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Hugh McGuigan.

An introduction to chemical pharmacology: pharmacodynamics in relation to ... online

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see page 80.

NITROBENZENE

C6H6NO2. The boiling point of this oily liquid is 208''C.
which is higher than that of phenol (183^C.) consequently most
of it will appear in the last part of the distillate: It is nearly
insoluble in water but very soluble in ether and if only traces are
present, the distillate should be shaken with ether, the ether
evaporated at about 40°C. and tests made on the residue. For
tests see page 110. Convert it into aniline, by reduction with
hydrogen and then make the aniline tests, page 112.

PHENOL

Phenol boils at about 180° and distils readily with steam. The
distillate may be cloudy and is recognizable by its odor, though
this may be masked by putrefactive odors. Traces of phenols
are formed in all putrefactions. For tests see page 99.
Quantitative Estimation of Phenol

An excess of saturated bromine water precipitates phenol in
aqueous solution as tribromophenyl hypobromite — C6H2Br80Br.

Method. — Place an aliquot part of the liquid under examina-
tion in a stoppered flask. Add bromine water from time to time
and shake until the supernatant liquid has a red brown color and
bromine vapor is visible above the liquid. Let ^tand 2-4 hours
and filter through a weighed Gooch crucible. Dry in a desiccator
over H2SO4 to constant weight. The weight of the dried precipi-
tate multiplied by 0.2295 gives the amount of phfenol, since
C6H2Br40 . CeHsOH ^ 905 ^
409.86 • 94.05 409.86

CREOSOTE (Creosols)
See page 96. Creosotes are methyl phenols and distil over
similar to carbolic acid. Some commercial creosotes contain



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TOXICOLOGY 391

phenol. The tests are in many cases similar to phenol and hard
to distinguish from it.

1. With pure creosote iron chloride gives a green color, while
with phenol it gives a blue-purple color.

2. HNO3 when added to creosote gives picric acid, HNO3 does
not form picric acid directly with phenol.

3. When equal volumes of colloidon and creosote are shaken
together there is no visible change while with phenol, a gelatinous
coagulum is fprmed.

NON-VOLATILE ORGANIC POISONS

Before non-volatile organic poisons can be extracted from
stomach contents, organs, etc. the proteins, fats, carbohydrates
and resinous material must be removed. As an aid to their
removal and to lessen the Ukelihood of removing poisons with
these materials, the organs are cut, or ground so that no piece is
larger than a pea. The finely chopped material is then placed
in a flask of suitable size and three times the volume of absolute
alcohol which has been redistilled from tartaric acid is added.
The alcohol has been redistilled to remove basic material which
often is present in commercial alcohol. Just enough tartaric
acid is added to acidify the mixture. The whole is extracted on
a water bath for 30 minutes using a reflux condenser. Cool the
flask and contents, in order to help solidify fats present, and
filter through cheese cloth if much solid material is present.
Wash with absolute alcohol, and filter through paper to remove
fat and solid matter. Wash again with alcohol. Evaporate the
filtrate in a glass or porcelain dish on a water bath to a syrupy
consistency, and thoroughly mix with about 100 cc. water.
This precipitates resins. Filter, wash with water and again
evaporate to a syrup. Mix thoroughly with 150 cc. absolute
alcohol. This precipitates proteins, albumoses, peptones, dextrin-
like bodies, some inorganic salts — while the tartrate salts of the
poisons are dissolved. Filter and wash with alcohol. Again
evaporate oflf the alcohol and dissolve the residue in about 50 cc.
of water. This should be relatively clear and free from proteins,
fats, carbohydrates and resins, but if not the above processes
should be repeated until a clear solution is obtained. This is
the most important part of the analysis, as upon the removal



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392 CHEMICAL PHARMACOLOGY

of all foreign matter depends the success of the tests which follow.
At all stages the solution should be acid — but a large excess of
acid should be avoided as its presence interferes with the tests.
When the solution ia. so prepared it is ready for the Stas-Otto
method of extraction. This method consists in extraction of
the poisons with immiscible solvents first with acid alcohol, then
changing the solvent to water solution; and then successive
extractions of the prepared liquid with ether and chloroform in
acid and alkaline reactions as given below.

Acid ExtractioQ — Stas-Otto liilethod. — Place a portion, or all,
of the prepared acid extract in a separatory funnel. Add an
equal volmne of ether, shake well, allow to settle and remove the
ether into an evaporating dish. Repeat the extraction 3 or 4
times. Unite all extracts and allow to stand for 30 minutes. If
water separates out, it may be removed by filtering through
a dry filter. A dry filter will absorb and retain considerable
water. Evaporate the ether at a temperature of 40°C. Since
only a small residue may be expected after evaporation,
it is best not to have this spread over a large surface. To avoid
this let the ether extract drop from a separatory funnel into a
small evaporating dish at a rate about equal to the evaporation.
In this way whatever residue remains is on a small surface and
more easily examined. The completion of the evaporation may
be carried out on a water bath at a higher temperature if the
residue remains too moist for examination.

Even when none of the first group of poisons is present, some
little residue may remain which consists of tartaric acid, lactic
acid, resins, etc. which are not completely removed in the process.

The residue may contain any of the following poisons.



Acetanilide


Caffeine


Antipyrine


Picrotoxin


Phenacetine


Picric acid


Salicylic acid


Veronal


Colchicine




Also traces of


mercuric cyanide:




Cantharidin




Digitalin




Veratrine



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TOXICOLOGY 393

and Atropine may occur in this extraction. An examination of
the general appearance, taste, odor, color, etc. of the residue should
be made. Then a microscopic examination for crystals should be
made. Since usually only one of the poisons of the group is
expected, tests for the most likely should be made first.

II. After the acid solution has been extracted with ether, it is
made alkaline with sodium hydroxide. The alkali liberates most
alkaloids from this salt«, and these are then readily extracted
with ether. Morphine, apomorphine, and narceine are more
soluble in the water alkaline solution than in ether, consequently
are not extracted, with ether. Note this exception to the general
alkaloidal solubilities. The water solution should be saved for
further investigation. The ether extract from alkaline sodium
hydroxide should be examined for:

Page Page

Aniline 112 Narcotine 265

Antipyrine 119 Nicotine 255

Atropine 272 Physostigmine 295

Brueine 257 Papaverine 283

Caffeine 288 Pilocarpine 275

Cocaine. . . 267 Pyramidone 119

Codeine 281 Quinine 261

Coniine 252 Scopolamine 272

Hydrastine 263 Strychnine 257

Thebaine 282

Veratrine 294

The figures refer to pages in the text where the tests are
given.

III. The alkaline sodium hydroxide solution, after extraction
with ether, is slightly but distinctly acidified with tartaric or
sulphuric acid. Then made alkaline with ammonia, and ex-
tracted in a separatory funnel with ether, and afterwards with
chloroform.

A. The ether extract may contain, apomorphine and traces of
morphine.

B. The chloroform extract may contain morphine, narceine
and antipyrine and caffeine that was not previously removed.



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394 CHEMICAL PHARMACOLOGY

METALLIC POISONS

To detect poisonous metals, in animal or vegetable matter,
it is first necessary to destroy or remove the organic material
after which the tests are made in the same way as in inorganic
chemistry. In toxicological analysis therefore a most important
part of the process is the removal of the organic material.

Method

Various methods may be used, the principle in all is essentially
the same. The Fresinius v. Babo method is taken as the type.
Since all the organic poisons are also destroyed when the organic
matter is being destroyed, one may work either with an orig-
inal portion of the material or with the residue that remains
after the organic poisons have been removed. A portion of
the material is mixed to a fluid mass and placed in a large
flask Fig. 9.

About 30 cc. concentrated HCl is added per 100 cc. mate-
rial, and 1-2 grams of KCIO3 added. The flask is heated on
a boiling water bath in a hood. Nascent chlorine is evolved
which destroys the organic matter. When the flask is hot, it
is frequently shaken and a trace of KCIO3 added from time to
time until the solution is a pale yellow color and longer heating
produces no further change. Fat is very resistant to oxidation in
this way, yet is easily oxidized in the body.

When oxidation is complete dilute with hot water and add a
little sulphuric acid to precipitate possible barium, filter and
evaporate in a porcelain dish on a water bath nearly to dryness
to remove excess of acid. The decomposition of some KCIO3
may give a brown color at this point. If necessary filter, wash
with water and evaporate again almost to dryness. Dissolve
in water, and filter. There will be some insoluble white residue
wholly unaffected by the action of chlorine (see test for Ba).

Examination of Filtrate

This should have only a faint yellow color, and be slightly acid.
Place in a flask and heat on a water bath. While heating saturate
the solution with H2S from a Kipp generator. The gas should
be run for 30 minutes in the hot solution, and again for 30 min-
utes after the flask has cooled, then the flask is tightly stoppered



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TOXICOLOGY



395



and allowed to stand for several hours — preferably over night —
and filtered. The filtrate may contain chromium or Zn. The
precipitate may contain As, Sb, Sn, Cu, Hg, Pb, Bi, Cu, Cd.




Fia. 9. — (After Autenreith.)

Examinatioii of the Precipitate

The precipitate is thoroughly washed with hydrogen sulphide
water, then the moist precipitate is dissolved in about 25 cc. of
a mixture of equal parts of ammonium hydroxid and yellow
ammonium sulphide and heated to boihng — filter and wash
several times with some of the hot ammonium — sulphide mixture:
The filtrate may contain As, Sb, Sn, or Cu. The precipitate
Hg, Pt, Bi, Cu or Cd.



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396 CHEMICAL PHARMACOLOGY

Examination of the Filtrate

Evaporate the solution to dryness dn a water bath — cool,
moisten with HNOs and again evaporate to dryness. Then mix
the residue with 3 times its volume of a mixture containing 2 parts
sodium nitrate and 1 part sodium carbonate. Evaporate this
mixture to dryness and add it little by little to a crucible contain-
ing a little sodiimi nitrate heated to redness. The heating is
continued until the whole is fused. If copper is present the melt
is gray or black. Sodium arsenate, sodium pyroantimonate and
sodiiun stannate may also be present. When the crucible is
cold, add a little hot water and wash into a flask. If sodiiun
stannate is present^ a Uttle sodium bicarbonate is added to
precipitate the tin as stannic oxide. Filter. The filtrate may
contain As as sodium arsenate and the residue will contain
sodiiun pyroantimoniate (Na2H2Sb207), stannic and copper
oxides.

Arsenic Test

Acidify the filtrate with arsenic free sulphuric acid. Evaporate
over a free flame, and add sufficient sulphuric acid to expel nitric
acid. Heat until copious white fumes of sulphuric acid appear.
Arsenic if present is in the form of arsenic acid and is tested in the
Marsh Apparatus, see Fig. 10 (Autenrieth, Warren).

Place 30 grams of arsenic free zinc in flask A, Pour 15 per
cent, arsenic free sulphuric acid on the metal. The flask should
be kept cool during the analysis by keeping it surrounded with
cool water and by generating hydrogen slowly. If the tempera-
ture gets too high SO2 is formed and this in presence of hydrogen
is reduced to H2S, which interferes with the test. All joints of
the apparatus should be tight to avoid escape of AsHs and also to
prevent explosions. Air should be completely expelled before
igniting also to prevent explosion, to determine whether the air is
expelled catch some of the escaping hydrogen in a test tube and
test from time to time until it ignites without detonation. It
may require 10 minutes to expel the air. When lighted and
before adding the solutions to be tested, one should test to see
that no arsenic is present in the chemicals. If the hydrogen is
arsenic free, the solution to be tested is gradually introduced into
the sulphuric acid — zinc flask, Ay through the^ funnel — at the



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TOXICOLOGY 397

same time the tube C. is heated to redness just back of the
constriction D. If the solution contains As, a shining metalUc
arsenic mirror is deposited, just beyond the point of ignition.

2. If the flame is removed from C. and a cold porcelain dish
pressed down on the arsine-hydrogen flame a brownish black
spot is formed upon the dish. This spot dissolves readily in sodium
hypochlorite solution. Antimony spots will not dissolve.

3. If the hydrogen flame is extinguished, and the end of the
tube dipped into a dilute silver nitrate solution, arsine produces
a black precipitate of metallic silver.



Fig. 10.

4. Arsine produces a yellow stain, on a piece of filter paper
moistened with cone, silver nitrate solution. A drop of water
added to this changes the yellow spot to black. This is Gutzeit's
test.

Detection of Antimony

The insoluble residue after fusion may contain Cu, Sb, or Sn.

1. Test for Cu. — Dissolve in dilute HCl. The solution may
be colored light blue, excess of NH4OH produces a deep blue
color. Potassium ferrocyanide gives a deep red precipitate.

Test for Tin. — The insoluble residue is dissolved in HCl as
in testing for copper. The tests for tin depends on the fact
that tin chloride is a reducing agent.

1. Add a few drops of mercuric chloride. If tin is present it



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398 CHEMICAL PHARMACOLOGY

reduces this to calomel which precipitates. When heated this
precipitate is changed to metallic mercury.

Test for Antimony

Dissolve in dilute hydrochloric acid by aid of heat. Introduce
into Marsh gas apparatus and test in the same way as for arsenic.

1 . Differences between Arsenic and Antimony. — The antimony
mirror in the Marsh gas apparatus is deposited on both sides of
the flame. The metal in contact with the heated flame fuses
to the glass and is silver white. It sublimes with diflSculty.
Arsenic volatilizes readily.

2. Nitric acid dissolves both antimony and arsenic mirrors.
When neutralized with ammonium hydroxid, silver Mitrate
precipitates silver arsenate Ag3As04 which is reddish, with
antimony there is no reddish precipitate.

3. The spot produced on a cold porcelain surface when held
to the Marsh gas flame by arsenic is not heavy, is brown and
lustrous, and dissolves readily in sodium hypochlorite.

The antimony spot is heavy velvet like, not lustrous and is
insoluble in hypochlorite.

Detectibii of Metals Whose Sulphides are Insoluble in Ammonium

Sulphide
This group includes:

Bismuth Copper

Cadmium Lead

Mercury

1. Treat these sulphides on the filter with dilute nitric acid.
All dissolve except mercury — save the filtrate for further work.

Test for Mercury. — Dissolve the sulphide with hot dilute HCl
containing a crystal of potassium chlorate. Filter, evaporate
to dryness on a water bath, and dissolve in 5 cc. 5 per cent. HCl,
filter and test filtrate for mercury, as follows :

1. To a portion add a few drops of stannous chloride. The
mercuric chloride is reduced to calomel which is precipitated.
Excess of stannous chloride especially if heated reduces the calo-
mel to metallic mercury.

2. Place a few drops of the solution to be tested on a piece of
clean copper. A gray spot with silver luster is deposited if



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TOXICOLOGY 399

mercury is present. Wash with water, alcohol, and ether, dry
and place the copper in a small test tube. Heat over free flame.
Mercury sublimes and collects in metallic globules on the cool
sides of the tube. A crystal of iodine placed in the warm tube
vaporizes and scarlet mercuric iodide is formed.

.3. Dilute potassimn iodide added to a solution of HgCU pre-
cipitates the red iodide Hgl2.

Examination of the Nitric Acid Solution

This may contain Pb, Cu, Bi and Cd nitrates. !

Evaporate to dryness and dissolve in a little hot water, add
dilute sulphuric acid. Lead precipitates — filter. The sulphates
of Cu, Bi and Cd are soluble. Test the filtrate for these.

Copper and Bismuth Tests. — Add excess of ammonium hy
drate, if Cu is present it produces a blue color. If Bi is present,
it is precipitated as Bi(OH),. . Filter dissolve ppt. in dilute HCl.
Pour into 50 cc. water. A white precipitate of BiOCl proves the
presence of bismuth. If cadmium be present, it will give a
yellow precipitate with hydrogen sulphide. If present with
copper, add solid KCN to the blue color, until the color dis-
appears.

Then pass hydrogen sulphide. The copper remains in solu-
tion. As K4Cu2(CN)6 while yellow CdS is precipitated.

CHROMIUM AND ZINC
If present these are found in the H2S filtrate.
Detection of Zn

Make one half of the filtrate alkaline with ammonium hydrate
and add ammonium sulphide. This will precipitate Zn, but
there may be a precipitate even if no Zn is present, because
solutions from animal matter contain traces of iron, alkaline
earths, phosphates, etc. Add acetic until faint acid reaction;
this dissolves phosphates except ferric phosphate. Filter, wash
with water, dry and ignite in porcelain crucible. A drop of
ammonium nitrate aids oxidation — cool. Add dilute sulphuric
acid, boil and filter. This converts Zn into ZnSO^ — divide the
filtrate into two equal parts.

(a) Add dilute NaOH to precipitate iron which may be present



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400 CHEMICAL PHARMACOLOGY

as ferric phosphate. Filter, add a few drops of ammonium sul-
phide. This precipitates ZnS as a white fiocculent precipitate.
(6) Add ammonium hydroxide and filter to remove ferric
phosphate. Acidify filtrate with acetic acid. Zn if present can
be precipitated with hydrogen sulphide as a white precipitate.

Detection of Chromium

Evaporate a portion of the hydrogen sulphide filtrate almost to
dryness, add about 1 gram each of sodium carbonate and potas-
sium nitrate — dry and add a little at a time to a hot crucible
containing fused potassium nitrate. Heat until fusion is com-
plete. This oxidizes chromium to chromates. Cool and dis-
solve in water, and filter. The filtrate is yellow if chromium is
present, acidify with acetic acid and add a little lead acetate;
yellow lead chromate is precipitated.

Detection of Lead, Silver and Barium
The residue from the fusion with potassium chlorate may con-
tain lead, silver or barium. The residue is dried in an air oven,
and groimd in a mortar. Then 3 times the amount of a mixture
of potassium nitrate and sodium carbonate is added and the
mixture fused in a crucible adding a little potassium nitrate to
complete the fusion. This destroys fats and other organic
matter. Cool and dissolve in water. Transfer to a flask and
pass CO2 through the flask. The precipitates lead as the car-
bonate. Filter, the precipitate may contain lead and barium
carbonate and metallic silver and silver oxide. This silver gives
the precipitate a gray color. Wash with water and dissolve in
dilute nitric acid. Evaporate to dryness and dissolve in hot
water. Add HCl and heat, this precipitates silver, filter and
add H2S to precipitate lead. Filter and heat to expel the excess
of H2S. Add dilute H2SO4 to precipitate barium. The con-
firmatory tests need not be given.

SYNOPSIS OF METALLIC POISONS

The material is boiled with dilute hydrochloric acid (about
12 per cent.) and potassium chlorate added until a pale yellow
solution results. This destroys organic matter and dissolves the
heavy metals. A little sulphuric acid is added and the solu-
tion filtered.



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TOXICOLOGY



401



Filtrate may contain — As, Sb, Sn, Cu,
Hg, Pb, Bi, Cu, Cd, Cr, Zn.
Add H2S



Precipitate may — con-
tain — Pb, Ag, Ba.



Precipitate— ^Dissolve precipitate with
yellow ammonium sulphide and am-
monium. Filter.



Filtrate contains — Cr
. and Zn.



Filtrate contains —
As, Sb, Sn, Cu.



Residue— Hg, Pb,
Bi, Cu and Cd.



SULPHURIC ACID

Sulphates are present in small amounts in all vegetables and
animal matter. The appearance of the tongue and stomach as
well as the amount after sulphuric acid poisoning should settle
any case of doubt. The tongue may be dark or boiled looking
due to the formation of methemoglobin, hematin, etc.

I. The finally divided stomach and tissues reacts strongly
acid. When extracted with water and filtered, the filtrate is acid.

II. The barium chloride gives a precipitate which is insoluble
in HCl. The amount of H2SO4 may be determined by igniting
the precipitate, and weighing in a weighed crucible or by titra-
tion of the water extract as under HCl.

III. When the water extract is evaporated on a water bath
and then over a free flame white fumes of SO2 are evolved. A
particle of sugar, or any organic matter added to this heated
solution will be carbonized.

Nitric Acid. — Nitrates occur only in traces in foods and or-
ganic matter. In a case of poisoning with nitric acid, the parts
of the body touched by it are yellow — xantho-proteiii test. If
taken in dilute form nitric acid is excreted in the urine as nitrates.

Tests

I. The water in extracts gives the tests for mineral acids.

II. It distils after it reaches a certain concentration. The

26



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402 CHEMICAL PHARMACOLOGY

protein material in the distillation flask is yellow — xantho-pro-
tein. If distillation is carried far enough, the brown vapors of
nitrogen peroxid appear.

III. Brucine test: Mix part of the distillate with an equal
voliune of a solution prepared by mixing 1 gram brucine in 5 cc.
dilute sulphuric acid and 95 cc. water. Pour this mixture care-
fully on concentrated sulphuric acid in a test tube. If nitric
acid is present, a black ring is formed between the solutions.

IV. Saturate the liquid to be tested with ferrous sulphate.. Pour
this upon concentrated H2SO4. A black zone appears between
the liquids.

V. Nitric acid evolves red brown vapors of NO2 when clean
metallic copper is added.

OXALATES AND OXALIC ACID

Extract the finely divided material with 3-4 volumes of hot
absolute alcohol acidified with HCl. Cool to about 10°C. and
filter through dry paper. Fats and proteins are removed. Add
20 cc. water to prevent the formation of ethyl oxalate and evapo-
rate the alcohol. The residue may again be extracted with
alcohol and evaporated. Make alkaline with ammonia, filter
if there is a precipitate and to the clear filtrate add calcium
chloride solution. A precipitate of octahedron crystals or en-
velope shaped crystals of calcium oxalate results. These should
be examined under the microscope. If it is desired to determine
the amount of oxalic present, this may be done by igniting the
precipitate in a weighed crucible as CaO.

CaO:H2C2042H20 : : 56 : 126
56 :126 = 0.444

Consequently the weight of the precipitate multiplied by 0.444 =
gives the amount of oxalic acid.

To get purer crystals of calcium oxalate, for identification, it
is sometimes advised to extract the water solution from the
alcohol filtrate with ether, and use the residue after evaporation
for the test. This gets rid of some interfering bodies which may
be present in the alcohol extract.



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TOXICOLOGY 403

ALKALIES

The tissues after alkali intoxication react blue to litmus and are
soft and greasy, if poisoning has occurred from ammonia it may
be recognizable by its odor. To detect ammonia, or to estimate
the amount, it, will be sufficient to extract with water, filter —
add 20 cc. strong NaOH and distil. The distillate reacts alkaline
and the amount may be titrated with N/1 NaOH, using cochineal
as the indicator.

FIXED ALKALIES

Extract with water, filter. The filtrate reacts alkaline, the
fingers moistened with it feel slimy. The amount may be
titrated with N/1 acid using phenolphthalein as the indicator



Online LibraryHugh McGuiganAn introduction to chemical pharmacology: pharmacodynamics in relation to ... → online text (page 28 of 30)