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Ted Mooney, P.E. RET
Pine Beach, NJ

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Problem related to cyanide addition

Q. I am facing problem when I need to add sodium cyanide in copper alkaline and brass bath
when the bath is freshly prepared the amount of sodium cyanide which we add is about 115 g/l but the analysis result shows the amount of sodium cyanide is about 12-15 g/l I would like to know what is the mystery behind this that without any working the concentration will be goes that much down ? and after working about 100kg of material the concentration will become 7 g/l so how we calculate the amount of sodium cyanide to replenish the bath ?

thanks

Azhar Ali
- Pakistan
2007

"Analysis of Electroplating & Related Solutions"
by Langford & Parker

on Abebooks

or Amazon

(UTL on eBay)

(affil links)

"The Chemical Analysis of Electroplating Solutions"
by Terrance H Irvine
irvine_chemical_analysis

on eBay or

AbeBooks

or Amazon

(affil links)

A. Good afternoon,

Is your analysis determining the free cyanide in the baths? Have you taken into account the amount of cyanide that is used to complex the copper and zinc in the plating baths?

Steve Bizub
- St Louis, Missouri

A. Azhar,
There appears to be a mistake in the make up, or the analysis procedure for free sodium cyanide. Unless you have a heavy drag-out of solution there should be very little cyanide you should have to add. Upon bath make up are you heating the water to operating temp, then mixing in the sodium cyanide? Is it possible that some of it is settling on the bottom of the tank? I would also double check your analysis procedure with a given amount of cyanide in a beaker , check the concentration to rule out a bad batch of sodium cyanide.
It is impossible to give you an addition rate based on weight plated. All platers and lab personnel I know of determine free Cn by analysis.

Mark Baker
Process Engineer - Syracuse, New York

A. The titration only measures "free" cyanide. That which is complexed to copper is not detected. The addition of sodium hydroxide to the titration mixture will liberate that which is complexed to the zinc, in the case of the brass bath.

Dave Wichern
Consultant - The Bronx, New York

Q. hi,
it's Azhar ali from Pakistan I have sent a question related to cyanide addition in the alkaline copper and brass bath ... but still I didn't get a clear answer to my question. Now I am giving some details and hope this will help you to give me a clear answer.
We are following the titration procedure for cyanide determination which is given below

- take 5 ml of sample and add 100 ml of water
- then 10 ml of potassium iodide (10%) ⇦ this on eBay or Amazon [affil links]
- titrate with silver nitrate 0.1N ⇦ this on eBay or Amazon [affil links] till yellow color

Please tell me if there is any alternative method for cyanide determination..

NOTE:this method gives free cyanide content in the bath and we are interested in cyanide content; and if we have free cyanide content then how do we calculate total sodium cyanide content in the bath?

Azhar Ali [returning]
- Pakistan
2007

A. If adding 115 g/l of sodium cyanide raises the concentration of free cyanide by 12 - 15 g/l then adding 57.5 g/l of sodium cyanide will raise the free cyanide concentration by 6 - 7.5g/l.

John Martin
- Cardiff

A. All of the copper in the bath will be copper cyanide, so after initial makeup you do not care about the amount of cyanide as copper. You care greatly about the free cyanide. You also care about the amount of copper in the bath which is frequently referred to as copper cyanide, but it is really a copper analysis with the result of the titration multiplied by an appropriate factor to give the result as copper cyanide.
Since it requires the addition of a small amount of nitric acid, I will pass on giving the complete method. It is available in any number of reference books. Whoever you bought your copper cyanide salts from should be able to give it to you and may even have a tech services person to show you how to safely do it.

James Watts
- Navarre, Florida

A. Metal Finishing Guidebook & Directory 2005 issue,
Page 409,TableVII-Test method of Electroplating Solutions
Line 4.

Gives you the information you need.

Hamilton Solidum
- Mays Landing, New Jersey
2007

A. Doing the exact same analytical procedure with several ice cubes in with your sample will give you the free cyanide. The complexed cyanide will stay complexed and will not titrate.

James Economus
- Orange, California, U.S.A.
August 18, 2010

Q. Good day all,

I run my alkaline copper bath at 30 g/l copper metal content with specification from the supplier. The tank working volume is 350 liters.

I analyse the copper metal content using the PAN method, and the formula for the titration value is as follows:
A. Endpoint x 3.18 = g/l metal content
B. Endpoint x 4.48 = g/l copper cyanide

My queries are:
1. If I use formula 1, I can calculate the copper metal content in g/l.
For example, let's say I get 28.5 g/l of copper metal content. From the bath specification, 30 g/l - 28.5 g/l is 1.5 g/l. For 350 liters, 0.5 kgs will need to be added.

Now, what do I add?? Copper cyanide???
If I add copper cyanide, how much copper in copper cyanide will be replenished?
The cyanide in copper cyanide, what will it add to???

Please I need a valid statement on the addition of copper cyanide to replenish copper metal.
Thank you all.

Subdurally Rhiaz Muhammad
Laboratory technician - Port-Louis, Mauritius
April 23, 2013

A. In a cyanide Copper Electrolyte you add Copper cyanide to replenish the Copper content. But you need to be aware that the addition of Copper cyanide will reduce the amount of free cyanide in your solution, which also should be analysed. Reaction formula is : CuCN + 2NaCN -> Na2Cu[CN]3
From this you can also calculate the amounts you should add

For 1,5 g/l Cu you need to add 2,11 g/l CuCN. This will consume 2.33 g/l of your free NaCN to form the Copper-Cyanide Complex .

Marcus Hahn
- Zug, Switzerland

Dear Marcus Hahn,

I thank you for your response.
It was very detailed, and I found it very useful.
Thanks again.
Cheers

Subdurally Rhiaz Muhammad [returning]
- Port-Louis, Mauritius

Problem related to cyanide addition

Q. Added 100kg of sodium cyanide to a 30t tank ... is it good or does it have negative effects apart from being hazardous?

King Lito
Employees mining - Harare, Zimbabwe
November 13, 2024

A. Huh?

Sorry King, I have no idea what you're talking about. But maybe a reader from the mining industry will be able to read between the lines.

Luck & Regards,

ted_yosem
Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

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