Rubber stoppers boring

Air Jacket For the air jacket, use a standard glass 38- x 200-mm test tube with a lip and fitted with a cork or rubber stopper bored with a hole into which the sample container can easily be inserted up to the lip. 

When boring rubber stoppers, lubricate the borer well, either with aqueous glycerine or with vaseline. Then clean well and dry before using. 

Wider passages are provided for vapours and the comparatively narrow tubes, which are usually fitted through holes bored in cork or rubber stoppers, are absent this considerably diminishes danger in violent reactions and also tends to give better results in distillation under reduced pressure as well as diminishing the hazard of choking. ... 

H is placed at the highest available level (Note 5) and connected with the tubes 7, 7, and K in such a manner as to secure a pressure of liquid sufficient to more than balance the steam pressure (Note 6). E and F are specially constructed condensers of unusual length (160 cm. and 85 cm., respectively) and bore (40 mm.) made from large glass tubing and rubber stoppers (Note 7). I he top of condenser E is connected to a good draft chamber. 

An assortment of small corks for closing small bore tubing can, in addition, be very useful. If the flame is to come near to a cork or a rubber stopper it is best to wrap either in thin asbestos paper before inserting into the tube. When pyrolysis of the cork or rubber stopper seems probable it is best to use a cork and not a rubber stopper, because the pyrolysis products from a cork can be cleaned olf more easily than those from rubber. Sometimes a plug made from damp asbestos paper is adequate for closing a tube of small bore, and this plug can be heated quite strongly. 

The capillary tube is inserted (with a little glycerol as lubricant), tip first, into a narrow-bored, undamaged rubber stopper which fits tightly into the neck a of the Claisen flask. The correct position of the tip is immediately above the deepest part of the bulb of the flask. A thermometer, likewise pushed through a rubber stopper, is inserted into the neck b. If it is desired to prevent contact of the substance with rubber, Claisen flasks with constricted necks are used. The capillary tube and thermometer are held in position in these necks by means of small pieces of rubber tubing drawn over each neck and its capillary or thermometer. The proper use of cork stoppers in vacuum distillations requires much practice. 

A 5-I. round-bottom flask is fitted with a rubber stopper or a cork stopper coated with pitch, carrying two glass tubes, one of which (for the entrance of steam) reaches to the bottom of the flask, while the other extends into the open end of a condenser set for downward distillation. The stopper should be wired into the flask. The glass delivery tube into the condenser should not be less than a 12-mm. bore, and the condenser should consist of two 120-cm. water-cooled condensers attached end to end. To the end of the condensing system, an adapter is attached, the small end of which is at least 8 mm. in bore and is fitted tightly into a stopper in a 2-1. suction flask. To the side-... 

Attachment of dropping funnel and thermocouple well to the p3Tolysis tube may be made with a rubber stopper suitably bored. 

The determination of the temperatures of crystallization of the mixtures was carried out in a closed glass apparatus with a manual stirrer. This entered the vessel through a hole of tight bore in the rubber stopper, which was greased with vaseline, so that the accession of atmospheric moisture was reduced to a minimum. Temperatures above 0°C were measured with a mercury thermometer with scale divisions of 0-1°, which was calibrated by the ice-water mixture at 0° and by the Na2S04 0H2O transition point at 32 38°. For temperatures below 0° an alcohol thermometer with 0 2° scale divisions was used. It was calibrated also at 0° with the ice-water mixture. Since the thermometer capillary was at room temperature in the course of the determinations, a correction for its expansion was applied. The low temperatures were obtained by means of dry ice-acetone mixtures. 

Rotatory power, determination of, 504 Rubber, natural unvulcanised, 1022 synthetic, 1022 Rubber stoppers, 55 boring of, 56... 

Boring of Corks.—Sharp borers should always be used. The end of the cork is placed against some solid object and bored half-way through from one end. The boring should then be completed from the other end. The boring of rubber stoppers may be greatly facilitated by moistening the borer with caustic soda. Mechanical borers are now available. 

No corks or rubber stoppers are, in general, required and the selection, boring and fitting of corks is largely eliminated, thus resulting in a considerable sav-... 

To bore a rubber stopper, it is essential to employ a very sharp cork borer of the same size as the tube to be inserted into the hole. The borer is lubricated with a little glycerol or alcohol and steadily rotated under only very slight pressure. The operation requires a good deal of patience and time and frequent lubrication may be necessary if too much pressure is exerted on the borer, a hole of irregular shape and diminishing size will result. 

---