(Mishnah): One can use Demai to contribute towards an Eiruv Chatzeiros or a Shitufei Mavuos; one makes upon it Birkas HaMazon and one who ate it may join a Zimun (even though he was not permitted to eat it); he may tithe it when naked and he may tithe it in Bein Hashmamos (the twilight time at the onset of Shabbos); if he separated Maaser Sheni from it before Maaser Rishon, it is fine.

The oil that a weaver rubs between his fingers is obligated in Demai; but the oil that the comber adds to his wool is exempt from Demai.

(Gemara): He may tithe it when naked since a blessing is not made when tithing it.

He may tithe it in Bein Hashmamos - this is like the Mishnah (in Maseches Shabbos) that discusses that time period when it is doubtful whether it is after nightfall, that permits tithing Demai.

Baraisa (R. Chalafta ben Shaul): One may redeem Demai in the bathhouse, since a blessing is not made.

But for definite Tevel, a blessing is required.

R. Mana to R. Yudan: How does he make the blessing? If he is redeeming Maaser Sheni produce, he says, "about the redemption of Maaser Sheni''; if he has brought Maaser Sheni money to Yerushalayim and he wishes to transfer the sanctity onto food (as required), he says, "about the exchange of Maaser Sheni''. If he separated Maaser Sheni before Maaser Rishon, it is valid. That's only post facto, but ideally, it may not be done.

(R. Ba son of R. Chiya bar Vava/ R. Chiya citing R. Yochanan): For Demai, it is permitted to separate Maaser Sheni before Maaser Rishon.

(R. Yaakov bar Acha bar Idi citing R. Yehoshua ben Levi): He should not do this, but if he did, it is valid.

Question: Could he fix (declare) the Maaser Sheni (without actually separating it) before he fixes the Maaser Rishon? (Should we be concerned that he will also declare the Maaser Rishon in the same place as the Sheni? Is it permitted to separate Maaser Rishon from the place that he fixed to be Maaser Sheni?)

Answer: R. Yosi ben Shaul was brought fruit by his sharecropper. R. Yosi told him to first go and fix the place of the Maaser Sheni (Demai) and then he told him to fix the place of the Maaser Rishon. Why wasn't he concerned that he would fix both in the same place? This shows that it is permited to fix the Sheni in the place of the Rishon.