166 THE ATOMIC WEIGHTS. 



CoC.,0^.2H.^O. 



1-6355 grm- gave -781 grm. CO.^. 47.753 per cent. 



1. 107 " .5295 " 47-832 '• 



2.309 " i.ioi " 47-683 



3.007 " 1.435 " 47-722 " 



Mean, 47-7475. ± -0213 



The following were the percentages found for cobalt : 



32.552 

 32.619 

 32-528 

 32-523 



Mean, 32.5555, ± .0149 



In a later paper* Schneider also gives some results ob- 

 tained with a nickel oxalate containing but two molecules 

 of water. This gave him 47.605 per cent, of CO2, and the 

 following percentages of nickel : 



31-4115 

 31-4038 



Mean, 31.4076, ± .0026 



The conclusion at which Schneider arrived was, that the 

 atomic weights of cobalt and nickel are not identical, being 

 about 60 and 58 respectively. The percentages given above 

 will be discussed at the end of this chapter in connection 

 with all the other data relative to the constants in question. 



The next chemist to take up the discussion of these atomic 

 weights was Marignac, in 1857. t His original paper is not 

 accessible to me, and I am therefore obliged to give only 

 such features of it as I can get from abstracts and reviews. 

 He worked with the chlorides and sulphates of nickel and 

 cobalt, using apparently common gravimetric methods. 

 The sulphates, taken as anhydrous, were first ignited to 

 expel SO 2+ 0, after which the residues were heated with 

 weighed amounts of lead silicate. The increase in weight 



* Poggend. Annal., 107, 616. 



f Jahresbericht, 1857, 225. Bihl. Univ. de Geneve, fnouv. s.,) i, 373. 



