the Carinthian Molybdate of Lead. 291 
some alkali in the two first substances, so as to form an imper- 
fect neutral salt with the molybdic acid, but that the yellow 
powder is in the state of a simple oxyde. 
This yellow colour probably occasioned the supposition 
that the lead was mineralized by the tungstic acid ; but the 
blow-pipe is sufficient to distinguish them. The yellow oxyde 
of molybdasna loses the colour as soon as the point of the, flame 
touches it, inclines to an olive colour, and melts into small 
grains, which are immediately absorbed by the charcoal. In 
the phosphate of ammoniac and soda it dissolves, and commu- 
nicates to it a green colour. On the contrary, the yellow 
oxyde of tungsten by ignition becomes blue or black, remain- 
ing refractory, and with phosphate of ammoniac and soda it 
produces a sky-blue glass. 
Mr. Klaproth concludes his paper by saying,, that he 
could not exactly determine the proportions of the ingredients, 
as the quantity of the ore in his possession was not sufficient 
to make the necessary allowance for the solubility of the oxyde 
of lead in the alkalies, and especially that of the molybdic acid 
when in a state of combination. 
These experiments of Mr. Klaproth certainly prove that 
this ore is a molybdate of lead ; but as the quantity which he 
had was too small, either to make a greater number of experi- 
ments, or a regular analysis, I was induced to attempt a fur- 
ther investigation of it ; and therefore in the course of the last 
summer I made the experiments and analysis which are de- 
scribed in this paper. 
