Closing tubes with rubber caps

As soon as micro-bubbles only are being produced in the nitrometer close the stop-cock on the connecting tube, detach the rubber connecting tube from the combustion tube, close the latter with a cap made from rubber tubing, and leave to cool whilst maintaining the internal carbon dioxide pressure. Remove the nitrometer to a somewhat cooler room (room in which the barometer is kept preferably) after raising the bulb so that the surfaces of the two columns of liquid are at the same level. 

Great care must be taken that, when no gas is passing through the drying apparatus, its side tube, which leads to the combustion tube, remains closed by means of a rubber cap in order to protect the calcium chloride from atmospheric moisture. When the calcium chloride at the outlet is exhausted—-the sodium hydroxide-asbestos lasts much longer— the stopper is removed and about half of the column is replaced with fresh calcium chloride. 

During the analysis the calcium chloride tube is attached directly to the sodium hydroxide-asbestos tube. When the apparatus is not in use this calcium chloride tube is closed with a rubber cap.-... 

Add 10 mL of the basic solution to 1 mL of the ether extract in a screw-cap test tube. Close the test tube with a Teflon-rubber septum cap. 

The rubber inserts in the caps for the bottles can be cut from silicone rubber sheet ( 2-mm thickness). These ensure a very close fit with the Marprene tubing to maintain an airtight seal... 

The determinations of the solubility can be carried out in various ways- One of the simplest methods, which also gives sufficiently accurate results when the temperature is not high or when the solvent is not very volatile, can be carried out in the following manner. The solid substance is finely powdered (in order to accelerate the process of solution), and placed in sufficient quantity along with the solvent in a tube carefully closed by a glass stopper the latter is protected by a rubber cap, such as a rubber finger-stall. The tube is then rotated in a thermostat, the temperature of which does not vary more than one or two-tenths of a degree, until saturation is pro-... 

The reaction tube described on p. 87 (Fig. 69) is used for the preparation of sodium nitroxylate. Two grams of repeatedly crystallized and carefully h h vacuum dried NaNC are placed in leg b and tube c is sealed off. Fresh Na (0.4 g.) is placed in a. The ground glass cap d is put in place and its tube connected with rubber or tombac vacuum tubing to a high-vacuum apparatus (via stopcock 5). The apparatus is evacuated, stopcock 5 is closed, and... 

If the electrical terminals of these clamps consist of water-cooled copper tubing, then the seal to the glass caps is made with rubber tubing. A clamp is made by closing one end of the copper tube, welding on a piece of thin wall stainless steel tube and... 

Filling the Oxygen Gas-holder.—Open the cocks a and b (Fig. 37) and so fill the lower container completely with water. Now close both cocks, unscrew the cap c, introduce a rubber tube connected with an oxygen cylinder through the opening c and fill the holder with oxygen. Screw on the cap and fill the upper container with water. When the cocks a and b are opened oxygen flows out at b. 

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