'I'hc ~ncchanical agglomeration of barium sulphate suspended in organic media into essentially spherical masses has been studied. The presence of a small quantity of \\rater IS nccessar!. for the phenomenon to occur. This is regarded as a bridging agent that forms liquid lenses bct\\.cen the particles and binds them together. An equilibrium is set up for this water between the surface of the solid and the bulk suspending medium. The methods of formation of the spherical agglomerates are discussed and their properties examined.l;locculation of the solicl constituents, which is frequently desirable to promote more r'ipitl settling i l l suspension, almost invariably results in a large ir~crease in tlie final volun~e of tlic s e d i m e~~t obtained. An exception to this general behavior was reported by Stock ( I ) , \1ho observed that when clriecl, finely clividecl barium sulpliate suspencled i l l dry benzene in cyli~idrical containers was shalten with a reciprocating motion, cliscrete spheres of 0.5 t o 1.0 m m in diameter were formed. These settlecl rapiclly to a volume consiclerably less than that obtainecl from an equal amount of tlie suspension that had ~~o t been shaken. I t \\-as tentatively suggested that the phenomenon was owing to the tendency of tlie hyclrophilic barium sulpliate to aggregate in sucli a way that a minimum surface was exposed to the liyclrophobic benzene. Thus tlie phenomenon was considered to be son~e\\-hat analogous to the formation of clroplets when two immiscible liquids are shaken together.The pronounced flocculati~ig influence of small quantities of water on suspensions of solicls havi~ig li~~clropliilic surfaces in organic media has been frequently reported (2, 3, 4, 3 ) . X few preliniinary euperiments demonstrated that the phenomenon observed by Stock ( I ) clicl not occur if the system \\-ere thoroughly clry and the present work was u~iclertalie~i to ascertain the conclitions necessary for the formation of spllerical agglonierates ~vitli barium sulpliate suspenclecl in benzene a~icl, if possible, to give a n indicatioi~ of ho\v the tcclinique niight be applied to other sj7stems. IJr.ocedlireSuspensio~is \\-ere prepared by \veigliing 4-g portions of pure barium sulpliate directly into sa~iiplc holders \vliich were subsequently sealed to a vacuum system equipped \\-it11 facilities for U.E.T. surface area measurements. The barium sulphate \\-as freed from water by licati~ig the sarnples to 200' C ancl reclucing tlie pressure to about 10-j mm I-Ig. H.E.T. surface areas (6) were cleterminecl in the usual way. The nitrogen adsorption isotherms ~verc all of the reversible S-type, characteristic of adsorption on a non-porous solid. A kno\vn volu~iie of benzene, ~~s u a l l y about 20 ml, was then condensed from a doser into the saniplc holder ancl, similarly, water was added if desired in quantities from 2 mg up\vards. *After being sealed off, the vessel was shaken for a period of 12 hours or niore. For niost of the \vork a mechanical horizontal shaker that hacl a frequency of...
The process of spherical agglomeration provides a method for making rapid and efficient separations of solids from liquid suspensions. Because preferential wetting of the solid surface by a second liquid, which acts as a bridging agent between the particles, is a basic requirement of the operation, a novel method for the separation of multi‐component solids becomes available. The procedure is also useful in the breaking of emulsions through the addition of a finely divided solid, the surface of which is repellent to the continuous phase and wetted by the emulsified phase. The process operates equally well in aqueous or in organic media. A number of illustrative examples are given.
The kinetics of the thermal decomposition of n-butane has been investigated at pressures from 5 to 60 cm. and temperatures from 513 to 572 °C. The initial first order rate constants at high pressures are given by[Formula: see text]The results are in good agreement with the work of Frey and Hepp, but differ greatly from that of Paul and Marek. The reaction rate falls off strongly with diminishing pressure; this is rather surprising for a molecule as complex as butane. The first order constants in a given run fall rapidly as the reaction progresses. The last two facts suggest that chain processes may be involved.A large number of analyses of the products of reaction have been made at various pressures, temperatures, and stages of the reaction, the method being that of low-temperature fractional distillation. The products are virtually independent of temperature and pressure over the range investigated. The initial products, obtained by extrapolation to zero decomposition, are:—H2, 2.9; CH4, 33.9; C3H6, 33.9; C2H4, 15.2; C2H6, 14.1%. The mechanism of the reaction is discussed, and the results are compared with those of the other paraffin decompositions.
The thermal decompositions of cellobiose, maltose, dextrose, and potato starch have been studied over a temperature range, by following the production of volatile products. Carbon dioxide, carbon monoxide, and water with small quantities of acids, aldehydes, and volatile solids were produced in all cases. With cellobiose, the first step of the reaction, which involved the elimination of two moles of water per mole of sugar, could be separated from the second step, where the oxides of carbon were produced, by controlling the reaction temperature. Dextrose first dimerized by a rapid reaction and then decomposed in much the same manner as cellobiose. The behavior of maltose was anomalous and no dehydration by a separate step could be detected. The decomposition of potato starch was similar to the second step of the cellobiose reaction.
The molecular weights of organic compounds of known constitution have been determined with satisfactory accuracy, using milligram quantities of materials, by a static measurement of the vapor pressure difference between pure solveilts and solutions of the con~pounds. T h e method may be used over a considerable temperature range. The suitability of solvents is governed by their chemical stability and vapor pressure. Results obtained using conlpounds in the molecular weight range of 600-1000 are reported.
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