How can i tell if a liquid is LSD? not by taking some?

Question

does it smell or have any caracteristics visually?

Answer 1

find a reagent for  it but maybe the reagent also reacts with other kind of drugs.

Answer 2

Ehrlichs reagent will test for the presence of indole compounds, which LSD is one.  It will turn it purple.  Other indoles provoke false positives as well.

Also hold it under a black light.  If it glows it could be LSD, but if it does not you know it isn't.  This isnt the most accurate test, as alot of substances will also glow.