A computer program has been developed to calculate the critical properties of binary mixtures from Deiters' equation of state. The critical properties of over 50 binary mixtures of permanent gases, alkanes, benzene and alkanes, cyclohexane and alkanes, and acetone and hydrocarbons have been calculated. The Guggenheim equation has also been used to enable comparison with a simple 'hard sphere plus attractive term' equation. Deiters' equation gives good results for mixtures of moderately different size molecules whereas Guggenheim's equation is superior for dissimilar size molecules. The values of an interaction parameter, zeta, obtained from our analysis are also reported.