Crystallization experimental procedures

EXPERIMENTAL PROCEDURES AUTOMATED TURBIDIMETRIC TITRATION. A method for the automated aqueous turbidimetric titration of surfactants has been published (10) in which anionic surfactants are titrated against N-cetylpyridinium chloride to form a colloidal precipitate near the equivalence point. N-cetylpyridinium halides have a disadvantage in that they have the tendency to crystallise out of solution (15), consequently the strength of the solution may alter slightly without the knowledge of the operator, also the crystals suspended in solution may cause damage to the autotitrator. In view of these drawbacks hyamine was preferred as the titrant. 

Forages, as ruminant feed, 10 863 Foraminifera, 17 690 Forastero cocoa beans, 6 353 Forced air cooling, of food, 21 560 Forced circulation crystallizer, 8 136 Forced-circulation evaporators, in sodium chloride solution mining, 22 803, 804 Forced convection, 13 245 Forced drainage experimental procedure, 12 12... 

Zeolite membranes are generally synthesized as a thin, continuous film about 2-20 xm thick on either metallic or ceramic porous supports (e.g., alumina, zirco-nia, quartz, siHcon, stainless steel) to enhance their mechanical strength. Typical supported membrane synthesis follows one of two common growth methods (i) in situ crystallization or (ii) secondary growth. Figure 10.2 shows the general experimental procedure for both approaches. 

Figure 10.2 Schematic of the experimental procedures involved for two common zeolite synthesis methods including in situ crystallization and secondary (seeded) grow.

The experimental procedure was as follows. One litre of supersaturated aqueous solution was prepared, of which 0.8 was poured Into the crystallizer. After a constant temperature (of 298.2 K) was attained, the solution concentration was determined, and a seed crystal (0.59-0.71 mm) was put Into the solution and was allowed to grow for either 600 or 900 s. The crystal was then taken out of the crystallizer and put Into a 50 ml beaker In which a small quantity of alcohol was placed. The crystal was removed from the beaker and dried In the air for a few mlnltes, then Its weight and surface area were measured. The same crystal was again placed Into the crystallizer and allowed to resume growth. 

For a number of years now we have been involved in crystallization of bacterial ribosomal particles. From the very beginning of our studies, the crucial need for a stable, very intense, and perfectly focussed synchrotron beam was evident, even for preliminary and basic information (e.g. whether crystals diffract at all). Thus our studies have always been dependent on the availability of synchrotron beam time and hampered by only partial (and very occasional) feedback to assess our experimental procedures for growing bacteria, preparing the ribosomes and obtaining crystals. 

There has been a clear emphasis, in the CD literature, on II-VI semiconductors, mostly CdS, some CdSe, and recently on ZnS. This being the case, the reader may reasonably expect this chapter to be a voluminous one. On the other hand, many of these studies have focused on deposition mechanisms and kinetics (which are dealt with in the previous chapter), with photovoltaic cells, and, to a lesser extent, with quantum size effects, both of which will be dealt with in subsequent chapters. Two detailed descriptions of the experimental procedure (for CdS and CdSe) are given in Chapter 2. This leaves the obvious question What s left The present chapter will answer that question. This includes properties of the films not explicitly discussed in other sections, such as crystal structure, optical and electrical properties, as well as variants of the deposition process. Also, more detail will be given on non-Cd chalcogenides. In short, there is indeed much left. 

This review will be concerned with recent progress made towards an understanding of conduction phenomena in typical homomolecular crystals, e.g. anthracene and the phthalocyanines, with certain charge-transfer complexes, selected biological systems, certain novel one-dimensional systems and other materials which serve to illustrate a particular theoretical approach or the value of an experimental technique. Little attention will be given to experimental procedures other than when these are not in common use and have not been adequately described in the earlier reviews. 

La-RuSb. The crystal structure of the LaRu4Sbi2 compound was studied by Braun and Jeitschko (1980). It was found to crystallize with the LaFe4Pi2 type, a = 0.92700 (X-ray powder diffraction). The purities of starting materials and experimental procedure were the same as for LaFe4Sbi2. 

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