1144 



with Canadiibalsaai, a very strong Tindall-effect became apparent in 

 the tield between the separate |)arlicles, but no visible network as yet. 



By local heating np to the inelling-teinperature of the glass a 

 strongly liiininons fibrous conglomeration was formed, but no 

 network. The somewhat less intensely-iieated parts, where the glass 

 had not been deformed, again presented a field fidl of separate 

 particles, among which a strong Tindall-effect was noticeable, (cf 

 tig. Plate I). 



Compared with tungsten and platinum, molybdenum shows a 

 rather marked tendency to coalesce inio separate particles or even 

 accumulations of particles. Apparently this is even the case at a 

 temperature of liquid air. But it is highly probable, that under these 

 circumstances a homogeneous sublimate arises first, and the separate 

 particles are only formed when heated to room temperature, with or 

 without the co-operation of Canadabalsam. 



As appears from the entering of a Tindall-effect during intense 

 heating, the separate particles do not represent all the molybdenum. 

 A predominant part is once more optically insoluble, and it seems 

 that even under intense healing it can only convert itself into very 

 small ultra-microns and can either mtt at all or but veiy partially 

 coalesce with the cores already existing. 



§ 9. Nickel. 



This again forms a non-coloured, black sublimate. On account of 

 the risk of oxidation, in this case, too, 'the precipitate was covered 

 with Canadabalsam when still in vacuum. Apparently this causes 

 no change. 



Ultramicroscopically a rather black and consequently an already 

 fairly thick precipitate, formed at room temperature, displayed, a 

 field pretty full of extremely fine, weak separate particles, contracted 

 here and there to somewhat larger conglomerates, around which 

 the smaller particles are absent. Another lamp which had been im- 

 mersed in liquid air during the time of burning gave a similar 

 image. No connected mosaic such as with An and Ag exists. 



With metals such as nickel, iron, molybdenum great care had 

 to be devoted to the exhausting of gases. They were carefully 

 "burned out on the pump". ^) 



§ 10. Iron. 



A precipitate formed by very slow sublimation (total duration 7 



1) Molybdenum, evaporated in an atmosphere of nitrogen under low-pressure 

 forms a spongy sublimate. I Langmuih, J. Amer. Ghem. Soc. 38, 2277 (1916). 



