( 417 ) 



That nothing can be seen here of the proportionality found by 

 me, may probably be ascribed to some extent to errors of obser- 

 vation ; the more so, as the object of the measurements was not to 

 determine the relation between the strength of the magnetic field 

 and the two phenomena, but to compare the behaviour of bismuth 

 with that of bismuth-tin alloys. 



Moreover their bismuth was cast. Therefore disturbances, caused 

 by irregular crystallisation were probably present. 



Chemistry. — Professor Bakhuis Roozeboom presents a commu- 

 cation by Dr. Ernst Cohen, " On the velocity of electrical 

 Reaction. II." 



The velocity of the reaction Zn + %o SOi ^ H(jo, + Zn 80^. 



1. An open galvanic element is not a system in equilibrium ; 

 this is obvious from the fact that if the circuit of such an element 

 is closed by means of a wire, the reaction which can take place in 

 the cell at once occurs. 



We must assume, that, owing to the resistance of an open cell 

 being very (infinitely) great, the velocity of the reaction is practically 

 reduced to zero ^). 



2. If, on the other hand, it is, for example, desired to study 

 the course of a chemical reaction at different temperatures as a 

 function of the temperature, a galvanic element may be constructed 

 in which the reaction will take place as soon as the circuit is 

 closed. 



In what follows I shall describe briefly the results obtained in 

 the study of the reaction 



1) Compare Nehnst, Tlieor. Obeinie. 2e Aufl. 1898, 658. 



