1. Rebbi Akiva: An object that is Sheni k'Tum'ah creates a Shelishi l'Tum'ah in Chulin.
2. Rebbi Akiva similarly derives that liquid that is a Sheni causes food to become Tamei.
3. Rebbi Akiva similarly derives that liquid that is a Sheni causes other liquids to become Tamei.
4. The Torah sometimes teaches us a lesson despite the fact that it can be derived from a Kal va'Chomer.
5. Rebbi Yosi: Revi'i l'Tum'ah invalidates a Kodesh item.
A BIT MORE
1. Rebbi Akiva derives this from the verse, "Any earthenware vessel into which something falls will be Metamei." This implies that the item that falls into the Tamei earthenware vessel and become a Sheni can make something else Tamei as a Shelishi.
2. This is similarly derived from the verse, "And any liquid. will be Metamei."
3. This is derived from the fact that the words, "it will be Metamei," are repeated twice.
4. Although the Torah does not use extra words or even letters, the Torah will sometimes state a law explicitly despite the fact that it can be derived from a Kal va'Chomer even without these words.
5. Rebbi Yosi seems to disagree with Rebbi Akiva, who implies that even a Chamishi b'Kodesh is invalid.