i.ys 



Dr. Alder Wright and Mr. C. Thompson. [Fob. IL>, 



in a much more marked fashion. The formula Zn 4 13i 7 requires 

 Zn = 15*1, and Bi = 84'9 per cent. 



Mixtures of Bismuth, Zinc, and Tin. 



Two scries of experiments were made, one at a temperature rang, 

 ing between 600 and 700, and averaging near to 650 s ; the other 

 ranging between 700 and 800, and averaging near to 750. The 

 results indicate that in presence of tin the solubility of zinc in bismuth 

 and that of bismuth in zinc are both materially increased by incre- 

 ment of temperature. A few experiments at a somewhat higher 

 temperature, averaging near 800, were also made, the results of which 

 indicated a notable further increment in solubility ; but, as considerable 

 difficulty was experienced in getting even moderately concordant 

 figures at this higher temperature, these observations were not 

 carried far enough to enable average curves to be deduced. In every 

 case the mixture of metals employed contained equal quantities of 

 bismuth and zinc with varying proportions of tin ; as in the case of 

 the lead-zinc-tin alloys previously described, the effect of volatilisation 

 and oxidation caused a small decrement in the proportion of zinc 

 present in the compound ingots ultimately obtained relatively to the 

 other two metals contained therein, especially in the experiments at 

 the higher temperatures. 



In analysing the alloys prepared, we found that the method of 

 analysis used for lead-zinc-tin alloys could not be adopted without 

 modification, because the stannic oxide formed by the action of nitric, 

 acid on the alloys retained variable amounts of bismuth in such a condi- 

 tion as not to be removed by copious washing with dilute nitric acid, or 

 even by boiling therewith.* In some instances we weighed the crude 

 stannic oxide retaining bismuth, and then fused it with sodium carbon- 

 ate and sulphur, whereby sodium sulphostannate was formed, soluble 

 in water, and bismuth sulphide insoluble therein. By precipitating the 

 stannic sulphide by means of hydrochloric acid from the aqueous solu- 

 tion, and cautiously roasting it, the corrected weight of stannic oxide 

 was obtained ; this we found always concorded sensibly with the weight 

 deduced by converting the undissolved bismuth sulphide into oxic 

 (by dissolving in nitric acid, precipitating boiling with ammonium 

 carbonate, and igniting the precipitate), and subtracting the weight 

 of this from that of the crude stannic oxide. In other cases, we 

 dissolved the alloy in hydrochloric acid containing a little nitric acid, 

 diluted and treated with sulphuretted hydrogen, separating the tin 



* It is noteworthy that no trace of lead appears to be thus retained by stannic 

 oxide when alloys containing tin and lead are treated with nitric acid ; on the other 

 hand, when alloys containing antimony and lead are similarly treated, the undis- 

 Bolved antimony oxide retains a notable amount of lead, just as stannic oxide retains 

 bismuth. 



