OHBMISTRY. 



[lIVDUOOE.V. 



tnuufernxl by UMM OMMU will be at once proved by 

 applying a light to each TCMO!, when that which has 

 rig. U. previously contained air 



will at onoo be toon to 

 ouuUin hydrogen l>y iU 

 oootenta txiing ignited. 



The light specific gra- 

 vity of hydrogen may 

 be pleasingly illustrated 

 by means of small bal- 

 loons made of gold- 

 beater's skin. These, if 

 filled with hydrogen, will, 

 on being liberated, at 

 once ascend in the air. 

 As the material of which they are composed is, however, 

 easily acted on by the acid employed to generate the hy- 

 drogen, the following arrangement is recommended to 

 minify the gas before it is allowed to pass into the 

 balloon. 



following engraving, in which the gas is first conducted 

 through a tube containing chluridu of calcium, to free it 

 from moisture. 



In the above engraving, a represents the vessel in 

 which the hydrogen is generated ; b is a bent tube 

 fitted into the nock of a, and running nearly to the 

 bottom of the vrasel :, which is to be three-parts filled 

 with water. This tube, and d, which rises out of the 

 neck of the vessel c, and to which the balloon, e, is 

 attached, are to bo fitted air-tight in the purifier by- 

 means of a cork. The gas will thus pass from a through 

 6, into the vessel containing the water. It will here 

 be cleansed from acid, and, rising in bubbles to the 

 surface, will escape by d, which only just passes into 

 its neck. The balloon, when filled, is to be tied at 

 its neck, to prevent the escape of the hydrogen. In 

 balloons of large size, coal gas is always employed ; 

 which, although much heavier than pure hydrogen, 

 answer* well for the purpose. 



>gen may be obtained from water by other means 

 than those we have suggested. If steam from water be 

 passed through an iron tube, heated to redness, it will 

 be decomposed, and its oxygen uniting with the iron to 

 f"rm an oxide, the hydrogen may be collected in the 

 usual way at the pneumatic trough, by fitting a bent 

 pewter tube to the end of the iron one. 



Hydrogen is obtained ht the purest state by decom- 

 posing water by means of voltaic electricity. The best 

 mode of doing this lias already been described in the 

 section of Electricity.* 



The most important compound of hydrogen is the 

 well-known lmui.1 water, which, in its purest state, 

 consists of eight parts of oxygen, united with one of 

 hydrogen by weight. The gases unite, by bulk, in the 

 proportion <>( two volumes of hydrogen to one of oxygen. 

 The symbol of water is HO. and its equivalent = 9. 

 The following experiments illustrate the production of 

 water by the union of its elementary constituents. 



Ki^nmrni 36. Hold a cold glass vessel over the jet 

 of the bottle described in Experiment 33, whilst the 

 gas is b<irning. The vessel will scon become coated 

 with dew, owing to water being produced by the com- 

 biwtion of the hydrogen in contact with the oxygen 

 contained in the surrounding air. Another mode of 

 conducting the experiment, is that illustrated in the 

 8M0, p. 1M; Fit. M. 



' 



r\g. 47. 



7. If a long glass tube, an inch in <lia- 

 raeter, be held so as to inclose the jut of the hydrogen 

 bottle in the way shown in the an- rig. . 



uexed engraving, some singular musi- 

 cal sounds are produced. The pitch 

 of those sounds depends on the dia- 

 meter of the tube ; the bass being 

 produced by those of a large, and the 

 shriller tones by those of a small 

 diameter. Any intermediate sound 

 can be produced ; and thin plan has 

 been proposed as a means of form- 

 ing a new kind of musical instru- 

 ment. This effect results from a 

 series of vibrations being produced, t 

 which arise from numerous explo- 

 sions caused by the combination of 

 the hydrogen with the oxygen of the 

 acid. Of this, the next experiment gives a better illus- 

 tration. 



Erj>eriment 38. Into a strong glass vessel, introduce, 

 by means of the pneumatic trough, one part of oxygen 

 and two parts of hydrogen, by volume. For this 

 purpose, an ordinary soda-water bottle answers ex- 

 ceedingly well. Apply a lighted taper to the mixture, 

 when an explosion will instantly take place. After tho 

 expansion consequent thereon has ceased, it will bo 

 seen that the gases have lost their gaseous condition, 

 and the result will be found as pure water in the form of 

 vapour, or condensed in dew-like drops on the side of 

 the vessel. This is simply a more rapid way of pro- 

 ducing water by tho combination of its elements, than 

 those we have described in the preceding experiments. 



The oxy-hydrogen blowpipe is a means of producing 

 the most intense heat by the combustion, through a 

 proper jet, of a mixture of oxygen and hydrogen gases, 

 in the same proportion as that in which they form 

 water. 'for the sake of safety, the two gases are kept 

 in separate reservoirs, and are not allowed to mix, ev 

 at nearly the point of their combustion. The application 

 of this arrangement to the purposes of illumination, and 

 to optical instruments, has been already fully expl.i 

 under the section on Light;! and a drawing of the most 

 improved form of jet which can be used for the purpose, 

 has also been given. We may here add, however, that 

 by moans of the oxy-hydrogen jet, the otherwise most 

 infusible substances may be rendered liquid Mich as 

 porcelain, platina, wrought iron, Ac. 



The general uses of water are too well known to 

 require any lengthened remarks on our part. In the 

 laboratory it is employed as a general solvent, and purt 

 water is therefore an object of constant requirement. 

 This is obtained by the distillation of river or spring 

 water in glass retorts, when great purity, as in 

 toxicological analyses, is desired. In ordinary cases, 

 the steam proceeding from any metal vessel, as a kettle, 

 4c., may be condensed by means of a pewter tube, 

 which should be kept cool by damp cloths. In mt 

 large towns, distilled water can bo readily obtain. .1 ; 

 and, in many cases, ordinary rain or river water may be 

 employ. -.1. Water of the OMU always contains many 

 soluble matters, such as chloride of sodium, chloride of 

 magnesium, iodide and bromide of potassium, <tc. This 



f See ante, p. 27i ; Section, " Acoutic." Afitt, p. J. 



