Sciencemadness Discussion Board

Insoluble salts

weiming1998 - 3-2-2012 at 06:50

If HCl is added to Ag2SO4, then H2SO4 and 2AgCl will form, right? AgCl is much less soluble than Ag2SO4 and thus, the precipation will drive the reaction forward. So I have been looking for a sulfate and a particular acid that if combined, a precipation forms. The first option is iron oxalate, but it forms stable, soluble complexes in acidic solutions. Does any of you know precipates that will not react with cold, dilute H2SO4(carbonates won't work!)/won't form soluble complexes?

Of course, I could Google, but I'll have to look through thousands of salts and acids. I wouldn't prefer that.

phlogiston - 3-2-2012 at 07:26

Lead phosphate?

3 seconds of googling yields the following table:

http://www.saltlakemetals.com/SolubilityProducts.htm

lead phosphate sol. prod = 1.6 x 10-32
whereas lead sulphate = 1.6 x 10-8

There must be others.

I suspect the process will be very slow though.

AirCowPeaCock - 3-2-2012 at 07:26

AgCl is soluble in concentrated sulfuric acid. Maybe if you dilute the HCl to say, 10% you could get an appreciable equilibrium. But they you end up with something like 1.5 molar solution.. hardly worth it if you ask me.

weiming1998 - 3-2-2012 at 07:37

Quote: Originally posted by phlogiston  
Lead phosphate?

3 seconds of googling yields the following table:

http://www.saltlakemetals.com/SolubilityProducts.htm

lead phosphate sol. prod = 1.6 x 10-32
whereas lead sulphate = 1.6 x 10-8

There must be others.

I suspect the process will be very slow though.


CuSO4+Pb does not make much PbSO4 at all, and a hot NaHSO4 solution does not corrode Pb. I could use a battery, but I don't own an old car batery right now.

AirCowPeaCock - 3-2-2012 at 07:42

you could...oh..western Australia..good luck... Lead sulfate shouldn't be too hard to get, even there. But I don't know if Lead sulphate is the way to go, they both are pretty insoluble. It's gonna take, oh, I have to imagine weeks for a small amount of dilute sulfuric acid. Ever thought of oxidation of sulfur dioxide/sulfurous acid? I have to imagine you can get sulfur, can't you?

[Edited on 2-3-2012 by AirCowPeaCock]

weiming1998 - 3-2-2012 at 07:43

Quote: Originally posted by AirCowPeaCock  
AgCl is soluble in concentrated sulfuric acid. Maybe if you dilute the HCl to say, 10% you could get an appreciable equilibrium. But they you end up with something like 1.5 molar solution.. hardly worth it if you ask me.


At least more efficient than bubbling SO2 through water, then oxidizing with air/MnSO4 catalyst.

AirCowPeaCock - 3-2-2012 at 07:44

Quote: Originally posted by weiming1998  
Quote: Originally posted by AirCowPeaCock  
AgCl is soluble in concentrated sulfuric acid. Maybe if you dilute the HCl to say, 10% you could get an appreciable equilibrium. But they you end up with something like 1.5 molar solution.. hardly worth it if you ask me.


At least more efficient than bubbling SO2 through water, then oxidizing with air/MnSO4 catalyst.


Oxidize in solution, you can get 3% H2O2 right?

phlogiston - 3-2-2012 at 14:08

Quote:
CuSO4+Pb does not make much PbSO4 at all, and a hot NaHSO4 solution does not corrode Pb. I could use a battery, but I don't own an old car batery right now.


Copper acetate does dissolve lead quite well. Then add any available soluble sulphate (MgSO4 and K2SO4 are common fertilizers) to precipitate lead sulphate.

Alternatively, electrolyse a sodium carbonate solution with a lead anode, and lead carbonates/hydroxides should start flaking off. I haven't tried that though with lead (but with many several metals always with good success). Then dissolve in acetic acid and proceed as above.

Or use the old-fashioned way of making lead oxide pigment (look up white lead). IIRC it involves beer, which is always good IMO :)

weiming1998 - 3-2-2012 at 16:39

Quote: Originally posted by AirCowPeaCock  
Quote: Originally posted by weiming1998  
Quote: Originally posted by AirCowPeaCock  
AgCl is soluble in concentrated sulfuric acid. Maybe if you dilute the HCl to say, 10% you could get an appreciable equilibrium. But they you end up with something like 1.5 molar solution.. hardly worth it if you ask me.


At least more efficient than bubbling SO2 through water, then oxidizing with air/MnSO4 catalyst.


Oxidize in solution, you can get 3% H2O2 right?


Oh come on, 100mls of 3% H2O2 costs 5 dollars here! 34grams of H2O2 will oxidize 64 grams of SO2 to 98 grams of sulfuric acid. So, 11 100ml bottles of H2O2 (55 dollars!) And 32 grams of sulfur (but I cannot burn sulfur and collect its gases[no oxygen!] without combining an oxidizer, and combining an oxidizer will make the SO2 evolve so fast it will literally blow up my container!) Or 158 grams of sodium thiosulfate (costs something like 20-30 dollars, plus I'm never, ever going to Sigma Chemicals every again!) So after 80 dollars of investment, I get only 100 grams of sulfuric acid (assuming no losses of acid from boiling, etc). Better to buy it from eBay, which has it listed as 20 dollars of 950 mls.

weiming1998 - 3-2-2012 at 16:46

Quote: Originally posted by phlogiston  
Quote:
CuSO4+Pb does not make much PbSO4 at all, and a hot NaHSO4 solution does not corrode Pb. I could use a battery, but I don't own an old car batery right now.


Copper acetate does dissolve lead quite well. Then add any available soluble sulphate (MgSO4 and K2SO4 are common fertilizers) to precipitate lead sulphate.

Alternatively, electrolyse a sodium carbonate solution with a lead anode, and lead carbonates/hydroxides should start flaking off. I haven't tried that though with lead (but with many several metals always with good success). Then dissolve in acetic acid and proceed as above.

Or use the old-fashioned way of making lead oxide pigment (look up white lead). IIRC it involves beer, which is always good IMO :)


I'll try the lead+copper acetate. it might not be useful for precipating, but I might use it to create other lead salts.

AirCowPeaCock - 4-2-2012 at 09:32

EBay sounds great! But just so you know. Sulfur burns just fine in atmospheric oxygen. Nurd rage has a somewhat messy video on how to make sulfuric acid from sulfur. Sodium metabisulfite works great too! Really 100 ml for 5$! I can get a L for 3 bucks! Western Australia is a sad place for the amateur chemist!

weiming1998 - 4-2-2012 at 17:24

Quote: Originally posted by AirCowPeaCock  
EBay sounds great! But just so you know. Sulfur burns just fine in atmospheric oxygen. Nurd rage has a somewhat messy video on how to make sulfuric acid from sulfur. Sodium metabisulfite works great too! Really 100 ml for 5$! I can get a L for 3 bucks! Western Australia is a sad place for the amateur chemist!


No, the hydrogen peroxide is sold in 100ml bottles in every pharmacy I went to. Some don't even sell H2O2 at all! Sodium metabisulfite releases 2 moles of SO2/mole, so that might be better, but I am not sure about the legal status of home-brewing here. Also, sulfur wouldn't burn because the container is entirely closed (prevent SO2 from escaping!). And SO2 is heavier than air. So the resultant SO2 covers the sulfur, smothering it. Any idea on how to keep the SO2 from smothering the sulfur?

I found this video, and the person used a fish pump. http://www.youtube.com/watch?v=xHLeFSY_OJU
Could I put an ozone generator (produces mainly air) into the can, and another tube to lead the SO2 out? Or would the sulfur dioxide be so heavy that the bubbles produced on the other end are the air that I just pumped through?

watson.fawkes - 4-2-2012 at 18:58

Quote: Originally posted by weiming1998  
No, the hydrogen peroxide is sold in 100ml bottles in every pharmacy I went to. Some don't even sell H2O2 at all
If you cannot buy hydrogen peroxide, I'm guessing the next-best route to H2SO4 is the lead chamber process. Search for the thread titled "H2SO4 by the Lead Chamber Process - success" here. The Wikipedia article is also informative.

Note: Since I'm guessing that you can't get nitrates either, you'll have to use gaseous nitrogen oxides (NOx) instead. This means working with high voltage and setting up an arc generator to burn air. This is also a way of getting to nitric acid, but in the lead chamber process you don't need to dissolve the NOx in water first, meaning you don't need an absorption tower, just the arc generator.

weiming1998 - 4-2-2012 at 19:44

Quote: Originally posted by watson.fawkes  
Quote: Originally posted by weiming1998  
No, the hydrogen peroxide is sold in 100ml bottles in every pharmacy I went to. Some don't even sell H2O2 at all
If you cannot buy hydrogen peroxide, I'm guessing the next-best route to H2SO4 is the lead chamber process. Search for the thread titled "H2SO4 by the Lead Chamber Process - success" here. The Wikipedia article is also informative.

Note: Since I'm guessing that you can't get nitrates either, you'll have to use gaseous nitrogen oxides (NOx) instead. This means working with high voltage and setting up an arc generator to burn air. This is also a way of getting to nitric acid, but in the lead chamber process you don't need to dissolve the NOx in water first, meaning you don't need an absorption tower, just the arc generator.


I looked at the price for a high-voltage transformer. 200 dollars????? Also, I don't think that the high-voltage thing is safe enough for me (I haven't worked with voltages higher than a 9 volt battery)

AirCowPeaCock - 4-2-2012 at 21:01

This is not the same video, but it might give you some ideas. http://www.youtube.com/watch?v=xHLeFSY_OJU

weiming1998 - 4-2-2012 at 22:51

Nevermind, I've got some potassium nitrate now, so I can try the lead chamber process. Surprisingly, the potassium nitrate was found in a Chinese food shop, in the spice section. I have never though of looking there.