THE BEHAVIOUR OF MIXTURES OF HYDROGEN PEROXIDE AND WATER

PART 1.-DETERMINATION OF THE DENSITIES OF MIXTURES OF HYDROGEN PEROXIDE AND WATER

BY MISS M. F. EASTON, MISS A. G. MITCHELL AND W. F. K. WYNNE-JONES Department of Physical Chemistry, King's College, Newcastle-upon-Tyne

Received 5th March, 1952

The densities of mixtures of hydrogen peroxide and water have been determined at 0", lo", 25", 50" and 96" C by a simple displacement method. The method is found con- venient and accurate for determining the concentrations of mixtures of hydrogen per- oxide and water. The data have been fitted to equations and the agreement of the data and equations is about 1 part in 5000 for all temperatures except 96" C where it is about 1 part in 1400.

Although several authors have previously made measurements of the densities of mixtures of hydrogen peroxide and water, the reactivity of the system has made it difficult to obtain reliable results over a wide range of both temperature and composition. In the course of a general study of the properties of electrolytic solutions in these mixtures we required an accurate knowledge of the densities so as to enable rapid determinations of composition to be made and it seemed desirable to extend the measurements over as wide a range as possible.

Since the main experimental difficulty in determining the densities of these mixtures is the formation of gas bubbles from the decomposition of the hydrogen peroxide, we decided not to use pycnometers but to apply a simple displacement method. This method turned out to be both quick and accuraie and the results obtained by weighing a carefully cleaned Pyrex glass sinker in the hydrogen peroxide solution compared favourably with those of the pycnometric method. We made measurements at 25" then at 0", lo", 50" and 96" C and even at the highest temperature the accuracy is about 0.1 %,while at temperatures up to 50" our results are at least as accurate as those of previous workers at 0" C although it has been frequently reported that the solutions are insufficiently stable about 0" C for accurate measurements to be made.

E X P E R I M E N T A L

DENSITY OF MIXTURES OF HYDROGEN PEROXIDE AND WATER AT 25", OD, 10" AND 50" C.- The method employed was to weigh a glass sinker in air, water and hydrogen peroxide solutions and hence calculate the volume of the sinker and densities of the solutions. The sinker (volume approximately 1 cm3) was suspended by means of a glass fibre in a glass density vessel. The fibre was attached to the left-hand arm of an analytical balance which could be read to O-OOOl g. The sinker and fibres were constructed from Pyrex glass rod and the hooks used to handle the sinker and fibres from Pyrex glass tubing. In order to eliminate surface tension effects the part of the fibre which passed through the surface of the liquid had its diameter reduced to approximately 0.03 mm. The density vessel was a Pyrex glass weighing bottle 9 cm high and 2-5 cm ext. diam. It fitted closely into a water jacket which is shown in fig. 1 (a) and (b). The walls were made of glass so that the density vessel and its contents could be observed during weighings and any trace of decomposition detected immediately. By a friction drive the jacket could be moved up and down on the stand and fixed in any desired position. Thus it was not necessary to have the glass fibres of a uniform length ; also by lowering the jacket the sinker could easily be detached from, or attached to, the fibre with a glass hook. Any oxygen bubbles

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MISS EASTON, MISS MITCHELL A N D W. F. K . WYNNE-JONES 797

which formed on the sinker were removed simply by lowering the jacket until the sinker was above the level of the liquid, then slowly raising it into position. The tightly fitting Perspex cap protected the upper metal end-piece. The Perspex lid was designed to exclude dust and moisture from the hydrogen peroxide solution. During weighings a slow stream of dry dust-free air was passed through the hollow screw. A rapid stream of water from a thermostat (& 0.05") was circulated through the jacket. It was impos- sible to carry out an accurate weighing of the sinker in hydrogen peroxide unless the glassware was specially treated, so that no trace of decomposition occurred on the surfaces in contact with the peroxide solution.

FIG. la. A-heavy metal stand ; B-bakelite platform with friction drive ; CI, C2-metal end pieces ; D1-Perspex cap ; D2-Perspex lid.

m FIG. lb.

1

The sinker was placed in the density vessel and they were cleaned together by rinsing with alcohol then adding a little nitric acid. Vessel and sinker were then washed thoroughly with water and soaked in distilled water for several hours. The vessel was rinsed with distilled water and tested with hydrogen peroxide. If any decomposition occurred on the surface of the vessel or sinker, the cleaning process was repeated. When the surfaces were properly conditioned the vessel was completely filled with a fairly concentrated hydrogen peroxide solution and stored under a bell jar to prevent contamination with dust. The sinker was always kept in a density vessel and was handled by means of a glass hook which was carefully cleaned at each stage. Fibres and hooks were drawn out from glass rod and tubing which had previously been thoroughly cleaned by the alcohol + nitric acid method. They were stored in test-tubes containing hydrogen per- oxide solution. Small glass caps were placed over the tubes and they were placed under a bell jar.

Immediately before use, the density vessel, sinker, fibre and hook were rinsed thoroughly with distilled water, carefully dried in an oven at 105-110" C and cooled in a desiccator. The sinker was kept in the density vessel and the fibre and hook in test-tubes. The glassware was never left exposed to the air for longer periods than were absolutely necessary.

To reduce the risk of contamination by dust the following method was used for all weighings. The density vessel containing the liquid and sinker was stoppered and placed in the water jacket. After 30 min, when the temperature of the liquid had reached

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798 DENSITIES OF MIXTURES

equilibrium, the stopper was removed from the density vessel, the Perspex lid closed and the air stream turned on. The sinker + fibre, fibre alone, then sinker + fibre were weighed. The Perspex lid was kept closed as much as possible during the weighings.

MEASUREMENTS AT 25" C.-The weight of the sinker in vucuo and the volume of the sinker were determined at the beginning and end of the series of measurements. The solutions used were obtained by diluting High Test peroxide (unstabilized) supplied by Messrs. Laporte with triply-distilled water. Laboratory-distilled water was distilled from a trace of potassium permanganate then again distilled in a Pyrex glass still. Im- mediately after weighings had been made in a hydrogen peroxide solution, a sample of the solution was removed for analysis. The analysis was carried out by titration with potassium permanganate by the method recommended by Huckaba and Keyes 1 with the following modifications.

The sample was transferred by means of a clean, dry Pyrex glass dropping tube to a weighing bottle containing a few ml triply-distilled water and was weighed. The weight of the sample chosen varied from about 0.3 g for a 90 % solution to about 13 g for a very dilute solution. All glassware used in the analysis was carefully cleaned before use. The solution in the weighing bottle was diluted to 100 ml with triply-distilled water. 50 ml of a sulphuric acid solution containing 50 ml concentrated sulphuric acid per litre solution and 100 ml triply-distilled water were placed in a 250 ml beaker. Sufficient potassium permanganate solution was added to impart a faint pink colour to the solution. A 10-ml sample of the diluted hydrogen peroxide solution was then added and the titra- tion carried out in the way recommended. The end-point was reached when the initial pink colour was reproduced. Best agreement in a series of titrations was obtained when the initial pink colour was only just detectable as it was almost impossible to repeat exactly a definite colour in such a large volume of solution. The light from a mercury lamp was used to detect the pink colour. The lamp was fixed up with an adjustable shutter alongside the titration beaker and the shutter opened during the initial tinting process and at the end point determination. The end point was determined to 0.01 ml. The 10-ml pipette and 50-ml burette each had a standards certifkate and were rechecked before use.

The potassium permanganate was standardized with sodium oxalate by the method of Fowler and Bright.2 One sample of sodium oxalate was purified by Sorensen's 3 method and a second sample was kindly sent to us by the National Bureau of Standards : the two samples gave good agreement.

The experimental results are given in table 1 (A).

TABLE I(A).-DENSITIES OF H202 +H2O MIXTURES AT 25" C

% H202 b l w ) 0.0 1.91 5.99 9.23

13.47 17-44 21.14 24-58 27-96 29-99 34.23 39-12 40-67 42.97 47.02

density g/cm3

(0.9970) 1-0036 1.0179 1.0295 1.0452 1.0597 1,0737 1.0868 1 -0996 1-1078 1.1244 1.1450 1-1515 1,1610 1.1785

% H 2 0 2 (wlw) 49.88 53.48 55-08 59.68 62-55 64.88 68-97 73-15 73.66 76.66 80.64 84.97 89-68 89.78 89.89

density g/cm3

1-1909 1.2067 1-2143 1.2353 1-2490 1.2593 1 -2790 1.2996 1-3024 1.3166 1.3378 1-3595 1-3848 1.3855 1.3855

The experimental results were plotted on a large scale graph on which one division corresponded to 0.0002 for density and 0-1 % for composition. The points can be represented quite accurately by a smooth curve. At high concentrations of hydrogen peroxide when the percentage error arising in the analysis is greatest, the deviation of the points from the curve was never greater than 0-1 % hydrogen peroxide.

MEASUREMENTS AT 0", 10" AND 50" C.-The method described for measurements at 25°C was used. No appreciable decomposition of a solution occurred during a

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MISS E A S T O N , MISS MITCHELL A N D W. F. K . W Y N N E - J O N E S 799

determination at 50" C. The mass in vucuo and the volume of a sinker at 25" C were determined at intervals during the three series of measurements. The volume of the sinker at 0", 10" and 50" C was calculated using the value 9.6 x 10-6 for the coefficient of cubical expansion of Pyrex glass. Immediately after a weighing had been made in hydrogen peroxide solution the density vessel was taken out of the water jacket, the sinker removed and the solution rapidly brought to approximately 25" C. The density of the solution at 25" C was then determined and the concentration of peroxide read from the large scale density composition graph.

The experimental results are given in tables 1 (B), (c) and (D).

TABLE ~(B).-DENSITIES OF H202 +H2O MIXTURES AT 0" C % H 2 0 2 (w/w) 0.0 7.36

17-14 24.36 33.23 44.62

density dcm3

0-9999 1 *029 1 1.0690 1.0987 1.1370 1.1860

% H202 (w lw)

55.69 65-07 74.96 83.27 91.55 96.65

density g/cm3

1,2373 1-2822 1.3321 1.3759 1-422 1 1.4517

TABLE 1 DENSITIES OF H202 +H2O MIXTURES AT 10" C

0.0 4.32

10.69 17.28 23-65 29.93 36.33 41-82 49-27

density slcm3

0.9998 1.0150 1.0394 1.0652 1 *0906 1.1 163 1-1432 1.1668 1.1997

% H 2 0 2 (w/w> 55-15 60.24 65.32 70.69 77.04 80.2 1 86-77 89.00 94.25 98.60

density glcm3

1 -2266 1.2503 1.2747 1.3012 1.3335 1.3499 1.385 1 1.3973 1 -426 1 1.4515

TABLE 1 (D).-DENSITIES OF H202 +H20 MIXTURES AT 50" C % H202

(wlw)

0.0 6.96

12.53 20.36 30.21 39.25

density glcm3

0.9880 1.0106 1 *0289 1.0564 1.0914 1-1267

% H 2 0 2 (wlw) 47.07 57.21 59.60 66.22 74-37 86.53

density glcm3

1.1580 1.2020 1.2123 1 -2425 1.2814 1.3419

DENSITIES OF MIXTURES OF HYDROGEN PEROXIDE AND WATER AT 96" C.-The experi- mental method for the determination of density has been described earlier. The only difference in procedure was the method of controlling the temperature. The solution was maintained at 96 f 0-15" C by surrounding the density vessel with water boiling under reduced pressure.

The density vessel and water jacket are shown in fig. 2. The water was heated by an electric hot plate controlled by a Sunvic regulator. A window was cut in the asbestos lagging so that the contents of the density vessel could be observed during measurements. The manostat was similar to that described by Simon.4 Solutions containing Laporte's unstabilized High Test peroxide decomposed rapidly at 96°C so it was necessary to use stabilized material for the density measurements. Solutions were made with triply- distilled water, each containing 81 mg zinc sulphate per litre. Some decomposition of the stabilized solutions occurred at 96" C but no appreciable change in the concentration occurred during a density determination.

It was clear from a few preliminary tests that the temperature at which the water in the jacket was required to boil to maintain the peroxide solution at 96" C depended on the concentration and rate of decomposition of the solution. The rate of evaporation

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800 DENSITIES OF M I X T U R E S

of the solution and the amount of condensation of liquid on the upper part of the density vessel increased as the concentration of hydrogen peroxide in the solution decreased.

C

It was therefore necessary to determine the manostat setting for each solution under investigation. The following pro- cedure was used. The electric hot plate was switched on and the whole apparatus assembled. A thermometer was sus- pended in the peroxide solution and a rapid stream of cold water passed through the condenser. Water at approximately 96" C was introduced into the water jacket through tube A and the electric hot plate clamped into position. The pump was switched on and the manostat regulated until the reading on the thermometer became steady in the range 96 0.15 "C. The manometer reading varied from 658 mm for approximately 90% (w/w) hydrogen peroxide to about 700 mm for very dilute solutions. The solutions were investigated in order of decreasing concentration hydrogen per- oxide. With a little practice we were able to estimate fairly accurately the pressure required for solutions in the concentration range 90-40 % (w/w) hydrogen peroxide and to adiust the manostat before the

FIG. 2. volume of solution had changed appreci- A, Tube for filling water jacket; ably. For solutions containing less than B, Liebig condenser ; C, asbestos lagging ; 40 % hydrogen Peroxide an approximate D, rubber bung ; E, B34 socket; setting of the manostat was obtained, F, density vessel mounted on B34 cone ; water was added to bring the volume of G, electric hot plate. solution up to the required mark and

the final adjustment quickly made. The volume of the sinker at 96" C was calculated from the volume at 25" C using the value 9.6 x 10-6 for the coefficient of cubical expansion of Pyrex glass.

The experimental results are given in table 2.

TABLE 2.-DENSITIES OF H202 $- H2O MIXTURES AT 96" c % HzO2 dcnsity % Hz02 density

(WlW) glcm3 (wlw) slcm3 0-0 0.96 15 52.55 1.1390

11.40 0-9950 60-65 1.1726 14-84 1 a0054 66.20 1.1952 26.80 1.0428 73.40 1.2299 37.97 1.0834 84.30 1.2788 45.03 1-1116 89-30 1.3038

ANALYSIS OF DATA.-At each experimental temperature the data have been fitted by the method of least squares to cubic equations of the form

where d is the density and w the weight fraction of hydrogen peroxide in the solution. d = A + BW + C W ~ + D w ~ ,

RESULTS

0" C, d = 0.9998 + 0.39939~ + 0.01758~2 + 0.05470~3, 10" C, d = 0.9997 + 0.36790~ + 0.06208~2 + 0.02954~3, 25" C, d = 0.9970 + 0.34672~ + 006995~2 + 0.02885~3, 50" C, d = 0.9880 + 0.31382~ + 0.09402~2 + 0*01910~3, 96" C, d = 0.9612 + 0.27652~ + 0.11956~2

(1) (2) (3) (4) (5)

The agreement of the data with the equations is about 1 part in 5000 at all temperatures except 96" C, where it is about 1 part in 1400.

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MISS E A S T O N , MISS M I T C H E L L A N D W . F . K . W Y N N E - J O N E S 801

D I S C U S S I O N

The early values for the densities of mixtures of hydrogen peroxide and water reported by Maass and Hatcher 5 are now considered to be too low as also are those of Kubaschewski and Weber.6 More recent determinations have been made by Huckaba and Keyes 7,8 and by Gigukre and Geoffrion.9 These workers carried out measurements at 0" C by a dilatometric method and Huckaba and Keyes also measured the expansion of a few solutions over the range 0"-20" C. For comparison of these results with our own we give in table 3 (A) the actual results of Gigukre and Geoffrion together with interpolated values from Huckaba and Keyes' results read from table 2 of their paper 7 and our own values calculated from eqn. (1) above. There is good agreement between our results and those of Huckaba and Keyes over the whole range of concentration but Giguere and Geoffrion's values are consistently higher. Such a difference could. arise with the more concentrated solutions if decomposition of the hydrogen peroxide occurred between the density determination and the analysis of the solution.

The general agreement between Huckaba and Keyes' data and ours is further illustrated by taking the expansions directly determined by Huckaba and Keyes of five mixtures over the range 0-20" C . The densities of the five solutions at 20" C thus calculated are compared in table 3 (B) with the values derived from our results at 25" C using our own temperature coefficients.

TABLE 3 (A)

density at 0" C g/cmJ % H202 (w lw) Giguere Keyes this work

9-32 10.21 12.21 18.32 19.27 29.54 41-23 49-87 68.37 69.05 78-61 79-63 89.64

1.0377 1-0410 1-0493 1-0748 1.0783 1-1209 1-1722 1-21 19 1 -3006 1-3037 1.3535 1.3590 1.4136

1-0366 1 -0402 1 *0484 1-0735 1.0774 1.1206 1-1715 1.2104 1-2990 1.3024 1.3515 1.3569 1.4116

1.0372 1 -0408 1 -0489 1.0739 1.0778 1-1207 1.1713 1.2101 1 -2986 1 -3020 1.3512 1.3566 1.4113

TABLE 3 (B) density at 20" C

wt fraction a x 104 (0-20") u x 104 (10-250) - Keyes this work

0.96877 7.759 7.674 1 -4306 1 -4303 0-78529 7-344 7.439 1.3316 1.3313 0.59083 6.656 6.817 1.2370 1.2364 0.39159 5.846 5.763 1.1490 1.1485 0.21 525 4.326 4.278 1.0773 1.0775

HzOz Keyes (obs.) this work

1 Huckaba and Keyes, J. Amer. Chem. SOC., 1948, 70, 1642. 2 Fowler aad Bright, J. Res. Nat. Bur. Stand., 1935, 15, 497. 3 Sorensen, Kolthoff and Stenger, Volumetric Analysis (Interscience Publishers Inc.,

4 Simon, Ber., 1927, 60, 568 ; Ber., 1928, 61, 2173. 5 Maass and Hatcher, J. Amer. Chem. SOC., 1920, 42, 2548. 6 Kubaschewski and Weber, 2. Elektrochem., 1950, 54, 200. 7 Huckaba and Keyes, J. Amer. Chem. SOC., 1948, 70,2578. 8 Huckaba and Keyes, J. Amer. Chem. SOC., 1950, 72, 5324. 9 Gigubre and Geoffrion, Can. J. Res. B, 1950, 28, 599.

New York), 2nd rev. ed., 1944-47, vol. 2, p. 74.

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