THE TERNARY-SYSTEM H2O-NH4NO3-AL(NO3)(3) - ISOTHERMS AT -25, -20, -18.2, -10 AND 0-DEGREES-C AND SPATIAL DIAGRAM UP TO 0-DEGREES-C

A study of the solid-liquid equilibria in the ternary system H2O-NH4NO 3-Al(NO3)(3) has been undertaken in order to find an invariant transfo rmation at low temperature. Five isothermal sections have been establi shed under atmospheric pressure at -25, -20, -18.2, -10 and 0 degrees C. The solid phases observed at these temperatures are: at -25 and -20 degrees C, ice, NH4NO3(V) and Al(NO3)(3) . 9H(2)O; at -18.2 degrees C , ice, NH4NO3(IV) and Al(NO3)(3) . 9H(2)O; at -10 degrees C, ice, NH4N O3(IV), Al(NO3)(3) . 9H(2)O and Al(NO3)(3) . 8H(2)O; at 0 degrees C, N H4NO3(IV), Al(NO3)(3) . 9H(2)O and Al(NO3)(3) . 8H(2)O. The X-ray diff raction pattern of the octahydrated aluminium nitrate has been establi shed. The spatial diagram shows four isobaric invariant transformation s whose temperatures have been specified by thermal analysis. They cor respond to the reactions: At -33.6 degrees C, liquid reversible arrow ice + NH4NO3(V) + Al(NO3)(3) . 9H(2)O At -18.6 degrees C, liquid + NH4 NO3(IV) reversible arrow ice + NH4NO3(V) liquid + NH4NO3(IV) reversibl e arrow NH4NO3(V) + Al(NO3)(3) . 9H(2)O At -12.3 degrees C, liquid + A l(NO3)(3) . 8H(2)O reversible arrow NH4NO3(IV) + Al(NO3)(3) . 9H(2)O