The Boy's Playbook of Science Part 18

_First Experiment._

Box and various woods, dried bones, and different organic matters, placed in a nearly close iron or other vessel, and heated red hot, so that all volatile matter may escape, leave behind a solid black substance called charcoal. If that kind obtained from bones, and termed bone black or ivory black, is roughly powdered, and placed in a flask with some solution of indigo or some vinegar, or syrup obtained by dissolving common moist sugar in water, and boiled for a short period, the colour is removed, and on filtering the liquid it is found to be as clear and colourless as water, provided sufficient ivory black has been employed.

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_Second Experiment._

Charcoal is a disinfectant, and is used for respirators; it has even been recommended medically, and charcoal lozenges can be bought at various chemists' shops. If a few drops of a strong solution of hydrosulphuret of ammonia (which has the agreeable odour belonging to putrid eggs) is mixed with half a pint of water, it will of course smell strongly, and likewise precipitate Goulard water, or a solution of acetate of lead black; but on shaking the water with a few ounces of charcoal, it no longer smells of sulphuretted hydrogen, and if filtered and poured into a solution of lead does not turn it black. This chemical action of charcoal, independent of its seeming mechanical attraction for colouring matter, would appear to show that the pores of charcoal contain oxygen, which in that peculiar condensed state destroys colouring matter, and oxidizes other bodies.

_Third Experiment._

A very satisfactory experiment, proving that the diamond and plumbago or black lead are identical with charcoal, although differing in outward form and purity, can be made at a little cost, by purchasing a fragment of refuse diamond, called "_boart_," of Mr. Tennant of the Strand. A small piece costs about five shillings. The fragment should be carefully supported by winding some _thin_ platinum wire round it, as, if the wire is too thick, it cools down the heat of the bit of diamond and prevents it kindling in the oxygen gas. A difficulty may arise in preparing the fragment, in consequence of the wire continually slipping off. The "boart" should therefore be grasped by the thumb and first finger, and the wire wound round; then it must be carefully turned and again wound across with the platinum wire, as in the sketch below. (Fig. 145.)

[Ill.u.s.tration: Fig. 145. A. The platinum wire. B. The fragment of "boart" or refuse diamond.]

A piece of black lead (so called) may now be taken from a lead pencil and also supported by platinum wire; likewise a bit of common bark charcoal or hard c.o.ke. Three bottles of oxygen should now be prepared from chlorate of potash and oxide of manganese, an extra bottle being provided for the diamond in case there should be any failure in its ignition. The bark charcoal can be first ignited by holding a corner in the spirit lamp for a few seconds; when plunged into oxygen it immediately kindles and burns with rapidity, and if the cork is well fitted, the product of combustion--viz., carbonic acid gas--is retained for future examination. The small piece of black lead is next heated red hot in the flame of the spirit lamp, and being attached by its platinum support to a stiff copper wire thrust through a cork, which fits the bottle of oxygen, is placed whilst red hot in the gas, and continues to glow until consumed. The fragment of diamond is by no means, however, so [Page 154] easily ignited, the flame of the spirit lamp must be urged upon it with the blowpipe; when quite red hot, an a.s.sistant may remove the stopper from the bottle of oxygen, and the person heating the diamond should plunge it instantly into the gas; if this is dexterously managed, the fragment of _boart_ glows like a little star, and the combustion frequently continues till the piece diminishes so much that it falls out of its platinum support.

Sometimes the diamond cools down without igniting, the same process must therefore be repeated, and a few extra bottles of oxygen will prevent disappointment, as every failure destroys the purity of the gas by admixture with atmospheric air when the stopper is removed. (Fig. 146.)

[Ill.u.s.tration: Fig. 146. A. Bottle containing bark charcoal. B. Ditto the plumbago or black lead. C. Ditto the diamond.]

The combustion having ceased in the three bottles, the corks are removed, and the gla.s.s stoppers again fitted for the purpose of testing the _products_, which offer no apparent indication of any change, as oxygen and carbonic acid gas are both invisible. In each bottle a new combination has been produced; the charcoal, the black lead, the diamond have united with the oxygen, in the proportion of six parts of carbon to sixteen parts of oxygen, to form twenty-two parts of carbonic acid gas, which may be easily detected by pouring into each bottle a small quant.i.ty of a solution of slacked lime in water, called lime water. This test is easily made by shaking up common slacked lime with rain or distilled water for about an hour, and then pa.s.sing it through a calico or paper filter. The test, though perfectly clear when poured in, becomes immediately clouded with a white precipitate, usually termed a _milkiness_, no doubt in allusion to the London milk, which is supposed to contain a notable proportion of chalk and water, for in this case the precipitate is chalk, the carbonic acid from the diamond and the charcoal having united with the lime held in solution by the water and formed carbonate of lime, or chalk, a substance similar in composition to marble, limestone, Iceland or double refracting spar, these three being nearly similar in composition, and differing only, like carbon and the diamond, in external appearance.

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The milkiness, however, must not be held as conclusive of the presence of carbonic acid gas until a little vinegar or other acid, such as hydrochloric or nitric, has been finally added; if it now disappears with effervescence (like the admixture of tartaric acid, water, and carbonate of soda), the little bubbles of carbonic acid gas again escaping slowly upwards, leaving the liquid in the three bottles quite clear, then the experimentalist may sum up his labours with these effects, which prove in the most decisive manner that common charcoal, black lead, and the diamond, are formed of one and the same element--viz., carbon.

_Fourth Experiment._

Having effected the synthesis (or combining together) of the diamond and oxygen, it is no longer possible to recover it in its brilliant and beautiful form. If the product of combustion is retained in a flask made of thin, hard gla.s.s, and two or three pellets of the metal pota.s.sium are placed in directly after the diamond has ceased to burn, and the flame of a spirit lamp applied till the pota.s.sium ignites, then the metal, by its great affinity for oxygen, takes away and separates it again from that which was formerly the diamond; but instead of the jewel being deposited, there is nothing but _black_, shapeless, and minute particles of carbon obtained, if the potash produced is dissolved in water, and the charcoal separated by a filter.

_Fifth Experiment._

Chalk is made by uniting carbonic acid gas with lime; it may therefore be employed as a source of the gas, by placing a few lumps of chalk, or marble, or limestone, in a bottle such as was used in the generation of hydrogen gas; on the addition of some water and hydrochloric acid, effervescence takes place from the escape of carbonic acid gas, and the cork and pewter pipe being adapted, it may be conveyed by its own gravity into gla.s.ses, jugs, or any other vessels, and a pneumatic trough will not be required. Carbonic acid gas has a specific gravity of 1.529, and is therefore rather more than half as heavy again as atmospheric air.

_Sixth Experiment._

In order to satisfy the mind of the operator that the gas obtained from chalk is similar to the _product of combustion from the diamond_, some lime-water may be placed in a gla.s.s, and the gas from the bottle allowed to bubble through it; instantly the same milkiness is apparent, which again vanishes on the addition of acid. And this experiment is rendered still more striking if a lighted taper be placed in the gla.s.s just after the addition of the acid, when it will be immediately extinguished.

_Seventh Experiment._

If a lady's m.u.f.f-box, supported by threads or chains, is hung on one end of a scale-beam, and counterbalanced by a scale pan and a few shot, it is [Page 156] immediately depressed on pouring into the m.u.f.f-box a quant.i.ty of carbonic acid gas, which may have been previously collected in a large tin vessel. After showing the weight of the gas, the box is detached from the scale-beam, and the contents poured upon a series of lighted candles, which are all extinguished in succession. (Fig. 147.)

[Ill.u.s.tration: Fig. 147. A. Carbonic acid gas poured out of the tin box into B, the m.u.f.f-box. B B. Detached m.u.f.f-box, and candles extinguished by the carbonic acid gas poured from it.]

_Eighth Experiment._

The property of carbonic acid gas of extinguishing flame, as compared with the contrary property of oxygen, is nicely shown by first pa.s.sing into a large and tall gas jar one half of its volume of oxygen gas; a large cork perforated with holes may be introduced, so as to float upon the surface of the water in the gas jar, and is usefully employed to break the violence with which the carbonic acid enters the gas jar, as it is pa.s.sed in to fill up the remaining half volume of the gas jar, which now contains oxygen at the top, and carbonic acid gas at the bottom. On testing the contents of the jar with a lighted taper, it burns fiercely in the oxygen, but is immediately extinguished in the [Page 157] carbonic acid gas, being alternately lighted and put out as it is raised or depressed in the gas jar.

_Ninth Experiment._

A little treacle, water, and a minute portion of size, may be placed with some yeast in a quart bottle, to which a cork and pewter or gla.s.s pipe is attached; directly the fermentation begins, quant.i.ties of carbonic acid gas may be collected, and tested either with lime-water or the lighted taper.

_Tenth Experiment._

Some clear lime-water placed in a convenient gla.s.s is quickly rendered milky on pa.s.sing through it the air from the lungs by means of a gla.s.s tube; thus proving that respiration and (as shown by the ninth experiment) fermentation, as well as the combustion of charcoal, produce carbonic acid gas.

_Eleventh Experiment._

[Ill.u.s.tration: Fig. 148. A A. The box model of the Grotto del Cane. B B.

Cardboard fixed in front of box, and painted to imitate rocks. C.

Carbonic acid gas bottle, with bent tube pa.s.sing through hole in the side of the box. A taper introduced at D burns in the upper, and is extinguished in the lower, part of the model.]

Carbonic acid gas is not only generated by the above processes, but is liberated naturally in enormous quant.i.ties from volcanoes, and from certain soils: hence the peculiar nature of the air in the Grotto del Cane. Dogs thrust into this cave drop down immediately, and are immediately revived by the tender mercies of the guides, who throw them into the adjoining lake. This natural phenomenon is well imitated by taking a box, open at the top, and nailing on to it a frame of cardboard, [Page 158] which may be painted to represent rocks, taking care that a portion (about three inches deep) at the lower part is well pasted to the box at the edges, so that the gas may be retained; a hole is perforated at the top side to admit a lighted taper, and another at the side for the pipe from the carbonic acid bottle; when the bottom is filled with gas, a taper is applied, which is found to burn in the upper part, but is immediately extinguished when it reaches the lower division, where the three inches of pasteboard prevent it falling out: thus showing in a simple manner why a guide may enter the cave with impunity, whilst the dog is rendered insensible because immersed in the gas. (Fig. 148.)

_Twelfth Experiment._

Many fatal accidents have occurred in consequence of the air in deep pits, graves, &c., becoming unfit for respiration by the acc.u.mulation of carbonic acid gas, which may arise either from cavities in the soil, where animal matter has undergone decomposition, or it may happen from the depth and narrowness of the hole or well preventing a proper draught or current of air, so that it becomes foul by the breathing of the man who is digging the pit. Air which contains one or two per cent. of carbonic acid will support the respiration of man, or maintain the flame of a candle; but it produces the most serious results if inhaled for any length of time; a lighted candle let down into a well (suspected to contain foul air) before the descent of the person who is to work in it, may burn, but does not indicate the presence of the small percentage of the poison, carbonic acid. Frequently no trouble is taken to test the air with a lighted candle; a man is lowered by his companions, who see him suddenly become insensible, another is then lowered quickly to rescue him, and he shares the same fate; and indeed cases have occurred where even a third and a fourth have blindly and ignorantly rushed to their death in the humane attempt to rescue their fellow creatures. What is to be done in these cases? Are the living to remain idle whilst the unfortunate man is suffocating rapidly at the bottom of the pit? No; provided they do not venture themselves into the pit, they may try every known expedient to alter the condition of the foul air, so as to enable them to descend to the rescue. One should be despatched to any neighbouring house or cottage for a pan of burning coals; if any slacked lime is to be had, it may be rapidly mixed with water, and poured down the side of the pit; a bundle of shavings set on fire and let down, keeping it to one side, so as to establish a current; or even the empty buckets constantly let down empty and pulled up full of the noxious air, may appear a somewhat absurd step to take, but under the circ.u.mstances any plan that will change the air sufficiently to enable another person to descend must be adopted; in proof of which the following experiments may be adduced:

Fill a deep gla.s.s jar with carbonic acid, and ascertain its presence with a lighted taper; if a beaker gla.s.s to which a string is attached is let down into the vessel and drawn up, and then inverted over a lighted [Page 159] taper, the utility of this simple plan is at once rendered apparent; the beaker gla.s.s represents the empty bucket, and can be let down and pulled up full of carbonic acid until a sensible change in the condition of the atmosphere is produced. The best plan, however, is to set the air in motion by heat obtained from burning matter, or even a kettle of boiling water, lowered by a cord, and this fact is well shown by putting a small flask full of boiling water, and corked, at the bottom of the deep gla.s.s jar containing the carbonic acid gas, which rises like other gases when sufficiently heated, and pa.s.sing away, mixes with the surrounding air. (Fig. 149.)

[Ill.u.s.tration: Fig. 149. A. Deep jar containing carbonic acid gas, which is being removed by the little gla.s.s bucket. B. Jar containing corked flask of boiling water on a pad; the heated gas rises and the cold air descends to take its place.]

_Thirteenth Experiment._

Carbonic acid gas dissolved in water under considerable pressure, forms that most agreeable drink called soda-water; the gas is not only useful in this respect, but has been applied most successfully by Mr. Gurney to extinguish a fire on a gigantic scale, which had been burning for years in the waste of a coal mine in Scotland. The same gas, generated suddenly by the combustion of a mixture of nitre, c.o.ke dust, and clay, or plaster of Paris, in vessels of a peculiar construction, has formed the subject of a patent by Phillips, since merged into the Fire Annihilator Company. The instrument is peculiarly adapted for shipping, and might, if properly used, be the means of saving many ships and valuable lives. (Fig. 150.)

Its practical value is established by the test of actual use: in the streets, by the Leeds Fire Brigade, and by firemen of the Fire Annihilator Company, temporarily stationed at Liverpool and Manchester.

The Fire Annihilator has been formally recognised by the Government Emigration Commissioners, who introduced into the Pa.s.sengers' Act, 1852, in --24, the alternative, "_Or other apparatus for extinguishing fire_,"

with distinct reference to this invention, and subsequently by formal order authorized their officers to pa.s.s ships carrying Fire Annihilators.

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[Ill.u.s.tration: Fig. 150. A. A carriage with six fire annihilators, No. 5 size, fitted with moveable pipes. The body of the carriage forms a tank for forty gallons of water; the tank is filled at a bunghole in the platform; a patent tap is fitted to the rear of the carriage; a spigot is placed near the end upright of the rail; a hand-pump is placed in the box at rear of carriage; a leather bucket with foot-holds and three canvas buckets are hung on the carriage; a hammer for removing and driving on the cover of the fire annihilator, and a nut wrench for the No. 10 truck, are placed in the box. B. A fire annihilator, No. 10 size, with moveable pipe, on a spring truck, is attached to the carriage.