1835.] and Analysis of the Vanadiate of Lead. 35 



brown mineral from Zimapan, by Del Rio, in which the 

 Mexican chemist it was stated, had discovered a new metal. 

 The mineral was considered similar to specimens from 

 Schoppau in Saxony, Hoff in Hungary, and Pollaven in 

 Brittany.* 



Andre del Rio appears to have examined the Zimapan 

 mineral in 1802, and to have written a memoir in which he 

 expressed his opinion that this substance was not a phosphate, 

 and that it contained neither uranium nor chromium ; and 

 stated that he procured from it 14-8 per cent, of a new 

 metal, which at first he called Panchrome, on account of 

 the variety of colours presented by its oxides and precipi- 

 tates, and afterwards Eritrone, because it formed with alka- 

 lies and earths, salts which became red either by heat or by 

 acids. t But having read in the work of Fourcroy that 

 the chromates afford by evaporation yellow or red salts, he 

 came to the conclusion in 1804, that the brown mineral 

 was a chromate of lead, with an excess of base, in the state 

 of protoxide of lead. % 



In his Spanish translation of the Third Edition of Kars- 

 ten's Mineralogical Tables, published in Mexico in 1804, he 

 used language still more strongly opposed to his original 

 opinion, and affirmed that the mineral consists of 



Oxide of lead . . . . i 80-72 

 Chromic acid . . . ' . .14*80 



Arsenic, oxide of iron, and muriatic acid 4*48 



100-00 



He found the quantity of arsenic to amount sometimes to 

 two per cent., and always observed its presence, both by 

 distillation and the blow-pipe. 



It is quite obvious, from these two separate recantations, 

 that Del Rio was convinced, from his own researches, that 

 the substance which he at first considered new, was one 

 which was already known to chemists, and that his original 

 experiments were not valid. The observation, therefore, 



* Gehlen's Neues Allgemein journal der Chemie, 6th part, vol. ii. 695. 

 t Annates de Ciencias Naturales de Madrid, No. 19, February 1804. Annales 

 des Mines, iv. 499. 



% Annales de Ciencias, No. 19. 

 § Gilbert's Annalen der Physik, Ixxi. 7. 



D 2 



