Which preposition to use with diluents

for Occurrences 2%

WARM WATER.Warm water is preferable to cold water, as a drink, to persons who are subject to dyspeptic and bilious complaints, and it may be taken more freely than cold water, and consequently answers better as a diluent for carrying off bile, and removing obstructions in the urinary secretion, in cases of stone and gravel.

of Occurrences 1%

Its proper character, however, is that of a cooling summer vegetable, not very nutritive, but serving as a corrective, or diluent of animal food.

Which preposition to use with  diluents