All the measuring apparatus necessary for making the legal tests is one of the measuring tubes called burettes. It is most convenient to have this of a size to contain 25 to 50 c.c.--that is, cubic centimetres--and have these divided into tenths. The best form of burette is the Mohr’s, which is closed by a glass stop-cock. Besides this, only a dropping-tube, called a pipette, graduated to deliver 6 and 10 c.c., will be needed. These tubes are to be obtained of any philosophical or chemical apparatus dealer, being articles generally kept in stock by them for common use, like yard-sticks. The only two chemicals needed in determining the strength of a vinegar are such as can be obtained of any competent apothecary in any city of the State. They are simply a small vial of a 1 per cent. solution of Phenol-phthalein in diluted alcohol, and a sufficient quantity of a solution of caustic soda, prepared as directed for “Volumetric Solution of Soda” upon page 399 of the last ‘U. S. Pharmacopœia,’ a book which is in the hands of every competent apothecary, as it contains the formulæ according to which he is required by the law of the State to prepare all such medicinal preparations as are mentioned therein. 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