1137 



that even slight quantities of water-vapour may affect the nature of the 

 deposit, great care was devoted to the evacuation. By means of the 

 affixture of a tungsten auxiliary-lamp (a), which was now and then 

 burned at over-tension, we cleaned uj) as well as possible the gases 

 that remained after the melting-off of the air-pump or that might 

 once more arise in the lamp ^). 



When aftei' the heating of the metalwire a snblimate had been 



deposited on the glass- wall in (c) and this had 

 been covered by the Canadabalsam, then 

 the lamp was opened and a fragment of 

 the glass-wall was observed under the 

 ultramicroscope. For lighting we used a 

 Lilliput arc-lamp of E. Leitz or a Philips 

 projection-lamp of 500 Watt, the latter 

 being highly satisfactory on acconnt of 

 its tranquil and steady light. To concen- 

 trate the light we used a cardioidcondensor. 

 By making sure that the thickness of 

 the glass-wall was no more than 0.6 mm. 

 we succeeded in bringing the metal-film 

 on the glass exactly in the focus of the 

 condensor and could observe it with the 

 microscope. For our objective we used 

 Zeiss' special-objective V with glycerine- 

 immersion. 



§ 3. The investigated elements. 

 We investigated carbon and the metals 

 W, Mo, Pt, Fe, Ni, Au, Cu, Ag, %, 

 Z?i and Cd. Except carbon and zinc, they 

 were all brought into wire-mould by the 

 tensile process. Zinc was got into that 

 state by squeezing it during gentle heating 

 through a narrow opening into a diamond. 

 From lead and tiu, too, wires were similarly formed; but the 

 vapour tension of these metals under temperatures below their 

 melting-point is so slight, that no sublimate could be obtained 

 with them. Neither did we succeed with aluminium, in which case 

 it is probably a thin oxide coating that constitutes the impediment. 

 Tellurium, antimony, arsenic and bismuth, sublimate very well 



1) I. Langmuir, Journ. Amer. Ghem. Soc. 35, 105, 931 (1913). 



