80 DETERMINATION OF COPPER. 



cipitated by the battery, using two Buuseu cells, coupled zinc to zinc, 

 and carbou to carbou. The following results were obtained : 



Per cent. 

 2. 7081 grams gave 0. 3507 Cu=12. 95 

 2. 7423 grains gave 0. 4355 Cu=15. 88 

 2. 1279 grams gave 0. 3106 Cu=14. 59 



Average 14.47 



Multiplying this by the Hampe constant, we have 24.44 as the per 

 cent, of CiijjO that should be present according to his formula, but the 

 direct oxygen determination shows only 4G.67 per cent, to be present. 



If we assume that all the copper present as Cu 2 in the metal was 

 transformed into the insoluble nitrate by the action of the AgN0 3 we 

 have 14.47 per cent. Cu= 16.29 per cent. Cu 2 0, which is sufficiently close 

 to 16.67 per cent., as found by the O determination, to warrant the as- 

 sumption as being true. 



Thirty grams of the above material were mixed with unequal weight 

 of the pure copper, and the mixture thoroughly melted, when it was 

 removed from the muffle. 



The method of examination was enlarged and slightly modified in 

 certain points suggested by the work upon the first sample, with the 

 hope of obtaining more closely concordant results. 



The drillings were crushed fine and thoroughly mixed, then thewliole 

 was spread out and marked off into twelve squares, and four of these 

 squares were taken for each analysis. Especial attention was given to 

 securing uniformity in the samples weighed out, since some of the 

 differences in the first set of results are due to differences in the sam- 

 ples taken. 



The silver separated by the reaction was determined, and the iron 

 remaining in the solution after the separation of the copper was also 

 determined. The following results were obtained : 



O Fe Insol. Cu ' 



Percent. Percent. Percent. Percent. 



1.504 trace. 11.042 



1.491 11.300 



1.475 0.00-2 10.840 



1.493 11.06 



Dividing the total amount of silver precipitated, 29.6207 grams, by 

 the total amount of material taken 9.6662 grams, we nave 3.0643 grams 

 as the amount of silver precipitated by 1 gram of the material. 



Theoretically, 1 gram of a mixture containing 80.67 per cent, copper 

 and 13.33 per cent. CujO should precipitate 3.1544 grams silver, thus 



