i\IE. C. GEETILLE WILLIAMS ON ISOPEENE AND CAOETCIIINE. 
245 
Bouchaedat can be identified with that just described; and although the formulse 
and H® have often been vaguely apphed to the numerous isomers of turpentine, 
yet none of the hydrocarbons obtained by the above chemists have been shown to con- 
tain for four volumes of vapour. The hydrocarbon discovered by Coueebe* in 
the fluid obtained by the powerful compression of resin gas, although of the same com- 
position, differs too much in density (0-709) and boiling-point (60'^) to be considered as 
identical. 
Action of Atmospheric Oxygen on Isoprene. 
If isoprene be left in a partly filled bottle for some months, it gradually loses its 
fluidity, and at last even becomes quite viscid ; at the same time it is found to have 
acquired powerful bleaching properties. It readily decolorizes sulphate of indigo, and, 
under certain chcumstances, converts sulphide of lead into sulphate. It is, in fact, 
ozonized. 
ScHOXBEm was the first to show that oil of turpentine absorbed ozone when kept for 
a long time, and I subsequently observed several cases where ozone was capable of exist- 
ing in contact with organic and inorganic matters without exerting any material action 
on them so long as the temperature was kept down. In these instances, immediately 
the heat rose beyond a certain point, the substance in contact with the ozone underwent 
oxidation. Thus, if a slip of lead test-paper be exposed to the vapours of sulphide of 
hydrogen until the paper has acquired a deep brown colour, and a drop of an ozonized 
oil be placed on it, no change ensues at ordinary temperatures ; but if the paper moist- 
ened -with the oil be warmed until the latter begins to volatilize, the sulphide is imme- 
diately oxidized and bleached. 
But the most remarkable phenomenon perhaps yet known in connexion with the 
ozonization of essential oils, takes place on submitting ozonized isoprene to distillation. 
If the temperature be kept as low as is compatible with the volatilization of the 
unaltered portion of the oil, a colom’less limpid fluid distils over, having the composition 
and boiling-point of pure isoprene. As the operation proceeds the fluid thickens, 
causing the temperature to rise somewhat suddenly. The ozone at this point instantly 
begins to act with energy, a cloudy vapour rises, accompanied by an intensely sharp 
odour, and the contents of the retort instantly solidify to a pure white, spongy, elastic 
mass, haAng. when successfully prepared, but slight tendency to adhere to the fingers. 
When pure, it is opake ; but if allowed to become exposed to the air, especially when 
warm, it becomes transparent, first on the edges, and subsequently throughout the whole 
mass. When burnt, it exhales the peculiar odour hitherto considered characteristic of 
caoutchouc itself. It is not easy to prepare or to preserve this substance of definite 
composition. If the heat be allowed to rise too rapidly during its formation, it becomes 
decomposed ; and if not heated sufiiciently, a portion of the original hydrocarbon obsti- 
nately adheres, in spite of its extreme volatility when separate. However prepared, its 
* Ann. de Chim. et de Phya. vol. Ixix. p. 184. Jonrn. Pratt. Chem. vol. xviii. p. 165. Gmelix’s Hand- 
book, vol. X. p. 411. Cay. Soc. Traual. 
