Ground joints

A flask is provided with a long side neck (Fig. II, 25, 1) through which a capillary is inserted and attached externally by a short length of rubber pressure tubing. With this type of connexion there is essentially no contact of hot vapours with the rubber and little or no contamination results. The neck of the flask is preferably fitted with a standard ground joint if attack of the organic vapours on the rubber stopper is likely to occur. 

A similar apparatus, but without the advantage of the central ground joint is marketed under the name Buechner stable filter f (Fig. 11,35, 2, a) one method of use is shown in Fig. II, 35, 2, b. The Buechner stable filter is made of porcelain the filtrate is drawn off through a vacuum chamber below the perforated plate, the whole apparatus is supported by a cylindrical base, and sits firmly on the bench. The sizes of perforated plate available are 56, 91, 111, 126, 186, 241 and 308 mm. diameter respectively, and it would appear that these will... 

Fig. II, 55, 3 depicts a ground joint with glass hooks, to which light springs may be attached. Figs. II, 55, 4 and II, 55, 5 are drip cones for condensers and the like the latter is generally employed for joints larger than 29 mm. in diameter, the orifice being reduced to about 18 mm. Fig. II, 55, 6 is a double-cone joint in which two cones, e.g., B19 and 524, are made like a single joint this is valuable as it saves the use of an adapter.

The swan neck adapter of Fig. II, 56, 12 is useful for distillations as it permits the use of a capillary tube (held in position by a short length of heavy-walled rubber tubing) not sealed to a ground joint. It may also be used for inser tion of a thermometer or a gas-inlet tube in the narrow neck and a reflux condenser into the ground joint this device virtually converts a three-necked into a four-necked flask. Common sizes are cone fil9, 24, 29, or 34 socket 19, 24 or 29. 

Some of the more obvious sources of contamination of solvents arise from storage in metal drums and plastic containers, and from contact with grease and screw caps. Many solvents contain water. Others have traces of acidic materials such as hydrochloric acid in chloroform. In both cases this leads to corrosion of the drum and contamination of the solvent by traces of metal ions, especially Fe. Grease, for example on stopcocks of separating funnels and other apparatus, e.g. greased ground joints, is also likely to contaminate solvents during extractions and chemical manipulation. 

B Immersion well (quartz or pyrex), fitted with inlet (a) and outlet b) for cooling liquid (water or filter solution), and with ground joint (c) to C Reaction flask, fitted with gas inlet d) and outlet (e adapted to hold, e.g., a reflux condenser). 

B Immersion well (pyrex), fitted with inlet (a) and outlet (b) for cooling water, and with ground joint (c) to... 

C Reaction flask equipped with inlet (c)) for sampling and ground joint (d) to... 

Socket Weld ASA B16.11. Steel to Steel Seats, Ground Joint. No Bronze... 

Fig. A.5. An apparatus for the lsO-labclling of the CO2 produced in biolumines-cence reactions. The stopcocks A-E and the ground joint of reaction vessel are lubricated with high-vacuum grease, and the connections between the glass tubes are made with short pieces of thick-walled silicon rubber tubing. The stopcocks C and D are high-vacuum type, such as Ace Glass, Cat. No. 8197-04 and 8195-236, or Corning, Cat. No. 7473-3.

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