WATER
Water is the most abundant compound. It covers about three-fourths of the earth’s surface, is present in the air as water vapor and is found in all plant and animal tissue.
The human body consists of about 70% water. Bacterial cells contain about 85% water.
The formula for water is H
2
O or more correctly, HOH which emphasizes its structure.
Water is a bent molecule in which two atoms of hydrogen are covalently bonded to one atom of oxygen. The angle between the two hydrogens or the bond angle is 105 0 . A molecule of water looks like the following:
O
H
The molecular weight of the compound is 18.
H
PHYSICAL PROPERTIES OF WATER
1.
Water is a colorless, odorless, tasteless liquid.
2.
It freezes at 0
0
C and boils at l00
0
C at standard atmospheric pressure.
3.
Water has a heat of fusion of 80 calories/gram.
4.
Water has a specific heat of 1 calorie/gram/ 0 C.
5.
It is a very good solvent for many substances.
It is known as the “Universal solvent”. It is also the primary vehicle for embalming fluids.
The physical properties of water such as boiling point, melting point, heat of vaporization, heat of fusion, and specific heat have abnormally high values.
Consider the boiling point of water in comparison to that of H
2
Te, H
2
Se, and H
2
S.
Compound Molecular Weight (g) Boiling Point 0 C
H
2
Te
H
2
Se
H
2
S
H
2
O
129.62
80.98
34.08
18.02
-2.2
-41.5
-60.7
100.0
Since tellurium, selenium, sulfur, and oxygen are all in Group VI of the periodic table, the compounds formed from them with hydrogen are expected to show similar trends in physical properties. As the molecular weights decrease, the boiling point of H
2
Te, H
2
Se,

and H
2
S also decrease. Water, having the lowest molecular weight of the four compounds, is expected to boil at a temperature less than –60.7
0
C, but it does not follow this trend. Boiling point has been defined as the temperature at which a substance changes from the liquid to the gaseous state. Water boils at a higher temperature than predicted because attractive forces between individual liquid molecules must be broken before boiling can occur. Because of the polarity, the hydrogen atom in every water molecule is slightly positive and the oxygen is slightly negative. Attractive forces occur between the hydrogen on one water molecule and an oxygen on the other molecule. The attractive forces are called HYDROGEN BONDS. Hydrogen bonds are depicted by the dashed lines below.
H
O
H
H
H
O
O
H
H
These bonds are about 5% as strong as the normal covalent bond. In addition to existing between hydrogen and oxygen, hydrogen bonds also form between hydrogen and nitrogen, and between hydrogen and fluorine. Hydrogen bonds involving nitrogen and oxygen are extremely important in the structure of proteins, as we will discuss later.
Water boils at a higher temperature than is expected because energy must be added to break the hydrogen bonds before water molecules are free to make the transition from the liquid state to the gaseous state. These bonds also account for the high value of the heat of vaporization of water. Water has the highest heat of vaporization of any known liquid.
The specific heat, melting point, and heat of fusion of water are also unusually high because of hydrogen bonds. Water molecules in the solid state are held together in a special arrangement by hydrogen bonds. It is an open network, which explains why ice is less dense than liquid water. Upon melting, the open structure collapses, and as a result more molecules of liquid water fit into the space occupied by the ice.
Another property of water with an unusually high value, due to hydrogen bonding is
SURFACE TENSION. All liquids have surface tension. It is defined as a force that causes the surface of a liquid to contract. Molecules within the bulk of a liquid are attracted equally in all directions by neighboring molecules. The molecules at the surface of a liquid are attracted only downward or sideways. As a result the surface contracts.

The surface tension in water is high, compared to that in other compounds. Molecules within the liquid are attracted equally in all directions by hydrogen bonds. Molecules at the surface experience an unbalanced pull into the liquid, since they cannot hydrogen bond with the air above the surface. Its high surface tension allows water to support a needle on its surface. Its surface tension also causes water to form spherical droplets at the end of a medicine dropper. Water will spread out on a clean glass surface, because glass is a polar substance. Likewise, it curves upward at the walls of a glass graduated cylinder, forming a meniscus. A Meniscus is the part of the water in a glass container that curves upward. Surface tension is an important factor in embalming because it also occurs at interfaces of solutions and cell membranes. This interferes with diffusion of embalming chemicals from the capillaries into the tissues. To correct this problem, surface tension reducing agents (surfactants) are usually incorporated into embalming fluids.
CHEMICAL PROPERTIES OF WATER
1.
Water is a very stable substance. It is thermally stable. If heated to temperatures near
2000
0
C decomposition is minimal.
2.
Water chemically reacts with active metals to liberate hydrogen. These active metals are listed in the electrochemical series.
3.
It reacts with some metallic oxides to form bases:
2
2
2
Calcium Hydroxide
Base
4.
Reacts with some nonmetallic oxides to form acids:
2
2
3
Carbonic
acid
5.
Water will form HYDRATES – a compound in which there is a chemical union between water and certain substances when they crystallize. Plaster of Paris is an example of a hydrate:
4
2
.
2
6.
Water will enter into hydrolysis reactions.
7.
Water is a key factor in both the decomposition of the human body after death, and the attempt to control that process – the embalming process.

HARDNESS IN WATER
Hard water contains certain minerals in solution, which destroy the cleansing action of soap. Soft water does not contain these minerals in sufficient amounts to create the same reaction. The minerals include calcium, magnesium, and sometimes iron (II).
Hardness can be divided into two classes
TEMPORARY HARDNESS – Can be removed by boiling and is due to the presence of the bicarbonate salts of calcium and magnesium.
Ca(HCO
Mg(HCO
3
3
)
)
2
2
– Calcium Bicarbonate
– Magnesium Bicarbonate
Boiling water containing these salts produces a decomposition reaction converting these soluble substances into insoluble substances.

3 soluble in water
2
3
2
2 insoluble in
water
The white crystal deposit found around bathtub and sink faucets is evidence of this reaction. When very hot water is run through these outlets, the heat decomposes the bicarbonates dissolved in the water. As a result, the insoluble carbonates are deposited on the fixtures.
PERMANENT HARDNESS – This type of hardness can not be removed by boiling. Other methods such as the addition of chemicals must be used.
Permanent hardness is caused by the chloride and sulfate salts of calcium and magnesium.
CaCl
2
– Calcium Chloride
CaSO
4
– Calcium Sulfate
MgCl
2
– Magnesium Chloride
MgSO
4
– Magnesium Sulfate
Permanent hardness can be removed in several ways.
1.
Removal of hardness by adding sodium carbonate (washing soda).
The chemical reaction is:
2 soluble in
water
2
sodium
3 carbonate
3 insoluble in
water

The double-replacement reaction, which occurs, converts the soluble calcium chloride into the insoluble calcium carbonate.
2.
Use of soap to remove hardness
Hard water, by definition, destroys the cleansing action of soap. This happens because soap chemically reacts with the hard water minerals to form a deposit called curd. Since the formation of curd effectively removes the minerals from the water, the use of soap qualifies as a method for softening water. The main drawback of this method is its lack of economy. A certain portion of the soap is used by the dissolved minerals before the remainder of the soap is able to function as a cleansing agent.
3.
Use of ion-exchange systems
Manufacturers of water-softening devices usually include in their advertising some statement regarding the savings on soap that consumers will experience.
We have already discussed that hard water uses a certain proportion of soap.
Softened water does not use as much soap, so more is available to do what it was intended to do, clean. Most commercial water softeners contain some kind of an ion-exchange system, in which hard-water ions such as calcium are exchanged for soft-water ions such as sodium. In many instances ions are exchanged in a medium called a resin. This resin is composed of thousands of plastic beads, which are charged with sodium ions. When hard water passes over the resin, calcium ions displace the sodium ions and stick to the resin.
The sodium ions are released from the resin and pass into the solution. An ion-exchange system simply “swaps” one type of ion for another type.
4.
Distillation
This process consists of the vaporization and condensation of water. All the substances that cause hardness in water are soluble. When water is vaporized, these substances remain in the distillation vessel or container.
RELATIONSHIP OF HARD WATER TO EMBALMING
The presence of ionized calcium in the blood is very important in the blood-clotting process. It has been shown that hard water contains ionized calcium salts. Therefore the use of very hard water should be avoided as a diluent for embalming fluid. The use of water containing an abnormally large amount of these salts favors blood coagulation and interferes with the blood drainage process. Since most tap water is unsoftened, the majority of manufacturers of embalming fluids have water softeners or anticoagulants included in their product lines.

CLASSES OF IMPURITIES IN WATER
The substances which cause hardness in water represent the first class of impurities in water, the soluble solids. The other classes of impurities in water are:
1.
Insoluble solids
2.
Bacteria
3.
Gases
1.
Distillation – This process represents the most efficient method of purifying
Water. In addition to soluble solids, this process also removes insoluble solids and some bacteria. Gases with a lower boiling point than water, such as oxygen, carbon dioxide, ammonia, and chlorine, can not be removed.
2.
Filtration – This method consists of the physical removal of particle which are too large to pass through the pores in a filter. It is sometimes aided by the use of certain chemicals, which have the effect of building particles which are normally small enough to pass through the filter into substances large enough to be held back by the filter. Another method associated with filtration is called carbon adsorption or carbon filtration. Adsorption is a process in which certain substances adhere or stick to the surfaces of other substances. If a form of carbon called “activated charcoal” is used in conjunction with filters, gases and color can be removed from water.
3.
Boiling – This purification method has traditionally been used to remove bacteria from water. Most vegetative forms of bacteria are killed after five minutes of exposure to boiling temperatures. Boiling also removes gases and some soluble solids.
4.
Aeration – This process consists of spraying water into the air. It removes gases and oxidizable organic matter, which sometimes give an unpleasant odor or taste to water. Many wastewater treatment facilities use aeration as an
intermediate step in purification of sewage.
5.
Chlorination – Chlorine’s ability to destroy odors and arrest putrefaction has
been known since 1774. Chlorine and chlorine compounds have been the
most widely used of the chemical disinfectants. They have universal
application for treating both water supplies and wastewater effluent. Calcium
hypochlorite has been widely used since 1908. It has an available chlorine
content of about 35%, but loss occurs even when it is stored in tight drums.
Except in emergencies the use of this compound has been abandoned owing
to deterioration in quality, the complexity of equipment needed, the
difficulty of preparation and application, odors produced, and its corrosive
action. Relatively stable hypochlorite powders such as HTH and Perchloron,
with available chlorine content of around 70% were subsequently developed.
The widespread acceptance of chlorine as the disinfectant of choice in the

purification of drinking water and wastewater appears to be due to its ability
to maintain a residual. This constitutes an extra margin of safety in case of
recontamination of purified water.
SOLUTIONS
In everyday life, as well as in embalming, we use mixtures. A special type of mixture is the SOLUTION. Solutions are such things as air, carbonated drinks, embalming fluids, salt water and brass.
TYPES AND COMPONENTS OF SOLUTIONS – True solutions are homogeneous mixtures of two or more substances. Components of a solution can be elements or compounds, as well as gases, liquids, or solids. In a GASEOUS SOLUTION, at least one gas is dissolved in another. When gases are placed into a container, they mix in all proportions. Any mixture of gases is homogeneous and meets the requirements of a true solution. A LIQUID SOLUTION is one in which a gas, liquid, or solid is dissolved in a liquid. Dissolving of salt in water, and of iodine in alcohol are liquid solutions. The latter is referred to as a tincture. If the liquid is water, the solution is an AQUEOUS
SOLUTION. An example of an aqueous solution is embalming fluid. Embalming fluid consists primarily of formaldehyde (gas), glycerol (liquid), and sodium chloride (solid) dissolved in water to form a homogenous mixture. A SOLID SOLUTION, also called an
ALLOY, is defined as a metallic substance that is composed of two or more metallic elements. In these solids the components are randomly dispersed throughout each other.
Examples of alloys are:
ALLOY COMPONENTS
Brass Copper and Zinc
Bronze
Stainless steel
Sterling silver
Copper, tin and sometimes zinc
Iron, chromium and nickel
Copper and silver
Both stainless steel and bronze are used in casket construction.
The usual terms used to describe the components of a solution are SOLUTE and
SOLVENT. A solute is the substance that is dissolved. It is usually the part of the solution that is present in a lesser amount. A solvent is the substance that does the dissolving. It is usually the part of the solution that is present in a greater amount. In an

aqueous solution, water is the solvent. In embalming fluids, the solvent is also called the
VEHICLE.
SOLUBILITY
An important property of a specific solute-solvent pair is solubility. To understand this concept, imagine adding salt (solid solute) to water (liquid solvent). As you slowly add the salt you can see it dissolve. After a certain amount has been added, it will no longer dissolve. This suggests that there is a limit to the amount of solute which can be dissolved in a given quantity of solvent. That limit is the solid solute’s SOLUBILITY in a liquid solvent. Solubilities are usually expressed in grams of solute per 100 grams of solvent and are calculated at a specific temperature (25
0
C). For example, the solubility of sodium chloride in water is 36g/100g H
2
O at 25
0
C. A solution that contains all the solute the solvent can hold at a given temperature is described as SATURATED.
If a solute is to dissolve in a solvent, they must be similar in structure or in electrical properties. That is to say, “Like dissolves like”. For example, water is a good solvent for salts such as sodium chloride, but water is not a good solvent for iodine. Water and salts are alike in that they are polar molecules. Iodine in contrast is a nonpolar molecule. In a polar molecule there are regions of positive and negative charges. All ionic compounds are polar, and those covalent compounds in which there is unequal sharing of electrons are polar. Since sodium chloride is ionic and water is polar covalent, salt dissolves in water. Nonpolar molecules are formed by covalent bonding with equal sharing of electrons in the bonds. All homonuclear diatomics and most organic compounds are nonpolar. Since iodine (I
2
) is nonpolar, it will not dissolve in polar water molecules.
Likewise, oil, which is an organic nonpolar molecule, will not dissolve in water.
Another factor that influence solubility is temperature. The solubility of gases in liquids is decreased by an increase in temperature. Boiled water tastes flat, since boiling decreases the solubility of air in the water. Similarly, if carbonated beverages are left open in a warm room for several hours, they lose their characteristic taste, owing to the decreased solubility of carbon dioxide. Another consequence of temperature’s influence on solubility is that the procedure of hot water embalming is less efficient than room temperature embalming. The lower solubility of formaldehyde gas in embalming fluids at elevated temperatures results in low formaldehyde concentrations in these fluids.
There is no general rule for the effect of temperatures on the solubility of liquids and solids in liquid solutions. To predict the effect of temperature, the energetics of a dissolving process must be considered. Recall that an exothermic process is one in which heat is liberated and an endothermic process is one in which heat is absorbed. An equation for an exothermic dissolving process can be written as follows:

The addition of heat shifts the reaction in the backward direction, decreasing the solubility. Therefore, in an exothermic dissolving process solubility is increased by lowering the temperature.
An equation for an endothermic dissolving process can be written as follows:
The addition of heat shifts the reaction forward, favoring the formation of solution.
Therefore, in an endothermic dissolving process, solubility can be increased by raising the temperature.
Another factor that affects solubility is pressure. Its influence is limited to gases. The solubility of all gases is increased as the partial pressure of the gas above the solution is increased. When a can of soda is opened, the pressure decreases, causing the carbon dioxide solubility to decrease. Consequently bubbles of gas escape.
CONCENTRATION TERMS
Qualitative Terms
The concentration of a solution may be expressed qualitatively or quantitatively.
Two qualitative terms are dilute and concentrated. A DILUTE solution contains a relatively small amount of solute, while a CONCENTRATED solution contains a relatively large amount of solute. Other qualitative terms we should be familiar with are unsaturated, saturated, and supersaturated. A SATURATED solution contains all the solute the solvent is able to hold at a certain temperature and pressure. A solution that has not reached saturation is UNSATURATED. A
SUPERSATURATED solution contains more of the solute than the solvent is normally able to hold. Supersaturated solutions are difficult to prepare and to maintain. The slightest bump to the container can bring the solute out of solution.
The terms dilute and unsaturated are not the same. For example, a saturated solution of sodium chloride contains 36 grams in 100 grams of water. If a solution contains 30 grams of NaCl/100 grams of water, it is unsaturated and concentrated. If it contains 5 grams of NaCl/100 grams of water, it is unsaturated and dilute.
Quantitative Terms
1.
PERCENTAGE – This may be expressed as a percent by mass or a percent by volume. When formaldehyde gas is dissolved in water, the resulting solution, called FORMALIN, is 37% formaldehyde by mass and 40% formaldehyde by volume.
2.
ppm – A unit that is frequently used to express very small concentrations.
For instance, a typical carbon monoxide level in heavy smog is approximately

40ppm by volume. This means that if we have 1,000,000 parts 40 of them will be carbon monoxide.
3.
RATIO - Some concentrations are expressed as the weight of solute to the weight of solution. A common concentration for the disinfectant HgCl
2
is
1:1000.
4.
INDEX – This term expresses the concentration of formaldehyde in an embalming fluid. The definition of index is the number of grams of pure formaldehyde gas in 100 milliliters of solution.
PROPERTIES OF SOLUTIONS
Since solutions are homogeneous mixtures of two or more substances, their properties may be different from those of the individual substances. For example, a solution containing a nonvolatile (does not evaporate readily) substance as a solute, boils at a higher temperature and freezes at a lower temperature than does the pure solvent of the solution.
A solution of sodium chloride and water has a higher boiling point than pure water. The boiling-point elevation is proportional to the concentration of the solute. Similarly, a solution shows a freezing-point depression in contrast to the freezing point of the pure solvent. Salt is placed on roads in the winter to lower the freezing point of the water and thus avoid ice formation. Elevation of the boiling point and depression of the freezing point are physical properties of solutions.
Another physical property is stability of the solution when filtered. Since true solutions are homogeneous, the solute can not be removed by filtration. Similarly, the solute will not separate from the solution while standing.
Another important physical property of solutions is diffusion. When the components of a solution are initially added to one another, regions of unequal concentration may result.
To attain a uniform concentration throughout the solution, particles move from regions of higher concentrations to regions of lower concentrations. This is the definition of diffusion. The rate of diffusion is influenced by such factors as temperature, pressure, and molecular weight of the diffusing substance. High temperatures tend to increase the rate of diffusion. Lower molecular weight molecules will diffuse faster than high molecular weight molecules. Agitating the solution (stirring) will also increase the rate of diffusion.
A form of diffusion that is important to living systems is OSMOSIS. Osmosis is diffusion through membranes. Consider two aqueous solutions of different concentrations separated by a membrane through which only solvent particles can pass.
Such a membrane is described as semipermeable. In order to equalize the concentrations on both sides of the membrane, there will be a net flow of water from the solution of lower solute concentration to the solution of higher solute concentration. The diffusion of the water is from a region of higher water concentration to one of lower water concentration. Water is diffusing from a dilute to a more concentrated solution. In

reference to osmosis certain terms are used to compare concentrations. Two solutions of equal concentration are described as ISOTONIC. If two solutions are of different concentrations, HYPERTONIC AND HYPOTONIC are used. Hypertonic indicates a more concentrated solution. Hypotonic indicates a less concentrated solution. For example, if we have two solutions separated by a semipermeable membrane.
5g of NaCl 15 g of NaCl
Solution 1 is hypotonic (less concentrated). Solution 2 is hypertonic (more concentrated).
If both solutions had 5g of NaCl then they would be isotonic. A good way to keep these two terms straight is to remember that a hyperactive person has more energy than normal.
Membranes of red blood cells allow ions and other small molecules in addition to solvent molecules to pass in and out of the cell. Flow in and out of the cell can be altered by surrounding the cells with solutions other than what is normal to a living organism.
Placing a red blood cell in a hypertonic solution causes it to shrink. Water moves from a dilute solution to a more concentrated one, or out of the blood cell. This is shrinking of the cell is called CRENATION. It is the result of the net flow of water from inside the cell to the outside.
Similarly, is a red blood cell is placed in a hypotonic solution it will swell, and may burst.
Water once again moves from a dilute solution to a more concentrated one. However, this time the movement of water happens to be into the blood cell. This is called
HEMOLYSIS. It results from a net flow of water from outside the cell to the inside.
If a blood cell is placed in an isotonic solution, it will neither swell nor burst.
When a body with a normal moisture content is embalmed, the injected fluid should be slightly hypotonic to the contents of the tissues. In this way the fluid will pass through the membranes and inside the tissues. If isotonic fluids are used, the rate of flow into the tissues will be too slow to prevent decomposition. One of the products of the reaction between formaldehyde and proteins is water. Following this reaction, tissue contents become hypotonic to their surroundings and water flows into the capillaries. Based on osmotic principles, the initial fluid injected into edematous bodies for embalming should be slightly hypertonic in order to bring water out of the tissues. Similarly, fluids that are more hypotonic than those used on “normal” bodies are recommended for dehydrated bodies to replace moisture. These solutions need only be slightly hypotonic so as not to waterlog the tissues and increase the decomposition rate.

COLLOIDS AND SUSPENSIONS
To this point we have only discussed true solutions. Another name for a true solution is a
CRYSTALLOID. When solutes and solvents are mixed together, two other solution-like systems can be formed: COLLOIDS and SUSPENSIONS.
Some examples of colloids are protoplasm, blood plasma, soap solution, mayonnaise and smoke. A notable quality of colloids is Brownian movement.
Particles in colloids move randomly, owing to their bombardment by solvent molecules.
Suspensions are mixtures such as milk of magnesia, and clay and water. The major distinguishing factor of true solutions, colloidal solutions, and suspensions is particle size. Suspensions have the largest particle size. True solutions have the smallest particle size and colloids have an intermediate particle size.
Colloidal particles can be separated from true solution particles by the process of
DIALYSIS. Certain natural membranes such as found in animal kidney tubules allow small ions and molecules, but not larger colloidal particles, to diffuse through them. This selective diffusion is called dialysis.