464 



Dr. C. R. A. Wright and Mr. C. Thompson. [Mar. 28, 



These and various other similar experiments led us to the con- 

 clusion that the greater the proportion of tin present (provided it 

 does not exceed the limiting amount beyond which no separation 

 takes place) the more zinc is contained in the heavier alloy, and the 

 more lead in the lighter one ; but that the distribution of the tin 

 throughout the entire mass is by no means uniform, the lighter alloy 

 containing the greater percentage when the proportion of tin in the 

 total mass is low, and vice versa when it approaches towards the 

 limiting amount ; so that with a particular proportion of tin in the 

 total mass uniform distribution as regards weight percentage occurs, 

 but with no other proportion. 



These first indications appeared to be of sufficient interest to be 

 worth following up by the examination of a large number of mixtures 

 so as to enable curves to be drawn representing the variations in 

 composition of the heavier and lighter alloys relatively to one another 

 and in the distribution of the tin throughout the compound mass. 

 Accordingly, we first of all attempted to find out whether a moderately 

 large variation in the temperature at which the mass was kept molten 

 had any great influence on the end result ; for if not, obviously much 

 laborious work would be saved, thermostats and arrangements for 

 keeping constant temperatures for long periods of time together and 

 such like devices, involving much complexity of working, being far 

 less indispensable than would otherwise be the case. For this pur- 

 pose we prepared two series of mixtures, in each of which equal 

 quantities of lead and zinc were weighed up with varying quantities 

 of tin. The metals were melted in a crucible (previously heated to a 

 dull red heat) with a little cyanide of potassium, well stirred together 

 with a clay rod for some minutes, and then poured into the red-hot 

 bowl of a plugged clay tobacco-pipe and kept therein molten for four 

 to five hours. In the first series the bowl was kept hot in the flame 

 of a bunsen burner lapping all round the bowl ; in the second, the heat 

 was intensified by surrounding the bowl with a clay cylinder so as to 

 jacket it. A bundle of pieces of thick platinum rod heated in exactly 

 the same way and transferred to a calorimeter, gave with bowls not 



