17 
always a matter of interest to note and place on record the first 
step towards its solution, although the commercial application 
y be remote. 
Such a first step has been achieved by Dr. Tilden, F.R.S., 
Professo or of Chemistry in the Royal College of Science, South 
: "He as ki 
more recent revisions. They have also been republished in th» 
Chemical News. 
* Note on the Spontaneous Conuet sion of Isoprene into 
Caoutcho 
* [Read before the Birmingham penes. Society, 
May 18th, 1892.] 
“Tsoprene is a hydrocarbon which was discovered d: Greville 
Williams many years ago among the products of the destructive 
> i (Tr 
upon oil of turpentine and other terpenes. It is a very volatile 
liquid, boiling at about 36°. Its molecular formula is C; H,, and 
it forms a tetrabromide, C, H, Br, but no metallic derivatives like 
the two homologues of. acetylene. 
* Bouchardat (Compt. rend., vol. 87, p. 654, and vol. 89, pp. 361 
and 1117) observed that when isoprene is heated to a temperature 
near 300°, it gradually polymerises into a terpene, which he called 
diisoprene, but which is now called dipentene. This compound 
produced by the action of heat upon turpentine, is formed at the 
^ Aem : 
sam n isoprene is brought into contact with strong 
ids, aqueous hydrochloric acid for example, a small portion of it 
is rted into a tough elastic solid, which has been examined 
by G. Bouchardat and by myself. It appears to be true india- 
rubber. 
“Specimens of isoprene were made from several terpenes in 
the course of my work on oe compounds, and some of them 
have preserved. Iw rised a few weeks ago at finding the 
contents of the bottles S naniu isoprene from turpentine 
entirely changed in appearance. In place of a limpid colourless 
liquid, the bottle contained a dense syrup in which was floating 
several large masses of a solid of a yellowish colour. Upon 
isoprene by spontaneous polymerisation has not, to my knowledge 
been observed before. I can only account tor it by the hypothesis 
that a small quantity of acetic or irs acid had been produced 
by the oxidising actior diee - air, and that the presence of this 
compound had bee n the ns of t ransforming the dee The 
Mua was acid à De Sera yor yielded a small portion of 
nchanged isopre 
* The har. india-rubber, like natural ety. appears t 
consist of two substances, one of which i ore soluble in 
nzene or carbon bisulphide than the other. 
25781 B 
