# dry ferts expiry date



## mattwood (13 Oct 2012)

I attempted to do an EI tank a while ago but have been out of the country for over a year and the fertilizers havent been touched. I am planning on starting another one soon and wondered if they will be out of date, if ever?

thanks


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## Nathaniel Whiteside (13 Oct 2012)

Nah bang em in.


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## Antipofish (13 Oct 2012)

They are essentially mineral salts right ?  How long do you keep salt in your cupboard for cooking   They will be fine mate.  People have the same ferts for years.


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## mattwood (13 Oct 2012)

cheers guys, puts my mind at ease, they have been sealed and kept dry so shouldnt be a major issue just wanted to double check.

thanks


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## Antipofish (13 Oct 2012)

Well if you change your mind send em my way LOL


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## dw1305 (14 Oct 2012)

Hi all,
I nearly wrote that they last "_for all eternity_", but I know we have this question before, and somebody pointed out that that wasn't entirely theoretically correct, so. 


> Potassium decays with a half-life of 1250 million years, meaning that half of the K atoms are gone after that span of time, so don't store your solution longer than 1250,000,000 years or you will have to use them at double strength.


<http://www.ukaps.org/forum/viewtopic.php?f=11&t=20883>

cheers Darrel


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## Nathaniel Whiteside (14 Oct 2012)




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## ian_m (15 Oct 2012)

Actually they change into a less usable form, as some of the EI salts absorb atmospheric water and turn to one solid lump. I failed to seal my bag of magnesium sulphate once and it clearly absorbed atmospheric water and turned to a solid lump.

A couple of days in airing cupboard and general smashing the lump about sorted that.


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## ceg4048 (15 Oct 2012)

That's not the same as going off. "Going off" means that the chemical was converted to something else. That does not happen. The powder is hygroscopic and therefore absorbs water, but that just means that it is MgSO4 plus lots of water, which does exactly the same job as MgSO4 plus a little bit of water. If water gets into your salt shaker the material in the shaker is still salt, regardless of how much water got in. These fertilizers are all salts, and salts do not turn into something else until time as we know it comes to an end.

Cheers,


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## ian_m (15 Oct 2012)

ceg4048 said:
			
		

> That's not the same as going off.


Corrected....


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## dw1305 (15 Oct 2012)

Hi all,


> Actually they change into a less usable form, as some of the EI salts absorb atmospheric water and turn to one solid lump.


 A lot of salts are "hygroscopic" <http://en.wikipedia.org/wiki/Hygroscopy> and form hydrates, but this really is just added water as Clive says. You can think of salt (NaCl) as an example, where in a dry climate you can naturally go from salt lake to salt pan to salt lake to salt pan etc. as the water content rises and falls. 

This affinity for water is also why "Epsom Salts" are MgSO4.7H2O, even as a dry powder. When you heat MgSO4.7H2O, you can drive off the "water of crystallisation", but then MgSO4 will pick up atmospheric moisture into it becomes the stable heptahydrate form, which even then is still hygroscopic as you've found out. Compounds like NaOH are almost impossible to maintain as dry salts as they have such a strong affinity for water that they rapidly deliquesce to form solutions. As a general rule any salts that dissolves easily (like nitrates) will be hygroscopic and should be kept in a sealed container. 

You get the reverse effect "efflorescence", when compounds lose their water to the atmosphere (salt lake to salt pan) or the fluffy white efflorescence you get on new bricks.

cheers Darrel


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