244 § 124. ANALYSIS OF ASHES. 



B. ASH RICH IN SILICA, MIXED WITH BARYTA. 



«. Determine carbonic acid and clilorine, and pre- 

 pare the solution for the complete analysis, precisely as 

 under A. 



The residue, insoluble in hydrochloric acid, on eliminat- 

 ing silica in the usual way, contains, besides sand and 

 unconsumed carbon, baric sulphate, in which is the sul; 

 phuric acid of the ash, and it must be treated accord- 

 ingly. Collect it on a dried and weighed filter, wash it, 

 dry it at 110° C, and weigh. Then treat it with sodio 

 carbonate (§ 58, «, 2) ; but, as the baric sulphate is not 

 readily decomposed by the carbonated alkali, the boiling 

 must be repeated several times, with fresh portions of the 

 carbonate, the insoluble part allowed to settle completely 

 after each boiling, and the clear liquid decanted without 

 transferring any notable quantity of the solid to the filter ; 

 when the filtered liquid gives no reaction for sulphuric 

 acid, after acidification with hydrochloric acid, the decom- 

 position may be considered as ended ; if the portion with 

 which the test is made gives a reaction with baric chlo- 

 ride, it should be jmt back into the liquid to be boiled. 



Transfer the silica and coal to the filter, after the boil- 

 ing is finished, jiour dilute hydrochloric acid over it as 

 long as there is any efiervescence, wash the filter care- 

 fully with water, dry at 110°, weigh, ignite, and weigh 

 again, and so estimate sand and unconsumed carbon, as 

 imder A. 



Evaporate the alkaline solutions and washings to dry- 

 ness, and eliminate silica (§ 58), and determine sulphuric 

 acid in the filtrate from the silica, with the aid of baric 

 chloride (§ 59). 



b. Complete analysis* — Examine the solution obtained 

 in a, and filtered from the silica, etc., according to Scheme 



