Calcium carbonate is also used in the purification of iron from iron ore in a blast furnace. The carbonate is calcined in situ to give calcium oxide, which forms a slag with various impurities present, and separates from the purified iron.
One re-hydrated package fills about 15-20 dishes. Mix 1 level teaspoon of dehydrated agar with 100 ml (3/8 cup) of water and then bring to a boil to make 100 ml of agar solution. Prepare Petri Dishes: Fill petri dishes to just cover the bottom. Typical 90-100mm dishes require 10-15 ml agar. Rotate the dish to obtain even surface coverage. Cover the dish immediately and let stand until firm. Store upside down in the refrigerator until ready to use.
Agar is a gelatinous medium that provides nutrients and a stable, controlled environment for bacteria growth. Most bacteria will grow well using nutrient agar, but some more fastidious bacteria prefer tryptic soy agar. To prepare agar plates, just heat agar and pour it into a sterile petri dish. Swab along any surface to test (your mouth, the bathroom counter, etc.) and then lightly smear in a zig-zag pattern on the surface of the agar plates. Signs of bacteria growth should show within 1-2 weeks. Getting started: