When the microscope has detected chicory, and it is certain that nothing but chicory is present, the most reliable guide is the density of the infusion. Of the strength given, if the specific gravity of coffee infusion be taken as 1008.5 and that of chicory as 1023-0, then the following table, from the author's experiments, will be a fair guide to the amount of adulteration. The error usually lies within 3 per cent., while with calculations based on soluble ash, the possible error is higher. It hence follows that the analyst must be very careful in his statements as to the percentage of chicory. The certificate should say "about per cent.;" or supposing that from the soluble ash and from the specific gravity, as well as from the microscopical examination, a coffee seems to contain 40 per cent. of chicory, it will be safe to subtract 5 per cent. for error, and give the amount as "at least 35 per cent." TABLE XXVIII., GIVING THE APPROXIMATE PERCENTAGE OF CHICORY IN A DECOCTION OF COFFEE AND CHICORY. $217. 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 these 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. The 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. 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 dextrin, and quickening the filtration. 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 colouration is produced by iodine in an infusion of coffee. In order to apply this test properly, the infusion should be decolorised, 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. DESSAULT.-Journ. Chim. Méd., 5e série, 1866, t. ii., p. 435. FRANZ, A.-Arch. Pharm. [5], 4, 298, 302. GENIN, V., in C. Girard and A. Duprè's "Analyse des Matières alimen taires. Paris, 1894. GIRARDIN, J.-Ann. d'Hyg. et de Méd. Lég., 1834, t. xi., p. 67 et p. 96. HLASIWETZ.-Ann. Chem. Pharm., cxlii. 219. HORSELY.-Pharm. Journ., 1855, t. xv. HUSEMANN."Die Pflanzenstoffe." Berlin, 1871. HUSSON, P.-Etude sur le Café, le Thé et les Chicorées. Ann. de Chemie et de Physique. 1879, 419. KORNAUTH, C.-Rev. Inter. Scient. des Falsifications, iii., 195, 196. LASSAIGNE, J. S.-Journ. Chim. Méd., 3e série, 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.-Schweigger's Journ., Ixii. 31. ROCHLEDER.-Ann. Chem. Pharm., 11, 300; lxiii. 193; lxi. 39; lxxxii. 194; Journ. Pract. Chem., lxxii. 392; Wien. Akad. Ber., xxiv. 46. ROCHLEDER & HLASIWETZ.-Ann. Chem. Pharm., lxxij. 338. SPENCER, G. L.-Tea, Coffee, and Cocoa preparations, U. S. Dep. of Agricult., Div. of Chemistry. Bull., No. 13, 1892. WANKLYN, J. A.-" Tea, Coffee, and Cocoa." Lond., 1876. 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 Byttneriacea, 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 1 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. The cocoas of commerce are deprived of the husk, and consist of the ground or entire cotyledons. The cotyledons are made up of a parenchyma of small, polygonal, thin-walled cells (fig. 61). Within these cells are the very small starch granules, measuring about 5 micro-millimetres [002 inch]. In some of the cells the starch is in little lumps, mixed with fat and albuminous matters. B, Fig. 61.-Tissues of cocoa, x 160. A, Epidermis, beneath which are seen cells containing two different kinds of crystalline cell contents; f, crystals of fatty acids; t, crystals of theobromin; h, a hair. The tissues of the seed proper; sp, spiral vessels; a, thickened cells; P, parenchyma, some of the cells of which are filled with various cell contents. The starch is distinguished from rice-starch by the granules being round and not angular. It possesses considerable resistance to hot water, and the reaction with iodine is slow-a quick-blue colour being only brought out by the addition of the chlor-iodide of zinc. Careful measurements made by Ewell give the maximum diameter as 0.012 mm., minimum 0.002 mm., average about 0.006 mm. Some of the cells contain "cocoa red," which is coloured blue by a solution of ferric chloride, and dissolved by strong potash to a green, by dilute sulphuric acid to a red, and by acetic acid and alcohol to a violet solution; but the fresh seeds are colourless. The cotyledons are covered with a thin glass-clear epidermis, consisting of at least two layers of cells, and where it folds between the cotyledons of several layers.* These are very transparent, they often contain crystals of theobromin, and other crystals supposed to be those of a fatty acid. Attached to the epidermis are to be found curious club-shaped hairs (fig. 61). The chief distinguishing marks of the husk are a large-celled epidermis, and small thick-walled cells; but, unless as an adulteration, the husk will not occur in ordinary cocoa. |