574 MINERALOGY 



until all water is driven off, then in a hot R. F., holding the coal 

 close up to the burner and using the blue portion of an 0. F., which 

 is reducing. Note the coat is quite yellow while hot and is sur- 

 rounded by the bluish border which serves to distinguish a coat 

 of this color and position from an ash. After cooling, the coat will 

 be white. Moisten with cobalt solution and heat carefully in an 

 O. F. so as not to blow the coat off ; let cool, when the coat will be 

 grass-green, at least in spots. If the green does not appear, the 

 assay is heated in the R. F. to drive off a little zinc ; let cool and the 

 green color will appear. 



Manganese, Mn. Atomic weight, 54.93. Fusing point, 1245 C. 



a. Bead reactions. Oxides of manganese when dissolved in 

 either the borax or S. Ph. bead yield in 0. F. an amethyst or violet- 

 red color, which becomes colorless in R. F. Small charges 

 should be used at first, as very little manganese will yield an opaque 

 bead reducing in R. F. with difficulty. The color is much lighter 

 in S. Ph. than in borax, and as some silicates are not decomposed in 

 S. Ph., borax will therefore yield the better results. 



6. Soda and niter test. Any compound of manganese when 

 fused with soda on platinum wire in O. F. and again fused with a 

 small grain of niter in the O. F., if manganese is present the bead 

 will be green, bluish-green, or a dark opaque blue according to the 

 amount of manganese present. This is a very delicate test; 

 amounts as low as .1 per cent, can be easily detected. The color 

 is due to the formation of sodium manganate, Na2MnO4. 



Illustration. Use any compound of manganese, as pyrolusite, 

 Mn0 2 . 



Cobalt, Co. Atomic weight, 58.97. Fusing point, 1530 C. 



a. Bead test. Compounds of cobalt when dissolved in borax 

 or S. Ph. yield in both flames a dark smalt-blue, a very delicate test. 

 If copper or nickel are present they may conceal the cobalt when in 

 small quantities ; in this case the borax bead is taken from the wire 

 and reduced beside tin on coal, when copper and nickel are reduced 

 to metal and absorbed by the tin, when if cobalt is present the 

 borax will be blue. See also under nickel. 



Illustration. Use oxide of cobalt. Sulphides, arsenides, and 

 antimonides must be roasted before dissolving in the bead. 



Nickel, Ni. Atomic weight, 58.68. Fusing point, 1484 C. 



a. Bead reaction. Oxides of nickel color the borax bead in 

 O. F. a violet, which on cooling becomes brownish, or if highly 

 charged a reddish brown ; in R. F. the bead is gray, due to metallic 



