Chemical Forums
Chemistry Forums for Students => Inorganic Chemistry Forum => Topic started by: Gerbil on March 05, 2013, 10:24:30 AM
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I use an ammonia test kit to test the water in my fish tank.
The chemicals are supplied in two bottles and are as follows:
1. polyethylene glycol and sodium salicylate (this is colourless)
2. sodium hydroxide and sodium hypochlorite (this is colourless)
When these chemicals are mixed into a sample of water the initial colour is a bright yellow (before the blue dye develops and turns the sample green in the presence of ammonia). Is anyone able to tell me what reaction is occurring to produce this initial colour?
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The Salicylate Method
References: Krom, Michael D., Spectrophotometric Determination of Ammonia: A Study of a Modified Berthelot Reduction Using Salicylate and Dichloroisocyanurate, The Analyst, V105, pp. 305-316, 1980.
In the ammonia test method that employs the Salicylate chemistry, free ammonia reacts with hypochlorite to form monochloramine. Monochloramine reacts with salicylate, in the presence of sodium nitro-ferricyanide, to form 5-aminosalicylate, a green-colored complex. This test method measures free ammonia and monochloramine. Results are expressed in ppm (mg/L) ammonia- nitrogen, NH3-N.
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Thanks Hunter2 but unfortunately that doesn't answer my question. I'm aware of how the salicylate test works but there's no information on what reaction takes place to produce the initial bright yellow colour that appears immediately the chemicals are mixed. This colour occurs whether the sample contains ammonia or not.
Anyone clarify?
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I think the Nitroferricyanide is yellow.
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I think the Nitroferricyanide is yellow.
No, as I indicated in the first post, both chemicals from the bottle are colourless. They instantly turn bright yellow when mixed. This particular version of the test doesn't use nitro-ferricyanide (it acts as a catalyst when it is used).
However, assuming that one of the bottles does contain nitro-ferricyanide, what reaction would be taking place to instantly turn two colourless reagents a bright yellow?