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How to use Oxalic Acid

oxalic acid varroa treatment wood bleach

Oxalic Acid uses, facts, tips and instructions


Oxalic acid is an organic chemical compound, the simplest dicarboxylic acid. Found in many plants (including sorrel and rhubarb), it takes the form of a white powder or crystals, without a distinct smell. It is obtained by heating sodium formate to approximately 400 ° C to form sodium oxalate which is then converted to oxalic acid with dilute sulfuric acid.

Another method is to pass carbon dioxide over metallic sodium or potassium at 360 ° C, and oxidize ethylene glycol or oxidize many other organic compounds (e.g. sugars) with nitric acid.
Oxalic acid can also be obtained by reacting acetylene with potassium permanganate. This compound is dissolved both in water and in organic solvents (ethanol, diethyl ether). It crystallizes from an aqueous solution in the form of a dihydrate. Forms salts and hydro-salts - oxalates


Oxalic acid is widely used in many industries, beekeeping. It is a wonderful chemical that removes rust. It is often used in GRP / fiberglass cleaners.
Oxalic acid from HD Chemicals LTD is present in 99.5% pure form, which, if needed, should be converted into a solution of oxalic acid with an appropriate concentration. Examples of concentrations and applications are presented below:


Oxalic Acid for Rust Removing

Prepare an oxalic acid solution. The desired concentration will be mixed in the range of 10 to 20%. Add oxalic acid to warm water and stir until the crystals dissolve in the water. Use warm water to mix the acid more easily. For 1 liter of 10% concentration we need 100g of oxalic acid and 900ml of warm water.
The solution is ready to be applied immediately to the rust. It is recommended to leave rusty objects in the solution for a period of several to several hours, depending on the degree of rusting of the material.

You can find ready mixed 5% oxalic acid solution in our shop


Wood Bleaching

Oxalic acid works brilliantly as a wood bleach. We suggest preparing a 10% solution with warm water. We apply the bleach to the wood with a brush. After drying, we can clean the wood before varnishing or other activities.

It is very important to prepare the wood before applying oxalic acid. The slime must penetrate the wood and therefore it is necessary to sand the surface prior to the bleaching process.

You can find ready wood bleach based on oxalic acid in our shop


Fighting Varroa with Oxalic Acid


Oxalic acid is the primary agent recommended for the treatment of varroa by the European Specialist Group, which in 1998 developed a year-round method of combating varroa.

Preparation of the oxalic solution:

In 400 g of warm water, dissolve 400 g of sugar, pour in 30 g of acid and mix with a plastic spoon. In this way, we get about 600 ml of solution. These proportions should be kept and we do not recommend modifying the concentration.

Performing the procedure:

We lift the covers or take out the bars, smoke a little and pour a thin stream of warm solution over the bees, 5 ml per street

small family - 20-25 ml,

normal - 25-30 ml,

large - 30-35 ml.

We dose the solution using a plastic syringe without a needle or with a dispenser.

When working with oxalic acid, use glasses and rubber or latex gloves

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  • Nigel Barfoot on

    Hi HD. Thanks for your recent delivery & note re eBay, etc.
    Could you please recommend the concentration of oxalic acid to clean a GRP hull on a boat?
    No rust, just all the other crap that accumulates.
    Afterwards I’ll be polishing etc. Thanks for your help. Nigel

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