INDUSTRIAL A N D ENGINEERING CHEMISTRY
674
Vol. 21. No. 7
The Vapor Pressures of Glycerol Trinitrate and Certain Glycol Dinitrates' Willard deC. Crater EXPERIMENTAL
STATION, HERCULES POWDER CO., KENVIL,N. J.
D
URING a study of the relative volatilities of glycerol trinitrate and certain of the glycol dinitrates, a search of the literature showed that but little work has been reported on the vapor pressures of these compounds. Marshall (S),* by a gas saturation method, found the vapor pressure of nitroglycerin a t 70" C. to be 0.0051 cm., or nearly the same as mercury a t that temperature, and it was assumed to have the same vapor pressure as mercury a t lower temperatures. Later this figure was questioned by Chiaraviglio andcorbino (8)because they believed that (1)globules of nitroglycerin may have been carried over mechanically, and (2) the air was not completely saturated. They attempted to measure the vapor pressure by an entirely different method, which depended on the fact that in high vacuum the rate of cooling of a hot body is a function of the concentration of the gaseous molecules present. From their experiments they concluded that the vapor pressure of glycerol trinitrate was less than 0.0001 mm. a t ordinary temperatures, but their work was later shown to be unsound by Marshall and Peace (4), who determined the vapor pressure of nitroglycerin over a wide temperature range by passing air through ground cordite. They assumed the vapor pressure of nitroglycerin in a gel to be the same as when it is in the free liquid state. Rinkenbach (6) reported the vapor pressure of ethylene glycol dinitrate a t 0" and 22' C., and stated that its pressure was about 150 times greater than that of nitroglycerin. Rinkenbach (7) also reported the vapor pressure of diethylene glycol dinitrate a t 22' C. Because of this unsatisfactory state of knowledge relative to the vapor pressures of the nitric esters of the glycols and glycerol, the work herein reported was undertaken. Samples of the following esters were prepared in a high state of purity and vapor pressures determined over the temperature range from 15" to 55' C.: glycerol trinitrate, ethylene glycol dinitrate, diethylene glycol dinitrate, propylene glycol dinitrate, and trimethylene glycol dinitrate. Table I-Analysis GLYCEROL (c. P . ) Origin Sp. gr. 15.6°/15.60 C. Silver test
Eimer & Amend
1,26067~
dilute sodium carbonate solution. They were then given three fresh-water washes and a second dilute sodium carbonate wash followed by six more fresh-water washes. These repeated washings insured the neutrality of the product and the removal of any lower nitrates which might have been formed during nitration. Following the final wash the esters were dried for 2 t o 3 days in a vacuum desiccator over anhydrous calcium chloride, anhydrous calcium chloride was then introduced directly into the compounds and they were placed in an evacuated desiccator for several days more. The dried samples were then filtered and subjected to specific gravity and nitrogen determinations. Gravity tests were made by pycnometer, while nitrogen contents were determined by the du Pont nitrometer. Table I1 shows the results. Table 11-Nitroeen
C o n t e n t a n d Snecific Gravitv of Esters
FORMULA
::fgl %
Glycerol trinitrate Ethylene glycol dinitrate Diethylene glycol dinitrate Propylene glycol dinitrate Trimethylene glycol dinitrate
Found
(i
b
% 1.599
1.5978
18.42
18.31
1.4962
1.4955
14.29
14.24
1,3908
1.3901
16.87
16.85
1.368
1.3939
16.87
16.81
1.393
1.4708
a
From Lawrie, "Glycerol and the Glycols,'' p. 340 (1928).
Method
The method used for vapor pressure determinations was essentially the same as the dynamic method employed by Baxter, Hickey, and Holmes (I), in the determination of the vapor pressure of iodine. Figure 1 is a detailed sketch of the apparatus used. of Raw Materials PROPYLENE GLYCOLTRIMETHYLENE GLYCOL
1,11907
Globe Soap Company
1,0436
1.0634 Black colloidal Ag Per cent 0.06 0.006 Trace 0 : i 'CC.
1.4384
After drying. At 20° C. in diffused daylight.
Materials
The raw materials used to make the corresponding nitric esters gave on analysis the data shown in Table I, the analyses being made by the international standard specifications. The materials were nitrated with a mixed acid having 53.62 per cent total sulfuric acid and 46.67 per cent total nitric acid. Each of the nitrated materials was given a fresh-water prewash, followed by a neutralizing wash with 1
Found
18.506 18.42
Slight reddish brown, no ppt, No color, no ppt, Slight darkening, no ppt. Faint reddish brown, no ppt. Per cent Per cent Per cent Per cent 0.03 0.033 0.016 0.012 Char 0,014 None 0,002 0.006 Ash 0,0007 Chloride None None 0.0006 Ariditv. 50 cc. took 1 N NaOH 0 . 0 6 CC. 0.07 cc. 0,0033 cc. 0.13 cc. 8 0 cc. took 1 N HCI i.43i4 1,4469 i.430i idexb . .. .
. .
15O/15O C.
Actual'"
(20" C.)
Carbide & Carbon Chemicals Corporation
~~
SPECIFIC GRAVITY
(200 C.) C3H6(N03)2
ETHYLENE GLYCOLDIETHYLENE GLYCOL
1.11726
I
NITROGEN MATERIAL
Received February 26, 1929. numbers in parenthesis refer to literature cited at end of article.
* Italic
The air was purified and dried by passing it through granular, anhydrous calcium chloride, then over solid sodium hydroxide, and finally through more anhydrous calcium chloride contained in a modified U-tube set in the constanttemperature bath. The U-tube also served to bring the air to the temperature of the sample under test. I n order to prevent any dust being carried over into the first Geissler bulb, glass wool was placed in the outlet of the TT-tube. The purified and conditioned air was then drawn through the sample contained in the Geissler bulbs a t such a rate as to insure complete saturation in the first bulb. The rate of
INDVSTRIAL A N D EXGINEERING CHEMISTRY
July, 1929
Table 111-Vapor
I
TEMPERATURE
GLYCERO,, TRINITRATs
1 Train 1
~~~~
C. 15 25 35 45 55
Train 2 Average
1
Pressures of Glycerol Trinitrate a n d Glycol D i n i t r a t e s
ETHYLENEGLYCOL DI-
I Train 1
675
NITRATE
Train 2 Average
I
DIETHYLENEGLYCOL DI-
1 Train 1
NITRATE
Train 2 Average
1
PROPYLENEGLYCOL DI-
1 Train 1
NITRATE
Train 2 Average
I
TRIMETHYLEKEGLYCOL DIKITRATE~
1 Train 1
Train 2 Average
~~
Mm. 0.00129 0.00177 0.00445 0,01338 0.03638
.Mm. 0,00131 0.00177 0.00473 0,01249 0.03535
Mm. 0.00130 0.00177 0.00459 0.01294 0.03587
Mm. 0.02469 0.07058 0.21810 0.44250 0.95880
Mm. 0.02291 0.07060 0.21960 0.44250 0.96500
Mm. 0.02330 0.07059 0.21890 0.44250 0.96190
Mm. 0.00201 0.00592 0.01480 0.02862 0.08658
air flow was controlled by a capillary tube and screw clamp on the outlet arm of the siphon. All joints and connections, except those under water, were sealed with paraffin. The temperature of the bath was regulated t o *0.1" C. in the usual way by means of immersion heaters controlled by a mercury regulator and relay. Cooling was accomplished by passing cold water through a coil in the bath which was constantly agitated by air.
Mm. 0.00247 0.00594 0.01478 0.02819 0.08690
Mm. 0.00224 0.00593 0.01479 0.02840 0.08674
Mm. 0.03766 0.09886 0.25318 0,49370 0,99480
Mm. 0.03958 0.09803 0.25326 0.49732 0.99530
Mm. 0.03862 0.09844 0.25322 0.49551 0.99505
Mm. 0.01187 0.03458 0.06137 0.14667 0.32079
Mm. 0.01137 0.03101 0.06289 0.14651 0.32367
values for all samples had been obtained a t 15", 25", 35", 45O, and 55" C.
CALCULATIOK OF REsuLTs-The dynamic method was first used by Regnault (5) in 1845, and is based upon the principle that when an inactive gas is saturated with vapor the following relation holds: Total volume - total pressure pressure of vapor Volume of vapor
The vapor pressure of the sample then
-
T *fer
-Level
A rprrator
fifure 1
Mm. 0.01162 0.03980 0.06213 0.14659 0.32223
-.
volume of sample as vapor .Y volume of sample as vapor volume of air barometric pressure
+
3
which may be expressed as follows: VZ HO Vapor pressure = VO where V , = volume of volatilized substance, x Vo = volume of volatilized substance x, plus volume of gas (air) at 0' C. and 760 mm. Ho = barometric pressure at 0' C.
Assuming that the vapor of 1 mol of the sample under test, x , occupies 22.4 liters, then Experimental
I n order to standardize the apparatus, vapor pressure tests were made on distilled water which had been boiled t o remove carbon dioxide. The tests were made a t 15" and 25" C., and the pressures found to be 12.699 and 23.903 mm., respectively, as compared to Smithsonian Institution Table (8) figures of 12.790 and 23.763 for the same temperatures. In making tests the Geissler absorption bulbs were filled about half full of the sample and weighed carefully t o the fourth decimal place. Four Geissler bulbs were used-that is, two two-bulb trains-to give check results. The bulbs were connected and placed in the constant-temperature bath, as shown in Figure 1, with all joints carefully sealed. The bath was then filled and brought t o the desired temperature and the regulator adjusted. I n the case of nitroglycerin it was necessary to pass from 18 to 25 liters of air, depending upon the temperature, while for the nitroglycols from 10 to 15 liters of air were sufficient. A test having run sufficiently long, as indicated by experience, the Geissler bulbs were removed from the system, carefully dried, and weighed. Careful drying of the bulbs was essential, and was done by first wiping off as much water as possible with a clean, dry cheesecloth and then immersing the bulbs in acetone to remove any remaining moisture. They were again wiped and quickly immersed in ether, removed, and immediately dried with a dry cheesecloth. The bulbs were then weighed and the weights recorded. With the first bulb only showing a loss in weight, there was assurance that the air had been completely saturated before reaching the second. In order to check the method of drying the bulbs, they were placed in a calcium chloride desiccator overnight and reweighed after 16 hours. The tests were repeated until satisfactory vapor pressure
W v, = 22400 M where W = weight of x in grams M = molecular weight of x
The volume of air saturated with the material under test was reduced to standard conditions by&heEfollowingequation:
676
INDUSTRIAL AND ENGINEERIXG CHEMISTRY
vo= v-Ho -760h - m
X-
273
t
+ 273
where V = volume of water run out of aspirator in cubic centimeters HO= barometric reading corrected to 0" C. lz = vapor pressure of water a t t m = reduction in pressure indicated by the manometer t = final temperature of the aspirator
Table I11 gives the results obtained. From these results curves were plotted (Figure 2) which show clearly the relationship of the vapor pressures between the various nitric esters. Also, the logarithms of these values were plotted against temperature and the resultant curves were found to be practically straight lines. Discussion The results obtained in these tests on nitroglycerin are higher than those reported by hfarshall and Peace (4). This is probably due t o the fact that free liquid glycerol trinitrate either has a higher vapor pressure than nitroglycerin in a nitrocellulose gel, or that their air current never became saturated under conditions of their tests. The results reported by hIarshal1 and Peace are given in comparison with the writer's values:
c. 20 30 40 50
MARSHALL A N D PEACE
CRATER
Mm.
Mm.
0.00028 0.00083 0,0024 0,0073
0.0016 0 0033 0.0068 0.0238
Vol. 21, No. 7
The vapor pressure of ethylene glycol dinitrate as reported by Rinkenbach (6) is 0.0072 mm. a t 0" C., and 0.0565 mm. a t 22" C., as against 0.0465 mm., the value from the curve in Figure 2 for this temperature. He also reported the vapor pressure of diethylene glycol dinitrate ( 7 )as 0.0098,0.0079, and 0.0044 mm., average 0.007 mm., of mercury a t 22.4" C. as against 0.0055 mm. taken from Figure 2. The following arrangement of the nitric esters studied is according to their increasing vapor pressures: (1) glycerol trinitrate, (2) diethylene glycol dinitrate, (3) trimethylene glycol dinitrate, (4)ethylene glycol dinitrate, (5) propylene glycol dinitrate. Because of the higher volatilit'y of the latter esters their use is limited in the explosives industry. For instance, they do not lend themselves to making certain types of propellant powders, which require 'high drying temperatures. On the other hand, if proper care is exercised in the manufacture and if the formulas are adjusted t o care for the higher vapor pressure, ethylene glycol dinitrate, for example, is an excellent substitute for nitroglycerin in dynamite. Literature Cited (1) Baxter, Hickey, and Holmes, J . A m . Chem. SOL.,29, 127 (1907). Chiaraviglio and Corbino, Gaze. chim. ital., 43, 390 (1913). Marshall, J . SOL.Chem. Ind., 23, 158 (1904). Marshall and Peace, I b i d . , 109, 298 (1916). Regnault, A n n . chim., 15, 129 (1845). Rinkenbach, 1x1. Esc. CHEX., 18, 1196 (1926). Rinkenbach, I b i d . , 19, 925 (1927). Smithsonian Physical Tables, 6th revised ed.. 3rd reprint, p. 154
(2) (3) (4) (8) (6) (7) (8)
Use of Super-Cel in the Sugar Refining Ind u stry1j2 Arthur Elsenbast, R. D. Elliott, and E. J. Sullivan JOHKS-MANVILLE CORPORATION, 292 MADISON A m . , NEW YORK,X. Y .
T
HE application of diatomaceous silica to sugar refining problems was not brought to a satisfactory state until within the last fifteen years. At that time the Celite Section of the Johns-Manville Corporation, through the availability of a tremendous supply of pure diatomaceous silica, was able t o produce the first standardized filter-aid product, known as Filter-Cel. This product, which has been used for many years as a standard in the sugar industry, has now been supplemented by the addition of two mechanically and chemically processed materials known as Standard Super-Cel and Hyflo Super-Cel. This gives the sugar refiner the choice of three entirely different filter materials to meet the conditions existing in a particular plant and on a particular liquid. The recommended filter aid will vary in different plants, according to the layout and the type of sugar being turned out. It was thought that a general survey and summary of the determined and known characteristics of the different sugar filtrations would be of interest to the entire sugar industry. All of these filtrations have now been carried out over long periods of time, and on a factory scale. The costs are known, and the benefits judged. Tables I, 11, and I11 give, in a general way, a summary of the major filtrations. 1 2
silica.
Received M a y 18, 1929. Super-Cel is t h e trade name of a patented processed diatomaceous
Application of Hyflo Super-Cel to Sugar Liquids The sugar refiner very early recognized that 'a high-quality sugar could not be obtained except from clear, sparkling liquids. A pure, colorless, white sugar could not be boiled except from clear, sparkling sirups. A good grade of plantation white sugar can be boiled from a comparatively highly colored 75 to 85 purity sirup if the sirup is clear. The art of manufacturing filter presses has also received a very marked advance within the last ten years. A combination of improved filter materials and filter presses has now made i t possible to filter economically every different type of sugar sirup produced in the various refining processes. The basis of most clarification systems is t o obtain a precipitate which can either be settled or filtered out of suspension. The Hyflo Super-Cel is a neutral, inert, and ready-made precipitate which acts mechanically t o make filtration possible. In various sugar refining processes it has been found of decided economic advantage to filter the liquors a t various stages, and the reasons for the filtrations specified in the tabulations are outlined in the following discussion. Refinery Cane Sugar from Raw 96" Test Cane Sugar The flow chart shows the general diagrammatic handling of the cane-sugar liquors in a modern bone-black refinery. The two most important liquids that are filtered are the washed sugar liquor, which totals 85 per cent of the total
