§ 215. W. L. Hiepe, taking into consideration the fact that pure coffee has 03 per cent. of chlorine, while chicory has 28 per cent. of chlorine, has proposed to calculate the percentage of mixtures on this data. If this method should be accepted, it will necessitate a most careful incineration; for in the majority of ordinary cases involving ash-taking, two-thirds of the chlorine is volatilised. Prunier, again, has attempted to determine the coffee directly by weight: 2 grms. of the mixture of coffee and chicory are weighed out, and the finer powder is separated by sifting through fine silk. This is composed entirely of coffee, as may be proved by microscopic examination. That which remains on the silk sieve is moistened with water in a test glass; after some hours it is thrown upon a piece of stretched cloth, and crushed with the fingers. The grains of coffee resist the pressure, whilst those of chicory penetrate under these circumstances into the cloth, and adhere to it. The cloth is dried, and it is then easy to detach the coffee, which is added to the fine powder from the first operation, and weighed after complete drying; the chicory is calculated from the loss. H. Hager's recent investigations into coffee adulteration may be detailed as follows:-To examine the unroasted coffee for artificial colouring-matters, he treats the berries with cold water; when, if the berries are in their natural state, the water is scarcely coloured. 50 grms. are next macerated with water, to which 1 per cent. of nitric acid has been added, and then hydric sulphide is passed through the filtrate; from this solution chloroform will extract indigo if present. Berlin-blue and alkanet pigment may be dissolved out from the berries by carbonate of potash solution, and then precipitated by hydrochloric acid. He finds also that when thrown into water, imitation or artificial berries will sink to the bottom, while good berries swim. On treating 3 grms. of powdered coffee with 20 grms. of cold water, and filtering, after the lapse of half an hour the filtrate should be feebly yellow, and not taste in the least degree bitter; in presence of lupin-seeds the taste is markedly bitter. With regard to the "swimming test," he recommends a saturated solution of rock salt. 2 grms. of the coffee are placed in a narrow test cylinder with 15 to 20 cc. of the cold saline solution; the coffee is shaken up with this, and then allowed to stand for an hour; after this time the coffee swims to the surface, and the water remains uncoloured. Lupin-seeds generally colour the salt solution yellow, and give a strong deposit. The filtrate from pure coffee gives no precipitate with picric acid, tannin, iodine, or alkaline copper. Ferric chloride strikes a green colour with false coffee; with starches iodine strikes a blue colour; with astringent matters, ferric chloride a black colour; if sugar from chicory, dates, &c., is present, alkaline copper solution is reduced. Lupin-seeds give, when extracted by weak sulphuric acid water, only a slight turbidity with mercury potassic iodide. Coffee, on the contrary, under the same circumstances, gives a strong turbidity; but if this is doubtful, the theine can be extracted from the solution by shaking it with chloroform or benzole, which dissolves the theine, but leaves the lupin. Hager has also a different method of taking the "extract:" 10 grms. of coffee, 1 grm. of oxalic acid, and 80 cc. of water are mixed by shaking, and digested at 100° for 3 hours, filtered, and washed with water until the filtrate is no longer coloured. The filtrate is evaporated to dryness. Pure coffee at the most yields in this manner 2.5 to 3 grms. of extract (including the oxalic acid), while chicory gives 5 to 7 grms., and other substances similarly much increase the extract. His reason for using oxalic acid is because of its changing starch into dextrine, and quickening the filtration. § 216. The seeds of Cassia occidentalis* are now being, to some extent, used as an adulterant, and as a substitute for coffee. In Germany the ground and roasted seeds have been sold under the name of " Mogdad" coffee, and it is said that neither by the taste nor by the general appearance can the addition of cassia seeds be detected, if such addition does not exceed one-fifth of the weight of the coffee. The seeds are small, flattened, oval, smooth, marked on each side of the two flattened surfaces with a slight circular groove or depression; when magnified the surface of the seed is somewhat tuberculated. The integuments are wonderfully hard and leathery, and in the fresh state most difficult to grind or cut; they are, indeed, about the consistence of the leathery seeds of Nux vomica. The microscopical structure is very distinctive; the covering of the seed has first a layer of hard tissue, with fine striæ-like, perpendicular tubes radiating from the centre towards the circumference. These have a marked resemblance to the dentine of teeth, and may be appropriately called the dentine-like layer. There is a dark layer beneath the dentine layer, and this passes into some thick-walled four to five-sided oblong cells, filled with an orange-red colouring-matter. Within the coloured cells are oval, round, or angular cells (according to the pressure), * Holler: J. Dingl. Pol. Journ., 237, p. 61; 238, p. 164. filled with granular matter, and making up most of the substance of the seed (see fig. 40). Fig. 40.-Section of Seed of Cassia occidentalis, x 170. The composition of Mogdad coffee is as follows:: $217. Date Coffee.- Recently there has been established a company for the manufacture of what is termed "Date coffee," a preparation made from torrified dates, and mixed with coffee, in the proportion of one-fourth coffee and three-fourths dates. A sample recently examined presented the appearance of a darkbrown, rather sticky powder, having a sweetish smell, but no coffee odour. On being thrown into water the water was immediately coloured, and the powder sank to the bottom. The specific gravity of the infusion was nearly that of pure chicory, viz., 1019-6. The microscope showed some fragments of coffee, as well as large loose cells and structures, quite different from *The seeds of Cassia occidentalis give 10 per cent. of ash. those of coffee, and there was scarcely a trace of theine. The general analysis gave : 5 The ash contained 262 P2O, and 13 silica; 628 per cent. of an oily and resinous matter was also separated. The large amount of sugar would alone be sufficient to distinguish it from coffee, and there will not be the slightest difficulty in the identification of the substance should it be ever used in such a manner as to come under the Sale of Food and Drugs Act. In regard to other adulterations, a great variety of starchholding substances, with the cereals, may be entirely excluded, as certainly not present, if no dirty-blue or violet coloration is produced by iodine in an infusion of coffee. In order to apply this test properly, the infusion should be decolourised, which is most rapidly done by a solution of permanganate of potash. Coffee itself, as before stated, contains no starch. Burnt sugar, or caramel, is usually detected by observing the rapid darkening of water on which a little coffee is sprinkled, and the particles (on examination in water by the microscope) reveal themselves by the absence of organised structure, and the coloured ring, arising from partial solution, round each. BIBLIOGRAPHY. ALLEN, A. H.-Chem. News, vol. xxix., 130, 140; Analyst, Jan., 1880. p. 408; Sur l'enrobage des cafés, Journ. Chim. Med., 4e série, 1869, DESSAULT.-Journ. Chim. Méd., 5e série, 1866, t. ii., p. 435. FRANZ, A.-Arch. Pharm. [5], 4, 298, 302. GIRARDIN, J.-Ann. d'Hyg. et de Méd. Lég., 1834, t. xi., p. 67 et p. 96. HAGER, H.-Zeitsch. Anal. Chem., vii. 388; xii. 232; xiii. 80; xv. 474. HLASIWETZ.-Ann. Chem. Pharm., cxlii. 219. HUSEMANN.- "Die Pflanzenstoffe." Berlin, 1871. HUSSON, P.-Etude sur le Café, le Thé et les Chicorées. Ann. de Chemie et de Physique, 1879, 419. HORSLEY.-Pharm. Journ., 1855, t. xv. LABICHE.-Journ. Chim. Méd., 4e série, t. iv., 1858, p. 627. LASSAIGNE, J. S.-Journ. Chim. Méd., 3e serie, 1853, t. ix., p. 365. LEVESIE, O.-Arch. Pharm. [5], 4, p. 294. ORMAN, V.-Falsification de café moulu avec la semence de ricin. Journ. Chim. Méd., 3e série, 1852, t. viij., p. 50. PFAFF.-Schweigg's Journ., lxii. 31. ROCHLEDER.-Ann. Chem. Pharm. 11, 300; lxiii. 193; lxi. 39; lxxxii. COCOA AND CHOCOLATE. §. 218. The cocoa of commerce is made from the roasted seeds* of the Theobroma cacao, a tree belonging to the natural order Byttneriaceae, whole forests of which exist in Demerara. It is also more or less extensively grown in Central America, Brazil, Peru, Caraccas, Venezuela, Ecuador, Grenada, Essequibo, Guayaquil, Surinam, and some of the West Indian Islands; and its cultivation has also been attempted (in most cases successfully) in the East Indies, Australia, the Philippine Islands, the Mauritius, Madagascar, and Bourbon. The principal kinds of cocoa in commerce are known under the names of Caraccas, Surinam, Trinidad, Grenada, Jamaica, Dominica, Guayaquil, Venezuela, Bahia, Brazil, and St. Lucia. The seeds are officinal in the French and Norwegian pharmacopoeias. They are ovate, flattened, 2 to 2 cm. [7 to 9 inch] long, and 1 to 14 cm. [39 to 58 inch] broad, and covered with a thin red or grey-brown friable shell. The taste of the fresh seed is oily, bitter, and rather unpleasant. The seeds, on being submitted to a kind of fermentation (technically called the sweating process), lose in a great measure this disagreeable flavour, and develop an aromatic smell. Seeds which have been subjected to this treatment are best suited for the manufacture of chocolate, while those which have been simply roasted are richer in cocoa-butter. § 219. Microscopical Structure of the Seed.-The seed, when deprived of the husk, consists for the most part of several irregularly-shaped angular divisions, filled with a large number of oval cells, within which is contained a peculiar starch, as well as a fatty matter. Near the surface these cells are angular, and of a pronounced red colour, but the tint is somewhat variable. The starch-granules are perfectly round, normal measurement * The seeds simply dried are also sold. |