Stability of Pure Hydrogen.Peroxide E. M. ROTH, JR., AND E. S. SHANLEY Buffalo Electro-Chemical Co., Inc., Division of Food Machinery & Chemical Corp., Station R , Buffalo 7 , Iv. Y .
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0 DATE there has been relatively little information published concerning the stability of hydrogen peroxide in concentrations above 90% by weight. Shanley and Greenspan (8) presented approximate data for the stability of 90% by weight hydrogen peroxide. Schumb (7) presented the results of an extensive investigation on the stability of 90% by weight hydro-
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gen peroxide and evaluated several factors which are known to affect ita stability. The purpose of this investigation was to determine the stability of pure hydrogen peroxide and to study the effects of several factors expected to influence its rate of decomposition.
For practical considerations most R orli on hydrogen peroxide stability is concserned with the evaluation of room temperature stability. A technique has been developeJ n-hich measures room temperature stability quickly and without the possibility of error inherent in the standing test method. In principle it is based on the determination of the volume of gas liberated from a peroside sample during a timed interval by measuring the pressure increase in a closed system, using a constant volume manometer, This method was successfully applied to studies at elevated temperatures up t o 66" C. for the purpose of evaluating temperature coefficients of hydrogen peroside decomposition.
.\IANORIETRIC TECHNIQUE
The determination of hydrogen peroxide stability has previously presented t o the experimenter the dilemma of having t o choose between two procedures, each having serious limitations. When conventional chemical analysis is used to determine the decrease in peroxide concentration with time, the sample under investigation must either be kept a t an elevated temperature for a reasonable length of time (days) or a t room temperature for a very long time (years) in order to obtain a measurable drop in concentration. The elevated temperature technique is not very accurate, and there is evidence t o indicate that the prediction of room temperature stability from elevated temperature determinations is of questionable value. However, the room temperature "standing" test procedure also has serious drawbacks. The time required t o obtain measurable concentration changes is a t least a year for samples of average stability, and the possibility of error due to evaporative losses and accidental contamination acts as a deterrent t o any extended research program.
Figure 2.
Figure 1. Apparatus For Manometric Determination Of Hydrogen Peroxide Stahility
Warburg Manometer and Flask
Construction and Calibration of Apparatus. The 30" and 66" C. water thermostats (Figure 1) were made from 30-gallon aluminum containers with agitators and regulating systems for maintaining constant temperature. The 30' bath was held constant a t 30.10"i 0.002' C.; the 66" bath was held constant at 66.0" i 0.01' C. A layer of mineral oil over the water in the 66' bath prevented excessive evaporation. A conventional Warburg manometer with the small reaction vessel replaced by a 125-ml. flask (Figure 2) comprised the constant volume closed system. The flasks were made from 125ml. Florence flasks by fusing on the outer sections of borosilicate glass ground joints which fitted the inner joints of the manom-
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INDUSTRIAL AND ENGINEERING CHEMISTRY
eters. Each manometer, with it- ,individual flask, was calibrated t o determine the constant, K , of the unit, cf. Dixon ( 2 ) . This constant served as a conversion factor for changing the pressure units (mm. of confining fluid, as indicated by the manometer) to volume units (cubic mni. of osygen gas evolved in the flask). This constant is represented b),
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able displacement of the kerosine colunm, from 1 t o 24 hours depending upon the stability of the peroxide sample, the closed arm column was reset at the 150-mm. mark by means of the elastic reservoir, thereby effecting constant volume. The increase in height of the kerosine level in the open arm above the 150-mm. mark and the time n-err noted.
(1)
where K = constant in square mm. V o = free gas space of the unit in cubic mm. T = absolute temperature of the constant temperature bath in degrees I
