N2 28.01

Nitrogen.
Nitrogen [7727-37-9].

Packaging and storage— Preserve in cylinders.

Identification— The flame of a burning wood splinter is extinguished when inserted into a test tube filled with Nitrogen.[NOTE—Exercise caution.]

Odor— Carefully open the container valve to produce a moderate flow of gas.Do not direct the gas stream toward the face,but deflect a portion of the stream toward the nose:no appreciable odor is discernible.

Carbon monoxide— Pass 1000±50mLthrough a carbon monoxide detector tube (see under Reagentsin the section Reagents,Indicators,and Solutions)at the rate specified for the tube:the indicator change corresponds to not more than 0.001%.

Limit of oxygen— Not more than 1.0%of oxygen is present,determined as directed in the Assay.

Assay— Introduce a specimen of Nitrogen into a gas chromatograph by means of a gas sampling valve.Select the operating conditions of the gas chromatograph such that the standard peak signal resulting from the following procedure corresponds to not less than 70%of the full-scale reading.Preferably,use an apparatus corresponding to the general type in which the column is 3m in length and 4mm in inside diameter and is packed with a molecular sieve prepared from a synthetic alkali-metal aluminosilicate capable of absorbing molecules having diameters of up to 0.5nm,which permit complete separation of oxygen from nitrogen.Use industrial grade helium (99.99%)as the carrier gas,with a thermal-conductivity detector,and control the column temperature:the peak response produced by the assay specimen exhibits a retention time corresponding to that produced by an oxygen-helium certified standard (see under Reagentsin the section Reagents,Indicators,and Solutions),and is equivalent to not more than 1.0%of oxygen when compared to the peak response of the oxygen-helium certified standard,indicating not less than 99.0%,by volume,of N2.

Expert Committee:(AER)Aerosols

USP28–NF23Page 3041

Phone Number:1-301-816-8269