Enthalpies of formation of alloys in the pseudobinary LaAlxNi5-x system

The pseudobinary system LaAlxNi5-x has a composition limit at x approximate to 1.4. The standard molar enthalpies of formation Delta H-f(m)0(298.15 K) for this system were determined by solution calorimetry in HCl (c = 6 mol. dm(-3)) to be: -(129.4 +/- 6.5) kJ.mol(-1) for x = 0; -(159.5 +/- 15.9) kJ. mol(-1) for x = 0.25; -(185.9 +/- 6.7) kJ.mol(-1) for x = 0.375; -(191.8 +/ - 12.4) kJ.mol(-1) for x = 0.5; and -(283.2 +/- 8.9) kJ.mol(-1) for x = 1. Uncertainties correspond to twice the standard deviation of the mean and in clude contributions from the scatter of the calorimetric results and electr ical calibrations, as well as analytical uncertainties. Previous results fo r Delta H-f(m)0(LaNi5) fall into two groups; they are compared with the pre sent determination. The plot of Delta H-f(m)0 against x is linear within ex perimental error. (C) 2000 Academic Press.