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One of the disadvantages of pure silver chloride as a cement is its high melting point of about 450 deg C. Mixing silver chloride with lead chloride or thallous chloride reduces the melting point and possibly reduces the coefficient of linear expansion. The Phase diagram for the AgCl/PbCl2 system is plotted in the figure ( after Trent & Welsh 1966)
The eutectic at about 40% Mol ratio of lead chloride melts at about 310 deg C. A small quantity of this eutectic mixture can be prepared by taking 5 gms of silver nitrate crystals and 6.5 gms of lead nitrate crystals and dissolving them together in 5o ml of distilled water. When the nitrates have fully dissolved, 15ml of concentrated hydrochloric acid is added, resulting in a white precipitate of the mixed chlorides. The mixture is allowed to stand in the dark overnight and then filtered and the precipitated washed with a little distilled water and dried. The resultant dried material is ground to a fine powder in a mortar.