On Chemical Equwaleiili. 1 15 



a vegetable acid, containing combined water, whose prime equi- 

 valent is to be determined by experiment. A crystallized salt is 

 made with it, for example, and a determinate quantity of soda. 

 Suppose the alkali to form 26 per cent, of the salt, Tiie rest is 

 water and acid. Dissolve 100 grains, and add them to an inde- 

 finite quantity of the solution of any salt, with whose base the 

 vegetable acid forms an insoluble compound. Dry and weigh 

 this precipitate. Without decomposing the latter, we have suf- 

 ficient data for determining the prime equivalent of the real acid. 

 We make this proportion : As the weight of soda is, to its prime 

 equivalent, so is the weight of the precipitate to the prime of the 

 compound. Suppose 14S grains of an insoluble saltof lead to have 

 been obtained; then 2G : 3-95 : : 148 : 22-1 = the prime of the 

 salt of lead. From this, if we deduct the weight of the prime 

 equivalent of oxide of lead, =14, we have 8* I for the prime 

 equivalent of the acid. And the crystallized salt must have con- 

 sisted of Dry acid, ..' 53-3 



Soda, . , . . 2() 



Water, .. 207 



1000 



As the above numbers were' assumed merely for arithmetical 

 illustration, the u'ater is not atomically expressed. Indeed the 

 problem of finding the acid ])rime, does not require the salt to 

 be either dried or weighed. A solution would suffice. Saturate 

 a known weight of alkali, with an unknown quantity of the crv- 

 slallized acid. Add this neutral solution, to a redundant quan- 

 tity of solution of nitrate of lead. Wash, dry, and weigh the 

 insoluble precipitate, and apply the above rule. 



There are three systems of equivalent numbers at present em- 

 ])loyed : 1st, That having oxygen as the radix; 2d, That having 

 one volume of hydrogen as the radix ; 3d, That having two 

 volumes of hydrogen as the radix, on the Daltonian supposition, 

 that two volumes of hydrogen contain the same number of atoms, 

 as one volume of oxygen. As this hypothesis is destitute of proof, 

 it evidently should be discarded from phvsical science. Since 

 the volume of hydrogen, is equal in weight to 1- 16th the weight 

 of the volume of oxygen, the former two systems arc mutually 

 convertible, by multiplying the number oxygen, in the oxvgcn 

 ratio, by 16, or 4 x 4, to obtain the number in the hydrogen 

 scale; and this is reconverted by the inverse operation, namelv, 

 dividing by 16, or by 4x4. 



Dr. Wollaston's scale, and Sir H. Davy's proportional luim- 

 bers, ftrc adapted to the idea that water is a compound of 

 1 hydrogen -\- 7\} oxvgen by vveight, or l.> + 1 by volume. 



P 2 Their 



