Mikvaos 10:6-7

Mikvaos 10:6

Beis Shammai say that hot water may not be immersed in cold, nor vice versa, nor foul water in fresh, nor vice versa; Beis Hillel say that such things may be immersed. If one immerses a vessel full of liquid, it’s as if it hasn’t been immersed. If it was full of urine, it is treated as water (and the vessel is purified when the liquid connects with the mikvah water). If it held purification water, it remains unclean until the water of the mikvah exceeds the purification water. Rabbi Yosi says that even if a vessel that can hold a kor (more than 70 gallons) contains only a quarter-log of liquid (about three ounces), it’s as if it hasn’t been immersed.

Mikvaos 10:7

All foods combine to make up the quarter-loaf that renders one’s body unfit; all liquids combine together to make up the quarter-log that renders one’s body unfit. This is a case that’s more stringent regarding one who drinks ritually unclean liquids than it is for a mikvah because regarding the former the Sages made other liquids like water.