CYCLOPEDIA: ^^ 



OR, A NEW 



UNIVERSAL DICTIONARY 



OF 



ARTS and SCIENCES. 



WATER. 



WATER. This important fluid was believed by the an- 

 cients to be one of the four elements out of which they 

 imagined every other fubftance is compofed. This opinion 

 maintained its ground for a very long period. At length, 

 however, it began to be fufpefted, from the experiments of 

 Van Helmont, Boyle, and others. Van Helmont (hewed 

 that plants would grow for a very long time in pure water, 

 whence it was concluded that water was capable of being 

 changed into all the fubftances found in vegetables. Mr. 

 Boyle fuppofed, that by long digeftion and boiling in glafs- 

 veflels, he had converted water partly into an earth. Mar- 

 graafF, who repeated his experiment, drew the fame conclu- 

 fion ; but the opinion was never very generally admitted, 

 and at length was proved to be erroneous, the earth being 

 fhewn to be derived from the glafs-veffels employed in the 

 experiments. 



The combuftible nature of hydrogen gas was obferved 

 about the beginning of the 1 8th century, and the celebrated 

 Scheele, many years afterwards, was the firft who attempted 

 to difcover what was produced by this combuftion. In 

 this, however, he did not fucceed ; nor were Macquer, 

 Bucquet, Lavoifier, Dr. Prieftley, and others, who fub- 

 fequently repeated the experiment with fimilar views, 

 more fortunate. The diftinguifhed honour of difcovering 

 the compofition of water was referved for Mr. Cavendi/h, 

 who, in 1781, proved beyond a doubt that the combuftion 

 of hydrogen and oxygen produced this fluid, and nothing 

 elfe. Water, therefore, fince the period juft mentioned, has 

 been univcrfally admitted to be compofed of thefe two 

 gafeous principles. 



Water is found in abundance in every part of the globe, 

 and is abfolutely neceflary for the exiftence of organized 

 beings. When quite pure, as obtained by diftillation, it is 



Vol. XXXVIII. 



perfeftly tranfparent and colourlefs, and free from tafte 

 and fmell. 



A cubic foot of diftilled water, according to the bell 

 experiments, weighs, at a temperature of 40°, 437102.4946 

 grains troy. Hence, a cubic inch of water at the fame 

 temperature weighs 252.952 grains; and at the tem- 

 perature of 60°, 252.72 grains. The fpeciilc gravity of 

 water is always fuppofed to be i.ooo, and it is made tlie 

 meafure of the fpecific gravity of every other body. (See 

 Specific Gravity, and Hydrostatics.) Water, at a tem- 

 perature of 32°, becomes folid, and aiTumes the form of ice. 

 In this ilate it pofTefTes confiderable hardnefs and elafticity, 

 and its fpecific gravity is diminifhed to .94. See Freezing, 

 and Ice. 



When water is railed to the temperature of 2 1 2° it boils 

 and is gradually converted into (learn, which is an invifible 

 and highly elaftic fluid like air. The fpecific gravity of 

 fteani, according to the moll recent obfervations, is .625, 

 that of air being reckoned i.ooo. See Boiling, Ebul- 

 lition, and Steam. 



Water is capable of undergoing a flight degree of com- 

 pre(rion. See Compression. 



Water undergoes no alteration by expofure to heat or 

 light. Thus it may be made to pafs through a red-ho|f; 

 tube without fufFering any change. 



On expofure to the atmofphere, it abforbs a portion of 

 air, the greater part of which is capable of being again 

 driven off by boihng. To expel the whole, however, it is 

 ftated to be necelTary to continue the operation at leaft two 

 hours in a flaflc, with its mouth inverted over mercury. 

 To this fmall proportion of air which it holds in folution, 

 water chiefly owes its agreeable flavour, boiled water being 

 infipid. Sec Absorption, and Gas. 



B Hydrogen 



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