50* Drs. Will and Fresenius on the 



of manganese, the acids and bases enumerated above are found 

 in almost all vegetable ashes. Several chemists have stated 

 that alumina also is found in the ashes of plants. Berthier, 

 on the other hand, did not find a trace of it in the ashes which 

 he examined, and we have been unable to detect it in all care- 

 fully prepared ashes. De Saussure states that the ashes of 

 the bilberry, the pine and the rose-laurel, contain respectively 

 17*5, I'^'S and 28*8 per cent, of alumina; it is evident however 

 that he has mistaken the earthy phosphates for that substance, 

 and when in subsequent analyses he determined the phosphates, 

 he found no alumina, or merely a trace of it. The behaviour 

 of alumina with solvents sufficiently proves that it cannot be 

 taken up by plants. Pure alumina is equally insoluble in 

 solutions of phosphoric and of carbonic acid ; and though we 

 find in almost all vegetable ashes phosphate of the peroxide 

 of iron, which is so nearly allied to alumina in insolubility, it 

 has probably been taken up by the plant as phosphate of the 

 protoxide, which is soluble in a solution of carbonic acid. If 

 the aluminous compounds, which are so abundant in the soil, 

 were soluble, we should find them in all vegetable ashes; and 

 even were the presence of alumina demonstrated in particular 

 cases, we have sufficient reason for supposing that it, as well 

 as the sand, which is frequently met with in the analyses of 

 ashes, has been derived from dust, which has not been re- 

 moved from the plant with sufficient care previously to the 

 preparation of the ash. 



Oxide of copper has also been found occasionally in vege- 

 table ashes ; Meissner and Saczeau observed it in those of 

 the Cerealia. In some parts of Germany the seeds of the 

 Cerealia are steeped in a solution of sulphate of copper before 

 being sown, with a view of preventing the destruction of the 

 crop by blight : and when oxide of copper is found in vege- 

 table ashes, it may be attributed either to such treatment, or 

 to the presence of cupreous minerals in the soil ; it is always 

 however to be looked upon as unessential or accidental, and 

 not as a necessary constituent of the ashes of the plant. 



The relative proportions of the constituents of vegetable 

 ashes vary so much, according to the nature of the plant, or 

 the part of the plant (and also according to the properties of 

 the soil), that it has been attempted to classify plants by re- 

 ference to the predominant constituent of their ashes. Such 

 a classification will only be attainable when we can, with re- 

 spect to a large number of analyses, ensure the necessary ac- 

 curacy : for our immedialepurpose, however, that of arranging 



almost constantly accompanies phosphoric acid, and must therefore be al- 

 most as generally diffused on the earth's surface as that acid itself, which 

 is so indispensable bo\^x for the vegetable and animal kingdoms.— H. Will. 



