The experiments of these chemists have given as a minimum for green coffee a density of 1041, a maximum of 1368; for roasted coffee, a minimum of 0·500, and a maximum of 0.635; a very high roasting will, however, give less than 0.500. The density taken in this way is also stated to indicate factitious coffees.

The hygroscopic moisture, theine, gum, astringent principles, and ash are all determined precisely as in the case of tea. According to the chemists of the Paris Municipal Laboratory the hygroscopic moisture in green coffee should not exceed 12 per cent., in roasted 3 per cent.

The coffee fat may be conveniently estimated by putting a known quantity in the fat-extraction apparatus figured at page 67; the best solvent to use will be petroleum ether, since it has less solvent action on the theine than ether. When the process is finished, the petroleum is evaporated to dryness in a tared dish. As thus obtained, the fat is almost, but not quite, pure.

ADULTERATIONS OF COFFEE AND THEIR DETECTION.

§ 214. The sophistications of coffee are numerous; chicory, roasted cereals of all kinds, wheat, rye, buck-wheat, potato flour, mangel-wurzel, acorns, lupine seeds, ground date-stones, caramel, and various leathery seeds have all been detected. Coffee damaged by sea-water is also commonly washed, first with water, then with lime water, dried and roasted, or sometimes coloured with an azo dye to give it a bright appearance.

Imitation coffees or coffee substitutes are manufactured on a large scale in America, Hamburg, and also in this country. Wiley has given a useful list of imitation coffees which have been examined in the laboratory of the U. S. Department of Agriculture; the list comprises the following mixtures which were pressed and moulded into berries or pellets:*

Coffee, bran, molasses.

Wheat flour, coffee and chicory.
Wheat flour, bran and rye.

Chicory, peas (or beans), barley.

Wheat, oats and buckwheat.

Wheat flour and sawdust.

Hulls of leguminous seeds formed into granules with molasses and roasted.

Pea hulls and bran.

* U. S. Dep. of Agriculture, Div. of Chem., Bull., No. 13.

It may be stated generally that such adulterations are best detected by a microscopical examination, but that they usually also present marked chemical differences, being for the most part, deficient in caffeine, high in sugar, low in fat and having high aqueous extracts. The general percentage composition of various imitation berries, as given by various chemists, is summarised in the following table:

Microscopical Detection of Adulterations in Coffee.-A practical, though not a scientific, distinction of substances used for the adulteration of coffee, is to divide them, for microscopical purposes, into two classes, the hard and the soft. If ground coffee is sprinkled in water, and allowed to soak for a little time, there is scarcely a particle which does not feel resistant or hard when rubbed between the fingers, the only soft portions of the coffee berry being the embryo, and this is so insignificant in quantity that it is not likely to cause embarrassment. The soft substances which have been used to adulterate coffee are chicory, figs, dandelion roots, and portions of the fruit of the ceratonia or carob-bean; while the hard substances are vegetable ivory, date-stones, acorns, and other hard seeds.

The soft tissues of the roots of the chicory* and dandelion

* Chicory is so readily detected that we scarcely require a direct chemical test. A. Franz has, however, pointed out that an infusion of coffee, when treated with copper acetate and filtered, yields a greenish-yellow filtrate; an infusion of coffee containing chicory yields, when similarly treated, a dark red-brown filtrate.-Arch. Pharm. [5], ix. 298-302.

A method of detecting chicory has been described by C. Husson. Accord

abound with vascular bundles, and it
is never difficult to see the spiral and
other vessels; similarly, the laticiferous
vessels in the tissues of the fig are
extremely distinctive. In the softer
tissues of the ceratonia or carob-tree
fruit are to be found large cells con-
taining bodies which, at first sight, look
like starch granules, the surface being
in wrinkles (see fig. 56). They are in-
soluble in water, alcohol, and dilute
sulphuric acid. The characteristic test
is, however, that they strike a blue or C7
violet colour with a warm solution of
potash. And as these bodies are widely
distributed throughout the fruit, the
test reacts with the smallest fragment.

Finely ground date-stones and vegetable ivory are not so easy to detect, mainly because the particles are, for the most part, opaque, and it entails considerable trouble and some skill to prepare sections sufficiently clear to make out the details of structure.

Vegetable ivory is derived from the Phytelephas macrocarpa, and is much used for buttons and various other purposes. In the working of the ivory there is considerable waste, ing to the latter, the chicory is often prepared by roasting with rancid fat. He discovers this by putting in a flask 10 grms. of chicory with 50 grms. of glycerin and 20 drops of hydrochloric acid, and the mixture is boiled and filtered. The filtrate is added to an equal volume of ether, and placed in a flask which, again, is put in a bath with boiling water. When pure ether-vapour rushes out of the bottle, the vapour is lit, and under the combined heat, the fatty matter rises to the surface of the glycerin, and is dissolved in the ether. When the flame diminishes in intensity, it is extinguished, and the ether allowed to evaporate spontaneously. On exposure to cold, fatty drops form gradually; these are examined by the microscope, and are drops of crystalline fats, such as are not yielded by pure coffee.

Fig. 56.-A section of the carob

tree fruit, x 160-ep, epidermis superficial view, showing a stoma, st; p, brown parenchyma; cr, cells containing crystals; b, bent fibres; st, hard cells, thickened by deposit; r, a layer of thin walled cells, but scattered throughout are fibres and thickened hard cells; m, the middle layer containing spirals; sp, and the peculiar bodies, g, described in the text.

hence it may be obtained at a very low rate, being, indeed, so much refuse. The ivory consists of elongated, equally thickened cells (see fig. 57 B), perfectly colourless, and dotted all over with

Fig. 57.-A, Section through the vegetable ivory nut-o, outer coating of the seed; e, endosperm, composed of thickened porous cells.

B, Individual fibres separated from o, the outer coating of the seed, x 160 (after MOELLER).

pores; the contents of the cells are granular, and seem to be composed of a vegetable albumen, with here and there a few drops of fat. In sections of the ivory nut itself, there is also to be seen a thin shell or epidermal layer (see fig. 57, A) consisting of peculiar fibres. The ends of the fibres are often thickened or clubbed; they are about 02 mm. broad and 2 long, are thickened by deposit, and contain a reddish-brown substance. The largest fibres are on the outside of the layer, while the shorter fibres occupy the inner part of the seed-coating; the fibres are interlaced or felted in every direction. The seed-coating bears a very small proportion to the vegetable ivory, and is not likely to be found as fragments of the ivory itself.

Date-stones* possess a very distinctive structure.

The epi

* Date Coffee.-There was established, a short time ago, 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

dermis consists of elongated cells, forming, when looked at from above, irregular oblongs, the cell-walls are thickened irregularly, and they are frequently pitted (see fig. 58). In the parenchyma

Fig. 58.-Tissues of the date-stone, x 160-E, endosperm; B, epidermis; T, irregularly shaped tubular cells filled with tannin-like substances.

of the stone are curious irregularly-shaped long cells, which contain a tannin, and are coloured dark-green by ferric chloride solution. The endosperm is the hardest part of the date-stone, and is very similar in structure to vegetable ivory, but the cells are smaller and rounder, and the cell membranes are not so thickened by deposit.

The leguminous seeds are all built on a similar plan; they have at least two characteristic structures-viz., a layer of regular lengthened cells with their long axis set radially (see

and three-fourths dates. A sample recently examined presented the appearance of a dark-brown, 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 those of coffee, and there was scarcely a trace of theine. The general analysis gave:

Per cent.

The ash contained 262 P20, 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.