837
V O L U M E 2 4 , NO. 5, M A Y 1 9 5 2 The amounts of anhydride found in the variods grades of lactic acid will fall within the following limits. Anhydride Content, % 0 8t01.2 15to4 9 to20
Lactic .kcid, 2%
44.50 80
BILB LIOC;R,4I’HY (1) Allen’s “C’oiiiinercial Organic Analysis,” 5th e d . , Yo]. I, pp. 763-8, Philadelphia, B l a k i s t o n Son & Co., 1923. Chem. Z ~ Q .35, , 26-7, Collegiurn, 1910, ‘73- 9 ; (2) Hesson. .4.A4., 1209-10 ( 1 9 1 1 ) : 36, 297 (1912). (3) Brindle, I I . , Quart. J . Yharm. Pharmacal., 4, 394-7 (1931). (4) Eder. R . , a n d Kutt,cr. F.,Helc. (‘him. i l c t a . , 9, 557-78 (1926).
(5) Gchrke, AI., a n d JVillrath, H. I€., 2. p h y s i b . Chem., .t142, :101-5 (1929). ( 6 ) G i r a u l t , F.. H7111. sci. pharmocol., 41, 331-8 (1934). (‘7) Afonin, I,., Rev. gin. mot. color., 14, 279-81 (1911). (8) National F o r m u l a r y , V I I I t h ed., p p . 290-1, 1946. (9) Selson, AI. E., “ M e t h o d s for D e t e r m i n i n g Lactic Acid and Theii, .\pplications in Studies on F e r m e n t a t i o n , ” thesis, Iowa S t a t e College, 1933. (10) T h o m p s o n , F. C., a n d Suauki, IC., ./. A m . Leuther Ciiemists’ .4ssoc., 13, 334-41 ( 1 9 1 8 ) ; ,J, Soe. I.ciith.er Trodrs’ Chem., 2, 115-21 (1918). (11) ITlaer, I,’,,a n d Seidel, I f . , M o / i , r / d ( , 18, , 138.41 (1897). (12) \Vatson. P. D., I n d . Eng. Chem., 32, 399-401 (1940). R ~ , C I ; I V EfDo r review N o w i u b e r 5 . 1!)51, Accepted Fehruary 6 , 1 l I X .
Analysis of the System Methanol-Ethylene Glycol-Water F K i S K It. CONKiD, SI. C. FLINT’, 1L 11. llb!YEKz, A N I ) J. W. SJOBEHG3 School of M i n e s and .IIetaEEurgy, L’nicersity of JIissouri, Rolln, .)Io.
In s t u d j ing the vapor-liquid equilibrium relations of the system methanol-ethylene glycol-water it was necessary to develop a method of quickly analyzing a mixture of these three components. Mixtures of known composition were prepared and the refractive index and density of each were determined and used to plot a triangular diagram. I t is possible by obtaining t h e refractive index and density of any mixture of these three components
to ascertain quickly the percentage composition of each component from these two determinations and the use of the diagram. Other samples of known composition w-ere tested for density arid refractive index. The results from the triangular plot compared favorably with the known compositions and were considered to be of sufficient accuracy for analysis of mixtures of these three components.
T”’
%\ stein metlianol -ethylene glycol-water a a s first investigated by Conrad, Hill, and Ballman ( I ) , who determined the freezing points of the system to ascertain the suitability of such mixtures for use as an antifreeze. The low freezing points obtained sceni to warrant further investigation of other properties of the syst>em. \Pork is in progress a t present, to determine the equilibriuni liquid-vapor compositions of tlrc system. It
address. T h e Atlantic Refining Co.. Washington, D. C. Present address, Dow Chemical Co., Pittsburg, Calif. Present address, Socony-Vacuum Oil Co., Augusta. Kan.
I Present
8
1.38 1.37
9 ’ 1.36
X
w n
z
1.32 00 0.I 02 MOLE FRACTION GLYCOL AT CONSTANT WATFR
I
Figure 2.
Refractive Index of Methanol-GlycolWater Mixtures
W
a
I
i
i 1.32 0.0 0.2 0.4 0.6 OS 1.0 MOLE FRACTION WATER AT CONSTANT GLYCOL Figure 1. Refractive Index of Methanol-GlycolWater Mixtures
was ncceisrry to evolve a suitable method for the anslysis of the system. The data presented here enable analysis of the system by use of the easily and rapidly determined properties, density, and refractive index. The ethylene glycol used in obtaining the data was obtained from the Carbide and Carbon Chemicals Corp. and was purified by distillation under a pressure of 40 mm. of mercury. -4twobulb distilling head filled with short lengths of glass tubing was used. Most of the glycol distilled a t a temperature of 119” C. Only the niiddle third of the distillate was retained tor use.
838
ANALYTICAL CHEMISTRY
The glycol thus obtained had a refractive index of 1.4314 nL0 and an absolute density of 1.1105 dz6. Values of refractive index found in the literature are 1.4311 nI,O (7), 1.4318 nZ,O ( 6 ) , 1.4314 n v ( S ) , 1.43178 nZ,O ( 4 ) ,and 1.4304 nLo ( I ) , and values of density are 1..1110 dzs ( d ) , 1.1097 d i 5 ( 7 ) , 1.1103 dzs ( I ) , and an absolute densityof 1.1101 d25(8). The methanol used was Baker and Adams absolute methanol, purified by fractionation in a Young distilling head having 20 constrictions and a length of 670 mm. Only the middle third, which distilled a t a constant temperature of 64.5" C., was retained for we. The methanol thus obtained had a refractive index of 1.3303
nb7 and an absolute density of 0.7865 dz5. The accepted value for the refractive index is 1.3304 nL7, and the density, calculated from the International Critical Tables ( 5 ) ,is 0.7869 di5. Distilled water from the laboratory still was further purified for use by addition of potassium hydroxide and potassium permanganate and redistillation through the same t e of column used in the methanol purification. The redistilB water was stored in aged bottles. It had a refractive index of 1.3333 nSo; the accepted value is 1.33335%so. The Abbe-type refractometer used in this work was checked against the standard crystal supplied with the instrument and was found to be correct a t that point. All thermometers used in this work were calibrated a t standard reference points. The refractometer was maintained a t a constant temperature of 20" f 0.1' C. and the water bath used for the density determinations was maintained a t 25 O 0.05' C. It was found most convenient to prepare a series of mixtures having a constant mole fraction of one component and varying mole fractions of the other two. The samples were prepared by first calculating the volume of each component required to give the desired concentrations. The methanol, glycol, and water were then added from burets to tared glass-stoppered weighing bottles. The bottle and its contents were weighed after the addi-
*
L
1.43 0 NJp
C 1
X
1.41
W
n
z W
1.39
L:
+
8 w
MOLE FRACTION WATER AT CONSTANT GLYCOL Density of Methanol-Glycol-Water
Figure 3.
Mixtures
1.37
LL
1.35
I
I
1.33
0.0 0.2 OS4 06 0.8 1.0 MOLE FRACTION WATER AT CONSTANT METHANOL Figure 5 .
Refractive Index of Methanol-GlycolWater Mixtures
1.43
1
I
0.3
I
I
0.4
0.5 MOLE FRACTION METHANOL AT CONSTANT WATER
02
Figure 6.
Refractive Index of Methanol-GlycolWater Jlixt iircs
V O L U M E 2 4 , NO. 5, M A Y 1 9 5 2 1.1 4
839
I
Table 11. Density and Refractive Index o f Various Mixtures of Methanol, Glycol, and Water Mole Fraction Methanol 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0,000 0.000
0.100 0.100 0.098 0.100 0.099 0.099 0.099 0 100 0.099 0.099 0 200 0 198 0 199 0 199
0.90
0.0 02 0.4 0.6 0.8 I1 MOLE FRACTION MITER AT CONSTANT METHA JOL Figure 7. Density of Methanol-Glycol-Water Mixtures
Tahle 1.
I k n s i t ) and Refractive Index of Various Mixtures of Methanol, Glycol, and Water \lolr l’raction Glycol 0,000 0.000 0 000 0 000 0.000 0 . 000 0,000 0.000 0.000 0.000 0.000 0 000 0 000 0.000 0.000 0 000
Xlole Fractlnn Water 0 0 0 0
Density dz 5
050
099
151 196
0 238
0.000 0.000 0.000 0.122 0.122 0.122 0.126 0.118 0.123 0.121 0.124 0.104 0.121 0,201 0.201 0.200 0.200 0.201 0.200 0.201 0.199 0.198
-~
Itefiactive Index, 1 3307 1 3325 1,3342 1,3358 1.3366 1,3383 1 ,3396 1,3405 1.3410 1,3423 1.3426 1.3429 1 ,3428 1,3426 1.3418 1.3414 1.3402 1 ,3386, 1.3362 1,3500 1.3530 1.3555 1.3583 1.3608 1 ,3637 1.3651 1.3670 1.3630 1.3658 1.3620 1.3640 1.3670 1.3700 1.3730 1.3756 1.3780 1.3792 I ,3797
__
tion of each coinponent and the correct composition of each sample was calculated from the weights thus obtained. The refractive indexes of these mixtures were measured and their densities were determined by use of Weld-type specific gravity bottles of 20- to 25ml. capacity. The data thus determined are given in Tables I a n d 11, and are plotted in Figures 1, 3 , 5 , and 7 . Figure 1 isa plot of refractive index against mole fraction water a t constant mole fraction glycol. The data are from Table I. Figure 2 was obtained from Figure 1, and is a plot of refractive index against mole fraction Figure 8.
Density of MethanolGlycol-Water Mixtures
0 198 0 199 0.199 0 213 0 198 0 295 0 310 n 300 0 299 0 299 0 397 0 399 0 393 0 401 0 399 n 499 0 601 0 498 0 500 0 500 0 299 0 405 0.275
Table 111.
Mole Fraction Water 0.105 0.199 0.295 0.400 0.501 0.601 0.703 0.801 0.895
n ooo
0.098
0,200
0.300 0.402 0 501 0 601 0.701 0.801 0.901 0,000 0 106 0,200 0.300 0.402
0.500 0.600 0 675 0,802 0.000 0.104 0.200 0 301 0 403
0.104 0.201 0.298 0 401 0 500 0.601 0.101 0 200 0.320 0.400 0.500 0.502 0.366 0.725
Density d25 1,1084 1,1055 1,1024 1.0977 1,0920 1,0843 1.0739 1.0587 1,0334 1,0891 1.0862 1.0818 1 ,0778 1.0693 1.0601 1.0488 1.0313 1.0076 0.9698 1.0666 1.0618 1.0551 1 0473 1 0370 1 0251 1.0066
0.9356 0.9469 1.0446, 1.0317 1.0259 1.0151 1 0009 1.0058 0.9922
0.9783 0.9596 0.9350 0,9028 0.9722 0 9561 0.9337 0.9127 0.8809 0.9824 0,9588 0.9419
Refract;\ e Index, 7 ~ 1 : 1.4288 1.4267 1.4220 1.4171 1.4112 1,4034 1.3930 1.3797 1.3608 1 ,4259 1.4228 1.4191 1.4140 1,4079 1 ,4009 1.3914 1 ,3797 1.3621 1.3374 1.4190 1.4152 1.4110 1.4050 1.3976 1 ,3888 1.3775 1.3618 1 3416 1.4121 1 ,4059 1.4014 1.3944 1.3860 1 3980 1 3910 1 3840 1 3722 1 3600 1 3430 I 3876 I 3799 1.3680 1.3566 1,3421 1,3753 1.3617 1,3429
Analysis of Mixtures o f Known Composition Actual Composition, iMole Fraction Water Methanol Densitv o.1009 0.0993 1 ossi 0 8185 0.2003 0.6002 1 0070 0.5971 0.2020 1.0375 0.3318 0.2214 Composition from Graph, Mole Fraction Glycol Water Methrtno 0.802 0.099 0.099 0.195 0.208 0.597 0.600 0.201 0.199 0.220 0.443 0.337
Glvcol o 599s 0.1994 0.2008 0.4468
Refractive Index 1 4230 1 3655 1 3775 1 4003
ANALYTICAL CHEMISTRY
840 glycol a t constant mole fraction water. Figures 3 and 4 are similar to 1 and 2 except that density instead of refractive index is the property plotted. Figure 5 is from the data of Table 11, and is a plot of refractive index against mole fraction water a t constant mole fraction methanol. Figure 6 was obtained from Figure 5 and is a plot of refractive index against mole fraction methanol a t constant mole fraction water. Figures 7 and 8 are similar to Figures 5 and 6 except that density instead of refractive index is plotted. The triangular plot, Figure 9, w&sobtained from the information on the previous plots. If the density and refractive index of an unknown mixture of methanol, glycol, and water are known, the concentrat,ions of the components can be obtained by reference to Figure 9. For practical use an enlarged plot of Figure 9, measuring about 16 inches (40.64 cm.) on theside, was constructed
0.040 DOTTED CURVES ARE CONSTANT DENSITY
SOUD CURVES A R ~ CONSTANT REFRACTIVE INDEX
and found to be satisfactory. Two 1.0 0.0 pairs of proportional dividers are a 0.0 0.1 0.2 0.3 0.4 05 0.6 0.7 08 0.9 1.0 MOLE FRACTION GLYCOL great aid in interpolation. Figure 9. Density and Refractive Index of All Methanol-Glyeol-Water Mixtures The accuracy of the data and chart was checked by preparing four samples (4) Heilbron, I. M., ”Dictionary of Organic Compounds,” Vol. 11, Of various mole fractions of the components. Their refractive p. 31, New York, Oxford University Press, 1936. indexes and densities were measured and the analyses of the (5) “International Critical Tables,” Vol. 111, p. 27, New York, samples mere taken from the plot (Figure 9). The results are McGraw-Hill Book Co., 1928. compared in Table 111. (6) Lange, N. A., “Handbook of Chemistry.” 6th ed., p. 928, Sandusky, Ohio, Handbook Publishers, 1940. (7) Lawrie, J. W., “Glycerol and the Glycols.” AMERICANCHEMICAL LITERATURE CITED SOCIETY Monograph 44, pp. 331-80, New York, Chemical (1) Conrad, F. H., Hill, E. F., and Ballman, E. A., Ind. Eng. Chern., Catalog Co., 1928. 32, 542 (1940). (8) Spangler, J., and Davies, E., IND. EXQ. CHEM.,Ax.41,. ED., (2) Dunstan, A. E., 2. physik Chem., 51, 732 (1905). 15, 96-8 (1943). (3) Gallaupher, A., and Hibbert, H., J . Am. Chmn. Sac., 58, 818 (1936). RECEIYED for review April 16, 19.51. Accelited Februaiy 6 , 1952.
Fire Assay for Iridium R. R. BAREFOOT AND F. E. BEAMISTI Uniuersity of Toronto, Toronto, On turio, Canudu
M
ETHODS for the deterniination of precious metals in ores and other materials by fire assaying have been in use for many years. Few attempts have been made to check the accuracy of these methods and very little work has been done on the accurate determination of iridium in ores. This paper deals with the efficiency of the collection of iridium in fire assays and is one of a series of papers describing the work done in this 1:al)oratory on the analytical chemistry of the platinum metals. In a fire assay, iridium does not alloy with lead but is collected as a suspension in the molten metal. I n order to avoid mechanical losses during the pouring of melts containing iridium, Davis ( 4 ) recommended that the fusion be cooled in the pot. Ilowever, even greater losses may occur in attempting to break t’he pot away sufficiently to free the pool of lead for analysis. I n t’extbooks on fire assaying ( 3 , so), procedures are outlined for t’he analysis of the lead button by cupellation, in which the platinum metals are concentrated in silver and gold. Iridium does not alloy with silver, and as a result serious mechanical losses occur in addition to any losses to the slag. Plaksin and Marenkov
(15) reported that almost 4% of a 5-mg. sample of iridium was lost from a 75-mg. silver bead obtained by cupellation. Gilchrist (6) modified the Deville-Stas method for the determination of iridium in platinum alloys. The lead button obtained by fusing the alloy in lead !vas treated with nitric acid and then aqua regia, leaving the iridium undissolved. Iron, if present, contaminated the residue and was difficult to remove. This method could not be applied directly to lead buttons obtained from fire assays because of the insoluble slag ivhicti can never he conipletely removed from the lead. Impurities-e.g., iron and nickel-in the lead button may alfio increase the error, Iridium can be converted quantitatively to soluble salts by dry chlorination in the presence of sodium chloride ( 1 2 , 14). Procedures for the removal of base metals from solutions of platinum metals have been described ( 2 , 9, 10, I S , 1 7 ) , in which the base metals are precipit,ated a t a convenient p H while the noble metals are held in sohtion as complex nitrites. Iridium map then be determined gravimet.rically by precipitation ~ t sthe Iiydi.:ited oxide ( 7 , 8, 11).
