ACS Style is a suggested structure and set of guidelines (including citation style) for articles in the field.
For ACS Style you use superscript numbers within or after cited information
Example: Fluoridated water as well as various fluoride products such as toothpaste provide fluoride ions necessary for remineralization.¹
The number you use will correspond to the citation you are referring to.
(Examples from the Williams College Library)
Chang, R. General Chemistry: The Essential Concepts, 3rd ed.; McGraw-Hill: Boston, 2003.
Article from an online journal
Peacock-Lopez, E. Exact Solutions of the Quantum Double Square-Well Potential. Chem. Ed. [Online] 2007, 11, 383-393 http://chemeducator.org/bibs/0011006/11060380lb.htm (accessed Aug 23, 2007).
National Library of Medicine. Environmental Health and Toxicology: Specialized Information Services. http://sis.nlm.nih.gov/enviro.html (accessed Aug 23, 2004).
Prefer paper? Come to the library, where we have two copies of the ACS style guide on reserve behind the Help Desk.