100 ScientifiG Intelligence. 



have recently described further investigations in regard to this 

 matter. They are convinced that this substance is an independ- 

 ent radio-active principle, and that it is distinct and separable 

 from ordinary lead, although standing close to that metal in its 

 chemical properties. The interesting fact was observed that 

 solutions of radio-active lead are capable of inducing very great 

 activitj^ in metals which are placed for a long time in contact 

 with them, but upon which the}^ exert no chemical action, for 

 instance platinum, gold and silver palladium, and particularly 

 iridium. The metals remain perfectly bright under these circum- 

 stances ; the activity, which is often greater than that of the 

 original substances, is not removed by washing with water or by 

 rubbing with paper, but it is quickl}^ lost by ignition in most 

 cases. The theory is advanced that the a radiation (the less pen- 

 etrating kind, following Rutherford's designation) is a finely- 

 divided kind of matter the particles of which, like hydrogen, are 

 occluded by metals. — Berichte, xxxvi, 1040. h. l. w. 



4. Colloidal Silver. — Some observations upon Carey Lea's col- 

 loidal silver have been made recently by Hanriot. The work 

 was done with a commercial form of the substance which is sold 

 in France as a therapeutic agent under the name of collargol, and 

 which corresponds to Lea's first modification of colloidal silver. 

 It was found that solutions of this substance, upon being sub- 

 mitted to electrolysis, deposit silver upon the positive electrode, 

 whereas metals are deposited from solutions of their salts upon 

 the ojjposite pole. This and other properties of the solutions 

 have led this investigator to the conclusion that colloidal silver 

 is the salt of an acid to which he gives the name " coUargolic 

 acid." This acid is evidently composed largely of silver, and it 

 is energetic enough to displace carbonic acid. The black deposit 

 upon the positive electrode which has been taken for silver is not 

 ordinary silver but collargolic acid, for, while it is insoluble in 

 water, it dissolves in alkalies and alkaline carbonates, forming red 

 solutions. The author believes that this acid is combined with 

 ammonia in the original substance, and he proposes to make a 

 further study of the matter. — Goraptes Rendus^ cxxxvi, 690. 



H. L. W. 



5. The Iodides of Caesium. — The iodides Cslg and Csl^ were 

 described by Wells and Wheeler in this Journal in 1892. H. W. 

 FooTE of the Sheffield Scientific School, using theoretical consid- 

 erations which are mainly based upon the phase-rule of Gibbs, 

 and employing chiefly solubilit}^ determinations, has found that 

 the periodides mentioned are the oiAj ones existing between 

 — 4° and 73°. The method employed appears to be novel in its 

 application, and it will doubtless be very useful when applied to 

 the study of other complex compounds, particularly of double- 

 salts. — Amer. Chem. Jour., xxix, 203. h. l. ^\. 



6. Quantitative Chemical Analysis by Electrolysis ; by 

 Alexander Classen. Translated, revised, and enlarged by 

 Bertram B. Boltwood. Svo, pp. 315. New York 1903 



