OXYGEN (Symbol, 0 ; atomic weight, i6).—The most abundant element. It is present in the air we breathe, it forms :ths (by weight) of water, and is present, to a great extent, in the solid part of the earth.
Oxygen can only be obtained from something that contains it. For this purpose chlorate of potassium is the most convenient, as by merely applying heat it separates into potassium chloride and oxygen, thus KC1+ 30 One molecule of the salt yielding three atoms of oxygen gas.
In the preparation of oxygen for commercial purposes, the potassium chlorate with about half its weight of black oxide of manganese is used.
In the following description* will be found a simple method of manufacturing oxygen gas on a small scale: Oxygen gas is obtained by subjecting to heat in a copper retort a mixture of one part of black oxide of manganese with four parts of chlorate of potash. The exact proportions are not arbitrary. The gas comes from the chlorate, and the office of the manga nese is only to separate the particles of chlorate, that the gas may gener ate evenly and be more readily con trolled.
A pound of chlorate should yield about cubic feet of gas.
A test of the chemical should be made before using. This may be done by putting a little in an iron dish or spoon and holding over a lamp. If the chemicals are good they will melt, dry up and leave a gray residuum, but if not good they will flash up, in which case they would not be safe to use.
The copper retort must be clean and dry. Put into it sixteen (i6) or eighteen (i8) ounces chlorate of potash and about one-quarter as much black oxide of manganese first thoroughly mixed. Close the retort tightly and attach the rubber hose to the pipe on top of retort. The other end of the rubber hose goes on the nozzle connecting the tube running inside one of the purifying bottles. From the other nozzle of the bottle another piece of rubber hose connects the bottle with the gas bag.
The purifying bottle must contain water enough to cover about an inch of the lower end of the brass tube. The gas passes from the retort through the rubber hose and the brass tube into.
the water, which washes it as it passes through; it is then carried by its own force out at the other nozzle into the bag. Before making all the connections, blow through the tubes to see if they are clear.
After connecting retort and wash bottle place the lighted lamp under the retort, turning the light well up. In a few minutes the water in the bottle will bubble as the gas generates. Allow it to escape for a while. Test its strength by holding before the open orifice a piece of charred wood with remaining sparks of fire ; when strong enough to fan these into a flame, the rubber hose connecting with the gas bags may be attached and the gas allowed to flow into the bag. Be sure the cock on the gas bag is opened to allow the gas to enter.
Very violent agitation in the bottle should be checked by removal of heat from retort.
Action will go on some time after lamp is removed and perhaps long enough to fill the bag, but should it not, heat must again be applied to retort. A little care in regulating heat of retort will insure a regular flow of gas until the bag is full.
When the bag is full, disconnect rubber hose from bottle, close stop cock on the bag, dis connect bottle from retort and then remove the heat.
• This description is supplied by Messrs. J. B. Colt & Co., if Beekman Street, N. Y., who manufacture the apparatus depicted.
Cleanse the retort by a thorough washing with water until all black sediment is removed and then put it where it will dry completely, as there must be no moisture in it when gas is made. Blow through pipes and hose and see that they are free from obstructions.
The apparatus used for the generation of one of the gases should never be used for the other, therefore it will be well to mark plainly the bag, bottle and connections with the name of gas for which they are first used.
The action of the manganese is not properly understood, but the evolution of the oxygen is rendered considerably more rapid even with a much lower temperature. Clean, coarse sand is equally efficacious.