JRelations of the Alloys of Platinum. 429 



electrical behavior of as many alloys as possible of one given 

 group. On perusing Matthiessen and Vogt's results, it appears 

 tliat lead alloys,* tin alloys and iron alloys will have to be ex- 

 cluded from the present consideration, inasmuch as the data 

 are either insufficient in number, or lie too far apart from each 

 other and from the extremes of this series, or because of 

 mechanical difficulties encountered in making the alloys and 

 shaping the wires. There remain a very full series of copper 

 alloys, viz : CuSn, CuZn, CuFe, CuP, CuAs ; a series of silver 

 alloys, viz : AgAu, AgPt, AgPd, AgCu ; and a few gold alloys, 

 viz : AuCu, AuAg. In view of the importance of these data 

 I have computed the following tabular statement of Matthies- 

 sen's results, re-arranging the data in a way which for my spe- 

 cial purposes is expedient. I have also added Matthiessen'sf 

 results for pure, soft metals. In table I, X\ denotes the con- 

 ductivity in Matthiessen's standards (Ag- 100), a the tempera- 

 ture coefficient of the alloy, of which the composition is given 

 on the same horizontal row. I have rounded off Matthiessen's 

 long numbers, because the arbitrary errors introduced during 

 the mechanical preparation of the alloys, together with the 

 errors of structure and hardness and the more serious errors of 

 imperfect homogeneity, make the extreme accuracy of the 

 electrical datum illusory. The table furthermore contains ^ , 

 the electrical conductivity in microhms referred to the cubic 

 centimeter. This reduction is made by means of mercury.J 

 In the last two columns of table I, the value of a computed by 

 the formula a-\-m=nk and the corresponding errors are in- 

 serted. Of these results further mention will be made below, 

 and I need here only state that the constants m and n given at 

 the end of the table are those which I derived from all the 

 relevant observations, by the method of least squares. 



The compositions given are volume per cents, except in the 

 cases of phosphides and arsenides of copper where mass per 

 cents are meant. 



In interpreting these results by graphic methods, it is neces- 

 sary to proceed with caution, for inasmuch as specific resistance 

 enters into them reciprocally, large values of resistance will 

 only be inadequately represented. Neverthless, although the 

 tables contain many such values, enough data remain to exhibit 

 the striking linear character of the curves on which the gold, 

 silver and copper points respectively lie. The initial tangent 



* The metallic ingredient present in larger amount may be fitly used in desig- 

 nating the alloy. 



f Matthiessen and v. Bose : Pogg. Ann., cxv, p. 353, 1 862. 



% Jenkin who made similar reductions in the case of pure metals by means of 

 lead, arrives at somewhat different numbers. A perfectly satisfactory absolute 

 table can not be deduced. 



Am. Jour. Sci.— Third Series, Vol. XXXVI, No. 216— Dec, 1888. 



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