38 BULLETIN 1413, U. S. DEPARTMENT OE AGRICULTURE 
spread for any other constituent whose percentage in the samples 
was determined. Assuming 53 per cent as the fat content of pure 
roasted nibs, and accepting 3.5 per cent (the average reported 
figure) as the fat content of pure shells, it follows that the two 
samples of commercial shells (Nos. 115 and 117) with a fat content 
of about 8.5 per cent, must contain approximately 10 per cent of 
nibs. The presence of this quantity of nib material in these sam- 
ples of commercial cocoa shells accounts for the favorable analytical 
results obtained in the laboratory determinations of the solubility 
and quality of their nitrogen. It may be noted, for example, that 
relatively much more soluble and active insoluble nitrogen was 
found in these samples than Cathcart (5, p. 45) found in the sample 
discussed on page 35, which must have contained little or no nib 
material. 
Comparison of the composition of the shells samples (Table 5) 
with the average composition of the cocoa press cakes, as given in 
Table 2, shows that these commercial cocoa shells contained less 
than three-fourths as much total" ammonia," slightly less phosphoric 
acid, but appreciably more potash than the average for by-product 
press cake. The shells also contain more potash than the dried 
extracted cocoas (Table 4), but only about two-thirds as much 
ammonia and phosphoric acid. 
The percentage solubility of the nitrogen of these commercial 
shell samples, it will be noted from Table 3, is a little less and the 
quality of the insoluble nitrogen is somewhat lower than is the 
case with the by-product press cakes and colvent-extracted cocoas; 
but the differences are hardly sufficient to affect adversely the rela- 
tive market value of a unit of ammonia in shells in comparison 
with that of a unit of ammonia in the other cocoa materials. 
A unit of ammonia in the commercial shells or cocoa-shell 
meal, as a matter of fact, commands a slightly higher price in the 
fertilizer materials market than a unit of ammonia in the cocoa 
press cake; whereas the ammonia in the commercial extracted cocoa 
ordinarily has been rated at the same price per unit as that in the 
shells. The reason that cocoa shells, in spite of the slightly lower 
quality of their nitrogen, can maintain a better price per unit than 
the by-product cake, is to be found in the better physical condition 
of the shell material after grinding. Shell meal is a good absorb- 
ent material and drier and, being more fibrous than cocoa powder, 
it has less tendency to get sticky in moist mixtures. It is porous 
and very light in weight, 1 cubic foot of the powdered shells weigh- 
ing only 32 pounds, according to Knapp (24) > These properties 
and the fact that the material has a dark, rich color recommend the 
shells to commercial fertilizer mixers. As a conditioner for mixed 
fertilizers and " rough ammoniate " filler, cocoa shells appear to 
have given satisfaction to fertilizer manufacturers using them. 
An estimate has been made of the relative market value for fer- 
tilizer purposes of shells, press cake, and extracted cocoa, based on 
the current prices for ammonia and potash in this type of material. 
Assuming the price for a unit of ammonia in press cake to be 90 
per cent of that for a unit in shells or in extracted cocoa, and using 
the average figures for the ammonia arid potash contents of the 
