The Starches.

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Rice. The engraving shows the appearance presented
by starch granules of rice when magnified 420 diameters.
The cells of rice are also shown in this engraving. The
starch corpuscles are very small, angular, and have de-
pressed centres, and raised edges.

Wheat starch granules magnified 420 diameters. Some are very small, others very large; they are chiefly round and have generally a depression (hilum) in their centres. The larger granules appear like thin-edged discs.

Rye. This engraving depicts the starch corpuscles of rye flour, magnified 420 times in diameter. The cross on the granule is that observed through the polariscope. The granules resemble those of wheat starch, but differ from the latter in the smaller ones being much smaller than the lesser wheat starch corpuscles, whilst the larger rye granules often have a three or four-rayed hilum.

Oats.-The engraving shows the structure of the starch corpuscles of the oat, magnified 420 diameters. They are small, many sided, do not show concentric layers, have central depressions, and thickened edges, and occur often in clusters.

Indian Corn.-The starch corpuscles of Indian corn magnified 420 times, present the appearance shown in the figure. They resemble those of the oat, but differ from them in being detached from each other, in being much larger, and in exhibiting under the polariscope well marked crosses.

Bean. The starch corpuscles of the bean shown (magnified 420 diameters) in the engraving are kidney. shaped their hilums are long and divided.

Arrowroot.-In the engraving is shown the appearance presented by maranta or West Indian arrowroot, when magnified 420 times their diameter. They are irregularly ovate, sometimes nearly triangular, are marked by delicate concentric lines, and have at their larger end a circular or valley-like depression or hilum.

Tous-les-Mois.-This (Canna) arrowroot is composed of enormous granules; mostly flat, ovate, and with hilum at narrow end. Magnified 100 diameters in the engraving.

Tapioca. This starch (magnified 420 diameters in engraving) occurs in small detached granules, and in groups of corpuscles. They are oblong, but when viewed endways appear circular.

Potato starch occurs in oval, circular, and oyster shapes. The concentric lines are well defined, and the hilum is situated at the narrow end. Under the polariscope the cross is not so regular as in the case of tous-les-mois.

Sugar is generally met with in a pure state. Finzel's "crystals" I find contains 999 parts per 1,000 of absolutely pure sugar. I

have only met with one case of adulteration, and that was with flour. The sand and clay in raw sugar are only accidentally present, and always in small quantity. Raw sugar contains the spores of plants and various vegetable impurities, and sometimes vast numbers of a species of mite, the Acarus sacchari. The low class sugars are often acid, and on the whole it seems best to use filtered sugar, of which high and low qualities are on sale.

Tea. An extensive botanical knowledge is necessary to enable one to discriminate all the foreign leaves found in tea; if, however, we are familiar with the appearance of the tea leaves, we can at least ascertain whether or not a sample under examination is composed of them. Steep the tea in water, unrol the leaves, place them on thin pieces of glass and examine them with low microscopic power. Tea contains from 3 to 5 per cent. of a crystallisable nitrogenous substance termed thein, about 14 per cent. of albuminous compounds, from 15 to 25 per cent. of tannin, 20 to 30 per cent. of cellulose, and smaller amounts of starch, gum, fats, mineral matter, &c. Hot water should extract at least one-third of its weight from good tea. According to Wanklyn, A. H. Allen, Wigner, Peligo, and Zöller, &c, tea yields from 5 to 6 per cent. of ash, which is mostly soluble in hydrochloric acid. In Assam tea the ash is least soluble; but in other kinds a larger amount of insoluble ash is generally indicative of adulteration. To determine the amount of extractive matter, treat with boiling water, and having dried the exhausted leaves, weigh them. The loss of weight tells the amount of soluble matter, making allowance for the amount of water contained in the leaves. Tea is adulterated with exhausted leaves, rotten leaves (rarely), foreign leaves, and mixed with catechu or some similar substance, gums, dextrin, iron filings, &c. When the watery extract is evaporated to dryness, the mere appearance of the residue often affords a clue to the nature of the sophistication, especially in the case of such gums as catechu. When tea contains less than 30 per cent. of soluble matter it is, in all probability, adulterated, and certainly so when the extractive matter is under 20 per cent.

The colour of green tea is sometimes imparted to it in England by Prussian blue, indigo, and other dyes. The amount is small, and if it do not exceed 0.5 per cent. may be disregarded. In Dublin several thousand pounds weight of tea, composed chiefly of exhausted leaves and catechu, have been destroyed on my certificate by order of the magistrates. Iron filings (to darken the infusion by striking a black hue with the tannin) have been detected in tea. The magnet extracts them from the leaves, and when treated with acid, inflammable hydrogen gas is evolved.

Coffee berries contain from 30 to 40 per cent. of cellulose, 10 or 12 of water, 10 to 12 of fats, about 15 of dextrin, and 1 of caffein. The ash of coffee, according to Allen, averages 4 per cent. of which four-fifths are soluble in water; whilst chicory, which is the common adulterant of coffee, yields 5 per cent. of ash, 34 parts of which are

soluble in water. Coffee loses by roasting from 15 to 25 (generally 18) per cent. of its weight, and becomes lighter. Its sugar varies from 1 to 6 per cent. ; sometimes it is absent. Hot water extracts from 20 to 35 per cent. of soluble matter from roasted coffee. Coffee is adulterated with chicory, burnt sugar, and biscuits, roasted grains of different kinds, mangel wurtzel, malt, spent tan, iron rust, earthy matters, &c. The only adulterants which I have met with were chicory (in most samples), burnt sugar, farina of different grains, and earthy matters. As starch never occurs in pure coffee, the microscope readily detects that adulteration. Chicory is easily discovered by the same means, owing to the circumstance that when it is present abundance of vasa laticentia, and dotted or barred ducts are observable. The cells of mangel wurtzel, carrot, and parsnip resemble chicory. The examiner should familiarize himself with the microscopic appearance of these substances, unmixed, and mixed with coffee. A rather weak tincture of iodine added to coffee causes any starch granules it may contain to become deep blue. A few grains of coffee placed on water remain for some time before sinking into the fluid, but if chicory or caramel (burnt sugar) be present, they sink at once and colour the water, The amount of chicory may be determined by the microscope, and examination of soluble portion of ash. Sugar may be estimated by the copper method in the usual manner. Chicory contains nothing which warrants its use as a food or stimulant; and as it is very astringent, its constant use may, in some cases, prove injurious.

(a) coffee (b) chicory (c) wheat starch. The engraving shows the microscopic appearance presented by coffee adulterated with chicory and roasted wheat flour. The dotted

or barred spiral vessels, so abundant in the chicory, do not occur in coffee, and, therefore, their presence in coffee indicates adulteration by chicory. The starch granules of wheat or other grain are also readily detected by the microscope, especially when coloured blue by the application of dilute tincture of iodine.

Cocoa often contains about 50 per cent. of fats, and 20 per cent. of albuminoids; and it includes (as stated) from a trace to 19 per cent. of starch. The high proportion of starch may have been found in adulterated cocoas. The analyses of this substance published are very discordant, except with respect to the fat, which varies from 44 to 52 per cent. Foreign starches may be detected by the microscope. As there is no sugar, or, at most, a trace, in cocoa, this substance, when present, is added. Sugar and farina are generally mixed with cocoa to form chocolate. Flake cocoa consists of nibs

and shells ground together.

"Soluble" cocoa is generally prepared by abstracting fat from the nibs, and replacing it by farina and sugar. Wanklyn says that good cocoa nibs ought to yield to cold water 9 per cent. of its weight. A mixture of chicory and cocoa gives a deep coloured, and cocoa alone a pale, infusion. Cocoa leaves from 3 to 4 per

cent. of ash after its combustion.

Confections. During the year 1870 I made an examination of 123 specimens of sugar confectionary. Those manufactured at three establishments were quite pure: the collections obtained at ten other shops contained poisonous pigments and other impurities in a large proportion of the items.

Out of 40 confections coloured yellow, only 2 owed their hue to saffron. One was coloured with gamboge; and all the others were coated with chromate of lead, or plumbic chromate, commonly termed chrome yellow. The amount of the latter pigment varied fromth to less than oth of the weight of the confections. The common sugarstick sold at 14d. per two ounces contained the largest proportion of chromate of lead. 12 articles-chiefly lozenges and "sugar almonds "-had a bright orange hue, due to the presence of a variety of chromate of lead. 38 of the specimens-comprising "peaches," sugar almonds, lozenges, comfits, sugarstick, sugar balls, &c.-had various shades of red, from a faint pink to a bright scarlet. Of these, 36 specimens were coloured with cochineal, 2 contained vermillion (mercuric sulphide, or bisulphide of mercury) in the proportion of 4 grains per ounce of the confection-which was the cheapest kind of sugarstick.

At one time arsenite of copper was frequently used to impart a brilliant green colour to confectionary; but the numerous accidents which occurred from the employment of this poisonous pigment have so alarmed the public that green confectionary is now scarcely to be met with. Only one of the specimens examined by me was coloured green, and that was only a small figure of a baby, with a green frock on it. The colour was composed of a mixture of Prussian blue and chromate of lead.