Tubing inserting into stoppers

Two sets of stoppers are very useful, one set unbored and a second set with a single hole bored in them to carry blowing-tube connectors. A longer piece of glass tubing inserted into the hole will also form a very adequate handle when working small pieces of apparatus. 

A 1.8 Sample Transfer Connection—This is a device for removing liquid from the sample container without interfering with the vapor space. The device consists of two tubes inserted into a two-holed stopper of appropriate dimensions to fit the opetung of the sample container. One of the tubes is short for the delivery of the sample, and the other is long enough to reach the bottom comer of the sample container. Fig A 1.2 shows a suitable arrangement. 

This test was prepared and is limited to type 1 (low-density) polyethylenes. Specimens are annealed in water or steam at 212°F (100°C) for 1 h and then equilibrated at room temperature for 5-24 h. After conditioning the specimens are nicked according to directions given. The specimens are bent into a U shape in a brass channel and inserted into a test tube that is then filled with fresh reagent (Igepal). The tube is stoppered with an aluminum-covered cork and placed in a constant temperature bath at 122°F (50°C). 

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. 

Centrifuging the screw-cap vial can easily break emulsions, which often form during extraction. The vial will survive up to 6000 g if rubber stoppers are inserted into the centrifuge cup to provide a flat base for the vials. The required phase (usually the top layer) can be easily removed with a pipet or, if it is to be discarded, it can be removed using a disposable pipet connected by tubing to a suction flask and vacuum line. 

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. 

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,... 

Fig. 53a). Take two small U-tubes, close their upper openings with rubber stoppers, and their side offtakes with short rubber tubes having glass rods inserted into them. Weigh the tubes. Fill one U-tube with the prepared activated carbon, and the other with ordinary charcoal. Again weigh both tubes and connect them by a tee-piece to a source of chlorine.

Preparation of Chromium(II) Chloride. (Perform one of the following two experiments.) 1. Put several pieces of metallic chromium into a test tube, pour in 2-3 ml of a 20% hydrochloric acid solution, and insert a stopper with a gas-discharge tube. Connect to the latter a rubber tube with a slot closed by a glass rod (a Bunsen valve. Fig. 125). What is the role of the slot in the rubber tube Identify the substance in the solution. Write the equation of the reaction. 

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... 

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. 

It is essential that the hot nitric acid shall not come into contact with rubber, in order that no nitrous acid may be formed. To avoid this, the top of the tube ground into the cover is sealed off, and the side-arm delivery tube lengthened to at least 25 cm. The side arm is then inserted 7 to 8 cm. below the water-cooled part of the condenser tube, which should allow of very little clearance, in order that no nitric acid may come in contact with the rubber stopper joining the two. 

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