Isocyanuric Acid Test Lab Report

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Abstract: The safety of pool water is reliant on chemical sterilisation, to destroy dangerous pathogens. The most common steriliser is chlorine, in the form of hypochlorite ions (OCl-) and hypochlorous acid (HOCl). However sunlight causes drastic decomposition of these chemicals, thus methods to protect chlorine from sunlight have been created for pools. Some of these include pool covers, or chemical stabilisers which combine with the free hypochlorite ions to reduce decomposition. The most common stabiliser is isocyanuric acid ((CONH)3), added until a concentration of 50mg/L is reached. An experiment was devised to test whether the pool cover or the stabiliser would be more effective at retaining chlorine concentrations, however the results …show more content…

For a pool to be safe and comfortable to swim in the pH cannot be too acidic or basic, as both acids and bases are corrosive. The ideal pH for a pool is between 7 and 7.6, with a lower pH causing eye irritation, and a higher pH causing skin rashes (Victoria State Government, 2017).

Pool chlorine levels can be difficult to maintain as both OCl- and HOCl are subject to rapid decomposition under UV rays from sunlight (photolysis), and a high exposure day can reduce chlorination by up to 90 percent in just two hours. The chemical decomposition for both free chlorines are demonstrated in reactions 2 and 3 (Becker, 2018).

There are multiple methods used to stop the effects of sunlight, one such being chlorine stabilisers. The most common stabiliser is isocyanuric acid ((CONH)3) which bonds with the hypochlorite ions to form dichloroisocyanuric acid (C3O3N3Cl2H), which is stabilised chlorine (reaction 4) (Smith, et al., …show more content…

Since there is no light causing photolysis the chlorine should remain unaffected and undergo a slow ‘natural’ decomposition over time. Contrary to this, the light sample should have the highest chlorine loss, as there is no protection at all and the chlorine is under constant exposure to UV light, hence the highest rate of decomposition. The cover and stabiliser samples should fall between these two extremes, and over all the chlorine concentration of all samples should decrease. The pH of all samples should trend toward 7, as the NaOCl causes higher alkalinity, and as it breaks down and the chlorine is decomposed, it should decrease to approach the pH of water. However, since the (CNOH)3 is an acid, it would be expected that the pH drops significantly after adding, before the rate of pH decrease stabilises and becomes more

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