Porous plate

The phenomenon of thermal transpiration was discovered by Osborne Reynolds [82], who gave a clear and detailed description of his experiments, together with a theoretical analysis, in a long memoir read before the Royal Society in February of 1879. He experimented with porous plates of stucco, ceramic and meerschaum and, in the absence of pressure gradients, found that gas passes through the plates from the colder to the hotter side. His experimental findings were summarized in the following "laws" of thermal transpiration. 

When the pressure is the same on both sides of the porous plate, gas moves from the colder to the hotter side. The flow depends on the nature of the gas, its temperature, the relation between its density and the size of the pores in the- plate, the temperature difference between the faces and the thickness of the plate. 

A clean dry porous plate is then broken into fragmentsf about... 

Another method, which is especiafly suitable for low melting point solids or solids which decompose at low temperatures, is to place the material on a porous plate or pad of drying paper, and to cover the latter with another sheet of Alter paper perforated with a number of holes or with a large clock glass or sheet of glass supported upon corks. The air drying is continued until the solvent has been completely eliminated. 

Small quantities of solids may be spread upon unglazed porcelain plates. The chief disadvantage of this method is the comparatively high cost of the porous plates, since they cannot be conveniently cleaned nor can the same area be used for different substances. However, a plate may be broken and used for small amounts of material. 

If a m.p. determination is required soon after recrystallisation, a small quantity may be rapidly dried by pressing it several times upon a pad of several thicknesses of filter or absorbent paper and placing it upon a watch glass in a warm place. A piece of unglazed porous plate may also be used. 

Equip a 500 ml. three-necked flask with an efficient stirrer (e.g., a Hershberg stirrer. Fig. II, 7, 8) and a reflux condenser stopper the third neck. Place a solution of 30 g. of sodium hydroxide in 100 ml. of water, and also 20-5 g. (17-1 ml.) of pure nitrobenzene in the flask, immerse it in a water bath maintained at 55-60°, and add 21 g. of anhydrous dextrose in small portions, with continuous stirring, during 1 hour. Then heat on a boiUng water bath for 2 hours. Pour the hot mixture into a 1 litre round-bottomed flask and steam distil (Fig. II, 40, 1) to remove aniline and nitrobenzene. When the distillate is clear (i.e., after about 1 htre has been collected), pour the residue into a beaker cooled in an ice bath. The azoxybenzene soon sohdifies. Filter with suction, grind the lumps of azoxybenzene in a mortar, wash with water, and dry upon filter paper or upon a porous plate. The yield of material, m.p. 35-35-5°, is 13 g. Recrystallise from 7 ml. of rectified spirit or of methyl alcohol the m.p. is raised to 36°. ... 

Dissolve 2-3 g. of methyl p-toluenesnlphonate in 10 ml. of dry benzene, add 1 g. of the amine, and boU the mixture for 20-30 minutes. Cool, and filter the precipitated quaternary salt. Recrystallise by dissolving the solid in the minimum volume of boiling ethyl alcohol and then adding ethyl acetate until crystallisation commences. Filter the cold mixture, dry rapidly on a porous plate, and determine the m.p. immediately. 

Sodium anthraquinone-p-sulphonate ( silver salt ). Place 60 g. of fuming sulphuric acid (40-50 per cent. SO3) in a 250 or 500 ml. round-bottomed flask and add 50 g. of dry, finely-powdered anthra-quinone (Section IV,145). Fit an air condenser to the flask and heat the mixture slowly in an oil bath, with occasional shaking, so that at the end of 1 hour the temperature has reached 160°. Allow to cool and pour the warm mixture carefully into a 2 litre beaker containing 500 g. of crushed ice. Boil for about 15 minutes and filter off the unchanged anthraquinone at the pump. Neutralise the hot filtrate with sodium hydroxide and allow to cool, when the greater part of the sodium anthra-quinone-p-sulphonate separates as silvery glistening plates ( silver salt ). Filter these with suction and dry upon filter paper or upon a porous plate. A second crop of crystals may be isolated by concentration of the trate to half the original volume. The yield is 40-45 g. 

Fig. 16. Typical distributor grid designs for fluidized-bed applications (a) porous plate, (b) cone, (c) perforated plate, (d) downward dish, (e) upward dish,...

TABLE 14-17 Wet Permeability of Alundum Porous Plates 1 in Thick ... 

Chromium ammonium sulfate (I2H2O) [34275-72-4 (hydr) I3548-43-I (anhydr)] M 478.4, m 94 loses 9H2O then dehydr at 300 , d 1.72. Crystd from a saturated aqueous soln at 55° by cooling slowly with rapid mechanical stirring. The resulting fine crystals were filtered on a Buchner funnel, partly dried on a porous plate, then equilibrated for several months in a vacuum desiccator over crude chromium ammonium sulfate (partially dehydrated by heating at 100° for several hours before use) [Johnson, Hu and Horton J Am Chem Soc 75 3922 1953]. 

Dissolve about i gram of an organic base (brucine, strychnine, quinine, c.) in 10 c.c. of a mixture of equal volumes of concentrated hydrochloric acid and water. To the clear hot solution add excess of platinic chloride and let it cool. Yellow microscopic crystals of the chloroplatinate of the base separate. (If the chloroplatinate of the base is very soluble in water, such as aniline, it must be washed with strong hydrochloiic acid, pressed on a porous plate and dried in a vacuum-desiccator over solid caustic potash.)... 

Filter on the porcelain funnel with the pump and wash three or four times with small quantities of cold water. Press the piecipitate down and dry on a porous plate in the vacuum-desiccator. When thoroughly dry, weigh out about 0-5 to i gram of the compound into a porcelain or platinum crucible, and heat gently with the lid on, and then moie strongly until the organic matter is completely burnt away. Cool the crucible in the desic-ca.or and weigh. 

Colourless liquid b. p. 213—214° (ordinary pressuie). To convert the anhydiide into citraconic acid tlae calculated quantity of water is added (i mol. acid i mol. water), and the mi-vture well stirred. The whole solidifies, on standing, to a mass of colourless crystals of citraconic acid, whicb arc dried on a porous plate m. p. 84—86°. 

MES.A.CONIC Acid.—To a saturated solution of citraconic acid in ether (4 parts citraconic acid require about 5 parts of anhydrous ether), about i part of chloroform is added, and a few drops of a moderately strong solution of bromine in chloroforna-The mixture is placed in strong sunlight, when mesaconic acid, which is insoluble in ether and chloroform, begins at once to deposit on the side of the vessel nearest the light. Drops of bromine are added from time to time until no further precipitation occurs. The pasty mass is then filtered, washed with ethei, and dried on a porous plate. Yield 73 per cent, of the citraconic acid m. p. 203°. See Appejidix, p. 265. 

Reaction.—Make a solution of 4 grams stannous chloride in TO c.c. cone, hydrochloric acid, add 2 grams aminoazobenzene, and boil for a few minutes. On cooling ciystals of the hydrochlorides of aniline and yi-phenylenediamine separate out. The liquid is filtered and washed with a little cone, hydrochloric acid to remove the tin salts. If the precipitate is dissolved in water and made alkaline with caustic soda, a mixture of liquid aniline and solid/-phenylenediamine is precipitated, from which the former may be removed by filtering, washing, and draining on a porous plate. 

The fi-compound is dissolved in 50 c c. pure dry ether, and dry hydiogen chloride is passed in with constant shaking to prevent the delivery tube from becoming blocked. Colourless crystals of the hydrochloride of the /3-o ime separate and aie filtered and washed with dry ether and then placed in a separating funnel and covered with a layer of ether. A. concentrated solution of sodium carbonate is gradually added with constant shaking until no further effervescence is observed. Sodium chloride is precipitated and the /3-oxime dissolves in the ether. The ether extract is sepaiated, dehydrated over sodium sulphate, and the ether remoi ed as rapidly as possible at the ordinary temperature by evaporation in vacuo. The residue crystallises, and when pressed on a porous plate leaves a mass of small silky needles, m. p. 126—130A It may be re-... 

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