Sciencemadness Discussion Board

really, really long term storage of food grade NaOH

DieForelle - 27-8-2012 at 17:01

After a great deal of searching around, I managed to find someone willing to sell me some true food grade (Fisher FCC/USP) HCl and NaOH last spring.* After a brief bout of food and nutritional related experiments, I've decided they have no immediate utility to me. But given I practically had to spend days scouring the interwebs to obtain them, I certainly never want to have to try to buy them again. Would it make sense to turn the NaOH cap real, real tight to seal it, double bag it, and throw it in the freezer? My thinking is basically that the freezer is always going to be the driest air in a house, and moisture is the main long term enemy to storing NaOH. Of course, when I take it out to cure olives in 20 years from now or whatever, I will have to let it come to room temp. before opening it, or I'd defeat the whole point of storing it in the freezer.
From what I've gleaned on the web, my understanding is that the HCl should last several years at least, in the type of glass it's sold in. With the possible issue of the boron concentration creeping up, since there is some boron in the glass.


*FWIW there are people claiming to sell food grade NaOH quite cheaply...just google it. But if you actually look at the C of A, those big pure industrial distributors like Univar do not seem to test for lead or mercury. They only test for iron and a couple other things and call it "food grade". The lab chem. suppliers like SAFC, Fisher, Avantor et al. do test for everything on the FCC monograph, and sometimes more. Really makes you wonder where the producers of industrial food are buying their chems: SAFC (Sigma's food/pharma arm) even has an elaborate grading system for their food additives with several levels...but why would any manufacturer even bother with the top grade? Who's going to know? When you can buy the same stuff from China or someone like Univar for 10X less? I asked "Modernist Pantry" for a C of A of something they were selling, and they said it was the first time a customer had ever asked for one.


[Edited on 28-8-2012 by DieForelle]

phlogiston - 27-8-2012 at 22:50

Theoretically, I think you would want to exclude CO2 as much as possible too, to reduce the formation of Na2CO3. However, I do wander if, in practice, a little carbonate will hurt in the food processing applications you use it for.

Since most plastics are quite permeable to CO2 (ever inflated a balloon with CO2?), it would probably best to place your (presumably plastic) container in a bigger glass or metal container.

DieForelle - 28-8-2012 at 09:26

Thanks, that's a good tip and no I wasn't aware how plastic was permeable to C02. I was a little surprised to see the default container for it was PE, although maybe because it's food instead of ACS grade they assume it will be used up quickly to manufacture something? There's no expiration date as Spectrum sometimes puts on their food grade products...maybe there's a way to treat the plastic to lower CO2 permeability? It's a silvery looking polyethylene.

EDIT: looks like everybody sells NaOH in poly these days, although I was sure I've seen really old bottles of it on ebay in glass. Oh well. I'll take your advice and find a larger air-tight container.


[Edited on 28-8-2012 by DieForelle]

unionised - 28-8-2012 at 12:09

If you kept it in a closed container in a desiccator over ordinary cheap NaOH it wouldn't pick up CO2 or H2O.

kristofvagyok - 28-8-2012 at 12:27

Quote: Originally posted by DieForelle  
Would it make sense to turn the NaOH cap real, real tight to seal it, double bag it, and throw it in the freezer? My thinking is basically that the freezer is always going to be the driest air in a house, and moisture is the main long term enemy to storing NaOH.

From what I've gleaned on the web, my understanding is that the HCl should last several years at least, in the type of glass it's sold in. With the possible issue of the boron concentration creeping up, since there is some boron in the glass.
[Edited on 28-8-2012 by DieForelle]

Last week in the storage room I have found boxes, 1 one was food grade NaOH from Merck, expired in 2003 and another one what have been expired 10 more years earlier. They had absolutely no problem, no carbonates, no water, no adhesion, no nothing, they were perfect for every use. And there were no bags, no freezer and no nothing, just a normal plastic box with a plastic cap in a room what contained a lot other chemicals.

To seal it in 2 bags and put in in the freezer? Why? The NaOH always contains some water, "dry" NaOH also contains 0,5-to 3 percent, if you need waterfree, then put it in a silver crucible and melt it till it boils.

And the HCl and the boron... I won't write down the same story with a glass of cc HCl from 1980...

P.S.: HDPE containers are perfect for cc HCl;)

Arthur Dent - 30-8-2012 at 08:58

I have some fine granular NaOH that came in a 1l widemouth HDPE bottle. The Sodium Hydroxide is labeled as industrial-grade drain cleaner, and MSDS indicates it's technical grade NaOH (99%+). When I bought it over a year ago, it only had a little styrene plastic film sealing the bottle under the cap.

It has been a year + later, and the only thing I noticed is that the NaOH behaves like salt in humidity, it clumps a little bit together but just squeezing the bottle loosens it. I only used about 10% since then and it may last me many years.

The idea of keeping the bottle under some sort of vacuum is good, but I can't dedicate my Pyrex dessicator for just that purpose... I thought of putting it in a large ziploc bag with a pouch of silica gel or a box of anh. CaCl2. Perhaps a good alternative?

Robert