Harold_V said:
goldsilverpro said:
With a little copper, the crystal is harder, denser, and shorter.
I'd fight you to my death over that comment. I processed WITHOUT the addition of copper and watched with each iteration as the silver crystals grew softer as copper accumulated. Never, once, did the absence of copper create soft crystals, and, in fact, it was the complete opposite. The first silver to be deposited was a sheet that was difficult to remove, followed by coarse crystals that adhered tightly to the cathode. As copper content rose, the crystals were much easier to dislodge, and as the copper content grew greater, thin threads of silver were the result. These results were consistent, time and again, as was my procedure. Had you made electrolyte without copper content, you, too, would have experienced much the same thing.
I'm not suggesting, not for a moment, that copper is the wrong approach---I witnessed the positive side of its use. I also witnessed the shorter electrolyte life, the result of copper accumulation.
I'm all for detailing the benefits of copper, but I'm not too keen on information I found to not be true. Copper does not make a harder deposit. It never did, not once, not for me. Do note that I also used a generous amount of silver in my electrolyte (30 ounces in about 2½ gallons).
Harold
Edit:
As an afterthought----can there be a connection between the industry standard for silver (999) and the process involved? The standard for electrolytic gold is 9999. I am of the opinion that the 999 standard for silver is due to the use of copper to improve conductivity, which also encourages co-deposition of copper. Thoughts?
H
I retract the word "harder" from my statement, mainly because I realize that you think of this term as related to such things as Vickers or DPH hardness. I shouldn't have used it. However, that doesn't change my basic argument.
A few of the quotes from T.K. Rose: "An electrolyte containing 60g Cu and 60g Ag per liter shows good conductivity and gives heavy, dense silver crystals." "Increase in silver content of the electrolytes causes the production of coarser crystals, while with the additions of copper the aggregates are more compact." "Mulligan(?) states that an increase in the copper content from 55 to 75gpl resulted in a better production of silver crystals." Whatever that means.
From Butts and Coxe. There is a chart which lists 5 large silver cell operations, including ASARCO and INCO, and the make up and operating conditions of each. The intentional copper concentration ranges from 7 to 80gpl in these facilities. In all cases, the anodes only contain Ag, Au, and Cu. In the anodes, the Ag ranges from 94% - 98.5%, the Cu from .3 to 1.2%, with the remainder Au. Quote: "The productions of the refineries described above range between 999.4 and 999.9 silver, with copper as the major impurity." It also says that - "The variations in silver and copper nitrate, and the ratio of one to the other, are based on obtaining certain objectives, such as:
(1) Efficient anode reaction
(2) Type of deposit desired for removal routine
(3) Consideration of anode impurities
(4) Maximum conductivity with minimum silver tie-up"
Harold, I've thought a lot about this. In looking at your cell, I think that, due to it's uniqueness, it is apples and oranges compared to the Moebius and Thum cells used in industry. The main difference I see (correct me if I'm wrong) is that the ratio of cathode area to anode area in your cell is much larger that the approx 1:1 in the Moebius cell and the approx. 1.5:1 in the Thum cell.
Besides the solution make-up, the factor that alters the deposit characteristics the most is the cathode current density, which (on average) is the total current divided by the area of the cathode. For the same amount of current, a larger cathode will have a lower current density than a smaller cathode. I don't know what your cathode area is, but if it's, say, 3 or 4 times greater than the anode area, the crystal characteristics could be appreciably different. If that is the case, I would think the data you've obtained would not necessarily be valid when applied to a traditional Moebius or Thum cell setup.
I'm not saying that your cell is good or bad and it obviously worked for your purposes. However, unless one has a SS cell exactly like yours, the results could be very different.
I usually started my solutions with 30gpl copper and got excellent crystal results. I had no way to determine whether or not I had 999.9 or not, but I always dissolved some well rinsed crystal, made a portion of this solution ammoniacal, and looked for any trace of blue against a white background. I never saw any blue unless my solution was completely out of whack, which was rare.
At one time there were probably 100s of 1000s of silver cells in existence. Silver cells are probably one of the most-studied piece of equipment ever. Everything was tried and the system was perfected - solution makeup, cathode/anode area ratio, electrode spacing, shape of the tank, anode and cathode current densities, etc. The closer you can come to these same parameters, the closer you come to achieving success, even with small systems. From all the patented systems, they ended up with only 2 types, the vertical Moebius and the horizontal Balbach-Thum.
In every case I've ever found, copper was intentionally added to the solution and the average amount they added was huge - 50-60gpl. Why would they do this if the added copper didn't produce benefits? After all, their solution wouldn't last as long. Or, would it? They probably kept the solution perfectly balanced by frequent removal and replacement of specific amounts of solution, based on knowing the material going in and, most probably, analysis. Also, Rose says the older the solution, the better it works. He says this is possibly due to the buildup of ammonium nitrate.
The more I study these cells, the more convinced I am that some added copper is very desirable. I would strongly recommend that anyone building a cell add some copper.
