As we stand in the twentieth century and peer curiously down the corridors of Time, we find at all periods a deep interest in chemical phenomena.

From the age when wisdom devoted itself in vain to the discovery of an elixir of life and a method of transmuting the base metals into gold, to the present day, when scientists pursue their experiments with more reasonable and far worthier hopes, chemistry appears never to have suffered any dearth of devotees, despite the fact that in olden times one had either to occupy a high position or be a man greatly daring if the Black Art was to be followed without fear of molestation.

To-day matters are different, so that the junior chemist need only anticipate interference from materfamilias—a truly excellent person, who, however, invariably regards chemical concoctions with hostile contempt.

The obstacles instanced in the previous paragraph being foreseen, perhaps no better initiative can be taken than to conciliate the household deities by the performance of some particular experiment which has an obviously beneficial result. This might happily be the removal of ink stains from white linen; and naturally, if no cloth happen to be so disfigured, some arrangement must be made whereby the ink is accidentally spilt!

Experiments with Chlorine

(1) Apparatus.—Erect a 4-oz. round-bottom flask about 8 inches above the table (A, Fig. 1), by clamping its neck in a wooden clip or twisted stiff iron wire, and fastening this to a firm standard. Introduce three or four tablespoonfuls of powdered manganese dioxide (obtainable cheaply in qr. lbs. at most druggists’), and pour over this spirits of salt until the flask is one-third full. Into the neck now fit a cork provided with two circular holes, through one of which a stem funnel passes, and into the other a glass tube fits tightly, being bent at two right angles, as shown in Fig. 1. The glass tube may be readily bent by softening it first over a spirit lamp—the flame being colored distinct yellow when the glass reaches a pliable state. Slide a 4¹/₂-inch disc of paper (B, Fig. 1) on the free limb of the tube, and also soak several 4-inch circles of cardboard in water. These will make satisfactory covers for the small glass preserve jars, in which the gas is to be collected.

(2) Preparation.—Place one jar beneath the glass tube so that the latter’s orifice reaches nearly to the bottom, and slide the paper disc down until it covers the mouth of the jar C. On warming the glass flask gently with a spirit lamp or, if available, Bunsen gas flame, a greenish-yellow gas is evolved, and gradually expels the air from flask, tube, and jar, until this latter is filled with heavy chlorine. The warming is then interrupted whilst the one jar is removed, covered with a moist cardboard disc, and replaced by another. The heating again proceeds, and so on until each remaining jar is successively filled.

Chlorine Experiments (1).—Damp an addressed envelope, received through the post, by pressing between sheets of wet blotting-paper, and stand it in a jar of chlorine with the cover replaced (A, Fig. 2). The writing ink address will soon begin to fade and finally disappear, whilst the postmark, which has been impressed in indelible printing ink, remains unaltered. This reaction shows that chlorine possesses the valuable property of bleaching writing ink. It may be turned to account in removing stains from cloth by wetting the spoiled material first and then standing in a vessel containing the yellow gas (Fig. 3). The fabric must be quite damp, however, as bleaching only proceeds in the presence of moisture. Coloring matters, other than black ink, are readily removed by chlorine, as may be strikingly shown by steeping a wet rose blossom or bunch of violets in a jar of the gas (Fig. 4); the flowers assume a transparent waxy appearance, that will puzzle any spectator as to their real identity.

Chlorine Experiments (2).—The energetic gas attacks many substances spontaneously. If thin blotting-paper be soaked in turpentine, drained, and dropped into a jar of chlorine, the oil takes fire at once, burning rapidly amid smoky black fumes. Metals are attacked just as readily as the inflammable oil of turpentine. Powdered antimony metal or iron filings shaken into a jar of chlorine scintillate brilliantly with the evolution of thick white fumes. Similarly Dutch metal leaf, used for gilding cheap picture frames, ignites in the gas; a salt of copper being precipitated to the bottom of the jar when the action has ceased.

All dealings with chlorine should be conducted in a well ventilated—even draughty—room, and care must be taken not to inhale the gas. It corrodes animal tissues just as eagerly as it attacks turpentine and metals. The gas is very heavy, however, and is therefore the less difficult to keep under control.

Niter Paper.—Touch-paper burns quickly, surely, and without flame. It is prepared by soaking thin tissue paper with a saturated solution of saltpeter in weak vinegar, and when dry feels rough and crisp to the touch. Moreover, it burns with a rather pleasant smell. The advertisement scheme of bygone days, wherein a lighted match was placed on a particular spot of a paper sheet, and thence the name of the advertised commodity gradually burnt itself out over the surface, was a modification of this preparation (Fig. 5). The name or design is simply drawn with a pointed stump of wood dipped repeatedly in the saltpeter solution, and the starting-point marked conspicuously by a cross or black spot. When dry a match is applied to this mark. If there is a tendency for other parts of the paper than the design itself to burn, a short immersion in dilute alum solution, when the saltpeter lines have dried, may be resorted to.

Electric Fire.—This compound is in no way of an electric nature, except that it burns rapidly with brilliant blue illumination. The constituents are flowers of sulphur, saltpeter, and antimony, four parts of the former being intermingled with ten parts of powdered saltpeter, and then one-seventh the total quantity of powdered antimony finally added. Thorough mixing by gentle stirring must be insured. A good method of firing the powder is to pack it round a twist of touch-paper in a small mustard tin, threading the fuse (A, Fig. 6) through a hole in the lid, so that it may be lighted easily. The mixture burns not only brightly, but with intense heat—sufficient to melt the thin iron of the inclosing tin.

The Lightest Element.—Hydrogen is a gas at ordinary temperature, and has the honor of being the lightest element, for all practical purposes, known. For this reason it finds wide employment in filling balloons and airships. The most common methods of preparation consist of decomposing water or an acid in their several constituents, either by the influence of electricity or the reaction of a metal. For instance, if a pea’s bulk of sodium or potassium metal be thrown into a basin of water, A, Fig. 7, (the experimenter should not bend directly over the vessel), a violent reaction ensues, the metal decomposes and hustles round the surface as though in feverish excitement, and in the case of potassium a purple flame springs up spontaneously. The sodium may also be ignited if it is thrown on to a floating piece of blotting-paper, or if the water be thickened with starch. This metal burns with a yellow flame, or rather colors the hydrogen flame yellow.

Preparing hydrogen by the foregoing method is inconvenient and expensive if any quantity is to be collected, and so in this case the following plan is usually adopted:—Support a flask (A, Fig. 8), and place zinc chips (B) in it to the depth of about ¹/₄ inch. Fit the mouth with a cork, through which passes a delivery tube (C) and a “thistle” funnel (D), dipping nearly to the level of the zinc. When the gas is required, dilute sulphuric acid—one part oil of vitriol to ten parts water—is poured down the funnel until the flask is about one-third filled (E).

Five or ten minutes should be allowed after bubbling has commenced before an attempt is made to light the gas at the delivery tube, as otherwise air from the flask may be intermingled in the exact proportion to cause a bad explosion. No danger need be feared if several minutes are allowed for the air to be thoroughly dispelled, or, as an additional measure of safety, a damp towel (F) is wrapped round the flask to prevent scattering of the glass in the event of a mishap. The glass delivery tube should have been softened in a spirit flame and drawn to a fine point where the hydrogen issues. The gas will be found to burn with an almost colorless flame.

If a glass tube (A) of larger bore than the delivery pipe be slid over this latter while the gas burns, a peculiar musical note is produced—hollow-sounding and shrill (Fig. 9). It is caused by the rapid succession of slight explosions which constitute the combustion of hydrogen.

The extreme lightness of hydrogen, as well as its combustibility, is well illustrated by blowing a soap bubble. Connect a clay pipe with the glass delivery tube by means of a length of india-rubber tubing, and provide this latter with a small clip—tie-clip, for example—so that the gas supply may be shut off at will (Fig. 10). Let the hydrogen pass for a minute or so, to clear air out of the clay pipe, and then, having shut off the gas, dip the pipe bowl into soap-suds. Next open the clip until the hydrogen has blown the bubble large enough, and then shut off, shaking the shimmering globe free. It will rise very quickly, just like an unballasted balloon, and if a lighted taper be applied to its surface it will explode to annihilation with a loud report.

Spirits of Hartshorn.—Commercial ammonia is actually an aqueous solution of the gas, which dissolves to an abnormal extent in water. When it has been absorbed as much as possible the liquid weighs only 22.25 as much as an equal bulk of water, owing, of course, to the latter’s association with a compound far lighter than itself. So great is the energy of solution that heat is dissipated from the liquid as absorption proceeds. Conversely, if the gas be dispelled by blowing air through strong liquor ammoniac, heat is rapidly absorbed at the expense of surrounding objects. To show this, stand a small flask in a pool of water on a wood block, and having about half filled the flask with fresh ammonia, blow into this through a glass tube connected with the mouth by a length of rubber tubing (Fig. 11). No long time should elapse before enough heat has been abstracted from the water to convert it into ice, so that the flask is frozen firmly to the wood.

Another demonstration of water’s avidity for ammonia gas is afforded by the following performance. Erect one large flask (A) in an inverted position, so that the distance between its neck and the table is several inches greater than its own height. Some distance away, as shown in Fig. 12, erect a small 4-oz. flask (B), and half fill it with a mixture of four parts sal-ammoniac to three parts slaked lime (C). Fit the neck with a cork and a delivery tube, which has been so bent as to pass through a stopper in the mouth and reach nearly to the bottom of a jar (D) packed with quicklime (E).

Another glass tube (F) issues from this chamber—but only from just below the cork’s under surface—and passes upwards into the orifice of the large flask. A square of paper (G, in Fig. 12) is pushed over the glass tube and presses against the mouth of the flask.

If now the mixture in the 4-oz. flask be warmed, ammonia gas is produced, and having been robbed of moisture by the quicklime through which it passes, travels upwards, and collects in the large inverted flask. When the action has continued for a little while, stop the heating and remove the delivery tube, and bring an open spirits of salt bottle near the inverted flask’s mouth. If dense white fumes are immediately formed, the flask is known to be filled with ammonia gas, and must be corked up.

Beneath this container is next stood another large flask filled with red litmus solution (A) and fitted with a stopper, through which pass two glass tubes (M and N, in Fig. 13). One of these (N) is bent outwards, and extends only just inside the flask’s neck, whilst the other is long enough to reach from the bottom of the lower flask almost to the top of that holding the ammonia. Instead of red litmus solution, a liquid made by boiling red cabbage leaves in water, and adding just enough vinegar to dispel entirely the bluish coloration, may be used with equal success.

The position then is that two flasks—of which the upper (B) holds ammonia gas, whilst the lower retains a pink solution—are supported one above the other, their necks approaching and joined by a glass tube (M). A second glass tube (N) also emerges from just above the surface of the pink liquid, and is bent outwards from the flask, so that it may be held in the mouth. When this is blown through, the pink water is forced up the connecting tube (M) and sprays out, fountain-like, within the upper flask. Moreover, as the ammonia is so rapidly absorbed by the incoming water, this continually ascends to fill the vacuum, which tends to form as the gas is dissolved. The fountain continues to play when the blowing has ceased, and further, although the spray presents a reddish tinge on entering the flask, it immediately turns blue as the ammonia dissolves (C, Fig. 13). This reaction indicates the alkalinity of ammonia, such substances being capable of neutralizing acids, which redden solutions of vegetable blues.