TRANSACTIONS OF THE SECTIONS. 51 



setting fire to a floor-cloth manufactory. He felt convinced that this unfortunate 

 young man was an innocent victim of the law, and that spontaneous combustion 

 was the cause. An instance recently occurred in London, in which two persons 

 were apprehended and remanded at a police office on suspicion of setting fire to a ma- 

 nufactoiy of patent felt, which was afterwards found to be produced by spontaneous 

 combustion. He considered the subject as of high importance in a social point of 

 view, and particularly where large constructions were concerned, as in the case of 

 the late fire on board the Talavera. 



On some instances of Restrained Chemical Action. By E. A. Parnell. 



The object of this paper is to add to the list of circumstances which modify or 

 prevent the action of chemical affinity, the presence of water in the sphere of de- 

 composition producing a force of considerable power, and one whose action has not 

 been hitherto recognised. Its existence has been traced by observing the want of 

 action of certain gases, and especially sulphuretted hydrogen, when in a perfectly 

 dry state, on substances on which they exert a vigorous action in the presence of 

 water. Thus papers impregnated with salts of lead, mercury and copper, were 

 preserved from the action of sulphuretted hydrogen if rendered absolutely dry. 

 That the effect of water in permitting action between these same bodies, does not 

 wholly depend on diminution of the force of cohesion, by dissolving either the gas 

 or the salt, is proved by several circumstances. 1st, This want of action is perceived 

 only on particular salts ; 2nd, to restore the action, water may be present in a state 

 of combination with the salt, and can then exert no solvent power ; 3rd, on moisten- 

 ing different dry salts with absolute alcohol, which dissolves six times its volume of 

 sulphuretted hydrogen, and exposing to the gas, still no action ensued. 



On considering the nature of the salts on which the action of sulphuretted hydro- 

 gen is restrained, it appears that the function of water, in permitting action, is to 

 combine with tlie acid, which should be rendered free by sulphuretted hydrogen im- 

 mediately on its liberation. One equivalent of water is not in every case sufficient 

 to satisfy the acid ; for all anhydrous salts of the oxides of mercury, copper or lead, 

 can produce one equivalent of water with sulphuretted hydrogen. 



The action of water may in some measure be assimilated to that between sulphuric 

 acid of different degrees of strength, and metallic iron or zinc. These metals, as is well 

 known, undergo no change in oil of vitriol ; while in this case, as well as when dry 

 sulphate of lead is exposed to dry sulphuretted hydrogen, it would be said all is pre- 

 sent that is necessary to produce decomposition. But in both cases water must be 

 added for action to ensue ; in the one, to unite with sulphate of zinc about to be 

 formed, and in the other with the sulphuric acid. But there are some salts of those 

 metals which are unacted on by sulphuretted hydrogen when dry, whose acid, or 

 hydracid of its salt-radical, possesses but little affinity for water, and consequently 

 to which this explanation will not apply. In considering the cause of the want of 

 action here, it must be remembered that sulphur is in reality a weak radical ; that, 

 if the salt be soluble, a force is called into action, when its solution is acted on by 

 sulphuretted hydrogen, which possesses great power over the results of chemical ac- 

 tion, namely, insolubility of the sulphuret ; and water being present, with which the 

 acid can unite when free, it does not follow that decomposition must occur iu one case, 

 because it will in another under the influence of other forces. The author concludes 

 by suggesting an explanation of the singular action between potash and carbonate of 

 lime, in presence of a small quantity of water, observed by Prof. Liebig — carbonate 

 of potash and caustic lime being formed. Both caustic potash and carbonate of 

 potash have a strong affinity for water, but of the two, caustic potash the greater. 

 Here is sufficient water to supply the demands of the carbonate, but not of caustic 

 potash ; the result is, carbonate of potash and caustic lime are formed. 



On some subjects connected with the Sulphocyanides. By E. A. Parnell. 



The author referred to a paper published in the Phil. Mag. for October 1840, in 

 which it was shown that the substance supposed to be the isolated radical of the 

 sulphocyanides (obtained by the action of chlorine or nitric acid on sulphocyanide 

 of potassium) contained hydrogen as an essential constituent, and could not there- 



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