The Middlebury register. [volume] (Middlebury, Vt.) 1850-1882, 1851-07-09
Caoutchouc

Ia a vegetable constituent, the produce
ofseveral trees. The most prolific in this
substance are. Siphonid caoutchouc Uiceota
eidsticd, Ficus eidsficd, &c. or these, the
SiPhonid cdouichouc extends over vast
district in Central America, and the ca
outchouc obtained from ihis tree is the beet
adapted for manufactures. Over more than
lO,OUO square miles in Assam the Ficus
elasiica is abundant. The Urceola eios,icd
(which produces The Ginawnn Of the Ma
Iavs) abounds in the islands Of The Indian
Archipelago. 1t is described as a crcepcr
OF growth 80 rapid. that in five years it ex.
tends 200 feet and is from 90 20 80 inches in
cirth. This tree can. without being injur-
ed, yield byapping from so 10 so lbs orca
outchouc in one season. A curious cons
trast ia exhibited in the tardy growth Of the
tree from which the gutta percha il obtained.
This tree does moi come to ils prime in less
than 80 TO 100 years. The produce canno,
be Obtained but by the sacrifice of the lree.
IL is found in a concrete stale between the
bark end the wood after the tree has been
cut down and it is in this condition that,
having been scrapej out, it is sent to our
market. When coagulaied by evaporation
or agitation, caouithouc separates from the
aqueous portion oflhe sap of the trees which
yield 1t. This solid and fluid cannot after
wards be re-uni:ed, any more than butter is
capable OF mixing with the milk from which
it is separated. Caouchouc is a hydrocar.
bon. This chemical character belongs TO
all varieties OF The substance, and many
other vegetable constituents, though they
differ materially in physical qualities.
Some specimens arc harder than ruua
percha itself, while others never soidiiy,
hut remain in The condition Of bird lime or
Ireace The process termed the ruican-
t:'ng of caoutchouc was discovered by Mr..
Thomas Hancock in lS43. A sheet Of ga
outchouc immersed in melted sulphur alb,
Serbs portion Of it, and at The samelime
II undergoes some important changes in
many Of its characteristic properties. 1t is
nc longer affected by climatic temperature !;
1t is neither hardened by cold nor soflened
by any heat which would not destroy it,.
It ceases 10 be soluble iu the Solvents of
common choulchouc, while It's elasticity be,
comes greatly augmented and permanent.
The ZANE effect may be produced by kuead-
ing sulphur into caoutchouc by means o (
powerful rollers or the common solvents
naphtha and spirit OF lurpcniine may be
charged with sufficient amount of sulphur
IN solution 10 become compound sol
vent Of rubber. In these cases articles
may be made in any required forms before
heating Tor the charge OF condition. [, is
necessary, however, Tor this purpose, that
the form should he carefully maintained
during the exposure 10 the heat necessary
to effect the INFLAMMATION, which leaves il
IN normal stale. A yulcanized solid sphere
OF l-2 inches in diameter when forced be.
tween two rollers quarter Of an inch apsrt
was found TO maintain its form uniniurcd.
In lac'' is is the exclusive properly of vul.
eanized caoutchouc TO be able to retain any
iorm impressed on it, and to return to that
form on the removal of any disturbing force
which has been brought to act on it. Cn.
ou'chouc slightly expands and contracts in
different temperatures: it is aIso capable Of
being condensed under pressure. 4 cube
oil Ia inchea impaclIy secured, was SUBJ
jected 10 force of 200 tons. The result
was,a compression amounting to one>tenth
great heat appeared TO have been evolved
and the excessive elasticity of The substance
caused fiy'wheel weighing tors 10 reco
with an alarming violence. The evolution
oil heat from caoutchouc under condeusa.
ton is properly possessed by it in common
with All and The metals. 1t differs, how.
ever. from the laIrer in being able to exhibit
cold by reaction. Mr.. Brocksdon stated
that he had raised the temperature of an
ounca OF water two degrees in about fifteen
minutes by collecting The heat evolved by
the extension Of caouichoue thread. He
refers this effect to the change in specific
gravity. He contends, that this heat thus
produced is not due TO friction; because
The same ainount OF friction is occasiened
in the contraction ne in The extension of the
subslance,-and the result of this eonlrnc-
ton 10 to reduce the caoutchouc thus acted
on 10 Ia original temperature. Attention
was directed 10 some Of The lates' applca-
lions Of the elastic force Of caoulchouc.-
London Athsnaum.