A table with many null values VS many tables
As I understand you now, a "water" is kind of a recipe.

For such a recipe you want to record a) what additives where added and b) what the outcome was.

That's two entities, recipe and additives. Both have a many to many relationship with a relationship attribute, which is the amount. The outcome of a recipe is of course an attribute of the recipe and not one of a relation between a recipe and an additive. It's the whole mixture that counts.

A typical and normalized solution are three tables.

One for the additives.

CREATE TABLE additive
             (id serial,
              name text,
              PRIMARY KEY (id));


Another one for the recipe.

CREATE TABLE recipe
             (id serial,
              name text,
              drinkable boolean,
              dangerous boolean,
              PRIMARY KEY (id),
              CHECK (NOT drinkable
                      OR NOT dangerous));


Note: I added a check constraint, that a receipt deemed dangerous cannot be marked as drinkable.

And a table linking the additives for a recipe.

CREATE TABLE recipe_additive
             (recipe integer,
              additive integer,
              amount integer NOT NULL,
              PRIMARY KEY (recipe,
                           additive),
              FOREIGN KEY (recipe)
                          REFERENCES recipe
                                     (id),
              FOREIGN KEY (additive)
                          REFERENCES additive
                                     (id));