1^25.] Method of analysing Sulphate of Zinc, 371 



These were my reasons for pitching upon 5*25 as the atomic 

 weight of an atom of zino. I consider the analysis by means of 

 chloride of barium as the experimentum crucis from which, 

 knowing l^y approximation the quantity of water and oxide of 

 zinc, we can determine the amount of each with mathematical 

 accuracy. ' The uncertainty respecting the quantity of sulphuric 

 abid may be reduced almost without limit by concentrating the 

 liquid before applying the test of muriate of barytes \ and I made 

 myself certain that the error which I could have committed did 

 not amount to toVo^'^ ^^^ grain by that method. 



:'6. Jlaving determined the composition of sulphate of zinc in 

 i^Q way just stated, I calculated the composition of carbonate of 

 zinc, as given in page 60 of my late work, in this way. The car- 

 bona.te of zinc obtained by precipitation from 90*63 grains of 

 si^lphate of zinc, weighed 31*03 grains, and was composed of 



:«"anqiii^ lOxide of zinc 20*37 or 6*25 



luomi? tofJarbonic acid 10*66 2*747 



'Wbw' "2*747 approached so near 2*75, which I Jsnew to be the 

 atomic weight of carbonic acid, that I considered myself entitled 

 to consider the carbonate of zinc when anhydrous as a com- 



pound of '^;^^".; '" 

 ^ ''M e.Bm r/iitn^jijp- JO 



1 atom oxidfi of 



Zinc • 5-25 



1 atom carbonic acid .,,..., 2*75 



8*00 



I thought it better merely to state the general results in my 

 preliminary chapters than to enter into tedious details. Who- 

 ever will take the trouble to repeat the analyses which I have 

 given with the requisite care will obtain results i)ot deviating 

 more than -p—o^h P^^* f^^"^ those which I have given. I am 

 afraid that in actual analyses we can seldom come nearer the 

 truth, except indeed by peculiar contrivances, some of which I 

 employed in determining the fundamental points of the atomic 

 weights of bodies. 





^ Mil Hi' 



2b2 



