GAS. 



as that from iron is apt to be contaminat- 

 ed with carbon. Muriatic acid, diluted 

 with twice or thrice its weight of water, 

 may be emplbyed, but it is less econo- 

 mical 



Hydrogen gas is the lightest of all pon- 

 derable substances, particularly if receiv- 

 ed over quicksilver, and freed from any 

 humidity which it may cojitain, by expo- 

 sure to any substance that attracts water 

 strongly. When perfectly dry, it is free 

 from smell, but when it contains moisture, 

 it is slightly fetid. Though highly in- 

 flammable, it extinguishes burning bodies, 

 if completely enveloped in it without the 

 contact of oxygen. It is incapable of sup- 

 porting life, but does not appear to pos- 

 sess any directly noxious quality, as it 

 may be breathed for several respirations, 

 or even nearly a minute. Fired, in com- 

 bination with oxygen, it explodes very 

 loudly ; but if kindled as it escapes from 

 the extremity of a capillary tube into the 

 atmosphere, it burns calmly, with a white 

 flame, the colour of which, however, may 

 be varied by different substances dissolv- 

 ed in the gas. It is thus the philosophical 

 fireworks without smoke or smell are 

 formed. If a tube of glass, metal, or any 

 elastic material, be held over a jet of in- 

 flamed hydrogen gas, musical tones will 

 be produced, varying in depth and 

 strength, according to the length, diame- 

 ter, and material of the tube. A glass 

 jar has a similar effect, but it must not be 

 too wide, or so narrow as to extinguish 

 the flame. Dr. Higgins first discovered 

 this property. 



A very high temperature is generally 

 considered as necessary to produce the 

 combination of hydrogen and oxygen. 

 Biot compressed the two gases together 

 in the syringe of an air gun ; they took 

 fire, exploded violently, and burst the 

 'inge ; but here the temperature was 

 ifficiently increased by the pressure. A 

 Mitleman of Orkney, however, introduc- 

 nearly equal quantities of the two gases 

 ito a glass jar over mercury, which stood 

 a room without fire, and with little 

 ight, from the beginning of January to 

 "ic end of May, when he found that, of 

 velve cubic inches, three and a half had 

 lisappeared. The residuum was still a 

 mixture of the two gases. 



The chief practical application of hy- 

 drogen gas is for the filling air-balloon's. 

 GAS, hydrogen arsenicated. Scheele, dis- 

 solving tin in arsenic acid, observed the 

 extrication of an inflammable gas, holding 

 arsenic in solution. Proust afterwards 

 obtained it by digesting arsenious acid 

 and zinc in diluted sulphuric acid. It may 

 VOL. V. 



be procured, likewise, by treating arse* 

 nious acid, or arsenic and iron fillings, or_ 

 arsenic and tin filings, with muriatic acid; 

 but still better by treating four parts of 

 granulated zinc, and one of arsenic, with 

 sulphuric acid diluted with twice its 

 weight of water. 



This gas is insoluble in water ; does 

 not render lime-water turbid; mixed with 

 atmospheric air no diminution of bulk en- 

 sues, but the mixture, when fixed, deto- 

 nates loudly, and deposits metallic arse- 

 nic; it has an alliaceous smell ; it extin- 

 guishes burning bodi.es, and is fatal to 

 animals; it is decomposed by oxygenated 

 muriatic acid gas. If a lighted taper be 

 immersed in a phial of this gas, it is in- 

 stantly extinguished ; but the gas burns 

 at the mouth of the phial with a lambent 

 white flame, which diffuses white fumes 

 of arsenious acid. If it be inflamed in a 

 phial with a small orifice, the flame gra- 

 dually descends to the bottom of the phial, 

 which becomes coated with crystallized 

 metallic arsenic. Two parts of this gas, 

 with one of oxygen, will explode loudly, 

 and the products are water and arsenious 

 acid; soap bubbles, made with a mixture 

 of these gases, explode with a bluish 

 white flame. Equal parts of the gases ex- 

 plode with a much more vivid flame, but 

 less noise. A stream of this gas, burned 

 in a large receiver filled with oxygen, 

 emits a blue flame of uncommon splen- 

 dour. According to Tromsdorff's calcu- 

 lation, a cubic inch of the gas contains 

 about a quarter of a grain of the arsenic. 

 Its specific gravity is rather more than 

 half that of atmospheric air. 



GAS, carburette.'l hydrogen. There are 

 several varieties of this gas, the hydrogen 

 holding different proportions of carbon 

 in solution, according to the process by 

 which it is obtained. 



The gas of stagnant water, which may 

 be procured by stirring the mud at the 

 bottom with a stick, and collecting the 

 gas, as it rises in bubbles, in an inverted 

 bottle, is this compound, as is also the 

 fire damp of coalmines. The vapour of 

 water passed through a tube containing 1 

 ignited charcoal consists of this gas and 

 carbonic acid, which may be separated by 

 agitating the mixture with lime diffused 

 in water. The vapour of ether, or of al- 

 cohol, passed through a red hot tube of 

 porcelain, coated with clay, affords the 

 same products. If three parts of concen- 

 trated sulphuric acid, and one of alcohol, 

 be distilled in a glass retort with a gentle 

 heat, acarburetted hydrogen comes over. 

 This is distinguished by the name of ole- 

 fiant gas, from its property of forming an 



O o 



