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only now to proceed to the different papers of the present volume, according to their clalification ; commencing with the division appropriated 10

Scu Of the strength of acids, and the proportion of ingredients in neutral falts. By R. Kirwan, Eiq.

This very elaborate memoir may be considered as the second edition of a paper on the same subject hy Mr. Kirwan, formerly inserted in the London Philofophicai Transactions. He informs us that he has devoted the leisure of ten years to the ins quiry, which is undoubtedly of the first importance to the ac, curacy of chymical analyses. When we speak, of the proportion of acid, for instance, in neutral falis, we speak without definite ideas, unless we mean an acid of tome given strength, To introduce this degree of correctness is Mr. Kirwan's purpose. He has now fixed, for fiandards, on marine acid of 1,500, vitriolic of 2000, and nitrous of 1,5543 : but why he fhould not have used the vitsiolic acid of commerce, and the others at Specific gravities, at which they can be readily procured, we fee no fatisfactory reason. The first tables are intended to thew how much fiandard acid any acid liquor of a given density, and at a given temperature, contains :- there is one for each acid. They are construcled partly on the author's experiments, and partly on M. Pouget's formulæ, as given in a former volume of these Transactions.-- To enter into an examination of the feveral points disculied in this extensive ellay would not only be a trespass on the space which we can allot to any ingle paper, but would prove interesting only to a small part of our readers; who, after all, would compare the two editions and decide on the merit of the latter for themselves, We do not besitate to believe that the author, by omitting some precarious hypothetical poftulata, and by an improvenient in his method of operating, has made nearer approximations than before.

The two following quotations will give some idea of his presens principles. On the marine acid, he realons thus :

* 100 vebic inches of marine acid air weigh as nearly as I could ettinate 60 barometer 29,6, thermometer 57°. 10 grs. of water abforb 10 of this air, bar.29,6, ther. 49o. i he spirit of salt thus formed occupies the space of 13,3 grs. nearly ; hence its specific gravity is 1, vo nearly, and the ipeciñc gravity of the purest marine acid in its condensed state is 3,03.

I could not observe whether the absorption of this air produced heat; molt probably it did, but this is no proof that the conden. ' fation was greater than that f und by calculation.

· The specific gravity of the ilrongeit marine acid that can easily be procured and preserved is 1,196. 100 parts of this will be found by calculation to contain about 49 of that wliole Specinc gravity is

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1,500, and which I call the standard of the marine acid. The error arising from condensation will scarcely exceed 1 or 1,5 grs. per cent. ; by mixing this spirit of salt with different proportions of water I have had the results from which the ensuing table is calculated.'

In investigating the ingredients of neutral falts, he builds this process; which, so far as it goes, is fimple and satisfactory :

• First, I saturate a known quantity of alkali or other basis with an acid whose specific gravity is known, and whole proportion of standard is determined by the tables. I then make another solu., tion of a known quantity of neutral falt of the same species as that formed by faturation, and examine the specific gravity of both solations in the same temperature, adding water to the stronger of the two, until their densities become equal, and thence infer that an equal proportion of falt exists in both, but the proportion in one of them is known; and therefore the proportion in the other, the weight of the whole being found, is also determined. Even this method is subject to a small inaccuracy, for a slight excess of acid is always left, lest any loss of liquor should eniue from trials of saturation with vegetable blues, and this renders the density of the solution of the regenerated salt somewhat greater than would ensue from the proportion of salt it contains, besides that in many cases the proportion of water of crystallization must be discovered by exposure to heat.'

Mr. K.'s conversion to the antiphlogistic system has alone made a considerable variation in the matter as well as in the manner of his memoir.

Chemical communications and enquiries. By R. Perceval, M.D.

Dr. P. divided the products of the distillation of marine and nitrous acids into three portions. In four experiments with the former, what came over first and last had greater specific gravity than the middle portion. As marine acid is more voJatile than water, the first portion of acid should naturally be more saturated : but why the last portion should be stronger than the intermediate, it is not easy to understand ; unless, as Dr. P. conjectures, the vitriolic acid acts on the salt in a more concentrated state at the close of the process. In the case of the nitrous acid, the products were of greatest specific gravity at first, and the last was lightest. The caustic volatile alkali had leaft fpecific gravity at first.

In the observations on the process for dephlegmating the vitriolic acid, (which are not very important,) we apprehend that Dr. P. is mistaken in supposing the depofition to be gypfeous. We believe that it is always, at least in part, vitriol. ated lead.

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Account of a chan:ber lamp furnace. By the same. This lamp seems ingeniously contrived; and, by putting it more in the power of persons who have not an elaboratory at command to make experiments, it may contribute to diffuse the practical knowlege of chemistry. The effential parts are an Argand's lamp enclosed in a cylindrical body, and furmounted by a truncated cone, which serves as a capsule to hold the subject of experiment. If the cylindrical body were double, and the interval filled with charcoal in powder, it would probably produce a greater effect, as the surrounding air would not cool it so fast. We invite ladies and gentlemen, dilettanti in chemistry, to procure a furnace of this construction.

Extract of a letter from the Rev Charles Perceval, to Robert Perceval, M. D.

Mr. P. gives a short account of an extraordinary construction in the eyes of a poor girl, aged 11. Their motion, inAtead of a regular horizontal one from side to side, is tremulous in all directions, and partly perpendicular, with a prominent motion of the globe of the eye.

The child cannot easily see any object placed above her eyes, but reads perpendicularly from the bottom upward. The whole globe of the eye is of a reddish caft; the white, streaked with fainter red; the iris of an uniform deep red approaching to brown. Both eyes are weak and watery, and, when turned from the light, glow with a more vivid colour than when exposed to it.

Description of a portable barometer. By the Rev. Gilbert Austin,

One of the principal advantages of this barometer is, that the surface of the mercury in the bason is determined more accurately than can be done by Aoating gages, and there is no waste of mercury. We cannot convey a satisfactory idea of this invention without the plate.

Observations on the variation of the magnetic needle. By Mr. Thomas Harding.

The result of Mr. H.'s remarks, during 19 years, is that the change in the variation is uniform at Dublin. From the year 1657, in which it was none, it has been going on at the medium rate of 12' 20' annually, and was, in May 1791, 27o. 23 west. He brings proof of his affertion of the uni. formity of the variation, from different authentic records, and states the operations by which it is calculated. He concludes with reconimending accuracy in marking the existing variation when maps are made, as not only conducing to the exact definition of boundaries, but as laying the best foundation for a discovery of the longitude by sea or land.

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Description of an instrument for performing the operation of trepanning with more ease, safety, and expedition

than those now in gener al use. By Sam. Croker King, Esq.

After an historical account of the use of the trepan and trephine in these kingdoms, with remarks on their several de. fe&ts, Mr. K. describes one which is a kind of compound of both.

Descriptions of a felf-registering barometer, by the Rev. Arthur Macguire, and of a method of cutting fine screws, by the Rev. Gilbert Austin, are only to be understood by reference to the plates.

An attempt to determine, with precision, such injuries of the head as necessarily require the operation of the trephine. By Sylvester O'Halloran, Esq. Surgeon to Limerick Hospital.

Mr. O'Halloran arranges his observations under fraflures of the cranium, and deposits on the surface of the brain, or on its membranes. He selects three cases of fractured skulls cured without trepanning, and subjoins two, in which, symptoms, fupervening many days after the fracture, were removed by the operation. These symptoms were drowsiness, coma, and convulsions; and it is their occurrence which seems to him the proper guide for trepanning in fimple fractures. He altogether disapproves the operation in wounds of the skull with a cutting initrument. Fractures with depression require the operation in the firit instance, though he fhews, by some cales, that it may succeed after considerable delay.

With respect to depofits of matter on the surface or membranes of the brain, he confiders them, from his own experience, as alınost certainly mortal, whether the operation be or be not performed. However, he advises having recourse to the trephine, as the only chance. As to concussions, he does not agree with Mr. Poti in approving of trepanning in ftupors which immediately follow a hurt; thinking them owing to concussion only, and not to extravatation. He divides concussions into three claffes ; 1. mortal; 2. where there is recovery with insanity; 3. where there is perfc recovery; and he adds two cases in which the patienis perfectly recovered without any operation,

Demonstration of Newton's theorem for the correction of spherical errors in the object-glasses of telefcopes. By the Rev. Dr. Macthew Young

Newton, in his optics, proposed a contrivance for perfe&ting telescopes, consisting in cementing Together two concavo-con

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vex glasses with water between them ; and he gives a theorem for their construction, by which the refections on the concave fides of the glasses will very much correct the errors of the refractions of the convex fide, so far as they arise from the phericalness of the figure :--but in this an evident error occurs, arising from the corruption of Newton's text, which Dr. Y. from an investigation of the demonftration, bere corrects.

Account of a fistulous opening in the stomach. By G. Burrowes, M. D.

This paper adds one to the cases on record of wounds in the stomach remaining unclosed without any irremediable incon. venience. The subject of the case was a man who received a wound from a blunt-pointed wooden inftrument, between the cartilage of the 8th rib on the right side, and the navel: and which penetrated the stomach. Much fever and inflammation succeeded; after which a fiftulous orifice remained, which was kept stopped with a plug. He lived during 27 years in this ftate, though extremely irregular in his habits; and he ate with good appetite and digestion. If the plug was withdrawn, the liquids which he had swallowed partly escaped through the opening; and, when his stomach was empty, a sweet whitish fluid adhered to the plug. He had no pain, and no kind of food disagreed with him. After his death, the wound was found to have penetrated the stomach in the centre of the greater curvature. From the adhesions which it had formed with the liver, colon, and integuments, a stricture was produced, giving to the stomach the appearance of a double bag, with the fiftulous opening in its middle. The duodenum was enlarged beyond the fize of the colon, and seemed to have performed some of the functions of a second stomach. The colon was firmly attached to the somach by a ligamentous substance.

A case of enlarged spleen is next related by the fame writer. It occurred in a man 44 years old, who died of fever with vomiting six days after admission into an hospital, into which he was taken for a fupposed dropsical swelling in the abdomen. On opening, the stomach and intestines were found all thrown to the right side, while the left was entirely occupied by the spleen, which was neither indurated nor discoloured, but enor. mously enlarged. When taken out, it measured 141 inches long, and weighed 11 pounds 13 ounces.

It does not appear that any symptoms, beside those which were merely owing to weight and preffure, accompanied the amazing increase of this organ. The foft and equable teel of the abdomen might have led even an experienced surgeon to suspect water, and to proceed to tapping ; which, Dr. B. properly observes, would have caused a fatal bæmorrhage.

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