Presežni molski volumni raztopin cikloheksana z ogljikovim tetrakloridom in toulena z benzenom pri različnih temperaturah

Excess molar volumes of binary mixtures of cyclohexane-carbon tetrachloride at 288.15, 293.15, 298.15 K and toluene-benzene at 293.15, 298.15, 308.15 K have been determined using a vibrating tube densimeter. Flory\u27s theory of liquid mixtures has been applied to calculate the excess entalphy of cyclohexane-carbon tetrachloride at 298,15 K. The calculated value for the equimolar mixture is in fairly good agreement with experimental results.Z gostotomerom smo izmerili gostote raztopin cikloheksana z ogljikovim tetrakloridom pri 288.15, 293.15 in 298.15 K ter raztopin toluena z benzenom pri 293.15, 298.15 in 308.15 K in iz njih izračunali presežne molske volumne. S pomočjo Floryjeve teorije za raztopine smo za sistem cikloheksen-ogljikov tetraklorid pri 298.15 K izračunali presežno molsko entalpijo. Izračunana vrednost za ekvimolarno mešanico se relativno dobro ujema z eksperimentalno določeno

Localized dissolution kinetics of low carbon steel

Localized dissolution of low carbon steel in saturated calcium hydroxide with different amount of sodium chloride has been investigated, using a dc technique. Potentiokinetic polarization curves indicated that pitting potentials ($E_{pit}$) decrease linearly with the log of chloride concentration. The rate of pit nucleation (1/$t_i$), and the rate of pits growth increases with increasing concentration of $Cl^-$ ions. Initiation of pitting attack could be ascribed to the adsorption of $Cl^-$ ions on the oxide surface. Adsorption of $Cl^-$ ions is physisorption and follow the Langmuir isotherm with $Δ_{ads}G^0$ = -21.1 kJ/mol.S pomočjo dc tehnike smo raziskovali lokalizirano raztapljanje malo-ogljičnega jekla v nasičeni raztopini kalcijevega hidroksida ob dodanih različnih množinah natrijevega klorida. Poteciokinetične polarizacijske krivulje so pokazale, da se kritični porušitveni potencial ($E_{pit}$) linearno zmanjšuje z logaritmom koncentracije kloridnih ionov. Hitrost nastajanja luknjic (1/$t_i$) in hitrost rasti luknjic se povečuje s povečanjem koncentracije $Cl^–$ ionov. Iniciacijo točkaste poškodbe lahko pripišemo adsorpciji $Cl^–$ ionov na oksidno površino. Adsorpcija $Cl^–$ je fizisorpcija in sledi Langmuirjevi adsorpcijski izotermi z $∆_{ads}G^0$ = –21.1 kJ/mol

Volumetric properties of ethanol-water mixtures under high pressure

Densities of ethanol-water mixtures have been measured using a vibrating tube densimeter and a different arrangement high-pressure experimental set-up. Measurements were carried out at 298,15 K in a pressure range from 0.1 MPa to 5MPa. Partial molar volumes, excess molar volumes and coefficients of isothermal compressibility were calculated. The molar volumes of alcohol and its partial molar volumes in mixtures with water are found to decrease monotonously with increasing pressure. Excess molar volumes are negative at all pressures. The numerical P-V relations at each composition are correlated satisfactorily as a function of pressure by the Hayward equation.Gostote mešanic etanola z vodo smo izmerili z gostometrom, ki je bil prirejen za visokotlačne poskuse. Meritve so potekale pri 298,15 K v območju tlakov od 0,1 MPa do 5 MPa. Iz izmerjenih gostot smo izračunali parcialne molske prostornine, presežene molske prostornine in koeficiente izometrične stisljivosti. Molske prostornine etanola in njegove parcialne molske prostornine v mešanicah z vodo se monotono zmanjšujejo s povečanjem tlaka. Pri vseh tlakih so presežene molske prostornine negativne. Numerične P-V zveze v odvisnosti od tlaka so za vsako sestavo raztopine podane s Hayworthovo enačbo

Zgodnja faza nastanka pasivne plasti na AISI 420 nerjavnem jeklu pod potenciostatičnimi pogoji

The kinetics of the early stage s of passive film formation on AISI stainless stell in mixtures of 0.1M ▫$H_2SO_4$▫ and 0.1M ▫$Na_2SO_4$▫, with pH-values of 2.42, 2.85 and 3.33, were studied at different anodic potentials. The potentiostatic step method was used as an electrochemical technique in which the anodic current density was measured as a function of time. For analysis of the measured data, the theory of "topochemical reaction" was applied for the charcterization of the exponent n in that part where the steepest current decay was observed. Through this theory, which includes the Erofeev equation, the number of conversion steps could be obtained, as well as the number of directions in which the nuclei grow. It was found that this theory can be successfully applied to the passivation process of AISI 420 stainles steel.V prispevku smo obravnavali kinetiko pasivacije martenzitnega jekla AISI 420 v modelnem mediju. Kot korodirni medij smo izbrali mešanico raztopin 0,1 M $H_2SO_4$ in 0,1 M $Na_2SO_4$ različnih pH-vrednosti (2.42, 2.85 in 3.31). Študija je bila osredotočena na zgodnjo fazo nastanka pasivne plasti izbranega jekla. Uporabljena metoda za elektrokemijska merjenja je bila potenciostatska metoda, pri kateri smo merili tok kot funkcijo časa. Za analizo eksperimentalnih podatkov v področju najstrmejšega padca toka smo uporabili teorijo »topokemijskih reakcij«, ki vključuje Erofeevo enačbo. Dobljeni rezultati kažejo na dobro ujemanje z uporabljeno teorijo