acid, to which order of bodies its qualities much more nearly assimilate it, than to the earths, their composition becomes readily intelligible. They will then be neutral salts, silicates, either simple or compound. Zeolite will be a compound salt, a hydrated silicate of alumina and soda, and hence a compound of alumina not very dissimilar to alum. And topaz, the singular ingredients of which, discovered by Mr. Klaproth, have called forth a query from the celebrated Mr. Vauquelin, with regard to the mode of their existence together, will be likewise a compound salt, consisting of silicate of alumina, and fluate of alumina.

drated tour

mealine?

Our acquaintance with the composition of the several Is zeolite a hymineral substances, is yet far too inaccurate, to render it possible to point out with any degree of certainty the one of which zeolite is a hydrate, however the agreement of the two substances in the nature of their constituent parts, aud in their being both electrical by heat, directs conjecturè towards tourmaline.

St. James's Place, Jan. 22, 1811.

Addition to the Account of native Minium.

After I had communicated to the President the account of the discovery of native minium, printed in the Philosophical Transactions for 1806†, I learned, that this ore came from the lead mines of Breylau in Westphalia.

XII.

Extract from a Paper communicated to the American Philo·~sophical Society on the Discovery of Palladium in a Native · Alloy of Gold; by Mr. J. CLOUD, Director of the Chemical Processes at the Mint of the United States‡.

IN 1807 about 820 ounces of gold bullion were brought Gold from into the mint of the United States. They consisted of 120 Portuguese

Annales du Museum d'Hist. Nat. tome 6, p. 24.

See Journal, vol. XVI, p. 127.

Annal. de Chim. vol LXXIV, p. 99.

America.

small

Analysed.

No silver.

No metal easily oxidable.

Gold.

No platina.

Some other metal.

Palladium.

small ingots, each stamped on one side with the arms of Portugal, and the inscription Rio das montis, and on the other with a globe. The fineness of each ingot too was marked on it. Among these were two differing from the others so much in colour, that Mr. Cloud preserved one, weighing 3 oz, 11 dwts, 12 grs, to examine it. The following were the experiments he made.

1. Nitromuriatic acid was employed on one portion of the ingot, to find whether it contained any silver; and none was discovered.

2. Twenty four carats were mixed with 48 carats of fine silver, and cupelled with lead, to separate any oxidable metal that might be present: but there was no diminution of weight, consequently the alloy contained no metal easily oxidable.

3. The fine metals of the preceding experiment were flattened between rollers, and subjected to the action of pure nitric acid. The silver and the native alloy mixed with the gold, were dissolved by the acid, which acquired a deep brown red colour. The metal that remained, washed with pure water, and dried by the fire, weighed 22 carats 1gr. It had all the appearance of fine gold.

4. The metals not dissolved in the latter experiment were subjected to the action of nitromuriatic acid. The whole was dissolved, except a small quantity of silver, which had escaped the action of the nitric acid. The solution was assayed with muriate of ammonia, and other tests, from an expectation of finding platina, but no trace of this metal was discovered. The gold thrown down was pure to T

5. Pure muriatic acid was poured into the metallic solution resulting from Exp. 3, till the silver was completely thrown down, and the acid was in considerable excess. None of the colouring matter was precipitated from the solution, which remained red, and did not appear at all changed, notwithstanding the precipitation of the silver.

2

From these preliminary experiments it appeared, that the alloy was a compound of gold and some metal capable of resisting cupellation, and soluble both in nitric and nitromuriatic acids. In adopting the following mode of analysis

evident

evident proofs of the existence of a metal possessing all the properties of palladium were obtained.

I. The whole ingot was combined with twice its weight of Analysis of fine silver, and cupelled with lead equal in weight to the the whole.

mixture.

II. The cupelled metals were reduced to thin plates, and kept in boiling nitric acid till the silver and palladium were dissolved. The deep brown red solution was decanted, and the remaining gold washed with distilled water, which was afterward mixed with the decanted solution.

III. Pure muriatic acid was added to the preceding solu tion, till it was in excess, and nothing more fell down. The liquid retaining its red colour was decanted off, and the precipitate washed with distilled water. The waters of elutriation were added to the decanted liquor, which then held nothing in solution but palladium.

IV. A solution of pure potash * was poured into the metallic solution of the preceding experiment, till the whole of the palladium was thrown down in a brown flocculent precipitate. This was washed with distilled water, collected on a filter, and dried.

V. A portion of the precipitate obtained in this experiment was put into a crucible without addition, and exposed to a heat of about 60° of Wedgwood; when a metallic button of palladium was obtained of the spec. grav. of 11-041.

VI. Another portion of the precipitate of Exp. IV was mixed with black flux, and exposed to the same degree of heat as in the preceding experiment. The result was the

same.

A metal supposed to be palladium, thus obtained from a The alloy was source where it was not known to exist, required to be com- palladium; pared with the palladium obtained from crude platina, to confirm its identity. Comparative experiments were accordingly made with prussiate of mercury, fresh muriate of tin,

and other tests. The metals from these two sources did not exhibit the least difference.

Native gold is never found perfectly pure. Hitherto it and no other

Carbonate of potash will not answer so well, because part of the

palladium would remain dissolved in the carbonic acid,

was present.

has

Analyse

No silve

has always been seen alloyed with iver or copper, and most commonly with both, and with other metals 150. Tx gold that was the subject of the preceding experments ap pears to have been alloyed with anladium acne. If it had been alloyed with any other metal, excent aiver or platima, the experiment No. II would have shown it; and silver would have been discovered by the irst experiment, and platina by the fourth.

Analysis of it.

XIIL

Analysis of the Cement of an antique Mosaic, found at Rome by Mr. D'ARCET*.

HIS cement is of a yellowish white, very compact, witheat grains, and pretty hard. It blackens a little in the fire. Before calcination it effervesces briskly: but after it has been calcined, nitrous acid dissolves it without evolving any carbonic acid. In the former case a few yellowish focks remain, and some fragments of a reddish brown colour, but little compact, and resembling the porous lavas, or pazzolana. The yellowish flocks are destructible in the fire.

Sulphuric acid precipitates nothing from these soin bons, therefore they contain no lead.

Ammoniac throws down only a little alumine and oxide of iron.

5 gram. [77-29 grs] of this cement, calcined under a muffle for eight hours, no longer effervesced, and weighed only 2-815 gr. [43-48 grs]; which indicates in 100 parts

56-3 of quicklime; and

43.7 of vegetable or animal matter and carbonic acid. 10 grammes of this cement left 4·1 of carbonic acid, when acted on by nitric acid. We have therefore in 100 parts 59 of quicklime and animal or vegetable matter, and 41 of carbonic acid.

• Ann. de Chim. vol. LXXIV, p. $13. This cement was sent by Mr. Belloni, Director of the Imperial School of Mosaic, who considered it as one of the best cerpents the ancients had employed in the fabrication of their mosaics, and of their pavements in compartments.

On

On comparing these two analyses we find, that the cement

In this cement, we see, the lime, if it were employed The Kme quick, has resumed from the air, and in the lapse of time, nearly satu. nearly all the carbonic acid necessary for its saturation.

rated.

This is the first time of my observing this fact. As I This singular.
have never found the lime in mortar, however ancient, satu-
rated with carbonic acid, I am inclined to suppose, that the

vegetable or animal matter, that served as a gluten, pro- How effected.
moted the absorption of carbonic acid; or rather, that the
cement in question was made with carbonate of lime (whit-
ing), and not with quicklime.

In the latter case about 97 parts of carbonate of lime, and
3 of oil, glue, or cheese, must have been employed.

In the former the cement would have been composed of about 56 parts of quicklime to 3 of vegetable or animal

matter.

It is obvious, that these proportions, which are found at présent to form the cement in question, were not followed in its preparation.

If oil were employed, it would have increased in weight in drying; and then less than 0.03 must have been used, which appears to me impossible.

It is more than probable therefore, that the substance em- Its probable ployed was analogous to the caseous part of milk, and then composition, it would have diminished in weight by losing the water it

contained, which served to reduce to a paste the lime or
carbonate of lime.

From this analysis it appears, that the cement was very
simple; and that those we now compose on the same prin-
ciple would become equally hard in time.