460 Capt. W. A. Ross on Pyrology, or Fire Analysis. [June 20, 



Sulphur. 



47. If sulphur be added to aP bead as described in paragraph 45, and 

 then treated with a P. P., the curious result of chromatic reactions exactly 

 similar to those of copper, i. e. green hot and blue cold, is produced. The 

 addition of plumbic oxide heightens this effect ; and the resulting blue bead 

 is quite indistinguishable from a cupreous one placed alongside. 



Nitrogen. 



48. If a P bead be constantly dipped in the strongest possible solution 

 of ammonia or in concentrated nitric acid, and immersed as often in a H. P., 

 as fig. 4, numerous black specks will be found on the surface like carbon, 

 but much more difficultly burned away. After a time these appear to 

 combine with the metallic-looking film which is formed by the H. P., and 

 the substance is then by no means easily volatilized. The glass thus im- 

 pregnated with nitrogen will be found to be clear hot, yellow and gelatinous 

 on cooling, therein exactly differing from those of the alkalies, the volatizable 

 oxides, and some of the earths, which are yellow hot and clear cold. 



Oxide o f Copper in P. 



49. If we add pure cupric oxide to a weighed P bead, and treat it with 

 a P. P. (2, fig. 1), we find that it takes exactly 5 per cent, of the whole bead 

 to produce distinctly the peculiar blue of copper. The glass must be care- 

 fully held in the position indicated, as O. P. w T ould leave it green * : 5 per 

 cent., then, maybe taken to represent the standard of copper for quantita- 

 tive measurements as described in paragraph 44 ; but in such cases as Cu 

 pyrites, where there is a chromatic interference of other oxides, something 

 more is necessary. 



50. It requires one third more than the weight of a P glass in sulphur 

 to give it the cupreous blue appearance referred to in paragraph 47 ; that 

 is to say, a 50 mgrs. glass of P requires 75 mgrs. of flour sulphur added by 

 degrees for that purpose. But it is found that by treatment in H. P. the 

 flour sulphur, when it assumes the metallic appearance referred to in para- 

 graph 17, is reduced to one fifth of its bulk ; so that 75 mgrs. of flour sulphur 

 only represent 15 mgrs. of the allotropic sulphur, and 15, therefore, is taken 

 as the standard of sulphur. It has also been ascertained that 16 mgrs. per 

 cent, of oxide of copper, when added to this sulphurous P bead, cause it to 

 remain green even after a P. P., probably on account of the disposal by the 

 sulphur of the superfluous oxygen ; 16, therefore, is taken as the equivalent 

 standard of copper to sulphur. If we now add oxide of lead to the green 

 cupreo-sulphurous P bead thus produced, we shall find that, on the addition 

 of 24 mgrs. per cent, the glass will again appear blue ; 24, therefore, is 

 taken as the equivalent standard of PbO to sulphur. 



51. Copper pyrites dissolved in a P glass has a dirty green appearance, 

 without any shade of blue in it, after a P. P. 



* This is not the case with borax or microcosm ic salt. 



