Prof. Roscoe on Vanadium. 67 



a light yellow insoluble powder on precipitating the tribasic sodium 

 salt with a soluble lead salt ; it yielded on analysis 11*75 per cent, 

 of vanadium, the calculated quantity being 12*04 per cent. 



2. Vanadinite, the Double Orthovanadate and Chloride of Lead, 

 3Pb 3 V0 4 + Pb Cl 2 , can be artificially prepared by fusing for a few 

 hours a mixture of vanadic acid, oxide of lead, and chloride of lead, in 

 the above proportions, together with an excess of sodium chloride. 

 After cooling, a greyish crystalline mass is left, containing cavities 

 filled with long crystals having the same colour as the mass, which 

 under the microscope could be distinguished as six-sided prisms. 

 The crystalline powder is then boiled with water until no further 

 traces of soluble chlorides are extracted. 



The following analysis shows that this substance has the same 

 composition as the vanadinites from Zimapan and Windischkappel, 

 analyzed by Berzelius and Rammelsberg* : — 



Natural vanadinite. 

 Calculated. Zimapan, Windischkappel, Artificial 



3 (Pb 3 V0 4 ) Pb Cl 2 . Berzelius. Eammelsberg. vanadinite. 



Lead 73*08 70*4 71*20 71*96 



Vanadium.... 10*86 9*77 11-11 



Chlorine .... 2*50 2*54 2*23 2*31 



Oxygen 13*55 — — 



The specific gravity of the artificial vanadinite at 12° C. is 6*707, 

 that of the natural being 6*886. 



' 3. Basic Di-Lead Vanadate, 2(Pb 2 V 2 7 ) + Pb O.— This salt is 

 precipitated as a pale yellow powder when acetate of lead is added 

 to a solution of disodium vanadate, the liquid acquiring an acid reac- 

 tion. It is completely insoluble in water and in dilute acetic acid, 

 but dissolves readily in nitric acid. 



Pb = 1035*0 



V 4 ° = 205*2 



1 = 240*0 



Calculated. 



Mean found. 



69*92 



70-18 



13*86 



13*3 



16*22 





1480*2 



Silver Vanadates. 



1 . The Ortho-Silver Vanadate, Ag\, V0 4 , is obtained as an orange- 

 coloured precipitate by mixing a freshly prepared solution of the tri- 

 sodium salt with a solution of silver nitrate, in which every trace 

 of free acid has been neutralized ; unless these precautions are at- 

 tended to, the precipitate consists of a mixture of the ortho- and 

 pyro-salt. The trisilver vanadate is insoluble in water, but readily 

 dissolves in ammonia and nitric acid. Analysis gave the following 

 results : — 



* Pyroinorphite and apatite have already been artificially prepared by Deville 

 and Caron, and also by Debray, whilst mimetesite has been obtained artificially 

 by Lechartier. 



F2 



