POTASH. 271 



of Italy, by the incineration of trees and other vege- 

 table matters that are not species of marine plants. 

 In the manner of pursuing the process necessary for 

 the production of potash from these materials, much 

 care and skill are required. When trees are burnt 

 for the purpose, it is essential to the formation of good 

 potash, that the whole of the wood be thoroughly 

 reduced to ashes. Previously to being used, these 

 ashes should pass through a wire sieve, where none 

 but such as are completely reduced to dust can find a 

 passage. Neglect of this precaution not only renders 

 the evaporation more difficult, but deteriorates the 

 potash. The alkaline salt is extracted from the ashes 

 by means of water, which holds it in solution ; the 

 filtrated fluid, consisting of such salt and the water, is 

 called a ley; the aqueous portion of which being 

 evaporated, the alkali is obtained. The results of 

 various experiments to ascertain the relative quantity 

 of potash contained in different plants, show that 

 weeds in general yield more ashes, and their ashes 

 much more salt than an equal weight of wood; and 

 in proportion as plants recede from the ligneous 

 and approach to the herbaceous character, they are 

 found richer in potash. Three times the quantity 

 of ashes are obtained from shrubs, and five times 

 as much from herbs as from trees. Equal weights 

 of the branches of trees produce more ashes than 

 the trunk, and the leaves more than the branches. 

 Green vegetables produce more ashes than when dry, 

 and herbs arrived at maturity are richer in their 

 saline product than at any other time. Fumitory 

 yields a greater proportion of potash than any other 

 plant; it produces much more ashes than an equal 

 weight of wormwood. With reference, however, to 

 equal weights of ashes, those of wormwood are found 

 to contain the most alkali. 

 The salt obtained from plants is not pure potass ; 



