_Example._—Suppose the weight of the dried sodium carbonate prepared as above directed is 0.6989 gram. ½Na₂CO₃, ½N₂ Then 0.6989 : 53 = x : 14 Whence x = 0.184615 gram of nitrogen. Suppose further that twenty cubic centimeters of sulfuric acid solution require ninety-four cubic centimeters of barium hydroxid for complete saturation and after treatment with the above amount of sodium carbonate, ten and a half cubic centimeters of the barium solution to neutralize the remaining acid. Then 94 - 10.5 = 83.5 And 0.184615: 83.5 = x: 94. Whence x = 0.207830 gram of nitrogen corresponding to twenty cubic centimeters of the sulfuric acid used. Then 0.20783 ÷ 94 = 0.002211 gram of nitrogen corresponding to one cubic centimeter of the barium hydroxid solution. If then in the analysis of a fertilizer it is found that 60.5 cubic centimeters are required to neutralize the excess of sulfuric acid after distillation the percentage of nitrogen in the sample is found as follows: 60.5 × 0.002211 = 0.13377. 0.20783 - 0.13377 = 0.07406. 0.07406 × 100 = 7.406 = per cent nitrogen in sample when one gram is taken for the combustion. =184. The Official Kjeldahl Method. Not Applicable in the Presence of Nitrates.=[153]—_Reagents._—(1) _Acids._—(_a_) _Standard hydrochloric acid_ the absolute strength of which has been determined by precipitating with silver nitrate, and weighing the silver chlorid as follows: To any convenient quantity of the acid to be standardized, add solution of silver nitrate in slight excess, and two cubic centimeters of pure nitric acid, of specific gravity 1.2. Heat to boiling-point, and keep at this temperature for some minutes without allowing violent ebullition, constantly stirring until the precipitate assumes the granular form. Allow to cool somewhat, and then pass the fluid through the asbestos. Wash the precipitate by decantation, with 200 cubic centimeters of very hot water, to which have been added eight cubic centimeters of nitric acid and two cubic centimeters of dilute solution of silver nitrate containing one gram of the salt in 100 cubic centimeters of water. The washing by decantation is performed by adding the hot mixture in small quantities at a time, and beating up the precipitate well with a thin glass rod after each addition. The pump is kept in action all the time, but to keep out dust during the washing the cover is only removed from the crucible when the fluid is to be added.