Sciencemadness Discussion Board

detect the presence of water of crystallization

handsome - 3-10-2007 at 06:29

describe how to detct the presence of water of crystallization in an inorganic salt??

Mr. Wizard - 3-10-2007 at 06:44

A quick old fashioned way is to put the material in a dry glass test tube and warm it over a flame. A ring of condensed moisture indicates water driven out of the material. You can also detect a weight change, by weighing the material before heating it and then again after it has been heated.

This is only the simplest test you can do, and is often used in school to demonstrate the water of crystallization in common organic salts, such as Copper Sulfate.

JohnWW - 3-10-2007 at 14:45

A non-destructive method would be in the IR spectrum of the crystals. Any water of crystallization would show O-H stretching absorption bands.

Antwain - 4-10-2007 at 09:15

are we talking qualitative or quantitative? ie. do you want to show whether there is water or not or do you want to measure how much water there is?

*Most* hydrated salts will lose some water on heating, and possibly all. But some salts (magnesium salts jump to mind) will not lost all their water to give the anhydrous slat, but rater to give acids or oxides etc as well as water.