Cork stoppers boring

A 6-1. round-bottomed flask is used as the reaction vessel. This is fitted with a cork stopper, bored to carry a gas inlet tube, a reflux condenser, and an efficient mechanical stirrer. The inlet tube should penetrate as far as possible into the flask and is best fitted with a T-piece above the stopper, so that in case the end of the tube becomes blocked during the reaction a wire may be pushed through to free it. The other arm of the T is connected to an ammonia cylinder via a safety valve and a long potassium hydroxide drying tube, the latter being unnecessary when dry ammonia is used. 

Repeated flicking of centrifuge tubes with the finger tip is, at times, quite painful. To avoid repeated discomfort, a simple flicking device can be constructed with a shaded pole a.c. phonograph motor (cost about 3.00). The motor is screwed onto a wooden board and a cork stopper, bored slightly off-center, is fitted to the motor shaft. When in operation,... 

Flask F is provided with a two-hole cork stopper connected with tube E, and with tube G which connects with the first condenser II and may be of smaller bore than tubes C and E. H is. a. condenser with a 30-cm. water jacket. H is connected with I by means of an adapter. / is a i-l. round-bottom flask supported in a pan which is at first filled with ice and later used as a water bath. Flask I is fitted with a two-hole cork stopper carrying the adapter connected with condenser H and a Vigreux column K of 2-cm. diameter and a length of 30 cm. to the side arm. Flask I and condenser H are covered with black cloth (Note 2). The side arm of K is connected with a 90-cm. water-jacketed condenser L which leads into M through an adapter, iff is a 750-cc. Erlen-meyer flask immersed in an ice bath. Flask M is provided with a two-hole stopper connected with the adapter from L and an upright bulb condenser that is provided with a tube leading through a window or to a hood. 

The apparatus illustrated in Fig. 3 is assembled, in a large hood if possible (Note 3). A is a 5- . round-bottom flask heated by a large ring burner and provided with a specially treated four-hole cork stopper covered with tin foil (Note 4). To these holes are fitted the column Z), the tube B reaching to the bottom of A, the specially bent tube C reaching up the inside of D, and the tube K connected with the tubes leading to the 2-I. separatory funnel H, so that the distance between the stopper of A and the stopcock of H is at least 100 cm. The bottom of the column D is of 20 mm. bore while the main portion is 30 mm. The side arm should be at least 85 cm. above the stopper of 4. The tube C... 

The apparatus consists of a 100-ml distilling flask equipped with a dropping funnel and arranged for distillation through an efficient condenser. The condenser is connected to two receiving flasks in series, the second of which contains 20-30 ml of ether. The inlet tube of the second receiver dips below the surface of the ether and both receivers are cooled in ice baths. All connections in the setup are made with bored cork stoppers and all glass tubing is fire polished (Fig. 17.1). 

The air condenser used here was 65 cm. long and of 13 mm. bore and the vertical water condenser, 40 cm. in length. Cork stoppers were used and it was found desirable to protect their exposed surfaces by coating them with water glass, allowing these to dry, and then coating with lead foil. It is best to boil the mixture on a sand bath and to cover with asbestos that part of the flask not immersed in the sand. 

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. 

Since over-ozonisation must be in any case avoided, attach a second wash bottle containing acid potassium iodide solution to the outlet tube of the first before the calculated time has elapsed. If no ground glass joint1 is available, use a long bored cork stopper which has been dipped in molten paraffin wax. 

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-... 

Continuous steam distillation, 147, 148 Cooling baths, 61 Cooling curve method, 26 Copper bronze, activated, 193 Copper - chromium oxide catalyst, for aldehyde synthesis, 318, 321 for hydrogenation, 872, 873 hydrogenolysis with, 872J Copper phthalocyanine, 983 Copper powder, 192 Copper sulphate, as desiccant, 40, 41 Cork stoppers, 55 boring of, 56... 

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. 

The connection between the condenser and the flask should be made with a rubber stopper in most cases. However, it should be noted that many solvents attack rubber (benzene, ligroin, etc.), not only causing damage to the stopper, but also introducing impurities into the materials. In such cases, it is preferable to use cork stoppers which have been carefully rolled before boring. If the vapors attack both cork and rubber, the use of an apparatus with ground glass joints is necessary. 

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. ... 

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. 

Fit apparatus together carefully and compactly, paying particular attention to the clamping that holds the apparatus steady and to the fitting and boring of corks and stoppers. 

The stoppers in the reaction flask and at the top of the dropping funnel are of rubber the other two are well-selected corks, bored perfectly and painted both inside and out with water-glass, one day previous to being used. 

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. 

---