Problem dissolving salicylic acid!

Unknown Member, PCF student
edited March 2014 in Formulating

I'm having a difficult time dissolving 2% salicylic acid. I’ve read over numerous of forums and here as well but I did not find any answers. I don’t want to incorporate any alcohol in the formula. I’ve tried using propylene glycol with heat, which seemed to work but after a day SA started to recrystallize. I tried to increase the amount of propylene glycol and again it was unsuccessful. 

Does anyone have any idea what went wrong? Any advice would be helpful. Thank you guys!

Comments

  • cherricherri Member
    mix it with alcohol it will dissolve easily or use glycols.. or tween mix together and heat up till 40-45C
  • DavidWDavidW Member, PCF student
    What is your end product?  What else is in your formula?  Salicylic Acid is finicky sometimes.  Need more info to help you.
  • Chemist77Chemist77 Member, PCF student
    David is right, without knowing the product it is difficult to opine.
    Though for a feet callus remover I used MPG, 2% Salicylic Acid, DPG and a surfactant to aid in solubility. I have a stable formula with no recrystallization even after months.
  • MicroformulationMicroformulation Member, Professional Chemist
    You could consider an easier Salicylic acid such as Salvona's product. Much easier to work with especially at the lower level you need.

    http://www.innovadex.com/documents/1126638.pdf?bs=4678&b=195800&st=1&sl=28010429&crit=a2V5d29yZDpbc2Fsdm9uYV0gPiBJbmdyZWRpZW50cw==&k=salvona
    markfuller@microformulation.com Microformulation.com Microformulation Cosmetic Consulting provides Custom Formulations for both large Commercial accounts as well as smaller entrepreneurs. We can provide Naturally compliant Formulations under the NSF, NPA, Whole Foods and USDA Organic Certifications. BS.Pharm Albany College of Pharmacy, Union University.
  • Unknown Member, PCF student
    edited March 2014

    Thanks for responding guys! 

    I'm trying to make a very basic 2% clear salicylic gel for acne/blemish skin with pH ~3.5. I've used propylene glycol to dissolve salicylic acid with the aid of heat. Then I incorporated this mixture into the gel I preped prior using hydroxyethylcellulose. Glycerin was also added along with other extracts in this gel. That was pretty much it!

    Any thoughts? 

  • Chemist77Chemist77 Member, PCF student
    Add a little Disodium Lauroamphoacetate and a little DPG, should keei it clear if you have recrystallization issue.
  • DavidWDavidW Member, PCF student
    I have always found with a lot of water in the formula the sal acid drops out.  However, I usually work with higher amounts of sal acid.

    If you are making a face wash it should stay.
  • mikebavingtonmikebavington Member
    Have you tried adding the HEC at the end of your formulation process? First mix the SA with the PG. Then add it to the water AND THEN try to incorporate the HEC last.
  • Bill_TogeBill_Toge Member, Professional Chemist
    edited March 2014
    if you don't want to use alcohol, surfactants and co-solvents are the way to go

    I've found ethoxydiglycol/diethylene glycol monoethyl ether works well at low levels (1-2%)

    also, at my last workplace we produced a medicated shampoo with 2% salicylic acid, about 11% active SLES and no organic solvents; provided the batch was heated to 40-50°C prior to addition, and the salicylic acid was given enough time to mix in (1-2 hours for a 5000kg batch), we had no solubility issues even at low temperatures
    UK based formulation chemist. Strongest subjects: hair styling, hair bleaches, hair dyes (oxidative and non-oxidative) I know some stuff about: EU regulations, emulsions (O/W and W/O), toothpaste, mouthwash, shampoos, other toiletries
  • ZinkZink Member
    edited March 2014
    See my thread about the same issue in a oil in water emulsion:
    https://chemistscorner.com/cosmeticsciencetalk/discussion/222/acidic-scar-healing-lotion-curdled-under-cooldown-help-me-fix-my-recipe#Item_10

    I've modified a solubility table to show how many grams of SA will dissolve in a liter (typ 1000 grams) of solvent and est how many % of solvent you'll need in your 2% formula not accounting for the specific gravity of the solvents.

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