An extensive investigation of the isotopic thermalhyphen;diffusion factor agr;0of argon in the mean temperature range 127deg; to 653deg;K has been carried out with a fourhyphen;tube swing separator employed previously in similar work with helium and neon. Because of a linear variation of agr;0withTin the lowhyphen;temperature region, the mean temperatureTmacr;= (T2mdash;T1)/ln(T2/T1) has been used instead of the arithmetic mean ofT1andT2. This temperature assignment has been verified by varying the temperature gradient significantly. The experimentally determined value of agr;0increases from 0.068plusmn;0.015 atTmacr;= 127deg;K to 0.485plusmn;0.035 atTmacr;= 653deg;K, in fair agreement with earlier experiments. Just as for helium and neon, a Lennardhyphen;Jones 12:6 potential model fails to account for the observed temperature variation of argon agr;0values. The best fit for an expmdash;six force model occurs for agr; = 17 and egr;/k= 176deg;K. Using these force parameters, the best fit with experimental viscosity data yieldsrm= 3.535 Aring;. These parameters are then used to calculate the diffusion coefficient and second virial coefficient for argon. There is fair agreement with the experimental values of these other transport coefficients.
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