A chemical Analysis of some Calamines. By James Smithson, Esq. F.R.S. Read November 18, 1802. [Phil. Trans. 1803, p. 12.]

The uncertainty that has till now prevailed concerning the nature and composition of the ores of zinc called Calamine, has induced our author to enter upon the investigation now before us. In the first part of the paper, we find the analysis of four kinds of calamines ; the first from Bleyberg in Carinthia, the second from the Mendip hills in Somersetshire, the third from Derbyshire, and the fourth an electrical calamine from Regbania in Hungary. Referring to the paper for the detail of the four processes there circumstantially described, we must content ourselves with reciting here the results deduced from each of them.

1000 parts of the Bleyberg ore were found to consist of 714 calx of zinc, 135 carbonic acid, and 151 water. Some carbonate of lime and lead were likewise found in it; but these appeared to be mere accidental admixtures, and in too small quantities to deserve notice.

1000 parts of the Mendip ore consisted of 648 parts of calx of zinc, and 352 of carbonic acid, and yielded no water.

In the Derbyshire ore were found 652 of calx of zinc, and 348 of carbonic acid.

And in the Hungarian ore, 683 of calx of zinc, 250 of quartz, 44 water: and here there moreover appeared a loss of 23, owing, no doubt, to some defect in the manipulation. The water was by no means considered as an essential part of this ore; and hence the proportions of the two other ingredients were as 739 to 261.

In a second part of the paper, the author communicates some observations to which he was led by the uncertainty that still prevails in our chemical researches, and the want of uniformity in the results of the multitude of experiments that are daily made, which appear to him to clash essentially with the simplicity of nature. When we consider, he says, the simplicity found in all those parts of nature which are sufficiently known to come within the reach of our observation, it appears improbable that the constituent parts of bodies, which we consider as endowed with reciprocal affinities, should be so loosely united as is often indicated by the most accurate analysis. Hence he is led to conjecture, that in all chemical combinations, those ingredients which are really essential to the compound are but few in number; that they are by nature certain aliquot parts of the whole compound; and that as the aliquot may be expressed by fractions, the denomination of these fractions will always be a small quantity, perhaps never exceeding the number 5.

The author applies this theory to the above-mentioned experiments on calamine; and finding that, with a trifling correction, the results coincide with this theory, he entertains sanguine hopes that future investigations will finally establish it. If so, he thinks that the discovery will introduce in chemistry a rigorous accuracy, of which it has not hitherto been thought susceptible; that it will enable the chemist, like the geometrician, to rectify by calculation the unavoid

able errors of his manual operations, and authorize him to eliminate from the essential elements of a compound those products of an analysis whose quantity cannot be reduced to any admissible proportion, and may therefore be considered as extraneous.

The author, at the close of his paper, controverts the opinion of those who think that crystallization requires a previous state of solution in the matter crystallized; and contends, that as long as any quantity of fluid is present in a solution, no crystallization can possibly take place.

Experiments on the Quantity of Gases absorbed by Water, at different Temperatures, and under different Pressures. By Mr. William Henry. Communicated by the Right Hon. Sir Joseph Banks, K.B. P.R.S. Read December 23, 1802. [Phil. Trans. 1803, p. 29.] After a short recapitulation of what has of late been done by Mr. Cavendish, Dr. Priestley, Dr. Nooth, and others, respecting the impregnation of water with different gases, our author observes, that the circumstance of the different degrees of temperature and pressure had not been as yet sufficiently attended to. Dr. Priestley, indeed, had long since remarked, that, in an exhausted receiver, Pyrmont water will actually boil at a common temperature, by the copious discharge of its air; and that hence it is very probable, that by means of a condensing engine, water might be much more highly impregnated with the virtues of the Pyrmont spring: but this conjecture remained as yet to be proved by experiments; and this is the task our author has undertaken in the present paper.

This paper consists of two sections; the first treating of the quantities of gases absorbed by water under the usual pressure of the atmosphere; and the second, of the influence of pressure in promoting the absorption of gases. The apparatus contrived for these experiments may be described as a siphon, of which one side, or leg, is a glass vessel of comparatively a considerable diameter, and the other a long glass tube of about a quarter of an inch bore; the junction of these two parts at the bottom being a short pipe of India rubber, well secured by proper integuments of leather, thus forming a joint, which admits of the vessel being briskly agitated. This vessel has a stop-cock both at top and bottom, in order to insert and emit fluids and gases; and both the vessel and tube are accurately graduated. It may now be understood, that a known quantity of water and of a certain gas being put in the vessel, and the tube being filled to a certain extent with mercury, the absorption of the gas will be accurately measured by the column of mercury in the tube. Those who are particularly interested in this inquiry will find in the paper various precautions and additional contrivances, all tending to insure the success and accuracy of the investigation.

The first experiments were made on the absorption of carbonic acid gas by water: and here a singular disagreement was observed in the first trials made under exactly the same circumstances.

It

soon occurred that this might be owing to the variable amount of the residua of the gas, after the absorption; and this was actually confirmed by the observation, that, of a greater quantity of gas, more would be absorbed than of a smaller, though both quantities were sufficient for saturation of equal quantities of water. This was found to be owing to the quantity of common air, which will ever be extricated from the water, though it be ever so pure, and which will form a greater proportion of the smaller than of the greater dose of the residuary gas.

A table of nine experiments is next given, in which are entered the temperature, the quantities of water and gas, the quantities of gas absorbed, the residua, and the quantities absorbed by 100 inches of water. The two extreme results are, that, at the temperature of 55°, 13 measures of water, exposed to 32 measures of gas, absorbed 14 measures, leaving a residuum of 18 measures; so that the absorption of 100 measures of water would be 108 measures of gas. In the temperature of 110°, 20 measures of water, exposed to 20 measures of gas, absorbed 9 and left 11; so that 45 in 100 was the total of the absorption.

A series of experiments on other less absorbable gases have afforded for one temperature, viz. 60°, and in 100 cubic inches of water, the following results :-nitrous gas 5 inches, oxygenous gas 2.63, phosphorated hydrogen gas 2·14, azotic gas 1.20, and hydrogen gas 1.08. Some experiments are next described on the quantity of atmospherical air that may be extricated from water; the general result of which is, that 100 cubic inches of common spring water will yield 4.76 of gas; which, being analysed, was found to consist of 3-38 carbonic acid, and 1.38 atmospherical air.

The object of the second section being to ascertain the ratio between the addition of pressure and the increased absorption of gases by water, Mr. Henry made some alteration in his apparatus, which consisted chiefly in lengthening the tube, so that, by the addition of mercury, any required addition of pressure might be obtained on the water and gases.

The results of a series of at least fifty experiments on a variety of gases were, that under equal circumstances of temperature, water takes up, in all cases, the same volume of condensed gas as of gas under ordinary pressure; but that as the spaces occupied by every gas are inversely as the compressing force, it follows that water takes up of gas, condensed by one, two, or three additional atmospheres, a quantity which, ordinarily compressed, would be equal to twice, thrice, &c. the volume absorbed under the common pressure of the atmosphere.

Experiments and Observations on the various Alloys, on the specific Gravity, and on the comparative Wear of Gold. Being the Substance of a Report made to the Right Honourable the Lords of the Committee of Privy Council, appointed to take into Consideration the State of the Coins of this Kingdom, and the present Establishment and Constitution of His Majesty's Mint. By Charles Hatchett, Esq. F.R.S. Read January 13, 1803. [Phil. Trans. 1803, p. 43.]

From the introduction to this paper we learn, that in the year 1798, His Majesty was pleased to appoint a committee of members of his Privy Council, to take into consideration the state of the coins of the kingdom; and that this committee, having remarked the considerable loss which the gold coin in particular had sustained by wear within certain periods, had applied to Mr. Cavendish and Mr. Hatchett for their opinion what were the causes of this diminution, and what remedy might be applied to the defects by which it is occasioned. The mode of carrying on this investigation having been agreed upon by these two gentlemen, it fell to Mr. Hatchett's lot to perform the preconcerted experiments, and to draw up the account of them. Of this account, as it was too voluminous, and consisted of too many tables to be read in public, Mr. Hatchett has been pleased to communicate to the Society the Abstract, the reading of which took up the whole of this and the preceding meeting. On a general contemplation of the subject, it soon occurred that the inquiry was to be directed to two principal points;-1st, which of the two sorts of gold, whether that which is very ductile, or that which is as hard as is compatible with the process of coining, suffers the greatest loss under the general circumstances of friction;-and 2dly, whether coins with flat, smooth, and broad surfaces, wear less or more than coins which have certain protuberant parts raised above the ground or general level of the pieces. With a view of arriving at some certain data respecting these questions, three objects were principally kept in view, which gave rise to the three sections that compose the body of the paper. The first of these comprehends the chemical experiments, those which relate to the effects produced upon gold by the addition of different metals in certain relative proportions ;-the second includes those experiments which relate to the different degrees of density observed in gold when differently alloyed;—and the third consists of those experiments which may be called mechanical, and which were expressly intended to ascertain the comparative wear of different kinds of gold by various modes of friction.

In the numerous set of experiments which are described in the first section, the effects of every metal and semi-metal upon the colour and ductility of gold were ascertained with all possible care and precision. All the semi-metals were found to affect the quality of gold too essentially, though in different degrees, to be ever used as alloys. And among the metals, lead in very small proportions was likewise found to render gold so completely brittle, as to be absolutely unfit for coinage. Tin was not near so pernicious; and iron, though it

turned gold much paler, yet did not materially affect its ductility. With respect to platina, one-twelfth of this metal, alloyed with gold, turned the latter metal to a colour similar to that of tarnished silver, but did not essentially diminish its ductility. Hence it is inferred, that a mixture of platina with gold, with a view to the adulteration of coin, need not be so much apprehended as was once the case, since the remarkable change of colour is a sufficient criterion to detect the fraud. The ultimate results of the experiments on copper and silver are, that these, either jointly or separately, are the only metals fit for alloys to reduce fine gold to the standard; care only must be taken that they, especially the copper, be of the purest sort; for which purpose, the fine granulated Swedish copper is recommended as the most proper. A mixture of the two metals ought to have the preference, as the colour of the gold is least affected by it.

2. In examining, in the second section, the specific gravity of gold made standard by different metals, single or mixed, it was found that several variations take place from causes independent of any defects in the hydrostatical operations. These are imputed to occasional imperfections in the interior texture of the mass during the processes of melting and casting; to a difference of density in parts of even the same mass; to the nature and position of the mould in which the metal is cast,— -a long mould in a vertical position always producing a bar of metal more dense at the bottom than towards the top; to peculiar effects which certain metals produce when employed as alloys, and which are often very different from the results of calculation; and, lastly, to the effect of friction, which, as it is well known to generate heat, cannot, by the expansion it occasions, but affect the specific gravity of the metal. It hence follows, that as the specific gravity of metals is liable to be influenced by such a numerous variety of causes, it is almost in vain to expect absolute precision in the results of such experiments, and that a near approximation is all that can be demanded.

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From the experiments made upon separate and entire ingots of gold, reduced to standard by silver and copper, separately and conjointly, it was proved that their specific gravities were as follows:gold made standard by silver, 17·927; gold made standard by equal parts of silver and copper, 17.344; and gold made standard by copper, 17.157. Hence it appears that the specific gravity of our gold coin, which is generally alloyed by a mixture of the two metals, must be found somewhere between the two extremes just now mentioned; or, making allowances for small variations, arising from accidental causes, between 18 and 17.

3. In the third section, which treats of the comparative wear of gold when variously alloyed, we find, in the first place, an account of three modes or contrivances for ascertaining the quantity of abrasion by friction, according to the different circumstances of alloy and figure in the coins. In the first, two sets of coins were fastened, each in a frame, one of which was made to move backwards and forwards over the other with certain determined degrees of velocity