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and the event fully justifies the former account. The failures complained of appear to have arisen, chiefly, from want of patience ; for the absorption of the air goes on exceeding flowly, requiring several weeks for its completion *. In one of the trials that were reckoned unsuccessful, by Dr. Van Marum, there seems to have been a deception : the alcaline solution, which had absorbed the acid, was judged not to be saturated, 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 some of the mercury being diffolved, in consequence of a surplus of the acid ; as was the case in one of the experiments here described. Experiments on the Formation of Volatile Alcali, and on the Afini
ties of the phlogisticated and light inflammable Airs. By William Auftin, M. D. &c.
Volatile alcali appears, from experiments of its decompofition, to consist 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 elastic ftate, Dr. Austin has never been able to produce any volatile alcali; on account, as he apprehends, of their bases 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 diftance asunder, especially those of the infammable air, which is known to be eleven times more rare than the phlogisticated. But when the inflammable air in its nascent ftate, or immediately on its extrication from the bodies that produce it, was admitted either into pure phlogisticated air, or into aeriform Auids containing it (such as the air of the ata mosphere, and more particularly nitrous air), he constantly found volatile alcali to be formed; diftinguishable by its smell, by changing paper blued by radilh juice to a green, and paper greened by solution of copper to a blue.
Many instances 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 so
This circumstance, we think, was not sufficiently pointed out in the former paper; the author having probably been more attentive to the ulcimate effect, than to the time that the materials stood to- . gether. It will be proper to observe, that this process is essentially different from that in which inflammable air is used instead of the phlogisticated, though electricity be the agent in both : there, the two airs are instantaneously decomposed, by combustion : here, an evolution of the acid principle is succeflively and slowlv effected by many repeated transmissions of the electric Spark. 3
considerable as in an experiment exhibited some years ago at Sir Joseph Banks's, which is now laid before the publie, we believe for the first time: a few ounces of powdered tin are moistened with moderately Atrong nitrous acid; and after they have stood 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 supposes that the water, as well as the nitrous acid, is decomposed ; that depblogisticated air from each of them combines with the metal; and that their other constituent parts, viz. the phlogisticated air of the acid, and the inflammable air of the water, being disengaged at the same instant, unite and form the volatile alcali.- This paper was read to the Society in May 1787, when the doctrine of the decomposition of water was in vogue ; but we suppose the author will now permit us to differ from him in that respect, and to ascribe the origin of the inflammable air, if any was really produced, to the phlogiston of the metal. Experiments on the Effea of various Substances in lowering the
Point of Congelation in Water. By Charles Blagden, Sec. R.S. &c.
According to these experiments, water, by one tenth of sal ammoniac diffolved in it, bas its point of congelation depressed u degrees below 32, that is, it freezes at 201 of Fahr. With the same proportion of common salt, it freezes at 211; of nitre, at 27 ; of Rochelle falt, at 29% ; of sal catharticus amarus, at 30; of green vitriol, at 30%; and of white vitriol, at 31o. All the salts were used in a crystallized state.
Dr. B. examines different proportions of each of these falts ; and finds the depression of the freezing point to be, in all of them, nearly in the fimple ratio of the quantity of the salt, or the inverse ratio of that of the water. Whence, if the freezing point of one solution (which, for distinction's sake, we shall call the standard) be known, that of any other solution of the same falt may be found by the following analogy: as the quantity of water in the given solution (calling that of the salt 1) is to the quantity of water in the standard, so is the depretion of the freezing point in the standard, to its depression in the given solution. The ascertaining of this law in the salts above mentioned, and some apparent deviations from it in others, make the prin cipal object of this paper.
The substances which seemed to deviate from the general law are, acids, alcalies, and spirit of wine; but the variations are inconfiderable, and we cannot enter into the particulars of them. We shall only mention the points at which mixtures of the
several fubstances with the above-mentioned proportion of water, were found to freeze; which will serve to give some idea of their comparative powers in impeding the congelation.
Oil of vitriol, whose specific gravity was 1.837, mixed with 10 times its weight of water, froze at 241° ; smoking spirit of nitre, gravity 1.454, at 22°; and spirit of salt, gravity not mentioned, at 25°. It is observable that this last acid, within the limits in which it was tried, viz. from about što jó of the water, accorded perfectly with the general law, which the author is disposed to attribute to its being a very weak acid, so that the variations were not perceptible ; though it appears to have resisted congelation almost as much as the oil of vitriol. Crystal. lized foda, disolved in 10 times its weight of water, froze at 30° ;
salt of tartar, at 274, and volatile sale of sal ammoniac, at 25.
As a saturated solution of one falt will, in many inftances, dissolve a considerable quantity of another, the Doctor examined some compound solutions of this kind, and found the depression of the freezing point to he nearly the same as it ought to be by calculation from the quantities of the different falis separately ; generally a little less, and in one instance, where three falts were dissolved together, about 11. greater. From this last fact he was led to conclude, that greater cold would be produced with snow by a mixture of salts, than by means of either of them taken separately; which, on trial, he found to be universally the case. Common salt, mixed with snow, funk che thermometer to 5 below zero; sal ammoniac, sunk it only to 4 above ; but when some of the latter salt was mixed with the former, che composition produced with foow, a cold of 12 below. On this principle, he observes, it is, that impure common salt always makes a stronger freezing mixture than the pure; the former being, in fact, a composition of salts. And the curious experimenis of producing a great degree of cold by diffolving a mixture of sales in water *, depends in part on the same principle; the water being capable of reducing more falt from a solid to a Auid state, when several 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 assistance of ice or fnow. The most powerful frigorific mixture which Mr. Walker has yet discovered, is the following: Strong, smoking, spirit of nitre
* See Review for March 1788, p. 185; and the following article.
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 salt, in fine powder, are added : the mixture is well stirred, and, immediately afterward, three parts and a half of nitrous ammoniac are stirred in. The falts should be procured as dry and transparent as posfible, and freshly powdered. These appear to be the best 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 diminished or increased. This mixture funk the thermometer 52 degrees, viz. from 32 above zero to 20 below. Nitrous ammoniac alone, during its solution in rain water, produced a cold not much inferior, finking the thermometer 48 or 49 degrees ; viz. from 56 to 8 when the salt 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 consider the easiest and most oeconomical method of using them. He finds a mixture of equal parts of sal ammoniac and nitre, in fine powder, to be sufficient for freezing water or creams at Midsummer. In a very hot day, he poured a quarter of a pint of pump water, wine measure, on three ounces averdupois of the mixture previously cooled, by immerfing the vessel containing it in other water, to 50°, for spring waters are nearly of that temperature at all seasons. After ftirring the mixture, its temperature was found to be 14°; and the solution being evaporated to dryness, and added to the same quantiiy of water, under the same circumstances as before, it sunk the thermometer again to 14° ; nor was any diminution observed in its effe&t, after many repeated evaporations.
Mr. W. mentions a very curious circumstance in the congelation of Glauber's salt when liquefied by heat: it did not become solid till its temperature was reduced to 70°, and then the thermometer rose immediately 18 degrees, viz. to 88°, the freez. ing point of this salt. This great quantity of heat, extricated in its congelation, seems 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 Auid; and this property, he intimates, may account, in a great measure, for the intense cold which it produces during its solution in the diluted mineral acids. He finds that alum and Rochelle salt, each of which contains nearly as much water of cryftallization as Glauber's salt, produced no considerable effe&t during their solution in the diluted nitrous acid; neither did their temperatures increase in palling from a liquid to a folid ftate.
We shall just mention another interesting phenomenon, of water continuing fluid till cooled 22 degrees below its freezing
point. Mr. Walker filled the bulbs of two thermometers, one
To the common register of the weather, Mr. Barker has here added tables of the growth of the oak, ash, and elm, for upward of forty years past. There seems to be little difference in the growths of the different kinds, or at leaft not more than in those of different individuals of the fame kind. The annual in. crease was about an inch in girth; fume 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 observes, grow more timber in a year than small ones, the additional coat being applied over a larger circumference, and the thickness of the coat being in both cases the same.
The volume concludes with the usual List of Presents to the Society, and an Index.
* See Dr. Blagden's experiments on this fubject, page 324 of our Review for November last.
ART. IV. The Connexion of Life with Respiration ; or, an experie
mental Inquiry into the Effects of Submerfion, Strangulation,
the Humane Society for the best treatise on suspended animation,
The author commences his inquiry with experiments, which thew that, in drowning, a small quantity of water commonly paffes into the lungs, but not sufficient to produce the changes that take place on submerfion. 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 investigating the mechanical and chemical effects of the air on the lungs in respiration. We are here presented with some experiments, which clearly shew that the de