OF ARTS AND SCIENCES. 297 



monic salts, has any yellow tint, vanadic acid salts are almost surely 

 present. It occurs with phosphoric acid in most of the mineral bodies 

 named above. The physical character of color of the rock is the only 

 indication I now know. The green and plum colors of slates and por- 

 phyries ; the greenish epidote color of many aggregates ; the changed 

 colors, seen in sandstones, and esjjecially in rooting slates, from world- 

 wide localities, are guiding marks merely. My observations have been 

 quite numerous, and as yet no proper ore of vanadium has been found, 

 but sources of economical separation have been suggested. 



As vanadium occurs in many well-trodden paths, I deemed it im- 

 portant to devise a direct way of obtaining it, in which no metal and 

 the fewest reagents are employed. 



PROCESS. 



Crush in the diamond mortar 1 to li grms. of greenish slate to a 

 fine and coarse powder ; place in a watch crystal, and wet thoroughly 

 with a solution of one-fourth sulphuric hydrate, leaving a little excess. 

 Expose freely to dry, warm air, — sunshine, if possible; and, if the 

 slate is acted on, after 2 to 4 days, when the mass is nearly dry, the 

 salts formed crystallize. Under a lens, a number of green or bluish-black 

 spherical crystalline aggregates, unlike any other matter present, will be 

 seen. These are a double salt, in which blue oxide of vanadium exists ; 

 and from such a small weight, often, enough crystals can be picked out 

 for showing the characters of vanadium compounds. It is best to use 

 several differing specimens, which by their colors indicate proto-silicates, 

 and to be sure that they have been carefully washed, as granites are 

 often invested with a lichen of a hemispherical form. One is often 

 surprised to see the number of these crystals extruded from the mass 

 of salt, and formed under constraint. The oxidized rocks do not 

 afford these crystals, but we see bands of yellow vanadium compounds, 

 denoting the condition of the substance. 



The ordinary tests of vanadium are best applied to the vanadates, 

 and among them the gall test is delicate and discriminating. If the 

 greenish-black precipitate it forms in acid solutions be burned, the 

 insoluble oxide obtained (when the precipitate is entirely free from 

 any chloride) has characteristic reactions with acids, and in the blow- 

 pipe flame with fluxes. The salts of vanadium in mixture with man- 

 ganous salts, precipitated by excess of ammonic hydrate, afford a blue 

 solution above the oxides, rivalling that of cupric oxide. 



By oxidizing the blackish-blue salt obtained by sulphuric hydrate, 

 the yellow compounds form, and may be tested under both modifications. 



