406 Scientific Intelligence. 



The question of chemical action between solids is by no 

 means new but is being constantly extended. I may say I be- 

 lieve chemical action may take place wherever the product or 

 products are liquid or gaseous even though the reagents are solid, 

 with perhaps the added condition that one or both the reagents 

 be soluble in the liquid produced. If this be true my new 

 method of forming alloys is but a special case of the above 

 general principle.* 



Phys. Lab. U. S. Geological Survey, Washington, D. C. 



SCIENTIFIC INTELLIGENCE. 

 I. Chemistry and Physics. 



1. On the Spectrum of Magnesium. — Liveing and Dewar have 

 studied the spectrum of magnesium produced by the arc dis- 

 charge. Most of the lines produced by the spark discharge are 

 observed in an electric arc formed between electrodes of magne- 

 sium. The greater number of lines seen in the arc discharge, how- 

 ever, may be due not to lowness of temperature but to the greater 

 mass of incandescent matter and to a wider range of temperature 

 at different portions of the discharge, recombinations occurring 

 at its edge. The electric discharge itself may also give rise to 

 vibrations distinct from those due to heat. The seven bands in 

 the green are due to the oxide, as they are produced only in the 

 presence of oxygen or of its compounds. If a piece of burned 

 magnesium wire be heated in the oxyhydrogen flame, the 

 spectrum of magnesium is produced, the .metallic lines appearing 

 if the hydrogen is in excess. The triple line near M, which is pro- 

 duced when magnesium is burned, is found to be produced in the 

 arc between magnesium electrodes and in many other cases when 

 oxygen is present, but not in an atmosphere of nitrogen or hydro- 

 gen ; hence it is due to the oxide. Vacuum tubes are found to be 

 very untrustworthy for the ultra-violet spectra as the water- 

 spectrum and lines of nitrogen are nearly always present and the 

 spectra sometimes vary unaccountably. The authors describe in 

 their paper a pump in which rubber connections and free contact 

 of mercury with air, are both avoided. — Proc. Hoy. Soc, xliv, 

 241 ; J. Chem. Sod., lvi, 89, February, 1889. g. f. b. 



2. On a Lecture Experiment for showing RaouWs Molecular 

 depression of the Freezing Point. — Cimician has described an 

 apparatus for showing, as a lecture experiment, Raoult's law of 

 the lowering of the freezing point." A large test tube, 2*5 cm. in 

 diameter and 16 cm. high, is used to contain the solution, which 



* Experiments endeavoring to produce carbon disulphide from the elements at 

 ordinary temperatures are in hand and give promise of positive results. Also ex- 

 periments on the interaction of potassium nitrate and sodium acetate have been 

 started; it will however be sometime before further results can be given. 



