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From Wikipedia

Nitrate test

A nitrate test is a chemical test used to determine the presence of nitrate ion in solution. Testing for the presence of nitrate via wet chemistry is generally difficult compared with testing for other anions, as almost all nitrates are soluble in water. In contrast, many common ions give insoluble salts, e.g. halides precipitate with silver, and sulfates precipitate with barium.

The nitrate anion is an oxidizer, and many tests for the nitrate anion are based on this property. Unfortunately, other oxidants present in the analyte may interfere and give erroneous results.

Brown ring test

A common nitrate test, known as the brown ring test can be performed by adding iron(II) sulfate to a solution of a nitrate, then slowly adding concentrated sulfuric acid such that the sulfuric acid forms a layer above the aqueous solution. A brown ring will form at the juction of the two layers, indicating the presence of the nitrate ion. Note that the presence of nitrite ions will interfere with this test.

The overall reaction is the reduction of the nitrate ion by iron(II) which is oxidised to iron(III) and formation of a nitrosyl complex.

NO3- + 3Fe2+ + 4H+→ 3Fe3+ + NO + 2H2O
[Fe(H2O)6]2+ + NO → [Fe(H2O)5(NO)]2+

Devarda's test

Devarda's alloy (Cu/Al/Zn) is a reducing agent. When reacted with nitrate in sodium hydroxide solution, ammonia is liberated. The ammonia formed may be detected by its characteristic odor, and by moist red litmus — very few gases other than ammonia evolved from wet chemistry are alkaline.

3 NO|3|- + 8 Al + 5 OH|- + 18 H|2|O → 3 NH|3 + 8 [Al(OH)|4|]|-

The aluminium does the reducing in this reaction.

Diphenylamine test

Diphenylamine may be used as a wet chemical test for the presence of the nitrate ion. In this test, a solution of diphenylamine and ammonium chloride in sulfuric acid is used. In the presence of nitrates, diphenylamine is oxidized, giving a blue coloration. This reaction has been used to test for organic nitrates as well, and has found use in gunshot residue kits detecting nitroglycerine and nitrocellulose.

Other oxidants such as chlorate, bromate, etc. interfere by similarly oxidizing diphenylamine. They may be removed by reduction with sodium sulfite. Where nitrite is present, a false negative result may be observed due to sulfite reducing nitrate in the presence of nitrite.

The diphenylamine test may be selective for nitrate by reducing nitrite with sodium azide, prior to treatment with sodium sulfite. Other derivatives have been reported as well.

From Yahoo Answers

Question:Ok my 20 gallon marine tank is finished cycling and everything is fine EXCEPT for the diatoms at the bottom on the aragonite. i thought i was leaving the light on to long so i did not turn it on when i left for work this morning but when i get back its even worse The lighting i have is a Coral life 50/50 10000k 65w single linear strip How can i stop this please help its so irritating.

Answers:If the tank was finished cycling it wouldn't have diatoms. The diatoms are the result of nitrates. Diatoms are eating your nitrates up before they show up on a test kit. You may stir the sand/ gravel but no more than 1" deep. If you have sand look for a sand sifting goby in a store that IS sifting.This will aerate your substrate and keep it turned over. Cerith and Nerite snails eat diatoms readily. Keep up with large water changes, at least 10% weekly until it clears up. Also a 20 gallon will be a long hard fight with cyano and diatoms. I recommend researching the word "sump" and "refugium" and see if you can incorporate one into your system. It will be the best investment and can be done extremely cheaply with an old tank, silicone, and acrylic. Also, think of fish. Smaller fish will help with keep your tank clean and so will a good "clean up crew." I recommend sump, skimmer, and clean up crew before you ever consider adding fish. Also keep in mind that every fish you add starts a new mini cycle. You are adding more poop and food thus new ammonia, nitrite, then nitrates. So add a fish wait a month. It hurts but this hobby teaches patience before all else. Check out reefcentral.com for any other questions. You get alot of freshwater nuts in here and rarely find a saltwater expert. GL.

Question:I was given a mixture of salts with two acid and two basic radicals. I identified the basic radicals as Ba and K. I also found one of the acid radicals as Cl. But I suspect the other one is Br as I got 1) brown vapors on heating with conc. sulfuric acid( I am not sure if I get such on dry Test Tube Heating) 2) reddish brown gas was evolved when heated with the same along with manganese dioxide. But the problem is I cannot confirm Br in wet test as I am getting Chlorine too.(sure) But my Lab instructor said that it was Nitrate. I agree there may me nitrate,(I have not done Brown Ring Test and so cannot say) but how can I be sure that there is no Bromide ion.

Answers:the reddish brown gas sounds like nitrate how can I be sure that there is no Bromide ion? dissolve some in water, add a polar organic solvent like hexane, then add an oxidizer like chlorine/water ... & shake bromine will be produced in the presence of the chlorine, will dissolve into the hexane & color it orange

Question:I ve set up my marine tank for 3 months now. All water test kit shows all okay. I have two clown fish and two cleaner shrimp. Should I get some hermit crabs and snails? Do they go together with the cleaner shrimps? How else do I get rid of the brown algae?

Answers:Do a water test, too many nitrites/nitrates or amonia will sometimes cause an brown algae bloom, I am guessing that the algae is covering the rocks and you may have just set up a brand new tank and it needs to run it's course, before it will leave and your tank will be picture pefect. Also add some damsel fishe they will establish good bacteria and Calurpa green algae will help filter your water naturally. . But due to the newness I am guessing that this is the reason for that algae, my tank went through that phase too, I would scrub off the algae in a bucket of salt water I had saved from a water change. Try adding water to top it off instead of doing a regular change, use fresh de-chlorinated water to top it off to where it was before evaporation, so you do not unknowningly raise the salinity over time. tay on top of it and do not change a lot of water at once either, your tank will have to start over. Cleaner Shrimp form symbiotic relationships with other marine creatures, mainly vertabrates cleaning paracites fron the gills, scales etc, they do not eat algae. Snails are grazers and may eat a bit of it but usually eat green macro algae attached to the substrate.

Question:we pour 1 mL of hexane with 3 drops of KMnO4 and cover with cork and then shake... we do the same test with Benzene. but our assignment is about the equation.but we haven't yet discuss about equation....i hope you can help me...thank you

Answers:Hexane is not going to react with the oxidizing agent, KMnO4. Hexene will however to form a vicinal diol (two hydroxy substituents on adjacent carbons). This is confirmed by the loss of purple permangante color and the formation of a brown precipitate, MnO2. Benzene however will not react with the permanganate since the resonance of the benzene ring (aromaticity, specifically) renders it more stable, and less prone to oxidation. The equation would depend on what alkene was used and the position of the double bond, but you will end up with a vicinal diol and manganese (IV) oxide.

From Youtube

How to Test if Fertilizer Has Nitrates in it :In this video we show you how to test if a fertilizer has nitrates rather than urea or ammonia as its nitrogen source. The idea is quit simple, in a strongly acidic solution the nitrates will behave like nitric acid and dissolve copper metal releasing nitrogen dioxide gas. Looking for this gas is a strong indication for the presence of nitrates. WARNING: these reactions produce toxic nitrogen dioxide gas, this must be performed outside or in a fume hood. To perform the test, simply mix some of your fertilizer with water to dissolve the nitrates and then mix it with hydrochloric acid. Then add in some copper metal. The reaction is very slow to start up unless you heat it. A nerdy way of heating it on the spot without using a heater is to add a small ball of aluminum metal, don't use too much or it will go out of control. Stir the mixture as the aluminum dissolves to distribute the heat evenly. After the mixture is heated, place a glass container over the mixture to keep the gases in. If nitrogen dioxide is forming the distinctive brown nitrogen dioxide will fill the container. And that's how you can tell if there are nitrates in your fertilizer. If you want to test for ammonia (in case you have ammonium nitrate) just mix some fertilizer with half as much sodium hydroxide and add a little water to cover it. If it starts bubbling and releasing ammonia gas then it contains ammonia. Our website www.nurdrage.com For more information on the chemistry visit the web page at sites ...

Episode 4: Test for Nitrite Ion :Hello Chemists. Today I will be performing the test for Nitrite. Off Camera I mixed Potassium Nitrate and Sugar in a 50/50 Ratio. I ignited the mixture and dissolved the burn residue in water. This was then filtered to remove undissolved carbon. I prepared a fairly dilute solution of Iron(II) Sulfate and carefully added 3mL of Concentrated Sulfuric Acid to acidify it. I poured the residue solution into the Iron Sulfate and Sulfuric Acid mixture. The brown color shows a positive result for Nitrite.