﻿T. B. Osborne — Higher Oxides of Copper. 339 



Oxygen continued to be evolved for some hours and the 

 precipitate was kept floating on the surface. After standing 

 twenty-four hours on ice, it had settled. A portion of the 

 solution containing this precipitate was drawn off and washed 

 with lime water. Under the microscope this precipitate ap- 

 peared perfectly homogeneous and with a decided pink tint. 

 The oxygen was determined with ferrous sulphate in 50 c. c. of 

 the solution containing the precipitate as before described, and 

 likewise the copper and the calcium. 50 c. c. of the clear solu- 

 tion were drawn off and found to be free from copper and the 

 calcium determined. By subtracting the calcium found in the 

 solution from that found in the solution plus the precipitate, 

 the calcium of the precipitate was found. The error due to 

 the amount of the solution displaced by the precipitate was too 

 small to make any serious difference in the results. 



In this way I found 



In sol. 4- precipitate 





Solution alone. 



CuO = -1869 grams 





none 



CaO = -1798 





*li04 grams. 



= -0108 





none 



Precipitate. 



Weight. 





Weight. Katio. 



CaO in p. p. + sol. *1798 



CuO 



— -1869 = 23-54 



CaO in sol. -1104 



CaO 



= -0694 = 12-39 



CaO in p. p. -0694 



O 



= -0108 = '0675 



The oxygen found in this case is much lower than in the other 

 analyses given, but from the wide variations in the former 

 results its determination cannot be considered more than a 

 qualitative test. The calcium it will be seen is in nearly a 

 ratio of two atoms of copper to one of calcium, but I consider 

 this single analysis by no means evidence of anything more 

 than the presence of calcium in the compound and is so far as 

 I can find the only direct evidence that copper ever acts as an 

 acid. 



The rest of the precipitate from which this sample was 

 taken for analysis was allowed to stand a week packed in ice. 

 It grew gradually more and more dense and of a brighter pink, 

 until finally it was of a very brilliant rose red, and formed in 

 places on the sides of the flask very thin layers of a dazzling 

 crimson. In the hope of being able to analyze this as Kriiss 

 did the dioxide of copper, I arranged a filter packed in ice and 

 covered with a bell jar communicating with the air through 

 potash tubes, so as to keep out all carbonic acid, but before I 

 could wash the precipitate it began to turn blue next to the 

 paper. The middle portions were dried in the cold over sul. 

 phuric acid and remained quite pink when dry, but the decom 



