APPENDIX I. 463 



of water. I may mention this additional consideration that, with respect 

 to hydrogen peroxide, we may look for its effecting still farther substitu- 

 tions of hydrogen by means of which we may expect to obtain still more 

 highly oxidised water compounds, such as Hj0 3 and H,,O 4 . These Schonbein 

 and Bunsen have long been seeking, and Berthelot is investigating 'them 

 a,t present. It is probable, however, that the reaction will stop at the 

 last compound, because we find that, in a number of cases, the addition of 

 four atoms of oxygen seems to form a limit. Thus, Os0 4 , KC10 4 , KMn0 4 , 



4 , Na.,P0 4 , and such like, represent the highest grades of oxidation. 1 

 As for the last forty years, from the times of Berzelius, Dumas, Liebig, 

 Gerhardt, Williamson, Frankland, Kolbe, Kekule*, and Butleroff, most theo- 

 retical generalisations have centred round organic or carbon compounds, 

 we will, for the sake of brevity, leave out the discussion of ammonia deriva- 

 tives, notwithstanding their simplicity with respect to the doctrine of substi- 

 tutions ; we will dwell more especially on its application to carbon compounds, 

 starting from methane, CH 4 , as the simplest of the hydrocarbons, containing 

 in its molecule one atom of carbon. According to the principles enumerated 

 we may derive from CH 4 every combination of the form CH 3 X, CB^X,, 

 CHX 3 , and CX 4 , in which X is an element, or radicle, equivalent to hydrogen 

 that is to say, competent to take its place or to combine with it. Such are 

 the chlorine substitutes already mentioned, such is wood-spirit, CH a (OH), in 

 which X is represented by the residue of water, and such are numerous other 

 carbon derivatives. If we continue, with the aid of hydroxyl, further substi- 

 tutions of the hydrogen of methane we shall obtain successively CH 2 (OH) 8 , 

 CH(OH) 3 , and C(OH) 4 . But if, in proceeding thus, we bear in mind that 

 <5H 2 (OH) 2 contains two hydroxyis in the same form as hydrogen peroxide, 

 HjO 2 or (OH)*, contains them and moreover not only in one molecule, but 

 together, attached to one and the same atom of carbon so here we must 

 look for the same decomposition as that which we find in hydrogenperoxide, 

 And accompanied also by the formation of water as an independently 

 existing molecule ; therefore CH,j(OH) 8 should yield, as it actually does, im- 

 mediately water and the oxide of methylene, CH.^0, which is methane with 



1 Because more than four atoms of hydrogen never unite with one atom of the ele 

 ments, and because the hydrogen compounds (e.g. HC1, HjS, H 3 P, H 4 Si) always form 

 their highest oxides with four atoms of oxygen, and as the highest forms of oxides (Os0 4 , 

 Eu0 4 ) also contain four of oxygen, and eight groups of the periodic system, corresponding 

 to the highest basic oxides B-jO, BO, B 2 O 3 , BO 8 , RjOs, R0 3 , B 2 7 , and RO 4 , imply the 

 above relationship, and because of the nearest analogues among the elements such as 

 Mg, Zn, Cd, and Hg ; or Cr, Mo, W, and U ; or Si, Ge, Sn, and Pt; or P, Cl, Br, and I, 

 and so forth not more than four are known, it seems to me that in these relationships 

 there lies a deep interest and meaning with regard to chemical mechanics. But because, 

 to my imagination, the idea of unity of design in Nature, either acting in complex 

 celestial systems or among chemical molecules, is very attractive, especially because the 

 atomic teaching at once acquires its true meaning, I will recall the following facts re- 

 lating to the solar system. There are eight major plarets, of which the four inner ones 

 are not only separated from the -four outer by asteroids, but differ from, them in many 

 respects, as, for example, in the smallness of their diameters and their greater density. 

 Saturn with his ring has eight satellites, Jupiter and Uranus have each four. It is evi- 

 dent that in the solar systems also we meet with these higher numbers four and eight 

 which appear in the- combination of chemical molecules. 



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