[N8TRUMENTS AM) CHEMICAL Ti.STS 575 



nickel. The S. Ph. bead is reddish yellow while hot, yellow on 

 cooling in both flames. Small quantities of cobalt and copper will 

 interfere with the head reactions of nickel. Cobalt and nickel are 

 closely associated in minerals, generally in sulphides and arsenides; 

 in this ca>e the mineral is fused in the K. F. to a round globule and 

 a large proportion of the arsenic and sulphur is roasted off. A piece 

 of borax double the size of the globule is placed beside it on coal 

 and treated with the O. F. a short time, when the color of the borax 

 i ol iserved. If the globule contains iron, nickel, cobalt, and 

 copper, they will be oxidized not all at once, but one at a time in the 

 order mentioned, each in turn imparting its characteristic color to 

 fresh charges of borax. The amount of each metal present can 

 be roughly judged by the number of fresh charges of borax it takes 

 to absorb it. If it takes only two or three beads to remove the 

 cobalt, it is present as a minor component of the arsenide and after 

 the blue of cobalt bas disappeared, nickel will oxidize and color 

 the borax reddish brown. 



Illustration. Use a fragment of niccolite, NiAs, which always 

 contains some cobalt, about the size of a rice grain and fuse it on 

 coal in a hot R. F. to a round globule ; place some borax beside it 

 and treat with the O. F. The two globules will roll around under 

 the flame in contact, but will remain quite distinct; any cobalt in 

 the arsenide will be oxidized by the 0. F. and be absorbed by the 

 borax. Carefully pick the arsenide globule out of the borax, with 

 the steel end of the forceps, and place to one side for future treat- 

 ment ; while still hot pull the borax out with the forceps in a thread ; 

 it will be blue from cobalt, or if opaque, some of it is dissolved with 

 fresh borax on wire and the color observed. Return the arsenide 

 globule to the coal after cleaning the cavity of all old borax and 

 repeat the treatment with a fresh supply. After several treatments 

 all cobalt will have been oxidized and the borax will become red- 

 dish brown from nickel. 

 \jlron, Fe. Atomic weight, 55.84. Fusing point, 1600 C. 



a. Bead reaction. Oxides of iron when dissolved in the borax 

 bead in O. F. yield, while hot, a light yellow to dark red color 

 according to the amount present ; this becomes colorless, or if well 

 charged, yellow when cold. In R. F. the bead is green, and if well 

 charged a dirty yellowish green on cooling; if reduced beside tin 

 on coal, this bead is a clear bottle green. The moderately charged 

 S. Ph. bead in O. F. is yellowish red while hot, becoming yellow 

 and finally colorless when cold. In R. F. the well-charged bead 



