Add water & salt to 1 domain

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I would like to know how to add 2 or more materials to a specific geometry, because I add water to domain 1 (liquid) and KCl (liquid ) to domain 1 , the model generates and error that is shown in the attachment.

I want to simulate a system of water and salt in this geometry that corresponds to a reactor. at supercritical conditions for my undegrade tesis

thank you very much

Juan Sebastián Álvarez