V O L U M E 23, NO, 2, F E B R U A R Y 1 9 5 1
377
Ite chief
8%. The lower limit of reliability was found a t a concentration of :illout 8 mg. of lactose per 100 ml. of protein-free filtrate.
sugars or to sugar phosphates. firming method.
Thr procedure developed for pure sugar solutions was applied dirc*rtly to zinc sulfate-bariuni hydroxide filtrates of mammary gl:tntl honiogenates. Aniong the rul)stances that were frequently atlited to homogenates such as itdenosiiie triphosphate, diphosphopyridine nucleotide, magnesium chloride, succinate, phosphate, Ii u v t o u r diphosphate, and cieatine, only the last compound wae fontid to interfere with the sugar drterminations. \Vlitw galactose wa+ not addrd the analysis was somewhat *i1iiplifid. No galactow could b i z detected in lactating tissue : r i d the glucose content WNQ also very low. \Ithough the glucose content waq generally determined by dift t ' i t ' i i w a , it as found p o 4 h l e to obtain an independent check by tlicb i i w of the Tauher-Kleiner method ( I . < ) .
Various phases of this investigation were supported by the Office of S a v a l Research, Contract N6 onr-218, by the Graduate Research Council, Oregon State Board of Higher Education, and by the Cyrus AI. Warren Fund of the American hcademy of Arts and Sciences. The authors are indebted to the Itohm & Haas Co., Philadelphia, for a sample of Lactase A concentrate; and to L. J. Wickerham, Northern Regional Research Laboratory, Peoria, Ill., to L. E. Wise, Institute of Paper Chemistry, Appleton, Wis., and to the Red Star Yeast and Products Co., Milwaukee, Wis., for yeast cultures and yeast products.
ACKNOWLEDGMENT
SUMMARY
1 ~ ; : r c ~ hot the methods investigated is applicable to the deterof lactose in mammary honiogenates, and presumably materials, when glucose and galactose are the only othvr sugars present. Kac.11 su1)stratc. or coenzyme added had to I N ' t t ~ t ~ a l c tt tu a separate vnriahlv t t n d appropriate measures taken t o r i ~ t i ~ o veach e interfering substarice not normally present in ni:i tuiiiarj. gland. When lactose was determined i n aliquots of t I i i a siiiiie wniple with each niethotl, the same result as olit,ained \vi thin the limits of experimental error. T h v i*olorimetrir method i,+ by fttr the most corivcnient, but i i i i i s t be taken markidly to lower the concentration of reclriciriy pugars other than lactose, to remove sugar phosphates, :rml t o rilniove cal(ium :illti 1):iriuni ion$, 1 tic, iise of lactase hm bren fourid v t q . convenient for :~rialyses w h i ~ r conl>~ glucose, p:rlactose. :ind I:icatose are present in tiwie 1)rel):tr.:itions. Tlits clifferential fermc.tit:itioii i i i t s t h o i t i h much more cuml)er. * i i t i i i . :ind tinie-cori.uniiiiy l i u f is rt*l:rtivclly inwnpitivca t o ot1ic.r niiii:ttioii
otlic~r.similar
( * N ~ ( L
r 7
value is that of a coli-
LlTERATURE CITED
Fearon, W. R., Analyst, 67, 130 (1942). Folley, S. J., B i d . Rea., 24, 332 (1949). Grant, G. A., Biochem. J., 29, 1905 (1935); 30,2027 (1936). Harding, V. J., and Grant, G. A., J . B i d . Chem., 94, 538 (1931) Hawthorne, J. R., Suture, 160, 714 (1947). Malpress, F. H., and Morrison, A. R., Biochem. J . , 45, 455 (1949).
Ibid., 46, 307 (1950). Nalder, M.E., University Microfilms, Ann Arbor, SIich., Pub. 224 (1940).
Selson, N.,J . Biol. Chem., 153, 375 (1945). Ramsdell, G. A.. J . Dairw Sei.. 28, 671 (1945). Scott, M., and West, E. F.. Proc. Soc. Exptl. Biol. .Wed., 34, 52 (1936).
Somogyi, M., J . B i d . C'hem., 160, 61 (1945).
Ibid.,p. 69. dprague, C. F., and Bellamy, W.I).J,. Bact., 57,95 (1949). Tauber, H., and Kleiner, I. Y., J . B i d . Chem., 99, 249 (1932). Voorst, F. T. van, Z . T 7 n f / r s u c h .Leb,nsm., 83, 414 (1942). Winder, R. J., Science. 99, 327 (1944). RECEIVED J u n e 26, 1950. Presented in part at the Regional Meeting of the A M E R I C ~CHEIIICAL V SOCIETY. Richland, Wash., J u n e 1950.
Determination of Oxygen in Zirconium Metal by the Vacuum Fusion Method J . K. STANLEY, JOAN YON HOENE, AND GEORGE WIENER Westinghouse Research Laboratories, East Pittsburgh, Pa. TWO methods are generally used for determining the oxygen content of metals: residue methods in which the metals are rtsinoved by some chemical action, leaving unattacked oxides, VArbides, nitrides, etc., which can then be further analyzed :iiiit the oxygen estimated. and reduction methods in which the ii\ictc,s are generally reduced 11y the action of carbon, but somet i tile3 by hydrogen, and the gases formed are analyzed These mc~thodsdetermine only the total oxygen. To date only the residue methods have been used for determiiiiiig oxygen in zirconium metal. Lilliendahl, Wroughton, : i t i d Gregory ( 4 ) discuss tITo nirthods. One method consists of votiipletely burning the metal to oxide and calculating the oxygen t i o m the increasc in weight. Obviously, one must have a comp l t b t t l analysis of the sample for nietallics, including hafnium, :iiicI iionnietallics, such as carbon and nitrogen. The other iiic~tliod consists of reacting the zirconium with chlorine and vaporizing the zirconium tetrachloride. The oxide, carbide, :inti possibly nitride, then remain. The carbon and nitrogen cwntt,nts must be known Itclad and Zopatti ( 7 ) have devised a method of determining
I
oxygen, which is bawd oii the fact that zirconium and most of the metallic impurities may be volatilized as chlorides upon treatment with dry hydrogen chloride gas a t temperatures as low as 450" C. The residue methods generally require long times (hours) to make a single analysis; the procedures are tedious because of the many manipulations, and in many cases the results are open to various uncertainties (1-9). In view of these considerations, it seemed desirable to consider the w l l developed vacuum fusion niethod for determining oxygen in metals. This method is rapid; the analyses require 15 to 30 minutes for a single determination. The procedure is relatively simple and the analysis is more positive; the presence of other metals, oxides, carbidw, nitrides, etc., does not interfere VACUUM FUSlON METHOD
The vacuum fusion method depends upon the reduction of the oxides by carbon in the fluid metal; the carbon monoxide formed is converted into carbon dioxide and this is then measured in ternis of its pressure exerted in a calihrated volume. The
ANALYTICAL CHEMISTRY
378 apparatus used has been described by McGeary, Stanley, and Yensen ( 5 ) . The vacuum-fusion method was first devised for determining oxygen in ferrous metals, but can be used for nonferrous metals as well. The determination of oxygen in nonferrous metals is generally done in a molten iron bath contained in a graphite crucible. In this way, the iron is saturated with carbon. The addition of a metal such as zirconium gives a dilute soIution of zirconium in iron. The zirconium oxide can then react with the carbon: ZrOl
+ 3C +ZrC + 2CO
When the present work was undertaken, there was some doubt as to the applicability of the method to the determination of oxygen in zirconium. However, Prescott (6) and more recently Kroll and Schlechton ( 3 )have shown that reduction of zirconium oxide with carbon can take place in vacuum. Walter (9) and Derge ( 1 ) have demonstrated successful methods for the determination of oxygen in titanium by vacuum fusion. Similarity of zirconium oxide and titanium oxide can be expected on the basis of the positions of titanium and zirconium in the periodic table and from thermodynamic data. The free energy and equilibrium constant for both the reduction of titanium oxide and zirconium oxide with carbon were calculated and indicate that the reduction of the oxides is possible. Consider the reaction: TiOa(s)
+ 3C(graphite) +2CO(g) + TiC(s)
K A = (PCo)* (A) The free energy, AFa, at 2173" K., is calculated to be -73,675 calories. (The temperature of 1900" C. was chosen for the rereaction because i t gave more reliable results than lower temperatures.) I n making this calculation a linear extrapolation of the data for titanium carbide and titanium oxide had t o be made from 1800" to 2173" K. Inasmuch as no transitions occur, this was believed to introduce only a minor error. The equivalent equilibrium constant, Ka, is 2.82 X lo7 a t this temperature. Consider the reaction:
The free energy, A F B , a t 2173" K. is calculated to be -19,200 calories, and an equilibrium constant, K B ,equals 87. The values for AFB and K B were calculated from the data of Preacott (6), which involved an extrapolation from 2015" to 2173" K.
Table I. Typical Results
Samvle Temuerature
c.
1
Sn
3 4
1050/1900
% 0.205
Spproxiniate Oxygen Content b
%
0.215 0.225 0.240 0.236 0.226
10
0.072 0.092 0.073 0 078
0.099 0,123 0,179 0.172
0.089D 0.089 0.089 0.089
Addkd
10 10
0.098 0,090
0.124 0.133
0.13~ 0.13
ldded Added
10 10
0.078 0.127
0.286 0.220
0.17D 0.17
...
10
Sddkd Added
10
1900 1850/1900
Oxygen by T'acuum Fusion
0.16D 0.18 0.16 0.16 0.16 0.16
1850/1900 Sdded Added Added
2
Reaction Sample Timea Weight Min. Gram 10 0.097 10 0.091 10 0,087 10 0.102 10 0.078 10 0,055 10
... 10 0.080 0.282 0.32C 10 0.065 0.292 0.32 Added 10 0.113 0.325 0.32 a Includes time at which sample was dropped t o time reaction was discontinued-Le., when gas evolution ceased as measured by thermocouple vacuum gage. b Analyses run b y chlorine volatilization method (C) discussed b y Lilliendahl, Wroughton, a n d Gregory (4), or were doped samples (D)-i,e., samples to which oxygen has been added deliberately and oxygen estimated b y weighing. 5
1900
Because no data are available for zirconium carbide, no independent check of the experimental results can be made. Subsequent experimental results given below, and the methods of Walter and Derge, qualitatively bear out the thermodynamic calculations, which indicate that both reactions are strongly favored to proceed as written. Procedure. The vacuum fusion apparatus, its manipulation, and a survey of the results obtainable have been presented ( 5 ) . However, certain modifications had to be introduced into the procedure before reliable and consistent results u ere possible on zirconium. This discussion therefore is concerned with the modifications which were necessary to get reliable data. The three modifications made in the procedure \?ere: 1. The addition of the zirconium sample must result in a dilute solution of zirconium in the iron. The required dilution can be obtained by using small samples (0.05 to 0.10 gram) and introducing about 15 to 20 grams of iron prior to the first zirconium samples. Thereafter about 1.5 grams of iron should be added before each sample is analyzed. Improper dilution of the zirconium with iron results in obtaining less and less oxygen on subsequent samples. 2 . The reaction temperature should be between 1850" and 1950" C., preferably on the higher side for consistent results. Temperatures as l o a as 1650" C. can be used, but in general the results will be on the low side. 3. The addition of tin in amounts up to 25% appears to facilitate the reduction of zirconium oxide. Additional amounts up to 50% tin did not noticeably affect the procedure. I t may be argued that increasing the heating time per sample would give results comparable t o those obtained by the use of tin. However, experiments with longer heating periods than 10 minutes failed to show any maasurable increase in the oxygen content.
The exact role of tin in this connection is not known. Originally Reeve (8) added tin as a flux to lower the melting point of his charge, but in the authors' case the operations are carried out a t about 1900" C., so that the tin in some Kay may affect the fluidity of the molten charge, n-hich mav be conducive to more rapid reaction of the carbon with zirconium oxide. PREP4RATION OF SAMPLES
The work reported here was carried out with small samples cut from large pieces of zirconium. As the success of the analysis depends upon the proper dilution of the zirconium sample in a mixture of iron and tin, samples of the order of 0.1 gram were used, because the apparatus could not easily be adapted to use greater quantities of iron and tin. The use of such small samples is no liability if the oxygen i h uniformly distributed. If the oxypt'n were heterogeneously distributed in a large section. samples of 1to 5 grams would hardly be representative. The nature of the sample touches on the whole philosophy of sampling. The best one can do is to take a sufficient number of samples, regardless of size, until a representative average value of oxygen in a section is obtained. The samples used xere cut to size x i t h a hacksaw and burrs were filed off, as they have a high oxygen content. After cutting and filing, the sample was washed in benzene and acetone. If necessary after cutting, the sample was etched in dilute hydrofluoric acid and washed in acetone. One precaution had to be observed in these analyses Invariably, if the zirconium sample came in touch with the graphite crucible at about 1900" C., as it 13-as introduced into the crucible for analysis, it immediately wetted the crucible above the molten iron and no oxygen analysis could be obtained. In order to avoid this difficulty, samples were wrapped with annealed iron foil approximately 0.5 X 0.5 inch (1.25 X 1.25 cm.) (SAE 1010 steel, 0.0015 inch thick) and neighing about 0.080 gram. The wrapped sample was then washed in benzene and acetone and introduced into the molten iron without difficulty, and reliable results were obtained. Oxygen due to the steel foil analyzed at 0.025% was equivalent to 0.002% on a 1-gram sampIe and this n-as subtracted with the blank, which averaged about 0.004%
V O L U M E 23, NO. 2, F E B R U A R Y 1 9 5 1
379
oxygen, based on a 1-gram sample, for a 10-minute analysis. This is higher than normal blanks (0.0005 t o O.OOl%), but could be decreased with longer degassing time. (Four hours at 2000 O C. were used in t,his work.) However, the blank as found is accurate enough for most sampltxs with high oxygen content. Oxygen content of the tin uscd for dilution was found t o he 0.007%. R ESU LT S
Some typical results and operating conditions are givrri in Table I. The results approximate the oxygen suspected in the samples prepared by deliberate additions of oxygen or by Lilliriidahl’s chlorine method ( 4 ) . The oxygen determined by vacuum fusion is higher than that estimated by doping-i.e., oxygen is added deliberately by oxidation and t,he weight increase is determined; this might be expected if the oxygen content of the starting material before doping is not accurately known. The agreement between the vacuum fusion method and the chlorine mtlthod is reasonably good.
The vacuum fusion method is very rapid, as it requirrs only about 20 minutes per sample. LITERATURE CITED
(1) Derge, G., J. Metals, 1, 31-3 (1949).
(2) Kelley, K. K., U. S. Bur. Mines, Bull. 476 (1949). (3) Kroll, W.J., and Schlechton. A. W., Tmns. Electrochem. Soc., 93, 247-58 (1948). (4) Lilliendahl, JT. C., Wroughton, D. M., and Gregory, E. D., J . Electrochem. SOC.,93, 235-47 (1948). (5) McGeary, R. K., Stanley, J. K., and Yensen, T. D., Trans. Am. SOC.Metals, 42, 900-16 (1950). (6) Prescott, C. H., J . Am. Chem. SOC.,48, 2534-50 (1926). (7) Read, E. B., and Zopatti, L. P., “Determination of Oxygen in Zirconium Metal.” Pittsburgh Conference on Analytical Chemistry and -4pplied Spectroscopy, Pittsburgh, Pa., Feb. 15 to 17, 1950. (8) Reeve, L., Am. I n s f . M i n i n g Met. Engrs. Trans., 113, 82 (1934). (9) Walter, D. I., ; i s . i L . CHEM.,22, 297 (1950).
RECErVED June 16, 1950. Laboratories.
Scientific Paper 1525, Westinghouse Research
Effect of Temperature on Density and Refractive Index on Organic Compounds of Various Cox Chart Families R . R. DREISBACH T h e Dow Chemical Co., Midland, Mich.
THE author’s paper on the Eykman equation ( I ) , it was demI onstrated that this empirical equation relates liquid density for a narrow temperature range S
and refractive index accurately around room temperature. Kurtz, Amon, and Sankin ( 4 )demonstrated that this equation was applicable over a wide range of temperature. Ward and Kurtz ( 5 , 6 ) iecommended that the empirical equation, An = 0.6 Ad, was accurate for hydrocarbons for small changes of temperature, and a column in the tables ( 4 )demonstrated the variation of the value of ~ E Icalculated by this formula from determined values Griswold ( 3 )differentiated the Eykman equation:
(n2 - 1) (n
1
+ 0.4) x -d = c
and obtained: An/Ad = dn,/dd =
+ 0.4)’ + 0.1)2 + 0.81
C(n (n
Griswold ( 3 )demonstrated that the coefficient 0.6 was good for hydrocarbons where the C value was 0.74 or greater, but that where the C value was low, as in the case of nonhydrocarbons, the coefficient of proportionality b e t w e n n and d might be as low as 0.3. Iheisbach and Martin tabulated the C values for 98 organic compounds in 15 Cox chart families. This C value varies from 0.80806 for m-divinylbenzene t o 0.31522 for 1,2,3-tribromobutane. This coefficient is in all cases very close t o 0.80 times the C value and, hence, the variation of refractive index with density can he represented by: An/&! = 0.SC
Table I. Refractive Index at 20” C., C Value of Eykman Equation, Variation o f Refractive Index with Density, a n d Ratio of Variation with C Value Compound
1.37500 1.50110 1,52406 Chlorobenzene o-Dichlorobenzene 1,55145 1.55972 Bromobenzene o-Dibromobenzene 1.51101 1,53763 1-Ethyl-4-vinylbenzene 1-Brorno-3-vinylbenzene 1.59268 1,57610 Divinvlbenzene 1.37850 Methyl ethyl ketone 1.42913 n-Octyl alcohol 1.37160 Acetic acid 1.37239 Ethyl acetate Xitropropane 1.40161 1.54662 Nitrotoluene 1.41195 n-Amyl ether 1.50735 Phenetole 1.52521 p-Chlorophenetole 1,52684 Propionphenone 1.36638 Propionitrile 1,53262 8-Phenylethyl alcohol 1.54178 Phenol 1,58545 Aniline 1.4021 1 n-Butyl chloride 1.43901 1,2-Dichloropropane 1,50534 Perchloroethylene 1.53865 1 2-Dibromoethane 1,58597 1’2 3-Tribromoethane 1,46006 Carbon tetrachloride a Values from (1); all the rest from ( 8’).
C 0.76093 0.75000 0.62170 0.55211 0,48900 0.40000 0.78880 0.54459 0.80806 0.60854 0.47428 0.69036 0.55346 0.53488 0.61809 0.70009 0.69101 0.61209 0.68425 0.61778 0.68402 0.67055 0.74616 0.60481 0.50377 0.40947 0.32366 0.31822 0.38171
dn/dd 0.600 0.608 0.510 0.452 0.401 0.331 0.644 0.449 0.665 0.481 0.552 0.374 0.436 0.425 0.506 0.557 0.561 0.499 0.558 0.495 0.558 0.548 0.615 0.480 0.404 0.329 0.264 0.260 0.307
(l/C) x (dn/dd) 0.79 0.81 0.82 0.82 0.82 0.83 0.82 0.82 0.82 0.79 0.80 0.79 0.79 0.79 0.82 0.79 0.81 0.81 0.81 0.79 0.81 0.82 0.82 0.79 0.80 0.80 0.81 0.82 0.80
that) the difference between the two values of An is 0.0001 and, hence, when the value 0.80 is used the error in An v\-ould be less than 0.0001. LITERATURE CITED
(3)
The relat,ionship of Equation 3 holds a t temperatures of 10’ C. u p to 50” C., a t least in every case tested. Table I records the C value, the refractive index a t 20°C. ( n g )from ( 1 , 2 ) ,the dn/dd values calculated by means of Equation 2 and the ratio (dn/dd)/C. I n every case the ratio of Equation 2 lies between 0.79 and 0.82, except in the case of o-dibromobenzene, where it is 0.83. When the coefficient 0.80 in Equation 3 is replaced by 0.79 in one case and 0.82 in the other, it is found
n ‘2
(1) Dreisbach, R. It.,I n d . Eng. Chem., 40, 2269 (1948). (2) Dreisbach, R. R., and Martin, R. A., I b i d . , 41, 2875 (1949). (3) Griswold, J., Ibid., 42, 930 (1950). (4) Kurte, S.S., Jr.. Amon, S., and Sankin, A., I b i d . , 42, 174 (1949). (5) Ward, A. L., and Kurtz, S.S., Jr., ISD. EXG.CHEM.,ANAL.ED., 10, 573 (1938). (6) Ward, A. L., Kurte, S.S.,J r . , and Fulweiler, W. H., “Science of Petroleum,” Vol. 11, P. 1146, London, Oxford Universitv Press, 1938. REChIVED
lhIay 29, 1950.
