Martin & Pleasance Schuessler Tissue Salts Nat Phos: Acid Neutraliser - A Homeopathic remedy traditionally used for the temporary relief of acidity, indigestion, dyspepsia and heartburn. Nat Phos is the acid neutralising tissue salt and is present in the blood, muscles, nerve and brain cells. It is used in conditions of excess acidity which are characteristically sour smelling. This salt regulates the balance of fats and acids in the body at all times. This tissue salt is known as the alkalinizer and can alleviate arthritic/ rheumatic tendencies.