Composition of Brittle Platinum. 87 



rather a difficult operation, secondly by soldering the platinum 

 points on to similar gold wires with pure gold. A photo- 

 graph of each point was taken side by side with the spectrum 

 of the pure platinum electrodes. 



A careful examination of photographic enlargements up 

 to a scale of 10 diameters showed that with the exception 

 of thirty-five gold lines the two spectra were practically 

 identical, or in other words that the lines unmistakeably due to 

 iron did not appear, namely, the group of five very strong 

 lines about 2743*4. 



The thirty-five gold lines which appear when gold wires 

 are used are here given, tbe wave-length quoted being 

 according to Eder and Valenta's measurements (K. Akad. der 

 Wissenscliaft. vol. lxiii. Vienna, 1896). 



Gold Lines. 



4488-43 3230-73 2913-63 2820-09 



406520 3204-75 2907-16 2802-39 



4053-00 3122-88 2906-07 2748-35 



4016-27 3029-32 2893-51 2676-05 



3898-03 2995-13 288569 2641-70 



3804-22 2990-38 2883-60 2503-42 



3635-21 2954-64 2838-15 2128-10 



3633-40 2932-33 2825-59 2364-80 



3586-66 2918-48 2822-87 



The following are the prominent iron lines seen when the 

 pins were held in steel clips, the ends of which were covered 

 with thin platinum foil. These wave-lengths are taken from 

 Liveing and Dewar's measurements of the spark-spectrum of 

 iron. 



Iron Lines. 



2755-5 2742-8 



2753-0 2739-2 Also arc. 



2749-0 Also arc. 2736-5 Also in arc, weak. 



2746 

 2746 



•l} Alsoarc * 2631-0 } 



The lines bracketed appear as separated lines on my photo- 

 graphs. Two strong lines, however, seemed to be common to 

 all four spectra, that is to say to iron, brittle platinum, tough 

 platinum, and the two specimens of pure platinum. Here 

 then is a fresh difficulty of a different character to contend 

 with. This is scarcely a matter for surprise because of the 

 very large number of iron lines and the manner in which 

 they are very closely grouped together at a part of the 

 spectrum where the lines of platinum are somewhat numerous. 



