INDEX osmolality

Various lecithin-based MEs were also characterized by Hasse and Keipert [131]. The formulations were tested in terms of their physicochemical parameters (pH, refractive index, osmolality, viscosity, and surface tension) and physiological compatibility (HET-CAM and Draize test). In addition, in vitro and in vivo evaluations were performed. The tested MEs showed favorable physicochemical parameters and no ocular irritation as well as a prolonged pilocarpine release in vitro and in vivo. 

The freezing point depression, refractive index, osmolality and specific conductance are all listed in Table 2.30. An et al. (1978) list activity and osmotic coefficients. The water absorbed by solid calcium chloride is listed in Table 2.41 and Fig. 2.81. 

Having outlined the product composition it is useful to calculate the approximate osmolality from published tables, for example in the CRC Handbook of Chemistry and Physics (CRC Press Inc.), The Merck Index (Merck Co. Inc.) and The British Pharmacopoeia (HMSO). Ingredients for which osmolality values are not available can be allowed for by using values for substances of similar molecular weight and ionic character. 

Physical tests including pH, relative density, optical rotation, refractive index, conductivity, viscosity and osmolality are generally used as in-process controls or as simple laboratory tests for the finished product. 

The Density, Viscosity, Index of Refraction, Freezing Point Depression, Osmolality and Specific Conductance of Calcium Chloride Solutions at 20°C (Weast, 1977)... 

A% = anhydrous solute weight per cent, g solute/100 g solution p or D4 = relative density at 20°C, kg/liter Cj = anhydrous solute concentration, g/liter M — molar concentration, g mol/Uter n = index of refraction at 20°C relative to air for sodium yellow light A = freezing point depression, °C O = osmolality, Os/kg water 17/170 — relative viscosity, ratio of the absolute viscosity of a solution at 20°C to the absolute viscosity of water at 20°C. (Water s viscosity at 20°C is 1.002) y= specific conductance (electrical) at 20°C, mmho/cm. 

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