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CHEMISTRY FOR NURSES
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THE MACMILLAN COMPANY
NKW YORK • BOSTON • CHICAGO - DALLAS
ATLANTA • SAN FRANCISCO
MACMILLAN & CO., Limited
LONDON • BOMBAY • CALCUTTA
MELBOURNE
THE MACMILLAN CO. OF CANADA, Ltd.
TORONTO
CHEMISTRY FOU NURSES
BY
REUBEN QTTENBERG, A.M., M.D.
LECTURER TO THE NURSES' TRAINING SCHOOL, MT. SINAI
HOSPITAL ; INSTRUCTOR IN BACTERIOLOGY, COLLEGE
OP PHYSICIANS AND SURGEONS, COLUMBIA UNI-
VERSITY ; AND ASSISTANT IN CLINICAL
MICROSCOPY, MT. SINAI HOSPITAL
THE MACMILLAN COMPANY
AU riffhUi reserved
OOPTBIGHT, 1914,
bt the maomillan company.
Set up and elcctrotyped. Published September, 19x4.
Reprinted December, 1914; June, October, 191S;
January, November, 1916 ; August, October, 1917*
J. S. Cashing Co. — Berwick & Smith C*.
* '. NkffwoodjM^SQ,, U'.S.A. r r ,,
^D33
j83
1917
PKEFACE
The teaching of chemistry to nurses is a new
thing, but the development of medicine has made
it inevitable. Some knowledge of the fundamental
conceptions of chemistry is as indispensable as
anatomy in the modern treatment of disease. In-
deed it puzzles one to understand how, in the past,
without chemical instruction, nurses have made
any sense at all of much that was taught them in
materia medica, physiology, and diet cooking.
How rapidly this opinion is gaining adherents is
shown by the responses to an inquiry sent by the
author to the examining boards of thirty-two
states of the Union; in twenty-two states, the
answers showed, questions in chemistry formed
part of the examination for registered nurses.
This book has been written therefore in response
to what the author believes to be a real need.
There is no simple yet modern textbook on this
subject. In the past nurses anxious for informa-
tion were compelled to refer either to textbooks
written for medical students and much too difficult
for the average nurse, or to school textbooks,
VI PREPACK
written from a different point of view and paying
no attention at all to many subjects of peculiar
importance to nurses.
Chemistry to the nurse is an accessory study, —
an aid to the understanding of other studies of
undoubtedly greater practical importance. For this
reason the present book is to be used by the nurse
not as a catalogue of facts to be learned outright,
but as a reasoned explanation of things which
otherwise would remain obscure. The author
therefore has avoided all technicalities and has
attempted to make the text as readable and enter-
taining as possible. The subject of chemistry
with its innumerable and important bearings on
everyday life usually fascinates every beginner who
overcomes the initial fear of its technical difficulty.
This book is the development of a short course
of lectures given to the undergraduate nurses of
the Mount Sinai Hospital at various times in the
past two years. The experiments described have
all been demonstrated to classes of nurses and can
easily be performed with the simplest equipment.
It is suggested that teachers perform these experi-
ments before their classes.
The author wishes to thank several of his friends
for their kindly criticism: Dr. Samuel Bookman,
PREFACE VU
Chemist to Mount Sinai Hospital; Miss George,
Dietitian to Mount Sinai Hospital ; Dr. A. S. Blum-
garten, author of "Materia Medica for Nurses";
and particularly Mr. Joseph Loew of the De Witt
Clinton High School, New York.
TABLE OF CONTENTS
OHAFTEB PAGB
I. Elements and Compounds 1
II. Atoms and Molecules 12
III. Chemical Names and Formulas. Chemical
Affinity 18
IV. Energy and Oxidation 27
V. Acids 36
VI. Bases 44
Vn. Salts 50
Vin. Organic Chemistry 56
IX. Carbohydrates 65
X. Fats 79
XI. Proteids 90
XII. Digestion 101
XIII. Urine 113
XIV. Stomach Contents^ and Feces .... 130
INDEX 135
CHEMISTRY FOR NURSES
CHAPTER I
Elements and Compounds
Two Kinds of Changes in Matter. — Since the
earliest times men have been studying the different
kinds of matter or substances of which the world is
composed, and have noticed that these substances
frequently undergo changes in appearance and form.
Gradually they have come to see that these changes
are of two different kinds : the one kind is more or
less transient. Thus the change from solid to liquid,
as in the melting of ice, or from liquid to gas, as in
the boiling of water, the glowing of metal when it
is heated, are temporary changes. The water can
freeze again, the steam can condense, the metal can
cool. Changes of this kind in matter are known as
physical changes, and their study constitutes the
science of physics.
Chemical Changes. — But substances also undergo
another kind of change much more permanent in
2 CHEMISTRY FOR NURSES
nature. Wood may burn in the flame until nothing
is left but ashes, or metals rust and lose their origi-
nal appearance entirely. Such deep-going changes
in matter are known as chemical changes, and their
study is the science of chemistry.
Elements. — Chemical changes often result in
breaking up one substance into several products.
Thus, for instance, when a piece of wood burns there
are fumes given off ; at a certain stage there is a black
residue composed of carbon (charcoal) ; and if the
burning is continued for a long while, white ashes.
The products of such chemical changes can often
be further decomposed into still other substances.^
When this process is continued, certain forms of
matter are finally obtained which cannot by any
means whatever be resolved into other substances.
These are called elementary substances or chemical
elements.
Compounds. — By studying all sorts of substances
in this way the chemists have discovered that all
the matter in the universe is composed of about
^ When the combined weights of all the substances''produced
by such decompositions are compared with the weight of the
original substance, they are found to be exactly equal. Matter
has been changed into different states, but no matter has been
made or destroyed. This is the law of the indestructibility of
matter.
ELEMENTS AND COMPOUNDS 3
eighty of these elements ; everything from a microbe
to a star is composed of these same eighty elements
in different forms and combinations.
It took centuries to find this out because it is not
easy to discover what elements are present in a sub-
stance. The reason for this difficulty is that when
different elements combine to form a new substance
they lose their properties entirely. The properties
of the compound are nothing like the properties of the
elements themselves. Who would think from the
properties of water, for instance, that it was composed
of two light gases which explode when they are mixed
together and ignited? Or, consider common salt,
sodium chloride. It is a combination of two ele-
ments, — sodium and chlorine. Chlorine is a yellow
poisonous vapor. Sodium is a soft metal, very hard
to keep in its natural state because it corrodes and
combines with almost everything it touches. These
two violent things with their peculiar properties
combine and the result is our harmless table salt.
Difference between Mixtures and Compounds. —
But it must not be supposed that just because ele-
ments are mixed together the result is necessarily
a new compound. Substances may be simply
mixed together very intimately without undergoing
any combination (in such a way as to form new
4 CHEMISTRY FOR NURSES
properties) at all. If you mix particles of carbon
(lamp black) and of sulphur, the mixture has no new
properties and the two kinds of particles can be
recognized separately under a microscope. But if,
instead of this, sulphur in the form of vapor is made
to pass over the red-hot charcoal, an entirely new
substance (carbon disulphide) is formed. It is a
volatile and strong-smelling liquid which is of enor-
mous importance in the manufacture of rubber and
various perfumes. This, then, is the difference be-
tween a mixture and a compound: in a mixture
the substances are present in their original form and
are easily separated; in a compound the elements
have undergone a peculiar change by which they
not only acquire entirely new properties, but are
firmly united so that it takes some powerful force
like great heat or a strong electric current or power-
ful chemical action to separate them.
All sorts of elements combine with each other and
thus there are thousands of compounds: the
number of possible compounds is almost infinite.
Constant Composition of Compounds. — In spite
of the great number of compounds formed by the
union of different elements each compound always
has precisely the same composition, no matter under
what conditions you find it. If you take specimens
ELEMENTS AND COMPOUNDS 5
of water from a dozen different sources and separate
the elements in them, you will always find exactly
the same proportion of hydrogen and oxygen.
You never find more oxygen in one specimen
of water than in another. This fact, that the ele-
ments in any chemical compound are always present
in precisely the same proportions, is another one
of the things that distinguish compoxmds from
mixtures. It is obvious, of course, that in a mixture
any amoimt of the one or the other ingredient may
be present. There is a fundamental reason for this
constancy of composition of compounds. This
reason will be made clear in the next chapter.
How can Different Compounds be composed of
the Same Elements? — But the same elements may
combine in several different proportions to form
several different compounds. For instance, take an-
other compound f 2 hydrogen and oxygen, namely,
peroxide of hydrogen. It is a combination of exactly
the same elements as water, but the elements are
combined in a different ratio. The amount of oxygen
present in any given amoimt of peroxide of hydrogen
is twice as large as in the same amount of water. On
this account peroxide of hydrogen is entirely different
in its properties from water. It attacks and de-
composes organic things such as blood or bacteria.
6 CHEMISTRY FOR NURSES
But peroxide of hydrogen in its turn does not vary.
The proportions of hydrogen and oxygen obtained
from different specimens of it are always the same.
There are two general methods of studying com-
pounds, — analysis and synthesis. Analysis means
decomposition of a compound into the elements
which compose it: synthesis means combining
different elements to form new compounds.
The Most Important Elements. — Below is a
partial list of elements. The list includes all the
elements which are met in everyday life and which
play an important part in medicine or nursing.
Many of them, such as carbon and sulphur and the
metals, are already familiar in their natural state.
The student will easily be able to think of compounds
of most of the others. A short description of most
of these is found in the appendix W Chapter I.
1 — Aluminium 11 — Hydrogen
2 — Arsenic 12 — Iodine
3 — Bismuth 13 — Iron
4 — Boron 14 — Lead
5 — Bromine 15 — Lithium
6 — Calcium 16 — Magnesium
7 — Carbon 17 — Mercury
8 — Chlorine 18 — Nickel
9 — Copper 19 — Nitrogen
10 — Gold 20 — Oxygen
ELEMENTS AND COMPOUNDS
21 — Phosphorus 27 — Sodium
22 — Platinum 28 — Strontium
23 — - Potassium 29 — Sulphur
24 — Radium 30 — Tin
25 — Silicon 31 — Zinc
26 — Silver
IMPORTANT ELEMENTS AND COMPOUNDS
1. Aluminium — a light, white metal, which, combined
with other elements in the form of clay or of va-
rious minerals, forms a large part of the earth's
crust. Its compound, aluminium acetate, is used
in surgical dressings.
2. Arsenic — a metal. Its compounds are exceedingly-
poisonous, and some are used as drugs.
3. Bismuth — a heavy, lustrous metal whose compounds
are mostly insoluble (do not dissolve in water) and
are used in medicine. On account of being in-
soluble, bismuth compounds when given as medicines
are found in the stools again. They undergo a
chemical change which gives the black color to bis-
muth stools.
4. Boron — mentioned because of its compounds, horic
add and borax.
5. Bromine j;::^-a heavy, very poisonous, and irritating
brown liquid, the compounds of which, known as
bromides, are of great use in medicine.
6. Calcium — a yelldw metal which when heated takes
fire and burns. One of its compounds (calcium
carbonate) forms marble and limestone; another
(calcium phosphate) is the chief constituent of
8 CHEMISTRY FOR NURSES
bones. We could not live without calcium and it
is present in all animals and vegetables.
7. Carbon — occurs as diamond, graphite, charcoal.
Its compounds are very numerous and all living
things are composed chiefly of them.
8. Chlorine — a poisonous, greenish gas, similar in many
ways to bromine and iodine. Its compounds, such
as hydrochloric add, sodium chloride, potassium
chlorate, are of great importance in physiology and
medicine.
9. Copper — a common metal, one of whose compounds,
copper sulphate, is a valuable cauterizing agent.
10. Gold — a metal which has very few compounds.
This is what makes it a ^* precious '' metal. It
does not combine readily with other elements, and
therefore does not corrode or rust, but remains un-
changed for centuries.
11. Hydrogen — a non-poisonous gas, the lightest sub-
stance known, and one of the most abundant
and important of all the elements, — present
in all living matter. Not present as such in the
air.
12. Iodine — shining black crystals, which, dissolved in
alcohol, are the familiar tincture of iodine. Traces
of it are found in the thyroid gland, and it is im-
portant for health, though exactly why is unknown.
Some of its compounds {iodides) are valuable
drugs.
13. Iron — important not only as a metal, but also in its
compounds, some of which are valuable drugs, and
one of which, hoemoglobin, is the red coloring matter
of our blood and is essential for respiration.
ELEMENTS AND COMPOUNDS 9
14. Lead — is a heavy metal ; it can easily be fluidified
by heat. Its soluble compounds are poisonous.
Some of them are used in medicine {lead acetate).
15. Lithium — is a light metal, some of whose compounds
are used in medicine.
16. Magnesium — a silvery white metal which burns
brilliantly in the air. (The flash light of photog-
raphers is powdered magnesium.) Some of its
compounds, such as magnesium sulphate^ citrate^
carbonate J and hydroxide (milk of magnesia), are
important drugs.
17. Mercury — a heavy fluid metal whose compounds are
familiar and important drugs (calomely bichloride
of mercury).
18. Nickel — a metal.
19. Nitrogen — an inert (not chemically active) gas which
forms about | of the air. Its compounds, am-
wjonia, nitrous oxide or laughing gas, nitric add,
niter or saltpeter (potassium nitrate), are used in
medicine. In the form of proteid it is not only
an essential food, but is present in every living
cell.
20. Oxygen — is a colorless, odorless gas which forms
about J of the air and | of the earth. It can com-
bine with almost every other element, and the pro-
cess x)f its combination is known as oxidation or
combustion. It is essential to respiration and is
present in every living cell. Of its innumerable
compounds, water is the most important. - Oxygen
gas can be readily recognized by the fact that glow-
ing substances are set on fire or burning substances
burn much more brightly when introduced into it.
10 CHEMISTRY FOR NURSES
21. Phosphorus — is a waxlike solid which shines in the
dark and readily catches fire. It is used in making
matches and is very poisonous. Some of its com-
pounds, such as sodium phosphate, are used as drugs.
Another of its compounds, calcium phosphate, forms
about 60 % of hone, and is also present in all
fertile soils, — is, in fact, essential to the growth of
plants. Other important compounds are present in
the blood, in the brain, and in the urine.
22. Platinum — a metal used in jewelry ; does not enter
into the body. It is a " precious '' metal for the
same reason as gold.
23. Potassium — a. shining white metal which readily
forms compounds with a great many other ele-
ments. When thrown into water it unites with it
so actively as to take fire. It has a great number
of important compounds, such as caustic potash
(potassium hydrate), potassium chlorate, potassium
iodide, potassium bromide, potassium nitrate, and
many others.
24. Radium — a peculiar metal which gives off very pene-
trating rays like X rays. It was recently discovered
by Mme. Curie. It is used in the treatment of cer-
tain skin diseases and cancers.
25. Silicon — is not of much importance to our bodies,
but it is, nevertheless, next to oxygen the most
abundant element. It forms a large part of
rock, sand, clay, and soil. Glassware contains
much silicon, as do a great many other things
that we handle; it is contained in the many
forms of stone and crockery dishware. It is very
insoluble.
ELEMENTS AND COMPOUNDS 11
26. Silver — a metal, some of whose compounds such as
silver nitrate, argyrol, protargol, are used in
medicine.
27. Sodium — a very widespread element, the sister
metal of potassium, and with very similar proper-
ties. Some of its compounds, as sodium chloride,
carbonate, bicarbonate, are important constituents of
the blood.
28. Strontium — is somewhat similar to sodium and
potassium. Some of its compounds, such as stron-
tium bromide, are used as drugs.
29. Sulphur — is a yellow, inflammable solid used directly
as a drug. Its compounds, such as sulphuric acid,
magnesium sulphate, etc., are important in medicine.
It is found in many parts of the body, such as skin
and hair.
30. Tin — a metal.
31. Zinc — a metal some of whose insoluble compounds,
such as zinc oxide, are used in medicine for their
soothing properties. Its soluble compounds, like
zinc sulphate and zinc sulphocarbolate, are poison-
ous and are used as disinfectants and cauterizing
agents.
CHAPTER II
Atoms and Molecules
The Use of Hypotheses in Science. — In order
to explain the phenomena of nature, scientists often
use hypotheses, or working theories. These are sup-
positions which explain the facts, but which for the
time being cannot be proved completely. One of
the most useful and important of these hypotheses
is the atomic theory, — the idea that all substances are
composed of extremely minute particles. Although
nobody has ever seen one of these particles, the
theory is so useful and explains so much that the
whole development of modern chemistry has been
built up on it.
Molecules. — Suppose that we commenced to
divide any substance, say a drop of water, into
smaller and smaller particles, and suppose that we
had instruments fine enough so that we could con-
tinue this division as long as we wanted to, we would
finally reach a particle so small that if it could be
further divided, it would no longer be water. These
12
ATOMS AND MOLECULES 13
particles of which water is believed to be formed
are called molecules.
If the molecule of water were broken up into its
constituents, hydrogen and oxygen, it would no
longer have the properties of water. Hence a mole-
cule is defined as the smallest weight of any kind of
matter in which the original properties of the matter
are retained.
^ Atoms. — But suppose that instead of starting
with a compound we were to start with an element
itself. Here, too, an overwhelming array of evidence
has led scientists to make the hypothesis that ulti-
mately particles would be reached which could not
be further subdivided. These particles are known
as atoms}
Molecules Composed of Atoms. — In the first
chapter it was stated that the composition of any
compound is absolutely constant; when any com-
pound is analyzed into its elements we always get
exactly the same amount of each of the elements
from any given amount of the compound. We see
now why this is so. Each molecule of a compound
* Recent discoveries in connection with radium and X rays
have brought to our knowledge particles far smaller even than
atoms, — particles out of which probably atoms themselves are
made.
14 CHEMISTKY FOR NURSES
has the same number of atoms as every other molecule
of the compound. Every molecule of water has
one atom of oxygen and two atoms of hydrogen.
Therefore, water, no matter where or how obtained,
always has constant amounts of oxygen and hydro-
gen.
Size of Molecules. — The absolute size of atoms
and molecules is not known. All atoms and even
the largest molecules, those known to contain thou-
sands of atoms, are far too small to be seen through
the most powerful microscope. It will give you some
idea of their size to know that it has been calculated
that if a single drop of water were magnified to the
size of the earth, the molecules would be something
like the size of baseballs.
Weight of Atoms. — The atoms of the different
elements have different weights ; the atoms of the
same elements are all alike. Though their absolute
weights are not known, the relative weights of all
the atoms are known with great accuracy. Hydro-
gen is the lightest and is taken as the standard,
while the atom of radium, one of the heaviest, weighs
two hundred and twenty-five times as much as the
atom of hydrogen.
ATOMS AND MOLECULES 15
PHYSICAL STATE OF MATTER
Changes in Physical State of Molecules. — A sub-
stance remains unchanged no matter what vicissi-
tudes it goes through as long as the atoms in its
molecules remain together. The molecule of water
is the same whether in steam, or water, or ice. But
the positions and motions of the molecules may vary.
In steam and in all gases the molecules are separated
by space and vibrate to and fro. This causes the
pressure of gas on the containing wall (for instance,
the pressure of the gas in a balloon). In fluids the
molecules are packed much more closely together,
but they still move to and fro. In solids their rela-
tive positions are fixed. The physical state of a sub-
stance, whether it is solid, fluid, or gas, depends on
temperature and pressure, and it is possible to ob-
tain most substances in any one of these three forms.
Thus we have reached a different idea of chemical
and physical changes from that given in the first
chapter. Chemical changes are those in which the
atoms in the molecule are changed. Physical changes
are changes in which the molecules retain all their atoms
intact. This is the reason that chemical changes are
generally more permanent and deep-going than physi-
cal changes.
16 CHEMISTRY FOR NURSES
Many physical processes, such as dissolving, boil-
ing, distilling, crystallizing, are made use of in chemi-
cal operations.
Solution. — When sugar or salt is put into water
it disappears (dissolves), but its presence in the water
can be recognized by the taste. If more salt or
sugar is gradually added, a limit is finally reached,
at which no more can be dissolved. The solution is
saturated} If now the water is warmed, it will dis-
solve some more sugar or salt, for the solubility of
most solid substances increases as the temperature
rises. If the solution is saturated while very hot
and then allowed very slowly to cool, some of the
sugar or salt will appear again in the form of crystals.
Crystallization. — Likewise, if some of the water
evaporates from a saturated solution, crystals form.
Crystallization is one of the methods used in chemis-
try and in manufacturing to obtain substances in a
pure state. For a crystal contains not a mixture of
two substances, but only one substance.
The Right Solvent must be Chosen. — Substances
may dissolve not only in water, but in other fluids.
Moreover, the solubility of different substances in
different fluids varies greatly. Thus water will dis-
1 See Chapter on Solutions in Blumgarten's " Materia Medica
for Nurses."
ATOMS AND MOLECULES 17
solve large amounts of salt, but will not dissolve fat
at all . Ether, on the other hand, dissolves fat readily,
but not salt.
Solubility of Gases. — A fluid may dissolve not
only solids, but also various fluids and gases. For
instance, ether or chloroform will dissolve to some
extent in water. A familiar example of a dissolved
gas is carbonated water (carbonic acid gas dissolved
in water). Oxygen is soluble in water and fish live
by breathing dissolved oxygen gas. Dissolved gases
do not follow the same rule with regard to tempera-
ture as dissolved solids, but on the contrary as the
temperature rises, less, not more, of the gas will
dissolve.^
Distillation. — When fluids change to gases at
ordinary temperature we speak of the process as
evaporation. When heat is applied so that the
change from fluid to gas is violent we call it hoiling.
When gases are cooled sufficiently, or are subjected
to pressure, or both, they condense and form liquids
again. Distilling consists of first boiling a fluid
and then cooling the escaping vapor to a liquid.
Distillation is very useful in purifjdng and separating
various substances.
* The reason that boiled water tastes " flat " is that the heat
drives all the dissolved air out of it.
c
CHAPTER III
Chemical Names and Formulas. Chemical
Affinity
Chelnical Names tell the Composition of Sub-
stances. — To make the study of their science as
easy as possible, the chemists have tried to give
every compound a name that in general tells what
its composition is. This can be done, however, only
with relatively simple compounds. When we get
molecules that contain two or three hundred atoms
it is impossible to name them all, but in the more
simple compounds the name indicates the atoms,
and even in the very complicated ones the name
often tells a great part of the story.
Thus, combinations of oxygen are known as
oxides. Some of the simple oxides already familiar
to you are carbon dioxide (the bubbles of carbonated
beverages), nitrous oxide (laughing gas), zinc oxide.
Most of the elements can form oxides.
Many (but not all) compounds of chlorine are
called chlorides. It is evident from the name that
sodium chloride is a compound in which two ele-
ments, sodium and chlorine, have combined. The
18
CHEMICAL NAMES AND FORMULAS 19
same is true of bromides and iodides and sulphides.
Each of them is a simple combination of some ele-
ment with bromine or iodine or sulphur. In general,
the name suggests the combination.
Reason fox Using Formulas. — In the more com-
plicated parts of chemistry short names have to be
used for long compounds. But in order to state
simply and completely what atoms form each mole-
cule a system of abhreviations has been invented.
In addition to the name for each compound there is
a formula that tells in a few letters the chemical
structure. In writing formulas each element has a
letter or pair of letters which represents it. These
abbreviations are used by all chemists of the world ;
a chemist speaks a sort of international language.
It helps greatly in understanding chemistry to know
the most important of these abbreviations : —
Bromine .
. Br.
Iron . . ,
, Fe.
(for the Latin
Calcium .
. Ca.
Iodine . .
I.
ferrum)
Carbon .
. C.
Oxygen . ,
, 0.
Chlorine .
. CI.
Nitrogen . .
. N.
Hydrogen
. H.
Phosphorus .
Potassium
. P.
K.
Because phosphorus was known before potassium
it has the initial letter ^^ P ^' for its abbreviation ;
potassium must have some other initial and so the
20 CHEMISTRY FOR NURSES
Latin name of kalium is used for potassium and its
abbreviation is simply K.
Sodium . . . Na. (natrium)
Silver . . . Ag. (argentum, Latin for silver)
Sulphur . . . S.
How to interpret Formulas of Compounds. —
Each initial written alone stands for a single atom.
When two or more initials are written together they
stand for a compound whose molecule contains as
many of each kind of atom as is represented by the
little figure written to the right of the letter. For
example : KI means a molecule containing one
atom of potassium and one of iodine (potassium
iodide). The abbreviation CO2 means that each
molecule of carbon dioxide contains two atoms of
oxygen and one of carbon. The formula for silver
nitrate is AgNUg, which means that ona. atom of
silve^ is united with ^e of nitrogei^ and Jjiree of
oxygen^ Thus there are §ye-..aion^ in the one
molecule of silver nitrate. The formula tells at
once exactly what silver nitrate is.
CHEMICAL AFFINITY
What makes Atoms Unite ? — Why do the atoms
unite to form molecules? In order to explain this
CHEMICAL NAMES AND FORMULAS 21
scientists have had to assume the existence of a
powerful and Httle understood force known as
chemical affinity. This tendency to unite with
other atoms is very strong in some instances, very-
weak in others. Thus the tendency of the elements
sodium and potassium to combine with other ele-
ments is so great that it is extremely hard to keep
these substances, even when one gets them, in a pure
state. They combine with anything they touch.
When thrown into water potassium combines with
it so violently as to burst into flames. On the
other hand some elements, such as gold and plati-
num, have very little tendency to unite with other
elements and they form only a few compounds and
these with difficulty. This is why they are used as
jewelry.
Special Affinities of Different Atoms. — Not only
do the atoms^ vary in the strength of their unions,
but they show peculiar preferences; each atom
shows a greater tendency to unite with certain
atoms than with others. The laws that govern this
chemical affinity are quite definite, so that when a
number of different kinds of atoms are mixed together
in such a way as to be free to combine, one can always
predict with certainty which ones will unite with
each other.
22 CHEMISTRY FOU NURSES
Thus if any metal such as iron, or even silver or
gold, is put into a watery solution of the element
chlorine, the metal will always unite with the
chlorine, — never with oxygen or hydrogen, because
the chemical affinity of chlorine for all metals is very-
great. On the other hand, most metals, if kept in
water containing no chlorine, or even in moist air, will
gradually rust or tarnish, due to union with oxygen.
THE USE OF CHEMICAL FORMULAS
To show how we can express chemical reactions
or changes and think out how they will happen, let
us take the action of h ydrochlor ic acid on ^Iver
^itrate,_ Hydr o Qhlor ic acid contains to each mole-
cule one atonuiLhydrQgeji and one of chlorine. Its
formula is HCl.
Mix a drop of clear silver nit rate solution in a
test tube with a little .h^dxachlQiLc acid ; a thick,
white substance or precipitate forms at once.^ Silver
has a very powerful affinity for chlorine and when
they unite they form silver ch loride. This is what
the precipitate is composed of.
^ A precipitate is a solid formed in a solution as a'result of
chemical action. The fluid can be separated from the solid
by filtering through filter paper. When this is done, the clear
fluid that comes through the paper is known as the filtrate, the
solid powder left on the paper is called the residue.
CHEMICAL NAMES AND FORMULAS 23
The formula which expresses what happens is : —
AgNQa + HCl = AgCl + HNO3
(Silver Nitrate + Hydrochloric Acid = Silver Chloride + Nitric Acid)
This says that on adding silve r nitrate to hydro-
(chloric add the ^Iver leaves its combination with
nitrogen a nd oxyge n and joins the chlorine, for which
it has a greater affinity. The hydr ogen which was
originally present in the hydroch loric acid being
torn from its chlor ine unites with the equally deserted
nitr ogen-oxvgen _combination to form another new
substance which will later be recognized as nitric
^cid. Thus formulas show the exchange of atoms
between molecules.
Any compound which contains chlorine united
with on e other elem ent will act in the same way as
hydrochloric acid when brought into contact with a
^ilver /^, ompound.
Thus let the student find out what happens if
sodium chloride (NaCl) instead of hydrochloric acid
(HCl) is mixed with silver nitrate. Write the
formula. i^#y4y'Na^/'=: A^C/ ^//g^/^ff^
• VALENCE
The reader will have already noticed that in
forming compoands some atoms combine only with
one other atom, others join with two, three, or more.
Thus the atom of oxygen unites with two atoms of
24 CHEMISTRY FOR NURSES
hydrogen to form the molecule of water (H2O),
while the atom of clilorine unites with only one
atom of hydrogen to form hydrochloric acid (HCl).
This is subject to a definite rule which explains why
the molecule of any substance contains always fixed
numbers of the same atoms grouped in the same
way. This explanation is really another working
hypothesis, known as the theory of valence.
Valences are Imaginary Points of Attachment for
Other Atoms. — Imagine the atom as having arms by
which it can hold on to the arms of other atoms.
Each kind of atom has always a f,xpd number of arms,
or valences, as they are more properly called. Thus,
for instance, the atoms of hydrogen, spdium, j)otas-
sium, chlorine, bromine, iodine, have each only
one arm to hold on to the other atoms with. When
they unite with each other these atoms therefore
form compounds having two atoms only to each
molecule. Picture to yourself the atoms with their
imaginary arms: —
Hydrochloric Acid @ (§)
Potassium Iodide @ (J)
Sodiiun Bromide ® @
The atom of oxygen as well as that of sulphur has
two such arms or valences. The atom of nitrogen
CHEMICAL NAMES AND FORMULAS 25
has three (and in reality it has two extra arms which
it occasionally can use, but which in its ordinary
combinations it does not use). The atom of carbon
has four arms.
A knowledge of these facts will enable you to
understand much more clearly the reason for the
structure of some of the molecules that we have been
considering. Thus take, for instance, the molecule of
water (H2O). In water we have the two-armed
atom, oxygen, holding with each of its arms to the
arm of a one-armed atom, hydrogen, thus : —
® — @ — ®
Or consider ammonia (NH3). Here we have the
nitrogen atom holding by its three arms to the arms
of three atoms of hydrogen : —
Y
Two atoms may often be joined by more than one
arm or valence. Thus, for instance, in CO2 (carbon
dioxide) the Garhoiuiom divides its four arms, giving
two to each of the oxv^en ato ms with which it is
united : —
(Q)=<G)==<Q)
26 CHEMISTRY FOR NURSES
What is meant by Structural Formulas? — All
the complicated structure of the much larger mole-
cules of the more complex compounds is built up in
exactly the same way. Each atom holds to the
other atoms by one or more of its available arms.
Those formulas which are written out in such a way
as to show how each atom of the molecule is attached
to the others by the proper number of xslences are
known as structural formulas, because they show
what is believed to be the actual structure of the
molecule. Thus the structural formula of silver
nitrate, AgNOs, is : —
© (0)
Write the structural formula for potassium ni-
trate, KNOs (niter, saltpeter).
CHAPTER IV
Energy and Oxidation
ENERGY
Even superficial observation shows that there
must be some close connection between chemical
changes and such manifestations as heat, light,
electricity, and motion. Almost all combustions, for
instance, raise the temperaturej and many of them
produce light as well. Any chemical reaction that
occurs suddenly may show violent motion in the re-
sulting explosion (gunpowder, for instance). And
every one knows that the electric current comes from
the interaction of the chemicals that are put into an
electric battery.
And, on the other hand, not only do chemical
changes produce- heat, light, or electricity, but just
as often heat, light, or electricity produce chemical
changes. The roasting of coffee, the bleaching of
muslin, and the silver plating of household utensils
by means of the electric current are everyday in-
stances of this.
27
28 CHEMISTRY FOR NURSES
How Different Forms of Energy are Related. —
WTiat is the connection between chemical changes
and all these forces? Or perhaps before we try to
answer that we should ask : Is there any connection
between these different forces themselves? There is.
They are all of them different forms of motion.
The first inkling of this remarkable fact came as
far back as the beginning of the nineteenth century,
when Count Rumford proved that by continued
friction one could produce heat in any amount.^
Hence, he said, heat is not a material substance, but
a mode of motion. Gross motion by friction is con-
verted into motion of molecules. (Before that time
heat had been regarded as a fluid.)
Forms of Energy mutually Convertible. — And
then as a result of a series of wonderful discoveries
it gradually became clear that by suitable means
any one of these forms of so-called energy could he con-
verted into any other. Practical inventions grew out
of these discoveries. The steam engine was invented
to convert heat into motion. But the heat that
drives the steam engine comes from the burning of
coal, — a chemical process. So the steam engine is
really a machine for converting chemical fenergy into
motion. The motion provided by the steam engine
^ The heat produced by friction is what lights a match.
ENERGY AND OXIDATION 29
in turn can be changed to electricity by the electric
dynamo and sent on wires to long distances. And
the electric current of the dynamo provides both
light and heat or is converted back into motion
again at convenient places by the electric motor.
Conservation of Energy. — From all this resulted
a great generalization (first formulated by Mayer,
a German physician, about 1840). It is known as
the principle of the conservation of energy and is re-
garded to-day as one of the most fundamental doc-
trines of all scientific thought. The principle in
brief is that energy can neither he created nor destroyed,
neither come into existence nor be annihilated.
When energy seems to have been produced it has
really only been changed from some hidden to some
visible form ; when energy seems to have been lost
it has only been dissipated, not destroyed.
Hidden Energy of Chemical Compounds. — Now
let us go back to our question. What connection is
there between chemical change and all these different
forms of energy? It is this: when energy in any
form is manifested as the result of a chemical pro-
cess, that energy must have been lying hidden in the
substances that entered into the chemical process.
When coal burns the heat is not newly created, but
is energy that has been lying dormant, locked up in
30 CHEMISTRY FOR NURSES
the molecules of the coal for untold ages. And, con-
versely, when energy is used to bring about a chemical
changCj that energy is not lost, but put into the newly
formed chemical substances} And from these sub-
stances it can be liberated again either in the same
or another form, only by a subsequent chemical
change. The energy of the coal was obtained from
the sun's rays millions of years ago. All chemical
processes either use up or free energy.
The Animal Body a Machine for Transformation
of Energy. — Of what significance is all this to us ?
We are interested, first of all, in the care of the hu-
man body. " A living body is a machine, by which
energy is transformed, in the same sense as a steam
engine is so, and all its movements are to be accounted
for by the energy which is supplied to it." (Huxley.)
Measuring Energy. — As we need standards to
measure weight and distance, so also we need a stand-
ard to measure so universal a commodity as energy.
A number of such standards have been proposed and
used for special purposes (for instance, the foot
pound, the horse power). But the standard in most
^ Just so work done in lifting a weight is not lost, but can be
recovered again if the weight in falling is connected with a pulley.
The energy latent in the lifted weight might be compared to
the energy in the altered molecule.
ENEKGY AND OXIDATION 31
general use (and the one most important to us because
it is used in measuring the hidden energy of foods)
is based on heat. The unit is the amount of heat
needed to raise one kilogram of pure water one degree
on the centigrade scale,^ and this amount of heat is
called a calorie.
The Meaning of '' Food Value." — Thus when we
say that a gram of starch has four calories, or a gram
of fat nine calories, we mean that the complete burn-
ing up of these substances (whether in the test tube
or in the body) would produce enough heat to raise,
respectively, four and nine kilograms of water one
degree on the centigrade scale. Or if we say that a
child of one year needs every day seventy calories
for every kilogram (one thousand grams) of body
weight, we mean that the child needs food which if
burnt up would provide that amount of energy. So
substances have '' food value " in proportion as they
supply the body with energy. Water and salts are
absolutely essential in the diet, but in this sense they
have no " food value."
OXIDATION
Energy can be manifested by all sorts of chem-
ical changes; but the kind of chemical change
1 From 0° C. to V G.
32 CHEMISTRY FOR NURSES
which most commonly produces energy is oxidation,
the entering of any substance into combination with
oxygen.
What happens in Oxidation? — This was dis-
covered by the great French chemist Lavoisier
soon after the discovery of oxygen itself in 1774.
It was noticed that oxygen was consumed or trans-
formed during the combustion of any substance, and
that the weight of the substance (or of its products)
was increased by just so much as the weight of the
oxygen that disappeared.
Oxidation may go on slowly, as in the rusting of
iron or the glowing of charcoal. Or it may go on
very rapidly with the liberation of heat and light.
This latter is called combustion. Substances which
oxidize slowly in the air (which contains only about
20 % of oxygen) will burn brightly if put in pure
oxygen. Thus a piece of glowing charcoal or a
glowing match will flare up with a brilliant white
light for a few moments if dropped into a test tube
filled with oxygen (from an oxygen tank such as is
used for the sick). This combustion lasts only a
few moments, until all the oxygen in the tube has
been used up. Or a piece of steel wire (a watch
spring), which of course oxidizes only very slowly in
the air, will burn with a brilliant white light if heated
ENERGY AND OXIDATION 33
to redness in a Bunsen flame ^ and held in a stream
of pure oxygen.
Oxidation may decompose Substances. — Oxida-
tion may mean merely the attachment of oxygen
atoms to other atoms without any very extensive
breaking up of molecules; thus when a piece of
phosphorus or a piece of sulphur burns in the air,
phosphorus or sulphur atoms unite directly with
oxygen atoms. Or oxidation may mean the complete
breaking up of complicated molecules so that the vari-
ous atoms can combine with oxygen.
An instance of the latter class is the burning of
wood. Wood is composed chiefly of carbon and
hydrogen, with a very small proportion of oxygen.
When wood burns the carbon and hydrogen are split
apart, the carbon uniting with oxygen to form carbon
dioxide, CO2, the hydrogen uniting with oxygen to
form water, H2O.
Production of Carbon Dioxide and Water by
Burning Wood. — You can convince yourself of this
^ The Bunsen gas jet is one in which air is allowed to be sucked
in with the gas at an opening a few inches away from the flame.
The result of this intimate admixture of air and gas is a non-
luminous flame, because the oxidation is very complete and there
are no luminous particles of unoxidized carbon to give light.
An ordinary luminous flame is not so hot and a certain amount
of carbon fails to burn and is given off as soot. The burners of
our gas stoves are modified Bimsen burners.
D
34 CHEMISTRY FOR NURSES
by a very simple experiment. Hold a burning
match under an inverted wide test tube so as to
catch the fumes. Near the neck of the tube little
beads of water (condensed steam) are formed on
the glass (ordinary smoke contains a considerable
amount of moisture). As soon as the match stops
burning, quickly turn the tube right side up and
pour some limewater into it. The limewater turns
milky, due to a precipitate of calcium carbonate
formed by the union of carbon dioxide with calcium.
(This is the most convenient test for carbon diox-
ide.i)
The Same Substances are produced by the Hu-
man Body. — Thus the products of the oxidation
of anjrthing composed of carbon and hydrogen are
carbon dioxide and water. This is just as true of
our bodies (which are composed largely of carbon
and hydrogen) as it is of the match. Just as CO2
and H2O are given off by the match, they are given
off by our bodies. This can be easily proved.
Breathe out through a glass tube into a test tube of
limewater; the limewater quickly becomes cloudy
from the CO2 of the breath. The water produced
^ It is due to this reaction that a bottle of Hmewater left un-
stoppered gradually turns cloudy and looses its strength fron>
the traces of carbon dioxide in the air.
ENERGY AND OXIDATION 35
by oxidation in our bodies is given off as sweat and
urine, and as vapor from the lungs.
Why we need Air. — During respiration the air
(which is practically nothing but oxygen diluted with
about four times its volume of nitrogen'^) is drawn into
the lungs and deprived of a small part (about 5 %) of
its oxygen. In exchange it receives the carbon diox-
ide which the body has to get rid of. The oxygen
that is absorbed from the air is taken up by the red
blood corpuscles. It enters not into firm chemical
union, but into loose combination with the red sub-
stance called haemoglobin in the corpuscles. Hsemo-
globin that is carrying oxygen in this way is bright
red in color, whereas after it has given up its oxygen
to the various organs and tissues it is deep purple.
This is the cause for the difference in color of blood
flowing from arteries and that flowing from veins.
And so it is oxygen, after it has reached the tissues
of the body, that liberates the energy necessary to
produce the muscular contractions, the warmth, the
nerve actions, and the thousand other manifestations
of life.
* It also contains small amounts of carbon dioxide and water
vapor and traces of a number of other gases.
CHAPTER V
Acids
Three Principal Kinds of Compounds. — As there
are only eighty elements, most of the substances
we know are compounds. Of the thousands of in-
organic or mineral compounds the majority belong
to one of three classes : they are acids, salts, or bases.
r The acids have very striking characteristics in
common. They form a sharply defined group. It
might be well to begin the study of acids by examin-
ing cautiously ^ bottles of a number of common acids
(hydrochloric, sulphuric, nitric, acetic). The bottles,
though of the same size and contents, vary greatly
in weight. The bottle of sulphuric acid is sur-
prisingly heavy.
Taste. — If you dissolve a single drop of any of the
acids in a glassful of water, you will notice that a
strong sour taste has been given to the water. All
acids in dilute solution taste sour, and almost all
things that are sour are acid. Acetic acid is what
gives the sour taste to vinegar, citric acid to lemon,
^ Some of them are dangerous poisons.
36
ACIDS 37
phosphoric acid to the '^ phosphate " at the soda
water fountain.
Several of the bottles give off rather irritating
fumes (hydrochloric, nitric, acetic acids). This is
because these acids are volatile (easily given off in the
gaseous form).
Physical State. Solubility. — Though, for con-
venience, we examine the acids in fluid form, or at
least in solution, they are not all fluids at ordinary
temperatures. Some are solids and others are gases
(hydrochloric acid, for instance). All of them can
be made either solid, fluid, or gaseous by suitable
temperature and pressure. They are all easily
soluble in water. In fact, they have a special kind of
affinity for waier and some of them unite with it
very violently. Thus if a few drops of sulphuric acid
are carefully ^ (drop by drop) put into a test tube
with a little cold water, the water instantly becomes
very hot.
Let us try the effects of some of the acids on cer-
tain solid substances and see what we can learn about
the characteristics and composition of the acids.
* Hold the tube with the opening pointed away from your-
self and away from any one else. This is a safe rule for all
test tube experiments. If the water or acid is hot or the acid is
all added suddenly, the mixture may splutter into somebody's
face.
38 CHEMISTRY FOR NURSES
Acids attack Metals. — Put a ten-cent piece in a
test tube with some strong nitric acid and heat very
gently.^ The dime dissolves slowly (as can be de-
termined later by seeing the corroded surface) and
gives off little bubbles of clear gas. The solution
turns green (due to the fact that the nitric acid dis-
solves some copper out of the dime ; the compounds
of copper are mostly green). Set the tube aside and
a little later you can return to it and perform an
experiment that will convince you that silver is also
dissolved in it.
Drop a very small piece of zinc into some strong
hydrochloric acid. The zinc dissolves and bubbles
of gas come away from it in a lively manner as though
the solution were boiHng. After a while the zinc
disappears entirely.
Acids form Compounds with Metals. — In both
of these instances a solid substance has been dis-
solved in an acid. It might be thought that the
result was simply a solution of the solid in the fluid
like the solution of salt or sugar in water. But this
is not so. If we evaporate the salt or sugar solu-
tion, we get back simply salt or sugar. But if we
could evaporate the tubes in which the dime and the
1 If heated too much, large volumes of intensely irritating
brown fumes are given off.
ACIDS 39
zinc were dissolved^ we would recover not copper, or
silver, or zinc, but a green compound of copper called
copper nitrate, a crystalline compound of silver
called silver nitrate, a white saltlike poisonous com-
pound of zinc called zinc chloride. Furthermore,
if we could examine the amount of acid in each of the
tubes before and after the addition of the metal, we
would find that the acid had diminished. The acid
used itself up in attacking the metal and forming
the new compounds.
The most striking characteristic of the adds, then,
is their power of decomposing and dissolving certain
other substances, with the formation o£ . new c om-
pcxwnds.
All Acids contain Hydrogen. — Note also that
in both experiments hubbies were given off. If we
were to collect and examine these bubbles, we would
find in both instances that they consisted of hydrogen
gas. Hence, since the hydrogen could not have
come from the dime or the zinc, it must have come,
in each instance, from the acid. Acids contain
hydrogen.^
And now (since we have not time to completely
* Not all acids give off free hydrogen under similar conditions,
but there are other methods of proving that all acids contain
hydrogen.
40 CHEMISTRY FOR NURSES
analyze the acids) let us see what we can learn by
examining the formulas of a number of acids : —
Hydrochloric Acid HCl
Sulphuric Acid H2SO4
Nitric Acid HNO3
Carbonic Acid H2CO8
Phosphoric Acid • HaPOg
Hydrocyanic Acid HON
You will notice that besides some element (chlorine,
sulphur, nitrogen, etc.) after which the acid is named,
and besides oxygen, present only in some of the acids,
all the acids have one characteristic in common, —
they all have at least one hydrogen atom.
What is peculiar about the Hydrogen in Acids ? —
There are many other substances that have hydro-
gen atoms in their molecules (water, for instance) ;
but the hydrogen atom in the acid molecule is pecul-
iar. It is loosely attached, so that you may think
of the acid as constantly trying to get rid of it. But
the acid can only get rid of the hydrogen atom on one
condition, — namely, if it can replace the gap in its
structure filled by the hydrogen atom with some
other atom for which the acid has a greater affinity.
It is this peculiarity of replaceable hydrogen atoms
that gives all the acids their "acid" characteristics.
ACIDS 41
Action of the Nitric Acid on Silver. — Thus let
us take the first experiment above (page 38) — the
dissolving of silver in nitric acid. The formula for
this reaction is : —
Ag + HNO3 = AgNOs + H
(Silver) (Nitric acid) (Silver nitrate) (Hydrogen)
What happened was that the molecule of nitric acid
simply threw off its hydrogen atom and replaced
it with a silver atom. The excluded hydrogen was
given off as bubbles. The presence of dissolved silver
nitrate can he proved by pouring off the nitric acid in
which the dime has partly dissolved and adding to
it some hydrochloric acid. At once a dense, curdy
white 'precipitate forms and sinks to the bottom of
the tube. (A precipitate is any solid that is formed
as the result of a chemical reaction in a fluid ; usu-
ally it is heavy and is ^^ precipitated " down to the
bottom of the tube.) If you take a granule of silver
nitrate (such as you are already familiar with in
the caustic stick), dissolve it in water and add a little
hydrochloric acid, you will get the same kind of
white precipitate. The formula for the reaction
by which the precipitate is formed is : —
^gNO,
+ HCl =
.HNO3
+ AgCl
(Silver
(Hydrochloric
(Nitric
(Silver
nitrate)
acid)
acid)
chloride)
42 CHEMISTRY FOR NURSES
This equation shows that the silver has left its at-
tachment to the nitrogen-containing molecule (silver
nitrate) and has replaced the hydrogen of the hydro-
chloric acid. In this test there was a contest be-
tween the nitric and the hydrochloric acid for the
possession of the silver atom. The hydrochloric
acid had a greater afl&nity for silver than nitric acid
had, and the resulting compound, silver chloride, being
insoluble, was precipitated down as a solid.
Similarly, all of the acids have particular affinities
for certain elements or combinations of elements
and combine with these rather than with others.
The substances with which acids combine in this
way are chiefly metals and the combing itiQns or
compounds are known as salts. ♦^■^ ^-'^^^d^^^'^ jhfUf
There are Strong and Weak Acids. — The solvent
powers of some acids, as, for instance, the strong
mineral acids, hydrochloric, hydrofluoric,^ nitric,
sulphuric, are very great. Other acids, like phos-
phoric and carbonic, are relatively weak. Another
group of acids, of which acetic acid is an example, is
known as organic acids. (See chapter on organic
chemistry.)
^ Hydrofluoric acid is so powerful a solvent that it dissolves
even glass, and hence cannot be kept in glass bottles. It is
used for etching on glass.
ACIDS 43
Decomposing Power of Acids. — Acids not only
combine with those substances for which they have
chemical afl&nity, but in order to get at those sub-
stances, they often break down and disintegrate other
molecules. The acids are therefore very powerful de-
composing agents. To illustrate this action, drop a
small splinter of wood into a test tube of sulphuric acid
and warm gently. The fragment of wood rapidly
becomes charred and black and finally disappears
completely.^
The Litmus Test. — There is a very simple test
for the presence of acid in any solution, — namely,
the litmus test. Litmus is a colored substance de-
rived from the root of a plant. In the absence of
acid it is purple or blue, but it is turned bright red hy
any acid. We generally use pieces of paper which
have been soaked in litmus. Dip several such pieces
of paper in different acids and all of them turn bright
red. It will help you to remember that the red
color of litmus indicates acid, if you remember it in
connection with the fiery nature of acids.
Acids play a very important part in the chemistry
of our body. The most important acid is the hy-
drochloric acid found in the stomach juice.
^ Other experiments in which acids are used to split mole-
cules are described in the chapter on carbohydrates.
CHAPTER VI
Bases
As peculiar as the acids and yet in their properties
entirely different, in fact almost exactly the opposite
are the important substances called bases (also called
hydroxides or hydrates).
Properties of Bases. — Let us examine the watery
solutions of a few typical bases, such as : —
Sodium hydrate (caustic soda)
Potassium hydrate (caustic potash)
Ammonium hydrate (ammonia water)
Calcium hydrate (limewater)
We notice that when applied to the skin they give
it a peculiar soapy feeling. Some of them (sodium
potassium, ammonium hydrate^) applied to mucous
membranes are strong irritants and corrosive poisons.
When diluted well (for safety) they are found to have
an unpleasant soapy taste. Tested with litmus, they
are found to do exactly the opposite to acids, —
they turn litmus a deep blue (whether it was red or
^ These are the bases whose characteristics are most pro-
nounced, — the strong bases, — and are known as alkalies.
44
BASES 45
purple to start with) . This is the best test for bases ;
anything that turns Htmus blue is basic or alkaline
(the two terms can practically be regarded as inter-
changeable) .
But the most important property of the bases is
their power of neutralizing acid^ When strong
bases and acids are mixed together they react
violently — almost explosively — with each other.
If potassium hydrate, for instance, is mixed with
hydrochloric acid, the mixture is found to have be-
come very hot, and if enough of the alkali has been
added the peculiar properties of the acid will be
found to have entirely disappeared.
Decomposing Powers. — The alkalies have power-
ful dissolving and decomposing properties also, though
generally to a less extent than the acids. It is this
property that makes them so useful as cleansing
agents (ammonia, washing soda, lye, etc.). Sodium
and potassium hydrate actually have some decom-
posing effect (though it is slight) on glass ; so that if
you shake up a bottle of one of these substances that
has been standing on the shelf for some time, you will
see in it shavings of glass dissolved by the fluid from
the inside of the bottle.
What gives these bases their peculiarities? Why
do they neutralize acids? In other words, what is
46 CHEMISTEY FOR NURSES
their chemical composition? We can find out best
if we manufacture some alkaH ourselves. Let us
make some sodium hydrate.
Soditim combines with Water. — Throw a small
piece of metallic sodium^ into a beaker of water;
it floats on the surface, melts (from the heat of the
reaction), rolls about, and rapidly disappears ; at the
same time it seems to evolve bubbles of gas. After
the sodium has disappeared in the water the solution
is found to be strongly alkaline and to have all the
properties of caustic soda (sodium hydroxide) ;
and if the gas given off is collected in an inverted
test tube, it can be shown to be hydrogen gas. In
other words, sodium hydrate has been formed by
the sodium driving some of the hydrogen out of the
molecule of water. This is shown in the formula : —
Na + H2O = NaOH + H
(Sodium) (Water) (Sodium Hydrate) (Hydrogen)
So in general bases are formed by the combination
of some metal with water; and in fact all the metals
can combine in this way to form hydroxides (though
most of them do not unite directly and violently
as sodium does).
1 Ordinarily kept in a bottle of petroleum because the sodium
oxidizes rapidly in the air and petroleum is one of the relatively
few things it does not combine with.
BASES 47
The Atom Group OH. — Now let us compare the
formula of sodium hydrate with the formulas of a
couple of other bases, in order to determine what the
common factor is : —
Sodium hydrate NaOH
Potassium hydrate KOH
Ammonium hydrate NH4OH
Calcium hydrate Ca(0H)2
Magnesium hydrate Mg(0H)2
Iron hydrate Fe2(0H)«
It is apparent at once that every one of these bases
contains the atom group qxygen-kiidrogen (OH). It
is, then, this OH group, combined with a metal,^
that makes a base.
How can we explain the EfiFect of Bases on Acids ?
— In the OH group the oxygen and hydrogen atoms
are very firmly bound together so that when the
molecule is broken up in any chemical change the
split never comes between them, but always between
the OH group and the metal atom. The metal
atom in alkalies (or bases) can be thought of as always
ready to be split off and replaced by a hydrogen atom,
^Ammonium hydrate is an apparent, not real, exception.
Though nitrogen and hydrogen themselves are not metals,
when united in ammonia they show the chemical behavior of
a metal.
48 CHEMISTRY FOR NURSES
just as the hydrogen atom in acids is always ready
to be replaced by a metal atom. Thus when an
alkali and an acid are brought together the condi-
tions for an exchange are perfect. Each has the
atom that the other desires. This explains the neu-
tralizing effect of bases on acids.
Neutralization. — Take, for instance, what happens
on mixing sodium hydrate with hydrochloric acid : —
NaOH + HCl = NaCl + H^O
(Sodium (Hydrochloric (Sodium (Water)
hydrate) acid) chloride)
Hydrochloric acid rejects its hydrogen atom in ex-
change for the metal sodium for which it has such a
strong afl&nity. The alkali (sodium hydrate) rejects
its metal (sodium) atom in exchange for the hydrogen
atom freed from the acid and forms water. You see,
then, that the alkali and the acid on being mixed
formed sodium chloride (salt) and water. The salt
is neutral ; it is neither acid nor alkaline. Litmus
paper dropped into it does not change color at all.
This experiment, the neutralization of an acid hy
an alkali, and the resulting formation of a salt is simple
and can be performed by any student. Test some
weak hydrochloric acid with litmus paper. It turns
the litmus paper bright red. Weak sodium hydrate
turns litmus paper blue. Add the sodium hydrate
BASES 49
solution to the hydrochloric acid little by little, test-
ing with litmus paper after each new addition to
see whether the solution still turns the paper red.
A point is finally reached where the paper no longer
changes. This is the neutral point and the solution
is no longer a solution of acid or alkali, but a solution
of sodium chloride, — ordinary table salt, — and can
be safely identified by the sense of taste. The re-
action which has taken place is the same as that
shown in the formula above. By mixing a power-
ful acid and a powerful alkali neutral, harmless
table salt has been formed.
Bases play an important role in the chemistry of
our bodies. The blood is weakly alkaline, and cer-
tain of the digestive juices (bile and pancreatic juice)
are decidedly alkaline. (See chapter on digestion.)
CHAPTER VII
Salts
The salts are the third great group of compounds.
They are more numerous in the world and play a
more important part in our bodies than either acids
or bases. Although they have no true nutritional
value {i.e. supply no energy), salts are absolutely in-
dispensable in the diet of all animals.^
From the two preceding chapters their chemical
composition is already clear. They are all formed
by the y^nion of an acid with a metal. The metals
which combine with acids to form salts are not only
the familiar metals like iron and silver, but also cer-
tain others such as sodium, potassium, calcium, and
magnesium. Besides this there are some groups of
atoms, themselves not metals, but which combined
act like metals. The most important of these is
ammonia (NH3). In the study of organic chemistry
^ So essential is salt in human food that the high tax put on
salt by a rapacious government was one of the immediate causes
of the French Revolution.
50
SALTS 51
we will learn that there are many other such com-
binations.
Salts are more numerous than acids because for
each acid there are as many different salts as there
are metals that the acid can combine with. Thus,
for instance, consider the more familiar salts of the
common acids : —
Hydrochloric acid forms chlorides.
Sodium chloride (ordinary table salt)
Potassium chloride (present in the blood)
Iron chloride
Calcium chloride
Ammonium chloride
Mercury bichloride
all used as drugs
Sulphuric acid forms sulphates.
Magnesium sulphate (Epsom salts)
Sodium sulphate (Glauber's salts)
Calcium sulphate (plaster of Paris)
Copper sulphate (used as a cauterizing agent)
Iron sulphate (used as a drug)
Zinc sulphate (disinfectant and cauterizing agent)
Nitric acid forms nitrates.
Sodium nitrate
Potassium nitrate (niter, saltpeter) „ , ,
T5. ii, u -x X all used as drugs
Bismuth subnitrate
Silver nitrate
52 CHEMISTRY FOR NURSES
Carbonic acid forms carbonates.
used medicinally
Sodium carbonate (washing soda)
Sodium bicarbonate
Ammonium carbonate
Bismuth subcarbonate
Calcium carbonate (which constitutes marble, chalk, and
limestone)
Phosphoric acid forms phosphates.
Sodium phosphate (present in the blood, used as a drug)
Calcium phosphate (which constitutes the hard part of
bones)
There are innumerable other important salts
formed by the action of various acids on metals in
exactly the same way.
Bromides and Iodides. — Thus the elements bro-
mine and iodine are very much like the element
chlorine and form acids corresponding in name and
behavior to hydrochloric acid.^ The salts formed
from bromine are known as hromides. Sodium, po-
tassium, and ammonium bromides are important
drugs. The salts formed from the iodine are
^ The three elements, chlorine, bromine, and iodine, behave
very much alike and constitute a group of elements known as
the halogen elements (because their salts were first derived from
the sea or from seaweeds ; the word " halogen " is a Greek word
meaning " coming from the sea ")•
SALTS 53
known as iodides, such as potassium iodide (KI),
and ammonium iodide.
Importance of Salts in the Body. — Salts play
many and varied parts in our body. Thus our
blood is practically salt water in which are dissolved
some albumin and sugar and in which are suspended
or floating around the little red corpuscles which make
the blood opaque and red.
A nurse should not only be acquainted with the
use of normal salt solution, but also should understand
why it is so important that this have exactly the
right strength, namely, 0.6 % to 0.9 %. The
reason is that this strength is the same as the strength
of the salt solution of the blood.
Effect of Distilled Water on Blood. — It is in-
teresting to see what happens to blood when it is
deprived of its salt. Take a test tube containing
some sheep's blood obtained from the slaughter-
house. It is opaque and dark red in color like the
blood that flows from a vein at an operation.^ Pour
* This dark color incidentally is due to the fact that the blood
has been standing in a narrow test tube open only to the air at
the top and that it has used up its oxygen, for if you pour a
little of the blood into another test tube and shake it up well
so that it can'' absorb oxygen from the air, it turns bright red,
but is still opaque. In obtaining the blood at the slaughter-
house it has to be defibrinated, i.e. beaten or shaken up with
glass beads, in order that it will remain fluid.
54 CHEMISTRY FOR NURSES
a little of the blood into a test tube containing some
normal salt solution; the blood retains the same
opaque appearance. But pour some of the blood
into a test tube of ordinary water or of distilled
water and the appearance is entirely changed. In a
moment or two the tube instead of being opaque
becomes perfectly transparent.
What has happened is that in the absence of the
salts (or what is the same thing, when the salts were
greatly diluted so as to be present in only a little
strength as compared with normal salt solution)
the red blood cells became completely dissolved and
destroyed. This is called the " laking '' of blood,
or hcemolysis, (Lysis means dissolving.) It is be-
cause of the danger of hsemolysis that plain or dis-
tilled water cannot be used for intravenous or sub-
cutaneous infusions, but saline solution has to be used.
What is true of the red blood cells is also true, in
large part, of the other body cells. They are in-
jured or killed by contact with plain water or with
water that contains insufficient amount of salt.
Actually all of our body cells, excepting those at
the surface of the body, are bathed and live in salt
solution.
Functions of Special Salts. — Each of the salts
has important special functions in the body. Thus
SALTS 65
calcium chloride is absolutely essential for the clotting
of blood; if we did not have it, our blood would never
clot and we should bleed to death from the slightest
cut. This is the reason why calcium compounds are
used as drugs in certain diseases in which the blood
does not clot properly.
Basic and Acid Salts. — Not all salts are neutral
in reaction. Some are alkaline or acid. For instance,
the carbonate and bicarbonate of soda are alkaline
(and are used medicinally to neutralize excess of
hydrochloric acid in the stomach). Their alkalinity
is due to the fact that they consist of a very strong
alkaline metal (sodium) in union with a very weak
acid (carbonic acid). On the other hand acid-
sodium phosphate (the best drug known for the
purpose of making the urine acid) derives its acid
properties from the fact that in its formation phos-
phoric acid does not get all of the sodium it could
unite with, i.e. is incompletely neutralized. When
phosphoric acid gets all the sodium it can combine
with it forms the ordinary sodium phosphate used
as a laxative.
CHAPTER VIII
Organic Chemistry
A HUNDRED years ago, when people were first
studying such things earnestly, it was noticed that
there was a large group of substances entirely distinct
from any of the substances we have mentioned so
far. The substances of this group were all derived
directly or indirectly from plant or animal organisms
and hence were called " organic '^ (as distinguished
from inorganic or mineral substances).
Organic Matter completely Combustible. — They
were peculiar in that they were all easily comhustihle,
and that when heated they would first char (thus
revealing the presence of carbon as one of their
constituent elements) and would then finally
burn up completely without leaving any ash or
residue,
(Compare in this regard the behavior of a typical
mineral substance, table salt, and a typical organic
substance, sugar. Heat a grain of sodium chloride
and a grain of cane sugar side by side on a platinum
dish over a Bunsen flame. The sugar turns black
§6
ORGANIC CHEMISTRY 57
and disappears ; the salt simply melts, and remains
as a solid mass after cooling.)
Elementary Composition. — When the fumes given
off were examined they proved to consist chiefly of
carbon dioxide and water. Sometimes oxidized
forms of nitrogen, sulphur, or phosphorus were
obtained also. (It is noticed that all these elements
are such as burn very readily and have volatile oxida-
tion products.) Thus it came to be recognized that
organic compounds are made of carhon, hydrogen, and
oxygen with occasionally the addition of nitrogen, suU
phur, or phosphorus,
I But here progress was halted for a long while.
The organic substances seemed to defy more exact
analysis. And especially it was found impossible to
manufacture any of them out of the elements. Ap-
parently they could only be produced by the living
cell. It was thought that this must be due to
some sort of " vital force '' which no one at
that time thought of identifying with " chemical
affinity."
Organic Substances not limited to Living Things.
— But this difficulty was presently overcome.
Beginning with the epoch-making synthesis of urea
(a nitrogen containing organic substance found in
urine) from the elements, by Wohler in 1828, the
58 CHEMISTRY FOR NURSES
organic substances have one by one been put together
by scientists in the laboratory. The old idea that
organic substances are peculiar to living matter had to
he given up. And to-day, out of over one hundred
thousand organic substances known, the great
majority have been made by man and are never
found in living organisms.
What is Synthetic Chemistry ? — This wonderful
development of synthetic chemistry — of the mak-
ing of new and ever new organic compounds —
has played an enormous part in the scientific progress
and the industry of modern times. To-day we
hardly go through an hour of our lives without using
some of these marvelous new substances, new drugs,
dyes, flavors, perfumes, fabrics, chemicals, even
foods.
Biological Chemistry. — Furthermore, with the
development of organic chemistry it was possible to
begin the study of the chemistry of life. It was
found that the body is a chemical laboratory with
all sorts of intricate changes constantly going on.
And although this new branch, biological chemistry,
is still in its beginnings, it has already contributed
greatly to our understanding not only of the normal
processes of the body, but also of the changes in dis-
ease. There is a whole group of diseases, such as
ORGANIC CHEMISTRY 59
gout, diabetes, ursemia, due solely to disturbances
of the chemical processes of the body. (These are
called diseases of metabolism.)
Different Compounds may have the Same Ele-
ments. — But it must not be thought that this
progress was easy. The deciphering of the organic
molecule encountered the most baffling difficulties.
For not only was it found that most organic sub-
stances were made of the same few elements, but it
was often discovered that a number of substances,
each one having properties widely different from the
others, would all on analysis turn out to have exactly
the same number of carbon, oxygen, and hydrogen
atoms. Thus there are actually eighty-two different
substances known having the formula C9H10O3.
How is it possible to have so many different sub-
stances with the same formula ? The answer to this
riddle dawned gradually on the chemists, beginning
about 1823 with the great Liebig and Wohler. It is
the greatest discovery of organic chemistry, namely,
that the properties of a substance depend not only
on the kind and number of its atoms, but also (and
especially) on the relative positions of the atoms in
the molecule.
Structural Chemistry. — Thus organic chemistry
has become a study of the architecture of the mole-
60 CHEMISTRY FOR NURSES
cule. Each atom has as definite a place to fill in the
molecule as each brick and beam in a house. Often
if a single important atom is displaced, the whole
molecule disintegrates.
The unraveHng of the intricate plans of the organic
molecules has proceeded on two routes : first, by the
analysis of known substances ; and, second, by put-
ting already known substances together and making
new substances.
In the former or analytic method the chemist first
finds out how much carbon, hydrogen, and oxygen
the substance has and what simpler compounds are
obtained when the substance is decomposed. And
then, knowing the combining power (valence) of
each kind of atom, he tries diagrams of all the pos-
sible positions in which the atoms could be linked
together. Often he is unable to decide which of
several diagrams corresponds truly to the molecule
he is studying until he has succeeded in imitating
the molecule by synthesis (building up). The man
who builds a house knows where all the beams and
stones lie.
Importance of Carbon. — As more and more of
these diagrams were deciphered one thing became
clear : the organic molecule is huilt up around the
carbon atom, or rather aroimd groups and chains
ORGANIC CHEMISTRY 61
of carbon atoms. ^ For it was found that the atom
of carbon has the remarkable property (not pos-
sessed by the atom of any other element) of com-
bining — holding hands — with itself.
So the four valences or arms of the carbon atom,
— C — , are really the key to all the complications
I
of organic chemistry. For when two carbon atoms
I I
are attached to each other thus, — C — C — , they
need use only one each of their valences. This
leaves all the other arms free to combine with other
atoms of carbon, oxygen, hydrogen, or other elements.
So the molecules of organic substances are built up
around chains of carbon atoms linked together like
this : —
H
H H H O H
H---0— C--(>-<>-C— C--C = O
I I I I I I
H O H O H
(Plan of the molecule of grape sugar)
*For this reason organic chemistry is sometimes described
as the chemistry of the compounds of carbon.
62 CHEMISTRY FOR NURSES
or around rings of carbon atoms like this
H
A
H ^\ H /C,
h
C
C
I
H
(Plan of the molecule of phenol, — carbolic acid i)
Such formulas, of course, are not representations
of actually seen arrangements, but, like the atoms
and molecules themselves, are theories; they are
accepted because they explain the behavior of the
substances.
Organic Acids. — Many organic compounds have
either acid or basic properties like the inorganic acids
and bases referred to in earlier chapters (Chapters
V and VI). The acid properties are all due to the
* Substances built up on this " ring " plan belong to a group
known as the aromatic group of substances, because of the strong
odors or tastes of many of them. Some other members of the
group are camphor, menthol, benzol, turpentine, quinine,
salicylic acid, benzoic acid, phenacetine, indigo.
ORGANIC CHEMISTRY 63
same replaceable hydrogen atom which gives the acid
properties to the mineral acids. And, similarly, when
these atoms are replaced, salts result. Thus from
the well-known organic acids, acetic acid (vinegar),
lactic acid (som* milk), tartaric acid (grapes, baking
powder), oxalic acid (many vegetables), citric acid
(lemons) are formed organic salts known, respectively,
as acetates, lactates, tartrates, oxalates, citrates.
The most important of the organic acids are the so-
called ^' fatty acids" (see Chapter on Fats), such as
acetic, butyric, oleic acids.
Organic Bases. — Among the organic substances
with more or less basic properties (i,e, neutralizing
acids) the alcohols are very important.* They have
the same atom group, OH, which we found in the in-
organic bases like sodium hydrate (NaOH) or am-
monium hydrate (NH4OH). Some of them have
several of these OH groups. Thus ordinary glycerin
is an alcohol with three OH groups in its molecule
so that it can neutralize three different acid mole-
cules at one time. (See Chapter on Fats.)
Another group of organic bases is the alkaloids, —
substances like morphine, codeine, cocaine, strych-
* For reasons which cannot be gone into here the alcohols do
not turn litmus blue and lack certain other " alkaline " prop-
erties.
64 CHEMISTRY FOR NURSES
nine, and atropine, — derived from plants and used
as drugs. They all form salts such as morphine sul-
phate, cocaiue hydrochloride, etc.^
There are three groups of organic substances
which dominate the chemistry of food and of the
body. These are carbohydrates, fats, and proteids.
They will be discussed in the succeeding chapters.
* See Blumgarten, " Materia Medica for Nurses."
CHAPTER IX
Carbohydrates
The sugars and starches form a large part of the
staple food of man. There are many different kinds,
but they all resemble each other both as to chemical
constitution and as to the functions they perform in
the living organism. On this account they are all
grouped together under the name of carbohydrates.
The carbohydrates are the first of the three great
classes of food and body substances which we are to
study.^
Of What Use are Carbohydrates? — The prin-
cipal function of carbohydrates, both in plants and
animals, is to provide energy by being oxidized. There
are many circumstances, however, under which both
plants and animals need to store away energy for
future consumption. Under these circumstances
the plants store away their energy chiefly in the form
of carbohydrates, the animals chiefly in the form of
^ This book is intended to give the principles underljdng the
study of dietetics. For a practical discussion of different foods
see Mclsaacs, " Hygiene for Nurses," Chapter on Foods.
F 65
66 CHEMISTRY FOR NURSES
fat. Thus the starch packed away in the roots, the
sugars treasured up in the fruits, are reserves on
which the plant draws in time of need. In the ani-
mal body the fat performs this storehouse function,
and carbohydrates, though they form a large part
of the food, are used up almost as quickly as they are
taken.
What Elements form Carbohydrates ? — A glance
at the chemical formulas of carbohydrates will show
why they serve so well as som-ces of energy. They
are all composed of carbon, hydrogen, and oxygen,
and the hydrogen and oxygen are always present
in the same proportion as in water, namely, two
atoms of hydrogen to every one of oxygen. Thus
grape sugar is C6H12O6; cane sugar, C12H22O11.
Note this ratio, — twice as many hydrogen as
oxygen atoms ; it is significant. It means that the
hydrogen is enough to exactly satisfy the oxygen
already in the molecule ; thus all the carbon can com-
bine with oxygen and provide energy. The products
of the oxidation are therefore carbon dioxide (CO2)
and water.
Three Classes of Carbohydrates. — There are three
chief classes of carbohydrates : (1) the simple sugars or
monosaccharides, very soluble and digestible and hav-
ing always six carbon atoms to the molecule ; (2) the
CAKBOHYDRATES 67
double sugars or disaccharides, almost as soluble and
digestible and having always twelve carbon atoms;
and (3) the polysaccharides or complex carbohydrates,
dissolved and digested with much more difficulty
and having large numbers of carbon atoms to the
molecule.
I. MONOSACCHARIDES (siMPLE SUGARs)
Dextrose (glucose, grape sugar)
Levulose (fruit sugar, fructose)
Glucose is found in plants and fruits as well as in
the blood, the muscles, and the liver of animals.
Levulose is found in sweet fruits and is especially
abundant in honey.
The Arrangement of the Atoms determines the
Properties of the Substance. — There is no class of
substances which illustrate more beautifully and
simply than the monosaccharides how a slight differ-
ence in the position of the atoms in the molecule
may change the nature of a substance. All the
monosaccharides ^ have exactly the same composi-
tion ; they are all C6H12O6. Not only this, but they
are all built on the same general plan, — a chain of
* There are many more than the two monosaccharides men-
tioned, but here, as under each heading, only the examples that
are of practical importance are given.
68 CHEMISTRY FOR NURSES
six carbon atoms, to whose side arms (valences) are
attached the hydrogen and oxygen atoms. Never-
theless, the different sugars differ from each other
in all their properties.
Thus consider grape sugar and fruit sugar. Grape
sugar (dextrose) is the form in which sugar exists
in the human body ; it circulates in the blood and
is found in the muscles; if it is injected into the
body, it is all utilized (unless injected in very great
excess). Levulose, on the other hand, is foreign to
the blood and tissues. If it is injected, most of it is
promptly thrown out again by the kidneys. It is
much sweeter than dextrose. Likewise the two
differ markedly in their chemical properties.^ Yet
compare the plan of grape sugar and of fruit sugar :
H
H H H O H
H-~0— C— C— C— C— C— C = O
u u u
Grape Sugar
* If a beam of a peculiar kind of light called polarized light
passes through a dextrose solution, it is twisted to the right, if
through a levulose solution, to the left. This remarkable prop-
erty, which is due to the conformation of the molecules, is used
in detecting and measuring sugars and other substances.
CARBOHYDRATES 69
H
H H H O H
H-O— C— C— C— C— C— C— 0— H
I I I I II I
H O O H O H
Fruit Sugar
The two are so nearly alike that by simply shifting
the position of two hydrogen atoms they could be
made identical.
The properties of the simple sugars will be dis-
cussed together with those of the double sugars.
II. DISACCHARIDES
Sucrose (cane sugar ^)
Lactose (milk sugar)
Maltose (malt sugar)
Cane sugar occurs not only in the sugar cane, but
in beets, maple sugar, honey, and many other vege-
table products.
Milk sugar is found in the milk of all mammals.
It is less sweet and less soluble than cane sugar.
1 Sucrose (sometimes called saccharose) should not be con-
fused with saccharine, an intensely sweet substance used for
flavoring sugar-free, diabetic foods. Saccharine is not a car-
bohydrate and is not nutritious. It is chemically one of the
aromatic substances (like carbolic acid), but is not poisonous.
70 CHEMISTRY FOR NURSES
Maltose is a sugar derived artificially from starches
by digestion or chemical splitting. Ordinarily, it is
made from starch by the digestive action of a sub-
stance obtained from sprouting barley grains and
called malt extract or diastase. How this substance
works will be explained in the Chapter on Digestion,
Maltose is a valuable food and is the chief constit-
uent of such preparations as malt soup, Mellin's
food, malted milk.
The double sugars, or disaccharides, are so called
because their molecules consist of two simple sugar
molecules linked together; so that the formula of
all disaccharides is C12H22O11. The various double
sugars differ from each other in being composed of
different simple sugars. Thus the molecule of cane
sugar contains a molecule of dextrose and one of
levulose, while the molecule of maltose contains
two dextrose molecules.-^
1 After the student is acquainted with Fehling's test for sugar
(see below, page 74) a simple experiment can be done to prove
that double sugars contain simple sugar molecules. It happens
that cane sugar, a disaccharide, does not give Fehling's test,
while all the simple sugars do. Hence if cane sugar can be split
into its two constituent molecules, dextrose and levulose, these
will give Fehling's test.
First boil some cane sugar with Fehling's solution : there is no
reduction. Now put a little cane sugar in a test tube with some
Btrong hydrochloric acid and heat gently. Neutralize the acid
CARBOHYDRATES 71
PROPERTIES OF THE SUGARS
The simple and the double sugars have certain
properties more or less in common. They are all
very soluble; they can be obtained as crystals; they
all taste more or less sweet; they are very digestible
and highly nutritious. Perhaps their most interest-
ing characteristic is their property of undergoing
fermentation.
FERMENTATION
The lowly and simple forms of life, the bacteria,
the molds, and the yeasts, have, after all, the same basic
requirements as the higher forms. They must
breathe and they must feed. Very many of them are
specially adapted to use carbohydrates as their chief
food. In so feeding they do the same thing as the
higher organisms, they oxidize the carbohydrates.
And the final products of this oxidation are the same,
— carbon dioxide and water. This decomposition of
carbohydrates by bacteria or yeasts is known as
fermentation.
(see page 48) with some 30 % sodium hydrate and then test a
little of the fluid with Fehling's solution. The result is complete
reduction. The acid has split the double molecule to its com-
ponent simple sugars. The same kind of molecule splitting
happens in the digestion of every disaccharide. (See Chapter on
Digestion.)
72 CHEMISTRY FOR NURSES
Experiment showing Action of Yeast on Dextrose.
— To demonstrate fermentation, mix a little piece
of baker's yeast with some glucose solution, and with
the mixture fill one of the small tubes known as Ein-
horn fermentation tubes. This is a U-shaped glass
tube, one Hmb of which is closed on top so as to col-
lect gas bubbles. Let the tube stand in a warm place
for a day and then examine it. Bubbles of carbon
dioxide will have collected in the closed end of the
tube, and the amount of this gas can easily be meas-
ured off from a scale engraved in the outside of
the tube. From this amount we can easily tell how
much sugar was originally dissolved; for as each
carbohydrate molecule has six carbon atoms,
and each carbon atom gives rise to one carbon
dioxide molecule when fermented, the amount of
carbon dioxide is proportional to the amount of
sugar.^
The production of gas bubbles by yeast growing
on carbohydrates is the principle underlying the
^^ raising " or leavening of bread.
By-products of Fermentation. — But our interest
in fermentation does not stop here. What is impor-
^This method is actually used to estimate approximately
the amount of sugar in the urine of diabetes cases. The scale
on the Einhorn tube reads directly in percentages of sugar.
CARBOHYDRATES 73
tant about fermentation is not so much the end products
as the by-products. For in fermentation (just as in
the body) substances are not at once and completely
oxidized, but the molecules are first broken up into
partly oxidized fragments, and then these are further
oxidized to carbon dioxide and water.
Alcoholic Fermentation. — These intermediate
products are different for each kind of carbohydrate
and for each kind of bacterium or yeast. Thus the
chief by-product of many kinds of fermentation is
alcohol; and each kind of alcoholic beverage is the
result of fermentation of the. carbohydrates in some
particular kind of grain or fruit, by a microorganism
that is specially adapted for the purpose.^
Lactic Acid Fermentation. Vinegar. — The by-
products in many kinds of fermentations are organic
acids, such as acetic, lactic, and butyric acids. Thus
in the manufacture of kumiss and matzoon and of
various kinds of sour milk and cheese lactic acid is
produced. The production of vinegar is an acetic
fermentation {i.e. a fermentation by bacteria which
1 If the wrong germ gets in, the wine spoils. Thus the whole
modern science of bacteriology started in the effort of Louis
Pasteur to discover why the wine soured in a certain wine-grow-
ing district in France. The discovery of a germ as the cause of
a " wine disease " led him to search for germs as possible causes
of human disease.
74 CHEMISTRY FOR NURSES
produce acetic acid). There are hundreds of manu-
facturing processes which depend on various kinds
of fermentation.
Gastro-intestinal Fermentation. — When fermen-
tations occur in the intestinal tract the acids pro-
duced are often very irritating and cause digestive
disturbances. Our chief means of combating such
troubles is careful regulation of the carbohydrates
in the diet.
TESTS FOR SUGARS
It is often necessary to test for sugar. This is
done, for instance, in order to determine whether a
patient has glycosuria (glucose in the urine, the chief
symptom of diabetes). The fermentation test with
yeast described above is frequently used.
More delicate and reliable than the fermentation
test are chemical tests based on the great avidity
of certain sugars for oxygen. These sugars have the
power of reductiou, i.e. the power of taking some of
the oxygen away from other compounds. The best
known of these tests is the Fehling^s test, in which
the sugar is made to '^ reduce ^' an oxidized copper
salt to a form containing less oxygen.
Fehling's Test for Sugar. — Fehling's test is per-
formed with two solutions. The first, known as
CAKBOHYDRATES 75
Fehling's copper solution, is a light blue solution of
copper sulphate. The other is a strong alkaline
solution called Fehling's alkaline solution. Equal
quantities of the two are mixed together in a test
tube; the result is a beautiful deep blue fluid; if
this solution is boiled, it retains its color. But if
a little dextrose (or some urine containing dextrose)
is added, and the mixture is boiled again, a thick,
reddish yellow precipitate forms. This is reduced
copper oxide, — a copper compovind from which
some of the oxygen has been withdrawn.
Sometimes in pregnant or nursing women milk
sugar appears in the urine. This gives the same
reduction in Fehling^s test as does dextrose. But
as lactose is not fermented by yeast, while dextrose
is, we have only to do the fermentation test to make
sure that the patient has not diabetes.
III. POLYSACCHARIDES
Starch
Dextrin
Glycogen (animal starch)
Cellulose (vegetable fiber)
The polysaccharides are important foods. Their
molecules contain great numbers of sugar molecules
compactly linked together. When these large mole-
76 CHEMISTRY FOR NURSES
cules enter the digestive tract they have to be broken
down to simple sugars before they can be used for
nutrition. (See Chapter on Digestion.)
Proof that Starch is made up of Sugar Mole-
cules. — The fact that the polysaccharide molecule
is really built up of sugar molecules can be demon-
strated by boiling some starch paste a few minutes
in hydrochloric acid, then cooling and neutralizing
the acid with sodium hydrate. Before the boiling
the starch fails to give any change with Fehling's
test. After boiling it completely reduces Fehling's
solution. Glucose and maltose have been produced
from the starch.
Why Starch needs Cooking. — Starch is the form
in which most plants store up their energy. It is
not soluble in water, but can be made into a paste
by boiling. In its natural form it occurs in little
granules of microscopic size. Under the microscope
each granule is seen to be composed of concentric
layers like an onion. The layers are separated, it is
believed, by very fine films of another carbohydrate,
cellulose, which is extremely difficult of solution
or digestion. This is the reason that it is so impor-
tant that starchy things prepared for human food
be well cooked : in the process of cooking the heat
sphts open the starch granules and the starch be-
CARBOHYDRATES 77
tween the layers of cellulose can be reached by watei
or by digestive juices.
Iodine Test for Starch. — If a drop of any solu-
tion containing iodine is added to starch, a deep blue-
black color is produced. This color can be shown
by adding tincture of iodine to starch direct or by
putting a drop of it on the cut surface of a
potato or piece of bread. The color is not given
by any other substance, and gives us a valuable
method of detecting starch. For instance, with
iodine we can tell whether gluten foods, claimed
^. to be starch free, are really so.
Y^ Dextrin (a polysaccharide not to be confused with
dextrose, a simple sugar) is a product of the begin-
ning chemical spHtting up of starch by acids, or the
partial digestion of starch by malt extract or diges-
tive juices. Thus it is seen that as the starch mole-
cule is split up there are produced the successively
smaller fragments, dextrin, maltose, and dextrose.
The molecules of dextrin contain still a great num-
ber of sugar molecules, but not nearly so many as
starch itself. It is more soluble than starch, more
digestible, and it does not give a blue color on the
addition of iodine, but either a mahogany-brown color
or no color at all. It is a valuable food. It has a
pasty consistency and is often used as a gum.
78 CHEMISTRY FOR NURSES
Glycogen (animal starch) is found in the liver and
muscles and is the form in which carbohydrates are
temporarily stored in animals. It is on account of
the large amount of glycogen in liver that liver is
forbidden for those diabetic patients who have to be
on a strict carbohydrate-free diet. Glycogen is very
similar to starch in its appearance and properties,
but is more soluble.
Cellulose is the carbohydrate which forms the
fibrous or woody part of plants. It is the chief con-
stituent of cottoUj linerij and paper. It is very insol-
uble and (by human beings) very indigestible ; but
the digestive tracts of the herbivorous (plant-eating)
animals break it down to its constituent mono-
saccharides and utilize it as food. It is possible now
to make human food (glucose) from it by treating it
with strong acids. (This can be demonstrated by
heating a little piece of wood with sulphuric acid,
cooling and neutralizing and testing for sugar with
Fehling's solution.)
In the study of digestion it will be seen that the
same breaking down of complex food molecules into
simpler molecules, which in the test tube we can bring
about with the aid of powerful reagents, can be per-
formed in the body by means of such harmless sub-
stances as saliva and pancreatic juice.
CHAPTER X
Fats
Fat a Source of Energy. — As explorers go toward
the north and south poles they notice that plant
life gradually dies out. Animals venture much
farther into these frozen regions than plants do.
And one thing is conmion to all these animals that
brave the polar cold : their bodies are saturated "with
fat. It is this that makes life possible for them, not
(as is often thought) by providing a warm coating,
but by supplying a constant source of highly
combustible fuel to keep up the body temperature.
The Eskimo knows the warmth-giving value of fat
and lays up large stores of it for his winter sus-
tenance.
The Storing away of Energy. — Just as carbohy-
drates are the principal form in which plants store up
their reserve energy, fats are the arsenal of chemical
energy in the animal body. Animals may simply lay
away in their tissues the fat which they eat and do
not need for oxidation at the time, or, as a result of
79
80 CHEMISTRY FOR NURSES
the wonderful chemical transformations the body
can perform, they may convert other forms of
nourishment, such as carbohydrates and proteids,
into fats. Persons who eat much sugar (candy),
for instance, tend markedly to adiposity. The
sugar in excess of the actual energy needs of the
body is retained not in the form of sugar, but of
fat.
Fats give more Heat than do Carbohydrates. —
Indeed in this regard the chemistry of the animal
body is more cunning than that of the plant.^ Fats,
weight for weight, have over twice as much heat-giving
power as carbohydrates; nine calories per gram as
compared with four. Where does this energy come
from? From the unoxidized carbon and hydrogen
of the fat molecule, of course. For though fats are
made of the same elements as carbohydrates, —
namely, carbon, hydrogen, and oxygen, — the rela-
tive amount of oxygen is much smaller, so that the
carbon and hydrogen atoms can take up more
oxygen and hence provide more energy than can the
carbohydrate molecule.
^ It must not be supposed that plants have no fats or that
animals have no carbohydrates. Some plants have large
amounts of fat ; think of peanut butter, cocoa butter, cotton-
seed oil, and olive oil. Cereals have small and nuts often large
amounts of fat.
FATS 81
CHEMICAL COMPOSITION OF FATS
It is worth trying to understand something of the
chemical structure of fats because of the help that
knowledge will give us in the study of soaps and of
fat digestion.
What are Fats Composed Of ? — Fats are combina-
tions of fatty acids and glycerin. When the fat mole-
cule is split apart by strong reagents or by digestion,
it breaks up into these two constituents. (An
experiment showing the production of fatty acids
by the splitting of fats is described in the Chapter on
Digestion. See page 109.)
There is very little Oxygen in Fatty Acids. — Fatty
acids (of which there are a great many) contain
in their molecules varying numbers of carbon and
hydrogen atoms, but no matter how many carbon
and hydrogen atoms, only two oxygen atoms.
Thus from acetic acid, C2H6O2; with its two carbon
atoms, to stearic acid, C18H36O2, with its eighteen,
they all have exactly two oxygen atoms. These
are the only oxygen atoms in the fat molecule.
Each fatty acid molecule has, of course (like all
acids), one hydrogen atom, which is replaceable
when the acid combines with a base.
The other component of fats is glycerin. Glycerin
82 CHEMISTRY FOR NURSES
(Chapter VIII) is an alcohol and has three OH groups.
Its formula is : —
CH2OH
CHOH
I
CH2OH
Now, alcohols act like bases ; that is to say, they
combine with and neutralize acids. (For instance,
the reader will remember that when sodium hydrate,
NaOH, is neutralized by hydrochloric acid, HCl,
the sodium atom separates from the OH group and
joins the acid, displacing, of course, the H from the
acid molecule. The same thing happens when glyc-
erin and fatty acids combine and neutralize each
other.) The OH groups separate from the glycerin
to be replaced by fatty acid molecules. And as
there are three OH groups to the glycerin molecule,
each one of them in turn can be replaced by a fatty
acid : all three of the OH group may be replaced
by the same fatty acid or they may be replaced by
different fatty acids. Thus one might get a fat whose
structure would look like this : —
CH2 — Stearic acid
I
CH — Stearic acid
I
CH« — Stearic acid
FATS 83
or one whose structure would look like this : —
CHz — Stearic acid
I
CH — Palmitic acid
I
CH2 — Butyric acid
As there are a great many different fatty acids to
choose from, there is a possibility of a great many
different fats.
The fats of no two animals or plants are the same
in composition. The different flavors of various
kinds are due to the different fatty acids. Like-
wise the exact temperature at which each fat melts
or solidifies is constant and characteristic. For all
fats can be obtained solid or fluid, according to the
temperature. Those which are fluid at ordinary
room temperatures (olive oil, for example) can be
solidified at lower temperatures.
PHYSICAL PECULIARITIES OF FATS
A little knowledge of some of the physical peculiar-
ities of fats illuminates a number of common domestic
phenomena. Fat readily soaks into many sub-
stances and changes their light-transmitting property
so as to cause grease spots. A drop of fat on a piece
of paper makes a spot which is translucent when
84 CHEMISTRY FOR NURSES
held to the light. This effect on paper offers a con-
venient test to determine whether any substance con-
tains fat.
Solubility. — Fat is not soluble in water, but is
somewhat soluble in alcohol and extremely soluble
in ether. Test this by pouring a drop or two of olive
oil into tubes of water, alcohol, and ether, and shaking
well. On standing, all the oil quickly collects in
droplets at the top of the water ; some of it is dis-
solved in the alcohol, and all of it disappears in the
ether.^ Ether and such commercial products as
naphtha, benzine, and gasoline owe their cleansing
power entirely to their ability to dissolve fats.
Emulsions. — When fat is mixed in certain kinds
of fluids it neither dissolves nor collects again as
large globules. Instead it divides automatically into
smaller and smaller globules, until the droplets be-
come microscopic in size and remain uniformly
suspended throughout the fluid. Such mixtures are
opaque and are called emulsions. Milk is a good
example of an emulsion.
In order that an emulsion can be formed, there
must be some substance in the solution which forms
1 Remember the inflammable nature of ether and do not
perform this experiment if there is an open flame in the same
room.
FATS 85
a film on the surface of the globules of fat and
prevents their running together. In milk this
function of preventing the fat globules from run-
ning together is performed by proteids. In other
instances soap performs this function. Dissolve a
little green soap in water and shake with it a few
drops of olive oil. Instead of coUecting'at the top,
the oil remains suspended in the solution as a milky
emulsion.
SOAPS
Ever since the time of the ancient Romans, perhaps
even longer, housewives have manufactured crude
soap for cleansing purposes by boiling together fat
and lye (an alkaline substance dissolved from the
ashes of plants). This traditional process was
handed down from generation to generation, but it
was not until the beginning of the nineteenth cen-
tury that the underlying chemistry was discovered,
so that purified soap could be made. And only in
relatively recent years has it been detected that soap
is formed in the intestines and plays an important
r61e in the digestion of fats.
Manufacture of Soap. — Let us manufacture
some soap ourselves. Then we will be able to un-
derstand its chemical composition. Soap is made hy
86 CHEMISTEY FOR NURSES
heating fat with strong alkali. Add some olive oil ^
to a 30 % solution of sodium hydrate in alcohol and
boil gently in a water bath. The oil gradually
disappears in the solution which remains clear, and
the result is an alcoholic solution of soap (like
tincture of green soap). Several tests can be appHed
to show that this is soap and not merely dissolved
fat. Thus a little of it poured into water forms
a smoky solution which on shaking lathers. No
oil globules are seen in the water.
The alkali is used up in this process of making
soap. If we were to keep on adding olive oil until
no more would disappear in the solution, we would
find that the sodium hydrate had been almost com-
pletely neutralized.
Now what neutralized the alkali? Evidently
the fatty acids present in the fats. So what the
sodium hydrate actually did was to split the fat into
its constituent fatty acids and glycerin, and then to
neutralize the fatty acids.^ So soaps are compounds
(really salts, see Chapter VII) of sodium or potassium
with fatty acids, just as fats are compounds of glycerin
1 One of the finest kinds of soap, Castile soap, is made from
olive oil, and has been so made for centuries.
^ Glycerin, of course, is set free in this exchange, and this is
the regular process of manufacturing glycerin ; it is a by-product
of soap making.
FATS 87
with fatty acids. Thus our ordinary hard soap con-
sists of sodium salts, and soft soap of potassium,
salts of fatty acids.
Solubility of Soaps. — Soaps have very character-
istic properties, a knowledge of which is of some
practical interest. Sodium and potassium soaps
are soluble in water and form rather smoky-looking
solutions which on shaking give a tj^ical foamy
lather. They are soluble in alcohol (for instance,
tincture of green soap), hut, unlike fats, not in ether}
Why Salt Water is not good for Washing. —
Soap, however, is not soluble in salt water ; in fact,
salt precipitates it. This can be demonstrated by
dissolving some tincture of green soap in water and
adding to it some strong salt water (made by dis-
solving a few grams of table salt in a test tube of
water). A dense white precipitate is formed at
once. This process is known as " salting out '' and
is used in. manufacturing in order to free soap of
impurities. The same '^ salting out " is what pre-
vents us from washing our hair with soap in the
^ This is the reason that in " scrubbing up " the skin for
operations with soap, alcohol, and ether, the three ought always
be used in the order named. The alcohol removes any soap
not washed away by water. The ether removes the alcohol
and any trace of grease not removed by the soap. What ether
is left on the skin disappears by evaporation.
88 CHEMISTRY FOR NURSES
ocean. The greasy lumps which form in the hair
are precipitated soap.
" Hard " Water. — Not every soap is soluble in
water; calcium soap, formed by the union of the
metal calcium with fatty acids, is insoluble. More-
over, calcium has a great aflSbiity for fatty acids, so
that whenever calcium in solution comes into con-
tact either with fatty acid or with ordinary soap
the insoluble calcium soaps are formed at once.
Thus pour some limewater into soap water. A
curdy white precipitate is formed at once. The
reason that so-called ^' hard water " which occurs in
certain parts of the country is not suitable for wash-
ing purposes is that it contains small amounts of
calcium salts dissolved from rocks in the ground.^
How Soap Cleanses. — Soaps emulsify fats. The
cleansing property of soap is largely due to this power
of emulsifying the fat and grease which collect on
the surface of the skin and of the objects we handle ;
by emulsifying this film of fat the soap removes with
it the particles of dust and the germs that are stick-
ing in the fat.^
1 See Mclsaacs, " Hygiene for Nurses."
2 The greasy scum left in the bathtub is due to the fact that
the large amount of water dilutes the soap until it is no longer
able to hold all the fat in emulsion.
FATS 89
The important points to remember in this chapter
are that neutral fats are compounds of fatty acids
and inorganic bases, that alkalies make soaps from
fats, and that soaps in turn emulsify fats. Under-
standing this will help greatly to understand the
splitting apart of fats that occurs in the process of
digestion to be discussed in a later chapter.
CHAPTER XI
Proteids
As the chemists made one successful attack after
another on various kinds of organic substances, as
they unraveled the complicated structures of car-
bohydrates, of alkaloids, as they made syntheti-
cally all sorts of compounds from indigo to rubber,
there always remained one class of substances that
contained nitrogen and that defied their keenest
efforts. And strangely enough these substances
seemed to be the most important of all. They were
found in every living cell; they turned out to be ab-
solutely indispensable in the food of every animal. In
fact, so fundamental were these substances that they
were often referred to as living matter par excellence,
as the physical basis of life. And yet until a few
years ago we had no conception of their chemical
structure at all.
To-day this is changed. The proteids are still
far from an open book. The exact structures of
only a few of the simplest ones are known. Their
90
PEOTEIDS 91
synthesis has been little more than begun. Yet the
general plan of the proteid molecule is no longer a
mystery.
Elementary Composition. — It is true that the
early chemists, from the time of Liebig and Wohler
on, knew the elements of which proteids were com-
pounded, — carbon, hydrogen, oxygen, and nitrogen
(and sometimes in addition sulphur, phosphorus,
and iron). They were even able to find out with
considerable accuracy how much of each of these
elements was present in a given proteid. '^But there
they had to stop. The proteid molecule was of such
enormous size (containing not merely dozens but
hundreds and sometimes even thousands of atoms)
and of so great complexity that analysis seemed
impossible.
Structure. — The solution of the mystery has
come from a careful study of the products of the
digestion of proteids, and from imitation of this
digestion by the splitting up of the proteid molecule
with strong acids. By these methods it was found
that the proteid molecules are vast congeries of linked-
together amino adds.
What are amino acids? They turn out to be
our old friends the fatty acids, into the molecule of
each of which a new nitrogen-containing atom group,
92 CHEMISTRY FOR NURSES
NH2 (known as amine and resembling in some
ways ammonia, NH3), has been inserted.
Not that proteids are composed exclusively of
these. There are other atom groups, such as, for
instance, aromatic groups (the closed rings of carbon
atoms referred to in the Chapter on Organic Chemistry ;
see page 62).
Classes of Proteids. — But before we get too
deeply involved in their chemical structure let us
get acquainted a little more closely with some of the
proteids themselves. The number of different pro-
teids is almost unlimited. Each animal or plant
possesses at least several proteids, and it is likely
that no two proteids in separate species of animals
or plants are identical. This is readily understood
when we think of the complexity of the proteid mole-
cule and remember that the shifting in position of a
few atoms makes a new substance. We will discuss
three principal classes of proteids, the simple pro-
teids, the compound proteids, and the albuminoids.
Simple Proteids. — The most important proteids
are the so-called native, or typical, or simple ^ pro-
teids such as the albumins and globulins found in egg
^ The term " simple, " though often used, is really poor be-
cause these are actually among the most complex of all pro-
teids and have molecules of very great size.
PROTEIDS 93
white, in blood serum and in milk whey, the gluten
and legumen of plants, the myosin or muscle proteid,
and the fihrinogen of blood plasma (from which is
derived the fibrin, — the tough part of a blood clot).
Compound Proteids. — Of equal rank with these
are the compound proteids from the molecules of
which some special non-proteid group can be split
off. Thus hcemoglohin, the important red coloring
matter of the blood cells, is composed of an iron-
containing fraction combined with proteid; the
caseinogen of milk (from which, on coagulation,
comes the casein, curd, cheese) is a compound of
phosphoric acid and proteid ; mucin, found in mucus,
is a compound of sugar with proteid.
Albtxminoids. — All the above proteids are very soluble
and when taken as food are easily digested and as-
similated. There are other proteids (called alhu-
minoids) which form the connective and protecting
tissues of the body ; they are more or less insoluble
and are of relatively little value in nutrition. Among
these are collagen (the basis of connective tissue
and tendons, from which by prolonged boiling we
obtain gelatin), and keratin, the proteid of skin,
hair, and nails. Keratin contains much sulphur,
and it is the oxidized sulphur which gives the dis-
gusting smell to burnt hair or skin.
94 • CHEMISTRY FOR NURSES
Now that we have an idea of what the proteids are
and where they are to be found, let us consider some
of their properties.
SOLUBILITY
Proteids (except the albuminoids) are very soluble
in salt water and also (except the globuHns) in plain
water. Their solutions are opalescent and are very
viscid and sticky, so that even very dilute solutions
(as dilute as one part of proteid in one thousand of
water) will form a more or less permanent /oam when
shaken. As found in living cells proteids are always
dissolved or, at least, combined with much water.
COAGULATION
Every one knows the change in appearance of meat or
eggs after cooking. This hardening is an instance of an
alteration produced by heat in almost all proteids,^ and
known as coagulation. Superficially it has a certain
resemblance to precipitation of a solid from a solu-
tion. But coagulation differs from precipitation in
this regard : it is not reversible, it is permanent; a
proteid once coagulated is unalterably changed;
nothing can restore it to its former state. And
1 Gelatin, certain vegetable proteids, and the partly digested
proteids (proteose and peptone mentioned below) are exceptions.
PROTEIDS 95
living cells whose proteids are coagulated are inevi-
tably killed.
This is the reason for the sterilizing effect of heat.
The remarkable resistance of the spores of certain
bacteria to heat sterilization ^ will at once occur to
the reader. Can this be explained? If all living
cells contain proteids, why are not the proteids of
the spores coagulated by steam and the spores at
once killed ? Proteids as they ordinarily occur con-
tain water; but when thoroughly dried they are
coagulated only by extreme degrees of heat. In
spores the proteids are condensed so as to be almost
free of water. The resistance of dried proteid to
coagulation explains also the well-known superiority
of moist heat (steam) to equal degrees of dry heat in
sterilization.
Coagulation Test for Albmnen. — Heat coagu-
lation affords a very delicate way of testing for any
coagulable proteid, even in small traces. Thus if
a drop of blood serum is mixed in a test tube of water
and the test tube, held by the bottom, is brought to
a flame so that the upper layer of fluid boils, a cloud
forms in the upper part. On addition of a drop of
dilute acid the cloud becomes much denser, because
a slightly acid reaction aids in the coagulation of
* See Mclsaacs, " Bacteriology for Nurses."
96 CHEMISTRY FOR NURSES
proteids. This method is used to detect traces of
albumin in urine.
Coagulating Effect of Salts of the Heavy Metals. —
Coagulation can be brought about not only by heat,
but by many chemical agencies} Thus if to a test
tube containing egg white or blood serum is added
a solution of bichloride of mercury or of silver nitrate,
a dense coagulum is precipitated at once. These
and many similar substances owe their disinfecting
power as well as their local poisonous properties to
their coagulating effect on proteids.^ Their mode of
action, however, betrays their limitations as disin-
fectants, because in coagulating proteid they com-
bine with it and hence are unable to penetrate deeply
or to disinfect matter containing much proteid.
^ TESTS FOR PROTEID
There are many useful tests. The coagulation
test is often applied. For proteids in general the
1 The term '* coagulation" is also unfortunately applied to the
clotting of blood and milk. These processes are different from
ordinary coagulation and are really due to the formation of
special new proteids, — fibrin from the fluid fibrinogen of
plasma, casein from the fluid caseinogen of milk.
* By no means all the things which precipitate proteids coagu-
late them. Thus alcohol (if applied for a short time), or con-
centrated salt solutions, precipitate without coagulating. Such
precipitated proteids can be redissolved.
PROTEIDS 97
nitric acid test is very convenient. Probably the
reader has already, in handling nitric acid, uncon-
sciously applied this test to the skin of fingers.
Nitric acid, though colorless, stains the skin a deep
yellow. If the very natural attempt is made to neu-
tralize the acid by applying some alkali, such as am-
monia, the stain instead of disappearing becomes
of an intense orange color. (Add a little strong
nitric acid to some egg albumin. The acid first
precipitates the albumin, then dissolves it, and turns
it yellow. On addition of an excess of ammonia
the color deepens and becomes a beautiful orange.)
THE FUNCTIONS OF PROTEIDS
It has already been stated that proteids are indis-
pensable in the diet of animals. The amount of
proteid actually needed may be exceedingly small,
but sooner or later every animal must receive proteids
to replace the burnt-up or destroyed proteids in its
own tissues, — otherwise it will die. An animal
can do without fats provided it gets enough carbo-
hydrates to supply it with energy, or without carbo-
hydrates provided it gets enough fats. But it is
constantly using up its own proteid in bringing about
the various chemical processes of life and the used-
up proteid must be replaced.
98 CHEMISTRY FOR NURSES
Where do Animals get their Proteid? — The
proteids in animals are all ultimately derived from
plants. In the case of the herbivorous or plant-
eating animals, the proteids are derived directly by
the process of digestion from plants. The carnivo-
rous or flesh-eating animals get their proteids second-
hand, so to speak, from the flesh of the plant-eating
animals. The plants in turn manufacture their
proteid from inorganic nitrogen compounds (am-
monia, nitrites, and nitrates) in the soil. An animal
could die of " nitrogen starvation ^' in spite of
breathing the pure nitrogen which forms 70% of the
air,^ if it were not supplied with proteid directly
or indirectly by plants.
Why are proteids so indispensable? We do not
know enough about the chemistry of the cell as yet
to give a complete answer to this question. For
some reason the cell must constantly destroy its own
proteid in order to maintain life. The proteids
have been compared to the kindlings of a fire, of
which carbohydrates and fats are the staple fuel.
1 Plants also are unable to utilize the nitrogen of the air.
The only way in nature, so far as we know, by which the inert
nitrogen of the air is converted into the forms in which plants
can utilize it, is by the action of certain bacteria which grow
in the soil. So ultimately all other animal and vegetable life is
dependent on these nitrifying bacteria of the soil.
PROTEIDS 99
Not every nitrogen-containing substance in the
body or in the food is proteid. There are many
other nitrogenous compounds, — mostly derived
from proteids. Meat extract , for instance, — bouillon,
beef tea, — consists of such nitrogenous but non-
proteid substances which although practically devoid
of nutrition are nevertheless of great value in diet
because of their flavor and their stimulating effect
on digestion.
PARTLY DIGESTED PROTEIDS (PROTEOSES AND PEP-
TONES)
The proteids we have discussed thus far occur as
part of the living organism. When, either as the
result of digestion or of the action of strong acids or
alkalies, the proteid molecule is broken up, the first
large fragments that result are the molecules of sub-
stances known as proteoses. When these are a little
further disintegrated the result is peptones. Proteose
molecules contain a large number of amino acids,
peptone molecules a smaller but still considerable
number. Proteoses and peptones are still proteids
and give all the proteid tests. However, they cannot
he coagulated. (This can be demonstrated by dis-
solving in water some powdered meat peptone, de-
rived from the ajiiificial dige^tipii of meat ;and; leally
100 CHEMISTRY FOR NURSES
containing proteoses as well as peptones. On boil-
ing and adding dilute acetic acid to this, absolutely
no trace of coagulation is seen.) When peptone
molecules are further broken up the resulting sub-
stances are no longer proteids, but amino acids or
small groups of amino acids called polypeptids.
Proteoses and peptones have not the bland or
pleasant taste of other proteids, but taste very hitter
(whence the bitter taste of peptonized foods).
CHAPTER XII
Digestion
OuK bodies are built up chiefly of proteids, fats,
carbohydrates, and inorganic substances : so is our
food. But the particular proteids, fats, carbo-
hydrates, and inorganic substances in our food are
entirely different from those in our body. The
process by which those in our food become chemically
changed into those in our body is the process of
digestion. It is purely a chemical process.
What brings about the Chemical Changes in the
Body ? — During digestion very profound changes
are brought about in the food materials. These
are brought about by the action of certain substances
known as enzymes, which are produced in the mouth,
stomach, and intestines. The enzymes (formerly
called ferments or unorganized ferments) are very
wonderful substances. Each enzyme is able to work
on one particular kind of substance, — and no other.
On this account an enzyme has been compared to a
key which will fit one particular lock, — that is,
will unlock one particular kind of molecule. En-
101
102 CHEMISTRY FOR NURSES
zymes do the work which otherwise can only be done
by very powerful chemical processes, such as strong
acids or alkalies, considerable heat, and similar
means. Yet enzymes themselves are present, even
when they produce great effects, only in small traces
and they are almost inert and inactive chemically
against anything excepting the particular kind of
substance that they can digest. Thus, to carry
the illustration a little farther: if enzymes corre-
spond to keys which will unlock only particular doors,
the ordinary chemical process might be compared
to battering rams which will break through any door.
Chemical Nature of Enzymes. — The exact chemi-
cal composition of enzymes is not known, but they
are almost certainly proteid. All of them can he
destroyed or killed by hoiling, and in general hy all
of the same things as coagulate proteids. Each enzyme
has certain particular set conditions which it must
have in order to work. Thus most of our digestive
enzymes work best at body temperature. Some
enzymes will work only if in slightly alkaline solu-
tion ; others only if the solution is acid ; some can
work in either acid or alkaline solution.
All Cells contain Enzymes. — We will discuss
only the most important enzymes that are found
in the human digestive tract, but the student ought
DIGESTION 103
to know that there are really very many more
enzymes than these. Every living cell contains
enzymes and, in fact, brings about most of the chemi-
cal changes which are necessary for its life, by means
of enzymes. Furthermore, the action of enzymes is
not only to break down substances into simpler forms,
as occurs in our digestive tract, hut also to build up
simpler substances into the more complicated ones
needed by the body.
SALIVA
The saliva is the first digestive juice which the
food meets. It contains one important enzyme, —
ptyalin or amylase. (The new system of naming
enzymes uses the ending ^' ase " to a word to in-
dicate enzyme, and attaches the ending to the name
of the substance that the enzyme works on : thus,
amylum (starch), amylase.) Ptyalin breaks starch
down to dextrin, then to maltose, and then, finally,
to glucose, or simple sugar.^
In the Chapter on Carbohydrates it was stated
that boiHng with a strong acid would reduce starch
to dextrose. Saliva will do the same thing and more
1 The action of diastase or malt extract (the vegetable en-
zyme of germinating barley) on starch is closely similar, but
does not proceed quite so far.
104 CHEMISTRY FOR NURSES
quickly, and without boiling. This can be proved
by a very simple experiment. Take a test tube
full of saliva obtained simply by chewing on a piece
of paper. Filter the saliva to make it clear. Take
a test tube of starch paste and first apply to the
starch two tests to prove that it is starch and is
free from any simple sugar. The addition of a drop
of iodine turns it a deep blackish blue. Boiling a
drop or two of the starch paste with Fehling's solu-
tion gives no reduction of copper (no yellow precipi-
tate). Now mix some saliva and starch paste in a
test tube and put the test tube in a water bath at
body temperature for only a few minutes. Then
test the contents of the test tube again with iodine,
and you wiU see instead of the deep blue color a
brownish color indicating that there is dextrin pres-
ent. Add a few drops to Fehling's solution and boil,
and you see an abundant yellow precipitate, — an in-
dication that some of the starch has been broken down
beyond the dextrin stage to dextrose (grape sugar)
by the action of ptyalin.
What Effect has Boiling on Enzymes ? — Now
repeat the experiment; only instead of using the
fresh saliva use some saliva whichis first boiled and you
will see that nothing happens. The starch remains
quite unchanged. The boiling kills the enzymes.
DIGESTION 105
Effect of Acids on Starch Digestion. — Saliva, as
one can see by the bluish color which it gives to lit-
mus paper, is weakly alkaline in reaction. Ptyalin
works best in an alkaline or neutral fluid. An acid
reaction not only stops its action, hut quickly destroys
it. If one adds a little hydrochloric acid to saliva,
lets it stand a few minutes, and again tests its effect
on starch, one can see that it has absolutely no diges-
tive power. The acid kills the enzyme quite as
effectually as boiling does.
•>
GASTRIC DIGESTION
The next digestive secretion is the gastric juice.
It is strongly acid in reaction due to the presence of
hydrochloric acid in the strength of about 0.2%.
Gastric juice contains two important enzymes, — rennin
and pepsin, Rennin has the power of coagulating
the caseinogen of milk. The coagulation of milk is
the preliminary stage to its digestion. Artificial
gastric juice, prepared by making an extract of the
stomach of the pig, is sold commercially as pepsin
and is used medicinally. This pepsin dissolved in
water and added to milk, which is then allowed to
stand at body temperature for a few minutes,
promptly curdles the milk.
106 CHEMISTRY FOR NURSES
Rennin. — Rennin is very difficult to separate
from pepsin. That is the reason that we use the
substance called pepsin, which is really not pure
pepsin, but an extract of stomach glands containing
both pepsin and rennin, for coagulating milk. After
the milk has coagulated, the fluid part which sepa-
rates out is whey. If whey is heated at once, the
pepsin does not have time to produce much peptone
or proteose. But if it is allowed to stand, the pro-
teoses and peptones which form give it a bitter taste.
The fat in the milk for the most part remains tangled
in the mesh of the coagulated casein. Rennin
works either in an acid or a neutral medium.
Pepsin. — Pepsin is the stomach enzyme which
digests proteids. It dissolves them and breaks
them down partly or entirely to proteoses and pep-
tones. It is active only in the presence of acid and
it is destroyed if the reaction becomes alkaline.
The effect of pepsin on little pieces of coagulated
egg white and on little shreds of washed blood fibrin
can easily be studied. Prepare the fibrin first by wash-
ing a piece of blood clot obtained at the slaughter-
house in running water until all the red blood cells
are washed out. From the yellow fibrous clot that
is left tear off five little shreds and put them in test
tubes. In other test tubes put five little cubes of
DIGESTION 107
boiled egg white. Prepare the pepsin solution by
dissolving a few grains of powdered or scaled com-
mercial pepsin in a few cubic centimeters of 0.2 %
hydrochloric acid. Add some of this to a tube con-
taining fibrin, and some to a tube containing egg
white. Boil a little of the pepsin solution and add
it to a second pair of tubes with egg white and fibrin.
Neutralize another portion with sodium hydrate
and add it to a third pair of tubes of egg white and
fibrin. To a fourth set of tubes add some strong
alcohol and then the pepsin solution. In a fifth
pair of fibrin and egg white tubes put hydrochloric
acid without pepsin. Put all the tubes in a water
bath at body temperature for an hour. At the
end of that time, in the tube containing pepsin and
hydrochloric acid alone, the egg white and the fibrin
will have become digested, whereas in the tubes
containing boiled pepsin, alkaline pepsin solution,
alcohol with pepsin, and hydrochloric acid alone,
digestion will not have occurred, — the egg white
and fibrin will still be there. In the two tubes, the
contents of which are undergoing digestion, at the
end of fifteen or twenty minutes both the egg white
and the fibrin will look rather swollen and semi-
transparent and be apparently fading away at the
edges. At the end of three quarters of an hour the
108 CHEMISTEY FOR NURSES
fibrin will have almost entirely crumbled away and
disappeared. The egg white too will be almost en-
tirely gone, but a little piece of it may still be left.
By boiling and filtering the fluid (to remove any
coagiJable proteid) and then with the clear filtrate
doing the nitric acid test for proteid, it is easy to
prove that in this solution are proteoses and peptones.
PANCREATIC DIGESTION
When the stomach contents are poured into the
intestine they meet at once the pancreatic juice and
hile, both of which are alkaline in reaction. The
alkalinit}^ at once stops the further action of the pep-
sin, but not the further digestion of proteids, as we
will see.
The pancreatic juice is the most important diges-
tive secretion in the body, and is emptied into the
duodenum along with the bile. It contains at least
three very important enzymes.
The first of these is amylase, a starch-digesting
enzyme which seems to be identical in action with
ptyalin. Its effect on starch is exactly the same as
that of saliva.
Trypsin. How it differs from Pepsin. — The
second important enzyme is a proteid-digesting
enzyme known as trypsin. It attacks the same
DIGESTION 109
proteids as does pepsin, but it only acts in an alka-
line medium and it digests the proteid much farther
than pepsin ; namely, it not only reduces the typical
proteids to the stage of proteoses and peptones, but,
also, if the digestion is continued long enough, to the
much simpler stage of polypeptids and even amino
acids. It is easy to demonstrate the effects of tryp-
sin by dissolving some commercial pancreatin in
a weak alkaline solution, namely, 0.4% sodium
carbonate solution, and adding some of this solu-
tion to little pieces of fibrin and egg white. When
these stand for three quarters of an hour at body tem-
perature the effect on the particles of proteid is very
similar to the effect of pepsin in hydrochloric acid.
What digests Fats? — The third important di-
gestive enzyme in the pancreatic juice is a fat-di-
gesting enzyme known as lipase. This has the power
of splitting up fats into their constituent fatty acids
and glycerin. In the Chapter on Fats I showed that
fats can be split up by boiling with powerful acids
or alkalies. The feebly alkaline pancreatic juice does
exactly the same thing. This can be conveniently
demonstrated by an experiment with the fat of milk.
An Experiment to show the Splitting of Fat by
Pancreatic Lipase. — Take a large test tube of milk
and to it add a little litmus solution as an indicator
110 CHEMISTRY FOR NURSES
as to whether the milk is acid or alkaline. Usually
the color is pinkish, indicating that the milk is
slightly acid. Make it slightly alkaline by adding
a little weak sodium carbonate solution. The color
is now bluish. Now divide the milk in two small
test tubes : to one test tube add a little of the arti-
ficial pancreatic juice, made by dissolving pancreatin
in sodium carbonate solution. The color of the
two tubes will still be exactly the same, or^ if it
is not, make it so by adding a little sodium carbonate
solution to one or the other. Now put both tubes
in the water bath. After a short while take them
out and the tube to which pancreatic juice was
added will now have turned bright pink. The
fatty acids 0/ milk fat will have been split off from the
glycerin and, being acids, will have turned the litmus
solution red. This same thing happens in the in-
testines; but in the intestines there is always an
excess of alkali present, both from the pancreatic
juice and from the bile, so that the fatty acids do
not turn the reaction actually acid, but are neutral-
ized to form soaps.
Of What Use is Bile ? — The bile secreted by the
liver contains no enzymes, but is nevertheless ex-
tremely important for fat digestion, as it keeps the
contents of the intestines alkaline and thus aids in
DIGESTION 111
the emulstfication of fats, which is essential to their
absorption. In neutralizing the fatty acids, of
course, it forms soaps from them.^
INTESTINAL SECRETION
Erepsin. — The secretion of the glands in the in-
testinal wall also contains a number of enzymes.
There are special enzymes for a number of functions :
for instance, enzymes for breaking down the di-
saccharides, like cane sugar and milk sugar, into
simple sugars; hut the most important enzyme con-
tained in the intestinal juice is a proteid-digesting
enzyme known as erepsin. Erepsin does not digest
the tj^ical proteids at all, but only attacks pep-
tones (which have been produced by the action of
pepsin and trypsin) and breaks the peptone down to
amino acids.
WHY DIGESTION IS NECESSARY
Now let us stop for a moment and consider what
is the purpose of all this chemical decomposition of
food products before absorption. Our bodies are
built up of carbohydrates, fats, and proteids. So is
our food. Why can we not simply absorb the pro-
1 Absence of bile causes the fatty stools of jaundice patients.
See Chapter XIV, page 134.
112 CHEMISTRY FOR NURSES
teid, fat, or carbohydrate from the food and use it
in our bodies ? Each species of animal has its own
particular kind of proteid, or fat, or carbohydrate.
Thus, though human muscle may be built up
by the eating of beef muscle, of chicken mus-
cle, of fish muscle, it is entirely different in its
nature from any of these. The muscle of the
Chinaman who eats nothing but fish differs in no
way from the muscle of the Englishman who
eats nothing but beef, and the reason is now
perfectly clear. The body breaks down all the pro-
teid that is offered to it, — whether in the form of
muscle, grain, milk, or any other form, — to the
simplest biiilding stones of proteid, namely, the
amino acids. It then from the mixture selects those
particular amino acids which it needs to build up its
own kind of muscle proteid (or blood proteid, or
other cell proteid) and rejects or burns up all the
other amino acids. It does the same thing to all
the fat and carbohydrate it gets, — disintegrates
and then reconstructs them to suit its own needs.
CHAPTER XIII
Urine
Functions of Kidneys. — The chemistry of mine
is of great practical importance, as the kidneys are
the chief excretory organs. The principal function
of the kidneys is to rid the body of waste products
derived from the burning up of nitrogenous compounds.
Besides this the kidneys have to keep the amount of
salt in the body adjusted to exactly the right point by
excreting all superfluous salt taken in with the food,
and they help the body get rid of various poisonous
substances whether manufactured by the body itself
or absorbed from the intestines or elsewhere.
How are Oxidized Carbon and Hydrogen Ex-
creted ? — In discussing the combustion of body sub-
stances in Chapter IV it was shown that the com-
bustion of organic substances always produce some
water and some carbon dioxide. The carbon dioxide
is excreted almost entirely by the lungs. Some of
the water is excreted by the lungs, some by the skin,
and some by the kidneys.
I 113
114 CHEMISTRY FOR NURSES
How is Used-up Nitrogen Excreted? — When
nitrogenous substances, particularly proteids, are
oxidized in the body the products of combustion of
the nitrogen are excreted chiefly by the kidneys, in
the form of several different substances. The sub-
stance which contains about three quarters of the
burnt-up nitrogen is known as urea. By measuring
the amount of urea excreted in twenty-four hours
doctors can get an idea as to whether the kidneys
are able to excrete nitrogenous waste sufficiently.
The most important of the other substances repre-
senting the rest of the burnt-up nitrogen is known
as uric acid; it is beheved to be produced from the
oxidation of proteids in the nuclei of the body cells.
Uric acid is a normal constituent of urine, although
there is a mistaken popular impression that its
presence in the urine means gout.
How Salt Balance is Maintained. — Next to
nitrogenous constituents the most important sub-
stances in the urine are the salts. Practically all of
our food contains more or less salt and we are thus
constantly taking into our bodies various amounts of
different kinds of salts. It is the function of the
kidneys to maintain the proper concentration of the
proper salts in the body by excreting all that is
unnecessary.
URINE 115
Purpose of Urine Examination. — The object of
urine examination is to determine (1) whether the
kidneys are performing their function properly,
(2) whether there is disease at any point in the
urinary tract, (3) whether there is any substance
indicative of disease of any other organ. There
are hundreds of different tests done on urine for
special purposes. Only those will be discussed
which are of great practical importance and which
the nurse should know the significance of.
A routine urine examination includes the follow-
ing most important points : —
(1) Amount in twenty-four hours
(2) Color
(3) Transparency
(4) Odor
(5) Specific gravity
(6) Reaction (whether acid or alkaline)
(7) Albumin
(8) Sugar
(9) Microscopic examination
(1) THE AMOUNT
The amount of urine passed in twenty-four hours
by an adult or child above eight years is on the aver-
age from 1000 to 2000 cubic centimeters. It rep-
resents about 60 or 70% of the water taken in.
116 CHEMISTRY FOR NURSES
Measuring Urine. — In measuring the amount
it is necessar}^ to start with the bladder empty, —
that is to say, the patient should void just before
the hour at which the twenty-four-hour specimen is to
be commenced, and the patient must, of course, empty
the bladder again just before the end of the twenty-
four-hour period, so that the actual amount formed
by the kidneys in twenty-four hours is obtained.
The urine is best collected in a 2-quart bottle or jar,
kept in a cool place, and often some preservative is
added (a few cubic centimeters of chloroform or
toluol or a few crystals of thymol).
Normal Variations in Amount. — The amount of
urine varies greatly even in health. It is diminished
in warm weather and in fact by anything which
causes much perspiration. It is increased by drink-
ing copiously and by anything which decreases the
amount of perspiration.
Pathological Variations in Amount. — The obser-
vation of the amount is of importance in many dis-
eases. The quantity is diminished in all fevers (due
largely to the much greater evaporation from the
skin in fevers), in acute nephritis (acute Bright 's
disease), in the final stage of chronic nephritis, and in
heart failure. It is also diminished in all diseases in
which a large amount of water is lost through some
URINE 117
other part of the body, as in diarrhea and dysentery,
in hemorrhage, and in vomiting.
Suppression of the urine (or failure of the kidneys
to secrete any urine) occurs in very acute forms of
nephritis, — such as nephritis caused by certain
poisons like mercury and carbolic acid. It may also
occur from the obstruction of the ureter, or occa-
sionally as a reflex nervous result of operation,
injury, or disease of some part of the urinary-
tract.
Retention of urine means failure of the bladder to
empty out the urine which has been secreted by the
kidneys. It is of importance practically to dis-
tinguish between retention and suppression. Re-
tention is due to a great variety of different causes,
such as paralysis of the bladder, obstructions of the
urethra by tumors, by a large prostate gland, by
urinary stones, etc.
Careful measuring of the amount of urine by the
nurse is a thing of the greatest possible importance
in all forms of kidney disease and in all such dis-
eases (for instance, scarlet fever) as are likely to be
complicated by kidney disease. In such cases the
increase in the amount of urine generally means that
the patient is improving or that the treatment is
effective. It is always desirable to measure the
118 CHEMISTRY FOR NURSES
amount of fluids taken hy the patient so that it can be
compared with the amount of urine excreted.
The amount of urine is increased (this is called
polyuria) chiefly in three diseases: (1) in diabetes
mellitus (the ordinary form of diabetes in which
sugar is foimd in the urine), (2) in diabetes insipidus
(the disease whose principal symptom is an excretion
of large amounts of urine), (3) in chronic Bright 's
disease.
(2) COLOR
The color of normal urine varies greatly. It de-
pends largely on the amount of urine excreted. It
varies from pale straw color in persons who are pass-
ing a great deal of urine to lemon yellow and to deep
amber color in persons who are passing a small
amount of urine. High-colored urine occurs par-
ticularly in fevers. Abnormal colors are caused by
a number of different things. The color of fresh
blood is easily recognized. Very small amounts of
blood give a smoky appearance without actual red
color. The yellomsh green color given to urine by
bile in cases of jaundice is characteristic. It is im-
portant to be able to recognize this color, as there are
cases of liver disease in which the amount of bile
retained by the body is too small to cause noticeable
URINE 119
jaundice in the skin, but in which bile nevertheless is
found in the urine. There are a number of chemical
tests employed by doctors to detect these small
traces of bile. Urine which contains bile stains
paper or linen a peculiar yellow, and if a little of it
is shaken up in a test tube, a foam forms on the top
which is a yellow color, — whereas the foam of normal
urine is white. Urine may be colored reddish after
the taking of certain drugs such as rhubarb, senna,
santonin ; or colored blackish in carbolic acid poison-
ing, or green after the use of methylene blue as a drug.
(3) TRANSPARENCY
Significance of Turbid Urine. — Normal urine is
perfectly clear, with a very faint cloud of mucus
which collects if the urine is allowed to stand for a
couple of hours. The turbidity of urine is an im-
portant thing for the nurse to notice. The turbidity
which is present when the urine is passed is the only
kind that is of any practical importance.
Turbidity which occurs in urine which has been
standing for any length of time may be due to growth
of bacteria in the urine or to the formation of various
kinds of deposit, such as deposits of phosphates or
substances known as urates. This latter urate de-
posit is likely to be brick duLst in color and is very
120 CHEMISTRY FOR NURSES
common in urine which has been left standing in the
cold, — so common, in fact, that it has been very
widely used in fraudulent advertisements to frighten
healthy people into thinking that they had kidney
trouble and taking some patent medicine. It is
never a sign of disease. It is easily recognized by the
fact that it dissolves if the urine is warmed.
The turbidity which is due to the growth of bac-
teria is accompanied by the development of an am-
moniacal smell and is a disturbing factor in making
several of the special tests on urine. For this reason
when urine cannot be sent to the laboratory at once
or when twenty-four hour specimens are collected,
the urine should be kept in the cold (ice box) or some
harmless preservative should be added, such as
chloroform, thymol crystals, or toluol. As some of
these substances may have an effect on certain chemi-
cal tests, it should always be noted which one has
been added.
In urine which has hecome alkaline on standing
there may be a heavy deposit of phosphates or of
carbonates. This, unlike the deposit of urates,
does not disappear on warming, but does dissolve
if acetic acid is added.
Turbidity of Fresh Urine. — Urine which is tur-
bid when passed may be so from the presence of pus
URINE 121
or of phosphates or carbonates. This occurs espe-
cially in cystitis (inflammation of the bladder), pye-
litis (inflammation of the pelvis of the kidney), and
various kidney inflammations (such as abscess or
tuberculosis), or the turbidity may be due to pus
from leucorrhea or gonorrhea. Pus settles to
the bottom in an hour or two as a thick creamy
layer. It can only be identified with certainty by a
microscopic examination.
It is especially important to watch for any slight
turbidity of the urine in cases in which a cystitis is
likely to develop, for instance, in cases which are
being catheterized frequently. The important tur-
bidity of course is due to pus. Turbidity which
clears up promptly on warming the urine over a
flame (in the case of urates), or on adding a little
dilute acetic acid (phosphates and carbonates) is
never due to pus.
(4) ODOR
The odor of freshly passed urine may vary from
the normal, especially after eating certain articles
of diet such as asparagus. Urine which is foul when
passed usually comes from a case of cystitis, or if the
odor is fecal, from a case of fistula connecting the
bladder and rectum. On being allowed to stand for
122 CHEMISTRY FOR NURSES
a day or more urine becomes foul-smelling from de-
composition caused by bacteria.
(5) REACTION
The reaction of urine is tested with litmus paper
(see Chapter V). Normal urine is usually acid, or
sometimes amphoteric ; that is, turning red litmus
paper blue and blue litmus paper red. Occasionally
when passed after a heavy meal it is found to be
slightly alkaline, due to the fact that the body is
using up the acid which ordinarily is excreted in the
urine to manufacture the acid needed by the stomach
for digestion. This is known as the alkaline tide in
the urine. Urine may also be made alkaline by the
giving of alkaline drugs such as bicarbonate or
citrate of soda. Aside from these instances urine
which is alkaline when passed is generally urine de-
composed as the result of cystitis. Urine which has
decomposed after being passed also becomes alkaline.
The alkalinity of decomposed urine is due to the
production of ammonia (NH3) by the action of a cer-
tain bacterium, — the micrococcus urei, which grows
on urea.
(6) SPECIFIC GRAVITY
What is Meant by Specific Gravity. — The specific
gravity of urine means its density, or what is the
URINE 123
same thing, the weight of any volume of urine as
compared with the weight of an exactly equal volume
of distilled water. Suppose we have two flasks each
containing 1000 c.c. of distilled water, their weight
exactly the same. If in the one flask we dissolve
10 grams of salt then the water in that flask will
weigh 10 grams more than that in the other flask. In
other words, its specific gravity will be 1010. Hence
the figure that represents the specific gravity of
urine really indicates to us the number of grams
of solid substance dissolved in 1000 c.c. of urine.
The specific gravity varies in health, depending
always on the amount of urine secreted ; so that the
figure representing the specific gravity really means
very little unless we know how much urine is secreted.
If we do know, then we can judge whether the patient
is excreting enough solid matter or not. The most
important solid matters to be excreted are urea and
salts. When the kidneys are diseased they are un-
able to excrete sufficient of these substances.
Cause of Dropsy. Reason for Salt-free Diet. —
In Chapter VII it was explained why it is very impor-
tant for the body to maintain the concentration of
salt in the blood at precisely a certain point. If
the kidneys are unable to get rid of the surplus salt,
then in order to keep the concentration of the body
124 CHEMISTRY FOR NURSES
fluids right, the body has to retain water also. This
leads to edema or dropsy. This is the reason for
salt-free diet, or salt-poor diet, in cases of kidney
disease.
The normal specific gravity of the urine is between
1012 and 1024^ The specific gravity is low in chronic
Bright ^s disease, in diabetes insipidus, and after
drinking large amounts of fluid. The specific grav-
ity is high when the amount of urine excreted is
small, as in fevers ; it is high especially in diabetes
in spite of the large amount of urine passed, due to
the sugar dissolved in the urine.
[ Method of Determining Specific Gravity. — In
practice, in order to measure the specific gravity of
urine we do not weigh it, but we use a much simpler
method the principle of which depends on the fact
that when anything floats in water in which salts or
any other solid substances are dissolved it is huoyed up
and floats higher than it would in plain water. Thus
in the Dead Sea there is so much solid matter dis-
solved that a person cannot sink. To measure the
specific gravity a special little instrument or buoy
called a urinometer is used. It is dropped into the
urine and made to float there without touching the
sides of the vessel. Its stem which projects above
the surface of the urine has marks on it at different
UEINB 125
levels and these marks are labeled 1000, 1010, 1020,
1030, and so on, and the intermediate figures are in-
dicated by strokes. One can tell the specific gravity
of the urine simply by reading off the level to which
this stem sinks in the urine.
(7) ALBUMIN
Heat Test for Albumin. — One of the most im-
portant things which urine is tested for is albimain.
There are a great many different tests ; the heat test
is the simplest and is very delicate. The test con-
sists of pouring some of the clear urine into a test
tube and boiling the upper layer of the urine, then
adding a few drops of weak acetic acid (2%) and
boiling again. If there is albumin present, a very
faint or heavy cloudiness (precipitate of coagulated
albumin) forms on boiling and persists or becomes
heavier on adding a few drops of dilute (2 %) acetic
acid and boiling again. // a precipitate occurs at
the first boiling hut clears up again entirely on adding
acetic acid, it is not alhuminy but harmless phosphates
or carbonates. In case the urine is alkaline before
the test is made it must first be neutralized by adding
a little weak acetic acid. In case the urine is not
clear before the test is done it must first be clarified
by filtration.
126 CHEMISTRY FOR NURSES
Significance of Albumin. — Albumin in the urine
generally means disease of some sort. The most
important disease in which it occurs of course is
nephritis (Bright 's disease). In acute nephritis it
occurs in large amounts, in chronic nephritis in mere
traces. When the heart is weak and also in fevers
there may be traces of albumin in the urine without
the kidneys being necessarily diseased. During
pregnancy an occasional test of the urine is of great
importance on account of the danger of kidney com-
plications. Urine which has pus in it or blood has
of course also albumin. This, however, does not
necessarily mean kidney disease.
(8) SUGAR
Sugar is found in the urine chiefly in cases of dia-
betes mellitus. In healthy people, however, small
amounts of sugar may occasionally appear in the
urine under special circumstances, — such as after
eating an excessive amount of carbohydrates. Oc-
casionally in pregnancy or during lactation, or par-
ticularly when lactation is suddenly ended, milk
sugar is found in the urine. The sugar found in the
urine in diabetes is the same which normally is
present in the blood; namely, dextrose (glucose,
grape sugar).
UEINE 127
Fehling^s test for sugar in the urine is the one usu-
ally used. The fermentation test is also often used.
Both tests are described in Chapter IX. The fermen-
tation test is of aid in distinguishing between dex-
trose and milk sugar : milk sugar is not fermented
by yeast but gives reduction with Fehling^s test.
The Amount of Sugar. — The amount of sugar in
the urine is one of the most important things for the
doctor to know in treating a case of diabetes ; and
as in these cases the amount passed by the kidneys
at different hours of the day varies, the only figure
that has any meaning is the total amount of sugar lost
hy the body in twenty-four hours. This in turn is only
of significance when it can be compared with the total
amount of carbohydrates eaten by the patient in the
same twenty-four hours. For this reason the mere
percentage of sugar in one specimen or urine really
means very little. It is not necessary for nurses to
learn the methods of measuring the amount of sugar.
Acetone and Diacetic Acid. — Besides sugar there
are two other things which are always extremely
important to test for in the urine of patients who
have diabetes ; these are acetone and diacetic acid.
In diabetes death most commonly results from the
so-called acid intoxication or diabetic coma. This
comes from the accumulation of certain acids in the
128 CHEMISTRY FOR NURSES
body, and the presence of these acids in the blood
is shown by acetone or diacetic acid appearing in
the urine. These same substances may also be
found in the urine during starvation or in diseases
in which the nourishment of the patient is very
greatly cut down. There are very few chemical
tests that nurses ever are called on to perform, but
the test for diacetic acid is so simple, and knowing
whether it is present in a given case of diabetes from
day to day is so important, that the test will be men-
tioned here. If to a few drops of urine containing
diacetic acid an excess of ferric chloride solution is
added, the fluid becomes a Bordeau red (red wine)
color. This color disappears or gets fainter if the
urine is boiled. (Adding an excess of ferric chloride
solution means adding more ferric chloride solution
than there is urine in the tube.)
Reason for Alkaline Medication. — When these
acids are found in the urine, as a rule alkalies are
ordered as medicines (sodium bicarbonate, sodium
citrate) and the diet is made much more liberal even
if the amount of sugar excreted becomes greater. In
such cases the doctor sometimes puts litmus paper
in the hands of the nurse and instructs her to give
the alkaline medication at regular intervals until
the urine becomes and remains alkaline.
URINE 12S
(9) MICROSCOPIC EXAMINATION
Nurses are never called upon to do a microscopic
examination of urine, but as such examinations are
often done on the patients that they are taking care
of, they should know what is meant by a few of the
terms used. In a microscopic examination the most
important things looked for are pus, blood cells, and
casts. Pus is recognized by the finding of so-called
pus cells, which are nothing but dead leucocytes
(white blood cells). The finding of red hlood cells
in urine is of great diagnostic value especially when
kidney stones are suspected. Small numbers of the
blood cells are often found in urine that is not the
least blood tinged. When urine is to he examined
for hlood cells it must he examined fresh, as the red cells
lose their outlines and are almost impossible to rec-
ognize after the urine has been standing for a day.
Casts in the urine always point to kidney disease.
Casts are very minute cylindrical bodies molded to
the shape of the inside of the fine kidney tubules in
which the urine is secreted. They are composed of
albumin which is coagulated or solidified in the tubules.
When present in large numbers they are of very grave
significance. Beside these things the urine frequently
contains crystals of various kinds, and bacteria.
CHAPTER XIV
Stomach Contents and Feces
stomach contents
Nurses are not expected to make chemical anal-
yses, but as they frequently have to assist doctors
in securing samples of stomach contents, and as they
have to make careful notes of the appearance of
vomitus, they should know something about the
examination of gastric juice.
Object of Examining Stomach Contents. — In the
examination of the stomach contents much depends
on the time and circumstances under which the
specimen is obtained. Ordinarily we desire to find
out how the stomach behaves in a definite number
of minutes after the taking of a definite kind of test
meal. Frequently we wish to find out whether the
stomach is capable of emptying itself in a certain num-
ber of hours. This is the object of the taking of the
stomach contents in the early morning before any
food is taken. The normal stomach should be
practically empty at this time of day. If there is
130
STOMACH CONTENTS AND FECES 131
much fluid in it, — especially if there are any rem-,
nants of food taken the day before, — then we know
that there is some delay in the emptying of the stom-
ach into the intestine.
Is the Pylorus Obstructed ? — When this question
is to be determined, usually some easily recognized
kind of food such as raisins, cranberry or currant
preserves, or a few grains of rice are given the night
before. The kind of food remnants recognizable in
the stomach contents or vomitus should be noted by the
nurse and she should report how long before the kind
of food seen was taken.
The quantity of the stomach contents should always
be accurately measured; an abnormally large amount
means either obstruction at the pylorus or an exces-
sive secretion. 'After a test meal usually 50 to 100
c.c. are obtained.
Gross Appearance. — Other facts in the gross ap-
pearance are also worth noting: whether (after
an Ewald test breakfast) the bread is chewed or not,
— whether there is bile present or not, — and above
all whether there is any trace of blood.
Blood in Stomach Contents. — Blood in the stom-
ach contents looks brown or black, and if there is much,
it has a coffee grounds appearance due to the action of
the hydrochloric acid of the stomach on the hsemo-
132 CHEMISTRY FOR NURSES
globin of the blood. Bright red streaks of hlood in the
stomach contents almost always come from the
mouth or throat ; and they should always he noted hy
the nurse, because if they subsequently become af-
fected by the acid and dissolved in the remainder of
the stomach contents, they may deceive the doctor
who makes the examination later. Blood can be
tested for by chemical means and an extremely
minute trace of it can be detected. Its finding is of
great importance and usually points either to an
ulcer or a cancer of the stomach.
Acidity. — Next to the finding of blood the most
important practical examination of the stomach con-
tents is the measuring of the amount of acid. This is
measured in terms of the number of cubic centimeters
of a particular strength of sodium hydrate (called deci-
normal sodium hydrate) which 100 c.c. of the stomach
contents will neutralize. Thus a doctor's report that
the acidity of the stomach contents is 60 means that
100 c.c. of the stomach contents have enough acid
to neutralize 60 c.c. of this kind of alkali. The
amount of acid is increased in certain kinds of stom-
ach troubles, and especially in ulcer of the stomach.
It is diminished in certain other stomach troubles,
and especially in cancer. In some diseases the ordi-
nary hydrochloric acid of the stomach is almost
STOMACH CONTENTS AND FECES 133
absent and a different kind of acid, namely lactic
acid, is found ; it is produced by the fermentation of
food through the agency of bacteria. Lactic acid
gives a sour odor which the nurse can often learn to
recognize.
As the saliva is alkaline, it is of great importance not
to get any saliva mixed with the stomach contents ; if
any is accidentally mixed in during the obtaining of
the stomach contents, one should make note of the
fact; otherwise, especially if the amount of the
stomach contents is small and the amount of saliva
considerable, the examination of the acidity may
be entirely misleading.
EXAMINATION OF FECES
The examination of the feces is a thing in which
the nurse is sometimes of assistance. Only one or
two points need to be discussed. The most impor-
tant single thing examined for is blood; it has the same
significance here as in the stomach contents ; namely,
ulceration of some kind in the stomach or intestine.
Large amounts of blood of course are easily seen.
Minute traces are detected by very delicate chemical
tests (benzidine reaction). As any blood taken
with meat will also give a positive chemical test for
blood, the patient has to he put on a meat-free diet for
134 CHEMISTRY FOR NURSES
three days before one can be sure that a positive
chemical test for blood in the stool really means a
little bleeding into the intestines or stomach.
Significance of Fatty Stools. — Aside from the
observation of blood the question of whether bile is
present or not is of much practical importance. In
cases of jaundice when the bile does not empty into
the intestines the stools are of a pale gray or slate
color and of a pasty consistency. This is due not
only to the absence of the pigments derived from bile
in the stools but chiefly to the large amount of un-
digested fat. It wiU be remembered that bile plays
an important part in aiding the digestion of fat by
emulsifying it. This is the reason that patients who
have obstructive jaundice have to get their nourish-
ment largely from carbohydrates and proteids, and
the amount of fat in their diet is to be restricted.
INDEX
Acetate, lead, 9
Acetates, 63
Acetic acid, 36, 63
Acetic fermentation, 73
Acetone, 127
Acid, acetic, 36, 63
amino, 91, 100, 112
effect of erepsin on. 111
effect of trypsin on, 109
benzoic, 62
boric, 7
butyric, 63
carbolic, 62
carbonic, 42
citric, 36, 63
diacetic, 127
hydrochloric, 36
absence in stomach contents,
132
presence in stomach contents,
105
hydrofluoric, 42
lactic, 63
in stomach, 133
nitric, 36
action of, 41
test for proteids, 97
oleic, 63
oxalic, 63
phosphoric, 37
salicylic, 62
sulphuric, 36
tartaric, 63
uric, 114
Acid intoxication, 127
Acids, 36, 63
fatty, 63
of milk fat, 110
organic, 42, 66, 62
power of neutralizing, 45
Affinity, chemical, 21
Air, 35
Albumin, 125
coagulation test for, 96
Albuminoids, 93
Albumins, 92
Alcoholic fermentation, 73
Alcohols, 63
AlkaUne medication, 128
Alkaloids, 63
Alimiinium, 7
Amino acid, 91, 100, 112
effect of erepsin on, 111
effect of trypsin on, 109
Ammonia, 44, 50
composition of, 25
in urine, 122
Ammonium hydrate, 44
Amylase, 103, 108
Analysis, 6
Animal starch, 78
Animals, carnivorous, 98
herbivorous, 98
Argyrol, 11
Aromatic substances, 62
Arsenic, 7
Arterial blood, 35
Atomic theory, 12
Atoms, IS
weight of, 14
Atropine, 64
B
Bacteria, 71
discovery of, 73
nitrifying, 98
Bacterial spores, 95
Bases, 44, 45
organic, 63
Basic salt, 55
Beeti, 69
Benzidine reaction, 133
Ben«ine, 84
Benzoic acid, 62
Benzol, 62
135
136
INDEX
Bicarbonate, sodium, 62, 65
Bichloride of mercury, sterilizing
effect of, 96
Bile, 108
in feces, 134
use of, 110
Biological chemistry, 68
Bismuth, 7
subnitrate, 51
Blood, arterial, 35
efifect of distilled water on, 63
in stomach contents, 131
venous, 35
Blood clot, 93
Blood serum, 93
Bone, 8, 10
Borax, 7
Boric acid, 7
Boron, 7
Bread, leavening of, 72
Bright's disease, 126
Bromides, 7
Bromine, 7
Bunsen flame, 33
Butter, cocoa, 80
peanut, 80
Butyric acid, 63
Calcium, 7, 10
Calcium chloride, 55
Calcium hydrate, 44
Calcium phosphate, 7, 10
Calomel, 9
Calorie, 31
Camphor, 62
Cane sugar, 69, 70
CarboUc acid, 62
Carbon, 8, 60
Carbon dioxide, 20, 25, 72
Carbonates, list of, 52
Carbonic acid, 42
Carbohydrates, 65
Carnivorous animals, 98
Casein, 93
Caseinogen, 93
Castile soap, 86
Casts in urine, 129
Caustic potash, 10, 44
Caustic soda, 44, 46
Caustic stick, 41
CeUulose, 75, 76
Cereals, amount of fat in, 80
Cheese, 73, 93
Chemical affinity, 21
Chemical elements, 2
Chemical formulas, 22
Chemistry, biological, 68
organic, 56
synthetic, 58
Chloride, calcimn, 65
silver, 22, 42
sodiimx, 3, 49
zinc, 39
Chlorides, 18
list of, 51
Chlorine, 8
Chloroform, as preservative for
urine, 120
Citrates, 63
Citric acid, 36, 63
Clay, 10
Cleansing, 88
Clot, blood, 93
Coagulation, 9^, 96
of milk, 105
test for albumin, 95
Cocaine, 63
Cocoa butter, 80
Codeine, 63
Collagen, 93
Coma, diabetic, 127
Combustion, 32, 56
Compound proteids, 93
Compounds, 2
Conservation of energy, 29
Cooking, 94
Copper, 8
Copper sulphate, 61
Cotton, 78
Cotton-seed oil, 80
Crystallization, 16
Curd, 93
Cystitis, 121
Dextrin, 75, 77
Dextrose, 67, 68, 77
action of yeast on, 72
in urine, 126
Diabetes, sugar in, 126
Diabetes insipidus, 118
INDEX
137
Diabetes mellitus, 118
Diabetic coma, 127
Diacetic acid, 127
Diastase, 70
action on starch, 103
Diet, meat-free, 133
salt-free, 123
Digestion, 101, 78
by malt extract, 77
effect of acids on, 106
gastric, 105
pancreatic, 108
starch, 104
Dioxide, carbon, 20, 25, 72
test for, 34
Disaccharides, 67, 70
list of, 69
Disinfection of skin, 87
Distillation, 17
Distilled water, effect on blood, 53
Dropsy, 123
Dynamo, 29 ^
E
Egg white, 93
Einhorn fermentation tubes, 72
Elements, chemical, 2
halogen, 52
list of, 6, 7
Emulsification of fats. 111
Emulsion, 84, 88
Energy, 27
as a mode of motion, 28
conservation of, 29
fat, as source of, 79
hidden, 29
Enzymes, 101
chemical nature of, 102
synthetic action of, 103
Epsom salt, 51
Erepsin, 111
Ether, 84
Evaporation, 17
Extract, malt, 70
meat, 99
Fat, a source of energy, 79
amount in cereals, 80
amount in nuts, 80
Fat, digestion of, 109
emulsification of, 111
Fatty acids, 63
of milk fat, 110
soaps from. 111
Fatty stools, in jaundice, 111, 134
Feces, bile in, 134
Fehling's test, 70, 74
Fermentation, 71
acetic, 73
alcoholic, 73
by-products of, 72
gastro-intestinal, 74
lactic acid, 73
Fermentation tubes, Einhorn, 72
Fibrinogen, 93
Filtering, 22
Filtrate, 22
Flash light, 9
Food value, 31
Formulas, chemical, 22
structural, 26
Fructose, 67
Fruit sugar, 67, 68
plan of molecule, 69
Gas, laughing, 17
Gases, solubility of, 17
Gasoline, 84
Gastric digestion, 105
Gastro-intestinal fermentation, 74
Gelatin, 93
Glassware, 10
Globulins, 92
Glucose, 67, 68
in urine, 126
Gluten, 93
Glycerin, 63, 81
Glycogen, 75, 78
Glycosuria, 74
Gold, 8
Grape sugar, 67, 68
plan of molecule, 61
Grease spots, 83
Green soap, 86
Heemoglobin, 5, 35, 93
Hsemolysis, 54
138
INDEX
Hair, burnt, 93
Halogen elements, 62
Hard soap, 87
Hard water, 88
Heat, 28
sterilizing effect of, 95
Heat test for albumin, 125
Herbivorous animals, 98
Hidden energy, 129
Honey, 69
Hydrate, ammonium, 44
calcium, 44
potassium, 10, 44
sodium, 44
Hydrates, 44
Hydrochloric acid, absence in
stomach contents, 132
presence in stomach contents,
105
Hydrofluoric acid, 42
Hydrogen, 8
peroxide of, 5
Hydroxide, sodium, 46
Hydroxides, 46
Hypotheses, uses of in science, 12
Indigo, 62, 90
IntestinaL fermentation, 74
Intestinal^isecretion, 111
Intoxication, acid, 127
Iodide, potassium, 20
Iodides, 8
Iodine test for starch, 77
Iron, rusting of, 32
Jaundice, stools of, 111, 134
urine in, 118
Keratin, 93
Kidneys, functions of, 113
Kumiss, 73
Lactates, 63
Lactic acid, in stomach, 133
Lactic acid fermentation, 73
Lactose, 69, 75
Laughing gas, 18
Lead, 9
Lead acetate, 9
Leavening of bread, 72
Legumen, 93
Lemons, 63
Levulose, 67, 68
Limestone, 7
Limewater, 34, 44
Linen, 78
Lipase, 109
Lithium, 9
Litmus solution, 109
Litmus test, 43, 44
Liver, 78
M
Magnesia, milk of, 9
Magnesium, 9
Malt extract, 70
Malt soup, 70
Malt sugar, 69
Malted milk, 70
Maltose, 69, 70, 77
Maple sugar, 69
Marble, 7
Matzoon, 73
Meal, test, 130
Meat, 93
Meat extract, 99
Meat-free diet, 133
Medication, alkaline, 128
Menthol, 62
Mercury, 9
sterilizing effect of bichloride, 96
Metabolism, diseases of, 69
Microscopic examination, 129
Milk, as example of emulsion, 84
coagulation of, 105
malted, 70
of magnesia, 9
sour, 63, 73
Milk sugar, 69
Milk whey, 93
Mineral substances, 56
Molecule, plan of fruit sugar, 69
plan of grape sugar, 61
Molecules, 12
size of, 14
INDEX
139
Monosaccharides, 66
list of, 67
Morphine, 63
Motion, energy as mode of, 28
Mucin, 93
Mucus, 93
Myosin, 93
N
Naphtha, 84
Nephritis, 126
Neutral point, 49
Neutral salt, 55
Neutralization, 48
Nickel, 9
Niter, 51
Nitrate, silver, 22, 39
formula for, 20
sterilizing effect of, 96
structural formula, 26
test for presence of, 41
Nitrates, list of, 51
Nitric acid, 36
action of, 41
test for proteids, 97
Nitrifying bacteria, 98
Nitrogen, 9
Nitrogen starvation, 98
Normal salt solution, 53
Nuts, fat in, 80
Oil, cotton-seed, 80
olive, 80
Oleic acid, 63
Organic acids, 42, 56, 62
Organic bases, 63
Organic chemistry, 66
Oxalates, 63
Oxalic acid, 63
Oxidation, 31, 32
Oxides, 18
Oxygen, 9, 32
Pancreatic digestion, 108
Pancreatin, 109
Paper, 78
Peanut butter, 80
Pepsin, 105, 106
Peptones, 99
test for, 108
Peroxide of hydrogen, 6
Phenacetine, 62
Phenol, 62
Phosphate, calcium, 7, 10
sodium, 10, 56
Phosphates, list of, 52
Phosphoric acid, 37
Phosphorus, 10
Plants, woody part of, 78
Plaster of Paris, 51
Platinum, 10
Polarized light, 68
Polypeptids, 100
effect of trypsin on, 109
Polysaccharides, 67
list of, 75
Potash, caustic, 10, 44
Potassium, 10
Potassium hydrate, 10, 44
Potassium iodide, 20
Powder, baking, 63
Precipitate, 22, 41
Preservative for urine, 120
Protargol, 11
Proteid, test for, 96
Proteids, 90
compound, 93
elementary composition of, 19
nitric acid test for, 97
simple, 92
Proteoses, 99
test for, 108
Ptyalin, 103
Pus in urine, 121
Pyelitis, 121
Quinine, 62
Radium, 10
Reaction of urine, 122
Reduction, 74
Rennin, 105, 106
Residue, 22
Respiration, 36
Retention of urine, 117
140
INDEX
Rock, 10
Rubber, 90
Rusting of iron, 32
S
Saccharine, 69
Saccharose, 69
Salicylic acid, 62
Saliva, 103
Salt, Epsom, 61
Salt, formation of, 48
in the body, 63
neutral, 55
table, 3, 49, 66
Salt balance, 114
Salt-free diet, 123
Saltpeter, 61
Salts, 4^, 60
acid, 65
basic, 65
Sand, 10
Saturated solution, 16
Scrubbing up, 87
Secretion, intestinal. 111
Serum, blood, 93
Silicon, 10
Silver, 11
Silver chloride, 22, 42
Silver nitrate, 22, 39
formula for, 20
sterilizing effect of, 96
structural formula, 26
test for presence of, 41
Skin, disinfection of, 87
Soap, Castile, 86
Soap, cleansing power of, 88
green, 86
hard, 87
manufacture of, 85
soft, 87
Soaps, 85
from fatty acids. 111
Soda, bicarbonate of, 22, 66
caustic, 44, 46
Sodium, 11
Sodium bicarbonate, 62, 65
Sodium chloride, 3, 49
Sodium hydrate, 44
Sodium hydroxide, 46
Sodium phosphate, 10, 65
Soft soap, 87
Solubility of gases, 17
Solution, litmus, 109
normal salt, 63
saturated, 16
Soup, malt, 70
Sour milk, 63, 73
Specific gravity, 122
Spores, bacterial, 95
Starch, 76, 76
action of diastase on, 103
animal, 78
effect of ptyalin on, 103
iodine test for, 77
Starch digestion, 104
Starch digestion by malt extract,
77
Starch digestion, effect of acids on,
105
Starvation, nitrogen, 98
Steam engine, 28
Steam sterilization, 95
Sterilization, heat, 96
steam, 95
Sterilizing effect of bichloride of
mercury, 96
Sterilizing effect of heat, 95
Sterilizing effect of silver nitrate, 96
Stick, caustic, 41
Stomach, lactic acid in, 133
Stomach, absence of hydrochloric
acid in, 132
blood in, 131
contents, 130
digestion in, 105 ;
lactic acid in, 133
presence of hydrochloric acid in,
105
Stools, fatty, in jaundice, 111, 134
Strontium, 11
Structural formulas, 26
Strychnine, 63
Subnitrate, bismuth, 61
Sucrose, 69
Sugar, 66, 126
cane, 69, 70
fruit, 67, 68, 69
grape, 67, 68
grape, plan of molecule, 61
in diabetes, 126
malt, 69
maple, 69
milk, 69
INDEX
141
Sugars, classification of, 66
properties of, 71
simple, 67
tests for, 74
Sulphate, copper, 61
zinc, 11
Sulphates, list of, 51
Sulphocarbolate, zinc, 11
Sulphur, 11
Sulphuric acid, 36
Suppression of urine, 117
Synthesis, 6
Synthetic action of enzymes,
Synthetic chemistry, 58
103
Table salt, 3, 49
Tartaric acid, 63
Tartrates, 63
Test, Fehling's, 70, 74
litmus, 43, 44
Test meal, 130
Theory, atomic, 12
Thymol as preservative for urine,
120
Tin, 116
Tincture of green soap, 86
Toluol, as preservative for urine,
120
Trypsin, 108
ejffect on amino acids, 109
effect on polypeptids, 109
Turbid urine, 119
Turpentine, 62
U
Urates, 119
Urea, 67, 114
Uric acid, 114
Urine, IIS
ammonia in, 112
amount, 115
casts in, 129
collection of, 120
deposit in, 119
dextrose in, 126
glucose in, 126
in jaundice, 118
measuring, 116
pus in, 121
preservative for, 120
reaction, 122
retention, 117
specific gravity of, 122
suppression, 117
turbid, 119
Valence, 23,24
Venous blood, 35
Vinegar, 63, 73
W
Water, 3
composition of, 25
hard, 88
Whey, 93, 106
Wood fiber, 78
Yeast, 71, 72
Z
Zinc, 11
Zinc chloride, 39
Zinc sulphate, 11
Zinc sulphocarbolate, 11
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Materia Medica for Nurses
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action of the drugs on every organ and tissue of the body — on the skin
and mucous membrane, on the heart, on the alimentary track, on the
kidneys — the rate of absorption and excretion, etc, etc.
The text begins with the definition of drugs, their derivation, prepara-
tion, active principles, nature of action, poisonous action, stimulants, de-
pressants, metric system, and dosage. The drugs are classified under two
main divisions of Stimulants and Depressants, followed by the pharmaco-
logical action, which is arranged in a simple manner to facilitate easy re-
membrance of the text. An unusual and entirely new feature is contained
in the vivid clinical pictures of the appearance of the patient after the ad-
ministration of each drug. Finally, and of especial importance, are the
complete Tables of Saturation Points and the chapter on Solutions, with
simple, arithmetical rules, by which the nurse can quickly, easily, and
accurately make up a solution of any strength and administer accurate doses
of a drug.
These are but a few of the many new features contained in this book,
which is up to the minute. It includes among the preparations all the new
and non-official remedies in common use, as well as a chapter on Prescrip-
tion Reading, the last-named subject being required by nearly all the
State Boards. The cross-index is also very complete and detailed.
THE MACMILLAN COMPANY
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NEW AND STANDARD BOOKS FOR NURSES
Bacteriology for Nurses
Including Schedule for Laboratory Exercises, etc.
By ISABEL McISAAC
Superintendent United States Army Nurse Corps; Author of Hygiene for
Nurses, etc.
Second Edition. Revised. Clothy illustrated^ $i^S
This is a completely revised edition of the well-known textbook which
has, for years, been the only book written dictinctly for the use of nurses,
and much new material has been added. The author has carefully con-
fined herself to the needs of the class for whom it is intended and she has
been singularly successful in avoiding unnecessary digression, making clear
the practical as well as the theoretical.
The scheme of the original work has been maintained. There are chap-
ters on Structure, Mode of Development, and Composition of Bacteria;
The Effect of Physical and Chemical Agents upon Bacteria, and the Effects
of Bacterial Growth ; The Relations of Bacteria to Disease ; Immunity ;
Inflammation, Suppuration, Pneumonia, Epidemic Cerebro-Spinal Men-
ingitis; Typhoid Fever (Enteric Fever); Asiatic Cholera, Relapsing
Fever ; Infectious Diseases of Unknown Cause and Bacteria in Air, Soil,
Water, and Food.
Nursing the Insane
By CLARA BARRUS
Woman Assistant Physician in the Middletown State Homeopathic Hospital,
Middletown, N.Y.
Cloth, 8vo, $2.00
This is an illuminative, sensible, straightforward book covering the vari-
ous features of the nurse's work in caring for the insane. There are
directions, not only for medical and clinical care of the insane, for their
occupation and amusements, with directions as to how they may be moved,
but above all there are some very interesting chapters on psychology, so
that the nurse may appreciate patients' states of mind and sympathize with
their peculiarities.
THE MACMILLAN COMPANY
Fubliehers 64-66 Fifth Avenue New Tork
NEW AND STANDARD BOOKS FOR NURSES
Textbook of Anatomy and
Physiology for Nurses
By DIANA C. KIMBER
Former Assistant Superintendent, New York City Training School for
Nurses, Blackwell's Island, New York. Fourth Edition, Revised, by
Carolyn E. Gray, R.N., Superintendent, New York City Training School
for Nurses
C/o^A, 8vo, illustrated^ $2.jo
This book is the accepted standard in American Training Schools for
Nurses.
" From her long experience in teaching classes the author knows exactly
what nurses need and how much can be reasonably given them in the short
space of two years' time, and for the assistance of the inexperienced teacher
her book is arranged in lessons covering the first or junior year. The sub-
jects are presented with sincerity and distinction, and illustrated by cuts
and plates of unusual merit." — TAe Trained Nurse,
Hygiene for Nurses
By ISABEL McISAAC
Superintendent U. S. Army Nurse Corps, Formerly Superintendent of the
Illinois Training School of Nurses
Clothf I2m0y $1.2^
The pages of this book are full of just the information that every woman
in charge of souls and bodies needs. The chapters on food, ventilation,
sewage, causes and dissemination of disease, household, personal and school
hygiene, the hygiene of occupation, disinfection, etc., are all of the most
vital interest and value to the nurse.
Primary Nursing Technique
FOR FIRST YEAR PUPIL NURSES
By ISABEL McISAAC
Clothy i2mo, t>i.2S
A valuable and thorough book for nurses starting on their course of study.
It is written with the one object in view of inculcating into the minds of
its readers the fact that an accurate knowledge of the human body is the
first essential to successful nursing.
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NEW AND STANDARD BOOKS FOR NURSES
The Life of Florence Nightingale
WITH PHOTOGRAVURE PORTRAITS
By sir EDWARD COOK
Two vols., cloth, Bvo. $y.^o
"A masterly biography which not only puts into a permanent
record her whole-souled devotion and humanity, but relates the his-
tory of one of the greatest and most fruitful movements of modern
times. He has put the essence of saintliness into good literature
and sober history." — Pall Mall Gazette.
" We have no hesitation in saying that this work will live as one
of the greatest biographies in the English language."— The Daily
Chronicle y London.
" No one can read this remarkable book with its detailed descrip-
tion of brave and unflagging work without endorsing so fine a tribute.
There are portraits in these volumes, and the work, apart from its
fascination as a biography, throws a flood of life on the manner in
which Florence Nightingale lifted nursing from a despised calling to
one of the most honorable vocations open to modern womanhood.''
— The Standard, London.
The Life of Florence Nightingale
By SARAH A. TOOLEY
Auflior of " Personal Life of Queen Victoria," etc. With twenty-two
Illustrations.
Cloth, i2mo, $i.7S
In writing this book the author has had the assistance of many of
Miss Nightingale's closest associates during her active years, and has
produced a singularly interesting volume that reflects Miss Nightin-
gale's character and personality in the happiest way.
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0b9 Chemistry fori nurses.