The three prototypes of this cell, the first of which was introduced into the United States in 1910, are shown in the accompanying 'cuts. The improvements have been along the lines of compactness, higher electrical efficiency and simplicity of construction.
From Liquid Air.— By fractional distilla tion. Since the boiling point of oxygen at atmospheric pressure is — 182.7° C., while that of nitrogen is —195.5° C., by a proper frac tionating apparatus the nitrogen in liquid air can be allowed to boil off first, leaving pure oxygen behind. Sec Liquefaction of Gases, p. 495.
Commercial Uses.— Because it costs noth ing, the oxygen which plays so large a part in the burning of fuel for the production of light, heat and power, or wherever fuel of any kind is burned, is generally overlooked in listing the uses of oxygen. However, each ton of coal burned consumes about three tons (about 70,000 cubic feet) of oxygen. The amounts of oxygen con sumed in this way are scarcely comprehensible. One moderate sized blast furnace uses 40,000 cubic feet of air per minute and since it is becom ing possible to make oxygen cheaply the use of super-oxygenized air for blast furnaces is being seriously considered. Experiments made on a 100-ton furnace in Belgium before the World War showed that by increasing the percentage of oxygen in the air only from 21 to 23 per cent, a saving of over 100 pounds of coke is effected in smelting 1 ton of iron, and at the same time the output of the furnace is in creased by from 10 to 15 per cent.
1. For Welding and Cutting of Metals.— Oxygen in conjunction with hydrogen or acety4 lene in the oxy-hydrogen or oxy-acetylene flame finds very extensive use for cutting all kinds of iron and steel even up to massive struc tures. The accompanying cut • shows an oxy-hydrogen torch fed by oxygen and hydro gen from two steel cylinders containing the compressed gases. The oxygen is supplied to the inner and the hydrogen to the outer tube: The quantity of the two may be regulated at will so that an oxidizing or reducing flame is obtained. For cutting an oxidizing flame is em ployed. When the metal upon which the flame is directed has attained the desired temperature the hydrogen gas is shut off. The stream
of oxygen plays upon the hot metal and combines with it to form Fe.,04 which is then blown away in the gas current. For autoge nous welding a reducing flame must be em ployed. The cutting out of a manhole in a boiler of average size by mechanical means will employ two workmen seven to eight hours; by means of oxygen this can be done in about eight minutes. Similarly large steel boiler plates, rails, girders (e.g., in demolishing buildings), etc., may be cut away with extreme ease and nicety. Metals autogenously welded are fre. quently stronger at the welded portion than elsewhere. The above properties of the oicy hydrogen and oxy-acetylene flame have found extensive application in the motor car industry, in railroad and boiler and machine shops, in mining and tunneling, also in the tinning and enameling industries.
2. For Combustion—Air enriched with oxygen allows the smokeless combustion of certain fuels in furnaces; also for the produc tion of producer and water gas. It is finding application as well for obtaining high furnace temperatures; e.g., in the glass industry, sav ing fuel and time.
3. In Varnish Manufacture.— Animal and vegetable oils, such as fish oil, linseed oil, soya bean oil, etc., may be oxidized by blowing with oxygen gas to form oils of much higher vis cosity and specific gravity.
4. Medicine.— Oxygen is advantageously used in cases of asphyxia, asthma, autointoxi pulmonary diseases, heart diseases, anaemia and diabetes. It has a cicatrising ac tion in the cure of wounds and prurulent in fections.
Oxygen in cylinders is used for freshening the air in submarines; for high altitude work in aeroplanes; for experimental and analytical work in laboratories; for medical purposes as noted above, for melting silicon and in the blow pipes used in the manufacture of synthetic gems.
The most important industrial use is for oxy-acetylene or oxy-hydrogen welding and cutting. Though a very recent development in the engineering and construction field, the amount of oxygen consumed in this way is enormous.