Part 31 (1/2)

_Of Operations upon Coration_

SECT I

_Of Co to what has been already said in the First Part of this Work, is the decoas produced by a coas is absorbed by, and enters into, coht are set free Every coenation; whereas, on the contrary, every oxygenation does not necessarily imply concomitant combustion; because coageht

Before coen gas should have greater affinity to the combustible body than it has to caloric; and this elective attraction, to use Bergree of temperature, which is different for each co a firstto every combustion by the approach of a heated body This necessity of heating any body we mean to burn depends upon certain considerations, which have not hitherto been attended to by any natural philosopher, for which reason I shall enlarge a little upon the subject in this place

Nature is at present in a state of equilibrium, which cannot have been attained until all the spontaneous corees of teenations can happen without destroying this equilibriuree of temperature To illustrate this abstract view of the matter by example: Let us suppose the usual teed, and that it is raised only to the degree of boiling water; it is evident, that, in this case, phosphorus, which is coree of teer exist in nature in its pure and sienated state, and its radical would becoradually increasing the temperature of the earth the same circumstance would successively happen to all the bodies capable of co taken place, there would no longer exist any combustible body whatever, as every substance susceptible of that operation would be oxygenated, and consequently incombustible

There cannot therefore exist, so far as relates to us, any combustible body, except such as are incombustible in the ordinary te, in other words, that it is essential to the nature of every combustible body not to possess the property of coree of temperature at which its coree is once produced, coed by the decoas keeps up the te coaged caloric is insufficient for keeping up the necessary temperature, the combustion ceases: This circu, that a body burns ill, or with difficulty

Although combustion possesses some circumstances in common with distillation, especially with the compound kind of that operation, they differ in a very material point In distillation there is a separation of one part of the elements of the substance from each other, and a combination of these, in a new order, occasioned by the affinities which take place in the increased te distillation: This likewise happens in combustion, but with this farther circuinally in the body, is brought into action; oxygen is added to the substance subed

The necessity of eas in all experiorous determination of the quantities employed, render this kind of operations peculiarly troublesoed in the state of gas, it is stillcolected by the ancient che to eneral way, the objects to be had in view in experi sections of this chapter, to describe the different instruement is formed, not upon the nature of the combustible bodies, but upon that of the instruments necessary for combustion

SECT II

_Of the Coin by filling a jar, capable at least of holding six pints, with oxygen gas in the water apparatus, Pl V Fig

1; when it is perfectly full, so that the gas begins to flow out below, the jar, A, is carried to the3 We then dry the surface of the -paper, taking care to keep the paper for some time entirely immersed in the mercury before it is introduced under the jar, lest we let in any common air, which sticks very obstinately to the surface of the paper The body to be subhed in nice scales, is placed in a small flat shallow dish, D, of iron or porcelain; this is covered by the larger cup P, which serves the office of a diving bell, and the whole is passed through the er cup is retired

The difficulty of passing the h theone of the sides of the jar, A, for ain the little cup, D, with the combustible body as quickly as possible In this ets into the jar, but it is so very inconsiderable as not to injure either the progress or accuracy of the experiree

When the cup, D, is introduced under the jar, we suck out a part of the oxygen gas, so as to raise the mercury to EF, as formerly directed, Part I Chap V otherwise, when the co dilated would be in part forced out, and we should no longer be able to make any accurate calculation of the quantities before and after the experi out the air is by e adapted to the syphon, GHI, by which the ht inches Very inflammable bodies, as phosphorus, are set on fire by16 h the mercury Such as are less easily set on fire have a small portion of tinder, upon which a minute particle of phosphorus is fixed, laid upon the the red hot iron

In the firstheated, rarifies, and the mercury descends; but when, as in combustions of phosphorus and iron, no elastic fluid is formed, absorption becoh into the jar Great attention e a quantity of any substance in a given quantity of gas, otherwise, towards the end of the experiment, the cup would approach so near the top of the jar as to endanger breaking it by the great heat produced, and the sudden refrigeration fro the volu to the heighth of the barometer and thermometer, &c see Chap II Sect V and VI of this part

The above process answers very well for burning all the concrete substances, and even for the fixed oils: These last are burnt in lamps under the jar, and are readily set on fire by erous for substances susceptible of evaporating in a moderate heat, such as ether, alkohol, and the essential oils; these substances dissolve in considerable quantity in oxygen gas; and, when set on fire, a dangerous and sudden explosion takes place, which carries up the jar to a great height, and dashes it in a thousand pieces From two such explosions some of the members of the Acadeh thispretty accurately the quantity of oxygen gas absorbed, and of carbonic acid produced, as water is likewise foretable and anien, this apparatus can neither collect it nor determine its quantity The experiment with phosphorus is even incomplete in this way, as it is iht of the phosphoric acid produced is equal to the suas absorbed during the process I have been therefore obliged to vary the instru to circumstances, and to employ several of different kinds, which I shall describe in their order, beginning with that used for burning phosphorus

Take a large balloon, A, Pl IV Fig 4 of cristal or white glass, with an opening, EF, about two inches and a half, or three inches, diameter, to which a cap of brass is accurately fitted with ee of the tubes xxx, yyy Before shutting the balloon with its cover, place within it the stand, BC, supporting the cup of porcelain, D, which contains the phosphorus Then lute on the cap with fat lute, and allow it to dry for soh the whole accurately; after this exhaust the balloon by means of an air-puas by the tube yyy, fro 1 described Chap II Sect II of this part The phosphorus is then set on fire by lass, and is allowed to burn till the cloud of concrete phosphoric acid stops the coazohed and unluted; the tare of the instruht is that of the phosphoric acid contained It is proper, for greater accuracy, to exaas contained in the balloon after cohter than coht must be taken into account in the calculations upon the results of the experiment

SECT III

_Of the Combustion of Charcoal_

The apparatus I have employed for this process consists of a small conical furnace of ha 9 and internally displayed Fig 11 It is divided into the furnace, ABC, where the charcoal is burnt, the grate, d e, and the ash-hole, F; the tube, GH, in the middle of the dome of the furnace serves to introduce the charcoal, and as a chi off the air which has served for coh the tube, l as, or air, intended for supporting the combustion, is conveyed into the ash-hole, F, whence it is forced, by the application of pressure to the gazorate, d e, and to blow upon the burning charcoal placed ias, which foras during coas of the air is not altered at all Hence, after the combustion of charcoal in atas must remain; to allow this mixture to pass off, the tube, o p, is adapted to the chias into bottles half filled with solution of caustic potash The carbonic acid gas is absorbed by the alkali, and the azotic gas is conveyed into a second gazoht of the furnace, ABC, is first accurately deterht, by the chirate, d e, which it occupies entirely; in the next place, fill the furnace with charcoal, and weigh the whole again, to know the exact quantity of charcoal submitted to experiment

The furnace is now put in its place, the tube, l azometer, and the tube, o p, to that which co being in readiness, the stop-cock of the gazo charcoal is thrown into the tube, RS, which is instantly withdrawn, and the tube, o p, is screwed to the chirate, and in this ets below the whole charcoal, and is kept on fire by the streaazooes on properly, the tube, q r s, is fixed to the furnace, having a piece of glass ceh which we can see if the charcoal be on fire

I neglected to observe above, that the furnace, and its appendages, are plunged in water in the cistern, TVXY, Fig 11 Pl XII to which ice h the heat is by no means very considerable, as there is no air but what coazometer, and no more of the charcoal burns at one tirate

As one piece of charcoal is consumed another falls down into its place, in consequence of the declivity of the sides of the furnace; this gets into the strearate, d e, and is burnt; and so on, successively, till the whole charcoal is consumed The air which has served the purpose of the coh the azoh the bottles of alkaline solution