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Some questions about my SLS powder
I purchase SLS powder locally and the supplier imports it. They say it has 95% active surfactants.
It has very high ph and it needs a lot of acid to reduce pH to 7.
2% of this SLS powder needed 1.5% citric acid to reduce pH to 7.
Today i added LABSA instead of citric and 5% of it reduced the pH to 7.
Questions:
1. Is it normal that 1.5% citric acid reduce the pH the same as 5% LABSA?
2. How much base would be in this 2% SLS powder that it needs 1.5% citric acid or 5% LABSA to reduce pH to 7?
Also, i mixed sodium hydroxide with 1.5% citric acid and 0.9% sodium hydroxide was needed to increase pH of 1.5% citric acid to 7. Does this mean my 2% SLS powder has ~0.9% sodium hydroxide in it? It is 45% of it’s weight.
I am very confused right now.
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2 Replies
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Yes, it is possible. Citric acid and LABSA have different acid strengths and buffering capacities, with LABSA being a stronger acid but requiring more to achieve the same pH shift, likely due to incomplete dissociation or interaction with other components in the solution. Citric acid, a triprotic acid, offers better buffering, making it more efficient at neutralizing the alkalinity of your SLS solution.
Your SLS powder is likely highly alkaline due to residual NaOH or Na₂CO₃ used in its synthesis.
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Thanks
About residual NaOH, for 1.5% citric acid, 0.9% sodium hydroxide is needed to adjust pH to 7. Now if 2% of my SLS has 0.9% residual NaOH in it, it means active surfactant percentage is less than 55% in this SLS powder. Am i correct or still messing something?
2% of this SLS powder needs 1.5% citric acid to pH 7.
0.9% sodium hydroxide needs 1.5% citric acid to pH 7.
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