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 3 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 3 of 6)
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Is ammonia present ? Why ?

If it is present, was it free or combined before you
added the potassium hydrate ? Give reason for answer.

Hold over the mouth of the tube a strip of moistened
red litmus paper, and heat as before. (?)

Does the change, if any, confirm your previous con-
clusion concerning the presence of ammonia. Explain.

Now hold over the mouth of the tube while heating
a stirring rod moistened with hydrochloric acid, HC1.
(?) Have you done a similar thing before? Was the
product the same both times ?

Are you convinced from the results of the three tests


that ammonia is present in the unknown solution?
Which test do you consider the most delicate and con-
vincing ? Why ?

If you were given a solid instead of a liquid to test,
what would you have done first ?


Experiment 65. Formation of a Salt. Place an evapo-
rating dish on a tripod-stand. Pour in about 3 CC of
dilute nitric acid, HNO 3 .

Add ammonia solution gradually, constantly stirring
with a stirring rod until the mixture is neutral. Test
the neutrality (?) with litmus paper. If necessary, add
minute quantities of acid if too alkaline, or ammonia if
too acid.

When neutral, evaporate the contents of the dish
gradually. Do not let the solution boil, as it drives off
the ammonia.

What is the solid substance in the dish on evapora-
tion ? Complete the equation NH 3 -f- HNO 3 = ?


Experiment 66, The Preparation of the Monoxide, N 2 0.

Arrange to collect two bottles of gas over water. Let
one bottle be small. Place the apparatus on the
tripod-stand and heat the water until it is hot to the
hand, but not necessarily to the boiling point. Why?
While heating the water, fit a test-tube with a sound
cork and glass delivery tube.

Place in the tube a few pieces of fused ammonium
nitrate, NH 4 NO 3 .


Remove the burner from beneath the pan, and heat
the contents of the tube gradually until it melts. Now
increase the heat enough to make the nitrate boil

As soon as it begins to boil place the delivery tube
under the larger bottle and collect the gas evolved, only
heating the tube enough to keep the contents boiling
briskly. Collect the small bottle of gas.

Show by the equation that nothing would be left
in the tube if heated sufficiently long. NH 4 NO 3 -\-
heat ? + ?

After the bottles of gas have been collected, replace
the burner under the pan to keep the water hot, until
the gas has been examined in the following experiment.

Experiment 67. Properties of the Monoxide. Stand the
small bottle, covered, upright on the table. Examine.
(?) Remove cover and inhale the gas. (?)

So far, what class of properties has been observed,
physical or chemical ?

Remove the larger bottle. Plunge into the gas a
glowing splinter of pine. (?) Compare the action
with the result of Exp. 22. (?)

How may this gas be readily distinguished from
oxygen ? Which is the more active ?

Experiment 68. Preparation of the Dioxide, NO. Proper-
ties. Place in a generating bottle, fitted with a glass
delivery tube, a few copper clippings. Arrange to col-
lect one bottle of gas over water.

Cover the copper with water, and then add 1 or 2 cc
cone, nitric acid, HNO 3 . Collect the gas evolved.


Examine the gas in the generator. (?) Color?

Does the color remain? Explain. Examine the gas

collected. (?) Color? Explain what yon see. Bal-

^ance the equation 3 Cu + ? HNO 3 = 3 Cu(NO 8 ) a + ? NO

+ ?H 2 0.

Remove the bottle of gas, keeping the mouth of the
bottle covered. Hold it before the window, for the sake
of good light, and remove the cover. (?)

Where have the same fumes been seen before ? Ex-
plain the action. What is the formula of the fumes?
Balance the equation 2NO + O 2 = ?

Experiment 69. Preparation and Properties of the Tri-
oxide, N 2 3 . Fit a test-tube with a cork and glass
delivery tube.

Place in a small bottle on the table a weak solution
of potassium permanganate, KMnO 4 .

Fill the curved part of the test-tube with starch and
add an equal volume of cone, nitric acid, HNO 3 .

Heat the acid gradually and gently, avoiding scorch-
ing the starch and continually shaking the tube, until
the starch dissolves. The heating may have to be con-
tinued a moment longer, but is generally unneces-
sary. (?)

As soon as action commences, insert the cork and
delivery tube and pass the gas through the solution of
permanganate. (?)

Carefully note the odor of the gas. (?) Compare
color with the brown gas observed in Exp. 68. (?)

The action on the permanganate solution is a test for
the gas. Try the decolorized liquid in the bottle, with
litmus paper. (?)


Nitrous acid, HNO 2 , is formed when N 2 O 3 reacts with
H 2 O. Complete and balance the equation N 2 O 3 + ?

As soon as the work of the experiment is completed
wash out the test-tube and flush the basin, as the gas is

Experiment 70. Preparation of the Tetr oxide, N0 2 .
Place in a damaged test-tube a crystal of lead nitrate,
Pb(NO 3 ) 2 and heat persistently in the hot flame. (?)

Compare the fumes given off with those observed in
Exp. 68. (?) Examine the dry yellow powder re-
maining in the tube. (?) Is it the same as the sub-
stance labelled Litharge, PbO ? Complete the equation
Pb(NO 3 ) 2 + heat = ? + ? + O.


Experiment 71. Preparation of Nitric Acid from a Nitrate.
Take about l cc of powdered potassium nitrate, KNO 3 ,
in a test-tube. Add about 2 CC of cone, sulphuric acid,
H 2 S0 4 .

Heat carefully. Examine the vapor arising in the
tube. (?) Note the liquid running down the side of
the tube. (?)

Have you a reason for thinking the vapor and liquid
are of the same composition? Bring a drop of ammonia
on a stirring rod over the tube. (?) A moistened
strip of blue litmus paper. (?)

In case a brown vapor is seen, it is caused by the
decomposition of the acid.

Equation : 2HNO 3 + heat = H 2 O + 2NO 2 + O.

Mention properties of nitric acid noted in this experi-
ment : color, odor, normal condition, etc. (?)


Notice bottles of cone, nitric acid which have been
exposed to strong light and compare with those unex-
posed. (?) Complete and balance the equation
KN0 3 + H 2 S0 4 = K 2 S0 4 + ?

Experiment 72. The Oxidizing Power of Nitric Acid.
Take 2 or 3 c c of cone, nitric acid, HNO 3 , in an evapo-
rating dish, and warm it gently.

Drop into the acid a small piece of freshly cut phos-
phorus. Care must be observed in this experiment to
avoid being burned by the slight tendency to explode.
The phosphorus should be carefully dried with bibulous
paper before using. (?)

In case white fumes are seen, give their formula.
Compare Exp. 28. (?) To account for brown fumes,
see Exp. 71.

If, in this case, the oxygen is in the nascent (?) state,
explain how it differs from oxygen as examined in
Exps. 26-9. (?)

Experiment 73. Oxidizing Power continued. Take some
powdered charcoal in an iron spoon, and hold in the 'hot
flame until it commences to glow.

Now by the use of a clean stirring rod drop some cone,
nitric acid upon the glowing charcoal . (?)

Equation: 5C + 4HNO 3 = 5CO 2 + 2H 2 O + 4N.

Does the equation account for the explosive action?
Read something on gunpowder to confirm your answer.

Would you expect the result obtained, when reference
is made to the action noted in Exp. 72 ?

Do you consider nitric acid a very stable compound ?
Give reasons for your answer.


Experiment 74. The Oxidizing Power of a Nitrate. Heat
charcoal again, just as in Exp. 73. Sprinkle powdered
potassium nitrate, KNO 3 , over the glowing charcoal. ( ? )

How does the action compare with that with nitric
acid ? Would you expect it from an examination of the
formulae of the two substances ?

Would common salt, Nad, act in the same way?
Explain your answer.

Complete and balance the equation 5C + 4KNO 3
= K 2 CO 3 + 3CO 2 -f- ? Compare the equation in
Exp. 73. (?)

Note the white substance remaining on the spoon.
It is potassium carbonate, K 2 CO 3 . Try it with moist-
ened litmus paper. ' (?)

Experiment 75. Dyeing with HN0 3 . Dip a piece of
white silk thread into very dilute nitric acid. Dry it
by holding over the flame. Examine. (?)

What color is produced when you get nitric acid on
your hands ?

Experiment 76. Nitric Acid and Vegetable Fibre. Pre-
pare a small ball of common cotton^ and one of gun-
cotton, each about .5 cm in diameter.

Place the common cotton in a clean evaporating dish,
touch a match to it, and watch it burn. (?) Any-
thing left ?

Now treat the gun-cotton in the same way. (?)
Any difference ? What causes the difference, 'if any ?

What element has caused more rapid combustion in
all these experiments ?

How does gun-cotton differ from common cotton ?


Experiment 77. A Delicate Test for Nitric Acid or a
Nitrate. Dissolve a small crystal of ferrous sulphate,
FeSO 4 , in about 5 CC of water.

Take in another tube a drop of the solution to be
tested, and add about 3 CC of concentrated sulphuric
acid, H 2 SO 4 .

Now pour, gradually, the ferrous sulphate solution
upon the contents of the second tube, taking particular
care not to let them mix. (?) Shake the tube. (?)

The brown ring is conclusive except in the presence
of a compound of bromine.

Study the reaction : 2KNO 3 + 4H 2 SO 4 + 10FeSO 4 =
K 2 SO 4 + 3Fe 2 (SO 4 ) 3 + 4H 2 O + 2(FeSO^ NO. The
last substance composes the brown ring.

Experiment 78. Another Test for a Nitrate. Place a
piece of copper in a test-tube, and pour over it about
5 c c of the solution to be tested.

Now add, a drop at a time, concentrated sulphuric
acid until action is noted. Look down the tube. (?)
Note the odor, if any. (?)

Compare color and odor with color and odor noted in
Exps. 68 and 70. (?) Study the equations 2KNO 3
4H 2 SO 4 + 3Cu = K 2 SO 4 + 3CuSO 4 + 4H 2 O + 2NO;
and NO + O = NO 2 .


Experiment 79. Preparation of Chlorine from Mn0 2 and
HC1. Fill the curved part of the test-tube with man-
ganese dioxide, MnO 2 .

Pour over this about 2 CC of concentrated hydro-
chloric acid, HC1. Warm the mixture gently. (?)


Cautiously inhale a little of the vapor which arises.
(?) Note color. (?)

Hold moist litmus paper over the mouth of the
tube. (?)

Complete and balance the equation MnO 2 + HC1
==MnCl a +?+?

Dry chlorine will not bleach dry litmus paper. Com-
plete the equation and show that the bleaching is an
oxidation process. H 2 O + Cl = HC1 + ?

Experiment 80. Preparation of Chlorine from KC10 3
and HC1. Properties. Fill the curved part of the test-
tube with KC1O 3 . Add l cc of HC1. (?) Compare
Exp. 79. (?)

Attach a cork and delivery tube to the test-tube and
let the gas bubble through some clear water for a mo-
ment. Examine the solution. Note color, odor, etc.

Add a drop of the solution to 5 c c of aniline solution
in a tube. (?)

Make some marks with ordinary red ink on a piece of
printed newspaper, place in an evaporating dish, and
pour over it the remaining solution of chlorine in
water. ( ? )

Printers' ink is mineral or inorganic ; aniline red,
organic. What statement may be made concerning the
bleaching powers of chlorine ?

Experiment 81. Chlorine and Combustion. Generate
chlorine in a test-tube by the action of hydrochloric acid
on potassium chlorate. By means of a delivery tube
pass the gas into a small empty bottle placed upright on
the table and nearly covered by a glass slip.

When the bottle is full of gas, as indicated by the


color, plunge a lighted match or pine splinter into the
bottle. (?)

Hydrogen has a strong affinity for chlorine. (?)
Carbon is set free. Note the loss of color after the
lighted stick has been placed in the bottle of chlorine.

Compare Exp. 22. (?) Show how they differ. Try
a strip of litmus paper in the bottle after using the
splinter. (?) Does chlorine support combustion ?

Complete the equation H 2 + C1 2 = ?

Does the litmus paper show the presence of an acid ?
When H burns in O, what is the product ? Form the

Experiment 82. Preparation of HC1 from Common Salt.
Take in a test-tube about .5 gram of anhydrous sodium
chloride, common salt, NaCl.

Add 1 c c of concentrated sulphuric acid, H 2 SO 4 . Heat
gently. (?) Very cautiously inhale a little of the vapor
arising from the tube. (?)

Compare the results of Exp. 79. (?) Bring am-
monia on a stirring rod over the mouth of the tube.

Complete the equation HC1 + NH 3 = ? Hold a
strip of litmus paper over the tube. (?) Compare
Exp. 79 again. (?) Complete the equation 2NaCl
+ H 2 S0 4 = ? + ?

Note the white vapors coming from the tube at the
outset of the experiment. (?) HC1 is very soluble
in cold water.

Experiment 83. Test for HC1 or a Chloride. Take 5 c c
of the solution to be tested in a tube. Add a few drops
of a solution of silver nitrate, AgNO 3 . (?)

Divide the precipitate into two parts : To the first add
a few drops of nitric acid. (?) To second, ammonia. (?)


It is necessary, in all tests, to remember that the color
of the precipitate, and its solubility or insolubility in
certain reagents, are distinguishing characteristics.

The presence of a chloride is proved by the fact that
no other class of substances will act in the same way
with the same reagents.


Experiment 84. Preparation of Bromine from a Bro-
mide. Take in a tube, fitted with a cork and glass de-
livery tube, a crystal of potassium bromide, KBr ; cover
with manganese dioxide, MnO 2 , and add l cc of cone.
H 2 S0 4 . (?)

Attach the delivery tube to the generating tube, and
put the end into a clean test-tube held upright in a
tumbler of cold water. The bromine vapors condense
on the cold sides of the tube. Note color, odor, effect
on litmus paper, etc. (?) It may be necessary to heat
the mixture slightly.

Balance the equation KBr + MnO 2 + H 2 SO 4 =
MnSO 4 + HKSO 4 + H 2 O + Br.

Experiment 85. Test for Free Bromine. The Ether
Test. Place in a test-tube about 5 CC of the solution to
be tested. Pour into this about 1 c c of ether. Shake
the tube and let contents settle. Keep the mouth of
the tube closed to prevent the escape of the ether.

Ether rises to the surface. Why ? Any change in
the color of the solution or ether ? What and why?

From the color of the vapor in Exp. 84, what color
would you expect for the ether in this case ? Add a
drop of potassium hydroxide, KOH. Shake. (?)


Experiment 86. Test for Free Bromine, The CS 2 Test.
Add to the solution of free bromine in a test-tube .5 c c of
carbon disulphide, CS 2 ; shake vigorously and let settle.

The CS 2 does not mix with water, but, being heavier,
sinks to the bottom of the tube.

Note color of the CS 2 ; also the color of the solution
before and after treatment with CS 2 . (?) Compare
the ether test. (?)

Experiment 87. Test for a Bromide. The Silver Nitrate
Test. Take about 5 c c of the solution to be tested in a
tube. Add two or three drops of a solution of silver
nitrate, AgNO 3 . (?) Compare the precipitate with
that obtained in Exp. 83. (?) It should be a little
more yellow. (?)

Shake the precipitate well and divide into three parts.
Try the solubility of the precipitate in nitric acid. (?)
In ammonia. (?) and in potassium cyanide, KCy. (?)

How does a test for a bromide differ from that for
a chloride ?

Experiment 88. Test for a Bromide. The Chlorine Test.
To 5 c c of the solution to be tested, add .5 c c of carbon
disulphide. Shake. (?)

Add a drop of chlorine water. (?) Shake. (?)
Continue to add the chlorine water by the drop, each
time shaking the tube. (?)

Chlorides are more stable than bromides or iodides.

Complete and balance the equation KBr + Cl = KC1
+ ? Compare Exp. 86. (?)

An excess of chlorine water will cause a disappear-
ance of color, owing to the formation of the compound,
BrCl 3 . Account for the brown color produced on first
adding the chlorine water.



Experiment 89. Preparation of Iodine from an Iodide.

Treat a crystal of potassium iodide, KI, precisely as you
did the bromide in Exp. 84, omitting the apparatus
for collecting. Compare results with Exp. 84. (?)

Examine the crystals collected on the sides of the
tube. (?) Heat them gently. (?) Compare Exp. 4.
(?) Note odor and weight of the vapor. Touch the
crystals with the finger. (?)

Experiment 90. Test for Free Iodine. Treat the solu-
tion to be tested with CS 2 as in Exp. 86. (?)

How may iodine be distinguished from bromine ?

Add a drop of the solution to l cc of starch solu-
tion. (?) See Exp. 46. (?)

Experiment 91. Some Brilliant Iodides. Take about
5 CC of a solution of mercuric chloride, HgCl 2 in one
tube ; of silver nitrate, AgNO 3 , in another ; of lead
acetate, Pb(C 2 H 3 O 2 ) 2 , in another.

Add one or two drops of a solution of potassium
iodide to each. Note the color of the precipitate in
each. (?)

Complete the equations HgCl 2 -f- KI = ? + ?, Ag NO 3
+ KI = ? + ?, Pb(C 2 H 3 2 ) 2 + KI = ? + ? Name the
iodides formed.

Experiment 92. Test for an Iodide. The Silver Nitrate
Test. To about 5 c c of the solution to be tested add
one or two drops of silver nitrate. (?)

The precipitate should have the same color and ap-


pearance as the second in Exp. 91. (?) Compare
with the test for a bromide, Exp. 87. (?)

Divide the precipitate into three parts : Try in turn
with nitric acid, (?) Ammonia, (?) and Potassium
cyanide, KCy. (?)

Compare the results with those of Exp. 87. (?)
How does the bromide test differ from the iodide ?

Experiment 93. Test for an Iodide. The Chlorine Test.
Treat the solution exactly as in Exp. 88, testing for
bromides. (?) Note difference. (?)

The colorless compound of iodine <ind chlorine has
the formula IC1 3 . Notice that the bromine and iodine
tests and, in fact, many of their chemical characteristics,
are similar.

Experiment 94. Detection of Chlorides, Bromides, and
Iodides in the same Solution. Preliminary Treatment.
Take about 10 cc of a solution containing NaCl, KBr,
and KI. Add two or three drops of AgNO 3 solution
and shake the tube vigorously. (?) See Exps. 83, 87,
and 92.

Continue to add the AgNO 3 by the drop, until no
further precipitation occurs. The precipitate consists
of AgCl, AgBr and Agl. Write the equations.

Filter and wash the precipitate well with hot water.
The last washings should give no precipitate with
HC1. (?)

Second Step. Separation of the Chlorides from the Pre-
cipitate. Wash the precipitate into a clean tube through
a hole in the bottom of the filter, using the least pos-
sible amount of water. Decant to 5 c c

Add 2 or 3 drops (not more) of a solution of KBr,


and boil for several minutes. The AgCl, only, is
affected. Reaction : AgCl + KBr = AgBr + KCL

Filter and test the filtrate for a chloride by Exp.
83. (?) The AgBr is insoluble, the KC1 is soluble,
and hence is found in the nitrate.

Third Step. Separate the bromides from the iodides
by treating the precipitate from which the chlorides
have been removed with 3 or 4 drops of a solution of
KI, as in the second step. *

This time the reaction is AgBr + KI = Agl + KBr.
The KBr is found in the nitrate on filtering, and is
tested by Exp. 88. (?)

The iodides are identified by the yellow color of the
remaining precipitate, and its difficult solubility in
NH 4 OH.

Fourth Step. Another test for the bromides and
iodides is applied directly to the original solution. It
depends upon the difference in degree of the chemism
of chlorine for the bromides and iodides.

Take 5 CC of the original solution. Add 2 or 3 drops
of CS 2 . Now add chlorine water, a few drops at a
time, shaking in order to mix, and note the changes.
Compare with the chlorine tests for bromides and

Note that the success of the test depends upon the
gradual addition of the chlorine water. Which are
more stable in the presence of chlorine, bromides or
iodides ?

Experiment 95. Hydrofluoric Acid, HF, and Etching
on Glass. (This experiment should be performed in the
gas chamber by the instructor.)

Coat a piece of glass, by dipping into melted paraffin,


and standing it on edge to cool. The coat should be
thin and smooth.

Trace with a pin or needle the desired figure, cutting
through the paraffin to the glass. It is now ready for
treatment with the acid.

Place in a lead dish some powdered CaF 2 , fluor-
spar. Pour over it about 5 CC of cone. H 2 SO 4 , and sus-
pend the glass, face down, over the dish, and as near as
possible to it.

After the action ceases, warm the glass over the
flame, and with a dry cloth wipe off the melted paraffin.

The design will be found etched into the glass.
Equations : CaF 2 + H 2 SO 4 = CaSO 4 + ? and SiO 2
+ HF = SiF 4 + ? Complete and balance.


Experiment 96. Some Properties of Charcoal. Arrange
a filter paper in a funnel. Place on it a small spoonful
of powdered charcoal. Pour on the charcoal about
10 c c of a solution of red aniline, and catch the filtrate
in a clean tube. (?)

As soon as the solution has passed through, pour
on the same or a fresh portion (the first will do) about
5 c c of a solution of potassium bichromate, K 2 Cr 2 O 7 ,
and catch the filtrate in a clean tube. (?) The first
is an organic color; the second, inorganic. (?)

Experiment 97. Hydrocarbons. Methane or Marsh Gas,
CH 4 . Fit a test-tube with a cork, and a delivery tube
fitted with a jet. Place in the tube about 5 c c of a mix-
ture of 2 pts. of sodium acetate, NaC 2 H 3 O 2 ; 8 pts. of
sodium hydroxide, NaOH ; and 2 pts. of calcium oxide,


Heat the tube and contents carefully, but strongly
and persistently, bringing the jet near the flame to
ignite the gas which is evolved. Note the odor of gas
(?) and flame. (?)

In this reaction is the calcium oxide changed?
Compare with the action of manganese dioxide in Exp.
25. (?) Complete the equation NaC 2 H 3 O 2 + NaOH
== Na 2 C0 3 + ?

Experiment 98. Hydrocarbons. Ethylene or Olefiant
Gas, C 2 H 4 . Fit a test-tube as in Exp. 97. Place in it
about 3 c c of alcohol and 2 c c of cone, sulphuric acid.

Heat the tube and contents carefully, bringing the
jet near the flame as before. Compare the flame with
that of Exp. 97. Complete the equation C 2 H 6 O = ?


The acid is not decomposed. It is hygroscopic (?)
and extracts water from the alcohol. Compare Exp. 18.

From an inspection of the formulae CH 4 and C 2 H 4 ,
would you expect the difference in the flames of marsh
and olefiant gases ? Explain.

Experiment 99. Destructive Distillation of Coal. Coal
Gas. Place in a test-tube, fitted with a delivery tube and
jet, a few pieces of coarsely powdered bituminous coal.

Strongly heat the tube and contents, noting changes
which take place. (?) Care must be taken to hold
the tube in a horizontal position, to prevent any moist-
ure, which may condense on the cooler parts, from
running down into the hotter part and breaking the

Bring the jet near the flame, as in Exps. 97 and 98.-
(?) Collect a small bottle of the gas and test, as in
Exps. 51 and 55. (?)


Experiment 100. Destructive Distillation of Wood.
Wood Gas. Treat a few thoroughly dried pine shavings
in the same way that you did the coal in Exp. 99, taking
the .same precautions, and noting the same points. (?)

Experiment 101. Detection of Ammonia, NH 3 , and Hy-
drogen Sulphide, H 2 S, in Coal Gas. Place on the top of
the burner under a hood or in a strong draught, a strip
of moistened red litmus paper and a strip of bibulous
paper moistened in lead acetate solution. Close the
holes at the base of the burner, and turn on the gas. A
current of gas will flow out against the papers. (?)
The ammonia, if present, will change the litmus. (?)
The hydrogen sulphide will change the lead acetate to
the sulphide which is black. (?)

Experiment 102. Detection of Carbon Dioxide, C0 2 , in
Coal Gas. Place a small bottle on the table, add 10 cc of
a solution of calcium hydrate, Ca( OH ) 2 and fill with

1 3 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 3 of 6)