Malachite is more floatable by using xanthate with δ-amino valeric acd than by using xanthate alone in the pH range where δ-amino valeric acid exists in a dipolar state. Xanthate adsorption on malachite increases with addition of δ-amino valeric acid, while there is an optimum addition of δ-amino valeric acid to obtain the maximum xanthate adsorption. Effect of δ-amino valeric acid on xanthate adsorption on malachite is greater in xanthate having a longer alkyl chain length. It was demonstrated by the CNDO MO calculation for a supermolecule composed of δ-amino valeric dipolar ion and ethylxanthate ion that both reagents should be adsorbed more densely in a stable orientation at a mineral-water interface when they existed together than they existed separately. Futhermore, a supermolecule with δ-amino valeric dipolar ion and amylxanthate ion is more stable than that with δ-amino valeric dipolar ion and ethylxanthate ion. In surface complex formation the 4 sp orbitals (not the 3 d orbitals) of copper play a dominant role in binding between copper and oxygen (δ-amino valeric dipolar ion) or between copper and sulfur (ethylxanthate ion). The π-π bonding makes a rather great contribution to form the above bonds.

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Preliminary laboratory scale gravity concentration tests using jig and table, and some flotation tests were performed on tungsten ore from Hidaka mine, Yamaguchi Prefecture so as to clear up an amenability of the ore to tungsten concentration. Results obtained were as follows
1) Jig test on -10+20 mesh and table test on -20+35 mesh showed an inferior results owing to incomplete scheelite liberation from gangue minerals. Good tungsten concentrate of 14.00% WO₃ was found from the table test on -35+65 mesh sample with 65.1% recovery.
2) From flotation tests on -100 mesh sample, addition of sodium carbonate to control pulp alkalinity to pH 9 was preferable to that of sodium hydroxide.
3) Best flotation concentrate on -100+150 mesh sample among seven sized fractions was obtained, showing the grade of 52.77% WO₃ and 98.5% recovery. Coarser or finer size fractions than the -100+150 mesh showed lower concentrate grade and recovery due to poor scheelite liberation or slime entrapment into the tungsten concentrate.
4) Cleaning tests up to 4th cleaning showed the final flotation concentrate of 20.37% WO₃ without middling recycling from low grade ore of 0.68% WO₃.
5) Combined use of sodium carbonate with sodium silicate was beneficial in getting high grade flotation concentrate of 34.94% WO₃ with fairy good recovery of 89.0%.
6) Since slime consisting mainly of chlorite gave poor flotation results, preliminary desliming was found to be of use to the better flotation performance.

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