Chemistry and Physics. 393 



3. Artificial Radio-Active Barium. — A. Debierne, who, it 

 will be remembered, is the discoverer of "Actinium," the radio- 

 active substance that is found with the titanium of pitchblende, 

 has apparently produced active barium chloi'ide from the inact ve 

 salt by induction due to contact with actinium in solution. The 

 effect is made more intense by precipitating barium sulphate in a 

 solution containing actinium. The latter is carried down by the 

 barium sulphate, the sulphates are then changed to chlorides and 

 the actinium is precipitated by ammonia in the form of hydrate. 



If barium and actinium are in contact in solution for a short 

 time, the induced activity in the barium is insignificant; but 

 this activity increases with the time of contact, at least for ten 

 days or so, and a product was thus obtained which had several 

 hundred times as much activity as ordinary uranium. The 

 author decides that the radio-active barium chloride prepared in 

 this way is different from the radiferous barium extracted from 

 pitchblende (Curie's radium). In both cases the activity per- 

 sists in all chemical transformations to which the barium may be 

 subjected. The rays emitted seem to be similar; they ionize 

 gases, cause phosphorescence in barium platinocyanide, act on 

 photographic plates, a portion of the rays is deviated in the mag- 

 netic field, and the anhydrous chloride is spontaneously luminous 

 in each case. Moreover, the "artificial" radio-active barium 

 chloride may be concentrated by fractional crystallization from 

 water or hydrochloric acid solution, when the crystallized part 

 increases in activity in the same way as with radium. However, 

 "artificial" radio-active barium differs from the radiferous kind 

 in showing no spectrum. Demarcay examined a specimen of it 

 which was about a thousand times as active as ordinary uranium 

 and was unable to detect the radium lines, while with a product only 

 ten times more active than uranium, extracted from pitchblende, 

 the radium spectrum was very clearly visible. The author has 

 observed a second difference, in that the activity of the artificial 

 product diminishes with time. In three weeks the activity of 

 some of it diminished to one-third, while the activity of radifer- 

 ous barium chloride and of salts containing actinium increases at 

 first and then remains constant. The author believes that the 

 induced activity which he has studied is not due to traces of 

 actinium or radium, on account of the methods of separation 

 used, and moreover it is difficult to understand how contamina- 

 tion by active substances should take place only when the solu- 

 tions had been mixed for a long time. — Comptes Rendus, cxxxi, 

 p. 333. h. l. w. 



4. The Relative Values of the Mitscherlich and Hydrofluoric 

 Acid Methods for the determination of Ferrous Iron. — It has 

 been known for a long time that concordant results were not 

 always obtained by the two methods mentioned above, in the 

 analysis of rocks and minerals. In Mitscherlisch's method the 

 substance is decomposed at a high temperature by means of a 

 mixture of three parts of sulphuric acid and one part of water, 



