Dosing soda lye

What is caustic soda?

Caustic soda is an aqueous solution of sodium hydroxide. Colloquially, it is often called "lye". It feels somewhat soapy and is an extremely alkaline solution. This property makes it often used for pH corrections when a solution is too acidic. This is done, for example, with a automatic pH control. It also finds application as a sink unblocker or for degreasing installations. 

When handling caustic soda, it is very important to take proper safety precautions. Gloves and safety goggles or face shield are minimally required when you are adding to a stock tank, for example.

Dosing caustic soda with a dosing pump

As indicated, sodium hydroxide is often used to correct the pH of a solution when it is too low. For corrections when pH is too high, hydrochloric acid or sulphuric acid is often used. For the dosing of caustic soda is often a dosing pump used. Often, this dosing pump is controlled directly or indirectly by a pH sensor. This is convenient, as pH correction is then automatic.

As caustic soda is an aggressive liquid, it is important that the selected dosing pump is constructed from the right materials. Caustic soda is considered corrosive if its concentration exceeds 2%. Given that one usually works with 30% in pH corrections, this is an important point. Suitable materials for use with caustic soda include EPDM, PTFE and PP. 

Dosing caustic soda for pH correction

For pH correction, it is important to measure the pH first. This can be done with a pH sensor. This signal can then be used by the computer in the dosing pump or controller to know how much to dose. 

For when the pH can be both too low and too high and needs to be neutralised, an acidic solution is needed in addition to an alkaline solution. After all, the pH should be controllable both ways. In this case, a single pump is not sufficient; at least two are needed. This is usually combined with a controller. We will gladly supply you with the necessary components. We also have ready-made panels available.

Are you looking for a dosing pump to dose caustic soda? Or a pH controller? We will be happy to help you choose the right pump. You will find our details at the bottom of the page, but you can also here request a quote.

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