Inorganic Constituents of Plants. 509 



To the filtered solution neutral oxalate of ammonia is added 

 as long as a precipitate is formed, and the quantity of lime is 

 determined in the usual manner. When it has been shown 

 by quantitative analysis, that besides phosphate of iron, the 

 ash contains peroxide of iron or oxide of manganese (in which 

 cases the presence of earthy phosphates is very rarely de- 

 tected), the solution, previously to the separation of the lime, 

 should be supersaturated with ammonia and precipitated by 

 means of sulphuret of ammonium ; the two oxides being after- 

 wards separated according to the known methods. 



If the ash under examination contained earthy phosphates, 

 the solution filtered from the oxalate of lime will contain free 

 acetic acid ; if otherwise, ammonia will be free ; it is next 

 somewhat concentrated, rendered ammoniacal, treated with 

 a solution of phosphate of soda, and sepai'ated from the pre- 

 cipitate, which is estimated as phosphate of magnesia, 



3. Estimation of the Alkalies. — The solution ip) is treated 

 with baryta water until it gives an alkaline reaction, it is 

 then gently heated and filtered. By this means we get rid 

 of all the sulphuric acid, phosphoric acid and peroxide of 

 iron, as well as the magnesia and most of the lime. The pre- 

 cipitate is washed upon a filter as long as the liquid renders 

 turbid a solution of nitrate of silver; the solution is next 

 warmed, treated with caustic ammonia and carbonate of am- 

 monia, and allowed to stand until the precipitate becomes 

 heavy and granular. The whole is now filtered, and the solid 

 matter is washed, after which the solution is evaporated to 

 dryness, and the residue heated to redness in a platinum cap- 

 sule to expel the ammoniacal salts. What remains consists 

 of the chloride of potassium or sodium, or more generally of 

 a mixture of the two. The weight being noted, a little water 

 is added, which mostly leaves undissolved a trace of magnesia; 

 this is collected on a filter, its quantity is subtracted from that 



II. 1-4787 of the salt dried at 300° to 400° C. lost by ignition in one ex- 

 periment 7'13 per cent., and in second 6"62 per cent, water; the mean is 

 6*87 per cent. = 5'61 per cent, of the salt not dried at an elevated tem- 

 perature. 



III. 0-409 of the salt dried at 300° (= 0-5015 dried over sulphuric acid) 

 yielded 0-158 peroxide of iron = 31*5 per cent. 



The composition of the salt is therefore— 



In 100 parts. 



JOO-OO 



