diluter

plural diluters

1. A substance used for diluting.

   Very little is prescribed in the Shops under this Intention, because the Kitchen so much better supplies all of this Kind, and furnishes the common Diluters, of which Sage Tea, Lemonade with a little Wine, and Wine and Water, are much the best […]

   1719, John Quincy, Pharmacopœia officinalis & extemporanea

2. chemistryA device that adds a measured amount of sample to a measured amount of diluent.