1892.] On certain Ternary Alloys* 15 



"flouring" of the molten metal, a considerable proportion of the 

 alloys being reduced to minute particles that did not coalesce with 

 the rest of the molten mass, and remained in the crucible when the 

 fused metal was poured into the clay test-tabes. This same flouring 

 action was equally observed when bismuth was substituted for lead ; 

 whilst with silver as solvent metal instead of tin it was still more 

 marked ; frequently not more than three-quarters or two-thirds of 

 the metals originally weighed up (40 to 50 grammes) were obtained 

 as final compound ingot, and sometimes even less; the deficiency 

 varying according to the success or otherwise of attempts to exclude 

 access of air whilst stirring. 



The analysis of the alloys thus prepared was carried out as 

 follows : A weighed portion was dissolved in hydrochloric acid con- 

 taining a little nitric acid, and the solution largely diluted. 

 Sulphuretted hydrogen in excess was then passed through, and the 

 solution containing aluminium, &c., filtered off from the precipitated 

 sulphides of tin and lead. These were then separated by sulphide 

 of ammonium, and finally weighed as Sn0 2 and PbS04 in the usual 



y. The filtrate was saturated with sulphuretted hydrogen, and 

 allowed to stand two or three days to ensure the separation of the 

 last traces of tin; finally ammonia was added, and the precipitate 



llected, washed, and ignited. The weighed impure alumina was 

 then redissolved by long boiling with hydrochloric acid, any silicic 

 acid present separated by evaporation to dryness, &c., and the iron 

 present estimated volumetrically. It was found impracticable to 

 obtain good results by treating the alloys with nitric acid alone, not 

 only because alloys containing much aluminium are only attacked by 

 that acid with great difficulty, but also because the tin as determined 

 by weighing the undissolved Sn0 2 was over-estimated to an unknown 

 amount on account of the presence of silicon, partly left undissolved 

 as such, partly converted into silicic acid more or less retained by 

 the tin oxide ; so that it was necesary to fuse the impure Sn0 2 with 

 sulphur and sodium carbonate to convert into soluble sulpho- 

 stannate, to precipitate tin sulphide from the filtered aqueous solu- 

 tion by acidulation, and ultimately to roast and weigh as Sn0 2 .* 



The following corrected percentages (reckoned on tin + lead + 

 aluminium = 100) were obtained from the examination of 25 com- 

 pound ingots representing 50 alloys. In the preparation of these the 

 lead and aluminium were originally weighed up in the proportion of 

 about 2'5 to 1 for the ingots containing smaller amounts of tin ; on 

 account of the low density of aluminium this resulted in the forma- 

 tion of approximately equal volumes of heavier and lighter alloy 



* With aluminium-bismuth-tin alloys the SnO 2 undissolved by nitric acid also 

 retains bismuth left behind as sulphide on conversion into sulphostannate and 

 treatment with water (vide Part III). 



