Thread: What is calcium Nitrate used for in this method?

ok, so this is all about a silver nitrate titration to determine cyanide.

5g of sodium cyanide is weighed out. This is put into a 250 ml volumetric flask with 85 ml calcium nitrate and topped up with deionized water. this is left to settle for 30 minutes. then its filtered.

25 ml is then measured into a flask along with 75 ml of water, this is then titrated to find cyanide and cyanate concentrations.

my quest is, what is the calcium nitrate used for in this method?

thanks for any help you can provide


Edit: Also, is there anything in this reaction other than cyanide that would react with NaClO?

Originally Posted by james2409

ok, so this is all about a silver nitrate titration to determine cyanide.

5g of sodium cyanide is weighed out. This is put into a 250 ml volumetric flask with 85 ml calcium nitrate and topped up with deionized water. this is left to settle for 30 minutes. then its filtered.

25 ml is then measured into a flask along with 75 ml of water, this is then titrated to find cyanide and cyanate concentrations.

my quest is, what is the calcium nitrate used for in this method?

thanks for any help you can provide


Edit: Also, is there anything in this reaction other than cyanide that would react with NaClO?

I am not expert in this but did find that carbonate can build up in cyanide plating baths: Removing/freezing excess carbonate from cyanide silver plating tanks

CaNO3 would obviously react with soluble carbonate to form insoluble CaCO3 which would settle and could be removed by filtration.

Further research on the web suggest that cyanide solutions tend to absorb CO2 from the air, forming carbonic acid which can then react with CN- to form HCN, and the corresponding carbonate.

So in summary, it looks to me as if the CaNO3 is to get rid of CO3 2- formed by reaction of CN- with atmospheric CO2.

Would this make sense?

By the way, these are not titrations I would fancy doing at all. Sounds effing dangerous to me.

Yes thanks this helps quite a bit.

they aren't too bad, just make sure to wear appropriate PPE and use a fume cupboard.

and of course dispose of it properly