Phelps — Determination of Nitrites in Absence of Air. 199 



the center and the flask placed well up on the higher part in the 

 preceding operation — and sulphuric acid (1-4) sucked in through 

 the funnel tube as the flask cooled, the cooling to the room 

 temperature being hastened by standing the flask in a dish con- 

 taining ice and water. In all, 7 cm3 of sulphuric acid were added, 

 this amount having been found by previous experiment to be 

 nearly but not quite enough to neutralize the sodium carbonate 

 used and also having been found to yield a little more carbon 

 dioxide than the apparatus can hold at the atmospheric pressure. 

 As soon as the diminished pressure in the apparatus was too weak 

 to suck in the acid, the position of the flask was again changed 

 on the wire gauze so that the exit tube was raised out of the 

 mercury into the layer of water which had condensed during 

 the preceding boiling and which then served to trap the appa- 

 ratus from the outside air. After the acid had been added and 

 had been washed in carefully, the nitrite solution to be analyzed 

 containing 2grms. of pure potassium iodine was introduced into 

 the flask through the funnel and this was followed by sul- 

 phuric acid (1-4) in sufficient amount (5 cm3 ) to render the con- 

 tents of the flask acid in reaction. Potassium bicarbonate was 

 then added in concentrated solution to alkaline reaction or until 

 the free iodine had been taken up, the mixture boiled for 

 about five minutes to expel the nitrogen dioxide, cooled, and 

 titrated to color with decinormal iodine in the presence of starch 

 paste. In making the various additions of liquid to the flask, 

 care was necessarily taken that no air was introduced with 

 the liquid. Table I records experiments made in this man- 

 ner upon a solution of commercial sodium nitrite, standardized 

 by treatment with potassium permanganate and oxalic acid in 

 acid solution according to the procedure of Kinnicut and Nef .* 



NaN0 2 



taken. 



grm. 



0-0958 

 0-0958 

 0-1916 

 0-1916 

 0-3832 

 0-3832 

 0-6716 

 0-6716 



Oxygen 



value of 



As 2 3 



taken. 



grm. 



0-01200 

 0*01200 

 0-03200 

 0-03200 

 0-05600 

 0-05600 

 0*08000 

 0*08000 



Table I. 



Oxygen 

 value of 

 As 2 3 

 found, 

 grm. 



0-00064 

 0-00066 

 0*00965 

 0-00965 

 0-01120 

 0-01118 

 0-00160 

 0-00158 



Error on 



Oxygen. 



grm. 



0*00025 + 

 0-00024 + 

 0-00017 + 

 0-00017 + 

 0-00043 + 

 0-00045 + 

 0-00076 + 

 0-00078 + 



9 0-1916 



0-03280 0-01003 0'00062 + 



* Amer. Chem. Jour., v, 388 (1883). 



Error on 



NaN0 2 . 



grm. 



0-0011 + 

 0-0010 + 

 0-0007 + 

 0-0007 + 

 0-0018 + 

 0-0019 + 

 0*0033 + 

 0-0034 + 



0-0027 + 



