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Vol.
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plants would save money by its immediate adoption, t h a t 3 6 O Be. nitric acid can a t present prices of ammonia be made as cheaply as from sodium nitrate even if i t drops t o pre-war prices, and t h a t ammonia has t o drop in price only a few cents per pound in order t o have concentrated nitric acid also made competitively b y t h e oxidation of ammonia. BUREAUO F M I N E S WASHINGTON, D. C.
STUDIES ON THE OFFICIAL METHOD FOR PYRIDINE I N AMMONIUM NITRATE By R. M. LADD Received September 17, 1918
I-From
FIG.13-Cosr Ammonia, by Oxidation
NITRICACID 11-From
OR
Sodium Nitrate
claims t o exactness. The following figures should, therefore, be considered simply as an "order of magnitude." They are round figure averages between t h e (1917-18) costs of one actual plant and t h e estimates of a reliable and experienced engineering and constructing firm for the erection and operation during 1918 of another To these figures in t h e case of acid costs, $3.00 per ton has been arbitrarily added as estimates of late have always proved low. It is, accordingly, t h e opinion of t h e writer t h a t t h e following figures may be considered high for 19191920. They include cost of vaporizing, oxidizing, cooling, absorption, weighing, and concentration systems with buildings and foundations, and an addition of 20 per cent t o operating costs for repairs, interest, and depreciation. P L A N T CONSTRUCTION COSTS
Plant for 25,000 tons As 50 per cent "0s.. As 94 per cent "0s..
"03
(100 per cent) per year
. . . . . . . . . $45.00 per ton year
.........
60.00 per ton year
PLANT OPERAT~ON COSTS
As NO gas.
Per ton HNOa (100 per cent) $ 5.00 plus cost of NHa . . . . . . . . . 15 00 plus cost of NHa 30.00 plus cost of NHs
................... .........
As 50 per cent "08.. As 94 per cent "0s..
I n order t o make a comparison with t h e cost of 94 per cent acid from sodium nitrate, $48.00 may be taken as fabrication cost per ton of nitric acid (100 per cent basis) and add thereto t h e cost of 2800 lbs. of commercial Chile saltpeter. Fig. 13 will then make plain the relation between t h e costs of the two methods of producing nitric acid on t h e basis above adopted. A study of Fig. 13 should give at a glance an idea as t o when t h e production of nitric acid by ammonia oxidation can compete commercially with the old methods from Chile nitrate. It is evident t h a t sulfuric acid
The original government directions for t h e determination of pyridine in ammonium nitrate read as follows : Dissolve a known weight, approximately IOO g., in IOO cc. of distilled water, using a I liter Kjeldahl distilling flask. A few drops of methyl orange and 5 cc. of normal sodium hydroxide solution are added. The pyridine and ammonia are then distilled into IOO cc. of sodium hypobromite solution (100g. sodium hydroxide dissolved in 500 cc. of water, 2 5 cc. bromine added, and the solution made up t o 1000 cc.) contained in an Erlenmeyer flask of approximately 800 cc. capacity. The ammonia is decomposed by the hypobromite solution while the pyridine passes unaffected into a second receiving flask containing I O cc. of N / I O sulfuric acid. From the acid used the pyridine is calculated. One cc. N / I O sulfuric acid is equivalent t o 0.0079 g. pyridine. Twenty minutes' boiling is sufficient. At first glance i t appears t h a t different analysts would interpret this test in different ways and hence would obtain different results. I n our laboratory we first set up t h e apparatus without any condenser. We found t h a t a t one of t h e other plants belonging t o t h e company a condenser was being used as shown in Fig. I. The inspector when he came advised t h e use of a condenser. Since t h a t time we have set up t h e apparatus as shown in the figure. But this is only one of t h e difficulties. The series of results in Table I will show what widely differing results can be obtained b y different interpretations of the method. TABLG I VOl. of Grams Distillate Pyridine SAMPLE Used Method1 Cc. Per cent A. 100 Ia ? 0.0000 300 Ib 40 0.0020 100 I C 75 0.0210 ? B . . . . . . . . . . . 300 Ia 0.0005 100 Ib 40 0.0150 100 IC 0.0350 50 0.0003 100 la J 500 Ib 100 0.0020 300 IC 100 0.0169 200 IC 75 0.0166 1 Method I a calls for 20 min. of slow boiling in hypobromite flask. Method I b calls for the destruction of the ammonia before boiling starts in the hypobromite flask, then rapid boiling until the required amount of distillate has been collected. Method IC calls for 20 min. rapid boiling in the hypobromite flask, without preliminary slow heat t o destroy the ammonia. Ammonia was invariably carried over by this method, hence the results were always too high.
..........
............
Table I1 shows a series of results which would seem t o indicate t h a t not all t h e pyridine is carried over by this method, even when the time of boiling is counted from the start of rapid boiling in t h e hypobromite flask.
June, 1919
T H E J O U R N A L OF I N D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y Vol. of
TABLE I1 Additional
DisSAM-Grams tillate Pyridine PLB Used Method Cc. Per cent 0.0120 Ib 40 G . . 150 0,0325 Ib 40 H . . 300 I b 40 0.0293 I... 300 Ib 50 0.0226 K.. 300 Ib 50 0.0155 L... 300
7 7
Distillate 100
40 40 200 100
Pyridine Per cent 0.0070 0.0081 0.0064 0.0005 0.0008
Additional c -
Distillate
Pyridine Per cent
90 90
0.0024 0.0012
and L residues1 550 Ib 50 0.003 1 Residues from R and L were filtered and run as new sample.
Evidently the method has given poor satisfaction in practice, for i t was modified in t h e following appendix of June 25, 1918: SPECIFICATIONS GE-32 1-1 APPENDIX IV
JUNE2 5 ,
1918
THf DETERMINATION OF PYRIDINE I N AMMONIUM NITRATE
The method as stated No. 8, page 4, of the Ammonium hTitrate Specifications, is modified as follows: Dissolve approximately 2 j o g. ammonium nitrate in z j o cc. of distilled water contained in a one liter Kjeldahl distilling flask. Add 4 to 5 drops of methyl orange and connect the distilling flask, through a Kjeldahl vapor trap, t o a tall narrow wash bottle. The dimensions of this wash bottle should be from 8 i o I O in. high by I ~ / Zto 2 in. in diameter. In the wash bottle are placed 300 cc. of sodium hypobromite solution. (This solution is made by dissolving IOO g. of sodium hydroxide in about 800 cc. of distilled water and then adding, very slowly, preferably by drawing through in vapor form, 30 cc. of bromine and making the solution up to one liter.) The sodium hypobromite solution must be a t least 3 in. deep in the wash bottle. The wash bottle is connected through a Kjeldahl vapor trap with a condenser fitted with a tube of blocked tin. Add 8j cc. of N / 2 sodium hydroxide solution to the solution of ammonium nitrate in the distilling flask, warm the solution in the wash bottle by setting it in a vessel of hot water, and begin the distillation. The distillate is caught through an adapter, in a beaker containing 2 5 cc. of N / I Osulfuric acid. During the distillation, the heat from the vapors should be sufficient to maintain the temperature in the hypobromite solution a t approximately 7 5 O t o 80' C. If this is not the case, additional heat must be applied. After IOO cc. have been distilled, the distillation is stopped and the distillate in the beaker is titrated with N / I O sodium hydroxide, using phenolphthalein, and the pyridine calculated. One cubic centimeter of N/IO sulfuric acid is equivalent to o 0 0 7 9 g. of pyridine. (Signed) C. C. WILLIAMS, Brig. Gen., Ordnance, N. A. Acting ChieE of Ordnance
5 53
will indicate how widely different are t h e results obtained by tests. TABLE I11 DistilPyriGrams late dine SAMPLE Used Method Cc. Per cent Ml..... 100 118% 100 0.029 M2 250 IIal ? 0.002 M3a 250 IIa ? 0.002 M4a.. No record of method 0.010 1 Method I I a calls for the holding of the temperature of the hypobromite between 70' and 80' C. for 11/z t o 2 hrs. regardless of the amount of distillate. 2 Method I I b calls for 100 cc. of distillate regardless of the temperature of the hypobromite. I n order to do this i t is necessary to increase the temperature t o or above 100' C. 3 Run by Government inspectors.
............ ................. ................. ..............
2---The other objection is t o the use of phenolphthalein as the indicator. Table IV shows t h a t this indicator is entirely unaffected by the alkalinity of pyridine. I t also shows a condition which has been mentioned t o me by three analysQ, namely, t h a t at times an added amount of acid gets into the receiver. TABLE IV DistilGrams late Methyl PhenolDouble SAMPLE Used Method Cc. Orange1 phthalein2 Ea 0 200 Ib 0.0251 -0,0051 0.0292 I. 300 Ib 0.0132 -0.0024 0.0155 250 IIb 100 0,0063 +0.0013 0.0050 P S ........ 250 IIb 100 0,0083 t.O.0045 0.0038 1 Methyl orange indicates the combined pyridine and ammonia. 2 Phenolphthalein indicates the ammonia and absorbed acid. 3 The difference in end-points represents the true reading for the pyridine.
....... ........ ........
2;
This additional acid will not be indicated by t h e methyl orange unless in amounts large enough t o more t h a n neutralize the pyridine obtained. T h e table also indicates t h a t ammonia is sometimes driven over, in which case t h e results will be high if methyl orange alone is used.
FIG. 1-APPARATUSFOR PYRIDIXE AS ORIGINALLY USEDIN THIS LABOHATORY
I n our laboratory we found t h a t check results could be obtained provided a n y definite procedure was followed. If t h e procedure was varied t h e results varied. I n order t o get concordant results, then, it is only WARDEPARTMENT necessary t o specify the method more in detail. The OFFICE OF THE ACTING CHIEF O F ORDNANCE WASHINGTON, D. C. question was, which modification of the method gave June 25. 1918 results which were a true representation of t h e amount There are two things about these specifications of pyridine present. which seemed t o me t o render them impractical. T o answer this question, pyridine-free ammonium I-lf t h e hypobromite be maintained a t a tempera- nitrate was prepared by taking the residues left from t u r e of 7 5 ' t o Soo C., i t would seem impossible t o ob- several pyridine determinations. These were first tain I O O cc. of distillate. Repeated attempts have filtered, then made alkaline with ammonium hydroxide shown t h a t z hrs. heating with t h e liquid in the Kjel- and evaporated until crystals appeared on cooling. dah1 boiling rapidly a n d t h e temperature in t h e hypo- These crystals were separated from the mother liquor, bromite flask maintained between 7 5 " a n d So" gave washed with water a n d then with alcohol (to remove no distillate. The conditions named are incom- excess methyl orange) , and were then redissolved, patible. Is t h e temperature or t h e amount of dis- made alkaline with ammonium hydroxide, filtered, tillate the more important consideration? Table 111 and recrystallized. The new crystals were separated
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shows t h e results on a series of known, and Table V I 1 t h e results on a series of unknown samples. These results would indicate t h a t this method is accurate t o the second place in decimals. When figures appear in t h e second decimal place, error should not exceed 1 5 per cent or 0 . 0 2 . When figures appear in first decimal place error should not exceed 5 per cent When figures appear in third decimal or 0 . 0 0 5 . place error should not exceed 0.001. Figures beyond t h e third decimal place are not significant. The method used is as follows:
FIG. 2-APPARATUS
i U
PYRIDINEAS Now USED IN THE AETNA LABORATORY The whole is set around a single ring stand. The hypobromite flask is 2 in. by 14 in. The hypobromite, 300 cc., occupies 71/2 in. of the height a t the start of the test FOR
from the mother liquor, washed and dried. The recovery was not more t h a n 50 per cent. T h e crystals thus obtained were long needles, absolutely colorless and odorless. They gave a clear, colorless solution. They were considered chemically pure. TABLE V-SERIES
OF DETERMINATIONS ON KNOWN BLANKS Pyridine Grams Used Per cent 170 170 1701 1701 2501 250 0.0003 250 0.0006 0.0003 250 1 Determination made in special apparatus which had no rubber connections or stopper. TABLE VI-DETERMINATIONSON KNOWNPYRIDINE Pyridine Percentage Grams Used Known Found Error Error 170 0.0385 0.0387 0.0002 0.5 170 0.1155 0.1114 0.0041 3.6 170 0.0041 0.0050 0.0009 18.0 ? 0.3816 0.3778 0.0038 1.0 250 0.0113 0.0095 0.0018 15.5 250 0.0113 0,0095 0.0018 15.5 TABLE VII-CHECKS O N UNKNOWN SAMPLES Grams Pyridine Percentage SAMPLE Used Per cent Average Error Error B1 250 0.0187 f0.0021 12.6 B2 150 0.0147 -0.0019 11.4 B3 100 0.0182 4-0.0016 9.6 B4 0.0155 -0,0011 500 , 6.8 B5 0.0173 100 +0.0007 4.2 0.0150 B6 100 9.6 0.0166 -0.0016 -0.0003 c1 250 0.0000 c2 250 0.0005 +O. 0003 0.0003 D1 300 0.0030 -0,0004 D2 0.0037 150 + O . 0003 0.0034 0.0030 4-0. 0005 250 El 0.0020 -0.0005 250 0,0025 E2 0.0108 4-0.0005 250 N1 250 0.0103 0.0098 N2 -0.0005
The results in Table V were obtained b y the use of this salt under the method specified later. Table V I
Dissolve 2 j O g . of sample in 300 cc. of distilled water, using a 1000 cc. Kjeldahl or Florence flask. Add a few drops of methyl orange and neutralize with I O per cent sodium hydroxide solution. Then add 15 cc. excess of I O per cent sodium hydroxide solution. Set up apparatus as shown in Fig. 2 , using 300 cc. hypobromite solution in the second flask and receiving the distillate in 2 5 cc. N/IO sulfuric acid. Distill until IOO cc. of distillate have been collected. The heating should he very slow until all the ammonia, driven off, has been destroyed. This point will be indicated first by an acid reaction of the methyl orange in the first flask and second by the gradual reduction of the amount of nitrogen given off, in very small bubbles, in the hypobromite. At this point the hypobromite flask should not be warm enough to burn the hand (not above 70' to 75' C , ) . It is now safe to increase the heat so that boiling occurs in the hypobromite in I O to 15 min. and IOO cc. of distillate comes over in 20 to 25 min. after active boiling starts. Titrate the liquid in the receiver, using N / I O sodium hydroxide solution with methyl orange as the indicator. Record the end-point; add l/z cc. of phenolphthalein ( I : 1000) solution and continue the titration until a red color which will persist for 30 sec. appears. Subtract the methyl orange endpoint from that obtained with phenolphthalein, and multiply the difference by 0.0079. The result is the pyridine bases in grams. Methyl orange indicates pyridine plus ammonia. Phenolphthalein indicates ammonia. Difference is due to pyridine.
Because of the fact t h a t the methyl orange and phenolphthalein end-points are never quite t h e same and because an absorption of carbon dioxide by t h e sodium hydroxide solution may bring it about t h a t they vary still more widely, i t is necessary t o standardize the solutions used t o both end-points and t o make a correction for their normal difference. This correction should be checked by a new standardization a t least once a week. We found t h a t with our solutions this difference was usually about 0 . 4 cc. I n case it is desired t o use a sample of a different size, maintain t h e proportions indicated above, except t h a t the total solution in the first flask should always be about 5 0 0 cc. The hypobromite solution is made up as follows: IOO g. sodium hydroxide are dissolved in 800 cc. of water, 25 cc. of liquid bromine are added, and the mixture shaken until the bromine is entirely dissolved and made up to 1000 cc. The solution should be made, up a day in advance. It will maintain its strength for a t least a week if kept in a stoppered, dark bottle. It will be brown in color. Should the brown color disappear during the distillation it would mean that an excess of ammonia is present. This should also be indicated and eliminated from the calculations by the double end-point called for, but in case this happens it is well to repeat the test, using more of the hypobromite solution.
A N D ENGINEERING CIIEMISTRY
34 ,357 0 . 6 3 8 E. ammonia is destroyed b y 6.699 z. sodium hypobromite Z N ~ O H nr? m ~ i o .manr IM) 80 1 hO 119 2 s EC. 1,romi,,e = 7 9 . 5 L. bromine , 3 0 0 C C . soli,iior, conta1iis 1 7 . i il. hyUohromifc tappron.)
+
-.+
+
+
There shoulil be a large excess of hypobromite. quirud for safcty.
This
is IC-
Soap should never be used in cleaniny any piece of apparatus used in this test. We found that beakers which 1r:id been washed with soap and were later used as receivers threw the results very much too high even after being rinsed 8 or I O times.
555
siderable degree of accuracy is required in the determinations made in this laboratory t o ensure compliance with the regulations. At first the method used was a slight variation of that published by Holde and Winterfeld,' as modified by Wolf.* As admitted by these authors, the results are below the truth. Holde and Winterfeld apply a correction of + 0 . 3 per cent. I t is obviously impossible t o obtain satisfaction from a method which calls for a correction equal t o 60 per cent of the probable total. Having satisfied ourscloes that the method is suhject t o errors arising both from the principles on which it rests and from its manipulative details, we have designed another means of measurcment which is both more accurate and more rapid. This is now adopted as the standard method for its purpose by the Inland Revenue Department of Canada. DESCRIPTIOX
OF
THE
1IOLDE-WINTERFELD-WOLFX
METHOD
To loo cc. of the alcohol-benzene solution, water is added till the sp. gr. is brought t o 0.96. This mixture is distilled, the first I O cc. (Hnlde-Winterfeld) or 20 cc. (Wolff) of distillate being collected and transferred t o a graduated vessel. The distillate is diluted with 20 cc. water (Holde-Winterfeld) or 80 cc. saturated brine (Wolff). The volume of benzene which separates is read, giving the percentage direct. I t usually takcs 2 t o 3 hrs. for the benzene to collect sufficiently for the reading to be made. The benzene layer is never clear and the accurate determination of its limits is usually very difficult. RESULTS B Y THE HOLDE-WINTERFELD-WOLFF METIIOD
Fro.
APPARATUS USINO G n o u ~ oC L A S S C u ~ ~ s c r r o.AND ~s S i o ~ ~ r TO r ~Ds K T ~ ~ R XTXB Z NINPLUIBNCB E OF Ruensa
J-SPBCLAL
The apparatus now used in this laboratory is indicated in Fig. 2 . During the course of our investigation the question arose as t o the influence of the rubber stoppers and connections. I n order t o determine this an apparatus was constructed in which all joints and stoppers were ground glass. The determinations made on this apparatus are indicated in Table V. Our conclusion is that the rubber is not objectionable, provided a good grade is used. AKTNRL~aoarronv d a r r a ExP,.osi"ns C O M P A N Y AWN*. INMAWA
The determinations tabulated below were made upon solutions of benzene in alcohol ( 9 5 per cent by volume) prepared with great care to known strengths. I n all cases the first portion of distillate taken was I O cc. I n some cases a second portion of the next I O cc. or 20 cc. was eoilected and examined separately. The figures show, however, t h a t this precaution is nnavailing, as the amount of benzene so collected is too small for detection by this method. Volmnc of Dirtillate Collecfuf First S s o n d RunR"n1Sn~r.n i n ~ s n m y s NO. Cc. Cc. 2I
10 "
in
10 10
I0
..
0.5 1.2
0.0
10
20
1.3
0.0
10 10
3
.I .5 6 7 3
T a a ~ sI Volume of Hazetie Found First Second RunRunnings ningr Cc. CE. o.n 0.0
10
10
0.0 0.3
0.4
0.0 0.0 0.0
...
Correction medc by addiiir f0.3
Tola1 H&zeneFoud Percent lincorPer Cent rectrd Corrected' 0.0 0.0 0.3
Benzene Aefually PreSenf Per cent
0.3
0.2
0.3
0.2
0.4
0.6 0.7
O.i 1.2 1.3
0.8 1.5 1.6
0.8 1.6 1.6
according
10
0.4
0.8
lluldr and Winter-
idd.
DETERMINATION OF SMALL AMOUNTS OF BENZENE IN ETHYL ALCOHOL B y F. W . BARINDTON A N D ALPLIIDTINGLB Received Ociaber 28, !Vi8
For certain war purposes, and under restrictions, the Inland Revenue Department of Canacla allows alcohol t o be denatured by the addition of benzene. Since o. j per cent of benzene is allowed t o suffice, a con-
It is evident that without the use of a correction, the figures obtained are so inaccurate as t o be useless, and thnt the "correction" is only correct for cases where the benzene is present t o the extent of nearly I per cent or more. For our purposes such a method is useless.
