7) Substances attacked (2) by moisture should be kept dry .
8) The elements of group I referred to collectively as the sodium family
and as alkali metals are among the most chemically active metals.
9) When considering (1) solvent extraction commonly available extractants should be first taken (2) into amount.
10) Having (1) prepared (2) some nearly black amorphous sulphur in the
laboratory and examined (2) it the following week the students noticed that
it had become (2) brittle and much lighter in colour.