The kit contains a set of seven cuvettes containing red color reference standards (identified sequentially from R1 TO R7) and 3 empty sample cells. The solutions are produced from 2 primary metal salt solutions of ferric(III) chloride and cobalt(II) chloride, in accordance with chapter 2.2.2 ′Degree of colouration of liquids′ of the European Pharmacopoeia (Ph. Eur.).