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II. On the Discovery of Gun' Cotton. 

 By Professor Schcenbein*. 



THE substance to which I have given in German the name 

 o'i schiesswolle^ and in English that of gun-cotton, having 

 excited a lively curiosity, it may be interesting to the scientific 

 world to become acquainted with some details of the way in 

 which I was first led to its discovery. 



The results of my researches on ozone led me in the course 

 of the last two years to turn my attention particularly to the 

 oxides of nitrogen, and principally to nitric acid. The nu- 

 merous experiments I have made on this subject have led me, 

 as I have stated in detail in Poggendorff''s Ajinalen, to adopt 

 a peculiar hypothesis on the so-called hydrates of nitric acid, 

 sulphuric acid, &c., as well as on the normal nitrates, sulphates, 

 &c. 



For a long time I had entertained doubts as to the exist- 

 ence of compound bodies of this nature, which cannot be 

 isolated, and which are stated to be capable of existing only 

 in combination with certain other substances ; for a long time 

 also I had come to the notion that the introduction of these 

 imaginary combinations had only been an apparent progress 

 in theoretical chemistry, and that it had even impeded its 

 development. 



It is well known that what has most contributed to the 

 admission of the existence of these compounds has been the 

 opinion generally received among chemists respecting the 

 nature of nitric acid. Starting from the existence of the com- 

 pound of nitrogen NO5, as an undoubted and demonstrated 

 fact, notwithstanding the impossibility ofisolating it, they always 

 cite nitric acid to prove the existence of compounds which 

 cannot exist in an isolated state. In my opinion, there is no 

 degree of oxidation which is represented by NO5, and what 

 these chemists designate by the formula NO5+HO must be 

 considered as being really NO4+HO2; 1 am even inclined 

 to regard the normal nitrates NO5+ RO, as compounds which 

 must be expressed by NO4 + RO2. Amongst other motives 

 which induce me to admit this opinion, I will mention the fact 

 that we can obtain hydrated nitric acid or a normal nitrate by 

 the direct mixture of NO4 with HO2 or ROg. Other consi- 

 derations, which I have had occasion to detail elsewhere, in- 

 duce me also to consider hydrated sulphuric acid to have the 

 form SOa-f HO2, and not that of SOg+HO, and a normal 

 sulphate that of SO2 + RO2. It is sufficient here to observe 

 that SO2 placed in presence of HOg gives rise to what is 



* From the Archives des Sciences Physiques et Naturelles, 



