to exhaust any convenient quantity with boiling alcohol, and to evaporate the alcohol to a syrup. This syrup is freed from fatty matters by ether, and the insoluble residue exposed successively to the vapours of nitric acid and ammonia. An amaranth red colour denotes the presence of these substances. M. Biot has, however, stated that wheat from the Caucasus responds to this test although perfectly pure, so that, like many other reactions, it must not in itself be taken as conclusive. M. Marten proposed to separate legumin, and M. J. Lemenant des Chenais has modified Marten's original process as follows:-The gluten is separated in the usual manner, and to the liquid containing the starchy matters is added ammonia, which is a good solvent of legumin. The starch is allowed to deposit, the liquid is filtered, and to the filtrate a very dilute mineral acid is added, which precipitates legumin if present. The legumin is filtered, collected, dried, and weighed. According to M. Lemenant des Chenais, 9 of legumin in 100 grms. of flour represents an adulteration of 5 per cent.

The most scientific process, which embraces a fairly complete examination of flour for the leguminous constituents, is that of Lecanu-The gluten is first separated in the usual way. The washing water, containing starch, soluble matters, and legumin, if present, is passed through a sieve to separate coarse particles in suspension, and then diluted sufficiently and allowed to deposit. The liquid is divided into two parts, and one part is allowed to putrefy or ferment spontaneously. With pure flours the lactic acid fermentation is most common; with flours containing legumin there is a putrid fermentation. The other portion is, after decantation and filtration, concentrated until a yellowish scum forms on the surface; it is allowed to cool, and separated from the albumen which all flours contain. Then legumin is precipitated by adding drop by drop acetic acid. Legumin is identified by its properties. It is without colour, taste, or odour. When dried it is of a horny consistence, insoluble in alcohol, not coloured by iodine, but very soluble in potash or ammonia water, from which solution it may be precipitated by the addition of an acid. The deposit is submitted to a careful microscopical examination, and tested with iodine to colour the starch and leave uncoloured the cellular tissue, or with potash in the way described on page 191. The suspended particles on the sieve are also examined microscopically, because they often contain large fragments of leguminous cellular tissue.

The leguminous starches contain more mineral matter than wheat flour-for example, pea flour contains, on an average, 2·65 per cent. of ash; flour, 7. It hence follows that if pea flour be

mixed with wheat flour in the proportion of 10 per cent., the ash would be '87 instead of '7, and it has been proposed to make this a test of the presence of such foreign starches, but, as the example just given shows, with moderate adulteration it would not be at all conclusive, and must only be considered one of the auxiliary means.

M. Rodriguez has ascertained that when pure flour is submitted to dry distillation in a stone retort, and the distillate is collected in a vessel containing water, the latter will remain perfectly neutral. But if bean, pulse, or pea meal has been added, the water will have an alkaline reaction. This test appears of doubtful value; for, provided the distillate is alkaline, the alkalinity may, it is evident, have arisen from a variety of causes besides the addition of the substances mentioned. It has also been shown by Bussy that certain cereals yield on distillation an acid product.

Lassaigne (taking advantage of the fact that haricot beans, as well as beans, contain a tannin in their envelopes) adds a salt of iron, which, with pure flour, gives a feeble straw colour, but mixed with either of the two mentioned, or, of course, with any substance containing tannin, gives various shades, from orangeyellow to very dark green.

§ 85. Detection of Alum and Mineral Matters generally in Flour. -The most important test for the detection of mineral substances generally in flour is, without doubt, what is known as the "chloroform test-a -a test which, it would appear, was first proposed by M. Cailletet, a pharmacist of Charleville, in 1869, and was in England brought prominently before the notice of analysts by the researches of Dr. Dupré. The principle of the method is simple and obvious. The chloroform is of sufficient gravity to float the starchy substances and allow the alum, sand, sulphate of lime, or other mineral matters, to sink to the bottom. It, besides, has no very appreciable solvent action on alum, and none at all on the generality of mineral or saline substances. No solution made of sufficient specific gravity, by dissolving salts in water, or any other means, will answer the same purpose as chloroform, because, directly the flour is moistened with water, most of the alum is decomposed by the phosphate of potash present in the flour, and alum also forms an insoluble compound with the gluten.

on

The method is as follows:-The tube figured in the article "Beer" is taken, and a weighed quantity of the flour, from a quarter to half a pound, is placed in it, and sufficient methylated chloroform added to form a thin sort of paste; the

cylinder is closed by a stopper, shaken up once or twice, and allowed to stand over night. The next morning the "rodstopper" is inserted and the cap removed; the latter will contain sand from the millstones, sulphate of lime, alum, or any other mineral powder of a greater specific gravity than chloroform, that happened to be in the flour; this fluid is placed in a burette, some more chloroform is added, and the matters allowed again to subside; lastly, the powder, with a little of the chloroform, is drawn off into a watch-glass, the chloroform evaporated, and the powder digested in warm water, filtered into a clean watch glass, and allowed to evaporate spontaneously. If alum were present crystals will be obtained, easily identified by their form, and these, if necessary, can be produced in court as a 66 corpus delicti." Most of the chloroform used may be recovered by filtration, and purified by distillation.*

The alum crystals may be easily identified by their form under the microscope, and by the reaction with gelatin and logwood. It may be a matter of some importance to be able to say whether the alum present is a potash or ammonia alum. The best method of detecting this is to take the smallest crystal, and having previously dropped a single drop of Nessler solution on a porcelain slab, stir the crystal into the Nessler; an immediate brown colour and precipitate is produced if the alum was an ammonia alum. Dr. Dupré has made some experiments as to the amount of alum which by this process it is possible to recover. Three mixtures were made, containing respectively 28, 10, and 2 grains of very finely powdered ammonia alum in 100 grains of a pure flour. On separation of the alum by the chloroform test, the residue or deposit obtained from the chloroform was dissolved in cold water, and precipitated by baric chloride, and the sulphate of baryta obtained calculated into ammonia alum; the result was that 27.1. 8.21, and 1·14 grains of alum were respectively recovered, instead of 28, 10, and 2 grains, which must. be considered as fairly satisfactory. The sand and silica obtained by the chloroform process will be filtered off, and should be dried and weighed, more especially since there has been found to be a relationship between the silica present and the alumina in flour not existing as alum, but as clay, &c.

The Logwood Test.-A freshly-prepared tincture of logwood becomes blue when alum and certain other salts are added to it; an excellent and readily applied test has been proposed based on this reaction. The process usually adopted for flour is as follows:

Fifty grms. of flour are weighed out and mixed by the aid of

Emmerling, instead of chloroform, uses a solution of zinc sulphate, 100 grms. of zinc sulphate dissolved in 72.5 grms. of water; such a solution has a gravity of 1·43 (Zeit. f. anal. Chem., 1894, p. 46).

*

a glass rod with 50 cc. of distilled water; to this is added 5 cc. of recently prepared logwood solution, alkalised by 5 cc. of solution of ammonium carbonate. If 100 part of alum is present, the flour will become of a lavender-blue colour instead of pink. An approximate estimate of the quantity may be obtained by having a standard solution of pure alum, 1 grm. to the litre, and adding known quantities to exactly similar emulsions of pure flour, and testing as before with logwood, until an emulsion is obtained of very similar hue to the flour originally tested. If the cold extract gives a blue tint with the logwood test, or if the flour be submitted to dialysis, and the diffusate responds, alum is present as alum, and is not derived from dirt, clay, or from the millstones themselves. The author uses little strips of gelatin to concentrate the alum on: a bit of gelatin is soaked in the cold extract of the suspected flour for twelve hours, it is then taken out and steeped in the ammoniacal logwood; if alum is present the gelatin becomes of a beautiful blue colour; and the spectrum shows the shifting of the band as described on p. 98. The same blue colour is produced by the presence of magnesia, and clayey matters may also cause a bluish tint. Nevertheless, if a flour or bread does not respond to this test, it is certain that alum in any quantity is not present; on the other hand, if a blue colour is produced, there is likely to be either an adulteration with alum or some other admixture, and the sample should be more thoroughly examined.

Hermann W. Vogel + has shown that alum and magnesia salts can be recognised by their influence on the spectrum of purpurine. It is evident that here is a process by which the analyst may be assisted in his diagnosis of the cause of any blue colour imparted to flour. Pure purpurine gives, in saturated solutions, a spectrum extinguishing wholly the blue part. An alcoholic solution diluted until it is of a straw-yellow colour extinguishes the blue only partially, and shows two marked absorption-bands at F and b E (see fig. 16, p. 94). A diluted watery solution does not show these absorption-bands, but instead there appears a stronger absorption in the green between F and b, a weaker in the yellow from E. This reaction is dependent on a trace of alkali, for it is intensified by ammonia, whilst a slight excess of acetic acid colours the fluid yellow, and then there is only a weak absorption. The

The millstones are sometimes mended with an alum cement. This circumstance will of course, from time to time, be utilised for purposes of defence.

+ Ueber eine empfindliche Spectral Analytische Reaction auf Thonerde und Magnesia.

solution of purpurine should be prepared from purpurine which has been purified by sublimation, and it should be made very feebly alkaline. To test for alum it is best to take the deposit from the chloroform process already described, and dissolve it in not more than 1 cc. of water. 2 cc. of water are now placed either in a test-tube or a little glass cell, and three drops of a saturated alcoholic solution of purpurine added, and then alkalised by a drop of fourfold diluted ammonia water. On observing this solution by the spectroscope, it appears as curve No. 12, fig. 16, p. 94. A drop of the alum solution is next added: in dilute solutions two bands gradually appear; in the presence of half a milligramme of alum, the bands appear after the lapse of several minutes. Magnesia presents similar appearances, but is at once distinguished from alum by the fact that the bands are destroyed by the addition of acetic acid.

Proximate Analysis of Flour.

§ 86. The constituents of flour to be determined are—

(1.) Water.

(2.) Fat.

(3.) Cold Water Extract.

(4.) Gluten.

(5.) Ash.

Sugar, Gum, and Dextrin

Vegetable Albumen.

Phosphate of Potash.

(1.) The water is taken in the ordinary way; that is, by weighing carefully about 1 to 3 grms. in a tared dish, and exposing it to the heat of the water-bath until it ceases to lose weight.

(2.) The fat, according to the researches of Peligot, must be determined in the perfectly dry flour, error resulting in any other

case.

(3.) The cold extract is obtained by digesting 10 grms. of flour in 500 cc. of water, and filtering and evaporating down 250 cc. in a platinum dish. According to Wanklyn, 100 grms. of flour yield to water

Sugar, gum, and dextrin,
Vegetable albumen,

Phosphate of potash,

Grms.

3.33

0.92

0.44

4.69

On igniting the extract, the ash should consist entirely of phosphate of potash. When the weight of the ash is known, it may be dissolved in water, and the quantity of phosphoric acid