586 MINERALOGY 



open end of the tube. If the fumes are allowed to escape in the 

 Bunsen burner flame they will color it violet ; antimony will color 

 it yellowish green. 



Compounds of arsenic when mixed with soda and potassium 

 cyanide will yield the mirror in the closed tube. 



c. Wet test. All compounds of arsenic may be tested as 

 follows. The substance is finely ground and mixed with 4 parts 

 soda and 3 of niter, and fused on platinum foil or wire. The 

 fusion is boiled in water to dissolve the sodium arsenate, NasAsO^ 

 and filtered ; the filtrate acidified with HC1, then a solution of 

 magnesium sulphate, and finally strong ammonia in excess is 

 added, the solution is shaken and let stand. Arsenic will separate 

 as ammonium magnesium arsenate, NH 4 MgAsO 4 . 6 H 2 O, which 

 is filtered off, washed with a solution of ammonia, dried, and tested 

 for the mirror as in 6. 



Illustration. Use arsenopyrite, FeSAs. 



Germanium, Ge. Atomic weight, 72.5. Fusing point, 900 C. 



Germanium is a very rare element found in only three minerals, 

 argyrodite, euxinite, and canfieldite. In the R. F. it is reduced, 

 then volatilizes, forming an oxide coat, GeO 2 , white near the assay 

 and yellowish at a distance from it. It also has a peculiar glazed 

 appearance. It, however, yields no odor or flame coloration. 

 Germanium when treated as in arsenic, b, yields a mirror. 



Molybdenum, Mo. Atomic weight, 96. 



a. Bead test. Molybdic oxide when dissolved in the borax 

 bead is colorless or nearly so in O. F. In R. F. it is brown to 

 black. In S. Ph., O. F., the bead is colorless or nearly so; in 

 R. F. a fine green. 



6. Coat. Some compounds of molybdenum yield on coal an 

 oxide, MoOs, coat, yellowish while hot, white on cooling. If the 

 R. F. is brushed over this white coat, it is partially reduced, 

 yielding a very deep blue color. On heating the white coat in 

 O. F. most of it is volatilized ; the coal, however, reduces some of 

 it to binoxide, which is non-volatile and remains on the coal as a 

 copper-red film. 



c. Flame. Some compounds of molybdenum when heated in 

 O. F. yield a green flame. 



d. Wet test. If compounds of molybdenum are fused on 

 platinum wire with 3 parts of soda and 3 parts niter, several of 

 these beads are dissolved in a test tube with boiling water. The 

 clear solution is decanted, acidified with HC1, a small piece of 



