I. A contribution to the knowledge of persulphide of hydrogen

This remarkable body was first observed by Scheele, and subsequently examined by Berthollet; our knowledge of this substance is, however, more especially due to Thenard, who, soon after the discovery of peroxide of hydrogen, was led also to investigate what was believed to be the corresponding sulphur-compound. The composition of persulphide of hydrogen has nevertheless remained doubtful. Thenard points out that the specimens analyzed by him, contained variable quantities of sulphur, but always more than would have been met with in a sulphur-compound corresponding to peroxide of hydrogen. If, nevertheless, several modern authors have not hesitated to represent the composition of persulphide of hydrogen by the formula H2 S2 , with or without a sign of interrogation, their statements are no longer based upon the secure foundation of experience.