References on salt use in industry
Salt’s many chemical properties allow the chemical industry – and many, many other industries – to exploit sodium chloride to make our lives better. These are some of the best resources:
Chlor-Alkali industry
The American Chemistry Council’s “The Chlorine Tree ” is a wonderful, interactive visual experience exploring its roots in saltwater and its multiple uses in nutrition, housing, health, transportation, personal safety, communications, leisure activity and industry. The ACC’s Chlorine Science Center offers classroom activities and other educational features (including downloadable coloring books for children) and a 6-minute video on chlorine as a "building block of our world."
EuroChlor has a great overview of the industry and an exceptionally effective graphic on “The chlorine tree” showing the derivatives of salt in the chlor-alkali industry.
The Environmental Literacy Council has a good explanation of how chlorine is produced from salt .
Learn how electrochemical cells operate. Electrolysis is explained well by the old Caveman Chemistry site (especially good for the brief history lesson), the University of Wisconsin , Georgia State University , the New Mexico Solar Energy Association (which has a simple science experiment ), and the National Aeronautics and Space Administration which has borrowed our materials and made them come alive with graphics . Answers.com collects several dictionary definitions and has some explanatory graphics.
A salt bridge is an important component of an electrochemical cell. This type of cell can produce an electric current as a product of a chemical reaction type known as oxidation-reduction (also known as redox). The cell reaction is divided into two parts: oxidation (electron loss) and reduction (electron gain). The salt bridge exists to provide the electrical connection between the two reaction vessels while keeping the two reactions separate. The salt bridge allows the electron transfer between the two vessels. A salt bridge can be a U-tube device filled with an electrolyte, such as potassium chloride. There are many examples of such a reaction, one being the modified Daniell cell. Others include dry cells, batteries, fuel cells, galvanic cells, and accumulators. Wikipedia has more.
There's a lot online about the component chemical products besides chlorine. These include sodium hydroxide or caustic soda , sodium chlorite and soda chlorate . More on the uses of sodium chlorite is provided by the Dutch firm Lenntech.
Useful introductions to how chlorine is used in drinking water disinfection are available from the American Chemistry Council
and the Water Quality and Health Council
.
Since 9/11, the world has awakened to threats of chemical terrorism
, adding the phrase "toxic trains"
to our vocabulary and increasing interest in on-site chlorination systems to avoid having terrorist-vulnerable tanker trucks as the primary distribution mode for chlorine.
Textile dyeing. The Knowne Whorl Spinning Guild website explains the process and history of dyeing . The Textile Artists' Newsletter explains how reactive dye works in textile dyeing and the Dye Fibre Association explains how salt is used in conjunction with reactive dyeing . Salt's vital role is also discussed by the Yale-New Haven Teachers Institute's tutorial on "How to Dye Cloth ." The process, however, does not incorporate the salt into the fabric, so proper management of the saline effluent is required as discussed by North Carolina State University scientists and incorporated as guidelines by the Australian State of Victoria's EPA .
Tanning animal hides to make leather. Seasonal deer hunters and professional leather tanners rely on salt. Deer hunters will want to check out this useful guidance from New Mexico State University Extension Service . The Tanners' Council of America and the Leather Research Center "Down Under" explains how professionals use salt in leather tanning; Taiwan's Food and Fertilizer Technology Center distills the basic process for use by small farmers in Asia and the Pacific islands. ThinkQuest explains how salt-loving halophiles aid in tanning leather .
Aquaculture. Salt is vital to healthy fish as propounded by the University of Florida Extension Service. The USDA-funded North Central Region Aquaculture Center at Purdue University has an excellent paper on salt's use in aquaculture (executive summary ). And, while salt was the very reason why medieval European fishing fleets sought codfish in the North Atlantic offshore from was later Canada and New England -- since they could salt their catch and ship it home, salt is used today to relieve the stress of live fish transported to market .
Manufacture of super-high quality lenses and prisms. See the Almaz Optics' website for more .
Waste incineration in molten salt. Safely incinerating such wastes as high explosives and hazardous chemicals utilizes salt as the Lawrence Livermore National Laboratory explains. Japan's Nittetu Chemical Engineering Co., Ltd. has schematics and photos of a plant. Salt is used to provide a heat transfer medium, catalyze the oxidation reaction, prevent the formation of acid gases by forming stable salts and efficiently capture ash particles and radioactive materials. It can also be used for radioactive nuclear powerplant wastes as explained by Swede H. Condé of the Department of Neutron Research, Uppsala University, and Russians Victor Ignatiev et al of the ,Kurchatov Institute, Moscow.
Energy production has been done using the geothermal heat of salt domes, molten salt reactors and salt gradient ponds. Charles Jacoby and Paul Dillip predicted that the most valuable use of salt domes would be geothermal energy production, not salt production, in a 1975 Mining Engineering News article (full article requires purchase). More recently, Leszek Pajak revived interest in the concept at the 2005 World Geothermal Congress . Also see the patent . The Oak Ridge National Laboratory developed a molten salt reactor back in the 1960s. But it is the salt gradient pond that is most discussed at present. The Encyclopedia of Alternative Energy and Sustainable Living illustrates the principles of salt gradient ponds graphically . There are good discussions by Wikipedia , The Green Trust , and Murdoch University's Research Center for Sustainable Energy (which also has a good graphic).
Greenhouse gas sequestration. One of the most promising technologies to mitigate the release of carbon dioxide into the atmosphere, which many scientists are convinced creates a "greenhouse effect" contributing to global warming, is sequestration of the gas underground (or under water). On obvious opportunities is to use salt mines for greenhouse gas sequestration ; the Lawrence Berkeley National Laboratory is studying the potential, but already, the U.S. Department of Energy believes that deep saline formations in the United States could potentially store up to 500 billion tonnes of CO2.
Salt bath furnaces are used to harden tools and many other heat treatment applications.
For a discussion of other industrial uses, see our page on Salt Use in Industry .