. Elements of modern chemistry . 428 ELEMENTS OP MODERN CHEMISTRY. ducts of the combustion, on tlie left with two large U tubes,the first of which is filled with pumice-stone impregnated withpotassium hydrate to absorb traces of carbon dioxide, thesecond with pumice-stone saturated with sulphuric acid toabsorb moisture. Through these tubes is passed the oxygen,at the close of the operation, to expel the last portions of carbondioxide and vapor of water. When the substance contains carbon, hydrogen, and oxygen,the proportion of oxygen is the difference between the totalpercentage of carbon and
. Elements of modern chemistry . 428 ELEMENTS OP MODERN CHEMISTRY. ducts of the combustion, on tlie left with two large U tubes,the first of which is filled with pumice-stone impregnated withpotassium hydrate to absorb traces of carbon dioxide, thesecond with pumice-stone saturated with sulphuric acid toabsorb moisture. Through these tubes is passed the oxygen,at the close of the operation, to expel the last portions of carbondioxide and vapor of water. When the substance contains carbon, hydrogen, and oxygen,the proportion of oxygen is the difference between the totalpercentage of carbon and hydrogen found and ^IG. 121. Determination of Nitrogen.—Nitrogen may be determinedby two processes. The first consists in burning a given weightof the nitrogenized substance with an excess of cnpric carbon of the substance is converted into carbon dioxide;the hydrogen is converted into water; the nitrogen is disen-gaged. The gases, nitrogen and carbon dioxide, are receivedin a graduated jar standing on the mercury-trough and con-taining potassium hydrate. The carbon dioxide is absorbed,the nitrogen remains. At the close of the operation, the lasttraces of nitrogen are expelled by a current of carbon volume of nitrogen is then measured, and its weight de-duced from its volume (Dumas). The second process (Fig. 121) consists in decomposing thenitrogenized organic matter with an alkali at a high tempera- ELEMENTARY ANALYSIS. 429 ture. By this means all of the nitrogen is converted intoammonia. The substance is intimately mixed with soda lime,that is, lime impregnated with caustic sod
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