200 DES. A. MATTHIESSEN AND C. YOGT ON THE CONDUCTING-POWEE OF ALLOYS. 
instead of 14-05, the volumes per cent, of silver deduced from that value would be 
52-62 instead of 48-20, the value calculated from the latter number. 
4. It may be as well to state in a few words how we determine to which class a metal 
belongs, whether to the lead, tin, &c., or to the gold-silver, &c. class ; to do this it is only 
necessary to alloy the metal with traces of lead, tin, &c., and if the conducting-power 
be equal to that of the mean of the components, we say it belongs to the lead class ; if, 
on the contrary, the alloy has a lower conducting-power than the mean of the compo- 
nents, we say it belongs to the gold-silver, &c. class. These are only some of one series 
of alloys which have a higher conducting-power than the mean of their components, 
and these are the amalgams. 
Table XXVIII. shows that the new metal thallium belongs to the gold-silver, &c. 
class. 
Table XXVIII. 
l. 
Thallium, containing 5 per cent., by weight, tin. 
Length 188 millims. ; diameter (M43 millim. 
Conducting-power found before 0 Reduced to 0°. 
heating the wire 8-196 at 12-6 8-522 
Ditto, after being kept at 100° 
for 1 day 8-131 at 12 - 6 8-455 
Ditto, for 2 days 8-097 at 9-8 8-347 
Ditto, for 3 days 8-111 at 9-6 8-356 
1 T ’ 
Conducting-power. 
10-0 
8-100 
55-0 
7093 
100-0 
6-313 
A = 8-355 - 0-02607 5 1 +0-00005654!;-. 
Table XXVIII. (continued). 
2 . 
Thallium, containing 5 per cent., by weight, cadmium. 
Length 163 millims. ; diameter 0-431 millim. 
Conducting-power found before 0 Reduced to 0°, 
heating the wire 8-670 at 14-4 9-141 
Ditto, after being kept at 100° 
for 1 day 8744 at 12-8 9-168 
T. 
Conducting-power. 
13-0 
8-737 
56-5 
7-454 
1000 
6-398 
A = 9- 165 - 0033663^ 4-0-00005998? 12 . 
These alloys were not analyzed, the 5 per cent, of foreign metal being added to the 
thallium fused under cyanide of potassium. From the results it will be seen that they 
both conduct in a lower degree than the mean of their components ; for both cadmium 
and tin conduct better than thallium, the conducting-power at 0° of cadmium being 
23*72, and that of tin being 12*36. 
5. In conclusion, we would point out that the law which we have deduced from our 
experiments only holds good in cases where the alloy may be considered a solution of one 
metal in the other, the metals belonging to the same class ; when the alloy is composed 
of metals of the two classes, then the law no longer holds good (except for a few of the 
alloys), even if the alloy be a solution of the one metal in the other. The results which 
we have obtained and described in this memoir fully bear out the views put forward in 
a former one regarding the chemical nature of the alloys*. 
Philosophical Transactions, 1860, p. 161. 
