FREEZING MIXTURES, AND OTHER MEANS OF COOLING (ante). In general, it may be said that artificial freezing is effected by three methods, that of liquefaction by mixtures, that of the expansion of vapors escaping from volatile liquids, and that of the expansion of compressed air. Before giving a description of ice-making machinery, we refer to the fact that water has more capacity for beat then any other substance, and therefore, for the purpose of cooling substances to moderately low temperatures, such as procurable water may have, that substance will be found the most economical. The freezing of water by rapid evaporation was long ago performed by means of the air pump; sir John Leslie having, in 1810, succeeded by the use of sulphuric acid, placed alongside the water in the receiver for the purpose of removing the vapor which would otherwise recondense on the descent of the piston. The experiments of Faraday, about 15 years later, with sulphurous acid are also familiar to those who have witnessed class room experiments. All these operations were on a small scale, and not till about 1850 was there anything like a commercial application of ice-making machinery. The begin ning of such machines was Made by an American, Jacob Perkins, who patented his invention in England, 1834. The apparatus consisted of a flat vessel containing ether, immersed in a vessel containing water, or any substance to be cooled. Vapor of ether was exhausted from this vessel by means of an air-pump, and again recondensed by forcing it through a coil of tube immersed in cold water, by the action of the same pump; and then forced, liquefied, into the original vessel. This answered the purpose of a domestic refrigerator, but was not an ice-producing apparatus. Perkins had many imitators, especially in France. Only one of these, however, made any advance; this was the apparatus of Bourgois• patented in 1840 for the use of hydrocarbons as the volatile liquids on the principle of Faraday's discovery 20 years before. The first important step towards any commercial results in the practical manufacture of ice was by another American, Alexander C. Twining, LL.D., professor of mathematics and natural philosophy in Middlebury college, Vt., in 1848 and 1849, and whose English patent was dated July, 1850. It was a re-invention of the Perkins apparatus in many respects, but, it is stated, without any knowledge of it. In many of its arrangements, especially that for the application of the cold and the use of steam-power, it was original. The fundamental patent was taken out in the United States in 1853; but the first ice-machines were made at Cleveland, O., in 1850, and from that time to 1850, machines were made capable of turning out a ton of ice in a few hours, 6 in. in thick ness. In 1856, James Harrison patented machines in London, and put them into use both in England and in Australia. Their construction was similar to that described in Twin ing's fundamental patent of 1853, and quotations from that patent apply to the descrip tion of one form of IIarrison's apparatus. The success obtained with the above-men tioned machines stimulated Ferdinand P. Carrii, of Paris, to invent ice-making machines, which were at first little else than a repetition of the American machine, but afterwards really resulted in the perfecting of apparatus which was operated without any mechani cal power. This improvement was the result of the use of aqua ammonia as the vola tile liquid, the vapor of ammonia having such peculiar affinities for water, that by an ingenious and simple contrivance mechanical powet could be dispensed with. Carre's apparatus is worked in the following manner. A wrought-iron boiler capable of resist ing a pressure of ten atmoRpheres is connected by a tube with a freezing-chamber having two concentric compartments, the outer One connected with the boiler, and the inner containing the vessel holding the article to be frozen. The freezing-chamber is placed
in a cold bath, and to the boiler, into which has been poured a quantity of a saturated solution of ammonia, sufficient heat applied to create a pressure of about six atmos pheres, which expels the gaseous ammonia and forces it into the outer compartment of the freezing-chamber, where, by its own pressure and the action of the cold bath in which the chamber is placed, it is condensed in about one tenth of its weight of water. A gauge connected with the condenser indicates when enough ammonia has been con densed, and then the boiler is cooled in a bath. The substance to be frozen is now pladed in the inner chamber (the condenser, till now), when the cooling of the boiler removes the pressure which till now has held the ammonia in solution in the inner com partment of the freezing-chamber; and its rapid evaporation in a short time produces an intense cold. Other ammonia machines are used, all constructed on the principle of non-use of mechanical power or effecting vaporization on condensation. The ptessure employed in them is from 130 to 180 lbs. per square inch. Rees Reece devised an improvement on Carre's apparatus, which was patented in 1867. A. cooler, independent of the boiler, is used to produce evaporation of the condensed ammonia. Variations of these machines are known under the names of the Atlas, Vaas and Littmann's, and others. Machines which employ sulphuric or methylic ether, gasoline and other derivatives of petroleum, have two .great disadvantages: the tension of the vapors of these fluids is weak, and therefore the evaporation has to be effected by the aid of pumps, and they are also dangerous from liability to explosions. The Siebe and West machine, which is of this kind and now in use, has a refrigerator, condenser, air-pump, and ice-making box. Johnston and Whitelaw's 'machine employs bisuiphide of carbon in place of ether. Hoitien'.1 machine employs a non-congealable liquid, as a vehicle of cold, it being passed through a pipe in a cylinder where the volatile liquid, as gasoline or chymogene, is evaporated. It is then conducted to the refrigerator, where, in connection with cur rents of air, it removes the caloric from the water to be frozen. It only remains to mention the air-machines, or those which operate on the simple principle of the expan sion of air. Probably the first of this kind was patented (both in England and America) in 1850, by John Gorrie, of New Orleans. The Windhausen machine, in present use, is an improvement upon it. There is no space in this article to describe the working of the apparatus, but an explanation of the general arrangement will probably suffice. The principle of cooling by gaseous expansion, as in the ether and ammonia machines, is employed, and in a similar manner; but instead of a volatile liquid, common air is us al. But it must first be compressed, and the more it is compressed the greater and more rapid will be the expansion when the pressure is removed, and therefore the more effective the refrigeration. Compressing the air, however, heats it, and therefore it must be cooled by passing it through pipes surrounded by cold water, or chambers into which sprays of cold water are injected. When it reaches the expansion cylinder it is cooled to nearly ordinary temperature. Here expansion is allowed to take place under various modes, according to the inventor's ingenuity, and the requisite reduction of temperature reduces the water exposed to ice. also Suit's, engines produce ice OD the principle of air expansion.