420 



Mr. W. Crookes. 

 Fig. 3. 



[June 18, 



Mixed Samarium and Yttrium Spectra. 



It was interesting to ascertain what spectrum a mixture of sama- 

 rium and yttrium would give. A mixture of 90 parts of samaria 

 to 10 of yttria was treated with sulphuric acid and then ignited, and 

 afterwards examined in the radiant matter tube. The result was as 

 remarkable as it was unexpected. Not a trace of the yttrium spec- 

 trum could be detected. The powder phosphoresced with moderate 

 intensity, but the spectrum was almost the facsimile of that given by 

 pure samaric sulphate, except that the sharp orange line, which in 

 the spectrum of pure samaric sulphate is only just visible, had gained 

 sufficiently in intensity to be measurable, and was found to lie at 



2693, on the ~ scale. A large number of experiments were next tried 

 \ 



on mixtures of samaria and yttria in different proportions, and the 

 results are given in full in the paper. 



Up to mixtures of 43 parts samaria and 57 parts yttria the 

 spectrum nearly resembled the lead-samarium spectrum. Not a band 

 of the yttria spectrum could be detected, and the brilliant orange line 

 stood out sharply in the whole series. This spectrum is represented 

 in fig. 4. 



Fig. 4. 



240' .260 280 300 320 34-0 



After that proportion had been reached a change rapidly came over 

 the spectra, and in the next trial mixture — samaria 35 yttria 65 — the 

 only indication of the samarium spectrum that could now be found 

 was seen in the two faint green bands next to the citron line of yttria, 

 and the new orange line, which shone out as brightly and sharply as 

 ever. 



