For example, for the Gases under pressure hazard class, the hazard categories are Compressed gas, Liquefied gas, Refrigerated liquefied gas and Dissolved gas. These classes relate to the physical state of the gas when packaged and do not describe the degree of hazard.
1 In 1596, a flush toilet was invented and built for Queen Elizabeth I by her Godson, Sir John Harrington. 2  The first patent for the flushing toilet was issued to Alexander Cummings in 1775. 3  During the 1800s, people realized that poor sanitary conditions caused diseases.
However, the ancient Babylonians were the ones who invented soap and evidence for this are Babylonian clay containers dated at 2800 B.C. Inscriptions on the containers present the earliest known written soap recipe and they state that the product was made from fats combined with wood ash and water.