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.
In chemistry, Cr OH 3 is the chemical formula for a molecule containing one atom of chromium, one atom of oxygen and three atoms of hydrogen. When written with notation as Cr(OH)3, the formula refers to the compound chromium(III) hydroxide, also known as chromic hydroxide.