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) oxide is the inorganic compound of the formula Cr 2 O 3.It is one of principal oxides of chromium and is used as a pigment. In nature, it occurs as the rare mineral eskolaite.hromium(III) oxide is amphoteric. Although insoluble in water, it dissolves in acid to produce hydrated chromium ions, [Cr(H 2 O) 6 ] 3+ which react with base to give salts of [Cr(OH) 6 ] 3â .