The authors measured the running quality of molten aluminium, and its binary alloys with copper, silicon, zinc, magnesium, manganese or nickel, which is contained within the limit of the industrial addition, by using the same apparatus as used by them on measuring the running quality of molten magnesium and its alloys and obtained the following results: (1) The running quality of aluminium, whose purity is about 99-5%, slightly decreases at repetitions of remelting and rectilinearly increases with the rise of the superheating temperature up to 100°, but conversely decreases at 1251° (2) The influences of the simple addition of the alloying element on the running quality of aluminium, about 99.5% Al, are as follows: The running quality of aluminium decreases by an addition of copper up to about 4%, but almost rectilinearly increases by 4% to 33% addition; by an addition of silicon up to about 2% suddenly decreases, but considerably increases by 2 to 15% addition. The modification with metallic sodium and sodium fluoride has no influence on the running quality of 11% Si alloy, but slightly increases it with 13% Si alloy. Zinc up to 3% suddenly decreases the running quality of aluminium from 3% to 10% slightly decreases it and from 10% up to 20% gradually increases it, but no further increase is observable between 20% and, 30%. Magnesium up to about 3% suddenly decreases the running quality of aluminium, but from 3% up to 16% gradually decreases it. Manganese up to 1% slightly decreases it, but 3% to 4% manganese considerably increases and 5% manganese rapidly decreases it again. Nickel up to about 1% suddenly decreases the running quality of aluminium and from 1% to about 5% gradually decreases it. These latter results may be explained by the solidification theory and the equilibrium diagram as on the case of magnesium alloys previously mentioned, excepting the cases of silicon manganese and nickel