194 E. von Aubel on the Influence of Magnetism 



II. Alloys. 



To obtain the alloys, two sandstone crucibles are used. 

 Bismuth is put into one, tin or lead into the other. These 

 metals have previously been weighed. When the bismuth is 

 melted it is kept liquid, being warmed gently to avoid too 

 much oxidation ; it is then poured upon the other metal, 

 which is also liquid. The contents of the crucible are then 

 poured into the other, and this decanting is repeated several 

 times. We have worked in this way in order to obtain 

 alloys in which the proportion of tin or lead should be given 

 almost exactly by the weight, and to avoid having to make 

 analyses of the alloys in order to know their approximate 

 composition. 



III. Analyses of the different Specimens of 

 Bismuth studied. 



We have measured the resistance of several specimens of 

 bismuth. They came from the manufactory of chemical 

 products of Messrs. Monheim at Aix-la-Chapelle, Trommsdorff 

 at Erfurt, and Schering at Berlin. Mr. Monheim's bismuth 

 is commercially pure metal. We have three different spe- 

 cimens from the firm of Trommsdorff, which we shall call, for 

 brevity, "Trommsdorff L," " Trommsdorff II.," and " abso- 

 lutely pure Trommsdorff." 



The two first, as well as the bismuth from the Schering 

 factory, are products referred to as very pure in the catalogue 

 of manufacturers. 



The " absolutely pure Trommsdorff" bismuth, of which the 

 cost was far higher than that of the others, has been specially 

 prepared for us in the Erfurt manufactory. 



As to the compressed bismuth, it has been obtained by 

 means of the commercial metal. Prof. Spring dissolves this 

 metal in HN0 3 , precipitates it by pouring the solution into a 

 large quantity of water, filters, and washes it. He then 

 redissolves the basic nitrate, precipitates a second time, 

 calcines, and reduces in a current of pure hydrogen. 



We give all these directions, so that it may be possible for 

 physicists to repeat our experiments, and in order to show how 

 little confidence ought to be placed in certain determinations 

 which have been made on the physical constants of bismuth. 



M. A. Classen, Professor of Analytical Chemistry at the 

 Upper Technical School at Aix-la-Chapelle, was so kind as to 



