What is the procedure you follow? Anything else in the solution?
My procedure is like this:
I use dried material(cu concentrate)in a 400 ml beaker. I add 10 ml HCl then 5 ml HNO3. When reaction finishes I add water in it and wait to dry,then 10 ml h2so4 1/1 for around 50 mins.After it,I add water and some drops of h2o2 and wait for boiling. I filtrate with blue filter.From the filtrated solution I take 100
Ml and add 1 spoon of nh4cl and boil again. Then precipitate it with nh4 and filtrate with black filter. Afer i leave around one hour in hot plate solution is ready (i let it to be cold)
Before titration: i add hcl 1/1 till color becomes from blue to white
Again nh4 1/1 till solution becomes blue, then I add buffer( ph 5,5) and at the end two drops of xylenol orange.
I hope i was clear…