Xenon1898
Harmless
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Registered: 19-1-2013
Location: United States
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Shelf Life of Chemicals?
I have long been unable to find anything coming close to a satisfactory reference for the useable shelf life of chemicals that might typically be used
in a laboratory. Can anyone point me to what you would consider a useful reference for the shelf life of chemicals?
Thanks
“If we knew what it was we were doing, it would not be called research, would it?”
-Albert Einstein
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Chemosynthesis
International Hazard
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If you don't have a manufacturer label, the MSDS can give general guidelines. I can only really remember reducing agents going bad. Lots of
chemicals can be good long after expiration date codes.
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woelen
Super Administrator
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In practice many many chemicals remain good 'forever'. Non-hygroscopic salts usually do, as do many non-volatile and non-hygroscopic organics.
Some examples:
K2Cr2O7
KClO3
KCl
KBr
Na2SO3
Na2SO4
H2C2O4
Na2S2O5
Na2S2O3.5H2O
CuSO4.5H2O
NiSO4.6H2O
CoSO4.7H2O
and so on....
The only thing is that these chemicals must be stored in a well sealed bottle, preferrably made of glass, with a tight fitting plastic screw cap.
Hygroscopic chemicals can remain good as well, but they need more care. They tend to clump and may become hard to handle.
Some chemicals which are very hard to keep good are chemicals which easily emit fumes of HCl or HBr (e.g. acyl chlorides, certain high oxidation state
metal chlorides or bromides). They literally make their containers rot away in a short time, so if you want to keep them good you need special
(expensive) containers with teflon liners in the cap. Similarly nasty are volatile strong oxidizers like Br2, CrO2Cl2, SO2Cl2.
The well known acids HClO4 (max. 70%), H2SO4 (max. 98%), HNO3 (max. 65%) and HCl (max. 37%) can be kept good for a very long time in well sealed glass
bottles. Easiest is concentrated H2SO4 (no fumes) or 70% HClO4 (no fumes), then 65% HNO3 and then 37% HCl. With the latter two you definitely need a
bottle with a teflon lined cap, or a cap, made of plastic which is especially chosen to withstand the acid.
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AJKOER
Radically Dubious
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How stored is important. Temperature, sunlight (especially vitamins and the like are destroyed in weeks), exclusion of humidity, CO2, and impurities
in the chemical itself (like traces of Mg(ClO)2 in Ca(ClO)2 have been linked to cargo ships fires/disasters), or from the vessel (a metallic cap
perhaps or not quite inert plastic), or exposure to sulfur compounds (H2S, SO2,..), or a seal on a bottle permiting the loss of gases including water
vapor or just hard to close properly, can also contribute greatly to the untimely destructions of your chemicals.
With respect to many chemicals, purchase in small quantities based on periodic usage. In a prior life, I was an Operation Research consultant for a
brief time and worked on inventory models. There is actual a formula for the correct inventory level based on such factors as the cost of money,
average demand, obsolence or spoilage with time and lost sales if item is unavailable. Such analysis may be appropriate for higher priced chemicals
with short shelf lives and in higher interest rates environments.
[Edited on 31-3-2014 by AJKOER]
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nezza
Hazard to Others
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Chemicals which do not keep well tend to be those which react with water and reducing agents. Chemicals such as Alkali metal sulphides, dithionites
and sulphites tend to oxidise in contact with moist air. Solutions of strong reducing agents like stannous chloride are not stable and obviously
ferrous salts. In general keeping reagents dry and in a closed container offers the best storage.
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