PCS Phos Acid Manual

IMPORTANT NOTICE All information, technical advice and recommendations provided herein or by PCS Sales personnel is intended for use by persons having skill and knowledge in the handling of industrial chemicals, and no such information shall be deemed as a representation or warranty with respect to the Product or Products discussed. Product information and handling procedures are based on our past experience and common practice in the industry. We believe all information given herein and by PCS Sales personnel is accurate and offer such information in good faith, BUT WITHOUT GUARANTEE OR OBLIGATION AS TO THE ACCURACY OR SUFFICIENCY THEREOF AND WITHOUT ANY WARRANTY OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. User is solely responsible for determining the suitability of use in each particular situation. PCS Sales specifically DISCLAIMS ANY LIABILITY WHATSOEVER FOR THE USE OF SUCH INFORMATION, including without limitation any recommendations which user may attempt to apply or may construe as permission to use the Product in a manner that would infringe any patent, license or copyright. 1101 Skokie Blvd., Northbrook, IL 60062 TABLE OF C ONTENTS Basic Properties . . . . . . . . . . . . . . . . . . . . . 12 Boiling Points . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Freezing Points . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Conversion Factors . . . . . . . . . . . . . . . . . . . . . . . . . . Corrosion Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Specific Heat . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Titration Curve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Density . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Dissociation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Electrical Conductivity . . . . . . . . . . . . . . . . . . . . . . . Enthalpy — Concentration . . . . . . . . . . . . . . . . . . . . Heat of Formation, Free Energy of Formation, Entropy . . . . . . . . . . . Latent Heat of Vaporization . . . . . . . . . . . . . . . . . . . Refractive Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Relative Sourness . . . . . . . . . . . . . . . . . . . . . . . . . . . . Vapor Pressure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Vapor Composition . . . . . . . . . . . . . . . . . . . . . . . . . . Viscosity in Centipoise . . . . . . . . . . . . . . . . . . . . . . . Kinematic Viscosity of Phosphoric Acid Solutions . . . . . . . . . . . . . . . . . . 12 12 13 13 15 15 16 17 17 17 18 18 18 19 19 20 21 22 1 1 2 2 2 Introduction . . . . . . . . . . . . . . . . . . . . . . . . 1 General Description . . . . . . . . . . . . . . . . . . . . . . . . . . Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Physical Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . Availability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Bulk Storage and Handling . . . . . . . . . . . . . 3 Storage Considerations . . . . . . . . . . . . . . . . . . . . . . . Construction Materials . . . . . . . . . . . . . . . . . . . . . . . 3 3 Health and Safety Information . . . . . . . . . . 6 Fire, Explosion and Health Hazard Data . . . . . . . . Toxicological Information . . . . . . . . . . . . . . . . . . . . . Personal Protective Equipment . . . . . . . . . . . . . . . . 6 6 6 Emergency Information . . . . . . . . . . . . . . . . 7 Spill Containment . . . . . . . . . . . . . . . . . . . . . . . . . . . Emergency First Aid Procedures . . . . . . . . . . . . . . . Transportation Emergencies . . . . . . . . . . . . . . . . . . . 7 7 7 Applications . . . . . . . . . . . . . . . . . . . . . . . 8 Chemical Production . . . . . . . . . . . . . . . . . . . . . . . . . 8 Food and Beverages . . . . . . . . . . . . . . . . . . . . . . . . . . 8 Metal Treating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Refractories and Ceramics . . . . . . . . . . . . . . . . . . . . 11 Miscellaneous . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 Analytical Methods . . . . . . . . . . . . . . . . . . 23 Determination of H3PO4 by Specific Gravity . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 Determination of H3PO4 by Molybdovanadate Method . . . . . . . . . . . . . . . . . . 25 Determination of H3PO4 by Thymolphthalein Titration . . . . . . . . . . . . . . . . . . 26 Endnotes . . . . . . . . . . . . . . . . . . . . . . . . . . 27 PCS Sales and Service . . . . . . . . . . . . . . . . 28 . . . . . . . . . . . . . . . . 21 Figure 13B Viscosity of 75% and 85% Phosphoric Acid versus Temperature . . . . . . . . . . . . . . . . . . . . . 18 Figure 11 Vapor Pressure versus Concentration . . . . . . . . . . . . . . . . . . . .5˚C versus Concentration . . . . . . . 12 Figure 4 Isocorrosion Chart for Type 316L Stainless Steel in Phosphoric Acid . . . . . . . . . . . . . 13 Figure 5A Corrosion Resistance of Non-Metals in 80% Phosphoric Acid . . . . . . . . . . . . . . . . . 19 Figure 12 Vapor Composition Over Boiling Solutions . . . . . . . 12 Figure 3 Freezing Point versus Concentration . . . . . . . . . . . . . . . . . . . . . . . . 20 Figure 13A Viscosity in Centipoise of Phosphoric Acid for Various Concentrations and Temperatures . . . . . . . . .F IGURES Figures AND TABLES Figure 8B Specific Gravity versus Concentration . . . . . . . 22 Figure 1 Schematic of Typical Phosphoric Acid Storage System . . . . 23 Table 2 Phosphoric Acid Solutions Specific Gravity at 25˚C/15. . . . . . .˚C versus Concentration . . . . . . . . . . . . . . 17 Figure 10 Latent Heat of Vaporization at 25˚C . . . . . . . . . . . . . . . . 24 . . . . . . . 3 Figure 2 Boiling Point versus Concentration . 15 Figure 8A Orthophosphoric Acid Specific Gravity @ 25˚C/15. . . . . . . . . . . . . . . . . . . . . . . . . . . 21 Figure 14 Viscosity in Centistokes of Phosphoric Acid for Various Concentrations and Temperatures . . . . . . . . . . . . . . . . . . . . 14 Figure 6 Specific Heat at 21. . . . 14 Figure 5B Corrosion Resistance of Metals in 80% Phosphoric Acid . . . . . . . . .3˚C . . . . . . . . 16 Figure 9 Enthalpy versus Concentration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 Tables Table 1 Specific Gravity Temperature Coefficient . . . . . . . . . . . . . . . 15 Figure 7 Titration Curve of Orthophosphoric Acid pH versus Increasing Sodium Hydroxide Additions . . . . I NTRODUCTION 1 . the phosphate ions are considered to be interconnected by hydrogen bonds. however it is not as strong as other mineral acids. usually referred to as phosphoric acid. Structure O | | HO — P — OH | O H CAS Registry No: 7664-38-2 The molecular structure of orthophosphoric acid represented above in two dimensions. it will dissociate to produce three hydrogen ions.I NTRODUCTION General Description Orthophosphoric acid (H3PO4). As dilution increases. in an aqueous solution. Phosphoric acid is a useful synthesis catalyst since it does not react violently with many organic compounds and exhibits catalytic and dehydrating properties. such as acetic. such as nitric. Phosphoric acid is a triprotic acid which means that. In aqueous solutions. consists of four groups at the corners of a tetrahedron with the phosphorus atom at the center. hydrogen bonding between phosphate ions decreases and is replaced by hydrogen bonding to water. water-white liquid which is derived from phosphate rock. Phosphoric acid is a stronger acid than the organic acids. These properties give phosphoric acid a wide range of industrial applications from metal finishing to food additives. is a clear. citric and lactic. sulfuric and hydrochloric. It will react readily with bases to produce alkali phosphates and will become fairly reactive with metals and metal oxides at elevated temperatures. Phosphoric acid in polyethylene drums is also available from your PCS distributor.629 1.686 75.0 – 85.6 1.574 1.0 – 75.5 10 3 5 3 3 Physical Properties Standard Concentration 75% P2O5 (%) Specific Gravity (25˚C/15.6 41˚F(5˚C) 0.629 13.5 80.5 Food Grade Specifications Component H3PO4 F As Heavy Metals Cd Pb % ppm ppm ppm ppm ppm w w w w w 75% Food Chemical Codex 75.5˚C) Phosphoric Acid (%H3PO4) 80% 85% Water-white liquid.518 29. 75%.Specifications Technical Grades 75% Appearance Specific Gravity (25˚C/15. Bulk shipments can be made in tank cars and tank trucks.686 14.493 43.5 80% 58. Availability PCS phosphoric acid is available in three standard concentrations. Approx. 80%. and 85% meeting the aforementioned specifications.5 10 3 5 3 3 85% Food Chemical Codex 85. colorless.1 0˚F(–18˚C) 0.0 85% 61.0 – 75.1 70˚F(21˚C) 0. 2 I NTRODUCTION .S. odorless. Specific Heat (cal/gm –˚C) Viscosity (25˚C) cp 54.0 – 80. 1.0 – 85.5 85.5 10 3 5 3 3 80% Food Chemical Codex 80.1 1.542 21.574 13.7 1. Gallon Melting Point*.5 * Purified phosphoric acid’s melting point is the same as its freezing point.0 – 80.5˚C) Pounds per U. electricity or hot water are recommended as heat sources. To avoid welding difficulties. It is this consideration that determines the tank location and need for an external heating source. A caution to be observed when considering stainless steel tanks is the detrimental effect of minor amounts of halide impurity (15 – 30 ppm Cl) in the acid. MIG welding should also be specified since the quality of the welds is superior. A schematic of a typical phosphoric acid storage system is shown in Figure 1. FIGURE 1: Schematic of Typical Phosphoric Acid Storage System Construction Materials Storage Tank Recommended materials for storing phosphoric acid are: • Stainless Steel Type 316L Stainless Steel is used successfully for storing all grades of phosphoric acid. and impart color to the product. Ni and Cr content in the acid. Low temperature steam. depending upon the location of the system. The corrosion rate for 316L in the temperature range from 77˚ to 120˚F is low. Temperature can be controlled using a recirculation loop with an external heat exchanger.B ULK S TORAGE AND H ANDLING Storage Considerations The primary considerations in the design of a bulk storage and handling system for phosphoric acid are its corrosive properties and freezing point. B ULK S TORAGE AND H ANDLING 3 . Phosphoric acid is subject to supercooling well below the freezing point if there is no seeding or agitation. extra low carbon (ELC) stainless steel should be specified. For this reason 75% acid can be stored outside with little danger of freezing. The 80% and 85% acid grades may require some form of external heat to keep them above their freezing points. The freezing point of phosphoric acid varies greatly with acid concentration. This amount of chloride will increase the aggressiveness of acid to stainless steel enough to increase the Fe. It is especially desirable for food grade acids. 304 and 316 stainless steel are less expensive than 316L. • Carbon Steel Although carbon steel is much less expensive than stainless steel. ARCO (Schoolcraft. However. It should be noted that elevated temperatures have a deteriorating effect on the rubber lining. the chloride concentration can reach a level which results in corrosion of the stainless steel. STONHARD ® Company. This is usually due to failure of the bonding cement used. 4 B ULK S TORAGE AND H ANDLING . Pure natural gum white rubber and chlorobutyl rubber are recommended. Blair Rubber Company produces VE 524WC FDA. if the acid is diluted with chlorinated water. white natural rubber and is suitable for installation on site. Do not use steam coils in FRP. though resistance varies with manufacturers.This is especially true where small amounts of acid remain in contact with a relatively large surface as in pipelines or in the bottom of a tank. However. None are considered suitable materials for storing or handling phosphoric acid. • 302. Forté Composites Inc. Goodrich produces ACID SEAL PW code 2004 which is a soft. However. (Corguard 9000). The most pronounced advantage of fiberglass is one of initial cost. The following materials are not recommended: • Glass-Lined Steel Glass lined tanks have superior corrosion resistance. it corrodes rapidly when in contact with phosphoric acid. • Fiberglass Reinforced Polyester (FRP) Filament-wound fiberglass with polyester resins is also used successfully. Fiberglass tanks are less expensive than rubber-lined tanks and can cost one-third as much as stainless steel.F. with each lining having its own “critical” temperature. The floor of the dike should drain towards a sump to allow any water accumulating in the diked area to be removed using a pump. They are also more sensitive to chloride contamination than type 316L. 304 and 316 Stainless Steel Type 302. The foundation around bulk storage tanks should be diked. B. the corrosion rates with phosphoric acid are greater. storage or handling of phosphoric acid. It should never be used in any aspect of the transfer. MI) also produces comparable materials: #8310 for field installation and #874 for the smaller applications. New rubber linings often impart some color to phosphoric acid but this usually drops to an undetectable level after several storage cycles. Some rubbers have a tendency to become detached from the steel tank. The sump and diked areas should be kept drained. Bisphenol-A-Fumarate is recommended as a polyester resin. PCS phosphoric acid contains less than 5 ppm of chlorides and will cause no difficulty. which is a white chlorobutyl rubber. the cost is excessive for this application. It is recommended that the dike be designed to hold 110 percent of the volume of the storage tank or of the largest tank in the tank farm. They impart a green color to the acid due to the increase in the heavy metals concentration. • Rubber-Lined Carbon Steel Rubber-lined steel tanks offer good corrosion resistance and are less expensive than stainless steel. ® STONHARD is a registered trademark of STONHARD Company. and AMERON PROTECTIVE COATINGS produce acceptable acid-resistant coatings. rather use hot water or electrical heaters. The dike walls and floor should be protected with an acid-resistant coating. Goodrich SANIPRENE code 1005 is a hard rubber for smaller tanks which are autoclave cured. The performance of the fiberglass tank surpasses that of the rubber-lined tank and is nearly equal to that of stainless steel. Centrifugal pumps capable of meeting the pumping capacity and dynamic head are sufficient. but are more expensive and not usually justified. Welding should be done by competent personnel according to methods approved by the stainless steel manufacturer. The flanged and welded piping system is preferred.Pumps Phosphoric acid pumps should have all wetted parts constructed of 316L stainless steel. Mechanical seals are recommended over packing due to their longer life span. Screwed stainless steel pipe. sealless Crane Chempump can also be used. any material suitable for storing phosphoric acid will be acceptable as a piping material with 316L being preferred. All 316L or Alloy 20 flanged valves with outside screw and yoke are recommended. B ULK S TORAGE AND H ANDLING 5 . These flanges have 316L welding and sealing surfaces with carbon steel back-up flanges. particularly when the piping is to be dismantled and reassembled. TEFLON gaskets are recommended. Schedule 40 pipe should be used with type 316L insert-type flanges. best results have been obtained using flanged and welded type 316L pipe. Piping In general. fittings and valves. When stainless steel piping is used. and valves are used but are not recommended because it is difficult to obtain tight joints. Centrifugal pumps such as the totally enclosed. fittings. IL.H EALTH AND S AFETY I NFORMATION Phosphoric acid is considered to be a stable chemical not subject to thermal or photochemical decomposition. Severe skin irritations or burns may occur. Phosphoric acid will cause eye burns.00 milligram per cubic meter of air and respiratory irritation from excessive breathing of mists of vapors will occur. Dermal toxicity is considered to be slight based on testing of similar products and/or the components. approved respiratory protective equipment must be used. caution should be exercised since the by-product hydrogen is very flammable. Personal Protective Equipment Properly fitted chemical goggles and protective clothing should be worn. Material Safety Data Bulletins should be consulted prior to use of the products and are available by contacting PCS Sales Customer Service Department. When vapor or mist concentrations exceed applicable standards. however it does not react as rapidly or violently as some of the more active acids. Phosphoric acid will react with some metals such as aluminum and zinc liberating hydrogen. Nevertheless. Hazardous decomposition products are the phosphorus oxides which are evolved at approximately 3000 to 3200˚F. There can also be moderate eye irritation and slight skin irritation. The Threshold Limit Value Time Weighted Average (TLV TWA) is 1. Hazardous polymerization will not occur. No special respiratory protection is required under ordinary conditions of use provided that adequate ventilation is maintained. Toxicological Information Phosphoric acid exhibits slight oral toxicity in rats with an LD50 of 1530 mg/kg of body weight. Impervious gloves and aprons are recommended. Explosion and Health Hazard Data Phosphoric acid does not burn and exhibits no unusual fire explosion hazards. North America 1-800-654-4514 Fire. Northbrook. 6 H EALTH AND S AFETY I NFORMATION . Detailed toxicological data is available from PCS Environmental Services Department. the name and location of the caller. Get immediate medical assistance. If medical assistance is not immediately available. flush an additional 15 minutes. Skin Contact Wash contaminated skin with mild soap and water. If contact is widespread. The primary concern in the event of a spill is to contain the material to prevent contamination of sewers or waterways. If clothing is contaminated. E MERGENCY I NFORMATION 7 . shovel the material into an approved waste disposal container for treatment or disposal in approved chemical disposal area. He will then give the recommendation for controlling the emergency situation until the shipper’s specialist can relay help. If breathing has stopped. etc. Transportation Emergencies For help with emergencies involving spill. Launder contaminated clothing separately before reuse. proximity of populated area. Then sprinkle hydrated lime or soda ash on the spill area. weather conditions. the name of the shipper. Give one to two glasses of water or milk immediately. CHEMTREC will advise PCS of the emergency and one of our specialists will contact the caller. remove clothes and wash skin under a safety shower.E MERGENCY I NFORMATION Spill Containment Phosphoric acid is not volatile or flammable. remove clothing immediately and wash exposed area with large quantities of water. immediately notify the closest Emergency Center: U. Ingestion Do not induce vomiting. Keep affected person warm and get immediate medical attention. the product. Inhalation Remove from further exposure.S. the shipping point and destination. leak. Finally. what happened. the nature of any injuries. Get medical assistance immediately. If the leak or spill is not contained in a diked area. Emergency First Aid Procedures Eye Contact Flush eyes thoroughly with water for 15 minutes. fire or exposure involving transportation equipment. CHEMTREC 1-800-424-9300 or 202-483-7616 Canada CANUTEC 613-996-6666 The information specialist on duty will ask for a brief description of the emergency. the spilled material should first be contained using dry sand banked around the spill to limit the affected area. use mouth-to-mouth resuscitation. Do not give anything by mouth to an unconscious person. acetic and lactic acids. and the alkali-to-phosphorus molar ratio. tartaric. diammonium phosphate. the temperature and process time. Because of its higher purity and lack of solids.05% phosphoric acid contributes to the unique taste of cola drinks. Phosphoric acid is also used in the manufacturing of aluminum phosphate catalysts and can be used to extend the life of catalysts by reducing coking. Fire Retardants Wood and cellulose materials can be treated to obtain flame. or ammonium polyphosphate. tetrapotassium pyrophosphate. dicyandiamide. Phosphoric acid can also be combined with an ammonia base to produce monoammonium phosphate. These compounds are used in fertilizer manufacture and flame proofing. Catalysts Purified Phosphoric acid is used in the production of several catalysts. 8 A PPLICATIONS . purified phosphoric acid is used for spray and house plant fertilizers. formaldehyde and phosphoric acid to form coatings. and exhibits a useful shelf life. The presence of 0. Food and Beverages Beverages Food grade phosphoric acid is used in the beverage industry as an acidulant and flavoring agent. The fire retardant formulation is stable and leach resistant. potassium tripolyphosphate. Phosphoric acid is also a less expensive additive for beverages than citric. impregnated substrates. It is claimed to deliver higher yields with better selectivity in the production of maleic anhydride from C4 hydrocarbons. Vanadium/phosphorus oxide catalysts have been produced (15) for use in hydrocarbon oxidation reactions. tetrasodium pyrophosphate. and trisodium phosphate. The properties of the resulting alkali phosphate are dependent on the method of drying. sodium hydroxide or soda ash (sodium carbonate) is reacted with phosphoric acid and the resulting “wet mix” is dried to form alkali phosphates in the ortho or condensed form. A base such as potassium hydroxide. The current formulation (17) uses urea.A PPLICATIONS Chemical Production Alkali Phosphates Phosphorus-based builders for the detergent industry is a major application for phosphoric acid. Some common phosphate builders are sodium tripolyphosphate. glow and decay resistance. (16) Specialty Fertilizers Purified Phosphoric acid is used as the phosphorus source in the production of specialty and foliar fertilizers. adhesives and resins. copper. fume suppressant. electronic components. Egg Products Phosphoric acid can be used to minimize the viscosity and browning in the spray drying of egg albumen. clean and coat a wide range of metals. and many more. Chemically polished aluminum can be utilized in a variety of applications including automotive trims. window frames. chemically remove the microscopic peaks of the aluminum surface to produce a highly specular or mirror-like finish. nitric acid. brass. Metal Treating In the metal finishing industry phosphoric acid is utilized to chemically polish. and sometimes sulfuric acid. including aluminum. Gelatin Phosphoric acid can improve the setting rates and clarity of gelatins. A PPLICATIONS 9 . Aluminum Brightening Most of the solutions employed in the metal finishing industry for the chemical polishing of aluminum are based on a mixture of phosphoric acid. athletic equipment. Pet Foods Phosphoric acid is used in the production of semi-moist pet food. home appliances. or etch inhibitor. phosphoric acid is reacted with lime to form a calcium phosphate precipitate which aids in the filtration of particulates. shower doors. commonly referred to as bright dip solutions. architectural structures. Sugar Refining In the refining of raw sugar. buffering and preservation. These solutions. Jams and Jellies Small amounts of phosphoric acid can be added to jams and jellies for acidifying. cosmetic containers. It is also used as a degumming agent during vegetable oil refining.Cheese Phosphoric acid is used in the dairy industry as an acidulant to cause curdling in the production of cottage cheese. Salad Dressings Phosphoric acid is used as an acidulant in some salad dressings. PCS’s Phosbrite and DAB solutions set the standard for bright dipping of aluminum and they can be custom formulated to include any combination of the following additives: copper metallic brightener. office equipment. Fats and Oils Phosphoric acid can be added to fats and oils as an emulsifier and to aid in the control of fatty peroxides. steel and stainless steel. aircraft construction. stamped. to improve paint bonding and to aid in forming or break-in processes. PCS provides analytical services at no charge to customers for determining the different operating parameters of the customer’s bright dip baths. which are normally carried through conventional alkaline or neutral cleaners. The phosphate coating is bonded tightly to the metal surface and is normally formulated to be porous. chlorate or a nitrite and serves to increase the reaction rate. Electropolishing18 Carbon steel. It has the advantage of being non-toxic and very effective at removing “milk stone” from the processing equipment. Dairy Equipment Cleaning Phosphoric acid is used in the dairy industry as a cleaner and sanitizer. PCS also provides. or extruded aluminum parts and leaves the aluminum surface “activated” for subsequent bright dipping or etching processes. Phosphoric acid is also less corrosive and volatile than other mineral acids. stainless steel. oil or grease. Aluminum Cleaning In the aluminum industry. 342 Acid Cleaner is designed as a second-stage cleaner that follows an alkaline cleaner. The surfactant acts as a wetting agent to improve the contact between the metal surface and the solution. it is of vital importance to have a clean surface on the aluminum part prior to implementing any finishing process. Phosphate Coatings Metal phosphate coatings are applied to various metal surfaces to reduce corrosion. a dissolved metal phosphate. The advantage of phosphoric acid is that the boiler surfaces will develop a light phosphate coating which will resist further oxidation. but it may be used as a single-stage cleaner where the soil load is light. 10 A PPLICATIONS . It will also remove some heat and watermarks. the pores can hold lubricant to improve the forming operations and reduce friction during equipment break-in periods. PCS maintains a technical staff with laboratory and pilot facilities to assist metal finishing customers with implementing process improvement modifications on existing bright dip/anodizing lines or with designing new lines. sample kits for sending bright dip samples to PCS’s lab and reagents to assist in bright dip bath control. which provides an excellent substrate for paint adhesion. as well as careful control of the entire finishing process. The accelerator can be nitrate. Boiler Cleaning Many boiler cleaning formulations utilize phosphoric acid to remove carbonate scale. caked-on buffing compounds and drawing oils from drawn.Consistent production of a high quality finish requires a thorough understanding of the bright dip bath and its function. The metal is made the anode and the bath selectively removes the microscopic metal peaks resulting in increased specularity. brass and aluminum can be electropolished using a bath of phosphoric-sulfuric-chromic acid in varying concentrations. The cleaning of aluminum can be accomplished by either an alkaline cleaner alone or an alkaline cleaner followed by an acid cleaner. The coating is formed when the free phosphoric acid reacts with the metal to produce a metal phosphate which is insoluble and precipitates. PCS offers a phosphoric acidbased cleaner referred to as 342 Acid Cleaner. In addition. an accelerator and a surfactant. and with troubleshooting to determine the cause of various finishing problems. copper. Many phosphatizing solutions have been developed but the most common ones contain free phosphoric acid. This cleaner is designed to remove ground-in. at no charge. Various additives have been patented to improve specific properties of the refractory compositions. A refractory with a large amount of chromic oxide has been proposed19 which is claimed to have improved thermal shock resistance and reheat expansion. (21) Miscellaneous Fuel Cells Phosphoric acid is used as an electrolyte in fuel cells which produce electricity from the conversion of hydrogen to water. Lead Fixation Phosphoric acid can be used to form non-leachable lead phosphate in land areas where potential lead runoff is a problem. A PPLICATIONS 11 . The high purity of PCS acid allows for an extended shelf life of the mixes plus consistently high strength bonds in the final refractory. It is also used as a raw material in the production of the improved bonding agents such as monoaluminum phosphate and monomagnesium phosphate solutions.Refractories and Ceramics Phosphoric acid is useful as a bonding agent in many refractories and ceramics. Waste Treatment Phosphoric acid is used as a nutrient for bacteria in activated-sludge waste treatment systems. Activated Carbon Production The production of activated carbon involves mixing wood fibers or sawdust with phosphoric acid followed by calcination in a rotary kiln. The addition of tetrasodium pyrophosphate and bentonite (20) has been shown to improve workability and storage life of ramming or hand mixes. Much research has been done on the bonding of high alumina refractories and these compositions display high temperature resistance and high strength. A refractory containing silicon metal and graphite has been claimed to be resistant to slag and hot metal erosion. 5˚F 40.1˚C 0.2˚F –17.0˚F 21.5˚C 4. ˚C +20 +10 0 -10 -20 -30 -40 -50 -60 -70 -80 -90 0 75% 80% 85% 70. Through the concentration range of 0% to 100%. The freezing points of standard concentrations are as follows: Acid Strength (% H3PO4) Freezing Point +80 +70 +60 +50 +40 +30 LIQUID + H 3PO 4 LIQUID + H 3PO 4 • 1/2 71.8% H 2PO 4 H 3PO 4 + H 3 PO 4 • 1/2 H 2 O H 3 PO 4 + H 4P 2 O 7 LIQUID + H 4P2O 7 – 1 16.5˚C LIQUID + H 4P2O 7 – 1 42.4˚C 54.5˚C 94.3˚C 29. boiling acid will give off very nearly pure water.6˚C LIQUID + ICE -85˚C H 3PO 4•1/2 H 2O + ICE 10 20 62. 170 160 150 TEMPERATURE.3˚C H 2O 23.5% H 3PO 4 91.6% H 3PO 4 30 40 50 60 70 80 90 100 110 WEIGHT PERCENT H 3PO 4 FIGURE 3: Freezing Point versus Concentration 12 B ASIC P ROPERTIES . ˚C 140 130 120 110 100 0 10 20 30 40 50 60 70 80 90 100 WEIGHT PERCENT H 3PO 4 FIGURE 2: Boiling Point versus Concentration Freezing Points Figure 3 (1) is the phase diagram of the H3PO4 -H2O system showing the freezing point curve for phosphoric acid through the range of 0 to 100 weight percent H3PO4.B ASIC P ROPERTIES Boiling Points The boiling point for orthophosphoric acid is shown in Figure 2 which graphs the boiling point at one atmosphere pressure versus the concentration expressed as weight percent phosphoric acid (% H3PO4). Concentrated phosphoric acid tends to supercool before crystallization occurs.6˚C TEMPERATURE. In addition. 14). ˚C 120 110 100 PE ES I B OIL NG TE M 10–50 MPY 1–10 MPY 90 80 70 60 50 40 0 10 20 30 40 50 60 70 80 90 100 0–1 MPY WEIGHT PERCENT H 3PO 4 FIGURE 4: Isocorrosion Chart for Type 316L Stainless Steel in Phosphoric Acid. To Convert From: H 3PO 4 P 2O 5 P X X X To: H 3PO 4 — 1.316 0.724 — 2. The values will be higher for PCS phosphoric acids depending on acid purity. numerous other metallic and non-metallic materials have been tested in phosphoric acid and are listed in Figures 5A and B (3) (pg. percent phosphorous pentoxide (%P2O5). Figure 4 (right) is an isocorrosion chart (2) for type 316L stainless steel showing the corrosion rate for various concentrations at various temperatures.291 P 0. or percent phosphorus (%P). 180 170 160 150 140 50 MPY RA TUR 130 TEMPERATURE.3% P2O5 Corrosion Data One of the most widely used alloys for phosphoric acid is stainless steel type 316L.Conversion Factors Phosphoric acid concentrations can be expressed in several ways: percent phosphoric acid (%H3PO4). to convert from 75% H3PO4 to % P2O5: 75% H3PO4 x 0. Fiberglass reinforced polyester is also a corrosion resistant and cost effective material for phosphoric acid (HF free) but only at ambient temperatures. The following chart gives the factors to convert from one of the above concentration units to another.724 = 54.381 3. The corrosion values are only applicable to high purity phosphoric acid.164 P 2O 5 0. B ASIC P ROPERTIES 13 .436 — For example. 000 75 — 100 — Other FIGURE 5B: Corrosion Resistance of Metals in 80% Phosphoric Acid 14 B ASIC P ROPERTIES .2 10 — — — — 1 1 — — — 50 2 0 3 5 5 2 150 20 Rate increases without aeration Discolors >50 Temperature˚C 50 11.3 — — — — — <1 <1 — 4.Material Carbon Chlorinated Polyvinyl Chloride (CPVC) Recommended Temperature Limit (˚C) 100 20 100 100 20 40 80 80 Effect on Material None None None Slightly permeable at high temperatures None Some weight loss Some weight gain Some weight gain Fiberglass Reinforced Vinylester (Hetron 942) Fluorocarbons (TFE & FEP) Polypropylene Polyvinyl Chloride (PVC) Chlorobutyl Rubber Fluoroelastomer FIGURE 5A: Corrosion Resistance of Non-Metals in 80% Phosphoric Acid Corrosion Rate (mils per year) Metal 25 Mild Steel Stainless Steel Type 304 Type 316 Type 347 Type 430 Hastelloy B Hastelloy C Carpenter 20 Nickel Monel — — — — <1 <1 — 0. 6 0.Specific Heat Figure 6 shows the weight percent of phosphoric acid in an aqueous solution versus the specific heat expressed as calories per gram — ˚C or (BTU/lb.2 pH and the second hydrogen at about 9. Titration of the third hydrogen does not display a pH break but it is calculated to occur at about 11.7 0.9 CALS/GRAM – ° C CALS/GRAM – ° C 0.4 0 10 20 30 40 50 60 70 80 90 100 WEIGHT PERCENT H 3PO 4 0 10 20 30 40 50 60 3 70 4 80 90 100 FIGURE 6: Specific Heat at 21.8 0. There are two distinct breaks in the titration curve which represent titration of the first hydrogen at about 4. — ˚F) at 21.0 pH.3˚C.7 0.0 1.5 pH. 11 10 12 9 11 8 10 7 96 pH pH 85 74 63 5 2 4 1 3 2 1 H 3PO 4 Na 2HPO 4 NaH 2PO 4 BASE ADDED Na 3PO 4 H 3PO 4 Na 2HPO 4 NaH 2PO 4 BASE ADDED Na 3PO 4 FIGURE 7: Titration Curve of Orthophosphoric Acid pH versus Increasing Sodium Hydroxide Additions B ASIC P ROPERTIES 15 .8 0.5 0.9 0.4 0.5 0.12 1.3˚C WEIGHT PERCENT H PO 12 Titration Curve Figure 7 shows the curve for the titration of a 0.6 0.0 0.1 molar solution of phosphoric acid with sodium hydroxide. 2932 1.0773 1.4143 1.7214 1.1467 1.8062 1.9433 7 1.8436 1.6290 1.5 1.1669 1.7095 1.8686 1.1807 1.1948 1.2616 1.1877 1.6067 1.9684 9 1. Specific gravity is an accurate measure of the concentration of phosphoric acid for laboratory analysis.9184 5 1.3605 1.7937 1.4425 1.0955 1.4714 1.0713 1.8311 1.3096 1.1016 1.4813 1.1336 1.6861 1.2238 1.0538 1.3347 1.8810 2 1.3781 1.0200 1.2694 1.9 1.5˚C versus Concentration 1.0423 1.4051 1.5529 1.3518 1.1271 1.9060 4 1.2387 1.4520 1.3 1.0595 1.9981 1.7455 1.1207 1.05% H3PO4 (see page 23 — Analytical Methods).9558 8 1.9309 6 1.6403 1.1534 1.0894 1.2019 1.1080 1. H3PO4 Wt.8186 1.6516 1.0145 1.2092 1.0833 1.0 0 10 20 30 40 50 60 70 80 90 100 WEIGHT PERCENT H 3PO 4 FIGURE 8B: Specific Gravity versus Concentration 16 B ASIC P ROPERTIES .8 1.5958 1.5013 1.2462 1.7578 1.2312 1.8935 3 1.4912 1.2164 1.5849 1.7688 1.5216 1.6178 1.Density The density (expressed as specific gravity) versus concentration of orthophosphoric acid is given in the following chart (4) (Figure 8A) and graph (Figure 8B).0311 1.1 1.0255 1.3263 1.3960 1.7 SPECIFIC GRAVITY AT 25 ° C 1.3870 1.5635 1.4236 1.7813 1.1143 1.6 1.5424 1.9933 1 1. Linear interpolation between the values given in Figure 8A will yield acid concentrations with an accuracy of ± 0.5320 1.5742 1.2852 1.1738 1.2772 1.4 1.5114 1.1400 1.3692 1.3014 1.7334 1.3178 1.6630 1.9808 FIGURE 8A: Orthophosphoric Acid Specific Gravity @ 25˚C/15.0480 1.2539 1.2 1.0367 1.6745 1.0654 1.4330 1.8560 1.0091 1.4617 1.6977 1.1601 1. % 0 10 20 30 40 50 60 70 80 90 100 110 0 .3432 1.0036 1. 5000 4000 ENTHALPY.020912T — Constant at 25˚C 0. The heat evolved when acid of one concentration (C1) is diluted to a second concentration (C2) is found by subtracting the enthalpy of the second from the enthalpy of the initial solution (Ec1 – Ec2). The electrical conductivity of any concentration increases with increasing temperature. Bates (5) developed the following: Hydrogen First H + Second H+ Third H+ Equation – log K2 = 799. Dissociation of the first hydrogen is very strong and is exothermic.5535 + 0.8 x 10 –13 * T is absolute temperature in degrees Kelvin Electrical Conductivity The specific electrical conductivity of phosphoric acid increases with increasing concentrations reaching a maximum value at about 50% H3PO4. CALS/MOLE H 3PO 4 3000 2000 1000 0 0 10 20 30 40 50 60 70 80 90 100 WEIGHT PERCENT H 3PO 4 FIGURE 9: Enthalpy versus Concentration B ASIC P ROPERTIES 17 .Dissociation Orthophosphoric acid is a triprotic acid which means that it can contribute or dissociate three hydrogen ions.31/T* – 4.7107 x 10 –2 7. respectively.99 x 10–8 4.9884 + 0. and both dissociations are endothermic. the conductivity decreases. As the concentration continues to increase. R.0/T – 5. Dissociation of the second and third is weak and very weak. Enthalpy — Concentration Figure 9 (8) (right).013486T – log K2 = 2073. This graph shows the heat evolved in calories per mole H3PO4 when a certain concentration of acid is diluted to an infinitely low concentration. is a graph of the enthalpy versus concentration for phosphoric acid.G. There is abundant research on the dissociation constants for the three hydrogens. (9) Heat (kcal/mole) H18 ˚C 100 wt. Entropy The following is the heat of formation.5 wt.8 wt.93 306.4 wt.5˚C – 1.7 wt.0 42.Heat of Formation. % H3PO4 1.5 wt. % H3PO4 (solid) 100 wt.17 –270.000792 x (weight % H3PO4) + 1.5˚C)(10) is: Refractive Index = 0.1 303. % H3PO4 = RI 17.04 305.74 Free Energy (kcal/mole) F25˚F — Entropy (cal/˚C) S — Latent Heat of Vaporization (8) The latent heat of vaporization for phosphoric acid at 25˚C is given in Figure 10. Free Energy of Formation.3346 or wt.26 305. % H3PO4 21.3 wt.49 304. The formula (17. % H3PO4 37. % H3PO4 9. % H3PO4 64. % H3PO4 302.3346 0. free energy of formation and entropy of orthophosphoric acid as a solid and as an aqueous solution of 400 moles of water to 1 mole of H3PO4.69 305.37 300. 12 KCALS/MOLE 11 10 0 10 20 30 40 50 60 70 80 90 100 WEIGHT PERCENT H 3PO 4 FIGURE 10: Latent Heat of Vaporization at 25˚C Refractive Index The refractive index of aqueous phosphoric acid solution is linear with concentration. % H3PO4 (liquid) Aqueous Dilutions 84.000792 18 B ASIC P ROPERTIES . 12 60˚ 149. The following table lists several acids.29 2.0 345.6 54.0 745.5 0.7 0. the same level of sourness can be obtained using less phosphoric acid.0 335.32 54.16 22.0 135.47 23.0 736.39 1.65 FIGURE 11: Vapor Pressure versus Concentration B ASIC P ROPERTIES 19 .0 388.1 349.0 141. Vapor Pressure Figure 11 below gives the vapor pressure of water over aqueous solutions of phosphoric acid at various temperatures.0 108.0 71.76 23.24 0.01 N solution of each and the pounds of the listed acid equivalent to one pound of 75% phosphoric acid: (11) Relative Sourness (0.Relative Sourness Phosphoric acid is frequently used as a flavoring agent.0 108.044 40˚ 55.0 262.13 1.5%) Citric acid crystals (91%) Citric acid solution (50%) Acetic acid (56%) Lactic acid (44%) Lactic acid (40%) Phosphoric acid (75%) 100 100 100 70 100 100 120 Equivalent Pounds of Acid 1.0 145. the relative sourness of a 0.5 15. or lactic acids.40 21.76 4.6 39.4 148.00 Bottled soda of the acid type has a sourness approximately the same as 0.66 2.5 1.0 3.43 80˚ 355.81 3.0 320.01 N) Tartaric acid crystals (99.0 713. tartaric.35 2.0 46.0 52.0 683.68 10.0 567.33 100˚ 760.2 49. however.4 5.0 176.4 25. tartaric and acetic acid. It imparts a sour taste similar to citric.01 N solutions of citric. % H3PO4) 0 5 10 20 30 50 65 85 100 Vapor pressure (mm Hg) at temperature (˚C) 25˚ 23.27 16.(13) Concentration (wt. 60 50 40 WEIGHT PERCENT P 2O 5 30 20 10 0 200 300 400 500 600 700 800 TEMPERATURE.Vapor Composition The composition of the vapor which exists over a boiling solution of phosphoric acid is depicted in Figure 12.(13) An aqueous solution of H3PO4 will give off almost pure water for temperatures up to about 300˚C at which point the acid strength is about 103%. For example. As the temperature of the solution increases. the approximate composition of the vapor at 760 mm pressure over a boiling solution at 600˚C is 25% P2O5. ° C FIGURE 12: Vapor Composition Over Boiling Solutions 20 B ASIC P ROPERTIES . the vapor evolved will contain increasing amounts of P2O5. 91 1. ° C FIGURE 13B: Viscosity of 75% and 85% Phosphoric Acid versus Temperature B ASIC P ROPERTIES 21 .(14) Figure 13B is a graph of the viscosity versus temperature for 75% and 85% phosphoric acid.4 67. 155.4 16. Temperature (˚C) Concentration (% H3PO4) 0 5 10 20 30 50 75 85 105 110 115 20˚ 1. 490.4 2.28 0.24 0.47 0.0 1.75 0.18 0.0 2.14 0.8 5.34 0. 110.6 3. 32. 140˚ 0.87 1. 23.4 3.4 12.22 0.72 1. 10800. 975.1 1. 2240. 80˚ 0.52 0.86 1.26 0.4 3.0 4.37 0. 16900.1 8.49 1.63 0.8 2.38 0. 40˚ 0.55 0.66 0.3 1. 365.4 13. 145. 2900.42 0.6 5.80 0.33 0. 600.65 0. 644.91 1. 60˚ 0. 47.82 1.4 FIGURE 13A: Viscosity in Centipoise of Phosphoric Acid for Various Concentrations and Temperatures 50 85% 40 CENTIPOISE 30 20 75% 10 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 TEMPERATURE.5 18. 40.19 0.2 2.15 0.7 24. 100˚ 0.0 1.Viscosity in Centipoise Figure 13A below gives approximate viscosity in centipoises of aqueous phosphoric acid solutions for various concentrations and temperatures.8 5.4 7.8 35. 4510. 30˚ 0.36 0. 250.48 0.2 1. 180˚ 0.8 2. 2 1.4 3.9 4.4 4.81 0.81 0.6 1.0 6.2 8.3 8.4 6.6 4.0 1.4 1.1 2.0 2.1 1.2 1.3 4.90 1.92 1.9 2.2 2.42 0.89 0.) % H3PO4 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 105 110 115 118 20˚ 25˚ 30˚ 40˚ 50˚ 60˚ 70˚ 80˚ 90˚ 100˚ 110˚ 120˚ 130˚ 140˚ 150˚ 160˚ 170˚ 180˚ 1.9 6.71 0.1 7.37 0.55 0.53 0.0 1.6 3.2 7.2 2.6 1.66 0.2 5.1 11 15 25 70 270 0.2 4.90 1.3 6.47 0.0 18 68 210 1.0 1.69 0.48 0.79 0.0 13 41 130 2.4 2.4 1.5 3. (˚C.0 2.0 3.78 0.2 1.3 1.42 0.7 3.8 9.8 2.3 4.6 1.6 8.33 0.1 6.3 11 25 67 380 0.4 3.1 2.6 3.4 1.8 3.0 2.48 0. FIGURE 14: Viscosity in Centistokes of Phosphoric Acid for Various Concentrations and Temperatures 22 B ASIC P ROPERTIES .56 0.8 6.8 10 14 19 30 53 173 810 0.43 0.54 0.8 28 87 2200 1600 1500 1000 2000 1200 Bichowsky & Rossini :“The Thermochemistry of the Chemical Substances.6 6.3 1.8 10 14 19 27 42 81 330 0.6 3.3 1.2 12 17 23 34 55 100 440 0.5 8.0 2.7 2.1 2.2 5.5 4.90 1.8 6.9 2.0 5.1 1.6 1.6 3.6 1.5 1.99 0.5 1.5 8.47 0.6 3.61 0.30 0.2 2.1 2.6 3.6 1.2 19 50 250 830 1.5 1.4 1.83 0.0 1.5 3.4 11 15 20 28 41 68 140 600 0.8 4.3 4.8 2.69 0.8 2.6 22 99 320 1.4 1.2 12 29 120 400 1.7 4.60 0.90 0.9 4.2 9.2 1.2 2.0 3.9 2.70 0.61 0.38 0.8 4.7 2.2 9.7 2.92 1.0 1.74 0.9 2.37 0.1 15 54 170 2.2 2.2 1.63 0.80 0.8 3.69 0.89 1.2 10 34 107 2.4 1.1 3.2 3.0 4.9 2.9 7.79 0.7 15 38 190 550 1.3 5.5 1.Kinematic Viscosity of Phosphoric Acid Solutions Figure 14 gives approximate viscosity in centistokes of aqueous phosphoric acid solutions for a full range of concentrations and temperatures.3 2.2 1.1 2.9 4.7 2.42 0.54 0.71 0.9 2.3 3.0 1.4 7.1 1.61 0.79 1.0 3.47 0.8 5.1 1.0 5.1 1.1 3.3 1.2 7.3 12 19 50 170 0.54 0.1 7.1 1.99 1.8 3.4 1.2 1.8 2.1 3.9 6.1 5.2 3.7 5.5 6.9 4.7 3.2 1. Temperature.4 3.94 1.8 2.” Reinhold Publishing Corp.5 5.5 8.1 1.3 1.6 10 14 20 36 110 410 0.33 0.3 2.62 0.3 2.7 14 33 100 600 0. 00076 0. 2. The reading should not be taken until the liquid is free of any air bubbles and the hydrometer is at rest. Add the sample. becomes a straight line. By sense of feel. In taking the reading. The free fall should be no more than 6 mm. the eye should be placed slightly below the plane of the surface of the liquid and then raised slowly until this surface.00076 0. Calculation 1.00074 0. Hydrometer cylinder. thoroughly mix the sample and rinse a clean hydrometer cylinder with the sample.00078 0. Procedure 1. streamline or torpedo design. seen as an ellipse. ˚C 15 0. a minus correction will result.00078 40 0. diameter 30 to 40 mm.5˚C If the temperature of the determination is higher than 25˚C. glass. Grasp the top of the stem of a clean dry hydrometer between thumb and forefinger and slowly lower it into the center of the cylinder containing the sample.00078 25 0. 3.A NALYTICAL M ETHODS Determination of H3PO4 by Specific Gravity Method: ASTM E358 Principle The specific gravity can be accurately related to the strength of orthophosphoric acid.5˚C in Table 2 (page 24) using the appropriate temperature coefficient factor in Table 1. Apparatus 1. with or without lip. 2. plus correction will result.00075 0. If lower than 25˚C. The point at which this line cuts the hydrometer scale should be taken as the reading.00080 A NALYTICAL M ETHODS 23 . precision grade for liquids heavier than water in ranges suitable to the acid strength of thermal orthophosphoric acid. Thermometer. 4. Adjust the temperature of the sample to be tested to 20˚ to 30˚C. 3. (sp gr at T) + (T – 25) (temperature coefficient factor) = sp gr at 25˚C/15. and place the cylinder in a vertical position in a location free of air currents. Determine acid strength opposite the appropriate specific gravity at 25˚C/15. Hydrometer. TABLE 1: Specific Gravity Temperature Coefficient H3PO4 Percent 75 80 85 Solution Temperature.00077 0. height 325 to 375 mm. No portion of the hydrometer should touch the cylinder. gently release it just before it comes to rest. 39 78.08 58.580 1.636 H3PO4 Percent 80.648 1.609 1.60 84.TABLE 2: Phosphoric Acid Solutions Specific Gravity Table based on ASTM Method E 358 H3PO4 Percent 74.52 58.03 60.50 57.51 76.632 1.17 57.622 1.78 55.584 1.681 1.680 1.683 1.75 60.664 1.639 1.78 61.30 79.35 61.85 60.00 57.88 57.647 1.623 1.691 1.618 1.19 60.33 59.594 1.605 1.51 90.34 56.11 55.52 59.64 56.90 76.20 85.70 81.91 80.20 80.574 1.30 85.12 60.01 63.48 78.11 78.601 1.31 75.01 89.668 1.71 56.23 59.28 55.71 82.571 1.18 82.621 1.68 59.71 80.81 84.98 56.595 1.21 56.50 80.576 1.39 85.49 85.578 1.692 1.722 1.675 1.80 85.697 1.25 60.32 83.09 82.585 1.01 P205 Percent 58.645 1.655 1.96 54.672 1.653 1.79 82.01 75.38 63.620 1.56 60.39 54.33 54.97 60.71 83.99 62.598 1.11 54.23 58.649 1.728 1.10 79.581 1.60 74.42 61.71 74.679 1.75 58.70 77.656 1.685 1.93 78.616 1.61 54.643 1.00 82.14 62.62 59.00 76.627 1.644 1.60 75.40 83.50 84.570 1.95 59.99 85.619 1.596 1.40 82.687 1.52 81.608 1.607 1.94 58.61 81.29 57.18 54.11 64.587 1.39 81.740 1.59 P205 Percent 53.01 84.77 56.575 1.669 1.677 1.19 79.82 58.635 1.615 1.43 77.29 62.660 1.698 1.16 58.614 1.74 59.684 1.617 1.597 1.61 77.5C 1.678 1.04 59.93 77.79 77.20 75.98 61.652 1.19 Sp.70 75.637 1.80 83.686 1.603 1.646 1.59 53.05 55.640 1.50 61.19 83.22 62.80 79.36 57.62 55.746 24 A NALYTICAL M ETHODS .80 80.58 82.41 60.661 1.08 56.30 81.673 1.00 87.94 57.92 82.00 86.12 81.91 84.46 58.69 54.21 81.63 60.630 1.31 82.47 64.90 86.20 78.592 1.62 83.81 59.00 80.654 1.90 75.59 85.40 75.80 74. 25C /15.29 77.69 79.18 55.39 59.27 61.628 1.01 83.11 56.70 85.97 55.573 1.39 79.590 1.582 1.593 1.42 76.61 78.99 79.21 57.09 80.10 84.00 81.612 1.71 61.638 1.74 64.20 77.670 1.30 80.76 54.704 1.65 63.663 1.601 1.02 78.88 83.12 61.572 1.11 59.5C 1. 25C /15.66 58.10 76.606 1.46 59.69 60.693 1.70 84.34 60.633 1.51 75.50 79.43 57.89 81.657 1.07 57.71 55.671 1.55 55.02 77.80 57.79 76.10 83.734 1.19 76.50 74.88 84.42 55.66 57.665 1.05 61.91 54.01 58.72 57.48 55.46 54.84 61.642 1.10 75.51 89.07 62.569 1.676 1.60 76.91 60.90 59.70 76.690 1.20 84.03 54.30 58.39 84.58 57.01 88.611 1.63 61. Gr.629 1.658 1.631 1.30 78.84 56.88 58.579 1.49 82.694 1.716 1.85 55.59 58.79 78.92 61. Gr.47 60.00 74.651 1.662 1.37 Sp.586 1.25 54.589 1.29 84.599 1.49 83.41 56.604 1.610 1.583 1.83 54.11 77.688 1.54 54.695 1.50 87.48 77.667 1.58 56.564 1.17 59.39 80.626 1.60 79.83 65.51 88.35 55.91 55.56 61.10 85.33 76.625 1.28 56.710 1.20 61.78 81.70 78.591 1.81 75.89 78.51 56. In the presence of vanadium. Place the sample in the spectrophotometer and read the absorbance (ASPL). Place standard in the spectrophotometer and read the absorbance (ASTD). Mix well. Pipet a 5 ml aliquot of above solution into a 100 ml flask. set the wavelength to 420 nm. b. Reagents Molybdovanadate Reagent: 1. to stand for 10 minutes.1 g of sample into a 100 ml volumetric flask. Stirring constantly. ammonium molybdate reacts under acid conditions to form a heteropoly acid. a reagent blank and a phosphate standard must be run.0 ml of molybdovanadate reagent. slowly add Solution A to Solution B. Analytical Procedure 1.3835 g reagent grade KH2PO4 (dried at 105˚C for 2 hours) in deionized water and dilute to 500 ml. Dilute to 2 litters with deionized water. Place the blank in the spectrophotometer and adjust the light control to read 0 on the absorbance scale or display.4 mg P2O5/ml standard phosphate solution into a 100 ml volumetric flask. Standard: Pipet 5 ml of 0. Record the weight (W) to the nearest 0. When the spectrophotometer has warmed up. Blank: Pipet 20 ml of molybdovanadate reagent into a 100 ml volumetric flask and dilute to the mark with deionized water. 5. Mix well. Allow all samples. The intensity of the yellow color is proportional to the phosphate concentration. including the reagent blank and phosphate standard. Make up weekly. 2. Standard Phosphate Solution — Dissolve 0. 6.4 mg P2O5/ml. molybdophosphoric acid. mix well. pipet 20 ml of molybdovanadate reagent and dilute to the mark with deionized water. They are prepared as follows: a. This solution contains 0. 2. and allow to warm up for the recommended period. yellow vanadomolybdophosphoric acid is formed. Add 40 ml of deionized water and. 3. With each set of samples. Weigh approximately 0.1 mg. Cool to room temperature and add 330 ml of concentrated (36%) hydrochloric acid. 7. Calculate the % P2O5 or the % H3PO4 as shown in the calculation section. 20. Dilute to the mark with deionized water.Determination of H3PO4 by Molybdovanadate Method Principle In a dilute orthophosphate solution. 8. Turn spectrophotometer on. A NALYTICAL M ETHODS 25 . from a pipet. 4. Solution A — dissolve 40 g ammonium molybdate tetrahydrate in 400 ml hot water and cool to room temperature. Cool to room temperature. Solution B — dissolve 2 g ammonium metavanadate in 250 ml hot deionized water. 3. Dilute to the mark with deionized water. Special Apparatus Visible Spectrophotometer. Add 40 ml of deionized water. adjust the zero to read infinite absorbance. Concentrated perchloric acid is an extremely strong acid and an extremely strong oxidizer. Sodium Hydroxide. Add 120 ml of distilled or deionized water.5 ml of thymolphthalein indicator solution. 2. It must be stored away from heat and other materials. Procedure 1. or HNO3 can be substituted for HCl.10 g of thymolphthalein in 100 ml of methyl alcohol. Never let any sample containing perchloric acid evaporate to dryness. Titrate with 1 N sodium hydroxide (NaOH) to the first appearance of a blue color. Add 0. 3. A final acid concentration of about 0.900 % H3PO4 = ____________________ Sample Wt. Determination of H3PO4 by Thymolphthalein Titration Reagents 1.6 to 1. Accurately weigh 1 ml (1. Thymolphthalein Indicator: Dissolve 0.8 g) of the sample into a beaker. 1. NOTE 2. Calculation ml NaOH x 4.0 N: Standardized Titration Reagent. HCIO4. 2.Calculation Weight % P2O5 = 4 • ASPL __________________ ASTD (Sample Wt. Stir.3807 NOTE 1.5 N is recommended. Contact with natural rubber or any other organic materials may cause a violent explosion. 26 A NALYTICAL M ETHODS .) Weight % H3PO4 = % P2O5 x 1. See Note 2 for HCIO4 precautions. E. 12. 127 (1951). Vol I.W. 4.S.. 44.. AL. 2165. N. E NDNOTES 27 ... Electropolishing. 988. M. 1929. Reinhold Publishing Corp. 21. 1920. Phosphorus – Properties of the Element and Some of Its Compounds. Handbook of Chemistry. Van Wazer. 14. 16.Y. Jones. Farr. 4. Bichowsky & Rossini. Teddington. 8. Patent No. 19..S Patent 4. 4.Y.113. I. McDowell.. p. T.899. Berlin.” 5th Ed. N. 4. Ltd.W.511.H.A. 7. McGraw-Hill Book Co. Vol. Ibid. 1923. Interscience Publishers Inc. Phosphorus and Its Compounds. Fedot’ev.356.E NDNOTES 1. 1966. National Research Council. Patent 3.S. 10. Julius Spring. D. Patent No. 1958. 47. Anodizing and Electrolytic Pickling of Metals.Y.149. 2. Bates..365.338. Washburn.D. National Bottler’s Gazette.467. 1946. Robert Draper. 17.D.S. U. The Thermochemistry of the Chemical Substances. Ross & H. Patent 4. Skinner and Sales. July 5. TVA #8. 3. National Association of Corrosion Engineers. 1952. Muscle Shoals. Journal of American Chemical Society. U. TVA #8. Patent No..887.069.S. Ohio. 1936.P. International Critical Tables. Sept. 15. N.066. 1. (1925). N. Handling Phosphoric Acid and Phosphate Fertilizers II. R. Ibid.. T. England. Farr. Lange. 6. 9. N. 20. Van Wazer. 5. 47. 13. 11. U.. Industrial Engineering Chemistry. U. U. W. G. 1959. Brown and Whitt.S.502. 615. Journal of Research – National Bureau of Standards. Handbook Publishers Inc. 18. “Physikalisch-Chemische Tabellen. U. 1975. Chemical Engineering. Senior Director of Sales www. Manager Co-Product Sales Dan Devens.potashcorp. Engineer John Jernigan. Manager Transportation Bryan Blau. Tech Services Engineer Customer Service PCS Sales Melvin Todd. Senior Sales Representative Dave McLeish. Planning & Logistics Coordinator Customer Service Paul Hayden. 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Senior Tech Sales Rep Randall Castro. Manager Co-Product Sales Customer Service www. Lab Supervisor Customer Service Randall Castro. Senior Tech Sales Rep Mary Socha.com (847) 849-4481 (847) 849-4482 (252) 322-8123 (800) 654-4514 (Toll Free) Purchasing PCS Products Co-Product Services (847) 849-4481 (847) 849-4482 (847) 849-4375 800-654-4514 (Toll Free) Emergency Contact Web site 28 PCS S ALES AND S ERVICE . Senior QC Chemist Ann Lang. Senior Tech Sales Rep Ann Lang. Phosphoric Acid Production and Distribution Stockton. NC Producing Point Acid Terminal New Orleans. PA Aurora. IL Cincinnati. FL Purified Phosphate Sales Regions WA OR NV CA AZ MT ID WY UT CO NM TX ND SD NE KS NM MN WI MI NY VT ME NH MA RI IA PA NJ CT IN OH IL DE WV MO VA MD KY TN NC AR SC MS AL GA LA FL Purified Acid Sales Melvin Todd Dave McLeish Paul Hayden Stacy Schnetzka Metal Finishing Mary Socha Midwest & Northwest Melvin Todd Southeast & Southwest Brian Corcoran Joe Detyens John Cooper West Manager East Manager Director PCS S ALES AND S ERVICE 29 . TN Philadelphia. LA Jacksonville. CA Chicago. OH Memphis. 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