Modern magic lanterns; a guide to the ... - Yesterday Image

22 MODEEN MAGIC LANTEENS.iron, rtjmoves. A prepared cake of manganese oxideand potassium chlorate is introduced, the top [put on, thehandle replaced, and the gas lit at the Bunsen burner, whichis enclosed in the hollow part underneath(only the stopcock isvisible in the figure) ;gas rapidlycomes off until, in a quarter of anhour or less, the cake is exhausted,and may be replaced by another.In case of any excess of pressurein the vessel, the springs at theside allow the lid to rise and thegas to escape. The cakes aremade by mixing four parts ofmanganese oxide to one part ofthe powdered chlorate, enoughwater being added to just moistenthe mass, which is then filled intoa mould. The cakes are allowedto dry, when the bottom of eachis coated with a thin paste ofmanganese oxide and water Fig. 16. Oxygen Eetout.to prevent it sticking to theretort. The use of the cakes entirely prevents the chokingup of the retort with the decomposed oxygen mixture, thebye-product coming away in a mass just as the cake wasinserted. We recently saw one of these working in conjunctionwith a large gas holder of the type shown in Fig. 14.It had been in use for many years, making oxygen forenlarging purposes, without the slightest hitch. Anotherform designed by Mr. Chadwick has a weighted Ud at theend, which acts when necessary as a dead-weight safetyvalve.For oxygen making, as we said before, the manganeseoxide should be got from a reliable source. The chlorate isbest bought ready powdered if to be made up into cakes asabove described ; if to be used loose, the crystals should beemployed (it is best not to attempt to powder it oneself), andthe manganese used should be the granulated form. Bothingredients should be carefully picked over for scraps of