Gastric acid
The main constituent of gastric acid is hydrochloric acid which is produced by parietal cells (also called oxyntic cells) in the gastric glands in the stomach. Its secretion is a complex and relatively energetically expensive process. Parietal cells contain an extensive secretory network (called canaliculi) from which the hydrochloric acid is secreted into the lumen of the stomach. The pH of gastric acid is 1.5 to 3.5 in the human stomach lumen, the acidity being maintained by the proton pump H/K ATPase. The parietal cell releases bicarbonate into the bloodstream in the process, which causes a temporary rise of pH in the blood, known as an alkaline tide.
Carlsberg Laboratory
The Carlsberg Laboratory was known for isolating "Saccharomyces carlsbergensis", the species of yeast responsible for lager fermentation, as well as for introducing the concept of pH in acid-base chemistry. The Danish chemist Søren Peder Lauritz Sørensen introduced the concept of pH, a scale for measuring acidity and basicity of substances. While working at the Carlsberg Laboratory, he studied the effect of ion concentration on proteins, and understood the concentration of hydrogen ions was particularly important. To express the hydronium ion (H3O+) concentration in a solution, he devised a logarithmic scale known as the pH scale.