Abstract: The invention relates to a process for the depositing on a substrate a thin film or layer of a compound having at least one cationic constituent C and at least one anionic constituent A, such as zinc sulphide.On the substrate are formed at least two superimposed ionic layers respectively incorporating the said cationic constituent or constituents C and the said anionic constituent or constituents A by successively immersing the substrate in a first solution e.g. containing a salt of C, such as zinc sulphate and in a second solution eg containing a salt of A, such as sodium sulphide, while rinsing the substrate between two immersion operations.

Abstract: The invention relates to a process for the preparation of high purity alpha mercuric iodide for use as a starting material source for the growth of monocrystals usable for nuclear detection.This process consists of synthesizing alpha mercuric iodide and subjecting the thus obtained alpha mercuric iodide to a purification treatment consisting of at least one vacuum distillation stage at a temperature of at least 255.degree. C.For this distillation stage, use is made of a reactor having three zones kept at different temperatures. The iodide to be purified is introduced into the first zone kept at at least 255.degree. C. The mercuric iodide vapors pass through the second zone kept at a higher temperature before being condensed in the air-cooled third zone.