Solubility of a compound fertiliser

[Andy Kells]

3 years, 7 months ago #2423

Why is it difficult to work out the solubility of a compound fertiliser?

[Forum Administrator]

3 years, 7 months ago #2429

Because of the different solubilities of the pure salts, the equilibrium solubility of a mixture, (at low water contents) is difficult to measure. Also, heat increases the solubility of the fertiliser salts in water. The hotter the water, the more salt it can dissolve.
Complicating this situation is the fact that the various salts behave differently as far as solubility is concerned at various temperatures. For instance, the solubility of ammonium nitrate increases about 753 g/dm3 between 0°C and 100°C. At 0°C, about 118 parts of ammonium nitrate will dissolve in 100 parts of water; at 100°C, 871 parts will dissolve. Similarly, the solubility of ammonium sulphate increases about 33 g/dm3, from 70 parts at 0°C to 103 parts at 100°C.