Examples from the Web for half-gallon
If hard soap is desired, put one quart of salt in half-gallon of hot water.Housekeeping in Old Virginia|Marion Cabell Tyree
The missionary put his hand into this sawdust, and drew out a half-gallon can.White Fire|Roy J. Snell
A half-gallon to a plant each week will be a sufficient normal feeding.Making a Rose Garden|Henry H. Saylor
Put some of them into a half-gallon stone jar, and pour over them a quart of boiling vinegar.
He is now to be seen more frequently in the skittle-ground, clasping a half-gallon, instead of a quart of beer.Rattlin the Reefer|Edward Howard