78 Intelligence and Miscellaneous Articles. 



In seeking for traces of chlorine or bromine, I operate thus : — 



A vertical platinum wire (about | of a millim. in diameter) is 

 bent up at its lower part in the form of a hook or a U. Upon this 

 half-ring I fuse, at a bright-red heat, 0*001-0 , 002 gramme of pure 

 carbonate of baryta ; then I place in the bend of the wire a little 

 drop of the liquid which is to be examined*, evaporate to dryness, 

 and even, fir a brief moment, push the heat to incipient redness. 

 The at least partial fusion of the mass is advantageous, by permit- 

 ting it to spread like a varnish at the surface of the platinum 

 wire. 



After cooling, a second platinum wire (of f to 1 millim. dia- 

 meter) is brought quite close (at 1 or 1-^ millim. distance) below 

 the bend of the first, a little forward towards the slit of the spec- 

 troscope. The induction- spark, not condensed, then gives a spec- 

 trum in which are seen the lines of BaCl 2 or BaBr 2 . One three- 

 thousandth of a milligramme of chlorine or bromine can thus be 

 recognized. No doubt, with some precautions, even this degree of 

 sensitiveness could be surpassed, especially for chlorine. 



If in such a sample the quantity of chlorine is somewhat consi- 

 derable, the wire can be heated to dazzling whiteness for several 

 minutes without detriment to the lines of BaCl 2 , of which it is often 

 very difficult to get rid by prolonged calcination of the platinum 

 wire. 



The resistance of BaBr 2 to heat appears to be notably less. — 

 Comptes Rendus de T Academie des Sciences, Dec. 6, 1880, t. xci. 

 pp. 902, 903. 



ON RADIOPHONY. BY M. E. MEROADIER. 



The phenomenon which I call radiophony is that recently dis- 

 covered by Mr. Gt. Bell, in which a radiation (such as constitutes a 

 solar ray) rendered intermittent according to a determined period, 

 on falling upon bodies cut into plates, produces a sound of the 

 same period. With a view to a possible application of this pheno- 

 menon to optic telegraphy, I have been obliged to study it closely, 

 and have obtained results of which the following are the prin- 

 cipal : — 



I. lladAophony does not appear to be an effect produced by the mass 

 of the receiving plate vibrating transversely in its entirety as an ordi- 

 nary vibrating plate . Indeed any plate whatever, in the conditions 

 in which the phenomenon is produced, (1) reproduces equally well 

 all the successive sounds from the deepest possible to shrill sounds 

 which, in my experiments, w T ent up to 600 or 700 double vibrations 



* If the material contains nitrates, it is expedient to expel NH0 3 by 

 SH a 4 , then this by pure BaO. If there is much sulphuric acid or sul- 

 phate, this is likewise got rid of by BaO. 



