216 COMPOSITION OF THE ASH OF WHEAT AND OF BARLEY. 



§ 3- On the relative proportions of the different inorganic compounds 

 present in the ash of plants. 



Having thus made you acquainted with the general properties and 

 composition of tlie several compound substances of which the ash of 

 plants consists, we now advance to the consideration of the relative pro- 

 portions in which these substances exist in the ash of the different kinds 

 of plants usually cultivated for f(X)d. 



We have seen (p. 178) that different species of plants leave very dif- 

 ferent quantities of ash when burned ; — the ash left by diflferent species 

 contains also the above earthy and saline substances in very unlike pro- 

 portions. This fact has already been stated generally (p. 180) ; we are 

 now to illustrate it more fully, and to show the important practical de- 

 ductions to which it leads. 



I. OF THE ASH OF WHEAT. 



According to the analysis of Sprengel, 1000 lbs. of wheat leave 11-77 



lbs., and of wheat straw 35-18 lbs. of asti, consisting of — 



Grain of Straw of 



Wheat. Wheat. 



Potash 2-25 lbs. 0-20 lbs. 



Soda 2-40 0-29 



Lime 0-96 2-40 



Magnesia 0-90 0-32 



Alumina, with a trace of Iron 0-26 0-90 



Silica 4-00 28-70 



Sulphuric Acid .... 0-50 0-37 



Phosphoric Acid . . , . 0-40 1-70 



Chlorine 0-10 Q-30 



11-77 lbs. 35-18 lbs. 

 If the produce of a field be at the rate per acre of 25 bushels of 

 wheat, each 60 lbs., and if the straw* be equal to twice the weight of 

 the grain, the quantity of each reaped per acre will be 



Grain . . . 1500 lbs. } c j mc u u i 



Straw . . . 3000 lbs. \ ^''^^^ ^ P'°^""^ "^^^ ^"'^^^'' 

 so that the quantity of the different inorganic compounds carried off from 

 the soil of each acre will be, in the grain i more than is represented in 

 the second column, and in the straw 3 times as much as is represented 

 in the third column. '^ 



II. — OF THE ASH OF BARLEY. 



A thousand pounds of the grain of barle}^ (two-rowed, hordeum di$ti- 

 chon,) leave 23i lbs., and of the ripe dry straw 52-42 lbs. of ash. This ash 

 consists of — 



* The proportion of the straw to the seed in g^in of all kinds is very variable. In wheat 

 St is said to average twice the weight of the grai i, but it is very often, even in heaty crops, 

 3 to 3}^ times that weight. 



