32 



Dr. Alder Wright and Mr. C. Thompson. [May 8, 

 FIG. 3. 



Figs. 2 and 3 represent these values respectively, the curves 

 marked 2 heing those obtained at the lower temperatures (near 650), 

 and those marked 1 being the corresponding higher temperature 

 mean curves (near 800) ; the dotted lines being those connecting 

 the points actually observed at near 800. 



Mixtures of Lead, Zinc, and Silver. 



Owing to the lesser degree of fusibility exhibited by some of these 

 mixtures, it was found necessary to employ throughout a temperature 

 ranging between 750 and 850, and generally pretty close to 800. 

 It is well known that on adding zinc to melted argentiferous lead 

 the zinc rises to the top, carrying most of the silver present with it 

 along with a little lead ; whence, evidently, the curve representing 

 the distribution of silver between the lighter and heavier alloys 

 formed resembles that obtained with lead, zinc, and tin alloys when 

 the proportion of tin present is but small, i.e., the curve at first 

 ascends above the base line ; but no information appears to be extant 

 giving any clue as to whether this kind of distribution would also be 

 observed with mixtures containing large proportions of silver, or 

 whether such mixtures would behave like lead-zinc-tin mixtures 

 containing large proportions of tin, i.e., furnishing a curve descending 

 again to, and finally dropping below, the base line. 



The analysis of the lead-zinc-silver alloys formed was made as 

 follows : a weighed quantity, usually some 5 or 6 grams, was dissolved 

 in nitric acid and the solution diluted with so much hot water that 

 on adding enough dilute hydrochloric acid to precipitate all the 



