This study demonstrates the Fourier transform infrared (FTIR) spectroscopic characterization of natural kaolinite from north-eastern India. The compositional and structural studies were carried out at room temperature by using X-ray fluorescence (XRF), electron microprobe (EPMA) analyses and Fourier transform infrared (FTIR) spectroscopic techniques. The main peaks in the infrared spectra reflected Al-OH, Al-O and Si-O functional groups in the high frequency stretching and low frequency bending modes. Few peaks of infrared spectra inferred to the interference peaks for quartz as associated minerals. The present study demonstrates usefulness of the spectroscopic techniques in determining quality and crystalline nature of kaolinite from the Assam and Meghalaya, northeastern India

We present here optical properties and crystallinity index of quartz (SiO 2 ) in natural rocks samples from the Mikir and Khasi hills, Assam, India. Infrared spectroscopy has been used to study the structure of quartz in rock samples and estimate the mining quality of quartz mineral, which is substantiated by calculating the crystallinity index. Systematic investigations of structure have been carried out in between 10 µm (1000 cm -1 ) and 20 µm (500 cm -1 ) bands of silicates. Investigation is based on the assignment of infrared bands to certain structural groups of SiO 4 tetrahedra. The crystallinity of samples has been ascertained by comparing the ratio of intensity of the characteristic peak at 778 and 695 cm -1 with the corresponding ratio for a standard sample. The crystallinity parameter is calculated by using a standard procedure which can be used to estimate the distribution of quartz in various rocks for mining purpose. The infrared spectroscopic investigation is found to be an ideal tool for structure elucidation and for estimating quartz crystallinity of the natural samples.

The bronchodilator drug, theophylline (THP), though a BCS class-I drug is considered as a representative compound to prepare variable stoichiometry cocrystals with isomeric aminobenzoic acids (o-ABA, m-ABA & p-ABA) as coformers. Cocrystals are synthesized using crystal engineering principles through liquid assisted mechanochemical grinding. Four different stoichiometry cocrystals of THP are isolated with o-ABA. Coformer m-ABA and p-ABA afforded only 1:1 cocrystals irrespective of crystallization media and different starting materials ratios. All cocrystal materials are subjected for aqueous solubility and diffusion/membrane permeability to examine drug biopharmaceutic properties to predict the in vivo performance of the drug. They exhibited different but improved solubility and modulated diffusion/membrane permeability when compared with pure THP. The interplay of drug solubility and membrane permeability that predicts the overall bioavailability is emphasized based on hydrogen bond synthons and solute···solvent interactions. Hirshfeld surface analysis is carried out in all cases to determine whether a correlation exists between permeability and drug-coformer interactions.