Detecting free Iron :   Spray the surface with a solution of potassium ferricyanide. If free iron is present, a blue color will appear. This test is extremely sensitive and often gives false positive results, that is, it gives an indication of iron being present when it really is not. The ferroxyl solution must be made fresh each day by addition with Nitric acid. The ferroxyl tests are described in ASTM A380.


Ferroxyl indicator is a solution containing potassium hexacyanoferrate(III) and phenolphthalein. It turns blue in the presence of Fe2+ ions, pink in the presence of hydroxide ions, it can be used to detect metal oxidation. It is often used to detect rusting in various situations.

It can be prepared by dissolving 10g sodium chloride and 1g potassium hexacyanoferrate(III) in distilled water, adding 10 cm3 phenolphthalein indicator, then making up to 500 cm3 with distilled water.

Personal Protective Equipment (PPE):

• Wear protective gloves: Choose gloves that are impermeable to tellurium. 
• Wear protective clothing: Wear clothing that covers exposed skin. 
• Wear eye protection: Use goggles or a face shield to protect eyes from dust. 
• Wear a dust mask: Use a dust mask (like an N95) to prevent inhalation of dust.

Acidic water causing problems for system. Acid neutralizer help to raise the pH levels.