Dear Raja,

you are correct that for electrochemical measurements you need really pure water, because a lot of contaminants will give their own specific electrochemical signals on VA curves etc. The most common method for preparation of your aqueous electrolyte for electrochemical experiments is usually deionization (MiliQ, Milipore methods, etc). There are various methods to obtain deionized water, and a lot of equipment for its generation is commercially available. The measured value of water resistance is usually provided as an indicator of its purity, with values above ~20 MΩ/cm considered deionized.

If your system is extremely sensitive to impurities, there are some specific methods for ultrapurification of water (ex. B. E. Conway, H. Angerstein-Kozlowska, W. B. A. Sharp, E. E. Criddle, Anal. Chem., 1973, 45 (8), pp 1331–1336).

Double distillation, as you ask, is actually pretty simple - you distill water according to the usual process, and then distill it again, thus trying to reduce salt content in it. From my experience, distilled water is not really good for fine electrochemical measurements, since remaining salts in it affect your measurements, and moreover, salt content from batch to batch can differ, which can lead to unexpected measurement errors in consequent experiments.

Hope it helps!

Electro chemical experiments normally require mineral free water.  which should be

Based on my previous experience, which turned out to be absolutely successful, i suggest you the following procedure which is quite easy.

1. Distill water using any distillation plant you have in your lab.

2. To the distilled water you get, add a very small amount of Potassium Permanganate, and redistill it. This will give you Double Distilled Water.

3. To the Double Distilled Water, add a very small amount of Potassium Dichromate and distill it. The final water you get will be Triple Distilled water , and will be free from ions, usually found in water.

    I applied this approach to get TDW for the synthesis of Manganese Ferrite Nanoparticles, and the characterization of the nanoparticles by various techniques e.g., EDX, confirmed that the samples were completely pure.

while preparing distill water with KMnO4, the colour changes from pink (when heated),,,

is there anything, I have to change or add some more kmno4 or ....