# Determination of volume of liquid in a tank



## snoman701 (Sep 12, 2018)

Note, not calculation of tank capacity.

This is one of those "yeah, I can figure out how to do it" type things, but it would be a lot easier knowing if there are shortcuts that are routinely used in industry. This is more of a process engineering type question. 

The story problem: 

So, you have a five gallon bucket that is mostly full of silver bearing solution that titrates at 9 toz per gallon....how much silver do you have? 

Simple right? Now make it an approximately 20 gallon tank, or 2000 gallon tank...and you want to add enough HCl to precipitate 95% of the silver. 

Do tanks like this have scales attached so that volume can be determined from density & mass? Is this strictly ultrasonic/visual/sightglass level detection compared to known volumes? Or is it a matter of approximation, precipitation with known volume HCl (or serial dilution with known volume diluent) followed by secondary titration? Or a combination of all of the above?

What's the smack me upside the head easy method that almost always works?


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## denim (Sep 12, 2018)

Maybe this would work....

Pi (3.14) x radius squared x height of liquid. Then do a simple calculation to find the conversion of that volumn to the desired volumn designation ie: liters, gallons etc.
This is assuming your vessel is cylindrical.

Dennis


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## snoman701 (Sep 12, 2018)

denim said:


> Maybe this would work....
> 
> Pi (3.14) x radius squared x height of liquid. Then do a simple calculation to find the conversion of that volumn to the desired volumn designation ie: liters, gallons etc.
> This is assuming your vessel is cylindrical.
> ...



I want something with reasonable degree of precision. I can think of a number of ways to do it...what I'm looking for here is the experience of someone who does it on a daily basis to say, the easiest way is titrate / precipitate portion / titrate or use specific gravity and mass of the liquid or install a graduated stainless tape measure into your tank and calibrate it. 

I can think of any number of posts where GSP and 4Metals have offered advice that follows with the idea of "yeah, in college you did this, but this way is ten times faster and gives the same results (or better)".


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## 4metals (Sep 12, 2018)

I just calculate cubic inches of the liquid and divide by 231 to tell me gallons. You want to calculate the total silver content as nitrate and drop a percentage of it? As a chloride? Why not all of it?


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## snoman701 (Sep 12, 2018)

I want to reuse the nitric. 

So 95, 98, 99.9....just not 101.




Sent from my iPhone using Tapatalk


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## Platinum (Sep 12, 2018)

One Mole (M) of dry, pure NaCl (58.45g) will precipitate one M of silver (107.88g) from a silver nitrate solution.

HCl is a little more iffy. It depends on the strength and the temperature.

One Mole of HCl weighs 36.46g. One M of HCl will precipitate one Mole of silver from solution.

A typical strength of commercial HCl is 37%. This contains 12.00 M of HCl. One liter @ 72F will precipitate 12 x 107.88 = 1295g of silver

A typical strength of muriatic acid is 31.45% HCl. This contains 9.96 M of HCl. One liter @ 72F will precipitate 9.96 x 107.88 = 1074g of Ag

This is only a guide and it is worthless if you have no idea how much silver you have or the strength of the HCl. Even if you know, i almost impossible to add the absolute correct amount09I always add the Cl source in increments, adding smaller amounts towards the end point. After each addition, I stir it and let it settle for a few minutes and then add one drop of the salt water or HCl with the eyedropper close to the solution to try and keep the drop at the surface. If you see more milkiness where the drop is, you need more Cl-. As you approach the point where most of the silver has precipitated, the AgCl produced will be finer and will settle much more slowly. For complete settling, it might take overnight.

I just thought of something else. If there is copper dissolved along with the silver and you are using HCl, you will find that, when all the silver has already precipitated, the drop of HCl will turn a clear yellow color.

Chris (GSP)


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## Platdigger (Sep 12, 2018)

So Chris, what's up with the name change?


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## Platinum (Sep 12, 2018)

It was a cut and paste. 
The author is Chris so i tag lined it.


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## snoman701 (Sep 12, 2018)

Platinum said:


> One Mole (M) of dry, pure NaCl (58.45g) will precipitate one M of silver (107.88g) from a silver nitrate solution.
> 
> HCl is a little more iffy. It depends on the strength and the temperature.
> 
> ...



I have witnessed what you describe, but hadn't made the correlation...I'll now think of you every time I see the phenomena. 

I guess my question is poorly worded, and I didn't want to bog the thread down with the details of the silver titration and stoichiometry, but now I'm glad it's out there. In this particular case, it's a dirty leach, and I prefer to use it over and over again as long as I can continue to regenerate the HNO3 through precipitation with HCl. Having excess HCl when I send it back to leach some more is not desired. 

I already have the stoichiometry in a spreadsheet...it's easy enough to determine concentration of silver ions in a known volume, and your points about temperature and concentration are why I planned to precipitate theoretical 95%. It's the volume of the liquid in the tank that's the unknown, and it seems like it should be a common enough engineering problem that there would be a shortcut. 

*So I guess for clarity, my question was more ascertaining the volume of a liquid in any given vessel of unknown geometry. *I know that in industry with large tanks, ultrasonic works and could easily be calibrated against known volumes...but it seems that for a five gallon size, or even 25 gallon, estimation within a liquid ounce should be well within general methods.


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## Platinum (Sep 12, 2018)

One gallon of Hcl will get you about 10 lbs of silver for around $7-8.
One bag of pool salt will get you 80 lbs of silver for about $7-8.


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## snoman701 (Sep 12, 2018)

Platinum said:


> One gallon of Hcl will get you about 10 lbs of silver for around $7-8.
> One bag of pool salt will get you 80 lbs of silver for about $7-8.



You pay more for HCl than I do for nitric.

The hydrogen ion remaining after the chloride precipitation recombines with the nitrate, regenerating nitric acid.

PLUS...it means less waste to treat.


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## Platinum (Sep 12, 2018)

Those are retail numbers. 
I pay less than that for salt and hcl. 
When i buy hcl or nitric i pay by the lb based on the amount of nitrate or chloride and not just the volume of the liquid. Nitric is $2.75 a gallon right now and Hydrochloric Acid 31.45% 530 lb. drum – Price Quote .18 per lb.

Sodium Formate 
101050-202001 x 10 bags quote .65/#
Formic Acid 
100381-113001 x 1 drum quote $.85/#
Caustic Beads 50# - 
100322 – 113001 x 10 bags quote .42/#


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## g_axelsson (Sep 13, 2018)

Shortcuts in the industry... calculate the volume and put a sight glass with a scale graduated in volume. Use a dip stick graduated in volume. Use load cells to measure the weigh of the vessel, an electronic indicator can be calibrated in volume. Use ultrasonic transducers to measure the surface of the liquid, calibrate after volume. Use a float that moves a resistive sensor.

It all depends on application and which liquids are in the vessel, but most methods depends on having a known geometry or volume of the vessel. If it is a transparent vessel just use a sharpie and mark it on the outside.

If you are worried about overshooting the mark, just put some of the liquid in a separate vessel and if you add too much HCl then you can remove it by adding some of the liquid you kept back.

Another method would be to titrate one sample, add a known amount of HCl. Then titrate a second sample. With some simple math you could calculate how much silver was removed from the sample and then you could calculate the total volume.

Your method is a known method. I've heard GSP describe it for removing silver from stainless aircraft bearings. Add HCl until 90% of the silver is precipitated, then reuse the solution.

Göran


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## 4metals (Sep 13, 2018)

As neat as it sounds to use electronic gadgets, the truth is in the environment of a refinery, complicated equipment doesn't last. So simple wins the day in my book. 

Back in the day when I digested a lot of silver to cement and run a nice clean silver cell, I did a few things consistently every time. I always used nitric acid diluted to the same strength. I saved the nitric in a tank with an overflow so I knew when it overflowed exactly how much was in the tank to process. The cost of nitric was never an issue so that is where what I did varied with what you are thinking. 

I would still use the tank with an overflow. Where that is useful is you can come up with (by titration) the strength of the silver nitrate and once you have calculated the volume of your tank to the overflow, the volume is never different. So set up the overflow so there is still capacity in the tank to add some more solution, and add a shut off valve to the overflow. When it starts to overflow you know it's time to process. titrate the solution and calculate how much HCl you want to add. Shut the valve on the overflow and add the calculated volume of HCl. Give it a good stir and wait for it to settle. Decant your solution, collect your chlorides, and the remaining acid with a little silver nitrate should be chloride free. 

The next time you process, titrate again and repeat. After a few times you have a good idea how much hydrochloric you need to add and you can skip the titration and add the average volume. In the event you have less silver and the HCl drops all of the silver out leaving excess chlorine in your acid, simply add silver nitrate from the bucket under the overflow to eat up the extra HCl. Depending on what other metals are eating the nitric, controlling the reaction without titrations may be the way to go once you know average usage and you run similar material. (like always running sterling)

I can for see problems if there is any gold in the silver, gold chloride will build up in solution but not settle out with the insoluble silver chloride. So any gold chloride will stay in the acid until it builds up so high in base metals that you cement out the values.


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## g_axelsson (Sep 14, 2018)

4metals said:


> I can for see problems if there is any gold in the silver, gold chloride will build up in solution but not settle out with the insoluble silver chloride. So any gold chloride will stay in the acid until it builds up so high in base metals that you cement out the values.


If the nitric acid is chloride free then any gold would stay with the solids. Or am I missing something here?

What would build up is palladium, copper and other base metals.

By the way, a tank with an overflow is a nice way to get a known fixed volume without having to monitor too close.

Göran


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## snoman701 (Sep 14, 2018)

4metals said:


> As neat as it sounds to use electronic gadgets, the truth is in the environment of a refinery, complicated equipment doesn't last. So simple wins the day in my book.
> 
> Back in the day when I digested a lot of silver to cement and run a nice clean silver cell, I did a few things consistently every time. I always used nitric acid diluted to the same strength. I saved the nitric in a tank with an overflow so I knew when it overflowed exactly how much was in the tank to process. The cost of nitric was never an issue so that is where what I did varied with what you are thinking.



And that is what I was looking for! 

I had planned to use a scribed line with known volume, and if I wanted to process early, just fill to the line...but then you are dealing with meniscus variations and subjective judgments. 

Thank you!


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## goldsilverpro (Sep 14, 2018)

Calibrate a bucket by adding a gallon jug full of water at a time and then marking a graduated scale on it. Loew's sold buckets that were graduated in both US and metric. They were also translucent, and you could see the liquid level. Probably my favorite buckets. It's been awhile since I bought one, but they probably still sell them.

I don't understand the problem of determining the volume of any size tank of any shape. just take inside measurements and do the simple math.

Were it me, I would probably go for 90% instead of 95%. 

If you are set up to titrate, you might set up to analyze the strength of the HCl, also. Very simple titration.


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## 4metals (Sep 14, 2018)

> 4metals wrote:
> I can for see problems if there is any gold in the silver, gold chloride will build up in solution but not settle out with the insoluble silver chloride. So any gold chloride will stay in the acid until it builds up so high in base metals that you cement out the values.
> 
> If the nitric acid is chloride free then any gold would stay with the solids. Or am I missing something here?



When the silver dissolves in the nitric, yes the gold is insoluble. When the HCl is added to drop silver chloride you will have the equivalent of reverse AR for a short time until the HCl reacts with the silver, at that same time the HCl is available to dissolve gold as well.


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## snoman701 (Sep 14, 2018)

goldsilverpro said:


> Calibrate a bucket by adding a gallon jug full of water at a time and then marking a graduated scale on it. Loew's sold buckets that were graduated in both US and metric. They were also translucent, and you could see the liquid level. Probably my favorite buckets. It's been awhile since I bought one, but they probably still sell them.
> 
> I don't understand the problem of determining the volume of any size tank of any shape. just take inside measurements and do the simple math.
> 
> ...



Yep, I've got some of those buckets...expensive but nice.

As for the volume of the tank, it's a stainless keg that I'll tig weld some bungs in to. So while I can calculate it, it will still just be an approximate....and this was mostly just a question of "if this were in industry by an experienced refiner, how would it be done?". I think that both you and 4Metals answered that when you said, just do it to effect.


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