Having these, the procedure for making the test will be as follows:—Fill the pipette by suction, and then quickly close the top of it with the forefinger. Raise the tube out of the sample of vinegar, and let it empty out by drops exactly down to the top graduation-mark, this bearing the mark of 0· c.c. Then holding it over a white mug or cup, let it run out exactly down to the 6 c.c. mark. Dilute the 6 c.c. of vinegar thus measured out into the mug with sufficient clean water to make it look about white, and then add to it about three drops of the Phenol-phthalein solution. Then having prepared the burette by filling it up to the top, zero, or any other noted mark of the graduation, with the volumetric solution of soda, let the soda solution run out cautiously into the diluted vinegar, which should be constantly stirred about. As soon as the vinegar in the mug begins to darken, the soda should then only be allowed to run into it by drops. This dropping is thus continued until at last a final drop of soda turns the vinegar suddenly to a permanent pink or cherry colour, which will not disappear upon further stirring. By now reading off from the graduations of the burette the number of full c.c. divisions and of tenths which have been emptied out to bring about this change of colour in the vinegar is known the per cents. and tenths of acidity equivalent to true acetic acid contained in the vinegar being examined. This, if it is a pure cider vinegar, and well made, will be upon the average about 6 per cent., but never under 5 per cent. If, in like manner, 10 c.c. of the vinegar is exactly measured off by the pipette into a small light porcelain dish, and then evaporated fully to dryness over boiling water, the number of grammes weight gained by the dish, when multiplied by ten, gives the percentage of solid residue contained in the vinegar.
There are certain characteristics peculiar to the residue of a pure cider vinegar, the principal of which are the following:—It will be about 3 per cent. in weight, and never less than 2 per cent. It is always soft, viscid, of apple flavour, somewhat acid and astringent in taste. A drop of it taken up in a clean loop of platinum or of iron wire, and ignited in a colourless Bunsen gas-lamp flame, imparts to it the pale lilac colour of a pure potash salt, without any yellow, due to sodium, being visible. The ignited residue left in the loop of wire will be a fusible bead of quite a good size, and it will have a strong alkaline reaction upon moistened test-paper, effervescing briskly when immersed in an acid. The presence in a vinegar of the slightest trace of any free mineral acid will prevent the ignited residue having any alkaline reaction, or effervescing with acids. The presence of any practical amount of commercial acetic acid added to “tone up” the strength of the vinegar will cause the igniting residue to impart another colour to the Bunsen flame, and the residue itself will have a smoky pyroligneous taste or odour. Any corn glucose used in the vinegar will cause its residue when ignited to emit the characteristic odour of burning corn, and, as the last spark glows through the carbonised mass, to usually emit the familiar garlic odour of arsenic, for the common oil of vitriol usually used in the production of glucose is now mostly derived from pyrites, which almost always contain arsenic. A glucose vinegar which has been made without vaporising the alcohol after the fermentation of the glucose will also have a strong reducing action upon a copper salt in an alkaline solution, and also will give a heavy precipitation of lime with ammonium oxalate. A true malt vinegar always contains phosphates, and a wine vinegar cream of tartar. The presence of any acrid vegetable substance in a vinegar is known by the residue having a pungent taste, especially if before the evaporation the vinegar has been exactly neutralised with soda.
In a pure apple cider vinegar hydrogen sulphide gas will not cause any discoloration, nor will the addition of a solution of either barium nitrate, silver nitrate, or ammonium oxalate cause anything more than the very slightest perceptible turbidity. But the addition of some solution of lead acetate—that is, of sugar of lead—will cause an immediate voluminous and flocculent precipitation, which will all settle out in about ten minutes, leaving a clear fluid above. In most of the so-called “apple vinegars,” made with second pressings of the fermenting pumice, the addition of some of this lead solution will cause but a slight turbidity, without any precipitate settling out for several hours, and even then the precipitate will not be of the same appearance as in apple cider vinegar.
Sophistications of cider vinegar that will not be detected by some one or more of the above given tests are not likely to be met with, for the simple reason that they are not profitable. To translate percentages of acid strength into the old commercial terms of grains of soda bicarbonate per troy ounce, the per cent. may be multiplied by 6·72, or, vice versâ, divide the grains by the same factor. To reduce it into grains of potash bicarbonate 8 would be the factor to be used in like manner.
The general Adulteration of Food Law of the State of New Jersey is the same as that of New York. The following is a copy of a special Act in relation to the sale of adulterated milk:—
An Act to prevent the adulteration of milk and to regulate the sale of milk.
Persons selling or offering for sale skimmed milk, to solder a label or tag upon can or package.
Penalty for violating this section.
1. Be it enacted by the Senate and General Assembly of the State of New Jersey, that every person who shall sell, or who shall offer or expose for sale, or who shall transport or carry, or who shall have in possession with intent to sell, or offer for sale, any milk from which the cream, or any part thereof has been removed, shall distinctly, durably and permanently solder a label, tag or mark of metal in a conspicuous place upon the outside and not more than six inches from the top of every can, vessel or package containing such milk, and said metal label, tag or mark shall have the words “skimmed milk” stamped, engraved or indented thereon in letters not less than one inch in height, and such milk shall only be sold or shipped in or retailed out of a can, vessel or package so marked, and every person who shall violate the provisions of this section shall be deemed guilty of a misdemeanour, and on conviction thereof shall be subject to the penalties prescribed in section eight of this Act.
Penalty for selling or offering for sale impure or adulterated milk.