here in the museum.

There are some specimens before have been pure. Having carefully gone over these you very beautifully crystallised. This calcite is pure car-experiments, I have no hesitation in stating that, as bonate of lime. So far as analyses tell us, some specimens I said just now, I consider them to be unsatisfactory. of Iceland spar are absolutely chemically pure. Some- "By the lens," he says, "this same surface was seen to times they contain about one-half per cent. of water, and be glazed all over, though irregularly, showing here and they not unfrequently enclose foreign matters, such as there some air-holes. In fracture it was semi-transparent, copper pyrites and sand. more vitreous than crystalline." Last of all, he uses Next as to the formation of calcite. Calcspar, or crystal-platinum, to obviate the effect of the iron. The effect of lised carbonate of lime, crystallises in the rhombic system. We have seen that it can be produced by means of water. We will now consider its production through the agency of fire only. We have all heard of the famous experiments of Sir James Hall, the record of which now lies before me. I think they were commenced in 1798, and the results were communicated to the Royal Society of Edinburgh. He informs us that he took amorphous carbonate of lime, or chalk, and by exposing it to a high temperature under considerable pressure he succeeded in converting it into saccharoidal limestone, like Carrara marble. I have had an opportunity of seeing one specimen prepared by Sir James Hall himself, and I must say that the result did not strike me as conclusive. But now for the evidence. He enclosed carbonate of lime in gun barrels, and resorted to various expedients of plugging those gun barrels, such as plugs of soft metal and so forth. He then exposed a portion of the gun barrel to a high temperature, taking care to arrange the tube horizontally in such a manner that the plug of soft metal should not be melted; and he obtained a hard substance like limestone after having exposed chalk to these conditions. He says, "My first application of this scheme was carried on with a common gun barrel cut off at the touch-hole, and welded very strongly at the breech by means of a plug of iron. Into it I introduced the carbonate, previously rammed into a cartridge of paper or pasteboard, in order to protect it from the iron, by which in some former trials the subject of experiment had been contaminated throughout during the action of heat. I then rammed the rest of the barrel full of pounded clay previously baked in a strong heat; and I had the muzzle closed like the breech, by a plug of iron welded upon it in a common forge, the rest of the barrel being kept cold during this operation by means of wet cloths." This gives you an idea of one of his experiments. Then he comes to the use of fusible metal. He employed tubes of glass. I wish particularly to examine the evidence upon this subject, because it is one on which much stress has been laid. do not wish to question unnecessarily the accuracy of Sir James Hall's conclusions, but I may remark that the carbonate of lime being heated to a high temperature in contact with glass, the result would be altogether vitiated, and the crystallisation could not be said to depend merely upon the outward conditions to which the substance was exposed. We find that in other experiments he used small quantities of carbonate of lime in contact with silica and clay; but the presence of these two bodies would very much modify the result. In other experiments he used borax, and that again would altogether vitiate the result. Therefore, the conclusions drawn from these experiments are unworthy of being received-at all events, without further evidence. He tells us, that in several cases the material which he obtained, although resembling crystalline limestone, fell to pieces on exposure to the air. That, however, is not the property of crystalline limestone. I have no doubt that the investigations of Sir James Hall were conducted with perfect honesty and candour, and they must have involved a great deal of expense; but, as far as I know, recourse was never had to chemical analysis, and, without that, no result ought to be received. Indeed, Sir James Hall himself confesses his deficiency in chemical knowledge. He tells us, that in various experiments he got a product in glass-like drops which were semi-transparent, and this clearly proves that the carbonate of lime operated upon could not

I

the iron would be to act as a strongly reducing agent upon the carbonic acid by the formation of carbonic oxide, and the tendency to decompose the carbonate would of course be facilitated by reasons which are well known to chemists. It appears, after all, that Sir James Hall obtained some results which would certainly lead us to believe that, by the application of a strong red heat, carbonate of lime would acquire a crystalline structure; but it is exceedingly desirable that these experiments should be repeated with all possible care, that the question may be cleared up satisfactorily. No doubt they would involve considerable expense; but if proper care were taken, and proper apparatus employed, I have no doubt that we should obtain something like very decisive results. I hope that you will not consider that I have shown the smallest disposition to speak disparagingly of the labours of Sir James Hall. I do attach some importance to these investigations, and I think they are in the highest degree creditable, considering the time at which they were made. They extended over several years; but, looking at the results, I cannot feel that confidence which seems to be generally reposed in them. Some years ago, Gustave Rose took up the subject, and came to the conclusion that Sir James Hall had been entirely mistaken; but more recently he has come to an opposite conclusion. But Rose's experiments are by no means so conclusive as they might be. In his recent experiments, which are published only this year, and will be found in the 118th volume of Poggendorf's Annalen, by employing a wrought-iron vessel, electro-plated with nickel, and capable of being closed-so avoiding the contact of iron at a high temperature with the carbonate of lime operated upon, and, consequently, the reducing action of that metal on the carbonic acid of the carbonate of lime-he succeeded in changing arragonite into a substance having the charcteristic appearance of Carrara marble. The experiment, he tells us, was conducted in a Siemen's gas-furnace--that is, a furnace capable of sustaining a long-continued and high temperature. A closed unglazed porcelain vessel was employed, and exposed to a white heat during half an hour, and he informs us, that under these conditions a piece of lithographic stone became greyish-white in fracture, and, under a lens, was found to be finely granular. The product was analysed, and contained,-Lime, 56.61; magnesia, 0'41; carbonic acid, 42-37; residue, 0'45. Pure carbonate of lime contains 56 per cent. of lime and 44 per cent. of carbonic acid. What was the undetermined residue? The presence of a small amount of silica might make a considerable alteration in the result. After carefully examining the way in which Rose's experiment was conducted, it appears to me inconclusive. It is obvious that there could have been no sensible degree of pressure. The porcelain vessel was not in the least injured, so that the temperature must have been much below that which we can now command-as, for instance, in the fusion of platinum. It is most desirable that we should have some further investigation on the subject. The British Association might take up the question with advantage; they have funds at their command, and it would be exceedingly desirable to settle this important point once for all.

What we call carbonate of lime in nature-take even the purest marble-is not pure. At one time I was anxious to investigate this point, and I went to a sculptor and obtained numerous varieties of marble, but in not one of them did I fail to detect alumina. Chalk is an impure body, and the presence of foreign matter might altogether

SCIENTIFIC AND ANALYTICAL

CHEMISTRY.

Chemical Studies on Copper, by MM. E. MILLON and
A. COMMAILLE.

is the result, insoluble in water, resisting lixiviation, and formed exclusively of sulphurous acid, water, and binoxide of copper.

In this salt, binoxide of copper is quadri-atomic, even when a large excess of alcohol, saturated with sulphurous acid, is used. The formula of this new combination is SO2,4CuO,7HO.

This constitutes a new example to add to those combinations wherein salts with polyatomic oxides are formed, in spite of the presence of an excess of acid.

Ammoniacal

Protochloride of Copper and Bichloride of Platinum.-The well-defined reaction of ammoniacal protochloride of copper on salts of silver, which are reduced and give a weight of metallic silver exactly proportionate to the quantity of protosalt of copper, has led us to examine the affinity existing between the protochloride of ammoniacal copper and the bichloride of platinum.

Sulphites of Copper. The composition of these salts, studied and discussed by so many chemists, seems to be decided by M. Péan de Saint-Gilles. By directing a current of sulphurous acid gas into a solution of acetate of binoxide of copper, a yellow precipitate is formed, which redissoves in the liquid; but, on boiling the solution, an abundant deposit of small red crystals takes place. M. Péan gives the composition of these crystals as Cu,O2,2SO2,2HO. The total amount of copper and sulphur contained in these red crystals accords with this formula; but, by separately estimating the copper in the state of protoxide and binoxide, it will be found that the proportion Cu2 is The platinum of the bichloride is not reduced to the too small by 2 per cent., and Cu too large by 3 per metallic state, but is simply brought back to protocent. Moreover, it is found that the salt contains just chloride; however large the excess of protosalt of copper, 3 per cent. of sulphuric acid mixed with sulphurous acid. the reduction proceeds no further. It does not thence The exact analysis of this combination indicates follow that the affinity of chlorine is greater for platinum 6 per cent. of sulphate of binoxide interposed in the than for silver. There is here a special influence, which salt described by M. Péan; washing removes none must be attributed to the intensity of the combinations of the sulphate before decomposing the sulphite itself. formed between protochloride of platinum with ammonia, Sulphate of binoxide seems to be constantly present-a-combinations whose constitution and nature M. Reiset fact we have verified by uniformly obtaining the same has so ably explained. figures in three successive preparations of red sulphite. This can, however, be avoided by altering the mode of operation adopted by M. Péan and by MM. Chevreul, Bottinger, Dopping, and Rammelsberg, who examined this salt before he did. The formula of this compound, obtained free from all mixture, and irreproachably pure, is CuO,2SO2,2HO, or Cu2O,SO2 + CuÒ‚SO2 + 2HO. It offers the rather curious analytical peculiarity of furnishing the same numbers in binoxide of copper and in sulphuric acid, whether it is pure or mixed with 6 per cent. of sulphate of binoxide.

The yellow deposit formed by sulphurous acid in a solution of acetate of binoxide of copper, M. Péan considers as a peculiar hydrate of the above salt; he assigns to it the formula CuO,2SO2,5 HO.

The whole determination of copper made by M. Péan agrees exactly with the preceding formula; but by estimating the relative proportion of Cu, and Cu, there appears irreconcilable deviations from this formula, and much more decided than in the analysis of red sulphite. We have obtained, in various preparations, 7.60, 11.66 and 19.72 per cent. of copper in the state of protosalts; the formula adopted by M. Péan would require 28.78 of copper in the state of protoxide. Notwithstanding the above-mentioned variations in the constitution of this compound, the total estimation of copper always gives the same number, precisely that indicated by M. Péan. Thus, this yellow product represents a mixture in which the weight of copper is a fixed quantity, while the degree of oxygenation of the metal varies enormously. It is probable that sulphurous acid and acetate of binoxide of copper first form an insoluble and unstable sulphate of binoxide, the molecules of which react on each other, the sulphurous acid oxidising at the expense of the binoxide of copper, until the appearance of the red sulphite, producing a new state of equilibrium among

the elements.

We have made several attempts to combine sulphurous acid with binoxide of copper, and succeeded by saturating absolute alcohol with sulphurous gas, and adding hydrate of binoxide of copper. A green powder VOL. IX. No. 217.-JANUARY 30, 1864,

This is what takes place :-On pouring a concentrated solution of bichloride of platinum into a very ammoniacal liquid saturated with protochloride of copper, a violet crystalline precipitate is formed, sometimes of a perfectly pure colour, somewhat like the beautiful tints of some cobaltic salts, sometimes with the colour verging on grey, in which case the crystals are smaller, and always in the form of long prisms with square ends, isolated or irregu larly grouped, and often scooped out with two conical cavities approaching at their points.

These crystals, very stable when dry, are insoluble in water or alcohol, and alter only at length by washing; their composition is exactly represented by[Pt. Cu CI,NII,.

2

Their formula may be doubled, and they may be considered as the combination of an ammoniacal bichloride of copper, CuCI,NII, described by R. Kane; with Magnus' chloride, PtCI,NH. But it is more probable that this combination represents the chloride of a base, containing two metals, analogous to the unimetallic bases described by M. J. Reiset; but it differs from the latter in containing both copper and platinum, whose reactions are equally masked. This is, we believe, the first instance of a bimetallic ammoniacal chloride. The reac tions of this new compound, both with acids and bases, hardly admit of any other supposition.

We shall have to describe several interesting compounds derived from it; but this would lead us away from the study of copper itself, to which for the present we wish to restrict ourselves.-Comptes-Rendus, lvii., 820, 63.

Copper Bronze for Paper Hangings.- Boil ten pounds of logwood twice in water, filter the decoction and tin salt. A precipitate falls, which is separated, washed, evaporate to half its bulk. Then add twenty ounces of and when mixed with soap-suds, spread on paper, and and dried. The precipitate has then a dark blue colour, well rubbed, it gives a brilliant metallic lustre. Alum, or bichromate of potash, may be used instead of the chloride of tin.-Deutsche Industrie-Zeitung.

On the Supposed Nature of Air prior to the Discovery
of Oxygen, by GEORGE F. RODWELL, F.C.S.
(Continued from page 28.)

5. Boyle's Experiments continued.-Experiment 17. A tube three feet long and a quarter of an inch in diameter, closed at one end, was filled with mercury, and inverted in a vessel of the same metal; the latter was placed within the air-pump receiver, and the tube passed air-tight through its cover; on exhausting, the mercury fell nearly to a level with that in the vessel; but the same level within and without the tube could never be attained, because, when the exhaustion was carried on for some length of time, air leaked into the receiver in spite of every precaution. When a quart receiver was used, the first downward stroke of the piston withdrew sufficient air to cause the column to fall eighteen and a-half inches. The falling of the mercury was not, however, entirely due to the removal of pressure, because a minute quantity of air was always present in the space above the mercury, and by its expansion the mercury column would be depressed. The mercury was never boiled in the tube in these early experiments, hence there was always a small amount of air, which was mechanically retained by the mercury, and rose into the so-called vacuum, when the tube was inverted. Boyle states that, when the tube was inclined, the mercury never reached quite to the top of it, and when a hot iron was held near that part of the tube above the mercury, a slight depression of the column was apparent. Experiment 18. The height of the mercury column in Torricelli's tube was found to vary from day to day, and it did not vary in conformity with the weather-glass.† According to Boyle the variation may be caused by ebbings and flowings in the atmosphere, and by sudden changes in its height and density, produced by causes with which we are unacquainted. That changes do take place, he considers is proved by the fact, that the refracting power of the air varies; and miners had related to him that a certain steam, called by them a "damp,"‡ sometimes arises within mines, and possesses such "thickness that it extinguishes candles; it may also happen, he says, that fumes ascend from the earth with such rapidity, that the air through which they pass is dragged upwards by them, and a consequent diminution of pressure on that part of the earth beneath the ascending currents, takes place.

Mr. Wren, being asked by Boyle to mention any experiment relative to the pressure of the air which he would wish to be tried, said it would be of importance to observe if the height of the mercury column varied according to the tides, inasmuch as, if it did not do so, Des Cartes' theory, that tides are produced by the increased pressure communicated to the air by the moon at certain times of the day than at others, would be disproved. Boyle did not find the height of the column affected by the state of the tides.

Experiment 19. Having observed, in experiment 17, to what extent a column of mercury could be made to fall on the removal of pressure, Boyle next tried the same experiment with a column of water, contained in a *This experiment, as mentioned in the third of these papers, was tried by a different but far more complete method by Pascal; we must bear in mind, however, that his treatise "On the Weight of the Mass of Air" was not published till 1663, whereas Boyle's PhysicoMechanical Experiments" appeared in 1661. Pascal undoubtedly made the experiment first, but Boyle was probably unaware of

the fact.

An account of some experiments made with the weather-glass here referred to will be given in the next Number of this Journal. From the German "dampf,"-vapour, steam, fume.

within a foot of the surface of water in the vessel into tube four feet long. On exhausting, the water fell to which the open end of the tube dipped. When air was re-admitted into the receiver, water was driven violently to the top of the tube.

In the 21st experiment Boyle declares he will not say for certain "whether or no air be a primogenial body," incapable of conversion into water; for, although many have affirmed that when water is heated it becomes air, he has observed in chemical distillations that the vapour of water quickly returns to water; and, in the Museum Kircherianum, Schottus states there is a hermetically sealed glass vessel half full of water, which had been sealed for fifty years, without the water becoming air. On the other hand, however, it appears that air can be produced, because, when a number of iron nails were placed in a mixture of oil of vitriol and water, Boyle found that a quantity of air was evolved, and, although this does not prove that water may become air, it proves, he considers, that air may be generated.

If, by any chance, Boyle had brought a candle near his newly-generated air, what a wide field would have been opened to him when he found that there were other airs differing from "the air;" but the possibility of there being different kinds of air does not seem to have entered his head; for even carbonic acid gas, although so totally different from ordinary air, was only distinguished by him as "thickened air."

Experiment 27. A watch was suspended by a thread in the air-pump receiver; on exhausting, the ticking ceased to be heard; but when air was re-admitted, it was heard as distinctly as before exhaustion.

A bell was supported in the receiver by a bent stick, the ends of which pressed against the sides of the receiver; when the latter was exhausted, and the bell rung, the sound was distinctly audible; hence Boyle concluded that sound can be conveyed by some rarer medium than air.

This is one of many examples of the great disadvantages under which the early experimenters laboured, and we must make every allowance for the false conclusions at which they sometimes arrived. When Boyle made this experiment, very little was known about the nature of sound; there were no previous experiments to tell him that the thread would not convey the vibrations to the receiver, whereas the stick would do so, and he, therefore, could have no reason for believing that there would be any difference in the result obtained, whether he suspended his sounding body by a thread or by a piece of wood, and yet perfectly contrary effects were produced, and he was thus led to a wrong conclusion.

the pressure of air on a known area.
Experiment 33 was made with a view of determining
The air-pump
receiver was removed from the pump, and the piston
forced to the top of the cylinder, the upper orifice of the
latter (into which the shank of the stop-cock of the
receiver fitted) being left open; weights were attached
to the piston until it was drawn down. The piston was
then forced to the top of the cylinder-the upper orifice
of the latter closed-and weights were again attached
until the piston was drawn down; the weights obviously
represent the force necessary to overcome the pressure
of the air, acting on the area of the piston + the force
necessary to overcome the friction between the piston
and pump barrel; the weight necessary to overcome the
latter source of resistance having been previously deter-
mined, it was subtracted from the total weight, and it
was thus found that 112 lbs. were competent to over-
come the pressure of the air on the piston. The experi-

ment was modified by drawing the piston to the bottom of the cylinder, against the pressure of the air, and seeing how much weight it would draw up-105 lbs. + the weight of the piston rod were raised.§

Experiment 34. Reasoning by analogy from the fact that two bodies of equal weight in air, but of different bulk, when weighed in water no longer balance each other, Boyle conceived that two bodies of equal weight in air would not be so in a vacuum. He, therefore, balanced on the opposite ends of a balance, capable of turning with nd of a grain, a piece of cork and a piece of lead; the balance was placed in the air-pump receiver: on exhausting, the cork was found to preponderate, but on readmitting air, it continued to preponderate from some cause which Boyle was unable to discover.

the air is condensed. When air is readmitted, the particles strike against the sides of the receiver, and the amount of mass motion previously produced is reconverted into the molecular motion which produced it; consequently, the deposited water again becomes vapour.

Experiment 40. In order to see whether the rarity of the air in an exhausted receiver would prevent insects from flying, Boyle placed a bee and a fly in the receiver on exhausting, they both fell down "as in a swoon."

Experiment 41. A lark was placed in the receiver; on exhausting, it was seized with convulsions, and although air was quickly readmitted, it failed to revive. pump had been worked ten minutes.

The

I have mentioned in the previous paper that the descriptions which Boyle gives of his experiments are exceedingly prolix; we have a good example before us in this experiment, which we should, in the present day, describe as above, but which Boyle, after telling us how he procured the bird, and how, when placed in the receiver, it did "divers times spring up in it to a good height," describes as follows:

Experiment 36. It is obvious, Boyle writes, that if we could place a balance above the atmosphere, or in a vacuum, we might weigh a quantity of air in the scales of the balance, just as we weigh substances in the air. In order to put this idea in practice, he procured a small "glass bubble," about the size of a hen's egg, and sealed it hermetically. It was then fastened to one end of the "The vessel being hastily, but carefully clos'd, the beam of the balance used in experiment 34, and was Pump was diligently ply'd, and the Bird for awhile counterpoised by a piece of lead. The balance was appear'd lively enough; but upon a greater exsuction of placed in the receiver; on exhausting, the vessel of air the Air, she began manifestly to droop, and appear sick, greatly preponderated, and by placing weights on the and very soon after was taken with as violent and irreother scale of the balance, so as to drag down the air-gular convulsions as are wont to be observ'd in Poultry vessel, it was found that, in a vacuum, the air in the when their heads are wrung off. For the Bird threw bubble weighed ths of a grain. On one occasion, herself over and over two or three times, and dyed with when the exhaustion had been continued for some time, her Breast upward, her Head downwards, and her Neck the included air burst the bubble with violence. awry. And though upon the appearing of these convulsions we turn'd the stopcock, and let in the air upon her, yet it came too late; whereupon, casting our eyes upon one of those accurate Dyals that go with a Pendulum, and were of late ingeniously invented by the noble and Learned Hugenius, we found that the whole Tragedy had been concluded within ten minutes of an hour, part of which time had been imploy'd in cementing the cover to the Receiver."

Boyle here describes several experiments which he made in order to determine the relative weights of air and water. The determination had been previously made by several different methods. Galileo found water to be 400 times heavier than air; Ricciolus (by weighing a bladder of air_in_air),|| 10,000 times; and Merseunus, 1356 times. Boyle's method was to heat a copper elopile of known weight to redness, stop up the orifice with wax, weigh, perforate the wax to allow air to enter, and again weigh; the elopile was then filled with water, and weighed. By this method water was found to be 938 times heavier than air.

Boyle next determined the relative weights of water and mercury, and found the latter to be 132 times heavier than the former. The relative weights of air and mercury were deduced from the above data, and were found to be as 14000 to 1. When in possession of these facts, Boyle was able to calculate that the height of the whole atmosphere, if we suppose it to possess throughout the same density as at the surface of the earth, would be seven miles; but, he writes, knowing as we do how readily air expands when pressure is removed from it, it is not improbable that the atmosphere may extend to a height of some hundreds of miles.

Experiment 37. Boyle frequently observed that when exhaustion was commenced the inside of the air-pump receiver became opaque, and that on the readmission of air the opacity disappeared. We now know this phenomenon to be produced by the deposit of minute particles of water, previously existing in the state of vapour in the air. The air in expanding performs work, and a certain amount of molecular motion is converted into mass motion; consequently, the aqueous vapour in

The diameter of the piston was three inches; hence its area =70686 square inches. The pressure of the air upon it would, therefore, be, in round numbers, 7:0686 × 15 lbs. 106 020 lbs.

It is obvious, as mentioned in the first of these papers (CHEMICAL News, vol. viii., p. 115), that a bladder of air, we ghed in air, weighs no more than the empty bladder.

We must certainly give Boyle credit for being an accurate observer, and an experimenter who did not pass over the most minute occurrences without mention; but conceive what a memoir would be in the present day if it were spun out like the above account of one experiment! Why, the Royal Society would have to publish folios, and the Philosophical Magazine would become a thick quarto, and it would require half a lifetime to master one branch of science.

After the success of the lark experiment, Boyle placed a sparrow and a mouse in the receiver. On exhausting, they both died. In order to see whether death was produced by the "steams" from the lungs stifling the animals or from want of air, a mouse was enclosed in a large receiver. At the end of several hours it was alive and well, but died when the receiver was exhausted, proving that want of air was the cause which had produced the previous deaths.

Boyle here enters into a discussion as to the nature of Respiration. Many of the philosophers of his time believed that the sole use of respiration was the cooling and tempering the heat of the heart and blood; and this theory was not only admitted by several of the ancient writers, but by the Cartesians and numberless learned men. But, Boyle answers, fishes and frogs, and "divers cold creatures," have need of respiration; and in the above-mentioned experiments, in which animals were killed in rarefied air, it did not appear that the interior of the receiver was hotter than the external air. Some believed that air passes from the lungs to the