Mixtures similarity property

The ideal solution approximation is well suited for systems where the A and B atoms are of similar size and in general have similar properties. In such systems a given atom has nearly the same interaction with its neighbours, whether in a mixture or in the pure state. If the size and/or chemical nature of the atoms or molecules deviate sufficiently from each other, the deviation from the ideal model may be considerable and other models are needed which allow excess enthalpies and possibly excess entropies of mixing. 

In all the above sequences, single isomers are produced by careful control of the reaction conditions combined with purification by selective isolation at various points in the synthesis. Occasionally two isomers are produced which give dyestuffs that have very similar properties in these cases it is often quite acceptable and economically beneficial not to separate the individual components but to use the total mixture in dye preparation. An example is the mixture of l-naphthylamine-6- and 7-sulphonic acids (4.46 mixed Cleve s acids), which arises by nitration and reduction of naphthalene-2 Sulphonic acid (Scheme 4.30). 

Cubic BC2N. Hetero-diamond B C—N compounds have recently received a great interest because of their possible applications as mechanical and optical devices. The similar properties and structures of carbon and boron nitrides (graphite and hexagonal BN, diamond, and cubic BN) suggested the possible synthesis of dense compounds with all the three elements. Such new materials are expected to combine the best properties of diamond (hardness) and of c-BN (thermal stability and chemical inertness). Several low-density hexagonal phases of B,C, and N have been synthesized [534] while with respect to the high-density phases, different authors report contradictory data [535-538], but the final products are probably solid mixtures of c-BN and dispersed diamonds [539]. 

The most frequently used mixture-"composition-property designs of experiments belong to simplex-lattice designs suggested by Scheffe [5], The basis of this kind of designing experiments is a uniform scatter of experimental points on the so-called simplex lattice. Points, or design points form a [q,n] lattice in a (q-1) simplex, where q is the number of components in a composition and n is the degree of a polynomial. For each component there exist (n+1) similar levels Xp0,l/n,2/n.1 and all... 

The physical and chemical properties of dyes are very important for even coloring. First a hair dye should have comparable affinities for the roots, damaged areas, and tips. Second, the combined yellow-to-blue dyes used for shading must have similar properties so that color shifts will not take place when the hair is washed, for example. The importance of these problems is illustrated by the number of patent applications disclosing new, custom-tailored dyes [35] and suitable dye mixtures [42], The relatively good colorfastness and stability of some nitro dyes allow them to be used in oxidation hair dyes as well, especially for the shading of brilliant (mainly red) fashion colors. 

Similar properties to the much more widely investigated sodium amide, but may be expected on general grounds to be more violently reactive. The frequent fires or explosions observed during work-up of reaction mixtures involving the amide were attributed to presence of unreacted (oxide-coated) particles of potassium in the amide solution in ammonia. A safe filtration technique is described.2... 

Products with similar properties are also obtained from mixtures of homoPP with PE as well as with ethylenepropylene elastomers. Such mixtures are interesting because of their high flexibility at low temperatures. These mixtures, which may contain up to 50 % elastomer, are designated as elastomermodified thermoplastics. Those materials with elastomer content over 50 % are referred to as thermoplastic rubbers. 

Plastics with similar properties and applications can be found in the form of polymer mixtures of PTFE with other polymers (see coating Section 2.3.7). 

In a so-called ideal solution, that is a mixture of several components with very similar properties, the ratio of pa/p is equal to the mole fraction x of component a in the liquid phase. Thus Raoult s law is valid ... 

The partitioning of a substance between two liquid phases (multistage partitioning, partition chromatography) and the extraction of solids require similar properties of a solvent [50-55]. When a substance has to be partitioned, a solvent system with limited miscibility of the components is required in order that the substance dissolves to a different extent in the two phases. The greater the chemical differences between any two solvents, the more limited their miscibility. Other requirements that the solvent system must fulfil are, inter alia, a favorable partition coefficient (the average partition coefficient of the component mixture should be between ca. 0.2 and 5), as high a separation... 

More recently, it has been reported [7] that similar properties were observed for Se-trifluoromethylated dibenzoselenonium salts. Se-(Trifluoromethyl) dibenzoselenophenium triflate (4) was successfully synthesized in high yield by the direct fluorination of an equimolar mixture of the selenide 5 and triflic acid (TfOH) with diluted molecular fluorine. The same salt was also obtained by cyclization of the selenoxide 6 with triflic anhydride (Tf2 0) - a reaction which probably occurs via the selenonium salt 7 (Scheme 1). 

The particular problem of separating mixtures of substances with similar properties when the equilibrium separation coefficient, a, does not differ greatly from unity can be solved only by using effective columns. The application of countercurrent operations in these processes is still confined to laboratory or semi-industrial experimental installations. 

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