Antimony Sb 120. III, V. ... ... ... "
Arsenic As 75. III, V 150. "
Barium Ba 137. II ... ... ... "
Bismuth Bi 210. III, V ... ... ... "
Boron B 11. III ... ... ... "
Bromine Br 80. I, (V) 80. Liquid
Cadmium Cd 112. II 56. Solid
Calcium Ca 40. II ... ... ... "
Carbon C 12. (II), IV ... ... ... "
Chlorine Cl 35.5 I, (V) 35.5 Gas
Chromium Cr 52. (II),IV,VI ... ... ... Solid
Cobalt Co 59. II, IV ... ... ... Gas
Copper Cu 63. I, II ... ... ... "
Fluorine F 19. I, (V) ... ... ... Gas
Gold Au 196. (I), III ... ... ... Solid
Hydrogen H 1. I 1. Gas
Iodine I 127. I, (V) 127. ... ... Solid
Iron Fe 56. II,IV,(VI) ... ... ... "
Lead Pb 206. II, IV ... ... ... "
Lithium Li 7. I ... ... ... "
Magnesium Mg 24. II ... ... ... "
Manganese Mn 55. II, IV, VI ... ... ... "
Mercury Hg 200. I, II 100. Liquid
Nickel Ni 59. II, IV ... ... ... Solid
Nitrogen N 14. (I),III,V 14. Gas
Oxygen O 16. II 16. "
Phosphorus P 31. (I),III, V 62. Solid
Platinum Pt 197. (II), IV ... ... ... "
Potassium K 39. I ... ... ... "
Silicon Si 28. IV ... ... ... "
Silver Ag 108. I ... ... ... "
Sodium Na 23. I ... ... ... "
Strontium Sr 87. II ... ... ... "
Sulphur S 32. II,IV,(VI) 32(96) "
Tin Sn 118. II, IV ... ... ... "
Zinc Zn 65. II 32.5 "
If more than one atom of an element enters into the composition
of a binary, a prefix is often used to denote the number. SO2 is
called sulphur dioxide, to distinguish it from SO3, sulphur
trioxide. Name these: CO2, SiO2, MnO2. The prefixes are: mono or
proto, one; di or bi, two; tri or ter, three; tetra, four; pente,
five; hex, six; etc. Diarsenic pentoxide is written, As2O5.
Symbolize these: carbon protoxide, diphosphorus pentoxide,
diphosphorus trioxide, iron disulphide, iron protosulphide. Often
only the prefix of the last name is used.
16. An Oxide is a Compound of Oxygen and Some Other Element, as
HgO. What is a chloride? Define sulphide, phosphide, arsenide,
carbide, bromide, iodide, fluoride.
In Experiment 6, where S and Fe united, the symbol of the product
was FeS. Name it. How many parts by weight of each element? What
is its molecular weight? To produce FeS a chemical union took
place between each atom of the Fe and of the S. We may express
this reaction, i.e. chemical action, by an equation:--
Iron + Sulphur = Iron Sulphide
Or, using symbols Fe + S = FeS
Using atomic weights, 56 32 = 88.
These equations are explained by saying that 56 parts by weight
of iron unite chemically with 32 parts by weight of sulphur to
produce 88 parts by weight of iron sulphide. This, then,
indicates the proportion of each element which combines, and
which should be taken for the experiment. If 56 g. of Fe be used,
32 g. of S should be taken. If we use more than 56 parts of Fe
with 32 of S, will it all combine? If more than 32 of S with 56
of Fe? There is found to be a definite quantity of each element
in every chemical compound. Symbols would have no meaning if this
were not so.
Write and explain the equation for the experiment with copper and
sulphur, using names, symbols, and weights, as above.
CHAPTER V.
MANIPULATION.
17. To Break Glass Tubing.
Experiment 8.--Lay the tubing on a flat surface, and draw a sharp
three-cornered file two or three times at right angles across it
where it is to be broken, till a scratch is made. Take the tube
in the hands, having the two thumbs nearly opposite the scratch,
and the fingers on the other side. Press outward quickly with the
thumbs, and at the same time pull the hands strongly apart, and
the tubing should break squarely at the scratch.
To break large tubing, or cut off bottles, lamp chimneys, etc.,
first make a scratch as before; then heat the handle of a file,
or a blunt iron--in a blast-lamp flame by preference--till it is
red-hot, and at once press it against the scratch till the glass
begins to crack. The fracture can be led in any direction by
keeping the iron just in front of it. Re-heat the iron as often
as necessary.
18. To Make Ignition-Tubes.
Experiment 9.--Hold the glass tubing between the thumb and
forefinger of each hand, resting it against the second finger.
Heat it in the upper flame, slowly at first, then strongly, but
heat only a very small portion in length, and keep it in constant
rotation with the right hand. Hold it steadily, and avoid
twisting it as the glass softens. The yielding is detected by the
yellow flame above the glass and by an uneven pressure on the
hands. Pull it a little as it yields, then heat a part just at
one side of the most softened portion. Rotate constantly without
twisting, and soon it can be separated into two closed tubes. No
thread should be attached; but if there be one, it can be broken
off and the end welded. The bottom can be made more symmetrical
by heating it red-hot, then blowing, gradually, into the open
end, this being inserted in the mouth. The parts should be
annealed by holding above the flame for a short time, to cool
slowly.
For hard glass--Bohemian--or large tubes, the blast-lamp or
blowpipe is needed. In the blast-lamp air is forced out with
illuminating gas. This gives a high degree of heat. Bulbs can be
made in the same way as ignition-tubes, and thistle-tubes are
made by blowing out the end of a heated bulb, and rounding it
with charcoal.
19. To Bend Glass Tubing.
Experiment 10.--Hold the tube in the upper flame. Rotate it so as
to heat all parts equally, and let the flame spread over 3 or 4
cm. in length. When the glass begins to yield, without removing
from the flame slowly bend it as desired. Avoid twisting, and be
sure to have all parts in the same plane; also avoid bending too
quickly, if you would have a well-rounded joint. Anneal each bend
as made. Heated glass of any kind should never be brought in
contact with a cool body. For making O, H, etc., a glass tube --
delivery-tube--50 cm. long should have three bends, as in Figure
6. The pupil should first experiment with short pieces of glass,
10 or 15 cm. long. An ordinary gas flame is the best for bending
glass.
20. To Cut Glass.
Experiment 11.--Lay the glass plate on a flat surface, and draw a
steel glass-cutter--revolving wheel--over it, holding this
against a ruler for a guide, and pressing down hard enough to
scratch the glass. Then break it by holding between the thumb and
fingers, having the thumbs on the side opposite to the scratch,
and pressing them outward while bending the ends of the glass
inward. The break will follow the scratch.
Holes can be bored through glass and bottles with a broken end of
a round file kept wet with a solution of camphor in oil of
turpentine.
21. To Perforate Corks.
Experiment 12.--First make a small hole in the cork with the
pointed handle of a round--rat-tail--file. Have the hole
perpendicular to the surface of the cork. This can be done by
holding the cork in the left hand and pressing against the larger
surface, or upper part, of the cork, with the file in the right
hand. Only a mere opening is made in this way, which must be
enlarged by the other end of the file. A second or third file of
larger size may be employed, according to the size of the hole to
be made, which must be a little smaller than the tube it is to
receive, and perfectly round.
CHAPTER VI.
OXYGEN.
22. To Obtain Oxygen.
Experiment 13.--Take 5 g. of crystals of potassium chlorate
(KClO3) and, without pulverizing, mix with the same weight of
pure powdered manganese dioxide (MnO2). Put the mixture into a
t.t., and insert a d.t.--delivery-tube--having the cork fit
tightly. Hang it on a r.s.--ring-stand,-- as in Figure 7, having
the other end of the d.t.
(Fig 7.)
under the shelf, in a pneumatic trough, filled with water just
above the shelf. Fill three or more receivers--wide-mouthed
bottles--with water, cover the mouth of each with a glass plate,
invert it with its mouth under water, and put it on the shelf of
the trough, removing the plate. No air should be in the bottles.
Have the end of the d.t. so that the gas will rise through the
orifice. Hold a lighted lamp in the hand, and bring the flame
against the mixture in the t.t. Keep
the lamp slightly in motion, with the hand, so as not to break
the t.t. by over-heating in one place. Heat the mixture strongly,
if necessary. The upper part of the t.t. is filled with air:
allow this to escape for a few seconds; then move a receiver over
the orifice, and fill it with gas. As soon as the lamp is taken
away, remove the d.t. from the water. The gas contracts, on
cooling, and if not removed, water will be drawn over, and the
t.t. will be broken. Let the t.t. hang on the r.s. till cool.
With glass plates take out the receivers, leaving them covered,
mouth upward (Fig. 8), with little or no water inside. When cool,
the t.t. may be cleaned with water, by covering its mouth with
the thumb or hand, and shaking it vigorously.
What elements, and how many, in KClO3? In Mn02? It is evident
that each of these compounds contains O. Why, then, could we not
have taken either separately, instead of mixing the two? This
could have been done at a sufficiently high temperature. Mu02
requires a much higher temperature for dissociation, i.e.
separation into its elements, than KClO3, while a mixture of the
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