V O L U M E 23, NO. 2, F E B R U A R Y 1951 ACKNOWLEDGMENT
293 Gruse, W. A., and Stevens, D. R., “Chemical Technology of Petroleum,” 2nd ed., p. 110, New York, McGraw-Hill Book Co., 1942. (5) Postovskii, Ya, Bednsaaina, N. P., and Mikhailova, M. 4., (4)
The authors acknowledge the aid of H. T. Rall of the Bartlesville Station in the preparation of the figures and text in this report. LITERATURE CITED
(1) Ball, J. S.,U.S. Bur. Mines, R e p t . Invest. 3591 (1941). ( 2 ) Birch, S.F., and Norria, W. S . G . P., J . Chem. SOC.,127, 898-907 (1925).
(3) Comay, S.. IND.ENG.CHEM..AXAL.ED.,8 , 460-2 (1936).
Compt. rend. acad. sn‘.%’.R.S.S., 44, 375-7 (1944). RECEIVED June 6, 1950. Presented before the Division of Petroleum ChemCHEMICAL SOCIETY, Houston. istry a t the 117th Meeting of the AMERICAN Tex. Investigation performed as part of the work of American Petroleum Institute Project 48A. “Production, Isolation, and Purification of Sulfur Compounds and Measurement of their Properties,” which the Bureau of Mines conducts a t Bartlesville, Okla., and Laramie, Wyo.
Determination of Purity and Water Content of Xanthates and Dithiocarbamates Use of Iodine Reagents A . L. LIKCIT Miscellaneous Zntermediates Area Laboratory, Chambers Works, E. Z. du Pont de Nemours & Co., Znc., Deeptcnter, ‘V. J .
Evaluation and development of suitable modifications of methods available for analysis of sodium and potassium xanthates and dithiocarbamates were required to determine accurately the yield, effectiveness of purification procedures, degree of hydration, and final purity of crystalline products isolated. A reliable, rapid method for water determination in crystalline xanthates and dithiocarbamate derivatives by titration with Karl Fischer reagent was developed. Iodine titration of xanthates in an aqueous barium chloride system gave reliable analyses, whereas dithiocarbamate salts required alcohol solu-
A
RAPID, reliable, and accurate method of determining water content was required to obtain a materials balance in the analysis of xanthates and dithiocarbamates. The widely employed Dean and Stark procedure (9, 18) for the estimation of water by azeotropic distillation with a hydrocarbon entraining agent suffers several serious disadvantages with respect to time required, failure to remove water completely from some hydrates, large sample requirements, and thermal decomposition of many xanthate and dithiocarbamate derivatives. Although the Karl Fischer reagent has been proposed for the rapid determination of xanthate purity directly (15, page 401), no reference to its application for the determination of water in these compounds was found. The ease with which iodine is reduced by thiol derivatives, unreacted amines used in the production of dithiocarbamates, by-products and decomposition products such as trithiocarbonates, thiosulfates, and sulfides was expected to interfere with the Fischer titration. Of the methods proposed for determination of xanthate and dithiocarbamate purity, direct titration with standard iodine solution offered the most promise as a rapid and accurate procedure, if interferences from by-products and decomposition products could be controlled (2-6, 7 , I S , 14). In the authors’ experience, titration with heavy metal salts (iron, nickel, lead, copper, or zinc) was not entirely satisfactory, owing to formation of basic salts and coprecipitation (1, 8, 1 6 ) . Improved accuracy obtained by isolation and determination of the metal content of the insoluble copper salts not only entailed laborious and time-consuming operations, but also failed to separate dithio-
tions for best results. The unexpected selective rcaction of Fischer reagent with water without oxidation of the active thiol group in either xanthates o r dithiocarbamates, and the negligible error introduced by amines and decomposition products, indicate wide application to other oxidation-sensitive materials. Although suitable for xanthate purity anal3 sis, the iodometric titration procedure can be applied with certainty only to relatively pure dithiocarbamate salts, and used only to supplement the more specific gravimetric determination of the thiuram disulfide derited f r o m the iodine oxidation.
carbamates trom impurities ( 6 , 10, 1 2 ) . Quantitative decomposition of sodium or potassium ethyl xanthate with acid wag not generally applicable to other xanthates or to dithiocarbamates (12). Estimation of purity by sulfur analysis (Parr bomb) was likewise time-consuming and subject to errors introduced by by-products, especially sulfides and disulfides. Gravimetric determination of the insoluble disulfides (dixsnthogens and thiuram disulfides) from iodine oxidation required more time than direct titratioii, but good results could be obtained Then conditions for quantitative recovery were developed. KARL FISCHER MOISTURE DETERMINATION
The determination of water by direct titration in chloroform with Karl Fischer reagent required no specialized technique to obtain accurate results rapidly with a visual end point, when the usual precautions to exclude atmospheric moisture were observed. Reagents. Karl Fischer reagent. Dissolve 404 id. of C.P. pyridine in 1000 ml. of anhydrouc; methanol and add 127 grams of iodine crystals. When dissolved, chill in ice and add 100 g r a m of sulfur dioxide as a gas under the surface of the liquid. Standardize against standard water solution in methanol (15, page 65). Chloroform, C.P. reagent. Procedure. Measure 25 ml. of chloroform into a dry 123-ml. Erlenmeyer flask (assembly described on page 72 of 16 is recommended for this determination), add Karl Fischer reagent d r o p wise through a two-hole stopper until a definite visual end point is reached (2 to 3 ml.) with vigorous swirling to wash down sides of the flask, and quickly add 0.5 to 5 grams of sample weighed to
,
ANALYTICAL CHEMISTRY
294
tion, and were difficult to separate from by-products, calculation of purity from total sulfur content contributed a majority of the deviations from 100%. Sodium thiosulfate, a xanthate decomposition product, introduced 5 to 10% (of the amount present) positive error, but sulfites did not produce high results. Sulfide contamination of crystalline xanthates and dithiocarbamates was not sufficient to require an evaluation of its effect on accuracy.
Table I. Accuracy of Moisture Determination (Direct titration, risual end point) Water Addeda, Compound Solvent 7% None Sodium di(P-hydroxyethy1)di- hlethanol thiocarbamate CHCla None Methanol 10 4 15 3 33 6 Diethanolaminr Sone None CHCIa Methanol 12 1 19 0 Sodium thiosulfate 36 3 CHCla 36 3 Back-titration CH&H 36 3 Sodium sulfite (66)-sodium sulfate (34) mixture CHCla 41 2
.
a
Water Found.
Relative Error,
7-
%
1.7 1.7 10.1 15.3 33.6 0.65 0.63 11.8 1 8 .B
. .
-2.9 Xi1 Xi1
... .... -2,s
38.Y 41.4
-2.6 f13.8 +7.2 f14.1
41.6
f1.0
41.3
IODOMETRIC DETERMIVATION OF XANTHATE PURITY
Includes water present i n initial sample
-
_
---
_
___
~
-
three decimal places. Haniples containing inore than 10% moisture should be reduced to 0.5 to 1.0 gram in size, while less than 1% moisture requires a 4.0- to 5.0-gram sample for accuracy Titrate to a permanent, end point nith constant sn-irling. Calculation
% HzO
=
nil. of_ _Fischer X factor (as grams of HzO per____ ml.) X 100 __ _ _ _ _ _ _ reagent __ sample weight
Discussion. The average accuracy of =t1% was not ;iffectrd h\the presence of such reactive amines as diethanolamine and ethylenediamine (Table I). Although the relative accuracy of the method applied to dibutylamine, ethylenediamine, a-pipecoline, and nionoethylaniline m s not determined, direct titration results and addition of these amines to the corresponding dithiocarbamate derivatives indicated no interferences. However, titration of diethanolamine to which known amounts of water were added has shown that the Fischer reagent can be applied to water analysis of amines which react with iodine, as well as xanthates and dithiocarbamates (Table I). Not only has the determination of water added in k n m n amounts to dithiocarbamates fallen within the useful limits of accuracy, but a majority of the sums of purity by sulfur analysis and m t e r content by Fischer titration (material accounted for) for 39 xanthate (Table 11) and dithiocarbamate (Table 111) determinations were within the range 98 to 101%. Because many of these compounds were relatively unstable, were converted appreciably to disulfide derivatives by atmospheric ouida-
Table 11. Structure ROCSK (Na) so. 1 2
3 4
5 6
7 8
I !
K methyl K ethyl N a ethyl
K n-propyl
Na n-propyl isopropyl
9 10 11 12 13 14
15 16 17 a
Contains water-insoluble oil
Analysis of Xanthate5
Iodine titration
Purity, 70 Sulfur anal.
~
Kelatirt. error, G& +0.6 -0.9 -1.1
+o.
1 +0.5 C2.8
-1.1 -1.6 f0.8 -1.H +2.2 -1.8 -4.oa -1.6 -2.5 -1.9 -0.3 -2.0 -6.9
+o. 1
-1.5 +4.7 -1.1
Satisfactory determination of xanthate purity by conventional titration of an aqueous solution with standard aqueous iodine has been obtained in the absence of more than traces of byproducts and decomposition products such as sulfites, thiosulfates, sulfides, and thiocarbonates, which were easily detected and results modified accordingly. Better accuracy was attained, a t the expense of time consumed, by pretreatment with harium chloride. Reagents. ilqueous iodine, 0.1 N (450 grams of potassium iodide plus 230 g r a m of iodine diluted to 18 liters). Barium chloride, 10% (10 grams dissolved in distilled water and diluted to 100 ml.). Starch indicator solution, 10 grams of corn starch (Argo) heated in 2 liters of water to boiling. Let stand overnight and decant off the clear supernatant solution. Procedure. Dissolve a 1-gram sample weighed to three decini:al places in 50 ml. of distilled water, add 5 ml. of barium chloride solution, stir thoroughly, and let stand 2 hours. Then add 150 nil. of distilled water and titrate with 0.1 N aqueous iodine almoit to an end point, add 5 ml. of starch indicator solution, and finish the, titration to a permanent blue or red end point (color somewhat dependent on the nature of the xanthate). Calculation
yo purity
= nil. of 0.1
-I‘ iodirie X factor X mol. wt. X 0.1 - -___sample weight
These xanthates were crystallized from the alcohol from which they were synthesized, but, with one or two exceptions, received no special purification. Most of the samples were stored several weeks to more than a year before analysis. Several were titrated in an alcohol system, but in every case an unreasonably high value was obtained. Titration with copper or nickel salts also Rave high results. Discussion. The rapid iodometric method for the estiniation of the purity of sodium or potassium xanthate derivatives in aqueous medium in the presence of barium chloride has shown * l % average accuracy, which is better than can be realized from calculation of purity from Materiala total sulfur content (Table 11). SuitBalance, fischer able conditions were not found for the Titration, S, Iodine Piirity + H d ) % H2O suppression of interference from sulfides 2 1 99.8 and thiocarbonates by precipitation 97.5 4 8 2 0 97.2 with lead in the presence of tartrates. 9 8 99.5 Therefore, the longer method of Grete 100,;i 0 5 20 0 100 (6, 10) must be used for samples con91.2 21 ‘I 2 6 100 taminated with these impurities. Com2 1 99.4 bination of total sulfur analysis, and 98.2 4 1 98.5 j 9 iodine titration directly and in the 4:2 99:s presence of barium chloride, yielded 100.8 4.2 reasonably reliable data on the sulfite 97.0 17.3 82.9 6.2 and dixanthogen content of a sample, 99.2 2.8 84.7 5.7 inasmuch as the difference in iodometric 96.8 3.7 titrations was produced by sulfites and 103.5 4.2 101.9 the “excess” purity by total sulfur was 98.3 94.1 derived from the disulfide derivative which did not titrate. Therefore, in Table TI positive errors were interpreted
V O L U M E 23, NO. 2, F E B R U A R Y 1 9 5 1
295
- .~
for which compensating techniques have not been developed; therefore, its use Structure Purity. ____ 7c Fischer Materials for purposes other than a quick approxiK2N-C-S Nit Iodine Relative TitraBalance, mation ( * 2 % under favorable condititraError. tion, % Iodine I1 .No. S Xitrogen tion" Sulfur % % H20 Purity + H20 tions), or to furnish auxiliary data, can1 Dimethyl 76.7 78.5 +0.6 21.2 100.2 not be recommended. Conditions whirh 20 8 100.5 ?s:7b 78.5 -1 5 permit titration of xanthate samplw 1 Diethyl 73.8 74.8 74.8 0 0 22.3 97.1 containing sulfites were not applicabh., 75.3 76.4 76.5 -0.1 23.4 99.8 3 Diisopropyl 76.7 80.0 83.0 -3.6 18.2 Y8.2 Di-n-butyl 93.4 87.8 92.6 --5.2C 6.0 93.8 and the elimination of sulfides by selec:I Djamyl 95.2 94.5 94.9 -0 4 2.7 !I?, 2 tive lead precipitation was not successful. ti Dtoctyl 86.9 77.1 87.1 -11.5 13.8 90.9 7 Bis(2-hydrouyethyl) 97.4 98.3 90.4 -1.1 1.7 I00 However, the iodometric met,hod ap76.5 80.1 -4.54 21.9 98 4 8 Phenylethyl 75.8 !I Pentamethylene 75.9 76.8 78.5 -2 2 17.3 94.1 peared t,o be as accurate as t>itratioii 10 Pentamethylenee 100.2 100.2 100.3 -0.1 1.0 101,2 with heavy metal reagents, and applird 1 I a-Pipecoline 84.0 85.9 85.7 +O. 2 13.4 99.3 I 2 -.-Pipecoline . . . 75.0 77.0 -2.6 22.0 94.0 to crystallized dithiocarbamates, mort. 13 2-Pyrimidyl GHaOH 93. 1 90.0 90 1 -0.1 7.7 97.7 14 Ethq-lene-his 68.7 68.9 70.0 -1.6 29.5 98 4 accurate than purity by sulfur analysis 69.6 72.0 70.6 A2.0 29.5 101 0 (Table 111). Titration results lower 15 Pilierazyl 80.3 85.4 83.6 +2.2 12.8 98.2 1 6 Piperazylenv 86.5 86.3 84.4 2 ,3 11.9 ini , 2 than sulfur purity were corrected h!. Alcohol solution titrated with alcoholic iodine. gravimetric determination of the waterh Purity by nickel ion titration = 75.3'3%. Sample contains 7.0% insoluble material. insoluble thiuram disulfide content. Ald Sample contains 2.8% insoluble disulfide; thrrefore, corrertad ~ 1 ' 1 ' 0 r= 0.7%. though reliable results were obtained i n Piivridinium salt. some rases by titration of an alcoholic .~ .~ _________ dithiocarbaniate solution with aqueous iodine (Tahle IV), in general the use of as sulfite (corrected by barium chloride) and negative errors alcoholic iodine titrant. was found necessary to avoid nonas dixanthogen contamination. r;toic~hionietricL relationships enrountered in some aqueous systems. Reactive amines (diethanolamine, ethylenediamine) introduced IODOMETRIC DETERMINATION OF DITHIOCARBAMATE PURITY errors considerably greater than the equivalent amount present (calculated as amine), and relatively "inert" amines, such as The best conditions for determination of dithiocarbamate dibutylamine, yield small, but significant, error. .4few (monopurity required titration of an alcohol solution of the sample with ethylaniline and pipecoline) evert a negligible effect. Probably standard alcoholic iodine reagent. The appearance of a bright the most accurate method for determination of purity is the. yellow color in the absence of starch indicator provided the most gravimetric procedure based on oxidation to the water-insoluble Ratisfactory end point which, in most cases, could be verified by thiuram disulfide (Table IV). arch solution as an outside indicator. However, the starchiodine blue color faded very quickly, and required practice t.o CONCLUSIONS locate the correct end point. Barium chloride employed in Appliration of the Karl Fischer titration for the determinaxanthate titrations could not he used to suppress impurities, as tion of water to the analysis of xanthates and dithiocarbamates the partial precipitation of insoluhle harium dithiocarhniiiates has furnished an improved method for the rapid and accurate int,roduced serious errors. determination of water of hydration as well as extraneous watei , Reagents. Ethyl alcohol, Fomiula 2R. Alcoholic iodiiic., 0.1 N with a rclative accuracy of * l % . M o s t alcohols and aniiii~>\ i l l 2H dcohol. Procedure. Dissolve a 1-gram sample weighed to three decimal p1:ccvs in 150 ml. of 89 to 90% ethyl alcohol (insoluble matter indiratcs presence of the thiuram derivative), and titrate to the Table 11.. Effect of Titration Technique on Accuracj first appearance of a bright yellow color which persists at lrast 1 (Uithiocarhaniate purity by titration with iodine. Sodium phenylethyl minute a t the end point. ThP end point can be confirmed by spot dithiocarbamate) test in starch solution on a white spot plate. Thg color is fugitive, hon-ever, and with some dithiorarhainatos requiii~soviJrt i t r:j t i t r r i N e t h o d for Detecting E n.d- Paint, . ... fnr a definite test. Inside yellow Spot plate Calculation Solvent for Solvent f o r color, no starch Table 111. iinalysis of Dithiocarharnates
~-
'/
(.
~
~
~
~
~~
-
Sample Ethyl alcohol (2B)
Good confirmatory results have bee11 obtained by titrating in an aqueous system, filtering off the insoluble thiuram disulfide derivative on a tared Gooch crucible, washing carefully with water. and weighing after drying to constant w i g h t a t 80" C. Calculation %purity = wt. of thiuram disulfide X 11101. a t . of dithiocarbamate X 200 sample weight X mol. wt. of thiuram disulfide Test for Sulfides. Dissolve approximately 0.1 gram of s:rmple ill 10 ml. of cold water, and add a few drops of a 2 7 , aqueous xolution of sodium nitroprusside. Immediate appearance of an intense red-violet color indicates presence of appreciable quanti ties of sulfidt~swhivh will interfere tyith iodomrtrir anal)-sis. These dithiocarbamate derivatives were crystallized from water, but, with the exception of 13 to 16, received no further purification treatment. Samples 4 to 6 represent commercial materials. Discussion. The iodometric: aiialysis of water-soluble dithiocarbamate derivatives has encountered several sources of error
Iodine starch solution Ethyl alcohol (2B) 75.2 76.5 Aqueous 75.0 76.3 Water Aqueous 78.6 79.5 Purity by sulfur determination (corrected for 2.8% water insoluble di-!tifide derivative) = 77.0 Gravimetric purity (calculated froin weights of dipulfide produced by iodine oxidation) = 75.1
Table V. Effect of lmpurities on .icciiracy (Dithiocarbamate purity by titration w i t h iodine) Purity "Impurity" AddedFound, Derivative Compound 0 % dodiuin bis(p-hydroxy- S o n e 98.3 ethyl) Diethanolamine 16:7 129 Sodium a-methylpenta- S o n e 78.3 methylene a-Pipecoline 12:s 81.0 Sodium phenylethyl Kone 76.5 Monoethylaniline 18:s 76.3 Sodium diamyl None 94.5 Dibutylarnine 14:s 102.2 1G.O 106.9 Disodiuin ethylene-bis Sone 72.0 Ethylenediaiiiine 20 135.1 a 1 6 . 3 calculated as diethanolamine. b 18.8 calculated as ethylenediamine. ~
Relative
E
~
% +ii:3*
....
+3.3 . . ., -0.3
....
+8.2 f13.1 +&b
-
~~.
~
~
~
,
ANALYTICAL CHEMISTRY
296
from which these compounds are synthesized did not react with the reagent, and decomposition products such a# thiosulfate and sulfites introduced only minor errors. Titration of aqueous sodium and potassium alkyl xanthates with aqueous iodine in the presence of barium chloride yielded results more rapidly and of a higher order of accuracy in the absence of sulfides and thiocarbonates than purity calculated from total sulfur content or titration with a heavy metal salt reagent. The iodometric procedure for the estimation of dithiocarbamate purity can be recommended only as a rapid approximate method, or aa a source of auxiliary information, except in cases where interferencea are known to be absent. However, reliable data can be obtained from most crystallized products, and valuable information relative to degree of oxidation to the thiuramdisulfide derivatives can be estimated. ACKNOWLEDGMENT
The author n-ishes to thank F. L. English, John Mitchell, Jr., and G. F. Palfrey for their suggestions and assistance in the preparation of this paper, and E. R. Beckett of the Miscellaneous Intermediates Laboratory for his assistance in developing experimental data.
LITERATURE CITED
(1) Andrews and Campbell, J . Am. Chem. SOC.,17,125 (1895). (2) Beilstein-Prager-Jacobsen, “Organische Chemie,” 111, 208, 209, 214; Ann. chim. phys., ( 3 ) 20,504(1847). (3) Beilstein-Prager-Jacobsen, “Organische Chemie,” 111, 214 [G 17, 80 (1887)j. (4)Ibid., IV,76 [B 35,820(1902)l. (5)Ibid., IV,121 [B 14,2756(1881)1. (6) Calcott, W.S.,English, F. L., and Downing, F. B., Eng. Mining J . Press, 118,980(1924). (7) Callan, T., and Strafford, N., J . SOC.Chem. Ind., 43,1-8 (1924). (8) Carpenter and Hehner, A n a l y s t , 8,37 (1883). (9) Dean, E. W., and Stark, D. D., J . Ind. Eng. Chem., 12,486-90 (1920);A.S.T.M. D 95-46. (10) Grete, E.A., Ann., 190,211(1877). (11) Hallet and Ryder, Eng. Mining J . Press, 119,690 (1925). (12) Hirschkind.Ibid.. 119.968 (1925). (13) Lieber, Eugene, and iVhitmore, K. F., IND. E m .CHEM.,ANAL. ED.,7,127 (1935). (14) Matuszak, M. P., Ibid., 4,98 (1932). (15) Mitchell,John,Jr., and Smith, D. M., “Aquametry,” New York, Interscience Publishers,1948. (16) Selivounof, Analyst, 54,488 (1929). (17) Sermais, B.,Rev. g h . mal. phstiques, 12,167 (1936). (18) Tate, F.G.H., and Warren, L. 4.,A n a l y s t , 61,367(1936) RECEIYED February 27, 1950. Presented before the Analytical Chemistry Division of the Delaware Chemical Symposium, Delaware Section, AMERICAN CEIEVICAL SOCIETY, Wilmington, Del., January 21, 1950.
Extraction and Purification of Nordihydroguaiaretic Acid JOHN 0. PAGE, Agricultural & Mechanical College of Texas,, College Station, Tex. It was desirable to work out an accurate method for the quantitative determination of nordihydroguaiaretic acid in creosote bush ( h r r e a divaricata). Isopropyl ether or isopropyl ether-carbon tetrachloride mixtures, rendered peroxide-free by a preliminary washing with aqueous sodium bisulfite solution, quantitatively extract the nordihydroguaiaretic acid from the creosote bush leafy material. The solvents are distilled and recovered. Extractions of the tarry residues with boiling distilled water quantitatively separate crude nordihydroguaiaretic acid (melting point, 116-180” C.) from the tarry or resinous residues. Yields of 2.14 to
T
HE phytochemical study of creosote bush (Larrea divaricata) was made by Waller (87, 38), who obtained nordihydro-
guaiaretic acid from this plant. Waller extracted the crude chemical with 95% ethyl alcohol and then recrystallized the nordihydroguaiaretic acid from hot dilute aqueous acetic acid or from sodium bisulfite solutions. In an attempt to separate the pure phenol from a large quantity of the plant extract by steam distillation, Waller (37) obtained impure crystals which were suspended in the water above the settled plant extract. He then found that water itself did not separate the pure nordihydroguaiaretic acid from the plant extract (or tar), and consequently used aqueous acetic acid or sodium bisulfite solutions to purify the chemical. The extraction of nordihydroguaiaretic acid is the subject of seven patents (1, 9-14) and one publication ( 8 ) ; the antioxidant properties of this chemical have been substantiated and demon16, 16, 18-85, F7-35). strated in twenty-three publications ($4, The fist of these patents (10) disclosed the process by means of which 2.50 to 2.66% yields of “90 to 100%” pure nordihydroguaiaretic acid were obtained from the creosote bush. The creosote bush is first extracted with an aqueous solution containing, usually, 5% sodium hydroxide and 2 or 2.5% of so-
2.35% of the crude were obtained from large samples of fresh green, machine-threshed, creosote bush. The percentage of nordihydroguaiaretic acid in the crude was not determined, but several methods were tried in order to evaluate the purity of crude nordihydroguaiaretic acid with accuracy. Methods of purification are given. Nordihydroguaiaretic acid is principally useful as a food antioxidant. It is separatedfrom creosotewith some impuritiesand weighed in the crude form. The resulting data are proximate assay recoveries, as the purity of the crude material, that was separated and recovered by this method, was not determined. dium hvdrosulfite (Xa2S204). This alkaline extract is then acidified with concentrated hydrochloric acid solution, after which ste a yellow-brown viscous, curdy, solid crude material separates bot{ a t the top of the acidified extraction liquor and a t the bottom of the tank. This is industrial practice in separating the crude nordihydroguaiaretic acid from the creosote bush material. Thie crude curdy material is purified by various means, including the method first described in a United States patent (10)vis., the crude curdy nordihydroguaiaretic acid sludge may be dissolved in an aqueous-alcoholic solution or medium. The nordihydroguaiaretic (together with some impurities) may be taken out or dissolved out of the aqueous-alcoholic environment with a water-immiscible solvent such as diethyl ether or isopropyl ether. The diethyl ether or isopropyl ether thus serves as a convenient solvent for the nordihydroguaiaretic acid (and associated impurities) and as a preliminary step before purification of the acid.
A patent (11) claims that diethyl ether or isopropyl ether may be used to obtain a crude extract, containing nordihydroguaiaretic acid, from creosote bush. However, it discloses no useful means or devices which can be employed to translate or convert the hazardous laboratory procedure of extraction with isopropyl ether into a useful art. The purposes of the present work are to gain accurate quantitative data on the amount of nordihydroguaiaretic acid present
