Chemistry and Physics. 471 



SCIENTIFIC INTELLIGENCE. 



I. Chemistry and Physics. 



1. Hydrates in Solution. — It has been known for some time 

 that many inorganic salts give abnormal results in the lowering of 

 the freezing points of their comparatively concentrated aqueous 

 solutions. They show in dilute solutions depressions of the freez- 

 ing point which correspond to their ionization as determined by 

 electrical conductivity, but when a certain degree of concentra- 

 tion has been reached the depression of the freezing point is abnor- 

 mally great in most cases. H. C. Jones and his co-workers have 

 made an extensive study of this matter, and it has been found 

 that all but nine of the forty-nine substances experimented upon 

 showed a minimum in the freezing-point curve ; that is, the effect 

 of the substance in lowering the freezing point gradually dimin- 

 ished as the concentration increased — on account of diminished 

 ionization — and then the abnormal increase of effect occurred to 

 such an extent that the curve showed a minimum point. Even 

 where the freezing-point curves did not show a minimum, there 

 was an abnormal depression of the freezing point in nearly every 

 case with concentrated solutions. It was found also that those 

 substances which crystallize out of solution with the larger number 

 of molecules of water of crystallization give the greatest molecu- 

 lar lowerings of the freezing point of water in concentrated 

 solutions. The boiling-point curves, as far as they have been 

 worked out, also show a minimum, but this occurs at a greater con- 

 centration than in the corresponding freezing-point curve. 



From the results of this work, the important conclusion is 

 reached that in concentrated solutions a part of the solvent is 

 combined with the dissolved substance, and such solutions are, 

 therefore, more concentrated than they would appear from the 

 amount of dissolved substance present in them. This view 

 explains the abnormal behavior of concentrated solutions in a 

 very simple and satisfactory way; for it is difficult to imagine 

 that substances should crystallize with water of crystallization, 

 unless they were capable of combining with this water while in 

 solution. If further work confirms this new explanation, a seri- 

 ous objection to the ionic theory of solutions will be removed. — 

 (Jones and Getman) Amer. Ghem. Jour., xxxi, 303. n. t,. w. 



2. A Microscopical Method of Determining Molecular Weights. 

 — This interesting method, described by George Barger, of 

 King's College, Cambridge, England, depends upon the increase 

 or decrease in size of alternate drops of two solutions in a closed 

 capillary tube. One of the solutions is prepared from a substance 

 of known molecular weight, while the other contains a known 

 amount of the substance whose molecular weight is to be deter- 

 mined. When the two solutions contain the same number of 

 molecules in a given volume, the vapor tensions will be equal and 



