Theodore James Bradley.

A laboratory manual of qualitative chemical analysis for students of pharmacy online

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and other compounds which liberate hydrogen sulphide or sul-
phurous acid when treated with sulphuric acid, must be oxidized
by means of nitric acid and then reduced by means of sulphurous
acid as directed under Preparation of the chemical to be tested,
before introducing them into the apparatus. Sulphur compounds
as well as hydrogen phosphide give a bright yellow band on the test
paper. If sulphur compounds are present, a simultaneous darkening
of the lead acetate test paper and glass wool will occur. If such is
the case, the operation as directed under Preparation of the chemical
to be tested must be repeated upon a fresh portion of the solution
being tested, using greater care in effecting the complete "emoval of
the sulphurous acid. In testing hypophosphites special care should
be observed to completely oxidize the solution being tested as
directed, otherwise a yellow stain may be produced through the
evolution of hydrogen phosphide, which might be confused with the
orange-yellow color produced by arsenic. Compounds containing
antimony should be tested for arsenic by Bettendorf's Test (see Test
No. 2).

The test apparatus should be thoroughly cleaned and dried
immediately before and after use.

2 Arsenic test, Bettendorf's. This test is employed only in test-
ing salts of bismuth and compounds containing antimony for the
presence of arsenic.

To a solution of the prescribed quantity of the substance to be
tested in 5 mils of concentrated hydrochloric acid contained in a
clean test tube, add 10 mils of saturated stannous chloride T.S.
which has been freshly prepared, and set it aside for thirty minutes.
If arsenic is present in non-permissible amounts, a brownish tint or
precipitate will be seen when the tube is placed over a white surface
and the solution viewed from above, comparison being made with
a mixture of 5 mils of concentrated hydrochloric acid and 10 mils
of concentrated stannous chloride T.S., prepared as directed above.

NOTE : It is absolutely necessary that for this test the solution of
stannous chloride be freshly prepared, and that nitrates, sulphates,
sulphites, sulphides and compounds of mercury, gold, and selenium
be absent from the reagents, and from the chemicals being tested.



118 TESTS OF UNITED STATES PHARMACOPEIA

3 Test for heavy metals. Chemicals. This test is to be used to
detect the presence of undesirable metallic impurities in official
chemical substances or their solutions; these must not respond
affirmatively within the stated time. Acidulate 10 mils of a solution
of the substance in distilled water (1 in 50), contained in a test tube
of about 40 mils capacity and of about 2.5 cm. diameter, with 1 mil
of diluted hydrochloric acid (unless otherwise directed), warm it
to about 50 C., add an equal volume of freshly prepared hydrogen
sulphide T.S ., stopper, and allow the mixture to stand at 35 C.
for half an hour. At the end of this time the mixture should still
possess the odor of hydrogen sulphide; if not, it should be thoroughly
saturated with the gas and again set aside for half an hour. The
color produced, if any, is not greater than that observed by a blank
test made in the same manner and with the same quantities of the
reagents (omitting the solution to be tested); the solutions being
viewed crosswise by reflected light while held against a white sur-
face. A slight turbidity due to separation of sulphur from the
hydrogen sulphide may occur.



DESTEUCTION OF ORGANIC MATTER.

If organic matter is present in a sample, it is necessary to destroy
it before proceeding with a qualitative analysis for inorganic bases
and acids. There are several methods for accomplishing this, of
which the most generally useful are the following :

A. Mix the sample with an excess of concentrated HC1, add some
crystals of KC1O 3 and boil under a hood until the mixture is decolor-
ized or a portion does not carbonize upon drying and igniting. Add
additional HC1 and KC1O 3 as necessary, avoiding a large excess.
Then evaporate the liquid to dryness on a water bath and examine
the residue by the method for the qualitative analysis of a solid.

This method destroys the organic matter, or changes it so that it
does not interfere with the analysis. The metals present are
oxidized to their highest valences, and ammonium salts are volati-
lized. Allowance must also be made for the potassium and chlorine
compounds added.

B. Mix tbe sample with about 4 times its weight of concentrated
H 2 S04 and twice its weight of concentrated HNO 3 , digest at the
ordinary temperature for several hours, and then heat in a hood until
the white fumes of H 2 SO4 are given off. If the mixture still contains
black carbonized organic matter, add more HNO 3 and repeat the
heating until white fumes are given off, repeating this treatment
with additional HNO 3 and heating several times if necessary. When
the mixture ceases to show the presence of carbon, cautiously add
about an equal volume of water and concentrate until the white
fumes of H 2 SO4 are given off, then cautiously add four or five times
the volume of water and filter, if necessary. Examine the filtrate
by the method for the qualitative analysis of a liquid. Any residue,
on the filter paper, may contain silica or the sulphates of lead,
barium, strontium and calcium. Examine it by the method for
the qualitative analysis of a solid, beginning with paragraph F on
page 108.

This is the most dependable method for the destruction of organic
matter. Allowance must be made, however, for the H 2 SO 4 and
HN0 3 used, and it is often necessary to use both of these methods,
or others, in making a careful qualitative analysis of a substance
containing organic matter.



REAGENTS AND TEST SOLUTIONS.

On- the following pages will be found directions for preparing the
test solutions called for in this book. Most of these are of the
same strength as is specified in the United States Pharmacopoeia,
but for performing the Pharmacopceial tests on official chemicals,
the reagents should be made according to the directions of the
Pharmacopoeia IX, pages 521-583.

In preparing reagents and test solutions, only pure chemicals
and distilled water should be used.

Acetic acid, HC 2 H 3 O 2 . Mix official acetic acid, containing about
36 per cent, of absolute HC 2 H 3 O 2 with twice its volume of distilled
water.

Ammonium hydroxide test solution, NH 4 OH or NH 3 + H 2 O. Use
the official ammonia water, containing 10 per cent, of NH 3 .

Ammonium carbonate test solution, (NH 4 ) 2 CO 3 . Dissolve 20 Gm.
of official ammonium carbonate in a mixture of 20 mils of ammonia
water and 65 mils of distilled water, and add sufficient distilled water
to measure 100 mils.

Ammonium chloride test solution, NH 4 C1. Dissolve 10 Gm. of
ammonium chloride in sufficient distilled water to make 100 mils.

Ammonium molybdate test solution, (NH 4 ) 6 Mo 7 O 2 + 4H 2 O. Mix
6.5 Gm. of finely powdered molybdic acid with 14 mils of distilled
water and 14.5 mils of stronger ammonia water to effect solution.
Cool and slowly add the solution, in small portions with agitation,
to a well cooled mixture of 32 mils of nitric acid and 40 mils of dis-
tilled water. Allow the solution to stand for twenty-four hours
and then filter through asbestos.

Preserve the test solution in the dark, and, if a sediment should
form in it after some days, carefully decant the clear solution.
This solution should be tested at frequent intervals. Add 2 mils of
sodium phosphate T.S. to 5 mils of the reagent; an abundant
yellow precipitate forms either at once or upon slight warming. If
only a slight precipitation or yellow opalescence results, the reagent
must be rejected. When employed as a reagent, ammonium
molybdate T.S. is always added in large excess to the solution being
tested, the latter having previously been strongly acidified with
nitric acid.

Ammonium oxalate test solution (NH 4 ) 2 C 2 O 4 + H 2 O. Dissolve
4 Gm. of ammonium oxalate in sufficient distilled water to measure
100 mils.



FERROUS SULPHATE TEST SOLUTION 121

Ammonium polysulphide test solution, Yellow Ammonium Sul-
phide, (XH 4 ) 2 Sx. Saturate three parts of ammonia water with
hydrogen sulphide, forming a solution of ammonium hydrogen
sulphide, XH 4 HS. Add to the solution two additional parts of
ammonia water, forming a solution of normal or colorless ammonium
sulphide, (NH 4 ) 2 S. Finally add a small quantity of precipitated
sulphur and preserve the solution in small, amber, glass-stoppered
bottles.

Barium chloride test solution, BaCl 2 + 2H 2 O. Dissolve 10 Gm.
of barium chloride in sufficient distilled water to make 100 mils.

Barium hydroxide test solution, Ba(OH) 2 + 8H 2 O. A freshly made
saturated solution of barium hydroxide in distilled water.

Barium nitrate test solution, Ba(NO 3 ) 2 . Dissolve 5 Gm. of barium
nitrate in sufficient distilled water to make 100 mils.

Bromine test solution (bromine water), Br. A saturated solution of
bromine, prepared by adding 3 mils of bromine to 100 mils of cold
water. The solution should be stored in a glass-stoppered bottle
in a cool place, protected from light and should be shaken well,
allowing the excess of bromine to settle before using.

Calcium chloride test solution, CaCl 2 + 2H 2 O. Dissolve 10 Gm.
of calcium chloride in sufficient distilled water to measure 100 mils.

Calcium hydroxide test solution (lime water), Ca(OH) 2 . A nearly
saturated aqueous solution of calcium hydroxide.

Calcium sulphate test solution, CaSO 4 + 2H 2 O. Mix 5 mils of
diluted sulphuric acid with 200 mils of distilled water, add 1 Gm. of
calcium carbonate and shake: when the acid is completely neutral-
ized filter the mixture.

Chlorine test solution (chlorine water), Cl. A saturated aqueous
solution of chlorine, prepared by generating the gas with manganese
and hydrochloric acid, washing and conducting it into cold water
until saturated. The solution should be preserved in small amber
glass-stoppered bottles in a cool, dark place and it should have a
strong odor of chlorine when used*

Cobaltous chloride test solution, Co 4 Cl + 6H 2 0. Dissolve 2 Gm.
of cobaltous chloride with the aid of 1 mil of hydrochloric acid in
sufficient distilled water to measure 100 mils.

Copper sulphate test solution, CuSO 4 + 5H 2 O. Dissolve 10 Gm.
of copper sulphate in sufficient distilled water to make 100 mils.

Ferric chloride test solution, FeCl 3 + 6H 2 O. Dissolve 10 Gm. of
ferric chloride in sufficient water to make 100 mils.

Ferrous sulphate test solution., FeSO 4 + 7H 2 O. Dissolve 10 Gm.
of clear crystals of ferrous sulphate in sufficient distilled water to
make 100 mils. This solution is to be freshly prepared immediately
before use.



122 REAGENTS AND TEST SOLUTIONS

Hydrochloric acid test solution, HC1. Use the official diluted
hydrochloric acid of 10 per cent, strength.

Hydrogen sulphide test solution, H 2 S. A saturated, aqueous solu-
tion of hydrogen sulphide. To prepare about 1000 mils of the solution,
treat 20 Gm. of ferrous sulphide in a suitable apparatus with a mixture
of 20 mils of sulphuric acid and 250 mils of distilled water, pass the gas
through a drying tube filled with granulated calcium chloride, then
from this through a tube of about 8 millimeters diameter and 40 centi-
meters in length, which contains about 5 Gm. of coarsely pulverized
iodine mixed with glass wool, and finally through a wash bottle which
contains a small quantity of potassium iodide T.S. The gas thus puri-
fied is conducted nearly to the bottom of a bottle of the capacity of
about 1500 mils containing 1000 mils of cold distilled water. Shake
the bottle occasionally to facilitate the solution of the gas. When
the gas is no longer absorbed, transfer the solution to small, dark,
amber-colored bottles, fill nearly to the top ; pass a stream of purified
hydrogen sulphide for a few minutes through each, and then at once
stopper them tightly, and preserve them afterwards in a cool and
dark place. Do not use this solution unless it retains a strong odor
of hydrogen sulphide, and, when added to an equal volume of ferric
chloride T.S., produces at once a copious precipitate of sulphur.

Iodine test solution, I. Dissolve 1 Gm. of iodine and 3 Gm. of
potassium iodide, in 50 mils of distilled water.

Lead acetate glass wool, Pb(C 2 H 3 2 )2 + 3H 2 O. Immerse glass
wool in a mixture of equal parts of lead acetate T.S. and water and
remove the excess of liquid by pressing it between filter paper. It
should be prepared immediately before it is to be used.

Lead acetate test paper, Pb(C 2 H 3 O 2 ) 2 + 3H 2 O. Immerse strips
of heavy white filter paper, 6 cm. in width and 8 cm. in length, in a
mixture of equal parts of lead acetate T.S. and distilled water, drain
off the excess of liquid and dry the paper in an oven at 100 C.,
avoiding contact with metal.

Lead acetate test solution, Pb(C 2 H 3 O 2 ) 2 + 3H 2 O. Dissolve 10
Gm. of clear transparent crystals of lead acetate, free from adhering
lead carbonate, in sufficient distilled water to make 100 mils. Pre-
serve the solution in well-stoppered bottles.

Litmus paper and test solution. Exjiaust powdered litmus with
three separate and successive portions (each equal to about 4 times
its weight) of boiling alcohol (which removes the undesirable color
erythrolitmin), each extraction lasting for about one hour. After
draining off the alcohol, digest the residue with about an equal
weight of cold water and filter. (This blue solution, which contains
some alkali, after being acidulated, may be used to make red litmus
paper.) Finally, extract the residue with about 5 times its weight
of boiling distilled water, and, after thoroughly cooling, filter. The



MERCURIC CHLORIDE TEST SOLUTION 123

addition of 1 drop of hundredth-normal acid or alkali V.S. to 50
mils of distilled water containing 5 drops of the indicator produces
a distinct change in color. Preserve the filtrate, as a test solution,
in wide-mouthed bottles stoppered with loose plugs of purified
cotton so as to exclude dust but admit air. The latter must be free
from acid or ammoniacal vapors. The blue color of litmus test
solution is changed by acids to red, and this red color by the addition
of alkalies is restored to blue.

Litmus Paper, Blue. Impregnate with the test solution just
described strips of white filter paper, and dry them by suspending
them on lines of clean twine, in an atmosphere free from acid or
ammoniacal vapors. This paper must quickly respond to a two
hundred and fiftieth-normal acid V.S.

Litmus Paper, Red Prepare this with the same kind of paper and
in the manner described under Litmus Paper, Blue, having added to
the test solution used to impregnate the paper just sufficient of a
highly diluted solution of hydrochloric acid to impart to it a faint
red tint. Neither blue nor red litmus paper should have an intense
color. Preserve the test paper in bottles, so as to exclude dust and
acid or ammoniacal vapors. This paper must quickly respond to a
two hundred and fiftieth-normal alkali V.S.

Magnesia mixture, MgCl 2 + 6H 2 O, NH 4 C1, NH 4 OH.- Dissolve
5.5. Gm. of magnesium chloride and 7 Gm. of ammonium chloride
in 65 mils of distilled water, add 35 mils of ammonia water, set the
mixture aside for a few day& in a well-stoppered vessel, and filter.
If not perfectly clear, filter the solution before using.

Magnesium sulphate test solution, MgSCX + 7H 2 0. Dissolve
10 Gm. of magnesium sulphate in sufficient distilled water to
measure 100 mils.

Manganese sulphate test solution, MnSCX + 4H 2 O. Dissolve 10
Gm. of manganese sulphate in 50 mils of distilled water and add
sufficient diluted sulphuric acid to make 100 mils.

Mercuric bromide test paper, HgBr 2 . Cut stiff, heavy quanti-
tative filter paper into strips 3 mm. in width and about 12 cm. in
length. Immerse these strips for five minutes in alcoholic mercuric
bromide T.S. Remove the excess of solution by pressing the strips
between filter paper and then dry them quickly on glass in an oven
heated to 100 C. Place the strips at once in a wide mouthed
bottle and stopper it securely.

Mercuric bromide test solution, alcoholic, HgBr 2 . Dissolve 5 Gm.
of mercuric bromide in 100 mils of alcohol, employing a gentle heat
to facilitate solution. Keep it in glass stoppered bottles protected
from the light.

Mercuric chloride test solution, HgCl 2 . Dissolve 5 Gm. of mercuric
chloride in sufficient distilled water to measure 100 mils.



124 REAGENTS AND TEST SOLUTIONS

Mercuric potassium iodide test solution (Mayer's reagent), HgI 2 +
2KI. Dissolve 1.358 Gm. of mercuric chloride in 60 mils of dis-
tilled water, and 5 Gm. of potassium iodide in 10 mils of distilled
water. Mix the two solutions, arid then add sufficient distilled
water to measure 100 mils.

Mercuric potassium iodide test solution, alkaline (Nessler's Reagent).
Dissolve 10 Gm. of potassium iodide in 10 mils of distilled water,
and add gradually in portions a saturated aqueous solution of
corrosive mercuric chloride with constant agitation, until a slight red
precipitate remains undissolved; to this mixture add 30 Gm. of potas-
sium hydroxide and, when solution has taken place, 1 mil more of
the saturated aqueous solution of mercuric chloride. Dilute this
solution with distilled water until it measures 200 mils. Allow the
precipitate to subside, and draw off the clear fluid. Two mils of
this reagent, when added to 50 mils of distilled water containing
0.05 mg. of ammonia, produces at once a yellowish brown coloration.

Mercurous nitrate test solution, HgNO 3 . Mix 10 Gm. of pure
mercury with 5 mils of nitric acid and 5 mils of distilled water, in a
porcelain evaporating dish and set it aside for twenty-four hours in a
cool, dark room. Separate and drain the crystals of mercurous
nitrate, and dissolve them in 100 mils of distilled water. Preserve
the solution in a dark amber-colored bottle in which a small quantity
of mercury has been placed.

Nitric acid test solution, HN0 3 . Add 36 mils of concentrated
nitric acid to 290 mils of distilled water and mix. This solution
contains approximately 10 per cent, of absolute HNO 3 .

Oxalic acid test solution, H 2 C 2 O 4 + 2H 2 O. Dissolve 5 Gm. of
oxalic acid in sufficient distilled water to measure 100 mils.

Phenolphthalein test solution. Dissolve 1 Gm. of phenol phthalein
in 100 mils of alcohol. It gives a red color with alkali hydroxides
or carbonates, and acids render the solution colorless. It is not
suitable as an indicator for ammonia nor in the presence of large
quantities of ammonium salts. Phenolphthalein paper is prepared
by impregnating white, unsized paper with the test solution and
drying it.

Potassium carbonate test solution, I\ 2 CO 3 . Dissolve 10 Gm. of
potassium carbonate in sufficient distilled water to measure 100 mils.

Potassium chloride test solution, KC1. Dissolve 10 Gm. of potas-
sium chloride in sufficient distilled water to measure 100 mils.

Potassium chromate test solution, K 2 CrQ4. Dissolve 10 Gm. of
potassium chromate in sufficient distilled water to measure 100 mils.

Potassium cyanide test solution, KCN. Dissolve 5 Gm. of potas-
sium cyanide in sufficient distilled water to measure 100 mils.

Potassium dichromate test solution, K 2 Cr 2 O?. Dissolve 10 Gm.
of potassium dichromate in sufficient distilled water to measure
100 mils.



SODIUM HYPOBROMITE TEST SOLUTION 125

Potassium ferricyanide test solution, K 3 Fe(CN) 6 . Dissolve 1 part
of potassium ferricyanide in about 10 parts of distilled water. This
solution should be freshly made when required, as it undergoes
decomposition with formation of ferrocyanide on standing. A
freshly prepared aqueous solution mixed with ferric chloride T.S.
which has been well diluted with distilled water shows a brown tint,
free from turbidity or a shade of green.

Potassium ferrocyanide test solution, I\ 4 Fe(CN) 6 + 3H 2 0. Dis-
solve 10 Gin. of potassium ferrocyanide in sufficient distilled water
to measure 100 mils.

Potassium hydroxide test solution, KOH. Use the official solution
of potassium hydroxide containing approximately 5 per cent, of
KOH.

Potassium iodide test solution, KI. Dissolve 20 Gm. of potassium
iodide in sufficient distilled water to measure 100 mils, and preserve
the solution in dark, amber-colored, well-stoppered bottles. The
solution should be frequently renewed.

Potassium sulphate test solution, K 2 O 4 . Dissolve 1 Gm. of potas-
sium sulphate in sufficient distilled water to measure 100 mils.

Potassium sulphocyanate test solution, KCNS. Dissolve 1 Gm. of
potassium sulphocyanate in sufficient distilled water to make 100
mils.

Silver nitrate test solution, AgNO 3 . Dissolve 2 Gm. of silver
nitrate in sufficient distilled water to measure 100 mils.

Sodium acetate test solution, NaC 2 H 3 O 2 + 3H 2 O. Dissolve 10
Gm. of sodium acetate in sufficient distilled water to make 100 mils.

Sodium carbonate test solution, Na 2 CO 3 + H 2 O. Dissolve 10
Gm. of monohydrated sodium carbonate in sufficient distilled water
to measure 100 mils.

Sodium cobaltic nitrite test solution, (NaNO 2 ) 6 Co 2 (NO 2 ) 6 + H 2 0.
Dissolve 4 Gm. of cobaltous chloride and 10 Gm. of sodium nitrite
in about 50 mils of distilled water, add 2 mils of acetic acid and
dilute with sufficient distilled water to measure 100 mils. A few
drops of acetic acid should be added to the solution from time to
time. The reagent must not be kept longer than three months.
Should any precipitate form on standing, filter.

Sodium cyanide test solution, NaCN. Dissolve 1 Gm. of sodium
cyanide in sufficient distilled water to measure 10 mils. The solu-
tion must be freshly prepared when required.

Sodium hydroxide test solution, NaOH. Dissolve 10 Gm. of sodium
hydroxide in sufficient distilled water to measure 100 mils.

Sodium hypobromite test solution, NaBrO. To a solution of 40
Gm. of sodium hydroxide in about 150 mils of distilled water add 10
mils of bromine and, after solution has taken place, add sufficient
distilled water to measure 200 mils. The solution must be freshly
prepared when required for use.



126 REAGENTS AND TEST SOLUTIONS

Sodium nitroprusside test solution, Na 2 FeNO(CN) 5 + 2H 2 O.
Dissolve 1 part of sodium nitroprusside in 19 parts of distilled water
immediately before using.

Sodium phosphate test solution, NaHPO 4 + 12H 2 O. Dissolve 10
Gm. of sodium phosphate, in clear crystals, in sufficient distilled water
to measure 100 mils.

Sodium tartrate test solution, Na2C 4 H 4 O6 + 2H 2 O. Dissolve 10
Gm. of sodium tartrate in sufficient distilled water to measure 100
mils.

Sodium thiosulphate test solution, Na 2 S 2 O 3 + 5H 2 O. Dissolve 2.5
Gm. of sodium thiosulphate in sufficient distilled water to measure
100 mils.

Stannous chloride test solution, SnCl 2 + 2H 2 O. Dissolve 10 Gm.
of stannous chloride crystals in 100 mils of distilled water to which
a small amount of hydrochloric acid has been added, and preserve
the solution in glass-stoppered bottles in which a fragment of tin
has been placed. The solution must be renewed at frequent
intervals.

Stannous chloride test solution, saturated, SnCl 2 + 2H 2 O. (For
Bettendorf s test for arsenic.) A saturated solution of stannous
chloride crystals in concentrated hydrochloric acid. After filtering
the solution through asbestos it has not more than a pale yellow
color.

Starch test solution. Triturate 1 Gm. of cornstarch with 10 mils
of cold distilled water, add boiling distilled water with constant
stirring to make about 200 mils, then boil the mixture for a few
minutes until a thin, translucent fluid is obtained. This solution
must be freshly prepared when required.

Sulphuric acid test solution, H 2 S04. Use the official diluted sul-
phuric acid, containing about 10 per cent, of absolute H 2 SO 4 .

Tartaric acid test solution, H 2 C 4 H 4 O 6 . Dissolve 1 part of tartaric
acid in 3 parts of distilled water. This solution must be frequently
renewed.

Turmeric tincture Digest any convenient quantity of ground
turmeric root repeatedly with small quantities of distilled water and
discard the liquids. Then digest the dried residue for several days
with six times its weight of alcohol, and filter.

Turmeric paper. Impregnate white, unsized paper with the
tincture, and dry it. The tincture, as well as the paper, turns brown
with alkalies, and the original yellow color is restored by acids, with
the exception of boric acid, which, especially in the presence of
hydrochloric acid, turns the color to reddish-brown, which is changed
to bluish-black by ammonia.

Zinc sulphate test solution, ZnSO 4 . Dissolve 10 Gm. of zinc sul-


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