Chemistry and Physics. 409 



sealed glass tube was allowed to act upon 30 cc of water for forty- 

 one days, it was possible to determine the amount of hydrogen 

 peroxide by titration with very dilute potassium permanganate. 

 The hydrogen evolved was collected and measured, and it was 

 found to be free from oxygen when the experiment was conducted 

 with the proper precautions for the exclusion of air. The 

 amount of energy calculated as utilized by the reaction under 

 consideration as compared with the known amount of heat 

 evolved by radium was 1 : 17,500 where a thicker tube was used, 

 and 1 : 11,600 with a thinner tube. The author believes that the 

 effect described is due entirely to the /?-rays, and that the y-rays 

 do not take part in the reaction, for he could not produce the 

 reaction by the action of the Rontgen rays under similar condi- 

 tions. — Comptes Rendus, cxlix, 116. h. l. w. 



3. The Decomposition of Water by Ultra-violet Rays.— A 

 method for the sterilization of water, consisting in immersing in 

 it a mercury-vapor lamp acting in a quartz tube for about a 

 minute, has been described by Courmont and Nogier, who failed 

 to find in water thus exposed to the ultra-violet light for a period 

 of ten minutes any evidence of the presence of ozone or other 

 powerful oxidizing agent. M. Keenbaum has found, however, 

 by extending the exposure to ten hours, that hydrogen peroxide 

 and hydrogen are thus produced, and consequently that the action 

 of the ultra-violet rays upon water is the same as that of the (3 

 rays from radium.— Comptes Rendus, cxlix, 273. n. l. w. 



4. Radio-activity of Potassium Salts. — Campbell and Mac- 

 Lellan, who have studied the weak radio-activity of potassium 

 salts, have attempted to concentrate this property by fractiona- 

 tion, but always with negative results. Henriot and Vavon, 

 using the fractional crystallization of the chloride, repeated pre- 

 cipitation of the chloride with gaseous hydrochloric acid, and 

 repeated precipitations of barium sulphate in a solution of potas- 

 sium sulphate, have also failed to find any concentration, and 

 the} 7 have thus strengthened the opinion that this radio-activity is 

 due to j^otassium, and not to an unknown impurity. They have 

 shown also that the radiation in a magnetic field behaves like a 

 negative flow of electricity, thus identifying it as composed of 

 f3 rays. — Comptes Rendus., cxlix, 30. h. l. w. 



5. The Cementation of Iron by Charcoal in a Vacuum. — 

 Conflicting views have prevailed in regard to the possibility of 

 the absorption of carbon by iron in the absence of gases. Guillet 

 and Griffiths have now made some careful experiments in 

 regard to this matter, and find that when the iron wire and the 

 sugar-charcoal have been first heated alone in a vacuum to 1000° 

 C, there is no appreciable cementation when they are heated in 

 contact to the same temperature. When, however, the materials 

 are heated under powerful pressure cementation takes place 

 slowly. They conclude that solid carbon plays an insignificant 

 part in industrial cementation. — Comptes Rendus, cxlix, 125. 



H. L. W. 



