ASHES OF PLANTS. 229 



seldom present in appreciable quantity in other ashes. 

 Even iodine, bromine, oxide of copper, and titanic 

 acid have been found, though generally in very minute 

 quantities, in some ashes. 



The process of analysis differs according as the 

 ashes do or do not contain more phosphoric acid than 

 is requisite to combine with the sesquioxide of iron, 

 protoxide of manganese, lime, magnesia, and alumina. 

 To the former (containing more phosphoric acid) belong 

 those of seeds, to the latter, those of woods, succulent 

 plants, &c. 



I. Ashes of seeds. About 50 grms. of the seeds 

 which have been dried in the air, or at 100, are 

 thoroughly carbonized by gentle ignition in a pla- 

 tinum crucible; the carbonaceous mass is powdered, 

 moistened with water, and exposed for some time to 

 the air, when the sulphides are converted into 

 sulphates ; it is then digested with concentrated acetic 

 acid, water added, the mixture filtered, and the residue 

 washed with hot water till the washings are only 

 slightly acid to test papers. The carbonized mass is 

 thus entirely, or almost entirely, freed from metallic 

 chlorides; it is introduced, while yet moist, into a pla- 

 tinum crucible, and incinerated as far as possible by a 

 protracted gentle ignition. (At a bright red heat, 

 phosphide of platinum is formed and the crucible 

 corroded.) Finally, a few drops of concentrated 

 nitric acid are added to the ash, which is then ignited 

 in the crucible, the cover of which is placed against 

 its mouth, until the last traces of carbon are burnt off, 

 and a perfectly white ash remains. This ash is added 

 to the saline mass obtained by evaporating the acetic 

 solution ; the mixture is gently ignited to decompose 

 the acetates, and weighed. 



The ash is dissolved by nitric acid in a carbonic 

 acid apparatus, and the carbonic acid determined from 

 the loss. 

 20 



