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Phosphoric Acid
Description: Phosphoric acid (C.A.S. 7664-38-2) can exist as a crystal or clear liquid. It is an oily, thick, colorless, and odorless liquid, or a thick, colorless, unstable crystalline solid. It is used in the manufacturing of phosphates, such as salts, soaps, and detergents; fertilizers; yeast; fire control agents; opal glass; electric lights; dental cements; waxes and polishes; gelatin; ethylbenzene, propylene, and cumene; and soft drinks. It is used as an acid catalyst, soil stabilizer, antioxidant in food, acidulant and flavor agent in jellies and preserves, bonding agent for refractory bricks, and gasoline additive. It is also used in the rustproofing and polishing of metals, cotton dyeing, tile cleaning, extracting penicillin, hot stripping for aluminum and zinc substrates, ceramic binding, water treatment, process engraving, electro-polishing, coagulating of rubber latex, operating lithography and photoengraving operations, and pickling. It is used to manufacture the phosphoric acid electrolyte fuel cell system which has created the largest fuel cell built. It has been used to treat lead poisoning. Chemical properties: Phosphoric acid is incompatible with strong caustics and most metals. It readily reacts with metals to form flammable hydrogen gas. The liquid can solidify at temperatures below 21 degrees C. It is corrosive to ferrous metals and alloys. It is soluble in alcohol and hot water. It can form three series of salts: primary phosphates, dibasic phosphates, and tribasic phosphates. It is deliquescent and hygroscopic. It is a chelating agent. It has a low vapor pressure at room temperature. Synonyms for phosphoric acid are orthophosphoric acid, metaphosphoric acid, and white phosphoric acid. Identification: Health effects: Phosphoric acid can affect human health through inhalation of mist, ingestion, and contact with the skin and eyes. It can severely irritate the upper respiratory tract, eyes, and skin. It can burn the skin, mouth, and eyes, and cause dermatitis, a sour acrid taste, coughing, conjunctivitis, tearing, blepharospasm, severe gastrointestinal irritation, nausea, vomiting, bloody diarrhea, difficult swallowing, severe abdominal pains, extreme thirst, acidemia, difficult breathing, convulsion, shock, and even asphyxial death. It can cause circulatory collapse with clammy skin, weak and rapid pulse, shallow respirations, and scanty urine. It can corrode the mucous membranes of the mouth, throat, and esophagus, with immediate pain and dysphagia. People at special risk of exposure to phosphoric acid include those with chronic pulmonary disease, and skin disease. Exposure Values: Economics: U.S. manufacturers of phosphoric acid are Agrium US Inc., Soda Springs; Farmland Hydro, L.P., Bartow, FL; IMC-Agrico Company, Donaldson, LA; Mulberry, FL; Nichols, FL; South Pierce, FL; Uncle Sam, LA; SF Phosphates Limited Company, Rock Springs, WY; U.S. Agri-Chemicals Corporation, Hq, Fort Meade, FL; Mobil Corp, Pasadena, TX ; PCS Nitrogen Fertilizer, L.P., Geismar, LA; PCS Phosphates Co., Inc., Auroro, NC; White Springs, FL; Albright & Wilson Americas, Charleston, SC, Cargill Fertilizer, Inc., Bartow, FL; CF Industries Inc., Bartow FL; Plant City, FL; Mulberry Phosphates, Inc., Mulberry, FL; Piney Point Phosphates, Inc., Piney Point, ; R Simplot Co, Pocatello, ID; U.S. Agri-Chemicals Corporation, Bartow, FL; Mississippi Phosphates Corp., Pascagoula, MS; Rhone-Poulenc Inc., Chemical Sector, Geismar, LA; Morrisville, PA; Nashville, TN; FMC Corporation, Chemical Products Group, Alkali Chemicals Division, Phosporus Chemicals Division, Carteret, NJ; Green River, WY; Lawrence, KS; Monsanto Company, Chemical Group, Carondelet, MO; Augusta, GA; Trenton, MI; and Purified Acid Partners, Aurora, NC. Regulation: The Occupational Safety and Health Administration (OSHA) sets permissible exposure limits for phosphoric acid of 1 mg/m3, time-weighted average, and 3 mg/m3, short-term exposure limit. Phosphoric acid is regulated under the Emergency Planning and Community Right-to-Know Act (EPRCA); the Comprehensive Environmental Response, Compensation and Liability Act; and the Federal Insecticide, Fungicide and Rodenticide Act. Under Section 313 of the Emergency Planning and Community Right to Know Act of 1986, releases of more than one pound of chlorine into the air, water, and land must be reported annually and entered into the Toxic Release Inventory (TRI). National Overview of 1998 Toxics Release Inventory See EPA's Toxic Release Inventory. Notations: The NIOSH recommended exposure limits (RELs) are time-weighted average (TWA) concentrations for up to a 10-hour workday during a 40-hour workweek. A short-term exposure limit (STEL) is designated by "ST" preceding the value; unless noted otherwise, the STEL is a 15-minute TWA exposure that should not be exceeded at any time during a workday. A ceiling REL is designated by "C" preceding the value. Any substance that NIOSH considers to be a potential occupational carcinogen is designated by the notation "Ca." The OSHA permissible exposure limits (PEL) are found in Tables Z-1, Z-2, and Z-3 of the OSHA General Industry Air Contaminants Standard (29 CFR 1910.1000). Unless noted otherwise, PEL are TWA concentrations that must not be exceeded during any 8-hour workshift of a 40-hour workweek. A STEL is designated by "ST" preceding the value and is measured over a 15-minute period unless noted otherwise. OSHA ceiling concentrations (designated by "C" preceding the value) must not be exceeded during any part of the workday; if instantaneous monitoring is not feasible, the ceiling must be assessed as a 15-minute TWA exposure. In addition, there are a number of substances from Table Z-2 (e.g., beryllium, ethylene dibromide, etc.) that have PEL ceiling values that must not be exceeded except for specified excursions. For example, a "5-minute maximum peak in any 2 hours" means that a 5-minute exposure above the ceiling value, but never above the maximum peak, is allowed in any 2 hours during an 8-hour workday. Information Sources:
Originally published in Environment Writer by the National Safety Council. Reprinted with permission. Environment Writer Metcalf Institute for Marine and Environmental Reporting University of Rhode Island Graduate School of Oceanography Office of Marine Programs Narragansett, RI 02882 Tel: 401-874-6211; Fax: 401-874-6485 Disclaimer * Copyright 2002-2006 * All rights reserved. * University of Rhode Island |