Czapek medium

Czapek medium, also called Czapek's agar or Czapek-Dox medium, is a growth medium for propagating fungi and other organisms in a laboratory. It was named after its inventors, Czech botanist Friedrich Johann Franz Czapek and American chemist Arthur Wayland Dox. It was developed to grow Aspergillus niger and Penicillium camemberti. It works well for many saprophytic fungi and soil bacteria such as species of Aspergillus, Candida, Penicillium, and Paecilomyces.
Friedrich Czapek's original recipe is as follows:

1000 g distilled water
30 g cane sugar – energy source and sole source of carbon
1 g dipotassium phosphate – buffering agent
0.5 g magnesium sulfate – source of cations
0.5 g potassium chloride – source of essential ions
0.01 g iron sulfate – source of cations

Arthur Wayland Dox added 2 g of sodium nitrate in his version, to provide a sole source of nitrogen that is inorganic. This makes the medium a selective growth medium as only organisms that can use inorganic nitrogen can grow. Czapek and Dox did not add agar but many recipes add 15 g to make a solid medium.