CH. XV] ASH. 299 



The addition of sulphuric acid greatly facilitates the 

 burning of the last portions of carbon, and the process may 

 generally be employed, but it must be remembered in this 

 case that the ash will weigh rather more than an original 

 ash, as CO2 and C\^ are replaced by SO3. 



Qualitative examination. 



Since the constituents of ash are almost invariably the 

 same it is seldom necessary to make a qualitative exami- 

 nation. 



The bases are potassa, soda, lime, magnesia, ferric 

 oxide, and small quantities of alumina and oxides of 

 manganese. 



The acid radicles are carbonic, sulphuric, phosphoric, 

 silicic acids, and chlorine. 



Quantitative examination. 



If a complete analysis is required the scheme given in 

 Fresenius (see above) may be followed, and it is easy to 

 estimate any of the constituents by modifications of this 

 process. 



Determinations of chlorine, phosphoric acid, and alkalies 

 may easily be made. 



Chlorine. 



A weighed quantity of the ash is boiled with water 

 and filtered, the chlorine can be estimated in a portion of 

 the filtrate after exactly neutralising with nitric acid by 

 standard solution of silver nitrate, using potassium chromate 

 as indicator. 



See Sutton, Volumetric Analysis, p. 112. 



