Chemical lecture experiments . of combustion-tubing. The finely powdered nickeloxide should be thoroughly mixed with the asbestos, towhich a large quantity of the powder will cling. Hydro-gen, purified by being passed through a solution of potas-sium permanganate, is conducted through the tube, which is then heated to low redness. As the reduction is effected,the green nickel oxide becomes converted to black no more water vapor escapes from the tube, tin1 re- COBALT AND NICKEL 41 duction may be considered complete, and the nickel isallowed to cool in a current of hydrogen
Chemical lecture experiments . of combustion-tubing. The finely powdered nickeloxide should be thoroughly mixed with the asbestos, towhich a large quantity of the powder will cling. Hydro-gen, purified by being passed through a solution of potas-sium permanganate, is conducted through the tube, which is then heated to low redness. As the reduction is effected,the green nickel oxide becomes converted to black no more water vapor escapes from the tube, tin1 re- COBALT AND NICKEL 41 duction may be considered complete, and the nickel isallowed to cool in a current of hydrogen. Carbon monoxide from the generator (Ex. 12, p. 298) isconducted through a calcium chloride drying-tube and thendirectly through the tube containing the reduced issuing gas is passed through a long glass elbow ex-tending nearly to the bottom of a test-tube fitted with atwo-holed cork. The gas issuing through a shorter elbowin the second hole of the cork should be conducted into the •HS ^^w^f&ip^m^m^ diN^vi^3-. Fig. 163 flue. The test-tube should be immersed in a freezing-mix-ture of salt and ice (Fig. 163). As the carbon monoxide comes in contact with the nickel,the temperature of the tube is materially increased, indi-cating the chemical action. The gas escaping from the glasselbow in the test-tube consists of carbon monoxide contain-ing a quantity of uncondensed vapor of nickel tetracar-bonyl, which, owing to its poisonous character, should notbe inhaled. The preparation of any considerable quantityof the tetracarbonyl requires too long a time for demonstra-tion on the lecture table, though, if the operation is begunbefore the hour, 2 or 3 cc. may be obtained. If the test-tube2e 418 CHEMICAL LECTURE EXPERIMENTS is somewhat constricted in the middle, the condensed liquidmay be sealed off in the glass tube. If the escaping gas is conducted into the base of a Bunsenburner, the flame becomes brilliantly luminous from the in-candescence of fine particles of nickel. T
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