The Boy's Playbook of Science Part 19

The battery is fitted with shafts for one horse. A pole is also provided to fix across the shafts, so that the battery may be drawn by hand.]

[Ill.u.s.tration: Fig. 151. A. Tank containing acid, communicating by a pipe with B, half filled with chalk and water. C C C C. Pipes conveying carbonic acid from the generator B, to the ceiling, where it is discharged from numerous holes on the fire beneath.]

Monsieur Adolphe Girard has proposed that all houses should be provided with an apparatus for the generation of carbonic acid gas, placed [Page 161] outside the building, which is to be conveyed along the ceiling by means of pipes perforated with numerous holes, and to be put in operation directly a fire breaks out. This plan, however ingenious, could hardly supply the carbonic acid gas with sufficient rapidity, and it is to be feared would utterly fail in practice. (Fig. 151.)

BORON.

Symbol, B; combining proportion, 10.9.

Discovered by Homberg, in 1702, in borax, which is a biborate of soda (NaO,2BO_{3}), and is used very extensively in the manufacture of gla.s.s; also for glazing stoneware and soldering metals; it is also a valuable flux in various crucible operations, whilst in testing minerals with the blowpipe it is invaluable. Borax is made either from tincal, a substance that occurs naturally in some parts of India, China, and Persia, or by the addition of carbonate of soda to boracic acid, a substance obtained from the volcanic districts of Tuscany, whence it is imported to this country, and used in the manufacture of borax.

The element boron may be obtained by placing some pure boracic acid and some small bits of pota.s.sium in a tube together, and applying the flame of a spirit-lamp, a glow of heat takes place, and when the tube is cold the potash may be washed away, and the boron remains as a dark brownish powder somewhat resembling carbon. M. St. Claire Deville and Wohler have lately made some important discoveries with respect to this element, and disproved the statement that it is uncrystallizable. Their researches prove it to be producible under three forms and of various colours, such as honey-yellow and garnet-red, the crystals in some cases being like diamonds of the purest water--_i.e._, limpid and transparent. A new combination of aluminium and boron is stated to possess the most remarkable properties. It is harder than the diamond, and in the state of powder will cut and drill rubies, and even the diamond itself, with more facility than diamond powder. Deville and Wohler incline to the belief that the diamond is dimorphous, and capable (in conditions yet to be described) of a.s.suming the same forms as boron. At a high temperature, boron, like t.i.tanium, absorbs _nitrogen_ only from the atmosphere, and rejects the oxygen. (Query, may not some of those remarkably hard black diamonds prove to be boron?)

SILICON.

Symbol, Si; combining proportion, 21.3.

The great Berzelius was the first to obtain this element in 1823.

Silicon in the pure state is a dark brown powder; if ignited at a very high temperature it a.s.sumes a chocolate colour, which is supposed to be the allotropic condition, because it no longer burns when heated moderately in oxygen or air, and is not attacked by hydrofluoric acid.

[Page 162] The most interesting combination of silicon is the teroxide called silicic acid, silica (SiO_{3}). Silicon is next to oxygen so far as regards its plentifulness, and is found in the state of silica in nearly every mineral, but especially in rock crystal, quartz, flint, sand, jasper, agate, and tripoli. It is largely used in the manufacture of gla.s.s, and a most useful "soluble gla.s.s" is obtained by melting together in a crucible fifteen parts of sand, ten parts of carbonate of potash, and one part of charcoal.

Cold water merely washes away the excess of alkali, and after this is done the powdered soluble gla.s.s may be boiled with water in the proportion of one of the former with five of the latter, when it gradually dissolves; the solution may be evaporated to a thick pasty fluid, which looks like jelly when cool, and on exposure to the air in thin films changes to a transparent, colourless, brittle, but not hard gla.s.s. Wood, cotton, and linen fabrics are rendered less combustible when coated with this gla.s.s, which excludes the oxygen of the air, and it has lately been employed to fill up the porous and capillary openings in stone exposed to the atmosphere, and is stated to be very efficacious as a preservative of the stone in some cases.

SULPHUR.

Symbol, S; combining proportion, 16.

Sulphur, like charcoal, is of common occurrence in nature, and is chiefly supplied from the volcanic districts of Tuscany and Sicily: there is an abundance of this element in the United Kingdom, but then it is locked up in combination with iron, copper, and lead, under the name of iron pyrites, copper pyrites, galena; and whilst Sicily and Tuscany supply thousands of tons weight in the uncombined state, it is not, of course, worth while to go through expensive operations at home for the separation of sulphur from the ores. During the dispute between Sicily and England, several patents were secured for new and economical processes by which sulphur was obtained from various minerals; and had this country been excluded from a supply of native sulphur, no doubt some of these patents would now be in active operation.

It is almost possible to estimate the commercial prosperity of a country by the sulphur it consumes, not, happily, by their warlike operations, but in the manufacture of oil of vitriol or sulphuric acid, which is the starting point of a great number of useful arts and manufactures.

_First Experiment._

Some very curious results may be obtained by heating sulphur at certain temperatures; in the ordinary state it is a pale yellow solid, and when subjected to a temperature of 226 Fahr. it melts to a brownish-yellow, transparent, thin fluid; according to all preconceived notions of the properties of substances which liquify by an increase of heat, it might be imagined that every additional degree of heat would only [Page 163]

render the melted sulphur still more liquid, but strange to say, when it reaches a temperature of about 320 Fahr. it changes red, and thick like treacle; and as the heat rises it becomes so tenacious, that the ladle in which it is contained may be inverted, and the sulphur will hardly flow out: at about 482 Fahr. it again becomes liquid, but not so fluid as at the lower temperature. If allowed to cool from 482 Fahr., the above results are simply inverted; the sulphur becomes thick, again liquid, and finally crystallizes in long, thin, rhombic prisms, which are seen most perfectly by first allowing a crust of sulphur to form on the liquid portion, and then having made two holes in this crust, the sulphur is poured out, when the remainder is found in the interior of the crucible crystallized in the form already mentioned. Sulphur takes fire in the air when exposed to a heat of about 560 Fahr., and burns with a pale blue flame; and, as already stated, it may be poured from a considerable height on a still dark night, and produces a continuous column of blue fire, just like an unbroken current of electricity. If the melted and burning sulphur is received into a vessel containing boiling water, it is no longer yellow, but a.s.sumes a curious _allotropic_ state, in which it is a reddish-brown, transparent, shapeless ma.s.s, that may be easily kneaded and used for the purpose of taking casts of seals, which become yellow in a few days, and are found then to be hard and crystallized.

_Second Experiment._

Sulphur vapour, in one sense, may be regarded as a supporter of combustion: if a clean Florence oil-flask is filled with copper turnings, and a little roughly-powdered sulphur sprinkled in, and heat applied, the copper glows with an intense heat, and burning in the vapour of the sulphur, produces a sulphuret of copper; from this compound the sulphur may be again obtained by boiling the powdered sulphuret with weak nitric acid, which oxidizes and dissolves the copper, leaving the greater part of the sulphur behind, which may be collected, melted, and burnt, and will be found to display all the properties belonging to that element. This experiment is a very good example of simple a.n.a.lysis; and if the copper is weighed and likewise the combined sulphur, a good notion may be formed of the principles of combining proportions.

_Third Experiment._

A little sulphur burnt under a gas jar, or in any convenient box (a hat-box, for instance), produces sulphurous acid (SO_{2}), which will bleach a wetted red rose or dahlia, and many other flowers. This gas is employed most extensively in bleaching straw, and sundry woollen goods, such as blankets and flannel, and likewise silk, and is perhaps one of the best disinfectants that can be employed; when fever has been raging in the dwellings of the poor, as in cottages, &c., all metallic substances should be removed, the doors and windows closed, the bedding, &c., well exposed, and then a quant.i.ty of sulphur should be burnt in an old [Page 164] frying-pan placed on a brick, taking care to avoid the chance of setting the place on fire; after a few hours the doors and windows may be opened, and the disinfectant will be found to have done its work cheaply and surely.

_Fourth Experiment._

The presence of sulphur in various organic substances, such as hair, the white of egg, and fibrine, is easily detected by heating them in a solution of potash, and adding acetate of lead as long as the precipitate formed is redissolved; finally the solution must be heated to the boiling point, when it instantly becomes black by the separation of sulphuret of lead.

_Fifth Experiment._

Sulphuric acid, HO,SO_{3}, or oil of vitriol, is made in such enormous quant.i.ties that it is never worth while to attempt its preparation on a small scale. In consequence of its great affinity for water, many energetic changes are produced by its action. Oil of vitriol poured on some loaf sugar placed in a breakfast-cup with the addition of a dessert-spoonful of boiling water, rapidly boils and deposits an enormous quant.i.ty of black charcoal. If a word be written on a piece of white calico with dilute sulphuric acid, and then rapidly and thoroughly washed out, no visible change occurs; but if the calico is exposed to heat, so that the excess of water is driven off, the remaining and now concentrated oil of vitriol attacks the calico, and the word is indelibly printed in black by the decomposition of the fabric of cotton.

A very remarkable process has lately been introduced by Mr. Warren de la Rue, by which paper is converted into a sort of tough parchment-like material, called ametastine, by the action of oil of vitriol and water of a certain fixed strength; and any departure from the exact proportions destroys the toughness of the paper. After the paper has been acted upon by the acid, it becomes extremely tenacious, and will support a considerable weight without breaking. Mr. Smee has used this ametastine in the construction of an hygrometer, and states that it may save many a traveller from catching a severe rheumatism in a damp bed.

_Sixth Experiment._

When the vapour of sulphur is pa.s.sed over red-hot charcoal and the product carefully condensed, a peculiar liquid is obtained, called bisulphide of carbon (CS_{2}), which possesses a peculiar odour, is extremely transparent and brilliant-looking, and enjoys a high refractive power. This liquid is used as a solvent for phosphorus and other substances, and is extremely volatile and combustible, and burns silently with a pale blue flame. The combustion of its vapour, mixed with certain gases, offers a good example of the fact that slow burning may be a peaceful experiment, whilst very rapid combustion often resolves itself into an explosion. Thus, if a few drops of bisulphide of carbon are dropped into a narrow-mouthed dry quart bottle containing common air, and flame applied, the combustion takes place with rapidity, a rus.h.i.+ng or [Page 165] roaring sound being audible, in consequence of the diffused vapour being supplied with more oxygen, and burning more rapidly than it would do if simply consumed from a stick or gla.s.s rod wetted with the fluid. A still greater rapidity of combustion is ensured by dropping some bisulphide of carbon into a long stout cylindrical jar, fifteen inches long and three inches in diameter, containing nitric oxide gas (NO_{2}); when flame is applied the mixture burns with a bright flash and some noise, and if burnt in a narrow mouthed bottle would most likely blow it to atoms.

The greatest rapidity of combustion, and of course the loudest noise, is obtained by shaking some bisulphide of carbon in a similar stout and strong cylindrical jar filled with oxygen gas, but in this case the jar must be protected with a double cylinder of stout wire gauze; it does not always break, but if it is blown to fragments each particle becomes a lancet-shaped piece of gla.s.s, which is capable of producing the most dangerous wounds. (Fig. 152.)

[Ill.u.s.tration: Fig. 152. A. Air and bisulphide of carbon. B. Nitric oxide and ditto. C. Oxygen and ditto. D D. Stout cylinder of double wire gauze, open top and bottom.]

SELENIUM.

Selenium ([Greek: _selene_], the Moon[B]); symbol, Se; combining proportion, 39.5.

This new metallic element is allied to sulphur, and is a species of chemical curiosity, being found in minute quant.i.ties in various minerals; it may be melted and cast into any form. Medallions of the discoverer (Berzelius) of selenium, in little cases, are imported from Germany, for the cabinets of the curious.

[Footnote B: Called selenium on account of its strong a.n.a.logy to the metal tellurium (_tellus_, the earth).]

[Page 166]

PHOSPHORUS.

Phosphorus ([Greek: _phos_], light; [Greek: _pherein_], to bear; symbol, P; combining proportion, 32.)

Monsieur Salverte, in his work on the Occult Sciences of the Ancients, quotes a remarkable story respecting the probable discovery of the nature of phosphorus in 1761:--"A Prince San Severo, at Naples, cultivated chemistry with some success; he had, for example, the secret of penetrating marble with colour, so that each slab sawed from the block presented a repet.i.tion of the figure imprinted on its external surface. In 1761, he exposed some human skulls to the action of different reagents, and then to the heat of a gla.s.s furnace, but paying so little attention to his manner of proceeding, that he acknowledged he did not expect to arrive a second time at the same result. From the product he obtained a vapour, or rather a gas was evolved, which kindling at the approach of a light, burned for several months without the matter appearing to die or diminish in weight. San Severo thought he had found, the impossible secret of the inextinguishable lamp, but he would not divulge his process, for fear that the vault in which were interred the princes of his family should lose the unique privilege with which he expected to enrich it, of being illuminated with a _perpetual lamp_." Had he acted like a philosopher of the present day, San Severo would have attached his name to the important discovery of the existence of _phosphorus_ in the _bones_, and made public the process by which it might be obtained.

This element, formerly sold at four or five s.h.i.+llings the ounce, has now fallen so much in price, from the greater demand and larger production, that it may be bought for a few s.h.i.+llings the pound, and is imported in tin cases in large quant.i.ties from Germany. It was discovered about two hundred years ago by Brandt, a merchant of Hamburg, and may be prepared on a small scale by distilling at a red heat phosphoric acid previously fused with one-fourth of its weight of powdered charcoal.

_First Experiment._

Phosphorus, when pure, is without taste or colour, but generally of a very pale buff-colour, and semi-transparent; it is extremely combustible, and is usually preserved under the surface of water; when perfectly dry, a thin slice will take fire at 60 Fah., and burns with great brilliancy. Considering the heat produced during the combustion of phosphorus, it might be thought that it would infallibly set fire to any ordinary combustible, such as paper or wood, but this is not the case when phosphorus is employed by itself, as may be proved by the following experiment.

Cut five very small pieces of phosphorus, and place them like the five of diamonds on a sheet of cartridge-paper laid upon the table, set the bits of phosphorus on fire, when they will be rapidly burnt away [Page 167] leaving only five black spots, but not firing the paper, as would be the case if some red-hot coals or charcoal were placed in the same position. The cause is very simple. Phosphorus in burning produces phosphoric acid, which is an anti-combustible, and coats the surface of the paper round the spot where the combustion occurs, and acting as a kind of glaze or gla.s.s, excludes the oxygen of the air, and prevents the fire spreading.

If some powdered sulphur is sprinkled round the spot where the bit of phosphorus is to be burnt, the case is very different; the heat melts and sets fire to the sulphur, which being uncoated with the phosphoric acid, communicates to the paper; and it is on this principle that lucifer-matches can be used as instantaneous lights. The tip of the wood of which they are composed is first dipped in sulphur, and then the phosphorus composition made of gum, chlorate of potash, vermilion, and phosphorus, is placed over it; and if the latter were used alone without the sulphur, not one match in a hundred would take fire properly.