690 EXPERIMENT STATION RECORD. 



uiiun clilorid tbe nitrogen of both the nitrite and the ammonium chlorid 

 is set free, as shown by the following equations: 



N203+2NH4C1=2N2+3H20 + 2HC1. 



The method is conducted as follows: Three cubic centimeters of a 

 solution which should contain not more than 300 mg. of nitrate with 

 500 mg. each of crystallized ammonium chlorid and crystallized i)hos- 

 X)horous acid are placed in the digestion flask of a sx^ecial form of 

 gas generator which is described, and 2 cc. of sulphuric acid (2 parts 

 of concentrated sulphuric acid and 1 of water) is added. The digestion 

 flask is i)rovided with a pipette in its mouth, in which 5 cc. of sulphuric 

 acid (2 to 1) is placed, and is also connected with an absorption ai)pa- 

 ratus containing soda solution for purifying the nitrogen generated. 

 This apparatus is placed in a cooling cylinder and the generating flask 

 very slowly and carefnlly heated with the smallest possible flame. 

 This soon produces a slow and uniform evolution of gas, which grad- 

 ually increases, so that after a time the flame must be removed in order 

 to check the too rapid generation of gas. The latter should be so reg- 

 ulated that the solution is not colored yellow, and when it has almost 

 ceased the sulphuric acid in the pipette is allowed to run into the flask, 

 which is warmed again and the solution gradually raised to the boil- 

 ing point. This is continued until no further evolution of gas takes 

 place, when the solution is strongly heated for a few minutes. This 

 heating, however, must not be continued so long that the solution 

 in the flask becomes colored by the concentration of the sulphuric 

 acid. The nitrogen evolved is collected in a eudiometer over water and 

 measured. 



Accurate results were obtained by this method or modifications of it 

 on nitrate of soda, nitrate of ammonia, nitrate of potash, nitrite of 

 soda, and drinking water. 



In applying the method to the examination of ultimate of soda 300 

 mg. each of phosphorous acid and ammonium chlorid instead of 500 

 mg. is used. 



The method can be employed in the determination of very small 

 amounts of nitric acid, and hence is api)licable to the examination of 

 drinking water. In this case the residue from the evaporation of 500 

 cc. of water is taken up in a little water and filtered into the digestion 

 flask, in which the filtrate is evaporated nearly to dryness. To the resi- 

 due 2 cc. of dilute sulphuric acid (2 to 1) and 100 mg. each of ammonium 

 chlorid and phosphorous acid are added, and the operation conducted 

 as above described. 



On a new volumetric method for determining phosphoric acid 

 in pure solutions, R. SEaAXLE {Ztschr. analyt. Ghem., 34 {1895), JVb. 1, 

 2)2). 33-39). — Various methods proposed for this purpose are briefly 

 reviewed, and determinations by gravimetric analysis, volumetric 



