On Chemical tanker, cargo density limitation (Load density as we call it), is available in the "procedures and arrangement manual" (P&A manual) of the vessel.

Apart from P&A manual and on other type of tankers, this information is also available in ship's trim and stability booklet. See below a screenshot of Trim & stability booklet of a product tanker.

Keep in mind that apart from load density, we need to check if there is any sloshing limitation. Sloshing limitation may sometimes be combined with load density restructions information but sometime you may find different section for each of these restrictions in the trim and stability booklet.