V O L U M E 23, N 0 . , 8 , A U G U S T 1 9 5 1 which the resultant ammonia is distilled, absorbed in acid, and determined by titration. Table I shows that the average difference between the two methods was 2.801,. Results using Procedure 3 agree well with those with Procedure 1 (Table 11). SCWR14RY
In the nesslerization procedure described careful control 01 conditions makes it unneressary to run a standard curve more than once. Many factors in the nesslerization procedure may cause inromplete color development, inconhistent color development, or turbidity: type of Sessler’s solution: digestion; temperature and alkalinity of solution to be nesslerized; amount of sodium sulfate; time interval between addition of base and making of colorimeter reading; and rate of mixing during addition of sodium hydroxide. The proper recognition and control of these factors make the prescribed prorrdure quantitatively reproducible from day to day. The use of two solution* (potassium mercuric iodide and aodium hydrouide) is introduced. An alternative procedure, presented in detail, will give accurate results, complete color development, and no turbidity even when the nesslerized \ample gives unsatisfactory results by the ordinary nesslerization procedure. A sample that har been fount1 unsatisfactory can IF :irialyzed by this prorcdurc.
1157 ACKhOW LEI)G.\IE‘YT
This work was applicable to the general purposes of research, being carried out in the Botany Department of the University of Rochester under grants from the Growth Committee of the Sational ReRearch Council and the National Cancer Institute to F. C. Steward. Technical assistance for this work was furnished from these grants and grateful acknowledgment is here made for this help. The authors greatly appreciate the encouragement and help of F. C. Steward. LITERATURE CITED
Hoffman, K. S., and Osgood, B., J . Lab. Clin. Med., 25, 856 (1940). James, W.E., Slesinski, F. A , , and Pierce, H. B., Ibid., 27, 113 (1941). Johnson, 3L. J., J . BioZ. Chem., 137, 575 (1941). Kirk, P. L., ANAL.CHEDI.,22, 354 (1950). Koch, F. C., and McMeekin, T. L., J . Am. Chem. SOC.,46, 2066 (1924). Leitch, J. L., J . F r a n k l i n Inst., 245,355 (1948). Lindner, R. C., and Harley, C. P., Science, 96, 565 (1942). . 20, 481 (1948). Miller, G. L., and Miller, E. E., ~ A L CHEM., Nichols, 11. L., and Willits, C. O., J . Am. Chem. SOC.,56, 769 (1934). Peters, A. K., J . B i d . Chem., 39,285 (1919). Treadwell, F. P., and Hall, W. T., “Analytical Chemistry,” Val. 1, p. 91, New York, John Wiley & Sons, 1937. Vanselow, A. P., IND. ENG.CHEM.,.\SAL. ED.,12, 516 (1940). Wicks, L. F., J . Lab. Clin. M e d . , 27, 118 (1941). RECEIVEDDecember 15, 1950
Syringe-Type Apparatus for Quantitative Hydrogenat ion At Constant Pressures Above 1 Atmosphere C. W. GOULL) AND HERBERT J . DK.%KE General Aniline & F i l m Corp., Easton, P a . The need in this laboratory for catalytic hydrogenolysis of 0.2- to 2.0-gram samples of azo dyes, nitro compounds, etc., led to the development and routine use of an apparatus wherein a metal syringe replaces the conventional mercury piston as a means of restoring the initial pressure. Pressures up to 5 atmospheres are used for reductions requiring 0.5 to 12.0 millimoles of hydrogen. The standard deviation of the per cent relative error is 0.7 for a single determination. No correction is necessary for solvent vapor pressure.
T
HERE is described below a rugged hydrogenation apparatuswhichin 2 years’ use has proved convenient and accurate for samples requiring 0.5 to 12 millimoles of gas. APPARATUS
Figure 1 shows that the arrangement is like many described previously (1-4, 6 ) , except that a metal syringe replaces the double manometer and mercury leveling bulb, a sensitive Bourdon gage serves as the pressure indicator, and a long stainless ateel capillary is used to connect the reactor with the measuring system. Figure 2 shows the arrangement of the component parts. Valves and Manifold. Connections are made with fittings having the standard l/pinch pipe thread. Lunkenheimer stainless steel needle valves are installed to resist leakage of hydrogen from the manifold. Syringe. The syringe consists of a water-jacketed cylinder 7 inches (17.5 cm.) long and 1.180 inches in bore, and a piston moved by a screw 18 threads per inch and 0.625 inch in diameter.
Each turn of the screw displaces 1.00 ml. On the circumference of a wheel attached to the screw are engraved ten divisions, each equivalent to 0.10 ml. A sectional drawing (Figure 3) shows the construction of the syringe. The cord packing in the piston is clamped tightly between washers held by a cap bolt. To prevent leakage of hydrogen through and around this packing, a thick mixture of gear oil (Texaco Thuban 250) and fine graphite provides a satisfactory seal. KO leakage of hydrogen a t 5 atmospheres can be detected in 24 hours. Gage. An Ashcroft laboratory test gage, 0 to 120 pounds per square inch in 0.5 pound per square inch divisions, was calibrated up to 5 atmospheres with a 10-foot open mercury manometer, and a new dial was made to read directly in absolute atmospheres. 4 n y deviation from 1 atmosphere cawed by barometric change is applied as a correction to the initial and final gage readings. Connection Between Manifold and Reactor. As the reactor is rocked by a shaker, a flexible connection is necessary. This is a 10-foot length of stainless steel tubing, 0.125 inch in outside diameter (1.25 mm. in bore), with two coiled sections as shown in Figure 2. This tube is important in preventing solvent vapors from diffusing back into the syringe and gage. Reactor. The reactor was made by the Corning Glass Works from standard heavy-walled 1-inch pipe according to the dimen-
ANALYTICAL CHEMISTRY
1158 slms bi Figiifi: 4. The open end is the regular Coming borosilicate glass pipe ending. The reactor is connected to the connecting tube by bolting the standard borosilicate glass fitting t o a flange brazed to the connecting tube. From a hook on the inlet tube hangs a sample cup made from a lipless 5-ml. borosilicate glass beaker. The inlet tube opens t o the side, rather than t.o the bottom, m order to avold blowing material from the sample cup when hydrogen enters the reactor. The gasket is of two layers: Next to the glass face is a layer of 0.125-inch Teflon; next to the Teflon is smooth '/te-inch neoprene. Shaker. A Bodine motor, Type NC-1-12 RH, 1/50 hp., with a 30 to 1 reduction gear, furnishes power a t 5'7 r.p.m. which is transferred to a Fisher clamp by a wheel, connecting arm, and crank arm as shown in Figure 5. A slot in the crank arm pernits changes in the amplitude of the rocking motion. Temperature Control. A centrifugal pump cud a t e s water at 2.3 liters per minute between the jacket of the os ringe and a constant-temperature bath (0.1 coutrol by mercury regulator), in which the reactor is immersed as far ae tho shaker clamp will all'ow.
8.
PROCEDURE
A water slurry containing abo
.. .~~. fresh Raney nickel was added to L .~.~. in the reactor. The sample cup, containing a weighed sample equivalent to 0.5 to 12.0 millimoles of hydrogen, was hung on the hook attached to the reactor inlet tube. The gaskets were very lightly oiled with TexarThuban 250 gear oil and placed on the flauge the reactor, then the sample cup and inlet tu1 were lowered carefully into the neck of the reactor, m d the flanges were bolted together. A 10-pound torque on the end o f B 6-inch wrench was more than enough to tighten the bolts and prevent hydrogen leakage.
Figure 2.
Component P a r t s of Apparatus
E Figure 3. Syringe
opened as necessary to give a gage readiiig of 5.00 atmospheres (or any other desired working pressure a bove atmmDheric) and than n l n c r A Than thn l..c .Lnlrinn -.,ntinued for 5 minutes while the catalyst and solvent were saturated with hydrogen; the pressure was maintained by adjusting the syringe. After this equilibration, the shaking was continued for 5 minutes more t o let the operator look for leaks or changes in bath temperature. Readings were made of bath temperature, and syringe reading was made a t the exact desired working pressure. The shaker was stopped, aud the reactor was unclamped and tipped so that the sample cup and its content@ fall into the catdyst;solvent slurry. Then the reactor was clamped as before and shaking was resumed. As hydrogen was used, the syringe 8crew w&sturned to maintain the original pressure. If necessary, the syringe could be refilled with hydrogen at a slight sacrifice in accuracy; during suoh refilling the shaker was stopped, so that hydrogen uptake was very slow. Near the end of the hydrogenation the reactor was unclamped and tipped so that solvent could w a d dawn any sample particles adhering in the neck of the reactor. Thcu the shaking was resumed. When the original pressure was maintained without further syringe adjustment, and the temperature was constant a t its original readins, the syringe . - reading .was recorded and used in the cal~ulation
"..~..
SYRINGE 75 d i n 0.lml.
WREXTIPE
-..~.."..~ .....
.Iyy
Millimoles of H, = P(V*- V,) 0.08206 T
.. .
_ . .. .. . . where'I IS the gage reading in atmospheres, corrected for changes in barometric prcssure, V , and VI are the final and initial syringe
1159
V O L U M E 23. NO. 8, A U G U S T 1 9 5 1
I n these exnerirnents 1.3 =am of Raney nickel m d 40 ml. of solvent were b e d . T h e working pressure in all cases was 5.00 atmospheres, and the bath temperature was 25'to 30'C., except in the case8 indicated, where temperatures near O'C. were used. R n n w nickel was chosen far this work because of Whitmore
t 5 l D . PYREX l" PIPE
T-2-
toted. The dye samples were purified until ebromatograpnrcally Iomogeneous and recrystallized t o constant melting point f r o m nethanol or ethanol. The solvents were of retLgent grade.
Figure 1. Reactor
Figure 5 .
Shaker
n readings in milliliters, i bath.
Arrangement for n Experiments
Data from Eeveral ty] in Table I.
Table I. Tests of Hydrogenation Apparatus Catalyst, 1.3 gram8 of fresh Raney nickel. Solvent, 40 ml. Pressure, 5.00 atmcwheres. Temperature. Toom temperature O r Ice temperature ~ i Miliimoles ~ ~ H, , % Wt., n~~L~.~... Solvent Mia. Theory Found Error +1.5 3.34 3.39 25' 1.4947 EtOH -0.3 6.71 6.69 20 3.9942 EtOH +0.3 7.28 7.30 30 1,0788 EtOH 7.09 +0.7 7.04 20 1.0426 BuOH -0.15 6.72 6.71 30 5.9964 MeOH f0.15 6.75 6.76 20 1,0002 D X T b
-~~_
0,3091 0,2612 0.3941 0,3160 0.3307 0.3505 0.4172 0.4283 0,3906 0.3355
EtOH EtOH EtOH EtOH
-1.5
BuOH
20 30
6.95 7.13 6.50 5.59
7.04 5.97 9.05 7.30 7.64 8.12 6.92 7.12 6.45 5.53
0.2983
EtOlI
180
5.80
5.82
+0.3
EIOQ-N=N-a
0.9953
DMFb
35
9.29
9.23
-0.6
0 % Competitive azo dye 11, M.W. 428.4, one nib tro and one &*O
2.0003
EtOH
90
23.35
22.85
-2.1
0%N--N=N--()--N/CH*
0.2024
DMFb
60
2,4-Dinitrodiphenyiamine
Competitiveeso dye I, M.W. 300.3,one nitro and 0"e
a710
BuOH
BuOH EtOH EtOH EtOH
'
105" 66 45 40 60 60 90' 168a
7.15 6.05 9.12 7.31 7.65 8.11
-1.3 -0.8 -0.1 -0.1 +O.l -0.4 -0.1 -0.8 -1.1
OH
\
'CAS 0
k
Ice temperature. Dimethyl formamide.
(Syringe refilled)
3
DISCUSSION
From the results in Table I it can he calculated that standard deviation of the errors is 0.7, excluding the next to the last case where thesyringe was refilled. There is no correlation between the errors and either the temperature or the solvent employed. The error in the case of cinnamic acid, for example, is no worse with methanol as the solvent than with %-butyl alcohol. If a correction for solvent vapor pressure were required, the errors caused by neglecting i t would be -3.2 and -0.17% for methanol and butanol, respectively [for reductions a t 25' C. and 5 atmospheres). The exnlandon for this lack of dependence on vapor pressure is b e lieved to be that the 10-foot connecting tube between manifold and reactor serves as an effective barrier egainst diffusion of solvent vapor back into the syringe-gage system, partioularly during a hydrogenation when there is a counterflow of gas to the reactor.
A N A L Y T I C A L CHEMISTRY
1160
In order to estimate the diffusion rate of solvent through the connecting tube, the following experiment was carried out. One end of a 2-foot length of borosilicate glass capillary, 1.25 mm. in bore, was drawn out to a fine tip. The other end was fastened through a 50-ml. filter flask as shown in Figure 6. Hydrogen gas was passed through the apparatus and forced through the capillary. The fine tip was dipped in methanol and a column of solvent allowed to rise in the capillary until the meniscus was 20 mm. above the drawn-down section; then the tip was removed and quickly sealed in the Bunsen flame. In this way, the solvent was sealed in the capillary under hydrogen. Finally, the capillary was mounted in a vertical position, and hydrogen was passed slowly (0.5 ml. per minute) through the filter flask for several days. The average rate at which the nieniscus receded was 2.5 mm. per day a t 25°C.; this rate was not changed measurably during an additional 24 hours with an increased hydrogen flow of 15 ml. per minute. In a control experiment, the capillary was evacuated, whereupon the methanol meniscus receded at a rate of 3 mm. per minute. The slow diffusion of methanol through hydrogen was thereby shown not to be a result of limitation by the extent of evaporation surface. These results suggest that in this case correction for solvent vapor pressure is not justified because no significant amount of vapor can enter the measuring system under the specified operating conditions. In the literature on laboratory hydrogenation at constant pressure, most experimenters who made a correction for solvent vapor had previously saturated their hydrogen before introducing it into their apparatus. The closest analogy to the authors’ apparatus is described by
Jackson ( I ) , who used a flexible glass helix and other connection6 totaling 3.4 meters of tubing 5 mm. in inside diameter (estimated) between measuring system and reactor. He did not saturate his hydrogen with solvent, but did make a correction for its vapor pressure. This correction may be justified because solvent vapor could reach his measuring system through a smaller diffusion barrier than the authors’, a t 1 atmosphere hydrogen pressure, during the 3 to 4 hours that Jackson alloxed for temperature equilibration. ACKNOW LEDGJIENT
The authors are grateful to Lawrence T. Hallett for his interest and encouragement in this work, and to J. P. G. Beiswanger, D. L. Fuller, and Clyde McKinley for many helpful conversations on the diffusion effects discussed above. To F. C. Snowden, and the draftsmen and machinists of this laboratory, the authors express their thanks for help in the design and construction of the apparatus. LITERATURE CITED
(1) Jackson, H., J . SOC.Chem. Ind.,57,97T (1938). (2) Johns, I. B., and Seiferle, E. J., IND.ENG. CHEM.,. ~ N A L .ED., 13, 341 (1941). (3) Joshel, L. M.,Ibid.,15, 590 (1943). (4) Ogg, C.L., and Cooper, F. J., rlwar. CHEY.,21, 1400 (1949). (5) Whitmore, W. F., and Revukas, A. J., J . Am. Chem. SOC.,59, 1500 (1937); 62,1687 (1940). (6) Zaugg, H.E.,and Lauer, W. M.,.IN.~L. CHEY.,20, 1022 (1948). RECEIVED Febiuary 10, 1951.
Organic Chemical Compounds in Raw and Filtered Surface Waters HARRY BRAUS, F. 31. MIDDLETON, AND GRAHAM WALTON U . S . Public Health Sercice, Cincinnati 2, Ohio KXORLEDGE of the kinds and concentrations of organic chemical compounds in surface waters is important in studies concerned with tastes and odors in drinking water, natural purification of streams, analysis and tracing of industrial wastes, and toxic and other physiological effects on man and animal. Direct determination of most organic compounds is not usually possible because of the minute concentrations that normally occur in surface waters. This study describes a method for the concentration and estimation of organic compounds in raw and filtered surface water. Possible applications of the techniques presented are discussed.
Figure 1. It is pieceded 1)san iroii cylinder approximately halffull of filter sand and fine gravel. Valves are arranged so that the sand filter may be by-passed, back-washed with the raw water, or rinsed by filtering to waste. 9 minimum head of 10 feet of water is necessary for the effective operation of this unit. A plastic filter, used for Inhorntory studies, consists of a 4foot
CONCENTRATION O F ORGANIC COMPOUNDS FROM RAW AND FILTERED SURFACE WATERS
The concentration of the organic compounds in the waters tested is accomplished by passing from 5000 to 75,000 gallons of water through small portable activated carbon filters. The average rate of flow through the filter is approximately 0.1 to 0.6 gallon per minute. Figure 1 shows the simplest type of activated carbon filter for use on filtered or finished water. This unit consists of a %foot length of iron pipe 4 inches in diameter. Between 1200 and 1500 grams of granular activated carbon are charged into this cylinder. The carbon is held in place by perforated cadmium-plated disks, equivalent to about a 16-mesh screen, soldered into the reducers a t each end. Figure 2 shows the assembly used when turbid or raw waters are sampled. The carbon filter is the same its that shown in
WATER METER F l N l S H E D WATER
I’
e!I
EFFLUENT - J
INFLUENT
Figure 1. Carbon Filter Installation Uhed for sampling filtered water for trace quantities of organic chemicals
