OF ARTS AND SCIENCES. 



255 



or two tenths of a milligram duriug the fusion. A drop of very dihite 

 permanganate solution was not decolorized by the solution of tiie 

 residual salt, showing that no reduction had taken place. A very small 

 amount of insoluble residue, consisting of the apparently unavoid- 

 able impurity in the sodic carbonate together with any iron or copper 

 which might be present, was determined in each case ; and the amount 

 was subtracted from the weight of sodic sulphate. Naturally, besides 

 this, it is necessary to subtract the amount of salt corresponding to the 

 acid added in titrating back and forth when determininsf the end 

 point of the acidimetric reaction. This end point had been taken as 

 the average of a number of readings. Below are the data of the 

 experiment under discussion. 



Weight of crucible + NagSOi (etc.) 



" " alone 



Uncorrected weight of NagSO^ 

 Subtract weight of salt added in titration 



" " insoluble residue 



Corrected weight of Na2S04 in air 

 Correction to vacuum (Sp. gr. = 2.631) 

 Weight Na2S04 in vacuum 



Grams. 



= 18.67040 

 = 16.92594 



= 1.74113 



Per cent of SO4 in CUSO4 . 5 HgO = 38.445 



« " " " found above = 38.439 



Atomic weight of copper (if Na2S04 = 142.166, from table) : 



Weight NaaSOi : weight Cu = 142.166 : 63.595. 



No copper was found in the solution of the sodic sulphate, and a 

 minute trace only in the insoluble residue. 



The object of the second experiment of the series was to determine 

 whether the method of weighing cupric sulphate in a tightly covered 

 crucible was an accurate one. The determination was in every respect 

 modelled after the mode of procedure adopted by Harape, a tightly 

 stoppered weighing-bottle being used to contain the salt. The result 

 sufficiently confirmed the previous experiment. For later experiments 

 a crucible was accordingly used, since the evaporation of sulphuric 

 acid at high temperatures is much more feasible in such an apparatus. 

 A mishap prevented the accurate determination of the acid. 



For the third experiment, a much larger amount of material was 



