OF ARTS AND SCIENCES. 



275 



as many different preparations, in making which various different 

 precautions were observed ; but in a paper ab-eady far too prolix the 

 omission of these minor points will be well pardoned. The cupric 

 oxide was ignited to constant weight at a dull red heat in a double 

 crucible, and cooled in a vacuum as usual. The outside crucible 

 was of platinum in the second and third experiments, and in these 

 cases the inner crucible was observed to have gained noticeably in 

 weight during the ignition. The last weight was adopted, for ob- 

 vious reasons. In the first and last cases the solution of the oxide 

 was conducted in the crucible, without transferring, while in the second 

 experiment the cupric oxide was dissolved in the platinum flask with 

 bulb tubes. In each case both nitric and sulphuric acids were added, 

 that the conditions might be similar to those of the preceding syn- 

 theses. The cupric sulphate used by Baubigny in his analyses was 

 prepared in a somewhat similar way, and hence in this respect his 

 result is comparable with these. 



Synthesis of Cupric Sulphate from Cupric Oxide. 

 Weights reduced to Vacuum.* 



Number of 

 Experiment. 



43 

 44 

 4.5 



Cupric Oxide taken. 



grams. 



1.0084 

 2.7202 

 1.0144 



Cupric Sulphate found. 



grams. 



2.0235 

 5.4770 

 2.0350 



Average 



Theory if Cii = 63.6 



" =0.3.34 



Baubigny's result 



Per Cent Cupric Oxide 

 in (Jupric Sulphate. 



49.835 

 49.830 

 49.848 



49.838 



49.856 

 49.774 



49.815 



The comparatively close agreement between the average and the 

 theory is solely due to an elimination of opposite errors. This fact 

 will be more evident in the following section. 



In order to show that no material was mechanically lost during the 

 syntheses, the last sample of cupric sulphate from each of the two 

 series was electrolyzed. The result of one of these electrolyses has 



* Specific gravity of CuO = 6.3 ; of CUSO4 = 3.61. 



