Please see below: Part II.

http://www.nist.gov/srd/nsrds.cfm

Also papers in Journal of Physical and Chemical Reference Data by Janz.

NSRDS 61 Part I Physical Properties Data Compilations Relevant to Energy Storage. I. Molten Salts: Eutectic Data - George J. Janz, Carolyn B. Allen, J.R. Downey, Jr., and Reginald P.T. Tomkins. NSRDS-NBS 61, 244p. (1978).

NSRDS 61 Part II Physical Properties Data Compilations Relevant to Energy Storage. II. Molten Salts: Data on Single and Multi-Component Systems - George J. Janz, Carolyn B. Allen, Narottam P. Bansal, R.M. Murphy, and Reginald P.T. Tomkins. NSRDS-NBS 61, 420p. (1979).

NSRDS 61 Part III Physical Properties Data Compilations Relevant to Energy Storage. III. Engineering Properties of Single and Polycrystalline Sodium Beta and Beta Alumina - G.R. Miller and D.G. Paquette. NSRDS-NBS 61, 19p. (1979).

NSRDS 61 Part IV Physical Properties Data Compilations Relevant to Energy Storage. IV. Molten Salts: Data on Additional Single and Multi-Component Salt Systems - George J. Janz and Reginald P.T. Tomkins. NSRDS-NBS 61, 870p. (1981).

R. Fernandez and T. Østvold, Acta Chemica Scandinavica, 43, 151-9, (1989)

Sorry, my mistake. The reference I gave covers NaCl and KF, but not KCl

Thanks for all

See also Y Marcus, Thermochim Acta 2013, 571, 77 and J. Chem. Phys. 2013, 139,124509 for critically evaluated molten salt data.