1883.] On Radiant Matter Spectroscopy. 265 



Cerite was accordingly the next mineral experimented on. The 

 powdered mineral tested in the tube in the original way gave a good 

 citron band. The mixed earths after extraction were converted into 

 sulphates, dissolved in water, and the cerium metals precipitated by 

 long digestion with excess of potassic sulphate. 



The precipitated double sulphates' were converted into oxalates, 

 and after ignition and treatment with sulphuric acid, the mixed ceri?, 

 lanthana, and didymia were tested in the radiant matter tube, but the 

 merest trace only of citron band was visible. 



This experiment proved the inadequacy of the didymium explana- 

 tion, and further tests showed that not only could I get no citron 

 band in pure didymium compounds, but the spectrum entirely failed 

 to detect didymium' in many solutions of the earth which gave the 

 citron band brilliantly. 



Attention was now turned to the solution filtered from the insoluble 

 double sulphates. Potash was added, and the precipitate filtered off, 

 and tested in a radiant matter tube. The spectrum, of extraordinary 

 brilliancy, was far brighter than any I had hitherto obtained. 

 Unfortunately, however, the quantity was toosmall to be subjected to 

 very accurate chemical analysis. 



Search was now made amongst other minerals rich in the rarer 

 earths. Thorite was finely powdered, treated with sulphuric acid, and 

 tested in the radiant matter tube. It gave the citron spectrum most 

 brilliantly — equal in fact to the mixture of earths obtained from 

 zircons at so 1 grfeat an expenditure of time and trouble. Orangite 

 treated in the same manner gave almost as good a spectrum. Pure 

 thorinic sulphate prepared by myself was found not to give the citron 

 band, but three specimens prepared and- given to me by friends all 

 gave it, so it was not unlikely that in thorite and orangite might at 

 last be found a good source of the long-sought element — that in fact 

 the body I was hunting for, if not thorina, might possibly be Bahr's 

 hypothetical wasium. Two pounds of orangite and thorite were 

 extracted with hydrochloric acid. The solution was precipitated with 

 potassic sulphate,- taking the usual precautions to secure complete 

 precipitation; A bulky precipitate ensued,- which contained the 

 thorina and cerium earths. These were separated and tested, and 

 found to give only a faint citron band. 



The solution of earthy sulphates soluble in potassic sulphate was 

 precipitated with amnionic oxalate. The precipitate ignited with 

 sulphuric acid, and tested in a radiant matter tube, gave the citron 

 spectrum with great brilliancy. 



Certain chemical facts concerning the behaviour of the sought-for 

 element which came out during the course of the tentative trials 

 described in the paper considerably narrowed the list amongst which 

 it might probably be found. All the evidence tends to show that it 



