Ampicillin (Sodium) for research purposes only.
Normal concentrations for plasmid selection are 100ug / mL. 1 gram makes 10 mL(mililiter) enough for 10 Liters of media.
A 1000x stock is made by adding 100mg per mL of distilled water. Then add 1uL(microliter) stock per mL of culture media.