denox process with formic acid..

[naandesh]

dear friends,
first thanks all of members who guide and support me. I learn by try and error formula ...get 8mg pure gold with 8 pinless processor and 6no. ram stick. it is reasonable or I loose some gold? now I try next batch denoxing AR with formic acid please give advice for it. how can identify AR solution are free with nitric?
thanks with regards...........

 

[Lou]

It won’t be an AR solution with nitric.

Buy an ORP meter. Voltage less than 500 mV

 

[rickbb]

I've not heard of using formic acid to de-NOx, I use sulfamic acid.

Some people use a sacrificial gold bead they put in the AR, when the gold stops dissolving you no longer have free nitric in solution.

Once you have a feel for how much gold your feed stock will yield you can calculate how much nitric to use and won't have much nitric to de-NOx. Search the forum, the information on this is here.

 

[naandesh]

It won’t be an AR solution with nitric.

Buy an ORP meter. Voltage less than 500 mV

confused.... I want to know denoxing process for aqua regia.... remove excess nitric acid by formic acid,,

 

[Yggdrasil]

I think Lou had a small typing error.
I belive it should be: without nitric it is not an AR solution, please correct me if I'm wrong.

Where did you find the information about using Formic acid to denoxx?
It may be that as the PMs precipitate the will redissolve until the nitric is gone.
First time I have ever heard about that, Sulfamic acid on the other hand, is effective,
I have not used it myself so the ones that have may give some information on that part.

Best is to not use to much Nitric in the first place.

 

[acpeacemaker]

It won’t be an AR solution with nitric.

Buy an ORP meter. Voltage less than 500 mV

HF?

 

[Lou]

HF as in hydrogen fluoride, or HF as in Harbor Freight?

 

[rickbb]

A quick google, (actually a duckduckgo search), found this on useless tube. May be where he is getting the info.

https://www.youtube.com/watch?v=gt08Wp6ygEY

 

[naandesh]

A quick google, (actually a duckduckgo search), found this on useless tube. May be where he is getting the info.

https://www.youtube.com/watch?v=gt08Wp6ygEY

hi rickbb,
i see this youtube video before post this query but its not satisfied me. something miss in chemistry. now i put my vessel to evaporating process ... gole is reduced 25 to 30% volume at 80 degree, cos 25% of nitric in whole solution by volume. i guess its work...well as my calculation after evaporation add formic acid kill some free nitric acid (3CH2O2 + 2HNO3 = 3CO2 + 4H2O + 2NO). IS I M RIGHT?

 

[acpeacemaker]

HF as in hydrogen fluoride, or HF as in Harbor Freight?

Hey,
Sorry Lou, I was referring to hydrofluoric.
Thought maybe you cracked a door saying it wont be an ar solution with nitric to maybe see if someone would open it lol.

Pdf on Formic with some info on hydrofluoric and hydrogen fluoride gasses.

https://tinyurl.com/s8ejm4v

 

[Lino1406]

Formic acid will de-nox, only it may need time, heat

 

[anachronism]

Formic acid will de-nox, only it may need time, heat

Yep a lot of heat. But a hot solution of AR does a lot of its own denox over time anyway.

 

[Lou]

Is he unable to use sulfamic or better yet, just use only enough nitric as required?

 

[rickzeien]

Is he unable to use sulfamic or better yet, just use only enough nitric as required?

This is two of the best processes I learned here on the forum.

The OP would do well to practice them.

Thanks GRF!

Sent from my SM-G950U using Tapatalk

 

[Alliedft]

Use less nitric at the start you can always add more but you waste if you have to denox. Easiest way to denox without chemicals is to reduce as much as possible add hcl, reduce again then all nitric will be gone unless you went way overboard.

 

[naandesh]

Use less nitric at the start you can always add more but you waste if you have to denox. Easiest way to denox without chemicals is to reduce as much as possible add hcl, reduce again then all nitric will be gone unless you went way overboard.

yes, next batch I will do as per your advice thanks for suggestion.....

 

[g_axelsson]

Just evaporate down to a thick solution, add a small bit of HCl. Repeat as needed. When there isn't a brown cloud of NOx when adding HCl you are done. Then go on and recover the gold with your method of preference. For example SMB, copperas, cementing...

It's all described in Hoke and on the forum many times.

I don't remember ever heard of denoxing with formic acid before.

Göran