Viscous Traction of Lead and Tin Alloys. 



197 



is a certain amount o£ association existing between the two 

 metals in the solid state, which is not made apparent when 

 they are fused, since the freezing-point curve is of the 

 ordinary type, indicative of no such loose combination. 











Fig. 



i. 











p/A? 















■ \ 















Sfi N 4-/ 

 5 ^ fy 



^ 

















r 

















1 



V. 



















r 



t 



















ID 



















- 



+ 

















y*LU£S OS A X 10' 



It is only natural to expect a greater degree of association 

 in the solid state. The enormous effect of the addition of 

 tin to lead may be explicable on the assumption of the com- 

 plexity of the tin molecule, which has been seen to approxi- 

 mate Sn 4 . The dissociation of this and the consequent 

 building up of lead-tin complexes would account for the 

 departure of the curve from the normal. The two outer curves 

 in fig. 2 (p. 198) represent the viscosity concentration curves 

 for greater loads than 500 grams, viz., 1000-1100 grams. 

 It is at once evident that the already low viscosity coefficient 

 of tin is not materially affected by increased stressing force, 

 but a very considerable effect is to be observed in the case 

 of lead and its higher alloys. 



It seems very possible that at a given limiting load these 

 two metals and their alloys would attain an equality of 

 mobility ; at any rate, the difference between their viscosity 



