GAS. 



ton Morveau considers it as Composed of 

 1T.88 pure carbon, and 82.12 of oxygen. 



Carbonic acid gas exceeds every other 

 in specific gravity, except the sulphur- 

 ous. Hence the vapour in the Grotto 

 del Cano rises but a little above the sur- 

 face ; and the choak damp of miners, 

 which is this gas, lies on the ground. 

 Thus, too, when it is emitted from a fer- 

 menting liquor, it first fills the empty 

 portion of the vat, displacing the lighter 

 atmospheric air ; and then flows over the 

 sides, almost as water would do. For 

 the same reason, if a bottle filled with it 

 be inverted over the flame of a candle 

 at some distance, it will descend, and ex- 

 tinguish it. According to the experi- 

 ments of Mr. Cavendish, one part of this, 

 mixed with nine of atmospheric air, 

 renders it incapable of supporting com- 

 bustion. 



From the powerful attraction of car- 

 bon for oxygen, the base of this gas is not 

 easily decomposed ; but Mr. Tennant ef- 

 fected it by introducing phosphorus into 

 a coated glass tube, closed at one end, 

 and over this powdered marble. A very 

 small aperture only being left in the. other 

 end of the tube, and a red heat applied 

 for some minutes, phosphate of lime and 

 charcoal were found in the tube. Dr. 

 Pearson did the same with phosphorus 

 and carbonate of soda. 



The carbonic acid gas is likewise de- 

 composed in part by hydrogen gas, as- 

 sisted by electricity. In a glass tube 

 eight lines in diameter, De Saussure 

 exposed a column of four inches in 

 height of carbonic acid gas, and three 

 inches of hydrogen gas, over mercury, 

 to the action of the electric fluid circula- 

 ting between iron conductors, for twelve 

 hours. The gases were at first condens- 

 ed very rapidly, but by degrees more 

 and more slowly, till in this period they 

 were reduced to four inches. Of this, 

 one inch was absorbed by potash, being 

 carbonic acid gas, and the other three 

 were nearly pure carbonic oxide, the hy- 

 drogen having formed water with the 

 oxygen, abstracted from the carbonic 

 acid. The mercury and the conductors 

 were but very little oxyded. De Saus- 

 sure had previously found that carbonic 

 acid and hydrogen gases, standing toge- 

 ther over mercury for the space of a 

 twelve-month, had decreased in volume. 



GAS, Carbonic oxide. This gas was first 

 made known by Mr. Cruickshank. Dr. 

 Priestley had observed, that, when scales 

 of iron mixed with charcoal, or with car- 

 bonate of barytes, were exposed to a 



strong heat, lai*ge quantities of a combus- 

 tible gas were extricated, which he sup- 

 posed to be heavy inflammable air, or 

 carburetted hydrogen. He considered 

 this as a strong argument against the mo- 

 dern theory of the formation of water ; 

 as, from the dryness of the ingredients, 

 which were previously exposed to a red 

 heat, and mixed and experimented upon 

 immediately, and the quantity evolved, 

 it could not be accounted for upon the 

 supposition of the decomposition of wa- 

 ter. This objection was successfully com- 

 bated by Mr. Cruickshank, showing that 

 the air did not contain hydrogen, but 

 was an oxide of carbon. It is equally pro- 

 cured from the oxides of other metals, 

 and charcoal ; but in proportion to the 

 facility with which these give up their 

 oxygen, the carbon is more or less satu* 

 rated with it; so that the product is 

 a mixture of carbonic acid gas and car- 

 bonic oxide, the proportion of the for- 

 mer decreasing as the process is conti- 

 nued. 



The carbonic oxide gas, freed from 

 carbonic acid by washing with lime-wa- 

 ter, is very little lighter than atmospheric 

 air. It does not explode, when fired in 

 atmospheric air, but burns with a blue 

 lambent flame : with oxygen gas it deto- 

 nates. It is noxious to animals. Water 

 absorbs about a fifth only of its bulk. It 

 is not absorbed by the pure alkalies, and 

 does not precipitate lime-water. If it be 

 mixed with hydrogen gas, and passed 

 through an ignited glass tube, its oxygen 

 unites with the hydrogen to form water, 

 and charcoal is deposited. De Saussure, 

 JUH. however, ascribes this appearance of 

 carbonaceous matter lining the tube to 

 the action of the hydrogen on the lead in 

 the glass, as he produced it by hydrogen 

 alone with a glass tube ; and could not by 

 hydrogen and carbonic oxide in a tube of 

 porcelain. The purest oxide of carbon 

 is obtained, by passing the carbonic acid 

 gas through red hot charcoal. 



GAS, hydrogen. This is generally ob- 

 tained from the reverse of the process 

 for the decomposition of water. Iron 

 moistened with water becomes oxyded, 

 by decomposing the water; but this pro- 

 cess is very slow. If the vapour of water 

 be passed through a tube, containing iron 

 wire, kept at a red heat, the decomposi- 

 tion will go on with much more celerity. 

 But the readiest method is to employ an 

 acid, as the sulphuric, diluted with five or 

 six times its weight of water," poured on 

 iron filings or turnings, or on zinc in 

 small pieces. Zinc affords it the purest, 



