Chemistry and Physics. 305 



made that it was not possible to force a discharge through argon 

 at a pressure of less than j- - mm - Helium was found to be non- 

 conducting at a pressure of ^V mm wnen pure, but in the presence 

 of any common gas, such as hydrogen or oxygen, one-hundredth 

 of this amount serves to reveal the D 3 line. This behavior of 

 the inert gases explains why they appear to " run out " in spec- 

 trum tubes so quickly, for when the traces of common gases 

 always present are absorbed by the electrodes, the inert gases are 

 left in the pure and non-conducting state. — Chem. JVews, xciv, 

 305. H. L. w. 



3. Neiv Method for Determining Halogens in Organic Gom- 

 poiinds. — E. (Jhablay has described a simple method, based upon 

 a new principle, for making these determinations. The appara- 

 tus is a tube similar to a large test-tube. If the substance is a 

 liquid, from 0*1 to 0*5 g of it is weighed in a bulb of thin glass 

 and this is placed in the bottom of the tube and broken. The 

 tube is then plunged into a freezing-mixture of solid C0 2 and 

 acetone, then ammonia gas is passed in until 5 or 6 C0 have been 

 liquefied. A fragment of clean metallic sodium is then added, 

 the liquid is agitated, the reaction being moderated by plunging 

 the tube into the refrigerating mixture if necessary. Further 

 additions of sodium are made until the blue color of the sodam- 

 monium is permanent. This usually requires only one or two 

 minutes. The excess of ammonia is allowed to evaporate, moist 

 air is passed into the tube to decompose the remaining sodium, 

 the residue is dissolved in water and the halogen determined by 

 Volhardt's volumetric method. If the substance is solid and 

 soluble in liquid ammonia, the same method of treatment is 

 employed ; if insoluble in the ammonia, it is dissolved in 2 or 3 C0 

 of ether, benzol, or toluene and the solution is allowed to drop 

 very slowly from a funnel into the sodammonium liquid. The 

 author has applied the method to a large variety of pure organic 

 substances with very satisfactory results. — Comptes Hendus, 

 cxliv, 203. v h. l. w. 



4. Hydrates in Aqueous /Solution; by Harry C. Jones. 8vo, 

 pp. 264. Published by the Carnegie Institution of Washing- 

 ton, February, 1907. — This is a monograph on the evidence of 

 the existence of hydrates in solution, their approximate com- 

 position, and certain spectroscopic investigations bearing upon 

 the hydrate problem. Professor Jones has been assisted in this 

 work by F. H. Getman, H. P. Bassett, L. McMaster, and H. S. 

 Uhler. The investigations are the outcome of observations, 

 made in the Johns Hopkins laboratory, that very concentrated 

 solutions of certain salts showed abnormally low freezing points. 

 As these facts were not explained by the then existing theories 

 of solution, Professor Jones advanced the explanation, that in 

 these concentrated solutions a part of the solvent is combined 

 with the dissolved substance, and no longer plays the role of sol- 

 vent. No less than four distinct lines of evidence have been 

 furnished experimentally, all of which point to the correctness of 



