64: Kuzirian — Correcting Silica for Included Salts. 







Table III. 







SiO a 



(blasted) 

 taken 



Eesidue left 

 by H 2 S0 4 

 + HF treat- 

 ment of first 

 precipitate 



Eesidue left 

 bv H 2 S0 4 

 + HF treat- 

 ing of second 

 precipitate 



Sum of 

 residues 



Error which 

 results from 

 calling the 

 residues ox- 

 ide instead 

 of sulphate 



grm. 



grm. 



grm. 



grm. 



grm. 





.a. 

 Desiccation at 110" 







0-5302 



o-ooio 



0-0012 



0-0022 



+ 0-0013 



0-5211 



o-ooio 



o-ooio 



0-0020 



+ 0-0012 



0-5440 



o-ooio 



0-0012 



0-0022 



+ 0-0013 



0-5351 



o-ooio 



0-0002 



0-0012 



+ 0-0007 



0-5436 



o-ooio 



0-0013 



0-0023 



+ 0-0014 





Desiccation 



B 

 at 137° in acetic i 



anhydride. 





0-5520 



o-ooio 



0-0003 



0013 



+ 0-OO0S 



0-5452 



o-ooio 



o-ooio 



0-0020 



+ 0-0012 



0-5347 



o-ooio 



0-0005 



0-0015 



+ 0-0009 



0-5521 



o-ooio 



0-0005 



0-0015 



+ 0-0009 



These errors, which are not inappreciable, were found when 

 the silica was separated, as well as possible, from sodium 

 chloride alone. When chlorides of other elements, such as mag- 

 nesium, calcium, and aluminium, are present the silica sepa- 

 rated is likely to be also contaminated with these salts which, 

 by the ordinary treatment, will be transformed to oxides when 

 the silica is ignited and to sulphates when the silica is 

 removed ; and these sulphates will be more or less refractory 

 under ignition, according to their natures and to the duration 

 and temperature of the ignition. The errors shown above for 

 the case in which sodium chloride is the only contaminating 

 salt are likely to be magnified in the analysis of ordinary sili- 

 cates of complex composition. The proposed modification of 

 treatment will, therefore, lead to a more accurate application 

 of the correction for impurities included in the silica. In this 

 procedure it is not necessary to blast either the silica or the 

 residue before and after the removal of silica as silicon fluoride. 

 The Bunsen burner will give a temperature sufficiently high to 

 volatilize the excess of sulphuric acid and to break up the 

 acidic and pyrosulphates of the alkali elements. The included 

 salts being weighed as sulphates, or as sulphates broken up to 

 practically the same extent in both ignitions, the correction to 

 be applied will be reasonably accurate. 



