Sieving continuous

Table IV. Dimensions of A.S.T.M. (American Society for Testing Materials) standard wire cloth sieves (continued).

The sedimentation methods of particle size analysis, both gravitational and centrifugal, have, over the years, generated many contributions and are still extensively used in many traditional industries. PSA 91 saw however only three such contributions [Allen (2) Bernhardt], one which was a Keynote lecture reviewing the historical developments of this fundamental method. The Andreasen sedimentation technique and sieving continue as essential methods used for the characterisation of many certified reference materials. 

Grateful acknowledgment is hereby made of an indebtedness to those who have contributed to previous editions and whose compilations continue in use in this edition. In particular, acknowledgment is made of the contribution of L. P. Buseth, who prepared the conversion tables for the thirteenth edition and who prepared the table on the U.S. Standard Sieve Series. 

Advances in fundamental knowledge of adsorption equihbrium and mass transfer will enable further optimization of the performance of existing adsorbent types. Continuing discoveries of new molecular sieve materials will also provide adsorbents with new combinations of useflil properties. New adsorbents and adsorption processes will be developed to provide needed improvements in pollution control, energy conservation, and the separation of high value chemicals. New process cycles and new hybrid processes linking adsorption with other unit operations will continue to be developed. 

Molecular sieves are also used widely in the dehydration ofHquid streams. Both batch-type and continuous processes have been developed for drying a variety of hydrocarbon and chemical Hquids. 

A continuous process has been developed for preparing borate esters usiag transesterification (24). Another modification of this method has been reported where use of molecular sieves (qv) to absorb the low boiling alcohol is used rather than distillation (25). 

To a solution of 33 g. (O.S mole) of potassium hydroxide (Note 1) in 1.5 1. of distilled water in a 5-1. flask or other appropriate container fitted with a mechanical stirrer is added 80 g. (0.5 mole) of methyl hydrogen adipate (Note 2). With continuous stirring a solution of 85 g. (0.5 mole) of silver nitrate in 1 1. of distilled water is added rapidly (about IS minutes). The precipitated methyl silver adipate is collected on a Buchner funnel, washed with methanol, and dried in an oven at 50-60°. For the next step the dried silver salt is finely powdered and sieved through a 40-mesh screen. The combined yield from two such runs is, 213 g. (80%). 

Normal paraffins in the C,o - C,5 range are recovered from petroleum fractions by adsorption-desorption using molecular sieves. Ammonia can be used to desorb the n-paraffins. By employing two beds of sieves, one on adsorption and one on desorption at all times, a continuous flow of the feed and ammonia is maintained. 

Durchlauf, m. sieve, colander running thru, flow, passage Med.) diarrhea, durchla en, v.i. filter run thru, flow thru. — — v.t. run thru, pass thru, traverse. — durchlaufend, p.a. continuous. Durchlkufermineral, n. mineral occurring in all zones. 

In these processes, a solid with a high surface area is used. Molecular sieves (zeolites) are widely used and are capable of adsorbing large amounts of gases. In practice, more than one adsorption bed is used for continuous operation. One bed is in use while the other is being regenerated. 

In summary, it becomes obvious that sieving should be continued until region 2 is reached. A good procedure might be to plot the time-weight curve on log probability paper and then... 

The sieving operation starts by mounting the sieves in a nest, the coarsest at the top. The sample is placed on the top screen, and the screens are shaken for several minutes. It is generally impossible to screen a sample completely the longer one shakes the screens, the more material comes thru, although to a continu-... 

Sieving Time Because sieving time depends upon the type of sieving motion and the provision for continuous movement of the sample over all parts of the sieving surface, the only requirement for sieving time appears to be that shaking be continued until equilibrium conditions are reached... 

A mixture of finely ground benzyltrimethylammonium fluoride (125 mmol) and molecular sieves (50 g, 4 A) in THF (50 ml) was stirred for 14 h at ambient temperature, and then the mixture was cooled to 0°C. A solution of l-(trimethylsilyloxy)cyclohexene (115 mmol) and methyl bromoacetate (105 mmol) in THF (50 ml) was added with stirring over 10 min. After stirring for a further 10 min at 0 °C, stirring was continued for 11 h at ambient temperature. The reaction mixture was filtered through Celite. concentrated and distilled, to give the ketoester (75 mmol, 65%), b.p. 90-100°C/1.2mmHg. 

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