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(III) sulfate usually refers to the inorganic compounds with the formula Cr 2 (SO 4) 3. x(H 2 O), where x can range from 0 to 18. Additionally, ill-defined but commercially important basic chromium sulfates are known. These salts are usually either violet or green solids that are soluble in water.