Formulating

Salicylic Acid crystallization

Posted by Christopher on May 26, 2016 at 3:15 am

I’m having
a difficult time keeping salicylic acid from recrystallizing. I managed to
dissolve 10 % in a solution of 75 % 1,3-propanediol and 15 % propylene glycol
and it stayed dissolved for over 1 week (I tossed it after that). However when
I added water to the solution, it almost immediately recrystallized.

I started
out by mixing and heating the three ingredients in a beaker until dissolved. In
a separate beaker, I mixed water, glycerin and preservative. I then combined both
phases and recrystallization occurred. I heated the mixture and everything
dissolved nicely, however when it cooled down it happened again.

Any recommendation?

PHASE A 1,3-propanediol	% 75,00	g 4,50
propylene glycol	15,00	0,90
salicylic acid	10,00	0,60

PHASE B	%	g
distilled water	76,00	22,80
glycerin	3,00	0,90
Phenoxyethanol, Ethylhexylglycerin (Euxyl PE 9010)	1,00	0,30

Edit: As you can see I’m using 6 grams of phase A to get a total of 2 % salicylic acid in the final product which is 30 grams.

Christopher replied 8 years, 3 months ago 6 Members · 10 Replies

10 Replies

ashish

Member
May 26, 2016 at 10:20 am

U can try Hexandiol, It will solve your problem.
MarkBroussard

Professional Chemist / Formulator
May 26, 2016 at 1:34 pm

You can also add 1% Sodium Citrate and use Methyl Gluceth-20 Benzoate (Finsolv EMG-20) instead of Propylene Glycol
chemist1

Member
May 31, 2016 at 7:07 pm

Finsolv EMG-20 works well to dissolve Sal acid.
chemist1

Member
May 31, 2016 at 7:07 pm

Sorry Mark. I just saw your post
cherri

Member
June 30, 2016 at 4:08 pm

@Christopher can’t you use surfactants?
DavidW

Member
July 15, 2016 at 12:16 am

Get rid of or drastically lower your water %.
Christopher

Member
July 16, 2016 at 2:00 am

Sorry for the late reply, I totally forgot about this topic. I tend to read through the posts without logging in and mine must’ve been way in the back.
Thanks for your replies guys, I will definitely keep them in mind for the future.

But it looks like things solved themselves. I tried the exact same recipe again with a different method and, to my surprise, it worked. The only difference this time around was that I took my time stirring and heating between each ingredient. It is now 24 hours later and everything’s still dissolved. I even lowered the pH without anything settling out.
DavidW

Member
July 17, 2016 at 2:02 pm

Watch it for awhile at room temp. I have seen the Sal acid drop out weeks later.
Christopher

Member
July 17, 2016 at 4:42 pm

Yeah, I’ll keep observing.
Christopher

Member
November 27, 2016 at 2:58 pm

Where would I source Sodium Citrate and Methyl Gluceth-20 Benzoate? I don’t own a company so ordering a sample from manufacturers websites won’t work.