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



It is to be seen that very fair results — very probably due, 

 however, to a balance between the now largely reduced error 

 due to incomplete conversion of the soluble alkali sulphate into 

 barium sulphate and a small error due to inclusion of foreign 

 matter — are obtained by the use of concentrated aqueous 

 hydrochloric acid to remove the sodium salt. Experiments in 

 which the removal of potassium chloride was similarly attempted 

 were not equally successful, no doubt on account of the greater 

 solubility of potassium chloride in hydrochloric acid and the 

 greater tendency of the barium sulphate to carry down the 

 unconverted potassium sulphate. 



This method of eliminating the effect of sodium salts in the 

 precipitation of barium sulphate would seem to have some appli- 

 cation in the analysis of sulphides and insoluble substances where 

 fusion with sodium carbonate is necessary. Where sodium car- 

 bonate and potassium nitrate are ordinarily used, sodium carbon- 

 ate and sodium peroxide may be substituted so that only sodium 

 salts need be removed by the treatment with hydrochloric acid. 



Whenever the sulphate ion is to be determined by precipita- 

 tion as barium sulphate from a solution containing sodium salts 

 the results of the analysis may be very much improved by 

 the removal of the sodium before precipitating the barium 

 sulphate. The method suggested may be summarized as 

 follows : 



The substance, representing about one gram of barium 

 sulphate, is dissolved (after fusion, if necessary, with sodium 

 carbonate and sodium peroxide) in the least convenient 

 quantity of water. It is then treated with five volumes of 

 concentrated hydrochloric acid and the resulting precipitate of 

 alkali chloride is filtered off on asbestos in a perforated crucible, 

 by the aid of suction, into a beaker under a bell-jar. After the 

 precipitate of alkali chloride has been completely washed by 

 concentrated hydrochloric acid contained in a gravity wash-bot- 

 tle, the filtrate and washings, diluted with an equal volume of 

 water, are evaporated to dryness on the steam-bath, the residue 

 taken up with a little water and l cm3 of four per cent hydro- 

 chloric acid and then filtered through a small filter. The solu- 

 tion is then diluted to 350 cms3 , heated to boiling and a slight 

 excess (l-2 c,n83 ) 10 per cent barium chloride solution added drop 

 by drop from a burette. The precipitate is allowed to digest 

 on the steam-bath for some hours, over night if convenient, 

 and then filtered on the perforated crucible, ignited at low 

 red heat and weighed. 



To Professor F. A. Gooch my thanks are due for kindly 

 assistance and counsel in carrying out this work. 



