Increasing urea percentage from 40 to 48%

Member
Good day -

Without going into too much detail, I have a 40% urea gel (commercial) and want to increase it to 48%. The 47% gel (for feet) costs over \$700 for 136 grams. Rather than try and build/buy a different formula, I wanted to increase the % urea, which by my calculations is about 8% more, or 8 grams.

I have done that, after milling the prills down as fine as I could, then mixing in a tiny amount of distilled water and mixing, then incorporating that into the urea gel.

While this does seem to work, I'm wondering where I've gone wrong here. I am not a chemist and have a rudimentary grasp of what I've done.

Can someone please educate me on this a bit?

Thank you

• Member, Pharmacist
If it does seem to work, the only thing you've done wrong is exact maths.
Assuming you added 8 g urea and 2 g water to 100 g gel, the result would be 110 g = 43.6% urea .
If you were to add 15.5 g pure urea, this would result in your desired 48% .
The one thing you did exactly right is not going for that \$ 700 product!
In my experience and given the great water solubility of urea, simply adding pure urea even in prill form, mixing, letting sit for some minutes, re-mixing (and probably repeating once more) is all it takes to fully dissolve and incorporate urea into creams or gels. It may transiently cause issues but if the end product can handle the added amount of urea, these issues will pass once homogeneously mixed.
In theory, urea is soluble at ~54% (w/w) in water and with the proper knowledge and one single ingredient (which you probably have in stock), a 73% (w/w) honey-like liquid is possible. A bit more knowledge and maybe some trial and error turns that into a gel (with obviously lower % than the initial 73).
• Member
Wow. Ok, so yes, I did fail maths. Several times. A literal F and a D. Am now senior software architect! I appreciate your help on this. I ruined one of my jars by adding the prills directly and mixing. I guess I wasn't paying attention. What happened was that they didn't dissolve at all. And in fact, ended up being sharper than needles! Not much fun, so I will go ahead and fix the formula to use 15.5g.

To clarify, the raw product is 113ml, if that changes the calculation at all.

Appallingly, there is like only one company that actually sells 47% urea. I can buy 50% cream out of Canada, but I need this on an ongoing basis.

So the 43% certainly has helped. Thanks again. I'll check back to see if the volume size makes any difference.
• Member, Pharmacist
VEN said:
...Am now senior software architect! ...And in fact, ended up being sharper than needles! ...
To clarify, the raw product is 113ml, if that changes the calculation at all...
Ah, the guy who programmed Windows Vista !
Okay, maybe you're above solubility then... what else is in your product?
Volume only matters if you want a v/v or w/v percentage but for w/w density is irrelevant.
• Member
why we don't just use only  these 2 ingredients water and urea plus a preservative such as a skin moisturizere ?
does it have no effect without other additives ?
• Member, Pharmacist
Water and urea will be too liquid I guess.
• Member
IN a vaporizer can have an effect?
• Member
Pharma said:
VEN said:
...Am now senior software architect! ...And in fact, ended up being sharper than needles! ...
To clarify, the raw product is 113ml, if that changes the calculation at all...
Ah, the guy who programmed Windows Vista !
Okay, maybe you're above solubility then... what else is in your product?
Volume only matters if you want a v/v or w/v percentage but for w/w density is irrelevant.
Lol No, I do database architecture and Winforms dev.

So, the ingredients. This is called 'Clear 40' from Scientific Solutions Group. In order, the ingredients are:

• Aloe Vera
• Carbomer
• Coconut Oil
• Emulsifiers
• Methylparaben
• Mineral Oil
• Preserved Water (what is THAT?)
• Propylene Glycol
• Tea Tree Oil
• Propylparaben
• Triethanolamine
• Xantham Gum (because MMMMM GUM!)

The active ingredient (4 oz/113 ML) is of course 40% urea, source unspecified. Just Urea.
• Member, Pharmacist
Preserved water aka aqua conservans is a pharmaceutical term for water preserved with methyl- and propylparaben .
Unless there's a lot of coconut and mineral oil in there, it seems unlikely that you reach saturation by upping urea to 48%. On the other hand, that composition isn't in decreasing weight-% order ;( . You don't happen to have a proper LOI, do you?
• Member
Sorry, LOI? So how would I go about increasing it? Pre-disolve it?
• Member, Pharmacist
LOI = List of ingredients according to INCI norms, not the marketing version.

Increase what? Urea? Better get that LOI cause I can't find it on Google.