Dry connectivity

Once the column is packed (gel bed just runs dry), connect the top of the column to a buffer reservoir, remove any air bubbles in the tube, and allow one column volume of buffer to run through the column. 

The samples were immersed in demineralised water for the ageing experiments and placed in an oven at 90°C + 2°C. After a certain immersion time, a sample was taken out of the oven and cooled in water at a temperature of 20°C. Subsequently, the sample was surface dried, connected with the measuring equipment and measured. This procedure was performed in about five minutes. A separate sample was used for each measurement. It is important to realise that although the samples were stored in water at 90°C, the resistivity measurement itself was performed at room temperature. The measuring procedure was kept as short as possible, j>(60) i.e. some time dependency of the measuring currents could stil be measured, to keep the moisture evaporation losses as low as possible. 

Heat pipe tubes The absorbed heat is transferred by using the heat pipe principle without direct contact to the heat transfer fluid of the solar loop. In this case, there are two different ways of connection (1) the dry connection, where the heat has to be transferred from the condenser through the material of the header tube. This way the installation and removal of the tubes is much easier than with direct flow pipes brazed to the header. On the other hand, heat-conductive paste often has to be used, thus requiring that the pipes be installed professionally and (2) the wet connection, where the fluid of the solar loop directly flows around the condenser of the heat pipes. In this case, no heat-conductive paste is needed, but the exchange of tubes is more difficult. 

In the Prefaces of both the 4th and the 5th editions the senior author commented on the tendency of wet and dry surface chemistry for differentiation into separate schools. This remains the case today also, academic research in wet surface chemistry continues to move from chemistry departments to engineering ones. On the other hand, new connections between the two areas have been forming apace with the current prominence of scanning microscopies. 

Concentrate each of the two solutions (or eluates) to about 20 ml, by distilling off the greater part of the benzene, the distilling-flask being immersed in the boiling water-bath. Then pour the concentrated solution into an evaporating-basin, and evaporate the remaining benzene (preferably in a fume-cupboard) in the absence of free flames, i.e., on an electrically heated water-bath, or on a steam-bath directly connected to a steam-pipe. Wash the dry residue from the first eluate with petrol and then dry it in a desiccator pure o-nitroaniline, m.p. 72°, is obtained. Wash the second residue similarly with a small quantity of benzene and dry pure />--nitroaniline, m.p. 148" , is obtained. Record the yield and m.p. of each component. 

Place 20 ml. (16 g.) of rectified spirit in F, and add slowly, with cooling and shaking, 40 ml. (74 g.) of concentrated sulphuric acid. Then add about 2-3 g. of clean dry sand, to ensure a steady evolution of ethylene subsequently. Connect up the apparatus and heat F over the sand-bath as shown. 

Fig. 11,10, 3, depicts a housing for the apparatus of Fig. 11,10, 2, a it is easily constructed from lengths of angle iron and asbestos board. If desired, torch bulbs may be fixed in the appropriate holders in the walls, and connected with a dry battery or accumulator in order to provide illumination of the melting point apparatus. The electric bulb immediately behind the apparatus should be connected to an inde pendent micro-switch. Alternatively,... 

Receiver adapters or connectors. Various forms of receiver adapters are shown in Figs. 11, 56, 26-29. The simplest form. Fig. 11, 56, 26, carries a glass hook for securing it to the condenser by means of a rubber band from the side tube to the hook an improved form, incorporating two ground glass joints is shown in Fig. 11, 56, 27. A useful adapter is illustrated in Fig. 11, 56, 28 when employed at atmospheric pressure, a drying tube may be attached to the side tube, if desired in a distillation under reduced pressure, the side tube is connected to the pump. Fig. 11, 56, 29 depicts a receiver adapter with an additional socket connection. 

A set-up for distillation under reduced pressure is shown in Fig. 11,60,3 it is generally more convenient to use a Kon receiver or a Perkin triangle (Fig. 11, 56, 31). The vessel at the side, connected to the assembly by rubber pressure tubing, may be immersed in a Dry Ice-acetone bath and serves as a trap for volatile materials. 

Allyl Bromide. Introduce into a 1-litre three-necked flask 250 g. (169 ml.) of 48 per cent, hydrobromic acid and then 75 g. (40-5 ml.) of concentrated sulphuric acid in portions, with shaking Anally add 58 g. (68 ml.) of pure allyl alcohol (Section 111,140). Fit the flask with a separatory funnel, a mechanical stirrer and an efficient condenser (preferably of the double surface type) set for downward distillation connect the flask to the condenser by a wide (6-8 mm.) bent tube. Place 75 g. (40 5 ml.) of concentrated sulphuric acid in the separatory funnel, set the stirrer in motion, and allow the acid to flow slowly into the warm solution. The allyl bromide will distil over (< 30 minutes). Wash the distillate with 5 per cent, sodium carbonate solution, followed by water, dry over anhydrous calcium chloride, and distil from a Claisen flask with a fractionating side arm or through a short column. The yield of allyl bromide, b.p. 69-72°, is 112 g. There is a small high-boiling fraction containing propylene dibromide. 

In a dry 500 ml. three-necked fiask, equipped with a mercury-sealed stirrer, a 100 ml. dropping funnel and a short fractionating column (1), place a mixture of 116 g. of anhydrous, finely-powered potassium fluoride (2) and 200 g. of dry ethylene glycol (3). Connect the fractionating... 

Mix 50 ml. of formalin, containing about 37 per cent, of formaldehyde, with 40 ml. of concentrated ammonia solution (sp. gr. 0- 88) in a 200 ml. round-bottomed flask. Insert a two-holed cork or rubber stopper carrying a capillary tube drawn out at the lower end (as for vacuum distillation) and reaching almost to the bottom of the flask, and also a short outlet tube connected through a filter flask to a water pump. Evaporate the contents of the flask as far as possible on a water bath under reduced pressure. Add a further 40 ml. of concentrated ammonia solution and repeat the evaporation. Attach a reflux condenser to the flask, add sufficient absolute ethyl alcohol (about 100 ml.) in small portions to dissolve most of the residue, heat under reflux for a few minutes and filter the hot alcoholic extract, preferably through a hot water fuimel (all flames in the vicinity must be extinguished). When cold, filter the hexamine, wash it with a little absolute alcohol, and dry in the air. The yield is 10 g. Treat the filtrate with an equal volume of dry ether and cool in ice. A fiulher 2 g. of hexamine is obtained. 

Mix 200 g. of adipic acid intimately with 10 g. of finely-powdered, crystallised barium hydroxide. Place the mixture in a 1-litre distilling flask, fitted with a thermometer reaching to within 5 mm. of the bottom connect the flask with a condenser and receiver. Heat the mixture gradually in an air bath (1) to 285-295° during about 90 minutes and maintain it at this temperature mitil only a small amount of dry residue remains in the flask this requires a further 2 hours. The temperature must not be allowed to rise above 300°, since at this temperature the adipic acid distils quite rapidly the best working temperature is 290°. The cycZopentanone distils slowly accompanied by a little adipic acid. Separate the ketone from the water in the distillate, and dry it with anhydrous potassium carbonate this treatment simultaneously removes the traces of adipic acid present. Finally distil from a flask of suitable size and collect the cycZopentanone at 128-131°. The yield is 92 g. 

---