and the Relation of Specific Heat to Atomic Weight. 245 



advantage of the slight solubility of purpureo-cobaltamine hydrochloride 

 in strongly acid solutions, and the nickel by deposition from the car- 

 bonyl compound and subsequent solution of the metal and electro 

 deposition. Both were fused by means of an oxyhydrogen flame, and 

 afterwards shaped into bars. For the estimations of specific heat 

 between 15° C. and 100° C. the differential steam calorimeter of 

 Professor Joly was employed. 



The mean specific heat of cobalt within these limits of temperature 

 was found to be 0-10303. 



The mean specific heat of nickel was found to be 0" 10842. 



In order further to test the method and the conclusion from the 

 case of cobalt and nickel, gold was compared with platinum, and copper 

 with iron. 



The following are the mean specific heats for these pure metals after 

 fusion, and within the same limits of temperature : — 



Gold 0-03035]^ 



Platinum 0-03147 J 



Copper 0-092321^ 



Iron 0-10983 J 



'V\Tien these values for the specific heats are multiplied by the 

 respective atomic weights of the several metals, the products are not 

 constant, as the law of Dulong and Petit would seem to require if 

 applicable at all temperatures. 



The influence of impurities on the specific heat of several metals 

 was then investigated, and a number of results are given, from which 

 it appears that small quantities of carbon or other non-metallic element 

 tend to increase the specific heat appreciably, while the presence of a 

 small quantity of a foreign metal seems to produce little eff'ect. 



A series of calorimetric experiments were next made by the method 

 of mixtures on the two pure metals cobalt and nickel, at the temperature 

 of solid carbon dioxide, - 78-4°, and at that of boiling oxygen, - 182-5°. 



The results, which are given below, show that as the temperature is 

 reduced the value for nickel declines more rapidly than that for cobalt, 

 and hence that, when the mean results are plotted out, the curves 

 steadily approach each other. 



The mean specific heats of cobalt and nickel now stand as follows : — 



Temperature. Cobalt. Nickel. 



From 100° to 15° 0-10303 0-10842 



„ 15° „ -78-4°...... 0-0939 0-0975 



„ 15° „ -182-4° ... 0-0822 0-0838 



and by calculation from the last two results from -78'4 to - 182*4°, 

 0-0712, 0-0719. 



