THE SPECTRUM 



307 



cleaned by boiling in acid, with solutions of the chloride salts, 

 which are better than the rnetals for small currents. 



Caution. In all such experiments as these, or in vaporis- 

 ing metallic sodium in the lantern, even with the oxy-hydrogen 

 flame , care should be taken to cover the condensers with a 

 sheet of thin glass, otherwise particles of melted metal or 

 oxide splutter on to the condenser, and fuse into its surface. 

 Many a condenser has been ruined in this way. The sheet 

 should be curved as in petroleum 

 lamps, to prevent its cracking. 



By employing salts of the 

 metals, excellent line spectra can 

 be projected with the oxy-hydrogen 

 flame, the most convenient ar- 

 rangement being the lamp shown 

 in fig. 167, devised by Edelmann. 

 It is practically an upright * safety ' 

 jet, a stream of oxygen passing up 

 through the centre of a larger 

 stream of coal-gas, supplied by the 

 taps at H and o. The whole can 

 be raised or lowered by the plate 

 t on the stand or pillar s, and at 

 the top is a nozzle N, on which 

 can be placed a hollow cone, &, of 

 carbon. The inside of this cone is 

 covered with a paste composed of 



the salt rubbed down smoothly in a mortar with picric acid, 

 ammonia, and alcohol ; as many cones as desired being pre- 

 pared beforehand. This is an excellent method for bright- 

 line spectra, such a burner being easily adjusted in the focus 

 of the condensers, and the coloured flame emerging from the 

 top of the carbon cone being very brilliant. 



Mr. E. Cleminshaw, F.C.S., improving on Bunsen and 

 Debray, places in the lantern a similar jet, but with a larger 



I?iCr. 1C7. Edelmann's Spectrum 

 Burner 



