Breakdown of Mischen Sie diese Chemikalie niemals mit Wasser!
Sie
you (formal)
das Wasser
the water
dieser
this / that (fem.: diese, neut.: dieses)
mit
with
Questions & Answers about Mischen Sie diese Chemikalie niemals mit Wasser!
How could I use a hier- compound in this sentence if water was already mentioned and I wanted to say 'Never mix this chemical with this'?
You would replace mit Wasser with the proximate pronominal adverb hiermit. The sentence would become: Mischen Sie diese Chemikalie niemals hiermit! Because water is an inanimate concept, German prefers combining hier- (this) + mit (with) rather than saying something like mit diesem.
Is there a difference between using niemals and just nie in this warning?
Yes, niemals is a stronger, more emphatic version of nie. While nie simply means 'never,' niemals carries the weight of 'never ever' or 'under no circumstances.' It is very common to see niemals in strict safety instructions or strong commands like this one.
Why does niemals come after diese Chemikalie rather than right after the verb?
In standard German word order, definite direct objects (like diese Chemikalie) generally come before adverbs of time or frequency (like niemals). If you put niemals right after the verb (Mischen Sie niemals diese Chemikalie...), it heavily stresses the chemical itself, as if you are saying 'never mix this chemical (but others are fine).'
How do I know the gender of Chemikalie to know it needs the feminine diese ending?