HYDROGEN. 



that, to satisfy this affinity, it caused the 

 oxidation of the metal at the expense of 

 the water, and then combined with the 

 oxide thus formed. In conformity to 

 Berthollet's speculations, it may be re- 

 ferred to the affinities of the acid to iron, 

 and to oxygen, conspiring with the affi- 

 nity of iron to oxygen : these co-operat- 

 ing produce a ternary combination, while 

 the hydrogen gas is disengaged. 



Hydrogen gas is permanently elastic. 

 When collected over water, it is observed 

 to have a peculiar smell, slightly fetid, 

 which is not so perceptible when it is col- 

 lected over quicksilver, and which is lost 

 when the gas is exposed to substances 

 which powerfully attract humidity. It is 

 not the only substance in which water 

 appears requisite to develope odour. 



This is the lightest of the gases, and in- 

 deed the lightest substance whose gravity 

 can be ascertained by weighing. Its spe- 

 cific gravity varies considerably, accord- 

 ing to its state with regard to humidity. 

 When it has been transmitted through 

 water, or has remained for some time ex- 

 posed to it, it is about ten times lighter 

 than atmospheric air ; when it has been 

 received over quicksilver, and exposed to 

 any substance which attracts water strong- 

 ly, as quicklime, it is nearly 13 times 

 lighter, or atmospheric air being 1,000, 

 hydrogen is 84. Its specific gravity in 

 this state, water being 1000, is stated by 

 Lavoisier at 0.0946.100 cubic inches weigh 

 2.613 grains. It is from this levity, that 

 it was applied with success to the con- 

 struction of balloons ; a varnished silk or 

 linen bag, filled with it, having a specific 

 gravity so much less than atnlospheric 

 air, as not only to rise in the atmosphere, 

 but also to elevate an additional weight. 



The chemical property, by which hy- 

 drogen gas is most eminently distinguish- 

 ed, is its great inflammability. When an 

 ignited body is approached to it, in con- 

 tact with the atmosphere, it is immediate- 

 ly kindled, and continues to burn while 

 the air is admitted ; if previously mixed 

 with atmospheric air, and a burning body 

 approached to the mixture, or an electric 

 spark sent through it, it instantly inflames 

 with detonation ; and when it has been 

 mixed with oxygen gas, the detonation is 

 more violent. When burning at the ex- 

 tremity of a capillary tube, on bringing a 

 wide tube over the flame, a singular 

 phenomenon, accidentally observed by 

 Dr. Higgins, is produced, that of sounds 

 of various tones, which vary in acuteness 



and strength, according to the width, the 

 length of the tube, and the kind of sub- 

 stance of which it is formed, owing, ap- 

 parently, as Picket and De la Rive have 

 explained it, to the vibrations excited in 

 the matter of the tube by the rapid ex- 

 pansion and condensation of the watery 

 vapour near and around the flame, and 

 which, regulated and equalized by regu- 

 lar reflections from the sides of the tube, 

 constitute a musical sound. (Nicholson's 

 Journal, 8vo. vol. i. p. 129 ; ibid. vol. iv. 

 p. 23). 



Though hydrogen gasbeinflammable,it 

 is incapable of supporting the combustion 

 of other inflammables. If a burning body 

 be quickly immersed in it, it is imme- 

 diately extinguished. 



This gas is incapable of supporting 

 animal life by respiration ; an animal im- 

 mersed in it is soon killed. At the same 

 time, it does not appear to be so positive- 

 ly deleterious as the other noxious gases. 

 Scheele long ago observed, that he was 

 able to breathe it for twenty inspirations. 

 (Treatise on Air and Fire, p. 160.) Fon- 

 tana showed, what Scheele indeedhad ob- 

 served, that if the lungs were previously 

 emptied as much as possible of atmo- 

 spheric air, by a forcible expiration, it 

 cannot be breathed so long, though still 

 it did not appear to him to be positively 

 deleterious, like some of the unrespirable 

 gases, (Opuscules Physiques, p. 2.) Ro- 

 sier, even after expelling the air from the 

 lungs, breathed hydrogen gas for several 

 respirations; and Mr. Davy, in his experi- 

 ments on the respiration of the gases, re- 

 marked, that in one experiment, after a 

 complete exhaustion of the lungs, he 

 found great difficulty in breathing hydro- 

 gen for half a minute, though in a subse- 

 quent experiment, with the same prepara- 

 tion, h'e breathed it for near a minute. 

 The first six or seven inspirations pro- 

 duced no sensations whatever ; in half a 

 minute, a sense of oppression was felt at 

 the breast, which increased until the pain 

 of suffocation interrupted the experiment. 

 (Chemical Researches, p. 400. 466.) Hy- 

 drogen, therefore, is incapable of support- 

 ing life ; the respiration of it can be con- 

 tinued only for a short time, and animals 

 confined in it soon die. It appears only 

 to prove fatal, not by a positively noxious 

 quality, but by excluding atmospheric air, 

 the due supply of which, by respiration, is 

 indispensable to life. Blood exposed to 

 it acquires a deep black colour, and the 

 gas suffers a diminution of volume. 



