Heating hard glass

The sodium fusion and extraction, if performed strictly in accordance with the above directions, should be safe operations. In crowded laboratories, however, additional safety may be obtained by employing the follow ing modification. Suspend the hard-glass test-tube by the rim through a hole in a piece of stout copper sheet (Fig. 69). Place 1 -2 pellets of sodium in the tube, and heat gently until the sodium melts. Then drop the organic compound, in small quantities at a time, down — =. the tube, allowing the reaction to subside after each addition before the next is made. (If the compound is liquid, allow two or three small drops to fall at intervals from a fine dropping-tube directly on to the molten sodium.) Then heat the complete mixture as before until no further reaction occurs. 

Action of heat. Heat about 0 2 g. of uric acid in a hard-glass test-tube. Note the charring and also the formation of a white sublimate on the cooler parts of the tube. 

A Combustion Tube of Hard Glass.—It should be about 13 mm. inside diameter, and the walls not more than i 5 mm. thick. Its length should be such that it projects at least 5 cm. (2 in.) beyond the furnace at either end. After cutting the required length, the ends of the tube are carefully heated in the flame until the sharp edges are just rounded. The tube is filled as follows. Push in a loose asbestos plug about 5 cm. (2 in.) from... 

Heat a little of the substance in a small, hard-glass tube and observe whether the substance melts, chars, explodes, sublimes, or volatilises whether an inflammable gas, water, etc., is evoKed also notice the smell. 

Contains Nitrogen.—First test the original solid ni liquid by heating in a hard-glass tube with soda-lime (p. 2), and notice if the smell is that of ammonia (ammonia salt, amide or cyanide), an amine (amine or amino-acid) or a pyridine base (alkaloid). 

Simple pumps for circulating gas or liquid can be made using two valves with a chamber between them. One ingenious pump uses a heat engine (A. R. Pearson and J. S. G. Thomas, 1925). The hard glass or silica bulb A (Figure 80, T) contains air initially at atmospheric pressure. This is heated with tap T closed and when the... 

The preparation was performed by Iandelli (1941) from the elements closed, in vacuo, in a hard glass ampoule. This was then heated up to about 700°C for 2 weeks. The slow reaction was observed with a gradual consumption of arsenic. 

According to B. Schindler,16 potassium iodide volatilizes in free air when heated to the softening temp, of hard glass, and, according to B. Bunsen, and T. H. Norton and D. M. Both, it volatilizes from 0-352 to 0-423 times as fast as the same quantity of sodium chloride when heated in the hottest part of a Bunsen s flame. According to J. Dewar and A. Scott,17 the vapour density of potassium iodide is 169 8. A. von Weinberg obtained 43"3 Cals, for the heat of sublimation of sodium iodide, and 44 9 Cals, for that of potassium iodide and A. Beis obtained for sodium and potassium iodides respectively 51 and 46 Cals., and between 15 and 35 Cals, for lithium iodide. 

Hypovanadic Chloride, vanadium tetrachloride, VC14, can be prepared synthetically from the lower chloride, VC13, by heating in a stream of chlorine at 600° C. Another convenient method consists in passing dry chlorine over ferrovanadium contained in a hard glass tube heated in a combustion furnace. The reaction is expressed ... 

Niobium Trichloride, NbCl3, is prepared by leading the vapour of niobium pentachloride through a heated tube.4 It is also formed in small quantity by the action of carbon tetrachloride vapour on niobium pentoxide contained in a hard-glass tube, and has probably been prepared in solution by the electrolytic reduction of the pentachloride.4 It forms a black, crystalline crust with an almost metallic lustre, which closely resembles the appearance of a film of sublimed iodine. It is not decomposed by water or ammonia, but is readily oxidised by dilute nitric add to niobium pentoxide. On being heated to a red heat in an atmosphere of carbon dioxide, a sublimate of niobium oxytrichloride, NbOCl3, is produced, the carbon dioxide undergoing reduction to the monoxide. 

Oxide Aluminum oxide, alumina AI1O3, white solid, insoluble, melting point 2020 C. formed by heating aluminum hydroxide to decomposition when bauxite is fused in the electric furnace and then cooled, there results a very hard glass ( alundum ), used as an abrasive (hardness 9 Mohs scale) and heat refractory material. Aluminum oxide is the only oxide that reacts both 111 H20 medium and at fusion temperature, 10 form salts with both acids and alkalis. 

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