Copper (I) hydride, CuH, is unique amongst the binary metal hydrides in that it can be synthesised, at room temperature, in aqueous solution. In recent years CuH generated in situ has found extensive use in synthetic organic chemistry as a mild reducing agent. CuH was first prepared by Wurtz in 1844 by the reaction of aqueous copper sulfate with hypophosphorous acid. This remains the most established method of preparation although several other routes have been developed including precipitation of the hydride from pyridine solutions of CuI and LiAlH4 and reduction of aqueous Cu2+ by borohydride ion. The fascinating problem with CuH is that all three routes apparently give different products. INS is an excellent tool for the investigation of these systems. CuH itself should give a characteristic spectrum and the presence of any other hydrogenous material will also be readily apparent.