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nity between that medium arid fenfible bodies? a certain attraction or ■cohefion by means of which bodies in general, or fome kinds of bodies in particular, may, fome how or other, impede this medium in its operations in conducting or transporting beat from one place to another r—It appeared from the refult of fcveral of my experiments, of which I have given an account in detail in my paper before mentioned, publifhed in the year i 786 Li the Ixx vith vol. of the l'hilofophical Tranfac"tions, that the conducing power of a Torricellian v&cuuru is to that of air as 604 to 1000; but I found by a fubfequent experiment, (fee my fecond paper on heat, publifhed in thePhilofophical Tranfaitious for the year !7qi)—that 55 parts in bulk of air, with r part of fine raw (ilk, formed a covering for confining heat, the conducting power of which was to that of air as ^ 76 to 12S4; or as 448 to 1000. Now, from the refult of this lalt-mentioned experiment, it fliouid frem that the introduction into the fpace through which the heat pafTc-d, of fo fmall a quantity of raw fil* as -j'jpart of the volume, or capacity of that fpace, rendered that fpace (which now contained .5 c parts of a,ir and t part of (ilk) more impervious to hieat than even a Torricellian vacuum,-- I'he (ilk muft therefore not only have completely deftroved the conducing power of (<the air, but mufi alfo at the fame time have very fenfibly impaired that of the ethereal fluid which probably occupies the interftices of air, and which ferves to conduct heat through a forricellian vacuum: for a Forricellian vacuum was a better conductor of heat, than this medium, in the proportion of 604. to 448. But I forbear to enlarge upon this fubjefi, being fenftble of

the danger of reafoning upon the properties of a fluid whole exiftence even is doubtful j and feeling that our knowledge of the nature of heat, and of the manner in which it is communicated from one body to another, is much too imperfect and ohfeure to enable us to purlue tbefe fpeculatious with any profpect of fuccefs or advantage.

"Whatever may be the manner in which heat is communicated from one body to another, 1 thi. k it has been futticiently proved that it pafles with great difficulty through confined air; and the knowledge of this fad is very important, as it enables us to take our mtafures wiih certainty and with facility for con* fining heat, and directing its operations to ufeful purpofes.

"But atmo(pheric air is not the only non-conductor of heat. All kinds of air, artificial as well as na» tural, and in general all eUuic fluids. fleam not excepted, feem to poflefs this property in as high a degree of perfection as atmofpheric air.

"That fleam is not a conductor of heat, I proved by the following experiment: a large globular bottle being provided, of very thin and very traufparent glafs, with a narrow neck, and its bottom drawn inward fo as to form a hollow hemifphere about 6 inches iu diameter; this bottle, w bjch was about S inches in diameter externally, being filled with cold water, was placed in a (hallow difh, or rfither plate, about 10 inches in diameter, with a flat bottom, formed of very thin QuOS. brafs, and raifed upon a tripod, and ■which contained a fmall quantity (about -'j ol an inch in depth) of water; a fpirit lamp being thea placed under the middle of this plate, in a very few miuutes the Water in the plate began to boil,

aad and the hollow formed by the bottom of the bottle was filled with clouds of (team, which after circulating in it with furprifing rapidity 4 or 5 minute:, and after forcing out a good deal of air from under the bottle, began gradually to dear up. At the end of 8 or 10 minutes (when, as I fuppoltd, the air remaining with the (team in the hollow cavity formed by the bottom of the bottle, had acquired nearly the fame temperature as th.it of the fteam) thefe clouds totally difappeared; and, though the water continued to boil with the utmoft violence, the contents of this hollow cavity became io perfectly invifihle, and fo little appearance was thereof fteam, that had it not been for the ftreams of water which were continually running down its lides, I fhould almoft have been tempted to doubt whether any fteam was actually generated.

"Upon lifting up for an inftant one fide of the bottle, and letting in a fmaller quantity of cold air, the cloud inftantly returned, and continued circulating leveral minutes with great rapidity, and then gradually difappeared as before. This expo iment was repeated feveraltimes, and always with the fime refult; the fteam always becoming vifible when cold air was mixed with it, and afterwards recovering its tranfparency when, part of this air being expelled, that which remained had acquired the temperature of the fleam.

"binding that cold air introduced under the bottle caufed theftenm to be partially condenfed, and clouds to be formed, 1 was defirous of feeing what vifible effects would be firocured by introducing a cold fold body under the bottle. 1 imagined that if fteam was a conductor of heat, forae part of the heat in the

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fteam paffing out of it into the cold body, clouds would of courfe be formed: but I thought if fteam was a non-conductor of heat,—that is to fay, if one particle of fteam could not communicate any part of its heat to its neighbouring particles, in that cafe, -as the cold body could only affect the particles of fteam actually in contact \\ ith it, no cloud would appear; and the refult of the experiment fhewed that (team is in fjet a non-conductor of heat; for, notwithftanding the cold body ufed in this experiment was very large and very cold, being a folid lump of i.e, nearly is large as an hen's egg, placed in the middle of the hollow cavity under the bottle upon a imail tripod or (land m.i.L- of iron wire; yet as footi as the clouds which v* ^re formed in confequ.mce of the 111 avoidable introduction of cold air in lifting up the boitr; to introduce the ice, were d<!:;..'ued, which foon happened, 1 n lheatn became fo perfectly u anfpareut and invifihle, that not ti'.e fm '.Heft appearance Of clo'>r,ir>rfs \\ ••; to bfi

fean any where, not ewn abo.it the ice, which, as it went on f< melt, appeared .>.s clear and astra:uj<.i~ent as a piece of th? finelt rock cryftal.

"This experiment, whic 1 i. firft made at Floieuce, in the month of Novemner, 1793, was repeated Several tim?3 in the prefenee of lord Palmerfton, who was then at Florence, and Monf. de Fontana.

"In thefe experiments the air was not entirely expelled from under the bottle; on the contrary, a coniiderable quantityof it remained mixed with the fteam even after the clouds had totally difappeared, as 1 found by a particular experiment made with a view to afcertain that tact; but that circumftance does not render the refult of this experiment lefs curious, on the contrary I think it tends to make it more furprifing. It fliould leem that neither the mat's of (team, nor that of air, were at all cooled by the body of ice which they fwrrounded, for if the air had been cooled (in mafs), it feerns highly probable thv the clouds would have returned.

"The refult of thefe experiments compared with thofe formerly alluded to, in which I had endeavoured to afcertain the mod advantageous forms for boilers,opened to me an entirely new field for {peculation and for improvement in tlie management of fire. They (hewed me that not only cold air,

but alfb hot air, and hot fleam, and hot mixtures of air and fteam, are non-conduclors of heat; confequently that the hot vapour which rifes from burning fuel, and even the flame itielf, is a non-conduflor of heat.

"This may be thought a bold aflertion, but a little calm reflection, and a careful examination of the phenomena which attend the combuftion of fuel, and the communication of heat by flame, will fliew it to be well founded; and the advantages which may be derived from the knowledge of this facr are of very great impoi tance indeed."

Account ofaMETHODofmaking Soap of Wool, withOBsaavATiom refpecling its Use in various Arts. By M. Chaptal.

[From the Annales Dechimie, and inferred in the Seventh Volume of the Repertory of Arts and .manufactures.]

I

Have already fhewn the manner of making, at all times, in every place, and at a fmall expence, a laponaceous liquor which may be conveniently tsfed, innead

of foap, for domeftic purpofes. (See the Report of Melirs. Pelletier, d'Arcet, and Le Lievre, on the art of making foap*.) 1 fliall now prefent to the public a fupplemeot

to

* " As that part of the report referred to by M. Chaptal appears to be of general utility, we (ball here give a tranflation of it.

"A very good way of ufing foap is, to employ it in a liquid ftate; that is, diflblved in water. In confequence of which, M. Chaptal propofes that laponaceous liquors lhccld be prepared, which may beuted inftead offolutionsof foap; and in order to be able to procure fuch liquors, at all times, in all places, and at a fmall expenct, he advitesoee or the'other of the following methods to he pia&iled. We fhall defcribe tliem exacilt at ivl. Chaptal communicated them to us, with obfervations thereon, made by himielf

"Firft Method.

"Take theafhes produced from the combuftion of wood which has not been floated, and make a ley of them, according to the ufual manner; mixing with the afhes a handful or two of quick-lime, well pounded or recently flaked. Let the ley ftand tiii it * grown cltar, by the fettling or fwimming of the foreign fubftances contained theiein; rhen pour it into another veffel, and keep it for ufe. When it is propofed to make afe of this ley, take any quantity of oil, and pour upon it thfrty or forty times as much of (he ley. Immediately a liquor as white as milk will be formed, which, by bems well

fhiirn.

to my former work, inftrufting tute for foft-foap, (which is at prethem how to prepare, as a fubfti- fent made ufe of in fulling almoft

every

(taken, or ftirred, lathers and froths like a good folution of foap. This liquor is to be poured into a warning tub, or other vefftl, and to be diluted with a greater or lcfs quantity of watei; after which, the linen meant to be warned, is to be deeped therein, lo be rubbed and wrung, in the ufual way.

"Obftrvaliatu.

"I. It is better that the ley (hould not be made until the time when it is to be ufcd: if it is left to (land in open veHtls, its power is weakened, and its nature is changed.

"2. Ftefh wood-aihes are preferable to old ones, particularly if the latter have been expoled to the air; in that cafe, they have no longer their ufual power, and we mult, in order to make them ferve our purpose, mix with them a greater proportion of quicklime.

"3. Thofe afhes alfo are preferable which are produced from hard wood: thore which are left after the burning of floated wood cannot be made ufe of with equal f'uccefs.

"4. Fat oils, of a thick confidence, are moft proper for the purpofe here fpoken •f: fine thin oils are by no means fit for it.

"5. If (linking oil be made ufe of, it isapttogivea badfmell to the linen; this may be removed by pairing the linen carefully through a ftrong pure ley; but in general, this fmell goes off as the linen becomes dry.

"6. When the mixture of oil with the ley is of a yellow colour, it muft be diluted with water. >

"7- When the oil rifes in the ley, and fwims upon the furface of it, in the form of fmall drops, it (hews that the oil is not fit for the purpofe, not being thick enough; or elic, that the ley is too ftrong, or not fufficiently cauftic.

"8. To prevent the quick-lime fromlofing its power, and that we may always have feme to ufe when we want it, it may be broken into fmall pieces, and kept in bottles well dried, and well corked.

« Second MtthoJ.

"Floated wood, which is made ufe of in many parts of France, produces afhes which contain very little alkaline fait, and which are confequently very improper for making leys; in that cafe, barilla, or potafh, may be ufed inftead of them.

"Take barilla, and break it into pieces about the fizc of a walnut; put thefc into a veflel of any kind, and pour upon them twenty times their weight of water: the water is to be left upon the barilla till it appears, by putting a little upon the tongue, to be (lightly fait.

"Some oil is then to be put into an earthen veflel, and forty times as much of the barilla-ley is to be poured upon it: the. mixture, which foon becomes milky, is to be well (haken, or ftirred; and, after being diluted with more orlefs clean water, according to its ftrengih, and the purpofe for which it is intended, is to be made ufe of like « folution of foap in water.

"Inftead of barilla, pot-afh may be employed, but it requires a fmall quantity of pounded quick-lime to be mixed with it. v

"Obfiriiations.

"I. Alicant or Carthagena baritla may be ufcd without any mixture of lime ; but the bad barilla of our country requires to have mixed with it a greater or less proportion, of lime, according to its degree of ftrength and purity.

"2. When barilla, of whatever kind it may be, is in a ftate of efflorefccnce, it canpot be employed without a mixture of lime.

Ji "3 1£

every kind of woollen fluff,') a kind of foap which cofls little, and which may be eafily made in every woollen manufactory.

"In all manufactories of cloth, . blanket*, and other woollen goods, it is the cuftom to full the fluff, as icon as it comes from the loom. The intention of this operation is, not only to fcour the cloth, &c. but alio to render it more compart; and, in performing it, about thirty pounds of foft-foap are ufed to eighty pounds of woollen Huff, la the fouth of France, before the revolution, foft-foap coft twenty livres the hundred weight. A great part of our oil, and alio that of Italy, is confumed in making it; fo alfo are the wood-afhes of the fires ufed for domeflic purpofes, in thofe countries where it is made.

«' From what has been faid, it is obvious how advantageous it would be to the manufacturer, and to commerce in general, to be able to fupply conveniently the place of lott-foap, by an article, the preparation of which is neither difficult nor expenfive. Ik-fides the faving which would take place in the manufacturing of woollen goods, great advantage would arife from the allies of our wood-fires being left either for domeflic ufes, or for (alt-works, or for manufactories of green glafs; arid at the fame time, the oil now ufed in making foap would remain to be wholly employed for purpofes wherein it is impoflible to find a fubfiitute for it.

"In all times, both the manu

facturer and the government have fought how to get rid of the abovementioned inconveniences. Fuller! earth, pure alkalies, and other things, have by turns been made ufe of. The f.rft performs the operations of bleaching and falling •very imperfectly: the fecond dhTolve the cloth; and the manufacturer* of Lodeve Hill recollect, with terror, a quack lent there by the government, fome years ago, who propofed to make ufe of mineral alkali or barilh, inftead of foap.

"To the inconveniences already mentioned wc may add, that inftead of rendering the cloth fufficiently foft and pliable, the fubtbtutes juft fpoken of leave it in a degree of harfhnefs, which nothing but foap completely removes. It is neceffary, therefore, that any fubfiinK propofed to be ufed inftead of foftfoap, fhould pofTefs the power of fcouring, of fulling, and of foftening the cloth. The eompoGtioo 1 am now about to defcribe unites all thefe advantages: experimentsbavt, by my deli re, been made with h,at Lodeve, by M.Michel Fabriguette; a perfon as well verfed in philosophical purliiits as in manufacturing of cloth.

"The whole procefs coofifts i* making a cauftic alkali ley or lixivium, with wood-afhes or potafli; in caufing the ley to boil; and then diflblving therein as great > quantity of old woollen rags, <* flireds of cloth, as the ley will diifolve. By this means a kind of foftfoap is produced of a greyiflvgrcen

"3. If the barilla-ley is too ftrung, the oil is apt to fwim on its Curtice ; it mni Oxi be diluted with a proper quantity of water.

"4. Fit oil is moll fit for this purpoie: fine light oils fhould not be ufed.

"£. When the iaponaceous liquor is greal'y, and the linens wafhed in itarefoKb* ife, they tnuft be paired through a pure barilla-ley, to have their gtealinrfs renwa!; which ley (houkl firftbe warmed a little to increafe in eflc£L

"6. When the water which was poared upon the barilla is all ufed, frefh wair HT be poured upon the remaining barilla. This water will acquire a (aline aftr, lilt <•fitft: thus, the lame barilla may ferve for ferenl fucctuive opciitiou.

COloUTi

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