An acid (from the Latin acidus/acÄre meaning sour) is a chemical substance whose aqueous solutions are characterized by a sour taste, the ability to turn blue litmus red, and the ability to react with bases and certain metals (like calcium) to form salts.he Swedish chemist Svante Arrhenius attributed the properties of acidity to hydrogen ions (H +) or protons in 1884. An Arrhenius acid is a substance that, when added to water, increases the concentration of H + ions in the water.
The surface of the inner wall of all of the body cavities is lined by a serous membrane which consists of a single layer of flat epithelium with a thin underlying propria (connective tissue). Within the thoracic cavity, this is known as the pleura. The visceral pleura which coats the outer surface of the lung is derived from the splanchnic mesoderm.
The walls of the ventral body cavity and outer covering of its organs contain a thin covering called the serosa (also called serous membrane). It is a double-layered membrane made up of two parts called the â parietal serosa â (lines the cavity walls) and â visceral serosa â (covers organs in the cavity). The serous membranes are separated by a thin layer of fluid called â serous fluid â. Serous fluid is secreted by both membranes and acts as a lubricant, allowing organs to slide in the cavity without causing friction. Typically, the serous membranes are named according to the cavity and organ they associate with.