1 48 Mr, Faraday on the mutual action of sulphuric acid 



to rise, the red colour became deep brown, and then a sudden 

 action commenced at the bottom of the tube, which spread 

 over the whole, and the acid became black and opaque. 

 Continuing the heat, naphthahne, sulphurous acid, and char- 

 coal were evolved ; but even after some time the residuum 

 examined by water and carbonate of baryta, was found to 

 contain a portion of the peculiar acid undecomposed, unless 

 the temperature had been raised to redness. 



These facts establish the peculiarity of this acid, and dis- 

 tinguish it from all others. In its solid state it is generally 

 a hydrate containing much combustible matter. It is readily 

 soluble in water and alcohol, and its solutions forms neutral 

 salts with bases, all of which are soluble in water, most of 

 them in alcohol, and all combustible, leaving sulphates or 

 sulphurets according to circumstances. It dissolves in naph- 

 thaline, oil of turpentine, and olive oil, in greater or smaller 

 quantities, according as it contains less or more water. As 

 a hydrate, when it is almost insoluble in naphthaline, it 

 resembles the heavier substance obtained as before described, 

 by the action of sulphuric acid on naphthaline, and which is 

 the solid hydrated acid, containing a little naphthaline, and 

 some free sulphuric acid ; whilst the lighter substance is a 

 solution of the dry acid in naphthaline ; the water present 

 in the oil of vitriol originally used being sufficient to cause a 

 separation of a part, but not of the whole. 



2. Salts formed by the peculiar acid with bases. 



These compounds may be formed, either by acting on the 

 bases or their carbonates by the pure acid, obtained as already 

 described; or the impure acid in solution may be used. 



