398 RECORD OF SCIENCE FOR 1886. 



Concerning the " radiant-matter test " for these phosphorescing bodies 

 Mr. Crookes says it proves itself every da}' more and more valuable as 

 one of the most far-searching and trustworthy tools ever placed in the 

 hands of the experimental chemist. It is an exquisitely delicate test, 

 capable of being applied to bodies which have been approximately sep- 

 arated, but not yet completely isolated, by chemical means; its delicacy 

 is unsurpassed even in the region of spectrum analysis; its economy 

 is great inasmuch as the test involves no destruction of the specimen; 

 its convenience is such that any given test is always available for 

 future reference, and the quantity of material is limited solely by the 

 power of the human eye to see the body under examination. Beyond 

 all these in importance is its trustworthiness, and during the five years 

 this test has been in daily use in his laboratory Mr. Crookes has found it 

 well-nigh infallible. Anomalies and apparent contradictions have arisen, 

 but a little more experiment has shown that the anomalies were but 

 finger-posts pointing to fresh paths of discovery, and the contradictions 

 were due to erroneous interpretation of the facts. (Chem. News, liv, 

 13.) 



On the Atomic Weight of the Oxide of Gadolinium, by A. E. Norden- 

 skj^ld. — The author signifies by "oxide of gadolinium" the mixture 

 of oxides of yttrium, erbium, and ytterbium first discovered in the 

 gadolinite of Ytterby. He shows that this mixture of three isomorphous 

 oxides, even when derived from totall}' different minerals found in local- 

 ities far apart from one another, possesses a constant atomic weight, viz, 

 about 262. The atomic weights of the three constituents vary greatly — 



Oxide of yttrium 227.2 



Oxide of erbium 380. 



Oxide of ytterbium 392. 



taking 0=16 and calculating as 52©^. 



The fact here demonstrated is one altogether new in chemistry and 

 confirms in a remarkable way the views announced by William Crookes 

 in his address to the B. A. A. S. on the genesis of the elements. It 

 would appear that the work of these savants on the rare earths, so called, 

 will result in revolutionizing views of chemists concerning the elements, 

 so called. (Comptes Rendus, cm, 795.) 



Isolation of Fluorine by Electrolysis of Anhydrous Hydrofluoric Acid, 

 by n. Moissan. — The preparation of fluorine in its elementary state is 

 a i)roblem which has long defied the efforts of chemists; the classical 

 experiments of Davy, Gore, G. J. Knox, Pfaundler, Baudrimont, and 

 others did not yield results satisfactory to all, and the alleged discovery 

 of Prat was soon nfter experimentally re'uted by Cillis. At the meeting 

 of the French Academy of Sciences, held June 2S, Monsieur H. Moissan 

 described the results obtained by electrolyziug anhydrous hydrofluoric 

 acid, and cautiously stated that fluorine was in all probability isolated; 

 this memoir was followed by another on July 19, and soon after by a 



