154: Scientific Intelligence. 



he finds that the discrepancy is due to the formation of some per- 

 sulphuric acid when the sulphuric acid is added to the hydrogen 

 peroxide. He finds that when acetic acid is used for acidifying, 

 the evolved oxygen corresponds with the theory. It is evident 

 that these results have an important bearing upon the customary 

 method of titrating hydrogen peroxide solutions, and that sul- 

 phuric acid should not be used in this operation. ^Jour. Chem. 

 Soc, lxxix, 1324. h. l. vv. 



3. The Atomic Weight of Calcium. — Hinktchsen has made 

 four determinations of this atomic weight by igniting Iceland- 

 spar and finding the loss in weight due to the expulsion of car- 

 bon dioxide. The material was carefully analyzed, and found to 

 contain no impurity except ferrous carbonate corresponding to 

 •032 per cent of Fe 2 3 . This impurity was taken into account in 

 making the calculations. The quantity used for each experiment 

 was about 30 s of the mineral. The ignitions were made in a 

 large bottle-shaped platinum crucible with a specially constructed 

 electrical furnace as the source of heat. During the ignitions 

 dry air was aspirated through the crucible in order to remove the 

 carbon dioxide as fast as it was set free. The results, 40*144, 

 40*14], 40*142 and 40*141, where oxygen is taken as 16 and car- 

 bon as 12, show a remarkably close agreement and indicate that 

 the usually accepted atomic weight, 40*0, is somewhat too low. — 

 Zeitschr. physikal. Chem., xxxix, 311. h. l. w. 



4. Silver Subhalides. — These compounds, which are supposed 

 to be represented by the formulas Ag 2 Cl, Ag 2 Br and Ag 2 I, are of 

 considerable interest because they are probably formed by the 

 action of light on the ordinary halides in photographic processes. 

 Many attempts have been made to prepare these substances in a 

 pure condition, and it has been supposed that Vogel had accom- 

 plished this by the reaction of the cuprous halides upon silver 

 nitrate in solution. Emszt has now shown, however, that the 

 products made according to Vogel are merely mixtures of the 

 ordinary halides with metallic silver. He has shown, contrary to 

 Vogel' s belief, that metallic mercury dissolves silver from the 

 products, and, moreover, he has found that it is possible to 

 change the compositions of the products by simple elutriation. — 

 Zeitschr. anorg. Chem., xxviii, 346. h. l. w. 



5. The Atomic Weight of Tellurium. — In the last number of 

 this Journal (page 60 of this volume) attention was called to an 

 investigation by Pellini on the atomic weight of tellurium, in 

 which results were obtained showing a value of 127*6, a number 

 higher than that of iodine, and closely agreeing with the results 

 of a number of other investigators. Kothner has now made an 

 elaborate research on the same subject, and by the ignition of 

 the basic nitrate, a method which orignated with the Americans 

 Norris, Fay and Edgerly, he has obtained an average result 

 which is precisely the same as that of Pellini. It seems probable 

 that this atomic weight is now established within very narrow 

 limits. — Liebig^s Annalen, cccxix, 1. h. l. w. 



