Sidor som bilder
PDF
ePub

PRACTICAL SCIENCE.

5. THE MOUTH BLOW PIPE.

(Continued from page 23.)

41. A proper place to perform your experiments is absolutely necessary, if they are to be extensive; and even when conducted upon a small scale, it is advisable to have some place set apart for working, because your instruments are apt to get jumbled together, and mixed with all sorts of things; the consequence of which is, that they get clogged with dirt, and are never at hand when most required. The old proverb of, "Have a place for everything, and everything in its place," should be always upmost in the mind of a student of "practical science;" but especially a blowpipe manipulator.

Those who use the blowpipe extensively should have a table to contain all the apparatus; but as I have remarked before, the student should endeavour to think for himself, and convert anything that comes to hand to his use.

42. The table used for blowpipe operations is something like a lady's worktable, only that it is made of deal. I have long been accustomed to use one with a shifting top made of sheet-iron, and covered inside with white cartridge-paper pasted upon it. This box is so constructed, that it fits upon the top of the table, by means of a peg placed at each corner, which drops into a hole underneath. The table, which is about thirty inches long, sixteen inches wide, and forty-five inches high, has five drawers in front, a long one at the top, and two on each side underneath it. The small drawers are used to contain the articles required to be in stock, such as extra nozzles and blowpipes, stock of fluxes, charcoal discs, lamp wicks, small pasteboard trays in nests, for containing specimens, extra porcelain capsules, and crucibles, with the lamp and such articles. The long drawer is kept for such specimens as you may require for examination; these are contained in the pasteboard trays, labelled, arranged, and covered so as not to be exposed to the dust. On either side of the table is a drawer which passes underneath the other drawers, and is nearly half the length of the table, but of the

entire width. The one to the right-hand is used to contain the blowpipes in use together with files, hammer, small anvil, microscope, &c.; and the one to the left is set apart for the appropriate fluxes, which are arranged in boxes, as already mentioned. These drawers are made to pull out to a certain distance, but are prevented from falling by a piece of wood fixed underneath. I always have a chair on my right-hand side, with a towel hanging over the back, and a basin of water, and soap placed upon the seat; this is extremely useful, and sometimes absolutely necessary, for you cannot be too particular about your hands being clean, when analyzing some substances.

Latterly I have added a small shelf, about four inches wide, and extending the whole length of the table, to the upper and back part. This is supported upon upright pieces, and is intended for the reception of solutions in test tubes, bottles, &c., and bottles with tests. projects beyond the table, and is so made that it may be removed at pleasure. If the table is required to be portable the legs should be made to unscrew, and it will then form a box.

It

43. Analysis by the blowpipe can seldom or ever be determinate, other tests must be employed afterwards; but quantitative analysis would be almost as useless without the aid of this valuable instrument, as the blow-pipe itself would be without a flame. In analyzing an unknown substance—say, for example a crystalline body—it is usual to submit it to certain operations, during which certain phenomena take place, which give us an insight into its nature. First, heat it in a small glass tube, closed at one end to ascertain what changes take place during the process; sometimes we perform this operation without the aid of reagents; while at other times we combine certain reagents with the substance to be acted upon. Secondly, we heat the body alone, before the blowpipe, in the open air, to ascertain whether, first, it is fusible; secondly, whether it inflames; thirdly, whether it changes colour; fourthly, whether it boils up, or becomes larger; fifthly, whether it becomes volatile and disappears altogether, or only loses part of its substance by the disengagement of volatile matter; sixthly, the colour im

parted to the flame of the blowpipe; and lastly, any difference that may be observed in its exposure to the oxidating and reducing flames. Thirdly, we heat the substance in a glass tube, open at both ends, for three reasons; firstly, to discover the action of a current of atmospheric air acting upon it, when exposed to a high temperature; and secondly, for the purpose of discovering the odour of the vapours given off; and thirdly, to ascertain what sublimates are produced. Fourthly, we may have to heat the substance in a tube closed at both ends-a process we shall explain hereafter. Fifthly, we heat the substance with reagents, either in tubes, or exposed to the flame of the blow-pipe in the open air.

1. HEATING BODIES IN GLASS TUBES
CLOSED AT ONE END.

In heating any substance in a tube closed at one end, take the precaution to hold it five or six inches above the flame of the lamp at first, and then gradually bring it closer to the flame, until at last the part where the substance itself is placed is kept in the hottest part of the flame. The tube should be held nearly horizontal at first, that is, on a level corresponding with the top of the table, and then gradually sloped until it is nearly upright; then the flame of the blowpipe should be brought to play upon the part where the substance to be operated upon is placed. By adopting this method we shall be able to ascertain if the body is an organic or inorganic substance; whether it is acid, alkaline, or neutral; if it is volatile, or not; whether it sublimes readily; the character of the sublimate, whether a metal or not, &c. We will now make some experiments, for the purpose of ascertaining the character of certain substances, commencing with organic bodies.

44. Organic bodies, when heated in a closed tube before the blowpipe flame or otherwise, blacken, and we also observe other changes takes place; but let us see for ourselves.

[Experiment 1]. Here is a glass tube which you observe is closed at one end, and you see that I place a piece of wood about the size of a barleycorn in the lower part of the tube. You also see

how careful I am not to heat the tube too suddenly; and now that the tube is heated by the flame of the spirit lamp, I will direct the flame upon the tube, and be sure to observe closely what takes place. (The tube is heated over the flame of a spirit lamp at first, and then by means of a blowpipe flame. As the heat is raised the wood becomes brown, then blackish, and at last black). The blackening or charring of the wood, is owing to the decomposition of the ligine or woody fibre of the wood, which consists of three. elements, carbon, hydrogen, and oxygen. There is a dense white smoke ascending from the wood, and some portion of the glass is covered with small drops of fluid, and you can observe a peculiar odour attached to the vapour issuing from the tube. When the heat is raised so as to decompose the wood, a portion of the carbon, together with the hydrogen and oxygen, pass off in the form of pyroligneous or acetic acid, with a tarry matter, and other volatile compounds, while another portion of the carbon is left behind at the bottom of the tube-this is charcoal. No doubt you wondered why I held a small strip of moistened blue litmus paper in the mouth of the tube; but as you saw it turn red, I suppose that you know now, it was simply to test if the vapour was acid; and the result was satisfactory. If it had not been acid, of course the blue litmus paper would not have turned red. Red turmeric paper would have turned yellow, had it been employed in the same manner.

We will now perform another experiment, and also test the frames as before, but with a different result.

[Experiment 2.] I have placed a small paring of my nail-the readiest substance at hand, for illustration-in the tube, and shall proceed as in the experiment above. [Does so, and the portion of nail is first observed to twist about and curl up, then to swell up and as it were to boil, becoming in the mean time a semi-fluid tarrylooking mass three or four times the size of the portion used.] You observe that there is a similar white vapour produced, a similar tarry-looking substance on the sides of the tubes, and that the residue is black and carbonaceous as in the former experiment. You could not distinguish one tube from the other if the mouths

of them were closed with corks and given you to examine; but remove the corks and the odour given off by the one containing the animal body will soon enable you to decide the matter, for it is far more disagreeable and powerful than the odour given off by the vegetable body. The former is like the odour of a burnt feather, and the latter like that of burnt paper. When I introduced a piece of yellow turmeric paper into the mouth of the tube you observed that it turned brown, clearly indicating that the vapour was alkaline. Red litmus paper would have turned blue. Now the alkaline nature of the vapour is owing to the presence of ammonia, which is almost invariably produced when any nitrogenous compound is decomposed by heat. I suppose you know that any body containing nitrogen in combination with other substances, is called a nitrogenous compound; but if you did not, please to remember the fact, because we shall have to use the term very often.

45. To distinguish organic from inorganic bodies. In examining bodies before the blowpipe, with a view to determine whether they are organic or inorganic, you should always observe the residue, as this will at once settle the matter. If, after the body has been exposed to the flame, either in a tube or out of one, the residue has only become blackened, you may be certain that it is not an organic body; because organic bodies always leave a charred mass behind, and moreover they give off copious vapours during their decomposition. I will perform an experiment to show you that organic substances are generally consumed by fire, when brought into contact with heated saltpetre.

[Experiment 3.]-Take a retort stand which has a movable slide (a), and then place a small Berlin porcelain evaporating dish (6) upon it. Place a few grains of nitrate of potass (nitre) in the dish, and apply the heat by means of an Argand gas-burner (c), supported on a heavy base, and furnished with a flexible tube of vulcanised India-rubber (d), or by means of a spirit lamp. When the nitre is melted and red hot, take a pinch of coarselypowdered charcoal between your finger and thumb, and drop it into the heated nitre. [The experiment is performed, and

a

d

the charcoal immediately deflagrates or is consumed when it reaches the saltpetre.] If you reduce the charred residue of almost any organic body to a coarse powder, and employ it instead of the charcoal, the same appearance will be observed.

COMMON SENSE.-Fine sense and exalted sense are not half so valuable as common sense. There are forty men of wit for one man of sense; and he that

will carry nothing about him but gold, readier change. will be every day at a loss for want of

SWIFT.-Swift having paid a visit at Sir Arthur Acheson's country-seat; and being, on the morning of his return to his deanery, detained a few minutes longer than he expected at his breakfast, found, when he came to the door, his own man on horseback, and a servant of Sir Arthur's holding the horse he was to ride himself. He mounted, turned the head of his horse towards his own man, and asked him in a low voice if he did not think he should give something to the servant who held his horse; and if he thought five shillings would be too much? "No, sir, it will not, if you mean to do the thing handsomely," was the reply. The dean made no remark upon this; but when he paid his man's weekly account, wrote under it, "Deducted from this, for money paid to Sir Arthur's servant for doing your business-five shillings."

172

SIGNIFICATION OF CHRISTIAN NAMES.-TREASURES.

SIGNIFICATION OF CHRISTIAN NAMES.

(Continued from page 147.)

Elisha. Heb. the salvation of God.
Emmanuel, Heb. God with us.

Enoch, Heb. iustructed or dedicated.
Ephraim Heb. fruitful.

Erasmus, Gr. lovely, worthy to be loved.
Ernest, Gr. earnest, serious.
Esau, Heb. completed.

Ethelbald, Sax. nobly bold.
Ethelbert, Sax. nobly bright.
Ethelfred, Sax. noble peace.
Ethelfred, Sax. noble in counsel.
Ethelstan, Sax. a noble jewe..
Ethelwald Sax. a noble keeper.
Ethelwold Sax. a noble governor.

Evan or Ivon, Brit. the same as John.
Everard, Ger. well reported.
Eugene. Gr. nobly descended.
Eusebius, Gr. religious.
Eustace, Gr. standing firm.

Ezekiel, Heb. the strength of God.
Ezra, Heb. a helper.

Felix, Lat. happy.

Ferdinand, Ger. pure peace.
Fortunatus, Lat. happy.
Francis, Ger. free.

Frederic, Ger. rich peace.

Gabriel, Heb. the strength of God.
Geoffery, Ger. joyful.

George, Gr. a husbandman.
Gerard, Sax. all toward liness.
German, Lat. a near kinsman.

Gervase, Ger, all sure.

Gideon, Heb. a breaker.

Gilbert, Sax. bright as gold.

Giles, Gr. a little goat.

Godard, Ger. a godly disposition.

Godrey Ger. God's peace

Godwin, Ger. victorious in God.
Griffith, Brit. having great faith.
Guy, Fr. the misletoe shrub.
Hannibal, Punic, a gracious lord.
Harold, Sax. a champion.
Hector, Gr. a stout defender.
Henry, Ger. a rich lord.
Herbert, Ger. a bright lord.

Hercules, Gr. the glory of Hera or Juno.
Hezekiah Heb. cleaving to the Lord.
Hilary, Lat. merry, cheerful.

Horatio, Ital. worthy to be beheld.

Howel, Brit. sound, or whole.

Hubert, Ger. a bright colour.
Hugh, Dutch, high, lofty.
Humphrey, Ger. domestic peace.
Jacob Heb. a supplanter.
James or Jacques, beguiling.
Ingram, Ger. of angelic purity.
Joab, Heb. fatherhood.
Job, Heb. sorrowing.
Joel, Heb. acquiescing.

John, Heb. the grace of the Lord.
Jonah, Heb. a dove.

Jonathan, Heb. the gift of the Lord.
Joscelin, Ger. just.

Joseph, Heb. addition.

Josias, Heb. the fire of the Lord.
Joshua, Heb. a Saviour.

Isaac, Heb. laughter.

Israel, Heb. prevailing with God.
Judah, Heb. confession.

TREASURES.

HE who jests upon the deformities of Nature, upbraids the God of nature.

FLATTERY is the base coin to which vanity gives currency.

WHAT is wanting in reason, upon an argument is too often supplied by rage.

THE reading of most men is like a wardrobe of old clothes-seldom used.

A FINE coat is but a livery, when he who wears it discovers no higher talents than a footman.

THE real use of talking is almost lost to the world by the excessive custom of lying.

COWARDS are like sorry horses; they have just mettle enough to be mischievous.

THE stoical scheme "supplying wants by lopping desires," is like cutting off our feet when we have no shoes.

SETTLE your disputes yourselves if you would make an end of them-would you prolong them, call in lawyers.

CRUELTY is so contrary to human nature that it is branded with the scandalous term inhumanity.

OUR passions are like convulsive fits, which though they make us stronger for a moment, yet leave us much weaker afterwards.

CHARLES the Fifth used to say, "that the cle. mency of a prince is like the heat of the sun, which hardens dirt, while it softens wax."

MANY who seem to carry the liberty of the subject highest, serve them like trouts-tickle them till they catch them.

CHEYNE observes, that "water is the most natural and wholesome of all drinks, quickens the appetite, and strengthens the digestion most."

PROFANENESS in conversation too commonly passes for wit; whereas it is in truth a certain sign of the want both of judgment and manners.

THE ancients personified and even deified health. Salus was the goddess of health and safety, to whom there were erected several temples dedicated at Rome.

A WISE man thinks none his superior who has done him an injury, for he has it then in his power to make himself superior to the other, by forgiving it.

A KING is to be envied for nothing so much as the supremacy of his power to do good; and if his inclinations be but equal to his power, he must necessarily be the happiest man in his realm.

ANTISTHENES wondered at mankind that in buying an earthen dish, they were careful to sound it lest it had a crack, yet so careless in choosing friends as to take them flawed with vice.

THE best way to prove the clearness of our understanding, is by showing its faults; as when a stream discovers the dirt at the bottom, it convinces us of the transparency and purity of the water.

USEFUL RECEIPTS.

Writing Inks.-It may be stated that, as a general rule, writing inks containing logwood do not flow readily from the pen. A solution of creosote in rectified spirit of wine, or pyroligneous acid, is the best preservative of ink from mouldiness.Pharmaceutical Journal

To make Casts of the appearance of Ivory.Make a paste of isinglass and brandy with some powdered egg-shells finely ground; press it while warm in your mould, which should first be well oiled, and leave till dry.-E. A. CoPLAND, Windsor.

New mode of Stopping Hiccup.-Dr. Piretty appears to have found a very simple means of arresting this disagreeable and often very obstinate symptom. It is sufficient to squeeze the wrist-preferably that of the right hand-with a piece of string, or with the fore-finger and thumb of the other hand.

Varnish for Furniture.-To one part of virgin white wax add eight parts of oil of petroleum; lay a slight coat of this mixture on the wood with a badger's brush, while a little warm; the oil will then evaporate, and leave a thin coat of wax, which should afterwards be polished with a coarse woollen cloth.-H. L. B.

To transfer the Patterns of Lace and Coloured Muslin on Paper.-Make a solution of yellow bichromate of potash in water (distilled), as much as it will take up; soak the paper on this for about a quarter of an hour; lay the lace, &c., on the paper when dry, place a piece of plate glass on it and expose to the light of the sun, then wash the paper in pure water, and dry in blotting paper.-F. C. S. D'ALQUEN, Brighton.

To clean Boot-tops.-Take a pint and a half of sour milk, one ounce of oil of vitriol, one ounce and a half of compound tincture of lavender, half an ounce of gum arabic, one ounce of lemon juice, and the white of one egg. Mix well, and apply with a sponge as usual; another form is as follows, a pint and a half of sour milk, one ounce of cream of tartar, and of alum and oxalic acid, each half an ounce. Mix well, and apply as above.-KAF.

Beautiful Ornament for a Room.-Dissolve in seven tumblers, in which is some warm water, sulphate of iron half an ounce, copper half an ounce, zinc half an ounce, soda half an ounce, alumine half an ounce, magnesia half an ounce, and potass half an ounce. Pour them altogether in a large dish, and stir with a glass rod; place the dish in a warm place free from dust or from being shaken. Most beautiful crystals will shoot out all over, forming a splendid ornament.— E. A. COPLAND, Windsor.

The Sting of a Bee.-In most cases the person stung can instantaneously obtain relief by pressing on the part stung with the tube of a key. This will extract the pain, and the application of aqua ammonia (common spirits of hartshorn) will immediately remove it. The poison being of an acid nature, is at once neutralized by the application of this penetrating and volatile alkali. A small quantity introduced into the wound on the point of a needle, or fine-nibbed pen, and

applied as soon as possible, will scarcely ever fail.-J. S. Norwich.

Method of taking Profiles in Black--Procure a wooden frame, about a foot square: divide each side into six portions, and stretch across strings at equal distances before marked, so as to make in all thirty-six squares. Purchase some of the black paper used by artists (three half-pence a sheet) and on the white side rule thirty-six equal squares corresponding to those on the frame. Then desire the person to sit about three yards from you, and in such a position that you see their profile through the squares of your frame. Then sketch on your paper with the ruled lines the profile as you see it through the squares, and draw it on yours correspondingly. Then cut out what you have sketched, and stick, with black side up on a piece of card. This is a capital way for one who has no artistic taste to take sketches of views, busts &c.-E. A. COPLAND, Windsor.

To wash Lace.-At page 203 of the 5th volume, Old Series, Family Friend, is given a receipt for washing lace, which is not quite correct, as the edge would lose its new appearance, and the lace the gloss; which faults will be entirely obviated by the following process:-Cover a bottle (the larger the better) with a linen (not calico) case made to fit tight; roll the lace round it, taking care that the edge is kept smooth, and that the head of the succeeding round covers it; tack the lace if there are several lengths in the slightest possible manner, and without any knots. When the lace is all rolled round the bottle, cover,it tight with linen. Then rub it well with soap (the best curd), or, if very dirty, make a strong lather, and let the bottle remain in it for a night; rinse it well by pouring water over it. If possible, expose the bottle to the sun, watering it frequently, and also to the night air, and let it dry thoroughly before you open it. Avoid hot water, as it destroys the look of newness. I enclose a small piece which I have had for fifteen years and which has always been washed according to the above direction.-E. B.

To fix the solid Brass Letters to Window Glass.As these letters sometimes fall off the plate glass or other windows, after long use, we have been requested by several correspondents to give a receipt for a cement, by means of which they may be reattached, we give four: 1. Take fifteen parts of sandrach and gallipot-resinvarnish, five of drying oil, and five of oil and essence of turpentine mixed: mix well, and then add ten parts of Spanish white and dry white lead.-2. Take fifteen parts copal varnish, five of drying oil, three of oil of turpentine, two of essence of turpentine, five of animal glue dissolved in a water bath, and ten parts of hydrate of lime: mix well.-3. Take fifteen parts of copal varnish and colophane resin, five of oil and essence of turpentine, two parts of isinglass in powder, three parts of iron filings or blacksmith's cinders, ground and sifted, and ten parts of washed earth, ochre or rotten stone.-4. Take fifteen parts of copal varnish and gum lac mixed, five parts of drying oil, three parts of a strong solution of caoutchouc or gutta percha, seven parts of tar oil, and ten parts of Roman cement and plaster of Paris in powder, mixed: Do not apply too much of the cement to each letter, and press the letter firmly and evenly against the glass.

« FöregåendeFortsätt »