Haslam — On the Volatilization of Zinc. 337 



hour of experiment. After this there is a steady decrease in the 

 amount of zino vaporized from the alloy. In one experiment the 

 alloy was heated for twelve hours, and it was found that the loss 

 sustained in the last hour only amounted to '004 grammes. 



The action of the other constituent, nickel, of the alloy is very 

 striking. It will he observed that No, 2 alloy contains the most 

 nickel and the least copper, and that the vaporization of the zinc 

 proceeds more slowly in it than in the other alloys, while No, 3 

 contains the least nickel and most copper, and is dissociated much 

 quicker. A specimen of brass of the same weight containing 30*6 per 

 cent, of zinc when heated for the same time gave a total loss of 

 •424 grammes, or nearly double that of the .Grerman silver contain- 

 ing the least nickel. The curves showing graphically this action of 

 the nickel are shown in the figure. 



From these carefully obtained results I am led to conclude that 

 Grerman silver appears to have much more the character of a perfect 

 alloy than brass, and that the tendency of zinc to volatilize from Ger- 

 man silver is determined by the quantity of nickel present in the 

 alloy, the nickel increasing the affinity of the zinc. Might not there- 

 fore more nickel and less copper be used with advantage in the 

 manufacture of this important alloy ? 



NOTE ADDED IK THE PEESS, 



[Since this Paper was read I have made some further experi- 

 ments on an alloy of nickel and zinc, having as near as possible the 

 composition NiZuj, On heating this alloy, it was found that in six 

 hours it had lost '122 grammes, or '060 less than the German silver 

 alloy containing the most nickel. It was also found impossible at 

 a bright-red heat to expel all the zinc from this alloy, 9 per cent, 

 remaining constant, while in the case of brass, the percentage of 

 zinc may be reduced as low as 1 per cent. I have not found it 

 possible to deprive brass entirely of its zinc by heating it in a 

 porcelain tube over a combustion furnace : from '6 to 1 per cent, 

 remains constant.] 



SCIEX. PitOC. K. U.S. — VOL. IV. PART TI. 2 G 



