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Tests for Chlorate and Perchlorate

The ability to be able to tell what, and how much of what, is in your product is very useful. The ability to test for trace amounts of Chlorate in Perchlorate is particularly useful when it comes to making other Perchlorates from Sodium Perchlorate especially Ammonium Perchlorate as you don't want any Ammonium Chlorate to be formed under any circumstances. The presence of small amount of Chlorate in Perchlorate is ok so long as you are aware of the problems/dangers that it poses. The problems arise when someone thinks that having 99% Perchlorate + 1% Chlorate is similar to having pure Perchlorate. This is not the case.
In order to ascertain how much Chlorate you have in a product you must do a titration. Another way is to destroy all of the Chlorate in the product and weigh the product before and after in order to ascertain how much Chlorate was there in the first place. This will not work if you have Chlorate and Perchlorate together. Wouters page explains this in detail and will not be repeated here. The following is some very useful tests that are quick and easy to do. Some of the chemicals will have to be purchased from the Lab supply store. It should by noted that some of the tests below will work better (or it is sometimes essential) if a SOLID sample of what you are testing is added to the reagent. You will have to take out some of the liquid sample and dry it on a watch glass and use the solid obtained, for the test.

Perchlorate tests

Methylene blue

The following test for Perchlorate is very useful when you are making Perchlorate by letting a Chlorate cell run and run untill all the salt/Chlorate has been converted to Perchlorate. This test will tell you when Perchlorate has started to form. This usually happens at about 10% Chloride concentration.
Methylene blue is used for staining specimens that are to be examined under a microscope. It may be possible to purchase it in a shop that sells dyes.
A 0.3% solution of Methylene blue is made by dissolving 0.3 grams Methylene blue in 100ml water. When a drop of this is put into a (liquid) sample from a cell that has Perchlorate in it the Methylene blue will form an insoluble purple coloured compound and you will get a purple precipitate. The solution should not be acid, if it is the purple ppt. will dissolve and you wont see it. It is fairly sensitive and will detect perchlorate levels at one gram per litre or less. You should add the methylene blue to the sample to be tested for to see the color change.
Nitrates form a blue precipitate which remains blue - so could interfere if nitrates are present.

Potassium Chloride

A very handy and simple test for Perchlorate that can be useful is to add a drop of concentrated KCl to a samply of a solution that you want to test. Since Potassium Perchlorate is not very soluble you will get an IMMEDIATE white precipitate of K Perchlorate. This test cannot (obviously) be used to detect K Perchlorate. The test is surprisingly sensitive. The test samply should be as cold as possible to get the best sensitivity. If the you are testing a very concentrated solution of Sodium Chlorate for the presence of Perchlorate you may mistake the precipitate of K Chlorate that you may get (since the solution is very concentrated). Dilute your solution a bit so that you are not getting a precipitate of K Chlorate.

Chlorate tests

N-Phenylanthranilic Acid

See Wouters page
This will have to be purchased from a lab supply store. It is added to some concentrated sulphuric acid. A red, orange or yellow colour indicates the presence of Chlorate in a Perchlorate sample. The test is fairly sensitive.

Mix about 0.1g of the phenylanthranilic acid with about 15cc concentrated Sulphuric acid to give a blackish/blueish solution. Some of the solid sample to be tested is put in the bottom of a small (preferable white) container and a few drops of the reagent added and put in contact with the sample. The colours above will appear if Chlorate is present. Be careful and do not use too much Perchlorate sample because if it contains alot of Chlorate you may get splattering when the Chlorate reacts violently with the concentrated acid.
You can also use the test by adding the test reagent to a sample of dissolved Perchlorate to be tested. This can be problematic because if the test reagent is made up for a period of time it seems to give a yellow colour when added to pure water.
The sensitivity of the test in solutions is thus:
A 0.4 g/l KClO3 solution gives a just barely visible discoloration. The best is to do the test both on clean water and on the unknown. If you then compare the colors of the precipitates side by side you can spot the yellow color more easily if you are testing low concentrations. For concentrations above 2 g/l or so this is not really necessary. The concentration of the indicator may also make a difference. 26.3 mg phenylanthranilic acid in 2.00 ml of 96% Sulfuric acid was used to prepare the indicator solution used here.
Be careful
A few drops of indicator solution was left over. A tiny bit of solid KClO3 was dropped into it. Two seconds later a -bang- followed. ClO2 I guess.
Lesson:
Be careful you don't have pure or nearly pure Chlorate as it will react when it comes into contact with the sulphuric acid.

Aniline Reagent

The Aniline Reagent is made by adding 3.6grams of Aniline to 100ml of 17% HCl acid solution. The 100ml of acid can be made by adding 50ml water to 50ml concentrated (35%) HCl acid. The 2g sample of solution (use solid for maximum sensitivity) is mixed with about 2ml of the reagent and 0.5ml water added. If Chlorate is plentyful you will get a red colour immediately which will turn to dark blue. If Chlorates are only there in smallish amounts, a blue or green colour appears within 30 minutes.
A solid sample can be added directly to the reagent and the solid left sitting on the bottom of the container. A blue colour will be seen on/at the sample if Chlorate is present.
Note: You can compare the Chlorate content by comparing the colour obtained from your test, with the colour obtained with solutions of pure Chlorate of known contents. I don't know if coloured solutions made up from known Chlorate concentrations will hold there colours for long periods of time. If they do hold their colours for long periods of time, then this test would be a good way to do a "quick and dirty" titration. You would simply have a row of coloured bottles for to compare your unknown with.

Aniline Sulphate

A small quantity (less than 0.5g) of the solid is mixed with 1ml of concentrated sulphuric acid and 2-3ml of aqueous aniline sulphate solution added. A deep blue colour is obtained if Chlorate is present. Sensitivity of this test is not known.

Indigo Carmine

Indigo Carmine is used for microscopical staining (similar to the methylene blue)
It will have to be purchased from a lab supply store. It is fairly expensive per gram but you will only need a few grams for to do alot of tests. This test in used in US Patent No. 2,392,769.
This test is extremely sensitive and will detect Chlorate levels down to parts per million.
A sample of the electrolyzed cell solution is added to a test indicator made of one gram per litre indigo carmine. The test is made by mixing 1ml of the indigo carmine with 5ml of concentrated Hydrochloric acid, and the mixture heated to boiling, To this boiling mixture, 5ml of the cell solution are added. Five parts per million of Chlorate will cause a sharp decoloration of the indicator, and one part per million can be detected. Sulphur Dioxide does not interfere with this procedure so it will be suitable for use with all the sulphite chemicals when destroying Chlorate.

Manganous Sulphate-Phosphoric Acid

Manganous Sulphate in syrupy (concentrated) Phosphoric acid solution reacts with Chlorates to form the violet coloured Mangani-Phosphate ion:
6Mn++ + 12PO4- - - + 6H+ + ClO3 - === 6[Mn(PO4)2]- - - + Cl - + 3H2O
Persulphates, nitrates, bromates, iodates and aslo periodates react similarly.
A drop of the test solution is put into a micro crucible and a drop of the reagent is added. Warm rapidly over a micro burner and allow to cool. A violet coloration appears. Very pale colorations may be intensified by adding a drop of 1% alcoholic diphenylcarbazide solution when a deep violet colour, dur to an oxidation product of the diphenylcarbaxide, is obtained.
Sensitivity: 0.05 ug (micro grams). ClO -.
Concentration: 1 in 1,000,000.
The reagent is made up by adding equal volumes of concentrated phosphoric acid and saturated manganese (II) sulphate solution.

Hypochlorites

Starch-Iodide paper

This can be purchased from lab supply house and is cheap. Dip a strip of KI-starch paper into the solution and if the paper does not turn immediately blueish/blackish, hypochlorites are absent. If there are alot of hypochlorites present the starch paper will not turn blue immediately but will be bleached by the hypochlorite. Take the paper out of the solution and hold it for a while and the paper at the solution edge (where it was wetted to) will turn blue after about 20 seconds if there are hypochlorites present.

Hypochlorites can be hard to eliminate completely by boiling the solution.
Hypochlorites can be destroyed be adding urea or formate to the solution, about 1g/l is usually sufficient, and heating a bit.

Chlorites

If hypochlorites are absent, add about 2ml of 0.1 N sulfuric acid to about 20ml of your solution and dip the KI-starch paper into it. If it does not turn immediately blue, chlorites are absent