Chemical lecture experiments . ized tosulphuric acid. Two grams of sulphur flowers are heated to boiling in a100 cc. Erlenmeyer flask with 10 cc. of fuming nitric diluting the mixture with water and pouring it upona filter, the filtrate will be found to contain considerablefree sulphuric acid, which will give a white precipitate withbarium chloride. S flowers ; fuming HN03. 68. By the action of nitric acid on sulphur dioxide. — Sul-phur dioxide, when conducted into concentrated nitric acid,becomes oxidized, forming sulphuric acid and setting free nitrogen peroxide. Incase dilute nitric
Chemical lecture experiments . ized tosulphuric acid. Two grams of sulphur flowers are heated to boiling in a100 cc. Erlenmeyer flask with 10 cc. of fuming nitric diluting the mixture with water and pouring it upona filter, the filtrate will be found to contain considerablefree sulphuric acid, which will give a white precipitate withbarium chloride. S flowers ; fuming HN03. 68. By the action of nitric acid on sulphur dioxide. — Sul-phur dioxide, when conducted into concentrated nitric acid,becomes oxidized, forming sulphuric acid and setting free nitrogen peroxide. Incase dilute nitric acidis used, nitric oxiderather than nitrogenperoxide is liberated. A current of sulphurdioxide is conductedinto a 300 cc. flask con-taining 75 cc. of con-centrated nitric cork of the flaskis provided with twoholes, through one ofwhich the sulphur di-oxide is conducted, while the other allows for the escapeof the nitrogen peroxide formed. An elbow in the secondhole conducts the nitrogen peroxide to the bottom of an. Fig. 72 SULPHURIC ACID 165 empty glass cylinder fitted with a two-holed cork (Fig. 72).All connections should be made with the glass tubes asnearly touching each other as possible, since the nitrogenperoxide fumes attack rubber. On conducting sulphurdioxide into the nitric acid, the liquid warms up of itselfand deep reddish-brown fumes of nitrogen peroxide escapeand fill the glass cylinder. After a few moments the liquidin the flask may be diluted with water and tested for thepresence of sulphuric acid by means of barium chloride. If the concentrated nitric acid in the apparatus is replacedby an acid of the specific gravity of and the experi-ment repeated, it will be found that the gas escaping intothe glass cylinder, while somewhat colored, consists chieflyof nitric oxide, as can be seen by opening the mouth of thecylinder and allowing the gas to come in contact with theair. The formation of red fumes indicates the presence ofnitric oxide. It will
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