62 



Kuzirian — Correcting Silica for Included Salts. 



Alkali sulphates, on the other hand, do not yield definite 

 and weighable oxides on ignition. Moreover, they may vola- 

 tilize as such at the high temperature of the blast-lamp. The 

 experiments of Table I show that the presence of silica does 

 not materially change this characteristic of alkali sulphates, 

 and that when a small amount of an alkali chloride is added in 

 solution to ignited silica, and the mixture evaporated to dry- 

 ness and treated with sulphuric acid, the residue left after 

 ignition with the Bunsen burner is essentially the neutral 



sulphate. 



Table I. 









Increase in 











weight of 











silica after 











addition of 



Error when 



Silica 



Silica 



Na 2 S0 4 



NaCl, treatment 



the impurity 



ignited with 



ignited with 



equivalent 



with H3SO4 and 



is corrected 



3unsen burner 



blast -lamp 



to NaCl 



ignition with 



as 



1/2 hour 



20 mm. 



added 



Bunsen burner 



Na 3 SO< 



grm. 



grm. 



grm. 



grm. 



grm. 



0-4779 



0-4776 



0-0122 



0-0131 



+ 0-0009 



0-5316 



0-5315 



' 0-0122 



0-0131 



+ 0-0009 



0-5266 



0-5264 



0-0122 



0-0122 



0-0000 



0-5311 



0-5293 



0-0115 



0-0115 



o-oooo 



That elements other than sodium and potassium, present orig- 

 inally with the silica as chlorides and converted to sulphates 

 by the action of sulphuric acid and gentle ignition, may be 

 recovered essentially as sulphates after treatment with sulphuric 

 and hydrofluoric acids and gentle ignition, is shown in Table II. 







Table II. 



Sulphate 





Silica 



Silica 



Sulphate 



determined 



Sulphate 



ignited with 



ignited with 



equivalent 



by increase 



left after re- 



Bunsen burner 



blast-lamp 



to chloride 



in weight 



moving silica 



1/2 hour 



20 min. 



added 



of silica 



byH,S0 4 + HF 



grm. 



grm. 



grm. 

 BaCl 2 added. 



grm. 



grm. 



0-5290 



0-5290 



00103 

 CaCl 2 added. 



0-0098 



0-0104 



0-5576 



0-5572 



0-0121 



0-0114 



0-0118 



0-5351 





0-0242 



0-0218 



0-0226 



0-5486 





0-0242 



0-0242 



00234 



0-5413 



. . 



0-0242 



0-0228 



0-0234 



0-5486 



0-5486 



0-0242 

 MgCl 2 added 



0'0242 





0-5441 



0-5436 



0-0200 



0-0195 



0-0197 



0-5446 





0-0200 



0-0215 



0-0220 



0-5456 



0-5456 



0-0200 

 A1C1 3 added. 



0-0203 





0-5456 





0-0195 



0-0200 



0-0195 



0-5447 





0-0195 



0-0192 



0-0205 



0-5490 



0-5490 



0-0195 



0-0188 





