves, traces of sul- 
phurous acid being at the same time evolved. On the addition of water, the greater 
part of the caoutchine rises in an altered state to the surface ; it is in the form of a thick 
adhesive fluid of the consistency of molasses. On saturating the acid solution with 
chalk, a very small quantity of the lime-salt of a conjugate sulphuric acid was obtained. 
It is excessively soluble in water, and deposits small granular crystals from a concen- 
trated solution. Dried at 200° C. it gave the annexed results on analysis. 
0’2594 grm. gave 0‘0736 of sulphate of calcium; or, in per-centages, — 
Experiment. Calculation. 
Carbon 
Q20 
120 
51-1 
Hydrogen 
15 
6-4 
Calcium . 
8-3 
Ca 
20 
8-5 
Sulphur . 
32 
13-6 
Oxygen . . 
0® 
48 
20-4 
235 
100-0 
From the agreement of the theoretical with the experimental numbers, the formula 
Ca S" O® 
is e-vidently that of the substance in question. 
On the Composition of Caoutchouc. 
The only analyses of caoutchouc which I have seen, are those of Faeaday and the 
late Dr. Uee. That of the latter chemist is obviously incorrect, as he obtained 90 per 
cent, of carbon and only 9T of hydrogen, a result incompatible with the phenomena 
which take place under the influence of heat. 
Faeadat’s analysis, made in the year 1826, is probably almost exactly the true com- 
position of a pure caoutchouc. It gave carbon 87 '2 and hydrogen 12 ’8 per cent 
These numbers would requhe to be slightly modifled, in consequence of the atomic 
weight of carbon, as now received, having a somewhat different value to that which was 
admitted at the time of the analysis. I analysed two small specimens which had formed 
