Inventions in the Century

by William Henry Doolittle

Electric Heating and Cooking.—Reference has already been made in the Chapter on Electricity to the use of that agent in heating and cooking. The use of the electric current for these purposes has been found to be perfectly practical, and for heating cars especially, where electricity is the motive power, a portion of the current is economically employed.

The art of heating and cooking naturally suggests the other end of the line of temperature—Refrigeration.

A refrigeration by which ordinary ice is artificially produced, perishable food of all kinds preserved for long times, and transported for great distances, which has proved an immense advantage to mankind everywhere and is still daily practised to the gratification and comfort of millions of men, must receive at least a passing notice. The Messrs. E. and F. Carré of France invented successful machines about 1870 for making ice by the rapid absorption and evaporation of heat by the ammonia process. The discoveries and inventions of others in the artificial production of cold by means of volatile liquids, whether for the making of ice or other purposes, constituted a great step in the art of refrigeration.

Vaporisation, absorption, compression or reduction of atmospheric pressure are the principal methods of producing cold. By vaporisation, water, ether, sulphuric acid, ammonia, etc., in assuming the vaporous form change sensible heat to latent heat and produce a degree of cold which freezes an adjacent body of water. The principle of making ice by evaporation and absorption may be illustrated by two examples of the Carré methods:—It is well known what a great attraction sulphuric acid has for water. Water to be frozen is placed in a vessel connected by a pipe to a reservoir containing sulphuric acid. A vacuum is produced in this reservoir by the use of an air pump, while the acid is being constantly stirred. Lessening of the atmospheric pressure upon water causes its evaporation, and as the vapour is quietly absorbed by the sulphuric acid the water is quickly congealed. It is known that ammonia can be condensed into liquid form by pressure or cold, and is absorbed by and soluble in water to an extraordinary degree. A generator containing a strong solution of ammonia is connected by a pipe to an empty receiver immersed in cold water. The ammonia generator is then heated, its vapour driven off and conducted to a jacket around the centre of the receiver and is there condensed by pressure of an air pump. The central cylindrical space in the receiver is now filled with water, and the operation is reversed. The generator is immersed in cold water and pressure on the liquid ammonia removed. The liquid ammonia now passes into the gaseous state, and is conducted to and reabsorbed by the water in the generator. But in this evaporation great cold is produced and the water in the receiver is soon frozen.

Twining’s inventions in the United States in 1853 and 1862 of the compression machine, followed by Pictet of France, and a number of improvements elsewhere have bid fair to displace the absorption method. In dispensing with absorption these machines proceed on the now well-established theory that air and many other gases become heated when compressed; that this heat can then be drawn away, and that when the gas is allowed to re-expand it will absorb a large amount of heat from any solid or fluid with which it is brought in contact, and so freeze it. Accordingly such machines are so constructed that by the operation of a piston, or pistons, in a cylinder, and actuated by steam or other motive power, the air or gas is compressed to the desired temperature, the heat led off and the cold vapour conducted through pipes and around chambers where water is placed and where it is frozen. By the best machines from five hundred to one thousand pounds of ice an hour are produced.

The art of refrigeration and of modern transportation have brought the fruits of the tropics in great abundance to the doors of the dwellers of the north, and from the shores of the Pacific to the Atlantic and across the Atlantic to Europe. A train of refrigerator cars in California laden with delicious assorted fruits, and provided with fan blowers driven by the car axles to force the air through ice chambers, from whence it is distributed by perforated pipes through the fruit chambers, and wherein the temperature is maintained at about 40° Fah., can be landed in New York four days after starting on its journey of 3,000 miles, with the fruits in perfect condition.

But the public is still excited and wondering over the new king of refrigeration—liquid air.

As has been stated, the compression of air to produce cold is a modern discovery applied to practical uses, and prominent among the inventors and discoverers in this line have been Prof. Dewar and Charles E. Tripler.

Air may be compressed and heat generated in the process withdrawn until the temperature of the air is reduced to 312° below zero, at which point the air is visible and to a certain extent assumes a peculiar material form, in which form it can be confined in suitable vessels and used as a refrigerant and as a motor of great power when permitted to re-expand. It is said that it was not so long ago when Prof. Dewar produced the first ounce of liquid air at a cost of $3,000, but that now Mr. Tripler claims that he can produce it by his apparatus for five cents a gallon.

Refrigeration is at present its most natural and obvious use, and it is claimed that eleven gallons of the material when gradually expanded has the refrigerating power of one ton of ice. Its use of course for all purposes for which cold can be used is thus assured. It is also to be used as a motor in the running of various kinds of engines. It is to be used as a great alleviator of human suffering in lowering and regulating the temperature of hospitals in hot weather, and in surgical operations as a substitute for anæsthetics and cauterising agents.