and the event fully juftifies the former account. The failures complained of appear to have arifen, chiefly, from want of patience; for the abforption of the air goes on exceeding flowly, requiring feveral weeks for its completion *. In one of the trials that were reckoned unsuccessful, by Dr. Van Marum, there feems to have been a deception: the alcaline folution, which had abforbed the acid, was judged not to be faturated, merely from the imperfect marks of deflagration, which paper dipped into it exhibited in burning; this might proceed, not from a deficiency of the nitrous acid, but from fome of the mercury being diffolved, in confequence of a furplus of the acid; as was the cafe in one of the experiments here described.

Experiments on the Formation of Volatile Alcali, and on the Affinities of the phlogificated and light inflammable Airs. By William Auftin, M. D. &c.

Volatile alcali appears, from experiments of its decompofition, to confift of phlogisticated air and light inflammable air; that is, of the bases or gravitating substances of the two airs, in the proportion of about four parts by weight of the former to one of the latter. By mixing the two airs together in their elaftic ftate, Dr. Auftin has never been able to produce any volatile alcali; on account, as he apprehends, of their bafes having a greater affinity to the principle of heat which gives them the aerial form, than to one another; and of their particles being thereby kept at a great distance asunder, especially thofe of the inflammable air, which is known to be eleven times more rare than the phlogifticated. But when the inflammable air in its nafcent ftate, or immediately on its extrication from the bodies that produce it, was admitted either into pure phlogisticated air, or into aeriform fluids containing it (fuch as the air of the atmofphere, and more particularly nitrous air), he conftantly found volatile alcali to be formed; diftinguishable. by its smell, by changing paper blued by radifh juice to a green, and paper greened by folution of copper to a blue.

Many inftances are to be found in chemical writings, of volatile alcali being produced in metallic folutions and precipitations, but not one in which the quantity of alcali appears fo

This circumftance, we think, was not fufficiently pointed out in the former paper; the author having probably been more attentive to the ultimate effect, than to the time that the materials food together. It will be proper to obferve, that this process is effentially different from that in which inflammable air is ufed inftead of the phlogisticated, though electricity be the agent in both: there, the two airs are inftantaneously decompofed, by combuftion: here, an evolution of the acid principle is fucceffively and flowly effected by many repeated tranfmiffions of the electric spark. confiderable

3

confiderable as in an experiment exhibited fome years ago at Sir Jofeph Banks's, which is now laid before the public, we believe for the first time: a few ounces of powdered tin are moistened with moderately ftrong nitrous acid; and after they have flood together a minute or two, about half an ounce of fixed alcali or quicklime is added to them: a very pungent smell of volatile alcali is immediately perceived.

In this experiment, and in many others of the fame kind, the Doctor fuppofes that the water, as well as the nitrous acid, is decompofed; that dephlogifticated air from each of them combines with the metal; and that their other conftituent parts, viz. the phlogifticated air of the acid, and the inflammable air of the water, being difengaged at the fame inftant, unite and form the volatile alcali.-This paper was read to the Society in May 1787, when the doctrine of the decompofition of water was in vogue; but we suppose the author will now permit us to differ from him in that refpect, and to afcribe the origin of the inflammable air, if any was really produced, to the phlogifton of the metal.

·Experiments on the Effect of various Subflances in lowering the Point of Congelation in Water. By Charles Blagden, Sec. R. S. &c.

According to thefe experiments, water, by one tenth of fal ammoniac diffolved in it, has its point of congelation depreffed 11 degrees below 32, that is, it freezes at 20 of Fahr. With the fame proportion of common falt, it freezes at 21; of nitre, at 27; of Rochelle falt, at 29; of fal catharticus amarus, at 30; of green vitriol, at 30; and of white vitriol, at 31°. All the falts were used in a cryftallized state.

Dr. B. examines different proportions of each of these falts; and finds the depreffion of the freezing point to be, in all of them, nearly in the fimple ratio of the quantity of the falt, or the inverse ratio of that of the water. Whence, if the freezing point of one folution (which, for diftinction's fake, we shall call the ftandard) be known, that of any other folution of the fame falt may be found by the following analogy: as the quantity of water in the given folution (calling that of the falt 1) is to the quantity of water in the standard; fo is the depreffion of the freezing point in the ftandard, to its depreffion in the given folution. The afcertaining of this law in the falts above mentioned, and fome apparent deviations from it in others, make the principal object of this paper.

The fubftances which feemed to deviate from the general law are, acids, alcalies, and fpirit of wine; but the variations are inconfiderable, and we cannot enter into the particulars of them. We fhall only mention the points at which mixtures of the

feveral

feveral fubftances with the above-mentioned proportion of water, were found to freeze; which will ferve to give fome idea of their comparative powers in impeding the congelation.

Oil of vitriol, whofe fpecific gravity was 1.837, mixed with 10 times its weight of water, froze at 241°; fmoking spirit of nitre, gravity 1.454, at 22°; and fpirit of falt, gravity not mentioned, at 25°. It is obfervable that this laft acid, within the limits in which it was tried, viz. from about to of the water, accorded perfectly with the general law, which the author is difpofed to attribute to its being a very weak acid, fo that the variations were not perceptible; though it appears to have refifted congelation almoft as much as the oil of vitriol. Crystallized foda, diffolved in 10 times its weight of water, froze at 30°; falt of tartar, at 274; and volatile falt of fal ammoniac, at 25.

As a faturated folution of one falt will, in many inftances, diffolve a confiderable quantity of another, the Doctor examined fome compound folutions of this kind, and found the depreffion of the freezing point to he nearly the fame as it ought to be by calculation from the quantities of the different falts feparately; generally a little lefs, and in one inftance, where three falts were diffolved together, about 1° greater. From this laft fact he was led to conclude, that greater cold would be produced with fnow by a mixture of falts, than by means of either of them taken feparately; which, on trial, he found to be universally the cafe. Common falt, mixed with fnow, funk the thermometer to 5 below zero; fal ammoniac funk it only to 4 above; but when some of the latter falt was mixed with the former, the compofition produced with fnow, a cold of 12 below. On this principle, he obferves, it is, that impure common falt always makes a ftronger freezing mixture than the pure; the former being, in fact, a compofition of falts. And the curious experiments of producing a great degree of cold by diffolving a mixture of falts in water*, depends in part on the fame principle; the water being capable of reducing more falt from a folid to a Aluid ftate, when feveral kinds are employed, than it could of one' of the kinds only.

Experiments on the Production of artificial Cold. By Mr. Richard

Walker, Apothecary to the Radcliffe Infirmary at Oxford. These are a continuation of the very curious experiments referred to at the end of the preceding article, on the production of great degrees of cold without the affiftance of ice or fnow. The most powerful frigorific mixture which Mr. Walker has yet discovered, is the following: Strong, fmoking, spirit of nitre

* See Review for March 1788, p. 185; and the following article.

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is diluted with half its weight of water: to three parts of this liquor, when cooled to the temperature of the air, four parts of Glauber's falt, in fine powder, are added: the mixture is well ftirred, and, immediately afterward, three parts and a half of nitrous ammoniac are ftirred in. The falts fhould be procured as dry and tranfparent as poffible, and freshly powdered. Thefe appear to be the beft proportions when the temperature of the air and ingredients is 50°; but at higher or lower temperatures, the quantity of diluted acid requires to be proportionably diminifhed or increased. This mixture funk the thermometer 52 degrees, viz. from 32 above zero to 20 below. Nitrous ammoniac alone, during its folution in rain water, produced a cold not much inferior, finking the thermometer 48 or 49 degrees; viz. from 56 to 8 when the falt was used with its water of cryftallization, and to 7 when evaporated gently to dryness.

From the obvious application of artificial frigorific mixtures to useful purposes, especially in hot climates, Mr. Walker is led to confider the eafieft and moft economical method of using them. He finds a mixture of equal parts of fal ammoniac and nitre, in fine powder, to be fufficient for freezing water or creams at Midfummer. In a very hot day, he poured a quarter of a pint of pump water, wine meafure, on three ounces averdupois of the mixture previously cooled, by immerfing the veffel containing it in other water, to 50°, for fpring waters are nearly of that temperature at all feafons. After ftirring the mixture, its temperature was found to be 14°; and the folution being evaporated to drynefs, and added to the fame quantity of water, under the fame circumftances as before, it funk the thermometer again to 14°; nor was any diminution obferved in its effect, after many repeated evaporations.

Mr. W. mentions a very curious circumftance in the congelation of Glauber's falt when liquefied by heat: it did not become folid till its temperature was reduced to 70°, and then the thermometer rofe immediately 18 degrees, viz. to 88°, the freezing point of this falt. This great quantity of heat, extricated in its congelation, feems to indicate a great capacity for heat in liquefaction; or its requiring a great quantity of heat to be combined with it for rendering it fluid; and this property, he intimates, may account, in a great measure, for the intenfe cold which it produces during its folution in the diluted mineral acids. He finds that alum and Rochelle falt, each of which contains nearly as much water of cryftallization as Glauber's falt, produced no confiderable effect during their folution in the diluted nitrous acid; neither did their temperatures increase in paffing from a liquid to a folid ftate.

We fhall juft mention another interefting phenomenon, of water continuing fluid till cooled 22 degrees below its freezing

point. Mr. Walker filled the bulbs of two thermometers, one with rain, and the other with pump water, and boiled the water in each till one third only remained. Neither of them could be made to freeze till their temperature was lowered nearly to 5o, whether the tubes were open or fealed: but unboiled water *, in the fame fituation, froze in a higher temperature.

Abstract of a Register of the Barometer, Thermometer, and Rain at Lyndon in Rutland; with the Rain in Hampshire and Surrey, in 1787. Alfo fome Account of the annual Growth of Trees. By Thomas Barker, Efq.

To the common register of the weather, Mr. Barker has here added tables of the growth of the oak, afh, and elm, for upward of forty years paft. There feems to be little difference in the growths of the different kinds, or at least not more than in thole of different individuals of the fame kind. The annual increase was about an inch in girth; fome of the thriving trees increased an inch and a half, or more; and the unthriving, only about three quarters of an inch. Great trees, he obferves, grow more timber in a year than fmall ones, the additional coat being applied over a larger circumference, and the thickness of the coat being in both cafes the fame.

The volume concludes with the ufual Lift of Presents to the Society, and an Index.

See Dr. Blagden's experiments on this fubject, page 324 of our Review for November laft.

ch.

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ART. IV. The Connexion of Life with Refpiration; or, an experimental Inquiry into the Effects of Submerfion, Strangulation, and feveral Kinds of noxious Airs, on living Animals with an Account of the Nature of the Disease they produce; its Diftinction from Death itself; and the most effectual Means of Cure. By Edmund Goodwyn, M.D. 8vo. pp. 126. 3s. Boards. Johnfon. 1788.

TH

HIS treatife was honoured with the gold medal given by the Humane Society for the beft treatife on fufpended animation.

The author commences his inquiry with experiments, which fhew that, in drowning, a fmall quantity of water commonly paffes into the lungs, but not fufficient to produce the changes that take place on fubmerfion. Hence he concludes, that the water produces all the changes that take place in drowning, indirectly, by excluding the atmospheric air from the lungs.'

He proceeds with inveftigating the mechanical and chemical effects of the air on the lungs in refpiration. We are here prefented with fome experiments, which clearly fhew that the dephlogisticated