Single crystals of undoped (pure) glycine potassium sulphate (GPS) and sodium sulphate doped glycine potassium sulphate have been grown by the free evaporation method and the grown crystals have been characterized by various studies. Effect of sodium sulphate on the properties of glycine potassium sulphate (GPS) has been investigated here. X-ray diffraction analysis indicates the structure of the crystals as orthorhombic. The functional groups have been identified using Fourier transform infrared spectral analysis. The UV –Vis-NIR spectral analysis shows that these crystals have their cut off wavelength around 200 nm. Second Harmonic generation (SHG) measurement shows that the grown crystals are NLO crystals. Microhardness measurement was carried out for samples. Solubility was measured for both the samples at different temperatures. LDT of the samples have been determined. Due to doping, there is an increase in optical transparency, microhardness, LDT and solubility of the GPS crystals., {"references":["1.\tM. N. Bhat and S. M. Dharmaprakash, J. Cryst. Growth 235 (2002)511-516\t. 2.\tA. Deepathyand H. L. Bhat, J.Cryst.Growth226 (2001)287-293. 3.\tR. Rajasekaran, P. M. Ushashree, R. Jayavel and P. Ramasamy, J.Cryst.Growth229 (2001)563-567. 4.\tG. Albrecht, R. B. Corey, J.Am.Chem.Soc.61, 1087(1939) 5.\tE. Fischer, Ber.Deutsch.Chem.Ges.38, 2917 (1905) 6.\tY. Iitaka, Acta.Cryst.11, 25 (1958) 7.\tY. Iitaka, Acta.Cryst.14,1 (1961) 8.\tM. N. Bhat and S.M. Dharmaprakash, J. Cryst.Growth236 (2002) 376-380. 9.\tJ. K. Mohan Rao and M.A. Vishwamitra, ActaCrystallogr. B 28 (1972) 1484. 10.\tS. A. Martin Britto and S. Natarajan, Mater. Lett. 62(2008) 2633-2636. 11.\tRa. Shanmugavadivu, G. Ravi and A. Nixon Azariah, J.Phys. and Chem. Solids 67 (2006) 1858-1861. 12.\tM. R. Suresh Kumar, H. J. Ravindra and S. M. Dharmaprakash, J. Cryst. Growth 306 (2007) 361-365. 13.\tT. Balakrishnan and K. Ramamurthi, Spectrochim. Acta Part A 68 (2007) 360-363. 14.\tT. Balakrishnan and K. Ramamurthi, Mater. Lett. 62(2008) 65-68. 15.\tR. Pepinsky, K. Vedam and Y. Okaya, Phys .Rev. 110(1958) 1309-1311. 16.\tS. Hoshino, T. Mitsui, F. Jona and R. Pepinsky, Phys.Rev. 107(1957) 1255-1258. 17.\tH. Lipson and H. Steeple Interpretation of X-ray power Diffraction Patterns, MacMillan, New York, 1970. 18.\tS. K. Kurtz and T. T. Perry, J. Appl. Crystallography 9 (1968) 3798-3813. 19.\tR. S. Krishnan, K. Sankaranarayanan and K. Krishnan, J.Indian Inst. Sci. 55 (1973) 313. 20.\tU. Le. Fur, R. Masse, M. Z. Cherkaoui and J. K. Nicoud, Z. Kristallogr. 210 (1995) 856. 21.\tP. N. Kotru, A. K. Razdan, B. M. Wanklyn, J. Matter. Sci. 24 (1989)793. 22.\tJ. B. Charles, F. D. Gnanam, J. Matter. Sci. Lett. 12 (1993) 1395."]}