Rubber stoppers removing glass tubing

The student need not work up the mother liquor hut may be interested in learning the result. Concentration of the solution to a small volume is not satisfactory because of the presence of dicyclopentadiene, formed by dimerization of excess monomer the dimer has high solvent power. Hence the bulk of the solvent is evaporated on the steam bath, the flask is connected to the water pump with a rubber stopper and glass tube and heated under vacuum on the steam bath until dicyclopentadiene is removed and the residue solidifies. Crystallization from 1 1 ethyl acetate-ligroin affords 1.3 g of adduct, mp 156-158°C total yield is 95%. 

FIGURE F.2. Removing glass tubing from a rubber stopper. 

Fig. 4. An elution chamber used in the removal of steroids from paper chromatograms prior to their analysis (A) Solvent reservoir, (B) rubber stopper, (C) capillary tube, (D) glass rod support for paper, (E) paper strip, and (F) volumetric flask.

Now fit the calcium chloride tube closely to the constricted part of the combustion tube and connect the sodium hydroxide-asbestos tube to the calcium chloride tube of the aspirator. Then remove the rubber stopper from the combustion tube, push back the stand carrying the drying apparatus so as to make more room, raise the copper block with the boat to the opening of the combustion tube, with the forceps insert the boat, push it inwards 4-5 cm. up to the furnace with a clean glass rod of suitable size, taking care not to tip the boat over, insert the rubber stopper loosely into the tube, moistening the stopper if necessary with a very thin film of glycerol,... 

To test the valve, remove the glass tube from the rubber stopper of the flask and note if the slot allows passage of air when some pressure is applied. Then connect the tube to a water pump and see if it creates a vacuum Refs i)Ciirt Fedoroff 3(1943), Chap II,p 13 2)Hackh s(1944), 888... 

Distillation heads (or still-heads) are shown in Fig. 2.13 (a)-(c). Type (a) is a bend ( knee-tube ) which is frequently employed for those distillations which merely require the removal of solvent. Type (b) is a simple distillation head when fitted into a flask with a ground glass socket, the assembly is virtually a distillation flask. For some purposes, a thermometer may be fitted into a one-hole rubber stopper of correct taper and then inserted into the socket the area of rubber which is exposed to the organic vapour is relatively so small that the amount of contamination thus introduced is negligible. If, however, all rubber stoppers must be absent because of the highly corrosive nature of the vapour, a thermometer fitted with an appropriate size cone is employed. Alternatively the... 

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