duced varies from 6 to 12 per cent of the weight of raw beans. The quantity of fines obtained to a certain extent is supplemental to the quantity of separated shells. Where the shells amounted to 6 or 7 pounds per 100 pounds of raw cacao, the fines amounted to 6 or 7 pounds, but where 12 pounds of commercial shells were obtained the fines amounted to little more than the weight of the germs. Probably Knapp's data are about as true for average American practice as they are for conditions in English factories. He reports (24) the production of 10.5 pounds of separated shells and 4 pounds of smalls or fines per 100 pounds of raw cacao.

QUANTITY OF COMMERCIAL SHELLS PRODUCED

The imports of crude cacao into the United States for the calendar years 1923 and 1924 were 207,118 and 189,141 short tons respectively, or, in round numbers, about 200,000 tons 2 of the beans per year (54, p. 48).

Since from 6 to 12 pounds of shells are produced per 100 pounds of raw cacao, it follows that the production of factory-separated shells in the United States amounts to between 12,000 and 24,000 tons annually. Estimating the quantity of commercial shells at 10 per cent of the weight of raw beans, it may be assumed that since the World War from 15,000 to 20,000 tons of cocoa shells have been produced each year in this country.

UTILIZATION

Cocoa shells, unlike the by-product cake and extracted cocoa, have long been recognized as an established article of commerce. Large quantities of the ground shells, known as cocoa-shell meal, are consumed in the manufacture of commercial mixed fertilizers. A certain quantity is used in this country in the preparation of proprietary feed mixtures, particularly in goods of the calf-meal type. Cacao shells also have been used by manufacturers of theobromine for the extraction of the contained alkaloid, but are considered less valuable for this purpose than the low-fat pressed cake. (See p. 27.) Most of the shells produced in the United States, it is believed. are consumed in the three ways mentioned.33

Doubtless the shells are occasionally burned for fuel under the boilers in the producing factories. The value of the shells for this purpose, like that of the cocoa cake, would be influenced by their fat content. Knapp has stated that cacao' shells have a slightly higher value than wood as fuel, the heat of combustion being 7,400 to 8,600 B. t. u. per pound for the shells (24).

COMPOSITION AND AGRICULTURAL VALUE OF SHELLS

There is little specific information relating to the value of cacao shells as fertilizer material to be found in the literature. The

The relative magnitude of this tonnage is shown by comparing it with the annual production of regular American crops. In 1923 the imports of cacao were equal in weight to 44 per cent of the total dry or navy bean crop or to 64 per cent of the peanut production of the country.

Later the

One manufacturer of chocolate mentioned an odd experience in connection with dis rosal of the shells, which, while seemingly trivial in relation to quantity utilization, may le of some significance. Some of the shells were used as bedding for dogs. keeper credited the cocoa shells with having caused the disappearance of fleas with which the animals had been infested. This suggests the possibility that the shells may contain a chemical principle repellant to certain insects.

Canada Experimental Farms report for 1898 contains an analysis showing the crude fertilizer and feed constituents of a sample of the by-product (42); and a similar analysis is given by Lindsey and Smith of the Massachusetts Agricultural Experiment Station (28). Cathcart, of the New Jersey station, investigated the solubility and quality of the nitrogen in a factory sample reported as cocoa shells (8, p. 45).

The Canadian analysis showing a content of 12.9 per cent of fat and 2.63 per cent of nitrogen indicates that the material contained an appreciable quantity of the nibs and was comparable with much of the commercial cocoa-shell meal now being used in fertilizers. This sample contained 1 per cent of phosphoric acid (PO) and 2.6 per cent of potash (KO). The analysis given by Lindsey and Smith, which is the average for two samples, shows their material to have been of the same type. The average figures were-nitrogen, 2.45 per cent, of which about one-third was rated available; phosphoric acid. 0.7 per cent; and potash 2.9 per cent. The New Jersey sample, on the other hand, contained only 1.92 per cent of nitrogen and undoubtedly represents a lower-grade product, as even pure cacao shell usually contains more nitrogen than this, and the presence of nib or germ would increase the nitrogen content. Phosphoric acid was found to the extent of 0.6 per cent. The quality of the nitrogen was investigated by the alkaline permanganate method, with the following results: Water-soluble nitrogen, 0.35 per cent; active insoluble nitrogen, 0.34 per cent; inactive insoluble nitrogen, by difference, 1.23 per cent (8, p. 45). This checks the Massachusetts figure for the "availability" of the nitrogen, as the sum of the water-soluble and active nitrogen amounts to about 36 per cent of the total nitrogen.

An actual field test of the value of cacao shells as a soil amendment is mentioned in a number of books on cocoa and chocolate. The experiment, which was made at Bournville, where one of the great English chocolate factories is located, showed, according to Knapp (26), that the availability of the plant food contained in cacao shells can be improved by keeping the shells in heaps soaked with water and turning over the mass from time to time. Shells that were applied directly to the soil, without previous soaking, did not decompose readily and yielded their plant food very slowly, whereas the shells that had been subjected to wet composting were in a decomposed condition when applied and gave good results, particularly when used to lighten heavy soil.

Much more space in the literature of cocoa and chocolate has been devoted to discussion of the use of cacao shells in the feeding of animals than as fertilizer material. A reason for this is found in the fact that a great deal of the published work is of English and continental European origin; and Knapp has stated that the bulk of the cacao shells produced in England is used in the manufacture of mixed stock feeds (26, 27). Below are given brief summaries of the more important references found in the literature relating to the feeding of cacao shells.

Albert (2) reported in a German periodical, in 1899, that the shells were a satisfactory auxiliary feedstuff for steers. Dean (11), of the Ontario Agricultural College, as a result of feeding experi

ments in 1903, suggested the employment of cocoa shells in the preparation of a substitute for skim milk for calves. Lucas (29) replaced 3.3 pounds of wheat bran, in the ration of dairy cows, with 4.4 pounds of cacao shells, with the result that the flow of milk was materially decreased. He concluded that the unfavorable effect of the shells was due not only to their low nutritive value, but to the presence of a substance inimical to milk secretion. Data on the amounts of digestible nutrients in cacao shells were reported by Kellner many years ago. More recently, Lindsey and Smith, of the Massachusetts station, working with sheep, determined the actual percentage of digestibility (coefficients of digestibility) of the nutrient constituents of commercial cocoa shells (28). They also fed shells to dairy animals and found that from 1 to 3 pounds, mixed with grain, could be fed daily.

The alkaloid content of the shells, in relation to their use as stock food, seems to have been ignored in these earlier investigations cited, and scant consideration appears to have been given to the possible toxic action of the theobromine and caffeine until, during the World War, several French army horses were fatally poisoned, following the feeding of 1.5 kilograms (3.3 pounds) of shells per day. Marchadier and Goujon (33), who were the first to report the poisonings, made a study of the toxicity of the shells in connection with one of the cases, in which seven horses died. The shells under suspicion were found to contain (average) 0.68 per per cent of theobromine and 0.22 per cent of caffeine; so that each horse ingested 13.5 grams of the alkaloids per day, or a total of 54 grams in the four days preceding death. The investigators concluded that the deaths were caused by the alkaloids in these cacao shells, and they suggest that the absence of ill effects following the feeding of shells to horses by earlier investigators may have been due to a lower alkaloid content of the shells used (Compare Zipperer (61)). Another case of poisoning of French army horses is reported by Fonzes-Diacon, who found 0.7 per cent of theobromine in a sample of the cacao shells that had been fed to the horses (15).

Later, Rothéa (40) reviewed both of the preceding investigations, and reported the analysis of a sample of ground cacao shells which he found to contain 1.09 per cent of theobromine. This material contained 9.36 per cent of fat, and 2.77 per cent of nitrogen, and may therefore have contained an appreciable amount of cacao nib, and have been comparable to some of the "cocoa-shell meal" marketed in America. Rothéa also suggests that the residues of shells made safe for feeding through extraction of the alkaloids would have but slight nutritive value.

One of the latest reports on the suitability of cocoa by-products for feeding purposes is that by Griffiths (17). After summarizing much of the preceding work, he concludes that the use of cocoa shells and meal as a feed stuff" can not be considered." A number of proximate feed analyses of cocoa shells are to be found scattered through recent experiment station reports (9, p. 10; 35, p. 230; 43, p. 69). For the most part these show that commercial shells generally contain appreciable quantities of nibs.

RESULTS OF THE PRESENT INVESTIGATION

Two samples of cocoa shells believed to be representative of the commercial product were obtained. One was furnished by a manufacturer of cocoa and chocolate, and represented the average run of his shells by-product. The other was a sample of a lot of cocoashell meal that had been purchased in the usual course of business by a manufacturer of commercial fertilizers.

These samples were analyzed not only to furnish information as to the type of product being marketed as cocoa shells in this country, but also to obtain data that would provide a standard with which to compare (for commercial purposes) the analyses of the relatively unknown cocoa press cake and extracted cocoa. It was thought that the shells, being a product closely related to the press cake and extracted cocoa, would serve admirably as a control material, by which to gauge the relative fertilizer value of the lastnamed products.

The results of a proximate analysis of the two samples of shells are given in Table 5; and the data on the solubility and quality of their nitrogen are included in Table 3.

The amounts of fat, crude fiber, and total “ammonia" found in the samples indicate the presence of important quantities of nib material. The proportion of nibs in a sample of this kind can best be estimated from its fat content, since the spread between the fat content of pure shells and pure nibs is much greater than the

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 samples 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 (8, 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 solvent-extracted cocoas; but the differences are hardly sufficient to affect adversely the relative 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 absorbent 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 weighing 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 fertilizer 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 and potash contents of the