M. Gay-Lussac's Observations un some Sulphurets. Ill 



hension of some combinations of sulphur, concerning which 

 M. Berzelius has made important researches. 



The existence of sulphurets formed by the alkaline metals 

 has been long known. In my memoir on Iodine, Annates de 

 Chirriiej vol. xci. p. 59, I have already shown that baryta is 

 reduced by hydrosulphuric acid, and that a sulphuret of ba- 

 rium is produced. Since that first observation, the researches 

 of M. Vauquelin and myself, An. de Chim. et de Phys. vol. 

 vi. p. 5 and 321, have placed the existence of the alkaline sul- 

 phurets beyond a doubt ; and the more recent investigations 

 of M. Berzelius and M. Berthier, vol. xx. p. 34, and vol. xxii. 

 p. 225, have given a further confirmation of it. 



The sulphurets formed with the alkaline metals may con- 

 tain several atoms of sulphur, and it is very easy to discover 

 when they have more than one atom. In fact, a protosulphu- 

 ret, decomposed by an acid, yields hydrosulphuric acid, without 

 precipitation of sulphur ; and for one atom of the sulphuret, 

 one atom of water will be decomposed, the hydrogen of which 

 combines with the sulphur, and the oxygen with the metal. 



When, on the contrary, the sulphuret contains more than 

 one atom of sulphur, and it is decomposed by an acid, sul- 

 phur is precipitated, because for one atom of metal only one 

 atom of water will be decomposed, and only one atom of hy- 

 drosulphuric acid procured. 



Now, M. Berthier, in his interesting inquiry on the decom- 

 position of the sulphates by charcoal at a high temperature, 

 has proved that they are converted into protosulphurets ; for 

 their weight, after their decomposition, was exactly equal to 

 the united weights of the metal and sulphur which they con- 

 tained : acids disengaged hydrosulphuric acid from them, 

 without precipitation of sulphur, and they reproduced, when 

 oxidized, perfectly neutral sulphates. 



On the other hand, however, every chemist knows, that when 

 a sulphate is decomposed by charcoal at a red heat, a sulphu- 

 ret is obtained with a more or less coloured solution, and from 

 which acids precipitate a large quantity of sulphur, though 

 the sulphuret contains but one atom of sulphur for one of the 

 metal. 



This last result, compared with that of M. Berthier, neces- 



