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 LXIX. Intelligence and Miscellaneous Articles, 



ON THE INFLUENCE OF THE ELECTRO-NEGATIVE ELEMENTS 

 UPON THE SPECTRA OF THE METALS. 



r\IACON has published an interesting paper upon the influence of 

 *-* chlorine, bromine,iodine, and fluorine upon the spectra of various 

 elements, and has confirmed and extended Mitscherlich's results. 

 The memoir is preceded by a good historical introduction, and 

 is illustrated by four excellent figures of spectra. The author sums 

 up his results as follows : — 



The chlorides of certain metals which are very rapidly decomposed 

 in the gas-flame are at least partially volatilized in a chloridizing 

 flame, and are therefore capable of producing spectra. These spectra 

 in general differ from those which are observed with the oxides of the 

 same metals in an oxidizing flame. 



The chloride, bromide, iodide, and fluoride of the same metal placed 

 in an oxidizing flame may give rise to bright lines, the position of 

 which is different according to the salt examined. These lines, the 

 duration of which is very variable, are always accompanied by the 

 spectrum which we obtain with the oxide. 



Since the lines which appear with the chlorides belong to spectra 

 which characterize these salts when volatilized in a chloridizing flame, 

 it is proper to regard the new rays which are presented by the 

 bromides, iodides, and fluorides as forming part of the spectra which 

 these compounds would give in flames which do not act upon them. 

 Hence it follows, that if it were possible to make with these salts 

 experiments similar to those made with the chlorides, we should 

 have for the same element, barium for instance, five different spectra. 



Diacon considers the influence of the electro-negative element upon 

 the spectrum to be placed beyond a doubt by his experiments, as 

 well as by Mitscherlich's. The spectra given by Bunsen and Kirchhoff 

 for the alkaline earthy metals are mixtures of the spectra which are 

 obtained when the oxide is ignited in an oxidizing flame, and those 

 obtained by igniting the chlorides in a chloridizing flame. The 

 spectra attributed by Mitscherlich to the chlorides are also in part 

 mixtures of the same spectra. In the first case, however, the spectra 

 of the oxides predominate, and in the second those of the chlorides. 

 — Ann. de Chim. et de Phys. S. 4. vol. vi. p. 5. (From Silliman's Ame- 

 rican Journal for March 1866.) 



ON THE DETERMINATION OF THE REFRACTIVE EQUIVALENT OF 

 THE ELEMENTS. BY A. SCHRAUF. 



Recent investigations have shown that the expression given by 



Newton and by Laplace for the refractive power, 



n 2 -\ 

 m= — -— , 

 d 



holds good, and adequately rep resents the dependence of the propa- 

 gation of light (expressed by t he refractive exponent n) on the den- 

 sity d, if the dispersion is taken into account. Some time ago, 



