Chemical Science. 363 



p, 145. The author, after stating the object of his researches, 

 namely, the cause and nature of the colours produced on the 

 surfaces of metals, when they are heated, proceeds to show, 

 what is generally known here, that they require contact of air 

 for their formation. Wires, and bars of steel, ^c, were heated, 

 part of some being immersed in mercury, part in the air, others 

 when enclosed in the Torricellian vacuum, and in other situa- 

 tions, and it was found that no colour was produced when air 

 was excluded, and that the tint was in proportion to its freedom 

 of access. Concluding from hence, tliat the colours were occa- 

 sioned by oxidation, some ingenious variations of the experi-' 

 ments were made. A wire of the gold of commerce was con- 

 nected with the positive pole of a strong voltaic apparatus, and 

 placed in water, opposite to a similar wire coming from the ne- 

 gative pole. After some hours, during which time the water 

 had been decomposing, but which had occasioned no turbidness 

 in the remaining portion, the point of the positive gold wire 

 which had been exposed to the nascent oxygen, had acquired 

 yellow, purple, and blue colours, as if it had been exposed to a 

 flame. These were extremely distinct, when viewed by a lens. 

 The negative wire which had developed hydrogen had not 

 acquired any notable colour. 



Platinum, in wire and laminae, exposed at the same time, and 

 under the same circumstances, with wires of iron, copper, sil- 

 ver, ^c, never acquired colour, though all the others did. This 

 the author offers as an additional pi-oof of their being occasion- 

 ed by oxidation ; and, after having drawn this conclusion from 

 all his experiments, proposes the discoloration of a metal by 

 heat, as an eudiometrical test of the presence of oxygen in mix- 

 tures of airs. 



Sig. Fusinieri then proceeds to ascertain the order of pro- 

 duction, and successive reproduction, of the colours. It is well 

 known that, with iron and steel, the first colour that appears is 

 yellow, to which succeeds a purple, inclining to violet, and at last 

 deep blue, which passes into light blue. This order is attendant 

 on the successive increase of temperature. The same order is 

 constant with all the metals. To shew this, it is only necessary to 



