# Shelf life of acids.



## knujiv (Sep 28, 2011)

So, I'm ready to start some very small scale experiments, I think. I have some acids I've had stored away for awhile. I bought this stuff in a failed attempt to make some testing solutions about 15 years ago. I have a 500ml bottle of nitric acid (69-71%) and a 500ml bottle of hydrochloric acid (36.5-38%). They've been kept in a dark cupboard, and have probably experienced a temperature range of approx. 50F - 100F seasonally. Question I have is if this stuff will perform as it should? I have searched for this on the forum, and did find a vague answer that indicated that they should be okay..... shelf live apparently usually being only a concern with some mixed solutions.


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## butcher (Sep 28, 2011)

15 years is a long time, what gas could escape from those bottles over the years would determine how strong they are now, even if gas could escape some (most gases can escape lids when pressure builds, the HCl is less likely to be dilute may have change color some but could be slightly stronger, nitric may also have a color change if some evaporation occurred (NO2 gas in solution) but should still be nitric acid 68% as long as solution is in the bottle, this is opinion not from experience from storing for 15 years, I am going by how these acids act when evaporated.

No matter, I would still use them, and the best place you can try then out is with the procedures Hoke's book walks you through getting acquainted with how metals react in acids, and making solutions of metals and testing them with stannous chloride made from tin and HCl, this will help you to know reactions these metals make in solutions, give you an understanding of how to approach a material to recover or refine and also help you understand your results, and testing will help you know where your values are when you can no longer see them.


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## knujiv (Sep 28, 2011)

Thanks Butcher,

I should have examined these bottles before posting. The hydrochloric acid bottle looks fine (just dusty), but something has happened with the nitric acid. There is brown staining of the cap and some white powdery deposits on both the cap and glass and a very weird mold like growth on what was a paper price tag/label. Also the bottle seems to have lost some volume (perhaps 50ml). I'm assuming this is all from the evaporation you thought may be possible. Seems it deteriorated the cap's seal was able to escape out in some form.


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## nickvc (Sep 29, 2011)

For the uses you have in mind I doubt the age will be a problem. Just do some small scale tests with a small amount of silver and some nitric mixed 50/50 with water, if it dissolves that you should be good to go. The strength of acids varies all over the shop depending on where you buy them and in the refining game you buy the cheapest that will do the job and mixing appropriately to get the right concentrations, if you can buy 45% nitric for half the price of 70% I know what I'd buy.


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