(_a._) I added a solution of alkali of tartar, drop by drop, to a solution of corrosive sublimate. I washed the brown-red precipitate obtained, and dried it; then I placed it, for reduction, upon the open fire in a small retort, which was provided with a bladder empty of air.

As soon as the calx began to glow, the bladder became expanded, and quicksilver rose into the neck. The fire-air obtained had some aerial acid mixed with it.

(_b._) Mercury converted into calx by the acid of nitre, or red precipitate, treated in the same way behaved similarly. In this case I obtained a pure fire-air, without any aerial acid in it.

+41. Eighth Experiment.+--I have proved, in a treatise on a.r.s.enic communicated to the Royal Swedish Academy of Sciences, that this poisonous substance is compounded of a peculiar acid and an inflammable substance. I also shewed in the same treatise how this acid can be sublimed into ordinary a.r.s.enic simply by continued heat; and although I clearly perceived the reason for this, even at that time, still I was unwilling to mention it there in order to avoid prolixity. I placed some of this fixed acid of a.r.s.enic in a small retort with a bladder attached, for distillation. When the acid had gone into fusion, and glowed brightly, it began to boil; during this ebullition a.r.s.enic rose into the neck and the bladder became expanded; I continued with this heat as long as the retort would hold out. The air collected was likewise fire-air.

In the same treatise I made mention of a peculiar explosion which took place in the distillation of zinc with the acid of a.r.s.enic. How clear, how manifest does the explanation of this phenomenon not become when one is satisfied that in this case fire-air is present in the retort in its greatest purity, and the zinc is in red hot fusion? What more is necessary for its ignition?

I have very often regarded with pleasure the brightly glowing sparks which are produced in a retort by heat alone, during the reduction of metallic calces, when only a very little coal dust is mixed along with it.

We shall now see whether this fire-air is not the same air which had been lost without fire (-- 8-15), and with fire (-- 17-23).

+42. First Experiment.+--I filled a bottle which was capable of holding 16 ounces of water with pure fire-air according to the method which is described in - 30, letter e. I placed the bottle, inverted, in a gla.s.s which was filled with a solution of liver of sulphur. The solution rose a little into the bottle hour by hour, and after the lapse of 2 days the bottle was filled with it.

+43. Second Experiment.+--I mixed in a bottle 14 parts of that air from which the fire-air had been removed by liver of sulphur (- 8), and which I have called vitiated air (- 29), with 4 parts of our fire-air, and placed the bottle, inverted and open, in a vessel which was also filled with a solution of liver of sulphur. After 14 days the 4 parts of fire-air were lost, and the solution had risen into their place.

+44. Third Experiment.+--After I had filled a bottle with our air, I poured some colourless animal oil into it and closed it tightly. After a few hours it had already become brown, and by the next day black. It is no small inconvenience to preserve this oil white in apothecaries'

shops. It is found necessary to pour this oil into small phials, and to preserve it most carefully from the access of air. When such a colourless oil is mixed with any acid, the acid, as well as the oil, becomes black even in an hour, although it has been diluted with water.

Even vinegar has the same effect. There is no other reason, therefore, why the oil becomes at once black in the air, than that the fire-air present in the air deprives it of its phlogiston, and thereby develops a subtle acid, previously united with this phlogiston, which produces the blackness.

+45. Fourth Experiment.+--(_a._) Into a bottle of 7 ounces, which was filled with fire-air, I put a piece of phosphorus from urine and closed it with a cork. I then heated, by means of a burning candle, the place where the phosphorus lay; the phosphorus took fire with very great brilliancy. As soon as the flame had gone out, the bottle broke into fragments.

(_b._) As the bottle in the foregoing experiment was very thin, I repeated it with a somewhat thicker bottle, and after everything had become cold I wanted to take the cork out of the bottle under water. It was not possible for me to do this, however, so tightly did the external air press the cork into the bottle. Accordingly I forced it inside the bottle; thereupon water entered the bottle and filled it almost completely. Since the first bottle was only very thin, the reason that it was crushed must be ascribed to the external air.

(_c._) When I mixed vitiated air with one third of fire-air, and burned a piece of phosphorus in the mixture, only 1/3 of it was absorbed.

+46. Fifth Experiment.+--I also repeated the same experiment which is described in - 19, only with this difference that I took the tube longer, and filled the flask with my fire-air. It was pleasing to observe how the water rose gradually into the flask; and how the flame went out when 7/8 of the flask were full of water.

+47. Sixth Experiment.+--I laid some glowing coals upon the stand (- 21, letter _c_), and placed over them a flask which was filled with fire-air. The coals had not even reached the air in the flask before they began to burn very brilliantly.

After everything had become cold, I made an aperture under the flask, whereupon the fourth part became filled with water. But when I removed, by means of milk of lime, the aerial acid which was present in the residual air (- 22) there remained in the flask only the fourth part. In this air a candle could still burn.

+48. Seventh Experiment.+--I also examined the behaviour of fire-air with sulphur (- 23). As soon as the burning sulphur came into contact with the fire-air contained in the flask, the flame became much larger and brighter. When this fire had gone out, the water in the dish had found a way to come through the ma.s.s into the flask, which became 3/4 filled with it. As I employed for these last 3 experiments a flask which was only of 30 ounces measure, I was obliged to arrange the stand (- 21) to suit.

+49.+ I have mentioned (- 16) that I found vitiated air lighter than ordinary air. Must it not follow from this that the fire-air is heavier than our air? As a matter of fact, I actually found, when I accurately weighed as much fire-air as occupied the s.p.a.ce of 20 ounces of water, that this was almost 2 grains heavier than the same bulk of common air.

+50.+ These experiments shew, therefore, that this fire-air is just that air by means of which fire burns in common air; only it is there mixed with a kind of air which seems to possess no attraction at all for the inflammable substance, and this it is which places some hindrance in the way of the otherwise rapid and violent inflammation. And in fact, if air consisted of nothing but fire-air, water would surely render small service in extinguishing outbreaks of fire. Aerial acid mixed with this fire-air, has the same effect as vitiated air. I mixed one part of fire-air with 4 parts of aerial acid; in this mixture a candle still burned moderately well. The heat which lurks in the small interstices of the inflammable substance cannot possibly make up so much heat as is felt in fire; and I think I am not mistaken when I conclude from my experiments that the heat is really brought forth and produced in the first place from fire-air and the phlogiston of the inflammable substance....

+80.+ I had long wished to have some of the precipitate of mercury _per se_, in order to see whether it also would yield fire-air during reduction by means of heat alone. At length I obtained some from my much esteemed friend Doctor Gahn. This so-called precipitate had the appearance of small dark-red crystals resembling cinnabar. Now, as I know that mercury cannot be dissolved in muriatic acid unless it has lost its phlogiston, which takes place during its solution in acid of nitre or in vitriolic acid; and as this is also the reason why nitre must be present in a mixture of calcined vitriol, common salt, and quicksilver, I therefore poured muriatic acid upon a part of this red precipitate; the solution was soon formed and was somewhat hot; I evaporated it to dryness and increased the heat. Everything sublimed, and a true corrosive sublimate was formed. Hence this precipitate, produced by heat alone, is a calcined mercury. I then placed the other part of this precipitate over the fire in a small gla.s.s retort to which I had fastened an empty bladder. As soon as the retort became red hot the bladder became expanded, and at the same time the reduced mercury rose into the neck. In this case no red sublimate arose as customarily takes place with that calx which is prepared by the acid of nitre. The air obtained was a pure fire-air. This is a remarkable circ.u.mstance, that the fire-air which had previously removed from the mercury its phlogiston in a slow calcination, gives this same phlogiston up to it again when the calx is simply made red-hot. Still we have several such phenomena, where heat similarly alters the attractive forces between substances.

+83. Air is a Dulcified Elastic Acid.+

In the foregoing experiments I have demonstrated the two proximate const.i.tuents of common air, because it was not necessary to know anything more about it for a clear knowledge of fire. I shall now go further, and see whether a still deeper decompounding of air is possible.

+First Experiment.+--I placed a rat in a flask capable of holding 4 quarts of water; I gave it some bread softened in milk and closed the flask with a wet bladder. It died 31 hours afterwards. I then held the flask, inverted, under water and made a hole in the bladder, when two ounces of water rose into it. This small diminution of the air was probably caused by the heat which the rat took with it, which had previously driven the air out.

+84. Second Experiment.+--I took a large soft bladder and fastened a tube into its opening; then I filled it with the air out of my lungs, and held the tube and bladder with my right hand and closed my nostrils with the left. I respired the air as long as I could, and was able to make 24 inspirations (regarding which it is to be observed that at the last I was obliged to draw the whole bladder full of air into my lungs at once, while at the beginning only the half of it was necessary). I then closed the tube with my finger, and tied up the bladder. This air had properties similar to the preceding in which the rat died. That is to say, it contained one-thirtieth part of aerial acid, which I separated from it by milk of lime; and a burning candle at once went out in it.

+85. Third Experiment.+--I placed a few flies in a bottle into which I had put some honey smeared upon paper. After a few days they had died.

They likewise had not absorbed any air; milk of lime, however, diminished this air about one fourth part, and the remainder extinguished fire.

I then took a bottle of 20 ounces measure and bored a hole in the bottom of it with the corner of a broken file (Fig. 5, A). Into this bottle I put a small piece of unslaked lime, and closed the mouth with a cork through which I had previously fixed a tube B. Round about this cork I placed a ring of pitch, and placed over it an inverted gla.s.s C, into which I had previously put a large bee and had given it some honey which was smeared upon paper; but in order that no air could penetrate within the ring of pitch, I pressed the gla.s.s firmly in; I afterwards placed the bottle in the dish D, into which I poured so much water that it was half immersed in it; as soon I observed that the bottle was raised by the water, I put a small weight upon the gla.s.s. The water rose a little into the bottle every day through the opening A; and I also shook the bottle a little sometimes in order that the skin which formed over the milk of lime might break. After the lapse of seven days the water had risen to E, and the bee was dead. Occasionally I put 2 bees into the gla.s.s C, when just as much air was converted into aerial acid in half the time. Caterpillars and b.u.t.terflies behaved in exactly the same way.

+86. Fourth Experiment.+--I placed some peas in a small flask, which was capable of holding 24 ounces of water, and poured so much water upon them that they were half covered with it; I then closed the flask. The peas began to strike roots, and grew up. As I found after 14 days that they would not increase further, I opened the flask, inverted, under water, and found the air neither increased nor diminished. The fourth part, however, was absorbed by milk of lime, and the remaining air extinguished flame. I kept fresh roots, fruits, herbs, flowers, and leaves, each by itself, in the flask, and after a few days I likewise observed the fourth part of the air converted into aerial acid. If flies are placed in such air they die immediately.

+87.+ These are accordingly strange circ.u.mstances, that the air is not noticeably absorbed by animals endowed with lungs, contains in it very little aerial acid, and yet extinguishes fire. On the other hand insects and plants alter the air in exactly the same way, but still they convert the fourth part of it into aerial acid. Accordingly I was curious to know whether the fire-air was not that which was here converted into aerial acid, because in these latter experiments just as much of the air was converted into aerial acid as there was of fire-air present in it.

+88. Fifth Experiment.+--In a bottle of 20 ounces capacity, I mixed one part of fire-air with 3 parts of the preceding air in which peas would not any longer grow, and from which the aerial acid was separated. (That is to say, I filled the bottle with water, and placed 4 peas in it; I then allowed one fourth of the water to run into the bladder in which fire-air was contained, and the remainder into another bladder in which this vitiated air was contained (- 30, _g._), while I took care that the peas did not fall into the bladder. I also left so much water behind, that the peas were half covered with it.) Here also I observed the peas growing up, and after they would not increase any more I found this air likewise not absorbed, but almost the fourth part was absorbed by milk of lime. Hence it is the fire-air which is here converted into aerial acid. In 3 parts of aerial acid and one part of fire-air peas do not grow. I mixed vitiated air (- 20) with fire-air which behaved in just the same way: that is to say the fire-air was converted into aerial acid.

+89. Sixth Experiment.+--I mixed, in the same proportions, fire-air and air vitiated by peas, and filled a bladder with it. Then when I had completely exhaled the air present in my lungs, I respired this newly compounded air as many times as possible. I then found that it contained very little aerial acid in it, and when this was separated from it, it extinguished fire. I believe that one must ascribe to the blood present in the pulmonary veins, the effect which animals endowed with lungs have upon the air. The following experiment gives me cause for this.

It is known that freshly drawn blood, when it stands in the open air, a.s.sumes a fine red on the surface, and that the under portions likewise become red when they come into contact with the air. Does the air in this case undergo any alteration? I filled a flask one third part with freshly drawn ox blood, closed it tightly with a bladder, and shook up the blood frequently. Eight hours afterwards I neither found aerial acid in this air, nor that its bulk was diminished; but the flame of a candle was immediately extinguished in it. I made this experiment in winter time, from which may be gathered that the effect cannot be ascribed to any putrefaction, for this blood was found still fresh 6 days afterwards, and besides, all putrefactions produce aerial acid. I was now curious to know how fire-air by itself would behave with animals and plants.

+90. Seventh Experiment.+--(_a._) I put 2 ounces of nitre into a small gla.s.s retort upon glowing coals, and attached a large bladder softened with water (- 35), and allowed the nitre to boil until I had received 3/4 of a quart of fire-air in the bladder. I then tied up the bladder and separated it from the retort; I then placed a tube in its opening, and after I had completely emptied my lungs, I began to respire air from this bladder (- 84). This proceeded very well, and I was able to make 40 inspirations before it became difficult for me; eventually I expelled the air again from my lungs as completely as possible. It did not seem to have diminished particularly, and when I filled a bottle with it and introduced a burning candle, this still burned. I then began to respire this air anew, and was able to make 16 more inspirations. It now extinguished the flame, but I found only some traces of aerial acid in it. (_b._) I was surprised that I was not able the first time to take away from this air the property of allowing fire to burn in it; I thought that perhaps the great humidity prevented me from drawing this air into my lungs so often as was really possible. Accordingly I repeated the same experiment, only with this difference, that I put a handful of potashes into the bladder before the fire-air was driven into it. I then began to draw this air into my lungs, and counted 65 inspirations before I was compelled to desist. But when I lowered a burning candle into this air, it still burned well, although only for a few seconds.

+91. Eighth Experiment.+--I closed the hole in the bottle at A (Fig. 5) with a cork, as also the tube B, and then filled the bottle with fire-air (- 30, _e._). Then I had at hand the gla.s.s C, in which I had placed 2 large bees, and had provided some honey for their stay. I opened the stopped-up tube, placed this gla.s.s over it as quickly as possible, and pressed it into the ring of pitch. I afterwards placed the whole in the dish D, which I had filled with milk of lime, and withdrew the cork at A. In this case I observed the milk of lime to rise a little into the bottle every day, and after 8 days had elapsed the bottle was almost completely filled with it, and the bees were dead.

+92. Ninth Experiment.+--Plants, however, will not grow noticeably in pure fire-air. I filled with this air a bottle capable of holding 16 ounces of water, and which contained 4 peas (- 88). They got roots, but did not grow up at all; with milk of lime the twelfth part was absorbed.

I then filled this air into another bottle which also contained 4 peas.

After 14 days they had got roots, but also did not grow up, and with milk of lime likewise only the twelfth part was absorbed. I repeated this experiment 3 times more with the same air, and it was observed that the fourth and fifth times the peas had grown upwards a little. There still remained one-half of the whole air, and in this fire could still burn. There is no doubt that the whole quant.i.ty of fire-air could have been converted into aerial acid if I had continued the operation longer.

It may also be observed that the peas act more strongly upon the fire-air when they send out roots than subsequently.

+93.+ Hence it is the fire-air by means of which the circulation of the blood and of the juices in animals and plants is so fully maintained.

Still it is a peculiar circ.u.mstance that blood and the lungs have not such action upon fire-air as insects and plants have, for the latter convert it into aerial acid, and the former into vitiated air (-- 29, 89, 90). It is not so easy to furnish the reason for this, yet I will risk it. It is known that the acids lose those properties by which they reveal themselves as acids, by the addition of the inflammable substance, as sulphur, the elastic acid of nitre, regulus of a.r.s.enic, sugar, and the like, plainly shew. I am inclined to believe that fire-air consists of a subtle acid substance united with phlogiston, and it is probable that all acids derive their origin from fire-air. Now, if this air penetrates into plants, these must attract the phlogiston, and consequently the acid, which manifests itself as aerial acid, must be produced. This they again give up. The objection that so great a quant.i.ty of aerial acid is nevertheless obtained in the destruction of plants, and that, consequently, these must attract the aerial acid, has no weight, since otherwise the air in my vessels in which the peas were contained must have become for the most part lost, which, however, did not take place.... If plants abstract the phlogiston from the air, the aerial acid must be lighter. But experiment shows me the opposite; I found it, after careful weighing, somewhat heavier, but this is not contrary to my opinion; as it is known that all acids retain water strongly, the aerial acid must possess the same property, and this may consequently cause the most of the weight. If all this is accurate, another question then arises: Why do not blood and the lungs likewise convert fire-air into such an aerial acid? I take the liberty here also of giving my opinion of this, for how would all these laboriously executed experiments help me if I had not the hope of coming by means of them nearer to my ultimate object, the truth? Phlogiston, which makes most substances with which it unites liquid as well as mobile and elastic, must have the same effect upon blood. The globules of blood must attract it from the air through the small pores of the lungs. By this union they become separated from one another, and are consequently made more liquid. They then appear bright red (- 89). They must, however, give this attracted phlogiston up again during the circulation, and in consequence, be placed in a condition to absorb the inflammable substance anew from the air at that place where they are in the most intimate contact with it, that is, in the lungs. Where this phlogiston has gone to during the circulation of the blood, I leave to others to ascertain. The attraction which the blood has for phlogiston cannot be so strong as that with which plants and insects attract it from the air, and then the blood cannot convert air into aerial acid; still it becomes converted into an air which lies midway between fire-air and aerial acid, that is, a vitiated air; for it unites neither with lime nor with water after the manner of fire-air and it extinguishes fire, after that of aerial acid. But that the blood really attracts the inflammable substance I have additional experiment to prove, since I have removed phlogiston by help of my lungs from inflammable air, and have converted this into vitiated air.