Addition tube, 3-way

Fit a 500 ml. round-bottomed flask with a dropping funnel and a double surface condenser alternatively, the flask may be provided with a two-way addition tube (Fig. II, 13, 9) and the dropping funnel and condenser inserted into the latter. Place 37 g. (46 ml.) of iso-butyl alcohol (b.p. 106-108°) and 40 g. (41 ml.) of pure pyridine in the flask and 119 g. (73 ml.) of redistilled thionyl chloride in the dropping funnel. Insert a cotton wool or calcium chloride guard tube into the mouth of the funnel. Introduce the thionyl chloride during 3-4 hours a white solid... 

A rapid distribution of the added material is necessary to prevent a local excess of the reagent added. This is very important when hydrochloric acid is added, as this tends to decompose the mercury compound. A convenient arrangement consists of a 3-way tube of about 15-mm. bore. The stirrer operates through the center tube. The other arms are used for the condenser and for the addition of material. A three-necked flask provided with a long-stemmed separatory funnel reaching below the stirrer may be used. 

I. Pure Hg is subjected to an additional purification over silica gel and is then slowly passed through a water-filled flask to saturate it with water vapor. The flask is held in an 85 °C thermostat. To avoid condensation of the water vapor thus taken up, the tube which connects the flask to the reactor is wrapped with electric heating tape and heated to about 100 °C. The Hg/HgO mixture then flows over a boat with WOg set in a porcelain or a quartz reactor tube surrounded a tubular electric furnace and heated to 800-900°C. The reduction is complete in 2 hours. The product is allowed to cool in an Og-free nitrogen stream. The nitrogen is admitted through a 3-way stopcock located between the water flask and the reactor. 

Other Cell Designs. Although not used in the United States, another important cell is based on designs developed by ICl (90). Cells of this type are used by British Nuclear Fuels pic and differ from the cells shown in Figures 2 and 3 in two ways (/) the anodes used are made of the same hard, nongraphitized carbon, but are more porous and 2) the cathodes are formed from coiled tubes and provide additional cooling (91). 

Phosphorus acid (260 mg, 3.17 mol) was placed into a 250-ml, threenecked, round-bottomed flask suspended in an oil bath. The flask was equipped with a three-way adapter, carrying a pressure-equalizing addition funnel, a reflux condenser with a drying tube, a mechanical stirrer, and a thermometer. Acetonitrile (33 g, 0.80 mol) was introduced to the reaction flask dropwise over a 2-h period while the phosphorous acid was agitated and maintained at a temperature of 138 to 142°C. After completion of the addition, the reaction mixture was maintained at that temperature for an additional 12 h. Methanol was then added to precipitate the pure l-aminoethane-l,l-diphos-phonic acid (13.9 g, 85%), which exhibited spectral and analytical data in accord with the proposed structure. 

For the elucidation of chemical reaction mechanisms, in-situ NMR spectroscopy is an established technique. For investigations at high pressure either sample tubes from sapphire [3] or metallic reactors [4] permitting high pressures and elevated temperatures are used. The latter represent autoclaves, typically machined from copper-beryllium or titanium-aluminum alloys. An earlier version thereof employs separate torus-shaped coils that are imbedded into these reactors permitting in-situ probing of the reactions within their interior. However, in this case certain drawbacks of this concept limit the filling factor of such NMR probes consequently, their sensitivity is relatively low, and so is their resolution. As a superior alternative, the metallic reactor itself may function as the resonator of the NMR probe, in which case no additional coils are required. In this way gas/liquid reactions or reactions within supercritical fluids can be studied... 

The mobile phase reservoir is made of an inert material, usually glass. There is usually a cap on the reservoir that is vented to allow air to enter as the fluid level drops. The purpose of the cap is to prevent particulate matter from falling into the reservoir. It is very important to prevent particulates from entering the flow stream. The tip of the tube immersed in the reservoir is fitted with a coarse metal filter. It functions as a filter in the event that particulates do find their way into the reservoir. It also serves as a sinker to keep the tip well under the surface of the liquid. In addition, in specially designed mobile phase reservoirs, this sinker/filter is placed into a well on the bottom of the reservoir so that it is completely immersed in solvent, even when the reservoir is running low. This avoids drawing air into the line under those conditions. These details are shown in Figure 13.3. 

Based on this equation one can predict the temperature increase to be expected for a defined annulus thickness as shown in Fig. 3. With the above-described approach one can in addition construct a monolithic annulus of a desired radius but limited thickness. By preparing a series of annuluses where the outer diameter of the smaller monolith is equal to the inner diameter of a larger one, a large volume monolithic unit can be constructed by forming a so called tube in a tube system, as shown in Fig. 4. In this way, a monolithic unit of the required volume and uniform pore size distribution can be prepared. Furthermore, the voids between the annuluses can be filled with the reaction mixture and polymerization is allowed to proceed for a second time. Since the voids are very thin, no increase in temperature during the course of the reaction is expected. 

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