Vanadic Acid. 435 



the carbonate. The boiling must be continued for several 

 hours, and even then the total extraction of the vanadic acid 

 is not effected. The filtered liquid containing silica and alumina 

 is neutralized with sulphuric acid, and then ammonia and 

 sulphydrate of ammonia are added. The whole is left at rest 

 for two hours to separate the silica and alumina ; the filtered 

 liquid contains sulpho -vanadate of ammonia, whence sulpho- 

 vanadic acid is thrown down by excess of acetic acid and boil- 

 ing. We can also separate vanadic acid by adding chloride of 

 ammonium in excess, boiling, filtering, and adding to the 

 filtered liquid a solution of tannin, which causes a blue precipi- 

 tate, nearly black, containing all the vanadium contained in the 

 liquid. M. Deville calcines the material from which vanadic 

 acid is to be extracted with a little caustic soda, and then sub- 

 mits the whole to lixiviation. The filtered alkaline solution is 

 saturated with sulphuretted hydrogen, which precipitates the 

 silica and alumina, whilst the vanadic acid remains in solution 

 as sulpho-vanadate of soda. In these cases the sulpho-vanadic 

 acid is transformed into vanadic acid by roasting. These pro- 

 cesses are somewhat tedious, and do not appear to yield all the 

 vanadic acid present in the substance experimented on. 



The method I prefer is simply a modification of Seftsronr's 

 original process. It is applicable to any mineral substance, and 

 gives very satisfactory results. 



About half an ounce of the mineral (iron ore, clay, etc.), 

 finely pulverized, is intimately mixed with half its weight of 

 saltpetre, and the mixture heated to a dull red heat for fifteen 

 or twenty minutes in a platinum crucible. The residue is 

 treated with boiling water, to which a small fragment of caustic 

 soda is added; it is then boiled for about a quarter of an hour, 

 filtered, and the residue washed with boiling water. The liquid 

 is nearly saturated with nitric acid, and precipitated by excess 

 of chloride of barium ; the precipitate is decomposed by sul- 

 phuric acid, the filtered liquid neutralized by ammonia, and 

 saturated with chloride of ammonium. The whole of the 

 vanadic acid present comes down as vanadate of ammonia in 

 the course of two days. In some instances the process may be 

 rendered more simple still ; and for extracting vanadic acid on 

 the large scale from iron ores, pitchblend, or from London clay, 

 it will be sufficient to calcine a given quantity of these sub- 

 stances with one-fourth to one-half of their weight of a mixture 

 of carbonate of soda and nitrate of potash ; the calcination 

 lasting about half an hour. The calcined mass is then boiled 

 for some time with a little water, the liquid filtered, and super- 

 saturated with chloride of ammonium. If the filtered liquid is 

 too bulky it must be evaporated. All the vanadic acid is pre- 

 cipitated as vanadate of ammonia in the course of twenty-four 



