Department of Chemistry & Biochemistry, Punjab Agricultural University, Ludhiana Manuscript received 8 February 1974; revised 18 November 1974; accepted 19 November 1974 Diffusion coefficients of magnesium nitrate in water in the concentration varying from 0.05-0.14 /11 have been determined by a modified form of diaphragm cell. The experimental results indicate a good agreement with the theoretical results obtained from the Onsager and Fuoss theory.