Comentário sobre Terumot 5:7

If a seah of terumah fell into a hundred [of hullin] and he lifted [a seah] out, and then another fell in, and he lifted another out and another fell in, the pile is permissible as long as the amount of terumah does not exceed that of the hullin. A seah of terumah falls into one hundred seahs of hullin and then one seah is removed. The rabbis hold that the seah removed is not the seah of terumah. Therefore, the mixture remains about 1/100 terumah. If another seah of terumah falls in, it too is neutralized and a seah can be taken out. However, there are now about 2/100 terumah in the mixture. This process can keep on repeating itself until there are more parts terumah in the mixture. Once that happens, the mixture can no longer serve to neutralize the terumah that falls in. We should note that as long as the mixture is less than fifty per cent terumah, it is treated as hullin.

הגביהה – according to the law of heave-offering that is neutralized in one-and one-hundred.

הרי זו מותרת – and one needs to lift it up [out of the mixture].

עד שתרבה תרומה על החולין – that is, until there would fall there fifty-one [parts] of heave-offering/Terumah, but half by half is permitted.