OP ARTS AND SCIENCES. 



253 



water and alcohol, and dried at 103°. The crucible was supported 

 upon a platinum triangle in the interior of a large breaker, and was 

 covered by a watch glass into 'which was fused the positive electrode. 

 The wires conducting the current into the beaker were of platinum. 

 The whole apparatus was covered with a large watch-glass, which 

 effectually excluded impurity. Several times before the conclusion 

 of the electrolysis the drops adhering to the inner watch-glass were 

 washed back into the crucible by means of apparatus especially 

 adapted for the purpose. After the maintenance for 120 hours 

 of a weak current,* the electrolysis was interrupted, and every trace 

 of the acid iu the crucible was washed as rapidly as was consistent 

 with scrupulous care into a large platinum bottle. The crucible was 

 then washed with pure alcohol, dried at 103°, and finally weighed. 



Crucible + Cu before electrolysis (Bar. = 767 ; t° = 20°) 

 + additional Cu after (Bar. = 750 ; t° = 20°) 



Apparent weight of copper 



Correction for change in temperature and pressure 

 " to vacuum 



True weight of copper in vacuum 



Percentage of copper in CUSO4 . 5 HgO 



" CUSO4 dried at 255° 

 " " " " dried at 250° (Hampe) 



" " « " dried at 365° 



Grams. 



= 36.12120 

 = 36.90000 

 = 1).77880 

 = + .00007 

 = — ■00001 

 = .77886 



Per Cent. 



= 25.452 



= 39.744 



= 39.725 



= 39.811 



Further comment here is unnecessary. 



The earlier experiments had already shown approximately the 

 equivalent ratio of sodic carbonate to copper. Accordingly a very 

 little less than the amount of sodic carbonate corresponding to the 

 data above was carefully weighed out from the second sample of this 

 material, and the salt was ignited at a dull red heat until constant 

 in weight. f 



Weight crucible -f- NaoCOg 



" " alone 



(( 



sodic carbonate in air 



" " in vacuum (Sp. gr. 



Grams. 



= 21.60095 



= 20.30260 



= 1.29835 



2.466) = 1.29880 



* Tliese Proceedings, XXV. 202. 



t See description of sodic carbonate, page 247 of tliis paper. 



