618 Dr. A. 0. Crehore on the Construction of 



triangle about the stable equilibrium size, all three atoms 

 partaking in the oscillation. 



It may be remarked that this molecule of H 3 is not known 

 to chemists, but that in his novel method of analysis 

 Sir J. J. Thomson has discovered the existence of it. Pos- 

 sibly the degree of stability is not great enough for ordinary 

 conditions on account of its comparatively large size, and 

 because of the freedom with which the atom H x may revolve 

 around the other atoms. 



I have not discovered any way to unite four atoms of 

 hydrogen alone into a single molecule, though no direct 

 proof has been obtained that this cannot be done. 



Compounds of Hydrogen ivith Carbon. 



Carbon cannot take a single atom of hydrogen and remain 

 stable. The only situation in which any two atoms can 

 unite is when their two axes of rotation are in the same 

 straight line. In the case of carbon and hydrogen or carbon 

 and carbon, the force perpendicular to the radius vector from 

 the origin at the distance of equilibrium on the ^-axis is away 

 from the axis, showing instability in this direction. In this 

 respect it differs from hydrogen acting on hydrogen, where 

 the force perpendicular to the radius vector is toward the 

 axis at the equilibrium distance *. 



Carbon will take two hydrogen atoms, the distances and 

 location being as in Pi. XII. fig. 6. It is also shown again on 

 a smaller scale in comparison with fig. 5 for H 3 , where the 

 difference in the size is very striking. While this is a stable 

 arrangement, yet in the presence of hydrogen the carbon 

 readily takes on more hydrogen. Four is the maximum 

 number of hydrogen atoms that I have succeeded in uniting 

 to a single carbon atom, though, as above stated, no positive 

 proof that this is the maximum number has been attempted. 



PL XII. fig. 7 shows four hydrogen atoms united to one 

 carbon atom. This requires a geometrical figure in space 

 shown in perspective resembling a tetrahedron with the carbon 

 atom at the centre. The figure is symmetrical with respect to 

 the axis of the carbon atom, the line connecting the two upper 

 hydrogens being at right angles to that joining the lower two. 

 The figure is not a regular tetrahedron, however, the height 

 being 195 and length and breadth 159 units each. The top 

 and bottom edges are 224 each, and the four other edges 

 252 units each. Each hydrogen atom is, however, located 



* See equations (48) and (49) and following, p. 768, Phil. Mag. 

 vol. xxix. June 1915. 



