Apparatus, assembling ground-glass

Although apparatus employing ground-glass joints is excellent for work on a macro scale, it is not always suitable for very small-scale work as the joints are often disproportionately large compared with the rest of the assembly. The semi-micro apparatus described on pp. 59-72 can therefore be considered as being of general utility for this scale of work, especially as the use of corks has been reduced to a minimum. 

Ensure that all the individual components in the assembly are adequately supported when in position the friction between contiguous ground-glass surfaces does not provide adequate support. Therefore always use clamps, the claws of which are lined with rubber or other soft material. When assembling apparatus, allow some play in the clamps until the individual parts are in position, and then secure the position of the assembly by gently increasing the pressure of the clamps. 

For this preparation, which must be performed in the fume-cupboard, assemble the apparatus shown in Fig. 67(A). C is a 150 ml. distilling-flask, to the neck of which is fitted a reflux single-surface water-condenser D, closed at the top E by a calcium chloride tube. The side-arm of C carries a cork F which fits the end E of the condenser for subsequent distillation. The side-arm of C is meanwhile plugged by a small rubber cork, or by a short length of glass rod. (Alternatively, use the ground-glass flask and condenser (Fig. 22 (a) and (c), p. 43), and... 

All glass apparatus is dried in an oven at 100°C and assembled while still hot under dry nitrogen flow. All ground glass joints are tightly sealed with a Teflon tape and then wrapped with parafilm. 

Preparation of Sodium Sulphide. Assemble an apparatus as shown in Fig. 67. Put 0.2 g of finely triturated highly pure sulphur into test tube 1 with a ground-glass joint, and lower the tube into a beaker with a mixture of dry ice and acetone. Connect a source of dry ammonia (see Fig. 62a) to cock... 

Assemble an apparatus as shown in Fig. 102. Lubricate the ground-glass joints with phosphoric acid. Fill the apparatus with dry carbon dioxide using offtake 2. Pour 10 ml of dry carbon disulphide from dropping funnel 3 into flask 1. 

Preparation of Zinc Iodide in Absolute Ether. Assemble an apparatus (see Fig. 119a), replacing dropping funnel 4 with a glass stopper provided with a ground-glass joint. Put 3 g of powdered zinc,... 

An alternative and quickly assembled apparatus employs a Buchner flask fitted with a ground glass joint to which is attached a dropping funnel. Ammonium chloride is placed in the flask, moistened with concentrated hydrochloric acid, and concentrated sulphuric acid added dropwise from the funnel at such a rate that the evolution of gas may be controlled. 

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