RICHARDS. — RETENTION AND RELEASE OF GASES. 403 



would constitute a research of some magnitude in itself. For present 

 purposes the above will suffice. 



Two forms of apparatus were used for determining the amount and the 

 composition of the occluded gases. The first was identical in every 

 respect with the most convenient of the three forms described in the origi- 

 nal paper.* It consists of several bulbs blown in the bend of a glass tube 

 bent at a right angle. One arm of the tube is temporarily closed by a 

 stopcock, (not shown in the cut in the original paper, although men- 

 tioned in the letterpress,) and in this arm the gas, evolved in the bulbs 

 by the solution of the cupric oxide in acid, is collected and measured 

 over boiled water. "When necessary the gas may be readily removed 

 through the stopcock at the end of the arm ; if a gas burette is attached 

 here, of course the gas may be analyzed at once without further trouble. 



For most of the experiments, however, Scott's modification of another 

 of the original forms f was used. The mode of operating this apparatus 

 was essentially similar to the method just described, although the bent 

 tubes and bulbs are replaced by a small flask and funnel-tube. Scott's 

 addition of a side tube to remove the displaced water distinctly increases 

 the convenience and accuracy of the contrivance. For the details his 

 paper should be consulted. 



The two pieces of apparatus give identical results, which cannot be far 

 from the truth. If at all in error the amount of gas collected must 

 be too small rather than too large, for both oxygen and nitrogen are 

 slightly soluble in water. This consideration was verified by fusing 

 a specimen of oxide (another portion of which had been repeatedly 

 analyzed in the usual fashion) with carefully prepared acid potassic 

 sulphate in a Sprengel vacuum. The amount of gas evolved by this 

 treatment was slightly greater, but only slightly greater than the amount 

 obtained by the usual method, and its composition was essentially identi- 

 cal with that of the gas collected over boiled water. Since the question 

 is one of relation, rather than of absolute values, the method iHvolving 

 the use of aqueous solutions was adopted because of its far greater ease 

 of execution. Pains was taken to have the conditions of the solution 

 of the oxide always as nearly as possible the same, so that the results 

 should be strictly comparable with one another. 



The first object of the present paper is to show more clearly the rela- 



* These Proceedings, XXVI. 284. (1891.) 



t These Proceedings, XXVI. 285, middle of page. 



