George Willard Benton.

A laboratory guide for a twenty weeks course in general chemistry : containing detailed illustrations for the successful performance of over 150 experiments in general inorganic chemistry and useful tables of reference for pupil and teacher online

. (page 2 of 6)
Online LibraryGeorge Willard BentonA laboratory guide for a twenty weeks course in general chemistry : containing detailed illustrations for the successful performance of over 150 experiments in general inorganic chemistry and useful tables of reference for pupil and teacher → online text (page 2 of 6)
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Other gases are collected over water in the same way,
the delivery tube being attached by means of a cork to
the vessel in which the gas is being generated.

Experiment 25. To collect Several Bottles of Oxygen.
Fit a test-tube with a good cork and delivery tube.
Arrange four bottles to collect the gas over water.

Place in the tube 10 c c of a mixture of four parts of
KC1O 3 and one part of MnO 2 . Replace the cork in
the tube and heat the mixture gently, passing the gas
evolved into the bottles in succession.

To avoid loss, care should be taken to heat the mix-
ture only sufficiently to cause the gas to come off mod-

When the bottles have beer; filled, remove the delivery
tube from the water at once, as the water may be drawn
back into the test-tube as it cools.

The gas thus collected is to be used in the four fol-
lowing experiments.

Reaction : KC1O 3 + MnO 2 = KC1 + MnO 2 + ?

By reference to the equation it will be seen that the
MnO 2 is left after the reaction is complete.


Compare the amount of heat necessary in this experi-
ment with that required in Exp. 23. (?) Compare the
ingredients used. (?)

What inference may be drawn concerning the influ-
ence of the MnO 2 . (?)

The MnO 2 may be recovered by washing well with
water and filtering. It remains on the filter.

Experiment 26. To burn Charcoal in Oxygen. Remove
a bottle of oxygen from the pneumatic trough and stand
it upright on the table, keeping the bottle covered with
the glass plate. The bottle should contain a little
water, to prevent breaking in case the charcoal should

Make a small loop at the end of a wire and place in
it a piece of charcoal about the size of a pea.

Heat in the flame until lighted, and then plunge the
charcoal into the gas. (?) Compare Exp. 23. (?)

What is the product of the combustion ? C + 2O = ?

Experiment 27. To burn Iron in Oxygen. Wind a
piece of 'fine iron wire into the form of a spiral by means
of a round pencil. Make a small loop at the end as
large as a pin-head.

Holding the wire in a pair of nippers, heat the loop
and coil until red hot, plunge while hot into some
flowers of sulphur, and then quickly into the bottle of
oxygen and replace the cover, as the gas will otherwise
escape. (?) As before, the bottle should contain some

Does iron burn readily in air ? Is oxygen an active
supporter of combustion?

Equation : 3Fe + 4O = Fe 3 O 4 .


Experiment 28. To burn Phosphorus in Oxygen. Place
on the table another bottle of oxygen, containing a little
water, and covered.

Take a small piece of dry phosphorus in a combustion
spoon. (Phosphorus must never be handled with the
fingers. Use nippers. It is kept under water to pre-
vent contact with the oxygen of the air.)

Ignite the phosphorus by holding the spoon in the
flame for an instant. Quickly plunge the spoon into
the bottle and replace the cover. (?) Phosphorus
pentoxide is formed. Reaction : 2P + 5O = P 2 O 5 .

Let the bottle stand for a few moments. (?) 3H 2 O
+ P 2 O 5 = 2H 3 PO 4 . H 3 PO 4 is phosphoric acid. Try
the liquid with litmus paper. (?) What has hap-
pened to the white fumes ?

Experiment 29. To burn Magnesium in Oxygen. Hold
a strip of magnesium ribbon in your nippers. Ignite
and plunge the ribbon into a jar of oxygen. (?)

Compare the product with the magnesium. Are any
black particles mixed with the white ?

Equation : Mg + O = ?

Magnesium oxide is a white powder. Should there
be any black particles ? Compare the burning of mag-
nesium in air (Exp. 8) with that in oxygen.


Experiment 30. Structure of a Flame. Bring a piece
of cardboard, held horizontally, against the wick of a
burning candle.

Quickly bring the card to a vertical position against
the wick. The flame is outlined on the card, and pre-


sents a longitudinal section. Remove the card quickly
to prevent burning.

Now bring a fresh card horizontally down over the
flame, and nearly touching the wick. A cross section
of the flame is produced.

Now examine the flame closely. Note the cup-shaped
blue or colorless portion surrounding the wick; the
cone-shaped continuation of the colorless zone above
the wick ; the surrounding envelope of luminous flame
and the very thin envelope of non-luminous flame sur-
rounding all.

The sections on the cardboard give only two distinct
zones. (?)

Draw a diagram indicating the zones of no combus-
tion, incomplete and complete combustion.

Experiment 31 Structure of Flame continued. Hold

a pine splinter across the top of the wick of a lighted

When the stick begins to char, quickly remove it and
stop its burning. Observe both upper and under sur-
faces of the stick. (?)

Is this result consistent with what has already been

Experiment 32. Structure of Flame continued. Hold
the lower end of a glass tube in the centre of the lumi-
nous flame, the tube slanting upward at an angle of
about 45 degrees. Hold a lighted match at the upper
end of the tube. (?)

What is the condition of the inner part of the flame ?


Experiment 33. Source of the Light of the Luminous
Flame. Hold a cold dry iron spoon, down in the lumi-
nous flame for a few seconds, but not long enough to get
the spoon red hot. Remove and examine the spoon. (?)

Notice the black smoke rising the instant the spoon
touches the flame. (?)

Now open the holes at the base of the burner. (?)
Hold the spoon with the black deposit on it in the non-
luminous flame, and note effect. (?)

What was the black substance ? What causes the light?

Why .does the light only appear when the holes at
the base are closed ? (?)

Hold the cold spoon in the flame of a candle as
before. (?) What is the deposit ?

Hold the spoon in the non-luminous flame of the
burner as before. (?) Is the light of the candle due
to the same cause ?

Carbon and hydrogen are the fuels in both cases.
One is solid, the other gaseous. (?)

When they burn in oxygen, what are the products ?
Reactions : C + O 2 =?; H 2 + O=? Both products
of combustion are colorless. This explains the fact that
a flame burning quietly has a well-defined outline and
no visible products.

Experiment 34. Air and Combustion. Invert a com-
mon glass tumbler over a candle flame, excluding the
outside air. (?) Explain. Has oxygen any connec-
tion with that action?

Try the same thing again, except that this time hold
the tumbler so that the candle may be near its side, and
free access of air be allowed. (?) Explain.


Experiment 35. Ventilation and Combustion. Stand a
lamp chimney down over a lighted candle completely
excluding air from below. Note the effect on flame.

Raise the chimney a little from the support and allow
free circulation of air. Any effect ? Explain.

Still holding the chimney free from the support, place
a strip of glass over the top. (?) Explain.

What do you learn about draughts and ventilation in
this experiment?

Experiment 36. Ventilation and Combustion continued.
Hang a strip of tin or zinc, about 4 to 6 in. long, from
the top of a lamp chimney, to partition the chimney
into two parts.

Bring the chimney, thus prepared, firmly down over
a lighted candle, excluding the air from below, as be-
fore. (?) Bring a strip of lighted touch paper over
the chimney. (?)

Why does the candle continue to burn? How does
the touch paper aid in explaining the action ?


Experiment 37. The Oxidizing Process. Make a small
loop at the end of a platinum wire. Heat the wire, dip
it into borax, and heat with the blowpipe until a color-
less bead is formed.

Touch the bead while hot to a very small particle of
manganese dioxide, MnO 2 . Heat strongly for a moment
in the oxidizing flame.

Hold the bead up to the light, and note the color
while hot, and when cold. (?)


What is meant by the term oxidizing ? Does oxygen
come from or go to the bead in this experiment? How?
How is the oxidizing flame produced ?

Experiment 38. The Reducing Process. Heat the red-
colored bead produced in Exp. 37 persistently in the
reducing flame until the bead becomes clear.

The flame contains an excess of carbon and hydrogen,
highly heated. Both elements have a strong affinity for
oxygen. Hence the oxidized bead heated in the pres-
ence of carbon and hydrogen is caused to give up its oxy-
gen. This is called reduction. Compare oxidation. (?)

Experiment 39. Dip a bead, while hot, into a solu-
tion of cobalt nitrate, Co(NO 3 ) 2 .

First heat the bead in the oxidizing flame. (?) Then
in the reducing flame. (?) Compare the action with
that observed in Exps. 37 and 38. (?)

From the results observed, would you think the bead
test for a metal might be relied upon ? Confirm your
answer by reference to your text-book.


Experiment 40. Varies with the Substance. Place on a
piece of porcelain, as far apart as possible, a small piece
of phosphorus, one of sulphur, and one of iron. The
substances must not touch.

Now place the porcelain on a tripod-stand, and heat as
long as changes are noted, taking care that each sub-
stance on the dish is equally heated. (?)

Which burns first ? Which last ? Does the iron burn ?
Why not ? Could it be made to burn ? How ?

Which has the lowest and which the highest kindling
point ?


Experiment 41. Effect of cooling a Flame below the Kind .
ling Point. Take a cold candle. Light a match and
bring it slowly down over the wick until the tip of the
wick is surrounded by a flame.

As soon as it lights, remove the match and note the
changes which the candle and flame undergo until the
flame burns uniformly and steadily.

A flame is a burning gas. Have you evidence of a
gas being produced by the flame ?

Now bring a piece of wire gauze slowly down over
the flame. Note the effect on the flame, on the gauze,
and above the gauze, as the flame-tip is reached. (?)

Continue to lower the gauze until it nearly touches
the wick. Note appearances above and below the gauze
as before. (?)

Hold a lighted match over the gauze and near enough
to ignite any gas which may be rising from the can-
dle. (?)

Will a gas burn when cooled below the kindling
point ? Read the description of the Davy safety lamp.

Experiment 42. Place the Bunsen burner, with holes
at the base closed, under the tripod and about two inches
below the centre of the gauze covering. Turn on the
gas and hold a lighted match above the gauze. (?)

Repeat the experiment, but this time hold the match
below the gauze. (?) Compare Exp. 41. (?)

Under what circumstances would the gas burn above
if lighted below only ?


Experiment 43. Make a coil by winding a piece of
iron wire around a pencil ten or twelve times.

Bring the coil vertically down into a candle flame, so
that the wick may pass up into the coil. (?)

Repeat the experiment, having heated the coil red hot
in the flame of the Bunsen burner, and before the coil
cools. (?)

Explain the difference in action. Compare Exps. 41
and 42. (?)

Experiment 44. Ignition of Fuels Affected by Size of
Particles. Hold the lighted burner in a horiontal position
over an evaporating dish.

* Sprinkle some fine iron filings over the flame. (?)
Compare Exp. 27. (?)

Examine the filings which have fallen into the dish.
(?) Which would burn more readily, the larger or
smaller particles ?

Since temperature and quantity of heat are not sy-
nonymous terms, and the same heat which would raise
one particle 10 degrees would raise a particle ^ as large
100 degrees (see Physics), it follows that a very small
particle of iron falling through the flame would reach a
very high temperature, while larger particles would not
become even red hot. From this it follows that very
fine dry dust becomes very combustible and easily rises
to the point of ignition.


Experiment 45. Preparation by Electric Discharge.

Turn the wheel of the Holtz machine. At all angles
and points a silent discharge may be noted.


Inhale a little air near one of the brushes. (?) The
odor is that of ozone.

Compare the odor arising from a pie.ce of phosphorus
exposed to the air. (?)

The molecular formula of oxygen is O 2 ; that of ozone
is O 3 . Complete the equation 3O 2 ^= ?O 3 .

Problem. If a molecule of ozone occupies the same
space as a molecule of oxygen, how many cub. cent,
of ozone would be obtained from 45 c c of oxygen ?

Experiment 46. Preparation by the Reduction of Potas-
sium Permanganate. Take in a test-tube about 5 c c of a
strong solution of potassium permanganate, KMnO 4 .

Add a few drops of cone. H 2 SO 4 . Odor? Heat
gently to boiling. Odor?

Dip a strip of bibulous (?) paper into a solution of
potassium iodide, KI, and starch. Hold over, but not
touching, the tube's mouth. (?) In case no immediate
effect is noted, heat the tube again. (? )

Ozone liberates the iodine from the KI, and iodine
when free attacks the starch, turning it blue. (?)

What reasons have you for inferring that ozone was
set free ?

Equations : (a.) 6KMnO 4 + 9H 2 SO 4 = ?K 2 SO 4 +
?MnSO 4 + ?H 2 O + ?O 3 . (6.) 6KI + O 3 = ?K 2 O+ ?I.
The blue substance formed is called " Iodized Starch."


Experiment 47. It contains Moisture. Calcium chloride,
CaCl 2 , is deliquescent. (?) Place a small piece on a
dry plate and expose to the air for a few moments. (?)


Experiment 48. It contains Oxygen, (a) Take a small
piece of metallic lead in a porcelain capsule. Place the
capsule on a stand over the hot flame. (?)

When the lead melts, stir it with an iron wire until it
becomes a powder. (?) The substance formed is an
oxide of lead.

Try the same thing again, this time using a piece of
zinc. (?) The product is yellow while hot, white
when cold. It is zinc oxide, ZnO.

(>). Heat a piece of lead, as in (a), first covering
the lead with a layer of borax. (?) The latter pre-
vents the air coming in contact with the metal.

Is the same effect produced as when the air reached
the metal ?

Since in forming the oxides the air is made to give
up oxygen, might air be deprived of oxygen by burning
something ? (See the preparation of nitrogen.)


Experiment 49. Preparation from Sodium Amalgam.
Put a piece of freshly prepared amalgam in a dish of
water. Invert a small test-tube, filled with water, over
the amalgam and collect the gas. Complete the equa-
tion Na + H 2 O = NaOH + ? What is collected in
the tube ?

Place a finger over the mouth of the tube and, hold-
ing it mouth down, remove from the water and plunge
a blazing pine stick up into the tube. (?)

Does hydrogen burn or support combustion ?

NaOH is a white solid, very soluble in water.

Evaporate a few drops of the liquid in the dish.


(?) Touch the residue with a strip of moistened red
litmus paper. (?)

Moisten a piece of the paper with the solution of
NaOH found on the table. ( ? )

NaOH is alkaline. Has the water in the dish
acquired alkaline properties?

Experiment 50. Preparation from Zinc and Hydrochloric
Acid. Arrange to collect two bottles of gas over water,
as in Exp. 24. Place in a 4 oz. generating bottle
enough granulated zinc to cover the bottom of the
bottle. Cover the zinc with water.

Add about 5 CC of cone. HC1, quickly press the cork
attached to the delivery tube into the bottle, and pro-
ceed to collect the gas as before.

Joints in the apparatus must be especially tight in
this experiment, as hydrogen is very diffusible.

As soon as the gas is collected, wash the remaining
zinc in the generating bottle, and leave in your evap-
orating dish. It may be used again.

Complete and balance the equation Zn -f- HC1
ZnCl 2 + ? Gas collected will be used in the next two

Experiment 51. Physical and Chemical Properties of
Hydrogen. Examine the gas collected in Exp. 50.
Note color (?), odor (?), etc.

Recall whether the bubbles of gas as they rose in
the collecting bottles in Exp. 50 appeared to grow
smaller or not. In case they grow rapidly smaller the
gas is quite soluble. If they do not decrease percepti-
bly, it is comparatively insoluble. What can you say
as to the solubility of this gas ?


Now take a blazing pine splinter in one hand ; remove
a bottle of the gas, mouth down, and pass the blazing
splinter up into the bottle of hydrogen. (?) Slowly
withdraw the stick. (?)

Did the stick burn in the gas ? Did the gas burn at
the mouth of the bottle? Does hydrogen support com-
bustion ? Is it combustible ?

If the hydrogen burns, what compound is produced ?
H 2 + 0=?

Experiment 52. Dif fusibility and Lightness of Hydrogen.
Remove the remaining bottle of hydrogen with the
cover glass, and stand it up on the table, mouth up, and

Bring a second bottle, empty or filled with air only,
down over the bottle of hydrogen, mouth down.

Remove the cover glass, arid hold the two bottles
firmly together.

After a half-minute slip the glass cover between the
bottles again. .

Present the mouth of the upper bottle to the
flame. (?)

Now, remove the cover and present the lower bottle
to the flame. (?)

Which bottle gave evidence of the presence of a
larger proportion of hydrogen ?

Show how the lightness and diffusibility of hydrogen
would give rise to the phenomena noted.

Experiment 53. Osmosis. Performed by the Teacher.

Take a glass tube about 18 inches long and 1 inch in
diameter. Seal one end with a thin (about | inch)
layer of plaster of Paris. Set it away until dry. The
plaster plug must under no circumstances be, moistened.

A3C3S3ion Ho..


Fill the tube with hydrogen by the displacement of
air. (?)

Place the open end of the tube in a beaker of water,
vertically, and allow to stand, noting the level of the
water from time to time. (?) Explain the rising and
falling of the liquid in the tube.

Experiment 54. Combination of Hydrogen and Oxygen.
Performed by the Teacher. Fill a strong pint bottle,
having a narrow mouth, with water.

Replace two-thirds of the water with hydrogen, and
the remaining one-third with oxygen.

Let the bottle stand for a few moments to insure
thorough mixing of the gases.

Place the thumb over the mouth of the bottle and
stand it down on the table, tightly closed.

Remove the thumb and quickly bring a lighted match
close to the mouth of the bottle. (?)

Notice the flame seen throughout the bottle at the
instant of the explosion. What is the product of
the combination ? 2H + O = ? Explain the origin of
the sound.

Experiment 55. Comparison of Coal Gas and Hydrogen.

Arrange to collect a bottle of gas over water.

Detach the burner from the gas-tube. Put the end
of the tube under the mouth of the bottle of water and
turn on the gas.

When the bottle is full, examine it. (?) Insert a
blazing match as in Exp. 51. (?)

How does the action compare with that of Exp. 51 ?
In what noticeable features are the two gases differ-



Experiment 56. Generation of Water by Ordinary Com-
bustion. Hold a clean, dry, and cold glass tumbler over
a candle flame.

Notice the bottom and sides. (?) What is collected
there ? What chemical action has taken place ? What
physical action? Why should the tumbler be cold and

Hold a cold, dry, glass plate for an instant over the
hot flame of the Bunsen burner. (?)

If air contains oxygen ( see Exp. 48 ) and the fuel
constituents of the candle and gas are carbon and hydro-
gen (see Exp. 33), would water probably be in all
cases a product of the burning of a gas which con-
tained hydrogen? See the equation in Exp. 54.

Experiment 57. Analysis of Water by Electrolysis. Per-
formed by the Teacher. Fill the electrolysis apparatus with
water acidulated with H 2 SO 4 ( 1 to 20 ), and pass the
current until enough gas has been collected to examine.

Note the volumes of the gases, and particularly which
gas is in contact with respective poles of the battery.
(?) Remove and carefully test each gas in succession.
(?) Compare Exp. 54. (?)

Experiment 58. Water of Crystallization. Heat a crys-
tal of copper sulphate, CuSO 4 , on an iron spoon. (?)

When completely changed, and cold, drop a little
water on the powder. (?)

Put some of the powder into a test-tube and add l cc
of water. (?)

Pour the contents of the tube into an evaporating dish
and evaporate the liquid slowly without boiling. (?)


Compare the product with the copper sulphate with
which you started. (?) Most crystals on examina-
tion will prove to contain more or less water. See text
for formulae of crystalline substances.


Experiment 59. Preparation from Air. Float a tin
box-cover on water in a pneumatic trough. Place on
the float a small piece of dry phosphorus.

Ignite the phosphorus and bring an inverted glass
tumbler quickly down over the pan, enclosing the air
and burning phosphorus.

Another method. Bend the handle of a combustion
spoon to the shape of the letter V ; place the phosphorus
in the spoon, ignite, and bring an inverted wide-mouth
bottle quickly down over the spoon, closing the mouth
of the bottle with water as before.

In case the former process is used, it will be well to
transfer the gas prepared from the tumbler to the wide-
mouth bottle for further examination.

Why did a few bubbles of air escape at the outset of
the experiment?

What element in the air combines with phosphorus to
form white fumes ? Confirm your answer by reference
to Exp. 28.

While the phosphorus burns in the enclosed air, does
the volume of the air remain the same ? Estimate the
new volume as compared with the old. Account for
the fact noted.

Let the bottle stand until the fumes settle. The
collected gas will be examined in the next experiment.


Experiment 60. Properties. Remove the bottle of gas
and place it upright upon the table, covered with the
glass plate. Note color, odor, if any, and effect on
litmus paper. Insert a blazing pine splinter. (?)

Pour the gas from the bottle. Does it rise or fall ?
Its sp. g. is 0.97. Which should it do ?

What gas has been prepared and examined ? Are its
properties active or passive ?

Moisten a strip of blue litmus paper in the water left
in the pan. (?)

Balance the equation P 2 O 5 + H 2 O = H 3 PO 4 . Com-
pare Exps. 28 and 48.


Experiment 61. Preparation from NH 4 C1 and lime, CaO.
Place in the palm of the hand, side by side, but not
touching, about one grain of dry lime, CaO, and an
equal bulk of ammonium chloride, NH 4 C1.

Note the odor, if any, of each. (?)

Mix the two substances with a finger and rub the
mixture vigorously for a few moments. (?) Examine
the mixture, is it moist ? Complete the equation
CaO + 2NH 4 C1 = CaCl 2 + ? 4- ?

Give such properties of ammonia as you have observed.
Is it solid, liquid, gaseous, visible, invisible, odorless,

Experiment 62, Preparation from a Solution of an Am-
monium Salt, Place in a test-tube about 5 c c of a solu-
tion of ammonium chloride, NH 4 C1.

Add four or five drops of a solution of potassium
hydroxide, KOH, (?) Heat geutly. (?) Any odor?


Dip a clean glass stirring rod into hydrochloric acid,
HC1, and bring it over the mouth of the tube. (?)

Hold a moistened strip of red litmus paper over the
tube. (?)

Show by completing the following equation that am-
monia was produced: NH 4 C1 + KOH ? + ? + KC1.

Other solutions of ammonium salts will yield ammonia
in the same way.

Experiment 63. Preparation from Organic Sources,
Place a piece of hoof-clipping in a dry test-tube. Heat
it carefully and gently, without burning. (?) Any
odor? Hold over the tube a strip of moistened red
litmus paper. (?) Is the presence of ammonia proved?

Hair, finger-nails, and many other organic substances
will respond to the same test.

Experiment 64. Simple Tests for Ammonia in Solution.
Take about 5 CC of the solution to be tested in a test-
tube. Add a few drops of potassium hydroxide, KOH.
Heat the tube and contents gently. (?) Any odor?

2 4 5 6

Online LibraryGeorge Willard BentonA laboratory guide for a twenty weeks course in general chemistry : containing detailed illustrations for the successful performance of over 150 experiments in general inorganic chemistry and useful tables of reference for pupil and teacher → online text (page 2 of 6)