LUNGE AND IAVOFF'S PROCESS 473 



nitrite-free distilled water, adding the reagents as above. At 

 the end of the time stated (30 minutes) examine the depth of 

 the pink color formed, and by comparing the unknown with 

 the known an accurate determination of the amount of nitrogen 

 present as nitrites may be made. 



If much gas be burning in the room, nitrites will be in the 

 atmosphere. Hence, cover the tubes or remove them from the 

 room during the half-hour interval before reading. 



It may be worth while to call attention to the fact that the 

 error due to the presence of burning lamps is often much great- 

 er than is suspected. In Mason's water laboratory the pure 

 distilled water is prepared by the use of a large copper retort 

 heated by a very broad bunsen burner. Only one ether lighted 

 burner is constantly in the room, and that a small one. 



405. Lunge and Lwoff's Process for Nitrous Acid. The re- 

 action of nitrous acid with a-naphthylamin, first described by 

 Griess, may be made reliable, quantitatively, by proceeding as 

 below : 90 



Boil o.ioo gram of pure white a-naphthylamin for 15 min- 

 utes with loo cubic centimeters of water, add five cubic centi- 

 meters of glacial acetic acid, or its equivalent of dilute acid, and 

 afterwards one gram of sulfanilic acid dissolved in 100 cubic centi- 

 meters of hot water. The mixture is kept in a well closed flask. 

 A slight red tint in the mixture is of no significance, inasmuch as 

 this completely disappears when one part of it is mixed with 50 

 parts of the liquid to be examined. If the coloration be very strong 

 it can be removed by adding a little zinc dust. One cubic centi- 

 meter of this reagent will give a distinct coloration with o.ooi 

 milligram of nitrous nitrogen in 100 cubic centimeters of water. 



The analysis is conducted in cylinders of white glass marked 

 at 50 cubic centimeters. One cubic centimeter of the above 

 reagent is placed in each of two cylinders with 40 cubic centi- 

 meters of water and five grams of solid sodium acetate. In one 

 of the cylinders is placed one cubic centimeter of a normal solu- 

 tion of a nitrite prepared by dissolving 0.0493 gram of pure 

 sodium nitrite corresponding to 10 milligrams of nitrogen in 100 

 cubic centimeters of water, and adding 10 cubic centimeters of 

 Zeitschrift fur angewandte Chemie, 1894, 7 : 349- 



