Preparation of sulfur dioxide
Preparation of sulfur dioxide from copper and sulfuric acid
Sulfur dioxide is prepared by gently heating in a flask scrap copper with concentrated sulfuric acid.
To a round bottom flask 100 g of copper (small pieces, turnings, etc.) are placed. From a dropping funnel 100 ml of concentrated sulfuric acid is slowly added dropwise. The reaction flask is gently heated and obtained sulfur dioxide is dried by passing through a wash bottle with concentrated sulfuric acid. If reaction is to rapid additional 80 ml of sulfuric acid is added in order to cool the reaction mixture. At the end of the reaction heating is applied more rapidly in order to complete the reaction. Sulfur dioxide can be absorbed in water and used as a solution of sulfurous acid or absorbed in caustic alkalies forming bisulfites which may be again used to generate sulfur dioxide by the action of concentrated sulfuric acid. Furthermore, sulfur dioxide also could be liquefied (boiling point -10° C) by passing through a freezing mixture made of 1 part of common salt and 3 parts of crashed ice (-21° C). Sulfur dioxide prepared by described method, however, is liable to contain sulfuric acid which is not readily removed.
Sulfur dioxide can be generated by the action of ordinary concentrated sulfuric acid on sodium, potassium, calcium sulfite (or bisulfite):
Sodium sulfite or bisulfite is placed in the bottom of the 300 ml Erlenmeyer flask of the apparatus. The dropping-funnel is filled with dilute sulfuric acid, made by pouring one volume of concentrated sulfuric acid into an equal volume of water and cooling the mixture.
The glass elbow is connected with a gas washing-bottle containing concentrated sulfuric acid, and the dry gas is collected by displacement in two or three empty cylinders. On allowing the dilute sulfuric acid to drop slowly upon the sodium acid sulphite, a very regular evolution of sulfur dioxide is obtained.
Instead of using an inorganic acid for the evolution of sulfur dioxide, it is convenient to use sodium hydrogen sulfate (NaHSO4). A mixture of equivalent quantities of the respective salts in powder gives, when wetted with water, a regular stream of the sulfur dioxide gas, which will be free from the impurities usually derived from the use of an acid.
Laboratory manual of inorganic preparations, by H. T. Vulte, 27-28, 1895
Anhydride, Sulfurous, Dioxide, Sulfur, Sulfur Dioxide, Sulfurous Anhydride
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Sulfur oxide, Sulfate ion, Dioxide, Sulfur, Anhydride, Sulfurous, CID1119, D013458, 12624-32-7, SO4