Smoking (chemistry)
The fuming is a separation process in the chemical , which among other things, the acid digestion is used. The aim is to remove ions from a sample that are interfering with the chemical analysis . This process gets its name from the rising vapors.
A mostly water-insoluble, ionic substance is heated together with a strong acid to just below its boiling point. The anions of the acid displace the anions of the substance into the solution, where the displaced ions react with the protons of the acid and the resulting molecules are entrained as the evaporating solution continues to narrow. After the reaction is complete, z. B. from a mixture of salts with different anions a solution of salts with the same anions.
Nitric acid or sulfuric acid is usually used for smoking . However , sulfuric acid is not suitable for smoking phosphates and silicates, as they are not displaced by it. In such a case, e.g. B. perchloric acid can be used with appropriate safety precautions.
After smoking with nitric acid, it is often necessary to smoke with hydrochloric acid or another very strong acid , as the nitrate ions of the nitric acid would later interfere. The process is carried out in the fume cupboard, as nitrous gases are released (red-brown nitrogen dioxide in the picture).
Individual evidence
- ^ Walter Wittenberger: Chemische Laboratoriumstechnik , Springer-Verlag, Vienna, New York, 7th edition, 1973, pp. 131-132, ISBN 3-211-81116-8 .