The Plant. 



105 



sium sulphate and calcium phosphate, in the ash. Any excess of 

 the basic elements over the acid forming elements will combine 

 with the carbonic acid present in the air as a result of the process 

 of combustion, and will occur in the ash as carbonates. The large 

 amount of potassium carbonate in wood ashes is formed in this 

 manner. On the other hand, any excess of acid forming elements 

 in the plant will be lost by volatilization and will fail to appear 

 in the ash. It is thus evident that the composition of the ash 

 gives little clue to the previous status of its constituents in the 

 plant. 



In some cases, as with corn grain, where the basic elements of 

 the plant are low, a large part of the sulphur and chlorine may 

 be lost during incineration. The following data from Fraps il- 

 lustrates this point. 



Loss of Plant Elements by Burning. 



In timothy hay and the tobacco leaf, where these losses have 

 been slight, the plants contain a high proportion of base forming 

 elements. In the other plants tabulated above, a lack of basic- 

 constituents, together with a high percentage of phosphorus, pre- 

 vents complete retention of the other acid forming elements dur- 

 ing combustion. With corn, Fraps recovered, as an ash con* 

 stituent. but one-fiftieth of the total sulphur in that grain. 



