1819.) extracted from Pyrites at: Fahlun. 403 
aslight excess of caustic ammonia (which does not dissolve oxide 
of tellurium), let fall a white precipitate, which, when treated by 
the blow-pipe, gave out a strong smell of tellurium, and left a 
metallic globule of lead. The quantity of the precipitate was too 
small to extract tellurium from it; but we considered it im con- 
sequence of its smell of horseradish as a tellurate of lead. The 
liquid which had been saturated with ammonia, being evaporated 
to dryness, detonated, and was dissipated without any other 
residue than some black stains on the platinum crucible employed 
in the process. 
2. More particular Examination of the Substance which emitted 
the Smell of Horseradish when the Reddish Matter. was burned. 
Experiments to obtain it in.a separate State. 
The appearance of a substance so rare as tellurium in the 
sulphur of Fahlun, induced me to endeavour to obtain it m a 
separate state, in order to be able to form more accurate notions 
respecting it. I, therefore, took out the whole mass which was 
at the bottom of the leaden chamber. . While still moist it had 
a reddish colour, which, on drying, became‘alimost yellow. It 
weighed about 4 lbs. It was treated with nitro-muriatic acid, 
added in such quantity as to make the mass into a pulp; it was 
then digested in a moderate heat. Its colour changed by 
degrees ; the red disappeared ; and it became greenish yellow. 
After 48 hours’ digestion, water.and sulphuric acid were added, 
and the whole was thrown on a filter. The liquid which passed 
through had a deep yellow colour. The mass remaining on the 
filter had not sensibly diminished in bulk. It consisted chiefly 
of sulphur mixed with sulphate of lead and with other impurities. 
A small quantity of the filtered liquid was taken to find out the 
method of separating the substance which it was presumed to 
contain. This portion was precipitated by ammonia. The pre- 
cipitate being well washed and dried, mixed with potassium and 
heated in a barometer tube, was decomposed’ with ignition. 
When put into water, a portion of it was dissolved, and the 
liquor assumed a strong colour of beer, very different from the 
wine-red colour communicated by hydrotelluret of potash ; but 
after some hours, it became muddy, depositing red flocks, the 
quantity of which increased on the addition of nitric acid. This 
precipitate was collected, and when a part of the filter on whic’. 
it was deposited was burned, it gave the circumference: of the 
flame a blue colour, and emitted a very strong smell of horse- 
radish. A portion of pure tellurium precipitated in the same 
manner from a solution of hydrotelluret of potash had a grey 
colour, gave a green tinge to the circumference of the flame, 
and emitted no perceptible odour of horseradish. On examining 
more closely the purified tellurium, which had served in my 
former experiments on the oxide of tellurium and on ‘telluretted 
hydrogen gas, I found that it produced no odour, neither when 
2¢2 
