140 E. W. Morley — Amount of Moisture in a Gas. 



Art. XXI. — The amount of moisture which Sulphuric Acid 

 leaves in a Gas; by Edward W. Morley. 



Berzelius and Dulong,* about 1S20, and Erdmann and 

 Marchand.f about 1842, employed calcium chloride in deter- 

 mining the atomic weight of oxygen, and were probably not 

 aware that it leaves unremoved a comparatively large amount 

 of water. Dumas,;}; in 1842, and Pettenkofer,| in 1862, men- 

 tioned as well known, the fact that calcium chloride will not 

 dry a gas as completely as sulphuric acid. FavreJ in 1844 > 

 proved that sulphuric acid at ordinary temperatures dries a gas 

 so completely that neither sulphuric acid at —17° C. nor phos- 

 phorus pentoxide will absorb a sensible quantity of moisture 

 from 40 liters of gas, nor even from volumes "bien plus con- 

 siderables." He also attempted*[ in a most ingenious way to 

 determine whether a gas dried by either of these agents was ab- 

 solutely dry. He passed air dried as perfectly as possible over 

 red-hot copper, and then again through a drj'ing tube. In one 

 experiment, 148 liters of air were reduced to 117 liters of 

 nitrogen, and deposited *0025 gram of wuter; in the other, 

 110 liters of air were reduced to 87 liters of nitrogen, and de- 

 posited "0015 gram of water. Hence he concluded that a liter 

 of gas dried by sulphuric acid or phosphoric oxide contained 

 not more than -00006 or '00008 gram of water. 



He also proved"* that no other force than the tension of the 

 vapor of water causes it to be retained in certain gases. Favre 

 further proved, ff as did Regnault in 1845,^ that drying tubes 

 of no large dimensions are required to utilize the whole drying 

 power of the drying agent with which they are filled. In 1864 

 and again in 1865, Fresenius§§ published experiments, which, 

 if they were affected by no source of error at that time unsus- 

 pected, would show that sulphuric acid leaves one or two 

 deci milligrams of moisture in a liter of gas. But in 1876, 

 DibbitslH published experiments in which precautions were 

 taken against the leakage of moist air through caoutchouc con- 

 nectors, which showed that 308 liters of air dried by sulphuric 

 acid at ordinary temperatures gave up but 7 decimilligrams of 

 moisture to phosphorus pentoxide. 



Dibbits also proposed a method for solving the remaining 



* Ann. Chim. Phys., 2d Series, vol. if, p. 388. 



f Journ. Prakt. Chemie, vol. xxvi. p. 464. 



1 Ann. Chim. Phys., 3d Series, vol. viii. pp. 193. 210. 



8 Lieb. Ann. Supp., vol. ii, p. 29. 



I Ann. Chim. Phys., 3d Series, vol. xii. p. 223. «j Ibid., vol. xii, p. 225. 



** Ibid., vol. xii, p 227. §S Zeitschr. Anal. Chem., vol. iv, p. 180. 



ff Ibid., vol. xii, 228. ||fl. Zeitschr. Anal. Chem., vol. xv, p. 160. 



jjlbid., vol. xv, p. 152. 



