Differtation I. On the Aerial Acid..

This effay contains an experimental inveftigation of Fixed Air, firft publifhed in 1775, in one of the volumes of the Transactions of the Swedish Royal Academy of Sciences. One of the prin cipal defigns of the Author is to prove the acidity of fixed air; to which he gives the name of the Aerial Acid. Among the various proofs of this quality, exhibited by M. Bergman, it is rather remarkable that, though he obferved its property of readily combining with alcaline falts, rendering them milder, and cryftallizable (in which laft cafe he erroneoufly confiders them as faturated with that acid); yet he feems not to have proceeded to a ftill more decifive proof of that quality, which had occurred to another inquirer into the fame fubject; who has fhewn that folutions of alcaline falts may be completely neutralifed by fixed air, or the mephitic acid, and may even be rendered fubacid; in the very fame manner as the neutral folutions of Glauber's falt, nitre, or fea falt, may be rendered acidulous, by a few additional drops of vitriolic, nitrous, or marine acid.

When the oleum tartari per deliquium is expofed to fixed air, the cryftals which very soon appear, and which have been obferved by the Author, the Duc de Chaulnes, and others, are by no means neutral. The fact is, that the neutral mephitic falt is not equally foluble in water, as the mild alcali; so that, in their experiments, when the infide of a receiver wetted with . tartar. or a faturated folution of mild alcali, is exposed to fixed air, crystals are formed before the alcali can have acquired a fufficient quantity of the mephitic acid to neutralife it; because there is not water enough to hold the falt, though yet only partially neutralifed, in a ftate of folution. To render the alcaline folution, therefore, perfectly neutral, or fubacid; the fal tartar fhould be diffolved in a larger quantity of water than will barely diffolve it.

In the paper above referred to, it has been fatisfactorily fhewn, that the marks of acidity exhibited by fixed air are not to be afcribed to the vitriolic or any other acid, employed in the ufal proceffes for procuring it; as was fuppofed by fome foreign philofophers. In the prefent differtation, however, we meet with an obfervation, which, if not explained, might throw' fome doubt on the intrinsic acidity of fixed air, and which therefore deferves fome notice,

It is well known, that when a weak infufion of litmus has been made red, by being impregnated with Aked air, the rednefs gradually difappears on expofing the liquor to the common

See Experiments and Obfervations on Fixed Air, &c. by Mr. Bewley, il Dr. Priestley's Second Volume of Experiments on Air, pag. 337%- &c.

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air.

air. It has been alleged that this circumftance is not peculiar to fixed air; for that the colour given to this infufion is equally fugitive, when the water has been weakly impregnated even with the mineral acids. The Author has detected the fallacy of this experiment, by obferving that the prepared litmus ufually contains alcaline matter; that the mineral acid combines with this last, and expels from it its fixed air, which enters the infufion. So that, in this cafe, it is not the diluted mineral acid which gives the liquor its redness, and which af terwards flies off, fo as to caufe the infufion to reaffume its blue colour; but it is the fixed air expelled by it from the alcaline fubftance that produces both thefe appearances: the mineral acid remaining combined with the alcali in the litmus; and having no other concern in the appearances than diflodging the mephitic acid from the litmus. Suppofe the alcali to require the quantity of mineral acid before it is perfectly faturated; it is evident that the quantity of acid may be added to times fuc

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ceffively, fo as to produce as many fucceffive appearances of this fugitive rednefs: one portion more added will render the redness permanent.

Of the numerous combinations of fixed air (or rather of wa◄ ter faturated with this acid) with various fubftances, which are here defcribed by the Author, we fhall mention only a few. He affirms that fpirit of wine will abforb double its bulk of this fluid, and that the fame is nearly true of oil of turpentine; which, at first, absorbs it with great avidity. Nay, he affirms that a portion of oil of olives will abforb almost an equal bulk of fixed air. The impregnated water diffolves zinc, and a femimetal which he calls Magnesium, as well as iron. It diffolves likewife a notable quantity of magnefia; ledth part, the Author fays, of its weight. We have formerly diffolved nearly an ounce of magnefia, reduced to the state of a moft fubtile powder, in three pints of water, which was fupplied from time to time with fixed air. The folution, when faturated, had a faline, earthy, and, at the fame time, a bitter taste, like that of the fal cathart. amarus: from which it only differs with refpect to the acid wherein the earth is diffolved. This preparation appears to us well adapted to anfwer various medical intentions, where the defign is to introduce a large quantity of fixed air into the fyftem

The Author,, who appears to have been one of the first wha difcovered the method of impregnating water with fixed air, and thereby imitating the Pyrmont, Spa, Seltzer, and other waters, fpeaks highly of the benefits he has derived from the use of the artificial Seltzer water in particular, during eight years, in the cure of what he calls an hæmorrhoidal colic, to which he has

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been periodically fubject. The flux, from the haemorrhoids, which has been flopped, particularly, in the cold feason, has conftantly been brought on by this regimen, after fix days perLeverance in it; and fometimes, eyen on the third or fourth day. He relates likewife a few out of many inftances, which he could produce, of the good effects that have ensued from the fame regimen, in Sweden; where the process of impregnating water with fixed air, &c, is become familiar in families of all ranks: and he affirms, that the moft obftinate intermittent fevers which raged throughout that whole kingdom, for fome years paft, and which would not yield to the bark, have almost conftantly been removed by the artificial Seltzer water, or other fimilar impregnations of water with fixed air.

Diflertation II. On the Analysis of Waters.

This valuable paper contains, within a Imall compass, a most excellent fet of obfervations and rules for examining waters; or for difcovering, collecting, and afcertaining the nature of their various and heterogeneous contents. Befides the ufual. methods, and those which bave been fuggefted by the numerous difcoveries that have been very lately made in the chemical branch of experimental philofophy; it contains many others peculiar, we believe, to the Author. Such, we apprehend, is his method of detecting the prefence of fulphur, in certain waters of the foetid kind, by adding a fmall quantity of concentrated nitrous acid; by which the foetid fmell is corrected, and finally deftroyed, and the fulphur is precipitated. We hall only mention another new and curious teft, by which the prefence of calcareous earth in water is detected.

This teft is the acid of fugar, difcovered, we believe, by the Author, and of which we fhall have occasion to speak presently. If the malleft portion of calcareous earth, combined in any manner whatever, be contained, even in a very large quantity of water [Cantharo' *], a fmall cryftal of this acid, no larger. than the head of a pin, being dropped into it, will produce Aria and clouds; caused by a precipitate formed of the calcareous earth, combined with the faccharine acid, and which is infoluble in water. Scarce any water, the Author obferves, is perfectly free from calcareous earth. Even with respect to that. which is reputed the pureft, this teft is fo fenfible, that when the water has flood twenty-four hours after it has been dropped into it, it will prefent fome appearance, though perhaps a faint one, of this peculiar precipitate. A combination of the faccharine acid, with an alcaling falt, produces the fame effect, ftill: more fenfibly, in confequence of a double affinity. No acid,

The Swedish Cantharus, as we are told in a note, confifts of eight quadrantes; each of which contains 12 cubic Swedish inches.

alcaline,

alcaline, or earthy body whatever, is capable of decompounding the compound thus formed of the faccharine acid, and calcarous earth.

Differtations III, and IV: On the Waters at Upfal and on the Acidulous Waters in the Parifh of Danemarks.

Thefe two articles, independent of the immediate or local purposes for which they were drawn up, furnish useful exemplifications and illuftrations of the rules contained in the preceding differtation;

Differtation V. On Sea Water.

Dr. Sparrman, who joined Dr. Forster in the last expedition to the South Seas, brought home with him, and gave to the Author for his examination, feveral glafs bottles filled with fea water, drawn up from very great depths, in the latitude of the Canary Islands. We fhall not take any further notice of this Analyfis, than juft to obferve, that the water was perfectly inodorous, and though not grateful to the taste, it did not excite a naufea, like that which is taken from the furface of the fea.

M. Bergman accounts for this laft circumftance, by obferving, that the immenfe number of fishes who die in the fea, rife up to the furface, in confequence of the inflation attending putrefaction; fo that the water, at great depths, is not contaminated by them. When there is a fcarcity of water, in a fhip, he thinks much fresh water might be faved, by boiling the ship's victuals in an equal quantity of this purer fea water. Differtation VI. On the Method of imitating the Cold medicated Waters.

By the cold medicated waters, the Author means those whose faline, metallic, or earthy ingredients, are held in folution by fixed air; fuch as thofe of Pyrmont, Spa, Seltzer, &c. After giving an exact analysis of the contents of four of the principal of thefe natural waters; he teaches the method of preparing each of them by art, or by fynthesis. From the late difcoveries relative to this fubject, no doubt can be entertained that art, in this one inftance at leaft, is capable of excelling naturewhatever the mayor and burgeffes of Spa or Pyrmont may allege to the contrary. In this, and the following Differtation, the Author appears in the light of a good patriot as well as chemist: exhibiting, in a note, the fums paid by Sweden for the natural waters imported into that kingdom in 1773 and 1774; which may now be faved, by fubftituting the artificial waters in their place. We shall not dwell on this fubject, but shall attend to the next differtation, which contains matters lefs known. Differtation VII. On the Method of imitating the Hot medicated Waters.

It appears extremely fingular to us, that the curious procefs defcribed in this differtation, by which the warm or fulphureous

waters,

. waters, fuch as thofe of Aix-la-Chapelle, &c. are perfectly imitated, fhould have been fo long overlooked: at least, this is the first notice that we have received of it. It confifts fimply in adding the vitriolic acid to hepar fulphuris, and impregnating water with the peculiar fpecies of air that arifes from this mixture; in the fame manner as when water is impregnated with the fixed air, arifing from the mixture of that or any other acid with chalk. This, hepatic air †, as the Author calls it, is very readily abforbed by water; to which it gives the fmell, tafte, and all the other fenfible qualities of the fulphureous waters. A Swedish cantharus of diftilled water, will absorb about fixty cubic inches of this hepatic air; and on dropping into it the nitrous acid, as we have mentioned under the fecond differtation, it will appear, that a real fulphur is contained, in a ftate of perfect folution, in this water, to the quantity of eight grains. It does not appear that any other acid, except what the Author calls the Dephlogifticated Marine Acid, will produce this effect.When any particular fulphureous water is to be imitated, we fcarce need to obferve, that the faline, or other contents peculiar to it, are to be added to the artificial hepatic water. Inftead of the liver of fulphur, the operator may use a mixture of three-parts of filings of iron, and two-parts of fulphur melted together 1.

It may perhaps be thought that water thus prepared does not differ from that in which a portion of the hepar fulphuris has been diffolved: but to us it appears evidently to differ from it in this material circumftance;-that in the folution of hepar fulphuris, the fulphur is held in folution by the water, through the means of the alcali combined with it: whereas, in M. Bergman's procefs, it does not appear probable that the hepar fulphuris rifes fubftantially, in the form of air; for, in that cafe, its prefence in the hepatic water might be detected by means of the weakest of the acids (even the mephitic), which would precipitate" the fulphur from it. Nor can it be fuppofed that any portion, or conftituent part, of the alcali itfelf (except a part of its remaining fixed air) can come over. The water therefore muft owe its impregnation to the fulphur, raised, in fome peculiar manner, into the ftate of an elaftic vapour; permanent, when the experiment is made in quickfilver; but condenfible in water, and rendered foluble in that fluid through the means of fome unknown principle combined with it, and which the Author fuppofes to be the matter of heat, combined with it through' the medium of phlogiston.

Part of this air, as we have found, is fixed air, proceeding from the falt of tartar.

In this cafe, there appears to us, to be very little abforption: the bepatic air, or vapour, feming to be diffolved, or fufpended in inflammable air.

In