OP ARTS AND SCIENCKS. 



251 



The ratio between the copper and the sulphuric acid, or rather 

 between the copper aiul sodic carbonate on the one hand and sodic 

 sulphate on the other, affords a new twofold basis for the calculation of 

 the atomic weight of copper. This basis is entirely independent of the 

 always uncertain weight of the cupric sulphate and the objectionable 

 method of calculation from difference. The results correspond to the 

 new atomic weight, but the complete discussion of this phase of the 

 subject will be reserved until more definite data have been given. 

 It is interesting to note that these comparatively crude experiments 

 differ only by one or two units in the second decimal place of the 

 result from the far more carefully executed work yet to be described. 



Analysis of Cupric Sulphate. — First Series: Data and Results. 



Welgltts reduced to Vdcuum Slandard. 



Second Series. 



Although from the earlier experiments it appeared that the defi- 

 ciency in the sum of the analytical results might be explained by the 

 hypothesis of the existence of water in the so-called anhydrous cupric 

 sulphate, it was possible that at least a part of this deficiency might be 

 due to experimental error. The next step of the research was therefore 

 to start again upon a more refined basis. It was important, too, that 

 some proof of the above mentioned hypothesis more definite tlian an 

 indirect inference should be obtained. The cleare.st idea of the various 

 operations may probably be acquired through a detailed statement of one 

 of the experiments, and accordingly such a statement is given below. 



Experiment 4. — The cupric sulphate,* having been cautiously 

 powdered in an agate mortar and dried to constant weight over the 

 desiccating mixture already described, was gradually heated to 255° 

 in a platinum crucible with a very closely fitting lid. 



* See page 245 of this paper. 



