Table 1.
Determination of m-Benzenedisulfonyl Chloride
% SO2Cl Analyst
Proposed method
Neitzel’s method
point of 63” C. and the following analysis: sulfur, 23.31%; chlorine, 25.78%. The compound was analyzed by the proposed method and by Neitzel’s method. The sample was refluxed with sodium hydroxide for 3 hours to ensure complete hydrolysis. Each analyst performed the analysis 10 times by the
proposed method and three times by Neitzel’s method. The results of these experiments are listed in Table I. The average value for all the determinations by the proposed method was 71.1% SO&l with an average deviation of 3 parts per thousand. Neitzel’s method gave an average of 71.2% S0,Cl with an average deviation of 1 part per thousand. KO free acid was found in this compound. The complete analysis for the sulfonyl chloride group can be completed in 15 minutes. The concentration of reagents is not critical. Consistent results are obtained with 5 to 25 ml. of water or chloroform, Low results are obtained with less than 10 ml. of pyridine. This method can be adapted to many
other sulfonyl chloride compounds. It has been used on m-nitrobenzenesulfonyl chloride and on diphenyl sulfone-3,3-disulfonyl chloride. The results by the proposed method and Seitzel’s method agree to within =l=O.l’% and are consistent with the purity of the compound as determined by elemental analysis. LITERATURE CITED
(1) Keitzel, F., Chemiker Ztg. 43, 500 (1919). (2) Seaman, m., Sorton, A. R., Woods, J. T., MaEsad, E. A,, IND.ENO.CHEM., ANAL.ED. 16, 517-19 (1944).
RECEIVEDfor review October 20, 1958. Resubmitted December 30, 1959. Accepted December 30, 1959.
Com position of Aluminum Nitrate-Nitric by Spectrophotometric Measurements
Acid Mixtures
ROBERT W. HENRY and GLENN L. BOOMAN Atomic Energy Division, Phillips Petroleum
Co.,Idaho Falls, Idaho
b The ternary system of aluminum nitrate-nitric acid-water was studied spectrophotometrically. Acid and aluminum concentrations are determinable by correlation of measured absorbances a t 295 mp and 2.667 microns. Use of these measurements enabled the prediction of free acid and aluminum concentrations to 0.03 and 0.02M (95% confidence limits) respectively, a t the 1M range. Consideration of the limiting factors on the measurements indicates the feasibility of increasing the precision b y a factor of seven, using a special-purpose instrument.
possible method for in-line application. Schneider and Schwieger (6) report that a miniature high frequency oscillator possesses sufficient linearity to be applicable for the monitoring of acid and aluminum when used with another measurement that produces significantly different relationships between the effects of acid and salt concentrations. A radio-frequency monitor for nitric acid concentration in process feed has been successfully operated for several months a t Oak Ridge (4). Hydronium ions and undissociated nitric acid absorb in the infrared region (3) but the spectrum of each species is complex and has not been fully defined. Measurements in the near-infrared region were chosen for study because use of a quartz absorption cell, a tungsten filament source, and a lead sulfide detector makes this spectral region practical for in-line measurements of radioactive nitric acid solutions. Although specific absorption bands for hydronium ion or undissociated nitric acid, without overlapping bands of other species, were not found, absorption measurements a t 2.667 microns and 295 mp were shown to define the ternary system clearly.
M
decontamination from fission products in uranium recovery by solvent extraction and prevention of precipitation of hydrolyzable ions during storage are strongly dependent on acidity. For continuous process operation, a method for the determination of acid adaptable to inline operation would be of great value. Existing routine analytical methods in use a t the Idaho Chemical Processing Plant are not so adaptable. A literature survey shows that most current methods are based on complexation of the hydrolyzable ions followed by titration with standard base to an appropriate end point ( I , 2, 6). High frequency conductivity has been studied as a 832
AXIMUM
ANALYTICAL CHEMISTRY
EXPERIMENTAL DETAILS
Apparatus. Absorbance measurements were made with a Cary Model 14 recording spectrophotometer using
O.l-mni. Aminco short-path quartz cells. The spectrophotometer was equipped with a thermojacketed cell holder and temperature was controlled a t 25’ + 0.1’ C. with water circulated from a constant temperature bath. T h e sample compartment was continually swept with nitrogen passed through a column of Drierite. For measurements a t the 2.667-micron peak, a 2.5-micron band pass filter with 0.25 ho half-width (A0 = mean wave length pass of filter) and a long wave length pass filter with a cutoff slope of 0.09 = 2.25 microns) a t approximately 2.25 microns were used to pre-
-100.0 IS0 190 200 210 220 230 240 2.50 2.60 2 7 0 WAVE LENGTH ( p )
Figure 1. water
Near-infrared spectrum of
vent heating of the sample. Because of the high absorption of the source energy in the quartz oiitics, the gain was increased to give a 2.0-nim. slit width at the 2.667-micron 1;eak. Cell absorbance a t 2.667 microns \!-as calculated from absorbance nieasurement's of a Tvater-acetone mixture a t 0.101-nim. and 0.503-mni. path lengths assuming equal absorbance for the two cells. Cell path length was determined from interference patterns of the empty cells. The cell absorbance a t 295 mp was assumed to be the absorbance obtained ryitli distilled ivater in the cell. Density measurements were made with a Christian Becker Westphal balance and use of :ippropriate correction tables. Reagents. C . P . grade reagents were used \v ibli o 11 t pu ri f ic a t i on. T h e nlu minuni nitrate stock solution was standardized by ignition t o t h e oxide. S i t r i c acid solutions n-ere standardized by t'itration with standard base. A 4 x 1 latin squ:tre series of these t n o constituents was prepared in steps of 0.511.ffrom 0 t o 1.SM of each. Free acid, on solutions containing aluniinmn nitrate, was determined with a precision of ? ~ 0 . 0 5 ~standard V deviation liy the metliod of Boonian et al. ( 2 ) . , Frce acid is &fined as that amount of acid which renmins if the hydrolyzable ions \vcrc reniowd from the solution as stoichiometric salts ( 2 ) . Procedure. Because of alxorption by quartz cells nnd quartz optics of t h e s pee t ro p li o t o me t er a t 2.667 microns, only s small portion of t h e source energy reaches t h e detector. This difficulty n-as somen-hat overcome by increasing instrument gain. The consequent increase in noise level \vas reduced by loner pen gain. T h e cell compartment was flushed for 20 minutes with d r y nitrogen before measuring the sample absorbance. Ten absorbance readings, 1 minute apart, were averaged to give the sample absorbance. The standard deviation for the average of IO reading, v a s *0.002. A11 absorbances at shorter wive lengths v-ere measured with normal gain settings. The cell compartment was flushed with dry nitrogen for 20 minutes prior to a11 near-infrared measurements
DISCUSSION
After mixing, aluminum nitrate and nitric arid were shown to reach absorbance st,abilit,ywithin 15 minutes a t room temperature. Absorbance a t 2.G67 niicrons (see later discussion) and free acid \vere followed on a 1M aluminum nitrat,e-lM nitric acid mixture. Slimpies of the mixture were heated on a steam bath for 1, 3, and 6 hours, respectively. Absorbance and free acid remained constant from the final readings a t 15 minutes through the 6-llour sample. The spectrophotometric study was limited to an upper wave length of 2.67 microns, the limit of energy transmission by the instrument's quart'z optics. The spectrum of water from 1.80 to 2.67 microns is shown in Figure 1. Peaks are at' 1.925 and 2.667 microns and a weak plateau is observed a t 2.55 microns. Don-n to the ultraviolet cutoff of the instrument, there is only one more peak, also in the near-infrared, a t 1 .45 microns. Scans of various mixtures of nitric acid and aluminum nitrate produced only; one additional peak. 295 mp in tht- miltravidet. Further studies shon-ed the absorbance of the 295-nik peak to be a direct function of total nitrate concentration. The absorbances a t 1.43 and 1.925 microns n-ere insensitive to changes in solution composition. -it the 2.667micron peak and the 2.55-micron plateau. absorbances vary with solution composition but not as any ~ i m p l efunction of the variables. The absorbances a t the three wave lengths of 295 m p , 2.55 microns, and 2.667 microns were plotted on linearlinear graph paper in the three possible pair combinations. The 295-mp-2.667micron pair, shonm as Figure 2, gave the only correlation useful for predicting aluminum nitrate and nitric acid concentration. The standard deviation in
absorbance units a t both n-ar'e l r i i g t b m s 0.002, correppontling t o 95% confiderice limits in predicting romposition of 0.03X in nitric arid and 0.02.11 in aluminum nitrate. Inasmuch as thr: 295-1111, measurement follows total nitrate, density is a possible substitute. Hoivewr, a precision (standard deviation) oi better than 0.002 density is required to give the same precision as the spectrophotometric measurement and it is questionable Ivhether this degree of precision could be obtained ivith in-line density nieasuring instrumentation suitable for highly radioactive process streams. I n grneral, the absorbance a t 2.667 microns is due to hydrogen bonding which can include HzO, 1 1 3 0 L, various nitric acid species, and aquo and hydrolyzed aluminum nitrate species. I n an attempt, to interprct the absorb:tnce a t t'his wave length, an absorbance, A,, was calculated as follow: :lobs - .4,,11 1000 DH,O - g./1.€INO, 1000 DH,O
A,
c
g./1.ALIFI)~)~]
AH~O
in which Aobs =
observed absorbance
Acell = absorbance of cell A I T , ~= absorbanre of Tvater DH~= O density of Rater a t 25' C.
The calculated absorbance, A = , is the total absorbance of the solution corrected for the absorbance of water alone, Significance of the nitric acidaluminum nitrate interaction is then made apparent. The absorbance A , is a funct,ioii of all the species in solution except water. d plot (Figure 3) of A , os. absorbance a t 295 nip indicates that one or more species due to the presence of nitric acid and one or more species attributable to aluminum nitrate contribute about equally, on a molarity basis, to the 2.667-micron absorbance. By considering the partial derivatives
I273 I260
1250 I240
N
1223
L. c
5
Ill0
P
I200
m
c m 1190
ABSOR0ANCE 1 2 9 5 n r ) AElSORBWCEI 2 9 5 m l i ;
Figure 2.
Wave length correlation plot uncorrected for water
Figure 3. for water
Wave length correlation plot corrected
VOL. 32, NO. 7,JUNE 1960
833
i t is evident that a significant concentration of hydrolyzed aluminum species is present. A full interpretation of the results would require the study of simpler systems. The utility of this wave length depends on the absorptivities of the aluminum nitrate and nitric acid species as well as the change in water concentration due to displacement of water by the salt and acid. The practical use of the 295-mp2.667-micron correlation depends mainly on the design of a suitable instrument.
A single-beam, narrow-band-n5dth1 filter instrument n-ith an optimum damping circuit a-ould give a calculated improvement in precision of a factor of seven. The use of quartz in the optical system and the fast response time intrinsic in the design of the Cary Model 14 spectrophotometer produces an unfavorable signal to noise ratio a t 2.667 microns. LITERATURE CITED
(1) Blaedel, 1%'. J., Panos, J. J., ANAL. CHEM.22,910-14 (1950). (2) Booman, G. I,., Elliott, hZ. C., Kim-
ball, R. B., Cartan, F. O., Rein, J. E., Ibid., 30, 284-7 (1958). (3) Falk, M., Giguere, P. .1.,Can. J . Chem. 35, 1195-204 (1957). (4) ORNL Analytical Chemistry Division, Annual Progress Rept., U. S. Atomic Energy Commission, Rept. ORNL-2453, 12 (1957). (5) Pepkowitz, L. P., Sabol, W. W., Dutina, D., ASAL. CHEM.24, 1956-9 f\19.52). ----,
(6) Schneider, H., Schwiege:, L. G., U. S.
Atomic Energy Commission, Rept. IDO-14419 (1957) confidential. RECEIVED for review December 21, 1959. -4ccepted March 28, 1960. The Idaho Chemical Processing Plant is operated by Phillips Petroleum Co. for the U. 9. Atomic Energy Commission under Contract Xo. A4T(10-1)-205.
ZirconyI- Aliza rin Chelate in Spectrophotometric Determination of Trace Amounts of Fluorine R. P. ASHLEY Aluminium laboratories Ifd., Arvida, Quebec, Canada
The preliminary separation of the fluoride ion from fluoride-bearing materials by the Willard-Winter steam distillation invariably yields a distillate which is slightly contaminated with the acid used for the distillation. This free acid is an undesirable feature of absorptiometric procedures requiring precise control of pH. A simplified method for the determination of microgram quantities of the fluoride ion involving a zirconium-sodium alizarin sulfonate reagent is presented. Good precision and accuracy are obtained without the tedium of pH adjustment, and adequate sensitivity coupled with strict observance of the Beer-Lambert law in the fluoride range 0 to 1.9 y per ml. makes possible the precise measurement of concentrations of the order of 0.05 y per ml.
cision can be achieved only by careful control of pH, and where large numbers of samples are handled routinely, this is undesirable because of time expenditure. EXPERIMENTAL
Stability of the Zirconyl-Alizarin
Lake.
I n t h e search for a simpler method, unaffected by small changes in hydrogen ion concentration, t h e zirconyl-alizarin complex which had been recommended by various workers -for example, Sandell (6)-was investigated. I t s reported greater stability (3) at relatively high acidities in contrast to most of the other metal chelates was promising. The formation of the zirconyl-alizarin lake and its subsequent bleaching by the fluoride ion may be represented by the following equations:
A
various photometric methods are available for the determination of the fluoride ion in microgram quantities, there has long been a need for a simple procedure capable of good accuracy and precision. One very widely used method of measuring fluorine in vegetation relies on the bleaching action of F- on the thoriumalizarin chelate ( 2 ), folloFving preliminary isolation of fluorine by the steam distillation of Willard and Kinter ( 7 ) , in conjunction with some suitable ashing technique (4, 5). This absorptiometric procedure offers good sensitivity but the thorium lake is seriously affected by small changes of hydrogen ion concentration. Thus accuracy and pre-
Preliminary tests showed that an alizarin concentration of 0.01 mg. per ml. of lake solution containing zirconium and alizarin in equimolar ratio gave n reasonably deep color for spectrophotometric measurement with cuyettes of 5cm. light path. Absorbance readings within the p H range 2.86 to 0.66 confirmed that the lake could be used at fairly high hydrogen ion concentration, thereby minimizing the effect of free acid in steam distillates containing the fluoride ion. Apparatus and Reagents. Beckman Model DU (or B) spectrophotometer with 5-cm. light path cuvettes. Stock fluoride solution reagent grade sodium fluosilicate is dissolved in 500 ml. (0.8249 gram) of water. Ten milliliters of this solution are diluted t o 1 liter and stored in a
LTHOUGH
834
ANALYTICAL CHEMISTRY
ZrO(OH),
&0
0
-
+ &OH
SO, No
II
I/
0
0 -2rO
ll
I
I
I
I
t 2 H,O
/I
0
0
0-ZrO
SO,
No
