108 Sir Robert Kane on the Chemical Constitution of the 



however, variable ; and it will be seen that a variation takes 

 place in the quantity of sulphuric acid exactly of an opposite 

 character ; so that in the plant, the proportions of organic 

 salts and of sulphates would appear to have been such, that an 

 increase in one replaced any deficiency of the other. Thus 

 when the quantity of carbonic acid in the ash was 25*235, the 

 sulphuric acid was 6"174-; but when the sulphuric acid was 

 12'091, the carbonic acid fell to 9'895. I do not however 

 mean absolutely to assert that the sulphuric and the organic 

 acids of the plant are, in all cases, or exactly, mutually re- 

 placing. 



The small quantity, as well as the narrow limits of fluctua- 

 tion of the silica, is worthy of notice ; particularly when com- 

 pared with that which I shall have to notice as regards the 

 composition of Irish flax. It does not appear connected with 

 any of the bases in particular, nor to follow any special varia- 

 tion among them. 



There is nothing more peculiarly characteristic in the com- 

 position of the ashes of the flax plant, than the quantity of 

 phosphoric acid which is found therein. In order to bring 

 this into full evidence, I shall extract from the works of other 

 chemists the determination of the quantity of phosphoric acid 

 in the ash yielded by the stems of other plants. 



Tobacco stalk and leaves . . 2*73 



Wheat stems 3*10 



Oat stems 3-00 



Clover plants 6*30 



The stems of flax are, then, more than double as rich in 

 phosphoric acid as the stems of even the cereal grasses or 

 leguminous plants ; and if we even look to the constitution of 

 the ash of many substances used as food by man, we shall find 

 that, in 100 parts, there are from the ash of — 



Oats . . . .14*9 phosphoric acid 

 Potatoes . . . 11'3 

 Turnips ... 6*1 



whilst the average of the analyses of Belgian and Dutch flax 

 ashes show that there are present no less than 10*77 per cent. 

 It was this enormous quantity of the most valuable ingredient 

 of manure that first impressed me with the importance of its 

 oeconomy, and induced me to endeavour to fix the attention of 

 agriculturists upon the fact ; for if we calculate, from the pro- 

 duce per acre, the quantity of phosphoric acid taken from a 

 statute acre of ground by an ordinary crop of any of the usual 

 kinds, we shall find that it amounts in the case of flax to very 

 nearly as much as with any of the ordinary grain or root crops ; 



