24 BULLETIN 1413, U. S. DEPARTMENT OE AGRICULTURE 
cent was water-soluble and 65 per cent was available. The water- 
soluble nitrogen amounted to 0.88 per cent, and the active insoluble 
to 2.55 per cent, making the total so-called available nitrogen 3.43 
jDer cent. From Table 3 it may be seen that for the cocoa cakes 
the water-soluble plus active insoluble, or so-called available nitro- 
gen, as determined by the alkaline permanganate method, ranges 
from 1.78 to 2.26 per cent, and for the solvent-extracted cocoas 
from 2.00 to 2.39 per cent. These values amount to from 46 to 
57 per cent of the total nitrogen. 
If, however, the average alkaloid nitrogen percentages determined 
(0.85 per cent for the press cakes and 0.94 per cent for the extracted 
cocoa) be deducted on the grounds that the alkaloid nitrogen can 
not be classed as available, the nitrogen availability percentages are 
greatly reduced. Similarly, the water-soluble plus active, or total 
soluble nitrogen as determined by the neutral permanganate method 
in the pressed and the extracted cocoas amounts to 2.47 to 3.60 per 
cent of the material, but after deducting the presumably valueless 
alkaloid nitrogen, the range becomes 1.53 to 2.75 per cent for the 
soluble nonalkaloid nitrogen. 
One reason for discounting the value of the soluble alkaloid nitro- 
gen is the fact that experiments have been reported showing 
theobromine and caffeine to have injured certain plants in water 
or sand cultures. The significance of this is discussed below. But 
even if it could be shown that in the soil these alkaloids were not 
especially harmful to plants, the work of Kobinson, Winter, and 
Miller on the effects of alkaline permanganate on various organic 
compounds containing amino- and imino-nitrogen (38), suggests 
that the alkaloid nitrogen may be so linked in the alkaloid molecule 
as to be somewhat resistant to conversion into forms that are avail- 
able to growing plants. 
Some idea of the relative fertilizer value of the cocoa products 
may be obtained by comparing their contents of plant-food constitu- 
ents, total " ammonia,*' phosphoric acid, and potash, as shown in 
Table 2 (p. 14), with the quantities of these plant nutrients in seed 
residues of a similar nature. The average ammonia content of 72 
samples of commercial castor-bean pomace, examined at the Con- 
necticut Agricultural Experiment Station in 1923, was 6.2 per cent ; 
and it is stated that this material usually contains about 2 per cent 
of phosphoric acid and 1 per cent of potash (If). The cocoa cakes, 
then, contain on the' average about three-fourths as much total "am- 
monia " and phosphoric acid and twice as much potash as ordinary 
commercial castor pomace. The by-product cocoas more nearly re- 
semble commercial cottonseed feed in plant-food content, however, 
than they do any other material whose fertilizer analysis has been 
found. Henry and Morrison (21) report that the average nitrogen 
content of 406 samples of cottonseed feed was 3.92 per cent. This 
is equivalent to 4.77 per cent of ammonia. The percentages of phos- 
phoric acid and potash in cottonseed feed are given as 1.47 per cent 
each, so the contents of the principal plant-food constituents of 
average cottonseed feed agree rather closely with the corresponding 
figures for the cocoa press cakes examined. 
The amount of plant-food elements present in the straight cocoa- 
nibs cakes, in general, will vary inversely with the amount of fat 
present. This is borne out by the data for total ammonia in Table 2. 
