Friday, September 6, 2013

Glycerin is water soluble!

I addressed this the other day, but I think I need to say it again as I've seen a three posts or e-mails in the last two days referring to glycerin as oil soluble. Glycerin is water soluble. It is the very epitome of being water soluble. Let's take a look at the chemistry - and don't zone out on me as this is interesting!

In the post on solubility, we took a look at why oil and water don't mix. The reason for this is that water is polar - meaning it has a slightly more negative charge near the oxygen atom and a slightly more positive charge near the hydrogen atoms. (The red is oxygen, the white is the hydrogen.)

The same is true for the glycerin molecule. The oxygen atom is slightly more negative and the hydrogen atom is slightly more positive. So it is also a polar molecule.

Like dissolves like means that something polar will dissolve something polar. Water is polar and glycerin is polar, so we should expect that glycerin will dissolve in water. If something dissolves in water, we call it water soluble. As its solublity is really high in water - it's called "completely soluble" so add as much as you want - we can call this water soluble.

If you want to see if what I've written is valid, get a glass of room temperature-ish water. (Solublity is generally tested at 25˚C, but we can do it at room temperature of 18˚C to 20˚C.) Add some glycerin to it - let's say a dollop from your bottle - and mix. Add some more and mix. And so on. If it remains mixed, then it's water soluble.

If you want to test if something is water soluble, get a glass of water and add the ingredient. Mix. Let it sit for a bit at room temperature and see what happens. If it floats to the top or sinks to the bottom and you can see it's a different thing from the water - for instance, it's a white solid or a yellow liquid - that means it didn't mix in and isn't soluble. Do the same for something being oil soluble.

Can I ask the question? Where are you getting the idea that glycerin is oil soluble? It's definitely coming from somewhere! Could it be this post at Livestrong that calls it "glycerin oil", something I have never heard it called before? Or this post from eHow that does the same thing? 

Glycerol: Jack of All Trades
Glycerine: An overview
Powerpoint from the University of Idaho
My chemistry classes


Artemis said...

I know that I commented on a post quite a while ago, regarding choosing an emulsifier to use in a rinse-off oil cleanser (or rather, enquiring as to whether you'd received my email about it!), but I'm afraid that I can't find the post I commented on so I hope you don't mind me putting my final recipe here. Apologies for the delay but I eventually managed to find a supplier of polyglyceryl-4 oleate and, after some experimentation, came up with the following recipe:
40% Soybean oil
20%Hazelnut oil
15% Apricot kernel oil
10%Jojoba oil
1% Vitamin E
1% Lavender essential oil
1% Rosemary essential oil
12% Polyglyceryl-4 oleate

I know that this is quite a lot of polyglyceryl-4 oleate to use, but I didn't want to risk any trace of the cleanser being left on my face. Personally, I have found it an absolute joy to use and it leaves my skin feeling fantastic- never dried out, but it doesn't become too greasy again quickly either. I hope you enjoy it too!

Stephany&Stacia said...

Hi Susan,
First of all thank you for all your help, your blog is a godsend and I appreciate your work so much!

Now speaking of oil soluble/water soluble, would it be possible to do a serum that is roughly 80% oils and 20% water? I couldnt find anything on your blog about it. I want to make a serum with MAP at 10%, 10% water and was thinking maybe 72% oils and 8% Ecomulse? Or do I use a polysorbate to just disperse the water in the oils instead of emulsifying them together? Please help if you can and thank you so much!

Anonymous said...

Extremely unrelated, but Halloween is coming up and I am going to make some borax slime. Since I happen to have preservatives do you think I should add them?
Do you have any cool fun Halloween experiments to share?

robyn m said...

Just wanted to say that I love this blog. I recommend it all the time. thank you for sharing your knowledge with us.

Stephanie said...

Thank you for this post. Actually, thank you for all of your posts. They're really helpful and not just about pretty-fying yourself. There actually are explanations here, which some readers - like me - prefer.

Amelipou said...

Hi! Artemis' cleansing oil recipe seems promising. I've been trying to find Polyglyceryl-4 oleate. It's difficult to find, more so because I'm in Hong Kong. I find several version of Polyglyceryl-4 oleate with different HLB values. Can you tell me what HLB value should be used, please?