Reference for Chullin 217:12
א"ל רב אחא מדיפתי לרבינא
Perhaps all are of the opinion that even when the forbidden substance can be is extracted it is still forbidden, but they differ [about the neutralization<span class="x" onmousemove="('comment',' The position would then be: all bold that the piece upon which the drop of milk fell is wholly forbidden as nebelah, but the dispute is concerning the other pieces in the pot. R. Judah holding that the entire contents of the pot are forbidden because the forbidden piece can never be neutralized amongst other pieces, and the Sages holding that neutralization even in a mixture of homogeneous substances can take place. The attitude of Rabbi who holds, first that when the forbidden substance can be extracted the piece is still forbidden, and secondly that neutralization cannot take place between homogeneous substances, is expressed thus: The words of R. Judah are acceptable to me, namely, that the entire contents of the pot are forbidden, in the case where the pot was not stirred at once but only later on, for then one piece was first rendered forbidden and it would later render the entire pot forbidden. But the words of R. Judah are not acceptable to me in the case where the pot was stirred straightway, for then the drop of milk was immediately evenly distributed among the contents of the pot. In this latter case the words of the Sages are acceptable to me, namely that the entire contents of the pot are permitted, for the apprehension lest the pot was not well stirred or well covered need not be taken into consideration.');"><sup>7</sup></span>