Chemistry and Physics. 413 



hypothesis that the physical molecule in concentrated solutions is 

 more complicated than in diluted solutions. — Ann. der JPhysik 

 und Chemie, No. 4, 18S8, p. 577. j. t. 



7. Wave-length of the two red lines of potassium. — A determi- 

 nation by M. H. Deslandres gives for the stronger line 766-30, 

 for the weaker 769*63. As a measure of comparison the wave- 

 length of D 2 was taken as 588*89. — Compte Hendus, March 12, 

 1888. j. T. 



8. Explosion of gases. — A. von (EiTiNGEisr and A. von Gernet 

 have repeated the work of Bunsen, Berthelot and Vieille, 

 and also that of Mallard and Le Chatelier upon this subject 

 making use however of instantaneous photography to study the 

 phenomena. A rotating mirror was employed with a metallic 

 pointer to which an electrical spark passed when the mirror was in 

 the right position to reflect an image of the eudiometer tube, in 



.which the explosion took place, into a photographic camera. The 

 same spark served to explode the gases. The most sensitive 

 Beernaert plate gave no trace of an image. No results could be 

 obtained by staining the plates with cyanine or with azaline. 

 Eastman's negative film paper, however, gave a faint image. The 

 authors were compelled to sprinkle certain powders in the 

 eudiometer tube. Chloride of copper gave the best results. 

 Plates of the phases of the explosions accompany the paper. The 

 experiments show that the explosion of hydrogen is not accom- 

 panied by light. The resulting high temperature, however, pro- 

 duces a disintegration of the glass of the eudiometer tube and 

 produces a certain illumination. Three species of wave motion 

 are observed : first, a fundamental wave, which is entitled Ber- 

 thelot's wave; second, more or less parallel secondary waves; 

 third, polygonal waves of smaller amplitude. The photographic 

 image of the electric spark which was received upon the same 

 plate as that of the explosion, enabled the authors to estimate the 

 velocity of the explosion. The result obtained, 2800 meters per 

 second, is -of the same order of magnitude as that obtained by 

 Berthelot. The authors agree, in the main, with Berthelot's con- 

 clusions, differing only in reference to the beginning and the end 

 of the explosion. They explain the secondary waves on Bunsen's 

 hypothesis of the reflex action of waves due to successive ex- 

 plosions produced by the electrical spark. They, therefore, term 

 these Bunsen's waves. — Ann. der Physik and Chemie, No. 4, 

 1888, pp. 586-609. j. t. 



9. Dust particles in the Atmosphere.— John Aitkin in an arti- 

 cle read to the Royal Society of Edinburgh, gives a method 

 of estimating the number of these particles in the air. The 

 method is based upon the hypothesis that in a receiver filled with 

 super-saturated air when there are few dust particles present the 

 fog particles are large and are seen to fall like rain inside the 

 receiver. A small glass receiver was connected with an air pump 

 and with a cotton wool filter. Inside the receiver was placed a 

 small stage with a silvered mirror ruled with fine lines which 



