Učenici osnovnih škola gotovo redovito izvode pokus krstalizacije modre galice i kuhinjske soli. Modra galica je otrovna i štetna za okoliš, a veće kristale kuhinjske soli teško je dobiti. Umjesto pokusa kristalizacije modre galice i kuhinjske soli bolje je izvesti pokus kristalizacije limunske kiseline i običnoga šećera. Te su tvari jeftine, lako dostupne, biorazgradljive i nisu štetne za okoliš. Middle school students almost regularly perform experiments of crystallization of copper(II) sulphate pentahydrate and kitchen salt. Copper(II) sulphate pentahydrate is poisonous and harmful to the environment, and larger crystals of kitchen salt are difficult to obtain. Instead of experimenting with the crystallization of copper(II) sulphate pentahydrate and kitchen salt, it is better to carry out crystallization of citric acid and common (table) sugar. These materials are inexpensive, easily accessible, biodegradable, and not environmentally hazardous.