Wine Analysis Home

Preparation of a 25% volume/volume Orthophosphoric Acid (25% v/v H₃PO₄)

As the accuracy of this solution is not critical, the preparation is simply a matter of diluting commercially available strengths. Follow safety procedures applicable to acids.

e.g. Using a measuring cylinder, measure out 294 ml of 85% w/w orthophosphoric acid (H₃PO₄) and slowly add to 700ml of distilled/deionized water in a 1-2 L beaker, mixing all the time.

Note: always add acid to water not the other way around.

Alternatively

Using a measuring cylinder, measure out 280 ml of 90% w/w orthophosphoric acid (concentrated H₃PO₄) and dilute it to 1 L with distilled/deionized water with similar precautions.

Safety Note:
When mixing acids with water always add the Acid to Water (Mnemonic A before W).

As in this case, heat can be generated during addition and therefore should be carried out slowly and the container exterior may require cooling in a bath containing an ice and water mixture.