Lubricant glass

Extrusion is primarily used for lower-melting point, nonferrous metals (see Table 7.2) but with the aid of lubricants and improvements in presses, the extrusion of steel has become available. Most carbon steels and stainless steels are extruded at temperatures of about 1200°C, in which glass is used as a lubricant. Glass is inexpensive, easy... 

The gases can be introduced into the vessel by the use of an all-metal system or a Kel-F lubricated-glass vacuum system equipped with a fluorine-resistant pressure gagef and a soda-lime trap to protect the vacuum pump. The author s preference for an overall system is the all-metal transfer line and the reaction... 

This compound darkens upon loss of tetrahydrofuran, which can occur even at near room temperature. The compound is sensitive to air and moisture in the sohd state and in solution. Reaction with water results in quantitative hydrogen evolution according to the equation [FeHe]" + 6H2O Fe + 6H2 + 6HO . This hydride titer is conveniendy performed in a small septum-capped vial, and the hydrogen evolution measured by an oil-lubricated glass syringe. ... 

It is often advisable to lubricate ground-glass joint surfaces with an extremely thin film of vaseline. This applies particularly to joints employed in assemblies for distillation under reduced pressure. For distillations under greatly reduced pressures or at very high temperatures it is essential to employ a special lubricant, e.g., silicone grease. 

Some simple apparatus, suitable for high vacuum distillation, are collected in Figs. 11, 26, 1-4. Fig. 11, 26, 1 represents an apparatus, which is particularly well adapted for solids the ground glass joint must be lubricated with a grease of negligible vapour pressure. Hickman s vacuum still is shown in Fig. 11, 26, 2 it is about 60 mm. in diameter. 

Lubrication of all ground glass surfaces is essential for distillations under reduced pressure. Suitable lubricants are Apiezon grease L, M or N and Silicone stopcock grease also Alkathene (a polyethylene plastic), which is especially suitable for high temperatures. 

Dissolve 180 g. of commercial ammonium carbonate in 150 ml. of warm water (40-50°) in a 700 ml. flask. Cool to room temperature and add 200 ml. of concentrated ammonia solution (sp. gr. 0 88). Introduce slowly, with swirling of the contents of the flask, a solution of 50 g. of chloroacetic acid (Section 111,125) in 50 ml. of water [CAUTION do not allow chloroacetic acid to come into contact with the skin as unpleasant burns will result]. Close the flask with a solid rubber stopper and fix a thin copper wire to hold the stopper in place do not moisten the portion of the stopper in contact with the glass as this lubrication will cause the stopper to slide out of the flask. Allow the flask to stand for 24-48 hours at room temperature. Transfer the mixture to a distilling flask and distil in a closed apparatus until the volume is reduced to 100-110 ml. A convenient arrangement is to insert a drawn-out capillary tube into the flask, attach a Liebig s condenser, the lower end of which fits into a filter flask (compare Fig.//, 1) and connect the... 

Ethylene. Under the influence of pressure and a catalyst, ethylene yields a white, tough but flexible waxy sohd, known as Polythene. Polyethylene possesses excellent electric insulation properties and high water resistance it has a low specific gravity and a low softening point (about 110°). The chemical inertness oi Polythene has found application in the manufacture of many items of apparatus for the laboratory. It is a useful lubricant for ground glass connexions, particularly at relatively high temperatures. 

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