Sciencemadness Discussion Board

NaOH in hotel swimming pool ?

metalresearcher - 7-2-2011 at 11:18

During my holiday in a hotel in La Palma (Canary Islands) I watched what pool chemicals thy used: I found several jerrycans of a concentrated NaOH solution and as pool desinfectant I found 'granular chlorine' UN 2468 which should be Trichloroisocyanuric acid which should be no acid at all as it contains no hydrogen.

Why so much NaOH ?


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rrkss - 7-2-2011 at 11:30

chlorine stays in solution as the hypochlorite ion when the water is alkaline and gases off as chlorine gas when the water becomes more acidic.

bbartlog - 7-2-2011 at 13:45

TCCA hydrolyzes to hypochlorous acid and cyanuric acid. Leading to the situation rrkss describes.

Ozone - 7-2-2011 at 16:18

It also causes all of the Fe ions to precipitate as colloidal Fe(OH)2, which can be easily removed with the pool vacuum.

O3

BromicAcid - 7-2-2011 at 17:56

People swimming and doing their business in the pool wreaks all kinds of havoc with the pH and organic content. Combined with the effects of the suns rays and the atmosphere adjustments of the pH are usually done on a somewhat regular basis. Sodium hydrogen sulfate for acid and sodium carbonate or bicarb for base. NaOH is occasionally used by some 'trained' individuals, usually the same people that insist on using elemental chlorine. It's always interesting to do pool chemistry on a large pool and calculate out how much base you need only to find that 25 kg unit you just bought is insufficient ;)