Combination of Bodies -jcith Oxygen. 325 



would not have interfered with the result if the experiment 

 had been performed at a teniperatm-e sii})erior to 100° C. If 

 we assume the latent heat of sjeam at 20"^ to be 611 units, the 

 heat evolved by the condensation of 1'125 grni, steam will be 

 687, which, taken from 4226, leaves 3539 for the true heat i\\.\e 

 to the chemical combination of 1 grm. oxygen with hydrogen ; 

 and a similar correction may be applied to the other numbers. 



Carbonic Oxide and Oxj/gcn. 



The carbonic oxide was prepared by the action of sulphuric 

 acid on oxalic acid, the carbonic acid formed during the pro- 

 cess being absorbed by a solution of caustic potash. To en- 

 sure complete combustion, an excess of oxygen was always 

 employed. The residual gas, after being deprived of its car- 

 bonic acid, was measured, and the original volume of carbonic 

 oxide was deduced from the reduction of volume of the mix- 

 ture after combustion. As before, I have endeavoured to 

 correct the volumes actually found for the errors inevitable to 

 eudiometric experiments performed over water. A small 

 allowance was also made for the air extracted from the water 

 (about 20 grms.), which was always left in the inner vessel. 



In the subsequent tables, M designates in cubic centimetres 

 the volume of the gaseous mixture before combustion ; Mc, the 

 same corrected for absorption by water during the transference 

 from one vessel into another, &c. : II, the volume of the residue 

 (consisting chiefly of the excess of oxygen) after combustion 

 and removal of the carbonic acid ; Re, the same corrected. 

 The other letters have the significations already explained. 



2. 3. 4. 



362-r) c.c. 362-0 c.c. 361*8 c.c. 



361-6 c.c. 361-1 c.c. 360-9 c.c. 



24. 2 c.c. 23-3 c.c. 23-9 c.c. 



24-3 c.c. 23-4 c.c. 24'0 c.c. 



30-09 in. 30-08 in. 3004 in. 



15°- 8 15°-5 15°'7 



0°-9 0°-9 I°-0 



2°-132 2°-151 2°-167 



2°-137 2°156 2°-172 



272-0 grms. 27 1 '0 grms. 266*6 grms. 



27*9 grms. 27*7 grms. 27*7 grms. 



The heat evolved during the combustion of one litre of dry 

 carbonic oxide gas, measured at 0° and under a pressure of 

 29*92 inches, is therefore — 



1. 2. 3. 4. 



3063 3053 3060 3051 



