Koenig and Hubbard — Poioellitefrom a new Locality. 357 



third to fourth order), and dichroism (a. — blue, y — green). 

 Before the blowpipe the mineral is infusible, decrepitates, and 

 in the closed tube gives no volatile products. With the fluxes, 

 borax and microcostnic salt, the reactions are strongly indica- 

 tive of molybdenum and faintly of tungsten. The salt of 

 phosphorus bead in the inner flame being emerald green for 

 molybdenum and blue for tungsten, it is evident that tungsten 

 cannot be directly recognized when present in small quantity 

 alongside of molybdenum, except in a modification of the 

 green color. One mg. of the mineral being dissolved in 50 mg 

 of vitrified microcosmic salt and 0'8 mg of Mo0 3 (specially puri- 

 fied) in the same quantity of the salt, both treated thoroughly 

 in the inner flame, exhibit very nearly the same color on cool- 

 ing ; it is noticed, however, that the bead containing the mine- 

 ral is slightly fainter in intensity and of a slightly increased 

 bluish green. Without such comparative test the examiner 

 would not be aware of any difference. The fine powder dis- 

 solves readily in hydrochloric and nitric acids, making slightly 

 yellow solutions in which an excess of ammonium hydrate 

 produces but a very slight flocculent precipitate (Fe(HO) 3 , SiO a ). 

 When the fine powder (0'l mg ) is mixed with potassium-hydro- 

 gen sulphate, moistened with a drop of water, and the paste 

 kneaded on the palm of the hand, it assumes a deep blue color, 

 which intensities at first upon breathing upon the material, 

 but on continued breathing the color fades away and finally 

 disappears altogether. The color may be brought back by 

 heating the paste on plat. -foil and by again breathing upon it. 

 (The latter part of this delicate reaction for Mo seems to be 

 new). If l mg of the mineral be dissolved in l cc of cone. HC1 

 and tin foil be added, the solution turns first green, then color- 

 less and then carmine red. It is stated in all text books that 

 acid molybdic solutions turn brown or brown red when treated 

 with Zn or Sn. This is true for Zn but not for Sn. The 

 ammoniacal solution precipitates with oxalic acid white CaC 2 4 

 and thus the mineral is proved to be essentially a calcium 

 molybdate. The quantitative separation of the oxides of Mo 

 and W is not possible by any of the published methods. The 

 following two analyses were made by two independent methods. 

 In (I) Mo and W were precipitated by Hg 2 (NO,) 2 and 

 weighed as nearly white oxides. These were then subjected 

 at a yellow heat to a current of dry air until no further volatil- 

 ization was noticed. A small bluish green residue was left in 

 the boat. In microcosmic salt this residue gave a bead pur- 

 plish gray instead of blue. With borax the reaction for Mo 

 was obtained. It was found by colorimetric trials that a mix- 

 ture of oxides (specially purified) 



WO 1-7"'? 



of Mo0 3 J-3- in S ' Pl1 ' 5 ° ms 



