Conductivity produced by Heating Salts. 



741 



iodide were anhydrous as supplied by Kahlbaum ; the others 

 were kept in a desiccator for some time. 



The velocities are given in cms. per second for one volt 

 per cm. J^o great accuracy for the absolute values of the 

 velocities given is claimed. Their relative values are nearer 

 the truth, since as far as possible the conditions for each set 

 of observations were the same. 



Temp, 

 degree 



Cent. 



Pressure 

 in mm. of 

 mercury. 



Zinc 

 iodide. 



Bismuth 



iodide. 



Lead 

 iodide. 



Cadmium 

 iodide. 



Pressure X Velocity 

 for Bismuth iodide. 



215 



„ 



j> 



j» 



j» 



»> 



» . 



>) 



10 



15 

 20 

 25 

 30 

 35 

 40 

 45 

 50 

 55 

 60 

 70 

 90 



•055 

 : 044* 

 •035 



•obi' 



•024 

 •022 



•06 

 •055 



•041 



•032 

 •03 

 •027 

 023 



014 



•009 



•061 

 •054 



036 



•032 



•0*25 



•02T 



•12 



•087 

 •073 



•06" 

 •05 



•600 

 •825 



1025 



1-120 

 1-200 

 1-215 

 1-150 



•980 

 •810 



A number of determinations at other temperatures and 

 pressures were also made with the same compounds. In all 

 cases I found that the positive ions produced by heating zinc 

 iodide, lead iodide, and bismuth iodide move with practically 

 equal velocities under the same conditions; while the positive 

 ions from cadmium iodide move with just about twice the 

 velocity of the positive ions from the other three compounds. 



Quite recently Gehrcke and Reichenheim * have found 

 that when various salts, chiefly chlorides, are made the anode 

 in a vacuum-tube, and when this anode is heated, positively 

 charged particles, which they call anode rays, are emitted. 

 These effects seem to be the same as those studied here, 

 except that the temperatues in their case are higher. They 

 find the anode rays give the metal lines in the spectrum, 

 from which it seems that the positive ions are metallic. 

 They may, however, have attached to them, combined or 

 otherwise, products of the chemical change. If this were 

 not so, we should expect their velocities to be more unequal 

 and to be roughly inversely proportional to their atomic 

 weights. Zinc iodide very quickly and readily absorbs water, 

 and it was found that the velocities obtained for positive ions 

 from this salt were made much smaller by moisture. Bismuth 



* DeutscJi. Phys. Gesell. Verh. viii. 21. pp. 559-566, Nov. 1906. 



