Antonyms of adj insoluble

3 senses of insoluble

Sense 1
insoluble (vs. soluble), indissoluble -- ((of a substance) incapable of being dissolved)

soluble (vs. insoluble) -- ((of a substance) capable of being dissolved in some solvent (usually water))
        => alcohol-soluble -- (soluble in alcohol)
        => dissolvable, dissoluble -- (capable of dissolving)
        => fat-soluble -- (soluble in fats; "fat-soluble vitamin A")
        => meltable, disintegrable -- (capable of melting)
        => oil-soluble -- (soluble in oil; "oil-soluble pigments")
        => water-soluble -- (soluble in water)

Sense 2
insoluble (vs. soluble) -- (admitting of no solution or explanation; "an insoluble doubt")

soluble (vs. insoluble) -- (susceptible of solution or of being solved or explained; "the puzzle is soluble")
        => answerable -- (capable of being answered)
        => solvable, resolvable -- (capable of being solved; "such problems are perfectly solvable")

Sense 3
insoluble -- (without hope of solution; "an insoluble problem")

INDIRECT (VIA hopeless) -> hopeful -- (having or manifesting hope; "a line of people hopeful of obtaining tickets"; "found a hopeful way of attacking the problem")

Similarity of adj insoluble

3 senses of insoluble

Sense 1
insoluble (vs. soluble), indissoluble -- ((of a substance) incapable of being dissolved)
       => water-insoluble, non-water-soluble -- (not soluble in water)

Sense 2
insoluble (vs. soluble) -- (admitting of no solution or explanation; "an insoluble doubt")
       => insolvable, unsoluble, unsolvable, unresolvable -- (not easily solved; "an apparantly insolvable problem"; "public finance...had long presented problems unsolvable or at least unsolved"- C.L.Jones)
          Also See-> inexplicable#1, incomprehensible#1

Sense 3
insoluble -- (without hope of solution; "an insoluble problem")
       => hopeless (vs. hopeful) -- (without hope because there seems to be no possibility of comfort or success; "in an agony of hopeless grief"; "with a hopeless sigh he sat down")