H. L. Wells and 8. L. Penfield — Gerhardtite, etc. 57 







Found. 





Calculated for 





I. 





II. 



6Ag + 4CuO.N 2 6 .3H 2 0. 



Ag 



57-66 



57-60 





57-46 



CuO 



28-23 



28-24., 



....66-68 



28-17 66.22 



H 2 





4-62. 



...10-91 



4-79. ..11-26 



NA 





9'49. 



...22-41 



9-58 22-52 





99-95 



100-00 



100-00 100-00 



Graham* states that the basic cupric nitrate will withstand a 

 temperature near that of melting lead without decomposition. 

 We find, on the other hand, that it begins to decompose when 

 heated to 180-200°, blackening and giving off both water and 

 nitric acid. The product made in sealed tubes and that made 

 by Casselmann's method were both subjected to this experi- 

 ment with like results. 



The empirical formula for the compounds under considera- 

 tion is H 6 Cu 4 N 2 ;13 or H 3 Cu 2 N0 6 . Cookef developes this 

 to (HO) 3 , (Cu0 2 H) 3 , Cu0 3 , viii, N 2 0. A simpler formula is 

 H(H0Cu) 2 N0 4 . The latter has the argument in its favor 

 that some other basic nitrates can best be formulated as deriva- 

 tives of the hypothetical acid H 3 N"0 4 (corresponding to H 3 P0 4 ), 

 but the union of hydroxyl to both acid and basic radicals 

 is possibly an objection to it as well as to Cooke's symbol. 



It is an interesting fact that the monoclinic (?) mineral tagilite 

 has the formula 4CuO .P 2 5 . 3H 2 0, exactly corresponding to 

 the nitrate. 



Method of analysis. 



Owing to the small quantity (less than '8 gram) of the native 

 nitrate at our disposal, it was important to use a method which 

 would give a complete analysis on a single sample. The 

 apparatus having been set up and tested, it was found to be so 

 satisfactory and convenient that it was used for the other 

 analyses given in this article. 



The substance was ignited in a boat in a current of pure, 

 dry C0 2 in a combustion-tube. The CuO remaining in the 

 boat was weighed. The gases passed over a hot roll of 

 copper gauze, then through a weighed calcium chloride tube, 

 which absorbed the water, into an azotometer containing a con- 

 centrated solution of potassium hydroxide where the nitrogen 

 was measured. 



The carbon dioxide was made from crystallized calcite. 



The removal of the air from the apparatus before the ignition 



and the collection of the nitrogen afterwards was accomplished 



by passing the C0 2 only about J hour in each case. The C0 2 



in the CaCl 2 tube was replaced by dry air before weighing. 



Laboratories of Chemistry and Mineralogy, } 

 Sheffield Scientific School, Juno 6, 1885. f 



* Loc. cit. f Chemical Philosophy, 3*79. 



