Iron test kits

Hello everybody

I was asked for the recipe for Iron test kits the other day and here is 
the recipe

A 20% Potassium thiocyanatesolution with 1M HCl or HNO3.
The post the other day was wrong where I said that it was Sulphuric acid, 
it should not be used because it can form complexes with the iron and 
reduce the colour development. Phosphate is a serious inhibitor of colour 
development and I personally beleive that colour development under these 
conditions may take several hours (not the three minutes that sera test 
kits recommend).

All of the tests that are used in the aquarium test kits can be found in 
the book "Vogel's text book of quantitative inorganic analysis". There 
are three "Vogel's" make sure that you get the quantitative one and not 
the qualitative or organic ones.

Peter Hughes