334- Di". T. Andrews 072 the Heat disengaged during the 



M 0-764 grm. 0-773 grm. 0-729 grm. 

 T 4°-5 4°-8 4.°-l 



E l°-2 1^-4 l°-7 



I 2°-504 2°-498 2°-321 



Ic 2^-5 1 1 2°'509 2°-336 



W 1644 "i-ms. 1659 grms. 1658 grms. 



V 117 grnis. 117 grms. 117 grms. 



1. 2. 3. 



5788 5764 5688 



Hence we have for the heat evolved durinjj the combina- 

 tion of- — 



One gramme phosphorus with oxygen . 5747 

 One gramme oxygen with phospliorus . 4509 

 One litre oxygen with phosphorus . , . 6479 



Zific and Oxygen. 



The zinc employed in the following experiments was care- 

 fully distilled from the purest varieties of the metal in com- 

 merce. It was scarcely attacked in the cold by dilute sul- 

 phuric acid. It still however contained 0005 lead : but this 

 tiace of impurity could exercise no influence on sucii experi- 

 ments as the present. 



To prevent the agglutination of the fine parts of the zinc 

 during the combustion, it was mixed in the state of very fine 

 filings with one-half its weight of pulverized quartz. The 

 ignition of the zinc was effected by the assistance of a small 

 portion of phosphorus (about 0008 grm. in each experiment), 

 which was inflamed in the usual way by the voltaic battery. 

 In calculating the results, the heat produced by the combus- 

 tion of the phosphorus was estimated and deducted. 



In the case of this metal, it would have been manifestly im- 

 possible to collect the oxide formed by the combustion ; nor 

 was it practicable to ascertain the weight of metallic zinc which 

 had escaped oxidation, as an alloy was formed in every expe- 

 riment between the zinc and platina. To protect the platina 

 cup from being rapidly destroyed by the latter action, it was 

 even found necessary to place a thin sheet of platina below 

 the zinc, and this required to be renewed after every experi- 

 ment. For these reasons, no alternative remained but to 

 measure the oxygen consumed in each experiment. This was 

 effected by ascertaining, after the increment of temperature 

 had been observed, the volume of gas which had disappeared. 

 There was some difficulty in making this determination with 

 accuracy, but every possible precaution was taken to avoid 

 error. In the next two tables, M is the volume of oxygen 

 consumed. It was measured in a moist state. 



