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.
Hexavalent chromium is also one of the substances whose use is restricted by the European Restriction of Hazardous Substances Directive. The LD50 for chromium(VI) ranges between 50 and 150 mg/kg.In the body, chromium(VI) is reduced by several mechanisms to chromium(III) already in the blood before it enters the cells.The chromium(III) is excreted from the body, whereas the chromate ion is transferred into the cell by a transport mechanism, one by which sulfate and phosphate ions also enter the cell.The acute toxicity of chromium(VI) is due to its strong oxidative properties.exavalent chromium is also one of the substances whose use is restricted by the European Restriction of Hazardous Substances Directive. The LD50 for chromium(VI) ranges between 50 and 150 mg/kg.