Using nitric acid to convert scrap silver to silver nitrate. Has anyone heard of a method where you get the reaction going initially with a small amount of nitric acid, and soon after add a large amount of distilled water. Apparently this doesn't smell as bad as with straight nitric acid. Any thoughts? Thanks in advance as you guys always come up with fantastic help. EDITED: I'm talking about 68 to 70% percent solution, btw.
My 1 cent worth of comment on nitric acid is that don't meddle with it. The fumes is highly toxic and when it needs to be handled, one need to wear the appropriate personal protective equipment with a full face respirator (with correct cartridge) mask. I work in an industry which handle nitric acid. Keep away from children reach.
Makes no difference to the reaction if you add the distilled water at the beginning, or shortly after adding the acid. However, as Argentum mentioned, this is more dangerous, because acid should always be added to water, and not vice versa, or you risk an explosion/splash through excessive heat produced when mixed. My guess is what is being observed is that initially, the silver begins dissolving in the nitric, but the reaction begins to slow rapidly - silver is not very soluble in concentrated (say 70%) nitric acid. This is because the solution is already heavy with ions. The addition of distilled water gives the silver nitrate somewhere to dissolve after reaction with the acid (silver nitrate 219gm / 100ml solubility in H2O). So, the addition of distilled water would give the false appearance that it is making the reaction proceed, when really, it is allowing the silver to be more easily dissolved into solution. Hope this helps.
I've always assumed nitric acid is very difficult to obtain. Being familiar with the adventures of one Alfred Nobel (or was it Yahoo Serious) I just accepted this substance would be unavailable to the average backyard mechanic. Even if it is readily available I would probably rather not mess with it. I think I'll just buy silver and rejoice in the incredibly low prices we currently have. So. just out of idle curiosity. Is nitric acid readily available to the public? I would find that very surprising given it's many ummm, interesting applications.
Okaaay, I am frankly amazed at this. Better not say anything or some apparatchik will wise up and outlaw this as well. Can't have the kiddies getting hold of nasty things that fizz and go bang. Then, I s'pose hydrogen peroxide, along with many other common chems are almost as bad as potential sources of mayhem.
I didn't find it difficult to obtain to my surprise. I did check with various state and fed government sources before proceeding and found no issues. Some suppliers required in person collection and ID in the form of credit card.
I've considered trying this out just for the fun of it. As others have said, you can certainly get nitric acid. Definitely do be careful with it, though. I don't want to sound like I'm saying not to do it - I'm definitely not saying that and I think that anybody who wants to be able to do chemistry should be able to do it and encouraged to do so - but nitric acid will do nasty things to you if you're not careful, so read up thoroughly on how to safely handle it and start with a very small scale.
Cheers. This is exactly what i've heard. I did see one video where the guy pours a small amount of nitric acid on the silver he wishes to refine. The reaction gets started and the toxic fumes begin to be produced. Very soon after that he carefully and steadily adds distilled water. The reaction continues but with much less toxic gas, and apparently at a similar rate to what it would with only acid.
Silver reacts with nitric acid in two ways both of which are redox reactions and not acid/base reactions. Adding more water reduces the smell but should not increase the rate of reaction (unless hot water then its the increased temp rasing the speed of reaction not increased volume of water. if the reaction is with concentrated acid the major product is nitrogen dioxide (NO2) which is released as red-brown fumes: Ag + 2HNO3 --> AgNO3 + NO2 + H2O If the acid is dilute, the major product is nitrous acid which stays in solution(hench less smell for the original op.) 2Ag + 3HNO3 --> 2AgNO3 + HNO2 + H2O sorry but the above is bollocks.
Yes, that brown gas is nitrogen dioxide. It is produced via thermal decomposition of nitric acid, so a more vigorous reaction (more heat) will increase the rate at which the acid decomposes, meaning that some of it is wasted and only making the whole process more dangerous. It hydrolyses (i.e. reacts with water) to produce nitric and nitrous acids... so, inhaling it will result in nitric acid in very un-fun places, like your lungs. This can result in pulmonary oedema.
Any time you're diluting a concentrated acid, you should always slowly add the acid to the water. "Do as you oughtta, add acid to water." This is because the reaction between water and a strong acid (they actually react when you mix them) is quite exothermic. Adding a small amount of water to a large amount of acid will result in an initially very concentrated solution of acid which can get hot enough to boil and spit the solution.
acid into water is safer bust still needs to be done carefully (no splashing) add it down the side of the beaker
I did establish that it was 100% ok to obtain this chemical for this express purpose, and well before trying to locate and buy it. To be truthful I wasn't expecting to be able to obtain it for reasons you might be alluding to. Happily PC etc hasn't found its way to nitric acid ... ?? yet ??
