refractometer/reefrakʹtomitə/ noun

• on one's conscience
• on one's feet
• on one's hands
• on one's haunches
• on one's high horse
• on one's honour
• on one's last legs
• on one's mettle
• on one's mind
• on one's own
• on one's own account
• on one's own initiative
• on one's plate
• on one's/the doorstep
• on one's tod
• on one's toes
• on one's uppers
• on order
• on paper
• on principle
• on purpose
• on/quite the contrary
• on record
• on relief
• onrush