Dear Rod:

I recall a qualitative method from "Spot Tests in Inorganic Analysis" (Feigl) regarding
chromates.  You may need to refer to the text for the exact analysis.  However, as best
I can recall, the method was as follows.  (Incidentally, we used this method as a means
of evaluating the effectiveness of acid cleaners at removing chromate/zincate
conversion coatings during the early development of such cleaners.)

Reagents
Phosphoric/sulfuric acid (75% v/v phosphoric acid (85% w/w) and 25% sulfuric acid (98%
w/w)
di-para-nitrodiphenylcarbazide (0.1% w/w in ethanol)

Procedure
1.  Place 3-4 drops of the phosphoric/sulfuric acid solution on the surface of the
copper to be tested.
2.  Wait 1-2 minutes then add 1 drop of the diphenylcarbazide indicator.  Formation of
a violet color indicates the presence of chromate.

The test should be performed on copper free of chromates to assure no interference from
copper ions.

Regards,

Ted Stern


Rod Semen wrote:

> Does anybody know of a quick test to see if I am removing chromate
> coating on laminate foil? I know about EDX, but I want to do this in
> our lab.
>
> Thanks,
>
> Rod
>
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