Made May the 6th, 1782. before the Rev. Mr. Anderson; Capt. Francis Grose; Mr. Russell and Mr. D. Grose, the Gentlemen mentioned in the Introduction as the most proper witnesses of the process, then resident in Guildford.
Half an ounce of Mercury provided by Capt. Grose (bought at an apothecary's of the town) was placed in a small hessian crucible, brought by Mr. Russell on a flux composed of Borax, (also brought by him) a small piece of charcoal, taken out of a scuttle (fortuitously) by Mr. D. Grose, and examined by the rest of the company; and a small piece of Nitre also taken out without selection, by the Rev. Mr Anderson, from a quantity in common use, in the Laboratory; these being pounded together in a mortar which all the company had previously inspected, were pressed down into the crucible with a small pestle: on this flux the Mercury was poured by Mr. Anderson, and upon it half a Grain, carefully weighed out by Mr Russell, of a certain powder of a deep red colour, furnished by Dr. P. was put on it by Mr. Anderson.
The crucible was then placed in a fire of a moderate red heat by Dr. P. who from his greater facility in managing the fire from long habit, was thought most eligible to conduct the experiment. He repeatedly called the attention of the company to observe the stages of the process, and to remark in every part of it that any voluntary deception on his part was impossible.
In about a quarter of an hour, from the projection of the powder, and the placing of the crucible in the fire, he observed to the Company, who on inspection found his observation true, that the Mercury, though in a red hot crucible, shewed no signs of evaporation, or even of boiling: the fire was then gradually raised, with attention on the part of the company, and repeated calls for that attention from Dr. P. that no undue addition might be made to the matter in the crucible; in a strong glowing red, or rather white-red, a small dip was taken on the point of a clean Iron Rod, and when cold, the scoriae so taken being knocked off, were shewn to the company and found replete with small globules of a whitish coloured metal, which Dr. P. observed to them could not be Mercury as being evidently fixed in that strong heat: but as he represented to them might be an intermediate substance between Mercury and a more perfect metal.
A small quantity of Borax (brought by Mr. R.) was then injected by him and the fire raised, but with the same precautions on the part of Dr. P. to subject every thing to the minute inspection of the persons present; and after continuing the crucibles in a strong red-white heat for about a quarter of an hour it was carefully taken out, and gradually cooled: on breaking it, a globule of yellow metal was found at bottom, and in the scoriae smaller ones, which collected and placed in an accurate ballance by Mr. Russell, were found to weigh fully Ten Grains. This metal was in the presence of the above mentioned Gentlemen sealed up in a phial, impressed with the Seal of Mr. Anderson, to be submitted to future examination, though every one present was persuaded that the metal was gold.
The seal being broke the next morning, in the presence of the former company, and of Captain Austen, and the metal hydrostatically examined, the weight of the larger globule (the others being too minute for this mode of examination) was found to be in air 9 Grains and a Quarter, and in distilled water of temp. Fahren. 50 plus, it loft, something more than 3/8 (but not quite an half) of a grain: the difference was not appreciable, as no smaller weight than the eighth of a grain was at hand, but was judged by all the company to be nearly intermediate; i.e. 7/16:- at half a grain the sp. gr. would be rather more than 18:1; if only 3/8 were loft in water the sp. gr. would exceed 24:1. the intermediate, would be 21.1/7 nearly; but as the loss seemed rather more than the intermediate, though apparently and decided less than half a grain, the specific gravity must have been nearly as 20:1. and in this estimate all present acquiesced.
After this hydrostatical examination, the globule was flattened by percussion into a thin plate, and examined by Mr. Russell in the manner of artists for commercial purposes; on finishing his scrutiny he declared it to be as good gold as the grain gold of the refiners, and that he would readily purchase such gold as that which he had just examined at the highest price demanded for the purest gold.
The plate being then divided, one half was before the company sealed up by Mr. A. to be submitted to a trial of its purity, which Dr. P. proposed, requesting his friend, Dr. Higgins, of Greek Street, to make; the remainder being put into Aq. Regia of Nit. acid and Sal. Ammon. afforded a solution sufficiently rich, before the company separated, to yeild with sol. of Tin, a richly coloured crimson precipitate.
Capt. G. was accidentally absent when the precipitate was made, but saw it next day. In about four hours the portion of metal employed was completely dissolved, and the next morning before Capt. and Mr. D. Grose, and Mr Russell (Mr. A. being prevented from coming) the solution being divided into three portions the following experiments were made *.
[* The small plate falling by accident on a globule of Mercury on the table readily amalgamated with it. This is mentioned in consequence of an observation in the Critical Review. The Smiris Hispanica is not in the least employed in the Preparation injected on the Mercury.
The Process is more analogous to that of Dr. Brandt, referred to by the ingenious Reviewer of this article, in his very candid and satisfactory Critique.]
To the first portion, diluted with water, was added a quantity of Caustic Vol. Alk. and the precipitate, which was copious, being duly separated and dried, about a grain of it, placed on a tin plate, was heated and found to explode smartly. This experiment was repeated three times.
To the second portion, diluted, was added a portion of Sol. of Tin, in Aq. Reg. A beautiful crimson coloured precipitate was immediately formed in considerable quantity; which when dried, was mixed with a fusible frit, composed of flint-powder, and the fluxes proper for the Ruby Glass of Cassius, in the proportion of 5 Grains of the precipitate to 3ij of the frit, and in a vitrifying heat afforded in about three hours a transparent glass, which by heating again, assumed an elegant crimson colour: and the remainder which continued in the fire also acquired a bright red colour.
The third portion being mixed with Vitriolic Ether, imparted to it the yellow colour given to this fluid by solutions of Gold: and the Ether being evaporated in a shallow vessel, a thin purplish pellicle adhered to the fide, spotted in several places with yellow.
Dr. Higgins soon after receiving the piece of Metal, favoured the Author with an answer, in which he notified that the packet came to him under the proper seal:- That he was well satisfied of the purity of the gold he received; and that he considered the author's experiments as exclusively sufficient to have ascertained the nature and purity of the metal.
EXPERIMENT II.
Made at Dr. Price's, May 8th, 1782, before Sir Philip Clarke, Dr. Spence, the Rev. Mr. Anderson, Capt. Grose, Mr. Russel, and Mr. D. Grose.
Half an ounce of Mercury, procured from one Mr. Cunningham an Apothecary of the town, was placed on a flux composed of an ounce of powdered Charcoal, two drachms of Borax, and one scruple of Nitre, and on it when a little warmed was projected one grain of a white powder, furnished by Dr. Price.
After the Crucible had acquired a red heat, the Company all saw the Mercury lying quiet at the bottom, without boiling or smoking in the least, and it continued in this tranquil state after it had gained a full red heat. It was continued in a fire gradually augmented to a white heat, near three quarters of an hour, a smaller crucible previously inspected, being inverted on it, to prevent coals from falling in: and the crucible being then withdrawn and cooled, many globules of white metal were found diffused through the whole mass of scoriae: of these globules were collected to the weight of ten grains, before the company separated, and consigned to the care of Mr. Russel, who took them away with him.
Part of the remaining globules being afterwards collected, by pounding the crucible and washing over the powder, the whole when melted together amounted to thirteen grains.
Dr. Price remarked on this process, that having taken too great a quantity of Charcoal, the globules were thereby dispersed over the whole mass, and the powder having been sprinkled against the sides of the crucible had not produced its greatest effect. And that some of the Mercury which had escaped its action must have been volatilized by the heat; and this on inspection of the covering crucible was found to be true. The Experiment was therefore the next morning repeated in presence of Mr. Anderson, Capt. and Ensign Grose and Mr. Russel.
EXPERIMENT III.
The remaining half ounce of Mercury was employed; the charcoal and borax both taken without selection from large quantities in the laboratory, were powdered by Mr. Grose, and the Mercury placed in the crucible as in the former Experiment.
Barely half a grain of the White powder, weighed out by Mr. Russel, was projected on the Mercury, which by some accidental delay had begun to boil in the Crucible; but on the application of the powder the ebullition ceased, although the crucible and contained Mercury was subjected to a much greater heat; and it continued without boiling, even when of a red heat. The crucible was gradually heated to a white heat, and when cooled and broke, there was found in the bottom a well collected bead of fine white metal, weighing four grains.
EXPERIMENT IV.
On the fame day, and the fame persons being present as at the preceeding experiment, the following was made on Silver.
Mr. Russel weighed out sixty grains (one Drachm) of Grain Silver, which he had purchased of Messrs Floyer and Co, refiners in Love Lane, Wood Street, Cheapside: this quantity was placed in a small Crucible on some of the flux made as above, before the Company; and on the silver, when in fusion, was projected a bare half grain of the Red Powder, used in Experiment I. The crucible was then replaced in the fire, and continued there for about a quarter of an hour; a piece of Borax taken at a venture, out of a jar containing a large quantity, was thrown on the metal by Mr. Grose.
Dr. Price soon after, from the appearance of the flux imagining the crucible to be cracked (by the cold and moisture of the borax) took it out of the fire, and finding that what he suspected had happened, did not replace it; when cool it was broke, and the button of Metal was found in the bottom, which when weighed, appeared not to have loft any of its original weight, so that fortunately only the flux had transuded.
EXPERIMENT V.
That no doubt might arise from the failure of the Crucible in the last Experiment, a similar one was made in the presence of the fame persons, with the addition of J. D. Garthwaite of --- Esq; who was also present at the latter part of Experiment IV.
Thirty Grains of the abovementioned Grain Silver was by Mr. Russel weighed out, and put into a small Hessian Crucible on a flux of Charcoal and Borax made before the company, with the fame precautions as in Experiment I. On the Silver when fused, was projected by Mr. Anderson a bare half grain of the Red Powder, and about five minutes after, some Glass of Borax (to avoid the moisture contained in crude Borax) was thrown in by one of the Company. The Crucible after being kept in a red-white heat for about fifteen minutes was taken out, and when cold broke: at the bottom of the scoriae or rather flux, which in this Experiment was neatly fused, lay the button of metal which was found nearly, if not exactly, of its original weight.
It was then tried by Mr. Russel in the artists' manner; as was also the piece of metal obtained in Experiment IV. He found both of them to contain gold; the latter in larger quantity, as might be expected, from the relative proportion of the Powder and Silver in the two Experiments.
Dr. Price also examined the metal on the touchstone (Basaltes) and with Nitrous acid; when all the company saw the mark of Gold remaining, while a mark made by a piece of the very parcel of Grain Silver from which the portion used in these Experiments had been taken, and placed by the fide of the mark from the enriched Silver, totally vanished on wetting it with the Aqua Fortis.
The mark from the enriched Silver remained (of a yellow colour) after repeated affusions of weak and strong Aqua Fortis. So that the Company were entirely convinced that Gold was now contained in the fused Silver.
The Chemical Reader will probably anticipate the Author's observation; - that of the known metallic substances of a Gold colour, Sulphurated Tin, could not without decomposition, have sustained the heat employed in these Experiments; and that Copper, or Regulus of Nickel, would have been dissolved by the Nitrous acid, equally with the Silver. The remark is indeed scarce necessary; for had it been possible to have secretly introduced into the Crucible any of these metals, (and none of the Company would for a moment tolerate the idea of such an attempt having been made) the identity of weight observed was sufficient to prove that nothing but the crimson powder had been added.
After the pieces of metal had been thus separately examined, they were melted together, and when cool it was remarked that the surface of the culot of metal was elegantly radiated with alternate striae and furrows; an appearance not usual in fused Silver. Ten grains were reserved by Dr. P. for his own examination; and the other 80 grains were taken by Mr. Russel, to be assayed in the refiners' manner.
Dr. P. found the proportion of Gold to be 1/8 of the whole mass.
Mr. Russel in the course of a few days caused all the abovementioned Gold, Silver, and the mixture of Gold and Silver, to be assayed in the artists' manner, for the refiners, at the office of Messrs Pratt and Dean, Assay-Masters near Cheapside.
They assayed each portion separately, and reported the Gold and Silver to be of the most compleat purity: and the enriched Silver to contain Gold in the proportion of one eighth of the joint weight: and this report he also repeated before the Spectators of Experim. VII. on May. 25.
It was remarkable that both the Refiner and Assay-master at first affirmed the impossibility of success in the process; and prejudiced by received opinions, questioned the purity of the metals, though they owned they looked much like ordinary Gold. The assay removed their doubts; and they owned with surprize, that the metals were entirely pure, and certified their purity in their official report.
EXPERIMENT VI.
Made May 15, 1782, before Sir Philip Horton Clarke, the Rev. B. Anderson, Capt. Grose, Dr. Spence, Mr. D. Grose and Mr. Hallamby, and several times repeated before Mr. Anderson, and Dr. Spence.
Two ounces of Mercury were, by one of the company taken out of a Cistern in the Laboratory, containing about two hundred weight of Quicksilver (for experiments on the Gasses) and in a small Wedgewood's ware Mortar rubbed with a drop or two of Vit. Ether: on this Mercury, which was very bright and remarkably fluid, barely a grain of the white powder was put, and afterwards, rubbed up with it for about three minutes.
On pouring the Mercury out of the Mortar, it was observed to have become blackish and to pour sluggishly; after standing ten minutes, on being poured out of the vessel in which it had stood, it was found considerably less fluid than before; and in a quarter of an hour's time so increased in spissitude as hardly to pour at all; but seemed full of lumps. Being now strained through a cloth, a substance like an amalgam, of a pretty solid consistence, remained behind; the unfixed mercury being expelled from this mass, by placing it on a charcoal and directing the flame of a lamp on it with a blow-pipe, a bead of fine white metal remained fixed in a strong red heat; which by every subsequent trial appeared to be Silver: the weight of the bead thus collected, weighed and examined before the company separated, was 18 Grains: but much remaining in the strained Mercury, this was afterwards separated and weighed 11 grains; the whole obtained was therefore 29 grains, or in proportion to the powder as 28:1.
Five drachms of Mercury, taken out in the same manner as the above two ounces, were rubbed up with Vit. Ether, and afterwards with barely a quarter of a grain of the Red powder; a mass like an amalgam being obtained by straining it after it had stood about a quarter of an hour, and the Mercury driven off before the blow-pipe, as in the former Experiment, a bead of yellow metal remained, weighing 4 grains; and after standing some time longer, Gr. 2 and 1/4 more were obtained, both which resisted Aqua Fortis on the touch-stone; and a small quantity being dissolved in Aqua Regia, a purple precipitate was produced from the Sol. by the Sol. of Tin and a brownish one by Sol. Ferri Vitriolati, Bergm. (Green Vitriol or Copperas;) in this Experiment therefore the quantity of Gold was to the powder employed, as 24:1, exclusive of the weight of the powder.
The former part of this Experiment was repeated on Saturday the 18th day of May, before the Rev. Mr. Manning, the Rev. Mr. Fulham, the Rev. Mr. Anderson, the Rev. Mr. Robinson and Dr. Spence.
Two ounces of Mercury, treated as before mentioned, (after exhibiting phaenomena similar to those above related) afforded a mass, one half of which only (to avoid the noxious fumes of the whole) after having the Mercury expelled from it by a white heat before the blow-pipe, yielded upwards of twelve grains of a white metal, that in every trail to which it was submitted, appeared to be Silver.
The product* therefore including the Silver contained in the strained Mercury would have been nearly as 28:1; as in the former Experiment.
A small portion (about 3ij) of the above Mercury being put into another vessel, and about the sixth of a Grain of the red Powder put on it, the Mercury after being ground up with it, and standing some time, was strained as the former, and the small mass so obtained, placed before the blow-pipe. It yielded something more than a grain of Metal, which examined by Nit. acid on the Touchstone, evidently contained Gold; as was apparent to the Company before their leaving the Laboratory. It was intended to have been submitted to other trials, but from its minuteness and form, was accidentally loft.
[* The Author by the words product, produced and the like, here and in other places means only to express that a quantity of precious metal was really obtained; and neither to affirm or deny any speculative opinions relative to the mode of action of the matter projected on the Mercury, or concerning the manner in which the precious metal is contained in Mercury.]
EXPERIMENT VII.
Made Saturday May 25th, 1782, in the presence of the Lords Onslow, King and Palmerston, Sir Robert Barker, Sir Philip H. Clarke, Bart., The Rev. O. Manning, G. Pollen, B. Anderson, J. Robinson, Clks; Dr. Spence, Wm. Mann Godschall, Wm. Smith, W. Godschall, Junr., Esqrs - Messrs Gregory and Russel.
3ij Mercury were taken from the Cistern formerly mentioned, and in a similar manner, and rubbed up with a few drops of Vit. Ether, in a small mortar, as in Experiment VI.
A bare grain of the white powder was projected, and afterwards rubbed up with it. The Mercury, which before the addition of the powder had been very bright and fluid, was now perceived by the company to be dull and run heavily: it was poured out into a small glass vessel, and after standing for about 45 minutes was put into a cloth to be strained. It now poured so sluggishly that the latter portions of it seemed in a state intermediate, between fluidity and solidity, or to use a term less scientific, but like many other vulgar ones, very descriptive, poured grouty.
Great part of the superfluous Mercury being strained off a mass similar to an amalgam was left in the cloth: and the remaining Mercury which could not be pressed out, being driven off by fire from a portion (about a fourth) of the whole mass, a globule of white metal which had all the appearance of Silver, remained, and was kept in a white heat for about two minutes, before the blow pipe.
On the same day and before the same respectable Company:- half an ounce of Mercury revivified from Cinnabar, brought by the Rev. Mr. Anderson, was by him placed in a small round English crucible, taken from among a number of others in the Laboratory, by Lord Palmerston, on a flux composed of a small piece of Charcoal and a piece of borax, both taken casually by some of the company from large quantities, and pounded in a mortar previously inspected by those present.
This flux being pressed down in the crucible with a small pestle, also examined, the mercury was poured into the depression, by one of the spectators, and on it half a grain, bare weight, of the Red Powder, was put by Lord Palmerston. The crucible being then covered with a lid taken in the same manner as the crucible from among many others, and shewn round to the company, was placed in the furnace surrounded by lighted charcoal.
One or more of the Company, particularly the Lords King and Palmerston were during the whole time of the Experiment close to the furnace and operator; and as requested by him gave the closest attention to every part of the process.
When the crucible had acquired a full red heat, the cover was removed, and several of the Company saw the Mercury in a tranquil state, neither evaporating, nor boiling: in which state it continued even when the Mercury itself was completely ignited.
The cover being replaced, the fire was gradually raised to a white heat: the crucible being continued in this heat for thirty minutes, was taken out, cooled, and broke.
A globule of Metal was found at bottom, neatly fused, and exactly fitting the concavity of the divided scoriae. This globule fell out by the blow, among the fragments of the crucible, and was taken up and shewn round to the Company by Lord Palmerston, and in their presence replaced in the hollow of the vitrified Borax, to which it was accurately adapted.
Many other globules were diffused through the scoriae attached to the sides of the crucible, fragments of which were distributed among the company at their request.
The bead which lay at the bottom, weighed about ten grains, and was taken away, together with the Silver, by Mr. Godschall; and by him afterwards transmitted to Lord Palmerston, to be submitted to proper examination.
Mr. Godschall returned the Gold, with the Assay-Master's report on it and on the Silver.
The Assay-Master, whom Mr. G. for greater certainty on this occasion had the precaution to have recommended by the Clerk of the Gold-smith's company, reported both the Gold and Silver to be perfectly pure.
Dr. Price, though acquainted with the characters employed by Assay-Masters in making their reports (which are peculiar to them) unwilling to rely entirely on his own knowledge, and being desirous to offer collateral evidence to the public, shewed the Gold and the Report to Mr. Lock, an experienced Goldsmith of Oxford, without informing him of any of the above particulars.
Mr. Lock affirmed the metal to be by the Report Pure Gold: which he added, was confirmed by it's appearance: and that it consequently was superior to Gold of the English standard.
Two Experiments, similar to those made on Saturday May 25th, were repeated on a larger scale, before some of the above company on the Tuesday following; with the fame attention on their part, and more on that of the Author to the regulation of the fire, which he observed to them, being now less engaged, and his attention not divided, he could employ to produce a much greater effect.
By twelve grains of the White powder were obtained from thirty ounces of Mercury upwards of an ounce and a quarter, or six hundred grains of fixed white metal *; or in the proportion of 50:1. - And two grains of the Red powder, produced from one ounce of Mercury, two drachms, or 120 grains of fixed and tinged * metal; i.e. sixty times its own weight. [* The words fixed and tinged are not used in conformity to any theoretical notions, but merely to denote the obvious properties of the Metals obtained; and to avoid calling them Gold and Silver without the authority of an assay.]
These last portions of Gold and Silver, as well as a part of the produce of the former Experiment, have had the honour of being submitted to the inspection of his Majesty; who was pleased to express His approbation.
This honour may be mentioned with the less impropriety, as it is conferred by a Sovereign equally revered for his patronage of Science and beloved for his amiable condescension.
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