Through drying techniques

The ammonolysis of organochlorosilanes can be conducted by the continuous technique (Fig. 56). To avoid explosive concentration of the mixture of ammonia with air, the whole system is blown with nitrogen before the start. Then, to obtain gaseous ammonia, liquid ammonia is choked until the excess pressure is 0.07 MPa, heated in evaporator 6 and passed through drying tower 7 filled with alkali flakes. The dehydrated ammonia enters the lower part of bubble tower 5. After 20 minutes of blowing the whole system the supply of ammonia is not stopped the apparatus is filled with... 

There is no simple device which enables the measurement of dry deposition in a manner as convenient as for wet deposition. Instead, comparatively less direct methods must be used, none of which is fully proven as yet. For particle exchange, leaf-washing and through-fall techniques (1) can provide measurements of the accumulated deposit on natural surfaces. Likewise, accumulation on snow surfaces can be sampled, and subjected to subsequent chemical analysis. It is evident, however, that such methods only apply in certain circumstances. Budget techniques are sometimes advocated, such as in the case of calibrated watersheds, but these have rarely delivered unequivocal results. The difficulty that arises is that the dry deposition must necessarily be computed as the difference between poorly determined in-flow and out-flow measurements. These, and. a wide variety of other experimental methods, have been reviewed elsewhere (2). 

SFD is a combination of the two previously described drying techniques in which the microdispersed liquid particles are generated through the jet nozzle in the absence of heat, then collected and frozen in liquid nitrogen before sublimation occurs. The frozen particles are then lyophilized. SFD is used in place of SD when the protein cannot withstand the temperatures in the SD process. Preparation of SFD powders of DNase and an anti-IgE monoclonal antibody were found to be superior to those prepared by SD. ... 

Freeze-drying, called lyophilization by the pharmaceutical industry, is a drying technique by which a product is solifidied by freezing and the solvent that contains it (usually water) is evaporated by sublimation (a chemical phenomenon) upon heating. The transformation of the solid phase into the gas phase takes place with neither the water nor the solvent passing through the liquid state. 

Lui, A. Talbot, F.D.F Sourirajan, S. Fouda, A.E. Matsuura, T. Studies on gas transport through dry cellulose acetate membranes prepared by solvent exchange technique. Sep. Sci. Technol. 1988, 23, 1839. 

The powder X-ray diffraction patterns for the dried precursors correspond to a well crystallized material with a hydrotalcite-like structure. This fact indicates that highly homogenous precursors are obtained. The XRD results for the calcined oxides (Fig. 1) show diffraction peaks corresponding as much to a spinel-like phase as to metallic oxides such as nickel oxide. The relative proportion of these depends to a large extent on the catalyst composition. As these solids are poorly crystallized (except for the Ni-Co-Zn-AI catalyst), it is not possible to identify through this technique which divalent cation is present in the crystalline net, since there is hardly Table 1. Nominal composition and Sbet of the samples. any difference between the diffraction angles of the spinels corresponding to the different metallic cations. The tendency of Co and Zn to form a spinel-like structure, in which cobalt would occupy the octahedral sites, is very... 

Microparticles used on another polysaccharide, hydroxypropyl methylcellulose were prepared by spray-drying technique and designed to provide the absorption of a high polar drug through nasal mucosa [44]. 

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