ANALYTICAL EDITION
348
Natural light was found unsuitable on account of its variability. It was found necessary, therefore, to standardize the lighting. Accordingly, the apparatus is set up in a relatively dark place and dependence placed on artificial light. A lamp designed for microscope illumination, equipped with a 100watt bulb and daylight glass, is used for illumination. The daylight glass renders the smoke more readily visible than i t would be by uncorrected artificial light. The smoke point should, therefore, be observed by corrected artificial light. The apparatus must be set up in a place which is protected from drafts, as even a moderate current of air affects accuracy. Procedure
Melt the fat, allow moisture and suspended matter to settle out, and filter. Pour 50 cc. of the melted fat into the flask, Set the flask on the heater which has the large opening in the cover plate. Suspend the thermometer from overhead so that the bulb is immersed in the fat, leaving the flask unstoppered. Heat the fat to between 110" and 115" C. Then remove the flask to the other heater, placing it in such a position that its open mouth is illuminated by a horizontal beam of light from the lamp and viewed against the black screen. The
Vol. 3, s o . 4
lamp should be placed as near the heater as practicable to secure maximum intensity of illumination. Adjust the rate of heating with the rheostat so that the temperature rises at the rate of approximately 2" C . per minute. Take the temperature at which the first wisp of smoke is seen rising from the top of the flask as the smoking point. The first wisp of smoke should be followed by a plainly visible and continuous stream, Remove the thermometer when smoke is first observed. Smoke should then be seen issuing from the mouth of the flask. If not, replace the thermometer and continue heating until smoke again appears and continues after the thermometer is removed. I n such case, the temperature at which the second appearance of smoke is noted is taken as the actual smoking point. The method described has been in use for more than a year and has given satisfactory results. After proficiency has been acquired, duplicate determinations made on separate portions of the same fat should agree within 1 or 2" C. Closer agreement might be attained by slowing the rate of heating in the final stage. Literature Cited (1) Blunt, K., and Feeney, C., J. Home Econ., 7, 535 (1915)
Solubility of Water in Aviation Gasolines'~' Elizabeth W. Aldrich BUREAU OF STANDARDS, WASHINGTON, D. C.
A method is described for the measurement of the concluded that all commercial solubility of water in liquid petroleum products, which gasolines are normally satuwhich collects in traps is applicable to the determination of traces of water in rated with water when used in and carburetors is of many organic liquids. Sodium-potassium alloy free internal-combustion engines. considerable interest to the from oxide is added to a weighed sample of the waterAlthough the solubility of operators of automobiles and saturated liquid after the removal of dissolved gases. water in gasolines is of interest airplanes. Even after preThe hydrogen evolved is collected and measured. Data in connection with a number cautions have been taken to are given on the solubility of water in five aviation gasoof problems, very little data remove all suspended water lines at three temperatures. on the subject could be found from gasolines, there remain in the literature. Apparently very ;mall amounts of dissolved water. A decrease in temperature will cause the sepa- none of the methods previously used for the measurement of ration of some of the dissolved water which, if collected in the the amount of water in solution in gasoline are above critifuel feed system over a sufficient period of time, may stop the cism. Accordingly, an investigation was made of the method flow of gasoline to the engine, The flow may also be inter- based on treatment of the gasoline with an alloy of sodium rupted by the accumulation of partially hydrated aluminum and potassium and determination of the volume of hydrogen oxide formed by prolonged contact of water with aluminum evolved. Data for a number of aviation gasolines were obfittings. In winter weather, water in the fuel feed system tained. may freeze and damage traps and carburetors. Choice of Method When water dissolves in a gasoline, the total vapor pressure of the gasoline increases by an amount dependent upon PREVIOUS METHODS-A number of methods (1) have been the degree of saturation. When saturated, the partial pres- described for the measurement of the water in petroleum sure of water va@r is not measurably different from the vapor products. Of these only two seen1 to be sufficiently precise pressure of pure water a t the existing temperature. This for the quantitative determination of the water dissolved in abnormally large increase in the vapor pressure caused by the gasolines. presence of small amounts of %ter indicates the necessity for The first of these was used by Groschuff (4),who measured complete removal of dissolved water or the saturation with the solubility of water in kerosene, benzene, and paraffin water at all temperatures when making accurate vapor-pres- oil. The temperatures were determined at which turbidity sure measurements on gasolines. Accordingly, the amount appeared and disappeared when known amounts of the of water required for the saturation of gasolines at various liquid and water were cooled and heated in sealed tubes temperatures is of interest. The results of the present study In this phase change method it is difficult to determine when indicate that the solubility at room temperature is about 1 all the water is dissolved, since the water tends to stick t o the part of water in 10,000 parts of gasoline, from which it may be side of the tube. It is also difficult to prevent undercooling. Presented before t h e Division of Petroleum 1 Received March 17, 1931. The second method is that developed by Clifford (3). Air Chemistry a t the 6 1 s t Meeting of the American Chemical Society, Indiandried over calcium chloride was bubbled through waterapolis, I n d , March 30 to Apill 3, 1931 saturated gasoline, and the air and vapors obtained were f Standards of Publication approved by The led through weighed calcium chloride tubes. Gasoline vapors S Department of Commerce
HE a m o u n t of water
T
October 15, 1931
I N D U X T R I A L A N D ENGINEERING CHEMISTRY
were theri removed by passing dry air through the calcium chloride tubes for several hours. However, the vapor pressure of water above calcium chloride is approximately 0.2 mm. of mercury, so that a loss of mater vapor would be expected by this method since, during the period while water is being absorbed in the weighed tube, the dried air is diluted with gasoline vapor and the partial pressure of water vapor in it is reduced below 0.2mm. Checks were obtained on samples containing known amounts of water, and it is possible that the loss of water vapor was compensated for by incomplete removal of gasoline vapors from the calcium chloride tube. However, the generality of this compensation for gasolines containing different amounts of W water is doubtful. Figure 1-Shaking P R E S E NlhfETHOD-The T method T~~~ for Saturating Gasoline with Water adoDted is a refinement of the method ( I ) in which the hydrogen liberated by sodium is used as a measure of the water present. The procedure may be divided into five steps: (1) The saturation of the sample of gasoline with water by shaking for a predetermined time a t a constant temperature. ( 2 ) The transfer of a known weight of water-saturated gasoline to a suitable container filled with dry air. (3) The removal from the gasoline of those constituents which exert more than a very small pressure a t liquid air temperatures. (4) The introduction of sodium-potassium alloy with resultant evolution of hydrogen. ( 5 ) The separation of the hydrogen from the gasoline frozen in liquid air and its measurement in a buret a t a determined temperature and pressure.
Figure 2-Schematic
Diagram of Shaking Mechanism
The advantages of the method which led to selecting it for the present work are: (a) A very small amount of water will yield an easily measurable volume of hydrogen. ( b ) It involves only the reasonable assumption that the sole hydrogen-producing reaction is that between water and the alloy. In principle, it is otherwise free from serious sources of error.
The disadvantages of the present method are: (a) It is complicated and time-consuming. ( b ) The removal of all dissolved gases before the hydrogen is evolved and measured requires special equipment and technic. (c) Any oxide in the alloy will introduce errors.
349
I n view of these facts, it appears that, although capable of yielding the results required, the method is not especially adapted as a general one for determining the amount of water in gasoline, and that work on simpler methods would probably be more profitable than further development of this one. Detailed Description of Apparatus a n d Procedure
SATURATION OF GASOLINESWITH WATER-The shaking tube used for the saturation of the gasolines with water is shown in Figure 1. It is a Pyrex glass bulb of about 100 ml. capacity, fitted with an inner tube. At the lower end of the inner tube is a small bulb with eight or ten holes about 1mm. in diameter. The passage of the gasoline through these holes minimizes the carrying over, during transfer to a second bulb, of any of the undissolved water which settles to the bottom of To Vacuum
Figure 3 -Appardtus for Sampling Water-Saturated Gasoline
the shaking tube. To the upper end of the tube is fused a magnetic seal which furnishes a means of transferring a sample of the gasoline to the analytical apparatus. The use of the magnetic seal, which consists of a thin glass tip sealed within a glass tube having a side a m , will be described later. The shaking tube is sealed t o the vacuum system through the side arm A . The vacuum is produced by a rotary pump which is capable of evacuating to approximately 0.001 mm. of mercury. Further evacuation to better than 0.0001 mm. may be effected by means of a mercury diffusion pump. Pressures are read on a McLeod gage connected to the vacuum line. Approximately 60 ml. of gasoline and 1 ml. of water are introduced into the shaking tube through the side arm B. The tube is immersed in liquid air, and when the gasoline is frozen, the arm B is sealed off. The space above the gasoline is pumped to a pressure of approximately 0.01 mm., and the bulb sealed from the line a t C. Evacuation a t this time is necessary to avoid the pressures which would otherwise be developed on shaking the tube a t higher temperatures and which would introduce difficulties in transferring the sample to the analytical apparatus. The tube containing the gasoline and water is placed in a holder and shaken for 4 hours in a thermostated bath held a t the desired temperature within 0.1" C. A schematic diagram of the shaking mechanism is shown in Figure 2. In order to determine the time of shaking required to ensure saturation of the gasolines, a number of preliminary experiments were made in which samples were shaken with water for various lengths of time. The data on samples of fuel 19 shaken a t 30" C. for I, 2, and 4 hours are given in Table I. These data show that 1 hour is sufficient t o saturate the gasoline under these conditions. In the solubility measurements, the gasolines were shaken for 4 hours, since a somewhat longer time might be required for saturation under aome conditions.
350
ANALYTICAL EDITION To Vacuum
Vol. 3, No. 4
D is then broken by drawing the piece of iron to thegtop of the vertical tube by means of a magnet and letting it fall. Sufficientpressure is applied a t K to force a sample of gasoline over into F.
In those cases where the vapor pressure of the gasoline is greater than atmospheric, dry air under pressure is forced into F and the magnetic seal is then broken. The gasoline is drawn over from the shaking tube by gradually reducing the pressure in F until it is slightly less than the vapor pressure of the gasoline. When 30 or 40 ml. of gasoline have been collected in F , the stopcock L is closed. The shaking tube is removed from the remainder of the system by breaking the horizontal glass tube connecting it to the bulb F. The broken end of the line is then sealed off. The gasoline in F is frozen in liquid air, the space above it evacuated, and the bulb F sealed from the line a t M . F is weighed, together with the glass tube from M to J which is taken from the line by breaking the de Khotinsky seal J. The increase in the weight of the bulb F gives the weight of the gasoline sample. REMOVAL OF DISSOLVED GASES-Those constituents of the gasoline which exert a considerable pressure a t liquid air temperatures must be removed, or these gases would be measured together with the hydrogen in the final step of the procedure in which hydrogen is pumped from the frozen gasoline. The bulb F is connected to the vacuum line as shown in FigFigure 4-Apparatus for Removal of Dissolved Gases ure 4, t h r o u g h the magnetic seal N . A TRANSFER OF WATER-SATURATED GASOLINE TO ANALYTICALpiece of iron is placed hwARATus--After 4 hours of shaking, the tube is rapidly in the tube above the transferred to a second thermostated bath held at the tem- t i p at N , a n d t h i s perature of saturation and regulated to 0.1' C. The ends of t u b e sealed. The a the two glass tubes leading from the magnetic seal are broken, space between N and a piece of iron inserted above the tip in the vertical tube at t h e s t o p c o c k 0 is D (Figure 3) and this tube sealed. The other arm at D is evacuated, and after connected by glass tubing to the bulb F and to the two-way the gasoline in F has stopcock E, which can be opened either to the vacuum or to been cooled to liquid the air. Three side arms equipped with magnetic seals are air temperatures, the fused to the bulb F , one of them containing a sample of so- tip a t N is broken, divm-potassium alloy. This bulb is weighed before connect- using a magnet. The ing it t o the line by means of de Khotinsky cement at J . air and gases above t h e gasoline a r e Table I-Weight Per Cent of Water i n Fuel 19 after Shaking for Various Lengths of Time pumped off , and with ROR 2 HOURS SHAKING FOR 4 HOURS SHAKING FOR 1 HOUR SHAKING the stopcock 0 closed, wt.97, wt.% wt. % t h e gasoline is 0.0074 0.0065 0.0066 4F 0.0057 0.0046 .... warmed up to room 0.0056 ,... 0.0061 temperature. T h e 0,0051 .... .... 0.0056 .... .... gasoline is a g a i n Av. 0.0065 0.0058 0 0059 frozen and pumped. The stopcock E is opened to the vacuum, and the bulb F This procedure is reand the line leading to the tip at D are heated and pumped peated until the presto remove all moisture. Ordinarily this did not take more sure above the gasothan half an hour. Removal of moisture at this time is neces- line after freezing but sary, since the amounts of water which would ordinarily be before pumping is less contained in the air in bulb F would be approximately equal than 0.002 mm. The bulb is t h e n sealed to the amount dissolved in the sample of gasoline. Dry air is then admitted by opening the stopcock E to the from the line. INTRODUCTION OF air line. The air is dried by passage through the tube G, Figure 5-Apparatus for Se aration and T AsSIUM containing calcium chloride, the tube H , containing phos- SODIUM-PO Measurement of H y g o g e n phorus pentoxide, and the bulb I which is immersed in liquid ALL o y- Wi t h the air. The amount of air admitted depends on the vapor pres- gasoline frozen in liquid air, the magnetic seal holding the sodium-potassium alloy is broken and the alloy allowed to sure of the gasoline at the temperature of the bath. When the vapor pressure is less than 760 mm., the pressure run into the bulb. The tube is then sealed off a t P. The within the bulb F is adjusted until it is slightly less than at- gasoline is warmed up to room temperature or slightly above, mospheric. The tube a t K is broken so that the gasoline in and at intervals is shaken vigorously. The decomposition of the shaking tube is under atmospheric pressure. The tip a t the water by the alloy with resultant evolution of hydrogen is
f
October 15, 1931
361
INDUSTRIAL AiVD ENGINEERING CHEMISTRY
usually complete within 4 or 5 hours. The use of sodiumpotassium alloy involves the reasonable assumption that no gas is evolved by reaction of the alloys with the hydrocarbons constituting the gasoline.
When all of.the hydFogea above the ga placed into the buret, the mercury in X is top of Q. The liquid air surrounding the gasoline is removed and the gasoline allowed to warm up to room temperature. Care is taken that the pressure of the vapors does not become so high that gas is bubbled through the mercury. This process liberates additional hydrogen. The gasoline is again frozen and the hydrogen pumped off as before. These operations are continued until no further hydrogen is collected in the buret. The hydrogen is allowed to stand until it reaches the temperature of the water jacket. The stopcock W is opened to the atmosphere, and the difference between the barometric pressure and the height from the mercury surface in V to the mercury surface in U gives the pressure of the hydrogen. From the volume of hydrogen under these conditions of temperature and pressure, the weight of water which was dissolved in the known weight of gasoline is computed. Preparation of Sodium-Potassium Alloy
Figure 6-Apparatus for Preparation of Sodium-Potassium Alloy
Figure 7-Apparatus for Purification of Sodium Potassium Alloy
-
SEPAFUTIONAND MEASUREMENT O F HYDROGEN-The apparatus used for removing the hydrogen from the gasoline and for measuring its volume is shown in Figure 5. The bulb F containing the gasoline and hydrogen is connected through the magnetic seal R to the long inverted U-tube leading to the mercury displacement pump Q, of approximately 200 ml. capacity. The pump is connected a t the bottom to the mercury reservoir S which can be opened either to pressure or vacuum through the two-way stopcock T. A capillary tube from the top of the pump joins it to the buret Ul graduated in 0.2 ml. The buret is enclosed in a water jacket and is connected a t the bottom to the mercury reservoir 8. This reservoir can also be opened either to vacuum or to pressure through the stopcock W . The stopcock X affords a means of transferring mercury from one reservoir to the other by proper adjustment of the pressures. The height of the U-tube above the surface of the mercury in X must be greater than 760 mm. to avoid forcing mercury over into the sample when pressure is applied in X. The buret and pump are evacuated by opening to the vacuum through the stopcock Y . During evacuation, the pressure in S is adjusted so that the mercury does not rise to the joint with the inverted U-tube. The pressure in V is also adjusted so that the mercury does not close the capillary tubing. When the system is evacuated, the stopcock Y is closed and the mercury in V run up into the buret just above the joint with the capillary tube. The gasoline is frozen in liquid air and the magnetic seal at R broken. Air is admitted through T and the hydrogen in Q is displaced into the buret by the mercury from S. As soon as the mercury has run over into the buret, T i s opened to the vacuum and the mercury in ’ Q is drawn back into S. Time is allowed for the diffusion of hydrogen from F into Q, and this in turn is displaced into the buret. This process is repeated until all of the hydrogen above the frozen gasoline is collected in U . The efficiency of the pump depends upon the ratio of the volume of the bulb Q to the volume of the space between the top of the gasoline surface and the point a t which the connecting tube joins Q. I n the present case this ratio was approximately 7 to 1.
Sodium-potassium alloy, rather than either sodium or potassium alone, is used to liberate hydrogen from the water dissolved in the gasoline samples, because the alloy, when made up of approximately equal amounts of sodium and potassium, is liquid at room temperatures and can therefore be more easily introduced into the samples. The use of alloy instead of either sodium or potassium alone is also preferable because the liquid alloy maintains a fresh active surface.
J
I u
I
b.! 1
H
Figure 8 -Apparatus for Subdivision of Sodium-Potassium Alloy
Complete evolution of the hydrogen can be accomplished only if the alloy is entirely free from oxides, since the oxides react with water without the liberation of hydrogen. It is necessary, therefore, to remove all oxide from the alloy and t o store it in small samples in containers of a design suitable for introducing it into the gasoline without allowing it to come in contact with air. Diagrams of the apparatus used in the preparation of the alloy are shown in Figures 6, 7, and 8. The apparatus shown in Figure 6 consists of the three Pyrex bulbs B, C, and D, and the side arm A . The whole system is sealed to the vacuum line. The bulbs are connected by heavy-walled glass tubing or by constrictions, and just above each constriction is placed a fine-mesh copper screen which hinders the passage of oxide while allowing the alloy to pass through. The lower end of bulb D is closed with a magnetic seal. Small pieces of sodium and potassium in approximately equal amounts are
352
Ah7AL Y !!'I CAL EDITION
placed in the side arm A , and the open end is then sealed off. The bulbs are opened to the vacuum, but complete evacuation a t this point is not practicable because the removal of all the kerosene in which the sodium and potassium were stored requires ail extremely long time. While the system is being pumped, the side arm is heated to melt the sodium and poVacuum
Vol. 3, No, 4
the amount of water added and the amount computed from the hydrogen evolved. The apparatus used for drying the gasolines is shown in Figure 9. The bulb D, with the side arm magnetic seal B and the side arm C containing a sample of sodium-potassium alloy, was fused to the vacuum line. Gasoline was introduced through A and frozen in liquid air in the bulb D. The tube A was then sealed off and the space above the gasoline evacuated. The bulb D was next sealed from the line a t E , and with the gasoline still frozen, the tip in C 'was broken, allowing the alloy to run into the gasoline, after which C was sealed from the bulb. The gasoline was allowed to warm up and stand with frequent shaking until no further hydrogen was evolved. The next step in the procedure was the removal of the hydrogen and dissolved gases from the dry gasoline and the transfer of a sample into a second bulb. This was acccmplished by means of the apparatus shown in Figure 10. The bulb D containing the gasoline was sealed t o the vacuum line and t o the bulb F as shown. The bulb F had three side arms, H , I , and .I. The arm H contained a weighed amount of water; I , a sample of sodium potassium alloy; and J furnished a means of connecting the bulb to other apparatus without contact with air a t a later step in the procedure. The bulb F was thoroughly evacuated and, with the gasoline frozen in liquid air, the tip a t B was broken. The hydrogen and dissolved gases were then pumped off by a method similar to that previously described. Vacuum
A
Figure 9-Apparatus for Drying Gasolines
tassium. TVheii the pressure is reduced to approximately 0.01 mm., the tube leading t o the vacuum line is sealed off and the apparatus tipped until the alloy runs from the side arm into the bulbs, finally collecting in bulb D. This bulb is then sealed off a t the constriction. The alloy contained in D is further purified using the apparatus shown in Figure 7 . This consists of the two bulbs E and F , similar to those used in the first step of the preparation of the alloy. The bulb D is sealed to these two bulbs, a piece of iron introduced into the side arm, and this arm sealed to the vacuum line. The bulbs E and F are then evacuated to 0.0001 mm., and the magnetic seal broken. The alloy runs through the screen in E and is collected in F. The space above the alloy is again evacuated. The operation described above is repeated, after which the alloy is usually free from oxide, though occasionally it is necessary t o filter again. The final step is the subdivision of the large amount of alloy in F into individual samples which can be transferred to the gasolines without coming in contact with air. Figure 8 shows the apparatus used. The bulb G usually has as many as twelve side arms, H , each of which is closed by a magnetic seal. The bulb F is sealed to G and a piece of iron placed in the side arm which is then fused to the vacuum line. The bulb G and the arms H are evacuated to 0.0001 nim., and the magnetic seal broken. The alloy is collected in G, which is then sealed from the line. The bulb G is tilted until each side arm is separately filled with about 2 ml. of alloy and sealed off. These individual samples are then ready for use in the experiments previously described. Test of Method
The accuracy of the method used for determining the water dissolved in gasolines was tested by several experiments in which known amounts of water were added to previously dried gasolines. A comparison could then be made between
Figure 10-Apparatus
for Addition of Water t o Dry Gasolines
The dry, gas-free gasoline in D was distilled into the bulb F , which was then removed from the system by sealing a t G, the tip a t H was broken with the gasoline frozen, and the water condensed into F. The alloy was then allowed to run into the gasoline by breaking the tip a t I , and the two arms H and I were sealed off from F . The alloy was shaken with the gasoline which was allowed to warm up. Finally the hydrogen evolved was removed from the gasoline by means of the mercury displacement pump and measured in a buret as described in the general method. A comparison of the amounts of water added to 50 ml. of fuel 15with the amounts computed from the hydrogen evolved is shown in Table 11. Consideriiig the difficulty of weighing. out such small amounts of water, the agreement i s good. Table 11-Comparison WATERADDED Cram
of Amounts of Water Added a n d Amount Found by Analysis WATERFOWND Gram
0.0029 0 0026 0 0022
I
INDUSTRIAL AND ENGINEERING CHEMISTRY
October 15, 1931
Experimental Data
The method described above was used to measure the solubility of water in five aviation gasolines a t the temperatures lo", 30°, and 50" C. A description of these gasolines is given in Table I11 and their specification data in Table IV. Table FUEL 10 12 13 15 19
Ill-Description of Gasolines SOURCE Oklahoma natural gasoline West Virginia natural gasoline California crude Midcontinent crude Oklahoma natural gasoline
Table IV-Specification ---TEMPERATUREFUEL At 10% At 507, O C .
10 12 13 15 19
42 6s 68 68 48
O
C
64 80
93 101 65
Data on Gasolines
O C .
Loss 70
110 110 124 139 110
2 3 0 4 13 1 4 16
At 90%
6O0/6Oo SPECIFIC RESIDUE GRAVITY
% 0 9 1 8 13 1 3 12
0 0 0 0 0
677 695 733 718 682
The data recorded for each measurement are the volume, temperature, and pressure of the hydrogen. From these data the weight of water in the known weight of gasoline is computed, and finally the weight of water in 100 grams of gasoline according to the equation S =
In this equation, S is the solubility in weight per cent, P is the pressure of the hydrogen in millimeters of mercury, V is the volume of hydrogen in milliliters, t is the temperature of the hydrogen in " C., and W is the weight of the gasoline sample in grams. The data recorded and the solubility values computed from them are given in Table V. The solubility is very small and is roughly of the same order of magnitude for the fuels investigated-namely, 0.01 per cent. Based on check determinations, the average deviation in solubility is 0.0006, so that the precision of the method may be taken as somewhat greater than 0.001. Table V-Data on Solubility of Water i n Gasolines TEMP. OF SATURAWT. OF -HYDROGEN-FUEL TION SAMPLE Vol. Temp. Pressure SOLUBILITY C. Grams MI. C. Mm. W/.% 10 10 24 04 6 61 31 2 246 0 0128 8 67 26 0 283 0 0160 30 29 59 50 21.17 7 87 28 2 271 0 0193 22 01 12 10 3 05 31 0 193 0 0051 33 56 30 4 91 26 0 237 5 0 0067 32 29 50 5 26 29 5 237 0 0074 24 66 13 10 3 99 29 0 212 0 0066 18 98 10 3 81 34 2 201 0 0076 32 82 30 4 99 27 0 236 0 0069 50 37 84 8 15 32 0 270 0 0110 20 27 50 5 44 28 7 215 0 0111 15 10 22 84 3 27 32 0 214 0 0058 10 30 00 4 01 35 0 211 0 0053 30 31 06 8 67 25 0 295 0 0158 30 28 17 9 79 26 5 279 0 0187 50 28 41 10 39 27 0 295 0 0208 19 10 22 35 2 61 31 5 163 0 0036 32 05 3 93 30 26 0 214 0 0046 30 29 35 3 91 2s 2 216 5 0 0061 30 25 87 3 81 2s 0 217 0 0057 30 22 25 3 28 26 1 196 5 0 0056 29 25 4 22 30 25 3 205 0 0056 30 30.08 3 49 28 0 207 0 0051 20 14 30 3 23 26 0 211 0 0066 30 28 54 5 76 26 5 262.5 0 0065 30 5 81 27 50 24 2 239.5 0 0074 50 31 05 4 59 27 2 220.5 0 0063
The solubilities are also shown graphically in Figure 11 as a function of the temperature. With the exception of fuel 15, the datado not suggest that they should be represented by anything except straight lines. In the case of fuel 15, the change of solubility with temperature is much greaten than for the other gasolines. Since in good agreeinent, the data on
353
weight with those on the other fuels. This exception probably vitiates any general conclusions regarding the temperature coefficient of solubility, other than that the solubility increases with increasing temperature. The apparent exception observed in connection with fuel 15 is not unexpected when the effect of chemical composition on water solubility is considered. Thus Groschuff and Clifford have found that the solubility of water in benzene is approximately five times that in gasoline, and that the temperature coefficient of solubility is much greater than that for gasoline. Similar differences might be anticipated between the different hydrocarbon series. While the composition of fuel 15 is not known, it might reasonably be expected that there would be differences in the temperature coefficient of water solubility between gasolines from widely differing crudes or of diverse composition. Comparison with Previous Results
The only data found in the literature on the solubility of water in gasolines were obtained using the calcium chloride method. Clifford (3) measured the solubility of water a t three temperatures in a gasoline of specific grayity 0.70 and his results are as follows: SOLUBILITY
TEMPERATURE
c.
Wt % 0 0085, 0 0110 0 0161, 0 0121 0 0175, 0 0145
25 0
35 0 37 5
The Army Air Corps (e), using the same method, found that the solubility of water in a domestic aviation gasoline a t 75" F. (23.9" C.) was 0.007 per cent by weight.
Temp,
' C
Figure 11-Effect of Temperature on Solubility
This same method was used by Uspenskii (5) to measure the solubility of water in four gasolines a t two temperatures. The results obtained are as follows: GASOLINE Grozny "avis" Grozny, grade I Grozny, grade I1 Baku, grade I1
100 0 0 0 0
c.
007 006 006 005
SOLUBILITY 220
c
0 011 0 008 0.00s 0 008
The values obtained by these investigators m e of the same order of magnitude as those found in the present work,
354
ANALYTTCAL EDITION
and all of the results are in agreement that the solubility of water increases with increasing temperature. The only indication of the precision of the calcium chloride method is given by the duplicate determinations of Clifford, which show an average deviation from the mean values of 0.0016, as compared with 0.0006 by the sodium-potassium alloy method. However. too few data have been obtained bv either method to justify too close a comparison of the relitive precisions. Since the increased precision found was obtained by a very marked increase in the complications and time involved, additional work on simpler methods might be more profitable than further development of the method used in the present investigation,
Yol. 3, KO.4 Acknowledgment
This investigation was undertaken as part of a fundamental study of vapor lock in airplane fuel systems in cooperation with the Research Committee of the Society of Automotive Engineers, and was made possible by a contribution from the Naturaline Company of America. Literature Cited (1) Allen and Jacobs, Bur. Mines, Tech. Paper 25 (1912). ( 2 ) Army Air Corps, A i r Service Informatzon Circ. 320 (1922). (3) Clifford, J. IND. ENG.CHEM.,13, 628 (1921). (4) Groschuff, E2ektrochem,,17, 348 (1911). (6) Uspenskii, Neftyanoe Khozyaistvo, 17, 713 (1929).
Determination of Small Quantities of Sulfur and Chlorine When Present in Turpentine' W. C. Smith INDUSTRIAL-FARM PRODUCTS DIVISION, BUREAUOF CHEMISTRY AND SOILS,WASHINGTON, D C.
Small quantities of sulfur and chlorine in turpenITHIN the past few a method, D-90-26T (1, d ) , tine can be determined quantitatively by using the years there has apfor d e t e r m i n i n g sulfur in Kennedy sulfur lamp with A. S . T. M. Method D-90-26T. naphthas and i l l u m i n a t i n g p e a r e d on t h e Sulfur was found in all samples of refined sulfate wood naval-stores market of this oik. This method consists, turpentine tested. Chlorine was found in only three briefly, of burning the oil country spirits of turpentine out of ten samples tested. The sulfur content of wellrecovered during the manufor a specified t i m e in a refined sulfate wood turpentine is so small as to escape facture of paper pulp from weighed l a m p m a d e from detection by the usual qualitative methods. a small E r l e n m e y e r flask. p i n e wood b y t h e sulfate process. T h i s class of The gases of combustion are turpentine is known both here and in Europe as sulfate wood drawn by suction from the chimney through a known quantity of standard sodium carbonate solution. At the end of turpentine. Except as regards odor, sulfate wood turpentine can be the specified time, the flame is extinguished and the lamp is made to meet the generally accepted specifications for gum again weighed. The quantity of oil used €or the deternhaspirits of turpentine or steam-distilled wood turpentine. The tion is found by the difference in the two weights of the lamp. odor of refined sulfate wood turpentine, while mild and inof- A blank determination is made a t the same time by burning fensive, is characteristic. It can be readily distinguished from alcohol in place of the oil. The excess of sodium carbonate is the odor of gum spirits or the usual steam-distilled wood tur- titrated with standard acid. From the difference in the quanpentine, but may be confused with the odor of the turpentine tity of sodium carbonate neutralized by the blank and the oil determination, the quantity of sulfur in the oil can be obtained in the soda process of pulp making. Crude sulfate wood turpentine is known to contain sulfur calculated. In attempting to apply the lamp method of the American compounds. Although no reference to the sulfur content of refined sulfate wood turpentine was found, it was thought that Society for Testing Materials for sulfur, it was found imposthis product might contain sufficient of these compounds to sible to burn turpentine with a smokeless flame. This difserve as another means of identifying this class of turpentine. ficulty was overcome by diluting a volume of the sample with Samples of authentic gum spirits of turpentine, of steam-dis- two volumes of absolute ethyl alcohol, but it was still necestilled wood turpentine, of refined sulfate wood turpentine sary t o watch the operation closely, and it required too much from each concern in this country known to produce this time to burn a sufficient quantity of turpentine to give satisproduct, an&in addition samples from several lots of imported factory results. In place of the lamp mentioned above, the sulfate wood turpentine, were used for the tests herein de- Kennedy sulfur lamp (4) with slight modification was found more suitable for the purpose. I n fact, turpentine was burned scribed. The usual qualitative tests made on the turpentine itself with a smokeless, luminous flame without the addition of did not ehow the presence of sulfur in any of the samples. alcohol. For the best operation of the lamp in burning turThe results obtained in tests with a sodium peroxide bomb pentine, it was found necessary to insert in the tube leading were not satisfactory on account of the limitation of the size from the fuel regulator to the vaporization chamber a wick of the sample used. It was found that by a tedious process of long-fiber asbestos to insure even feeding, to reduce the inof oxidizing a 5- or 10-cc. portion of a sample with fuming side diameter (mouth) of the burner to 2 mm., and to replace nitric acid and precipitating any sulfuric acid formed as after a few runs the plug of glass wool in the vaporization barium sulfate, the presence of sulfur compounds in the tur- chamber. With the Kennedy lamp in connection with Method Dpentine could be detected. The fuming nitric acid oxidation method, besides being dangerous because of the extremely 90-26T, samples of sulfate wood turpentine and also authentic violent reaction, does not give concordant results and therefore samples of gum spirits and steam-distilled wood turpentine were tested for sulfur. Excellent checks were obtained on cannot be used quantitatively. The American Society for Testing Materials has adopted duplicate tests. Whenever this method indicated the presence of sulfur, a confirmatory test was made by transferring 1 Received April 25, 1931.
