When one wants to make celim (vessels) Kosher by purging non-Kosher absorbed tastes from it, one method is hagaleh, which normally is done with water. The Rema says in SA OC Siman 452:5 that b'dieved (if the ideal cannot be met) it helps to make hagalas kelim in "shar mashkim" (other liquids; ie., not water).
However, the Rema writes that if someone had made hagaleh on a lot of celim and from the "rov plitas hakelim" (from the large amount of stuff being purged from the vessels) the remnant water that became like "tzir" (brine) shouldn't be used for hagaleh.
The Mishnah Brurah there (SK 27) writes that this rule applies even b'dieved, meaning that not only is it not the preferred way to do hagaleh, but it simply doesn't work. The reason is because at this point there is no more strength in the water (meaning the water that is now briny) to be maflit (take out) what is balu'ah (absorbed) inside of the cli.
However why shouldn't hagaleh in such water and tzir be like that of shar mashkim that b'dieved would help?