126 Prof. Arthur Smithells on the 



saturator be jacketed by steam, or, more simply, if chloroform 

 be used in the saturator, these lines can be entirely eliminated. 

 We have, then, to deal with two distinct spectra — one given by 

 copper salts in the entire absence of hydrochloric acid ; the 

 other given when a large quantity of hydrochloric acid or 

 chloroform vapour is supplied to the flame. In the inter- 

 mediate case when there is some hydrochloric acid — but not 

 an excess — a mixed spectrum is obtained. It is obvious that 

 one of these spectra corresponds to the oxide of copper and 

 the other to the chloride. 



These spectra have been carefully mapped * and compared 

 with the maps of previous observers, with the following results 

 (see Plate IV.). 



1. The chloride spectrum corresponds almost exactly to 

 that given by Mitscherlich. He failed to map three bands 

 at the most refrangible end and to split up into three distinct 

 bands a region between X 460 and 480. 



2. The oxide spectrum bears a general resemblance to that 

 given by Mitscherlich, but with the exception of three bands 

 he did not map in any detail the vague bands of which this 

 spectrum is largely composed. One band at the least re- 

 frangible end is entirely omitted by Mitscherlich. 



3. Lecoq de Boisbaudran's map comprises all the chloride 

 lines and bands, with the exception of two on the extreme 

 violet which he mentions but does not map, and all the bands 

 of the oxide except those which it is impossible to discriminate 

 in the presence of a strong chloride spectrum. 



4. Diacon's map contains all the chloride lines and bands, 

 but the oxide bands are only vaguely marked. 



In addition to the appearances above described, there is one 

 other noticeable when using copper salts in the separator with 

 hydrochloric acid. When the flame of the outer cone is 

 turned blue by hydrochloric acid, a dull ruddy fringe is seen 

 to surround it. This becomes more developed as the quantity 

 of hydrochloric acid is increased. It gives a faint luminous 

 spectrum, chiefly in the red. As this red fringe is never 

 obtained except in the presence of a large quantity of hydro- 

 chloric acid or chloroform and a copper salt, it seems natural 

 to ascribe it to a compound of copper and chlorine. 



It seemed desirable to inquire further into the chemical 

 changes involved in the production of the different spectral 



* The readings of the instrument employed (a two-prism Steinheil 



spectroscope) have been plotted to the scale ^ , which while giving 



readings referred to a natural standard presents the spectrum very much 

 as seen with a glass-prism spectroscope. 



