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LVIII. Intelligence and Miscellaneous Articles, 



ON THE SPECIFIC HEATS AND MELTING-POINTS OF DIVERS 



REFRACTORY METALS. BY J. VIOLLE. 



I. -TVHE specific heat of iridium, like that of platinum, increases 



-*• regularly with the temperature. The experiments were 



extended up to 1400° ; and they are well represented by the formula 



found for platinum, 



C ==0-0317-f-0-000006*. 

 From this the following values are deduced for the mean specific 

 heat between zero and t degrees : — 



CJ 00 0-0323 



C 2 00 0-0329 



C 3 00 0-0335 



CJ 00 0-0341 



C5°° 0-0347 



OT 0-0353 



Cl 00 0-0359 



C° 0-0365 



Cg 00 0-0371 



CJ 000 ...... 0-0377 



C ,0 ° 0-0383 



C 20 ° 0-0389 



C 300 0-0395 



CJ 400 0-0401 



It was not without some little difficulty that the melting-point 

 of iridium could be determined ; that metal in fact necessitates the 

 employment of hydrogen and oxygen pure and dry in the blowpipe 

 of Deville and Debray ; and to melt 20 grams of iridium not less 

 than 500 litres of hydrogen and 250 litres of oxygen must be con- 

 sumed. Nevertheless three experiments were brought to a suc- 

 cessful issue, conducted in the manner indicated for platinum, and 

 in which 24, 8-970, and 8-404 grams of solid iridium gave up to 

 the calorimeter, at the temperature of the fusion, respectively 84*2, 

 85-3, and 83*9 units of heat per gram of metal, or a mean of 84-5 

 units. If, then, it be admitted that the formula above given repre- 

 sents the specific heat of iridium up to its melting-point, a tempe- 

 rature certainly very little below that of the blowpipe-flame, it fol- 

 lows that iridium fuses at 1950° C. 



II. Gold presents a mean specific heat which up to 600° hardly 

 varies at all, then sensibly increases in proportion as the melting- 

 point is approached : equal to 0*0324* (according to Eegnault) be- 

 tween 0° and 100°, still nearly the same at 600°, it reaches 0-0345 

 at 900° and 0-0352 at 1020 6 . The melting-point of gold, deter- 

 mined as usual, is 1035°. 



III. The melting-point of copper is very close to that of gold, 

 but a little higher f: pure copper melts at 1054°. 



IV. Collecting in a Table the melting-points given in this and 



* Gold of 2&L. I found a specific hea,t a little less, Cj 00 =0-0316, with 



1000 r ; ° ' 



a specimen of perfectly pure gold which I used in my researches, and fo r 

 which also I am indebted to the kindness of M. Debray. 



t The red copper of commerce melts before virgin gold, 15° to 30° before 

 gold like the specimen. 



