A　high-purity　hexadecyl　hydrogen　maleate　(HHM)　single　crystal　of　dimensions　60　×　40　×　3　mm3　can　be　grown　over　a　period　of　1　month　using　the　appropriate　method.　The　solvent　used　in　the　growth　of　the　crystal　consists　of　a　mixture　of　benzene　and　other　suitable　organic　solvents.　Diffraction　studies　on　the　crystal　have　indicated　the　suitability　of　this　system　in　the　dispersing　of　ultrasoft　X-ray　in　X-ray　spectroscopy,　larger　2d　spacing　(5.85　nm),　high　resolution　and　reflection　properties.　The　HHM　crystal　was　employed　in　an　X-ray　spectrometer　to　obtain　the　spectra　of　diamond　at　the　C　K-edge;　the　results　from　the　experiments　clarify　the　suitability　of　a　HHM　single　crystal　as　an　ultrasoft　X-ray　dispersant.　©　2002　Elsevier　Science　B.V.　All　rights　reserved.