250 
MR. C. GREVILLE WILLIAMS OX ISOPREXE AXD CAOriCHIXR. 
C““ H''* ; carbonic oxide, water, and empyreumatic products being fonned simultaneously. 
Disregarding the empyreumatic bodies, the following equation may be considered to 
explain the nature of the reaction : — 
C 20 H 16 + + 2HO + 2CO 
4 vols. oil of 4 Yols. carbonic 4 vols. 4 vols. 4 toIs. carbonic 
turpentine. acid. cjmole. water. oxide. 
Some experiments made by me a considerable time ago with oil of tiu*pentine, led me 
to conceive the idea of converting it into cymole, or an isomer, by the alternate action of 
bromine and a highly electro-positive metal, and the identity in certain cases of the 
reactions of oil of turpentine and caoutchine rendered it probable that a similar product 
would be yielded with the latter. Experiment has completely co nfir med this suppo- 
sition. 
If to a quantity of bromine and water in a stoppered flask caoutchine be gradually 
added, and the flask be shaken after each addition, a sharp hissing sound is heard, and 
combination takes place with great energy and considerable rise of temperatiu-e ; at the 
same time a heavy oil, red at first but finally colourless, sinks to the bottom. The pro- 
duct when cold is as viscid as treacle. Its characters do not ofier any great guarantee 
for purity ; and the production of hydrobromic acid at the same time, indicates that 
while one portion of the halogen combines with the caoutchine, another seizes the most 
easily removeable of its atoms of hydrogen, and fields the acid which is foimd dissolved 
in the water. 
I examined the reaction which takes place mth turpentine under these circirmstances 
some years ago, but at that time I was not fully alive to the true explanation, because I 
had not treated the resulting oil with alcoholic potash or sodium. The analyses I then 
made indicated the formula of the oil from turpentine to be C'“II^®Br, 2Br, 2 HO. 
One equivalent of hydrobromic acid was always found in the watery fluid. Assuming 
this to be correct, as I have no doubt it is, we have 
C20H‘®+4Br+2HO=e°H'^Br, 2Br, 2HO-fHBr. 
Every four equivalents of bromine yield, therefore, one equivalent of hydrobromic 
acid; and in an experiment where 33-2 parts of bromine were employed, 8‘2 of hydi'o- 
bromic acid were found in the aqueous fluid. If the above equation be correct, 8’4 
should have been obtained. 
The oil produced as above from caoutchine, when heated, yields torrents of hydro- 
bromic acid, and an oil distils over containing less bromine and hydrogen. "SMien 
cohobated with sodium in excess, a very fragrant and perfectly colourless liydi'ocai'bon 
was produced, distilling between 171° and 200°. It was received in four portions : 
a, between 171° and 177°; b, 177° to 181°; c, 181° to 186°; and d, 186° to 200°. A 
yellowish oil remained behind at this point ; it required a very much higher tempera- 
ture for distillation, and on cooling deposited a few very minute crystals. 
Caoutchine and turpentine behave in a p^-ecisely similar manner with the above 
