INDUSTRIAL AND ENGINEERING CHEMISTRY
March, 1941
The agar disk method of Olson and Hammer (6)for testing the germicidal property of paints was felt to offer a means of determining the actual killing effect under the closest approximation to actual conditions of use. Briefly the method employed was as follows: 1. Small droplets of saline suspensions were deposited upon the surfaces of painted and unpainted wooden panels by means of a capillary pipet, hypodermic needle, or pen point. The droplets were so small that evaporation took place within a few minutes. The concentration of organisms was varied to duplicate different practical conditions. 2. The treated panels were placed in a sterile hood. 3. After various hour intervals, about 10 cc. of properly melted and cooled 2.5 per cent a ar medium were poured over an area of contaminated surface and allowed to solidify. 4. A sterile spatula was used to transfer the agar disk thus formed into a sterile Petri dish so that the disk portion which had been in contact with the surface examined was toward the top of the dish. 5. .Incubation was according t o the character of the test orgamsm.
Results of such tests on a halogenated paint and three control paints in which saline suspensions of Staphylococcus aureus and Escherichia Coli were used are shown in I. The halogenated paint exerted some germicidal action, as based On comparisons with Obtained with the paints. The action, however, was not marked. The halo-
401
genated paint had been air-dried for 75 days, while the control paints had been air-dried for only 20 days. Summarizing the subject of antiseptic and germicida1 paints, it can be stated the halogenated-oil paint may be the best thus far developed, but i t is far from being actually antiseptic or germicidal under all practical conditions of use. While i t is a step forward, further development work will be required before a true antiseptic or germicidal paint is obtained.
Literature Cited (1) Epstein, S. S., F o o d I n d u s t r i e s , 9, 386-7, 419-20 (1937). (2) Ibid., 9, 513, 541-3 (1937). (3) EPstein, 8. 8.9 Am. Brewer, 70,41-63 (1937). (4) Gardner, H.A., “Physical and Chemical Examination of Paints, Varnishes, Lacquers and Colors”, 6th ed., pp. 445-52, Washington, Inst. of Paint and Varnish Research, 1933. ( 5 ) Hart, J. Thoracic Surgery, 6, 45-81 (1936). (6) Olson, H. c., and Hammer, B. w.9 A@. Exp. Sta. Iowa College, Bull. 300 (1933). (7) Portier, P., and Kling, A., Bull. m a d . mdd., 106, 305-9 (1931); Peintures, pigments, vernis, 9, 14-16 (1932). (8) Robb, H., Am. J. Obstetrics, 40, 451 (1909). (9) Troussaint, M., Bull. m a d . mdd., 109, 448-52 (1933). (10) Valentine, E., Proc. SOC.Exptl. Bid. M e d . , 34, 166-70 (1936). (11) Valleb, M. J., Chintie et industrie, 31, numero special, 962-4 (1934). (12) Wetchler, S., Lewis, A., and Battline, F., P a i n t V a r n i s h Production Mgr., 14, 12-18 (1936).
*.,
PR~SENTED before the Division of Paint and Varnish Chemistry at the 100th Meeting of the American Chemical society, Detroit, Mich.
Line Coordinate Chart for Vapor Pressures of Organic Solvents D. S . DAVIS, Wayne University, Detroit, IlIich.
I
N CONNECTION with his study of evaporative index, Gardner [IND.ENG.CHEM.,32, 226 (1940)l presented
vapor pressure-temperature data for eight organic solvents. From the actual coordinates of the plotted points given in a private communication, it is possible to show that the relationship between p , the vapor pressure in mm. of mercury, and t , the centigrade temperature, is given by logp =
A t + 253 +
where A and B are constants specific to the compound. The linearity of log p and l/(t 253) enables construction of the accompanying line coordinate chart which presents the data in a compact and convenient form. The broken line indicates that the vapor pressure of n-butyl acetate is 41 mm. a t 50” C. The nature of the agreement between values read from the chart and the actual data is shown in the table which includes values of A and B for each material.
+
T Compound n-Amyl acetate n-Butyl acetate
Diacetone alcohol Diisoamylene
Diisobutylene Ethylene glycol monoethyl ether Isodecane
Isooctane
~
~ Pressure, ~ , , Mm. Hg Data Chart 56.9 23.9 24.0 106 6 204 200 49.2 43.2 39 7 93.5 274 270 17.8 17.6 66.5 139.3 324 324 58.0 21.6 23 0 110.7 188 188 35.8 72.3 72.0 72.0 303 304 49.9 23.2 23.0 94.0 180 180 59.8 24.5 25.0 120.3 254 258 64.0 31.0 65.1 63.5 243 240
C.
B
1000 A -2.077
8.078
-1.964
8.099
-2.188
8.091
-1.953
7.641
-1.623
7.474
-2.139
8.416
-1.948
7.620
-1.592
7.413
2 4
n-Amyl Acetate n-duty/ Acstafc Di-accfone Akoho/ D i - /soamy/cne
7
/so-octme
I
z
..
ti
