42 Dr. R. D. Thomson on the History [Jan. 



tant liquor was drawn off, and the residue washed with 

 repeated additions of pure distilled water. The insoluble 

 matter when dried on the sand bath, possessed a brown 

 colour, and weighed 0*07 grain. This lost by a red heat 

 0*02 grain, leaving for the weight of the anhydrous powder 

 0*05 grain. Before the blow-pipe this substance fused with 

 carbonate of soda into an oblong green mass, which became 

 somewhat lighter coloured by a continuance of heat, and 

 with borax and salt of phosphorus into a light green glass 

 bead. Hence, it appears to have consisted principally of 

 vanadic acid, mixed however with some impurity, as is 

 obvious from the action which was presented with car- 

 bonate of soda. 



The liquid which had been drawn off from the insoluble 

 matter, as well as the washings, was concentrated and 

 precipitated by nitrate of silver, when a white substance 

 fell, becoming curdy by agitation. This precipitate was well 

 washed, and when dried on a watch glass by the heat of the 

 sand bath, weighed 3 grains exactly. It was melted by the 

 heat of a spirit lamp and lost 0*02 grain, leaving of dry chlo- 

 ride 2-98 grains. Now 18-26 : 4-5:: 2-98 : 0*734= chlorine. 

 After the separation of the chloride of silver, the liquid was 

 evaporated to dryness. The residue dissolved readily in 

 water, to which a few drops of nitric acid had been added, 

 leaving, however, a greyish powder, which proved to be 

 oxide of silver derived from the excess of nitrate of silver, 

 and was separated by filtration. 



A drop of muriatic acid occasioned no precipitate in the 

 liquor. Through the solution, which was yellow coloured 

 after concentration, a current of sulphuretted hydrogen 

 was passed for four hours. A copious precipitation of sul- 

 phuret of lead ensued, and the supernatant liquid assumed 

 a fine transparent blue colour. The precipitate was washed 

 with repeated additions of water, allowing it to subside, 

 and then drawing off the liquid. The sulphuret of lead 

 weighed in a watch glass after being subjected to the heat 

 of the sand bath 26*02 grains. 10 grains carefully heated 

 over a spirit lamp, for some time after it ceased to give off 

 sulphur, lost 0*37 grain. By another trial 10 grains lost 

 0*40 grain by a heat applied twice as long, so that in the 

 first experiment the free sulphur had not been completely 

 dissipated. This makes the loss upon the whole precipitate, 



