No. Under ADR, there is no quantity limit allowing UN 0021 to be carried with UN 0004: UN 0021 is prohibited from transport (“TRANSPORT INTERDIT”), so the permitted amount with UN 0004 is effectively zero (ADR 3.2 Table A, UN 0021, Volume 1, page 280; ADR 2.2.1.2.2, Volume 1, page 123).
This prohibition is reinforced by the classification rule: compatibility group K articles are not admitted for transport, including 1.3K, UN 0021 (ADR 2.2.1.2.2, Volume 1, page 123).
UN 0004 itself is listed as Class 1, classification code 1.1D, but that does not create an allowance to load it with UN 0021 because UN 0021 cannot be transported under ADR in the first place (ADR 3.2 Table A, UN 0004, Volume 1, page 280).
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