December 15, 1941
893
ANALYTICAL EDITION (8) (9) (10) (11) (12) (13) (14) (15) (16) (17)
Based on Rupp's original method and the findings mentioned above, a new procedure for determination of mercury in organic compounds was elaborated. The organic sample is decomposed by means of persulfate and sulfuric acid. The procedure is convenient, moderately rapid, and applicable in presence of halogens.
Acknowledgment Grateful acknowledgment is made t o Martha Torrey and Charles Judson, who prepared and purified several of the mercury compounds analyzed, and to Ezra Staple, who executed several series of confirmatory analyses.
(18) {igj (20) (21) (22) (23)
Literature Cited
(24) (25) (26)
Brindle, Quart. J . P h a r m . Pharmacol., 5 , 4 3 2 (1932). Brindle and Waterhouse, Ibid., 9, 519 (1936). Bruchhausen and Hanelik, Apoth. Ztg. 40, 115 (1925). Deal, J . Assoc. Oi9iciaZ A g r . Chem., 17, 432 (1934). Dhar, J . Chem. Soc., 111, 726 (1917); Ann. chim., (9) 11, 179, 214 (1917). (6) Ebler, 2. anorg. Chem., 47, 377 (1905). (7) Fenimore, E. P., thesis, University of Pennsylvania, 1929.
(1) (2) (3) (4) (5)
(27)
Fenimore and Wagner, J. Am. Chem. Soc., 53, 2453 (1931). Ibid., p. 2468. Ibid., p. 2472. Fitagibbon, Analyst, 62, 654 (1937). Knoevenagel and Ebler, Ber., 35,3065 (1902). Kolthoff, P h a r m . Weekblad, 60, 18 (1923). Kolthoff and Keijeer, Ibid., 57, 913 (1920). Koppeschaar, 2.anal. Chem., 15, 233 (1876). McNabb and Wagner, IND. ENG.CHEM.,ANAL.ED., 1 , 3 2 (1929). Organic Syntheses, Coll. Vol. I, p. 155, New York, John Wiley & Sons, 1932. Paooe. J . Assoc. OfficialAm. Chem.. 15. 409 (1932). Rauscher, IND. E&. CHEM., ANAL.ED'., IO, '331 (1938). Rupp, Ber. 39, 3702 (1906). Ibid., 40, 3276 (1907). Shchigol, 2. anal. Chem., 96, 330 (1934). Shukis and Tallman, IXD.ENQ. CHEM.,ANAL. ED., 12, 123 (1940). Van Name and Edgar, 2. P h y s . Chem., 73, 107 (1910). White, J . Am. Chem. SOC.,42, 2350 (1920). Whitmore, "Organic Compounds of Mercury", p. 225, New York, Chemical Catalog Co., 1921. Ibid., p. 259.
THISpaper represents a completed portion of the experimental study t o be submitted in partial satisfaction of the requirements for the Ph.D. degree at the University of Pennsylvania.
Photometric Method for Estimation of Minute Amounts of Mercury ALBERT E. BALLARD
AND
C. D. W. THORNTON, Eastman Kodak Co., Rochester, N. Y.
I
T HAS been shown by a number of investigators ( 4 , 5 , 2 ) that mercury resonance radiation of wave length 2537 A. is absorbed by mercury vapor. If a constant source of this radiation (General Electric 4-watt germicidal lamp) is placed at one end of a tube and a narrow-band photoelectric cell sensitive to this line is placed a t the other end, a microammeter, connected through an amplifying system to the photocell, will indicate the amount of light falling on the cell. It is evident that, if the tube contains mercury vapor, some of the light will be absorbed and the microammeter will give a different reading from that given when no mercury vapor is in the light path. This is the principle of the mercury-vapor detector developed by Woodson (6) to determine the amount of mercury vapor in air. Hanson (2) has shown that a number of organic solvent vapors absorb this radiation (although to a
sulfide) are completely removed by allowing solutions of the metal ions to filter slowly through filter paper impregnated lvith cadmium sulfide. Some modification of this recovery method is required, since filter paper or other organic matter would be decomposed on subsequent heating, with the formation of smoke, and this would seriously affect the photometric method for the estimation of mercury. The authors have observed that a pad of preignited asbestos fibers impregnated with cadmium sulfide is equally efficient in removing mercury ions from solution and the mercury sulfide so obtained is in an ideal condition for the subsequent thermal treatment. These adaptations of well-known principles are the basis of the method presented,
+
much lesser mercury vapor), degree andthan his Tri-Per-Analyzer an equal weight of is -..____ . . - -. . 5 based on the same principle. i\ These instruments have been designed to 5.1 estimate mercury or solvent vapors in large volumes of circulating air, and are not applicable to the estimation of minute amounts of mercury present in solution. The authors have observed that, on heating mercuric sulfide in a closed system in a quartz-$nded cell (Figure l), the amount of absorption of the 2537 A. radiation is constant and reproducible for a given amount of mercuric sulfide. It is obvious that if a simple means were available for converting mercuric ions to the sulfide and collecting the mercuric sulfide formed, the photometric method could be used for the determination of mercuric compounds in solution. Clarke and Hermance (1) have shown that minute amounts of metals (the sulfides of which are less soluble than cadmium D
I
$>
t
I
A
FIGURE 1. ABSORPTIONCELL
INDUSTRIAL AND ENGINEERING CHEMISTRY
894
Val. 13. No. 12
R e c o v e r y of Mercury
iir (S). Five grams df the wdl-fl&ed m&rid (generally freed from any hard pieces) are placed in 100 cc. of 15 per cent, cadmium acetate solution tLnd allowed to soak for 5 minutes. The asbestos is drained off through a coarse sintered-glass funnel. The pad, weighing approximately 45 grams. is ueeled from the sinteredglass funnei and most of the excess s o & n sulfide is removed hv ~
~~~.~
~~~~~
~~~
....
washed &s before, but &ch more thoroughly, the moist asbestos pad being removed from the filter and dispersed by stirrine in 2 a mufflefurnace at 550' for 1 hour. After coolini, one hilf of the
will settle to the bottom of the flask, as it was not possible t o fluff ~~~~~~~
&ie&ion &e diluted t o ~nuroximatelv450 free water.
~
ce.
~
with mereurv-
FIGURE 3. BATTERY OF EXI-RACTORS
A
FIGURE 2. APPARATUS FOR RECOVERY or MERCURY
Mercury-Free Water. This is prepared by stirring 25 cc. of, the cadn?ium sulfide-impregna>ed asbestos fiber suspension with approxunatcly 2 liters of distilled water md, after allowing to stand a few minutes. filterine the solution through a sinteredXhSS funnel. I
asbestos fiber suspension and, after standing ;few minut&, the solution is filtered through a clean sintered-glass funnel. fide-impregnateh pad.
(Tho short V-shaped slots are made with
December 15, 1941
ANALYTICAL EDITION
E95
The dried pads containing mercury are stable and a number of them may be prepared, using a battery of recovery units and the mercury determined later in a group, or for routine determinatioiis the recovery and determination of groups can be alternated, so that the operations are carried on simultaneously. If the solution contains suspended material, this must he removed by filtering through a clean sintered-glass Iilter or a filter paper that has been washedvith 1 to 4 nitricaeidsolution. Mercuric ions are adsorbed to glass from dilute solutions. The solutions used for calibration and those under investigation should, therefore, he run as soon as prepared. All solutions should he prepared in Pyrex glass. Tube B (Figure 2) containing the sintered-glass disk is rinsed with strong nitric acid, washed, and finally rinsed with mercury-free water just before use.
FIQURE 4. SCHEMATIC DIAGRAM OF CIRCUIT ~~
C-1. C-2.
0.002 mid.
R-8. M-1.
0.002 mfd.
C-3. 8-8 mid.
FJ-405.
Phototube
L. 16henry choke R-1. Bridge balance 3000 0. R-2. Senntlnty &ml, 1000 R-3. 1000 Y. R-4. R-5. R-6. R-7.
1000
W.
15,000 W. 5,000,000 W. 500.000 m.
m.
5000~. 0-300 D.
C. microammeter 0-130 A. C. voltmeter 8w-I. D. P. 9. T. on-off power BUPPIY switch SW-2. S. P. S. T.brldge bala?c ing and phototube dieconnecting switch T-1. VL-0 Universal Varitran T-2. Power transformer T-3. V L 2 Universsl Varitrsn M-2.
pump. A glass rad is introduced from the bottom of the tube and the glass disk is gently forced up to the level of the top of the standard tamr joint. The abestos pad is peeled off from the
Determination of R e c o v e r e d Mercury APPARATUB. Fiaure 4 is 8. schematic diagram of the circuit. Figure 1 is B front and side view of the absorption cell, a 4-om. Pyrex tube ground and nolisbed on the ends. to which two stopcocks and a standard tmer male
attach the m,&holdmn'tuhe. which is heated t o e;olve mercury vapor. To facilitate cleaning the cell, detachable quartz ends w e employed. Male threaded collars are cemented over the outside of the 4cm. tube, which Droiects 1 to 2 mm. I ~~~~
The pad is now ready for d e t e m h t i o n as dkcted bel&.
NOTES ON RECOVERY. The cadmium sulfide-asbestos pad should contain no very thin spots through which the solution could pass without completely removing all the mercury present; a simple visual observation will suffice to detect any thin spots. The dried pads weigh approximately 10mg. Through properly prepared pads the rate of flow of solution has been increased to approximately 10 cc. per minute with complete recovery of mercury. But, using a battery of eight extractors (Figure 3), there is no advantage in speeding up the rate because the pads must be prepared with much greater care and the routine can be so oraanized that no time is lost a t the rate of 4 cc. per minute. The efficiencv of the Dads in recovering mercury from solutions should be tested by allowing 0.5 microgram of mercury as nitrate in 200 cc. of solution to flow through a pad at the rate selected. The solution is collected in a flask and again passed through a new pad at the same rate. The pads are dried and the mercury is determined in each pad by the method given below. The second pad should not contain over 0,01 microgram of mercury (corrected for blank or untreated pad) as calculated from the calibration curve. A blank pad, when tested as directed below, should not give a deflection on the microammeter greater than that given by 0.02 microgram of mercury. I
~~~~~~
~~..
gaskzs similar to those used in pola&ope tubes. Figure 5 (coded t o agree with Figure 4) shows the arranaement
896
Vol. 13, No. 12
INDUSTRIAL AND ENGINEERING CHEMISTRY
TABLE I. REPRODUCIBILITY OF READINGS Micrograms of
Readinpa. Corrected for Blank Pad
The furnace Varitran is n o 6 readiusted to the Dredet;&ink;i ~o
~
~~
~~~~
~~~~
Successive readings are'mde it Z-nhute intervals; when the d z flection changes only 2 to 3 divisions from the previous reading, a final reading is taken. (This normally occurs 6 to 10 minutes after beginning the heating of the pad.) It is necessary t o construct a calibration curve for convertine ~
~
~~~
~~~
~~~~
~~
~
~
evolved from the pads &s outlined and the redings on the mi& ammeter ar? observed. FIGURE 6. EVOLUTION AND ABSORPTION UNIT
shows thr nrr.ingemmt of psrti of the evolution nnd absorption unit 'The niet31 wll holder g n d tlie ~rlrotocellnre tlierrnkllv insulated front orlwr nictil m i t i of the unit. whicli. : ~ l t h o u d ~ well vented in the rear and bottom. become $arm b< mdiati%
~
Table I shows the reproducibility of readings. Figure 7 was plotted from the data given in Table I and was used for converting microammeter deflections given by unknowns to mass of mercury.
ines and rottom with asbestos cloth. The inner f&me tem-
FIOURE 7. DETERMINATION OF MERCWY
Aft& the instrument has been brought to tem erature equilibr i m (approximately 1 hour), the instrument is fairly stable and necessary readjustments are slight.
NOTES ON DETERMINATION. If the shutter is kept open and light is allowed to pass continually through the cell, the reading on the microammeter will slowly sink to zero, even when mercury vapor was present in the cell before opening the
.
.
December 15, 1941
ANALYTICAL EDITION
shutter. This is not observed, or at least is not of the same tim. order, when the shutter is kept closed and only opened for a few seconds while readings are being made. Whether or not this effect is caused by mercury being deposited on the walls of the glass cell under the influence of the light has not yet been ascertained. (Calculations show that the amount of mercury required to saturate the nitrogen in the cell is much larger than the amounts present.) If the cell is filled with vapor containing mercury and the light source allowed to pass through until a zero reading is obtained, the shutter closed, and the cell allowed to stand, a partial regain of the absorption effect Tvill be observed. If carried over to a subsequent determination, this in effect will cause erroneous readings, and a probable explanation is that the ionized mercury vapor is more readily adsorbed to the glass surface than the unionized vapor. I n accordance with the above observation, the authors have found it necessary to keep the shutter closed except for the shortest time required to make a deflection reading. The apparatus should not be operated in a room illuminated by daylight, which is variable, unless the evolution unit (Figure 6) is shielded from the light. An inside room lighted artificially has been found satisfactory.
Summary The method presented allows the determination of 0.02 to 0.60 =t0.02 microgram of mercury in 150 to 400 cc. of solution. Using a battery of recovery units as shown, an operator in
891
these laboratories has been able to make 25 determinations per day. The instrument described has been in operation for 6 months without noticeable change in operating characteristics. The method has been used with water-miscible solvent mixtures and with solutions from the digestion of solid organic materials. It would appear to be applicable to the estimation of mercury in biological materials after suitable preliminary digestive treatment.
Acknowledgments The authors extend thanks to H. Crouch and E. Klodinski who designed and built the electrical circuit, to L. T. Hallett and J. Russell for helpful suggestions, and to the General Electric Company for the loan of an experimental mercuryvapor detector for preliminary experiments.
Literature Cited (1) Clarke, B. L., and Hermance, H. W.,IND.ENG.CHEM.,ANAL. ED., 10,591 (1938). (2) Hanson. U. F.. Ibid.. 13. 119 (1941). i3) Kaspin, B. L., Ibid., 12, 517 (1940). (4) Muller, K., 2. Phusik, 65, 739 (1930). (5) Muller, K., and Pringsheim, P., Naturwissenschajten, 18, 364 (1930). (6) Woodson, T. T., Rev. Sci. Instruments, 10, 308 (1939); Patent 2,227,117. Phvs. Rev.,36, 919 (1930). (7) Zemansky, 31.W., Co~hrnNIcaTIoNNo.
U. 9.
SO7 from t h e Kodak Research Laboratories.
Separation of Bismuth from Lead with Ammonium Formate SILVE KALLMANN Walker & Whyte, Inc., 409 Pearl St., New York, N. Y.
The sodium formate method, proposed by Benkert and Smith for the quantitative separation of bismuth from lead, shows definite advantages over other procedures, but there are obstacles to its general adoption. A new procedure is proposed, suited for both the quantitative separation and determination of bismuth and lead and for the quantitative separation of small amounts of bismuth from large amounts of lead. The nitric acid solution of bismuth and lead is neutralized with ammonia and ammonium carbonate. .4mmonium formate is added and the precipitate of basic bismuth formate is filtered off, washed with hot water, reprecipitated, and finally ignited to the oxide. The precipitate can also be dissolved in hydrochloric acid and bismuth determined as oxychloride. If the bismuth formate precipitate is very small it can be dissolved in dilute sulfuric acid and bismuth determined colorimetrically with potassium iodide. Lead is precipitated in the filtrate of the bismuth formate as chromate with potassium or ammonium dichromate.
M
ANY laboratories engaged in industrial or research analysis find it necessary to carry out numerous quantitative separations of bismuth from lead, and many cases arise where the time required to perform such a procedure must be kept a t a minimum. A comprehensive survey of the literature shows that a large amount of work has been done on methods for the quantitative separation of bismuth from lead, but in general the procedures have not been entirely satisfactory. The investigation here reported was undertaken with a view to developing a method which would be simple and easy of manipulation and a t the same time give results comparable with those obtained by the more complicated methods-in other words, a strictly routine method that could be really depended upon.
Existing Methods Methods given by standard texts for quantitative separation of bismuth from lead are, with few exceptions, based upon the fact that in weak nitric acid solution the bismuth ion is decomposed upon the addition of water or salts of weak acids, forming basic bismuth compounds. Probably the best known of these methods was suggested by Loewe (IS). Briefly, it consists in precipitating bismuth as
