Comment on the paper “Growth and characterization of a new non-linear optical l-histidinium dihydrogen phosphate single crystal”, V. Rajendran et al., Materials Letters 61 (2007) 3477–3479

It is shown that the crystal prepared and investigated in the paper “Growth and characterization of a new non-linear optical l-histidinium dihydrogen phosphate single crystal”, V. Rajendran et al., Materials Letters 61(2007) 3477–3479 actually is l-histidinium dihydrogen orthophosphate orthophosphoric acid (l-His+ · H2PO4− · H3PO4) and not l-His+ · H2PO4− · H2O as the authors believe.