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  • Jerry Brown
    #1 written by Jerry Brown 1 year ago

    ALL homemade soap has a high (>9) pH. Using pH paper to test for free alkalinity of soap dissolved in water will always be basic. Here’s a easy quick & dirty test to test for free alkali.
    Go / No-Go Test
    This method is particularly useful in hot process soap making.

    1 Make up an isopropyl alcohol (IPA)/pheolphthalein (phph) solution. Add 47-drops of a 1% phph/IPA to a full bottle (32-fl-oz., 946-mL) of 70% IPA. Mark bottle “+ phph”. You will not need to add any more phph to the IPA for future tests.

    2 Make up a dilute sodium hydroxide solution – 5-ppt (2.5-g NaOH in 500-g H20) NaOH/H20 solution

    3 Before each excess alkalinity test, add dropwise the NaOH/H20 to the IPA/phph until a faint pink to neutralize any acid in the IPA.

    4 To test the soap, transfer a small pea size sample of the uncolored soap into a vial & add several milliliters of the neutralized IPA/phph. Shake to dissolve the soap.

    5 No color change indicates no free alkali. A color change to dark pink indicates some alkali.

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