INDUSTRIAL A N D ENGINEERING CHEMISTRY
1382 W =
p X 1.0015 X M 273
+t
which, in cases where extreme accuracy is not essential, may be written
'
w=-273 + t pounds per 1000 cu. ft. Table I11 gives the weights of the compounds that will vaporize into chambers of 1000 liters and 1000 cubic feet capacities. The formula applies to all pure chemical compounds.
Vol. 20, No. 12
Absorption of the fumigant by any materials within the chamber or adsorption by the walls of the chamber has not been considered. This must, of course, be kept in mind during fumigating and allowance made for this loss. The amount of fumigant absorbed will depend upon the nature as well as the amount of material within the chamber and upon the temperature, although this factor may in most cases be disregarded. It cannot be determined beforehand with any degree of accuracy.
Vapor Pressures of Fumigants 11-Methyl, Ethyl, n-Propyl, Isopropyl, n-Butyl, Secondary Butyl, and Isobutyl Formates1 0.A. Nelson INSECTICIDE DIVISION. BUREAU OF CHEMISTRY AND SOILS. WASHINGTON, D. C.
HE experiments conducted by Cotton and Roark
T
on the toxicity of a number of alkyl formates against different kinds of insects indicated a decided insecticidal action of all the compounds tested.2 It was found, for example, that the lethal dose in the vapor phase for methyl, 1 Presented as a part of the Insecticide Symposium before the Division of Agricultural and Food Chemistry a t the 75th Meeting of the American Chemical Society, St. Louis, Mo., April 16 t o 19, 1928. 2 IND.ENG. C H E M . , 20, 380 (1928).
secondary butyl, isobutyl, and allyl formates against rice weevils in a flask half filled with wheat ranged from 35 to 39 milligrams per liter. The high insecticidal potency of these formates, in addition to their reasonable cost, their safety in handling, and the ease with which they can be made practically noninflammable, makes these compounds appear promising as practical fumigants. It is therefore desirable to determine some of their physical constants. The results of vapor pressure determinations are reported here.
Table I-Observed Vapor Pressures of Methyl, Ethyl, n-Propyl, Isopropyl, n-Butyl, Secondary Butyl, and Isobutyl Formates
ETHYL
METHYL FoR M A TE
Temp.
C.
Temp.
Press.
ISOPROPYL
%-PROPYL
FORMATE
FORMATE
Press.
Temp.
Press.
c.
Mm.
C.
Mm.
525.8 624.5 647.2 654.7 663.0 678.1 711.4 722.9 760.8 767.7
25.4 28.9 33.6 35.5 38.2 40.1 42.9 44.2 47.8 50.9 52.2 53.4 54.2 55.4
259.0 300.8 362.0 389.9 439.2 462.1 531.9 540.3 616.5 689.2 721.1 753.0 772.4 818.6
Temp.
c.
Mm.
26.2 30.8 33.2 40.5 46.2 50.0 58.4 63.7 63.9 70.5 71.0 73.5 75.1 78.9 80.5 82.3
88.2 109.1 134.5 170.4 216.5 252.9 348.6 421.8 430 7 540.3 554.8 600.0 648.9 724,O 759.4 798.8
25,l 29.8 35.0 41.2 48.0 48.2 63.7 57.8 63.9 68.6 70.3 71.7 72.1
Press.
Temp.
Press.
c.
Mm. 136.5 169.4 217.2 281.5 368.0 372.1 458.3 530.0 658.0 768.1 812.9 853.8 873.3
SECONDARY BUTYL FORMATE
n-BuTuL FORMATE
FORMATE
Temp.
Mm.
29.1 34.3 41.5 49.0 57.8 65.3 71.1 75.5 80.5 85.7 93.2 100.4 102.0 106.0 106.7 109.3 109.8 111.3 112.4
C.
Mm.
29.7 35.7 41.7 46.5 52.9 58.1 61.8 65.8 71.3 76.8 83.5 88.5 95.0 97.0 98.5 99.8
58.8 81.2 108.0 139.9 172.8 212.2 246.5 309,8 340.6 427.3 534.4 635.5 798.4 857,7 907.5 945.0
a
34.8 45.8 65.7 93.1 134.9 184.2 229.0 266.8 323.1 397.8 505.0 641.9 683.5 770.9 787.3 828.1 872.4 903.3 941.1
Press.
ISOBUTYL
FORMATE
Temp.
Press.
c.
MVk. 59.3 79.2 103.1 136.5 195.2 243.4 301.7 393.3 483.3 611.7 708.8 735.2 767.6 792.9 824.2
31.7 38.7 43.7 50.3 58.6 63.6 69.9 77.5 82.8 90.2 95.0 96.6 98.2 99.2 100.5
Table 11-Observed and Calculated Vapor Pressures of Formates TEMPERATURE
c. 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 105 110
ETHYL FORMATE
%-PROPYX. FORMATE
Calcd.
Ohsd.
Calcd.
Mm.
Mm.
Mm.
Mm.
206.5 255.0 312.0 382.0 462.3 558.0 668.0 791.0
204.8 253.6 311.8 380.9 462.3 557.6 668.8 797.6
64.5 85.0 107.0 134.0 166.2 203.5 248.0 303.5 269.5 343.5 531.7 634.5 747.5 877.6
67.1 85.2 107.3 134.0 166.3 205.0 251.0 305.4 369.5 343.3 531.7 633.0 749.7 883.9
Obsd.
ISOPROPYL FORMATE
%-BUTYL
FORMATE
SECONDARY BUTYL FORMATE
ISOEIJTYL
FORMATE
Calcd.
Obsd.
Calcd.
Obsd.
Calcd.
Obsd.
Calcd.
Mm.
Mm.
Mm.
Mm.
Mm.
Mm.
Mm.
Mm.
112.0 138.5 174.2 216.0 267.0 325.1 396.0 478.0 570.8 678.5 803.0
113.0 141.6 176.1 217.4 266.7 325.1 393.7 474.2 568.0 676.5 801.7
22.6 29.4 37.8 48.3 61.3 78.0 98.0 120.0 147.6 186.0 219.0 265.5 319.5 383.0 457.0 543.0 639.5 749.0 878.0
22.6 29.4 37.8 48.3 61.2 77.0 96.2 119.3 147.0 186.1 219.3 265.5 319.7 383.1 456.7 541.8 639.8 752.3 880.8
36.0 48.1 62.5 79.6 102.0 126.0 155.2 187.0 228.2 276.8 333.9 400.5 477.2 567.0 671.5 797.0 938.0
38.4 49.2 62.6 79.0 98.8 123.2 152.6 187.0 228.2 276.8 333.9 400.6 478.2 567.9 671.5 790.1 925.7
33.0 43.5 56.0 71.0 88.6 111.0 136.5 168.0 204.0 246.8 300.0 362.0 431.0 511.0 604.0 700.0 806.0
35.1 44.9 56.9 71.6 89.5 111.0 136.5 167.5 200.0 246.7 296.8 355.2 423.1 501.3 591.3 696.0 811.0
Obsd.
December, 1928
INDUSTRIAL AND ENGINEERING CHEiVI8TRY
1383
Procedure
The method of determining these constants was the same as that for determining the v a p o r p r e s s u r e s of monochloroacetates described on page 1380 of this issue. The temperature of the bath surrounding the isotensicope was ascertained by means of Anschutz thermometers standa r d i z e d a t the Bureau of S t a n d a r d s . The pressures were read directly from the m a n o m e t e r , and were recorded after corrections had been made for expansion of mercury due to change in temperature. The samples of n-propyl, isopropyl, n-butyl, secondary butyl, and isobutyl formates used in these determinations were prepared by the author, and the others were carefully purified from commercial samples by repeated fractional distillations. Most of these formates, particularly those of the higher alcohols, are hygroscopic, and for this reason it is essential that in drying with calcium chloride sufficient time be given the dehydrating agent to remove the last traces of water. Where the boiling points a t 760 mm. differed considerably from those reported in the literature, samples were distilled under reduced pressures, thus diminishing appreciably the possibility of c o n s t a n t boiling mixtures. The crit e r i o n f o r purity was the middle portion of a fraction whose boiling point was constant to within 0.10-0.20" C. Results
Ea
z
ii
P -
The observed vapor pressures are given in Table I. The figures in Table I were plotted on sheets of millimeter coordinate 'paper, 16 by 21 inches, and curves were drawn through the points thus obtained. I n Tables I1 and I11 the pressures a t regular intervals of temperatures are recorded. These figures were taken from the smoothed curves. Equations for these vapor pressure curves were devel-
1.
Tmperarure
"C
o ,
Figure 1-Vapor Pressure Curves Plotted against Temperature
oped, Ramsay-Young's boiling point law being used as the basis for calculations. These equations do not fit the observed values absolutely in every case, but it was thought advisable to present the simplified forms, in preference to more complicated equations. A. W. Porter3 has briefly discussed the connection between the Ramsay-Young boiling point law and Rankine's and Bertrand's vapor pressure formulas. Table 111-Vapor
Pressures of Methyl Formates Observed and Calculated PRESSURE
TEMPERATURE
Calcd.
Obsd.
c. 20 22 24 26 28 30 32
Mm.
Mm.
515.8 553.4 593.2 635.2 679.7 724.8 776.0
515.8 553.4 593.2 635.2 679.6 724.8 776.0
The equations developed for the compounds considered in this paper are:
P
METHYL FORMATE-bglo
ETHYL FORDIATE-IoglO
= 7.2203
P = 7.8457
P
IZ-PROPYL FORMATE-bglO
IZ-BUTYL FORMATE-loglo
P
* Phil. Mag., 13,724 (1907).
-1621.6 T(abs.)
-1806.5
= 8.1232
P
T(abs.)
= 7.8909
SECONDARY BUTYLFORMATE-IoglO ISOBUTYL FORMATE-hg1O
T(abs.)
= 7.9925
P
ISOPROPYL FORMATE-hg10
-1320.8
P
-1710.5 T(abs.) 1983.3 T(abs.)
-= 8.0306
= 7.9060
-1888.9
-1863.7 T(abs.)
T(abs.)
INDUSTRIAL AND ENGINEERING CHEMISTRY
1384
Tables 11 and 111 show the agreement between the observed and calculated pressures a t 5" C. intervals. Figure 1 shows the vapor pressures in millimeters plotted against temperature, and Figure 2 shows the log,, of the vapor pressure plotted against the reciprocal of the absolute temperature. The first paper on vapor pressures of fumigants (page 1380 of this issue) gives the following equations for calculating the weights of fumigant in grams per liter and pounds per 1000 cubic feet required to saturate these volumes a t atmospheric pressure: @VM @ X M 62.35Tand = 273 t = weight in grams = pressure in millimeters of mercury = volume in liters = molecular weight of fumigant = weight in pounds per 1000 cu. ft. = absolute temperature, oro(273 t ) , t being the observed temperature in C. x=-
where x:
p
V M W T
+
+
These equations are valid for all pure chemical compounds whose molecular weights in the vapor phase are known. Table IV shows the weights of the fumigants required to saturate the atmosphere in a 1000-liter and a 1000-cubic foot chamber. Previous determination of vapor pressures of methyl, ethyl, and propyl formates by Young4 give results a trifle lower than the ones here recorded. This slight difference in results may possibly be due to the methods used in their determina4
Sci. Proc. Roy. Dublin Sac., 11, 374 (1910).
Vol. 20, No. 12
t i o n , to purity of c o m p o u n d s or to temperature measurements. Boiling points of these compounds, as recorded in the International Critical Tables by Beilstein and Van Nostrand and in other books of reference, show variations considerably beyond what the e x p e r i m e n t a l errors of such determinations should be. I n most cases t h e published boiling points are a trifle higher t h a n those observed f r o m t h e Figure 2-Logro P Plotted against l/T(Abs.) vapor pressure curves here shown, indicating a higher degree of purity of the samples used in these experiments. The boiling points of the compounds considered herein were found to be: methyl formate, 31.6" C.; ethyl formate, 53.8' C.; 71propyl formate, 80.4" C.; isopropyl formate, 68.4" C.; nbutyl formate, 105.6" C.; secondary butyl formate, 93.6" C.; isobutyl formate, 99.9" C.
Simple Accelerated Exposure Test for Varnishes and Lacquers' Hugo V. Hansen STANDARD VARNISHWORKS,ELMPARK, N. Y.
URING some research on lacquers conducted in these
D
laboratories the following accelerated exposure test was worked out. The principles are the fundamental ones developed in the work of Nelson and Schmutz,2Gardner,3 Walker and Hickson,4 and 0thers.j The apparatus herein described has distinct limitations when compared with the more complete outfits used by those investigators. It has a small capacity and small test panels must be used. However, during practically a year's operation it has given results agreeing very satisfactorily with outdoor exposure on specific types of material such as unpigmented lacquers and varnishes and quick-baking enamels. It also has the advantages of being comparatively inexpensive and simple to set up and operate, the first cost being little more than that of a single ultra-violet lamp. It was therefore thought that the method might be of interest to users of varnishes and lacquers who desire a simple test which will give indication more rapidly than outdoor exposure. Test panels 2.5 X 13 cm. are exposed in a shallow pan under a source of ultra-violet light. By means of an intermittent siphoning apparatus, the panels are periodically 1 Received
June 12, 1928.
* IND. END.CREM., 18, 1222 (1926). * "Physical and Chemical Examination of Paints, Varnishes, Lacquers, and Colors,'' p. 309, Institute of Paint and Varnish Research, 1927. 4 IND. ENG.CKEM.,20, 59 (1928). 6 Muckenfuss, I b i d . , 6, 535 (1913).
covered with water and allowed to dry out. The material is thus subjected to wet and dry cycles in conjunction with light, giving rise to more or less rapid failures which can be correlated with the behavior of the material on weathering. No conclusions should be drawn from this type of test until the apparatus has been calibrated against standard materials, the durability of which toward outdoor exposure is well known. All tests on unknown materials should be accompanied by such a standard sample. Each distinct type of material should have its own standard; for example, finishing lacquers are tested against a standard finishing lacquer, furniture lacquers against a furniture lacquer, etc. Apparatus
A 4-liter bottle, A , is filled with distilled water, inverted, and supported over a dish, B , so as to form a constant-level reservoir. The water is led by the siphon C to the funnel D, which is provided with the stopcock E. This stopcock can be replaced by a piece of rubber tubing and a screw pinchcock if desired. The water stands a t the level W in the funnel, and by regulating the stopcock it is delivered at any desired rate to the measuring bottle H . The siphon C has a piece of muslin, f, tied over its inlet, and the funnel contains a fluted filter paper. These arrangements are necessary to hold back traces of suspended matter and atmospheric dust which find their way into the distilled
