For example, positive iron combined with negative oxygen to form positive ferrous oxide; positive sulphur combined with negative oxygen to form negative sulphuric acid; positive ferrous oxide combined with negative sulphuric acid to form neutral ferrous sulphate.
Manganese dioxide not only acts as a source of oxygen, but develops a pink tint in the glass, which is complementary to and neutralizes the green colour due to ferrous oxide.
The blue colouring substance is ferrous sulphide, the upper reddish layer contains more ferric oxide, which the predominance of decomposing organic matter in the substance of the mud reduces to ferrous oxide and subsequently by further action to sulphide.
Oxygen, probably dissolved in the iron as ferrous oxide FeO, also makes the metal red-short.
With oxygen it probably forms manganous oxide, which is less harmful than ferrous oxide.