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 2½ 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 1½ 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.[136]