1871).] 0)i a New Method of Studying Metallic Vapours. 271 



quite clear, although position of Bunsen is unchanged ; pump nearly 

 clicking ; hydrogen very bright in retort. New spectrum visible in 

 capillary. 



Pump clicking ; glass becoming attacked ; blue film one inch above 

 pole in retort ; glow extends back to metal ; line seen intermediate in 

 position between D and Na green. 



Red hydrogen very intense in capillary tube ; blue line brighter than 

 ever ; fluffy line in green (11*4 ?). 



Olive-green glow in retort; vapour becoming greener; green line 

 as bright as D; D now fainter than either the green or red Na lines ; 

 the red line gradually fades on cooling ; only one line more refrangible 

 than the green line. The green vapour does not appear to attack the 

 glass ; D now on point of disappearing ; green line far brighter. 



The tube then cracked and put an end to the experiment. 



This experiment, although not successful in so far as the isolation 

 -of the green Na line is concerned, is brought forward, as it shows the 

 details of the observations as dictated by me to my assistant while the 

 experiment was going on. The experiment has since been successfully 

 repeated several times, simply with the object of getting the green line 

 alone. This is best achieved by heating the metal before all the 

 hydrogen has been extracted by the pump.* 



The method has been tried also with potassium, calcium, and some 

 other metals, and with metallic salts. I do not, however, yet bring 

 forward the results I have obtained, as the experiments are beset with 

 difficulties ; and I am now carrying out a research with the hope of 

 eliminating all sources of error. 



I may state, however, that with potassium and calcium I get the 

 same inversion of phenomena, the yellow-green lines of potassium 

 being seen without the red ; while in the case of calcium the blue line 

 alone was seen. 



The fact that in these experiments we get, as before mentioned, 

 vapours which at one and the same time exhibit different colours and 

 different spectra at different levels in the tube, at once suggests the 

 phenomena of fractional distillation, and supports the following state- 

 ment which I made last March : — 



"Doublets and triplets, as a rule, reverse themselves more freely 

 than the irregular lines in the same spectrum; which particular 

 doublet or triplet will reverse depending upon the temperature, as if 

 the cooler vapour to which the reversal is due varied, as in the case of 

 fractional distillation." 



It is obvious that if, at any particular temperature, one particular 

 kind of vapour is given off in the manner indicated, in excess of all 



* In this extract from the laboratory note-book I have left out in most cases lists 

 of lines, as I have not as vet been able to assign to all of them their wave-lengths. 



