412 On Iodine. [Junb, 



the ether in oxygen gas ; for if it is well founded, the combustion 

 in this gas should be attended with flame. 



On calling to mind the different experiments in this memoir, we 

 shall see that there is not one which authorizes us to consider iodine 

 as a compound body, or as a substance containing oxygen. On the 

 contrary, we must be struck with the resemblance which it bears in 

 some cases to sulphur, and in others to chlorine. Like them, it 

 forms two acids, one by combining with oxygen, the other by com- 

 bining with hydrogen : and we may have remarked that the acids 

 formed at once by the combination of chlorine, iodine, and sulphur, 

 with the elements of water, present this remarkable property, that 

 when the acid formed by oxygen has its elements very condensed, 

 that formed by hydrogen has them very weakly united. 



Thus sulphur takes oxygen from iodine, and iodine takes it from 

 chlorine ; but, on the other hand, chlorine takes hydrogen from 

 iodine, and iodine from sulphur. 



If we follow this analogy still further, we find that it holds like- 

 wise with respect to carbon ; for sulphur deprives it of hydrogen, 

 but yields to it oxygen. Thus it would appear that the more a body 

 condenses oxvgen, the less it condenses hydrogen.* This is, with- 

 out doubt, a cause why the very oxidable metals, as iron, manganese, 

 &c. do not dissolve in hydrogen. I say one of the causes ; for if it 

 were the only one, we could not see how mercury, silver, and gold, 

 do not combine vvith hydrogen, though they have a very weak 

 affinity for oxygen. f 



The other analogies which Iodine has with sulphur and chlorine 

 are very numerous. Some iodates resemble the chlorates exactly ; 

 but most of them have a greater analogy with the sulphates. The 

 iodurets, sulphurets, and chlorurets, in general exhibit the same 

 phenomena with water ; and the action of sulphur, iodine, and 

 chlorine, upon the oxides, vvith or without water, is exactly similar. 

 In short, all the properties of iodine may be classed between those 

 of sulphur and chlorine. It is not necessary to remark, that though 



* From these coDsideratioiis I do not hesitate to class azote with oxygen, 

 iodine, chlorine, and sulphur. Nitric acid has a considerable resemhlance to iodic 

 acid and chloric acid by the property which it has of being easily decomposed; 

 and because azote takes, like chlorine and iodine, two and ahalf times its volume 

 of oxygen. The nitrates are decomposed by the fire, like the iodates. But wc 

 do not know any oxide from which azote disengages oxygen, from which we can 

 conclude only that it has much less energy than this last body. Azote forms like- 

 ■wise with chlorine and iodine combinations which are easily decomposed, which 

 shows that it has little affinity for them, and that it approaches them by the nature 

 of its energy. If it does not form an acid w ith hydrogen, this is doubtless because 

 in ammonia there are three volumes of h>drogenfor one of azote; and in all pro- 

 bability, ill order In produce an acid, only equal volumes are requisite. The acid 

 combination of azote and hydrogen a])pears to me realized in prussic acid, which, 

 from a.ime experiments that I have made, and shall soon pubIi^h, I am induced to 

 contider as an acid analogous to the combinations of chlorine, iodine, and sulphur, 

 with hydrogen ; only that its radicle is a compound of azote and carbon. Oxy- 

 genated prussic acid corresponds to chloric and iodic acids. 



-t- See uote B at tbe end uf this memoir. 



