December, 1942
INDUSTRIAL AND ENGINEERING CHEMISTRY -
the native celluloses. Obviously, if such a penetration occurs, the reactivity index does not necessarily indicate crystallite size. The agreement between calculations and actual recoveries of severely hydrolyzed residues (Table 11) was much better than expectation. It is possible that the precipitating action of both constituents of the ferric chloride reagent on hydrocelluloses and cellodextrins is responsible. Even in the case of the viscose, intact-appearing pieces of yarn were present after 7 hours of digestion. Examination revealed, however, that such pieces had form only and were extremely mushy.
Acknowledgment The author is grateful for the assistance Of J* A* Habrle, who repeated many of the experiments described here.
148s
G
Literature Cited Birtwell, C., Clibbena, D. A., and Geake, A., Shirley Inst. itfern.,
5, 37 (1926). Frey-Wyssling, A., “Submikroskopische Morphologie”, Berlin, GebrOder Borntraeger, 1938. Mark, H., J . Phys. Cfiem.,44,764 (1940). Nickerson, R.F., IND. ENQ.CHEM.,33, 1022 (1941).
Ibid.. 34. 85 (1942). Nickerson, R: F., IND. ENQ. CHEM.,ANAL.ED.,13,423 (1941). Nickerson. R. F., and Habrle, J . A., unpublished experiments. Ost, H., Ann., 398,313 (1913). Taylor,
H. S., “Treatise on Physical Chemistry”. 2nd ed., p.
1028,New York, D.Van Nostrand Co., 1930. Urquhart, A. R., and Williams, A. M., Shirley Inst. Mem., 4, 167 (1925).
PREeroNTm before the Division of Cellulose Chemistry a t the 102nd Meeting of the AMERICAN CHEMICAL SOCIETY,Atlantic City, N. J. Contribution from the Cotton Research Foundation Fellowship at Mellon Institute.
Nomograph for Pressure Drop in Isothermal GEORGE W. THOMSON Flow of Compressible Fluids Ethyl Corporation, Detroit, Mich.
L
OBO, Friend, and Skaperdasl showed that the pressure drop in the isothermal flow of a compressible fluid may be readily obtained by means of the equation:
Since Equation 1 is quadratic, the solution for p z / p l gives two answers. At the tangent to the curve for a given value of Gzui/gpi,
where
This can be readily rearranged, by substitution of p,vl = pzvz, to give G2V2/gp2= 1, corresponding to critical flow conditions a t the outlet. Obviously, if (pZ/pJ2is less than GZul/gpl, critical flow conditions will be exceeded, which is impossible. Therefore the proper value of pz/pl is the one nearer p / p 1 , and the other value should be disregarded. As an example of the use of the chart, take p s / p l = 0.765 and G2vl/gpl = 0.137. When these two points on the chart are connected by a line, pz/pl is found to be 0.638, in agreement with the solution given in the sample c a l c u l a t i o n of Lobo, 0*5 Friend, and Skaperdasl.
A plot of p,/pl vs. pz/pr for various values of G2Vl/gp1 was used to solve Equation 1 for pz/pl. To avoid the difficulty of interpolation between the curves on their plot, an alignment chart is presented which gives a direct solution for p J p l .
3
t
Nomenclature
0.6 L
Any consistent set of
0.3
4
units m a y be used: D = diameter of pipe, ft. f a Fannin equation friction factor g = = acceleration due to gravity, 32.2 ft. G = mass velocity, lb. sec.-l f t . - 2 L = length of pipe, ft. PI = inlet pressure, Ib. f L - 2 pz = outlet pressure, lb. ft.-2
K
pn = pseudoterminal pressure, lb. ft.-e defined by Equadon 2 VI = specific volume of fluid, ft.a lb.-l
-
Lobo, W. E., Friend, Leo, and Skaperdas, G. T.,IND. ENQ. CHEM.,34, 821 (1942).
