Chemistry and Physics. ^'^9 



SCIENTIFIC INTELLIGENCE. 



I. Chemistry and Physics. 



1. The Devitrification of Glass— It has been found by Albert 

 P. 0. Germanx that the well known peculiar behavior of many 

 samples of old glass upon heating before the flame is a surface 

 phenomenon, and that such glass can be restored to a workable 

 condition by simply washing it with dilute hydrofluoric acid in 

 order to remove a thin film of the surface. This observation is an 

 important one, as it gives a method for utilizing old glass and for 

 repairing old glass apparatus. It is the author's opinion that this 

 surface change is due to the absorption of moisture, but the mat- 

 ter does not appear to be perfectly simple, because it is mentioned 

 that a tube which devitrified badly at first showed no tendency to 

 behave in this way after having been exposed casually to labor- 

 atory fumes for more than six months. Perhaps the absorption 

 of carbon dioxide takes part in the devitrification since this might 

 be removed by the action of acid fumes. h. l. w. 



2. A Substitute for Thoulet's Solution. — A. Thiel and 

 L. Stole mention the employment of lieayy solutions for the 

 determination of the density of solids, by floating and sinking, 

 some of which solutions are mixtures of organic liquids and others 

 are aqueous solutions. Among the latter the best known are 

 potassium mercuric iodide (Thoulet) and barium mercuric iodide 

 (Rohrbach). For organic compounds the aqueous solutions are 

 practically the only ones employed, and for most of these solu- 

 tions of calcium chloride with a specific gravity up to 1.4 answer 

 the purpose, but the authors had occasion to use a heavier aque- 

 ous solution and found that lead perchlorate gave solutions up to 

 a density of 2.6. It is more agreeable to use than the mercuric 

 solutions, the solution is mobile and it does not attack the skin 

 to the slightest degree. It can be prepared cheaply by saturating 

 commercial perchloric acid with lead carbonate and evaporating 

 to saturation. This solution is evidently a very satisfactory one 

 for use with many, organic compounds, but unfortunately it 

 could be used only with the lighter minerals, since its maximum 

 density is slightly below that of quartz. — Berichte, 53, 2003. 



H. L. w. 



3. Priestley in America, 1794-1804; by Edgar F. Smith. 

 12mo, pp. 173. . Philadelphia, 1920 (P. Blakiston's Son & Co.).— 

 Professor Smith, in writing several recent books, has rendered 

 valuable service to the early history of chemistry in America, and 

 now he has increased this service by presenting the little book 

 under consideration. From contemporary newspapers, docu- 

 ments and books, he has found much interesting information con- 

 cerning the life and activities during his exile in America of this 

 noted discoverer of oxygen. It appears that Priestley's activi- 



Am. Jour. Sci. — Fifth Series, Vol. I, No. 3.— March, 1921. 

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