558
ANALYTICAL CHEMISTRY
used for several years in the authors' laboratory with very satisfactory results in the following special applications: Determination of water in stocks of high vapor pressure such as propane and the butanes. Determination of water in colored stocks such as lubricating oils, transformer oils, etc., in which the color bodies are not solubla in the glycol. Studies of the water solubility-temperature relationship for hydrocarbons over the temperature range 60" to 180" F. There seems no reason to doubt that the upper temperature may not be further increased. SUMMARY
-4modified Karl Fischer method for determining the water content of hydrocarbons and petroleum fractions involves extraction of the water from the hydrocarbon by dry ethylene glycol and subsequent titration of the glycol with Fischer reagent. With one extraction, over 90% of the watc,i present in the hydrocarbon is absorbed by the glycol. Increased accuracy with stocks of low water content mav be obtained by concentration of the water from a large volume of hydrocarbon in a small volume of extract. The difficulty of titration in a two-phase liquid is eliminated. The method is applicable t o high vapor pressure stocks such as liquefied petroleum gases. Colored stocks, such as lubricating oils, transformer oils, etc., in which the color bodies are not soluble in glycol, may be analyzed for water without difficulty. This method may be used to determine the solubility of water in hydrocarbons and petroleum frartions at temperatures up to about 350" F.
Ackci and Frediani, ISD. Esc,. ( ' H E M . , ANAL. ED., 17, 793 (1945). Aepli and McCarter,Ibid., 17,316 (1945). Almy, Griffin, and Wilcox, I / , i d . , 12, 392 (1940). Am. SOC.Testing Materials, Conmiittee D-2, "Standards uf Petroleum Products and Lubricants," Philadelphia, 1948. Boeke. J., P h i l l i p s Tech. Rea., 9, S o . 1, 13 (1947). Fischer, Karl, Angew. Chcm., 48, 304 (1935). Gester, C . G., Cheni. Eng. Progress, 43, 117 (1947). Graefe, E., J . SOC.Chem. Ind., 25, 1035 (1906). Gremeko, B., S m o s t i T t k h n i k i , 6, 43 (1938). Griswold and Kasch, Iiid. E i i g . C'hem., 34, 804 (1942). Groschuff. E., 2. Elektrochon.. 17, 348 (1911). Hachmuth, K. H., WerterrL(;ria. 8, 55 (1931). Johansson, A , , Svensk Pappo'atidn,, 50, 11B, 124 (1947). 10,195 (193s~. Larsen, R. G., ISD. E x . curr&UiVT~ 6 Y 6 U JO 2 0 20 38 COMPOUND 4 2903 COMPOUND 3 -17 1 p r e p a r a t i o n of the 903 CUMPOUND 5 > > CUb 4u 4 1 u 38 final report as 4 7 20 38 2 9 0 3 C O M P O U N D 77 couPouND 8 -* 6 2 0 38 c o M P o u l l o 10 2903 COMPOUND 9 1 5 follows : Previously prepared “compound 3 20 38 COMPOUND 2 11 1 2 9 0 4 COMPOUND 1 name cards” as well 1 6 20 38 COMPOUND 4 1 2 4 2904 COMPOUND 3 57 3 20 38 COMPOUND 6 1 6 2904 COYPOUND 5 as cards to control 2 4 20 38 2 COMPOUND 8 a904 COMPOUND 7 2 a0 38 8 COMPOUND 10 2 9 0 4 COMPOUND 9 the proper repetitive transfer of totals are Figure 2. Form Printed by I.B.R.I. Machine as Final Calculations Are Being Made m e r g e d w i t h cards Sample number is at extreme left, followed by two double columns listing compounds and their corresponding summarizing the rcvolume per cent. (Blank column represents decimal point, since machines d o not print deeimal points.) Final t w o columns are checks which indicate correct machine operation. “Sample 2901” is a check substitution of part sults of step 2 above. of original data into inverse matrix Figure 1.
Form Used to Transmit Absorbence Data to Tabulating Department
ANALYTICAL CHEMISTRY
560 Samples of the submitted data sheet and the final report ale shonn in Figures 1 and 2.
curvature viere high in concentration, accuracy decreased as evidenced by a departure from 10091, total concentration. CONCLUSIO\S
SOURCES AND COWTROL OF ERROR
In a complex multicomponent analysis and calculation, sources of error may be both numerous and cumulative. Therefore, it is essential to recognize every source of error. In the analysis discussed above, errors may be classified as those of measurement, calculation, and theory. Sources of measurement errors include dilution and spectrometry. When instrument temperature was maintained constant to 0.5” C., no significant wavelength shifts were observed. The instrument maker’s cIaim of less than 0.5% transmittance error was well substantiated. In the computation, human error may be involved in the keypunching of the data on cards. Use of the verifier should greatly reducc the probability of undetected error. Once the data are piope111 punched machine errors may be minimized by incorpoi ating numei ous automatic safeguards. The pessimistic assumption is made that the machines will make all possible e n ors The operation incorporates check methods which are printed on the final report. Thus, the machines will signal an e110 1 0 1 fail to print the proper check values in the event of a misplacwi or missing card, incorrect operation, machine part failure, etc. .1 final proof consists of the substitution of a column of the calihration matrix for the absorbence data. The results appear 0. There is a small systematic error of about 0 . 1 7 , which is the cumulative effect of dropping rather than rounding off the last significant figure in successive steps. By far the largest error is that introduced by the neglect of cuivature in the absorbence-concentration curve. Although it is possible to perform second-order corrections ( 2 )using the I B.M. machines, the increased machine time outweighs the inci eased accuracy for most process study programs. The effect of curvature was minimized by measuring all samples in dilute solution. The nominal concentration thus averaged 1 to 3 7 for any one component, When the compounds that evidenced the gi eatest
Use of automatic computing equipment reduced calculation time to 3 minutes from a minimum of 15 minutes by desk calculator or 11 minutes by analog computer. The 3 minutes represents combined operator and machine time per sample w\.hen calculated in groups of 25 samples. The machines require operator attention less than half of the time. The cost of materials consists primarily of 10 cents‘ worth of cards per sample computed. I n a 6-month period, 750 ten-component analyses and computations were performed without an undue strain on the spectroacopy group. The rapid accumulation of an array of analytical figures greatly facilitated the n-ork of the process study group. ACKNOWLEDG\IER[T
The w i t e r is indebted t o David J. Pye for his interest and criticism of this work. Thanks are due to R. E. Clement of the International Business Machines Corporation for his cooperation. The permission of The Dow Chemical Company to publish this material is gratefully acknowledged. LITERATURE CITED
(1) Beiry, C. E., Wilcox, D. E., Rock, S. II.,and Washburn, H. IT- , J . davlied Phus.. 17.262 (1946). Brattain: R. R.,kassmussen. R. ’S,, and Cravath, d. 51..Ihid.,
14, 418 (1943). Crout, P., Trans. A m . Inst. Elec. Eiigr.?., 60,1235 (1941). Eckert, IT. J., J . Chem. Education, 24,54 (1947). Eckert, W.J., “Punched Card Methods in Scientific Computation.” New York, Columbia University Press, 1946. Fry, D. L., Xusbaum, R . E., and Randall, H. hI., J . d p p l i r d Phys., 17, 150 (1946). International Business Machines Corp., Sew I’ork, “Poiriter 461.” King, G. TT., J . Chsm. Ediacution, 24, GI (1947). TTaugh, F. V.,and Dwyer, P. S.. A n n . M n t h . Stat., 16,259 (19453. ~ E I V E DSeptember
1, 1919.
Rapid Photometric Determination of Iron in High Temperature Alloys MICHAEL STEVENS PEP1 Fairchild Engine and Airplane Corporation, Farmingdale, Long Island, S. Y . A rapid method for the photometric determination of iron in high temperature alloys is based on the reaction of the ferrous ion with 1,lO-phenanthroline. The sample is dissolved in aqua regia and a few drops of hydrofluoric acid, and diluted to 500 ml. A 10-ml. aliquot sample is reduced with hydroxylamine hydrochloride and the orange colored complex is formed by the addition of 1,lOphenanthroline. The reproducibility is good and the average error is *0.02% of the amount present.
T
HE chief sources for the work reported in this paper are
Fortune and hiellon’s complete report on the spectrophotometric method for the determination of iron with 1,lO-phenanthroline (2), and the miter’s work on the determination of iron in aluminum alloys ( 4 ) . A number of papers ( 1 , S , 5 , 7 )have reported on the use of 1 , l O phenanthroline for the determination of iron in a variety of d e s . A summary of the work done with 1,lO-phenanthroline up io 1944 was made by Smith and Richter (6). The purpose of the work described in this paper was the de-
velopment of a rapid and accurate method for the determination of iron in high temperature alloys based upon the orange colored complex formed by ferrous iron and 1,lO-phenanthroline. EXPERIMENTAL WORK
The preliminary work covering the follotving problems is fully described by Fortune and Mellon ( 2 )and the writer ( 4 ) . A suitable reductant for iron. A 17‘ solution of hydroxylamine hydrochloride was reported as the most effective reductant.
