16 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 54 



oxide, and weighed the water produced. The copper oxide was prepared 

 from absolutely piire electrolytic copper, and the hydrogen was obtained 

 from three distinct sources, as follows : First, from pure zinc and hydro- 

 chloric acid; second, by electrolysis, in a generator containing dilute 

 hydrochloric acid and zinc-mercury amalgam ; third, by the action of 

 caustic potash solution upon sheet aluminum. The gas was dried and 

 purified by passage through a system of tubes and towers containing 

 potash, calcium chloride, glass beads drenched with sulphuric acid, and 

 phosphorus pentoxide. No impurity could be discovered in it, and even 

 nitrogen was sought for spectroscopically without being found. 



The hydrogen was weighed in a glass globe holding nearly five litres 

 and weighing 570.5 grammes, which was counterpoised by a second globe 

 of exactly the same external volume. Before filling, the globe was ex- 

 hausted to within 1 mm. of mercury and weighed. It was then filled 

 with hydrogen and weighed again. The difference between the two 

 weights gives the weight of hydrogen taken. 



In burning, the hydrogen was swept from the globe into the combus- 

 tion furnace by means of a stream of air which had previously been 

 passed over hot reduced copper and hot cuprie oxide, then through potash 

 bulbs, and finally through a system of driers containing successively 

 calcium chloride, sulphuric acid, and phosphorus pentoxide. The water 

 formed by the combustion was collected in a condensing tube connected 

 with a U tube containing phosphorus pentoxide. The latter was fol- 

 lowed by a safety tube containing either calcium chloride or phosphorus 

 pentoxide, added to the apparatus to prevent reflex diffusion. Full 

 details as to the arrangement and construction of the apparatus are 

 given. The final results appear in three series, representing the three 

 sources from which the hydrogen was obtained. All weights are cor- 

 rected to a vacuum. 



.0048 



Second Series. — Electrolytic Hydrogen. 



.4112 3.6930 15.962 



.4089 3.6709 15.955 



.4261 3.8253 15.955 



.4197 3.7651 15.942 



.4144 3.7197 15.953 



Mean, 15.953, ± .0022 



