Note 24 — Chapter XX · SULPHUR, SELENIUM, AND TELLURIUM
George Kamensky translation
Rebs took di-, tri-, tetra-, and pentasulphides of sodium, potassium, and barium, which he prepared by dissolving sulphur in solutions of the normal sulphides; on adding hydrochloric acid he always obtained hydrogen pentasulphide, whence it is evident that 4H2Sn = (n - 1)H2S5 + (5 - n)H2S. For example, if H2S2 were formed, it would decompose according to the equation 4H2S2 = H2S5 + 3H2S. The hydrogen pentasulphide formed breaks up into hydrogen sulphide and sulphur when brought into contact with water. Previous to Rebs' researches many chemists stated that all polysulphides gave the bisulphide H2S2, and Hofmann recognised only hydrogen trisulphide, H2S3.