Vanadic Acid. 483 



of Gentilly, near Paris, which is used to make the flower-pots 

 for the Jar din des Plantes. It was in that year that Professor 

 Pisani and myself procured some of these flower-pots, ground 

 them down to a coarse powder, and extracted vanadic acid from 

 them, but in very small quantities, for the process by which 

 we operated (that recommended by Beauvallet) proved rather 

 unsatisfactory. A little later, I submitted to the same investi- 

 gation, in Pisanr's laboratory, a variety of Belgian clays, from 

 the neighbourhood of Ypres, Ostend, Lacken, etc. ; and in 1860 

 and 1861, I made several new experiments on the extraction 

 of vanadic acid from these substances, in my own laboracory 

 in London. I examined particularly London clay and the 

 gault of Sussex, also a peculiar hydrated oxide of iron from 

 Saxony, which gave nearly two per cent, of vanadic acid, and 

 some English iron-stones; and in 1863 I published in the 

 Journal of the Chemical Society a short account of these re- 

 searches. It was not known until then in what state vanadic 

 acid exists in these iron-stones, clays, etc., but my analyses 

 show that it is found as phosphate of vanadic acid, a compound 

 described by Berzelius, and that the iron ores which contain 

 much phosphoric acid are also those which yield most vanadic 

 acid. 



As the results of these analyses, I found that London clay 

 contains from 0*023 to 0*056 per cent, of vanadic acid ; the gault 

 of Sussex yielded me 0*046 to 0*070 per cent. ; the white clay of 

 Ypres, in Belgium, 0*033 per cent. ; an English iron ore (red 

 hematite), containing much phosphoric acid, gave me as much 

 as 0*40, and another 0*92 per cent, of vanadic acid. But the 

 largest quantity was found in the iron-stone, which I have 

 termed vanadium ochre, from Saxony, from which I extracted 

 1*60 to 1*90 per cent. In several other specimens of clays and 

 iron-stone the presence of vanadium was put in evidence, but 

 its quantity was not determined. 



Other chemists have sought for vanadic acid in several 

 mineral substances. A. Miiller found 0*03 per cent, in an 

 hydrated oxide of iron from Wittemburg ; Eritsche found the 

 enormous quantity of 1*78 per cent, in a German copper ore 

 (Konichalcite), which doubtless contained some vanadate of 

 copper, as well as arseniate and phosphate of copper detected 

 by the author; Weibye found 0*22 per cent, of vanadic acid in 

 a Norwegian schist (silicate of alumina), and Schrotter detected 

 0*37 per cent, in the iron slags of Yerdenberg; whilst Kersten 

 found 0*15 per cent, in some sulphide of iron slags, a small 

 quantity also in the copper schist of Mansfeld ; and H. Deville 

 extracted as much as 0*32 per cent, from a specimen of rutile. 

 Wohler, Swanberg, and Ficinus have detected notable quan- 

 tities of vanadic acid in the pitchblend of Germany and 



