230 ASHES OF PLANTS. 



,The solution is mixed with 10 or 12 volumes of 

 water, and the residue, consisting of undissolved silica 

 (sometimes also of sand) and charcoal, is collected upon 

 a filter (previously dried at 100), weighed, carefully 

 removed from the filter, and digested with very dilute 

 solution of soda, which readily dissolves all the silica, 

 except that present in the form of sand j the residue 

 of sand and charcoal is collected upon the filter 

 previously employed; its weight, after being dried at 

 100, is deducted from the total weight of the ash. 

 The weight of the silicic acid is determined from the 

 loss. 



From the filtered solution containing the saline 

 constituent, the chlorine is precipitated by nitrate of 

 silver, an excess of the precipitate removed by hydro- 

 chloric acid, the sulphuric acid precipitated by 

 chloride of barium, and the excess of baryta separated 

 by careful addition of sulphuric acid. 



The filtrate is evaporated to dryness, the residue 

 treated with concentrated hydrochloric acid, and di- 

 gested with it for some time, in order completely to 

 expel the nitric acid, and to convert any pyrophos- 

 phoric acid into the tribasic form. The hydrochloric 

 acid is expelled as far as possible, a sufficient quantity 

 of water afterwards added, and the solution filtered 

 from the undissolved silica, which is ignited, weighed, 

 and calculated together with that previously obtained. 



From the solution, the iron, manganese, alumina, 

 lime, and magnesia, are precipitated by ammonia as 

 phosphates, which are collected, after six or eight 

 hours, upon a filter, ignited and weighed. The pre- 

 cipitate is dissolved by digestion with concentrated 

 hydrochloric acid, the free acid nearly neutralized with 

 soda, and the solution mixed with acetate of soda, when 

 the phosphates of sesquioxide of iron and alumina are 

 precipitated. These are ignited and weighed, and if 

 necessary (unless the ignited precipitate has a pure 



