42 W. A. Turner — Sulphur in Soluble Sulphates. 



sulphate to carry with it another sulphate, by inclusion or com- 

 bination, being much less marked in the case of copper sulphate 

 than in the case of the alkali sulphates.* For the experiments 

 to be described, the copper sulphate was prepared by twice 

 crystallizing the presumably pure (C. P.) salt from the hot water 

 solution while stirring vigorously to promote the separation of 

 the substance in finely divided form. These crystals dried in 

 air for two days gave, on analysis, the following results: 









Table I. 









Analysis 



of Pure Copper Sulphate. 









Theory 



Error in 





No. 



CuS0 4 5H 2 



BaS0 4 



for 



terms of 



Error in terms 



of 



found 



found 



BaSO-4 



BaSO-4 



of -SO* 



exp. 



grm. 



grm. 



grm. 



grm. 



grm. per cent 



1. 



1*1668 



1-0904 



1-0911 



— 0-0007 



— 0-0003 —0-03 



2. 



1-5373 



1-4383 



1-4375 



+ 0-0008 



+ 0-0003 +0-02 



3. 



0-9042 



0-8453 



0-8455 



— 0-0002 



—o-oooi —o-oi 



4. 



1*3812 



1-2906 



1-2915 



— 0-0009 



— 0-0004 —0-03 



These results are obviously very close to theory, but it is not 

 improbable that in them some slight tendency toward the carry- 

 ing down of copper sulphate with the barium sulphate may 

 have been counteracted by the inevitable inclusion of traces of 

 barium chloride.f 



Upon making the precipitation under exactly similar condi- 

 tions, excepting the presence of alkali salts, the error due to the 

 carrying down of unconverted alkali sulphate is at once made 

 evident bv the error of deficiency. This is shown in the results 

 of Table II. 









Table II. 













Theory 



Error in 



Error in 



Alkali 



No. 



CuS0 4 5H 2 



BaS0 4 



for 



terms of 



terms of 



salt 



of 



taken 



found 



BaS0 4 



BaS0 4 



-S0 4 



added 



exp. 



grm. 



grm. 



grm. 



grm. 



grm. per cent 



grm. 



1. 



1-0879 



1-0049 



1-0173 



— 0-0124 



— 0-0051 —0-50 



5* 



2. 



1-4373 



1-3154 



1-3450 



— 0-0296 



— 0-0122 —0-91 



5t 



* NaCl f KC1 



The next step was the attempt to eliminate the error, due to 

 incomplete conversion of the alkali sulphate, by the prelim- 

 inary precipitation and removal of the alkali chloride. An 

 accurately weighed portion of copper sulphate with an approx- 

 imately known weight of alkali chloride was dissolved in a small 



* Allen and Johnston (loc. cit.) find this to be true also of the sulphate of 

 another bivalent element, viz., magnesium. 



f Richards and Parker, Proc. Am. Acad., xxxi, 67, 1896, Zs. anorg. Chem. , 

 viii, 413, 1895. 



