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Dimensions and mutual relationships amongst fracture (cleat) parameters such as maximum aperture width, average aperture width, length, spacing etc. control the connectivity within a fracture network and the fluid flow in a coal seam as the matrix permeability, here, is negligible. In this paper, we document cleat size distributions and investigate lengthaperture relationships from coals of Raniganj coalfield in Eastern India. This coalfield has a proven extractable reserve of six billion tons of coal and holds immense potential to be one of the largest coal bed methane fields serving India's growing energy needs. Here, cleat length (L) correlates with corresponding maximum aperture width (D max) in a power-law function with an exponent of 0.84 (D max a L 0.84) instead of the commonly observed exponents of 1 or 0.5 applicable for other natural 'opening-mode' fractures. The conventional wisdom pertains that laminar fluid flow (Q) through an isolated, smooth-walled, parallel-plate fracture, embedded in an impermeable matrix, is directly proportional to the cube of its aperture width (b, equivalent to D avg ; cubic law: Q a b 3). This assumes a linear relationship between length and fracture aperture. However, the modified relationship between cleat length and average aperture width changes the cubic law applicable for Raniganj coal seam and now fluid flow correlates with aperture width in a power-law function with an exponent of 4.25 (Q a b 4.25) instead of 3 (cube). Such simplifications will come handy for the modeling and estimation of fluid flow as it will reduce the effort of cleat length measurement which is anyway difficult and can be misleading due to the risk of undersampling.

The application of Raman spectroscopy in studies of ionic liquid (IL) systems having water is presented here. The presence of water can be intentional or unintentional. Since water severely affects IL's physical and chemical properties, it is very important not only to identify but also to understand the role of water. It will be evident from this short review that Raman spectroscopy has immensely helped to understand the IL/water mixture at the molecular level.

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