Chemistry and Physics. 515 



6. On Sodium-amine and Di-sod-ammonium chloride. — Joan- 

 :nis has observed that at ordinary temperatures, sod-ammonium 

 slowly decomposes into hydrogen and sodium-amine (sodamine) ; 

 this decomposition tending toward a limit determined by the 

 pressure of the hydrogen evolved. The sod-amine, NH 2 Na, 

 appears in small colorless transparent crystals ; while that noticed 

 by Gay Lussac was amorphous and of a blue or green color. The 

 crystals dissolve in water with a hissing noise but without the 

 evolution of gas. Disodium-ammonium chloride, NH 2 Na 2 Cl is 

 an unstable compound which is obtained, mixed with sodium 

 chloride, when sodium is treated w T ith an excess of sodium chlo- 

 ride in presence of liquefied ammonia, insufficient in amount for 

 complete solution of the salt. On washing with liquid ammonia 

 this compound decomposes into sodium chloride which dissolves 

 and into sodamine which is left. By water it is broken up into 

 ammonia, sodium hydrate, and sodium chloride. — C. P., cxii, 392 ; 

 Ber. Berl. Chem. Ges., xxiv, (Ref.) 292, April, 1891. g. f. b. 



7. Velocity of electrical waves in insulating fluids. — Maxwell 

 has shown that the relation ?i 2 = ji is a consequence of his electro- 

 magnetic theory of light. In this formula n is the rate of the 

 velocity of the wave in a vacuum to that in the substance ex- 

 amined and jj. is its dielectric constant. L. Aeons and H. Reu- 

 bens, employing Hertz's method of studying electromagnetic 

 waves, have examined the relation given by Maxwell and find it 

 very nearly fulfilled in the case of the four fluids investigated by 

 them. — Ann. der Physik und Chemie, No. 4, 1891, pp. 581-592. 



J. T. 



8. The telephone in an optical apparatus for measurement of 

 electrical currents. — Max Wien" employs the movement of the 

 telephone diaphragm to measure both constant and alternating 

 currents and prefers this instrument to the usual form of dyna- 

 mometer. The iron diaphragm of the telephone is replaced by a 

 thin metallic plate similar to those used in aneroid barometers. 

 A piece of iron is placed upon this diaphragm opposite the pole 

 of the telephone magnet and the movement of the diaphragm is 

 communicated by a simple lever arrangement to a small mirror, 

 which deflects the excursions of a spot of light into the field of 

 view of a telescope. The amplitude of the movement of the spot 

 of light is a measure of the current strength. The author dis- 

 cusses the accuracy of the indications and shows that quantitative 

 results can be obtained by this simple instrument. — Ann. der 

 Physik und Chemie, No. 4," 1891, pp. 593-623. J. t. 



9. Photography of the ultra red rays. — In a communication to 

 the Royal Society, March 12, Mr. George Higgs stated that the 

 alzarine blue S possesses in a high degree sensitive giving proper- 

 ties for rays throughout the region comprised between wave- 

 lengths 6200 and 8000, and does not like cyanin lower the sensi- 

 tiveness to the violet and ultra violet. The method of preparation 

 of the alzarine was described. With a slit 1/1000 inch in width and 

 an exposure of forty minutes results have been obtained in the 



