EDTA

A chelating agent of particular economic significance is ethylenediaminetetraacetic acid (EDTA).

ethylenediaminetetraacetic acid (EDTA)

EDTA is a versatile chelating agent. It can form four or six bonds with a metal ion, and it forms chelates with both transition-metal ions and main-group ions. EDTA is frequently used in soaps and detergents, because it forms a complexes with calcium and magnesium ions. These ions are in hard water and interfere with the cleaning action of soaps and detergents. The EDTA binds to them, sequestering them and preventing their interference. In the calcium complex, [Ca(EDTA)]^2–, EDTA is a tetradentate ligand, and chelation involves the two nitrogen atoms and two oxygen atoms in separate carboxyl (-COO^–) groups. EDTA is also used extensively as a stabilizing agent in the food industry. Food spoilage is often promoted by naturally-occurring enzymes that contain transition-metal ions. These enzymes catalyze the chemical reactions that occur during spoilage. EDTA deactivates these enzymes by removing the metal ions from them and forming stable chelates with them. It promotes color retention in dried bananas, beans, chick peas, canned clams, pecan pie filling, frozen potatoes, and canned shrimp. It improves flavor retention in canned carbonated beverages, salad dressings, mayonnaise, margarine, and sauces. It inhibits rancidity in salad dressings, mayonnaise, sauces, and sandwich spreads. EDTA salts are used in foods at levels ranging from 33 to 800 ppm.

Create your S-Cool account | S-cool, the revision website

Create your S-Cool account | S-cool, the revision website

Breathalyzer

Chemistry of a Breathalyzer

A Breathalyzer makes use of the fact that alcohols (in this case ethanol) oxidize into carboxylic acids. It uses the strong oxidizing agent Potassium dichromate in a yellow solution of sulfuric acid, under the presence of a Silver Nitrate catalyst, to complete the reaction quickly. As ethanol oxidizes and the Potassium dichromate reacts, the chromate ion changes from Cr (VI) to Cr (III). This causes the color intensity of the yellow solution to decrease, and a spectrophotometer in the breathalyzer compares the absorbance of this solution with that of an unreacted solution


Using Beer's law, the spectrophotometer can relate concentration to absorbance levels of the chromium ion. The amount of alcohol present is proportional to the stoichiometric coefficients. An actual breathalyzer only needs to detect 25 micrograms of ethanol to give a reading 0.10 Blood Alcohol Level.

Credit : http://chem242.blogspot.com/2005/08/chemistry-of-breathalyzer.html

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Expanded PS

Polystyrene Boxes for Food

Concerns over the use of PS should best be analysed based on facts rather than on perception .

The fact that advanced countries like Japan , US and The EU continue to allow the use of PS as a food packaging material speaks volume about its safety .

Basically there are 2 forms of PS foam

·         Extruded polystyrene  [ foam plates , egg cartons  and other food food service applications ]

·         Expanded polysterene [ coffee cups , packaging of  delicate E & E appliances , consumer products ]

Both types are also used as thermal insulation in Industrial , commercial and residential construction.

[i]What is EPS?

EPS (Expanded Polystyrene) or as many know by The Dow Chemical Company's trade marked name, STYROFOAM, is an extremely lightweight product that is made of expanded polystyrene beads. Originally discovered by Eduard Simon in 1839 in Germany by accident, EPS foam is more than 95% air and only about 5% plastic.

Small solid plastic particles of polystyrene are made from the monomer styrene. Polystyrene is normally a solid thermoplastic at room temperature that can be melted at higher temperature and re-solidified for desired applications. The expanded version of polystyrene is about forty times the volume of the original polystyrene granule.

Expanded polystyrene (EPS) is a versatile, lightweight material that can be manufactured into a variety of products. EPS offers a high-performance yet economical support for a wide variety of items—from sensitive electronics to appliances to pharmaceuticals—to be safely delivered to market. Manufacturers rely on EPS packaging because of its ability to prevent or minimize product damage during transit and its excellent insulation properties required for food and medical shipments.

Yet EPS packaging, just like any disposable packaging, will eventually become a solid waste and have to be managed. But here’s the good news: EPS is recyclable. Although the availability of polystyrene recycling programs varies by community and can be limited, the EPS industry uses average of 50 percent of the post consumer material collected in the manufacture of new EPS transport packaging and loose fill packaging, which has reduced requirements for raw material resources, energy consumption has diverted material from landfills.