Royal Aqua

ROYAL AQUA (Aqua regia), a mixture of 3 parts of strong hydrochloric acid and 1 part of strong nitric acid. The name was given by alchemists due to the ability of R. a. to dissolve the "king of metals" - gold. The dissolving action of R. a. is due to the free chlorine released and the unstable compound - nitrosyl chloride (NOCl), formed during the interaction of hydrochloric and nitric acids: HNO₃ + 3HCl → NOCl + 2Cl + 2H₂O.

On the skin and especially on mucous membranes, R. a. has a strong destructive effect. In dental practice, R. a. is used to destroy the pulp, remnants of bone tissue, etc. From a toxicological point of view, R. a. is similar to the strong acids from which it is formed, taking into account the action of chlorine at the moment of release. In analytical practice, for the dissolution of sulfides, a mixture of hydrogen peroxide and hydrochloric acid is now preferred instead of the caustic and dangerous R. a. ZWEIFEL Paul (Paul Zweifel, 1848-1927), an outstanding German obstetrician and gynecologist of the late 19th and early 20th centuries. By origin a Swiss, Z. received his medical education in Zurich. Here he began to specialize with Gusserov, with whom he moved in 1873 to the newly opened University of Strasbourg.

In 1876 he received a chair in Erlangen, in 1887 - in Leipzig, where he remained for 34 years until his retirement. The works of Z. are very numerous (161) and cover almost all problems of obstetrics and women's diseases. Z. worked a lot on eclampsia, in the treatment of which he began to use systematic bloodletting, which has now become almost universal. An excellent teacher, Z. trained a number of outstanding modern German gynecologists. Among his printed works, his textbook on obstetrics, which went through five editions - "Lehrbuch der Geburtshilfe" (5th ed.-Stuttgart, 1903) and the widely known atlas of wall charts on operative obstetrics - "Operationes tocologicae" (Lipsiae, 1899) can be mentioned. In the last years of his life, Z. published together with Payer a 3-volume "Klinik der bosartigen Geschwulste" (Lpz., 1924-27) and - together with his son - "Grundriss der Gynakologie" (B., 1927).