1888.] PROCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 77 



jHAMPE'S METHOD OF DETERMINING Cu.O IN METALLIC COPPER. 



BY-^FRED. P. DEWEV. 



Having occasion to make a series of determinations of Cu 2 in cop- 

 per in some suites of specimens in the National Museum, representing 

 the process of refining pig copper to tough pitch metal, the Hampe* 

 method was selected as being the best so far proposed. 



The method is based upon the reaction between Cu 2 and AgN0 3 , 

 discovered by H. Eose,t and consists in treating the material to be 

 analyzed with neutral solution of AglST0 3 in the cold for several days, 

 when, according to Hampe, the following reaction takes place between 

 Cu 2 and AgN0 3 : 3Cu 2 0+ 6AgN0 3 + 3H 2 O=40uO, N 2 5 3H 2 0+ 

 2CuX 2 6 + CAg, whereby two-thirds of the copper is converted iuto an 

 insoluble basic nitrate, and remains with the silver precipitated, while 

 one-third goes into solution as normal nitrate. On filtering off the 

 residue and determining the amount of copper contained in it, we 

 can easily calculate the percentage of Cu 2 in the metal. The follow- 

 ing series of results, calculated on Hampe's formula: 



showed the method to be quite satisfactory as far as the agreement 

 of duplicates goes. 



Kaminelsbergf investigated the matter slightly and found that only 

 28.80 per cent, of the copper went into solution. He assigned the 

 following somewhat unusual formula to the insoluble nitrate: CiijoKg 

 ,0 35 . Hampe§ has replied that Eammelsberg's investigation was too 

 limited, being confined to a single determination, and proper precau- 

 tious were not taken, while his own work was very elaborate and ex- 

 tended, and his deductions based upon many determinations. Ram- 

 melsberg used pure Cu 2 'J; Hampe used both Cu 2 Oj| and metallic cop- 

 per containing a known amount of 0u 2 O, but with the latter material 

 the amount of Cu 2 U present was so small that the unavoidable errors 

 of determination would completely mask the difference between 28.8 

 per cent, and 33.33 per cent. 



Since, however, in the actual use of the method for determining Cu 2 

 in copper there is always a large excess of uucombined copper present 



* Zeit. f. Berg-. Hiitten- a. Salinen-Wesen, 1873, Vol. XXI, p. 218. 



tPogg. Ann., Vol. ci, p. 513. 



tBer. Deutsch. Chein. Ge., 1877, p. 1780. 



§ Zeit. f. Anal. Chem., Vol. xvn, p. 127. 



|| Hampe's CujO always contained CuO. 



