is, the gold must be as much less than the copper, as the fpecific gravity of gold is greater than that of copper: And as they muft both lose weight in proportion to bulk in water, therefore the gold, the leffer of the two, lofes lefs of its weight than the copper dces, and confequently, out-weighs the copper in water. I hope this is clear. The cafe is the fame, in proportion, in pure gold, and gold mixed with other metals. The bulk of the pure gold must be lefs than that of allay ed gold, and its weight greater in water; though both equiponponderate (a pound fuppofe) in air.

It is very plain, Sir, and I request you will proceed. You give me valuable information, and oblige me very much. This pleased the Chemift, and the ingenious little Ribble went on.

As to the fimplicity of gold, we mean, by a fimple body, that whofe minutest part has all the phyfical properties of the whole mafs. Now diffolve a grain of gold in aqua regia, and from a fingle drop of the folution, a particle of gold may be separated, and have all the characters of gold, (except thofe of magnitude,) though the feparated particle of gold fhall only be the millionth part of the grain.-Or, fuse a

fingle grain of gold with a mass of filver, and mix the whole together, fo that the gold fhall be equally distributed then take a particle thereof, and you will have a particle of perfect gold; for diffolve the leaft part of the mixture in aqua fortis, and a quantity of gold will precipitate to the bottom. It will bear the same proportion to the grain, that the part dissolved did to the whole mafs.

Having mentioned aqua regia and aqua fortis, I muft, to be intelligible, say two or three words in relation to them. Aqua regia is an extract by fire from fea-falt and fpirit of nitre. The acid liquor that comes over from them into the receiver, is aqua regis.-Aqua fortis, or spirit of nitre, is a nitrous acid feparated from its bafis, nitre, by the vitriolic acid. Aqua regis only will diffolve gold. Silver is not foluble by aqua regis; its proper folvent is the acid of nitre, or aqua fortis. But if you want to separate a mafs of gold and filver, either will do. You may diffolve the gold by aqua regia, and let the filver remain pure: or, diffolve the filver by aqua fortis, and let the gold remain pure. Only note in this cafe of a mixed lump of gold and filver, the operation by aqua fortis is preferable, for this reafon; that aqua regis in diffolving gold,

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takes

takes up likewife a little filver; but aqua fortis hath not the leaft effect on gold:And note further, that if there be equal parts of gold and filver in the mixture, they cannot be parted by aqua fortis. It has not then the leaft effect on the filver, which is very strange. To make aqua foris act duly on filver mixed with gold, the filver must be at leaft in a triple proportion to that of the gold. The reafon of the fingular effect is, that when the gold exceeds, or the parts of both are equal in quantity, then, as both are intimate, ‘united in the mafs, the parts or minims of the gold coat over the parts of the filver, and defend them from the action of the aqua fortis. In this cafe, aqua regia must be uied to diffolve the gold, and leave the filver pure: or, as aqua regia takes up a little of the filver, when it diffolves the gold, melt the metalline mafs, and add as much filver, as will make it a triple proportion to the gold. Then you may by aqua fortis take up all your filver in the diffolution, and leave all the gold pure.

But as to the third criterion of gold, its being the moft fixed of all bodies, this is evident from the violence of fire having no effect on it. An ounce of it expofed for the fpace of two months, in the eye of a

glafs

glafs furnace, does not lofe half a grain. It may from thence be faid to be incorruptible.

As to gold's refifting antimony, and not turning into fcoria by its force, it is moft certain from hence, that if you take a mass: confifting of gold, filver, copper, the other metals, with ftones, &c. and fufe it with antimony, the bodies will flow on the furface, and be easily blown off by the bel lows: the antimony all evaporates, and leaves the gold alone. This is called the laft teft of gold, to try the purity of it. If the remaining gold have loft nothing of its weight, it is allowed perfectly pure, and called gold of twenty-four carats; or if it be found lighter, it is faid to be twenty

three carats fine..

But as to the ductility of gold, this is the most extraordinary property of it. The

The wonderful ductility of gold.

arts of gold-beating and wire-drawing, fhew us things quite amazing. In leaf-gold, a grain and a quarter of the metal, may be made to cover an area of fifty fquare inches; and if the leaf be divided by parallel lines. To part of an inch, a grain of gold will be divided into five hundred thousand minute fquares, all difcernible by the eye

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yet

yet this is not the most can be done by the hammer. A fingle grain of gold may be stretched into a leaf that will cover a house, and yet the leaf remain fo compact, as not to transmit the rays of light, nor ever admit fpirit of wine to tranfude. This however is nothing to the effects of wire-drawing.

A gold wire is only a filver one gilt, and if you coat a filver cylinder of forty-eight ounces weight, with one ounce of gold, which is fufficient, this cylinder may be drawn out into a wire fo very fine, that two yards thereof fhall weigh only one grain, and 98 yards only 49 grains, fo that one grain of gold gilds 98 yards; and of course the ten thousandth part of a grain, is above one third part of an inch long. And fince the third part of an inch is yet capable of being divided into ten leffer parts visible to the eye, it is evident that the hundred thoufandth part of a grain of gold, may be feen without the help of a microscope: And yet fo intimately do its parts cohere, that though the gold wherewith the wire is coated, be ftretched to fuch a degree, there is not any appearance of the colour of filver underneath. Nor is this all.