Comments on the papers recently published by Sangeetha et al.

On the crystal growth of ‘tris thiourea chromium(III) sulphate’, ‘potassium thiourea thiocyanide’ and ‘bis thiourea iron(II) sulphate’

“…To avoid use of such nonstandard codes, compounds are referred to by numbers in this comment. In recent papers, we have highlighted on the importance of reporting the molecular formula for new compounds [4][5][6]. In this letter, we show the usefulness as well as limitations of unit cell data for characterization of new compounds, using the title compounds as examples.…”

Comments on the paper “Growth and characterization of semi-organic nonlinear optical crystal: urea thiourea cadmium sulfate”

“…Despite the claims of single crystal and powder X-ray diffraction, infrared and UV-visible spectra and thermal studies, the authors have not assigned any chemical formula for 1 excepting an unusual code LVFC for the so called new semi organic nonlinear optical crystal. In recent papers we have shown that use of abbreviations or codes as alternates for molecular formula of new compounds is an unscientific method of product characterization [2,3]. In this comment we show that the authors have characterized the title crystal not based on valid scientific proof but based on an incorrect assumption that mixing of L-valine and ferric chloride in 1:1 ratio will result in the formation of 1.…”

“…In view of the above mentioned contradictory experimental data, namely an infrared spectrum matching with that of pure L-valine, a very large unexplained unit cell volume compared to that of Lvaline, a highly questionable powder pattern, a brown coloured solid showing no absorption in the visible region and inappropriate dielectric data the so called "L-valine ferric chloride" cannot be considered as a new semi organic material but should be declared as a dubious crystal. A list of several dubious NLO crystal based on L-valine has been given recently [2] and most of these were characterized on similar lines. The so called "L-valine ferric chloride" is a new addition to the list of improperly characterized amino acid based crystal.…”

Comments on the papers recently published by Kalaivani et al.

“…Our calculation is correct as evidenced by the fact that all % add to 100. Despite literature reports showing that EDAX cannot be used to get quantitative elemental analytical data [10][11][12], this technique is more frequently and incorrectly used [23] for new compound characterization as observed in all the commented papers [16][17][18][19]. In all these papers the authors claimed "The chemical composition is confirmed quantitatively by EDAX analysis".…”

“…In addition to several valuable works by several research groups worldwide, the literature of amino acids unfortunately contains many erroneous reports in the area of crystal growth of amino acid based compounds. Several papers reporting pure amino acids or a well-known compound under the name novel nonlinear optical (NLO) crystal or semiorganic NLO crystal or novel optoelectronic material have been criticized by the research groups of Fleck, Petrosyan, Natarajan, Priolkar, Srinivasan, and Tylczyński [2][3][4][5][6][7][8][9][10][11][12][13][14][15]. The many difficulties associated with the growth and characterization of amino acid based crystalline materials, were first described in an extensive case study [2].…”