The Art of projection and complete magic lantern ... - Yesterday Image

—73bottles black, and hydrogen (or coal gas) bottles red. This, however,was no absolute safeguard, and the system now adopted (in addition tothe different colours of bottles) is to make all valve and other connectionsfor oxygen and hydrogen non-interchangeable.This absolutely precludesthe possibility of mixing gases in bottles, and when it becomes universal(as it must in a very few years), I feel convinced that the only realelement of danger in the use of high-pressure gas bottles will be removed."OXYGEN MAKING.Oxygen is a colourless invisible gas possessing neither taste nor smell,and is made for our particular use from potassium chlorate (commonlycalled chlorate of potash). If a small quantity of manganese dioxide(black oxide of manganese; be mixed with the potassium chlorate, theoxygen is given off from the chlorate at a much lower temperature andin a more regular manner, and thus the evolution of the gas is facilitated,but the manganese undergoes no change whatever. Although oxygenmay be obtained by heating manganese dioxide to red heat in an ironbottle, but this is out of the question for the average lanternist.The best proportions, which are the outcome of a great many years'practice are,—4 parts potassium chlorate, — i part manganese oxide, wellmixed and incorporated together. The chlorate may be obtained inpowder or crystals, the latter is prefered, it is easier to mix with themanganese, 3 lbs. of this mixture should produce 8 ft. of gas.The retort should be made of sheet iron with a double bottom, sothat the iron work or a new bottom may be renewed by any smith,when charged place on a fire, ordinary heat from a fire or bunsen issufficient to generate the gas, with a retort of this description, a cork orsafety plug of at least three quarters of an inch in diameter is fixed atthe top, in the event of any stoppage in the tube, this will force itselfout and the gas pass harmlessly away.Oil no account should cast iron or mercury bottles be used as retorts,an enormous heat is required to make them hot, and then the gas rushesoff at a terrific speed and there is no means of stopping it, and shouldthe retort cool down before all the gas is given off, it is the hardestmatter possible to get it to start again. This is not the case with asheet iron retort, which being thin is acted upon at once by the heat,an amateur may make gas for the first time in this form of retort, withthe greatest comfort and ease. The gas when given off by the retort ispassed through a