Part 3
=Note=: Always grasp a tube near the end when you insert it into a coupling or stopper, because if you hold it too far back you may break it. Insert it with a twisting motion, after wetting the end and the inside of the coupling or stopper.
[Illustration:
FIG. 68
A SYRINGE ]
Wet the inside of the large tube, wet the plunger and rub it on a cake of soap to make it slippery, then try it in the large tube. If the plunger is too large, stretch the coupling lengthwise; if it is too small, crowd the coupling together lengthwise. If the bulb is too large or too small, dry it, heat in the blowpipe flame until it shrinks, and blow another.
When the plunger is made, attach a No. 4 nozzle to the No. 6 tube with a large coupling, arrange as in Fig. 68, and your syringe is made.
Fill the large tube with water and see how long a stream you can make.
[Illustration:
FIG. 69
ANOTHER SYRINGE ]
Experiment 49. To make another syringe.
Heat a piece of No. 6 in the blowpipe flame at a length of 7½ inches and draw it out into a nozzle; smooth the other end in the lamp flame. Use the same plunger as in Experiment 48, and your syringe is made (Fig. 69). Try it out with water.
Experiment 50. To make a third syringe.
Heat a piece of No. 6 tube in the blowpipe flame at a length of 7½ inches, draw it out, and close the end, then smooth the other end.
Now to make a plunger: Heat a piece of No. 2 tube 8½ inches from one end in the lamp flame, draw it out into a nozzle, and break it off, leaving a small hole at the end of the nozzle. Smooth the other end in the lamp flame, flare it out slightly, allow it to cool, dip it into water and insert it into a small wet coupling.
[Illustration:
FIG. 70
A THIRD SYRINGE ]
Now fill the large tube with water and insert the coupling plunger (Fig. 70). Do you get a fine long stream?
Experiment 51. To make a diablo whistle.
Use the No. 6 tube and the No. 2 plunger from Experiment 48, arrange as in Fig. 71, blow across the top, and move the plunger up and down. Do you get a most diabolical sound?
[Illustration:
FIG. 71
THE DIABLO WHISTLE ]
The sound is produced by the vibration of the air column between the top of the tube and the top of the plunger. Do you find that the pitch of the note is higher the shorter the air column?
Experiment 52. Fun with the diablo whistle.
Start with the air column long and blow the note, shorten it a little and blow the next note, continue, and try to blow the eight notes of an octave.
[Illustration:
FIG. 72
JOINING TWO TUBES ]
Try to play a tune.
Try to make the most weird sound you can.
Experiment 53. To join two tubes end to end.
Take a piece of No. 2 tube about 7 inches long, close one end, smooth the other, and when cool cut the tube at the middle.
[Illustration:
FIG. 73
WORKING THE JOINT ]
Now join these two pieces as follows: Hold the ends opposite each other near the top of the lamp flame (Fig. 72), rotate constantly, and when nearly red hot bring the ends accurately together in the flame, press together slightly, draw out slightly, and remove from the flame.
The ends are now stuck together, but the glass is in a slight lump around the joint and if allowed to cool will crack very easily. It is necessary to work the glass back and forth to get rid of the lump and to make the glass uniform on both sides of the joint. Do this as follows: Heat one third of the joint in the blowpipe flame (Fig. 73), and when red hot blow a slight bulge. Now turn the joint one third, heat the next third red hot and blow a slight bulge. Repeat with the remaining third.
[Illustration:
FIG. 74
JOINING TUBES OF DIFFERENT SIZES ]
Now heat the first third again until it is red hot and shrinks, then blow a slight bulge again. Repeat this with the other two thirds.
Repeat this whole operation a third time and blow just enough to leave the joint the same size as the remainder of the tube or a little larger.
[Illustration:
FIG. 75
MAKING A LARGE HOLE ]
This heating and blowing has worked the joint back and forth until the glass is fairly uniform. It makes a strong joint.
Cut off the closed end and smooth the edge.
Repeat with a piece of No. 4 tube.
[Illustration:
FIG. 76
MAKING A TEE ]
Experiment 54. To join tubes of different sizes.
Take a piece of No. 4 tubing about 3 inches long and close one end.
[Illustration:
FIG. 77
THREE-ARMED SIPHON ]
Take a piece of No. 6 tubing, attach a handle to one end, heat the No. 6 tube in the blowpipe flame about 1 inch from this end and draw it down to smaller size.
Break the small part at a point where it is about the size of the No. 4 tube. If the hole is too large, heat the edge until it is a little too small and flare it out with the flaring tool. If the hole is too small, heat the edge and flare it out.
Now heat the ends of both tubes (Fig. 74), and join them as described in the last experiment.
Repeat the operation of heating and blowing at least three times.
Join a No. 4 and a No. 2 tube in the same way.
Experiment 55. To make a large hole.
Take a piece of No. 4 tube about 6 inches long, close one end, smooth the other, and allow it to cool.
[Illustration:
FIG. 78
A REPEATING AIR GUN ]
Now to make a large hole in the side of this tube, proceed as follows: Heat in the blowpipe flame the point at which you wish to make the hole, and blow a slight bulge (1, Fig. 75). Then heat the top of this bulge until it is red hot over an area about equal to the size of the hole you wish to make, and blow hard to make a thin bubble (2, Fig. 75). Break away the thin glass of the bubble, smooth the edges, and the hole is made. The edge of this hole will project beyond the side of the tube (3, Fig. 75). If you wish to make the edge even with the side of the tube, heat it in the blowpipe flame until it shrinks back level with the tube.
[Illustration:
FIG. 79
FOUR-WAY JUNCTION ]
Experiment 56. To make a tee.
Take a piece of No. 4 tube about 6 inches long, close one end, smooth the other, and allow it to cool. Take another piece 3 inches long, close one end, and allow it to cool.
Now make a hole in the side of the first tube at a point 3 inches from the closed end. Do this as described in the last experiment but leave the hole projecting beyond the side of the tube (1, Fig. 76).
[Illustration:
FIG. 80
MAKING A Y ]
Now heat the edge of the hole and the end of the short piece in the lamp flame, and make a joint (2, Fig. 76) exactly as described in Experiment 53. Be particular to heat and blow all around the joint at least three times to make the glass uniform, and on the last blowing leave the joint a little larger than the tube. Cut off the closed ends, make the arms equal in length, smooth the ends, and your tee is made (3, Fig. 76).
Your first attempt may not be beautiful, but if you will repeat the heating and gentle blowing often enough, the joint will be strong, which is the main point.
Repeat until you can make a tee easily.
Make a tee with No. 2 tubing.
Your flame is hardly large enough to make a tee with No. 6 tubing.
Experiment 57. A three-armed siphon.
Make a three-armed siphon as shown in Fig. 77. Put two arms in tumblers filled with water, suck air out of the third arm until the water runs, and then put it in an empty tumbler.
Stand the three tumblers on the table. Does the water run until the levels are the same?
Put one tumbler on a book. Does the water run into the other two tumblers until the levels are the same?
Return the one tumbler to the table and put the other two on the book. Does the water run from both tumblers to the lower tumbler until the levels are again the same?
Experiment 58. To make a repeating air gun.
[Illustration:
FIG. 81
BALANCING COLUMNS ]
Take a full length of No. 4 tubing, put a branch about 3 inches long at a point about 2 inches from one end; leave the end of the branch closed (Fig. 78). Now load the branch with shot or coarse dry sand, and your repeating air gun is ready for use.
Tilt the branch slightly above the horizontal and blow intermittently. Does your gun reload after each blow, until the ammunition is used up?
Experiment 59. To make a four-way junction.
Make a tee as in Experiment 56, but do not cut off the closed ends. Now attach a fourth arm, as in Fig. 79, and heat and blow gently as before to work the glass into uniform condition. Cut off the closed arms at equal lengths, smooth the ends, and your four-way junction is made.
Experiment 60. A four-arm siphon.
Make a four-arm siphon, repeat the experiments described in Experiment 57, and make others of your own.
Experiment 61. To make a Y.
Make a tee as in Experiment 56, then make a bend about ½ inch from the stem on each side (Fig. 80), and your Y is complete.
Experiment 62. Balancing columns.
Arrange the apparatus as in Fig. 81, put the arms together in a glass of water, suck a little air out of the top coupling and close it with a glass plug. Do you find that the water rises to the same level in each?
Place the arms in separate tumblers filled with water to the same level and repeat. Does the water rise to the same level?
[Illustration:
FIG. 82
THE WATER LEVELS ARE THE SAME ]
Add an extra length to one arm and repeat. Are the levels different but are they equal distances above the water in their respective tumblers?
Place the tumblers on the table, make one tube slanting, and repeat the experiment (Fig. 82). Are the levels again the same?
When you suck air out of the tee, you decrease the air pressure in the two tubes, and the atmospheric pressure on the water in the tumblers lifts the water into the tubes.
Experiment 63. Unequal columns.
Put a large handful of salt into a tumbler partly filled with water and stir until the salt is dissolved. Now pour fresh water into another tumbler until it is at the same height as the salt water. Make the arms of equal length, put one arm in the salt water and the other in the fresh water, then suck a little air out of the top coupling and close it with a plug. Do you find that the column of salt water is shorter than the column of fresh water (1, Fig. 83)? It is shorter because salt water is heavier than fresh water.
[Illustration:
FIG. 83
UNEQUAL COLUMNS ]
If you have gasoline or kerosene convenient fill one tumbler half full of either, and the other tumbler half full of water, then repeat the experiment. Do you find that the column of gasoline or kerosene is longer than the column of water (2, Fig. 83)? It is longer because gasoline and kerosene are lighter than water.
Experiment 64. To fuse wire into glass.
Find a piece of thin iron or copper wire about 4 inches long, heat the end of a piece of No. 2 tubing until it is nearly closed, insert the iron or copper wire into the small hole, and heat the glass around the wire until it shrinks and grips the wire firmly (Fig. 84). The glass then serves as a handle for the wire.
[Illustration:
FIG. 84
WIRE FUSED INTO GLASS ]
It is difficult to make a secure joint between iron or copper wire and glass because they both expand and contract more than glass when heated and cooled. It is easy to make a secure joint between platinum wire and glass because platinum and glass expand and contract at practically the same rate when heated and cooled. Platinum, however, is too expensive to be used for ordinary experiments.
Experiment 65. To cut window glass.
The common glass cutter is a small very hard steel wheel mounted on a handle (Fig. 85). Practice with one on a pane of glass: place a ruler on the glass, draw the wheel along the ruler (Fig. 86) with sufficient pressure to scratch the glass, place the under side of the scratch exactly over the edge of the table, and press down on both sides.
[Illustration:
FIG. 85
A GLASS CUTTER ]
Experiment 66. To bore a hole in glass.
[Illustration:
FIG. 86
CUTTING A PANE OF GLASS ]
Place a piece of window glass flat on the table, pour a little kerosene on the spot to be bored, clasp the file near the end, press the end down hard on the spot and turn it back and forth with a gouging motion (Fig. 87). You twist the file just as you would twist an awl to force it into hard wood.
You will soon penetrate the surface; use plenty of kerosene and continue the boring until you are nearly through; then turn the plate over and start a hole on the other side to meet the one you have made.
[Illustration:
FIG. 87
BORING A HOLE IN GLASS ]
Do not rush things; it will take you ten or fifteen minutes to bore through ordinary window glass.
Bore a hole in a bottle in the same way, except that the boring is all from the outside.
If the end of the file becomes dull, break off a small piece, with a pair of pliers, to expose a fresh surface.
Experiment 67. To cut a bottle in two.
[Illustration:
FIG. 88
BOTTLE READY TO BE CUT IN TWO ]
Wind a strip of blotting-paper or wrapping paper 2 inches wide around the bottle at one side of the line along which you wish to cut. Make three or more thicknesses and then tie the paper with cord within ½ inch of the edge to be cut. Wrap another similar piece on the opposite side of the place to be cut and ³⁄₁₆ inch from the first piece (Fig. 88).
[Illustration:
FIG. 89
HEATING THE BOTTLE ]
Now stand the bottle in a pail of water until the paper is thoroughly wet (about five minutes), take it out, rotate it in a horizontal position and direct the blowpipe flame against the glass between the papers (Fig. 89).
Continue this for four or five minutes, then if the bottle has not dropped apart, plunge it vertically into the pail of water.
The bottle will break into two parts along the line between the two papers (Fig. 90). If it does not do so, repeat the operation until it does. Smooth the rough edges outside and inside with the file. You cannot do this with the flame because the glass is too brittle.
[Illustration:
FIG. 90
THE BOTTLE CUT IN TWO ]
Experiment 68. To grind glass.
Rough edges of glass can be ground smooth by means of emery paper. For example, to smooth the edges of the glass bottle you have just cut in two, use the file for the rough work, then lay a piece of emery paper on a plate of glass, emery side up, pour a little kerosene on it and rub the rough surface on the emery with a rotary motion (Fig. 91). Finish with fine emery paper, and smooth the edges inside and out with the fine paper.
[Illustration:
FIG. 91
SMOOTHING THE EDGES ]
Experiment 69. To cement glass.
There are two important points to remember in cementing glass: first, to get the glass clean, and second, to press the surfaces together after applying the cement, to squeeze out as much of the cement as possible, and to keep them pressed together until the cement is hard. To clean the glass wash it thoroughly with soap and water, rinse, and dry with a clean cloth.
[Illustration:
FIG. 92
CEMENTING GLASS ]
There are many excellent glass cements on the market. Some of these are solid and are used only on hot glass; others are liquid and are used on cold or hot glass.
Cement two strips of glass together (Fig. 92) with sealing wax or solid shellac or some other solid cement as follows: Clean the glass thoroughly, place in the oven or on the stove, heat gradually until the glass just melts the cement, rub the cement over both surfaces, bring them together when the cement is fluid, press them together to squeeze out as much cement as possible, and keep them pressed together until the cement is hard.
Cement a strip of wood to a strip of glass in the same way.
Cement a strip of wood to a strip of glass with liquid glue, both wood and glass being cold. Keep them pressed together until the glue is dry, perhaps a day or two.
MAGICAL EXPERIMENTS
Boys, you can perform many magic experiments with apparatus made out of the glass tubes, rubber stoppers, and rubber unions supplied with “Experimental Glass Blowing.” We outline a number in the following pages. You can invent many more for yourselves.
MAGIC WITH FLAMES
Experiment 70. Magic lighting.
Light your alcohol lamp, blow it out, and bring a lighted match down toward the wick from above (Fig. 93). Does the lamp light in a most magical manner =before the match touches the wick=?
[Illustration:
FIG. 93
MAGIC ]
Repeat this with a kerosene lamp and with a candle. Do they light in the same magical manner?
The “why” of it
When the lamp is lighted, the alcohol or kerosene turns to a gas, and it is the gas which burns; when the candle is lighted, the wax turns to an oil, the oil turns to a gas, and it is the gas which burns.
The gas rises from the wick for a short time after the flame is blown out, and it is this gas which lights when you bring the match down toward the wick.
Experiment 71. Air used by flames.
[Illustration:
FIG. 94
THE CANDLES GO OUT AND THE WATER RISES ]
Drop melted candle wax on a tin can cover and attach the bottoms of two candles to the cover (Fig. 94); use one candle about 4 inches long and another about 3 inches, stand them upright in a pan of water, light them, and invert a wide-mouthed bottle over them. Does some air escape at first due to expansion, do both candles go out, the taller one first, and does the water rise until the bottle is about one-fifth full?
[Illustration:
FIG. 95
THE CORK RISES ]
Cut a piece of candle ½ inch long, float it on a flat cork or can cover in the pan of water, light it, and invert a fresh empty bottle over it (Fig. 95). Is the result similar?
The “why” of it
The water rises in the bottle because ⅕ of the air is used up by the burning candle. Air is ⅕ oxygen and ⅘ nitrogen. The oxygen unites with the burning gas of the candle and produces water vapor (H_{2}O) and carbon dioxide (CO_{2}); the nitrogen takes no part in the burning.
[Illustration:
FIG. 96
WATER FROM FLAME ]
The water vapor (H_{2}O) condenses to water on cooling and takes up very little space. The carbon dioxide remains a gas and occupies space, but this is offset by the volume of the air which escaped at first. The result is that the volume of gas at the end is about ⅕ less, and the atmospheric pressure on the water in the pan lifts water into the bottle.
The candle goes out because it must have oxygen to burn and the oxygen is used up.
Experiment 72. Water produced by fire.
It is certainly magic to produce water from fire, but you can do it easily as follows: Hold a clean, dry, cold tumbler over your alcohol lamp flame (Fig. 96). Does water deposit in the form of mist on the inside of the tumbler?
[Illustration:
FIG. 97
ATMOSPHERIC PRESSURE ]
Repeat with fresh tumblers with the flame of a kerosene lamp and of a candle. Are the results similar?
Direct the blowpipe flame into the end of a piece of No. 2 or 4 tubing. Does water deposit in drops inside the tube about 1 inch above the end?
The “why” of it
One of the chief constituents of alcohol, kerosene, and candle wax is hydrogen (H), and when this burns in the oxygen (O) of the air, it produces water (H_{2}O). It is this water which condenses on the cold glass.
MAGIC WITH AIR
Experiment 73. Atmospheric pressure.
Arrange a No. 6 tube as in 1, Fig. 97, and suck air out at the top. Does the water run uphill into your mouth?
Hold your finger over the top and lift the tube out of the pail (2). Does the water remain in the tube? Fill a bottle with water to overflowing, insert a No. 2 tube into your one-hole stopper, insert the stopper into the mouth of the bottle (3) without admitting air below the stopper, and try to suck water out of the bottle. Do you find that you cannot do so?
[Illustration:
FIG. 98
WATER DRIVEN UP TUBE BY ATMOSPHERE ]
Repeat (3) with the bottle half full of air (4). Do you find that you can now suck part of the water out of the bottle, and all of it if you admit air?
The “why” of it
The atmosphere which surrounds the earth exerts a pressure of 15 pounds per square inch on everything at the earth’s surface. It exerts this pressure equally downward, sidewise, and upward.
It is this atmospheric pressure on the water in the pail (1) which lifts the water into the tube when you decrease the pressure on the water in the tube by sucking out air and then water.
It is this pressure upward that supports the water in 2.
The water does not rise in 3 because the atmosphere cannot exert pressure downward on the water in the bottle.
[Illustration:
FIG. 99
A FOUNTAIN ]
The rise of the water in 4 is due to another fact, namely, that any gas expands when the pressure on it is decreased. When you suck air out of the tube you decrease the pressure on the water in the tube and thereby on the air in the bottle; the air then expands and lifts the water into your mouth.
Experiment 74. Great pressure of air.