Urea cream - gas emission
I have a problem formulating a foot cream and I can’t get my mind around what might be causing such a problem.
So basically I’m trying to formulate a foot cream with 15% Urea. As a buffer I am using 9% of Lactic acid pre-neutralised with Sodium hydroxide at a pH 4,5-5,0.
The formula is stable, the buffer works perfectly keeping my pH between the range of 4,5-5,5 but there is a big problem… When the product stays between this certain pH range, huge amount of gas is being produced, which makes the tubes swell up like balloons. I came to the conclusion that this gas is not ammonia because it doesn’t smell at all, so I think that most likely it’s CO2.
When I tried to start off at a higher pH (5.5) the phenomenon decreased significantly, although it is still visible. But at that case, the buffer didn’t work as effectively as it did the first time.
I should add that I was asked to formulate according to an existing product in the market that doesn’t seem to have this problem at all.
In the end I found a solution by keeping the product’s pH higher than I wanted at first, but I am still curious to know if anyone has come across this kind of problem before.
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