332 



PROCEEDINGS OF THE AMERICAN ACADEMY. 



hydrogen answered the purpose ; for the temperature at which the reduc- 

 tion takes place is so low that no trace of nickel was found outside of the 

 boat which originally contained the bromide, if a rapid current of the 

 gas was maintained. It is obvious that according to the law of mass- 

 action, the presence of a large proportion of hydrobromic acid resulting 

 from the reduction would tend to prevent the desired reaction, and hence 

 to facilitate the undesired sublimation ; therefore a large excess of hydro- 

 gen must be present. Of course the hard glass tube used for this pro- 

 cess was always afterwards treated mternally with nitric acid, and the 

 liquid was examined with minute care for traces of nickel. 



Fig. 1. Apparatus for igxitixg Nickelous Bromide in ant desired 



Mixture of Gases. 



The use of rubber was confinefl to the first part of tliis train, where it could do 



no harm (A B C D E F and A M N O P). 



The nickelous bromide to be analyzed was contained in a platinum 

 boat, and the method of drying and weighing it was in every respect the 

 same as that described in detail in the previous paper upon this subject. 

 After having been weighed, the boat was carefully placed in a hard glass 

 tube, in which the bromide was cautiously reduced to the metal. When 

 the reduction was completed and the apparatus had just cooled, the boat 

 and its contents were returned to their weighing bottle, where they were 

 enclosed in an atmosphere of dry air. The weight of the residue was 



