ANALYTICAL CHEMISTRY
886
ions, it is obvious that they cannot compete with oxalic acid when the rare earth ions are to be separated from other impurities. However, in the absence of impurities and when only a small amount of rare earth is present in solution (2 to 50 mg.), the relatively large volume of precipitate and the ease with which it can be ~ a s h e dand filtered make the determination somewhat more accurate than the oxalate precipitation. Apparently, under precipitation conditions describe here, considerable amount of coprecipitation makes it impossible to determine accurately the amount of the rare earth present from the weight of the dried precipitate. However, ignition to the oxide is rapid and yields very satisfactory results. 260
I
0
I
2
3 E a UIVALENTS
4
5
1 ACKNOWLEDGMENT
Figure 4. High-Frequency Titration of Praseodymium Chloride with Cupferron
The assistance of George E. Knudson in obtaining the absorption spectra of the rare earth solutions is gratefully acknowledged.
1 to 1 complex: PrCla, 0.04738M; 1.50 m l . cupferron, 0.1573M 1 to 3 complex: PrCla, 0.04738M; 4.65 m l . cupferron, 0.1573M
LITERATURE CITED (1)
Auger, V., Lafontaine, L., and Casper, C., Compt. Tend., 180, 376 (1925).
added, when, presumably, the precipitation is complete. The neocupferron titration curve illustrates the same mode of behavior, although somewhat less clearly. High-frequency titration of praseodymium chloride verifies the intermediate formation of the 1 to 1 complexes, M C u p + + and M(NeoCup)++. CONCLUSIONS
Cupferron and neocupferron seem to be excellent precipitating agents for the rare earth ions, provided that no interfeiing substances are present in the solution. Since cupferron and neocupferron are fairly general precipitating agents for many metal
Bandish, O., and Furst, R., Ber., 50, 324 (1917). (3) Furman, N. H., Mason, W.B., and Pekola, J. S.,ANAL.CHEW., (2)
21, 1325 (1949).
Bloeller, T., and Brantley, L. C., Ihid., 22, 433 (1950). Pinkus, A., and Martin, F., J . chim. phys., 24, 137 (1927). Smith, G. F., “Cupferron and Seocupferron,” Columbus, Ohio, G. Frederick Smith Chemical Co., 1938. (7) Spedding, F. H., and Porter, P. E., U. S. Atomic Energy Commission, ISC-142 (March 1951). (8) Spedding, F. H., and Wright, J. lI.,Ihzd., ISC-143 (March 1951). (9) Willard, H. H., Merritt, L., and Dean, J. A,, “Instrumental Methods of Analysis,” 2nd ed., Kew York, D. Van Nostrand Co., 1951. RECEIVED for revien October 2 , 1953. Accepted February 6 , 1954. (4) (5) (6)
Replacement of lead Peroxide in Carbon, Hydrogen Microdetermination C. K. CROSS and GEORGE F WRIGHT Department o f Chemistry, University o f Toronto, Toronto, O n t a r i o
When organic compounds containing 20 to 50% of nitrogen are analyzed by the micro carbon-hydrogen technique employing lead peroxide for absorption of nitrogenoxides, the carbon values tend to be high. This Pregl absorbent has been successfully replaced by trishydroxylamine phosphate contained in a tube interposed between the tubes used for absorption of water and carbon dioxide. Sulfamic acid also has been used, but its capacity for removal of nitrogen oxides is low, although its efficiency is high. The long absorptive life and the efficient removal of nitrogen oxides by the hydroxylamine salt commend its use when carbon values within a precision of 2% relative error are required for organic compounds which are high in nitrogen content. Moreover, elimination of the lead peroxide tends to increase the precision of the analytical results for nitrogen-free samples, since careful temperature equilibration of water and carbon dioxide versus the peroxide is no longer necessary.
M
A S Y attempts have been made to replace the troublesome lead peroxide by an alternative absorbent for nitrogen
oxides in the microcombustion of organic compounds containing nitrogen. These variations in the carbon-hydrogen determination have been reviewed by Elving and McElroy ( 7 ) , by Belcher
and Ingram (3) and, most recently, by Backeberg and Israelstam ( 2 ) . Opinions are divided between those who believe that nitrogen oxides should be removed in the absorption train, and those who recommend absorption or destruction of the nitrogen oxides within the combustion tube. The use of metallic copper within the combustion tube for reduction of nitrogen oxides has recently been revived and adapted to the micro scale by Kainz ( I S ) . This worker claims that the copper (heated to 500” C.) is effective for 12 analyses, after which it is quickly and easily regenerated by passing hydrogen ’ through the combustion tube. Previously, Millin ( 1 7 ) had used silver (at a lower temperature) for decomposition of the nitrogen oxides. However, Backeberg and Israelstam ( 2 ) believe that Millin’s results were satisfactory, not because of the silver, but because that part of the copper oxide closest to the sample was reduced by the vapor of this distilling sample. The observation that silver alone is ineffective when nonvolatile samples are being analyzed has been confirmed here. Despite opinions to the contrary (i?), nitrogen oxides may be removed satisfactorily by absorbents outside the combustion tube (16). Such absorbents are interposed between the water and the carbon dioxide absorption tube. Elving and iMcElroy ( 7 ) recommend the use of sulfuric acid solutions of potassium dichromate or permanganate. Dombrovski (6) uses p-aminoazobenzene moistened with a saturated solution of boric acid and potassium dichromate, but this absorbent is exhausted after
887
V O L U M E 2 6 , NO. 5, M A Y 1 9 5 4 five or six analyses. This limited capacity also is characteristic of the highly efficient sulfuric acid-diphenylamine in ignited silica which has been proposed by Irimescu and Popescu (11). Because of the short life of these and other "wet absorbents" the use of highly active manganese dioxide between the water and carbon dioxide absorption tubes has been proposed by Belcher and Ingram ( 3 ) . They find this dry absorbent to be efficient for a t least 50 determinations and Kirsten (16) claims that a single filling is sufficient for 200 microanalyses of nitrogen-containing compounds. Instead of the oxidative absorbents, a study of reducing agents as absorbents which should convert nitrogen oxides to nitrogen or nitrous oxide has been undertaken. One of these is sulfamic acid, which should react in the following manner:
+ X\TL + + HNOa H2SO4 + HNOa +.i XOZSOZH+ HzO
2 H2KSOaH
N204 +
C.) contains first a silver gauze plug wrapped in platinum gauze 2 em. long, followed by a platinum contact 7.5 cm. long by 0.8 cm. in diameter. Then a silver gauze packing extends from 0.5 cm. inside the long furnace to the end of the tube, which is equipped with a Friedrich choking plug. Measurements with a thermocouple show that thermal conduction via the silver gauze packing suffices to maintain the choking plug above 100" C., so that a heating mortar becomes unnecessary. [In so far as the experimental conditions have been described this is true. Hoaever Sievers and Hutton (21), using a tube filling of copper oxide plus metallic silver a t 10 cc. per minute flow rate, have found the temperature of the silver packing to be very critical (optimum about 100' C. as recorded by a heating mortar spaced 2 cm. from the long furnace) in respect to accurate hydrogen values.] However, the copper conducting rod which warms the capillary inlet of the Anhydrone tube is then absent, and must be replaced by an external heater in order to prevent condensation of water within the capillary. A vertically aligned 6-watt incandescent lamp surrounded by a glass tube covered with aluminum foil was used in this work. The position of this heater is shown in Figure 1.
When Divers and Haga ( 5 ) investigated the reaction between sulfamic acid and nitric acid in the presence of concentrated sulfuric acid, they found that only nitrogen and nitrous oxide were evolved as gases. The present authors have also studied the action of hydroxylamine salts, the reactions of which may be idealized as follows: 2 XH20H
+ NpOi
--c N z
+ NzO + 02 + 3 Hz0
It will be shown that one of these salts, trihydroxylammonium phosphate, is highly efficient in removal of the higher oxides of nitrogen. APPARATUS
I n order to avoid extraneous errors during this study of ci;ternal absorption of nitrogen oxides the apparatus shown in Figure 1 was used. The foretrain consists of a flowmeter ( 2 8 ) and open-end manometer, both filled with sulfuric acid, followed by a conventional preheater and an Ascarite-Anhydrone U-tube. The Vycor combustion tube is 53 em. long with an inside diameter of 0.85 em. and is equipped with an inner 5 / 1 2 joint member a t the oxygen inlet, an outer 1 2 / 2 ~ joint member a t the sample inlet, and an inner 5 / 1 2 joint member a t the other end of the tube. The joints are coated with graphite, as are the similar joints of the entire absorption train (16, 28, $0). The graphite is applied by covering the inner member lightly with the dry powder and turning i t within the outer member until a smooth continuous coating is obtained. By use of this coating the joints are gas-tight when attached with a slight twisting motion and there is no tendency toward transfer of graphite from one weighed tube to the other. The type of equipment is a modification of that employed by Friedrich (8-10). A quartz sample tube (8) is traversed by n short movable furnace. The tube inside the long furnace (825'
Figure 2.
Nitrogen Oxide Absorption Tube NA-3
The absorption train includes the control tube of Friedrich as well as the hscarite and dnhydrone tubes. Between the latter two is placed the tube which serves to remove nitrogen oxides. During attempts to remove nitrogen oxides quantitatively three types of absorber were used, each equipped with graphitecoated interjoints like the remainder of the absorption train. The first tube, SA-1, is a standard Pregl absorption tube. K h - 2 is of the same form but larger, with an over-all length of 19 cm., a filling length of 8.5 cm., and an inside diameter of 1 cm. 5.1-3 is of U-form, with arms of 1-cm. inside diameter and 6.5 cm. long from the base of the stopper a t the top to the juncture of the capillary bend at the bottom. The bottom capillary is 5.5 cm. long with 0.2-cm. inside diameter. The rraohited 5 / 1 2 interjoints extend 3.8-cm. from each of the arms, the over-all distance from inlet to outlet being 10 em. This third absorber, which is the type finally adopted for the approved procedure, is shown in Figure 2. This tube is clamped to the ends of the adjacent abporbers by clamps constructed from springy metal sheet. ANALYTICAL PROCEDURE
G
Figure 1. Apparatus for Determining External Absorption of Nitrogen Oxides F.
Flowmeter Manometer Preheater Scavenging U-tube C. Combustion tube SF. Short burner LF. Long burner S I . Silver wire gauze. 5 cm. P T . Platinum star M. P. S.
Platinum star, end view Silver wire roll wrapped i n platinum gauze, 2 cm. H . Heater, 6 watts, 120 volts A . Absorption tubes N A . Nitrogen oxide absorption tube 3 CL. Clamps 6. Guardtube
PTA. SIP.
The analysis has been carried out essentially according to Friedrich's procedure (8), except that the ground interchangeable joints such as those used by Muller and Willenberg (18) make i t possible to close the tubes during temperature and electric charge equilibration periods without the necessity of wiping these tubes during analyses. The use of these closures also facilitates the use of oxygen rather
ANALYTICAL CHEMISTRY
888 than air for saeeping out of the combustion products ($3). These techniques have been shown by Royer, Norton, and Sundberg (20) and by Kirsten (16) to contribute precision as well as convenience. Sample weights should not exceed 4 mg When the nitrogen content is low, such samples may be burned (800" C.) in 12 minutes. Explosive compounds like cyclonite which are high in nitrogen may require as long as 20 minutes for combustion, a variation which is adaptable to the Friedrich technique a t a flow rate of 4 cc. of oxygen per minute. Under the conditions of flow and tube size used a sweeping time of 20 minutes is adequate when the choking plug is adjusted to give a hydrostatic head of 1.6 cm. in the open-end manometer. 411 of the tubes comprising the absorption train are capped with graphite-coated interchangeable stoppers n hen they are removed from the train. These stoppers are removed from the Inhydrone, Ascarite, and control tubes just prior to weighing REMOVAL O F NITROGEN OXIDES BY SULFAMIC ACID
Although technical sulfamic acid is efficient in removal of nit'rogen oxides, the purified acid is ineffective. However, when vacuum-dry sulfamic acid, which has been recryst'allized from 2.75 times its weight of boiling water, is ground with concentrated sulfuric acid (0.38 gram per gram of sulfamic acid). the niisture possesses extremely high efficiency in removal of the oxides. The absorber NA-1 is filled with a I-cm. section of hnhydrone, then 1 mm. of glass wool followed by a mixture of 1.1 gram of pure sulfamic acid, 0.1 gram of asbestos, and 0.4 gram of concentrated sulfuric acid (5-cm. length), and then a glass wool plug. The absorber SA-2 contains a 1.9-em. length of Anhydrone and a 6-cm. length comprising 1.6 grams of sulfaniic acid, 0.14 gram of asbestos, and 0.6 gram of concentrated sulfuric acid. While t,he analytical results obtained with either of these absorbers are as good as any s h p m later with hydrosj-lamine phosphate as an absorbent, sulfamic acid cannot be recommended, for several reasons, for use in the apparatus described. First, the effective capacity of the filling is riot great. Absorber 5.1-2 has usually failed after about 25 analyses and this life is not predictable: one filling in absorber NA-1 failed after four analyses. This is probably due to shrinkage which allows gases to pass circumferentially around the filling. Secondly, the filling does not change in appearance during use, so its failure cannot be anticipated. However if these faults can be obviated, the useof sulfamic acid is indicated for absorption of nitrogen oxides because it reacts more rapidly than does trishydro REMOVAL OF NITROGEN OXIDES BY TRISHYUHOXYLAMMONIUM PHOSPHATE
tion tube a t a distance of 10 cm. fiom the end of the heated long furnace (in absence of the short furnace), the vaporization in an oxygen stream of 4 cc. per minute is complete in 5 to 6 hours. The combustion gases are passed through an hnhydrone tube with warmed inlet, and thence through the trishydroxylammonium phosphate tube. This treatment represents the equivalent of about 65 analyses of samples containing 23% of nitrogen. A standard analysis of cyclonite is then carried out t o ascertain whether the trishydroxylammonium phosphate is still effective, after which the treatment with nitromethane is repeated. By this means it has been ascertained that absorber XA-3 has a capacity of about 250 to 260 combustions before the relative error in the carbon value exceeds 2%. -1s the aging proceeds the trishydroxylammonium phosphate is found to become moist at the inlet, and finally to disappear leaving only the wet asbestos. \Then, after the equivalent of 260 analyses, the carbon value becomes higher than the acceptable 2% relative error, the outlet arm of the U-tube absorber is apparently unchanged. The inlet arm is empty, except for the moist asbestos, for about two thirds of its length. The next centimeter is moist and the final 0 5 cm. apparently is unchanged During the aging process the silver wire roll in the end of the combustion tube becomes dull in appearance. This is undoube edly due to reaction with the nitrogen oxides, because a large amount of dinitrogen tetroxide can subsequently be evolved from it by heating the outside of the tube n i t h a Bunsen burner. The silver then partially regains its luster. A series of analyses has been carried out using the first two absorbers, with results as shown in Tables I and 11. Absorher S.1-1 gives acceptable results with simple nitrogen compounds, though not always with picric acid and never with cyclonite. On the other hand, NA-2 gives consistently good results with picric acid and improved results with cyclonite. This behavior, coupled with the observation that partial failure of the absorber occurs when half the filling is seemingly unaffected, has led to the suspicion that contact time is significant when trishydIoxy1ammonium phosphate is the substance used for removal of the higher oxides of nitrogen. This suspicion was substantiated by a series of cyclonite analyses a t varying oxygen flow rates. It was found that carbon values within 2% relative error could be obtained with the use of tube SA-1 if the oxygen flow rate were reduced to 2 cc. per minute Conversely, the use of NA-2 a t a rate of 8 cc. per minute increased the relative error to 4%. Several explanations may be given for the incomplete removal of these oxides. Kitric oxide might pass through the hydroxylammonium phosphate, subsequently to be oxidized t o nitrogen dioxide and ahsolbed in the Bscarite tube. It is generally accepted that nitrogen and the nitrogen oxides are evolved from
This salt may be prepared from hydroxylamine hydrochloride ( 1 ) but the best analytical results were obtained using material prepared from the sulfate (11). I n order to prepare it for use in
removal of nitrogen oxides, it is crystallized from water, in which it is not very soluble (1.9 grams per 100 ml. a t 20" C. and 16.8 grams per 100 ml. a t 90" C.). -4saturated solution a t 90' to 100' C. when cooled rapidly precipitates a mass of ver?. fine crystals. These crystals are filtered off. vacuum-dried, and mixed with 0.1 of their weight of ast>rst,)s ( R a h l h u n i .\hest fur Goochtiegel) for use in the at)sorhers. Each of the three absorbers is filled with a I-cm. length of Anhydrone, followed by a 0.5-cm. glass wool plug. and then with 0.88 g, 1.1 g, or 2.75 grams of trishydro phate into the appropriate absorber. The largest absorber (Figure 2), has been chosen for use in ascertaining the capacity of the substance for removal of nitrogen oxides. For this demonstration an open hemicylindrical boat 6 cni. long by 0.5 cm. wide has been prepared by grinding off one half of a sealed glass tube having these dimensions. When the boat containing 200 mg. of nitronirthane is inserted into the combus-
Table 1. Hydroxylamine Phosphate as External ;ibsorbent for Nitrogen Oxides Sample Wt.,JIg. 3.378 3.791 3.741 3.700 3800 3737 3445 3441
(Absorbent tube X.4-1) Found Dev. Rel. Error, "0 H,% C,% H,% (2.7% H C Cyclonite (37.7% X , 2.73% H, 16.2% C ) 2 84 2 78 2.74 2.74
16.2 16.9 16.6 16 6
+ O 11 fO.05 +0.01 fO.O1
0.0
f0.7 f0.4 +0.4
4.3 1.8 0.4 0 4
Picric Acid (18.3% N, 1.32% H, 31.5% C) f 0 2 0 0 317 132 0 0 +02 0 0 318 0 0 132 +05 0 0 132 320 0 0 0 0 +07 322 132 0 0
0 0 4 3
2.3 2 3
0 6 Ofi 1 6
2 2
Bensonitrile (13.6% N , 4.87% H, 81.6% C) 1.297 1779 1 505
4 98
81.9
tO
11
f0.3
2 2
Acetanilide (10.5% N, 6.71% H, 71.1% C) 1 9 -03 6 84 + O 13 708 6 65
70 9
-0
06
-0.2
0 9
0 1
0 4 0 2
V O L U M E 26, NO. 5, M A Y 1 9 5 4
889
the burning sample in various ratios depending on the chemical constitution of this sample (7, 14, 15). However, the work of Richardson (19) shows that only nitrogen and nitric oxide will emerge after passage through the catalyst within the confines of the long burner a t 825" C. Subsequently the recombination 02-2 NO*) will occur a t such a rate, according reaction (2 NO to Bodenstein (4),that not more than a trace of nitric oxide should remain after passing the water tube a t the rate of 4 cc. per minute. Therefore the incomplete removal of nitrogen oxides under the conditions described here would seem not to be due to incomplete oxidation of nitric oxide.
+
Table 11.
Sample
Hydroxylamine Phosphate as External Absorbent for Nitrogen Oxides
Wt., Mg.
(Absorbent tube N.4-2) Found Dev. Rel. Error, % H,% C % H,% C,% H C Cyclonite (37.7% N, 2.73% H, 16.2% C)
3.578 3.549 3.589
2.85 2.82 2.80
2.347 3.503 3.547 3.468
Picric Bcid (18.3% S , 1.32% H , 31.5% 1.22 31.6 +O 1 -0.09 1.37 31.6 f0.05 $0.1 1.30 31.5 -0.02 0 1.41 31.8 fO.09 +0.3
16.5 16.5 16.7
+0.12 +0.09 +0.07
+0.3 fO.3 $0.5
4.4 3.3 2.6
2.0 2.0 3.0
C) 8 4 1.5
7
0.5 0.5 0 1.1
Sucrose (0% N, 6.48% H, 42.1% C) 2.347 2.143
tube through the equivalent of an analysis cycle. Therefore the loss of analytical time required for such a change is reduced to a minimum by use of the simplified filling. S o t only are satisfactory values obtained for ordinary substances like anilides, but also for compounds like cyclonite and l-nitro-2-nitramino-2-aminoimidazolidinewhich invariably prove to be troublesome when lead peroxide is used to remove the oxides of nitrogen. Therefore, the use of trishydroxylammonium phosphate in an absorber like NA-3 is recommended in lieu of lead peroxide inside the combustion tube. Finally the fact should be stressed that tube NA-3 has been designed for an analytical procedure employing 1 to 4 mg. of sample which is burned a t an oxygen flow rate of 4 cc. per minute.
6.39 6.56
42.1 42.1
-0.09 +0.08
0 0
1.4 1.2
0 0
It is more reasonable to presume that the reaction of trishydroxylammonium phosphate with nitrogen dioxide is sufficiently slow that the length of filling must be increased over that existing in tubes NA-1 and 2. I n order to discover whether the NA-3 absorber is sufficiently long for practical purposes, measured volumes of pure nitric oxide prepared according to Winkler (64) have been mixed with pure nitrogen t o total volumes of 7 cc. This volume is displaced by mercury into the sample inlet of the combustion tube during 14 minutes, while the normal rate of 4 cc. per minute of oxygen is also being maintained. The combustion tube is not heated and is filled with a closely fitting glass iod in order to reduce the contact time of nitric oxide with oxygen to a value comparable with. or less than, that which would prevail during a normal analysis. After the gas samples have been swept through completely, the ascarite tube is removed from the complete train and weighed, in order to discover the quantity of nitrogen oxides which have escaped from the third absorber. It has been found that 0.6 mg. (as nitrogen dioxide) is completely absorbed, while 98 to 99.2% of a 1.8-mg. sample, (as nitrogen dioxide) is absorbed by the trishydroxylammonium phosphate. Therefore the quantity and length of filling in the third absorber is adequate if reasonable weights of sample and hurning times are used at a flow rate of 4 cc. per minute. This adequacy is confirmed by the results shown in Table 111, M hirh have been obtained by use of the third absorber. The analysis of the hydrazine salt of phenylnitrosohydroxylamine, the 1mt shown in Table I11 (for which values of 6.15% hydrogen and 43.6y0 carbon were obtained with Pregl-type lead peroxide absorption), exemplifies the convenience of the simplified combustion tube filling. The 5-cm. silver plug in this filling has been ether-washed and vacuum-dried after two 9-cm. square gold leaves had been included nithin its folds. This modification retains the metallic mercury in the combustion of 2-methoxycyclohexylmercuric chloride (which otherwise gives a positive deviation of 0.15% hydrogen or 4.5% relative error). The satisfactory hydrogen value for the hydrazine salt shows that the gold continues to retain the mercury. Alternatively the silver-gold plug could have been replaced by a silver one within the time required to cool the furnaces, insert the plug, and reheat the combustion
Table 111.
Sample Wt., M g . 3.427 3.428 3.468 3.663 3.581 3.423 3.129 3.431 3.351 3.558 3.549 3.506 3.483 3 515
Hydroxylammonium Phosphate as External .4bsorbent for Nitrogen Oxides (Absorbent tube NA-3) Found Dev. Rel. Error, Yo H, % C, %' H, % C, % H C Cyclonite (37.7% N, 2.73% H, 1 6 . 2 % C) 2.79 16.4 +0.06 +0.2 2.2 1.2 2.73 16.2 0 0 0 0 2.83 2.83 2.77 2.90 2.72 2.75 2.82
16.4 16.5 16.2 16.4 16.3 16.3 16.3
+o. +o.
10 10 4-0.04 + O . 17 -0.01
+0.02 f0.09
+o.z f0.3 0
+o.z +o. 1 +o. 1 +o.
1
3.7 3 7 1.5 6.2 0 4 0.7 3.3
1.5 1.7 0 1.2 0.6 0.6
0.6
Picric Acid (18.3% N , 1.32% H, 31.5% C ) 1.34 31.5 f0.02 0 1.5 0
1.36 1.36 1.28 1.30
31.4 31.3 31.7 31.3
+0.04 f0.04 -0.04 -0.02
-0.1 -0.2 +0.2 -0.2
3.0 3 0 3 0 1.5
0.2 0.6 0.6 0.5
l-Nitro-2-amino-2-nitraminoimidazolidine (43.8% N, 4.20% H, 18.7% C) 3.191 2.132
4 34 4 19
1,529
Acetanilide (10.5% N , 6.71% H, 71.1% C) 6.78 71.1 +0.07 0 1 0 0
18 7 18 7
4-0 14 -0 01
0 0
3 3 0 2
0
0
2,4-Dinitrophenylhydrazine(28.3% N, 3.05% H , 36.3% C) 3.261 3.194 3.044 3.086
3.05 2.95 3.03 3.07
36.6 36.7 36.5 36.4
0 -0.10 -0.02
+0.02
f0.3 10.4 +0.2 +0.1
(8.3% N, 56.6% C) $0.10 -0.3 -0.02 4-0.2
p-Chloroacetanilide 56.3 56.8
0
3 3 0.7 0.i
0.7 1.0 0.4 0.2
4.75p% H,
1 629 1 671
4.85 4.73
2.099 2.105
4.65 4.63
2,070 2.023
p-Toluenesulfonamide (8.2% N, 5 . 3 0 7 H , 49.1% C) 5.43 49.2 +0.13 4-0.1 2 5 0.1 5.53 49.1 +0.23 0 4 3 0
3,283 3 374
1.97 2.01
2,980
3.90
2.1 0 4
0.6 0.3
Sulfanilamide (16.3% N,4.68% H, 41.8% C) 41.6 41.8
-0.03 -0.05
-0.2 0
0 6 1 1
0.5 0
o-Iodobenzoic Bcid (0% N, 2.03% H , 33.9% C) 33.9 33.8
-0.06 -0.02
0 -0.1
3 0 1.0
0 0.3
p-Bromoacetanilide (6.53% N, 3.77% H , 44.9% C)
1,647 1.642
6.45 6.61
44.8
+0.13
-0.1
3.5
Sucrose (0% N,6.48% H, 42.1% C ) 42.1 -0.03 0 0.5 41.9
$0.13
-0.2
2.0
0.3
0 0.5
2-Amino-4-leri-butyl-5-nitro-thiazole Hydrochloride (17.7% N, 5.09% H , 35.4% C) 1 939
2 069
5.11 5.28
35 4 35 6
fO.02 4-0.19
2.993
2-AIethylcyolohexylmercuric Chloride ( 0 % N, 3.33% H, 21.3% C) 3.30 21.5 -0.03 +0.18 0 9 0.8
3.351
6.02
0
+0.2
0 4 3.7
0 0.6
Hydrazine Salt of Phenylnitrosohydrosylamine (32.9% N, 5.92% H, 42.8% C ) 42.3
+0.10
0
l i
0
890
ANALYTICAL
If larger samples or more rapid gas flow rates are utilized, the absorption path of the absorber must be lengthened correspondingly. This admonition is exemplified by cyclonite analyses which were carried out using tube NA-3 and a gas flow rate of 8 cc. per minute. This causes an increase in the relative error of the carbon value to about 2% or about three times the average of the errors listed in Table 111. ACKNOWLEDGMENT
The authors are grateful for a grant-in-aid from the Scientific Research Committee of the University of Toronto, and to D. C. Sievers, Tennessee Eastman Co., for his help in checking the analytical procedure in his laboratories. LITERATURE CITED
Audrieth, L. F., “Inorganic Syntheses,” Vol. 111, p. 82, Kew York, McGraw-Hill Book Co., 1950. Backeberg, 0. G., and Israelstam, S.S., ANAL.CHEM.,24, 1209 (1952). Belcher, R., and Ingram, G., Anal. Chim.Acta, 4, 401 (1950). Bodenstein, M., 2. Elektrochem., 24, 183 (1918). Divers, E., and Haga, T., J . Chem. SOC.,69, 1634 (1896). Dombrovski, A , Mikrochemie ver. Mikrochim. Acta, 28, 136 (1940).
CHEMISTRY
(7) Elving, P. J., and AZcElroy, W. R., IND.EXG.CHEM.,ANAL.ED., 13,660 (1941). (8) Friedrich, A, “Die Praxis der Quantitativen Organischen Mikroanalyse,” Leipsig and Vienna, Franz Deuticke, 1933. (9) Friedrich, A , , Mikrochemie, 10,329 (1932). (10) Ibid., 19,23 (1935). (11) Hoffmann,R. A.1 and Kohlschutter, V., Ann., 3079 314 (1899). (12) Irimescu, I., and Popescu, B., 2. anal. Chem., 128, 185 (1948). (13) Kaine, G., Mikrochemie per. Mikrochzm. Acta, 39, 166 (1952). (14) Kirner. W.R.. ISD.ESG.CHEM..ANAL.ED.. 7. 366 (1938). il5; Ibid.. 10., 342 (1938). ~ ,
