88 CHEMICAL PBuPERTEES OF MINER AXS. 



required, and sometimes the use of soda. With borax iron 

 gives a bead with the oxidizing flame which is yellow while 

 hot, but colorless on cooling, and which in the reducing flame 

 becomes bottle green. 



Cobalt. — Minerals containing cobalt afford, with borax, a 

 beautiful blue bead. If sulphur or arsenic is present it should 

 be first roasted off on charcoal. 



Nickel. — In the oxidizing flame with borax, the bead i<? violet 

 when hot, and red-brown on cooling. In the reducing flame 

 the glass becomes gray and turbid from the separation of metal- 

 lic nickel, and on long blowing, colorless. The reaction is ob- 

 scured by the presence of cobalt, iron, and copper. 



31anganese. — With borax in the oxidizing flame, the bead is 

 a deep violet-red, and almost black if too much of the mineral 

 is used. To see the color examine by transmitted light. With 

 soda in the same flame the opaque bead is bluish green. 



Chromium. — With borax, both in the oxidizing and reducing 

 flame, the bead is bright emerald green. 



Titanium. — Titanium oxide with salt of phosphorus on 

 platinum wire in O.F. dissolves to a clear glass, which, if 

 much is present, becomes yellow while hot and colorless on 

 cooling; but in R.F. the hot globule obtained in O.F. reddens 

 and assumes finally a beautiful violet color. On charcoal with 

 tin the glass becomes violet if there is not too much iron 

 present. 



Zinc. — Zinc and some of its compounds when heated cover 

 the charcoal with zinc oxide, which is yellow while hot, but 

 white on cooling ; and this coating, if wet with cobalt solution 

 and then heated, assumes a fine yellowish-green color which 

 is most distinct when cold. 



.Lead, copper, tin, silver, when characterizing a mineral, give 

 with soda in the reducing flame minute metallic globules, which 

 are malleable, or may be cut with a knife ; they can be distin- 

 guished by their well-known physical properties. When two 

 or more of these metals occur together, or iron is also present^ 

 the globules consist usually of an alloy of the metals. 



Lead. — When the mineral is treated with soda on charccal 

 in the oxidizing flame, the yellow oxide coats the charcoai 

 around the assay. 



Copper. — The flame is colored, in most} cases, bright green. 

 With borax or salt of phosphorus in the reducing flame the 

 bead is red. In the oxidizing flame the bead is green when 

 hot and becomes blue or greenish blue on cooling. 



Mercury. — Heated in the closed tube with soda, a sublimate 

 of metallic mercury covers the inside of the tube. 



