300 Scientific Intelligence. 



SCIENTIFIC INTELLIGENCE 

 I. Chemistry and Physics. 



1. The Separation of the Isotopes of Mercury. — The idea that 

 isotopes exist not only in radioactive elements, but that their 

 occurrence is general among the elements appears to have been 

 well established by a number of recent investigations. J. N. 

 Bronsted and G. von Hevesy, of Copenhagen, have previously 

 made preliminary announcements of their partial separation of 

 metallic mercury into its isotopes by means of fractional distilla- 

 tion, and their observations have been confirmed by W. D. 

 Harkins in this country. They have now published a full 

 account of their work. Their method of evaporating the mer- 

 cury, which they call l ' ideal distillation, ' ' is interesting, since it 

 is carried out in the exhausted space between double flasks at a 

 temperature of about 40°, while the evaporated mercury is con- 

 densed in the solid condition by means of liquid air in the inner 

 flask. This operation was repeated with the distillates and the 

 residues, about 17 or 18 times in the last case, until the frac- 

 tions became very small. The resulting fractions were submitted 

 to specific gravity determinations with remarkably satisfactory 

 results. The extreme specific gravities found were 1.00023 and 

 0.99974, and in connection with the description of the work are 

 very convincing as to the existence of isotopes of mercury. 



The authors describe also some experiments upon the diffusion 

 of mercury vapor through small openings, and obtained an indi- 

 cation of a separation in this way. — Zeitschr. Physilcal. Chem., 

 99, 189. h. l. w. 



2. The Color of Ferric Ammonium Alum. — It is well known 

 to chemists, especially those who have supervised its preparation 

 by students, that this salt usually has a violet color, but is some- 

 times colorless or nearly so. Ostwald advanced the theory that 

 the colorless product is the pure form, while the color of the other 

 is due to the presence of manganese. Jane Bonnell and Edgar 

 Philip Perman have now carefully investigated this matter. 

 They were unable to detect manganese in a sample of the colored 

 variety, and they carried out the operation of separating any 

 manganese in this salt by precipitating the iron as basic acetate, 

 converting the precipitated iron into the alum, and even after 

 repeating the purification a second time in the same way, they 

 obtained the violet product in the presence of a considerable 

 excess of sulphuric acid. 



It was then shown experimentally that the colorless crystals 

 were not due to the presence of ferrous sulphate which had been 

 found in a certain sample of the colorless crystals, but it was 

 shown conclusively that the lack of color was due to the presence 



