2 1 e with a calculated slope equal to 0.0295V instead of 0.0885V. Similarly, the defect Vcd' would give a slope equal to 0.059V.The hypothesis can be made that the plateaus observed in the titration curves are due to impurities introduced in the sample, either during the cadmium electrodeposition or during the formation of the sulfide layer. Particularly, the samples could contain cadmium oxide and/or sodium sulfide. As sulfide and oxide species are similar the presence of dissolved cadmium oxide (i.e., the replacement of a sulfur atom Ss by an oxygen atom Os) could only slightly modify the cadmium sulfide properties. Sodium sulfide is an ionic compound which dissolves in CdS with more difficulty. It is also possible that the remaining sodium sulfide is transformed into cadmium sulfide during the oxidation of the cadmium in excess. However, as it stands now, it is not possible to state precisely what kind of impurities are involved. But the obtained results show that electrochemical analysis is a possible method of studying cadmium sulfide and, more generally, semi-conductors having a possible deviation from stoichiometry.

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