noted. The second portion is similarly treated. The first experiment serves as a guide to colour, etc.; the number of cubic centimetres used is ascertained, and the amount required by the non-volatile acids in 100 grams of fat calculated. For the purpose of comparison with fats used as adulterants, it may, perhaps, be convenient to convert this to stearic acid, C18 H36 02.

The Testing of Olive and other Fixed Oils. E. J. Maumené. (Journ. App. Science, Feb., 2nd, 1880.) After experimenting with all the known methods for testing oils, the author finds the following calorimetric process to be the best,—

In a graduated cylinder, to hold 150 c.c., put 50 grams of oil, ascertain the temperature of the same, and add with a pipette 10 c.c. sulphuric acid, stir with thermometer for a few minutes, and note the highest degree of temperature.

Pure olive oil gives an increase of 42° C.

Contributions to the Chemistry of Several Varieties of Wax. E. Hirschsohn. (Pharm. Journ., 3rd series, x., 749.) This paper deals with the solvent action of alcohol, ether, chloroform, petroleum spirit, and alcoholic solution of potash on the various kinds of wax met with in commerce, and the behaviour of the solutions with solution of ammonia and with alcoholic solutions of lead acetate and of ferric chloride. It concludes with the following very useful summary in the form of a systematic course of analysis for distinguishing the principal kinds of wax :

A sample of the wax to be examined is heated with ten times as much chloroform to boiling, and, when completely dissolved, cooled in cold water.

I. The chloroform solution remains clear after cooling.
A. Ether dissolves completely.

(a) Alcoholic solution of ferric chloride gives with the alco-
holic solution of the wax a precipitate insoluble on heating.
Wax from Myrica quercifolia.

(b) Ferric chloride colours the alcoholic solution black.

Wax from an undetermined species of Myrica. (c) Ferric chloride colours brownish but gives no precipitate. Wax from Myrica cerifera.

B. Ether dissolves only a part

Wax from Orizaba.

A sample is boiled with ten times the quantity of alcoholic potash solution till saponified, and the soap heated with 100 volumes of water.

(a) The soap is completely soluble.

(b) The soap is partially soluble.

Japanese wax.

Beeswax; African beeswax. II. The chloroform solution becomes cloudy on cooling. A. Alcoholic solution of acetate of lead gives with the alcoholic solution of the wax, after a few minutes' standing, a cloudi

ness.

Wax from stick-lac.

B. Alcoholic solution of acetate of lead gives no cloudiness.
(a) The ethereal solution of the wax becomes cloudy on the
addition of an equal volume of alcohol.

Brazilian and Carnauba wax.

(b) The ethereal solution remains clear.

Bahia wax.

The Detection of Bile Pigments in Urine. M. Masset. (Journ. de Méd. de Bruxelles, 1879, 446.) The author recommends the following test as more delicate than nitric acid :—

To about 2 grams of the urine contained in a test-tube are added 2-3 drops of concentrated sulphuric acid, and then a small crystal of potassium nitrite, taking care that the crystal does not adhere to the sides of the tube, but drops directly into the liquid. In the presence of bile pigments, green zones will thus be formed, and, after shaking, the whole fluid will appear distinctly green. The coloration remains for some time, and does not disappear even on boiling the mixture.

Estimation of Urea in Urine. J. Tattersall.

(Comptes

Rendus, lxxxix., 417.) The author finds that the results obtained by

treatment with sodium hypobromide are too high if the urine contains glucose, since the reagent evolves a considerable quantity of gas from the glucose. The greater the proportion of glucose, the greater will be the error in the urea estimation.

Indigo as the Predominating Constituent in a Renal Calculus. M. Ord. (Berlin Klin. Wochenschr., 1879, 25.) The author received for examination from Dr. Bloxam a renal calculus which proved to consist of coagulated blood, a small proportion of crystallized calcium phosphate, and a considerable quantity of indigo. A powdered portion of the calculus, when mixed with an equal weight of sodium chloride, and heated with glacial acetic acid, yielded a deep-blue liquid, which, on cooling, deposited a shining, coppercoloured, crystalline sediment. Submitted to sublimation, the behaviour of this deposit was exactly like that of indigo.

Ignited in a platinum crucible, the calculus left a white ash consisting of calcium phosphate.

Indigo. E. Schunck. (Journ. Chem. Soc., July, 1879.) In the first part of this paper reference is made to previous papers containing accounts of indigo-blue obtained from Isatis tinctoria, in which it exists in the form of a glucoside, indican; this, when treated with acids, splits up into indigo-blue and indiglucin. It is also decomposed by the action of caustic alkalies, a substance being formed which yields indigo-red, indifulvin, and leucine, when treated with acids. In some more recent experiments on indican from woad leaves, tyrosine has been found amongst the products of decomposition. The indican used consisted of a crude alcoholic extract of the leaves; it is therefore difficult to say whether the tyrosine existed ready formed in the leaves, or was the result of the decomposition of the indican; the latter is more probable, since tyrosine is almost insoluble in alcohol, and therefore would not be contained in the alcoholic extract in quantity. That there is some connection between indigo-blue and tyrosine is seen from the fact that tyrosine, C H11 N Og, is indigo-blue, C, H, NO+2 molecules of water, in which one atom of hydrogen is replaced by CH3. Its formation may be explained by supposing indican to split up into tyrosine indiglucin, acetic acid, and carbonic anhydride,—

5

C2H32NO18+3H,O=C,H11NO3 + 2(C6H10O6) + 2C ̧H ̧О1⁄2 + CO2.

26

9 11

In order to ascertain whether other indigo-yielding plants contain indigo-blue in the form of a glucoside, as in Isatis tinctoria, or in the free state, the following experiments were carried out:

Polygonum tinctorium.-The leaves of this plant, which are large,

L

oval, and glossy, and of a lively green colour, contain a large quantity of the colour-yielding substance. On cutting them to pieces and rubbing with water to a thin paste, filtering through calico, and separating the chlorophyll, albumen, etc., from the filtrate by precipitating with lead acetate, a liquid is obtained which yields indigo-blue on the addition of sulphuric or hydrochloric acid and allowing the mixture to stand for several hours. The isolation of the colour-yielding substance is effected by the method formerly employed to extract indican from Isatis tinctoria or by the following, which is preferable. The leaves are dried in a stove, and while still warm, ground to a powder, and exhausted with alcohol in a percolator. The alcoholic extract is evaporated at the ordinary temperature, and the residue freed from chlorophyll and other impurities by precipitation with lead acetate. Оп adding basic lead acetate to the filtrate, a primrose yellow precipitate is thrown down; this is washed with water and with alcohol, and finally suspended in absolute alcohol, and carbonic anhydride is passed through the mixture until the liquid assumes a yellow colour. On evaporating the filtrate at the ordinary temperature and adding water, a portion remains insoluble. This is separated by filtration, and the lead in the filtrate precipitated with sulphuretted hydrogen. The clear solution, evaporated at the ordinary temperature by means of a current of air, leaves a syrupy residue, from which the colour-yielding substance is obtained as a yellow syrup on treatment with absolute ether and evaporation. It shows no signs of crystallization, is soluble in water, alcohol, and ether, the aqueous solution possessing a more or less acid reaction. It assumes a deep yellow colour when treated with caustic alkalies, and gives a light yellow precipitate with lead acetate. When it is mixed with sulphuric or hydrochloric acid, indigo-blue separates out, and the filtered solution gives the characteristic test for glucose with Fehling's solution. If, however, the aqueous solution is allowed to stand or is boiled, or mixed with caustic alkali and allowed to stand, no indigo-blue is deposited on addition of acid. In all probability the substance analogous to indican undergoes a molecular change, resulting in the formation of a body which yields indirubin and resinous matters on treatment with acids.

By allowing a large quantity of the aqueous solution to stand in contact with acids, indirubin and indifulvin are deposited, besides indigo-blue, showing that a portion of the substance undergoes some change, which in all probability may also take place in the cells of the leaf; for from leaves gathered late in the season a

substance is obtained which, when treated with acids, yields far less indigo-blue and more indirubin and other products than the substance obtained from the younger leaves.

From these experiments it is inferred that the leaves of Polygonum tinctorium contain a substance identical with the indican from Isatis tinctoria, and also that no colouring matter exists ready formed in the healthy living plant.

If the leaves of Polygonum tinctorium be crushed, and after a short time plunged into boiling alcohol, the bruised portion assumes an intense blue colour, whilst the other portion becomes white.

If the leaves be immersed in water and the water frozen, the portion of the leaves which have been frozen appears of a dark colour after complete thawing, and after steeping in boiling alcohol they assume a dark-blue colour, whilst the unfrozen portions become white. The fresh leaves, after being plunged in cold alcohol or ether, and extraction of the chlorophyll, appear blue; this was supposed to prove the pre-existence of the free colouring matter in the leaves; but by plunging them in boiling instead of cold alcohol, the colour-yielding substance is dissolved before it can decompose, and the leaves become of a pale yellow colour. Moreover, the alcoholic extract on evaporation does not deposit a trace of indigoblue.

The explanation offered for these phenomena is as follows:The molecules of the glucoside, indican, are in a state of unstable equilibrium, and are enabled to preserve that equilibrium so long as they are contained in the cells of the living plant. As soon as that vitality ceases the indican begins to decompose, and the molecules arrange themselves as their chemical affinities predispose them; the result is, indigo-blue and indiglucin. This reaction takes place so rapidly that in some cases it would appear as if indigo-blue pre-existed in the living plant. By immersing freshly cut sprays of Polygonum tinctorium in dilute hydrochloric acid for some days, and exposing them to the air, the acid is rapidly absorbed by the stalk, passing first to the lower leaves and then to the upper. The absorption of the acid is attended with a change of colour from dark green to dirty yellow, and after some time to dark blue, commencing at the base of the leaf, and gradually extending to the apex, which is reached only in the case of the lower leaves. When the change of colour begins to appear in the upper leaves, they are immersed in hot alcohol, whereby the chlorophyll is dissolved, leaving those parts which have changed colour blue, and the other portions white.