144 REPORT 1900. 



Heat of Formation. 



It is probable that if two metals form compounds whose lieat of 

 formation is considerable, whether positive or negative, and if we could 

 determine the heat of formation of a series of binary alloys of these two 

 metals, we should find a maximum or a minimum heat evolution at 

 formulae corresponding to those of the compounds. Herschkowitz has 

 attempted to find these heats of formation by dissolving first the metals, 

 then the alloy, in a solution oE bromine and KBr in water, and taking 

 the difference as the heat of formation of the alloy. But his results, 

 though not unpromising, do not yet throw much light on our subject. 

 One objection to his method lies in the necessity of crushing his metals 

 and alloys to ensure rapid solution in the calorimeter. Now, as Mr. 

 Rosenhain has pointed out to me, it is certain that the crushed alloy, 

 each fragment of which has been strained, possesses more energy than it 

 did before crushing, and this may be quite important as compared with 

 the small heats of formation observed. 



Gait Q^) and other workers have followed similar methods, but the 

 solvent (nitric acid) used by him does not seem a safe one, as the gaseous 

 products of solution may be so varied that one can feel no certainty that 

 the final state was the same in the solution of the metals and of the alloy. 

 In Tayler's (^"') method of dissolving the metals and the alloy in mercury 

 there is not this danger, but the applicability of the method is more 

 limited. 



Electric Conductivity of Alloys. 



Since Matthiessen and Wiedemann studied the remarkable changes in 

 conductivity produced by alloying two metals, this subject has been one 

 of great ititerest. But it is doubtful if research in this direction will 

 help us much in detecting the existence of compounds. For the increase 

 in resistance due to alloying two metals, while partly due to the Peltier 

 effects at the innumerable surfaces of contact of the crystals forming the 

 alloy, is also due to the mechanical discontinuities and gaps which exist 

 in alloys. It would be very difficult to distinguish quantitatively between 

 the effects due to the two causes. The impossibility of drawing many 

 alloys into wire, and the changes caused by drawing those which are 

 ductile, also limit and complicate this method of research. 



PART II. 



Table of Intermetallic Cornpoundn. 



Column 2 contains the presumed formula of the compound. Column 3 

 indicates the kind of evidence on which the formula is based. In 

 column 3 the letters F.P.C. stand for freezing-point curve ; I. for the 

 fact that the body has been isolated and analysed ; M. for microscopic 

 proof ; E.M.F. for determinations of electromotive force, such as those of 

 Laurie. 



Column 4 gives the name of the experimenter, and a number referring 

 to the table of references, which is placed at the end of the report. The 

 more uncertain formulae are placed in brackets. Each alloy occurs twice 

 in the table. 



