480 DR GEORGE WILSON ON THE ACTION OF THE DRY GASES 



tion of quickening his metliods, that the practical bleacher probably desires im- 

 provement. One may expect, however, that the same amount of chlorine, espe- 

 cially if moist, should be more efficacious in bleaching, if assisted by sunlight, 

 than if debarred from it ; or what comes to the same thing, that a small amount 

 of chlorine should, in pi-actice on the great scale, bleach as powerfully in sunshine, 

 as a larger one in darkness. It might be possible, accordingly, to economise chlo- 

 rine, or chloride of lime, in this country, in the brighter seasons of the year, and 

 at aU times in sunny climates, if the bleaching operations were carried on in the 

 open air. 



III. Influence of Water over the Bleaching Action of Oxygen, Sulphurous Acid, and 



Sulphuretted Hydrogen. 



The fact that actinised chlorine bleaches, though dry, supplies no explanation 

 of the function which water performs, when it invests that gas with decolorising 

 power. With a view to solve this problem, I made two series of experiments ; 

 1st, The object of the one was to observe to what extent other bleaching gases 

 resemble chlorine in being dependent for bleaching power on the presence of 

 water, and likewise to ascertain whether the acid gases and the volatile alkali, 

 when made anhydrous, lose that power of changing the tints of dry organic colour- 

 ing matters, which characterises them when moist. These experiments promised 

 to shew whether the action of dry chlorine on colours is exceptional and anoma- 

 lous, so as to demand a special explanation, such as Davy gave, or but a parti- 

 cular case of a general law, to which all elastic fluids are obedient. 



2d, The object of the other set of trials was to determine, whether bleaching 

 power can be conferred upon dry chlorine, by dissolving it and anhydrous colouring 

 matters in liquids containing no oxygen. I begin with the experiments first re- 

 ferred to. 



Five gases besides chlorine have marked bleaching powers when in the condition 

 of perfect elastic fluidity, and not anhydrous, viz., chlorous acid, hypochlorous 

 acid, sulphurous acid, sulphuretted hydrogen, and oxygen.* To these may be 

 added provisionally, the curious body ozone, which Berzelius regards as an allo- 

 tropic form of oxygen, and Schoenbein as a volatile peroxide of hydrogen. I have 

 made no experiments with this substance, because, in the present state of our 

 knowledge concerning it, it could not supply crucial results. Chlorous acid is too 

 explosive to admit of satisfactory researches being made with it. The same re- 

 mark applies with limitation to liypochlorous acid, a substance so interesting, fi'om 

 its high bleaching power, and its containing, like chlorous acid, the two most im- 

 portant bleaching agents, chlorine and oxygen. I have made no experiments with 

 this substance, but Pelouze has quite recently supplied us with a new and much 



* I omit from tliis list hydrogen, because, although it bleaches powerfully in the nascent state, it has 

 no sensible bleaching action, whether moist or dry, after it has attained the condition of perfect gaseity. 



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