188 On Sulphuric Acid and Naphthaline. [1826. 



placed over sulphuric acid in an exhausted receiver. In some 

 hours it had hy concentration become a soft white solid, ap- 

 parently dry ; and after a longer period was hard and brittle. 

 In this state it was deliquescent in the air, but in close vessels 

 underwent no change in several months. Its taste was bitter, 

 acid, and accompanied by an after metallic flavour, like that of 

 cupreous salts. When heated in a tube at temperatures below 

 212, it melted without any other change, and on being allowed 

 to cool, crystallized from centres, the whole ultimately becoming 

 solid. When more highly heated, water at first passed off, and 

 the acid assumed a slight red tint ; but no sulphurous acid was 

 as yet produced, nor any charring occasioned ; and a portion 

 being dissolved and tested by muriate of baryta, gave but a 

 very minute trace of free sulphuric acid. In this state it was 

 probably anhydrous. Further heat caused a little naphtha- 

 line 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 opake. 

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

 coal were evolved ; but even after some time, the residuum ex- 

 amined by water and carbonate of baryta was found to contain 

 a portion of the peculiar acid undecomposed, unless the tem- 

 perature had been raised to redness. 



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

 stinguish 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 solution 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 naphthaline, oil of 

 turpentine, and olive oil, in greater or smaller quantities, accord- 

 ing as it contains less or more water. As a hydrate, when it is 

 almost insoluble in naphthaline, it resembles the heavier sub- 

 stance 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. 



