A bulk element is a mineral substance which, in contrast to a trace element (microelement), is present in a percentage by weight of more than 50 mg per kilogramme. Because bulk elements in an aqueous environment are usually present in an ionised form, i.e. as positively (Na+, K+, Ca2+, Mg2+) or negatively (Cl, HPO42−, SO42−) charged particles, for this reason they are referred to as electrolytes.