W. A. T\ 



urner 



Sulphur in Soluble Sulphates. 43 



amount (25 cm3 ) of water, the solution saturated with gaseous 

 hydrogen chloride, the precipitated alkali chloride filtered off 

 on asbestos in the perforated crucible and washed with concen- 

 trated hydrochloric acid. The filtrate was evaporated on the 

 steam-bath (after dilution with an equal volume of water to 

 prevent mechanical loss during the evaporation), the residue 

 diluted, filtered (to remove possible traces of silica derived from 

 the glass container), acidified with l cm3 of four per cent hydro- 

 chloric acid, and treated, as before, at a volume of 350 cmS , with 

 barium chloride. The results follow: 









Table III. 











Theory 



Error in 



Error in Sodium 



No. 



CuS0 4 5H 2 



BaS0 4 



for 



terms of 



terms of chloride 



of 



taken 



found 



BaS0 4 



BaS0 4 



-S0 4 added 



exp. 



grm. 



grm. 



grm. 



grm. 



grm. per cent grm. 



1. 



0-9774 



0-9196 



0-9139 



+ 0-0057 



+ 0-0024 +0-26 3 



2. 



1-0976 



1-0325 



1-0263 



+ 0-0062 



+ 0-0025 +0-25 3 



3. 



1-3255 



1-2444 



1-2395 



+ 0-0049 



+ 0-0020 +0-16 3 



4. 



1-2855 



1-2057 



1-2021 



+ 0-0036 



+ 0-0015 +0-12 3 



In this process the negative error of the former process, due 

 to incomplete conversion of the soluble sulphate to barium sul- 

 phate, is eliminated and replaced by a positive error which can 

 only be due to the inclusion of foreign matter, either barium 

 chloride, or, possibly, a trace of silica, derived from the glass 

 during the long evaporation of the hydrochloric acid solution 

 and not completely removed by one dehydration and filtration. 



In the following set of experiments aqueous hydrochloric 

 acid was substituted for the gaseous acid and the precipitation 

 of the sodium chloride was made by adding to the concentrated 

 solution of the weighed copper sulphate and sodium chloride, 

 (about 10 cc ), approximately five times its volume of the con- 

 centrated acid ; the precipitated chloride was filtered off and 

 the solution further treated as described above. The results of 

 this treatment are given in Table IV. 









Table IY. 











Theory 



Error in 



Error in Sodium 



No. 



CuS0 4 5H 2 



BaS0 4 



for 



terms of 



terms of chloride 



of 



taken 



found 



BaS0 4 



BaS0 4 



-S0 4 added 



exp. 



grm. 



grm. 



grm. 



grm. 



grm. per cent grm. 



1. 



0-8444 



0-7912 



0-7896 



+ 0-0016 



+ 0-0006 +0-08 3 



2. 



0-9775 



0-9145 



0-9141 



+ 0-0004 



+ 0-0002 +0-02 3 



3. 



0-9801 



0-9158 



0-9165 



— 0-0007 



— 0-0003 —0-03 3 



4. 



1-3620 



1-2742 



1-2736 



+ 0-0006 



+ 0*0002 +0-01 3 



