883 



atoms. Now however 1 bethought myself' that I had determined the 

 size of the hydrogen molecule already before, and (hat this size was 

 even the first molecide size that 1 had at least estiuiated. From 

 Regnault's observations, in \n hieli the volume under I meter pressure 

 was assumed as unity of volume, 1 had obtained values lying between 

 0,0005 and 0,0008, which for our unity of voluuie corres|)onds to 



0,00038, and 0,00(^01), from which for — a value would follow lyini»' 



Pk 



between 0,95 and L,5. And a value lying near 0,95 seems by far 



more probable to me than the value which would follow from the 



critical data, and leads me to conclude that at these low temperatures 



hydrogen associates to double mole(;ules for the greater i)art. 



But nevertheless the value of the volume of the atom H reuiaius 



decidedly smaller when it is bound to 74 P^^i"^ of the atom C, than 



when it is bound to a second atom H. And this is a result which 



has always appeared correct to me, viz. that the size of the 



volume of an atom is not only determined by its owu nature, but 



also by the nature of the atom to which it is bound. This is of 



course in flat contradiction with the assumption that an atom is a 



perfectly invariable corpuscle, not to be changed by any forces, not 



by atuimc forces either. With the molecules as wholes it must, 



indeed, have the property in common of being invariable to forces 



of collision of heat and of pressure. But when uniting with other 



atoms, in which forces of higher order come into play, they behave, 



I would almost say, as soft bodies, which can vary both with 



regard to shape and to size. And the conception that an atom is an 



oi-bii of electrons round a rigid centre formed by a point in which 



the atomic weight is concentrated, or when the atom is bi-, tri- or 



1 1 1 



tetravalent by 2, 3 or 4 orbits round centres in which — ,- oi- - 



•^ 2 3 4 



of the atomic weight is concentrated — a conception called into 



existence by the study of light phenomena^) — can give an explanation 



of this. We have only to assume the velocity in the orbits large 



with respect to the velocity of the thermal motion to account for 



the apparent hardness, and only to assume rotation of the molecules 



round one or more axes to convert orbits and planes to an apparent 



volume. When we have two similar atoms which have united, 



we have two ojbits of electrons lying in the same plane, and 



rotating in opposite direction. Where they aie in contact or almost 



in contact, the directions are in the same sense, hence we have 



1) Cf. among others Dr. Bohu, I'hil. Mag. 1913. 



