34 SCIENCE PROGRESS 



the expression £ 7 *" = constant, a relationship which he had 

 already found to hold good for pure substances. 



Finally, as regards the viscosity curve, it is evident that 

 "urethane itself possesses a much greater viscosity even than 

 trihydrol, so that, from the first, the addition of the solute 

 causes an increase in this property which more than compen- 

 sates for the diminution which would be brought about by 

 the dissociation of the trihydrol. The dissociation of the trihy- 

 drol is shown, however, by the bending of the curve at its lower 

 end. That the above assumption is not unreasonable is shown 

 by the enormous increase in viscosity, from 100 to nearly 

 250, as we pass from pure water to a 50 per cent, solution of 

 urethane. 



The interest of this investigation lies in the fact that several 

 distinct properties which at first sight appear to have little in 

 common can all be related to one another on the basis of the 

 single assumption that the presence of a solute occasions the 

 dissociation of trihydrol into simpler molecular forms. 



The Tri-atomic Hydrogen Molecule. — As is well known, Sir 

 J. J. Thomson first discovered evidence for the neutral mole- 

 cule H 3 as a result of investigation by means of positive rays. 

 More recently Duane and Wendt (Phys. Rev. 191 7, 10, 116) 

 have obtained further evidence for the existence of this polymer 

 of hydrogen. 



Bohr (Medd. K. Vet. Akad. Nobelinstitut, 191 9, 5, No. 28) 

 has studied the stabilit}' - of the molecule H on the basis of his 

 theory of atomic structure, and has shown that such a struc- 

 ture is quite capable of permanent existence. The configura- 

 tion of the molecule is shown to be such that the three electrons 

 rotate at equal angular intervals in a common circular orbit, 

 while the three nuclei are placed on the axis of this orbit, one 

 at the centre of the circle and the two others equidistant from 

 the central one, the three nuclei being in the same straight line. 

 Bohr shows, further, that a molecule possessing this structure 

 has the capacity of binding a free electron and still giving rise 

 to a stable system. In this configuration the three nuclei are, 

 as before, in the same straight line, while the electrons are 

 distributed in two distinct circular orbits of equal radii, each 

 orbit containing two electrons, and each orbit being situated 

 around each of the terminal nuclei. 



