On the Action of Sulphur and Aqueous Vapour. 521 



point, that is, about 190°. We must consider that point to be 

 the absolute boiling-point at which the cohesion of the liquid 

 is equal to and the coefficient of capillarity also 0, at which 

 the latent heat of evaporation is also 0, and at which the liquid 

 changes into vapour independently of pressure and volume. The 

 absolute boiling-point of ether is at 190° (Wolff), that of chloride 

 of silicon at 230° (MendelejefF), of chloride of ethyle at 170°. 

 For alcohol it must be about 250°, and for water 580°. 



Corenwinder announced more than ten years ago that sulphur 

 and hydrogen could be made to combine partially by bringing 

 them in contact by means of pumice heated to redness. He has 

 recently examined* the action of sulphur and aqueous vapour at 

 high temperatures. In the middle of a glass or porcelain tube 

 pieces of recently calcined pumice were placed, and near one end 

 some pieces of sulphur, some asbestos being placed between the 

 cork and the sulphur. The pumice was heated to redness and 

 the sulphur slowly distilled over it, while at the same time a cur- 

 rent of aqueous vapour was passed into the same end. After a 

 little time sulphuretted hydrogen in abundance was produced. 

 The phenomenon takes place in a still more distinct manner if 

 pure calcined silica be substituted for pumice. In no case does 

 the porous body undergo any alteration. 



The author recommends this observation to the attention of 

 geologists, for it explains the presence of sulphuretted hydrogen 

 in certain gaseous exhalations which has been observed by MM. 

 Boussingault, Ch. Deville, and Leblancf. 



It is well known that sulphurous acid is reduced, by the 

 nascent hydrogen disengaged by means of zinc and hydrochloric 

 acid, to sulphur and sulphuretted hydrogen. Kolbe has ob- 

 served! that sulphuric acid is also similarly reduced. This he 

 found by adding pure concentrated sulphuric acid through a 

 funnel-tube to a mixture of water and zinc placed in a Woulfe's 

 bottle. The gas is produced in larger quantities the hotter the 

 mixture is which gives off hydrogen, aud the more concentrated 

 the sulphuric acid on coming in contact with the zinc. 



When the sulphuric acid is previously diluted with double its 

 volume of water, the disengaged hydrogen is quite free from 

 sulphuretted hydrogen. If now concentrated sulphuric acid be 

 added, there is a perceptible smell of sulphuretted hydrogen. 



* Comptes Rendus,Ji\\y 1S61. 

 t Phil. Mag. vol. xvi. p. 284. 

 1 Liebi^'s Annalen, August 1861. 



Phil. Mag. S. 4. No. 150. Suppl. Vol. 22. 2 M 



