OF ARTS AND SCIENCES. 



271 



probably rendered the latter quantity of the salt about 0.007 per cent 

 too high; hence the true weight should have been o. 95123. The 

 correction is so small that it has not heretofore been applied. 

 From these values we obtain the proportions : 



NaoCOg : Cu = 7.25010 : 4.34583 

 = 5.95123 : 3.56697 

 Average 



106.108 : 63.003 



106.108 : 63.597 



63.600 



The highest individual result was 63.604, the lowest 63.592, when 

 entirely uncorrected. 



III. From Experiments 4, 6, 7, and 9 it is apparent that 10.95552 

 grams of sodic sulphate are equivalent to 4.90165 grams of electrolytic 

 copper. Hence : 



NaaSOi : Cu = 10.9555 : 4.90165 = 142.166 : 63.607. 



Highest value 63.614 



Lowest " 63.595 



The last determination (Experiment 9) is by far the most trust- 

 worthy. The value deduced from it is 63.600. 



IV. From Experiments 4 and 6 it is evident that 4.4855 grams of 

 sodic carbonate (average) are equivalent to 6.75463 grams of cupric 

 sulphate which has been dried at 360°. But it is reasonably certain 

 that this cupric sulphate still contained sixty-six hundred-thousandths 

 of its weight of water. Making the appropriate correction we have : 



NaaCOa : CuSO, = 4.4855 : (G.7546 - .0044 = 6.7502) 



= 106.108 : 159.681 



Highest value 

 Lowest " 



159,703 

 159.673 



Subtracting SO4 = 96.060, the average value Cu = 63.621 is 

 obtained. 



V. In the same way, from Experiments 4, 6, and 9, 9,31558 grams 

 of sodic sulphate are seen to correspond with 10.4715 — 0.0069 = 

 10.4646 grams of really anhydrous cupric sulphate. Hence: 



Na2S04 : CUSO4 = 9.3156 : 10.4646 = 142.166 : 159.701 



Highest = 159.73 



Lowest = 159.65 



From the average, Cu = 63.641. This result has a very large 

 probable error, in the chemical as well as in the mathematical sense. 



