Db. Thomson on the Meltinq Points of Alloys of Leady ^c. 79 



I was surprised to find the melting points of all these alloys so near 

 each other. Rudberg had observed the same thing, though from the 

 error in his thermometer wo cannot deduce from his tables the true 

 melting point. 



The molting point of lead, determined from the mean of a great 

 number of trials, is 607°, and that of tin 442°. The mean of these 

 two points is 524i°, which is 1G3J° above the actual melting point 

 We may conclude from this that tin possesses the important property 

 of lowering tlie melting point of other metals — a property which the 

 facts about to bo stated fully confirm. 



Lead and bismuth were now melted in the following proportions: — 



1 atom lead. i 1 atom lead. 



1 atom bismuth. | 2 atoms bismuth. 



The melting points of these alloys were — 



1, . . . . 274° I 2 2630 



In this case the two alloys have each a melting point peculiar to itself. 

 The melting point of bismuth is 497°, and that of lead 007°. The 

 mean is 552°. So that the melting points of alloys of lead and bis- 

 muth are respectively 278° and 289° below that mean. Bismuth has 

 a still greater power to diminish the melting point of other metals, or 

 at least of lead. The alloy is white and rather beautiful ; but quite 

 brittle. This is the case with all the alloys of bismuth, at least so far 

 as I have tried. 



When bismuth and lead unite, the bulk of the alloy diminishes, and 

 consequently the specific gravity is above the mean. The following 

 table shows the specific gravity, and the diminution of bulk in these 

 allocs — 



Sp. Or. Mean Sp. Qr. 1000 becomt 



1, . . . 10-831 10-580 977 



2, . . . 10-509 10-328 983 



Seeing that both tin and bismuth sink the melting point of alloys, 

 it became an object to observe what the melting point of alloys of these 

 two metals would be. The two following were made: — 

 1. 2. 



1 atom tin. 2 atoms tin. 



1 atom bismuth. 1 atom bismuth. 



The melting points of these two alloys were — 



1, . . . . 280» I 2, . . . . 274- 



These points are not lower than those of the corresponding alloys 

 of lead and bismuth. 



The alloy of tin and bismuth is white, and more pleasing to the 

 eye than pewter ; but, like all the alloys into which bismuth enters, it 

 is brittle. 



