Chlorine dioxide (ClO2) is a synthetic, green-yellowish gas with a chlorine-like, irritating odor. Chlorine dioxide is very different from elementary chlorine, both in its chemical structure as in its behavior. Chlorine dioxide is a small, volatile and very strong molecule. In diluted, watery solutions chlorine dioxide is a free radical. At high concentrations it reacts strongly with reducing agents. Chlorine dioxide is an unstable gas that dissociates into chlorine gas (Cl2), oxygen gas (O2) and heat. When chlorine dioxide is photo-oxidized by sunlight, it falls apart. The end-products of chlorine dioxide reactions are chloride (Cl–), chlorite (ClO–) and chlorate (ClO3–).
At –59°C, solid chlorine dioxide becomes a reddish liquid. At 11°C chlorine dioxide turns into gas. Chlorine dioxide is 2,4 times denser than air. As a liquid chlorine dioxide has a bigger density than water.
|CAS Number||10049-04-4||Molecular formula||ClO2|
|ChEBI||CHEBI:29415||Molar mass||67.45 g mol−1|
|ChemSpider||23251||Appearance||Yellow to reddish gas|
|Gmelin Reference||1265||Density||2.757 g dm−3|
|MeSH||Chlorine+dioxide||Melting Point||-59 °C, 214 K, -74 °F|
|PubChem||24870||Boiling Point||11 °C, 284 K, 52 °F|
|RTECS number||FO3000000||Solublity In Water||8 g dm-3 (at 20 °C)|
|UNII||8061YMS4RM||Vapor pressure||1 atm|
|Acidity (pKa) (kH)||3.0(5)|
|Solubility||soluble in alkaline and sulfuric acid solutions|
|Henry’s law constant (kH)||4.01 x 10−2 atm-cu m/mole|
Residual Measurement Of ClO2
Determination of residual ClO2 in process or potable water is a tricky situation. As there are several interferences from other oxidants present in water in addition to ClO2 and its disinfection bi-products. The test method for measurement of ClO2 is a normally interfered with its bi-products chlorite & chlorate due to the difficulty in measuring a specific oxidants among other oxidants.
Following are the methods available and selectively used for analytical measurement of ClO2
LGB ( Lissamine Green B) – Like amaranth and CPR,ClO2 selectively decolorizes LGB dye. With this method the minimum residue that can be measured is 2.5 mg/L. but again the method is only recommended at laboratory level and not in field.
DPD method –
This is the most commonly used method for testing ClO2 in industrial methods.
DPD forms a pink color & the intensity of the color is proportional to the concentration of ClO2. The problem with the method is chlorine & chlorite ion also reacta with DPD reagents. The system works fairly well in clean water system. But in cases of cooling tower & waste tower there are several interferences from hydrocarbon, SRB etc…
We SVS AQUA TECHNOLOGIES recommend three methods for measuring the residue of ClO2
The photometry is a method of analysis which is often used. Whether it is a public bathhouse, food and beverage industry, laboratories, or industrial disinfection – are everywhere photometer is used for the determination of concentrations in solutions. We are providing the world’s first photometer for the entire visible color spectrum with only one light source and only one sensor. The unique sensor combined with the several –year’s experience in water analysis, made this innovation possible. In addition, the sensor measures with a hitherto unknown devices with photometer accuracy. The Bluetooth technology (select models) and a programmed specifically for the PC software makes it easy to manage measurement and customer data..
Reagent tablets offer the highest level of assurance that always the exact amount of reagent needed will be used. Most marketed tablet types, such as DPD for determining Chlorine in water, are regulated by strict international standards aimed at guaranteeing that all tablets with that designation (e.g. DPD 1) can also be used in all designated measurement devices made by any manufacturer. Our devices and reagents can therefore be combined with other manufacturer’s reagents, and this is also true the other way around. One of the questions discussed often is the difference between RAPID and Photometer tablets. Basically both detect the same content but are different in one important point: RAPID tablets contain a material which “bursts” the tablet, e.g. chemical pulp that expands upon contact with water. This “burst material” would, however, disrupt the light ray of the photometer (suspended particles) which is why RAPID tablets should never be used with electronic devices such as photometers.
Other Related Products