COMPOSITION OF LIXIVIATED WOOD ASHES. 355 



(p. 187), this insoluble portion collects in large quantities. It is also 

 present in the refuse of the soap maliers, where wood ash is em- 

 ployed for the manufacture of soft soap. The composition of this inso- 

 luble matter varies very much, not only with the kind of wood from 

 which the ash is made, but also with the temperature it is allowed to 

 attain in burning. The former fact is illustrated by the following analy- 

 sis made by Berthier, of the insoluble matter left by the ash of five dif- 

 ferent species of wood carefully burned by himself: — 



Oak. Lime. Birch. Pitch Pine. Scotch Fir. Beech. 



The numbers in these several columns differ very much from each 

 other, but the constitution of the insoluble part of the ash he obtained 

 probably differed in every case from that which would have been left 

 by the use of the same wood burned on the large scale, and in the open 

 air. This is to be inferred from the total absence of potash and soda in 

 the lixiviated ash — while it is well known that common lixiviated wood 

 ash contains a notable quantity of both. This arises from the high tem- 

 perature at which wood is commonly burned, causing a greater or less 

 portion of the potash and soda to combine with the silica, and to form 

 insoluble silicates, which remain behind along with the lime and other 

 earthy matter, when the ash is washed with water. It is to these sili- 

 cates, as well as to the large quantity of lime, magnesia, and phosphoric 

 acid it contains, that common wood ash owes the xnoxe permanent effects 

 upon the land, which it is known to have produced. When the rains 

 have washed out or the crops carried off the more soluble part from the 

 soil, these insoluble compounds still remain to exercise a more slow and 

 enduring influence upon the after-produce. 



Still from the absence of this soluble portion, the action of lixiviated 

 wood ash is not so apparent and energetic, and it may therefore be safely 

 added to the land in much larger quantity. Applied at the rate of two 

 tons an acre, its effects have been observed to continue for 15 or 20 

 years. It is most beneficial upon clay soils, and it is said especially to 

 promote the growth of oats. 



I am not aware that in any part of the British Islands this refuse ash 

 is to be obtained in large quantity, but in North America much of it is 

 thrown away in waste, which might be advantageously restored to the 

 land on which the wood had grown. 



d. Kelp is the name given in this country* to the ash left by marine 

 plants when burned. It used to be extensively prepared in the Western 



* In Brittany and Normandy it is called varec^ while that of Spain is known by the name 

 of barilla. 



