EIvISHA MITCHELL SCIENTIFIC SOCIETY. 3 



ment. Water was poured into the flask and the whole 

 quickly filtered, and the copper remainingf unattacked 

 was then cleaned as well as possible by rubbino-, dried 

 and weig'hed. The copper, as sulphate, was determined 

 by electrolysis. The residue was burned in a porcelain 

 crucible, treated with concentrated nitric acid, ig-nited 

 and weig-hed as copper oxide. Sulphur was determined 

 by weig^liing- a dried portion of the residue, treating with 

 carbon disulphide, and the loss in weig-ht taken as sul- 

 phur. 



Primary Reactions. M}^ experiments showed that 

 the first of the primaryTreactions predominated when 

 copper was treated with concentrated sulphuric acid at 

 different temperatures (0"-27O" C.) At the highest 

 temperature it was found that that reaction alone took 

 place, but at all lower temperatures the second primary 

 reaction also occurred. The proportion of the material 

 following' the second equation increased from 0" to 100" 

 C, and then decreased to 270" C, when there was no 

 longer evidence of an}^ such reaction, that is, no black 

 residue was formed. 



At the lower ^temperatures, under 100" C, onl}- the 

 two primar}^ reactions seemed to take place; at the 

 higher temperatures the secondar}^ reactions if the 

 action were 'prolonged, frequently set in, complicating 

 matters as far as quantitative determinations were con- 

 cerned. If the time of action were shortened evidence 

 of the occurrence of the primary reactions alone was 

 found. Having an excess of" copper "present was also 

 necessary, because as soon as all the copper had been 

 attacked the secondary reactions set in at once. 



The conditions seemed most favorable for the forma- 

 tion of the insoluble residue at the temperatures from 

 100" to 130" C. as may be seen from the table. The 



