OF ARTS AND SCIENCES. 



"Weight of tube before connection 

 » after " 



279 





Grams. 



= 55.1920 

 = 55.1922 



The temperature changed from 15°. 7 to 16°.8 between the two 

 weighings, involving a correction of — .OOUl to the latter weight. The 

 tube therefore gained only the tenth of a milligram, showing the cupric 

 oxide to have reached a constant hygroscopic condition. 



During the ensuing reduction with carbon monoxide, the drying 

 tube was again connected with the apparatus. Before the last weigh- 

 ing of the tube, all carbon dioxide was expelled by pure air. The 

 tube weighed 55.2177 grams, showing a gain of 0.0255 gram, or 

 0.017 per cent of the weight of the cupric oxide. 



Two similar experiments led to like results. 



Ueduction of Clpric Oxide by Carbon Monoxide. 



Nothing in these results proved that the water was not formed from 

 the oxidation of hydrogen or hydrocarbons possibly contained in the 

 carbon monoxide, and indeed further examination showed that it 

 originated from this source. The metallic copper from the last ex- 

 periment was immediately oxidized by a stream of pure dry air, and 

 once more reduced with carbon monoxide. Four litres of gas required 

 to reduce the partially reoxidized copper yielded 19.3 milligrams of 

 water. Since this water could not possibly have come from the 

 oxidized copper, it must have been solely obtained from impurities in 

 the carbon monoxide. The quantity closely agreed with the amount, 

 18.3 milligrams, which one would have expected to find from the 

 volume of gas used, upon the basis of previous results. Considerii.g 

 the fact that the volumes of gas were not very accurately measured, 

 the difference is not greater than the experimental error. Hence 

 it may be safely concluded that the carbon monoxide contained about 

 four one-hundredths of a per cent of hydrogen by weight, but that the 

 cupric oxide retained no appreciable amount of icater at a red heat. 



