F. J. Rogers — Magnesium as a Source of Light. 305 



E. M. F. was negative, the E. M. F. in the original element 

 being considered positive. To eliminate this accidental E. 

 M. F., the thermo- junction was made in the form of a 

 T as in fig. 3 and the projecting portion which passed 

 through a porcelain screen was heated as 3. 



before by the different flames. Two deter- 

 minations by this method are given in Table II. 

 Third Method. — In this case a rather 

 large bead of metal was formed at the 

 junction. The junction was then directly 

 heated by the different flames, last of all by 

 the magnesium flame, and the galvanometer 

 "swings" were noted as before. The 

 thermo-element was not so quickly destroyed as 

 before ; nevertheless, only one reading for the 

 magnesium flame could be obtained before mak- 

 ing a new junction. Two determinations were 

 made by this method. 



Table II. 





\ 





Pi 



1 



.-J 



sj 







?i.-U- 





1 



Candle 

 flame. 



821 



765 

 792 



Luminous 

 gas-flame. 



992° 

 1018 



Bunsen 

 flame. 



1221° 



1233 

 1222 



Air blast 

 flame. 



1398 



1382 

 1404 



Method. Magnesium flame. 

 1345° 

 ^ 1315 1333° 



1280 



a , ( 1350 



Second j 133 3 



Third 



i! 



1320 

 345 



1342 

 1332 



The values for the flame temperature of magnesium, given 

 above, were obtained by a graphic method which is illustrated 



220 



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4. 











































Ai> o 



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ft 































P 









AtJ 























140 



2 



it 



rt- 





















Bimse 



V. ' i 









1 















- 



' '/ 







; ; 









100 















.-'" 























_-' 



*-' 

























60 





"STw 



u. 



















i ' 









1 











Te 



mpe' 



t-atu 



res. 











' 





