Dear Edwin,
I have recalculated the weight of MgCl2 that needed to be dissolved in 100 mL water to provide 2M MgCl2 Solution and found the following:
2 x 95.2 = 19.4 g in 1000 mL (liter) which means 1.94 g in 100mL. However, in the protocol they use 19g in 100 mL which is 10 times higher than the required (see text below). I think the number 19 g was mistakenly typed (should be 1.9 g).
Therefore, if you use the correct amount of MgCl2 1.9 g it will be easily dissolved in 100 mL water.
Just before use, add 5 ml of a sterile solution of 2 M MgCl2. (This solution is made by dissolving 19 g of MgCl2 in 90 ml of deionized H2O. Adjust the volume of the solution to 100 ml with deionized H2O and sterilize by autoclaving for 20 minutes at 15 psi [1.05 kg/cm2 ] on liquid cycle.)
Hoping this will be helpful,
Rafik
It is unusual. Most likely, either your water was not o.k., or your salt was contaminated with another chemical ( e.g. a Calcium salt). I recommend to get freshly deionized water and if possible newly purchased MgCl2. Use 194g/l for unhydrous MgCl2. Use a sterile filter and store in a clean sterile flask.
Dear Edwin,
The number of grams indicated in the protocol is correct; 19.4 g/100 mL. I suggest that you dissolve MgCl2 in water and heat for 15 minutes to make sure that no precipitation is observed. In cast the heat does not help use sonication for 30 minutes.
Good luck,
Rafik
Dissolve 19.04 g MgCl2 in 90 mL deionize dwater. Dissolve it an then make the volume 100 mL by addig deionized water. filter it and store in cleaned flask.
Good luck
For related RG discussions, see: https://www.researchgate.net/post/I_tried_to_prepare_a_MgCl2_4M_solution_using_anhydrous_magnesium_chloride_overnight_but_doesnt_dissolve_completely_in_water_Any_ideas
https://www.researchgate.net/post/I_m_preparing_a_modified_A_media_with_NaHCO3100mM_CaCl22mM_MgCl210mM_MgSO45mM_and_everytime_I_mix_them_they_precipitate_What_can_be_done
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