282 PROCEEDINGS OF THE AMERICAN ACADEMY 



was condensed by the substance. Frankland and Armstrong* found in 

 1868 that cupric oxide prepared from the nitrate contains both carbonic 

 acid and nitrogen. Hilditch f states that oxygen gas is occluded by 

 cupric oxide at a red heat, and estimates the effect of this impurity upon 

 the atomic weight of oxygen, without, however, adducing any experi- 

 mental data. More recently Morley t has found that cupric oxide 

 slowly gives off a gas in vacuum. It is a noticeable fact that cupric 

 oxide is almost as serviceable as platitium in preventing bumping 

 during ebullition. 



The simplest and surest method for the liberation of an occluded 

 gas is completely to dissolve the cupric oxide in a pure acid. It is by 

 no means certain that indefinite heating in a vacuum would accomplish 

 the end in view. Several pieces of apparatus more or less suitable 

 for the j^resent purpose were devised in succession, and by their means 

 it was proved that some varieties of cupric oxide occlude important 

 quantities of aeriform material. Nearly fifty determinations were 

 made. 



According to the first method a tube of the shape shown in Fig- 

 ure 1 was filled at the end with freshly ignited cupric oxide, and in the 

 middle with pure boiled sulphuric acid. When the whole had been 



¥lG. 1. 



completely exhausted by means of a Sprengel pump, the liquid was 

 allowed to come in contact with the solid, and the gas evidently set 

 free was pumped out and measured. But the action was of course 

 only a very superficial one, and no amount of long standing or violent 

 shaking could accomplish a more complete change. Three experi- 

 ments indicated that at least a small amount of gas, which appeared to 

 be chiiifly nitrogen, was set free. Since it was difficult to decide how 

 much cupric oxide had been combined, the method was abandoned. 



* Cliem. Soc. Journ., XXI. 89,03 (1868). 



t Chem. News, XLIX. 37 (1884). 



t Am. J. Sci., XLI. 231, March, 1891. 



