bakus.] PYRO-ELECTRIC PROPERTIES OF ALLOYS. 145 
however, exhibit more complicated relations. Indeed, our data 1 for 
alloys of silver with platinum, gold, copper, and zinc showed that, the 
results for steel were due to causes intrinsically different from the 
causes varying the electrical properties of alloys. Owing partially to 
this negative result and partially to the necessity of changing our 
laboratory location from Wurzburg to Prague and to Washington, 
these data 1 for alloys remained unpublished in German until 1884, and 
in English 2 until 1885. 
In the mean time M. L. Weber, 3 who, at the suggestion of Beetz, had 
sought for similar relations among the amalgams of mercury, was able 
|o publish a fine and elaborate research on the galvanics and thermo- 
electrics of those substances. In addition to the results of Strouhal 
and myself for silver alloys, and Weber's results for amalgams, it was 
Loped that the present results for platinum alloys would supply such a 
sufficiency of new data that from all the results thus in hand certain 
general inferences bearing on the properties of alloys might safely be 
Irawn. This discussion must, however, be deferred for the reasons 
already mentioned, page 125. 
Resistance and density. — Turning first to the columns for J ? s t I, and 
) t II, in Table 34, the number of strikingly large values of the specific 
•esistance of platinum alloys at once meets the eye. If the specific re- 
sistance of good commercial platinum be put s t =13, then it needs but 
rifling additions of chromium, or iron, or copper, or tin, or manganese, 
>r zinc, etc., to increase this resistance nearly fivefold. In discussing 
esults for silver alloys Dr. Strouhal and I observed that the galvanic 
fleet produced by alloying increased with the differences of density of 
he ingredients of the alloy. In view of the exceptionally high density 
f platinum and the pronounced tendency of this metal to form alloys 
f high specific gravity, these inferences seem to be substantiated here, 
earing in mind that the differences of density of the ingredients can 
nly be one of many factors which go to determiue the properties of the 
Hoy produced. To go into further particulars is undesirable, but I may 
mark that though the effect produced by aluminium is exceptionally 
nail, iridium and gold, both of large densities, produce small increments 
f resistance, whereas the enormous variations due to tin, chromium, 
on, zinc, copper, manganese, cobalt, silver, nickel, palladium, decrease 
i general in the order of their increasing densities. The absorption of 
ases, the want of homogeneity, and the very probable tendency to 
>rm alloys of definite chemical composition are the main causes which 
md to obscure the regularity of the physical phenomena. The differ- 
rces between s t I and s t II, derived, respectively, from the bars and the 
ires, are no larger than may be easily referred to difficulties of manipu- 
lation. In the case of chromium, of iron, of cobalt, and of aluminium 
1 Abb. konigl. Bobm. Gesell. Wiss., 6tb series, vol. 12, 1884. 
2 Bull. U. S. Geol. Survey, No. 14, 1885, pp. 76 to 88. 
3 Weber : Wied. Aun. vol. 23, 1 884, p. 447. 
(799) 
Bull. 54 10 
