188
ANALYTICAL CHEMISTRY
(6) Callan, T., and Henderson, J. A. R., J . SOC.Chem. I n d . , 41,157-
61T (1922). Cope, W. C., and Barab, J., J . A m . Chem. Soc., 38,2552 (1916). Cott,rell,T. L., MacInnes. C. A . , and Patterson, E. M., Bnalyst. 71, 207 (1946). DeVries, T., and Ivett, R. W., IND. ENG.CHEM.,ANAL.ED., 13, 339 (1941). Elving, P. J., and McElroy, W.R., Ibid., 14,84-8 (1942). English, F. L., J . I n d . Eng. Chem., 12,994-7 (1920). Friedrich, A., Mikrochemie, 7, 195 (1929). Friedrich, A., Kllhaas, E., and Schllrch, R., 2. physiol. C h m . , 216, 68-76 (1933). Hass, H. B., and Riley, E. F., Chem. Revs.,32,373-430 (1943). Heyrovskg, J., and Novak, J. V. 4.,X V I I I Cong. Chimie I n dustrielle A17ancy, 1938; Chimie et Industrie, 35, 1043-50 (1938). Knecht, E., and Hibbert, E., “New Reduction Methods ill Volumetric Analysis,” New York, Longmans, Green & Cornpany, 1st ed. 1910, reprinted with additions 1918 and 1925. Kolthoff, I. M., and Furman, N. H., “Potentiometric Titrations,” p. 304, New York, John Wiley & Sons,,!926. Kolthoff, I. M.,and Lingane, J. J., “Polarography, pp. 380-9, New York, Interscience Publishers, 1941. Kouba, D. L., Kicklighter, R. C., and Becker, W. W.,As.&L. CHEM.,20, 948-9 (1948). Kuhn, R., and Giral,,.!J Ber., 68, 387 (1935). Lunge, G., J . SOC.Chem. Ind., 9,547-9 (1890). Mehner, J . prakt. Chem., (2) 63,305 (1901). Mitchell, J., Jr., and Ashby, C. A., J . Am. Chem. SOC.,67,161-4 (1945). Muraour, H., Bull. soc. chim. France, 4546,1189-92 (1929). Niederl, J. B., and Niederl, V., “Organic Quantitative Microanalysis,” 2nd ed., New York, John Wiley & Sons, 1942. Pech, J., Collection Czechoslov. Chem. Commrin., 6, 126 (1934).
(27) Petels. J. P.. and Van Slvke, D. D.. “Quantitative Clinical
Chemistry, Val. 11, Metliodi.” Ralti&re, Williams and Wilkins Co., 1932. (28) Pierce, .4.E., and Riuing, M. M., J . .4m.Chem. Soc., 58, 13B:3 (1936). (29) Pitman, J. R., J . Soc. Chem. Ind., 19,982-6 (1900). (30) Pregl, r., “Quantitative Organic MicroanalyPis,” revised and edited by Julius Grant, 4th ed., London, J. and A. Churchill, 1946. (31) . , Rathsbure. -. H.. Ber.. 54B. 3183-4 (1921). . , (32) Rose, E. L., and Ziliotto, H., ISD. ENG.CHEM.,ANAL.ED., 17, 211-13 (1945). (33) Sargent, E. H., and Co., “Bibliography of Polarographic Literature,” June 1946. (31) Scott, W.W., “Standai cl Methods of Chemical Analysis,” 5th ed., Vol. I. D. 649, New Yo1.k. D. Van Nostrand Co., 1939. (35) Shaefer, W. E-, and Becker, W. W.,A X ~ LCHEM..19,307-10 (1947). (36) Shikata. M., Trans. Faraday SOC.,21,42 (1925). (37) Slotta, K. N., and Haberland, G., Ber., 65,127 (1932). (38) Sudborough, J. J., and Hibbert, H., J . Chem. SOC, 95,477-SO (1909). (39) Tachi, I., .Ifem. Coll. Agr. Kyoto I m p . Univ., 42,36 (1938). (40) Van Slyke, D. D., J . Biol. Chem., 9,195 (1911) to 23, 407 (1915). (41) Ibid., 83, 425 (1929). (42) Viebock. F., and Brechcr, C., b’er., 63, 2307 (1930). (43) Wienhaus, H., and Ziehl, H., Ibid., 65,1461 (1932) (44) Zerewitinoff, T., Ibid., 40,2033 (1807) to 47,2417 (1914). I
RECEIVED May 16, 1949. Presented before the Division of Analytical and Micro Chemistry, Symposium o n Determination of Nitrogen in Organic Compounds, at the 114th lreeting of the AVERICAN CHEMICAL SOCIETY, St. Louis, N o .
Physicochemical Micromethods of Test for Petroleum Products HARRY LEVIN, A. €5. MORRISON,
AND
C. H. REED
The Texas Company, Beacon, Y. Y .
Micromethods are described for pour point, titer, and vapor pressure, each of which employs less than 1% of the sample used in conventional macromethods. Comparisons are made between results by the micro- and macromethods.
B
ECAUSE the modern petroleum industry is concerned with
highly chemical operations and processes and miscellaneous organic and inorganic materials either as products of its own manufacture or items of purchase relating to its plant operations, microchemical procedures, both analytical and synthetic, are of intense interest and importance. However, miscellaneous physicochemical measurements-some very empirical-are also of great importance to this industry because they are used in control of manufacturing operations, included in customers’ specifications, and involved in analysis of samples from service and complaints. Macromethods are generally used, but occasionally the sample is too small; this frequently happens when the case is particularly important. Micromodifications of these macromethods have often proved a godsend. Methods for determining viscosity on microsamples of oil have been reported by Levin (7) and Cannon ( 4 )and micromethods for unworked and worked consistency of grease by Kaufman (6) and Hain (6). The present paper describes methods that have been successfully used on relatively small quantities of sample to determine the pour point of lubricating oil, titer of fatty acid@,and vapor pressure of gasoline. POUR POINT
By a simple modification of the well known practice of determining solidification or melting point of wax on a thermometer bulb, it has been possible on a drop of oil to obtain pour test re-
sults which agree very well, generally, with those obtained by the conventional A.S.T.M. method ( I ) involving some 30 or 40 grams of sample. The apparatus is shown in Figure 1. To make a determination, the bulb of the thermometer a t room temperature is dipped into the oil a t room temperature, to a depth of about 3 mm. If the drop of oil that adheres appears so large that it will be likely to fall off in subsequent manipulations, it should be reduced. The copper wire (No. 29 gage, 5 cm. long) is bent into a single loop 4 to 6 mm. in diameter a t one end a t a right angle to its stem, which should be cut to be 25 mm. long. The loop is applied to the drop of oil on the bulb where it adheres by surface tension, and the stem serves to magnify the movement of the drop in the subsequent observations. A vertically multiliied label pasted inside the pour test jar facilitates observation of the movement of the wire. The pour test jar, thermometer, etc., are now assembled in the customary manner and the assembly is preheated and cooled from bath to bath exactly as for an A.S.T.M. pour test. The assembly is removed for observation a t each temperature drop of 5’ F. (2.8’ C.). The maximurn period that the assembly may be kept out of the cold bath for an observation is 3 seconds, as in the A.S.T.M. method. The temperature a t which no movement is noticeable when the assembly is in a horizontal position for 5 seconds is 5’ F. (2.8 C.) below the pour point, as in the A.S.T.M. method. Oils of high pour point may be heated, before application on the thermometer bulb, to the same temperatures permitted in the A.S.T.M. maximum pour method. All manipulations, after the assembly of the apparatus, are in strict accordance with the A.S.T.M. method of test for maximum pour point.
V O L U M E 2 2 , NO. 1, J A N U A R Y 1950
189
The results obtained by this pour point microprocedure and by the A.S.T.M. (maximum) method on a number of types of oil commonly encountered are shown in Table I. The precision of the micromethod, as well as the agreement between its results and those by the -4.S.T.M. method, is within the tolerance of the A.S.T.RI. method. The one exception is that of undewaxed cylinder stock having a pour point on the order of 80" F. The authors have tried many conceivable variations of the pour point micronicthod, but could not correct the situation with regard to this stock. The micro pour test has been particularly useful as an aid i n establishing the identity of the unaltercd residue from used and oxidized lubricating oils, greaser, and deposits. TITER TEST
By still another simple modifiration, it is possible to obtain good indications of the titer on :t single drop of liquefied f:ttt\ :wids. The apparatus is shown in Figure 2. The tatty acid is melted on a steam bath and the bulb of the thermometer is clipped into the molten mass, as in the pour
point microdetermination. The thermometer is held in a test tube with a cork so that the copper wire is about 12 mm. from the bottom of the tube. With another cork the test tube is fixed in the pour test jar, which contains water a t room temperature; the cork has a small slit to permit vapors to escape. The assembly is placed in a beaker of water, a t room temperature, which is then heated until the thermometer is about 10" C. above the visible liquefaction point of the acids, and then the source of heat is removed. The pour test jar assembly is removed from the beaker and carefully tilted from the vertical position a t intervals of 0.3" C. fall in temperature, and the copper wire is observed for movement. The highest temperature a t which there is no movement of the wire is recorded as the approximate titer. The assembly is reheated, as before, to liquefy the acids and the observations on cooling are repeated, but this time the first observation is made a t 2 O C. above the approximate titer. The highest temperature at which there is no movement of the wire is rccorded as the microtiter, uncorrected. This value is corrected by a curve (Figure 3) correlating uncorrected microtiters with macrotiters (3) ohtained on acids recovered from the fats and greasrs, - _shown in Table 11.
In calibration the corrected value was seldom more than 1" C. away from the macrodetermination. The microtiter is generally reproduced within 0.6" C. The microtiter requires one drop of fatty acids, the macroprocedure some 20 VERTICALLY RULED PAPER Figure 2. Apparatus for Titer grams. PASTED TO INSIDE BACK Test The micromethod has contributed to the OF TEST JAR'\ OIL. ability to determine if grease left on ball and roller bearings which had "frozen" in storage was the grease intended, when the quantities available were much too small for macroproceCOPPER dures. The method was likewise uniquely applicable to the analysis of small amounts of grease recovered from bearings on a complaint that the product was too liquid and here, too, the qucstion was one of identitv. In each case the microtiter was Figure 1. Apparatus for Pour Point Test made on the fatty acids isolated from the soaps in which they were combined. The authors have used also a method Table I. ComDarative Data from Pour Point Methods involving a vacuum-jacketed microtube Viscosity, Pour Point, F. and thermocouple, to obtain a cooling Gravity, s. u. Viscosity A.S.T.31. Satnljle A.P.I. looo F. 210° F. Index max. hlicro curve simulating the macroprocedure for Pale oil 27.1 +20 +l5 180 , . 95 titer, but the results were no better than + -20 l5 Pale oil + lTo Paraflow .. .. .. .. those obtained by the much simpler de- 15 - 20 vice and procedure that are described in Pale oil + 1% Paratone .. , . , . .. +20 +l5 +20 +15 this paper. Pale oil 26.7 207 , . 84 +95 +95 A
rq; +95
Pale oil distillate
28.8
85
, .
68
Pale oil
23.5
104
..
57
Pale oil
20.4
311
..
0
Pale oil
19.5
761
, .
Airplane oil
27.0
..
97
94
Dewaxed cylinder stock (green)
22.9
..
191
85
Bright cylinder stock (red)
24.7
..
132
85
Undewaxed cylinder stock
22.1
..
161
75
Lard oil
..
..
..
6
..
+70
+70 - 45 45 -25 - 20 - 5 - 5 + 5 + 5 +35 +35
-
$9700 +65
- 40
- 40 -20
- 15
-5 0 0 0
4-30
+ 10
+c 255
+75 +40 +40
+50 +60 1-40 +40
+4-75 15
+ 5
VAPOR PRESSURE
An apparatus which has proved very satisfactory for determining vapor pressure on 1 ml. of sample in the gasoline range is shown in Figure 4. In use it is mounted on a stick calibrated in pounds per square inch, the customary system in the petroleum industry. The apparatus is a manometer (and leveling bulb) made of 8-mm. (outside diameter) glass tubing with a bulb, ap-
190
ANALYTICAL CHEMISTRY Table 11. Comparative Data from Titer Methods
Titer Test, O C . Nature or Source of F a t t y Acids ' Macromethod Micromethoda Neo fat 1-65 67.0 66.5 Palmitic acid 60.1 59.4 Snodotte acids 54.7 53.5 Stearic acid, commercial 52.9 51.4 Neo fat 1-13 50.8 50.0 hlyristic acid 48.8 47.2 Cocoa butter 48.2 47.0 Hydrogenated fish oil 46.4 45.0 Commercia! lubricating grease 44.5 43.7 Acidless tallow oil 42.1 39.8 Commercia! lubricating greaw 41.1 39.6 Conduit grease 40.2 38.3 Special lubricating oil 35.6 34.3 25% stearic acid 75% oleic acid 34.2 31.3 Oil from sheep hide 33.8 33.0 Commercial lubricating grraxr 32.4 31.3 Cottonseed oil 31.1 30 S o . 1 lard oil 30.8 28.6 Commercial lubricating grease 26.7 24.8 * Dirert thermometer reading; not from curve. I
~
30
20
Figure 3.
- ~~
40 50 T I T E R (MICRO) 'C
60
is closed. By lowering the leveling bulb a smallnegative pressure is imposed on the 15-cc. bulb. This effects equilibrium faster in subsequent operations. However, if the vapor pressure is relatively high, it may be necessary to raise the leveling bulb and impose a positive pressure to avoid loss of sample from the bottom of the 15-cc. bulb through the left arm of the manometer, during subsequent shaking. It wil! be pbvious nhen pressurizing is necessary. The apparatus is then put in a water bath at 100" F. (37.7" C.), and the rubber cap of an eyedropper is placed over the funnel-shaped outlet above the stopcock to keep water out of the apparatus. After 5 minutes the apparatus, exclusive of the leveling bulb, is shaken for about a minute without being removed from the water bath. The mercury level is returned to B by opening the pinchcock, which is then closed, and the pressure is read directly on the manometer. Several successive readings are taken to ensure acFigure 4. Apparatus for curacy. Determining Vapor To prepare for the next Pressure sample, the apparatus is taken from the bath, the rubber cap is removed, the stopcock is opened, the mercury level is raised into the opening above the stopcock, and the tested sample is removed with an eyedropper. It is advisable to remove also about 1 ml. of the mercury, in the same manner, to eliminate contamination by reaction products which tend to emulsify the surface layer of mercury and make precise level readings difficult. The mercury leveling bulb is lowered and raised several times to remove last traces of old sample by aerating the sample tube. The apparatus is then ready for a new sample. The elapsed time for a determination is about 30 minutes, during which several repeat readings are obtained on the contents of the microipparatus.
70
Correlation of Uncorrected Micro- and Macrotiters
proumately 15 cc., blown in the leg equipped with the s t o p cock, In the authors' apparatus the volume from line B to the stopcock is 4.18 cc. and 0.83 ml. of sample is used, thus retaining theS.S.T.M. (2)requirementof 4 to 1 vapor to liquid ratio. The volume from B to the stopcock was determined by drawing mercury into the inverted apparatus through the stopcock, then weighing the mercury and correcting for the contents of the bore of the stopcock. To introduce the sample a screw plunge] micropipet, shown in the figure, is used. To make a determination the apparatus, with stopcock open and mercury level a t A , is placed in an ice-water bath for 10 minutes, a rubber cap sealing the open end above the stopcock, to exclude moisture. After about 5 minutes the mercury level is checked and if necessary readjusted (to A ) by opening the pinchclamp. Beginning with the mercury level at A eliminates the need for correcting for the change in air volume on going from ice temperature to 100 O F. The position of A is established by bringing the mercury level to B a t 100' F. and adding, as sample, Octoil S, closing the stopcock, and bringing the assembly to ice temperature. The new position of the mercury surface a t this temperature is A . The vapor pressure of Octoil S (Distillation Products, Inc., Rochester, N. Y.) a t 100" F. is practically zero. With suitable precautions to exclude moisture, the pipet a t a temperature of 32" to 40" F. ( 0 " to 4.4" C.)is filled to the mark with sample a t the same temperature, the sample is introdured to the apparatus through the bore of the stopcock, and the stopcoch
VAPOR PRESSURES,lbs. l i n g MICRO vr.f+S,lM
Figure 5.
Comparative Results b y Macro- and Micromethods
V O L U M E 2 2 , NO. 1, J A N U A R Y 1 9 5 0
191 4CK ?\io# L E D G M E N l
Comparative results obtained on gasolines by the microniethoti on 1-nil. samples and by the A.S.T.M. method requiring 130-ml.
samples are shown in Figure 5. The solid line is A.S.T.M. vapor pressure, located by points X ; the dots are microvalues and the numbers a t the dots represent the numbers of identical results obtained for the points shown, about half of them being repeats on one filling, and the rest individual tests on separate fillings. In practically every case the micro result is within 0.2 pound of the A.S.T.M. value. The standard deviation of the micromethod is 0.2 pound. This apparatus and technique can probably be adapted to eve11 smaller samples. The vapor pressure microprocedxe is useful in carburetor studies, test tube synthesis, stability studies, cstc. Xatelson ( 8 ) described an ingenious method for drterniining vapor pressure on a single drop of liquid. Vnfortunatrl>-, it is limited by its authors to pure substances and the present authors’ experience confirms its inapplicabi!ity to a mixture of hydrocsart)ons like gasoline. The present method is, of coursp. applic~ahlralso t o purr hydrowrhons in the ensnlinp range.
The authors express their appreciation to H. A. Mayen, E. J. Sklendr, and D. S. Stairs for their capable assi3tance in various phases of the experimental work, and to C. J. lnderson fnr his valuable aid in the preparation of the manuscript. LITERATURE CITED
(1) Ani SOC.Testing Materials, Designation D 97-39. 12) . , Zbid D 323-43. (3) . h o c . Offic. Agr. Chemists, “Official and Tentativr Methods of
.Inalysis,” 4th ed., p. 408, 1935. (‘annon, M.R.. and Fen3ke, M . R , IND.E ~ GCHEM., . ANAL.Eu., 10, 297 (1938). ( 5 ) Hain, G. M., .\m. SOC.Testing Materials, Bull. 147 (1947). (6) Kaufman, G., Finn, W. J., and Harrington. R. J., INn. F ~ o . CHEIC., A N A L . E D . , 11, 108 (1939). (7) Levin, I1 . Ihid.,9; 147 (1937). (8) Natelson, S., and Zuckerman, J L.. I h i d . , 17, 739 (1945, (4)
RECEIVEDM a y l Y , 1949. Presented in [)art before the Division6 of .Inalytical and Micro Chemistry and Petroleurn Chemistry, Spniposium on Microchemistry and t h e Petroleum Industry, at the 115th l f w t i n g of t h P .AMERIC A T C H E \ I I C A L SOCIETY, 6an Franciaro. Calif.
Manometric Apparatus for Gas Measurements on Packaged Materials J. L. BLATT A y D PI’. P. TARASSUK Dairy Industry Division, University of Calijornia, Davis, Calif. \-RECEXT years, there has been an increasing interest in the
.relation of quality deterioration of various food and industrial products to the nature of t,he atmosphere surrounding the material during its processing or storage (1-5, 7-9). Some useful correlations have been made simply by the analysis of gases taken from containers before and after the material has been subjected to test conditions. However, in order to correlate certain quality changes with absolute gas pressures, or with milliliters (S.T.P.) of atmospheric gas per gram of packaged material, it is necessary also t o determine t,he effective volume and pressure of the confined atmosphere, and it is preferable, though usually not, possible with most equipment, to make all measurements in a continuous integrated procedure. Cartwright ( 3 ) has described a noteworthy apparatus xhich, in addition to permitting the determination of quality and quantity of gases about dry materials in all manner of containers, is adaptable to the detection of leakage in dry vacuumizcd packages, to the determination of gas permeabilities of packaging materials, to the determination of densities of dry irregular substances, and to the estimation of air entrapped in powders during manufacture. A portion of gas from a test container is transferred into a buret evacuated with a mechanical pump. The volume is read following compression under mercury to atmospheric pressure. By using a leveling bulb and manipulating three of the system’s five stopcocks, this gas is expelled and a similar fraction is introduced and measured. The original volume and pressure of gases in the container are derived from these values. The measurement of barometric pressure is determined separately. Samples of gas for analysis may be withdrawn from the container and transferred to an appropriat,e system. Fair reproducibility and accuracy are demonstrated when the packaged materials are essentially “dry” and relatively nondesorbing of gases during the procedure. In the use of a simplified manometric apparatus the limitations of moisture and desorption inherent in Cartwright’s method are largely overcome, and distinct advantages in simplicity of construction and operation and precision in measurement are gained.
I n this procedure, the gas piessure and free space volume in a container are derived from the measurement of pressure when the volume of the container gases is expanded b?? t n o fixed amounts,
Tf rontainer ) P, = original gas pressure in the container Va = volume of one expansion Vb = volume of another expansion PI = pressure of gases after expansion into V.-Le., pressure a t volume VI = ( V , V5) P, = pressure of gases after expansion into Vb-i.e., pressure a t volume Vp = ( V , vb) and the temperature and the number of gas molecules measured remain constant, = an rinhiown volume (the effective free space in a
+ +
PzVz = K = PiVi = Pi(Vz
+
Vo)
PzVp = P*(V.z +
V b )
from which
or preferably
and Once the Pp/P1 ratio is found, graphs or tables may be constructed to eliminate the individual calculations of V , anti the pressure factor
(‘
z:
inasmuch as V , and Vb are constants.
Components which of necessity are common to both manomrtric and volumetric systems are a puncturing device, a means for clearing the system of contaminating gases before measurements are made, a measuring chamber into which containrr gases are expanded, a leveling system for the transfer and compression of gases, and a communicating pmsagi. to a gas analyzing system.
