How many studies do use Chloride as major anion?
SELECT COUNT(?anions_labels) AS ?chloride_count
WHERE {
  orkgr:R110597 orkgp:compareContribution ?contrib.
  ?contrib orkgp:P37458 ?anions.
  ?anions rdfs:label ?anions_labels.
  FILTER(REGEX(?anions_labels, "Chloride"^^xsd:string))
}