4t^ o?» rrv. 



Facts and ob- ^'^^^ '^^^ those v/hich are determined by the affinities in genera!. 



serfatlons on The proof of this may be observed in the constant' properties 



nn an its ^ mosaic gold : it exhibits a crystalhsiible volatile combi^ 

 compounds. ... . 



nation, as invariable in the whole of its characters as cinabar 



is, whatever may be the process from which it is obtained. 



The following experiment offers a second proof cf the di- 

 minution of oxidation, which takes place in the oxide at the 

 mmimum, before the production of mosaic gold :— 



Fifty parts of sulphur and one hundred of the L^rey oxide, 

 or oxide at a minimum, deprived of water by a slight calci- 

 nation, were heated in a defective retort. A moment arrived 

 at which the mixture, though still at a very low temperature'', 

 entered into incandescence, and suddenly presented tliat phe- 

 nomenon of ignition which is common to most metals when 

 they combine with sulphur. After this appearance, the heat 

 was raised till the mixture was faintly ignited, and it was con- 

 tinued till all the excess of sulphur was condensed in the neck 

 of the retort. When cold, it was weighed, and was found to 

 have lost 8 or 9 parts of its weight. The mosaic gold re»- 

 , maining in the vessel weighed 120 or 121 parts. 



Let us now examine these results : — 



Sulphureous gas escapes from the retort, which accounts 

 for the 8 or 9 parts lost of the weight ; for nothing else escapes, 

 as the excess of sulphur remains in the neck of the retort. 

 Hence, if there were no formation of sulphureous acid, and 

 consequently no loss of oxigen, the mosaic gold obtained would 

 be composed of 100 parts oxide -f- 20 of sulphur. But there 

 is a deduction of oxigen : the mosaic gold is therefore com- 

 posed of oxide 100, — an unknown quantity of oxigen, 20 of 

 sulphur, -f 21 quantity of sulphur equal to that unknown 

 quantity of oxigen. Mosaic gold, therefore, is not a sul- 

 phurated oxide, in the degree hitherto imagined; or, in other 

 words, a combination of sulphur with one or other of the two 

 oxides of tin with which vvc are acquainted ; but it is a sul- 

 phuret, whose oxide is fixed at a degree inferior to their con- 

 stituting the minimum of oxidation of this metal : a constant 

 term, I repeat; because, whenever the attributes of a com- 

 pound present themselves without variation, whatever may be 

 the process by which it has been obtained, the invariability in 

 the proportion of its paits Is always an inseparable consequence. 



It 



