Naturally the addition of caramel or cider vinegar to whisky vinegar would greatly affect the above tests.

Attempts made to differentiate between the two samples by means of qualitative reactions for aldehyde and malic acid were not sufficiently distinctive in their results to be of much value.

It has been suggested that the presence of nitrates in vinegar would point to its origin from spirits. The apple vinegar manufacturer, however, frequently finds his product above the standard, in which case he reduces its strength by adding water, thus rendering this test of little or no avail.

Regarding the addition of mineral acids to vinegar in the United States, it is satisfactory to note that, of a large number of samples tested by the New York City Vinegar Inspector during the past year, not a single sample was found to contain these adulterants.

Fermented infusions of molasses, "black strap," etc., are occasionally employed in the manufacture of vinegar. The product obtained from these sources has been found in some instances to contain acrid and probably noxious ingredients.

PICKLES.

THE examination of pickles naturally includes a determination of the character of the vinegar used in their preparation. This is made by the methods just described. The practice of imparting a bright green colour to pickles which have become bleached by long preservation in brine or by other means, is doubtless still prevalent, and calls for a brief notice. The greening of pickles is effected either by the direct addition of cupric sulphate to the water in which they are heated, or by introducing some form of metallic copper into the bath. Alum is stated to be also occasionally employed for the same purpose. The presence of copper is readily detected by incinerating a rather considerable quantity of the pickles, treating the ash with a little nitric acid and adding an excess of ammonium hydroxide to the solution, when, in presence of the metal, a blue coloration will be produced. The quantitative estimation of copper is made by boiling the residue, obtained by the evaporation of the vinegar or the incineration of the pickles, with dilute nitric acid, adding a small quantity of sulphuric acid and expelling the excess of nitric acid by evaporating nearly to dryness. The solution is next diluted with water, filtered, and the filtrate placed in a platinum capsule. The copper is then deposited by electrolysis. In the Report of the Brooklyn Board of Health for the year 1885, a case is recorded where a child ate a portion of a pickle coloured with cupric sulphate (containing an estimated quantity of 2 grains of the salt), with fatal results.

OLIVE OIL.

OLIVE OIL is extracted from the pericarp of the fruit of the Olea Europea. When pure, it exhibits a pale yellow or greenish colour, has a specific gravity of 0.9176, and possesses a faint, pleasant odour and a bland and agreeable taste. It is insoluble in water, very slightly in alcohol, but dissolves in about 1 parts of ether. Olive oil boils at 315°, and begins to deposit white granules at 10°; at 0°, it solidifies to a solid mass which, by pressure, may be separated into tripalmetine and trioleine. Upon saponification, it is decomposed into oleic, palmetic, and stearic acids and glycerine. The best-known varieties of olive oil met with in commerce, in the order of their quality, are— Provence, Florence, Lucca, Genoa, Gallipoli, Sicily, and Spanish.

*

Owing to the high price of the pure article, and perhaps to the difficulty experienced in detecting foreign admixtures, olive oil is probably more extensively adulterated than any substance of general consumption. The oils most employed as adulterants are those of cotton-seed, poppy, pea-nut, sesamé, rape-seed, arachis, and lard. Although the subject of the adulteration of olive oil has received the attention of numerous chemists, including several of exceptionally high standing, the results obtained, while of service in indicating the presence of some foreign oil, are unfortunately often of but little use in the positive identification of the particular adulterant used. Of the

* It has been stated that American olive oil of superior excellence is made in the States of N.C., Miss. and Cal. ; but this product does not, as yet, appear to be generally known on the New York market.

many methods of examination that have been suggested, the following are the most satisfactory :—

1. Specific gravity.-The density of olive oil is lower than that of the majority of the oils with which it is mixed, and it is sometimes possible to detect the presence of the latter by means of this property, especially when they are contained in a considerable proportion. Cottonseed oil differs more in specific gravity than the other oils generally employed as adulterants. Donny* applies the test by placing in the suspected sample a drop of olive oil of known purity which has been dyed with ground alkanet root, and observing whether it remains stationary. A more satisfactory method is to determine the density by the gravity bottle. The following tabulation gives the densities (at 15°) of olive and several other oils liable to be met with as admixtures :—

2. Solidifying point.-Attempts have been made to utilise the fact that some of the oils added to olive congeal at a lower temperature than the pure oil. Thus, cotton-seed oil solidifies at -22°, ground-nut oil at -33°, poppy at -18°.

3. Elaidin and colour tests.-Pure olive oil is converted into a solid mass when treated with various oxidising agents, the change being retarded by the presence of some of its adulterants. The test may be made in several ways:

Frens. Zeitsch. 3, 1864, p. 513.

(a) Ten grms. of the sample are shaken with 5 grms. of nitric acid (sp. gr. 1'40) and I grm. of mercury, and the colour produced and time required for solidification noticed. In this manner the following results have been obtained :

(b) Or a few pieces of copper foil are added to a mixture of equal parts of the oil and nitric acid, the liquor occasionally stirred, and then set aside. If the oil be pure, it will be converted into a nearly white buttery mass in from three to six hours; sesamé oil yields a red, cotton and rape-seed a brown, and beech-nut a reddish-yellow colour, the solidification being delayed from 10 to 20 hours, while poppy oil fails to solidify at all.

(c) Nine parts of the sample are oxidised by heating with one part of concentrated nitric acid, the mixture being well stirred; pure olive oil forms a hard, pale-yellow mass in the course of two hours; seed oils (including cottonseed) turn orange-red in colour and do not become solid in the same time or manner.

(d) A portion of the sample is well mixed with onefourth of its weight of chromic acid; if pure, the oil will be converted into an opaque mass.

(e) Introduce 2 c.c. of the sample into a narrow graduated glass cylinder, add o'i gramme potassium dichromate, next 2 c.c. of a mixture of sulphuric and nitric