Poor man's nitric vs nitric cost

[Ultrax]

I have not tried it so don't take this for sure.
How about mixing the Sulfuric and water and then adding the Calcium Nitrate under heavy stirring?
Would that be a possibility?

Such a reaction will lead to large losses of HNO₃ acid due to the formation of poorly soluble calcium sulfate. Even with vacuum filtration, a lot(!) of acid will remain in the gypsum.
Without distillation, the result will be a 20% nitric acid maximum.
It is much more profitable to use potassium nitrate and concentrated H₂SO₄

 

[Yggdrasil]

Such a reaction will lead to large losses of HNO₃ acid due to the formation of poorly soluble calcium sulfate. Even with vacuum filtration, a lot(!) of acid will remain in the gypsum.
Without distillation, the result will be a 20% nitric acid maximum.
It is much more profitable to use potassium nitrate and concentrated H₂SO₄

Entirely possible, but the clue here is insoluble vs soluble.
The Potassium or Sodium Sulfate can to a certain degree be pushed out by freezing but the Calcium Sulfate will be out by solubility so the resulting Nitric will be relatively pure.
I think this was discussed thoroughly a few years back.

 

[Ultrax]

I wrote about the losses in the precipitated gypsum in terms of the mass of calcium nitrate and dilute sulfuric acid and, accordingly, about the amount of all subsequent work with filtration, etc. The more water in the sulfuric acid, the more gypsum will be dissolved.
In addition, in concentrated acid, the following reaction also occurs without precipitate (!):
Ca(NO₃)₂ + 2H₂SO₄ = Ca(HSO₄)₂ + 2 HNO₂.

Therefore, the benefit should probably be assessed by the availability of pure nitric acid and the amount and cost of work to obtain it from other chemicals.
For example, in my case, there is no point in doing this at all, since 70% nitric acid from the factory costs $4 per liter. In some countries it is completely prohibited by law, in others it is very expensive, so probably each country will have its own different cost.

 

[Yggdrasil]

I wrote about the losses in the precipitated gypsum in terms of the mass of calcium nitrate and dilute sulfuric acid and, accordingly, about the amount of all subsequent work with filtration, etc. The more water in the sulfuric acid, the more gypsum will be dissolved.
In addition, in concentrated acid, the following reaction also occurs without precipitate (!):
Ca(NO₃)₂ + 2H₂SO₄ = Ca(HSO₄)₂ + 2 HNO₂.

Therefore, the benefit should probably be assessed by the availability of pure nitric acid and the amount and cost of work to obtain it from other chemicals.
For example, in my case, there is no point in doing this at all, since 70% nitric acid from the factory costs $4 per liter. In some countries it is completely prohibited by law, in others it is very expensive, so probably each country will have its own different cost.

No doubt, if you can buy it readily that is the best.
This is for the ones that do not have this opportunity.

 

[Shark]

Here for a small refiner buying a liter at a time is about $65. For that price and to save hazmat shipping I have to pick it up in person. A 200 mile round trip drive. If I get it shipped it runs a total of $95 a liter.

2.5 liters is $105, plus hazmat shipping if needing it shipped.

I can get it cheaper by the keg, but that is enough to last me an average of two years, and many small hobby sized refiners won’t even be able to access that quantity. Nitric acid costs in small quantities is what drives a large part of the “I used vinegar and now it won’t work” posts of late.

 

[Ultrax]

Taking into account your prices, it may be better to build a distillation system for HNO₃ from sulfuric acid once for a couple of hundred dollars.
Taking into account the fact that when distilling 300 ml of 56% nitric acid, you need 500 ml of 96% sulfuric acid, and the price of 18M sulfuric acid is about $20 per liter in the USA (maybe more somewhere, I cited the price in North Carolina), then with price of potassium nitrate of $5 per 1 kg (KNO₃ is much better because it does not foam during distillation, unlike sodium nitrate), you will get a price for nitric acid of about $40 per liter ("in situ", without delivery cost).

P. S. 40 dollars per liter is my estimated price, which is the same as yours Apparently, even in the USA, it is easier to buy factory-made nitric acid, for example, to avoid unnecessary work and wasted time?

 

[Shark]

Another point when buying is some states require a business license or a tax ID, and more permits in some cases. It varies state by state. For some countries it is just out right unavailable for anyone short of a business. It is hard enough to help people over the internet, but even more so when they don’t fill in the location in their profile.

With that said, it is great having well educated professionals who are willing to help even the most untrained to do things the right way and still aid in work arounds that give them help to get started in refining. I for one really appreciate all the assistance I have had over the years. And will take time here say Thank You to all those have helped me and many others.

 

[kurtak]

I have searched the forum for any discussuon on the use of homemade nitric acid in silver refining. I would appreciate any links to this discussion

First I need to clarify what I posted the other day --- wherein I pointed out that making PMN (Poor Mans Nitric) is likely to result in nitric acid that has at least "traces" of chloride (= HCl) in the nitric which can result in the formation of AgCl when used to dissolve silver & that is because the nitrate salts used to make the PMN will have "traces" of chloride in it even if they are high purity (reagent grade) nitrate salts

Here is an example of what I am talking about ----

https://www.skylighter.com/collections/oxidizers/products/potassium-nitrate-salt-peter
This is high purity potassium nitrate (99.5%) & if you look at the assay of the salt you will note the "trace" of chloride (per the bold print) -----

Assay: 99.5% purity minimum.
Impurities:
Cl: 0.06% max.
Na: 0.2% max.
Moisture: 0.1% max.
Water Insolubles 0.01% max.

Now is that trace of chloride enough to be of concern ?

I don't know because like 4metals & Ultrax when I was doing refining for a living I bought my nitric in bulk (kegs &/or drums) so I got my nitric dirt cheap ($3 gallon 56% in 55 gallon drum or $10 gallon 68% in 13 gallon keg)

And - for what it is worth - the chloride in PMN also has the possibility to dissolve gold as nitric + HCl = AR --- even if it is weak AR

Here are some links to other discussions about PMN ------

https://goldrefiningforum.com/threads/poor-mans-nitric-and-silver.32279/page-2#post-341779
https://goldrefiningforum.com/threads/gold-disolving-in-nitric.1116/#post-9323
https://goldrefiningforum.com/threads/how-to-make-your-own-nitric-acid.332/page-2#post-9746
Kurt

 

[James Ball]

Thank you very much I will read your post and the other ones associated with it.

 

[James Ball]

I did an experiment today with my PMN at about 55% strength (from a density determination). I made a saturated solution of Ca(NO₃)₂ • 4 H₂O. I added 20-30 ml in 4 seperate additions. I filtered the solution through a Whatman 42 slow filter between each addition. I saw a white precipitate each time I added the saturated Ca(NO₃)₂. The 11 cm Buckner funnel and filter had alot (~1/4 in) of CaSO₄. I stopped here and concluded that PMN has too much Na₂SO₄ to dissolve sterling silver. I wonder how much that Na₂SO₄ contributed to the density of the solution giving an artificially high concentration of HNO₃. Titration of the HNO₃ with a standard base solution (one can buy 0.100 M NaOH) and phenolphthalein indicator solution (classic high school or basic chemistry procedure) would answer this question. At this point I am not going any further with PMN. I just confirmed what this forum had already determined - that PMN (without distillation) is not suitable for silver refining.

Edited to use subscripts

 

[FrugalRefiner]

[BTY I like using subscripts for chemical formulas. Is there anyway to add this option to the options listed above. There is bold, italalic size etc. but no subscript.]

Right after those controls for bold, italic, size, and color, you'll see three vertical dots. Click on them for more options. The first one on the row that drops down is superscript, and the second is subscript.

Dave