OF ARTS AND SCIENCES. 285 



funnel tube in such a manner that it at once attacked the oxide. 

 A short piece of glass rod in the large bulb together with constant 

 agitation prevented the formation of cakes. 



In the most carefully performed experiments the sulphuric acid as 

 well as the water was boiled, but repeated trials showed this precau- 

 tion to be unnecessary. In one blank experiment even ordinary dis- 

 tilled water and sulphuric acid evolved only about one thousandth of 

 a cubic centimeter of gas, while boiled water, which was invariably 

 used in tbe determinations, gave no trace even of the finest bubbles 

 with unboiled sulphuric acid. 



Tlie gas evolved on the solution of the cupric oxide was collected 

 chiefly in the largest bulb. The amount collected in the smaller bulbs 

 decreased in proportion with the increase of distance from the first, 

 and only a very small amount was lost through the open mouth. The 

 gas was measured in the right hand graduated tube, or drawn off for 

 analysis through a rubber connector attached at this end. 



The apparatus was afterwards modified to avoid the slight loss 

 through the open mouth. It then consisted of a small stoppered flask 

 with two concentric funnel tubes, and a delivery tube closed with a 

 rubber connector and a pinch cock. When the whole apparatus had 

 been filled with boiled water through the larger funnel tube, the 

 smaller one was filled with pure sulpiiuric acid and quickly placed 

 inside the larger one. Upon inclining the flask, it is evident that the 

 loss of minute bubbles must have been reduced to a minimum, while 

 the small annular openin": between the funnel tubes was quite suffi- 

 cient to allow the escape of the displaced water. The gas was readilv 

 drawn otf for analysis through the delivery tube, which just penetrated 

 the smooth rubber stopper. 



Many varieties of cupric oxide were examined. Material obtained 

 from the carbonate, or by precipitation from the sulphate, evolved little 

 or no gas, thus affording an admirable proof of the purity of the acid 

 and water. Check experiments with such material were accordingly 

 made from time to time. Other circumstances being equal, the purer 

 the oxide, the more gas was evolved. Solid impurities, such as alka- 

 line salts, seemed partially to prevent the occlusion. 



The volumes of gas are given without any correction, the temper- 

 ature and pressure remaining so nearly constant that the observations 

 are not recorded. The following table is intended only as a basis of 

 rouah comparison. The gas was frequently analyzed, with results 

 similar to those tabulated above. The results confirm those of the 

 preceding series. 



