December 1947
INDUSTRIAL AND ENGINEERING CHEMISTRY
has dissolved in the electrolyte. Such values are given in the last column of Table IV and are shown graphically in Figure 5 for comparison Kith other solubility values. Less coating is dissolved while the coating is being formed by the current than when the coated specimen is merely standing in the electrolyte. The presence of aluminum sulfate in the sulfuric,acid has been shown to decrease the solubility of anodically formed alumina. Knowing the method of forination for thick anodic coatings, it is concluded that the high concentration of aluminum sulfate within the pores causes a decrease in the solubility of the coating. It would appear that the electrolyte within t,he pores contains aluminum sulfate,. Many other esperinients of a similar nature viere made; all pointed to the usefulness of the weight of coating method for studying the mechanism of oxide coating formation, investigating n e x electrolytes, and accurately determining the effect of
1607
variables in the anodic oxidation procedure. Further knowledge in this field should be gained by an extension (of these experiments. L I T E R 4 T U R E CITED
(1) (2) (3) (4)
Anderson. Scott, J . A p p l i e d Phys., 15,477-80 (1944). Arlt, H . G., Proc. A m . Soc. Testing.Ilateriai8, 40, 9 6 7 4 7 (1940). Compron, K. G., and Mendizza, A., Ibid., 40, 978-87 (1940). Edwards, J. D., .IlortlhZy Rev. -4m. Electroplater’s Soc., 26, 513-32
(1939). ( 5 ) Edwards, J. D., Proc. Am. Soc. Testing Materials, 40, 959-66 (1940). (6) Edrards, J. D., and Iieller, Fred, Truns. EZectrochem. SOC.,79, 135-42 (1911). (7) Keller, Fred, Proc. A m . Soc. Testing Mate&cls, 40, 948-58 (1940). (5) Tarr, 0 . F., Darrin, M a r c , and Tubbs, L. G., IKD.ENG.CHEM.. 33, 1575-80 (1941). (9) ’Kork, H. K. (to Alurninuni Colors, Inc.), U. S. Patent 1,985,682 (July 10, 1934). RECEIVED August 1 9 , 1 9 4 6 .
Flammability of the Higher Boiling Liquids and Their Mists M. V. SULLIVAN1, J. K. WOLFE‘, AND W. A. ZISIIIAY llhval Research Laboratory, Washington, D . C .
T h i s investigation concerns the flammability of the higher boiling organic fluids and petroleum oils. The explosive hazard due to oil mists in the atmosphere was of especial interest. A new apparatus was devised for the measurement of the flammability of oil mists and was applied to numerous fluids. These fluids were also exposed to incendiary fire tests and the results were recorded by color photography. Measurements and comparisons were made of the flash and fire points and the spontaneous ignition temperatures of the same fluids. Fluids investigated were: hydrocarbons, chlorinated hydrocarbons and ethers, castor oil-base hydraulic fluids, aliphatic diesters, organic
phosphates and carbonates, silicones, polyalkylene glycols, and some of the glycols, glycol ethers, and their aqueaus solutions. The glqcols, their aqueous solutions, the higher po14alkjlene glycols, properly stripped silicones, several carbonates, and the highly chlorinated hydrocarboriswere the most resistant to oil mist explosions. Of the phosphate compounds studied, those ha1 ing the highest ratio of the number of phosphorus atoms to the number of carbon atoms were the most resistant to such fire hazards. I t was found that the spontaneous ignition temperature of the various types of silicones differed enough to permit their qualitative analysis.
A
point test (1, 9.3.T.11. >\lethod D56-36) or the Pensky-Martens closed cup flash point test (1, A.3.T.M. hfethod D93-42) has been much used, particularly on liquids in the gasoline, kerosene, and light fuel oil ranges of volatilit,ies. The usefulness of the Cleveland open cup flash point test (1, A.S.T.M. Method D92-45) for predicting the fire hazard of relatively nonvolatile petroleum fluids is not well established. This limitation of the flash point test for the evaluation of fire hazard has been recognized by the .1.S.T.X Committee on Petroleum Products and Lubricants ( 2 ) . FIREPOIST. The Cleveland open cup fire point (A.S.T.M. Method D92-45) is defined its the temperature at which “the liquid ignites in the presence of a specified source of ignition and continues to burn for at least 5 seconds.” With many lowboiling petroleum or other organic liquids the fire points are only a ferv d6,grees above the flash points. Higher boiling, less volatile oils and fluids exhibit a wider difference betwetm the flash and fire points. SPOST.&SEOUS IOSITIOX TEMPERbTURE. Methods of determination and the significance of spontaneous ignition temperatures (also referred to as the “autogenous ignition temperature) (2, A.S.T.11. b k t h o d D286-30) have been reviewed by Helmore ( 1 2 ) . The spontaneous ignition temperatures given here were
LTHOCGH the flammability of lubricating and hydraulic
oils has long constituted a hazard, their use has been made a more serious problem in modern n-arfare by the use of high velocity and incendiaiy ammunition. Information on the flammability of such fluids is much too limited (19), since past investigations of liquids in the lubricant and hydraulic fluid range have been concerned mainly with the flash point, the fire point, and the spontaneous ignition temperature. The more elaborate Etudies of flammability reported in the literature were concerned n i t h liquids and gases suitable for solvents or fuels or with dispersions of dusts in the atmosohere rather than with the higher boiling fluids. The acceptcd methods of measuring the flammability of liquids have been revien-ed by the Underwriter’s Laboratoi ies (I&’), which determined the flammability characteristics of a vaiiety of old and new liquids under fire hazard conditions of intercst. EVALUATION O F F I R E H 4 Z A R D S
FLASH . ~ N DFIREPOIIT. The evaluation of the fire hazards of light petroleum fractions bl- ineans of the Tag closed cup flash 1 1
Present address, Purdue University, Lafayette, Ind. Research Laboratory, General Electric Co., Bcbenectady, S . Y.
1608
INDUSTRIAL AND ENGINEERING CHEMISTRY
Vol. 39, No. 12
dispersing liquids and their greater e a ~ eof coalescence or condensation make important differenccbetween the &e hazards due t o oil and du,t acrosols. APPARATUS
\>htainedn-ith the ct)nveriiorit apparatus described hy Sortman, l3eatty. and IIcroii ( I ? ) . The air flon- rate x a s kept at 125 cc. per minute while a 1-nil. hypodermic syringe advanced with a micrometer screw served iis i n excellent nietiiod of introducing oil drops of linown volume. By using a Xo, 20 hypodermic needle, droplets of about 10 nig. 'uzre obtained. The rate of temperature rise did not e x c e c ~ l 2I-'.~ t)cr minute. Enough time was always allowed b e t w e n successive drops t o avoid missing a spontaneous ignition occurring v-ith a time lag of one minute (and usually several minutes). This was tmple t o perniit the observation t o be free from the complications arising from the ~\-ell-knowntime-lag effects ( 1 2 ) .
In any related fire hazard condition occurring in practice, the spontaneous ignition temperature will be determined by condit,ions such as the nature of the hot surface, t,he quaiit,ity of oil impinging on it, the volume of space enclosed, and the ventilation. IIence, thc relative values of the empirically defincd spontaneous ignition temperature may serve as rough indications of thc relative temperatures a t which such a type of ignition becomes a practical liazard. The rupture of a high-prcssure feed SPRAYFLAJIX%BILITY. line or pressurized tank or the impact on an oil tank by a n i i ' d e often results in the production of an oil mist or spray. The fire hazard involved during the existence of t'hat mist was studied u n a laboratory scale by a spray flammability method dcvelopctl for that purpose. The propagation of flames in gases has been intensively studitxi and reviewed in classic references like those of Bone and Ton.lisend (6) and Gibbs ( 2 1 ) . Flame propagation speed tcsts huve been used by the Underwriters' Laboratories on mistures of combustible gases used as refrigerants as a method for the evaluation of flaniniability (19). Diesel engineers have been interested iii the spray flammability of fuels in tlie light petroleum oil r m y e , but their method of ignition (adiabatic compression) and their goal (a good Diesel fuel) are reinovcd from the object. of this investigation. There has been interest but d a t i v e l y little n.ork on the electrical ignition of the higher boiling liquid fuel spmys or mists in contact n-ith air ( 1 4 ) . Dust explosions have bccn niueh invcst,igated and reviewed (11, IC), and here there is an obvious relat,ion to the explosiveness of dispersions of liquids in air. In a liquid spray most of the combustible material will be present as small particles dispersed in a gaseous medium; Iiowever, volatile components of the fluid will enter the surrounding medium to form an easily ignited gas. The greater ease of
The present apparatus evolved fIom a crude s;)i.ny flammability apparatus consisting of a cy/indried tin can mounted with its axis vertic,:al arid v-ith the upper end closed by a loose-fitting cap. Through the top a burning rod of niagriesiuni as held suspended on a wire. h hole \vas provided i n t h e side of the can close to thc bottom anti through it m s sprayed a fine mist of oil and ail. produced n-ith a liouschold insecticide sprayel'. Petroleum hydraulic oils fired readily in this apparatus arid the resulting rapid combustion a i d esplosion always blex the cap off tlie can. This apparatus was improved by mounting ir-ithin the r:tn :i carbon arc rvhich ignited the spray rnoI(> convenicutly. Later it was found desirable to u.-(' a high-voltage spark disch:trgc t o start a ccippti arc having a fixed gap. The early esperinientr wci'c conducted in the air. In order to ma!ie a quantitative comparison possible, controlled misturcs of oxygen and nitrogen were used instciati. By starring with a low oxygen concentration and increasing it in a series of successive exposures t o ignition, t,he minimum percentage of oxygen required to propagate tile flume in the oil spray was det'ermined. This miriimuni or liilliting oxygen concentration was used as a measure of the flfinnnability of t h e spray or niist of each Auid studicd and was ~!aniedthe "spray flammabilit'y limit."
.-I number of other improvements or refinements r e r e fourid necessary t o obtain adequate reproducibility and convenience. T h e apparatus finally evolved (Figure 1) consisted of the folloning clements: the flame propagation chamber, -4; the oil atomizer, B; the oil pump and metering device, C; t,he gas mixer aiid iion-meter system, D; and the electrical ignition system, E. The over-all dimensions were chosen t o make a compact apparatus capsble of quickly giving a flammability determination with f r o m 25 to 100 nil. of the fluid to be tested. E'L.NE PHOPAG.ATIOS C ~ A ~ E RThe . main part of the appar:ttus (Figure 2) consisted of a tratcr-cooled cylindricd flame propagation chamber constructed from two concentric tubes, B and C. The top view of the chamber shon-s the integral parts and the dimensions of the tube as constructed. d and Jf are brass tubes of 0.25-inch (0.6-em.) inside diameter, serving as water out1i.t and inlet, respectively, for the cooling jacket. Brass tubing of 0.025-inch inside diameter, D, serves as a holder for each of the tivo porcelain insulators, E, fitted on opposite ends of the tube. Llcctrodes, F , of 6 / i ~inch diameter copper r x l are fitted securely iiito t,lireaded brass hold The hexagonal iiuts, G, are fastened gnated I are soldered to the threitded e are gap width can be computed from the pitch of the screw thread. The broken 1ir:es shown as L indicattr the lend xires from a thermocouple having its hot junciion at point K , midway between the electrodes and the rear end of the tube. The lower end of the chamber is closed with a tigiitly fitted brass cap, which holds a porcelain thermocouple irisulator,in the top and a brass rod, 0, passing through the center of the gap to serve as a handle. hole 0.235 inch in diameter is rnnde m a r the bottom of the cap t o accommodate the nozzle of the spray gun. The forward end of the tube is left open to the :atmosphere t o decreax the explosion danger (the velocity of air through the tube being sufficient t o prevent appreciable diffusion in from the atmosphere\. The chamber is rigidly supported to give a slope of about 5' upward to the open end. X hole l / , e inch in dianieter underneat,h the cap near the lower edge provides an outlet for esccss oil drippings which collect in the lower end of the t uhe.
OIL . % m v r z m . The spray gun used was a. Psasche artist'> air brush, model ML-8. It was selected because it gave satisfactory results when used on low gas pressures (20 t o 30 pounds per square inch); it had a short liquid passage t o the tip; the
December 1947
1609
INDUSTRIAL AND ENGINEERING CHEMISTRY
rate of liquid flow required for the production of a finely atomized spray was small and n-as more in keeping Trith the amount of oxygen contained in the propagation chamber; and the tip of the air brush was particularly adaptable t o the chamber used, since the orifice tip could be easily fitted to the brass cap, allowing no atmospheric air to enter and dilute or enrich the carefully regulated gas mixture. T h e brush v a s operated a t maximum air and liquid flow ratcs and the silver needle adjusted so that, the resulting spray pattern was conical in shape, equaling the diameter of the propagation chamber approximately 0.5 inch before reaching the arc gap. The spray gun was mounted vcitli the longitudinal axis in line with the midpoint of the spark gap. I t m s observed that this spray gun adjustment produced the most reproducible measurements of the mininiuni oxygen concentration, OIL PUMP AND ~IETERISC: DEVICE.When zi constant pi ure and a fixed flow rate w r e used on the spray gun, the amount of oil passing through the gun and the condition of the spray lvere dependent, upon the amount of liquid dran-n through the orifice of the spray gun tip by the aspirator effect. The volume of oil aspirated perunit time decreased with increasing viscosity of the oil, hi^ difficulty avoided by the use of an oil pump rvhich delivered a h o r n volume per minute.
-
-
- - ------__----
Figure 2.
Top View of Propagation Chamber Scale, 6 inches = 1 foot
be a critical adjustment, although if the gap n-idth \vas incrc3itsed more than ticofold the spray flammability decreased appreciably. The syringe was filled with the EXPL;RI\II;ST.IL PROCEDCRE. liquid under study. JJ-ith the remainder of the system ope~l,the needle valves vere adjusted t o Droduce the desired oxvmxinitrogen mixture. T h e gas !vas ailowed t o flow for a t le:&; 45 seconds t o sweep out. the chamber. Fifteen seconds after conimencing the operation of the spray gun, the arc mas started and allowed t o burn for 5 seconds. If the therrnocouple millivoltmeter reading within 5 seconds was less than 1 millivolt (under YOo C . ) j the test was considered negative. Accordingly, the oxygen concentration was raised and the flammability nicasurernent n-as repeated until the thermocouple reading was 1 millivolt or more. I n this manner the minimum percent'age of os>-gennecessary for flanie propagation in t>heoil mist could,be ascertained. These measurements could be reproduced t o within =t1Yc oxygen in the loner oxygen percentages and *2% in the higher ranges. -4. positive test was usually accompanied by a muffled repoi,t, the intensity of which increased as the niinimum required conccntratioii of oxygen was exceeded. Before the flammability test or at. each new concentration, the chaniber was swept out ivith air or the gas t o be used for from 1 to 5 minutes, depcnding on the type electrodes were removed, cleaned, filed for each fluid and a t least once fo ig the same fluid. 11, was found riecessary, however, t o clean them more often alien consistent results could not be obtained otlierwise. This precaution was necessary when studying oils which charred readily on t,he hot electrodes. It necessary t o clean the apparatus carefully before making tests on each liquid.
The pump m s made from a motor-driven 100-mi. Bectonnickinson 707G glass syringe. -1hole was placed in the back end of the plunger and w&sclosed with a one-hole rubber stopper. .\ 7 r.p.ni. electrical motor having a long screlv 0.25 inch x 20 threads per inch on the end of the shaft and threaded into a nut tightly fitted into the hole in the stopper served t o advance the plunger. T h e gas introduced in the propagation chsniber through the spray gun a t the rate of 10 liters per minute m s sufficient t o prer e n t appreciable diffusion or dilution with atmospheric air through the open end of the chamber. simple calculation neglecting turbulence s h o w t'hat the c o l u n i ~of~ spray moves at a rate of 350 em. per minute. Th -gen and nitrogen used iyere piped through flon-meters to a rig chamber formed froln a labyrinth of concentric brass cylinders which provided the turbulence necessary t o assure proper mixing of the gases. -1 pressure gage and regulator \vas used a t this point t o regulate the pressure on the spray gun as well as the rate of flon.. A pipe connection was then mnde t o a T which carried the spray gun gas connector. -1T connection in the line permitted the use of compressed air to sweep out the .exhaust gmes produced in eilch run. Lnless other1vise stated, iii all these experiments, the oil n-as atomized Tr-ith a gas pressure of 25 pounds per square 'nch TABLEI. FLAMX~BILITY O F PETROLELX-BASEOILS n-hile the gas flon- rate a t a t m o s p k r i c piessure G s 10 liters pcr minute Flash Fire
ELECTRICAL IGSITION SY~TIXI.The system of spark ignition of the arc used n-as essentially the s a n e as t h a t described for spectroscopic work by Brockman and Hochgessng (8). Carbon electrodes weie tried but w r e found t o burn too rapidly, and copper electrodes having hemispherical and polished tips n-ere adopted. An electrode spacing of 0.10 inch (tn-o screv turns) was found to give satisfactory operation. When the gap was much wider the are was often blow1 out by the less flammable sprays. 1study was made of the effect of spark gap width on the spray fianimal ~ i l i t yof twoliquids. I t was not found to
Fluid
c(-_.__ op1ay
3.1
275
285
465
17.6 3.0 12 5
14 4
215
220
..
l:
28.:
230
250
504
41.8
315
310
505
59
,235
260
..
66
365
420
685
1050
555
615
._
0 62
S a v a l Ordnance hydraulic oil O.S. 1113 ~ r m yOrdnance recoil oil AXS-808 (Rev. 1)
a
HY D R O C ~ R B O S ~
Liquid I'iscosity, Point PoinL Flow Centistokes (C.oO.C.),(CoO.C.), S.I.T., Rate, a t l0OOF. F. E'. F. lII.,'hIin.
Benzene (analytical grade) n-Hexadecane (Conn. H a r d Rubber Co.) Aviation hydraulic oil A S TV-0-366b S a v a l Ordnance hydraulic oil O.S. 2963
S a v a l lubricating oil S . S . 2135 Naval lubricating oil s . S . 5190
.4SD
Tag closed c u p Sash point.
12a
...
1295
la J
10 6 5
3 1.8
Flaninia- Incendiary hi1it.y T e s t , Flame Liniit. Height, Oxygen Feet 30-35 12
12 12 12 12 12 12 12 12
0
.. 20
20
la
13 14
15
16
1
12 34 36 38
IO
50
4
10
12
INDUSTRIAL AND ENGINEERING CHEMISTRY
1610 TABLE 11.
E F F E C T O F CHLORISATIOS O S FLAM1IABILITY O F
Fluid a n d Source Benzene Chlorobenzene o-Dichlorobenzene 1,2,4-Trichlorobenzene (Hooker) Cuinene (iiopropylbencene) Trichlorocumene (Hooker) Trichlorodiphenyl (Aroclor 1242) Tetrachlorodiphenyl (Aroclor 1248) Diphenyl ether Chlorodiphenyl ether (Dow) Dichlorodiphenyl ,ether ( D o a ) Trichlorodiphenyl ether (Dow) Pentachlorodiphenyl ether (Hooker) Ethylbensene Polychloroethylbensene (Du P o u t ) Chloronaphthalene (Hallowax 1000) Herachlorobutadiene (Hooker) a
0
0.72 2.3
3 4 0
1
2 3 5 0 4.5 1.3 6
17.7 45.4 2.6 3.0 4.9 8.7
...
. .. 235
430 633d Sone 275 335d 465d 4901
350 380 265 260d 3OOd
325d
...
...
0.61 6.8 2.3 1.48
325 285 Sone
7 9 8
... b
,., 565 343 Sone
T a g closed cup Aash point.
cb Did ( 3 ) . not ignite under incendiary d hlanufacturer's d a t a .
fire.
RESULTS OBT.4IXABLE SPRAYFLAMMABILITY .4PPABATUS. The reproducibility found was adequate for the purpose of this investigation. HowEiiYIRICAL x.4TURE APiD SIGNIFICANCE OF
WITH
ever, only empirical results are obtained. Appreciable differences in the measurements will result from large increases in the electrode spacing and probably will arise from any large variations in the applied potential difference or the length of t'he exposure to the electric arc. With some fluids important differences in the results may be found if the nature of the electrode material is changed. Considerable changes in the wall temperature of the combustion chamber or the temperature of the liquid sprayed may cause significant alterations in the relative ratings of some oils. One of the most important variables in fl6me propagation phenomena is the composition of the mixture. For some vapor-air mixtures the range of fuel concentrations permitting explosions is narrow. It is hence t o be expected for them that, the weight concentration of the liquid dispersed in the gas vould be an important variable. The smaller the liquid drop size, t,he greater the area of contact of oil and orygen and the greater the oxidation rate. Hence, the drop size and distribution of sizes Tvill be important, In these esperiments the concentration and dispersion variables are controlled empirically by the oil feed rate, the gas pressure on the oil dispersing device, and the design and adjustment of that device. The empirical conditions w r e chosen t o give the most flammable condition obtainable in this apparatus when fluids were used in the light and viscosities. lubricat,ing or hydraulic fluid range of Table I reveals the vide flammability limits of the mists of sonic commonl!- used lubricant and hydraulic fluids. However, when the liquid florv rate was belon. 1 to 2 mi. per minute, appreciable rariations in the spray flammability limit often resulted, The effect of overrich fuel-air mixtures is exemplified by the results on a low-boiling fluid such as benzene. When atomized at the rate of 10 ml. per minute, benzene required from 30 to per millute and the same gas 33% oxygen, -kt a rate of 3 flow rate the spray flammability limit dropped t o 12% (the same value obtained for the light oils). Therefore, when t'he apparatus is used t o measure the flammability of more volatile fluids than those of interest in this investigation, the liquid flow rate should per minute (possibly t o 1 to 2 be decreased beloK 10 per minute) to get the proper fuel-air ratio.
made by shooting 50-caliber AI-1 incendiary bullets directly through 1-gallon Spray cans filled Kith petroleum-base hydraulic Flaniniability fluids, gave erratic results. Reproducible S;.T., 1,inlit. F, flammability results R-ere obtained only 1205 12 if the incendiary bullet was fragmented 14 c and ignited before i t reached the oil con29 >lo00 44 tainer. The procedure adopted was t o 12 fire a single incendiary bullet a t a range >lo00 3; of 15 feet through two baffle plates of 1230 45 1/,( inch cold-rolled steel spaced 1 foot 1300 64 apart and 1 foot from a 1-gallon tin com.. 11 .. 2: pletely filled with the fluid to be tested. .. 33 The filled and capped can (dimensions 42 .. 80 4 X 6.5 X 9.6inchesj was placed behind 12 the baffles in such a manner that the >lo00 50 bullet passed through the longest of these 2; >lo00 i7* dimensions. This procedure assured the bullet's being fragmented and ignited in passing through the steel plates. These high-vel'ocity fragments penetrating the can of fluid created a pressure sufficient t o burst the container and scatter the contents as a fine spray for a radius O f from 15 to 20 feet. Colored motion pictures (16-mm.) were taken a t 61 frames per second t o record the results of each test. It was found advantageous to use color photography, since otherLYise the flame could not always be distinguished from the smoke and spray. The burning of the incendiary bullet, which lasted about 0.01 second, occurred betn-een the t,rvo baffle plates and in the sample and occasionally flared u p 6 to 8 feet behind the sarnple as the fragments hit the ground. Unless otherwise stated, the oil tested was at atmospheric temperature (GO" to 80" F.). I n a firing test on a typical aviation petrolcu~nhydraulic oil the first motion picture frame sho\ved the intense flash of the incendiary. followed in later frames by the production of a liquid spray and the first appearance of fire in the third frame. T h e fire soon overtook the spray (about 0.1 second later) and reached its maximum height of 20 feet in the fortieth frame (in about 0.7 second).
HYDROC.~RBOSS
Atonis of Flash Fire Chlorine T-iscosity, Point Point per Cs.at (Cb0.C.), (CbO.C.), J f o l e d e 100' F. F. F. 0 0.58 12". 5 ... 1 0.59 90at 6 , , . 2 0.84 165b 3 1.1 260 r\loded 3
Vol. 39, No. 12
O B S E R V A T I O K S 03- FLhRIBZABILITY O F F L U I D S
OILS. Since petroleum oils constitute the large proportion of the lubricsting and hydraulic fluid3 in use, they wcre the first class studied, and the resulti are given in Table I. Observations on different samples of each fluid showed unimportant' the given. PETRoLEnf
The flash and fire points of the high viscosit,v index hydraulic
oils were lorn, varying from 215' and 220' F. for the aircraft
hydraulic oil (AS&T-O-36Qb) t o 316' and 340" F. for Kava1 Ordnance hydraulic oil (0,s.1113),while those of the lubricating s,s,2135 and x,s. 5190 varied from 3 6 5 ~and 4200 to 5 5 5 ~ and 615' F. The spontaneous ignition temperatures of all these petroleum oils were under 700" F. The spray flammability limits were all 12% osvgen, except for the several high-boiling oils K.S. 2136 and S.S: 5190, for Tvhich values of 34 a n d 507, ~ v e r eobtained. J$-hen oxygen concentrations a few, per cent above the spray flammability limit were used, violeIlt explosions resulted. Several of the polymer-thickened hydraulic fluids were not much less viscous than the unthickened oil S . S . 2135, yet they required only one third tho oxygen concentration. Clearly the flammabilit,y of spray or lllist of a polymer-thickened oil is dependent mainly on the nature and volatility of the base stock.
I K C E S D I A R Y FIRING T E S T
Incendiary firing tests on a number of samples of each oil of Table I established th!. essential reproducibility of the results and allo\ved a rough estimate t o bc made of the degree of flammabilit: by thc maximum height of the flame recorded on the motion picture (last column of Table I ) .
Sumcrous firing tests on fluids of interest were conducted at the Naval Proving Ground, Dahlgren, Va. The earliest tests,
-411 the polj-mer-t hickened hydraulic oils were practically equally flammable, the average msximum height of the flame be-
December 1947
TABLE 111.
INDUSTRIAL AND ENGINEERING CHEMISTRY
FLAUlIbBILITY O F
ORG.lSIC
PHOSPHATES,
Flash Fire Viscosity, Point Point Cs. a t ( C . O . C . ) , (C.O.C.), 100'F. F. F. 225b 245b 2'6 285 370 8 1 360 465 '9 500 685 38 3 >510 Kone 8 9 465 720 11.5 435 480
Fluid T r i m e t h y l phosphate" T r i b u t y l phosphatec Trioctyl phosphated Tricresyl phosphatee Hexamethyl tetraphosphated T e t r a b u t y l pyrophosphated Dioctylphenyl phosphonated Diphenyl monolp-fert-butyl phenyl) phospharei 40.3 Di-(0-chlorophenyl) phosphatel monophenyl 34.3 Diethylene glycol bis(n-butyl carbonate)g 10.1 Diethylene glycol his(2-n-butoxyethyl carbonate)g 18.0 Anilineh 2 6 p-(Methoxymethoxy) ethanoli 2.0 Laboratory preparation, J. O ' R e a r (carefully purified b y distillation a n d selective adsorption). b D a t a supplied by manufacturers. C F r o m Commercial Solvents Corp. 1 F r o m Victor Chemical Works.
the light lubricating oils ranging from the SAE 10 W through the SAE 20 grades.
CARBONATES, ETC. S:.T., F. 903
Spray Flammability Limit, %Oxygen 47 27 13 19 31 14 21
1611
C/P
CHLORIKATED HYDROCARBONS AND ETHERS. One 'well-knonm method of
producing less flammable liquids is t o halogenate a n organic compound such as a hydrocarbon or an ether. Comnionplace examples are carbon tetrachloride .. and the Freon refrigerants. The dif165 720 1076 12 22 ficulty of preparing completely halo510 >760 1296 21 18 genated hydrocarbons increases greatly as the molecular weight and complexity 360 400 800 >85 .. of the hydrocarbon increase. Hence the 355 410 786 >85 .. use of partially halogenated fluids was ,.. ... .. 14 .. 175 175 .. 12 .. given the most consideration Drior to the e F r o m Monsanto Chemical Co. war. .4 serious objection to many of the / F r o m D o n Chemical Co. 8 F r o m Pittaburgh P l a t e Glass C o . available partially chlorinated comh F r o m E a a t m a n K o d a k Co. pounds is their hydrolysis and the resulti F r o m Ammonia D e p t . , D u P o n t Co. ing evolution of hydrochloric acid. The to be very low rate of hydrolysis appears . . .. in compounds in which the chlorine is ing 20 feet and the explosion lasting 1.2 seconds. Lubricating directly attached to a n aromatic ring. Where halogen and hyoil N.S. 2135 was also very flammable, for it flamed t o a height of as in drogen atoms are both to the same carbon 12 feet. When the temperatures of the oil samples were changed, aliphatic compounds, the rate of hydrolysis is sufficient t o cause the expected differences in the flammability v'ere observed. serious corrosion in hydraulicsystems. For these reasons the comHydraulic oil 0,s. 1113 was fired while a t O", 55', and 180" F. into the atmosphere whose temperature mas 55' F. ht 0' F. the mercially available halogenated fluids discussfid here are corlfiIled flame height was half that a t 55' F., r h i l e at 180" F. it vas so to partially chlorinated aromatics or fully chlorinated aliphatics. greatly increased t,hat the largest fwes of all were encountered It W a s evidently valuable to determine the influence of the (over 25 feet height). Similarly, S . S . 2135 flamed 10 feet high at number of halogen atoms per molecule on the resistance to ig0" F. and 25 feet high a t 180" F. nition. The results of such a study using the available materials The decreased flammability of the more viscous oils revealed in are given in Table 11. Where possible the flammability data the spray and incendiary tests may be attributed to two factors: on the hydrocarbon before halogenatibn are also added for com(1) The lon-er vapor pressures of the more viscous oils reduce the parisons. The only fully chlorinated compound (liexacliloroamount of combustible material leaving the oil droplets suffibutadiene) did not have a flash or a fire point, the spontaneous ciently to prevent t'he formation of a n ignitable vapor-phase mixignition temperature was orer 1000" F., and the spray- flammature. (2) The viscous oils are less finely dispersed by the spraying bility limit was 77% 0x1-gen. During incendiary firing tests no device and therefure rxposed smaller surface areas to the atmossmoke or flame was observed other than t h a t due to the incenphere. The result is a decreased rate of attaining equilibrium diary bullet alone. As for the partially chlorinated compounds vapor pressure and also a decreased rate of oxidation. studied, it is evident from a comparison of the second and last Unsucces3ful attempts were made to relate the flash and fire points and the results of the spontaneous ignition temT . ~ B LIT:. E FLA~IIIABILITY OF THE SILICONE FLUIIJS perature spray, nnd incendiary test,s. Spray Incendiary AIany oils having widely different flash Flash Flamma- Fire Teat, and fire points showed the same flaniViscosity, PointQ bility Flame Manufacturer's CB. a t (C.O.C.), S.I.T.. Limit, Height, mability in t h r other tests. Ho\vever, Description of Fluid Designation 100° F. F. e F. %Oxygen Feet 6 bo 1170 920 84 5 630
3 12 24 21 1.5 8
I
Q
the results of the spray flammability and incendiary fire experiments can he correlated if allowance is made for the fact that the incendiary bullet cdrries its o i m supply of oxygen n.lrich must be added to the 2lcO of oxygen in the air. No fluid requiring over 45 to 50yooxygen in the spray test ever cau.ed a fire in the inrendiary test. The modern tieinand for hydraulic oils having the highc.st possible viscosity indices has caused the use of very 1on.-boiling petroleum-base fractions thickened to the desired vixosity and viscosity index 1,- the addition of linear polymers. Thereby much has heen u:tcrificed with regard to resistance to fire hazards, and when such oils are sprayed or dispersed in the atmosphere they create an exceedingl>- dangerous fire and explosion hazard. This conclusion also applies in a gradually- decreasing degree to
polymethylsiloxane
D.C. 190 D . C . (190-200)
22.6 201 393 D.C. 500 0.57 2.5 8.1 17.0 G . E . (0-73) 24.7 G . E . (0-69) 25.0 G.E. (O-i3) C 34.3 D . C . 500 44.9 57.8 D . C . 5OOd 65,O D . C . 200 82.5 G . E . (h-199B)d 84.4 D . C . 200 120 272 Polyethylsiloxane D . C . 400 10.5 19.3 D.C. 400B 38.3 D . C . 400BC 50.0 D . C . 400 96.0 o l y i m e t h y l , phenyl) D . C . 700 2.8 siloxane 17.8 32.0 61.5 D . C . 703 38.6 D . C . 7030 39.0 a When available. fire point is given in parentheses. b D a t a supplied by, producers, D o a Corning Corp. a n d C Stripped of volatiles b y thin laboratory. d Stripped of volatiles b y producer.
240 475 460 Below100 225 b 350 b 455(545)
860
...
...
920 905 875 860 890
470 465
900 905
$00b
s90
... ...
a05 615 625 b 256(260) 320(380) 360(445) 295(325) 305(325) 435(540) 43$(495) 440 6
...
... ...
905 890 910 610 540 505 590 610 940 975 980 980
...
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General Electric Co.
39 05 79 12
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23
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31
12 10
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>70
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INDUSTRIAL AND ENGINEERING CHEMISTRY
1612
I ) i l i t ~limits
Vol. 39, No. 12 of fioni 12 to 2 S c ;
Oiie
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dnnt
,
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ib
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-,..,,. coiuiiiii.; of Table 11 that a high proportioil of tlic Ii!.(ii~ogt~ii must be replaced by halogen to rake the at ray f l : ~ ~ i i - ' ' t y limit to over 40"; oxygen. K h e n tlie spray Il:inuilabilit>. s plotted against the number of chlorine atoins p ' r molt.culc,, smooth cun-es result. The partially clilorinnted fluid e\-olved much smoke during the spray and incentlinry fire t T h e ~ eivere unpleasant and probably toxic. Since WIW of ic, liquids studied are commercial preparations likelv to contain small concentrations of volatile impurities (as evidencc'tl by t hc, lon- flash points of several), it is sible illat a soiiie\vhat Iiiglic,i, reaijtance to ignition could be d loped for the samc~tlcgru* (JE chlorination by a more careful removal e volntilc inipuritic>.cement in the s1)r:txpresent. It is of interest to note the clo flamiiiabilitj- limits of trichlorodiphen d tricillorotliplieii?.l ether. T h e higher fire point of the former compound may I)(, evidence of the increased rate of oxidation of the etli pared with the hydrocarbon. Incendiary firing tests were made on Lenzcnc~, chlorobetizt,lic., and o-dichlorobenzene a t atmospheric and fluid teniperatur('> of 30" F. S o flame !vas observed from the tests o n either be~izene or chlorobenzene, but in the case of the o-dichlorobenzeni. a flame 8 feet high resulted. These observations are very in(1ic:itive. The lack of fire for the first t1.i-o fluids is presumably duc to t,he formation of a n overrich fuel-air mixture. The hoiling point of the o-dichlorobenzene is enough higher than that of tht. monochlorobenzene to bring this ratio down belot7 the uppcr limit of flammability, Finally, mixtures of 60';, by w i g h t of ethyl polgchlorobenzene arid 40% 1,2,-l-trichlorobenzeiie ~ w r i ' exposed twice to incendiary tests a t 55' F. No fire n-as ob but a dense gray irritating smoke was evolved. CASTOROIL-BASE HYDRAULIC FLUIDS. Because of tlic imiiy excellent and well-known properties of castor oil-base hydraulic fluids, their flammability properties m-ere also investigated. Such fluids are usually blends of blown castor oil thinned n-ith various proportions of organic solvents such as alcohols, ethers, or alcoholethers. Polymers are sometimes added to improve the viscosity index, and small concentrations of corrosion inhibitors are usual. Kenneth B. Kalker of the Ammonia Department of E. I. d u Pont de Kemours and Co., who has had much experience in the development of such fluids, was kind enough to cooperate by preparing a number of experimental batches of these fluids with the object of increasing t h e resistance t o spray flammability and to incendiary fire hazards. The blown castor oil, used in concentrations of from 10 t o 55%, was thinned by the addition of various proportions of one or more of the following fluids: 8-(methosyniethoxy) ethanol, &butoxyethanol, and propylene glycol. BILITY RESULTS.The flash points were all between 160' and 200' F. The spont,aneousignition temperature ranged from 785' t o 865" F., while all b u t two fluids had spray flamma-
_.
of tile aliphatic diesters ha- h : r c d t o some cstent i l l a recent publication of this I;ttmr:itor)- ( 7 ) . The syrithvtir- fluids used were carefull?- siri1jl)ed of volutilis impurities. The Itiricmatic visrositiw varicd froin 1.6 e.. (iiciglectiiig i. fen- of t h e most volatile diester fiuidsj up to GO e-, :tt IO0 a 1;. The spontaneous ignitiijn tempcrnturL, r:inged Eroi!~ iO03 t o 850 F. The sprav fiammabilit >- liiiiit varied from 113 t o 1s'; fur ail hut tlie fc\,v cc)nip:iratiwly T. iscous conip,)utidi l i k . di-(it~:r:Ldecyl) adipate nnd tli-(heptad(~cyl)adipate, for \vliic'!j i 110 liiiiit' were 25 and 4ZC;, i,ezpc:ctively. Dibutyl sebacnte an(1 di-(2-etliylhesyl) sebacate n-ere d i 4 l l e d untlcr dimiriished p r c sure aiid further puIified hy pt:rcolation through adsorptioil colulnlls of alumina and silica gel. Incendiary firing tests w e r i ~ iiiade on four samples of each fiuid. The liquids ivei'e fired n.hilt8 at 55' F. into the atmosphere a t 55' F. arid while a t 180" F. into the utmoqjherc a t 55'F. I n spite of tlic fact that these diesters 1i:iii around l,'jO tlio volatility of petroleum oils of tlie same vih(miry, they were just a$ flammable t o indendiarj- fire. Flamrs hi>iglitsof 10 and 20 feet were obtained with the first fluid, and 7 :tnd 28 feet with the sccond. These results are what might Ii:i\-e been predicted from the observed low values of the spraj. fiiininiability limit. It cau be coticludcd that the diesters ha\-e higher ilasii and fit.e pciintd and spontaneous ignition temperatures than petroleuiii oils of the same viscositj-, but their aerosols are onlj- slightly less flnnimable. Since these diesters are so niucli less volatile thari comparable petroleum oils, it is evident t h a t the spray flammabilities of finely dispersed fluids are not much affected by large differences in the volatilities. These conditions arc not surpi,ising, for other work of this laboratory (4,7 ) on R number o i other physical and oxidation propepties has shown t h a t t h r w fluids behave very much like aliphatic hydrocarbons of t i i c , wnie over-all structure. Here the d a t a can he interpreted ti! indicate that the ester groups have little influence on the thermal cisidation processes involved in the flammability tests ( 4 ) . ORGASIC PHOSPHATES ASD C-~RBONATES. Because of tlic high flash point and reputed flame-resistant properties of t ricresyl phosphate, the flammabilities of a group of homologous phosphates were studied. The results obtained using a number of such compounds in commercially available grades of purity Till be found in Table 111. The sources are given in order bettrtr t o identify the commercial materials used. Although the flash points varied from 225' t o 510" F. and the fire points from 243" t o over 760" F., the flammability limit ranged from 13% t o only 21 5 except in the case of the two phosphates having the highes t proportions of phosphorus. There are no evident relations between the flash and fire points and the spray flammability limits or between the viscosities at 100" F. and the spray flammability limits. I n the series of ~ ~ 1 I : ~ T J l:hi e~fIuiiiiixlii5tv ~ ~
Y ecember 1947
INDUSTRIAL AND ENGINEERING CHEMISTRY
1613
:: 8 ,.
4
1
.. i
..
..
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a l k ~ - suhstitution l on the benzene ring decrca,qe the fiammahility. I t is also coricludc'cl i1i:it I h(, liiglier ~ l T te0i 0 triailiyl orthophospliate? and the trinrj-I o r t h n ~ l l r J s ~ ~ l l at'(' flaniniablc in tlie form of oil mi.sts in thc atnio.;phc.ri: f ( i r u < t x iii developing nonflanimnl~lehydraulic oils. .-Ilthough only a feiv organic carbonates n-ere studied, it \vas found that two carbonates niadr availat,lc' a t the end of t h c ~ v a r had spray flainmability limits of over 85': oy-gell ( i TiliJk ~ 111). These are derivativei of diethylene glycol n-liicli desi~rvc furtlicr study. The exempli fy t lie lack of correlar ion t ict \ r e e n :tnd spray flash and fire points, jontaneous ignition tcnipci~:iturt~, flaniinahility. P ~ ~ . r c o sPOLITER r: FLUIDS.1Iucli interest has 11ccn arourcd in the silicone polymer fluids or pol?-orgnrioailoxane;j (6, 16). Their possibilities for use in lubrication and h>-draulicsliavc 1)ec.n investigated (9,IO) because of tlieir rcniarkab coefficients of viscosity and thrir unusual res oxidation in the air. The two manafacturers of these fluids have been most cooperative in making available a variety of samp1i.s of interest in this investigation, anti Table IT.' lists the flaminaliility data obtained. Each fluid is identified by a brief chemical description of the results of the analyses of this laboratorj- and hya reference serial number of the producer. The flash points are much higher than tliosc of petroleum oils of the same 100" F . viscosity, for they range from 223' to 625' F., increasing with the viscosity. The flash points of all the polyetti>-lsiloxanesare over 100' F. lower than those of the other polysiloxanes of comparable viscosities. This large difference may be due to a higher vapor pressure or a l o m r oxidation stability. That it is not due t o the presence of a volatile impurity is shown bl- the low value obtained for the stripped sample. The silicones do not have firc points when determined by the usual procedure. They can be made to burn after continued flaming with a Bunsen burner, but the flame burns poorly and tends to extinguish itself after the external source of flame has been removed. If the products of oxidation are allowed t o accumulate in a closed containcr for long enough, the resulting vapors can explode upon admission of a source of ignition. This has happened in oxidizing silicones in an oven at 250" C. Among the products evolved from the combustion of the polymethylsiloxanes are silicon dioxide, carbon dioxide, formaldehyde, and formic acid. Usually the fire points were not measured because they were not considered sufficiently significant.
Tiir spontaneous ignition tenipcrrttures ~ e r liigllcr c (csccIlt for t h e pol~etli~l.;iloxnncs) than n-rw tliosc observed iritli any of thc
l i d apnnt:incnus p:.trolcuin n i k -111 the pol~~metliylsiloxaties ignition temperntiire valiics of from 880 to 01 0 F. regardlcis of osity or source. The values of 504" to GOY" F. obtaincd for the Polj-etIiyljiloxancs arc so much loner thal. they are lx~licved to originatc in fundsniental differences in molecular structurc:. I n the thermal dccomposition of the polymeth!-lsiloz:2ncs b o t h the C-H bond in tlic methyl group a n d thc Si-0 bond in t h r polysiloxane chain are so much more stable that a Si-C bond prnhably is tlie first to be brolxm. In the polyethrlsiloxaneu twitles thc Pi-C bond there are the C-C lionds and alnc the, C-I1 I)ontl of the -CII;'group in t h ethyl side chain. Tliesr a t ' ( ! 1 J l O l ' ~ lilwly to hrc:rk t h n n thc Si~-O bond or the C---I1 tmitl in --CI13. The poly(nicth~-l. phenyl) siloxane copolymers have ,spontaneous ignition temperatures approximately 80 O F. highcii thnn t,lie polyi~ieth?-lsilox:ities,prrsuniably due to the greater Si-(aromatic C ) bond tli:in tho Si~-(aliphatic C) bond. The appearance of r h c ~:ish left in the cup of the spnntanrous igiiiiiort us n-as consistent with itlrntificatiori given nee the polynictli!.l..ilo~an(,~ ca particles, while thi: p l y (methyl, phenyl) siloxanes left a gray ash consisting of particle? of silica and of carbon black so typicul of the cracking of aromatic hydrocarbons. The result:: of the mes,surements of the spray fimnniability limits of the earlier silicones were very scattered, the limits varying from 31 to 79%. It n-as merely concluded t h a t the spray flammability limit decreascd with increasing viscosity. I t was observed later that individual samples under periodic observation gradually becomr less flammable. Information about, the precise composition of the samples was not then available, and the pungent odor frequently found in the early samples had been assumed to be inherent. It was finally concluded t h a t volatile material n-as present, whose gradual escape x a s causing the upn-ard drift in thp spraj- flammability limit. T o test this plausible hypothesis a sample of fluid 0-73 having a spray flammability limit of 31% oxygen n-as Tvarmed under diininished pressure to remove volatiles. ;ipproximately 10% of the fluid evaporated, the pungent odor disappeared, the viscosity a t 100' F. increased from 25.2 to 34.3 cs., and the spray flammability limit rose t o 55% oxygen. Following this experience both producers of silicones were asked
1614
INDUSTRIAL AND ENGINEERING CHEMISTRY
t o make avaiIable fluids for this and related investigations, using all possible care to obtain them as free as possible from volatile impurities or components. Such "stripped" fluids n-ere much less flammable, the higher spray flammability limits exceeding 70yc oxygen. But when the spray flammability limit, iyas exceeded, the resulting explosion was rather violent. An early pol!.methylsiloxane (sample 0-69) having a vixocity a t 100" F. of 25 cs. was found to flame 10 feet high in the iiicendiary firing t,est. The early D.C. 200 Yuids (having ties a t 100" F. of 57.8, 120, and 272 cs.) flamed 8, 8, an high in this test. However, when the fluids which had been st'ripped of the more volatile materials were b e d , they xere nonflammable, for the only flames seen in the motion picture records were due to the highly localized ignition of the incendiary bullets. The properties of properly stripped polymethylsiloxanes or poly(methy1, phenyl) siloxanes having viscosities at 100" F. in excess of 20 cs. are summarized as follows: The flash points are high; Tvhen the liquids are ignited the flames are readily extinguished; the spontaneous ignition temperatures are high: the spray flammability limits are high; and they are practically nonflammable t o incendiary fire. Obviously these fluids have much promise in applications where unusual resistance to fire hazards is necessary. Ucox POLYUER FLGIDS.Two netv series of polymer fluids have been made available bl- the Carbide and Carbon Chemicals Corporation ( I S ) . These are both polyalkylene glycol derivatives possessing several properties r h i c h make them interesting lubricants and hydraulic fluids. Fluids of the first series (designated by the manufacturer as the Ucon LB series) are able to dissolve only a few per cent of n-ater at 100 F. The second series (designated as the Ucon 5OHB series) is very soluble in cold water. Both classes of fluids require the addition of an antioxidant Ivhen used in aerated systems persistently maintained over 150" F. Unless otherwise stated the Ucon fluids in question contain 2% by !wight of the oxidation inhibitor recommended by the manufacturer. The Ccon LB fluids !yere furnished this laboratory in six viscosit,y grades ranging from 10 t o 100 cs. a t 100' F. Their behavior in the flanimability tests is summarized in Table V. As the flash and fire points varied from 310" t o 570", they %-ere somewhat above those of petroleum fluids of :he same 100" F. viscosities. The viscosit,y grades over 20 cs. at 100" F. had only small variations in the spontaneous ignition temperature. The spray flammability limit was 54% oxygen for all viscosities above 30 es. a t 100" F. Several incendiary firing tests were made on each of three viscosity grades. The least viscous fluid (LB-135) caused a flame 6 feet high, the most viscous (LB-400) gave no flame, and the intermediate fluid (LB-250) caused a flame 2 feet high. The presence of the antioxidant did not, appear t o have a particularly significant effect on the flammability as observed in this test.
.
vealed it t o be only slightly more flammable than tht: LB-250 fluid. Even when fired a t 180" F. it caused a flame only 5 feet high. Since the 50HB-260 fluid will dissolve a high proportion of water at ordinary temperatures, data were obtained on the flammabilit,y characteristics of a series of mixtures containing from 107, up t o 507, \vat,er. The spontaneous igiiit,ion temperature increased from 743" F. \\-hen no n-ater was present up t,o 815" F. with 507, water, and t,he spray flammability increased linearly with the water content, reaching Bit; oxygen in the 50:; aqueous soiution. Incendiary firing tests shelved that the addition of 15 t o 25% water cut the flame height down t o only 1 t o 2 feet, while over 357, water eliminated all evidence of flame propagation. Hence, the two classes of Ucon polymer fluids have higher flash and fire points and spontaneous ignition temperatures than petroleum oils of the same 100" F. viscosity. They have spray flammability limits so much higher that they can be described as very resistant. t o the fire hazards caused by incendiary fire.
Vol. 39, No. 12
GLYCOLS ASD THEIR AQTEOCSSOLTTIOSS. The dissolving of water in an organic liquid is a well-knoxn method of decreasing its flammability. Ethylene glycol is especially promising for use as the organic component because of its availability, its lorn viscosity at 100" F.. its limited action on packing materials, and its effectiveness as a freezing point depressant. Various proportions of ethylene glycol and water Tvere examined by the flammability tests described (see Table VI). By adding m-ater t o ethylene glycol the spontaneous ignition temperature could be raised from 856" F. (for the pure glycol) to 956 F. when 80% water was present. Khile the spray flammability limit of pure ethylene glycol was rather high (40% oxygen), it was not considered high enough for safety. When 357, water xas present the spray flammability limit had risen to 5 7 5 oxygen, and with 50% water present over 80Y0 oxygen Ivas necessary. Incendiary firing tests TTere made o n a number of ethylene glycol-11-ater solutions. Ethylene glycol alone was somem-hat flammable t,o incendiary bullets, for flames were from 3 to 8 feet high. The flame height decreased Tyith the increase in water content, and when 40rc or more water was present no evidence of flames or smoke was ever found. Observations were made on a number of other glycols and their derivatives and some appeared promising for use in aqueous and other special lubricant and hydraulic compositions. .Ittention is called to the much higher resistance t o spray flammability of the diethylene glycol t,han the propylene glycol or the monoethers of ethylene aiid diethyl glycol (Cellosolve and Carbitol). ACKKOWLEDG\IENTS
Thc authors are grateful to C. A. Heehmer and C . E. Saunders of thia laboratory for their help in obtaining t,he viscometric dat,a, the flash and fire points, and some of the numerous measurements of the spontaneous ignition temperature and spray flammability. The advice and criticisms of C. 51. Murphy and the excellent photographic assistance of D. L. Pickett svere invaluable. The pure trimethyl phosphate v a s prepared by ,J. O'Rear. The cooperation of the S a v a l Proving Grounds, Dahlgren, Va., in making the incpndiary firing tests \vas valuable and stimulating. LITERATURE C I T E D
(1) Ani. SOC. Testing Materials, "Standards on Petroleum Products
and Lubricants," 1945. (2) Am. Soc. Testing JIaterials, Proc. A m . SOC.Testing Mfaterialr, 34, 53 (1934). (3) Associated Factory Mutual Fire Insurance Co., Boston, "Properties of Flammable Liquids, Gases, and Solids," 1933. (4) Atkins, D . , Baker, H., Murphy, C., and Zisman, W., ISD.ENQ. CHEM.,39, 491 (1947). (5) Bass, S . , Hyde, J., Britton, E., and hlcGregor, R., M o d e m Plastics. 21, 124 (1944). (6) Bone, TY,, and Townsend, D., "Flame and Combustion in Gases," New York, Longmans, Green and Co., 1927. (7) Bried, E , , Kidder, H urphy, C., and Zisman, W., IND. Eso. C H E X . , 39, 484 (1947). (8) B: ockmnn, E., and Hochgesang, F., IND.ENG.CHEY., -4x.k~. ED.,14, 796 (1942). (9) Brophy, J., Militz, R., and Zisman, TI-., Trans. Am. SOC.Mech Eiigrs., 68, 359 (1946). (10) F i ~ z s i r n n ~ o IT,, ~ ~ sMilits, , R., Pickett, D., and Zisman, W., Ihid., 68, 361 (1946). (11) Gihbs, K. E., "Clouds and Smokes," Chap. VIII, Philadelphia, P . Blokiston's Son & Co., 1924. (12i Helrnore, IT., "Science of Petroleum," Yol. IT-,p. 2970. London, Oxford Gniv. Press, 1938. (13) I i r a t z e r . J . , Green, D., and TTilliam% D., S . A . E . Journal, 54, 22s (1948). (14) SIas~vell,G. B., and Kheeler, R. Y.,"Science of Petroleum,"' 1.01. I V , p. 2978, London, Oxford Univ. Press, 1038. ~ 1 5 )Price. L),, Brown, H. €I., Brown, H . R., and Iloethe, H., "Dust Explosions," Boston, S a t l . Fire Protective Assoc., 1922. (16) R o c h o x , E.. Chem. Eng. .\-ems, 23, 612 (1915). (17) Sortman, c., Bestty, H., and Heron, s., IND. EXG. CHEM., 33, 357 (1941j. (IS) U1:dern-riters' Laboratories, "Classification of Hazards of Liquids," 2nd ed., Chicago, Ill., 1915. (19) Underwriters' Laboratories, ISD.ESG.CHEY.,32, 880 (19.10). RECEIVEDOotober 17, 1946. T h e statements a n d opinions advanced are the indiriduai expressions of the authors a n d not those of t h e S a v y Department
