Webster’s Revised Unabridged Dictionary · 1913
Diluent
Dil′u·ent (dĭl′ū·ent), a. [L. diluens, p. pr. diluere. See Dilute.] Diluting; making thinner or weaker by admixture, esp. of water. Arbuthnot.
Dil′u·ent, n. 1. That which dilutes.
2. (Med.) An agent used for effecting dilution of the blood; a weak drink.
There is no real diluent but water. Arbuthnot.