Induced Alternating Current Discharge. 73 



made to get the absorption spectrum, the lines obtained were 

 so feeble and so few in number that it was impossible to make 

 a comparison of any significance in determining the coincidences 

 with the lines investigated. 



After considering the large amount of work done in the past 

 in studying this strongest group of the so-called water spectrum 

 and also the work done in this investigation, it seems hardly 

 possible that the lines are due to water vapor alone, but rather 

 that they are due to the various constituent gases of the air 

 and combinations of them which are facilitated by the presence 

 of water vapor. On the whole, owing to the small amount of 

 water vapor in the air, the experiments seem to point to the 

 conclusion that the lines of this group are due for the most 

 part to the nitrogen of the air and its oxides. 



Sloane Physical Laboratory, June 11, 1901. 



SCIENTIFIC INTELLIGENCE. 



I. Chemistry and Physics. 



1. The Ignition-temperature of Phosphorus. — The temperatures 

 given in chemical literature as the point at which phosphorus 

 takes fire in the air or in oxygen vary from 38-1 to 75°. The 

 amount of moisture present in the air or oxygen probably has a 

 great effect upon this temperature, as it is well known that phos- 

 phorus may be distilled in perfectly dry oxygen without ignition. 

 F. H. Eydman - , Jr. has now made a careful series of experiments 

 with air, oxygen, and air diluted with an equal volume of carbon 

 dioxide. These gases were used in a moist condition, in fact 

 they were made to bubble through molten phosphorus which 

 was under water in a test-tube. The test-tube, which contained 

 a thermometer, was placed in a flask of water, and the latter was 

 gradually heated until the phosphorus was ignited by the gas 

 which bubbled through. With air the observed temperatures of 

 ignition varied from 44*9 to 45*4°, with an average of 45° ; with 

 oxygen the mean of four closely agreeing results was 45*2 ; while 

 with the mixture of air and carbon dioxide two experiments gave 

 45° in each case. The interesting conclusion is reached that the 

 ignition-point of phosphorus does not vary with the concentration 

 of the oxygen. The author intends to extend his experiments by 

 using dry air and oxygen. — Recueil Trav. Chim. lays-Bas, xix, 



401. H. L. W. 



2. The Composition of "Card's Acid." — Baeyer and Villiger 

 have made an investigation of this powerfully oxidizing acid, 

 which is prepared either by treating a persulphate with con- 

 centrated sulphuric acid, by the electrolysis of rather concen- 



