ACS in-text citations point to numbered entries in your reference list. The number matches the order in which sources first appear in your text —not alphabetical order.
Superscript vs. bracketed
Superscript: ...as shown previously.¹ Bracketed: ...as shown previously (1). Both are acceptable in ACS publications; choose one and stay consistent.
Multiple citations
List multiple numbers separated by commas: (1, 3, 5) or ¹,³,⁰ For a range of consecutive references, some journals allow (1—). Check your target journal if you are writing for publication.
Placement in sentences
Place the number after the relevant clause or at the end of the sentence, before the period in superscript form or after punctuation in bracketed form depending on publisher preference. When quoting directly, include the page number if required by your instructor.