Prepare another large bottle to contain aerated mineral medium (to about one-third of its volume) plus test chemical and reference chemical at final concentrations normally the same as those in the other large bottles.
Hertil klargøres der endnu en stor kolbe med beluftet uorganisk medium (ca. en tredjedel fuld) plus teststof og referencestof normalt i samme slutkoncentrationer som i de andre kolber.