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PRACTICAL SCIENCE.

8. CHEMISTRY.
CHLORINE.

1. To make the gas. I intend making some chlorine gas for you to-day, and trying a few experiments with it; but before doing so, I must beg that you will not come too near the apparatus, and that you will not remove any of the stoppers from the bottles of collected gas, when my attention is directed to some other part of

the room.

You observe that I have a stand, with a moveable slide and ring to hold a retort or flask, and that the Florence flask, placed in the ring of the stand, is fitted with a cork, having a bent glass tube, securely fixed in it, and long enough to pass to the bottom of the bottle, which is also placed in the same manner as I shall require to use it afterwards, with a cover of greased cardboard, and a spiritlamp underneath the flask. You see that I have also several square pieces of cardboard and glass, all well greased, and some greased stoppers lying near to these different sized bottles upon the table; and that on my left-hand side, there are some pieces of printed calico, a sprig of parsley, and various other things, all of which we shall require. The reason that you were requested not to approach too near the apparatus is, because chlorine gas is exceedingly irritating to the lungs, and when breathed excites coughing, spitting of blood, and violent inflammation of the air passages. Even when largely diluted with the air it is very irritating, and therefore I have provided a

* Discovered by Scheele, in 1774. Chemical symbol, Cl-atomic weight=36-specific gravity =25, or about 24 times heavier than common air. The name of chlorine, which was given to this gas by Sir H. Davy. is derived from the Greek word chloros (xwpoc), which signifies yellowish

green

large bottle to receive the first portion of the gas that escapes from the flask, because it is mixed with the air, and consequently useless for experiment, and is usually allowed to escape in the room; but if received into this large bottle it will prevent you interrupting me by coughing, and the bottle may be afterwards placed in the garden, and the gas allowed to escape there.

I observe that some of you are holding your handkerchiefs to your noses; and this reminds me that I had forgotten to mention that it is advisable to sprinkle a strong solution of ammonia about the table, and also to have a towel saturated with it, near at hand. I have not neglected this precaution on the present occasion; as some of you have reminded me with tears in your eyes.

There are two methods of making this gas; and as I wish you to know how everything is done, we will prepare some gas by each.

You see that I have put some black powder into the mortar, and also an equal portion of common salt. The black powder is the black oxide of manganese; and when the two are well mixed by rubbing them together in the mortar, we will take two ounces of the mixture and place it in the retort ready for use. [Does so, after the salt and black oxide of manganese are mixed]. The bottle you see in my right hand contains sulphuric acid, or, as it is commonly called, oil of vitriol; and when this is mixed in a thick earthen jug, with an equal quantity of water, we shall have advanced another step in our preparation of chlorine. You must be careful in mixing sulphuric acid with water; because if the combination takes place in a thick glass or earthenware jug, it will probably break the vessel, in consequence of the sudden heat produced by mixing the acid with water. I would therefore advise you to use a wooden bowl and a stick, to mix them well.

Now that the acid is properly diluted, I will pour some into the flask, and by shaking it occasionally the powder will mix more readily with the fluid, and presently we shall see that the lower part of the flask contains a thin paste. It is very necessary to moisten the powder well; for ifthis precaution be not observed, the bottom of the flask would break when the flame of the spirit-lamp came in contact with it.

Some gas is passing out of the flask,

although I have not yet applied any heat, and therefore the cork fitted with the bent glass tube must be put in, and the gas collected at once. [Places the tube and cork in the flask, and the flask in the ring of the retort-stand, as in the figure, page 129]. You observe that I do not apply the flame of the spirit-lamp to the bottom of the flask at once, but that the flame is moved backwards and forwards underneath it. When this has been done for a few minutes, you should remove the flame of the spirit-lamp, and wipe the surface of the flask, so as to get rid of the superfluous moisture, the product of condensation.

The ordinary method of collecting gases in bottles for experimenting is by means of a pneumatic trough, as it is generally called; but as we shall consider this upon another occasion, I shall only allude to it here. You appear astonished that the plan was not adopted in the present instance, particularly as you have no doubt seen many lecturers collect it over water like other gases; but although it is done, yet the practice is bad, because, as we shall presently see, water absorbs chlorine gas, and therefore until saturated with it, you are expending the gas without any benefit, unless, indeed, you wish to make chlorine water at the same time. By using strong brine, the gas may be collected without losing much of it by absorption. The best plan is, to let the end of the bent tube pass to the bottom of the receiving-bottles,-which should be loosely covered with a piece of card, as in the apparatus on the table, This gas, being much heavier than the air in the bottle, displaces it, and when the bottle is full of the greenish coloured gas, we place a greased stopper firmly in the bottle, or cover the mouth of it with a piece of greased card-board, and supply its place with another receiving bottle.

We have now collected several bottles of the gas, and are therefore prepared to perform some experiments; but before doing so, I will describe the other method of obtaining chlorine.

Instead of putting a mixture of salt and black oxide (per-oxide) of manganese into the retort or flask, and adding diluted sulphuric acid, we place one part of the black oxide of manganese in the flask, and add two parts of strong hydrochloric acid, or spirit of salt. The small apparatus

we have upon the table serves for this method, and the manner of proceeding is precisely the same. Some chemists add two drops of oil of turpentine, to prevent the materials frothing up.

Chlorine gas in a pure state may also be obtained by acting on one part of powdered bichromate of potash in a small retort, with six parts of strong hydrochloric acid. The retort is gently heated at first, and then the heat withdrawn, as it is only required to commence the process. We will now try a few experiments with the gas already collected in the bottles.

[Experiment 1.] You remember I mentioned that this gas was highly irritating to the air-passages, and therefore is not calculated to sustain animal life. Here is a mouse which is racing about at full gallop in his cage, and you will see that when it is suspended in this jar, it will die instantly. [Drops the mouse into the jar, and it dies immediately.] Now although this gas is so irritating that it has already made some of you cough, and killed the mouse, yet it has been found that when largely diluted with atmospheric air, it acts beneficially upon persons affected with certain diseases of the lungs, and moreover, that the labourers employed in the bleaching manufactories, and those persons residing near to them, are seldom attacked with consumption.

[Experiment 2.] I stated that the reason this gas was not collected over water, was because the water absorbed chlorine. Let us see if such be really the case. Here is some distilled water, which I am going to pour into the bottle of chlorine gas before me. [Adds the water.] You see that about a third of the bottle is occupied by the water, and the remainder by the gas. I will shake the bottle well, and you will then observe the yellowish-green colour disappear from the upper part of the bottle. [Performs the experiment, and the water absorbs the chlorine.] We may now safely assert that one part of water will absorb two parts of chlorine gas. The solution we have made is called chlorine water, which is used as a bleaching agent, and for destroying offensive effluvia, and arresting putrefaction. In order that you may remember these properties of the aqueous solution of the gas, we will try some experiments with it.

[Experiment 3.] Here is a piece of putrid meat, and although the effluvia from it now is most offensive, yet soon after its immersion in the chlorine water, the noisome odour will be destroyed. [Performs the experiment.] If fresh meat be suspended over chlorine water or submitted to the fumes of the gas, putrefaction will not take place, and the chlorine water thrown down an offensive drain speedily removes the disagreeable effluvia arising from it.

[Experiment 4.] Here is a tumbler of a solution of indigo, and we will pour in a little of the chlorine water, and stir it with this glass rod, and you will then see the bleaching qualities of the gas. [Does so, and the colour of the solution is destroyed.] [Experiment 5.] Let us see if the gas will bleach as well as the aqueous solution of it. Here are two bottles. I shall suspend a sprig of damp parsley in one, and this piece of printed calico in the other. [Does so.] You observe that the parsley has already become rather yellow, and is rapidly assuming a white appearance, and the piece of printed calico is also white. If you took a small bouquet of flowers and dipped them into water, and then, having shaken off the superfluous moisture, immersed them in a jar of the gas, you would have a white bouquet of all kinds of flowers and leaves. [Experiment 6.] As chlorine gas unites with some substances with evolution of heat and light, it is termed a supporter of combustion, and yet it extinguishes a lighted taper immersed in a jar of it. Here is a disc of greased card-board, and we will pass this wire through it, and affix a lighted taper to one end. If you will hand me over that bottle of the gas, I will plunge the taper into it. [Does so.] You saw that when the taper was first placed in the gas that the flame was extinguished, but that it was afterwards re-kindled, and continued to burn with a small red flame, and emit a quantity of smoke, and that this flame was extinguished when the taper was removed from the bottle. Now the reason of what

you saw, is simply this. The oily vapour arising from the wick unites with the chlorine and becomes inflamed, because the gas has a remakable affinity (or attachment we may say) for hydrogen, which is contained in the inflammable matter of the taper. The following experiment will illustrate the truth of these remarks.

[Experiment 7.] Here is a piece of paper, moistened with oil of turpentine, and when it is plunged into this bottle of chlorine gas, it will burn with a brilliant flame. [Fixes the paper on the end of a wire, similar to that used for the taper, and plunges it into the bottle, when it instantly inflames, and a dense smoke (carbon) is deposited at the same time].

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[Experiment 8.] Let us try a few more experiments, to prove that chloride is a supporter of combustion. Here is a lump of charcoal, which was only made two hours ago, (in fact the experiment could not succeed well unless the charcoal was freshly made), and when it is reduced to a fine powder, and dried, I will pour some of it into this bottle of the gas, and the effect will be beautiful. [Pounds and dries the charcoal, and performs the experiment, when a vivid stream of fire is observed].

[Experiment 9.] If we affix a small sheet of gold-leaf to a wire, and plunge it into a bottle of the chlorine, we shall see it burn with a brilliant green flame. If we used silver leaf instead, the flame would be white; tin, when heated in a deflagrating spoon, or a small iron cup, at the end of a wire, burns with a blueish white flame when immersed in this gas; bismuth, heated in a platinum spoon, burns with a blue flame; and iron, heated in a platinum spoon, burns with a vivid red light.

Other metals may be burned in chlorine; but they should never be tried except by those who are skilled in the mysteries of chemistry, because the fumes from some of them are dangerous if inhaled. I could show you many of them, but let me particularly caution you against following the experiments given in any works, where sufficient caution is not enjoined, because you may either lose your life or health. Be assured, that whatever I tell you will be always sufficient guarantee that there is no danger, unless accompanied by the necessary warning, in which case, of

course, the pupil, and not the teacher, is to blame.

Chlorine unites with many metals, forming chlorides or chlorurets; but we must not stay now to consider them, further than to illustrate the truth of the observation by a simple experiment.

[Experiment 10.] Here is a solution of lunar caustic, or nitrate of silver, and when I add a little of the chlorine water to it, you will see that a curdy kind of deposit takes place, this is the chloride of silver. [Performs the experiment].

Let me once more caution you never to perform any experiments with chlorine and the following articles, until you are more conversant with PRACTICAL SCIENCE, otherwise the consequences may be serious. Arsenic, Mercury, Phosphorus, and Antimony, should never be experimented with by the inexperienced, and not even by those well versed in chemical knowledge, unless with EXTREME CAUTION.

STORIES FOR THE YOUNG.

FLOWERS.

VI. THE STAINED LILIES.

A family of white Lilies once dwelt beside a placid lake in the still woods. For many seasons they had lived in contented happiness; and generation after generation had blossomed into perfect loveliness, and flung their rich fragrance on the forest winds. They heard no praises save the hum of the insects, and the song of the birds. No rude touch ever sullied their purity; and when their lives were spent, they calmly scattered their leaves upon the bosom of the still lake that had alone reflected their beauty.

The Lilies were very happy in this sylvan solitude, and they dearly loved the bright clear waters that sent nourishment to their roots, and in whose transparent depths they saw constantly mirrored sweet images of themselves. No ripple disturbed the perfect calm of its surface, save when a passing breeze ruffled its waters slightly, and then the sweet, pure faces of the flowers, as they smiled fondly upon it, seemed soon to restore its wonted calm.

POLITENESS AND TRUTH.-Many persons plead a love of truth as an apology for rough manners, as if truth was never gentle and kind, but always harsh, morose, and forbidding. Surely good-manners and a good conscience are no more inconsistent with each other than beauty and innocence, which are strikingly akin, and always look the better for companionship. Roughness and honesty are indeed sometimes found together in the same person, but he is a poor judge of human nature who takes ill-manners to be a guarantee of probity of character; or suspects a stranger to be a rascal, because he has the manners of a gentleman. Some persons object to politeness, that its language is unmeaning and false. But this is easily answered. A lie is not locked up in a phrase, but must exist, if at all, in the mind of the speaker. In the ordinary compliments of civilized life, there is no intention to deceive, and consequently no falsehood. Polite language is pleasant to the ear, and soothing to the heart, while rough words are just the reverse; and if not the product of illtemper, are very apt to produce it. The plainest of truths, let it be remembered, can be conveyed in civil speech, while the nost malignant of lies may find utterance,

As the family of Lilies increased and

and often do, in the language of the fish-spread along the shores of the lake, one market. group that dwelt near an opening in the

The sunbeams peeped down among the thick foliage of the forest trees, and wove a network of gold upon the breast of the lake, and the little birds soared gaily above it, and dipped their wings in its waters as they passed. At night the quiet stars came out, and looked steadily down into the clear depths, for they love the Lilies because they are the stars of earth; and, beyond all, the blue sky was reflected in the still lake like another heaven.

But the constant Lilies only saw all these beautiful things as the lake showed them; and they were content to know that when the sun was veiled, and the birds gone to rest,-when the stars were set, and the sky obscured by clouds,—still the faithful waters reflected their images steadily and unbroken; nothing could shake the earnest affection of the lake: and for the Lilies, were not their roots embedded beneath its waves ?

wood, where the stream entered that supplied its waters, began to look longingly out upon the world beyond. They bent forward over the bank, and noticed not the calm reflection of the still lake while they eagerly gazed between the trees, where afar off they could see the little stream come tumbling over the stones with a mirthful rush, and only subsiding into quiet just before it joined the placid lake of the Lilies.

There was something in the rapid waters that fascinated the flowers; and when a wild Columbine, that had lately sprung up at their side, flung her blossoms on the still lake, and awakened no murmur of admiration in return, she spoke sneeringly to the Lilies.

"Such a quiet, prosy sheet of water as this lake is I never saw before," she said; "why, you have dwelt here time out of mind, and I don't suppose it has ever told you how lovely you are. I wonder you do not tire of such a monotonous life."

"But the lake loves and nourishes us, if it does not flatter us," replied the Lilies; "and let what will pass over its surface, it reflects always our images the same."

"That is all very well if it suit you," returned the Columbine, who resented the indifference with which the lake had received her advances; "but for my part I should soon die with weariness, shut up for ever in this still place, and seeing always the same things. I shall certainly beg Zephyr to carry me back to the spot whence I came,-I cannot live here." "Where is your home?" asked the Lilies, eagerly.

"Delightful, indeed," cried the other, pleased with the impression she had made, "and you can do nothing better than accompany me thither in the early spring; you will have a gay life, I can assure you, and enjoy more in one season than if you were to mope here in the woods for ever."

So the Lilies listened to the words of the foolish Columbine, and consented to take her advice; and without saying a word to the rest of their family, who they knew would oppose them, they carefully gathered their seed in the seed vessel, and, through the agency of Columbine, arranged with Zephyr to transport them away together in the early spring.

The inconstant Zephyr was enraptured with his mission, for the tall forest trees screened the Lilies from his insidious advances, and the stately flowers had scarcely ever bent their heads in acknowledgment of his salutations; he now anticipated much pleasure in moving the transplanted flower, and cheerfully fulfilled his task.

"Just at the side of the stream beyond," answered the giddy flowers; "we grow on a bank where the water flows most rapidly, and new eddies are continually forming as it rushes on, in which we see ourselves reflected in ever-varying forms; then the stream is always shouting and singing as he goes, and dashes the spray playfully at us, saying the drops are fairy mirrors in which to view our beauty, and the breezes whisper to us as they pass; while as for insects, they surround us, constantly humming our praises."

"How delightful such a life must be," sighed the Lilies, who were silly enough to be charmed with the chatter of their gay neighbour.

Accordingly, one lovely morning, the Lilies awoke in their new home, and were for a little while completely dazzled by the flood of sunshine that burst upon them. When they became accustomed to the bright light, so different from the softened shadows of their own green wood, they glanced eagerly around.

The merry stream went rushing noisily over the stones at their feet, and broke into a thousand fantastic eddies as it sped along; there were myriads of flowers upon the banks eagerly bending over to catch a glance at the laughing stream, and the hum of insects completely bewildered them.

There was no shade, no quiet anywhere, and before the Lilies had even time to see themselves reflected in the water, a new eddy dimpled its surface and destroyed the perfect image. Soon the stream flung drops of spray toward them, shouting that they were crystal diamonds to form a coronet for the lovely flowers; and every ripple that reflected them in new forms, the flattering stream declared only made them lovelier.

Soon Zephyr came with murmuring sighs, and whispered of their flexile grace and exquisite beauty, singing praises in tones borrowed from the musical reeds and the murmuring leaves. The bold sun

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