Stoppers, cork

Two points must be borne in mind when selecting a cork stopper. In the first place, the cork should be e.xamined for- edom from flaws unless corks of the highest quahty are employed, they are liable to have deep holes, which render them useless. In the second jrlace, the cork should originally fit as shown in Fig. II, 3, I, a and not as in 6. 

It is advisable to keep the picric acid in the moist condition (containing about 10 per cent, of water) in a bottle with a cork stopper. Small quantities may be... 

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). 

Korken, m. cork, cork stopper, -zieher, m. corkscrew. 

The oxidation of the crude /3-chloropropionaldehyde is carried out in a 200-cc. flask fitted with a cork stopper held by a clamp about 2 cm. %bove the opening of the neck. The stopper carries a mechanical stirrer, a separatory funnel, a thermometer and a glass delivery tube about 10 mm. in diameter which is connected to a water pump. The space between the stopper and the flask is closed by winding a strip of asbestos paper around it (Note 3). 

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. 

It is not advisable to leave the separatory funnel attached to the flask during the long period of stirring which follows, as the constant, heavy vibration tends to loosen the connection. As soon as it has been used, the funnel should be replaced by a tightly fitting cork stopper. 

An additional possibility could be the transport of polymeric tensides, which are themselves not able to destroy the polymeric liposomes, to the membrane of the cancer cell. For the release of the incorporated tenside the membrane of the carrier liposome must contain destabilizable areas comparable to cork-stoppers (11). The destabilizable areas could eventually be opened by pTiotochemical destabilization of the membrane ( 73), variation of pH (74), increase of temperature ( 75), or enzymatic processes. 

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. 

Glycerol (bottle with a cork stopper carrying a glass rod). Hydrochloric acid, concentrated. 

To obtain the free aldehyde 25 g. of the aldehyde ammonia are dissolved in 25 c.c. of water, a cooled mixture of water (40 c.c.) and concentrated sulphuric acid (30 c.c.) is added, and the acetaldehyde liberated is distilled from the water bath through a calcium chloride U-tube (gently warmed if the external temperature is low) and through an efficient coil condenser. In order to prevent autoxida-tion of the acetaldehyde the apparatus is filled with carbon dioxide before distillation, and, since the vapour pressure of the aldehyde is high, a slow current of carbon dioxide is passed again, for a short time only, at the end of the distillation. Since acetaldehyde boils at 21° the receiver, which is attached to the condenser by means of a cork stopper, must be well cooled in an ice-salt freezing mixture. 

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-... 

Cork stoppers can react with or contaminate certain chemicals and should not be used. 

In a i-gallon bottle are placed 1050 g. of 95 per cent ethyl alcohol and 200 g. of granulated anhydrous calcium chloride (Note 1). The mixture is cooled to 8° or below by immersion in ice water, and 500 g. of freshly distilled acetaldehyde (B. P. 20-22°) is slowly added down the sides of the bottle so that it forms a layer on the alcoholic calcium chloride. The bottle is then tightly closed with a cork stopper and shaken vigorously for a few minutes (Note 2). It is then allowed to stand at room temperature with intermittent shaking for one to two days. The mixture divides into two layers after one to two hours after the first twenty-four hours no appreciable change in volume of the two layers takes place. 

By means of a graduated pipette provided with a rubber suction bulb, transfer 2ml of MG to a La Motte Co comparator tube and add neutral water to the mark on (he tube. After this, add 0.5ml of La Motte Co bromthymol indicator, close the comparator tube with a clean cork stopper and shake... 

Ground-glass joints are preferred however, burnt-cork stoppers may be used. 

Drilling of Stoppers. Select a bit of the proper size (Fig. 26) for drilling a hole in a stopper. For a cork stopper, the bit diameter must... 

Take a cork stopper in your left hand and mark its narrow end with the bit where the hole is to be, next begin to revolve the drill hy its handle in one direction while applying a slight pressure. See that the drill and stopper axes coincide, otherwise the hole will be skew. When the bit almost reaches the end of the stopper, put the latter on a higger cork or similar material on the table and continue to revolve the drill until the bit emerges from the stopper. 

Preparation of Sodium Bicarbonate. Saturate 50 ml of a 10% ammonia solution with sodium chloride in the cold. Filter the solution, pour it into a flask, and close it partly with a cork stopper accommodating a gas-discharge tube almost reaching the bottom of the flask. Pass carbon dioxide (from a cylinder or a Kipp gas generator) into the solution until a precipitate stops separating (during 1-1.5 hours). Separate the crystals on a Buchner funnel, wash them with ethanol, and dry them at room temperature in the air. Write the equations of the reactions. What impurities does the product contain ... 

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