Some Uses of Phosphoric acid

Phosphoric acid, also called orthophosphoric acid,  (H3PO4), the most important oxygen acid of phosphorus, used to make phosphate salts for fertilizers. It is also used in dental cements, in the preparation of albumin derivatives, and in the sugar and textile industries. It serves as an acidic, fruitlike flavouring in food products.

Pure phosphoric acid is a crystalline solid (melting point 42.35° C, or 108.2° F); in less concentrated form it is a colourless syrupy liquid. The crude acid is prepared from phosphate rock, while acid of higher purity is made from white phosphorus.

Phosphoric acid(CAS.NO:7664-38-2) forms three classes of salts corresponding to replacement of one, two, or three hydrogen atoms. Among the important phosphate salts are: sodium dihydrogen phosphate (NaH2PO4), used for control of hydrogen ion concentration (acidity) of solutions; disodium hydrogen phosphate (Na2HPO4), used in water treatment as a precipitant for highly.

1. Food additive

Food-grade phosphoric acid (additive E338) is used to acidify foods and beverages such as various colas, but not without controversy regarding its health effects.  It provides a tangy or sour taste, and being a mass-produced chemical is available cheaply and in large quantities. The low cost and bulk availability is unlike more expensive seasonings that give comparable flavors, such as citric acid which is obtainable from citrus, but usually fermented by Aspergillus niger mold from scrap molasses, waste starch hydrolysates and phosphoric acid. Various phosphates, e.g., monocalcium phosphate, are used as leavening agents.

Phosphoric acid is deliberately added to soft drinks to give them a sharper flavor. It also slows the growth of molds and bacteria, which would otherwise multiply rapidly in the sugary solution.

Almost all of the acidity of soda pop comes from the phosphoric acid and not from the carbonic acid from the dissolved CO2. You can verify this by measuring the pH of fresh and flat soda pop; there's very little difference.

The phosphoric acid is corrosive, but actually the acid concentration in soda pop is lower than that in orange juice or lemonade. 

2. In medicine

Phosphoric acid is used in dentistry and orthodontics as an etching solution, to clean and roughen the surfaces of teeth where dental appliances or fillings will be placed. Phosphoric acid is also an ingredient in over-the-counter anti-nausea medications that also contain high levels of sugar (glucose and fructose). This acid is also used in many teeth whiteners to eliminate plaque that may be on the teeth before application.

3. General Side Effects

When phosphoric acid powders are inhaled or come in contact with skin and other body tissues, it can cause dermatitis, pain, tearing, blurred vision, difficulty swallowing or breathing and gastrointestinal problems. Most of these side effects occur in industrial manufacturing plants where concentrated levels of phosphoric acid are used. The amount of phosphoric acid added to sodas and other foods by comparison is a very small amount.