Immersion vacuum

Predicting end use applications Water immersion Vacuum or space conditions Pipe burst... 

Moisture trap attachments for rotary oil immersion vacuum pumps and glass vacuum desiccators have had impressive success when "0"-rings were fitted as vacuum seals. 

Due to the limited reversibility of consolidation treatments for ceramics, new consolidations are carried out only if the object is seriously endangered, e.g. when the ceramic body is crumbling or the surface decoration is flaking off the surface. Materials, such as Paraloid B72 (already mentioned for glass conservation) or silanes and siloxanes (used for stone conservation) can be applied by brush, injection, spray or by immersion. Vacuum impregnation might be useful to achieve deep penetration with the consolidant. 

Exposure time in each fluid may vary from a few days to a month and the alternate immersions are continued for us to 1 year or more. Several times during the ethyl silicate immersion vacuum is applied to remove water vapor from the wood to facilitate further penetration by the ester. The ethyl silicate is replaced with fresh liquid whenever it becomes viscous or cloudy. During the final cycle in the ester the specimen is soaked in 0.004% HNOj to hydrolyze the residual ester in situ. 

Such a device is a rotary vacuum filter of the type shown in Figure 11. In this, the crystal slurry is introduced into a tank in which a rotating drum, holding the filter medium, is partially immersed. Vacuum is applied to the interior of the drum, and this draws the olein fraction through, causing the stearin crystals to build up as a cake on the outer surface. A scraping device removes the filter cake, revealing a clean filter surface that allows the process to repeat itself. 

Equip a I litre three-necked flask with a mechanical stirrer and a thermometer, and immerse the flask in a bath of ice and salt. Place 306 g. (283 ml.) of acetic anhydride, 300 g. (285 ml.) of glacial acetic acid and 25 g. of p-nitrotoluene in the flask, and add slowly, with stirring, 42 5 ml. of concentrated sulphuric acid. When the temperature has fallen to 5°, introduce 50 g. of A.R. chromic anhydride in small portions at such a rate that the temperature does not rise above 10° continue the stirring for 10 minutes after all the chromium trioxide has been added. Pour the contents of the flask into a 3 litre beaker two-thirds filled with crushed ice and almost fill the beaker with cold water. Filter the solid at the pump and wash it with cold water until the washings are colourless. Suspend the product in 250 ml. of cold 2 per cent, sodium carbonate solution and stir mechanically for 10-15 minutes filter (1), wash with cold water, and finally with 10 ml. of alcohol. Dry in a vacuum desiccator the yield of crude p-nitrobenzal diacetate is 26 g. (2),... 

The combined ethereal solutions were washed with water and dried over magnesium sulfate. The greater part of the diethyl ether was distilled off at normal pressure through a 40-cm Vigreux column, keeping the bath temperature below 65°C (note 2), (see Fig. 5). The distillation flask was then cooled to 20-30°C and the remaining diethyl ether was removed in a water-pump vacuum, keeping the receiver immersed... 

A solution of 0.10 mol of freshly distilled diethylaminopropyne in 80 ml of dry (distilled from phosphorus pentoxide) acetonitrile was cooled to 5°C and dry carbon dioxide was introduced into the vigorously agitated solution at a rate of about 0.3 1/min. The temperature rose above 20°C within a few minutes, but was kept at about 30°C by occasionally immersing the flask in a bath of ice-water. The introduction of CO2 was continued until the temperature had dropped to 25°C and the typical odour of the yneamine had disappeared completely. The yellow solution was concentrated in a water-pump vacuum. The residue, a sirupy liquid, had the theoretically required weight and consisted of reasonably pure (about 955 ) allenyl-diamide. If desired the product car be distilled (short-path distillation) in a high vacuum. It solidified upon standing at -25 C. 

Vacuum arc remelting often is used to develop optimum solidification stmctures. Electroslag remelting, which utilizes a molten pool of slag in which the electrode is immersed, yields a cleaner and purer material. 

The disk filter is similar to the dmm in operation, but filtration is conducted using a series of large diameter filter disks that carry the filter medium on both sides of the disk. They are connected to the main horizontal shaft and partly immersed in the feed slurry. The central shaft is connected by a set of valves which serve to provide vacuum and air as in dmm filters. As the disk sections submerge during rotation, vacuum is appHed to form a cake on both sides of the disk. The cycle of operation is similar to that in a dmm filter. One unit can have as many as 12 disks of up to 5-m diameter. Disk filters, both compact and cost effective, are used extensively in the iron ore industry to dewater magnetite concentrates. 

These problems can be dealt with by usiag artificial test cloths impregnated with various approximations of natural soils such as vacuum cleaner dust, dirt from air conditioner filters, clays, carbon black, fatty acids, dirty motor oil, and artificial sebum, either alone or ia combination (37,94—98). The soils are appHed by sprayiag, immersion, or padding. If the soils are carefully appHed, reproducible results can be obtained. Soil test cloths can be of great help ia detergency studies, when used with an understanding of their limitations. 

In the static method the powder is isolated under high vacuum and surface gases driven off by heating the container. The container is next immersed in hquid nitrogen and known amounts of nitrogen vapor are admitted into the container at measured increasing pressures in the relative pressure range 0.05 to 0.35. 

If the flow of cooling water is stopped while the apparatus is cold, the water may freeze and crack the immersion well. The vacuum jacket provides greater insurance against this problem than is available in the commercially available wells used with the usual 450 watt lamps. ... 

Potassium (metal) [7440-09-7] M 39.1, m 62.3 , d 0.89. Oil was removed from the surface of the metal by immersion in n-hexane and pure Et20 for long periods. The surface oxide was next removed by scraping under ether, and the potassium was melted under vacuum. It was then allowed to flow through metal constrictions into tubes that could be sealed, followed by distillation under vacuum in the absence of mercury vapour (see Sodium). EXPLOSIVE IN WATER. 

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