>^^sm?'> ^ aind on Equivalent Volumes i \ B .T ';|^ :j^ 



of that of the parent ; in metamorphosis a similar ratio is always 

 observed. - iiiUir^Aui ;. 



Apart from the apjmrent exceptions about ;tO:*be noticed, the 

 weights of equal volumes of gases and vapours are their equiva- 

 lent weights, and the doctrine of chemical equivalents is that of 

 the equivalency of volumes. According to the atomic hypothe- 

 sis, these weights represent the relative weights of the atoms, 

 and as equal volumes contain the same number of atoms, these 

 must have similar volumes, so that we come at last to the 

 equivalency of volumes. As chemical combination is not a 

 putting together of molecules, but an interpenetration of masses, 

 the application of the atomic hypothesis to explain the law of 

 definite proportions becomes wholly unnecessary. Chemical 

 species are homogeneous ; " tota in minimis existit natural Solu- 

 tion is chemical union, as is indicated by the attendant conden- 

 sation ; mechanical mixtures are not accompanied by any change 

 of volume. 



As two volumes of water-vapour yield one volume of oxygen 

 and two of hydrogen, this was assumed to be the equivalent of 

 water and of hydrogen, while oxygen was represented by one 

 volume, w^hose weight was 8, that of the volume of hydrogen 

 being -5, so that the weight of the equivalent of water was 9. 

 But two volumes of hydrogen unite without condensation, with 

 two of chlorine, and the resulting four volumes of hydrochloric 

 gas are found to be equivalent to four volumes of chlorine, hy- 

 drogen or water-vapour. Hence four volumes are to be taken 

 for the equivalent of water, and it becomes H^O^, with an 

 equivalent of 18, corresponding to HCl, and to volatile species 

 generally, whose equivalents are represented by four volumes of 

 vapour; from these, the equivalents of non^-^olatiiew species are 

 determined by comparison. '- K> Yr\^\x^'^A:^ 



Ti Hydrogen, chlorine, and some other primary species offer 

 * apparent exemptions to the general law of condensation and 

 equivalency of volumes. When four volumes of chlorine unite 

 with four of olefiant gas, or naphthaline, the product is condensed 

 into four volumes ; but if the chlorine unite with the same 

 volume of hydrogen gas, there is no condensation, and eight 

 volumes or two equivalents of hydrochloric gas are produced. 

 iThis, however, is explained when we find that four volumes of 

 i^jhe chloro-hydrocarbon MH, CP, may break up into four of a 

 new species MCI, and four of HCl, a change which with the 

 chloride of etherene is effected by the aid of hydrate of potash, 

 and with the chloride of naphthaline takes place spontaneously 

 at an elevated temperature. In the production of hydrochloric 

 gas from chlorine and hydrogen, union takes place followed by 

 immediate expansion without specific difference or metamor- 



