the Electrical Resistance of Bismuth. 347 



for electrolyzed bismuth, slowly cooled . . 10 3 x 10 7 '99, 

 and for the same metal, tempered . . . 10 3 x 108*69. 



The coefficient of variation with the temperature' and the 

 influence of magnetism are very nearly the same for these two 

 specimens. The coefficient of variation with the temperature 

 besides is positive. 



In the case of impure bismuths the process of tempering 

 causes the coefficient K to decrease, and even to become 

 negative. The action of compression seems to be still 

 greater. 



As to the absolute values of the electrical resistance at 

 0°, they increase under the action of tempering and com- 

 pression. 



If we compare the results furnished by the electrolyzed 

 bismuth with those given by the other bismuths, we see 

 that the effect of traces of lead is to produce a dimi- 

 nution in the value of K, and an increase in the value 

 of R « It can also be seen that, in the case of impure metals, 

 a high value for R generally corresponds to a low value 

 forK. 



With regard to alloys of impure bismuth with lead and 

 tin, the results prove that these latter metals tend to increase 

 R , and can even in certain cases give a negative value for K. 

 But the molecular action, and above all the lead, produce a 

 much greater effect than the tin. 



The electrolyzed bismuth presents a peculiarity which 

 is not seen in the impure kinds. The coefficient K remains 

 sensibly the same at different temperatures between 0° and 

 100°, and this may be considered as a proof of the purity of 

 the metal. 



In short, one may say that, of all the methods both 

 physical and chemical, the determination of the electrical 

 resistance is certainly the most exact for ascertaining if the 

 bismuth be pure, and above all if it contain no trace of 

 lead. While spectrum analysis and the process of electro- 

 lysis have with difficulty discovered the existence of lead in 

 the bismuth Classen II. for example, the study of the elec- 

 trical resistance leads to very different results. 



When one considers all the difficulties I have met with in 

 procuring the pure metal, and the number of electrical 

 measurements which I have been obliged to make, so to 

 speak, uselessly, it is plain that, before studying the physical 

 properties of a metal, it would always be wise to submit the 

 metal to a very careful spectrum analysis, to assure one's self of 

 its purity. 



