SOME ALUMINUM REDUCTION EXPERIMENTS R. A. KARGES State Teachers College, River Falls. Wisconsin
nesium in a piece of tissue paper. This is a much more effective fuse than a piece of magnesium ribbon and much more easily ignited. The ignition and reduction of the charge is, of course, conducted out of doors. Because of the size of the aluminum particles the reaction proceeds a t a moderate rate without throwing out the contents of the crucible. When the product has cooled, the slag of aluminum oxide is hammered away and a regulus of metal is obtained. Students in a class in inorganic preparations regularly get a yield of from 70 to 100 grams. Half the above quantities may be used, but the metal is likely to be dispersed somewhat through the oxide instead of forming a single mass. By using an excess of aluminum (100 grams of aluminum to 250 of manganese dioxide) 2n alloy of lower melting point is formed, which is more likely to form a single regulus. Another interesting reduction with aluminum is the preparation of crystallized silicon from sand described by Biltz and Biltz (loc. cit., p. 13). Forty-five grams of h e dry sand, 50 grams of powdered aluminum, and 60 grams of flowers of sulfur are mixed and put into a 4inch clay crucible. A fuse prepared with magnesium powder is embedded about 2 cm. deep in the mixture. The reaction is conducted out of doors; it proceeds rather slowly. When cool, the crucible is broken and the contents placed in a dish of water. There is a violent evolution of hydrogen sulfidedue to the hydrolysis of aluminum sulfide. When reaction has ceased, water is run into the dish and allowed to overflow. A firm black regulus of silicon is found in the dish, usually with smaller globules. This may be left in hydrochloric acid for several days, or it may be broken at ' BILTZ,H. AND IV. BILTZ,"Laboratory methods of inorganic once. shows shining leaflets of chemistry," translated by 1" T. H ~ Jand J A. A. ~ ~ ~ ~ ~ The h inside ~ of ~ thed regulus , John Wiley&Son-, N ~ York w City, 1909, p. 12. silicon. MANGANESE dioxide can easily be reduced to metallic manganese with very simple apparatus and very inexpensive materials. Most authors1 state that this reaction is so violent that the manganese dioxide must first be transformed by prolonged heating in a gas or electric furnace to MnsO4. Even when this lower oxide is mixed with aluminum, the student is directed to start the reaction with only a small portion of the mixture and to add the rest as the reaction proceeds. We have found that this reaction can be made to proceed smoothly by using aluminum turnings instead of granular aluminum. The manganese dioxide is heated only enough to dry it. Five hundred grams of powdered pyrolusite is heated in an iron dish over a Bunseu flame for 20 minntes. When cool, this is mixed with 185 grams of aluminum turnings. The turnings are cut into about 1-cm. lengths with the tin shears. This labor may be avoided by purchasing the turnings in wide cuttings instead of long stringy pieces. These cuttings can be quickly broken up in an iron mortar. The mixture of manganese dioxide and alfiminum is placed in a 5-inch flower pot or an 8-inch clay crucible, embedded in a pail of dry sand. An igniting mixture is made of 10 grams of barium dioxide and 1 gram of aluminum powder. Half of this mixture is worked into the main charge to a depth of about 2 cm. and within a diameter of 5 cm.at the top center of the charge. The rest is put into a hole about 2 cm. deep pressed into the center of the mixture. In this is placed the lower end of a fuse made by wrapping 0.25 gram of powdered mag-
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