WAT

W A T

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not been examined: it is (aid that a mixtureof phofplurus and fulphur at a boiling heatdeconrpofes water, pholphuretted and fulphu-vetted hydrogen gas being difengaged. But ofall the combuftibles charcoal has the mod;marked adlion on water : if a glafs or earthen-ware tube be filled with pieces of charcoal,and then heated red hot, and if Hearn be palledinto it in this fituation, both the water andcharcoal will by degrees difappear, and therewill be generated a prodigious quantity ofmixed gas, confifting of carbonic acid, oxyd ofcarbon, and carburetted hydrogen.

Of the metallic fubftances, iron, zinc, tin,fend manganefe decompofe water by the affift-ance of heat, hydrogen gas being produced,and the metals being reduced to the Hate ofoxyd. Gold, filver, platina, and copper haveno a£lion on water even at a red heat; theefteft of the other metals has not been exa-mined.

The compofition of water is one of the mainpillars on which the theory of Lavoifier relts,it will therefore be proper to enter fomewhatat large into the fubjedf.

Water was confidered by the ancient philofo-phers, as a Ample elementary fubftance, unde-compofable, but which by mixture with otherbodies conftituted the principal part of thenutriment of animals and vegetables. The firftmodification of this theory was by Van Hel-mont, who having raifed plants fuccefsfully inpure water, concluded that this fluid aloneis convertible into all the vegetable principles.Soon after, Boyle having procured earthy fealesby long digeftion of water in glafs veflels her-metically fealed, concluded that this fluid was inpart at leaft convertible into earth: Margraafobtained the fame refult from the repeated flowdiftillation of water in glafs veflels. Butthough there was no inaccuracy in the fa&, itwas demonftrated by Lavoifier that the veflelsthemfelves during the procefs loft a portion oftheir weight exaftly equal to that of theearth produced, and therefore that the earthwas in all probability derived not from thewater, but from the glafs - t a conclufion whichwas further confirmed by Dr. Prieftley, whofatisfaftorily fliowed that water by long con-tact with glafs at a high temperature, alwaysdecompofes a part of it, probably in confequence«£ its affinity for the aikali.

While thefe difeuffions were going on, thedifeovery of the gafleous fubftances commenced.and. foon led to an entirely new theory concern-

-» Phil. Tranf.

ing the compofition of water. The firft faff ofany importance was obferved by Macquer whofound that a bottle filled with hydrogen ga*and expofed to the air burnt with a lambentblue flame unaccompanied by any fmoke, andthat the i fide of the veflel after the combuftionwas lined with drops of a fluid which appearedto be water. Some time afterwards Dr. Prieft-ley exploded in a glafs veflel a mixture ofoxygen and hydrogen gas, and found that theveflel became moift in the infide, and was linedwith a black matter, fuppofed by Dr. P. tooriginate from the mercury by which the gaffeswere confined.

Induced by the above refults, Mr. Cavendifh*’,in i'81, mixed together 500000 grain mea-fures of hydrogen gas from zinc and fulphuricacid, and about 2\ times as much of atmolphericair : by combuftion the bulk of the mixture wasdiminifhed to about -f- of that of the latter gas,there were obtained 135 grs. of pure water. Inorder to repeat the experiment in a more unex-ceptionable manner he exploded a mixture of19000 grain meafures of oxygen gas and 37000of hydrogen gas: 2950 grain meafures remainedunconfumed, and there were obtained 30 grs.of an acidulous fluid, which appeared to be amixture of water with a little nitric acid.In another experiment the proportion of hydro-gen was increafed, and the rel'ulting fluid ap-peared to be pure water, being wholly free fromany acid. From thefe he drew the conclufionthat the appearance of nitric acid was owing toaccidental impurities, and that water was com-pofed of oxygen and hydrogen. Soon afterLavoifier and La Place performed a fimilar ex-periment, from which they obtained 295 grs. ofpure water, and accordingly concluded thatwater was compofed of oxygen and hydrogen.Another well-condudfted experiment with thefame view was executed by Le Fevre de Gineau,of which the following are the principal parti-culars. 35085.1 cubic inches of oxygen gasobtained from black oxyd of manganefe, andweighing 254 gros. 10.5 grains, were explodedwith 74967.4 cubic inches of hydrogen gasprocured from foft iron and diluted fulphuricacid, and weighing 66 gros. 4-3 grains; hencethe whole weight of the gaffes operated on was== 320 gros. 14.8 grains. After the combuftionthere remained 39 gros. 23 grains of elaftic fluidconfifting of a mixture of oxygen, azot, and car-bonic acid, hence the amount of gas which haddifappeared amounted to 280 gros. 63.8 grains.But there was produced 280 gros. 30 grains ofIxxit. p;ls8.