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Magnesium Chloride - Potential reactions when exposed to Benzoic acid and/or heat
Hi everyone,
Thank you for allowing me to post a question, I appreciate people’s generosity in sharing their knowledge and experiences.I have been making a magnesium chloride spray (for myself and friends) and would like to make a cream as my research suggests that while MgCl2 is water soluble, it is better absorbed through the skin when combined with lipids.
I’m not new to making emulsified products and I’ve been using benzoic acid as my main preservative. (Depending on the product I usually combine with other supportive antimicrobial ingredients such as potassium sorbate, herbal ethanol extracts, glycerin, essential oils etc. These are not products that I sell, they are products that I make for myself and friends that have always worked very well for me)
I’d like to know if there are any potential chemical reactions that may occur between these two ingredients? (Magnesium chloride and Benzoic acid)?
My knowledge of chemistry is fairly basic but I do know that salts and acids will react, but it can be dependent on the strength of the acid and other factors such as heat etc…. To quote a reply I found on the internet
“It has not a simple answer!”
I have also tried to google specifically the reaction between benzoic acid and magnesium chloride but to no avail.I’m hoping that someone with a much deeper knowledge of chemistry will know the answer, or that someone has experience of their own that they are willing to share.
One more concern I had…… I believe Magnesium chloride has a reaction when exposed to heat. (Creating magnesium oxide and hydrogen chloride gas) When I make my cream I will need to heat the water phase (usually to 65c) I have also noticed that whilst blending in my benzoic acid to the water phase it actually creates a lot of heat and I wondered if this heat may interfere with the magnesium chloride/create a reaction, losing the benefits of the magnesium or even turning into something unpleasant to have in a topical product.
Thank you again and please be gentle with my ignorance of basic chemical reactions!
I really did try to research this on my own!Kind regards, R
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4 Replies
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Benzoic Acid has relatively poor solubility in water, so that is not your best choice of preservative to begin with. Why not choose something that is completely benign to MgCl such as Phenoxyethanol/EHG. And, if you are adding MgCl at a high enough percentage, the Mg Oils don’t generally need a preservative. Which raises another issue: MgCl creams can be quite tricky to make since the high level of MgCl (30%) wreaks havoc on the viscosity of an emulsion.
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MgCl hydrate crystals can produce HCl when directly exposed to high heat. Don’t think you’ll find this in formula.
Are you using Benzoic acid or Na Benzoate? You will have some Mg Benzoate produced.
As Mark said - your preservation is pretty poor with or with or without the “supportive” stuff. With Pheonoxy/EHG add something to address fungi -
@rab9 Inorganic salts are pretty stable in solution. What would happen in the pressence of an organic acid (as @PhilGeis mentioned) is that the Mg2+ counterion would interact with the carboxylic part of the acid. Nevertheless, at enough low pH, you’ll have the free acid back.
What is more worried as mentioned before, is that you might be using a weak preservative system, although as @MarkBroussard mentioned, high amounts of MgCl2 might reduce water activity enough to give you some protection, but that might not be beneficial if you’re making an O/W emulsion.
You’d be better off making a W/O emulsion, but the your MgCl2 will be “trapped” within the water phase of your emulsion and won’t be available for whatever you need (not sure there are specific aquaporines for Mg2+ transport).
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Thanks so much everyone for this specific information!
I am using benzoic acid at the moment. I’m aware it does have poor solubility but I use a mini milk frother to blend it into my hot water phase and it does the job. I’ve been using it a long time, have been resistant to change (even more resistant after a very unsuccessful round of experimenting with several ‘natural’ alternatives) but I have recently purchased some sodium benzoate. I have not tested it yet. (I understand that sodium benzoate releases benzoic acid anyway when combined with water so my concern about a reaction with MgCl would still be relevant when I make the changeover)
Firstly, thanks for the suggestions on preservatives that are specifically benign to MgCl2, that is extremely helpful for this product that I wish to make.
I also appreciate everyone being so emphatic about the need for strong preservation, and taking your duty of care seriously by pointing out the weakness in my preservative of choice. I’m aware of benzoic acid’s weakness against bacteria and finding an effective combination of preservatives that also align with my values (ethical/sustainable, preferably no parabens or formaldehyde) is a priority for me but it’s been a bit of a long process for me to sort through the minefield that is the trend towards ‘natural’ ingredients, the propaganda that has accompanied that and my own bias.
@MarkBroussard : I was happy to google EHG and discover it has no parabens or formaldehyde. Thank you for the specific suggestion.This forum has been a valuable source of rational information regarding preservatives, being offered by people that don’t have an agenda other than to make safe products. Thank you for that.
It seems that if I decide to use Phenoxyethanol/EHG I would still need an anti fungal and I know that my ‘old faithful’ Benzoic acid (or sodium benzoate when I make the change) is a great antifungal, perhaps they would support each other well. I will do my own research but if anyone feels it appropriate to comment on that combination I’d appreciate it.
I have gone off track from my original query, (please forgive) but it was somewhat relevant to suggestions that were made.
My main concern was that I might ‘lose’ my MgCl2 or the preservative properties of the benzoic acid to a chemical reaction if used in combination, or just end up with a substance unpleasant for topical use
@ketchito and @PhilGeis “Mg2+ counterion would interact with the carboxylic part of the acid. Nevertheless, at enough low pH, you’ll have the free acid back.”
Does this mean I don’t need to be concerned about this if my pH is low enough and that I could use sodium benzoate and MgCl2 in combination without worrying about ‘loss’ through chemical reaction?
Would you consider pH of 4 - 4.5 low enough? Thanks
Perhaps I would be better off researching an alternative anti-fungal to support phenoxy/EHG that is also benign to MgCl2…… (not an organic acid)
The heads up regarding how MgCl2 affects viscosity is helpful, thank you. I will keep that in my awareness and make small batches to experiment, perhaps keeping it lower than 30%.Also very helpful to know that my MgCl2 may be ‘trapped’ in the water phase of my emulsion anyway. I am going to do a bit more research on this.
I am very grateful for your time everybody, you have given me some fantastic additional relevant information that will help me in my research and experimentation of this product.
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