Ml'. A. Dick^s Contributions to the Metallurgy of Cojyper. 413 



when dry copper was operated upon, though in a less degree, 

 but still sufficient to render the method inaccurate. 



(c). By melting a known weight of copper wire under charcoal 

 and estimating the oxygen as loss. — Even when the heat was very 

 slowly applied, the satiic spirting sometimes took place, in con- 

 secjuence of v/hich the charcoal in the crucible, after the experi- 

 ment, was always washed by decantation from any globules which 

 had been projected into it. If these were weighable, they were 

 added to the large button. The loss which the copper under- 

 went by this treatment was estimated as oxygen. That the 

 metal does not take up an amount of carbon sufficient to in- 

 terfere materially with the results, will be shown further on. 

 Two diflFerent samples of wire were operated upon in the follow- 

 ing determinations of the amount of suboxide present in them, 

 which for the sake of convenience of reference will be called A 

 and B. A was thicker wii'e than B. 



A, 218"24 grs. lost, by melting under charcoal, 0'76 gr., 

 which corresponds to 3" 10 per cent, of suboxide. 



B, 176"48 grs. lost, by meltiug under charcoal, 0-635 gr., 

 which corresponds to 3'21 per cent, of suboxide. In another 

 experiment, 200'68 grs. lost 0'765 gr., which cori-esponds to 3'37 

 I)er cent, of suboxide. 



According to Karsten, the amount of suboxide in tough pitch 

 copper is under 2 per cent. ; but these experiments show that it is 

 pi'esent in larger quantity in the specimens met with in England. 



Although in the preceding calculations the oxygen has always 

 been estimated as present as suboxide, it is not maintained that 

 the whole of it exists in that state in the copper ; because com- 

 mercial copper contains small quantities of various metals, gene- 

 rally lead, or antimony, or both, which may occur in it as oxide 

 and not as metal. For this reason the quantity of oxygen found 

 has always been given, as well as the amount of suboxide it corre- 

 sponds to, supposing it to be combined with copper only. In 

 the copper wire previously alluded to as A, 0*17 per cent, of lead 

 was found by dissolving a known weight of it in nitric acid, 

 evaporating the solution to dryness with sulphuric acid, and dis- 

 solving the anhydrous sulphates in water. The sulphate of lead 

 was then collected on a filter, washed with water, and ignited 

 with the usual precautions. This wire contained no anti- 

 mony. Its specific gravity was 8'853. In the sample referred 

 to as B, 0*29 per cent, of lead was found by the same treatment, 

 and 0*31 per cent, of antimony: the antimony was separated 

 from the copper by digesting the mixed sulphides in sulphide of 

 ammonium containing excess of sulphur. The specific gravity 

 of this specimen was 8-733. In a sample of sheet copper, 0-27 

 per cent, of lead was found, but no antimony. All of these 



