Insoluble [adjective]
Definition of Insoluble:
mysterious, unable to be solved or answered
Sentence/Example of Insoluble:
Crystals of calcium oxalate are insoluble in acetic acid or caustic soda.
It is in this way that lime, which occurs in the soil principally as the insoluble carbonate, is dissolved and absorbed.
Starch is insoluble in cold water, but by boiling, it dissolves, forming a thick paste.
It is a white crystalline fusible solid, insoluble in water, but soluble in alcohol and in solutions of the alkalies.
The greater part of the organic matters are insoluble both in water and acids.
This condition of mind made her an almost insoluble psychological problem.
The plant, it will be remembered, was originally extracted with ether in which rhamnose is practically insoluble.
The Frankfort assembly had left the Austrian riddle unsolved, and apparently insoluble.
How far exactly the sudden tide of national impulse owed itself to his teaching, is perhaps an insoluble problem.
The described change in ionization can be roughly followed with the aid of an insoluble sulphate like barium sulphate.