As soon as the gold was in complete fusion, about four ounces of zinc were put into the large crucible.

A considerable flame, accompanied by a large quantity of white oxide of zinc, immediately arose, and part of the oxide adhered to the interior of the large crucible.

Within half an hour, the crucible containing the gold was removed, and was suffered to cool.

Upon examining the button, it appeared, that a portion of the volatilized zinc was combined with the gold; for the surface was dull, and of a Spanish snuff colour; moreover, it proved to be very brittle, similar to the former results.

From these experiments, it is evident, that zinc is highly injurious to the ductility of gold; that a portion of it is easily separated from gold by heat; that, when a large quantity of gold is alloyed with the standard proportion of zinc, only part of the latter is speedily volatilized, but, when small quantities are treated, the whole of the zinc becomes separated, and the gold remains pure; that, if zinc is previously combined with copper in the state of brass, it is not so easily separated by heat, when added to melted gold; and, lastly, that gold in fusion absorbs and retains a portion of zinc, when exposed to the latter metal in a volatilized state, even in open vessels.

GOLD ALLOYED WITH COBALT.

Experiment 1.

The effects produced by cobalt upon gold, do not appear to have been hitherto investigated; for this reason, the following experiments were made.

To eighteen pennyweights and ten grains of gold, 23 car. 31 grs. fine, when in fusion, one pennyweight and fourteen

grains of pure metallic cobalt were added, and, being well melted and mixed, the whole was poured into a dry cupel.

The external colour of this metal was a dull yellow; it was very brittle, and the fracture appeared of a pale yellow, with an earthy grain.

Experiment 11.

To eighteen pennyweights and ten grains of the fine gold, alloyed with 19 grains of pure copper, were added 19 grains of metallic cobalt, which being perfectly melted and mixed, the whole was treated as before.

The metallic button, externally, appeared of a pale yellow, slightly tinged with gray; it was brittle, and shewed a finegrained earthy fracture.

Experiment 11.

Eighteen pennyweights and ten grains of the fine gold, alloyed with one pennyweight and six grains of copper, being melted, eight grains of cobalt were added, and mixed.

The colour of this ingot was like that of the former, but the yellow colour was rather deeper. It soon broke under the hammer, and the fracture was still of a fine grain, inclining to an earthy appearance.

Experiment IV.

To eighteen pennyweights and ten grains of gold, alloyed with one pennyweight and ten grains of copper, four grains of cobalt were added. The colour of this metal resembled that of gold made standard by copper, excepting that it was rather paler. This ingot was but slightly brittle.

As the last metal began to be ductile, the experiments with cobalt were not continued.

GOLD ALLOYED WITH NICKEL.

Experiment 1.

Eighteen pennyweights and ten grains of the fine gold, were alloyed with one pennyweight and fourteen grains of pure metallic nickel, and the whole was then poured into a cupel.

This button was of the colour of fine brass; it immediately broke under the hammer, with a coarse-grained earthy fracture.

Experiment 11.

Eighteen pennyweights and ten grains of fine gold, being alloyed with 19 grains of copper, were afterwards melted, and mixed with 19 grains of pure nickel. The external colour of this metal resembled gold made standard by copper, but was paler in a slight degree. It was brittle, and shewed a fine-grained fracture, of an earthy appearance.

Experiment 111.

Eighteen pennyweights of the fine gold, alloyed with one pennyweight and six grains of copper, being melted, eight grains of nickel were added, and mixed as before. The colour of the ingot was like that of the former experiment, and the metal proved to be only slightly brittle.

Experiment iv.

To eighteen pennyweights and ten grains of fine gold, alloyed with one pennyweight and ten grains of copper, when in fusion, were added four grains of nickel. The colour of this button was like that of gold made standard by copper, and, under the hammer and rollers, it was found to be perfectly ductile.

From these and the following experiments it appears, that, of all those which have been improperly called semimetals, nickel is that which is the least injurious to the colour and ductility of gold.

GOLD ALLOYED WITH MANGANESE.

› From what is at present known, it does not appear that this combination has till now been made.

Experiment 1.

480 grains of gold, 23 car. 33 grs. fine, being put into a crucible, were covered with about half an ounce of pure black oxide of manganese. The crucible was then exposed to a strong heat, in a wind furnace, during one hour and an half; but not any alteration was thus produced in the properties of the gold.

Experiment 11.

A quantity of olive-oil was several times mixed, and burned, with some of the oxide of manganese, after which, about one ounce of the oxide was put into a crucible lined with charcoal.

A piece of fine gold, weighing one ounce, was then placed in the middle of the oxide, over which a stopper of charcoal was put, and the whole was closed by a cover, firmly luted.

After a strong heat of one hour and an half, the crucible was removed, and, when cold, was broken.

The manganese, in which the gold had been embedded, still remained in a pulverulent state, but, from black, was changed to a dark green.

The button of gold at the bottom of the crucible was of a pale colour; it soon broke under the hammer, and shewed a spongy coarse-grained fracture.

Experiment III.

From the effects last mentioned, it was evident that manganese could be thus combined with gold; the experiment was therefore repeated, and the heat was continued during three hours, at the end of which time the crucible began to be melted.*

Upon breaking the crucible, which had been suffered to cool in the furnace, the manganese was found to be pulverulent in some parts, and indurated in others. There were not any metallic globules to be seen; and the colour varied from dark to pale grass green.

The button of gold at the bottom of the crucible was uniform, and externally of a pale yellowish gray colour, with a considerable lustre, almost equal to that of polished steel.

On that part of the button which had been next to the bottom of the crucible, were some specks of pale green enamel. The metal possessed a small degree of ductility, although extremely hard, for, when placed upon an anvil, being repeatedly struck with a heavy hammer, the button was in some measure flattened, before it could be broken.

The fracture was coarse, very spongy, and of a reddish gray colour; and many cavities, in the interior of the mass, were filled with the dark green coloured manganese.

It has been generally observed, that metals, when combined with manganese, are liable to a speedy change and diminution of lustre, colour, &c. when exposed to the air; but gold alloyed

• This reduction and union of manganese with gold, seems to have been effected by the double affinities between oxygen, carbon, gold, and manganese; and there is every reason to believe, that the above method may be advantageously employed, to form the alloys of the refractory metals with those of easy reduction and fusibility.