F L U
455
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Second. Water may be heated in a Papin's digester to 400°without boiling; because the steam is forcibly compressed, andprevented from making its escape, ff the mouth of the vessel issuddenly opened while things are in this slate, part ot the waterrushes out in the form of steam, but the greaur part still remainsin the form of water, audits temperature instantly sinks to 212°;consequently 188° of caloric have suddenly disappeared. Thiscaloric must have been carried off by the steam. Now as onlyshout onevtifth of the water is converted into steam, that steammust contain not only its own 188°, but also the 188° lost by eachof the other four parts; that is, it must contain 188° x 5, or about940°. Steam therefore is water combined with at least 940° of ca-loric, the presence of which is not indicated by the thermometer.This experiment was first made by Dr. Black, and afterwards withmore precision by Mr. Watt.
Third. When hot liquids are put under the receiver of an air-pump, and the air is suddenly drawn off, the liquids boil, and theirtemperature sinks with great rapidity a considerable number ot de-grees. Thus water, however hot at first, is very soon reduced tothe temperature of 70°, and ether becomes suddenly so cold, thatit freezes water placed round the vessel which contains it. Inthese cases the vapour undoubtedly carries off the heat of the li-quid: but the temperature of the vapour is never greater than thatof the liquid itself; the heat therefore must combine with the va-pour, and become latent.
Tourth. If one part of steam at 212° is mixed with nine partsby weight of water at 62°, the steam instantly assumes the form of■water, and the temperature after mixture is 178,6°, consequently«ach of the nine parts of water has received 116.6° of caloiic; ofcourse the steam has lost 0 x 116.6° = 1049.4° of caloric. But asthe temperature of the, steam is diminished by 33-.3 0 , we must sub-tract this sum. There will remain rather more than 1000°, which's the quantity of caloric which existed in the steam without in-creasing its temperature. This experiment cannot he made di-rectly; but it may be made by passing a given weight of steamtaiough a metallic worm, surrounded by a given weight of water.■I he heat acquired by the water indicates the caloric which thes team gives out during its condensation. From the experimentsof Mr. Watt made in this manner, it appears that the latent heat°f steam amounts to 940°. 'The experiments of M. LavoisierW'ake it rather more than 1000°. llv the experiments of Dr.■“lack and his friends, it was ascertained, that not only water, butall other liquids during flieir conversion into vapour, combine witha dose of caloric, without any change of temperature; ami thatevery kind of elastic fluid, during its conversion into a liquid,S'ves out a portion of caloric without any change of temperature.
Black’s law then is very general, and comprehends everychange in the state of a body. The cause of the conversion of a^plid into a liquid is the combination of the solid with caloric;that of the conversion of a liquid into an elastic fluid is the condu-ction of the liquid with caloric. Liquids are solids combined'' jth caloric. This law, in i[s most general form, may be stated as“flows: whenever a body changes its state, it either combines'' All caloric, or separates from caloric. No person will dispute“at this is one of the most important discoveries hitherto marie inN'dosophy . Science is indebted for it entirely to the sagacity of, r - Black. Other philosophers indeed have laid claim to it; but
*“ Se claims are either without any foundation, or tiieir notionslla y he traced to Dr. Black’s lectures, as their opinions originated“any years posterior to the public explanation of Dr. Black’s tile-'s! 111 the chemical chairs of Glasgow and Edinburgh .
.1- A very considerable number of bodies, botli solids and li-J 111 s > may be converted into elastic fluids by heat; and as long asole M' m P er ature continues sufficiently high, they retain all the me-tj ‘flfl.flai properties of gaseous bodies. It is exceedingly probable,( .j la *f "'e could command a heat sufliciently intense, the sameij a , n S. e might be produced on all bodies in nature. '1 his aceord-allli ' S - the opinion at present admitted by philosophers. But if>ti . “flies are convertible into elastic fluids by heat, it is exceed-
P r,> b;;b!o that all elastic fluids in their turn might be convert-l-ou-'t'^ 0 s °Bfl s ol liquids, if we could expose them to a sufficiently, n '‘fl'perature. In that case, all the gases must be supposed tosjq J ll, ir elasticity to a certain (lose of caloric: they must be cqn-1 A as compounds of caloric with a solid or liquid body. 1 his
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much ingenuity both by Dr. Black and Lavoisier, and his associ-ates. it is at present the prevailing opinion; and it is certainlysupported not only by analogy, but by several very striking facts.If its truth be admitted, we must consider all the gases as capableof losing their elasticity by depriving them of their heal: they dif-fer merely from the vapours in the great cold which is necessaryto produce this change. Now the fact is, that several of the gasesmay be condensed into liquids by lowering their temperatures.Oxymuriatic acid gas becomes liquid at a temperature not muchunder 40°; and at 32° it even forms solid crystals. Ammoniacalgas condenses into a liquid at—43°. None of the other gaseshave been hitherto condensed. It is well known, that the con-densation of vapours is greatly assisted by pressure; but the effectof pressure diminishes as the temperature of vapours increases. Itis very likely that pressure would also contribute to assist the con-densation ot gases. It has been tried without effect indeed in se-veral of them. Tims air has been condensed till it was heavierthan water; yet it shewed no disposition to lose its elasticity. Butthis may be ascribed to the high temperature at which the experi-ment was made relative to the point at which air would lose itselasticity. At the same time it cannot be denied, that there areseveral phenomena scarcely reconcilable to this constitution ofthe gases, ingenious and plausible as it is. One of the most strik-ing is the sudden solidification which ensues when certain gases aremixed together. Thus when ammoniacal gas and muriatic acidgas are mixed, the product is a solid salt; vet the heat evolved isvery inconsiderable, if-we compare it w ith the difficulty of con-densing these gases separately, and the great cold which they e»- 1dure before losing their elasticity. In other cases too, gaseousbodies unite, and form a now gas, which retains its elasticity aspowerfully as ever. Thus oxygen gas and nitrous gas combinedform a new gas, namelv, nitric acid, which is permanent till itcomes into contact with some body on which it can act.
FLUKE. See Plecronectes.
Fluke, in entomology. See Fasciola.
Fluke of an Anchor, that part of it which fastens in theground. See Anchor.
Fluke-Worm. See Fasciola.
FLUMET, a town of France , in the department of MontBlanc, 30 miles N. F,. of Chambery , and 31 S. E. of Geneva.
FLUMM FRY, a kind of jelly made of oatmeal, in the follow-ing manner: steep three large table-spoonfuls of finely ground oat-meal for 24 hours in two quarts of pure water, then pour off theclear fluid, and replace it by tlire e pints of freshwater; strain itthrough a fine hair-sieve, add to it two spoonfuls of orange-flow erwater, and one of sugar; boil the whole to the consistence of ahasty pudding, stirring it continually while boiling, till it becomeperfectly smooth. This preparation afibrds a grateful and nutri-tive breakfast to persons liable to cosliveness, in consequence of asedentary life.
FLUOR-SPAR. See Fi.uate of Lime, and the next article.'The fluates are principally used for smelting ores, being found toact as very powerful fluxes.
FLUORIC AG ID. '1 he mineral called fluor, or fusible spar,and in this country Derbyshire spar, was not properly distinguish-ed from other spars till Margiaif published a dissertation on it inthe Berlin Transactions for 1768. He first proved, that it coiv-tained no sulphuric acid, as had been formerly supposed: he thenattempted to decompose it, by mixing together equ.d quantities ofthis mineral and sulphuric acid, and distilling them. By this me-thod he obtained a white sublimate, which lie supposed to be thefluor itself volatilized by the acid, lie observed with astonish-ment, that the glass retort was corroded, and even pierced withholes. Nothing more was known concerning fluor till Scheele published his experiments three years alter, by which he provedthat it is composed chiefly ot lime and a particular acid, whichhas been called fluoric acid. The composition of fluoric acid isequally unknown with that of muriatic acid. Mr. Henry tried invain to decompose it by means of electricity. It is always obtain-ed from fluor spar, in which mineral it is found in abundance. Forthe investigation of the properties of this acid, we are indebtedchiefly to Scheele and l’riestley. 1. It may be obtained by put-ting a quantity of the spar in powder into a retort, pouring over itan equal quantity of sulphuric acid, and then applying a very gen-lie heat. A gas issues from the beak of the retort, which may be
received