LABSA Sulfonic acid to Sodium hydroxide ratio for dishwash liquid ?

I tried stochiometric ratio
Linear sulfonic acid molecular weight 326.49
Sodium hydroxide 40

but pH is still very acid
I made sure all Sodium hydroxide flakes were dissolved before adding sulfonic acid.

I tried the ratio posted here
https://www.happi.com/contents/view_/2011-03-04/formulating-manual-dishwash-detergents
but got the same problem.
I compensated for LABSA being 96% pure, and got the same results.

Comments

  • Gunther I have always realised that it is difficult to give one specific ratio in such neutralisation. For me it varied from.0.5% upto 1% and I could never tell my customers a fixed ratio. Better go in little incremental dosages. 
  • Just do a titration with an indicator eg. bromothymol blue, and use the result for the ratio needed. https://upload.wikimedia.org/wikipedia/commons/f/fb/Bromothymol_blue_colors_at_different_pH.png
    Design of anti-aging creams, gels, and serums; shampoos; and therapeutic cosmetics. In-house label and box design capability.
  • This info might be useful as a starting point.


    Ultimately the amount required will depend on your particular DDBSA. Don't forget that DDBSA contains free sulfuric acid that also needs to be neutralised.

    I would recommend using 50% NaOH solution for neutralisation rather than using flakes.

  • You have to titrate because for starters you don't know how much of the NaOH has reacted with air CO2 to form sodium carbonate. Just titrate it, it's not rocket science, why is there such reluctance to do basic chemistry? Buy a freaking burette and some indicator!
    Design of anti-aging creams, gels, and serums; shampoos; and therapeutic cosmetics. In-house label and box design capability.
  • Thank you guys
    At the end I ended up doing a titration with a pipette and pipette pump and pH paper (I don't like dipping pH meters in strongly acid or alkaline solutions).
    It took 0.4% of 50% NaOH (equal to 0.2% solid NaOH) to reach a mildly alkaline pH.

    @Belassi thanks for the Bromothymol blue idea. Titration was slow as some solid debris (maybe solid NaOH coming out of solution) formed on contact with the acid, taking a bit to redissolve.


    @ozgirl
    May I ask why 50% NaOH is preferable to flakes?

    Neutralization Information:
    Temperature and pH must be controlled during neutralization of BIO-SOFT S-101 to prevent darkening of the product and corrosion of stainless steel equipment. The reaction temperature should not be allowed to exceed 50°C and the pH should not go below 6.5.
    https://www.stepan.com/uploadedFiles/Literature_and_Downloads/Product_Bulletins/Surfactants/BIO-SOFT®/BIOSOFTS101.pdf

    I wonder if this only applies to steel tanks?
  • Funny, every high active DDBSA I ever saw was dark as espresso coffee. The pure 96% acid will darken 304SS when contacting for more than a few hours, but a quick treatment with peracetic acid solution takes care of that. In practice, you always add the alkali to water first (after determination ala Belassi or Stepan  lit) then slowly add the LABSA or DDBSA to the mixture until done. Cheapest way to make laundry detergent.  
  • @Gunther It is easier to handle and you don't have to ensure that it is dissolved.
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