On exposure to the air it loses water, and is gradually converted into basic ferric sulphate.

[Note 4: The ferric hydroxide precipitate tends to carry down some sulphuric acid in the form of basic ferric sulphate.

(1) Mordant with basic ferric sulphate and after allowing the silk to lie for some time, wash well and soap at 90°C.

!, 23, 383) ascribes it to hydrolytic action, which causes the formation of a basic ferric complex which is occluded in the barium precipitate.