ACTION OF SALTS. 



121 



it is the base chiefly which acts. The agricultural value of 

 ashes may be determined by reference to these tables. In 

 what state these elements may be combined in plants, we 

 can only determine theoretically. Thus, the phosphoric acid, 

 by its affinities, would be united in the hard woods as above, 

 with the lime and iron, forming in each 100 parts of the 

 insoluble portion of ashes, phosphate of lime, 5.40; phos- 

 phate of iron, 1.86. 



The average composition of the ashes of hemlock, spruce, 

 chestnut, white elm, black birch, black cherry, and red beech, 

 calculated on the analyses of Prof. Emmons, is as follows : 



100.000 



In the leach tub, the separation into soluble and insoluble 

 would take place as above. 



The composition of the insoluble part of ashes gives nearly 

 the constituents of leached ashes. If the soapboiler's pro- 

 cess was as perfect as that which the chemist employs, still 

 his leached ashes would show more lime than the above 

 6 



