Annie choi

Cobalt chloride hexahydrate

Discussion created by Annie choi on Nov 18, 2014
Latest reply on Nov 24, 2014 by James Francis


I have some questions about 'Reagent chemicals 10th edition' test method.


When I tested 'Cobalt chloride
hexahydrate-Nitrate test', Part 4. Monographs for reagent chemicals. book page

It refers to measure the absorbance of sample, control, blank. and calculate
by followed formula.


After tested that, absorbance value was like below.

* Sample value : -0.0508 (at 410 nm)

* Control value : 0.1526 (at 410 nm)


So I input this data to calculation fomula.

%NO3 = sample / (control - sample) = -0.0508 / (0.1526-(-0.0508)) = -0.24%


Here is questions,

I wonder sample value can be minus quantity (Is it possible and acceptable

Also %NO3 could be shown minus percent? does that mean nitrate is not
exist (or little) in cobalt chloride hexahydrate?


We followed reagent chemicals test recipe well.


Please, answer this questions. it will be helpful to test this compound.

I hope to receive your respond soon.