I S D C S T R I d L .4SD ESGI-ISEERISG CHEMISTRY
July. 1925
tion, sinal1 deposition, higher temperature; (1)erosion and flaking, diminishing depoqit. higher temperature. Soot, pitch, coke. graphite are descriptive only physically and miid not be taken t o indicate chemical characteristics. This cyclic change can be explained as due to a change in the state of the carbon due to a rising temperature. Since the carbon has a heat conductive power only one fiftieth that of iron, it can be seen that the greater the formation the higher the temperature. This in turn changes the soft deposit into the harder, graphitic type. This material erodes and flakes off, exposing clean surfaces and produces bettter heat transference through the head of the engine. The interesting photograph of a badly carbonized engine after running under full throttle showing diminished deposits of carbon iq a n example of this type of action12 (Figures 1 and 2 ) . Summary
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Acknowledgment
The authors wish to take this occasion of acknowledging their gratitude to those who have advised and helped them in this undertaking. In particular they would like to express their indebtedness to Kaldemar T*ernet, director of research of the Boyce Cf; S'eeder Company, and Samuel Isermann. president of The Chemical Company of America and Van Dyke & Company, for their valuable advice, help, and cooperation. They also acknowledge the help given by Donald Brooks, formerly of the U.S.Bureau of Standards, a t Washington, D. C., for his management of the dynamometer laboratory a t Springfield, S.J. Additional References
The major factors of carbon deposition in an automobile engine are: (1) The amount of lubricating oil projected into the combustion chamber. This is by far the greatest factor. ( 2 ) The kind of oil used. (3) The temperature of the combustion chamber. (4) The extent of time the preceding factors have been in effect. A 3tudy of the effect of a large number of chemical wb1
stances on carbon is being carried out a t the laboratory and the results will be published in the near future.
4ulomofree i l ~ g 15,499 (1924)
4tkins, Aulomobile Eng., 1919,426. Bryan, J . A m . SOL.N a v a l Eng., 27, E3 (1916). Garner, J . Insl. Pelroleurn Tech., 7, 98 (1921). Holde and Mueller, "The Examination of Ilydrocarhon Oils and of Saponifiable F a t s and Waxes," 2nd ed., 1932. John XXey & Sons, I n c . James, A m . Petroleum Inst., Bull. 4, N o . 73, p. 132 (December31, 1923). Robinson, Atloiific Lubricator, 3, 8 (February, 1920). Spielmann, "Bituminous Substances. Scientific Progress of Practical Iniportance during the Ldst Fifteen Years," 1925. D. Van Nostrand 8: Company.
Pressure-Temperature Charts for Organic Vapors' By D. S. Davis
T
15'0 years ago, Cox2 brought forth R very convenient method of plotting vapor pressure data of hydrocarbons of the paraffin series. The present paper will show that this method may be applied with equal success to alcohols, organic acids, and the series of halogen-substituted benzenes. Cox plotted pressures in pounds per square inch on a logarithmic scale as abscijsas against the temperature in degrees Fahrenheit on the ordinate scale, which was not a uniform scale. H e obtained the temperature scale bv dr:irvina a
VAPOR
Figure 1-Alcohols.
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straight line a t a convenient angle to the horizontal which was to represent the curve for steam. Then from a steam table he marked points on the line a t preswres corresponding to temperatures from 30" to 700" F. and drew through them horizontal lines to represent the temperature ordinates. Cox found that when the vapor pressure data of the paraffin hydrocarbons were plotted on paper constructed in this way, all the curves mere straight lines and, further, that they intersected in a common point. Thus after the curves for anv two of the series are drawn and the
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Homologous Series CnH?. -
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F i g u r e 2-Organic
Acids.
Homologous Series CnHmOz
736
INDUSTRIAL A N D ENGINEERING CHEMISTRY
drawing a straight line through the coordinates of the boiling point and the point of intersection. The same method was used in plotting the data in this paper, but with the slight change of inverting the temperature scale to make it increase upward in the usual manner. Centigrade temperatures and Pressures in millimeters of mercury were used instead of the English engineering units. Once the tem///
Vol. 17, No. 7
that of isoamyl alcohol and does not, therefore, pass through the intersection of the others. The amyl alcohol line is also somewhat irregular on the plot of Figures 2 and 3 are the plots for the organic acid series and a series of halogen-substituted benzenes, respectively. It will be seen that for acids above isovaleric in the range below 5 mm. the lines are curved. However, they straighten out nicely a t 5 mm. and converge with the others as far as the existing data show. The lines for the benzene series, the data of which cover the greatest range of all, strike the points particularly well. Concerning the point of convergence which was off his plot, Cox wrote: "The temperature of this point cannot be determined directly since the scale can only extend to the critical temperature of steam." This temperature may be found as follows: If a plot is made of y. the distance in centimeters from 0" C. to any temperature, t o C., against t, the resulting curve is hyperbolic and not convenient for extrapolation. However, a plot (Figure 4) of the reciprocal of y against the reciprocal of t is a straight line and may be used for such extrapolations. Thus the temperature a t any point may be obtained from the straight line or from the equation connecting y and t, 230 1 y t=37.17 y
-
The accompanying table gives the coordinates of the points of convergence calculated with the aid of the equation. I
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8 Figure 3 - B e n z e n e
I
Series
perature scale has been laid off, this method of plotting is somewhat superior to that of plotting the logarithm of the vapor pressure against the reciprocal of the absolute temperature. This is because the Cox method leads, not only to straight lines, but to lines that are convergent, whereas the older method gives rise to distinctly curved lines fur the organic vapors considered here. There is no particular virtue in using steam as the source of the temperature scale except that its pressure-temperature range is so great and the data so reliable. The steam line may make any angle with the horizontal; hence any of the vapors of a given series may be used to obtain the scale, since this is only the equivalent of choosing a different angle for the steam line.
SERIES
Alcohol Organic acid Benzene
O
c.
610 520 1970
Mm. Hg
-*\
1,500,000 240,000 2,700,000
Extrapolation in the region of 2000" C. is probably uncertain by 50 degrees, whereas that below 1000" C. is easily good to 5 degrees. Sources of Data (Asreported in Landolt-Bornstein, Tabellen, 4th edition.) WATER: Scheel and Heuse Ann. P h y s i k . 31, (4) 715 (1910). ALCOHOLS: Methyl Ethyl Propyl
Nernst Ver. deul.'physik. Ges. i2, 565 (1910). Wiebe ' Z . I n s l r u m e n f e n k 13 '329 (1893). Holboin acd Baumann, inn.' P h y s i k , 31, (4), 945 (1910).
Ramsay and Young, Phil. Trans., 178A, 313 (1887). I b i d . 177 I 123 (lS86). Schmidt, 2. d h y s i k . Chem., 8, 628 (1891). Ramsay and Young P h d . Trans., 180, 137 (1889). Schmidt, 2. physik. k h e m . , 8, 628 (1891). Ibid. Grassi, Nuovo cimenlo, (31 23, 109 (1888).
Isobutyl Isoamyl Amyl ORGANIC ACIDS: Formic Landolt Ann. SupPl. 6 129 (1868). Ram_s_ai and boung, 'J.' Chem. SOC.(London), 59, 9 0 3 Acetic (18Yl). Schmidt, Z . Physik. Chem., 7, 433 (1891). Propionic lhid Butyric lbid Isovaleric Kahlbaum, Z . p h y s i k . Chem., 13, 34 (1894). Caproic I b i d . , and 26, 577 (1898). Heptylic Ibid., 13, 34 (1894). Cap ry I ic Ibid. Pelargonic Ibid. Caprinic Ibid. Isocaproic Young, J . Chem. Soc. (London),55, 486 (1889). BBNZENE SERIES:
Film Standardizer to Help Make Better Pictures
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Figure 1 is the pressure-temperature chart for the series of homologous alcohols of the type C,H2.+20. Amyl alcohol (not shown) shows irregular behavior in that its line crosses
Selection of movie films, camera plates, and printing papers suitable to the work in hand is to be aided by an instrument for the testing and standardizing of light-sensitive emulsions developed by Raymond Davis of the Bureau of Standards, and known as a sensitometer. The emulsions with which plates, films, and papers are coated vary considerably in speed and contrast, and in sensitiveness to x light ofe different colors. All these properties affect the use to which the product can be put. The Davis sensitometer will permit the exact measurement of all these factors, and the setting up of standards for them. It is, in effect, an instrument for giving a precisely known set of exposures t o a strip of the emulsion, and for making these exposures with a light of known intensity and color.
