[plankk]

It is well-known that polyols such as glicol, glycerol make a navy-blue liquid with Cu²⁺. In every recipe I have found, they use copper(II) hydroxide. Creating this complex is possible only in such way? If yes, it means that the complex is rather with Cu(OH)₂ than with Cu²⁺. Am I right? And what about polyols which hyroxyl groups are remoted from each other far than 2 carbons, for example like in butane-1,4-diol? Do they make a colourful complex?