Remove the connecting tube from the gas burner.
Insert a short glass tube and pass the gas slowly through
the solution in the bottle.
If carbon dioxide is present the liquid becomes milky,
calcium carbonate being formed.
Equation: Ca(OH) 2 + CO 2 = CaCO 3 + H 2 O. (?)
Experiment 103. Carbon Monoxide, CO. Preparation and
Properties. Place in a test-tube fitted with a cork and
delivery tube with jet, a few pieces of coarsely pow-
dered potassium ferrocyanide, K 4 FeCy 6 with about
5 CC of cone, sulphuric acid.
Heat the tube carefully, and note the odor, color, etc.
of the gas which escapes. Bring the jet near the flame.
(?) Note -the color, odor, and reaction of the products
of the flame.
104 LABORATORY GUIDE IN CHEMISTRY.
Does the gas evolved change blue litmus paper?
Does the product of the flame change the paper ? Com-
plete the equation K 4 FeC 6 N 6 + 6H 2 SO 4 + 6H 2 O =
K 2 S0 4 + FeS0 4 + ( NH 4 ) 2 SO 4 + ?
Experiment 104. Carbon Dioxide, C0. 2 . Preparation from
CaC0 3 and HC1. Fit a generating bottle with a delivery
tube, and arrange to collect four bottles of gas over
Place in the generator a few pieces of marble, calcium
carbonate, CaCO 3 ; cover with water, and add enough
cone, hydrochloric acid, HC1, to cause a rapid evolution
of gas, which proceed to collect. Note color and odor
ofC0 2 . (?)
When the gas has been collected, wash and save the
remaining marble. Complete the equation CaCO 3 +
2 HC1 = CaCl 2 +? + ? The gas will be used in Exp.
Experiment 105. Carbon Dioxide, C0 2 . Some Properties.
() Place a bottle of CO 2 on the table, covered.
Light a pine splinter, and introduce into the bottle. (?)
Repeat the experiment, keeping the bottle covered
when possible. (?)
( b ) Take a fresh bottle of CO 2 , as in #, hold a strip
of magnesium ribbon with nippers, ignite and introduce
as before. (?*) Compare the action. (?) Does CO 2
support combustion ? Account for the presence of
black particles found. (?) Compare Exp. 29. (?)
Complete the equation CO 2 + 2Mg = MgO + ?
(<?) Place a small candle upright in a common
tumbler, near the side. Partly close the opening with
the hand, and pour over the flame the contents of a
bottle of carbon dioxide gas. (?) Is CO 2 a heavy
gas ? Why ?
106 LABORATORY GUIDE IN CHEMISTRY.
Experiment 106. Carbon Dioxide, C0 2 , continued. Pour
into a bottle of carbon dioxide about 5 c c of calcium
hydroxide, Ca(OH ) 2 . Cover quickly and shake vig-
orously, noting appearance from time to time. (?)
Complete the equation : Ca( OH ) 2 + CO 2 = ? + ?
Calcium carbonate is soluble in an excess of carbon
dioxide. Does that explain the changes noted during
the shaking ? Try the solution in the bottle with litmus
paper. (?) Moisten litmus paper with Ca(OH) 2 . (?)
Experiment 107. Carbon Dioxide, C0 2 , exhaled from the
Lungs. Place about 10 cc of a clear solution of calcium
hydroxide in a test-tube. By means of a glass tube
exhale air from the lungs so that it shall bubble up
through the liquid. (?)
Compare with Exp. 106. (?) Is carbon dioxide
exhaled from the lungs ? Explain your answer.
Experiment 108. Test for Carbonates. All carbonates
effervesce (?) when treated with strong acids, such as
hydrochloric and sulphuric acids.
Touch specimens of carbonates with a glass rod mois-
tened with one of these acids. (?) What is the gas
evolved? Compare Exp. 5. (?)
State the difference between common limestone and
Experiment 109. Cyanides. Carbon and Nitrogen. Test
for a Cyanide. Take about 5 CC of the solution in a test-
tube. Add about two drops of potassium hydroxide,
KOH ; then about three drops of a solution of ferrous
sulphate, FeSO 4 . Shake the tube, and acidulate (?)
with hydrochloric acid. (?)
Prussian blue is formed if a cyanide is present. (?)
108 LABORATORY GUIDE IN CHEMISTRY.
SULPHUR AND SULPHUR COMPOUNDS.
Experiment 110. Amorphous or Plastic Sulphur. Take
a spoon half full of flowers of sulphur. Hold in the
hot flame and notice that it first melts to a clear liquid,
then turns dark, thickens, and requires more heat to
again melt it.
Heat strongly and quickly until the sulphur boils
vigorously, and is thin enough to run. When suffi-
ciently heated, quickly pour the molten sulphur into a
dish of cold water. (?)
Examine the product. What does it resemble? Is
it still sulphur ?
Why is it called plastic ? Lay the product away and
examine to-morrow. (?) This experiment should be
performed under the hood.
Experiment 111. Sulphur Crystals deposited on Cooling.
Heat common sulphur in a tube until it boils freely
and pours easily. Now move so that the inside surface
of the tube is coated with the molten sulphur and let
it drain down.
As the cooling progresses, crystals of great variety of
form accumulate on the sides of the tube.
Examine the sublimate collected about the mouth of
the tube. (?) Compare with flowers of sulphur. (?)
Examine some of the yellow powder under the micro-
scope. (?) Is it sulphur ?
Experiment 112. Sulphur Crystals deposited from CS 2
Solution. Place on a watch-glass some flowers of sul-
phur. Pour upon the sulphur just enough carbon di-
sulphide to dissolve it. Let the watch-glass stand until
110 LABORATORY GUIDE IN CHEMISTRY.
the liquid has evaporated. (?) Examine with the
Draw in your note-book the outline of one of the
crystals. Are the crystals transparent?
Experiment 113. Hydrogen Sulphide, H 2 S. Prepara-
tion and Properties. Fit a test-tube with a good cork
and delivery tube with jet. Put in the tube three or four
pieces of ferrous sulphide, FeS, and cover well with water.
Add cone, sulphuric acid cautiously until evolution
of gas takes place freely. Odor? Color? Avoid
inhaling much of the gas, as it is poisonous.
Bring the jet near the flame. (?) Color of flame ?
Note the odor arising from flame ? Complete the equa-
tion H 2 S + 3O = ? + ? State the cause of the odor of
the products of the flame.
Complete the equation FeS + H 2 SO 4 = ? + ? Try
the gas with litmus paper. (?)
Experiment 114. Test for a Sulphide in Solid State.
Treat a small quantity of the powdered substance,
on charcoal with sodium carbonate, before the blow-
Now place the fused (?) substance on a bright silver
or copper coin, and moisten with a drop of water. . If a
sulphide is present a black spot appears. (?)
Wash the coin with water, and if the black spot is
persistent, drop upon it a small quantity of a solution of
potassium cyanide. (?)
The explanation of the reaction is that the sulphide
is changed to sodium sulphide, Na 2 S, which, moistened
in presence of silver or copper, forms silver or copper
sulphide, which is soluble in KCy.
112 LABORATORY GUIDE. IN CHEMISTRY.
Experiment 115. Sulphur Dioxide, S0 2 . Preparation
and Properties. Place in a test-tube fitted with a deliv-
ery tube a few copper clippings. Add about 5 CC of
cone, sulphuric acid. Heat until a gas is evolved.
Pass the gas into a test-tube containing about 10 c c of
water. Save the solution. Note properties of the gas,
as color, odor, etc. As the gas dissolves, the bubbles
become smaller. See Exp. 51.
Try the solution with litmus paper. (?) Complete
the equation SO 2 + H 2 O ? Compare the odor of
the gas with that noticed in Exps. 21, 40, and 110.
( ? ) Complete the equation Cu + 2 H 2 SO 4 = CuSO 4
Account for the color of the solution in the genera-
ting tube. (?) See Exp. 58.
Experiment 116. Sulphur Dioxide, S0 2 . Bleaching Pro-
cess. Moisten the petal of a rose or any colored flower
with the solution of sulphur dioxide obtained in Exp.
115. ( ? ) Compare with Exp. 79. (?)
Now place the petal in a weak solution of sulphuric
acid for a moment ; wash, dry, and warm. (?)
Show by comparison of equations that chlorine
bleaches by oxidation, while sulphur dioxide bleaches
by reduction :
Equations : C1 2 + H 2 O = .HC1 + ? and H 2 SO 3
+ H 2 = H 2 S0 4 + ?
Experiment 117. Test for a Sulphate in Solution. Take
in a tube about 5 CC of the solution. Drop into it
barium chloride, BaCl 2 . (?) Complete the equation
H 2 S0 4 + BaCl 2 = ? + ?
114 LABORATORY GUIDE IN CHEMISTRY.
Try the white precipitate obtained, with nitric, hydro-
chloric, and acetic acids. (?)
Most sulphates are soluble in water. Barium sulphate
is insoluble in water, and in acids ; hence the test.
Experiment 118. Hydrogen Phosphide, or Phosphine.
This experiment should be performed in the gas cham-
ber by the teacher, as the fumes are very poisonous.
Fit a 200 c c Florence flask with a cork and glass
delivery tube. Place the flask on a sand-bath and pass
the end of the QMiv'e^ tube beneath the surface of
water in a dish.
i> i * .
Pour into the flask enough of a strong solution of
KOH (about 1 to 5), to cover the bottom of the flask
to the depth of about inch.
Drop into the KOH solution three pieces of freshly
cut phosphorus, about the size of a grain of corn.
Now add about .5 c c of ether ; attach the cork and
delivery tube, taking care that the end dips below the
surface of the water in the dish.
Heat the sand-bath gradually until the contents of the
flask boil briskly. The ether is vaporized, and drives
out the air from flask and delivery tube ; the hydrogen
phosphide which is produced by the combined action of
phosphorus, KOH and H 2 O only coming in contact with
air upon bubbling up out of the water in the dish. (?)
To stop the action safely, first remove the cork and
delivery tube from the flask, then remove the flask from
Complete the equation 4P -f 3KOH -f ?
3KH 2 PO 2 + ?
UlU KAPH MIM LI
CHSM. 3LD7. U. C
A^c^ss ion No
116 LABORATORY GUIDE IN CHEMISTRY.
' Experiment 119. Tests for Common Acids. Examine
four liquids and four solids each containing one acid,
either as free acid, acid or normal salt, using the follow-
ing table :
A. IT is A LIQUID AND NEUTRAL.
Evaporate to dryness over a water bath. Proceed
B. IT is A SOLID AND NEUTRAL.
Place some of the solid substance in a test-tube
and add 1 cc of cone. H 2 SO 4 ; note results as
1. Rapid effervescence of an odorless, colorless
Try for a carbonate, Exp. 108 ; also pass the
gas through a clear solution of Ca(OH) 2 .
White precip. indicates a carbonate. See Exps.
106 and 107.
2. Slower effervescence of a gas possessing odor,
but not color :
(a) Odor of rotten eggs. Indicates sulphide.
See Exps. 113 and 114.
(b) Odor of burning sulphur matches. Indi-
cates H 2 SO 3 or H 2 S 2 O 3 . See Exps. 115 and 116.
(<?) Odor of peach blossoms. Indicates HCy.
See Exp. 109.
(d) Odor of vinegar. Indicates acetic acid,
HC 2 H 3 O 2 . Prove it is an acetate by dissolving
the solid substance in H 2 O, adding some Fe 2 Cl 6
and boiling. A red solution of ferric acetate.
118 LABORATORY GUIDE IN CHEMISTRY.
Fe 2 (C 2 H 3 O 2 ) 6 , whose color is destroyed by HC1
is produced, in case the substance is an acetate.
(e) An irritating odor indicates HNO 3 ,
Exp. 78 ; HC1, Exp. 83 ; or HF, Exp. 95.
3. On warming gently, a gas having an irritat-
ing odor and a color indicates HI, Exps. 89, 92,
and 93; HBr, Exps. 84 and 88; or, HNO 2 ,
4. A crackling sound or sudden explosion indi-
cates HC1O 3 . See text for the production of
chlorine tetroxide, C1 2 O 4 . Shep., p. 101.
5. If none of these acids are found, try for
H 2 SO 4 , Exp. 117.
C. IT is A LIQUID AND ACID : In this case it
may be a free acid or an acid salt. Try the solution
1. Try for a sulphate, H 2 SO 4 , by first acidu-
lating with HC1 and then proceeding as in
2. Try a fresh portion with HNO 3 and a drop
of AgNO 3 : white prec. indicates HC1 ; yel-
lowish white, HBr ; yellow, HI ; brown to
black, H 2 S. Try as in B for each in turn.
3. Try in order as in B for HNO 3 , H 2 CO 3 ,
HC 2 H 3 O 2 and HC1O 3 .
m ~9 m o
NOTE. The teacher should take care to use only the commonest
compounds for the above tests.
120 LABORATORY GUIDE IN CHEMISTRY.
COMMON METALLIC ELEMENTS.
Lead, Silver, and Mercury.
Experiment 120. Amalgams, (a) Take in a test-tube
a small globule of mercury. Cover the mercury with a
1 to 5 solution of silver nitrate, AgNO 3 . (?) Do not
shake the tube.
(6) Place in a tube small pieces of copper, zinc, and
iron. Cover them with a solution of mercurous nitrate,
HgNO 3 . After standing a few moments, examine.
(?) Remove the metals. Wipe them with the finger.
(?) Rub them a moment. (?) Which are perma-
nently affected ? Compare the two experiments, a and b.
Equations: (a) Hg + AgNO 3 = HgNO 3 + Ag. The
crystals obtained are composed of Hg and Ag. (5)
2 HgNO 3 + Zn = Zn (NO 3 ) 2 + Hg 2 . Copper and iron
reactions are similar. Write them. In this case the
mercury forms a coating on the metals, and no crystals.
Experiment 121. Lead. Precipitation by Means of Zinc.
Place in a test-tube a strip of metallic zinc. Pour over
it about 5 cc of a solution of lead acetate, Pb(C 2 H 3 O 2 ) 2 .
Do not shake the tube. Note any changes. (?) Ex-
amine product carefully.
Wash thoroughly with water, remove from the tube,
and scrape the deposit off the zinc. Save for testing in
Exp. 123. Complete the equation Pb (C 2 H 3 O 2 ) 2 + Zn
= Zn(C 2 H 3 O 2 ) 2 + ? Explain the action.
NOTE. Remember to pour all solutions containing silver into a
receptacle kept on th table for the purpose. Also never pour mercury
or mercury solutions into the sink.
122 LABORATORY GUIDE IN CHEMISTRY.
Experiment 122. Lead. Preparation from Galena on
Charcoal. Place on a piece of charcoal about .1 gram of
pulverized lead sulphide, galena, PbS. Cover with a
little sodium carbonate, Na 2 CO 3 , and heat in the redu-
cing flame before the blowpipe. (?)
Note appearance of globules. (?) Remove the glob-
ules and try hardness, malleability, etc.
Why did you use sodium carbonate ? Give properties
of lead noted.
Experiment 123. Tests for Lead in Solution. Place
the product of Exp. 121 in a tube ; cover it with dilute
nitric acid and warm. Why? As soon as action
ceases dilute with about 10 c c of water.
Now divide the solution into five parts, and treat as
follows: To one, add hydrogen sulphide. (?) To
second, potassium bichromate. (?) To third, ammo-
nium carbonate. (?) To fourth, potassium iodide.
(?) To fifth, sulphuric acid. (?)
The precipitates should be black, yellow, white, yellow
and white in order. (?)
Name the products and write the equations.
Experiment 124. Silver. Precipitation by Zinc. Treat
a strip of metallic zinc with about l cc of a solution of
silver nitrate, just as in Exp. 121. (?) Compare
Save the product as before, for use in testing for
silver. Complete the equation 2AgNO 3 + Zn = ? -+- ?
Experiment 125. Silver. Precipitation by Chloral Hy-
drate. Take about 1 c c of silver nitrate solution in a
tube. Add two drops of chloral hydrate solution, and
make alkaline with a drop of ammonia.
124 LABORATORY GUIDE IN CHEMISTRY.
Heat the tube, rolling it in the fingers until a brignt
coating appears. What is it? Chloral hydrate is a
reducing agent. What action has taken place ?
Since silver is soluble in nitric acid, suggest a good
way to clean your tube. (?)
Experiment 126. Silver. Tests for Silver in Solution.
Dissolve the product of Exp. 124 in dilute nitric acid
and add enough water to make about 10 cc of the solu-
tion. To one-half 'of the solution add about two drops
of hydrochloric acid. (?) Compare Exp. 83. (?)
Divide the precipitate into two parts: Try one with
nitric acid ( ? ) ; the other with ammonia. (?)
Through the remainder of the solution of silver, pass
hydrogen sulphide. (?) Divide the precipitate into
two parts : Try one with potassium cyanide, ( ? ) ; the
other with cone, nitric acid. (?)
Experiment 127. Mercury. Precipitation by Zinc. Treat
a small piece of metallic zinc with about 1 c c of mercu-
rous nitrate Hg 2 (NO 3 ) 2 as in Exps. 121 and 124.
Compare the product with the corresponding ones
with lead and, silver. (?) May they be easily dis-
tinguished in this way? Complete the equation
Hg 2 (NO 3 ) 2 + Zn = ? + ? Save the product for the
test in Exp. 128.
Experiment 128. Mercury. Test for " ous" Mercury in
Solution. Carefully wash the mercury obtained in Exp.
127 and wipe and remove the zinc remaining. Dissolve
the mercury in a little dilute nitric acid. (?) Make
it up to about 5 c c with H 2 O.
Add two or three drops of hydrochloric acid. (?)
Filter the precipitate and wash on the filter with a few
drops of ammonia. (?) Compare Exp. 126, first part.
126 LABORATORY GUIDE IN CHEMISTRY.
What is the action and what the black substance
produced ? Could you distinguish silver and mercury
in this way?
Experiment 129. Separation of Metals of Group I. in the
Part I. Take in a tube about 10 c c of the solution
containing the metals. Add hydrochloric acid, by the
drop, as long as a precipitate forms. Color?
Filter and wash the precipitate with a little cold water.
Why not much H 2 O? The nitrate may be thrown
The precipitate is composed of the chlorides of the
three metals. See Exps. 126 and 128, and remarks on
the precipitation of lead by hydrochloric acid, in text.
Part II. Wash the precipitate well with hot water, and
catch the filtrate in a clean tube. Lead chloride is solu-
ble in hot water. Hence it will be found in the filtrate.
The remaining precipitate will be disposed of in Part III.
Divide the filtrate into three parts ; try with potassium
bichromate, (?) potassium iodide, (?) and sulphuric
Precipitates should be formed in each case correspond-
ing with those of Exp. 123. Does this prove sufficiently
the presence of lead ?
Part ffl. Place the filter with the precipitate in-
soluble in hot water, over a clean tube, and wash well
with 2 CC or 3 CC of ammonia. See Exps. 126 and
The silver chloride dissolves and filters through, while
the black deposit remaining on the filter is sufficient
proof of the presence of mercury.
128 LABORATORY GUIDE IN CHEMISTRY.
It remains to show that the silver is present in the
filtrate. Add, by the drop, strong nitric acid until a
change is noted. (?) Explain by reference to Exp.
A reappearance of the familiar white precipitate of
Exps. 83 and 126 is proof of the presence of silver.
Arsenic, Tin, and Copper. 1
Experiment 130. Arsenic. Preparation from the Oxide.
Make a small ball of arsenic trioxide, As 2 O 3 , with pow-
dered charcoal and a drop of water.
Place the mixture in a tube closed at one end, made
by heating the end of a short glass tube (about three
inches long) in the gas flame until it melts and closes.
Heat carefully and strongly. Examine the inner
surface of the tube. (?) Note the odor, if any. Do
not inhale the vapor freely. (?)
Experiment 131. Arsenic. Marsh's Test. Arrange to
generate hydrogen by the action of pure zinc and dilute
H 2 SO 4 , in a test-tube fitted with a delivery tube and jet.
Before adding the H 2 SO 4 , put into the tube with the
zinc and water three or four drops of a solution of
arsenic acid, H 3 AsO 4 .
Pour in the H 2 SO 4 and pass the gas through the
apparatus until air is entirely expelled. (?) Now
light the gas issuing from the jet, and bring in contact
with the flame a cold piece of porcelain. A bright gray-
1 For other metals of this and following groups, see Shepard.
NOTE. As hydrogen arsenide is a highly poisonous gas, it would be
safest to have only one generator, and that in the gas chamber. Any
number of spots may be obtained from it.
130 LABORATORY GUIDE IN CHEMISTRY.
ish spot or mirror appears on the porcelain. It is
Produce several spots and immediately stop the action
by washing out the contents of the tube.
The action is thus explained: Nascent hydrogen acts
upon the arsenic acid, producing a gas highly poison-
ous and inflammable, hydrogen arsenide, AsH 3 . This
gas burns along with the hydrogen evolved from the
zinc and H 2 SO 4 , and when the cold porcelain surface is
brought to the flame, the arsenic is cooled below the
point of ignition and deposited as a mirror. Compare
Proceed to test the spots as follows : (a) Moisten one
with (NH 4 ) 2 S 2 ; it turns yellow.
(6) Add a drop of HC1 to another ; it does not
(tf) Treat another spot with a drop of a solution of
chlorine in KOH ; it dissolves.
(d) To another add hot HNO 3 ; it dissolves clear.
To the clear solution add a drop of AgNO 3 ; no change.
Now allow vapor of NH 3 to come in contact with the
solution ; it turns brick red or yellow.
These tests completely identify the arsenic, as anti-
mony, which also forms spots similar to the arsenic
spots, gives slightly different results with the same treat-
ment. Compare text on antimony.
Experiment 132. Tin. Precipitation by Zinc. Treat a
strip of metallic zinc with 5 CC of a solution of stannous
chloride, SnCl 2 , just as in the preparation of lead,
silver, and mercury. (?) Compare Exps. 121, 124,
and 127. (?) Mention any properties of tin noted.
Could crystals of lead, silver, and tin precipitated by
132 LABORATORY GUIDE IN CHEMISTRY.
zinc be distinguished by their form, color, and general
characters? Save the product to test for tin in the
Experiment 133. Tests for Tin. Remove the crystal-
line deposit obtained in Exp. 132 from the zinc ; wash
thoroughly with H 2 O, and dissolve in the least possible
amount of dilute HC1. Heat if necessary. Dilute
with H 2 O to 10 cc .
Take 5 CC of the solution in each of two tubes. To
one add a drop of mercuric chloride, HgCl 2 . If tin is
present in " ous " condition, a white precipitate, which
soon turns black, will follow ; if in " ic " condition, no
Through the second part, pass hydrogen sulphide,
H 2 S. A stannous salt yields a brown precipitate, SnS;
a stannic salt, a yellow precipitate, SnS 2 . What is the
character of the solution, " ous " or " ic " ?
Experiment 134. Copper, Precipitation by Iron. Put
a piece of bright iron wire in a test-tube, and pour over
it a solution of copper sulphate, CuSO 4 . (?)
Remove and examine the wire. (?) Give some
properties of copper noted. Complete the equation
Experiment 135. Copper. Eeduction on Charcoal. Treat
some powdered copper sulphate on charcoal with sodium
carbonate, in the reducing flame. (?)
It is difficult to obtain clear beads, but small particles
of the red-brown mass resulting may be washed with
H 2 O, and dissolved in the least possible amount of
dilute HNOo. Color of the solution ? Save this solu-
tion to test for copper in the following experiments.
134 LABORATORY GUIDE IN CHEMISTRY.
Experiment 136. Copper. The Bead Test. Prepare a
borax-bead on a platinum loop, just as before. Dip the
bead while hot into the solution to be tested, and heat
in the oxidizing flame before the blowpipe. >
If the copper is present the bead will be green while
hot, blue when cold. (?)
Now heat the bead in the reducing flame. (?)
Experiment 137. Copper. Tests in the Wet Way.
Dilute the solution remaining from Exps. 135 and 136
to about 10 c c . Divide into three parts.
To one, add two to ten drops of ammonia until changes
cease. ( ? )
Through the second, pass hydrogen sulphide. (?)
Compare the two resulting products. Give a distinc-
tion between solutions and precipitates. (?)
To the third, add one or two drops of potassium fer-
rocyanide, K 4 FeCy 6 . If copper is present in small
quantity, a reddish-brown solution is formed ; if plenti-
ful, a precipitate of the same color. (?)
Iron, Chromium, Aluminum, Nickel, Cobalt, and Zinc.
Experiment 138. Iron. Tests for "ous" and "ic"
Salts in Solution. Both ferrous and ferric salts are tested
by the same reagents. The condition of the salt is de-
termined by the action of the reagents, producing results
peculiar to each condition.
Prepare a solution of a ferrous salt by dissolving a
small clear green crystal of ferrous sulphate, FeSO 4 ,
in!0 cc of coldH 2 O.
Divide into four parts. To the first add one drop of
136 LABORATORY GUIDE IN CHEMISTRY.
potassium sulphocyanide, KCyS. (?) To the second,
one drop of potassium ferrocyanide, K 4 FeCy 6 . (?)
To the third, one drop of potassium ferricyanide,
K 3 FeC3v (?) To the fourth, add one or two dreps
of cone. HNO 3 , and boil for a moment. Any change
When cool, divide into three parts and add a drop of
the same reagents as before, noting carefully each re-