108 HOW CROPS GROW. 
According to Maschke, (Jour. fir Pr. Ch.,'79, p. 148,) 
the crystalloid aleurone that is abundant in the Brazil 
nut, is a compound of casein with some acid of unknown 
composition. This aleurone may be dissolved in water, 
and recovered in its original form on evaporation. 
Kubel’s analysis of aleurone, prepared from the Brazil’ 
nut by Hartig, gave its content of nitrogen 9. 46 per cent. 
Aleurone from the yellow lupin yielded him 9.26 per cent. 
Since pure casein has 16 to 18 per cent of nitrogen, the 
aleurone contained about 52 to 59 per cent of albuminoids. 
Estimation of the Albuminoids.—The quantitative sep- 
aration of these bodies is a matter of great difficulty and 
uncertainty. For most purposes their collective quantity 
in any organic substance may be calculated with sufficient 
accuracy from its content of nitrogen. All the albumin- 
oids contain, on the average, about 16 per cent of nitrogen. 
This divided into 100 gives a quotient of 6.25. If, now, 
the percentage of nitrogen that exists in a given plant be 
multiplied by 6.25, the product will represent its percent- 
age of albuminoids, it being assumed that all the nitrogen 
of the plant exists in this form, which in most cases is prac- 
tically true. 
Frihling and Grouven have recently investigated the 
condition of the nitrogen of various plants, and have found 
that nitric acid, (N, O,,) which in the form of nitrate of 
potash has long been known to occur in vegetation, is 
present in but trifling quantity in most agricultural plants, 
In mature clover, esparsette, lucern, wheat, rye, oats, bar- 
ley, the pea, and the lentil, it did not exceed 2 parts in 
10,000 of the air-dry plant. In maize, they found twice 
this quantity ; in beet and potato tops alone of all the plants 
examined was nitric acid present to the amount of four- 
tenths of one per cent, (Vs. St., IX, 153.) Salts of am- 
monia (N H,) likewise often exist in plants; but as a rule 
in quite inconsiderable quantities.. 
