CONDUCTING POWEE OF ALLOYS. 
171 
5. General Conclusions. 
The question now arises, What are alloys ] Are they chemical combinations, or a solu- 
tion of one metal in another, or mechanical mi xtures % And to what is the rapid decre- 
ment in the conducting power in many cases due 1 
To the first of these questions I think we may answer, that most alloys are merely a 
solution of the one metal in the other ; that only in a few cases we may assume chemical 
combinations, for example, in some of the gold-tin and gold-lead alloys ; and we may 
regard as mechanical mixtures some of the silver-copper and bismuth-zinc alloys. The 
reasons of the foregoing assumptions are the following : — 
1. That if we had to deal with chemical combinations, we should not find in the con- 
ducting power of alloys that regularity in the curves which certainly exists ; for on 
looking at those belonging to the different classes, we see at a glance that each class of 
alloys has a curve of a distinct and separate form. Thus for the first, we have nearly a 
straight line ; for the second, the conducting power always decreases rapidly on the side 
of the metal belonging to Class B, and then turning, goes almost in a straight line to the 
side of the metal belonging to Class A. For the third group, we find a rapid decrement 
on both sides of the curve, and the turning-points united by almost a straight line. 
If we now examine the part of the curve where the rapid decrement takes place, we 
find that in the lead and tin alloys it generally requires twice as much of the former as 
it does of the latter to reduce a metal belonging to Class B. to a certain conducting 
power; for instance, to reduce that of silver to 67, it would require 0‘9 vol. per cent, of 
lead, or about 0‘5 vol. per cent, of tin; to reduce it to 47*6, there would be required 1‘4 
vol. per cent, of lead, or about 0-7 vol. per cent, of tin*. Again, to reduce bismuth to 
0’261, there is requmed 1'4 vol. per cent, of lead, or 0'62 vol per cent, of tin; and to 
reduce it to the minimum point of the curve, which is, when alloyed with lead, 0‘255, 
and 0-245 when alloyed with tin, it requires 1-76 vol. per cent, of lead and 0-85 vol. 
per cent, of tin. 
2. We cannot explain the reason of the decrement of the conducting powers by 
assuming that the turning-points of the curves are chemical combinations, for it is not 
at all probable that there are such as contain only 0-6 per cent, of tin and 99-4 per cent, 
of bismuth; or 2 per cent, of lead and 98 per cent, of bismuth; or 2-6 per cent, of tin 
and 9-74 per cent, of silver, &c. 
3. That the alloys, at these turning-points, have their calculated specific gravities f. 
On Plate V. we find the curves of the alloys belonging to the third class : now here 
we might be inclined to think that we had to do with chemical combinations. But if 
we consider, taking the gold-silver cm’ve as a type, that the conducting power of silver 
is greatly reduced by small per-centages of any metal, and that the same may be said of 
gold, and if we suppose that this decrement has taken place, and join the two turning- 
points to which the metals have been reduced, we shall have the gold-silver curve. Take, 
* These values were read off from the curves. 
t See the specific gravities of lead-bismuth and tin-bismuth alloys in this volume, pp. 162, 165, 166. 
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