Page:The American Cyclopædia (1879) Volume XIV.djvu/603

Rh for salting fish on account of its property of attracting moisture. The mother liquors are run off to be treated for the other salts. From the salting tables the crystallized salt is taken and made up into pyramidal heaps, and during the summer season these are left exposed to the weather. The little rain that falls promotes the purification of the salt by removing the more soluble foreign matters. Nothing more is done to prepare the salt for the market. Its average price is one franc for 100 kilogrammes (220 lbs.). Steam or horse power is employed at these large salines to raise the water from the lower basins into the upper ones; the machines that take up the water are lifting wheels of 8 to 16 ft. diameter. The evaporating surfaces cover 815 acres, of which $1⁄10$ is devoted to the salting tables. The total annual product of salt is about 44,000,000 lbs. At Baynas, as M. Pay en states, the same amount is made with strong sea water on 370 acres.—The relative strength of the various brines employed in the United States and Canada for the manufacture of salt is thus given by Dr. Beck, the figures representing the number of gallons required to the bushel of ordinary dryness:

At Saginaw, Mich., the proportion is 25 to 30 gallons to a bushel, and at Goderich, Canada, 22. The following description of the methods employed in treating the brines of Onondaga, N. Y., will serve as an illustration of those generally employed elsewhere, especially in Michigan, Ohio, and West Virginia. These brines contain about one half of one per cent. of sulphate of lime, a very small percentage of the chlorides of calcium and magnesium, mere traces of carbonic acid and oxide of iron, and from 16 to 17 per cent. of salt. It is the object of the manufacturers to remove all of the iron, a part of the sulphate of lime, and as much as possible of the chlorides of lime and magnesium. The colorless and clear brine is first pumped into shallow vats, where it remains until the carbonic acid escapes and the iron is deposited as oxide. It is then either evaporated by the sun's heat for “solar salt,” or by artificial heat for fine or boiled salt. The first process is conducted in wooden vats protected by movable covers, sheds with sectional movable roofs being generally used. The evaporation is conducted very slowly, and as a consequence the salt appears in very large crystals and is known as “coarse salt.” The brine from which the iron has been separated is drawn into a lower set of vats, where it is left until crystals of salt appear on the surface. A considerable amount of sulphate of lime has meantime been deposited. The resulting

saturated brine, called “salt pickle,” is drawn off from the precipitated gypsum into a third set of vats. Whenever a sufficient amount of salt crystals has accumulated, they are washed in fresh pickle and allowed to drain from perforated wooden troughs, and thence removed to the storehouse. Three crops are produced in a season, the middle crop being the best. This coarse salt is considered best for packing meats and fish, as it dissolves more slowly than fine salt and prevents the meats from being packed too closely. Boiled salt is produced by several methods, of which three are the most important, viz.: the kettle, the pan, and the steam processes. In the first, most frequently employed in this country, from 50 to 60 kettles, having a capacity of from 100 to 120 gallons each, are set in a row and heated by a common flue and fireplace. Two rows are attached to one chimney. The settling tanks and store rooms are arranged along the sides of the kettles, and the whole roofed over. The precipitation of the iron is sometimes hastened by the addition of a small quantity of milk of lime. The clear brine is then drawn into the kettles, when evaporation goes on rapidly and at a higher temperature; consequently a larger proportion of the sulphate of lime separates before saturation than in the solar process. The removal of this precipitate is effected by placing an iron pan upon the bottom of the kettle, provided with an upright handle. The motion of the boiling liquid causes the particles of solid matter to collect in the central portion of the bottom upon the pan. The pan is removed and emptied from time to time until crystals of salt appear, when it is not replaced. The salt which accumulates is well washed in the remaining pickle and placed in baskets suspended over the kettles, when after draining a few hours it is emptied into the store rooms. A state law in New York prescribes that the salt shall be stored two weeks; also that it shall be inspected before being stored, and again when ready for shipment. The pan process is used in this country to some extent, and largely in England. The brine is either saturated cold or in a pan called the “foreheater.” It is then transferred to another pan and evaporated, either slowly or rapidly as a coarse or a fine salt is desired. If a very fine grain is desired, the pans are constantly stirred. The pans are of iron, set over flues, and vary in size from 60 to 20 ft. in length and 35 to 13 ft. in width, by 15 to 20 in. in depth. In these pans the evaporation is very rapid; the salt accumulates constantly, and requires to be withdrawn continually. In the steam process the brine freed from iron is drawn into the steam settlers, where it is brought to saturation. These are wooden cisterns about 100 ft. long, 8 ft. wide, and 6 ft. high. They are heated by several four-inch steam pipes, which pass through them from end to end. After the impurities have settled the brine is drawn into grainers, which are of about the same size as the settlers,