George B. Kauffman and Robin D. Myers California State University, Fresno Fresno, 93740
The Resolution of Racemic Acid
I
A classic stereochemical experiment for the undergraduate laboratory
Louis Pasteur (1822-1895) (Fig. I ) was the first to accomplish the resolution of an optically active compound. Althoueh he later went on to found microbiolow. --, Pasteur's earliest discovery immortalized his name in the annals of chemistrv. His discoverv that one of the forms of tartaric acid consists of two optically active isomeric constituents laid the basis for the field of stereochemistry, the study of the spatial arrangement of atoms in molecules. He attributed their activitv to what he called "molecular dissvmmetry" (une dissymetrie dans les molQcules),a phrase selected as the title of the first volume of his collected works ( I ) and inscribed on his mausoleum a t the Institut Pasteur in Paris. Pasteur's resolution of racemic acid has had a ~ r o found influence on research in stereochemistry, crystailography, biology, biochemistry, mineralogy, pharmaceutical chemistry, and organic and inorganic chemistry, to mention only a few of the fields that have henefited from his genius. This resolution belongs to that small group of classic experiments that radically changed our view of the world, o ~ e n e dun new oaths of research. and vet are s i m ~ l e enough tu'he dupiirated by the average undqraduare.'ln v w w of the interdisci~)linarv imolirntions of the exneriment (2), we feel that i t is;deall; suited for today's chemistry or science courses, both those intended for the nonscientist as well as for the chemistry or science major. As anyone with experience in the field can testify, resolution is as much an art as a science, and attention to the smallest detail often s ~ e l l sthe difference between success and failure. Thus numerous frustrating trials were necessary before we were able to convert and modify Pasteur's scanty reports of his work (3-5) into a reproducible procedure. Before giving our detailed procedure, however, a brief synopsis is required to provide the background necessary to appreciate Pasteur's contribution to stereochemistry. Historical Background In the late 17th century the Dutch physicist Christiaan Huygens (1629-95) observed that light which passes through a crystal of Iceland spar (a transparent variety of calcite, CaC03) is plane polarized, i.e., it vibrates in only one plane. In 1812 Jean Baptiste Biot (1774-1862) discovered that when polarized light passes tbrough a quartz plate cut perpendicular to its crystal axis, the plane of polarization is rotated through an angle proportional to the thickness of the plate, in some cases to the right, in others to the left (6). In 1815 be found that this rotation can also be produced when polarized light is passed through certain naturally occurring organic liquids, such as oils of turpentine, laurel, or lemon, or through solutions of certain naturally occurring organic substances such as camphor or sugar (7). This ability of a substance to bend or deflect a plane of polarized light is known as optical activity. Biot recognized that the optical activity of quartz is a property of the crystal whereas that of the organic compounds is a property of the individual molecules since it is observed even in solution. The French mineralogist, the
Presented before the Division of Chemical Education at the 168th National Meeting. American Chemical Saeietv. Atlantic City, N.J., September 19?4.
Figure 1. Louis Pasteur (1822-95).
Abbe Ren6 Just Haiiy (1743-1822) had observed that some auartz crvstals show hemihedral faces oriented to the right or to the left; they are enantiomorphs or nonsuperimposable mirror images of each other. In 1820 Sir John F. W. Herschel, the English astronomer (1792-1871), correlated the rotatory power of quartz crystals with the presence of hemihedral faces (8). I t was Louis Pasteur who initiated the investigation of optical activity as a property of molecules. The compound with which he worked, tartaric acid, H2CdHaOs (2,3-dihydroxybutaoedioic acid), is found in many plants and was known to the early Greeks and Romans in the form of its potassium acid salt-tartar-obtained as a deposit from fermented grape juice ( t h e German name for the acid is Weinsaure). The free acid was first isolated in 1769 by the Swedish apothecary and chemist Carl Wilhelm Scheele (1742-861, who boiled tartar with chalk and decomposed the resulting calcium tartrate with sulfuric acid (9).Its optical activity in solution was first recognized in 1832 (published in 1835) by Biot, who showed that it is dextrorotatorv ( 1 0 ) . Sometime around 1819 a second form of tartaric acid was obtained by Paul Kestner from crude tartar used to make tartaric acid in his chemical factory a t Thann in the Vosges in northeastern France. hut he mistook i t for oxalic acid. J. F. John recognized i t as a distinct compound and called it Siiure nus den Voghesen. In 1828 the French chemist Joseph Louis Gay-Lussac gave it the name by which i t is generally known today, racemic acid (acide racL.mique, from the Latin racemus, a bunch of grapes) and showed that it Volume 52, Number 12, December 1975 / 777
has the same composition as tartaric acid. Gay-Lussac's analytical results were confirmed in 1831 by the English chemist Thomas Thomson. Berzelius called it "acid of grapes" (Swedish, drufsyra; German, Traubensaure) as well as paratartaric acid, the term by which Pasteur first referred to it. In 1830 Berzelius referred to tartaric and racemic acids as isomeric hodies (isomeriska kroppar) ( I I ) , and in the following year he again cited these compounds and wrote that compounds with the same composition could have different properties, a phenomenon t o which he gave the name isomerism (from the Greek iooprpjs, composed of equal parts) (12). In 1838 Biot examined racemic acid and found it to be optically inactive (13). In 1841 FrBdBric Herv6 de la Provostaye (1812-63) examined the crystalline forms of tartaric and paratartaric (rrcemic) acids and their salts (14). The following year Remigius Fresenius (15) and Eilhard Mitscherlich, the discoverer of the law of isomorohism ( I f ? ) , prepared, analyzed, and characterized a numhe; or' its salts, including the dm~hlesodium ammonium salt (Traubensaures Narron-Ammoniak) destined to figure soprominently in Pasteur's work. Pasteur's Work
While gaining practice in research by repeating de la Provostaye's work, the 25-year-old Pasteur discovered a fact that de la Provostaye had overlooked, uiz., that crystals of tartaric acid and its salts, whose optical activity had been ohserved in 1832 by Biot (101, were hemihedral, i.e., they possessed only half the number of faces required by the symmetry of the crystal system, whereas crystals of paratartaric acid, the optically inactive isomer of tartaric acid, and its salts-with one important exception-were not. Pasteur found an unusual anomaly in the case of the sodium ammonium tartrates and racemates, which Mitscherlich, in a note to Biot, had claimed to he identical in crystalline form and all properties except for the ability t o rotate polarized light (17). His results are best described in his own words (56) I hastened therefore to reinvestigate the crystalline form of Mitseherlich's two salts. I found, as a matter of fact, that the tartrate was hemihedral, like all the other tartrates which I had previously studied, hut, strange to say, the paratartrate was hemihedral also. Only, the hemihedral faces which in the tartrate were all turned the same way, were, in the paratartrate inclined sometimes to the right and sometimes to the left. . . . I carefully separated the crystals which were hemihedral to the right from those hemihedral to the left, and examined their solutions separately in the polarizing apparatus. I then saw with no less surprise than pleasure that the crystals hemihedral to the right deviated the plane of polarization to the right, and that those hemihedral to the left deviated it to the left; and when I took an equal weight of each of the two kinds of crystals, the mixed solution was indifferent towards the light in consequence of the neutralization of the two equal and opposite individual deviations.
In modern terms Pasteur had treated separate portions of solutions of equal weights of racemic acid (d, 1, or
(a) Dextrorotatory. (b) bvorotatory. Figure 2. Hemihedral crystals of sdium ammonium tartrate (Pasteur)
778 / Journal of Chemical Education
(+)(-)-tartaric acid, acide paratartarique) with soda (Na2C03) and ammonia (NHB),combined the solutions, allowed the resulting solution to evaporate spontaneously, and obtained a salt, which was actually an equimolar rnixture of sodium ammonium d - or (+)-tartrate (dextrorac6mate de soude et d'ammoniaque) and sodium ammonium 1- or (-)-tartrate (leuorac6mate de soude et d'ammoniaque) (Fig. 2). In mechanically separating the two types of crvstals. which are mirror imaees of each other. Pasteur acthe most f&nous of all cokplished the first and resolutions. He had discovered what Mitscherlich and Biot had overlooked, uiz., that although the sodium ammonium "racemate" was hemihedral just like the tartrate, the hemihedral facets were turned sometimes one way and sometimes the other. Yet there were two elements of sheer luck in Pasteur's discovery. First, with the possihle exception of the sodium potassium salt (Rochelle Salt) (18, 19), the sodium ammonium salt is the only inactive tartrate that can be resolved in this manner. since the two forms of tartaric acid and the two forms of ail its other salts combine to form crystalline racemic acid and racemates. which show no hemihedrism or optical activity and may he classed as "double salts" of the (+)- and (-)- forms (20) (Figs. 3 and 4). Secondly was the fact that Pasteur had carried out his experiments in the cool Parisian climate rather than in a Mediterranean or tropical one. In the latter case he would prohahly not hive made his revolutionary discovery, for i t was later found (19, 21, 22) that the two sodium ammonium tartrates unite to form a single holohedral racemate (Fig. 5 ) a t temperatures above 26'C. The deposition of the L tartrates from a solution of Figure 3. Holohsdral crystal of the racemate can be attrihracemic acid. uted to the fact that the racemate, NaNH4(+)1-)[CaH406].H20, is stable in contact with its aqueous soluWTASSUM
SODIUM
WTASSIUM ANTlMONYL
Figure 4. Holohedral racemetes (Pasteur. 1850).
Inactive. Figure 5. Holohedral crystal of sdium ammonium racemate (Scacchi).
tion only above 26'C. Below this temoerature i t is resolved into the two optically active tartiates. Pasteur concluded that he "had separated two symmetrically isomorphous atomic groups which are intimately united in paratartaric acid" (5). T o prove that the "two species of crystals represent two distihct salts from which two different acids can be extracted," he precipitated each salt with a lead or barium salt solution and isolated the corresponding acids from the barium or lead (+)- or (-)-tartrate by treatment with sulfuric acid. In this way he isolated for the first time the hitherto unknown I- or (-)-tartaric acid (acide 1t.uoract.mique (3), acide 12uotartarique (4). now sometimes called "unnatural tartaric acid"). Like their double sodium ammonium salts, the two optically active acids exhibit hemihedral crystals (Fig. 6). Pasteur com-
(a) Dextrorotatory.
(b) Lavorotatory.
Figure 6. Hernihedral crystals of tartaric acid (Pastaw)
pleted the cycle of the proof of his assumptions by mixing concentrated solutions of equal weights of each acid, whereupon heat is evolved and racemic acid precipitates. Pasteur continued his previous work and proved in detail that paratartaric or racemic acid is composed of two optically active acids of opposite rotational signs (4). He included drawings of crystals of various tartrates and racemates and also extended Herschel's view of the insoluble quartz crystals (8)to the soluble tartaric acid and tartrates; he correlated crvstalline form with o ~ t i c a activitv l and regarded the hemihedral faces as a visible sign of optical activity. Actually, his view that crystals of every optically active suhstance exhibit hemihedral faces is not true; hemihedrism is a sufficient but not a necessary condition for optical activity. Pasteur's research on optical isomers, which are identical in all chemical and physical properties and differ only in their ability to rotate plane polarized light, constitutes a truly pioneering work. H e found that a solution containing equal amounts of right-handed and left-handed crystals was found to be optically inactive. Since the first such mixture to he discovered happened to be sodium ammonium racemate, an optically inactive equimolar mixture of (+)and (-)-isomers of any optically active compound is now known as a racemic mixture or racemate. Pasteur recognized what he called the principle of molecular asvmmetrv beaed on his correlation of crvstalloeranhic properties with optical activity (5). He that optical activitv in a substance is caused hv an asvmmetric arrangement of atoms in the individual moleculewandthat the molecules of the same substance that rotate the nlane of polarized light to the right and those that rotate it to the left are related to each other as object and nonsuperimposable mirror image. However, the exact relationship between optical activity and molecular structure eluded him, and he was unable to identify the configuration, i.e., the particular spatial arrangement of the atoms. Yet "in [Pasteur's] theoretical speculations as to the cause of the difference between optical isomers, so close an approach is made to the theory of van't Hoff and LeBel (1874), that it seems incredible that many years elapsed before the final step was taken" (5b).
-.
I t was not until 1874, the year considered to mark the founding of stereochemistry, that the 27-year-old Frenchman Joseph Achille LeBel(1847-1930) and the 22-year-old Dutchman Jacobus Henricus van't Hoff (1852-1911) indeoendentlv demonstrated that an arrangement of four difrerent atoms or groups a t the corners of a regular tetrahedron would produce two structures, one of which is the mirror image of the other, the latter being a condition for the existence of optical isomers already recognized hv Pasteur. By extending-the tetrahedral concept to compounds containing more than one so-called asymmetric carhon atom, van't Hoff was ahle to account for Pasteur's dextro (d- or (+)-I and levo ( 1 - or (-)-) tartaric acids as well as for the internally compensated, nonresolvable (meso) isomer that Pasteur had isolated in 1853. The tetrahedral configuration for the carhon atom has since been confirmed by the resolution of numerous carhon compounds and eventually by more direct evidence such as X-ray diffraction. Later Work Although more than a century and a quarter has elapsed since Pasteur's historic resolution, little has been forthcoming in the way of theories to predict when resolution is possible by crystallization procedures (24). However, a numher of investigators have carried out further experimental work on the first substance t o he resolved into its optical antipodes. Pasteur himself improved upon his original mechanical sortine method hv allowine the racemic svstem to crvstallize just partially and removing the initial crystals or mother liauor (25). D. J. B. Gernez found that a suDersaturated sol;tionof sodium ammonium (+)(-1-&ate deDosits onlv dextrorotatorv crvstals when a crvstal of (+)tartrate was placed in i t and deposits only levorotatory crystals when a crystal of (-)-tartrate was placed in it (26). Gernez's work was the first reported resolution based on seeding a su~ersaturatedsolution and led to similar resolutions Gith other compounds. Frederick Stanley Kipping and William Jackson Pope resolved sodium ammonium'(+)(-)-tartrate by fractional crystallization from aqueous solutions of (+)-glucose or (-)-fructose (27). Initially, they believed that the resolutions were caused by the asymmetric influence of the sugar present, but they later ascribed them to the presence of tically active crystals carried by contaminating laboratory dust 1281, and they concludedthat the of atmispheric dust is necessary t o form large single crystals. Our results tend to confirm Kipping and Pope's results, and, assuming that truly spontaneous resolution does not occur, they led us to speculate that the laboratory dust in Pasteur's and Biot's laboratories may have contained crystals of both (+)- and (-)-antipodes, thus accounting for the simultaneous deposition of mechanically separable crystals of both antipodes. Ostromisslensky resolved sodium ammonium (+)(-)tartrate by seeding a supersaturated solution with optically active crystals of other substances such as asparagine and alkali metal salts of (+)-tartaric and (-)- malic acids (29). Patterson and Buchanan (30) obtained large crystals of each antipode of sodium ammonium tartrate by suspending seed crystals of the corresponding antipodes on hairs in solutions of the racemate.
-
op-
Procedure Preparation of the Sodium Ammonium Racemate Solution Dissolve 3.00 g (0.020 mole) of racemic acid1 in 10 ml of boiling water contained in a 30-ml beaker. Slowly add with stirring 1.06 g (0.010 mole) of anhydrous sodium carbonate or an equivalent weight of any of its hydrates (Caution. Effervescence). If any
'DL-Tartaric Acid, Catalog No. T 40-0, Aldrieh Chemical Co., Milwaukee, Wisconsin 53233. Volume 52, Number 12, December 1975 / 779
Separation of Sodium Ammonium (+)- and (-)-Tartrates With a dissecting needle (not s forceps, which may break the crystals!) manually separate the (+)- tartrate crystals from the (-)-tartrate crystals from the combined crops under a low-power microscope (Fig. 2). Usually the earlier crops are richer in the (+)crystals, hut sometimes the (-)- crystals are deposited preferentially. The separation is not quantitative; all of the crystals will not be separable because not all of them will exhibit well-developed hemihedral faces and some will have grown together. About a gram of crystals (enough for measurement of optieal activity) can he separated in about an hour. The drawings n~ of the various crvstals deoieted in this oaoer \ F i g s . 2 6 and 81 are simplified, idcnlimd dmwmgs, and the cry"tals ohtained {Fig TI often hear little rrsemhlnnce to these h e r w s e of unequal development of faces, truncation of faces, and other imperfections. Although the differences between the (+I- and (-1crystals will be sufficient to permit manual separation, the student may not be able t o predict which crystals are dextrorotatory and which are levorotatory. Assignment of configuration can be made by measurement of optieal activity (see Section on Polarimetry). This is the method originally used by Pasteur. ~
..
~
~
Figure 7. Sodium ammonium tartrate. (left)l o r I-) form. (right)dor (bonom)racemate (+)I-) form.
(+)
form.
white precipitate forms, heat and stir until i t dissolves. After effervescence has ceased, add slowly with stirring -1.5 g of ammonium carbonate in small portions, waiting each time until effervescence ceases before adding more of the salt. If any white precipitate forms, heat and stir until it dissolves. The hot solution should smell strongly of ammonia. If excessive heating has caused loss of ammonia, add more ammonium carbonate. Decant the solution into another 30-ml beaker to remove any solid that might cause premature crystallization. Depending upon the conditions of crystallization, different products are ohtained. The yields from the various crystallization procedures amount t o 60-80%, depending upon the number of croos isolated. Since several davs are reauired for the crvstallization, the student should ' ' d o v e k ' this'work with other experiments or other parts of this experiment. Crystallization
Polarimetry 1)irections for the use of 3 pthnmeter and definitions olsperific rotation. [nl, are found in standard lnhoratory manuals 1 . 1 1 , Mrasure the opticnl actwrtier oinll the crystals obtained by accuraiel) weighing out to the nearest 0.1 mg, samples of approximately 1 g and dissolving them in a measured volume of water Gust enough t o fill a 1-dm polarimeter tube). Make all oolarimeter readinas a t the same temperature if possible. Preparation of (+)- and(-)-Tartaric Acids by CationExchange After measuring the optical activities of the sodium ammonium and (-)-tartrates separated as above, qunntitatiuely transfer the solutions to a cation-exchange column in the hydrogen form" and elute with water until the effluent is no longer acidic (litmus paper). Reduce the volume of the effluent t o a convenient volume for polarimetry by hailing (Caution. Avoid spattering.). Make up the solution t o the desired volume and measure the optical rotation. a. From the initial weizht of sodium ammonium salt. calcu-
(+I-
Allow the heaker of sodium ammonium racemate solution to cool and place it in an undisturbed area where the temperature is below 26'C., e.g., 20-25"C., throughout the duration of crystallization. Use of a refrigerator should be avoided. Although with other salts, evaporation s t low temperatures usually results in slower crystallization with resultant formation of larger, more perfect crystals, in this ease only a powdery, mechanically inseparable sulting crystals under the low-power microscope (Fig. 6). crust forms. As soon as crystals have begun t o form (-4 da) and before they begin to grow together, remove them by decanting the solution into another 30-ml beaker. Allow the solution t o continue to evaporate and repeat the process several times. Mixtures of (+Iand (-)-tartrates are obtained (Fig. 2). Usually the earlier frac2For example, Dowex 50W-X8, 50-100 mesh, medium porosity, tions are richer in the (+)-antipode, hut sometimes this behavior is hydrogen form; column, 19 em X 1.1cm diameter; flow rate 0.95 reversed. If the solution is not fractionally crystallized into sepaemlmin. rate crops, an inseparable mixture of interlaced (+)(+I(-I-NaNH,C,H,Os.HxO and (-)-tartrates is obtained. If difficulty in obSodium Ammonium Raremate taining crystals is encountered, scratch the beaker or [.loZ5 = OD introduce particles of ground glass t o serve as nuclei for crystal formation. Blot the ervstals.. which varv from 0.L10 mm in length, on filter paper to absorb any adhering syrupy mother liquor. Blot them gently so as t o avoid marring their faces and store each crop in small sample (+)-H,C.H,O. (+U-1-H&,H,O. (-1-HIC,H,O. I->-R~C.H.OI (+IH~c.H.o. bottles. The crystals must be dry before being placed (+)~Tartarie Acid Racemie or Para(-)-Tartaric k i d in bottles, or they will adhere to each other. However, weinaivre eaY.l A",, tartaric *=id e Q Y .A~ , "unnatural" they should not be allowed to dry by lying on paper ~ ~ occurring t EW"~ ~ ~ r~a v b e n s i ~u r e l Evan" ~ or they will adhere to it. 1.1~25 = + n o [ . l D ~ ~= o0
.
-
Z
or
(-1
d
or
(+>
Sodium Ammonium (+)-Tartrate l.lD37
= t23.5'
-
Sodium Ammonium (-)-Tanrate [.IDi7
=
-23.5'
Figure 8. Hemihedral crystals of ammonium tartrates (Pasteur, 1850). Figure 9. Relations between tartaric acas. r a c e m i c acid, and their sodium ammonium salts.
780 / Journal of Chemical Education
Specific Rotation,
Preparation of Acids and Sans From Commercial Acids
As standards or "knowns" for comparison purposes, measure the .optical activities of commercial samples of raeemic aeid,' (+)-tartaric acid,3 (-)-tartaric acid.' and meso-tartaric acid.%Pre~arethe sodium ammonium salts from these acids as above and measure their optical activities. Also quantitatively reconvert the four salts to the corresponding acids, whose optical activities should then he measured. Allow all the solutions to evaporate slowly and examine the resulting crystals under the low-power microscope for eomparison purposes (Figs. 2,3,5, and 6).
[el D Values
Experimentally Measured
Compound
Theoretice1 l o )
lo" Exch.. from Salt from Cornrn. Acid ('1
Commercia1 l o )
Ion Exch., from Salfr Sepd. from I+)(-)-Salt
Additional Projects For comparison purposes students may carry out the crystallizations under various conditions. For example, crystallization from desiccators over H&04 below 2fi°C, also yields separable crystals, while crystallization from open beakers or desiccators between 28 and 35'C yields only inactive holohedral crystals of the racemate (Fig. 5). Crystallization from open beakers or desiccators above 35'C yields inactive holohedral crystals of sodium racemate and ammonium racemate (Fig. 4). Crystallization in the presence of "seeds" of optically active material or pieces of silk, paper, or hair may yield preferential crystallization of one of the two antipodes. Students may prepare raeemic acid by mixing saturated aqueous solutions containing equal weights of (+)- and (-)-tartaric acids, both commercial and prepared as in above procedures. On seratching, heat is evolved, and precipitates of copious white crystals deposit. The same experiment may he carried out with sodium ammonium (+)- and (-)-tartrates, both below and ahove 2fi°C, followed by "seeding" or slow evaporation if necessary. If a mixture of the two solid tartrates is heated ahove 26'C. an increase in volume occurs and the liberated water dissolves part of the resulting racemate (21). Heating sodium ammonium racemate above 3 5 T results in formation of sodium racemate and ammonium racemate (32) (Fig. 4), while heating sodium ammonium (+)-tartrate to 58-59'C results in formation of sodium (+)-tartrate dihydrate and ammonium (+)-tartrate (33) (Fig. 8). The triand holurninescent properties ( 3 4 ) of the sodium ammonium (-)-tartrates and the pyroelectric properties (4) of t,he (+)- and (-)-tartaric acids mav also be investigated.
(+I-
mine the water content. Large crystals of any or all of the acids or salts may be grown by use of standard methods (30, 35, 36). The resolution of other substances by crystallization procedures may also be attempted (24).
Results and Discussion
The relations between the tartaric acids, racemic acid, and their sodium ammonium salts that are investieated in this experimenl are shown in Figure 9, and theoretical and experimental optical actkit). values for some of t h e various samples of acids and salts prepared in this experiment are shown in the table. The resolution is not quantitative, as even Pasteur himself ohserved (3-5). Furthermore, Pasteur used samples ahout ten times as large as ours, and he recrystallized his products at least twice t o ensure optical purity. The concentrations of the solutions that he employed for measuring optical activity (-50%) were at least ten times as concentrated as ours, and he used 5-dm polarimeter tuhes compared to our l-dm tuhes. Nevertheless, although the student may not succeed in exactly duplicating the actual theoretical values of the o ~ t i c a activities l of the various salts and acids, he will still have the satisfaction of having carried out one of the classic experiments of all time and will emerge from this experience with a real appreciation for the experimental and observational skills of a master scientist.
%-Tartaric aeid, 99+%, [a]oZL' = +12.35', Catalog No. T 10-9, .Aldrich Chemical Ca. '1-Tartaric aeid, 99%, Unnatural, Catalog No. T 20-6, Aldrieh Chemical Ca. &meso-Tartaricacid hydrate, 99%, Catalog No. T 60-5, Aldrieh Chemical Co.
The specific rotation of the above compounds increase with creasing temperature. Temp. 2 5 ' ~ . d ~ e m p1 . 7'~. b Temp. 2 3 ' ~ . eTemp. 2 1 ' ~ . f Salts from commercial acid CTemo. 2 0 ' ~ .
in-
Acknowledgment
Our thanks go to Edward Wolf, who attempted a similar hut unsuccessful mechanical resolution of K3[Co(C204)3]. 3 H H 2 0 (37). The senior author also wishes to acknowledge the assistance of the John Simon Guggenheim Memorial Foundation for a Guggenheim Fellowship and the California State University, Fresno for a sabbatical leave, and the National Science Foundation Undergraduate Research Participation Program (Grant GY-9916). Literature Cited 111 Pasteur, L., u-I.
"Oeuures de Paslaur," (Edilar Vsllery~Rsdot. R.I. Messon. Paris, 7
1977.1WQ
sVlneLtd..Ed~nburgh. 1948. 161 Riot. J. B., Mem. l n a l deFmnre. Closar Scr.Math at Phys., 13,1.1118121. 17) Riot. J. B.,Buli.Sri.Sor Philomoth. l815.190. (8) Herschel,J. F. W., Tmhs. CombridrePhil.Soc. 1.43 118221. 191 Retrius. A. J., Kongl. Suensko Vetenakopa Akod. H o d , 31.207 (17701. 110) Biot. J. B., Compt. Rend.. 13.157 118351. See also Patterson. T.S., Ann. Sci..3.431 119381. I111 Berzelius, J. J.. Kongl. Suensko Vetenshops Akod. Hondl.. 49. 70 (18301: Ann. Phyr., 19,305(18301. 112) Rerzeliu8,J. J.. Jnhresbericht, 11.44 (18.911. 1131 Bid. J. B.. Ann. Chim. Phys.. (21 69.22 (18381. 110 de la Provastaye,F. H., Ann. Chim. Phyr. (313. 129,353 (18411. 131 4,453 (1842):
.
.
iR, ,. , i A" .. ,,*A?, ,.. .. ,
(15) Frereniur.R.. Ann. Chem.. 41.1 118421 1161 Milscherlich. E.. BPI Berlin Akad.. 1842.246. (17) Hioi. J. B.,Compt.Rend., 19.719 11Sdll. (181 Wvmuhoff.G..R~IiSoc Chim Froncr 41.212ilRRdl . (19j Wyouboff. G., Ruil. Snc. Chim. Flonce. 45.62 11886):Ann. Chim Phys.. (61 9.221 11886). 1201 Lowry. T. M.. "Optied Rotatory Power,'' Dovor Puhliesfiun*,New York. 1964. ~
. .
~
Compl.
.
,
~
end.: 73. ,
~
(18661 (extract of a letter to Pasteurl: Ann.
~.~~~~
i3oi ~ . t t . ~ . , s..& ~. ~ ~ " h a n a c..~nn. n, sci. 6 . 2 ~ 8119471 ck. C.. "Exoerimental Riochemistrv." Jnhn Wilev
.. chemistry: An Experimental Approach: Appletan-Century-Crofts, New qork. 1969. pp. 4887489: Kaoffmsn, G. R., "Resolution of the T~ia(l.LO~phensnfhroline)nickel(lllIon." Modular Laboratory Pnlgram in Chemistry SYNT-123,W i l ~ lard Grant Press. Ruston, Mam. 1972. 1321 van', Hoff. J. H..and Goldichmidt, H..Z Physik. Chem.. 1'7,506IISSS):van't Hoff, J. H.,Cnldrchmidt. H., and Jarissen,W. P., Z Physik. Chem.. 17.48 118951. (33) van Leuwen, J. D . 2 Ph.wik. Chrm..23.48 118971. I:UI Cernez, D., Compt. Rend.. 140. 1339 (19051. 1351 Fehlnor. F. P.,J.CHEM. EDUC.33.449 (L9561. 1361 Holden, A , and Sinber. P., "Crvsials and Crystal Gmwing: Doubleday and Co., Gsrden City. New York, 1960. (371 Jaegor,F. M..RPC.T ~ OChim., U 38.247 (19191.
Volume 52, Number 12. December 1975 / 781
