what does WDFA colour index (in chemistry) refer to?

Question

for eg. eriochrome black T is also called WDFA no 2 i think. but what does WDFA here stand for? where can i get more information about it? is it an industry-based colour index?

actually i was wrong, eriochrome black t is WDFA no 203..
but i still havent got any answers!!!!!!!

yeah... actually i had a chemistry project on EDTA titrations using eriochrome black -T. so when i was searching on the internet, i came across this name for eriochrome black - T..- WDFA no 203//// anyway thanks for ur help.... but i couldnt find anything!!!!!

Answer 1

Eriochrome Black T is a dye that can be used as an indicator in some reactions.

This means that it might change from a blue color to a reddish color when it "forms complex with calcium, magnesium, or other metal ions".

Might you be thinking of a EDTA (ethylenediaminetetraacetic acid) titration reaction, perhaps referring to what color it changes to?

Does this help? Is there any more information you can provide?
Where did you hear of this from?


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Edit:
It appears that it may be an index code used by The ICI company ("A major paints, adhesives and specialty products company")