Table II.
High Frequency Response of Some Bile Acids Dissolved in
60%
Ethanol
to improve the stability of the apparatus.
Calibration Curve I Acid
0 0001'tl
0 00111f
0 002M
0 01M
0 02M
Volt Taurocholic Glycocholic Cholic Deoxycholic Lit hoc holic Dehydrocholic
0 79 0 40
7 6 2 77
14 9 4 23
0 92 0 97 1 57 1 26
1 51 1 63 2 27 2 00
ACKNOWLEDGMENT
The authors wish to thank Lennart Stigmark, Institute of Physics, Lund, for valuable help with the construction of the apparatus. LITERATURE CITED
acid is eluted with the front and glycodehydrocholic acid a t 20-30-40 ml. Figure 6 gives a separation of glycodeoxycholic acid a t 10-15-20 ml. and glycolithocholic acid a t 25-35-40 nil. The unconjugated lithocholic acid is eluted after the conjugates a t 70-80-90 ml., but no recording was obtained. For recording taurine conjugates with phase system D, the cell with the smallest sensitivity was used. A chromatogram of taurodeoxycholic and taurolithocholic acids is given in Figure 7. DISCUSSION
The chromatograms show that the response depends on the nature of the substance, mainly as a function of the conductivity. The free bile acids have a dissociation constant of the order of 7 X lo-' in 50% ethanol-water solution (IO). The conductance of these acids is so low that they could not be detected in the effluent concentrations encountered (Table 11). The conjugates are stronger acids. Their dissociation constants in water range from lo-* to 10-5 ( 8 ) . The bile acids with sulfonic substituents are the strongest acids. Thus it is possible to record
taurine conjugates in much smaller concentrations than can be determined by titration. It is difficult to predict the conductivity of a compound in organic solvent systems because of the complex nature of these systems. I n general, the acids and bases must have a dissociation constant of at least 10-6 in water to be detected by the method outlined, The high frequency technique will find many applications in chromatographic work, especially in partition chromatography where organic solvents with low conductivity are used. The method is suitable for the analysis of substances with dissociation constants greater than Sonaqueous solvents may be used if the solvent mixture is such that ion pairs can be formed. The amount of salt or acid in the solvent must be kept low; othernise the sensitivity will be decreased. I n this application, the demands on the stability of the high frequency apparatus are extremely high. Many precautions must be taken to avoid appreciable drift: Temperature change of the crystal will cause amplitude variations, and the tubes must be in excellent condition. K o r k is being carried out
Baumann, F., Blaedel, W. J., AKAL. CHEM.28, 2 (1956).
Bergstrom, S., Korman, A., Acta Chem. Scand. 7, 1126 (1953). Bergstrom, S., Sjovall, J., Zbid., 5 , 1267 (1951).
Blaedel, W,J., RLalmstadt, H. V., k A L . CHEM.22, 734 (1950). Clayton, J. C., Hazel, J. F., XcSabb, W. lI.> Schnable, G. L., Anal. Chim. Acta 14,269 (1956).
Hall, J. L., Gibson, J. A, Jr., ANAL.CHEY.23, 966 (1951). Hon-ard, G. il., Martin, A. J. P., Biochem. J . 46, 532 (1950). Josephson, B. A., Biochem. Z. 263, 428 (1933).
Karrman. K. J.. Johansson. G.. Mikrochim. Acta 1956. 1573. (10) Kumler, IT. D., Halveritadt, I. F , J . B i d . Chem. 137,765 (1941). (11) Sorman, A , , Acta Chem. Scand. 7 , 1413 (1953). (12) Sorman, A , , Arkiv Kemi 8 , 331 (1955). (13) Oehme, F., Chem.-Ztg. 80, 162 f19.56).
(14) R&i&; 'C. N., McCurdy, H. W., Jr., A s . 4 ~ .CHEX.25, 86 (1953). (15) Sjovall, J., Acta Phusiol. Scand. 29, 232 (1953).
RECEIVED for review October 28, 1957. Accepted February 21, 1958. Supported bv grants from Statens Naturvetenskapliga Forskningsrgd (Swedish Natural Science Research Council) and Statens bledicinska Forskningrgd (Sn-edish Medical Research Council).
Analysis of the Nonvolatile Acids in Cigarette Smoke by Gas Chromatography of Their Methyl Esters LOUIS D. QUlN and MARCUS E. HOBBS Duke University, Durham,
N. C.
b The nonvolatile acid fraction of cigarette smoke, after conversion to a mixture of methyl esters with diazomethane, was analyzed by gas chromatographic techniques. Of the 16 esters detected, 1 1 have been identified. Lactic, glycolic, succinic, 'and malonic acids constitute about 7570 of those identified, among which only succinic acid has been reported previously as a smoke constituent. Although some acids containing certain other functional groups cannot be 1400
ANALYTICAL CHEMISTRY
analyzed by the techniques described, the method may b e of value in the partial analysis of complex acid mixtures from sources other than cigarette smoke.
T( 4 ) ,
steam-volatile acids of cigarette smoke have been examined in debut little is known about the tail nonvolatile acids. I n a survey of the literature u p to 1954, Kosak (12) listed succinic, fumaric, citric, and phenolic acids as possibly present in HE
cigarette smoke. Nicotinic and glutamic acids ( 3 ) and three a-keto acids (glyoxylic, pyruvic, and a-ketoglutaric) (6) have been detected since this report. The present paper is concerned with the detection and determination of a number of nonvolatile acids in cigarette smoke. The presence of succinic acid has been confirmed, whereas the other acids detected have not been reported previously. Gas chromatography is the basis for the analytical method used. It is not
EMERSEUCE - I M E ,
Figure 1.
redissolved by tlie addition of methanol, as methylation of suspended acids r a s impractically slow. After 2 hours, the solution vias stripped to about 5 ml. and the exact volume was measured. The distillate was condensed in a dry ice trap and examined for diazomethane (yellow coloration). The residual solution was remethylated if no excess diazomethane appeared in this distillate. The diazoinethane rcquirement is difficult to determine in advance; the amount usually added was about 0.03 to 0.05 mole. The analysis of the ester mixture should be completed a few days after its preparation, as on aging of the sample some changes in t,he gas chromatograms n-ere noticed.
MIL
Gas chromatogram of smoke preparation at
138OC. Sample, 2 0 pl. of methanol solution, equivalent to 0.4 cigarette. Column, 2 meters of dioctyl odipate on firebrick, 1 to 3 w./w. Helium flow, 17 ml.,'per min.
practicable to apply this technique directly to tlie separation of a mixture of the acids under consideration, because of their instability and lack of volatility. The methyl esters of these acids are readily examined by this method and, with a fex exceptions, these esters can be obtained quantitatively b!- trcatiiig the mixture x i t h diazomethane. Such a met'liylation step is a n iniportant feature of the analysis. This approach has also been taken in the analysis of fatt,j- acids (7, IO), hut with thew acids direct gas chromatography has been successful ( 7 , 9 ) . EXPERIMENTAL
Preparation of Smoke Sample. Fifty bright toliacco cignrrttes \rithout atltiitix-es. 70 mni. long. were huniidificd o w r a saturated sodiuni were bromide solution. Tliese smoked Ti-itli a n sutomatic smoking machine using one 35-ni1. puff per niinute of 2-second duration ( 2 ) . Kormall\- c~:ichcigarette was puffed 11 times. :ind tlie averLige butt length n-as 20 inin. The smoke \vas coiidensed in a series of six traps in d r y ice-ethanol baths. The traps and connecting tubing n-ere n-ashed ivith 50 nil. of ether and then with five 20-ml. portions of 0.5% sodium hydroxide. The ether was extrackd with each of the sodium hydroxide washes. The combined sodiuni hydroxide solution ivas extracted with thrre 50-ml. portions of ether and retained. Isolation of Acids. PROCEDURE A. Follo\ving t h e method of Resnik, Lee. and Pow11 1\18).anions of organic acids in the .odiiiiii liylroxide extract Tvere adsorbed on a 2 x 20 cni. colunin of Dones-1 i CY&--). After washing n-itli 200 nil. of n-ater, the anions were r(3moved with 400 ml. of I . 5 S ammonium carbonate. I n a modification of Resnik's procedure, excess animoniurii carbonate in tlie eluent was destroyed by batch treatment with 300 grains of Dowex-50 (H-1, rather than by evsporation at 'TO" C. Supernatant, liquid and six t o eight 100-nil. n-atpr washes of the rcsin n e r e passed through a 2.5 x
20 cm. cdurnn of Don-ex-50 iH-) to ensure complete conversion to frce acids. Steam-volatile acids were removed by distillation a t 20 to 30 mm. a t a head temperature of 2.3" to 30" C.. riiough n-ater being added to provide 1.5 to 2.0 liters of total tiiqtillate. Then 50 ml. of benzene n ere added and distilled t o aid dehydration of the pot reaidue. The residue was dissolved in j 0 nil. of 50% v . k . methanol-ether and held for me t hyla tion. PROCEDURE R. The sodium hydro.;ide extract was distilled to drvnesq a t 25" to 30" C. a t 20 to 30 nini. The residue was twice takrn up in 300 ml. of n-ater and the solution n-as distilled to dryneqs. This ensured removal of neutral and hasic volatile. n hich niight give extraneous peaks on a gas chromatogram. The residiie was then taken up in 50 ml. of 4% acetic acid. Acids weaker than acetic were liberated; the stronger a d ; . formic and those classified as nonvolatile, remained in the salt form. Free acids were removed hy extraction of the solution Kith five 50-ml. portions of ether. The aqueous wlution TT-DS evaporated to dr) ness a t 20 to 30 mm. Dchydration was completed by the addition and stripping of 50 ml. of hmzenc. The residue was dissolved in 100 ml. of 50% v., methanol-ether containing about 30 meq. of hydrogen chloride added to the solvent as the anhi-drous gaq. The precipitate of qodiiiiii chloride and other insolubles n as removed by filtration and washed n i t h 10 ml. of methanal. The filtrate was stripped a t 20 to 30 mm. to about 10 nil.. removing much of the excess hydrogen chloride n hich n-oiild later consume diazomethane. The solution then was made up t o 50 nil. n i t h the methanol-ether miuture. If a precipitate formed. sufficient methanol TT as added to ensure the dissolution of a n y organic acids therein. Methylation of Acids. T h e solution of acids from either Proceduie A or B was chilled in ice and treated n-ith a moderate excess of diazomethane in ether. A prwipitate of organic acids occasionally foinied n hen t h e ether solution n as added : this n as 17.
Preparation of Methyl Esters of Known Acids. For qualitative gas chromatographic studies, methyl esters of a number of known acid; were prepared by adding diazoniethane t o a methanol-&her solution of 20 to 30 mg. of t h e acid. Excess diazomethane \vas stripped, and t h e residual solution was used directly in gas chromatography. This technique was successful for preparing t,he esters of most acids. After an ester peak in a gas chroniatogram of a snioke preparation had been identified, a larger quantity (0.5 to 1.0 gram) of the individual ester was prepared by methylation of t'he appropriate> acid and purified by distillation. Solutions of definite concentrations of thi. known esters in methanol were preparetl for quantitative gas chromatographic analysis. The solutions of all but tn.o est'ers \yere usable over a period of several mont'lis. Dimet'hyl malate solutions failed to give an elution peak after standing a fen- n-eeks, while after aging a second peak appeared in methyl furoate solutions. Qualitative Analysis of Methyl Esters. A Perkin-Elmer Vapor Frartometer Alodel 1.34-B with a Leecis & S o r t h r u p variable range recorder (Speedomas T y p e G) was used. The only niodification of t h e Vapor Fract'ometer vas the detachment o f t h e solenoid valve from the vent line. T h e vent line was wrapped with a Sichrome heater to prevent coiidensation therein. Coluniiis consisted of tn-o glass U-tubes. 6 mm. in outer diametrr and 1 meter long in series, or of a coil made from 3 meters of copper tubing. '1 inch in outer diameter. Useful stationary liquid phases are recorded in Table I. These were applied to Celite 54.3 (acid n-ashed, 60 to 100 nieslij or C-22 firebrick (30 to 60 mesh) in a ratio of 1 to 3 w./\v.! except for the use of a 1 to 5 mixture with the viscous liquid 11. Helium n-as used as carrier gas. The sample, injected into the gaq stream wit'h a hypodermic syringe. generally consisted of 20 to 40 pl. of :i methanol solution containing :I fenmilligrams per milliliter of the estrrs under consideration. VOL. 30, NO. 8, AUGUST 1958
1401
At a nominal temperature of 150" C., eight peaks were generally recognizable on chromatograms obtained from the use of column,. with liquids I to VIII. These peaks represented esters having boiling points from that of methyl lactate (144' C.) to just above that of dimethyl succinate (193" C.). Figure 1 is a chromatogram of this type for a snioke sample treated b y isolation Procedure A. The identity of the peaks Tvas established by comparing their retention times on the different columns with those of known compounds under
Table I. Used in
Stationary
Liquid
Phases
Gas Chromatography
of
Methyl Esters
Designation Description For 150" and 190" C. Separations I Flexol 8S8a[(C7HljCOOC2Ha)s PU'COC7HISI I1 Flexol R-2H5 (polyester) I11 Flexol4GOa (polyethylene glycol dioctanoate) For 150' C. Separations Flexol -4-260 (dioctyl adipate) v Flexol TOFa (trioctyl phosphate) 1-1 Tricresyl phosphate6 1-11 Didecyl phthalate6 1'111 Dinonyl sebacatec
IT
For Lactate-Glycolate Separationd IS Carbowax 15000 (polyethylene glycol ) s Carbowax 40005 (polyethj-lene glycol) a Donated by Union Carbide Chemicals Co., Sew York, N. Y . Obtained from Eastman Kodak Co. c Donated by Morton-Withers Chemical Co., Greensboro, N. C. Glycerol and diethylene glycol also permitted this separation but were too volatile at the required temperature.
Table 11.
the same conditions. Some typical results are given in Table IT. It Jvas not possible to effect a separation of methyl lactate and glycolate, comprising the first peak, with the columns used. However, with special colunins of liquids IX and X a t lower temperatures, this pair was successfully resolved (Table 111). -4t 190' C., esters having boiling points above that of dimethyl succinate and through that of dimethyl phthalate (282' C.) could be resolved. A typical Chromatogram of a smoke sample treated by Procedure A is reproduced in Figure 2; another unknown and dimethyl phthalate were eluted a t much longer retentions times and are not shon-n. Peak identification !vas accomplished using liquids I to 111. Data are recorded in Table IV. KO attempt was niade to detect esters boiling higher than dimethyl phthalate.
Table 111. Identification of Methyl Lactate and Glycolate
Columns and Conditions - _.___ Liquid phseea CarboCarboTT a s n-ax Solid support Length, ,m. Temp., C. He flow, ml./ min ~~
4000
1500
Celite
Firebrick
3 123 13
2 122 20
Retention Time. Min. .-~
Known Smoke Knoivn Smoke
Methyl lactate 21 0 21 1 15 2 15 2 Methyl glycolate 20 0 28 9* 22.0 21 9 c 0
Quantitative Analysis. The same equipment was used as for the qualitative analysis. Samples of fixed T-olume, usually 20 pl.] were injected into the apparatus with n Perkin-Elmer llicro-dipper pipet. Peaks on the chromatograms were enclosed by dran-ing a line connecting the base line just before and after the appearance of the peak; the areas enclosed were measured with n planimeter. Columns and operating .onditions n-ere selected to give well resolved peaks in reasonable retention times for the identified members of the mixed ester preparation. A summary of general conditions is given in Table V. Obviously, other combinations would also be practicable. Calibration with standard solutions of an individual ester was performed in conjunction with an analysis a t the same operating conditions. The solutions were of such concentration as t o provide peak areas blanketing the area of the corresponding peak in the smoke preparation. Calibration curves, weight of ester plotted against peak area, were prepared when the relationship was not of direct proportion. The weight of ester giving a certain peak area in an analysis was determined. By employing an aliquot factor, the weight of the ester in the original smoke preparation n ac obtained.
On solid support 1 to 3 a . / w .
* Combined with dimethyl oxalate.
Results of an analysis of a single smoke preparation are given in Table VI. The values are an average of two determinations, \vhich generally agreed within 5 to 10%. Quantitative analysis was also performed on ester preparations from mixtures of known amounts of certain acids to determine recoveries in the various procedures. The results are recorded in Table 1711. The acids in mixture I in methanol-ether qolution
c Well separated from dimethyl oxalate peak at 19.5 minutes.
Identification of Methyl Esters by Comparative Gas Chromatography at
I
Y
?I
150" C. Columns and Conditions Dinonyl Liquid phase" sebacate Solid support Firebrick Length, ,m, 2 Temp., C. 154 He flowv,ml./inin. 9
Didecyl phthalate Celite 3 146 11
.
Flexol 4GO Firebrick
Flesol -2-26 Firebrick
2 146
2 138 16
11
Retention Time, illin. Ester of Knon-n Smoke Known Smoke Known Smoke Lactic ~ ; 7 .~ 0 7 . 1~ 6 . 9~ 6 . 9~ ~ 5.0 5 0~ Oxalic 8.2 8.1 11.4 11.5 7.2 7.2 b Unknown , , . 11.8 ... 14.8 ... Malonic 13.3 13.1 17.1 17.3 11.8 11.6 Furoic 20.5 20.4 26.6 26.8 16.8 16.8 Levulinic 21.9 22.0 30.1 17.9 1T.8 Succinic 23.5 23.8 30.3 30.7 19.6 19.7 Lnknown , . . 26.8 ... 34.1 ... 20.8 On solid support 1 to 3 w./w. * S o t detected under these conditions. c Xot resolved from succinate peak. 1'
1402
ANALYTICAL CHEMISTRY
Known
6~ .0 8.7
...
13.9 20.8 23.1 25.6
.,.
Smoke 6 .j0
8i6 ~~ ~~
13.8 20.9 23.2 25.6 28.9
C
_~_ 2
4
6
8
.
10
I 2
14
EMERGENCE T M E , M i N
Figure 2. Gas chromatogram smoke preparation a t 1 9OoC.
of
Sample, 20 PI.of methanol solution, equivalent t o 1.8 cigarettes. Column, 2 meters Flexol R 2 H on firebrick, 1 to 5 w./w. Helium flow, 9 ml./per min.
were treated with diazomethane and stripped to a convenient volume. The acids in mixture I1 were dissolved in 0.5% sodium hydroxide and placed through isolation Procedure A and the methylation procedure. The acids in mixture I11 were dissolved in 0.57, sodium hydroxide and subjected to isolation Procedure B Tvith subsequent methylat ion. RESULTS AND DISCUSSION
Gas chromatography proved useful for the analysis of the nonvolatile acid fraction of cigarette smoke. The identification of 10 new acids (Table T) and the confirmation of succinic acid were possible b y examination of this fraction after conversion to methyl esters. The identifications were made b y comparing retention times of known esters with those of the peaks in a smoke preparation. Identification was considered conclusive when identity was established with each of three different columns. I n many cases. checks on five to six columns were made. Five other peaks, not yet associated with specific compounds, were also noted. The specificity of the ion exchange method used in the sample preparation indicates that these result from additional acids rather than frorn other types of smoke constituents, but confirmation is lacking. Probably further acids are present in the smoke sample but were not detected. The acids reported may result, partly a t least, from hydrolysis of esters in the smoke sample during the isolation procedures. Variations in the experimental conditions may cause differing extents of hydrolysis and thus influence the quantity of acids detected. Both Celite and firebrick were satisfactory as solid supports, and the use of either one does not indicate a n y preference in a certain application. Those liquids used a t 190" C. (stationary liquid phases) were sufficiently nonvolatile to permit sustained operations with the column for a few days, but prolonged use caused significant volatilization of the liquid. The methyl esters chromatographed were eluted in the order of their boiling points, although substantial relative differences in retention times were noted from column to column. When two coinpounds mere eluted with the same retention time on one column, their elution at different times was possible on another column-e.g , methyl levulinate and dimethyl succinate had essentially the same retention times on columns of liquids I, V, VI, and VI1 but different times with liquids 111, IV, and VIII. Methyl lactate and glycolate mixtures were not resolved on any of the above columns; the more polar polyethylene glycols (liquids IX and X) did effect the separation of these two
Table IV.
Identification of Methyl Esters by Comparative Gas Chromatography at
Liauid Dhase" Liduid t o sblid, w./w. Temp., "C. He flow, ml./min.
Flex018S8
190' C. Columns and Conditions Flexol4GO
1 to 3 189
18
Ester of II., Iiwantes, A., Rijnders, G. W, A., Anal. Chim. Acta 16, 29 (1057). -
(10) ill)
-
I
~
~
\
3 -
(12) Kosak, -1. I , Ezpeizentza 10, I39 (1954). (1:3) Resnik, F. E., Lee, L. -1, P o n d , JV. A , L4NA1J. CHEN 27, 028 11955). R ~ C E I V Cfor D rrview March 10, 1958. Accrnteti M a~ r . .12 1958 Southeastern RegiGnal Meeting, ACS, -Durham, N. C., Sovember 1957. Work supported in part by grants from The Damon Runyon %lemo;,ialFund. ~
I
Determination of Traces of Boron in Nickel C. L. LUKE Bell Telephone Laboratories, Inc., Murray Hill, N. J.
,Traces of boron in nickel can b e determined b y dissolving the sample in a small amount of a hydrochloric acid-platinic chloride mixture, isolating the boron by methanol distillation, and determining it by the photometric curcumin method.
s IVGESIOUS iiietliod for the tletermination of traces of boron in pure nickel has been proposed by Chirnside, Cluley, and Proffitt ( 1 ) . However, its applicability is someivliat limited by the fact that the sample to lic analyzed must be in sheet or rod form. Moreover, the method is ob~ i o u s l ynot designed to be used for the snalysis of all types of nickel, because 110 attempt has been made to remove 4 c o n and certain other metals which are known to interfere, when present in more than trace amounts, in thc photometric curcumin method for boron 13). To provide for nider applicability in the analysis of nickel a iiiethod has been developed in nhich the -miiple is dissolved under it reflux ihondeiiser in dilute hydrochloric acid plus a little platinic chloride; the boron IS isolated by mrthanol distillation and tlcterniinrd bv the photometric curI uinin iiiethod (3, 4). EXPERIMENTAL
T h e appaiatus (Figuie 1) consists of a 100-nil. standard-taper quartz conical flask n i t h a loiv-boron glass (Corning KO. 7280) air condenser. Preparation of Calibration Curve. Picpaie a calibration curve as directed ror drterniiiiation of boron in silicon ( i ) . hut add 2 drops of 0.5% rather than 2 ml.of 57’ sodium hydroxide solution to the aliquots of standard boron solution. Dissolve the alkali precipitate in 0.5 ml. of hydrochloric acid-platinic chloride solution [mix 2.5 nil. of I yGplaApparatus.
tinic chloride solutioii nitli 500 nil. of hydrochloric acid (1 I ) ] plus 0.5 ml. of n ater. Wash the solution into a 100nil. quartz flask nitli the aid of 25 ml. of redistilled inethaiiol. Add 1 drop of 0.1% methyl orange solution and ammonium hydroxide (specific gravity 0.90) dropwise until the pink color just disappears. Add hydrochloric acid (1 1) dropwise until the pink color reappears, and then add 3 drops in excess, Proceed to the distillation and photoniptric determination as dirccted (.$).
+
+
no higher tliaii ail inch ahol e the top of the flask. \Then solution i. complcte, cool the flask to room temperature, n ~ s h don 11 the condensed acid n ithin the air condewer into the flask n-itli 25 inl. of lon--boron methanol, and reiiiove the condenser. Add 1 drop of iiiethyl orange iiitlicator solution. Proceed as directed for preparation of calihrc‘1 t’ion curve. Carry a reagent blank through the entire analysis. With t h r aid of the calibration curvr determine the \I cight of boron in the \ample and rmgpiitq. DISCUSSION AND DATA
4
5c c u 9 CO’vDENSiR,
---
-
U CRO BdRNE9
-I
The m e t l i d r i m be used to dctcxrmine acid-soluble boron in iiiost nictals 1s that are soluble in Iiydrochloric. acid. To determine n lictlicr the boron i n iiickcl is likely to lie :itlid to check the accuracy of nicthod, a 0.03% hoioiinickcl alloy n a s prepared. Boron nictal was dissolved in molten nickel under a blanket of helium. A 0.1-gram portion of this sample n a s dissolved in 1 nil. of hydrochloric acidplatinic cliloridc solution. The solution n a s dilutcd to 250 ml. in a. dry volunictric flask n ith Ion -boron nictha n d . A 5-nil. aliquot of this solution, 20 nil. of loll-boron nipthanol, 0.5 nil. of h\-tlrochloric acid-platinic caliloride d u t i o i i , 0.5 nil. of nater. and 1 drop of
7p-Y Figure 1. denser
Flask with air con-
Table I.
Determination of Boron in Nickel
Salllplc T r a i i s f t ~0.100 gram of the subdivided saniple t o a d r y 100-ml. quartz conical standard taper flask i Figure 1). Add 1 nil. of hydrochloric acid-platinic chloridc solution, cap with a lowboron g1:i.s air condenser whose iiiale joint has been wetted with 1 drop of the acid mixture, and heat with a iiiicroburner so that the acid condenses Procedure.
Sivac Xivac 999 999
-1-30 -4-30
BTL-C.1-447 BTL-C.\-447
223 ‘225
Boron Fouritl, l’.P.lI. 0 0 0 0 0 0 2 2
5 6
VOL. 30, NO. 8, AUGUST 1958
2 3 6 6 7 8 0 4 6 0
1405
