Whether plain water is necessary for Baptism?

❌ Objection 1 : It seems that plain water is not necessary for Baptism. For the water which we have is not plain water; as appears especially in sea-water, in which there is a considerable proportion of the earthly element, as the Philosopher shows (Meteor. ii). Yet this water may be used for Baptism. Therefore plain and pure water is not necessary for Baptism.

❌ Objection 2 : Further, in the solemn celebration of Baptism, chrism is poured into the water. But this seems to take away the purity and plainness of the water. Therefore pure and plain water is not necessary for Baptism.

❌ Objection 3 : Further, the water that flowed from the side of Christ hanging on the cross was a figure of Baptism, as stated above (Article [3], ad 3). But that water, seemingly, was not pure, because the elements do not exist actually in a mixed body, such as Christ's. Therefore it seems that pure or plain water is not necessary for Baptism.

❌ Objection 4 : Further, lye does not seem to be pure water, for it has the properties of heating and drying, which are contrary to those of water. Nevertheless it seems that lye can be used for Baptism; for the water of the Baths can be so used, which has filtered through a sulphurous vein, just as lye percolates through ashes. Therefore it seems that plain water is not necessary for Baptism.

❌ Objection 5 : Further, rose-water is distilled from roses, just as chemical waters are distilled from certain bodies. But seemingly, such like waters may be used in Baptism; just as rain-water, which is distilled from vapors. Since, therefore, such waters are not pure and plain water, it seems that pure and plain water is not necessary for Baptism.