198 Jlixter — Formation of the Oxides of Cobalt and Nickel. 



so i-iipidlv that the temperature of tlie metal rose 30°, The 

 metal, marked J, was darker colored and more voluminous 

 than IX. 



5. Heat of comhustion of nickel. — The following are the 

 experiments : 



12 3 4 



Nickel 12-000(a) 18-003(J) 22-099(^>) 16-000 grams (a) 



Mica tray.. 0576 0-677 



Silver tray 3-1245 3-188 " 



Oxygen taken up 2-127 3-527 3-789 2-557' " 



Water equivalent of 



system 3,568- 3,666- 3,647- 3,674- " 



Temperature interval. 2-183° 3-470° 3-735° 2-508° 



Heat effect 7,789 12,721 13,622 9,214'= 



" of oxidation given —48 —50 50 50*= 



7,741 12,671 13,572 9,164" 



For 1 gram of oxygen . . 3,640° 3,593= -3582° 3,584<= 



The average is 3600° for 1 gram of oxygen combining with 

 nickel. For 16 grams it is 57,600' at constant volume and 

 57,900° at constant pressure. 



The product of a combustion was a sintered mass having the 

 shape of the layer of metal burned. The trays holding the 

 nickel were in all cases melted, the mica forming a slag adher- 

 ing to the nickel oxide and the silver falling away from it. It 

 was impossible to separate the metal from the oxide by a mag- 

 net as the two were so intimately mixed. In one trial an electro- 

 magnet removed 5/6 of the pulverized material from water. 

 The product of experiment 4, in which a silver tray was used, 

 contained a few black vitreous pieces which were also mag- 

 netic. Small globules of nickel were also present, showing 

 that temperature of the combustion was high. The metal oxi- 

 dized in experiment 1 was 65 per cent of the amount present; 

 in 2, 75 per cent ; in 3, 63 per cent ; and 4, 59 per cent. The 

 calculations are based on the oxygen taken up to form NiO, 

 and there is no good reason for supposing that a lower oxide 

 was formed. 



The heat of oxidation of cobalt has been regarded as a 

 little greater than that of nickel as indicated bv Thomson's 

 results, which are Co,O,H,O=63,400°, and M,0,H,0 = 60,840°. 

 Dulong's results '^' are of the same order, namely, Co,0 

 = 64,000° and Ni,0 = 59,700°, each, however, from a single 

 experiment found after his death recorded in his note-book. 



* Loc. cit. 



