COCOA BY-PRODUCTS 31 
DRYING THE EXTRACTED SLUDGE 
The favorable effect on the composition of the dried product of 
drying the sludge at the lower temperatures that prevail in steam- 
heated driers is obvious, but the nature of the extracted cocoa pre- 
sents a serious obstacle to drying large batches of the material by 
steam heat. As a first consideration, the cost of drying must be 
kept low, because of the comparatively low value of the dried prod- 
uct, and this is said to preclude the employment of a vacuum drier. 
But steam heat without the aid of a partial vacuum in the drier 
is reported to be ineffectual, as the physical condition of the sludge 
is such that, while a lump of it will dry readily on the immediate 
surface, the crust thus formed protects the doughy interior from 
further dehydration. On the other hand, the higher temperatures 
prevailing in the direct-heat rotary drier make it both effectual and 
economical, but its use is attended by some charring of the product. 
Certain effects of charring on the properties of the dried cocoa 
sludge are shown in Tables 3 and 4. Charring accounts for the 
abnormally low content of volatile matter of sample 107, which 
means a higher percentage of fixed carbon, as the latter is merely 
the total organic matter less the volatile matter. This in turn 
accounts for the high calorific value found for the nonf atty organic 
matter of this sample, the fixed carbon of such material being prac- 
tically the same as charcoal, which has a calorific value of about 
7,000 Calories per kilogram. That charring also slightly depresses 
the solubility in water of the nitrogen is indicated by a comparison 
of the results reported for the several extracted cocoas in Table 3 
(although more significance could be attached to these results if the 
samples were from the same lot of extracted cocoa). On the other 
hand, the solubility of the nitrogen in sample No. 106 was some- 
what increased by drying at 100° C. This apparent increase in 
solubility may be due to the fineness of the particles after drying 
and grinding. 
UTILIZATION OF EXTRACTED COCOA 
Laboratory tests with unextracted cocoas showed that, for a par- 
ticular sample, the solubility in water of the nitrogen was increased 
somewhat by a preliminary extraction of the fat with ether or 
petroleum ether. This is merely additional evidence in support of 
the theory that fat or oil, when present in large quantity in a fer- 
tilizer material of this type, tends to envelop and waterproof the 
particles containing plant food, delaying their dissolution when 
the material is applied to the soil and thus lowering the availability 
of the fertilizer constituents. It is to be noted that the true fat 
content of the commercial, dried, extracted cocoa averages less than 
2 per cent. 
The factory-dried extracted cocoa contains about 5.4 per cent 
of total " ammonia," as against 4.8 per cent for the average am- 
monia content found for all of the by-product cocoa cake samples 
examined. Two of the samples of dry-pressed cake, however, con- 
tained as much ammonia as the defatted residues; and on the basis 
of the dry, fat-free matter the straight cocoa press cakes surpass 
the extracted product in ammonia content. 
