A college text-book of chemistry . part ofsodium cut in pieces. Throw this mixture all at once into a Hes-sian crucible heated to bright red heat in a furnace. Add imme-diately 9 parts granulated zinc, and a layer of sodium chloridepreviously heated to drive off water. The crucible is then cov- 400 COLLEGE CHEMISTRY. ered, and the fire allowed to burn down. After cooling, theregulus of zinc containing the silicon is separated from the slag,washed with water, and treated with hydrochloric acid. Thezinc dissolves and leaves the silicon. This is again washed withwater, and then heated with nitric
A college text-book of chemistry . part ofsodium cut in pieces. Throw this mixture all at once into a Hes-sian crucible heated to bright red heat in a furnace. Add imme-diately 9 parts granulated zinc, and a layer of sodium chloridepreviously heated to drive off water. The crucible is then cov- 400 COLLEGE CHEMISTRY. ered, and the fire allowed to burn down. After cooling, theregulus of zinc containing the silicon is separated from the slag,washed with water, and treated with hydrochloric acid. Thezinc dissolves and leaves the silicon. This is again washed withwater, and then heated with nitric acid, and washed with water,when crystals of silicon, sometimes of great beauty, are the effect of heating a little of the silicon in the air. Try theaction of acids and of alkalies upon it. Silicon Teteaeluoride and Fluosilicic Acid. Experiment 197—Arrange an apparatus as shown in Fig. is a bottle of about 2 litres capacity, such as are commonlyused for transporting acids. This is about two-thirds filled with. S^ Fig. 77. alternating layers of sand and powdered fluor-spar, moistenedwith concentrated sulphuric acid. The bottle is put in the deepsand-bath B, and connected by means of a wide glass tube withthe funnel 0, which dips just below the surface of the water inthe large evaporating dish D. The sand-bath is now gentlyheated, when silicon tetrafluoride passes over. Coming in con-tact with water, it is decomposed, silicic acid being deposited andfluosilicic acid passing into solution. In order to prevent clog-ging, the gelatinous silicic acid is from time to time removedfrom the mouth of the funnel by means of a bent glass the action is complete, filter the solution. Take out one- EXPERIMENTS WITH SILICIC ACID. 4°* quarter, and to the rest slowly add a solution of sodium carbon-ate until the whole just begins to show an alkaline reaction ; nowadd the other quarter of the acid, and filter. Explain all the re-actions. Heat a little of the dried
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