Adaptability, fractionation techniques

Fractionation techniques at subzero temperatures require special devices. Commerical apparatus is sometimes adaptable, but in most cases new equipment must be built. In all cases the equipment must satisfy the following requirements it must be able to produce... 

Notes on the operation of a precision fractionating column. The following notes on the technique of conducting a fractionation under diminished pressure may be of value to the student their adaptation to fractionation at atmospheric pressure should not present any difficulty. 

Laser diffraction is a fast alternative for analysis of the size distribution of particles in an aerosol cloud. The theory of laser diffraction is well understood [124,125]) but this technique requires special measures to test inhalation devices and to interpret the results correctly. One of the major problems is that flow adjustment through the inhaler is not possible. Furthermore, the presence of carrier particles from adhesive mixtures may disturb the measurement of the fine drug particles and the size distribution obtained is of an unknown dehvered mass fraction of the dose. These practical problems and limitations have been solved by the design of a new modular inhaler adapter for the Sympatec laser diffraction apparatus (Figure 3.6). 

The apparatus developed for yb measurements of BLM deserves brief comment since it can be used not only to examine the effects of various substances on BLM but is readily adaptable for studying other types of interfacial films and related adsorption phenomena at either air-water or oil-water interfaces (and bifaces). Unlike both the Wil-helmy plate and film balance methods, the present technique measures 7i directly. From the description of the apparatus and procedure that the present method relies on the ability to measure the very small pressure difference across an interface (or biface). For certain BLM s, the pressure heads measured are only fractions of a millimeter of water. Therefore, the method described here has been possible only as a result of developing pressure transducers of high sensitivity. 

The vacuum distillation adapter also shown in Fig. 2.106 allows the collection of fractions when distilling under reduced pressure. Its operation is similar to the Perkin triangle or equivalent device ( intermediate receiver adapter ) described in Section 2.27. The general technique of conducting a fractional distillation is as follows ... 

Finally, attempts are being made to introduce a third differentiating force into two-dimensional techniques, namely, a pH gradient. Instead of using a buffer field with uniform pH, a series of vertical zones of different pH is built up (PI). For this purpose trickle feeding is adapted in such a way that each tooth of the upper edge of the paper receives buffer of a different pH. Thus the different fractions travel through sub-... 

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