Argon

Argon Ar = 39.95 (7440-37-1)

Laboratory cylinder grade of commerce containing not less than 99.995% v/v of Ar.

When used in the test for Carbon monoxide in medicinal gases (Appendix IX E), after passage of 10 litres at a flow rate of 4 litres per hour, not more than 0.05 mL of 0.002m sodium thiosulfate VS is required for the titration (0.6 ppm).