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 is a chemical compound. Its chemical formula is Cr2(SO4)3. It is a colored compound. It is made by dissolving chromium or chromium(III) oxide in sulfuric acid. It can also be made by reduction of chromates by sulfur dioxide.