INDUSTRIAL AND ENGINEERING CHEMISTRY
996
havior of n-pentane was studied in greater detail by Young and his associates than in the present instance. Figure 6 presents the phase behavior of propane and npentane in this system. The product of the equilibrium constant and the pressure was employed for this representation in order to show the behavior in somewhat greater detail than would be possible otherwise. The results are similar to those obtained by Kay (3) for the ethane-n-pentane system. The phase behavior of propane a t temperatures below its critical temperature is in reasonable agreement with the behavior of the ideal solution. However, above this temperature rather marked divergences are encountered. I n general, n-pentane follows the behavior of ideal solutions reasonably well up to a temperature of about 200' F. except under such conditions that the concentration of pentane in each of the phases is small. At the higher temperatures the divergences from this generalization become large.
Nomenclature b = specific gas constant (per pound) K = gas-liquid equilibrium constant P = pressure, pounds per square inch absolute T = thermodynamic temperature, F. absolute, O
V
=
specific volume, cubic feet per pound
R.
X Y Z
VOL. 32, NO. 7
= mole fraction of a component in liquid phase = mole fraction of a component in gas phase =
compressibility factor, PV/bT
Acknowledgment This work was carried out as a part of the activities of Research Project 37 of the American Petroleum Institute. Lee Carmichael contributed to the experimental program, and G. P. Hinds and Louise &I. Reaney assisted with the numerical calculations.
Literature Cited Beattie, Kay, and Kaminsky, J . Am. Chem. Soc., 59, 1589 (1937). Beattie, Poffenberger, and Hadlock, J. Chem. Phys., 3,96 (1935). Kay, IND.ENQ.CHEM..30, 459 (1938). Lewis, J. Am. Chsm. Soc., 30,668 (1908). Nysewander, Sage, and Lacey, IND.ENQ.CHEJI.,32, 118 (1940). Rose-Innes and Young, Phil. Mag., [5]47, 353 (1899). Sage, Backus, and Vermeulen, IND.ENQ.CHEM., 28,489 (1936). Sage and Lacey, Ibid., 32, 118 (1940). Sage, Lacey, and Schaafsma, Ibid., 27, 48 (1935). Sage, Schaafsma, and Lacey, Ibid., 26, 1218 (1934). Taylor, Wald, Sage, and Lacey, Oil Gas J.,38,No.13,46 (1939). Young, J.. Sci. Proc. Roy. Dublin Sac.. 12, 374 (1910).
Bactericidal Properties of Commercial Antiseptics A Further Studv of the Effect of pH' J
INCE the time of Pasteur (1879) it has been known that acidity has an effect on the growth of some bacteria. Subsequent work has definitely shown that bacteria are affected by acidic media and that some compounds are often more highly bactericidal in acidic media (1, 2, 6). Because of these facts a previous study of the effect of pH on the bactericidal properties of some commercial antiseptics was made (1). It was then found desirable to continue these studies on other commercial products. I n this type of study it is desirable to eliminate pH values below 3 because such solutions are bactericidal in themselves as a consequence of their high acidity, and no suitable comparisons can be obtained.
S
Solutions of Definite pH The apparatus used in adjusting these solutions to a definite pH consisted of a membrane-type glass electrode with a saturated calomel electrode as previously described (1). The glass electrode was checked against buffer solutions of known hydrogen-ion content before and after each period of use. The following commercial products were tested as supplied and at pH values of 3.0, 4.0, 5.0, 6.0, 7.0, and 8.0 in solutions 1 This is the fifth of a series of articles by Degering and oo-workers on the effect of p H and substituent groups on the bacteriostatic and bactericidal properties of certain antiseptics [IND.ENQ.CHEM.,30, 646 (1938),31, 742 (1939); J. A m . P h a r m . Assoc., 27,865-70 (1938). 28, 514-19 (1939)l.
W. A. BITTENBENDER, ED. F. DEGERING, P. A. TETRAULT, C. F. FEASLEY, ANDB. H. G W Y " Purdue University, Lafayette, Ind.
In a further study of the effect of pH on the bactericidal properties of commercial antiseptics, tests have been made on adjusted solutions of Amphyl, Chlorazene, gentian violet, Listerine, Lysol, malachite green, mandelic acid, Mercurochrome, Mercurophen, methylene blue, Pepsodent antiseptic, potassium dichromate, potassium permanganate, sodium nitrite, zinc sulfate, Zonite, and Sulphonmerthiolate. Eschericia coli and Staphylococcus aureus were used as test organisms, over a pH range of 3 to 8 and on the unadjusted solutions of the antiseptics. The bactericidal activity of Chlorazene, gentian violet, Listerine, Lysol,
JULY, 1940
INDUSTRIAL AND ENGINEERING CHEMISTRY TABLEI. B.WTERICID.II, PROPERTIES
Initial Diln. of Soln.
pH
Highest Diln. T h a t Kills in 10 Min. S. aureus E. coli 250 300 325 350 425 500 375
Chlorasene, 2%
Gentian violet, 4.93%
3 4 5" 6" 74 8" a,)
2100 1800 1650 1500 1350 1250 950
3 4 5'3 6" 7a 8"
40,000 40,000 31,000 31,000 30,000 26,000 40,000
a,b
Liaterine, 80%
3 4 54 6' 7" 8" b
L Y S O l , 2%
3 4 5'3 6' 75 8' o,b
SOME COXXERCIAL ANTISEPrIcS
OF
Lowest Diln. T h a t Survives 5 and 10 Min. S. aureus E . coli
800 450
300 400 425 450 550 600 475
300 350 675 700 850
2300 2050 1950 1650 1550 1450 1200
2400 2200 2000 2000 2000 1650 1350
48,000 48,000 40,000 40,000 36,500 32,500 49,000 3 75 3.5 3.12 3 12 2.5 2.5 2.5
800 750 700 650 650
2.5 2.0 1.87 1.87 1.25 1.25 1.25
2250 2000 1800 1800 1800 1350 1150 700 700 600 550 550 500 300 2.5 2.0 1.87 1.87 1.25 1.25 1.87
600 400 3.75 3 5 3.12 3.12 2.5 2 5 3.12
500 400 350 350 330 325 350
500 400 375 375 375 375 425
600 500 425 425 425 400 425
600 500 500 500 500 500 550
Initial Diln. of Soln. Malachite green, 5 %
pH
3 4 5a 6" 7s 8" a.6
Mandelic acid, 8 %
3 4 5 6 7 8
Survivps 5 and 10
Min.
.S. a w e u s
E . coli 800 800 750 650
5000 5000 4700 4500 3100 3000 6000
700 700 650 550 500 500 950
6000 (JOUO 3800 ,5500 3750 3600 7000
50 12.5
50 12.5
12.5 12.5 12.5 100
600
600 1150
53
hlercuroohrome, 4 % Mercurophen, 0 . 2 %
b b
100 1500
500 1500
125 2000
600 2000
Methylene blue, 570
3 4 5 6 7
SO 80 80 80 80
...
... ... ... ... ...
20 20 20 20 20 20
b
Pepsodent antiseptic, 80 %
80
...
3 4
7.5 7.0 6.5 5.62 5.62 5.62 7.75
10.0 5.0 2.5 2.5 2.5 2.5 2.5
10.0 7.5 8.25 7.5 7.5 7.5 9.5
7.5 4.37 4.37 4.37 4.37 4.37
... ... ...
20 10 10
10 10 10 10 10 10 10
30 20 20 10 10 10 20
3000 2000 1600 1500 1100 950 2600
4000 2400 2000 1750 2000 3000 3000
5"
3 4 5
3 4 50 6'3 70 8a a,b
...
Zonite, 50%
...
...
1%
9.6
7 8
b a
1250 1500 2250 2250
Did Did Did Did Did Did Did 9.6
6
1500
1760
b
3 4 5
3000 2000
800 650
b b
a,*
Sulphonmerthiolate.
10
2000 1500 1200 900
3 4 5a 6" 7a 5=
3 4 5' 64 7" 84
... ... ...
.. .
%b
Zinc sulfate, 3 0 . 8 %
25
80
6
Sodium nitrite, 3 8 , 8%
...
50
100 100
b
a,*
Potassium permanganate, 2%
... ... ...
8
60 7" 8"
Potassium dichromate, 10%
.., .. . .., ...
100 100 100 100 100 100 100
b
malachite green, mandelic acid, Pepsodent antiseptic, and potassium permanganate, is definitely enhanced by an increase in the hydrogen-ion concentration of the solution, which seems to indicate that the hydrogen ion effect may be independent of the molecular structure of the antiseptic. Mercurochrome, Mercurophen, and the zinc sulfate solutions were tested only as the unadjusted solutions. Negative results were obtained for sodium nitrite, in the concentrations tested. These results check, in general, with the postulates previously reported by Degering and collaborators and by other workers.
Lowest Diln. That
Highest Diln T h a t Kills in 10 Min S. aureus E . coli
100 100 2j 12.5 12.5 12.6 100
7 8
of the following initial concentrations: Amphyl, 2 per cent; Chlorazene, 2 ; gentian violet, 4.93; Listerine, 80; Lysol, 2 ; malachite green, 5 ; mandelic acid, 8; Mercurochrome, 4; Mercurophen, 0.2; methylene blue, 5; Pepsodent antiseptic, 80; potassium dichromate, 10; potassium permanganate, 2; sodium nitrite, 38.8; zinc sulfate, 30.8; Zonite, 50; and Sulphonmerthiolate, 1. Eighty milliliters of each of the test solutions were placed in a Berzelius beaker into which the electrodes were inserted. The pH of the solutions was then adjusted to the desired point by adding 0.1 N sodium hydroxide or 0.1 N hydrochloric acid dropwise, efficient mixing being insured by the use of a mechanical stirrer. (In adjusting solutions of the lower pH values, more concentrated hydrochloric acid was used.) After the pH had been adjusted satisfactorily, the solution was trans-
997
9.6
not not not not not not not
in in in in in in in
15.0
10 min. 10 min.
min. min. min. min. 10 min. 10 10 10 10
6.4 6.4 6.4
12.8 12.8 12.8
9.6 9.6 9.6
2
2 R 14 20 20 14 39
4 8 20 25 25 14
...
4 9 12 12 9 27
12 17 17 9 65
400 400 400 400 800 800 800
400 400 400 200 200 400 400
Average of two series of determinations.
kill kill kill kill kill kill kill
20
4
b
800 800 800 800 1000 1000 1000
87.5
800 800 800 400 400 800 800
Unadjusted.
ferred to a 100-ml. volumetric flask; the beaker, electrodes, and stirrer were rinsed well uTith water of the same pH as that of the solution, and the rinsings were added to the volumetric flask. The flask was then filled to the mark with water of the proper pH which had been adjusted with dilute sodium hydroxide and hydrochloric acid. The solutions were then thoroughly shaken and the pH was rechecked with the glass electrode, a drop or two of acid or alkali being added if necessary. The effect of the small concentrations of sodium and chloride ions introduced in adjusting the pH of these solutions has been shown to be negligible by the work of Goshorn, Degering, and Tetrault (2) and also by the work of Lundy (S), who found no effect when salt concentrations in phenol ranged from 2 to 10 per cent.
998
INDUSTRIAL AND ENGINEERING CHEMISTRY
The solutions marked “unadjusted” in Table I were made up with tap water to the desired concentrations. I n the bactericidal tests, dilutions were also made with t a p water in order to approximate actual conditions of use.
Bactericidal Tests The technique used in carrying out the bactericidal tests was essentially that described by the United States Deparb ment of Agriculture (6). Eschericia coli and Staphylococcus aureus were used as test organisms. The sample solutions were made up to a given dilution with water of the same p H which had been adjusted with dilute sodium hydroxide and hydrochloric acid. The culture was adjusted to the pH of each test before use. I n testing mercurials, the retransferculture modification (6) was used. Controls of inoculated nutrient broth were run for each pH value tested. The results of these tests of standard pharmaceutical preparations are shown in Table I. The significant dilution figures indicate, respectively, the highest dilution of the compound that kills in 10 minutes but not in 5 at 20” C. and the lowest dilution that does not kill at either 5 or 10 minutes at 20” C. A consideration of the data presented in Table I reveals a general trend toward a definite increase in bactericidal effectiveness with an increase in the hydrogen-ion concentration of the medium. These results are in direct accord with the data obtained from similar studies of the phenylalkanoic acids (2) and of other commercial antiseptics (1, 5 ) . These studies also indicate that the hydrogen-ion effect may be independent of the molecular structure of the compounds. I n this work mercury derivatives, phenolic compounds, dyes, halogen compounds, and inorganic oxidking agents have been shown to exhibit similar increases in bactericidal action with increased acidity. Mercurophen and Mercurochrome could not be adjusted to the desired pH values on account of their incompatability with acids and alkalies, and hence these compounds were tested only as unadjusted. The pH effect on Amphyl is not clearly indicated by the results presented here. It seems t o show a maximum effectiveness a t a pH of about 7.
VOL. 32, NO. 7
An aqueous solution of mandelic acid was effective only in the concentration used a t the lower pH values. Sodium nitrite gave negative results in the concentrations tested. The behavior of potassium dichromate as compared with potassium permanganate is in direct agreement with the results of Newton and Edwards (4).
Summary The data in Table I indicate that the bactericidal action of Chlorazene, gentian violet, Listerine, Lysol, malachite green, mandelic acid, Pepsodent antiseptic, and potassium permanganate is enhanced by an increase in the hydrogen-ion concentration of the medium. This is in direct agreement with the results previously obtained with the phenylallranoic acids ( 2 ) and with other types of commercial antiseptics (1, 6). These data also add further confirmation to the validity of the hydrogen-ion effect postulated by Degering and co-workers ( 2 ) which appears to be effective for some organic mercury derivatives, phenolic compounds, some types of dyes, halogen compounds, inorganic oxidizing agents, benzoic acid, the alkanoic acids, other closely related compounds, and some inorganic salts. Amphyl seems to show its maximum bacteriostatic and bactericidal effectiveness a t a pH of about 7, and Sulphonmerthiolate is most suitable in alkaline media. Mercurochrome, Mercurophen, and zinc sulfate were tested only as unadjusted solutions, Acknowledgment This project was sponsored by the Mallinckrodt Chemical Works. Literature Cited (1) Bittenbender, W. A,, Degering, E. F., and Tetrault, P. A., IND.ENQ.CHEM., 31, 742 (1939). (2) Goshorn, R. H., Degering, E. F., and Tetrault, P. A., Ibid., 30, 646 (1938). (3) Lundy, W.H., J. Bact.,35,633 (1938). (4) Newton, W., and Edwards, H. I., Sci.Agr., 12,564 (1932). ( 5 ) Stern and Stern, J. Bact.,19, 133 (1930). (6) U. S. Dept. Agr., Circ. 198 (1931).
Nomographs for Correcting Volumes of Perfect Gases JACK G. ROOF, Oregon State College, CorvdIis, Ore.
I
N THE quantitative volumetric analysis of gases it is not
necessary that each gaseous volume be referred to the usual standard conditions of 0” C . and 760 mm. pressure. However, the successive volumes must be referred to the same conditions of temperature and pressure-conveniently, some arbitrary standard most prevalent in the particular laboratory. I n certain systems of gas analysis (e. g., the micromethod of Blacet and Leighton, S ) , the gas is always dry, so that the perfect gas equation can be used. Tables and graphs could be calculated showing the corrected volume for any temperature and pressure. Greater accuracy can be obtained if use is made of a set of corrections to be added to the observed volume to obtain the “corrected” volume. A quite complete chart was worked out by Barr (2).
Use of this particular nomograph involves making two successive settings of a straightedge and drawing one line parallel to another. Also the corrections scale is small, but a greater disadvantage is that, to use it, one would have to copy the nomograph as i t is or plot anew the markings on the axes if it is to be enlarged for greater accuracy in reading. I n this laboratory we have developed a pair of simple nomographs for volume corrections due to variations from our “standard conditions” of 22” C. and 760 mm. Each chart can be constructed in a few minutes on readily obtained graph paper, and the relative location of the axes requires only a single calculation of one correction for any convenient volume and pressure (or volume and temperature). It is readily shown mathematically that the construction
