Sodium Hydroxide for pH Neutralization

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Sodium Hydroxide

There are many chemicals available on the market today that are suitable for use as neutralization chemicals. The most commonly used chemicals are discussed in an article available here:  Neutralization Chemicals.


Sodium Hydroxide NaOH

Sodium Hydroxide (NaOH): Also known simply as caustic, is the most widely used alkaline neutralizing chemical in use in industry today. Sodium hydroxide is easy to handle, inexpensive, and very effective for the neutralization of strong or weak acids. NaOH is available in concentrations of up to 50%, which is the most commonly used concentration.


Unlike chemicals such as lime NaOH is very highly soluble and relatively easy to handle. NaOH is a one normal solution meaning that one mole of sodium hydroxide liberates one OH- molecule for neutralization. The neutralization of hydrochloric acid, for example looks like:

HCl + NaOH → NaCl + H20


While the neutralization of sulfuric acid will require two moles of NaOH for each mole of sulfuric acid:

H2SO4 + 2NaOH → Na2(SO)4 + 2H20


One must be careful when using 50% NaOH because of the freezing point. NaOH at a 50% concentration will begin to freeze at temperatures below 600F. This happens to be a very common problem and can render a system useless. The best way to circumvent this problem is to use lower concentrations. We generally recommend using 25% NaOH since the freezing point at this concentration is -200F.


Caustic has a high affinity for CO2 in the atmosphere. The absorption of CO2 results in the formation of insoluble carbonate species. This results in the formation of solids that can be problematic for small pumps. A lower concentration of caustic not only alleviates the problem of freezing it also decreases solids formation as a result of CO2 absorption.


Caustic is more expensive than lime or magnesium hydroxide, but, due to its solubility it is much easier to handle.


Neutralization reactions form salts as the pH is brought near the end point. Sodium salts are normally quite soluble in water. Therefore reactions using NaOH will not normally generate high solids, unlike calcium products (lime) or magnesium products (magnesium hydroxide).


Generally this is a safe and inexpensive base to use for the neutralization of acidic materials.

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