548 



Dr. W. Huggins on the Spectra of 



[June 16 



jected to the oxyhydrogen flame, two bright bands were seen in the green. 

 One of these was found to be coincident with the triple line of Fraunhofer's 

 b, which distinguishes magnesium, and the other with a group of bright 

 lines which is seen between b and F, nearly in the position of the brightest 

 double line of nitrogen, when metallic magnesium is burnt in air. 



The chloride formed from magnesium, when introduced into the Bunsen 

 flame, gave the same bands, but the more refrangible band was exceedingly 

 faint. 



When an induction-spark was taken from a wire covered with cotton- 

 wool soaked with a solution of the chloride, the lines at b and the more 

 refrangible group were seen. If the heating-power of the spark be in- 

 creased by the introduction of a Leyden jar, the band between b and F 

 becomes scarcely distinguishable, while the lines peculiar to metallic mag- 

 nesium are much more intense. AVhen a spark is taken between electrodes 

 of the same specimen of magnesium from which the chloride was formed, 

 no trace of this band was detected. 



Baryta. — When pure caustic baryta is subjected to the heat of the 

 oxyhydrogen flame, a brilliant spectrum is seen identical with the well- 

 known spectrum which presents itself when chloride of barium is heated in 

 the Bunsen flame. Baryta furnishes a larger quantity of vapour than lime 

 and magnesia, and therefore the lines could be traced to a greater distance 

 from the solid baryta. 



Strontia. — Pure strontia was fused into a large bead upon a platinum 

 wire. "When this bead was heated by the oxyhydrogen flame, the same 

 spectrum of bright lines presented itself as is seen when chloride of 

 strontium is placed in the flame of a Bunsen' s burner. 



Zirconia. — One of the small pellets of zirconia prepared in France for use 

 with the oxyhydrogen blowpipe was found to give no trace of bright lines. 

 This great fixity of zirconia as compared with lime is in agreement with the 

 inalterability of the substance under the action of the oxyhydrogen flame 



Alumina. — Pure alumina treated in the same way as the magnesia gave 

 a continuous spectrum only, without any trace of bright lines. 



Glucina. — Glucina gave a bright line in the red, which I found to be 

 due to potassium. Glucina, therefore, appears not to form vapour of any 

 kind under the heat of the oxyhydrogen blowpipe. 



Titanic acid gave a continuous spectrum without lines. 



Oxide of uranium a continuous spectrum without lines. 



Tungstic acid a continuous spectrum without bright lines. 



Molybdic acid a continuous spectrum without bright lines. 



Silica (precipitated) a continuous spectrum without bright lines. 



Oxide of cerium a continuous spectrum without bright lines. 



The question presents itself as to the nature of the vapour to which the 

 bright lines are due in the case of the earths, lime, magnesia, strontia, and 

 baryta. Is it the oxide volatilized ? or is it the vapour of the metal reduced 

 by the heat in the presence of the hydrogen of the flame ? The experi- 



