ON THE HTDBATE OF HTDEO SULPHURIC ACID. 127 



In a second paper " On the Influence of Pressure on the Forma" 

 tion of Chemical Compounds"! "Wohler refers to the ahove obser- 

 vations, and adds, that in two tubes in which sulphur, but no liquid 

 hydrosulphuric acid, had separated, the crystals were found in large 

 quantity, they did not, however, make then appearance in a third 

 tube in which the bisulphide was enclosed together with some hydro- 

 chloric acid. Hence the author concludes that the crystalline com- 

 pound, which is no doubt a hydrate of hydrosulphuric acid, must be 

 produced when a small quantity of water is enclosed with the gas 

 free from any other acid, the water then combines with it under the 

 pressure of the condensing gas (17 atmospheres). Under this pres- 

 sure it is permanent at ordinary temperatures. If the tube be heated 

 to 86° Fahrenheit, the compound rapidly becomes fluid, returning 

 to the solid state again on being cooled to the ordinary temper- 

 ature. 



Several years since I had occasion to prepare the liquid sulphides 

 of phosphorus described by Berzelius ; they were preserved under 

 water in stoppered bottles, in one of which the stopper soon became 

 immovably fastened, by the deposition of what appeared to be 

 sulphur. 



About eighteen months afterwards, during an intensely cold win- 

 ter, I observed a quantity of crystals floating on the surface of the 

 liquid in this bottle, and the sulphide had entirely changed its ap- 

 pearance having become opaque and perfectly solid. The crystals 

 were precisely similar to the feathery forms of sal ammoniac, so much 

 so that they might readily have been mistaken for that substance, 

 and undoubtedly belonged to the regular system. 



On breaking off the stopper, the crystals began to disappear very 

 rapidly, but a small quantity of the substance was introduced into a 

 tube over mercury, where it was speedily converted into a gas which 

 exhibited all the properties of pure sulphuretted hydrogen. Owing 

 to the rapidity of decomposition it was impossible either to weigh or 

 to dry the crystals for a quantitative analysis, although the tempera- 

 ture of the room was several degrees below zero. 



There can be little doubt that this was the same compound as 

 observed by Wohler, but its formation in this case was not prevented 

 by the presence of an acid. Pelletier and Serullas have shewn that 

 the sulphide of phosphorus is decomposed under water with evolu- 

 tion of gaseous sulphuretted hydrogen, and formation of phosphoric 

 or phosphorous acid. 



\ Annalen der Chemic und Pharmacie, B. 85. 



