We use 10 M solution of lithium chloride for RNA precipitation. LiCl is crystallized in the almost empty jar during storage. Could it impact the molarity of solution made?
See attached file for the adsorption isotherm for LiCl.
These humidity values are actually relatively low compared to an average indoor environment, so to answer your question - yes, I think it is possible that water adsorption from air could significantly affect the weight of your LiCl stock (of course the relative molecular mass of LiCl doesn't change, but accurate measurement is made difficult by adsorption of an unknown amount of water).
You can remove the water from your stock by placing it (open) in an oven at 100°C for a few hours and sealing soon after removal. If doing this, it might be interesting to weigh it before and after and let us know how much water weight there was!
See attached file for the adsorption isotherm for LiCl.
These humidity values are actually relatively low compared to an average indoor environment, so to answer your question - yes, I think it is possible that water adsorption from air could significantly affect the weight of your LiCl stock (of course the relative molecular mass of LiCl doesn't change, but accurate measurement is made difficult by adsorption of an unknown amount of water).
You can remove the water from your stock by placing it (open) in an oven at 100°C for a few hours and sealing soon after removal. If doing this, it might be interesting to weigh it before and after and let us know how much water weight there was!
If your LiCl crystallized out of solution, it is likely that the solution evaporated until the LiCl became saturated. According to a table I found online, the solubility of LiCl at 20oC is 44 g/100 mL of solution in water. The molecular weight is 42.4. Therefore, a saturated solution would be 10.4M. If this number is right, then the supernatant of your solution with crystals in it is 10.4M, or about the same as it was originally.
Reference:
https://books.google.com/books?id=d1JMAAAAMAAJ&pg=PA370&lpg=PA370&dq=aqueous+solubility+of+lithium+chloride&source=bl&ots=BUPu8UKapD&sig=AEGWBVbJ8Kds9ETfoeDO5FFstWg&hl=en&sa=X&ei=8l_VVJnLA9LHsQSH0ILABQ&ved=0CCsQ6AEwAjgK#v=onepage&q=aqueous%20solubility%20of%20lithium%20chloride&f=false
Thank you, Angus for an advice. I have dried LiCl powder in an oven for several hours until it stops to lose weight significantly. As a result there was 12.67 % of water weight from the starting mass. in fact my 10 M solution is only 8.7 M or even lower.
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