Early wheels were simple wooden disks with a hole for the axle. In the early Roman empire, most horse-carts used a design featuring two chords across the wheel. The spoked wheel was invented much more recently, and allowed the construction of lighter and swifter vehicles.
Chromium(III) sulfide. Chromium(III) Sulfide is the inorganic compound with the formula Cr2S3. It is a brown-black solid. Chromium sulfides are usually nonstoichiometric compounds, with formulas ranging from CrS to Cr0.67S (corresponding to Cr2S3). Preparation.
Chromium - Compounds. 1  Chromium is a member of Group 6, of the transition metals. 2  The following is the Pourbaix diagram for chromium in pure water, perchloric acid or sodium hydroxide: [17] [24] 3  A large number of chromium (III) compounds are known. 4  Chromium (III) ions tend to form octahedral complexes.