Quantitative Infrared Determination of Ammonium Ion in Hydroxylamine Sulfate Everett S. Whitehead Industrial Laboratory, Eastman Kodak Co., Rochester, N. Y. 14650
THE AMOUNT of ammonium ion present in hydroxylamine sulfate (HAS) is of particular importance when it is used in the processing of color photographic images. Quantitative determination of ammonium ion in HAS is usually done by either a micro or a vacuum distillation technique. With either of these methods hydrolysis of the HAS can result in inconsistent analyses. The method as given in ACS Specifications ( I ) and Rosin ( 2 ) for hydroxylamine hydrochloride is not quantitative, and the method of Bourjol (3) is too time consuming. This paper describes an infrared method that is now in use in our laboratory for determining the amount of ammonium ion in hydroxylamine sulfate by use of the N-H deformation band of the ammonium ion at 1400 cm-1.
WAVENUMBER
2000
Ten milligrams of the HAS is weighed and added to 390 mg of spectrograde potassium bromide. Both materials are placed in a Spex steel mixing vial with two steel balls. The sample is mixed for 1 minute by use of a Spex Wig-L-Bug. Three hundred milligrams of the material is pressed into a pellet by use of a Perkin-Elmer evacuable die. The pellet is quickly transferred to a pellet holder and placed into the spectrophotometer. For our work we use a Beckman Model IR-8 that is flushed with dry air. The instrument is set for slow scan, gain at 6.5, the reference beam attenuator is set so that the minimum absorbance at 1850 cm-I is between 0.1 and 0.2. By use of absorbance paper, the spectrum is scanned from 2000 to 1200 cm-’. If the amount of reference screening is large, it may be necessary to use a wider than normal slit setting to obtain proper pen response. A base line is drawn between approximately 1450 and 1350 cm-I (Figure 1). The difference between the absorbance of the base line and at the absorbance maximum at 1400 cm-I is calculated. This value is converted to weight per cent ammonium ion by use of a calibration curve derived from Table I. In some samples (Figure 1) a band will be present at 1390 cm-I. This band is probably due to a trace of nitrate ion and does not interfere with the method. The straight line calibration curve was prepared by adding known amounts of ammonium sulfate, B & A reagent grade, to Eastman Grade hydroxylamine sulfate. The pellets were prepared as described above. (1) “Reagent Chemicals,” American Chemical Society Specifications, 4th ed., 1968, p 293. (2) J. Rosen, “Reagent Chemicals and Standards,” 5th ed., Van Nostrand, Princeton, N. J., 1967, p 230. (3) G. Bourjol, Chim. Anal., 41, 281 (1959); Chem. Abstr., 53, 187331’ (1959).
2,o
1200
t
O’I0
EXPERIMENTAL
CM-’
1500 1400 I300
u -
5
6
7
8
WAVELENGTH IN MICRONS
Figure 1. Infrared scan of hydroxylamine sulfate showing the presence of the absorption band due to the ammonium ion at 1400 cm-I and the absorption band at 1390 cm-1 attributed to nitrate ion
Table I. Per Cent Ammonium Ion Ammonium ion,
Absorbance at 1400 cm-1
0.00 0.10 0.20 0.30
0.000 0.058 0.116 0.174
RESULTS
The infrared method has decreased testing time and eliminated the possibility of high results due to hydrolysis of hydroxylamine. This method will supply both users and suppliers of HAS with a fast, simple, and accurate method of analysis. RECEIVED for review August 14, 1968. Accepted February 19, 1969.
VOL. 41, NO. 6, MAY 1969
829
