428 M. BECQUEREL ON CHEMICAL DECOMPOSITION AND 



plate is covered with fine tetraliedral crystals of protocliloride of copper, 

 exceedingly brilliant and possessing great refrangibility. If the experi- 

 ment be continued so as to exclude all contact with the air, the liquor 

 •changes its colour to a deep brown and the crystals are no longer vi- 

 sible. The carbon is then powerfully attacked, and the result is, a 

 combination which has not yet been examined. 



Of the Action of the Pile on the Alkaline Sulphurets. 



When a solution of protosulphuret of potassium or sodium is exposed 

 to the air, the metal and the sulphur are simultaneously oxidized ; there 

 is produced a hyposuljihite, in which the acid and the base contain an 

 equal quantity of oxygen : the solutions of the other sulphurets undergo 

 other changes ; so long as the solution retains a yellow tint, the hypo- 

 sulphite is all that is formed, but as soon as tlie sulphur is precipitated, 

 this salt is changed, first into a sulphite, and then into a sulphate. 



The alcoholic solution of sulphuret of potash produces likewise, in 

 contact with the air, hyposulphite of potash, which crystallizes at the 

 surface of the liquid, at the same time that the sulphur, dissolved by 

 the alcohol, is abandoned. The other alkaline sulphurets act in the 

 same manner. 



As to the sulphurets of barium and strontium, their solutions, in 

 contact with the air, undergo changes somewhat different : though there 

 is a formation of hyposulphate, there is none of hyposidphite. 



When, in one of the branches of a tube bent like the letter U, (the other 

 branch containing water,) a solution of one of the preceding sulphurets 

 is submitted to the action of the positive pole of a pile composed of a 

 small number of elements, by means of plates of platina, while the 

 water is in communication with the negative pole ; the solution under- 

 goes changes similar to those which take place in the air. In fact, the 

 solution of protosulphuret of potassium or sodium in water is affected, 

 at first, in the usual manner by the positi\'e pole ; that is to say, a por- 

 tion of it is decomposed, and there is a transfer of potash or soda into 

 the negative side of the tube, while the sulphur left alone on the other 

 side combines with one portion of the disengaged oxygen, which trans- 

 forms it successively into hyposulphurous acid, sulphurous acid, and 

 sulphuric acid, which combines with the base ; for, after some days, 

 we find only a sulphate. If the operation be continued, this last salt 

 will itself also experience the decomposing action of the pile. The 

 same phaenomenon is exhibited by the solution of the persulphurets, 

 except that there is a precipitation of sulphur. 



The alcoholic solutions of the protosulphurets do not produce any 

 particular phaenomenon. As to the solution of a persulphuret, in ad- 

 dition to the formation of the sulphate, it presents on the plate of platina 

 a fine deposit of crystals of sulphur, possessing great regularity of 

 form, and admitting an increase of their dimensions by changing the 



