Demonstrative pronouns replace or refer to nouns or noun phrases and, occasionally, larger units of a sentence.
In the decades following the Civil War, fifteen separate categories of
currency in multiple denominations were issued. These
included Demand Notes, U.S. Notes, National Bank Notes, and Federal Reserve
Notes.
[These replaces fifteen separate categories of
currency.]
--Schafrik and Church, "Protecting the Greenback," Scientific American (modified)
You can use demonstrative pronouns to reduce repetition and wordiness; however, be careful not to create broad pronoun reference. Good technical writing is precise.
Caution: Be careful not to mix alkaline earth metals with water, which may
cause an explosion. This is dangerous at best.
[What is dangerous, mixing alkaline earth metals with water or the explosion
that such mixing can cause?]
Caution: Be careful not to mix alkaline earth metals with water, which may
cause an explosion. Such an explosion is dangerous at best.