The HI84529-51 is a 120 mL bottle of alkaline titrant solution used for the High Range 20  range that determines 0.1 to 2.0% lactic acid in dairy products.

The methodology for titratable acidity in dairy products is based on a neutralization reaction of the acids in a sample (e.g., lactic acid) with a base (e.g., sodium hydroxide) to produce water:

H⁺+OH^- → H₂O

In an ideal solution, the endpoint of an acid titration corresponds stoichiometrically to the complete neutralization of the acids present. The endpoint for this reaction can be determined visually using a color indicator (e.g., phenolphthalein); however, this endpoint becomes very subjective in opaque and colored samples such as milk. The HI84529 removes this issue by titrating to a fixed pH endpoint that is potentiometrically determined by the FC260B half-cell pH electrode and HI5315 half-cell reference electrode.

Replacement reagents required to operate the HI84529 include: