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Namen magistrske naloge je bila vzpostavitev merilne naprave in razvoj ter uporaba metode viseče kaplje za merjenje površinskih napetosti in difuzijskih koeficientov v dvofaznih sistemih v okolici kritične točke. Geometrijo kaplje smo določali s pomočjo industrijske kamere Basler in programa OpenDrop 1.1. Gostote dvofaznih sistemov, ki smo jih potrebovali pri določanju površinskih napetosti in difuzijskih koeficientov, smo povzeli bodisi iz podatkovne baze NIST bodisi jih določili z gostotometrom Anton Paar DMA 602. V prvem delu magistrske naloge je prikazana uporaba metode viseče kaplje za določanje površinskih napetosti dvofaznih sistemov. Metodo smo umerili za dvofazni sistem voda/CO2 pri izotermah 25 °C in 45 °C v območju tlakov do 200 bar. Rezultati umeritve metode kažejo dobro primerljivost z literaturo, kar je zadoščalo za nadaljnje merjenje površinske napetosti še neraziskanim dvofaznim sistemom slanica/CO2, slanica/CO2+5 vol.% Ar in slanica/CO2+10 vol.% Ar pri izotermah 40 °C, 50 °C, 60 °C, 70 °C in 80 °C in območju tlakov od 50 bar do 300 bar. Podatke o površinskih napetosti izmerjenih dvofaznih sistemov smo uporabili pri določanju kapacitete shranjevanja ogljika (ang. Carbon Capture and Storage – CCS) v izbrano globokomorsko slanico Gorgon, kjer smo ugotovili, da dodatek Ar v sistem povzroči zmanjšanje kapacitete shranjevanja CO2. V drugem delu magistrske naloge smo razvili metodo za merjenje difuzijskih koeficientov iz geometrije viseče kaplje. Metoda je temeljila na predpostavkah psevdostacionarnega stanja sistema in prenosa snovi z ekvimolarno protitočno difuzijo. Razvita metoda se je umerila za sistem voda/CO2 pri izotermah 25 °C in 45 °C in območju tlakov od 50 bar do 600 bar ter izkazala dobro ujemanje z literaturo in teoretičnimi izračuni. Zaradi ugotavljanja vpliva dodatka soli v dvofaznem sistemu voda/CO2, smo pri enakih izotermah in tlakih izmerili difuzijske koeficiente za sistem slanica/CO2, kjer smo ugotovili, da dodatek soli povzroči porast difuzijskih koeficientov pri izotermi 25 °C, ne pa tudi pri izotermi 45 °C. The purpose of the master's thesis was the establishment of instrumentation and the development and application of methods of hanging drops for measuring surface tension and diffusion coefficients in a two-phase system in the vicinity of the critical point. The geometry of the drop was determined with the help of industrial camera Basler and software program Open Drop 1.1. Densities of two-phase systems, which we needed in determining the surface tension and diffusion coefficients, were taken either from the database of NIST or determined by densitymeter Anton Paar DMA 602. The first part of the master's thesis illustrates the use of hanging drop method for determining surface tension of two-phase systems. The method was calibrated for the two-phase system of water/CO2 at isotherms of 25 °C and 45 °C in the pressures up to 200 bar. The results of the calibration of the method showed a good comparison with the literature, which is sufficient for the subsequent measurement of the surface tension, yet unexplored two-phase systems, brine/CO2, the brine/CO2 + 5 vol.% argon and brine/CO2+10 vol.% argon at isotherms of 40 °C, 50 °C, 60 °C, 70 °C and 80 °C in the range of pressures from 50 bar to 300 bar. Surface tensions of the measured two-phase systems were used in determining the storage capacity of carbon dioxide (Carbon Capture and Storage - CCS) in a selected deep brine Gorgon, where we have found that the addition of argon in the system results in a reduction in capacity storage of CO2. In the second part of the master's thesis, we have developed a method for measuring the diffusion coefficients from the geometry of the hanging drop. The method is based on the assumption of pseudostationary state of the system and the mass transfer with an equimolar countercurrent diffusion. The developed method was calibrated for the system water/CO2 at isotherms of 25 °C and 45 °C in the range of pressures from 50 bar to 600 bar and showed good agreement with the literature and theoretical calculations. In order to determine the impact of the addition of salt in a two-phase system of water/CO2, we have, at the same isotherms and pressures, measured diffusion coefficient for the system brine/CO2, where we have found that the addition of salt causes an increase in the diffusion rate in the isotherm of 25 °C, but not in the isotherm 45 °C.