Sidebilder
PDF
ePub

will turn red as it enters the upper bottle. The result is explained in the same way, hydrochloric acid gas having a great liking for water.

2. Fill a long test-tube with the dry gas, and invert it over a saucer of mercury, letting the mouth of the tube dip below the mercury. Put a bit of ice into the tube by pushing it under the mercury. The ice and gas will both disappear, and the mercury will rise in the tube. This is because the gas likes water so well that it forces the ice to melt, and is then dissolved by the water which is made. The pressure of the outside air then forces the mercury up into the tube to take the place of the dissolved gas.

See also Experiment 3 under AmMonia.

HYDROGEN, Experiments with.

Processes and things merely alluded to in this article are freely explained in that on Chemistry, Experiments In. Hydrogen gas is described in OC. T. To make it, bore two holes in the cork of a wide-mouthed bottle, like those in which pickles and jam are sold, making sure that the cork is sound and tight. Through one of the holes put a "thistle-tube," and through the other a delivery-tube, the end of which is bent to collect the gas over water. The thistle-tube must reach nearly to the bottom of the bottle, but the deli very-tube must end near the top. Into the bottle put about a dozen small pieces of zinc. Scraps of zinc can be bought at a plumber's, and cut up with a pair of shears. Each piece should be bent or twisted a little, so that it will not lie flat on the bottom of the bottle. Instead of zinc, nails or scrap-iron may be used. The cork with its two tubes must now be put in place. Be sure that it is tight (hydrogen being quite explosive); blow into the delivery tube till the water rises into the funnel of the thistle tube, and then stop up the end of the delivery-tube with the

tongue. If the water stays at the same height in the other tube the bottle is tight, if not, the cork must be covered with sealing-wax. When all is tight, half fill the bottle with water, by pouring it through the thistle-tube. Then pour in sulphuric or hydrochloric acid slowly, half a tea-spoonful or so at a time, until bubbles begin to rise pretty briskly from the zinc. Gas will soon bubble up into the receiver. If it does not, pour in more sulphuric acid, and if it still refuses to appear it is probable that the cork is not tight, and that the gas is escaping into the air. The first jarful of hydrogen made must be thrown away, for it is mixed with the air which was in the bottle to begin with, and a mixture of hydrogen and common air is very explosive. When one or more jars of pure hydrogen have been collected, the experiments de

[graphic][merged small]

scribed below may be tried with it, or a large quantity may be made and stored in a gas holder for future use. The hydrogen made in this way comes from the acid used (see Acid in C. C. T.) The other substances in the acid prefer the zinc or iron to the hydrogen, and so let it go and unite with the metal instead. The substance so formed is sulphate of zinc or iron, if sulphuric acid be used, and chloride of zinc or iron, if the acid is hydrochloric. Any of these dissolves in water unless there is too much acid in it, when it sticks to the metal and stops the action. For this reason it is not well to put in too much acid.

EXPERIMENTS.

1. Holding a jar, in which hydrogen has been collected, mouth downward, touch a lighted match to it. If the gas is pure, it will burn quietly. Repeat the experiment, holding the mouth of the jar upward, the gas will burn quickly with a high flame. This is because hydrogen is lighter than air and so escapes and mixes with it when the opening of the jar is uppermost.

2. A jarful of hydrogen may be poured up into an empty jar. That the gas has really been poured into the empty jar may be proved by touching a match to it.

3. Remove the end of the deliverytube and substitute a glass jet. If the hydrogen is pure it may be lighted at this jet, and will burn with a very pale blue flame. This experiment must not be tried till several jars of gas have been collected, for if the gas in the bottle is impure it will explode. It is a good plan to wrap a cloth around the bottle, so that if there be an accident broken glass will not be thrown about. A jet of hydrogen burning thus is called the " Philosopher's Candle."

4. Hold a glass tube twelve or fifteen inches long and about one and a half inches wide over the flame of the Philosopher's Candle, and move it up and down. A position will be found where the tube will give out a musical sound. If it does not, the size of the jet and tube are not fitted to each other, and one or the other should be made larger or smaller. The sound is caused by a great number of little explosions, so close together that they form a musical sound. (See Sound, C. C. T.)

5. Blow soap-bubbles with the gas. as described in the article SoapBubbles. The gas must be drawn

from a gas-holder for this purpose. If the bubbles be blown with a mixture of hydrogen and air, or hydrogen and Oxygen, each will explode with a loud report, instead of burning, when touched with a lighted match.

HYDROSTATIC BELLOWS. A

scientific toy, made as follows: Cut out two pieces of board of the same size and shape, either square or round, and about two feet in diameter. Connect them by nailing leather to their edges, so that when it is stretched they will be about six inches apart. The apparatus must be water-tight. Bore an auger-hole in one piece of board, and fit in it tightly the end of a piece of leadpipe five or six feet long. Place the bellows on the ground with a heavy weight on it, so that the boards will be pressed together. Support the pipe upright and pour water into it through a tin funnel. The upper board of the bellows will rise, raising the weight. If the experimenter stand on the bellows, he can raise his own weight by pouring water into the tube. The reason is. that in fluids pressure is carried equally in all directions. If the pipe is one square inch in section, then every square inch of the bellows-boards is pressed on by a weight equal to the water in the pipe; and if the bellows be large, the entire pressure may thus amount to several hundred pounds.

HYGROSCOPE, an instrument to show whether the air is moist or dry. One of the simplest is made by taking a hair or piece of cat-gut a foot or two in length, and hanging it by one end to a nail in the wall, tying to the other end a small weight, just sufficient to stretch the hair tight. Hair or cat-gut will lengthen by absorbing moisture from the air, so the hair becomes longer in moist than in dry weather. To show a slight change in the length of the hair, a splinter of wood is fastened at one end to the hair near the weight, and is pivoted on a pin very near that end. A slight movement of the end fastened to the hair, will thus cause a greater one in the other end. The illustration shows one a little more carefully made. Fastened to the upper part, d, of the frame is a screw a b to tighten the hair, c is the hair, and p the weight. To relieve it of the tension caused by the weight, the hair is passed over a pulley, to which the pointer is attached. A little thermometer is fastened to the side of the frame.

Hair Hygroscope. This kind of migroscope can be made also of twisted cat-gut, which untwists by absorbing moisture. The little houses with figures of a man and woman, one of whom appears in moist and the other in dry weather, are made in this way.

Wet and Dry Bulb Thermometer, This form of hygroscope consists of two thermometers hung side by side. Around the bulb of one is tied a piece of soft cloth, the end of which dips into a cup of water. The cloth soaks up the water, and keeps the bulbcontinually wet. The evaporation of the water on the bulb keeps it cooler than the other, so it always stands lower. On very dry days

[graphic]
[merged small][graphic]

Wet and Dry Bulb Thermometers.

damp days the water does not evaporate so quickly, and so it stands only a little lower. Hence the instrument is used to tell whether the air is dry or damp.

Phial Barometer. This is really a kind of hygroscope, because it does not measure the pressure of the air, but shows only whether it is dry or moist. Cut off about half of the neck of a common glass phial (see Chemical Experiments, directions for glass-working) and nearly fill it with water, which may be colored if desired. Place the finger over the mouth of the phial and invert it; the water will not run out even when the finger is removed. Suspend the phial, neck downward, by a string. In dry weather the under surface of the water is either level or concave, but in damp weather a drop appears at the mouth of the phial, and keeps enlarging till it falls. This is caused by the deposition of moisture from the air.

[merged small][merged small][graphic]

The runners, three in number, are at the ends of the cross-beam (called the "runner plank") and at the rear of that running lengthwise (called "centre timber"). On the forward end of the centre timber is bolted the bowsprit. The rear runner servesasa rudder. The forward runners are fastened by a bolt on which they can rock forward and backward. There is one mast, which is placed slightly in advance of the cross-plank. An oval box, holding two persons, is fastened just above the rudder; except for this the boat is merely a frame. The largest ice-boats are 50 to 60 feet long, and 25 or 26 feet wide. They are rigged as sloops, cat boats (see Fig. 3), or with a lateen sail (see SailIng). Ice-boats may sail faster than the wind, as shown by Fig. 4:

Suppose the wind to be blowing in the direction of the arrow at the rate of twenty miles an hour; then, if A B is a mile, the boat cannot sail that distance directly before the wind in less than three minutes; but

the friction of the runners on the ice is so slight, that it will sail along A C in almost the same time. As AC is about two miles, the boat would be going twice as fast as the wind. Iceboats thus attain wonderful speed. On February 12, 1879, the " Lucille" sailed from Poughkeepsie to New Hamburg, on the Hudson River, nine miles, in seven minutes and ten seconds. At another time the "Snow Flake" is said to have made the same distance in seven minutes, and in 1882 the "Haze" did the same, making at one time two miles in one minute. Many similar instances of great speed are related, but it is hard to get an official record, for ice-boats go fastest when least expected, and the time made in regular races, as shown below, is far slower than that just given, though still very great.

The sails of the boat are set nearly fore and aft, and the boat is managed almost entirely by the rudder, the speed being so great that the helmsman has no opportunity to change the position of the sail. If the sail must be reefed, the boat is

[graphic]

thrust down to act as a drag. The boat is anchored by bringing her into the wind, loosening the jibsheets, and turning the rudder crosswise. The ice boat obeys her rudder very easily, and the steersman must be always on his guard, for if he turn it too suddenly the boat will spin around, throwing the crew out. To cross a crack, some sailors first head the boat so

[merged small][graphic]
[graphic]

her head to the wind, and then slackening the sheet. Many iceboats have a brake which can be

Fig. 4.

as to " spill" (or lose) the wind and then run over the crack so that both forward runners cross it at the same time; and some disembark and help the boat over. Others would simply slack both sheets and let the boat's momentum carry her over. The wind often forces the boat over so that the weather-runner is lifted clear of the ice, leaving only the leerunner and the rudder.

The boat is then said to "rear." and must be eased by bringing her into the wind, if the boat is beating to windward. One or two men often stand on the windward runner, to keep it down. The greatest speed, running free, is made by steering across the wind till a maximum velocity is reached, and then steering down the wind without slacking the sheet. The momentum will carry the boat faster than the wind for some distance, when she must again be brought up and headway regained. The yachtsman often wears coverings of wire gauze over his eyes and mouth to keep out flying snow.

The strain on the timbers of an ice-yacht makes it necessary that they shall be perfect in grain and well seasoned. The runners are

« ForrigeFortsett »