ISO 9001:2015 REGISTERED FIRM Precious Metal Manufacturer and Distributor

Cyanide DOES degrade when heated but, the temps usually have to be higher than 85C. A quick search shows greater than 170C for significant degradation and a much slower process at lower temperatures.

Mitigating Cyanide in solution, I have feedback where they use Sodium Hypochlorite in their destruct process before it is sent to wastewater treatment.  What I am unsure on is the sequence.   You can certainly add bleach to kill the cyanide but I’m not sure you would want that in your rinse tanks as it could have an effect on your part. 

A good option is a Gold Bug.  The Gold bug claims to destroy cyanide.  What I understand is it does that by breaking the bond between the metal and the cyanide making it a cyanate after it is oxidized.  We do sell the gold bugs if interested.   https://preciousmetals-pmpc.com/products/gold-bug/

Here's a good explanation of cyanide destruction by the Hach Company.  Hach also sells cyanide detection test kits in the ppm range which is what you may want to consider.

https://cdn.hach.com/7FYZVWYB/at/6z2h49q7hmx7jbmv95vp59c/Cyanide_Waste_Treatment.pdf

 For detection of free CN feedback is a simple titration method could work.   Here was some feedback:

TITRATION:

1. Pipette 5 ml of sample into a 250 ml Erlenmeyer flask containing

approximately 100 ml of DI water.

2. Add 2 ml of 20% KI.
3. While stirring, titrate with 0.1 N Silver Nitrate (AgNO3) to a yellow pearlescent

endpoint.

CALCULATION: Free CN (gm/l) = ml AgNO3 x 2.6

As far as real time tracking of CN levels in bath I can’t provide a recommendation.  As I mentioned we know some workers will wear a personal CN monitor but that is for CN in the air not the water.  I know they make Cyanide selective electrodes that you could use to set up with a benchtop detection sensor. https://www.thermofisher.com/order/catalog/product/9606BNWP 

I don’t have any personal experience with these, but they look pretty slick. 

The spec for antimony in PGC is less than 5 ppm. In conversations they have pulled an actual test and the test had less than one part per million in the test. That said I’m very comfortable in saying there’s not materially any antimony in the product. Just note less than 5 ppm is the specification.  

Cut a 1" x 2" coupon from a Hull Cell panel. Punch a hole and attach a wire to the panel. Weigh the panel and wire on a gram scale. Fill a 500 ml beaker with your gold bath, insert inert anodes, heat to proper temperature, and agitate. Plate the coupon at .25 amp for 10 minutes. Dry the panel and wire and reweigh. Divide the weight gained by 2.5 to achieve the efficiency measured in mg / amp minutes. For hard gold, approximately 45 mg/amp min equals 100% efficiency.

Add a weighed 1" x 1/2" coupon to the rack or in the barrel with your parts just before they go onto the gold bath. After gold plating, remove the coupon, dry, and reweigh. For a hard gold bath, divide the mg gained by 28.7 mg/sqin. Multiply the result by 100 to give you the estimated thickness in microinches. For a pure gold bath, divide the mg gained by 31.6 mg/sqin. Multiply by 100 to give you the estimated thickness in microinches.

Every gold bath has a narrow range of temperature, current density, and pH parameters under which the bath operates. Making minor adjustments in 1, 2, or all 3 parameters can change the softness or hardness of the deposit.  Generally: The higher the purity, the softer the deposit. The higher the temperature...the higher the purity of the deposit. The lower the current density... the higher the purity of the deposit. The higher the pH...the higher the purity of deposit.

Pure gold is equal to 24 karats. 18 karat gold means 6/24's or 25% is some other metal alloyed with the gold.

Pennyweights are a unit of measurement for precious metals that is mostly used only in the jewelry business. It originates from medieval time in England when an English Penny had to weigh exactly 1/20 of a Troy Ounce. Thus, 1 Troy Ounce equals 20 Pennyweights.

KH25 means Knoop Hardness under a 25 gram load. Knoop is a hardness measurement used for thin layers of precious metals. You start with a polished cross-section sample of the gold deposit. Using a Knoop hardness indenter with a microscope accurate to 0.5 micrometers, a rhombohedral shaped diamond indenter is dropped on the gold deposit under a 25 gram load. The long diagonal of the indent is measured.

The KH₂₅ hardness = 14.299 x L divided by d². Where L is the load (25 grams) and d is the length of the long diagonal measured in micrometers.