Intrinsic impurities

The quaHty, ie, level of impurities, of the fats and oils used in the manufacture of soap is important in the production of commercial products. Fats and oils are isolated from various animal and vegetable sources and contain different intrinsic impurities. These impurities may include hydrolysis products of the triglyceride, eg, fatty acid and mono/diglycerides proteinaceous materials and particulate dirt, eg, bone meal and various vitamins, pigments, phosphatides, and sterols, ie, cholesterol and tocopherol as weU as less descript odor and color bodies. These impurities affect the physical properties such as odor and color of the fats and oils and can cause additional degradation of the fats and oils upon storage. For commercial soaps, it is desirable to keep these impurities at the absolute minimum for both storage stabiHty and finished product quaHty considerations. 

He believe that the oscillations observed in our system are of a true kinetic nature or in the worst of cases the result of interaction between competing physicochemical processes and are not caused by the presence of impurities. However, the problem of eliminating all impurities from an intrinsically "impure" system such as the CO oxidation system under atmospheric conditions, is an academic one, especially when the type and the level of impurities involved far exceed the capabilities of any known in situ surface techniques. 

D (cm2/s) = 4.02 x 10 6 exp[-0.46(eV)/kT] when the hole concentration was between 10 and lOl /cm. The effect of the holes was explained in terms of vacancy diffusion mechanisms. It was concluded that In diffusion occurred via a dissociative mechanism, and that the solubility and activation energy of In were governed by the degree of doping. A vacancy diffusion mechanism predominated in Cl-doped material when the Cl content was at the intrinsic impurity level of about lOl /cm. ... 

All diversified point defects mentioned above, including intrinsic, impurity and electron defects, can be regarded as quasi-chemical species hke atoms or ions, which would exist or participate in chemical reactions as a composition of substance. 

Third, in both studies significant amounts of surface carbon impurities have been observed. Ertl and Thiele attributed the presence of the carbon to contamination, which occurred during handling of the samples. Analysis of the carbon Is spectra in the present samples led to the conclusion that at least some of the carbon is an intrinsic impurity of the iron compounds. On the other hand, the carbonate species found in the catalyst precursor is attributed to uptake of carbon dioxide by the alkaline promoter phases during storage of the catalyst. Therefore, the... 

The gel-to-fluid chain-melting transition in pseudo-two-dimensional lipid bilayer membranes induces formation of lipid domains of gel-like lipids in the fluid phase and and fluid-like lipids in the gel phase. The average domain size and in particular the average length of the one-dimensional interfaces between lipid domains and bulk have a dramatic temperature dependence with anomalies at the transition temperature. These anomalies are related to similar anomalies in response functions. The interfacial area may be modulated by intrinsic impurities which are interfacially active molecules such as cholesterol [1,2]. The properties of the interfacial area provide a means for understanding aspects of the functioning of certain biological membrane processes like the passive permeability of small ions and the activity of some membrane enzymes. 

Another intrinsic impurity in the reagent gases arises in a more subtle way. As described by Tanner, the gases from the ICP ion source can enter a collision cell and lead to significant side reactions. While the bulk of this gas is argon, there is substantial water, oxygen, nitrogen, etc. from... 

In general, the composition of polymer-salt complexes is a result of rather complicated equilibrium and some non-equilibrium, kinetically limited phenomena (Fauteux and Robitaille 1985 Fauteux et al. 1985 Lee and Crist 1986 Minier et al. 1984 Munshi and Owens 1986 Robitaille and Fauteux 1986 Stainer et al. 1984). According to the Gibbs phase rule (Gibbs 1870 Mindel 1962), for all the compositions ranging from pure polymer up to that of the thinnest crystalline complex, two phases should be present pure, crystalline PEO and pure PEO-salt crystalline complex. Nevertheless, polymeric materials are intrinsically impure , for example due to their polydispersity. Additionally, their crystallisation is kinetically limited, therefore in all polymeric materials there are always amorphous domains. Thus PEO-salt complexes usually consist of three phases (Fig. 2.4) - pure crystalline PEO, crystalline PEO-salt complex and amorphous PEO-salt complex the latter is of undefined composition (Wieczorek et al 1989). 

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