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RXN Hydrogen (H) FAQ - Q uestion and A nswer Table of Contents:


1. Information from the American Hydrogen Association.
2. What about water?
3. Other links to Hydrogen resources?

4. Return to the Previous Menu.
5. Return to the RXN Communications Home Page.

Q 1. Information from the American Hydrogen Association.
A The American Hydrogen Association is a non-profit association for the advancement of inexpensive, clean, and safe hydrogen energy systems. They provide answers to the following Frequently Asked Questions about Hydrogen:
Hydrogen: Frequently Asked Questions

Courtesy of: The American Hydrogen Association

I.      General Description
II.             Production Methods
                        A. Electro-chemical
                        B. Chemical
                        C. Biological
                        D. Photoconversion
III.            Storage
                        A. Gas
                        B. Liquid
                        C. Slush
                        D. Metal Hydrides
                        E. Other
IIIA.           Purification
                        A. Iron/Water cycle
                        B. Etc.
IV.             Transportation
                        A. Pipeline
                                1. Hythane
                        B. Other
V.              Use
                        A. Fuel Cells
                        B. Internal Combustion Engines
                                1. Rotary-Type Engines
                        C. Other
VI.             Sources For Further Information
                        A. Professional Associations
                        B. Periodicals and Newsletters
                        C. Calendar of Events
                        D. Publications Bibliography
                        E. Vendors List
                        F. Government Organizations
                        G. Related Electronic Lists/Newsgroups

Questions can be directed to Roy McAlister (aha@getnet.com). See also the
newsgroup Sci.Energy.Hydrogen or the listserver at listerv@uriacc.uri.edu.

Special thanks go to Roy McAlister, President of the American Hydrogen
Association, and Daniel Morgan, Ph.D. for their help in putting together
this FAQ.

I.      General Descriptions

        Hydrogen is the universes most abundant element, but most of it is
bound up in chemical compounds.  It must be extracted from these compounds
rather than simply collected before use.  Some methods of this extraction
process are outlined later in this FAQ.  The following chart is a summary of
some of the chemical properties of hydrogen:

--------------------------------------------------------------------
        TABLE 1.  PHYSICAL AND CHEMICAL PROPERTIES OF HYDROGEN

1.  Electron Structure                  S1
2.  Covalent Radius                     0.37 A (He = 0.93 A)
3.  Electronegativity (Pauling)         2.1
4.  Specific Heat                       (Cp)     3.44 Cal/Gram deg K
                                        (Cv)     2.46 Cal/Gram deg K
                                        (Cp/Cv)  1.40
5.  Gas Density                 (Deg. C, 1ATM)   0.0899 Gram/Liter
6.  Gas Specific Gravity        (Air - 1.0)      0.0695 Gram/Liter
7.  Gas Self Diffusion Const.   (Deg. C, 1ATM)   0.61 Cm2/Sec
8.  Boiling Point                       -252.7 C
9.  Melting Point                       -259.2 C
--------------------------------------------------------------------

        Hydrogen is extensively used in the chemical process, food,and
fuels industries.  Many electricity power plant generators are cooled by
gaseous hydrogen because it provides the highest specific heat and best
combination of dielectric strength and low viscosity.  Hydrogen is used
in hydride heat pumps, in Joule-Thompson cooling, and as a heat transfer
medium.

II.     Production Methods

        Since hydrogen must be extracted from other sources, it can be
considered an energy carrier rather than an energy source.  The energy
that is produced when it is used is simply the amount of energy that
was stored, minus any losses.  There are several different methods of
extracting hydrogen from sources.  They are outlined as follows:

                A. Electro-chemical

        Electrolysis is the process whereby electricity is passed through
a meduim, in the case of hydrogen is usually water, and the basic elements
are released.  In the case of water, one mole of water yields two moles of
hydrogen and one mole of oxygen.

        Common energy efficiencies for electrolysis are 65 percent, with
80-85 percent currently possible.  Cost of production is high, so
electrolysis is expected to be limited to niche markets in the near and
mid term.

        The primary idea in lowering the cost of electrolysis is in lowering
the cost of the electricity to run through the water.  In the solar
hydrogen scenario, solar collectors would be utilized to run electricity
from the sun through water and create hydrogen.  The hydrogen could then
be captured and stored or used immediately.  The cost of producing hydrogen
in such a manner would probably drop quite a bit.

                B. Chemical

        Every elemental metal that is less noble than hydrogen will displace
hydrogen from water.  A well known reaction is between an active metal such
as sodium or potassium and water:

                        2Na + 2H2O ----> H2 + 2NaOH + HEAT

        The "producer" reaction has been practiced since its discovery in
about 1800 for producing hydrogen from a carbon donor and water:

                        HEAT + C + H2O ----> H2 + CO

        Since the discovery of petrocarbons such as oil and natural gas,
hydrogen has been produced in large quantities by reacting steam with
petroleum hydrocarbons:

                        HEAT + CxHy + xH2O ----> (x + 0.5y) H2 + xCO

                C. Biological

        Bacteria and other microorganisms (particularly those that live in
anaerobic conditions) may release hydrogen in the process of creating
heavier hydrocarbons or oxygen for assimilation.  All methane that has been
produced from biomass probably involved the precursor steps of hydrogen
production by an anaerobic microorganism and fixing of the hydrogen with
carbon from carbon dioxide as the microorganism derived the oxygen for its
own use.

                D. Photoconversion

        Numerous bacteria and all green plants dissociate water into hydrogen
and oxygen as the first step of photosyntheses.  Hydrogen is retained to
build plant tissues by reactions that combine carbon from atmospheric
carbon dioxide with hydrogen.  Oxygen is released to the atmosphere in the
process.

                        LIGHT + H2O  -------> 2H2 + 0.5O2
                        LIGHT + H2 + CO2 --------> Plant Tissues
III.    Storage

                A. Gas

        Compressed gas storage and transportation has been widely used for
more than 100 years.  Common materials for storage canisters are mild
steel, aluminum, and composites.  Storage pressures of 3,000 to 10,000
PSI are common.

                B. Liquid

        Cooling hydrogen to below the boiling point of -252.7 C allows
storage as a cryogenic liquid without the need for pressurization.
Cryogenic storage of hydrogen allows regular commercial shipment by
truck and rail.  Many commercial processes such as glass manufacturing,
brazing, heat treating, food hydrogenation, and semiconductor
manufacturing are served by deliveries of liquid hydrogen.  Liquid
hydrogen has facilitated the U.S. space exploration program.

                C. Slush

        If liquid hydrogen is suddenly subjected to a vacuum it will
evaporate with a subsequent cooling of the liquid mass to cause the
temperature to fall below the freezing point of -259.2 C and solid
hydrogen will be produced.  This mixture of liquid and solid hydrogen
is called "slush" and provides more dense storage of hydrogen than
liquid hydrogen.

                D. Metal Hydrides

        Metal hydride systems store hydrogen in the interatom spaces of a
granular metal.  Various metals can be used.  The hydrogen is released
by heating.  These systems are reliable and compact, but they can be heavy
and expensive.

                E. Other

IIIA.   Purification

                A. Iron/Water cycle
                B. Etc.

IV.     Transportation

                A. Pipeline

        Hydrogen can be transported via pipelines much the same way natural
gas and oil are currently transported.

                        A1. Hythane

                B. Other
V.      Use

                A. Fuel Cells

        One type of fuel cell works because hydrogen is sent through a PEM
(proton exchange membrane).  The hydrogen atom is broken up so that an
electron is stripped off and sent through an electrical circuit while the
proton of the atom goes through the membrane.  The electron travels around
the circuit and rejoins the proton as it is oxidized to form water, having
been harnassed for energy along the way. In this manner, we are able to get
energy out of a fuel cell without any pollution.

                B. Internal Combustion Engines

        Engines can be converted from gasoline to hydrogen fairly simply.
The biggest cost involvement is in purchasing the tank, although in many
cities these tanks can be leased or rented.  Engines can also be made to
run on hydrogen initially.  These would be more effective since they would
be built to take advantage of the fast-burn and far-lean combustion
characteristics of hydrogen.  Many of the automobile companies have already
designed cars and trucks that use hydrogen, most notibly BMW, Mazda, and
many others have made prototype cars.  Contact the professional associations
listed below for more information as this is a rapidly changing field.

                        1. Rotary-Type Engines

        Mazda is currently pioneering this effort and have built several cars
running this type of engine on hydrogen.  There are numerous articles on this
type of engine, see SAE technical paper #920302 for more information.  This
type of engine also has been reviewed in many popular magazines.

                C. Other

        There are many other kinds of uses for hydrogen.  It is being used
in stationary turbines and aircraft engines.  Most notably, there were jets
that were powered by hydrogen, and in 1980 a propellor plane was fitted to
run on hydrogen.
VI.     Sources for Further Information

                A. Professional Associations

American Hydrogen Association
216 South Clark Drive, suite 103
Tempe, AZ 85281
(602) 921-0433

National Hydrogen Association
Suite 910
1101 Connecticut Avenue, S.W.
Washington, DC 20036
(202) 223-5547

International Association for Hydrogen Energy
PO Box 248266
Coral Gables, FL 33124

                B. Periodicals and Newsletters

Hydrogen Today
American Hydrogen Association
216 South Clark Drive, Suite 103
Tempe, AZ 85281
(602) 921-0433

                C. Calendar of Events

                D. Publications Bibliography

                E. Vendors List

                F. Government Organizations

                G. Related Electronic Lists/Newsgroups

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^ Return to Hydrogen (H) FAQ Table of Contents
   
Q 2. What about water?
A Water is made up of Hydrogen and Oxygen. The following facts about water are available:
 1.0  Definitions

      Acidity:  The quantitative capacity of aqueous media to react
           with hydroxyl ion.  [1]

      Alkalinity:  The quantitative capacity of aqueous media to react
           with hydrogen ion.  [1]

      Brine:  Water that contains dissolved matter at an approximate
           concentration of more than 30,000 mg/L.  [1]

      Cell Constant:  Conductivity measurements are affected by
           measurement cell geometry.  Specific conductivity is
           calculated by multiplying the measured conductivity by the
           electrode's cell constant.  For parallel plates, the cell
           constant is the distance of plate separation divided by the
           plate area.

      Conductivity, Electrical:  The reciprocal of the resistance in
           ohms measured between opposite faces of a centimetre cube
           of aqueous solution at a specified temperature.  [1]

                  1                              Cell Area
           ---------------  =  Conductivity  x  -----------
           Cell Resistance                      Cell Length

           Conductivity values are usually expressed in
           microsiemens/centimetre (uS/cm) or millisiemens/centimeter
           (mS/cm), where 1 siemen (S) = 1 mho.

      Hardness:  The polyvalent-cation concentration of water,
           generally calcium and magnesium.  [1]

      Ion Exchange:  A reversible process by which ions are
           inter-changed between an insoluble material and a liquid
           with no substantial structural changes of the material.
           [1]

      Ion Exchange Capacity:  The number of milliequivalents of
           exchangeable ions per millilitre of backwashed and settled
           bed of ion exchange material in its standard form.  [1]

      Ion Exchange Material:  An insoluble material that has the
           ability to exchange reversibly certain ions in its
           structure, or attached to its surface as functional groups,
           with ions in a surrounding medium.  [1]

      Ion Exchange Resin:  A synthetic, organic ion exchange material.
           [1]

      pH:  The negative logarithm of the hydrogen ion activity in an
           aqueous solution, or, the logarithm of the reciprocal of
           the hydrogen ion activity.  [1]

      Resistivity, Electrical:  The resistance in ohms measured
           between opposite faces of a centimetre cube of an aqueous
           solution at a specified temperature.  [3]

                                               Cell Length
           Cell Resistance  =  Resistivity  x  -----------
                                                Cell Area

           Resistivity values are usually expressed in
           ohm-centimetres, or in megohm-centimetres, at a specified
           temperature.  [3]

      Salinity:  The saltiness of natural water.  The salinity of
           normal seawater is 35 parts salt per 1000 parts water.  [4]


 2.0  Reagent Water [2]

                                      Type   Type   Type     Type
      Attribute              Units    I      II     III      IV

      Total Matter           mg/L     <0.1   <0.1   <1.0     <2.0
      Conductivity @ 25 C    umho/cm  <0.06  <1.00  <1.00    <5.00
      Resistivity @ 25 C     Mohm-cm  >16.7  >1.0   >1.0     >0.2
      pH @ 25 C              pH        [A]    [A]   6.2-7.5  5.0-8.0
      KMnO4 Color Retention  min      >60    >60    >10      >10
      Soluble Silica         ug/L     <1     <1     <10      any

      Note [A]:  The measurement of pH in Type I and Type II water is
      not useful as the electrodes are found to contaminant the
      solutions.

      2.1  Type I Water

           Type I reagent water can be used when maximum precision and
           accuracy are required.  This water is typically prepared by
           distillation followed by ion exchange polishing followed by
           membrane filtration.  This water should be protected from
           atmospheric contamination.

      2.2  Type II Water

           Type II reagent water can be used for most analytical
           procedures and all procedures requiring water low in
           organics.  This water is typically prepared by
           distillation.  This water should be protected from
           atmospheric contamination.

      2.3  Type III Water

           Type III reagent water can be used for general laboratory
           practice.  This water is typically prepared by suitable
           distillation, ion exchange, or reverse osmosis followed by
           filtration.  This water should be protected from
           atmospheric contamination.

      2.4  Type IV Water

           Type IV reagent water can be used for high volume
           applications for test solutions, rinse water, and wash
           water.  This water is typically prepared by suitable
           distillation, ion exchange, reverse osmosis, or
           electrodialysis.

      2.5  Microbiological Contamination

           Attribute           Type A   Type B   Type C
           Bacteria Count      0/ml     <10/ml   <100/ml


 3.0  Water Measures

      3.1  Electrical

                     Resistivity  Conductivity  Conductivity  NaCl
           Water     (Mohm-cm)    (umho/cm)     (uS/cm)       (ppm)

                      0.000004   226,000.      226,000.     Saturated
                      0.000014    67,200.       67,200.     50,000.
           Sea Water  0.00002     50,000.       50,000.     25,126.
                      0.0001      10,000.       10,000.      5,025.
                      0.0002       5,000.        5,000.      2,512.
                      0.001        1,000.        1,000.        502.5
           Tap Water  0.01           100.0         100.0        50.2
                      0.1             10.00         10.00        5.02
           Type IV    0.2              5.000         5.000       2.51
                      0.4              2.500         2.500       1.26
                      0.8              1.250         1.250       0.63
           Type II    1.0              1.000         1.000       0.50
                      1.6              0.625         0.625       ---
                      3.2              0.312         0.312       ---
                      6.4              0.156         0.156       ---
                     12.8              0.078         0.078       ---
           Type I    16.7              0.060         0.060       ---
           Ideal     18.3              0.055         0.055       ---

      3.2  Total Dissolved Solids (TDS)

           Conductivity can be used to estimate total dissolved solids
           (TDS) and salinity.  The general rule is that as the ion
           concentration increases, conductivity increases.

           This measurement will not differentiate between the
           contribution of different ions, but will give an estimate
           of total ion concentration.

           This estimate of TDS is accurate for fully ionized solids
           with no solution interactions (NaCl), but less accurate for
           solids with some ionic interactions in the solution
           (organics, concentrated solutions).

           Typical uS/cm to ppm conversion factors run from 0.48 to
           0.64, depending on solution.

      3.3  pH...


10.0  References

      [1]  ASTM D1129 'Standard Definitions of Terms Relating to
           Water', ASTM, Philadelphia, PA, 1988.

      [2]  ASTM D1193 'Standard Specification for Reagent Water',
           ASTM, Philadelphia, PA, 1988.

      [3]  ASTM D1125 'Standard Test Methods for Electrical
           Conductivity and Resistivity of Water', ASTM, Philadelphia,
           PA, 1988.

      [4]  R. J. Lewis, Hawley's Condensed Chemical Dictionary, 12th
           Ed., Van Nostrand Reinhold Company, NY, 1993.
^ Return to Hydrogen (H) FAQ Table of Contents
   
Q 3. Other links to Hydrogen resources?
A A good place to look for links to Hydrogen resources might be here.
^ Return to Hydrogen (H) FAQ Table of Contents
   

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