160 | . CAOUTCHOUC, 
6. cAoUTCHOUC. 
604. This substance, commonly known by the name of 
Indian Rubber, is the juice of the Haevea, which grows in 
the Brazils. It may also be obtained fromthe Urceolaelas- 
tica, the Jatropha elastica, and other Euphorbiacex, and the _ 
- Artocarpus integrifolia and Ficus elastica. Whennewlyex- 
uded, caoutchouc has a whitish-yellow colour ; but it turns _ 
black when exposed to the air for awhile. Itis distinguished 
by its great elasticity. When exposed to heat, it softens 
and swells, and emits an odour like that of burnt wool. 
When exposed in the air to a high temperature, it burns with 
a rich yellow flame. _ It is insoluble in water and in alcohol, 
but soluble in naphtha andin the volatile oils. According to 
Dr. Ure, it is composed of 
Carbon, . . x : F 90. 
Hydrogen, . = ‘; : ; 9.12 
Oxygen, . : : és : 0.88 
100 parts. 
The oxygen, being in such small proportion, may be regarded 
as adventitious. 
. CHAP. IIL_VEGETABLE ACIDS, MOST OF 
WHICH CONTAIN MORE ‘OXYGEN THAN 
WOULD BE NECESSARY TO FORM WATER 
. WITH THEIR HYDROGEN. 
—"s ‘Tas acids which exist ready formed in vegetables 
es seit nostic, deeluatid alipc. catato. benzoic, malic, gallic, 
and prussie acids. In the state in which we procure them 
they are combined with a considerable quantity of water. 
> Seren cae ee : 
