Cold trap Fig

Alternatively, distillations may simply depend upon a vacuum to strip volatiles from a food. The volatiles stripped from a food maybe condensed in a cold trap (Fig. 18.2, right) or passed through an absorbent trap (e.g. Tenax ) for collection. While these techniques have found substantial application in the past, in recent times they have seen less use. 

The apparatus for simple or countercurrent distillation at reduced pressures differs from that used at atmospheric pressure only by its wider dimensions (c/. section 4.11). A few additional components are necessary, such as a vacuum connection, which is generally provided with a cold trap (Fig. 188). Besides packed columns, empty columns (chap. 7.3.1) and columns with stationary (chap. 7.3.4) and rotating... 

Dihydroxyacetophenone. Finely powder a mixture of 40 g. of dry hydroquinone diacetate (1) and 87 g. of anhydrous aluminium chloride in a glass mortar and introduce it into a 500 ml. round-bottomed flask, fitted with an air condenser protected by a calcium chloride tube and connected to a gas absorption trap (Fig. II, 8, 1). Immerse the flask in an oil bath and heat slowly so that the temperature reaches 110-120° at the end of about 30 minutes the evolution of hydrogen chloride then hegins. Raise the temperature slowly to 160-165° and maintain this temperature for 3 hours. Remove the flask from the oil bath and allow to cool. Add 280 g. of crushed ice followed by 20 ml. of concentrated hydrochloric acid in order to decompose the excess of aluminium chloride. Filter the resulting solid with suction and wash it with two 80 ml. portions of cold water. Recrystallise the crude product from 200 ml. of 95 per cent, ethanol. The 3 ield of pure 2 5-dihydroxyacetophenone, m.p. 202-203°, is 23 g. 

Apparatus See Fig. 7 size of the flask, 2 1 a gas-tight stirrer should be used the top of the condenser was connected uia a plastic tube to 2 tubes filled with lumps of CaCl2- These tubes in turn were connected to 2 cold traps (-80°C) each of which contained 40 ml THF or CH3OCH2CH2OCH3 (free from peroxides). 

The experimental procedure is outlined schematically in Fig. 13 a detailed description was given by Hartog et al. 37). Benzene vapor and deuterium gas, in the molar ratio of 1 18, were passed through a catalyst bed and then through a cold trap immersed in liquid nitrogen in which the hydrocarbons were frozen out. The temperature of the catalyst bed was... 

Fig. 17. Thermograms recorded during the adsorption of doses of oxygen at the surface of nickel-oxide samples containing preadsorbed oxygen, the cold trap being cooled (A) or not cooled (B) (71). 

Fig. 22. Thermobalance for vapor pressure measurements. Schematic drawing of experimental equipment. A-Knudsen cell B-cold trap C-Ionization gauge D-Balance and housing E-Diffusion pumps F-Thermostatically controlled reaction chamber...

The apparatus and the special accessories necessary for this work are schematically illustrated in the Fig. 22. The reaction chamber used for the Knudsen effusion method is positioned above the balance. The reaction chamber is thermostatically controlled and connected with a cold trap. Both of them are protected from outside temperature effects by an insulating material. This protection leads to a more constant temperature and a straight line in the recorded loss in weight. 

Because the balance housing is separated from the reaction chamber (cf. Fig. 25), one diffusion pump evacuates only the balance housing whereas the other evacuates the reaction chamber. The reaction chamber is connected to the diffusion pump by a cold trap. The decomposition products can be taken from the gas outlet for analysis or condensed on the cold trap by means of a coolant. 

Fig. 4 Setup for continuous-flow asymmetric hydrovinylation using an IL/SCCO2 biphasic system. Liquid and gaseous substrates are mixed with the SCCO2 stream before entering the tubular reactor unit and bubbled through the catalyst-containing IL using a capillary. The CO2 flow leaves the reactor on top and the product is collected in a cold trap after controlled expansion to ambient pressure...

With longer-term operation it is always advisable to install, in place of the cold cap, a water-cooled shell or chevron baffle between the diffusion pump and the low-temperature baffle or cold trap (see Fig. 2.50). 

The purpose of the cold traps (see Fig. 2.1.) is two-fold (1) to trap volatile materials from the line on their way to the pumps and thus to protect the pumping system and (2) to trap the vapour and any pumping fluid before it can enter the line by back-diffusion. 

Fig. 2.4. Two types of cold traps. /I is a B.24 or B.29 joint, B is the well for liquid nitrogen or other coolant, C is a 3-5 mm bore solid-key tap.

Apparatus for CHjOeCH, C HjCsCH and H2C=CHCsCH a 1-1 three-necked, round-bottomed flask, equipped with a gas inlet tube, a mechanical stirrer and a "cold finger" reflux condenser (-75 C, fig. 17), cooled with dry ice and acetone the top of the condenser is connected to a cold trap ... 

Apparatus 2-1 round-bottomed, three-necked flask, equipped with a dropping funnel (combined with a gas inlet), a mechanical stirrer and a reflux condenser connected to a cold trap (-78 C all connections are made gas-tight a stirrer of the type displayed in fig. 3, is used. 

Fig. 9.4.2 Size histogram of In small particles produced by a gas flow-cold trap method in acetone. The pressure of He and Ar mixed gas was 1.3 kPa. The ordinate represents the number of samples at a given size interval. Tolal number of samples, 250. Broken line, calculated curve from the lognormal distribution with a = 2.13 and d = 20 nm. (From Ref. 4.)...

Fig. 9.4.8 Apparatus for the gas flow-cold trap method. One of the gas inlets is abbreviated in the figure. A cover in the figure is used to improve a collection yield. Without this, the particles produced just above a crucible are drifting in the chamber to deposit on the chamber wall. The end of the gas line is evacuated by a rotary pump so as to constantly flow the carrier gas. A solvent feeder is inserted on the gas line for the sublimation of organic liquid to deposit at the trapping apparatus cooled with liquid nitrogen. (From Ref. 10.)...

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