Sililation of Glassware and Plasticware

An alternative procedure used for large apparatus is to rinse it with a 5% solution of dichloromethyl silane in chloroform, then rinse several times with water before baking at 180°/2h (for glass) or drying in air (for plasticware). REPEL-SILANE (a solution of 2% w/v of dichloromethyl silane in 1,1,1-trichloroethane) is available commercially (LKB, Sweden). 

One of the most widely applicable and most commonly used methods of purification of liquids or low melting solids (especially of organic chemicals) is fractional distillation at atmospheric, or some lower, pressure. Almost without exception, this method can be assumed to be suitable for all organic liquids and most of the low-melting organic solids. For this reason it has been possible in Chapter 3 to omit many procedures for purification of organic chemicals when only a simple fractional distillation is involved - the suitability of such a procedure is implied from the boiling point. 

The boiling point of a liquid varies with the atmospheric pressure to which it is exposed. A liquid boils when its vapour pressure is the same as the external pressure on its surface, its normal boiling point being the temperature at which its vapour pressure is equal to that of a standard atmosphere (760mm Hg). Lowering the external pressure lowers the boiling point. For most substances, boiling point and vapour pressure are related by an equation of the form, 

For pressures near 760mm, the change in boiling point is given approximately by [Crafts B 20 709 1887], 

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