COCOA BY-PRODUCTS 26 
probably would not be far from 80 per cent activity (39). From 
Table 3 it will be seen that, on the basis of its activity by either 
permanganate method, the water-insoluble nitrogen of the cocoa 
products must be classed as of inferior quality. 
On the other hand, for organic materials, the cocoa products 
contain a relatively large share of their total nitrogen in a form 
soluble in water. Indeed, the press cakes and extracted cocoas 
contain a greater actual amount of water-soluble nitrogen than has 
been reported for typical samples of such standard organic am- 
moniates as cottonseed meal and castor-bean pomace (23). Such 
water-soluble organic nitrogen, in recognized fertilizer materials, is 
generally conceded to be highly available to growing plants. 20 
In the cocoa products, however, the water-soluble nitrogen in- 
cludes the alkaloid nitrogen, since practically all (94 to 99 per cent) 
of the theobromine and caffeine was found to be readily extracted 
by water at room temperature; and this alkaloid nitrogen probably 
has no plant-food value. 
The total amount of alkaloid nitrogen present in the samples 
examined ranges from 0.5 per cent for one of the cocoa shell samples 
to 1 per cent in samples of press cake and extracted cocoa. Of this, 
the Kjeldahl method is reported to recover, at best, less than 95 per 
cent (56). Table 3 includes the calculated amounts of alkaloid 
nitrogen that would be obtained by the method used in the nitrogen 
determinations, for the samples assayed for theobromine and caffe- 
ine; and it will be seen that the alkaloid nitrogen constitutes 50 to 
60 per cent of the water-soluble nitrogen. 
Theobromine and caffeine in the pure, uncombined state have 
been found to be toxic to certain plants in water cultures, and 
the significance of this is discussed on page 25. 
The sum of the amounts of water-soluble and active insoluble 
organic nitrogen (as determined by either permanganate method), 
commonly loosely termed the available nitrogen, is often used as a 
basis for judging the quality or fertilizer value of crude ammo- 
niates intended for use as a source of organic nitrogen. A regula- 
tion at one time in force in several of the Southern States required 
" that in unmixed fertilizing materials furnishing organic nitrogen, 
the sum of the water-soluble organic nitrogen and the permanga- 
nate soluble part of the water-insoluble organic nitrogen [as deter- 
mined by the neutral permanganate method] shall amount to 85 
per cent of the total organic nitrogen" (7). 'Though the cocoa 
products do not meet this requirement, it is interesting to compare 
the quality of their nitrogen as indicated by the alkaline permanga- 
nate test with data obtained by the same 'method by Jones on the 
nitrogen of cottonseed meal and castor-bean pomace. 
In a sample of very high-grade cottonseed meal containing 7.02 
per cent of total nitrogen, Jones (23) found 0.63 per cent of water- 
soluble nitrogen (less than 9 per cent of the total), and 4.09 per 
cent of active insoluble nitrogen. The so-called available nitrogen 
amounted, therefore, to 4.72 per cent, or 67 per cent of the total 
nitrogen. The sample of castor pomace examined by Jones con- 
tained 5.28 per cent of total nitrogen, of which less than 17 per 
28 The availability of water-soluble organic nitrogen is commonly accepted (23), but 
recently Robinson has pointed out that this has not been proved by experimental investi- 
gation (39). 
