CAR

( 230 ) CAR

" of animals; when they broke the elafticity" was fo great that each end inllantaneoufly“ returned to its rcfpective mafs. Through all“ thefe ftages the lead prelliire with the finger" and thumb united different portions as per-“ fectly . as if they had never been feparated,“ and without any clamminefs or fticking to the“ fingers.”

Alcohol lias no action whatever on caout-chouc.

Although caoutchouc is procured in quantityonly from the vegetable juices mentioned in theformer part of this article, yet it appears to becontained in feveral other plants. It is containedin the milky juices of the Indian fig fFicusIndicaJ, and of the bread-fruit tree (Artocarpusincifaj-, the berries of the mifeltoe, and probablyall the vegetable barks that yield bird-lime,abound with it. The caoutchouc however ob-tained from thefe fources differs from that whichwe have been defcribing in retaining a greateror lefs degree of vifcidity, and perhaps in otherrefpects, for no accurate comparative experi-ments have yet been made to decide this point.An inveftigation into the properties and com-polition of the birdlime from mifeltoe and holly-bark would in all probability lead to very in-terefting refults.

The ufes to which caoutchouc has hithertobeen applied are the following. It is employedvery extenfively for rubbing out black-lead pen-cil marks from paper, hence its ufual name ofIndia rubber: it is of value to the chemift as amaterial for flexible tubes to gazometers andother apparatus: the furgeon is indebted to itfor flexible catheters and fyringes; and finallyit enters as an effential ingredient into the com-pofition of the bell varnifh for balloons.

CAOUTCHOUC Mineral. See Bitumen.

CAPITAL. An article of Chemical Appa-ratus. See Appendix .

CAPUT MORTUUM. Tlte morte, Fr.Todtenkopje , Germ.

This term is at prefent obfolete: it was ufedby the old chemifts to exprefs the refidues ofdiftiflations after all the volatile parts had beendriven off by the a£tion of heat. Thefe refi-dues were at firfl thrown away as of no value.Glauber was the firfl who particularly employedhimfelf in their examination, and was rewardedfor his pains by the difcovery of fulphat of foda(Glauber’s fait) in the caput mortuum remainingafter the diftillation of muriatic acid from com-mon fait and green vitriol; and of fulphat ofpotafh (Sal fecretum Glauberi) in the refidue

after the diflillation of nitric acid from nitre andgreen vitriol.

CARBON. Carbone , Fr. Kohlenfloff, Germ.

CHARCOAL. Charbon, Fr. Kohle , Germ.

Although carbon is an effential conftituentpart of almoft all vegetable and animal fub-llanees, and is contained in vaft abundance inthe mineral kingdom, yet it is of very rare oc-currence in a Hate of abfolute purity. Whenuncombined with any other body it is crvdal-lized, colourlefs, intenfely hard,, and under itscommercial and mineralogical name Diamond ,is ranked at the head of the gems, and in pro-portion to its bulk is the mofl coftly of all Jub-ilances. The detail of its natural hiftory andexternal characters will be given under the termDiamond , the chemical fafits that have beendifcovered concerning it being all that we haveto do with at prefent.

The firfl fuggeflion of the inflammable na-ture of diamond is due to Newton. This phi-lofopher having obferved that inflammable bodiesin proportion to their denfity poflefs a greaterpower of refracting the rays of light than otherfubdances, was induced to rank the diamondamong them on account of the eminent degreein which it poffeffed this property. This con-jecture was verified in 1694 by the members ofthe Academy del Cimento at Florence, whoconfumed feveral diamonds by placing them inthe focus of a lens. Soon after Francis the firfl,emperor of Germany , contributed fome dia-monds which were confumed by the heat of afurnace. Rouelle, Macquer , Cadet, andD’Arcetrepeated the fame experiments with confiderableattention, and found that by expofure to heatand air, diamond was not only evaporated, butactually burnt with flame; but that even a veryhigh temperature when the air was excluded,,produced no alteration in this fubftance.

In 1772, an experiment was made byLavoifierwhich may be confidered as the firfl attempt to.effedl a chemical analyfis of diamond. Heburnt a fmall piece of this fubftance in a jar of.atmofpheric air by means of a powerful lens,and found that the original bulk of the air had.been diminifhed, and a quantity of carbonic acidwas produced, whence he concluded that thereexifls a confiderable analogy between charcoaland diamond. In 178$ Morveau difcoveredthat diamond when dropped into melted nitreburns like charcoal, and without leaving anyrefiduum. This fact fuggefted to Mr. Tennanta method of analyfing diamond which was ef-fected in 1795 with complete fuccefs.* The

Phil. Tranf. for 1797. p. I23.