516 Br, D. MendeUeff [May 31, 



the conversion of alcohol into acetic acid, that there is an interval 

 during which is formed aldehyde, C^H^O, which, as its very name 

 implies, is "alcohol dehydrogenaturo," or alcohol deprived of hydrogen. 

 Hence aldehyde combined with hydrogen yields alcohol ; and united 

 to oxygen, acetic acid. 



For the same reason there should be, and there actually are, 

 intermediate products between ammonia and nitric acid, NO-(HO), 

 containing either less hydrogen than ammonia, less oxygen than 

 nitric acid, or -less water than caustic ammonia. Accordingly we 

 find, among the products of the de-oxidisation of nitric acid and the 

 oxidisation of ammonia, not only hydroxy lamine, but also nitrous 

 oxide, nitrous and nitric anhydrides. Thus, the production of nitrous 

 acid results from the removal of two atoms of hydrogen from caustic 

 ammonia and the substitution of the oxygen for the hydi'ogen, NO 

 (OH) ; or by the substitution, in ammonia, of three atoms of hydrogen 

 by hydroxyl, N(OH)^ and by the removal of water; N(0HJ'-H20 

 = NO(OH). The ^peculiarities and properties of nitrous acid, as, 

 for instance, its action on ammonia and its conversion, by oxidation, 

 into nitric acid, are thus clearly revealed. 



On the other hand, in speaking of the principle of substitution as 

 applied to water, it is necessary to observe that hydrogen and 

 hydroxyl, H and OH, are not only competent to unite, but also to 

 form combinations with themselves, and thus become H" and H-O^ ; 

 and such are hydrogen and the peroxide thereof. In general, if a mole- 

 cule AB exists, then molecules AA and BB can exist also. A direct 

 reaction of this kind does not, however, take place in water, therefore 

 undoubtedly, at the moment of formation hydrogen reacts on the 

 peroxide of hydrogen, as we can show, at once, by experiment ; and 

 further because the peroxide of hydrogen, H-0^, exliibits a structure 

 containing a molecule of hydrogen, H-, and one of oxygen, 0^, either 

 of which is capable of sei)arate existence. The fact, however, may 

 now be taken as thoroughly established, that, at the moment of 

 combustion of hydrogen or of the hydrogen compounds, peroxide of 

 hydrogen is always formed, and not only so, but in all probability its 

 formation invariably precedes the formation of water. This was to 

 be expected as a consequence of the law of Avogadro and Gerhardt, 

 which leads us to expect this sequence in the case of equal interactions 

 of volumes of vapours and gases ; and in the peroxide of hydrogen 

 we actually have such equal volumes of the elementary gases. 



The instability of peroxide of hydrogen — that is to say, the ease 

 with which it decomposes into water and oxygen, even at the mere 

 contact of porous bodies — accounts for the circumstance that it does 

 not form a permanent product of combustion, and is not jDroduced 

 during the decomposition of water. I may mention this additional 

 consideration that, with respect to the peroxide of hj^drogen, we 

 may look for its effecting still further substitutions of hydrogen by 

 means of which we may expect to obtain still more highly oxidised 

 water-compounds, such as H'O^ and H-'O*. These Schonbeiu and 



