A report is given of light-scattering studies on solutions of polymethacrylic acid and carboxymethylcellulose in methanol water, aqueous HCl and aqueous NaCl solutions, The results are well in line with those obtained by other authors. The behavior in methanol and in aqueous solutions of high electrolyte content is much the same as for uncharged polymers. In water and in dilute salt solutions, however, a behavior is found which is typical for polyelectrolytes. Nevertheless, the change of dissymmetry with polymer concentration in water and in dilute salt solutions is almost normal for NaCMC. This is attributed to the low charge density of this olymer. Five series of isoionic mixtures of NaCMC and NaCl have been investigated. The effective radius calculated ;om the angular intensity distribution is in excellent agreement with that derived from viscosity in previous work. It is shown that the theory of Katchalsky and Lifson does not apply to our data. The second virial coefficients A are compared with values obtained osmometrically and with values reported by Doty and Schneider for a sample of NaCMC with twice the charge density of our sample. It is found that A is approximately proportional to the square of this charge density and to the z/* power of the reciprocal ionic strength.Recent studies on the scattering of light by solutions of charged colloid particles have been published, among others, by FuossWe will use the customary notations: 1, is the irradiance of the incident beam, Rs the reduced intensity: ior2/Io1 P(0) the factor which determines the deviation from Thomson's angular distribution 1 + cos2 8. I n those cases where c/Re is a linear function of the polymer concentration c, we use the well-known equation KcIR, = l/MP(O) + 2Acwhere K = 2T2nz(bn/dC)2/X4NA, N A being Avogadro's number, n the refractive index and X the wave length in uucuo. Finally, 28 is the ratio be-
A light-scattering apparatus is described. It is calibrated by means of Ludox solutions, whose absolute turbidities are determined in transmission measurements. A check on the method is made with solutions of sucrose octa-acetate in methanol and of the international polystyrene sample 2 (2-149) in butanone and in toluene. Of recent years there has been renewed interest in the determination of absolute turbidities. The values found by a number of American scientists differ considerably from those mentioned in earlier years, and it appears that the matter is still far from being settled (see Sect. 7).In view of the fact that our instrument has been calibrated by means of transmission by Ludox solutions, and the entire method has been checked with solutions of saccharose octa-acetate and of polystyrene, it will be necessary to give a brief outline of the procedure and of the formulae applied.
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