New specifications prepared at the 53rd JECFA (1999) and published in FNP 52 Add 7 (1999). | |
SYNONYMS |
INS No. 939 |
DEFINITION |
|
Chemical name |
Helium |
C.A.S. number |
7440-59-7 |
Chemical formula |
He |
Formula weight |
4.0 |
Assay |
Not less than 99.0% by volume |
DESCRIPTION |
Colourless and odourless gas |
FUNCTIONAL USES |
Processing aid |
CHARACTERISTICS |
|
IDENTIFICATION |
|
Flame test |
The flame of a burning splinter of wood is extinguished when inserted into an inverted test tube filled with helium. |
GC test |
See Method of Assay |
PURITY |
|
Air |
Not more than 1.0%, by volume |
Carbon monoxide |
Not more than 10 �l/l, by volume |
Odour |
Carefully open the container valve to produce a moderate flow of gas. Do not direct the gas stream toward the face, but deflect portion of the stream toward the nose: no appreciable odour is discernible. |
METHOD OF ASSAY |
Determine by Gas chromatography using the following conditions: Column: - material: stainless steel - length: 6 m - internal diameter: 4 mm - packing material: PoraPak Q, or equivalent Carrier: - gas: Helium (99.99% (v/v)) - flow 40 ml/min Detector: thermal conductivity detector Injector: loop injector Column temperature: 60� Detector temperature: 130� Procedure: Introduce a specimen of helium into a gas chromatograph by means of gas sampling valve. Select the operating conditions of the gas chromatograph so that the standard peak signal resulting from the following procedure corresponds to not less than 70% of the full-scale reading, and which permit complete separation of nitrogen and oxygen from helium, although nitrogen and oxygen may not be separated from each other. The peak response produced by the assay specimen exhibits a retention time corresponding to that produced by an air-helium certified standard (a mixture of 1.0% air in industrial-grade helium is available from most suppliers) and indicates not more than 1.0% air, by volume, when compared with the peak response of the air-helium certified standard, and not less than 99.0% of He, by volume. |