0.02840 0015 001510 27500 4000 4 498 4 498 2.60 6.50 9:00 0.06140.0014 0.00820 28270 4100 5 049 4 839 2 40 5 30 0.0277 0.00640 0002 016700 3111 5 897 5.897 1.40 0.0265 0.00380 01420 18900 3422 6 237 6 237 5:00 0.0471 0.00280 01340 21800 3180 6 237 6.086 1.80 0.02880 0050001240 220003470 6 048 6*048 4.80 0.06470 00540 01140 25090 4340 5 470 5'470 3.50 0.048400052 0·00680*15110*2578 5 330 3·893 2.50 0.0489 0.00460 01020 17550 3020 6 577 6.577 5.70 Faint Faint o 05070 0184 0.00800 07800 20307 069 4 309 2:00 7.70 9.80 11.20 7 20 12 20 9.20 11.00 8.20 13.00 4'50 8.00 7.50 9'00 8.80 11.30 6.80 12.50 12.00 14'00 Faint Faint 0 06110 01980 02800 12000 1852 7 409 5 481 6.00 11:00 17:00 trace trace Faint Faint o 13340 03800 0118010750 1762 8.468 8.468 3 20 10 40 13.60 trace trace 8:00 Mineral Matter. Total Solids dried at 110°. The variation in the composition of Croton water, at different seasons of the year, is exhibited by the table on p. 221, which gives the results of the semi-monthly examinations made by Dr. Elwyn Waller during the year 1885.* For the results of the analyses of the water of the Hudson River, recently made by Dr. C. F. Chandler, see table, pp. 222, 223. The rather common belief that freezing purifies water is incorrect. It is said, that the greater part of the ice supply of New York City (three millions of tons) is gathered from the Hudson River between Albany and Poughkeepsie, most being drawn within thirty miles of the former city, and therefore liable to be polluted with sewage. The average number of bacteria in one c.c. of ordinary ice is stated to approximate 400, but Hudson River ice has been found to contain nearly 2000 bacteria per c.c.† The number of bacteria in one c.c. of snow is usually about 9000; Hudson River snow-ice contains 20,000 per c.c.; and, although the great majority of these organisms are perfectly harmless, cases are on record where epidemics (as of gastro-enteritis) have been directly traced to the use of impure ice. * Jour. Am. Chem. Soc., viii. p. 6. † See paper read by Dr. T. M. Prudden before the New York Academy of Medicine, March 18th, 1887. VINEGAR. VINEGAR is a dilute aqueous solution of acetic acid, containing inconsiderable proportions of alcohol, aldehyde, acetic ether, and extractive matters, which, to some extent, impart a characteristic flavour and aroma. The process most frequently involved in the preparation of vinegar is known as the acetous fermentation, and may be induced in various saccharine juices and infusions, such as those of apples, wine, malted grain, etc., when, in presence of a ferment, they are exposed to the action of the air, at a temperature between 24° and 32°. In the oxidation of alcohol, an intermediate compound (aldehyde) is at first formed, which, by the continued action of oxygen, is ultimately converted into acetic acid. A dilute solution of alcohol is, however, not oxidised to acetic acid by simple exposure to the air; it is usually necessary that a peculiar microscopic plant (mycoderma aceti) should be present. This fungus includes two varieties, viz., minute globules (micrococci) and rod-like forms (bacilli) varying in size; and is often developed in old casks that have been long employed for making vinegar. It constitutes a gelatinous mass ("mother of vinegar") having the appearance of glue that has been soaked in cold water; the surface quickly becomes coated with a bluish mould (Penicillium glaucum). Pasteur regards acetification as a product of the development of the mycoderma aceti, i.e., as a physiological fermentation-but it appears probable that the process is rather one of oxidation, and that the fungus accelerates the change by condensing the oxygen upon its surface and delivering it to the alcohol, possibly in the form of ozone. Indeed, Q |