I'm looking at ordering some HCl for pH adjustment. I don't want to order a concentration so high that I'll need a fume hood to work with it safely. Just safety goggles, chem gloves, long sleeves. Would a 10% HCl solution be strong enough to adjust pH for typical cosmetic formulations? Or should I order a 25% solution? I can dilute down and create lower molarity stock solutions easily enough, but don't want to order HCl too weak to be generally useful or too strong to be an inconvenience or (respiratory) danger.
A 10% HCl solution is 100mg/mL HCl, or approximately 3.33mg/"drop" HCl (varies...). A log calculation shows that only 3.65 mg HCl is needed to reduce pH of 1 liter of pure water to 4.0.
I'm guessing that an order of magnitude more (~36.5 mg/L?) may compensate for 0.35% sodium benzoate, for example. That's still feasible with 10% HCl while trivially altering the volume.
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