146 



SCIENCE 



[N. S. Vol. XLVII. No. 1206 



chemistry of solutions, and from this into phys- 

 ical chemistry in its broadest sense. 



As far back as 1893 Jones did some work 

 ■with Arrhemus on the hydrates of sulphuric 

 acid. In 1900 he sug'gested that part of the 

 abnormal changes of the freezing-point with 

 concentrated solutions is due to the solute 

 forming a compound or solvate with the sol- 

 vent, so that the real concentration is or may 

 be much greater than the apparent concentra- 

 tion. From this time on Jones devoted prac- 

 tically all his time to a study of solvates in so- 

 lution. The results are remarkable in quan- 

 tity and in range. Jones points out, p. 346, 

 that " the following sixteen lines of evidence 

 bearing on the solvate theory of solution have 

 been established: 

 " 1. Relation between lowering of the freez- 

 ing-point of water and water of crys- 

 tallization of the dissolved substance. 

 " 2. Approximate composition of the hydrates 

 formed by various substances in solu- 

 tion. 

 " 3. Eelation between the minima in the 

 freezing-point curves and the minima 

 in the boiling-point curves. 

 " 4. Relation between water of crystallization 



and temperature of crystallization. 

 " 5. Hydrate theory in aqueous solutions be- 

 comes the solvate theory in general. 

 " 6. Temperature coefficients of conductivity 



and hydration. 

 " Y. Eelation between hydration of the ions 



and their volumes. 

 " 8. Hydration of the ions and the velocities 



which they move. 

 " 9. Dissociation as measured by the freezing- 

 point method and by the conductivity 

 method. 

 " 10. Effect of one salt with hydrating power 

 on the hydrates formed by a second 

 salt in the same solution. 

 " 11. Investigations in mixed solvents. 

 " 12. Spectroscopic evidence bearing on the 

 solvate theory of solution; work of 

 Jones and Uhler. 

 " 13. Work of Jones and Anderson on absorp- 

 tion spectra, in which the presence of 

 bands was first detected. 



This showed that the solvate had an 

 efPect on the absorption of light, and 

 this could be explained only as due to 

 a combination between the solvent and 

 the resonator, or something containing 

 the resonator. 



" 14. The work of Jones and Strong on ab- 

 sorption spectra established the exist- 

 ence of a large number of ' solvent ' 

 bands. They showed that these were 

 formed by many salts and in many sol- 

 vents. They could even distinguish 

 between the bands of a salt in a given 

 alcohol and in its isomer. This was 

 regarded as very important. The tem- 

 perature work of Jones and Strong 

 was strong evidence for the solvate 

 theory. 



" 15. The work of Jones and Guy on the effect 

 of high temperature on the absorption 

 spectra of aqueous solutions, and also 

 on the effect of dilution, led to results 

 which were also in keeping with the 

 solvate theory. The most important 

 work of Jones and Guy which bears on 

 the solvate theory of solution is that 

 in which the radiomicrometer was used. 

 It was here sho^vn that solutions of 

 certain strongly hydrated non-absorb- 

 ing salts are more transparent than 

 pure water having a depth equal to that 

 of the water in the solution. In the 

 case of non-hydrated salts the solution 

 was the more opaque. This shows that 

 water in combination with the dis- 

 solved substance — water of hydration 

 — has less absorption than pure water. 

 This is regarded as striking evidence 

 that some of the water in the presence 

 of salts which are shown by other 

 methods to hydrate is different from 

 pure, free, uncombined water; and the 

 simplest explanation seems to be that 

 this is the conibined water or water of 

 hydration. 



" 16. The work of Jones and Guy was re- 

 peated and extended by Jones, Shaeffer 

 and Pauls. They obtained results of 

 the same general character as those 



