1226
ANALYTICAL CHEMISTRY I
r
1
\I
t
-..
-L-?--
PARTICLE
P A R T I C L E SIZE * micron
Figure 9. Dotted line.
Graphical Determination of Pore Size Distribution
Plot of slope of solid line. Ironton metallurgical coke (J)
I t is s e n that macropores constitute ;:1 to 81% of thc total pore volume in metallurgical cokes. Macropore population densities range from 200 to 300,000 pores per gram of original coke depeiiding upon the size of the pore and origin of the coke. Pore surfacae areas are also of great interest. Calculated values shown in Tnble I V range from 52 to 133 sy. em. per gram, which are iu fair Ltgreement lyith the value? reported by Gilchrist and Taylor (5). l l a n y attempts have been made to correlate the porosity of porous materials--for example, coke-with their size stability and reactive and sorptive properties. Little progress, however, has been made, probably in part, because of the lack of reliable methods for determination of size distribution. The method tlescrihed here enables quantitative estimation of macropore size
Figure 10. Dotted line.
SIZE
.
micron
Graphical Determination of Pore Size Distribution Plot of slope o f solid l i n e , Philadelphia foundry coke
tlistrit,ution. Data on pore size. pore volume, pore population density. anti pore surface area are reported for six metallurgical cokrs. LITERATURE CITED
( 1 ) American Iron and Steel Institute and American Coke and
Chemicals Institute, Report on Coke Evaluation Project. (2) Ergun. S., ANAL.CHEY.,23, 151 (1951). (3) Ibid., 24, 388 (1952). (4) Ibid., 25, 790 (1953). (5) Gilchrist, J. D., and Taylor, J . , J . I n s t . F d , 24, 207 (1951). (6) Juhola, .I.J . , Ph.D. thesis, University of Rochester, 1946. (7) Smith, R. C., J r . , and Howard, H. C.. Ind. Eng. C h a . . 34, 138I 1 (1942). RECEIVED f o r review February 19, 1953. Accepted J I a y 6, 1953
Determination of Nitrogen in Nitrocellulose and of Nitrocellulose and Combined Phthalate in lacquers W. E. SEIAEFEK AND W. W. BECKER Hercules Experiment Station,Hercules Powder Co., Wilmington. Del.
A
QUANTITATIVE ferrous chloride reduction method was developed for measuring the nitrate nitrogen in nitrocellulose. This was found to be directly applicable to the determination of nitrocellulose in a lacquer, on the assumption that lacquer-grade nitrocellulose containq 12.0% nitrate nitrogen. Another ferrous chloride reduction procedure has been applied to lacquers containing alkyd resins to effect the removal of the nitrocellulose from them and thus make possible the determination of their combined phthalate content h>- a modified Kappelmeier method. DETERMINATION OF NITROGEN I N NITROCELLULOSE
The nitrate nitrogen content of nitrocellulose can be determined accurately by measuring the nitric oxide evolved from it by means of the well-known D u Pont nitrometer ( I ) , or a D u Pont type of semimicronitrometer ( 6 ) , or by the Devarda ( 4 )
or lluraour (IS') methods in which the iiitrata nitrogeri is reduced t o ammonia and distilled. The Du Pont nitrometer method, though accurate, requires the use of a large amount of mercury and careful training of analysts; the Devarda and Mumour methods are too lengthy for control work. The Dumas combustion method cannot be applied easily to a flammable material such as nitrocellulose, and the Schultz-Tiemann ( 5 ) method is apparently not sufficiently accuratr. The more recent titration method of Leclercq and Math6 (fa) i* suitable onl>- for those types of nitrocellulose which dissolve readily in 9501, sulfuric acid a t 0" C. Of the foregoing methods. only that of Devarda is applicable to films and mixtures of nitrocellulose with resins and plasticizers, and even this method often yields unsatisfactory results when applied to such mictures. From time to time the feasibility of a rapid titration mrthod applicable to all types of nitrocellulose hae been considered. One
1227
V O L U M E - 2 5 , NO. 8, A U G U S T 1 9 5 3
A t i t r a t i o n p m e d u r e s u i t a b l e for m e a s u r i n g t h e n i t r a t e n i t r o g e n c o n t e n t of nitrocellulose consists i n dissolving t h e s a m p l e i n hot acetic acid, boiling w i t h a special f e r r o u s salt reagent, a n d t i t r a t i n g t h e res u l t i n g ferric i o n w i t h s t a n d a r d t i t a n o u s chloride solution. T h i s p i w ~ e d u r eis more convenient t h a n the n i t r o m e t e r m e t h o d a n d avoids t h e oost a n d h a z a r d involved i n t h e use of large q u a n t i t i e s of meroury. W h e n nitrocellulose is p r e s e n t i n lacquers c o n t a i n i n g t h e new types of alkyd resins, it c a n n o t he isolated i n p u r e f o r m a n d d e t e r m i n e d gravimetrically by precipitation w i t h solvents. T h i s n i t r a t e nitrogen m e t h o d can b e applied directly t o a s a m p l e of t h e lacquer a n d t h e a m o u n t of nitrocellulose prese n t , calculated asstirnine t h e l a t t e r c o n t a i n s 12%
. .
.
nitrogen. T h e comhined p h t h a l a t e c o n t e n t of an alkyd resin i n a nitrocellulose lacquer c a n n o t be determined hy t h e uaual Kappelmeier saponification m e t h o d because of interference by t h e nitrocellulose. Ry dissolving t h e l a c q u e r i n acetic acid and t r e a t i n g with ferrous ohloride, the nitrocellulose is reduced largely to a water-soluble form. T h e alkyd resin m a y t h e n be extracted w i t h m e t h y l e n e ohloride, a n d t h e p h t h a l a t e c o n t e n t of t h e resin determined by a modified Kappelmeier procedure. If resins c o n l a i n i n g diglycolic acid are present, t h e m e t h o d m u s t h e f u r t h e r m o d i f i e d . T h e m e t h o d s developed have been applied to a lacquer of k n o w n composition, a conimereial lacquer, various alkyd resins, a n d known mixtures of p h t h a l a t e a n d diglycolate.
.
of the authors (8)applied the ferrous-titan0 ...-.....and Hihhert ( 2 1 ) to nitrogl>-cerin. In that _ _ " _ glycerin is dissolved in acetic acid and refluxed with ferrous chloride, whereby the follau-ing reaction takes place: C3Hj(N0&
+ CJFeCB + CJHCI nu
-
in mi^ L OD,.CII.
L2
~ I n2 u . n
The ferric iron is titrated aeninst standard titanous chloride solution with ammonium thiooyamte tts the indicator. HowI
.."& ":":,...."
^F..:.I&
..".
,"
1
12.04 12.10
2
3
,..-,Lnrl
+"
:,.
":+-mndl..ln.n n.alimino*.,
1 1 I 2
11.99
~
I n a re-examination of the ferrowtitanous method the samples were first heated with acetic acid t o incipient boiling, a t which point they were completely or almost completely dissolved, and then the reducing reagent was added. The concentration of hydrochloric acid and ferrous chloride in the reagent and the time of heating were varied extensively in an effort t o obtain results close t o those previously found by the nitrometer method. Unfortunately, under the most favorable conditions, the results were concordant hut about 0.05 unit lower than the nitrometer values. The addition of sulfuric and perchloric acids t o the reaction mixture oaused the results t o he discordant, possibly because of the oxidizing effect of both acids on ferrous salts. The addition of hydrobromic acid, which is much stronger than hydrochloric acid in acetic acid solution, proved t o he the solution of the difficulty. Under the chosen conditions, the results were concordant within a few hundredths of 1% and agreed closely with the accepted nitwmeter values, as shown in Table I. . . ~. . ~ ~ ~ ~ ~ ~ . atmosphere of either carbon d i o x i d e ~ rnitrogen during refluxing when a series of determinations is being made. The inert gas i s supplied to each reduction flask through the needle valve connected to a manifold. The water inlet,, outlet, and vent tubes on the Hopkins condensers are all polnted in the same direction (Scientific Glass Appitratus Co., Catalog No. 6-1191. ~~~~~~~~
Figure 1. Assembly of A p p a r a t u s for' Ferrous-Titanous Method modified). The acid vapors are absorbed in water in Fleming gas-washing bottles, the outlets of which lead into water in a sink. ,
-
ANALYTICAL CHEMISTRY
1228 Standardize the titanous chloride by titration of the total iron derived from a Kational Bureau of Standards sample of Sibley iron ore (Sample S o . 27b), which serves as a primary standard. Dry a 1-gram sample of the ore for 1 hour a t 105" C.. weigh it accurately into a 300-ml. reduction flask, add 50 ml. of 1 to 1 hydrochloric acid and a few particles of carborundum, and boil gently under reflux for an hour. Evaporate the solution to a small volume to remove most of the hydrochloric acid, dilute with water, and add 2 ml. of 307, hydrogen peroxide. Heat to boiling and boil for 5 to 10 minutes. Add excess ammonium hydroxide and boil for 5 to 10 minutes to decompose residual hydrogen peroxide completely and to remove most of the excess ammonia. Add excess hydrochloric acid and boil to dissolve the ferric hydroxide completely. Cool, pass a current of carbon dioxide or nitrogen through the flask for 5 minutes to remove air, dilute with 50 ml. of water, and titrate with titanous chloride while passing an inert gas through the flask and stirring with a magnetic stirrer, S e a r the end point add 5 ml. of 20% ammonium thiocyanate solution and titrate just to the disappearance of the red color. Ferric ammonium sulfate, approximately 0.4 iV, for use as a secondary standard. For each liter of solution, use 195 grams of ferric ammonium sulfate hydrate and 25 ml. of 95% sulfuric acid. Determine its concentration, which remains constant indefinitely, by titrating it with titanous chloride which has just been standardized with Sibley iron ore. Standardize the titanous chloride solution, the concentration of which may decrease slowly, with the ferric ammonium sulfate every day if the highest possible accuracy is desired. However, if the concentration of a bottle of titanous chloride solution is found to be constant, it need be confirmed only once or twice each week. Ammonium thiocyanate solution, 200 grams per liter. Procedure for Nitrogen in Nitrocellulose. Place a sample of approximately 0.50 gram of air-dry nitrocellulose in a small weighing bottle, heat it a t 100" t o 105" C. for 1 hour, cool, and weigh. Pass a current of carbon dioxide or nitrogen through a reduction flask for a t least 5 minutes in order to remove atmospheric oxygen completely. Momentarily detach from the flask the rubber tubing carrying the supply of inert gas and transfer the sample from the small weighing bottle to the flask. Add 100 ml. of glacial acetic acid to the flask and again pass inert gas through it. Bdd particles of 10-mesh Carborundum and a glasscoated stirring bar. Without attaching the flask to the condenser, heat the solution to boiling. Before the acetic acid vapor reaches the flask opening, place the flask above the rotating magnet, and 'add 25 ml. of the ferrous chloride reagent rapidly by using a pipet from which the capillary tip has been removed. Attach the flask to the condenser. Allow the reaction to proceed a t boiling temperature in the complete absence of air for 25 to 30 minutes while the color changes from greenish black to yellowish brown. In the meantime, heat the empty neighing bottle a t 105" C. for 10 minutes, cool, and weigh it. Cool the flask somewhat, add 50 ml. of distilled water, increase the inert gas stream so that it produces a visible ripple on the surface of the liquid, and titrate the ferric iron with titanous chloride while the solution is being stirred with a magnetic stirrer. Add 5 ml. of 2070 ammonium thiocyanate as the end point is approached. Titrate to the point a t which the red color due to ferric thiocyanate just disappears. This can readily be detected even though the solution is gray a t the end point. Determine blank values on the reagents under the foregoing conditions.
(RII. of TiCh - blank value) X normality of TiCI, X 0.1669 Grams ofsample where 0.4669 =
=
%i5
14.008 X 100
looo
DETERMINATION OF NITROCELLULOSE IN LACQUERS
The separation of nitrocellulose from other lacquer components and its gravimetric determination, until recent years, could be accomplished without serious difficulty by diluting the lacquer with a suitable solvent and precipitating the nitrocellulose by adding, with mechanical stirring, a hydrocarbon in which the nitrocellulose is insoluble. However, the introduction of ne)? formulations, especially those containing alkyd resins, during the past several years has rendered it impossible to isolate the nitrocellulose in pure form by the conventional method even by triple precipitation. In the case of some of these newer lacquers. it is possible to determine the total nitrogen by modified Kjeldahl
Table 11. Nitrocellulose Content of Lacquers Saniple Unpigmented lacquer of known compositiona Pigmented commercial lacquer
Present 8.7
Sitrocellulose, % Found 8 . 7 1 , 8 . 7 2 ,8 . 8 7 , 8.70, 8 . 6 4 ,8 . 6 8 Av. 8 . 7
6.3b
6.07,5.94.6.06, 6.07,6.26 Av. 6 . 1
a Solids, 29%: 2.9% tricresyl phosphate; 8.7% RS nitrocellulose, 0 . 5 second, dry; and 17.470 glyptal 2477. Solvents, 71%: 7.1% ethyl alcohol; 8.9% butanol; 28.4% xylene; and 26.6% butyl acetate. b B y formulation of manufacturer.
or Devarda methods and to calculate the amount of nitrocellulose present on the assumption that it contains 129" nitrogeri-i.e., the amount present in the type of riitrocellulose commonly used in the formulation of lacquers. However, the latter procedure is less satisfactory than is desirable and cannot be used when nitrogen-containing resiris are present. The authors a e r e able to determine the nitrate nitrogen content of the lacquer by the ferrous-titanous method described in the previous section ; the percentage nitrocellulose was then calculated. On applying the method to an unpigmented lacquer of known composition that had been quantitatively formulated and to a commercial pignirnted lacquer, the reasonably concordant results listed in Table I1 were obtained. The apparatus and reagents described in the foregoing section were used; the procedure as applied to lacquers is as follotw: Procedure. If a clear unpigmented lacquer is being examined, place 50-ml. portions of glacial acetic acid in 300-ml. reduction flasks. Transfer samples tvhich contain approximately 0.25 gram of nitrocellulose from a suitable closed dispenser to the flasks. Pass the inert gas through the flasks for a t least 5 minutes and swirl them to dissolve the samples. Heat the solutions to incipient boiling, add the ferrous chloride reduction reagent, boil, cool, and titrate with titanous chloride as previously described in the method for nitrate nitrogen in nitrocellulose.
( M I . of TiCI, - blank value) X normality of Tic13 X 0.4669 Grams of sample X 0.12 where 0.4669 =
14.008 X 100 3 x 1000
-
yonitrocellulose
and 0.12 = fraction of nitrogen in lacquer-grade nitrocellulose If a pigmented lacquer is being examined, it is advantageous to know a t the start whether any reducible metallic component is present. This can be ascertained most rapidly by a spectrographic analysis. If such a component is present, first remove as much as possible by centrifuging. Then determine the small amount of interfering component in the decantate and apply a suitable correction. For example, if ferric oxide is present, weigh samples of suitable size. usually 3 to 4 grams, into 250-ml. centrifuge bottles containing about 100 ml. of acetone. Stir the solutions and centrifuge them for about 5 minutes at about 2000 r.p.m. Decant. add more acetone, and again centrifuge as before. Evaporate the combined decantates to a volume of about 50 ml. (but not to dryness), transfer to a 100-ml. volumetric flask, and dilute with acetone to 100 ml. Shake the flask to be sure that a homogeneous suspension of ferric oxide is formed and immediately remove 5 ml. with a pipet. Determine colorimetrically the ferric iron (0.25 to 0 50 mg.) in this aliquot. Transfer the remainder of the acetone solution to a reduction flask, evaporate it to a small volume (but not to dryness), add 50 ml. of glacial aretic acid, and complete the reduction as just described for unpigmented lacquers. In calculating the result, subtract the amount of titanous chloride equivalent to the 5 to 10 mg. of ferric iron present ( 1 mg. of ferric iron is equivalent to 0.0179 ml. of 1 -1-titanous chloride). DETERMINATION OF CO\IBINED PHTHALATE I Y LACQUERS
The combined phthalate content of an alkyd resin alone may be determined readily by the gravimetric potassium phthalate
1229
V O L U M E 25, NO. 8, A U G U S T 1 9 5 3
Modification of Usual Kappelmeier Method. Because of the recognized superiority of (Dried a t 60' C. for 1 hour; on further heating a t 150' C . ) the Kappelmeier method for Phthalic Anhydride phthalate, another possible way Decrease in Amount calculated from of using the method was considWeight of decrease in weight Precipitate on Theoretical on heating precipitate ered. Kappelmeier had deterSample Heating a t amount a t 150' C. Correction wt., 150' C. for expected, Source of mined phthalate in the presence Gram 3 Hrs., Gram gram Gram % Factor Phthalate of adipate and succinate, whose Potassium acid 1.053a 95.0 0.2537 0.2411 0.3499 0.0750 phthalate potassium salts are insoluble in Potassium acid alcohol-ether solution, by mak95.3 1 . 04Qa 0.2598 0.3757 0.0808 0.2725 phthalate Dibutyl ing use of the fact that potas1.05Zb 95.1 0.2841 0.2701 0.5340 0,0840 phthalate Dibutyl sium phthalate alcoholate is 1.052b 95.1 0.3304 0.3141 0,6209 0.0977 phthalate stable a t 60" C. but loses its Ar. 1 . 0 5 2 alcohol a t 150" C. I t occurred a Saponification reaction mixture contained 10 ml. of benzene. b Saponification reaction mixture contained 50 ml. of benzene. to the authors that the amount of phthalate in impure potassium phthalate alcoholate derived from unknown resins Table IV. C o m b i n e d P h t h a l a t e i n Alkyd Resins, Calculated as P h t h a l i c Anhydride could be determined in a simiPhthalic Anhydride Found after Phthalic Anhydride l a r m a n n e r . T h i s loss-inApplying Ferrous Chloride Reduction Found by Direct Saponification Procedure, Results Calculated f r o m weight-of-alcohol p r o c e d u r e Result Escess Decrease Excess was applied to three samples of calcd. from K&Or in weight KzSOr potassium Formed Potassium on Formed approximately 0.5 gram of diphthalate from phthalate Potaaaium further from Espt. alcoholate, Precipitate, Expt. alcoholate, phthalate, heating, Preci itate, butyl phthalate having a purity Sample SO. 70 70 NO. 70 % % of 100.2% calculated from its Aroplaz 1 20.1 ... 9 23.7 ... ... 17.4 saponification value. The re906X 2 20.1 ... 10 20.0 ... ... 0.2 3 20.0 0 4 11 20.3 20.5 20.4 4.5 sults based on the weights of 4 20.0 0.0 12 19.8 19.8 20.8 2.5 potassium phthalate alcoholate 28.0 ... ... 3.4 Paraplex 5 28.0 0. 7 13 were 99.8, 99.7, and 100.0% of ... 2.6 SD-77 6 28.4 0.0 14 27.6 ... 15 31.1 31.8 28.6 7.6 the theoretical ; those based on 16 27.4 27.6 27.6 -0.7 t h e w e i g h t s of p o t a s s i u m phthalate were 100.2,100.2, and 100.4%; and those based on the decrease in weight on heating, calculated by using the theoretical factor, were 97.7, 97.2, and 98.0%. I n the experiments just described no benzene method of Kappelmeier ( 2 , 9 ) ,the volumetric potassium phthalate was present in the saponification reaction mixtures. method of Goldberg ( 8 ) ,the lead phthalate method of Swann (15), The foregoing results demonstrated the need of applying a suitaor the spectrophotometric method of Shreve and Heether ( 1 4 ) . ble correction factor if the results v, ere to be calculated from the However, when present in a lacquer containing an alkyd resin, loss in weight on heating a t 150" C. Since experience n i t h the nitrocellulose interferes. Unfortunately, the alkyd resin cannot analysis of alkyd resins indicated that it is advantageous to have be separated quantitatively from the nitrocellulose by any sola considerable amount of benzene present in the saponification vent precipitation method. reaction mixtures to assure that The resin samples are completely The authors' work on the determination of nitrate nitrogen in dissolved, either 10 or 50 ml. of benzene were used in subsequent nitrocellulose showed that nitrocellulose can be reduced for the experiments with resins. Determinations of the phthalate conmost part to water-soluble form by means of ferrous chloride in tent of pure potassium acid phthalate and of dibutyl phthalate glacial acetic acid. Such a mild reduction method decomposes were repeated under these conditions for the purpose of deterthe nitrocellulose without harming the alkyd resin and, after the reduction, the alkyd resin can be extracted with a suitable solvent mining the magnitude of the correction factor. Such a factor is required because of unavoidable errors resulting from premature and the phthalate content determined by the Kappelmeier loss of some of the alcohol of crystallization on washing the premethod. cipitates with ether and the extreme hydroscopicity of alcoholOne alkyd resin and a lacquer formulated with it were analyzed free dipotassium phthalate, both of which tend to make the resuccessfully by the simple reduction method just described. sults too low. The results of these determinations are contained However, when other alkyd resins were analyzed in the same manin Table 111. ner, the results were erratic and often considerably higher as The results found on analyzing three alkyd resins for phthalate, compared with those found on applying the Kappelmeier method both by direct saponification and by reduction with ferrous chlodirectly. By quantitatively converting the potassium phthalate formed in a number of these experiments to potassium sulfate, it ride followed by saponification, are shown in Table IV. The results were concordant when the resins were subjected to direct u as demonstrated that the potassium phthalate isolated by the direct Kappelmeier procedure was pure but that the potassium saponification. In most cases the results found after applying phthalate precipitates formed after subjecting the resins to the the combination of reduction and saponification procedures ferrous chloride reduction treatment often contained more than were reasonably concordant. However, in two cases (Experithe theoretical quantity of potassium. Therefore, the latter ments 9 and 15) the results calculated from the weights of potassium phthalate alcoholate and potassium phthalate were grossly precipitates must have contained a potassium salt of an acid in error, and these were the experiments in v hich 17.4 and 7.6% having a lower equivalent weight than phthalic acid. Because of this complication, the ferrous chloride reduction step followed of excess potassium sulfate were formed from the precipitates. by the usual Kappelmeier method could not be applied to nitroKevertheless, a reasonably accurate result n-as obtained by calcellulose lacquers containing unknown alkyd resins. culating phthalic anhydride from the decrease in weight on fur-
Table 111. D e t e r m i n a t i o n of Correction F a c t o r t o Be Applied t o Decrease i n Weight of P o t a s s i u m P h t h a l a t e Alcoholate
!i
1230
ANALYTICAL CHEMISTRY
Rinse the centrifuge bottle with 10 to 15 nil. of lieiizene, transfer thcr he:tting in all six experiments in which the decrease in the benzene to the separatory funnel. and shake the latter. weight \vLq nieasured. To obtain satisfactory results in all cases, Then filter the benzene, collecting it in the beaker along \vit,h the it is reconimeiided that the decrease-in-weight procedure be used. alcohol. Discard the interface residue. Evaporate the filtrate O F OTHERDIBASIC ACIDSPRESESTIN .II,KYD rapidly on a steam bath in a current of air. If the residue appears to contain droplets of water, add to it 10 to 15 mi. of 4:1 I~~CSISS I n. addition to phthalic acid, alkyd resins may contain benzene-anhydrous ethyl alcohol solution, and evaporate to a number of other dibasic acids, all of which form insoluble potxsdryness again to remove water completely from the residue. sium salts by the Kappelnieier mcthod. Shreve and Heethcr ( 1 4 ) Dissolve the residue in methylene chloride antl combine it with determined phthalic acid in alkyd resins by saponifying, filtering the methylene chloride filtrate in the j00-ml. Erlenmeyer flask. k h p o r a t e the methylene chloride solution to a small volume oft' the insoluble potassium salts. dissolving the latter iii water. on the steam bath and remove it from the steam bath. Then, aoidifyiiig, and measuring the :tbsorl):mce a t 276 mp by nieaiis of by using a current of air, evaporate it to dryness. Excessive an ultraviolet spectrophotometer. They were able to detci~ninc heating of the resins makes them ini.oluhle in benzene. Dissolve phtjhalate in the presence of a number of dibasic acids commonly the residue in 50 ml. of benzene. To the benzene solution of the resin. atld 150 nil. of freshly occurring in :dkytl resins. IIowevcr. since a spectropliotoiiictei~ filtered 0.6 S anhydrous alcoholic potassium hydroxide solution. is not available in all Ialioratorie.s, other possible \wys of malting Htopper the flask loosely wit.h a cork stopper and heat in an oven this determination x-ith simple laboratory equipment are 'giveii. a t 60' to TO' C. for 3 hours. Potassium maleate and potassiuni fumarate are both pracCool the flask, rinse down the walls with 50 ml. of ether, anti filter, within an hour, through a weighed, fritt,ed-glass crucible tically insoluble in alcohol-ether solutions. .ifter prceipitatea of of nietliuni porosity. Use 1 to 1 ethyl alcohol-ether wash soluthere substarices are dried a t 00" C. for 1 hour, only iiegligible tion for transferring the precipitate and washing the reaction amounts of solvents are retained in them. For example, such flask. Do not allow air t o be drawn t,hrough the crystals unprecipitates lost only 0.3 t,o 0.4% on being heated an additional necessarily. as they are hygroscopic. Finally, pour 25 ml. of ether into the crucible and draw it through the precipitate. 3 hours a t 150" C . This behavior makes it possible to determine \Vipe the outer surface of the crucible and heat i t at 60" C. phthalatc by the lossin-weight nictliod even if malcate or fumafor 1 hour. Allow i t to cool in a desiccator containing concenrate is present. Kappelmeicr ( I O ) has reported that atlipate and trated sulfuric acid for 30 minutes or longer and weigh it. succiiiate behave similarly, provitletl the potassium d t s are I!eat the crucible at 150" C. for 3 hours, cool it, and neigh i t again. The decrease in weight that occurs on heating represents properly w:whetl with ether. The behavior of diglycolate is disalcohol of crystallization in potassium pht>halatealcohol~tte. cussed later. On the basis of experimental work! the followiiig procedure for -~ Decrease in weight X 3.215 X 1.052 X 100 = 70phthalicanhydride the determination of phthalate in lacquers is suggested. If a Grams of sample pigment is present,, it must be removed by tlilut.ing with wetone, d i e r e :3.215 is the theoretic-a1 factor and 1.052 ie a correction centrifuging, nncl tiecanting as described earlier. factor whivh needs t o he applied under the prescribed conditions (Table 111). Reagents. Solution for the removal of water by azeotropic didtillatioii, coilaisting of benzene-anhydrous ethyl alcohol, 4:l. Absolute alcoholic: potassium hydroxide solution. approximately 0.6 N. Allow the solution to st:md overnight protected 'Table Y. Phthalic Anhydride in Lacquer of K n o w n from carbon dioside. Filter just before using. Prepare fresh Cornposition reagent once eiwh week. Time Allowed Procedure. Weigh, from a suitable closed dispenser, an Phthalic Anhydride for Reduction of amount of the lacquer t,hat contains phthalate equivalent t o Foontl, Present", DetrrniinaSitrocellulose, r c ,o approximately 0.25 gram of phthalic anhydride. Add 50 ml. tion ?io. Mnutes :C of' hot glacial acet,ic acid and a few particles of 10-mash car1 6.59 2 borunduni. Swirl the solution in order to dissolve the sample :3 without overheating it. Place the flask on a hot plate and heat I the solution until the acetir acid vapor ascends halfway to the top of the flask. ridd about 5 grams of powdered ferrous a Calculated from prr cent phthalic anhydride found in yesin hy analysis and from coniposition of lacquer stated i n Table 11. chloride tetrah drate, immediately fit, a condenser into the neck of the flask, anJboil the misture for 3 to 5 minutes. Cool the flask. Decant the liquid portion of the reaction mixture t o a 250-ml centrifuge bottle and rinse the flask with several portions of methylene chloride, using a total of 50 nil. Add about 100 ml. Table V contains results obtained by the los&n-weight method of water to the centrifuge bottJe, insert a rubber st*opper,shake for the phthalate content of a lacquer of known composition. the bottle cautiously, vent the nicthylene chloride vapor, reinsert Presumably thr loss of some phthalate. inrluded in the diwarded the stopper, and shake the bot,tle vigorously. Centrifuge and then draw off the upper aqueous layer by means of a 25-ml. insoluble nitrocellulose decompositioii product, causes the repipet connected to a water aspirator. Repeat the extraction sults t o bc about 2% low. with two more 1 W m l . portions of water as just described to Interference of Diglycolate. Diylycolic acid, when present in reduce the concentration of acetic acid, iron ealts, antl other an alkyd resin, forms on saponificat,ion of the resin an insoluble water-soluble substances to such a low point that thej- will not interfere. potassium salt which retains either alcohol or tvater of crystallizaI n order to extract the alkyd resin quantitatively froni the tion t,enaciousl>-a t 60" C. but loses it at 150" C. If diglycolate methylene chloride solution and the emulsion interface which is present along with pht,halate, the latter cannot be determined accompanies it, a special separation procedure is required. It by any heretofore published chemical modification of the Kappelconsists in separating the methylene chloride solution from the interface and then extracting the latter with alcohol and benzene. meier method. Transfer the contents of the centrifuge bottle to a separatory Digl>,cQolatecan lie detected 1)y the 2.;-dih?-droxynapIith:ilene funnel and filter the lower methylene chloride layer into a 500test. for glycolic wid given by Frigl ( 7 ) . B c m u x the test is so ml. Erlenmeyer flask, using a coarse-porosity fritted-glass fuiinel sensitive. the unknown alkyd resin must h e isolated from a nitroand a bell-jar filtering device. Rinse the bottle with methylene chloride, transfer the methylene chloride to the separatory funnel, cellulose lacquer as previously described, saponified, and a few and filter the lower layer. Repeat, this operation, this time milligrams of the filtered, washed, and dried (1 hour a t 60" C.) sivirling the methylene chloride gently over the walls of the potapsium salts must be dissolved in viater and tested. slight separatory funnel before filtering. By this technique the formapink coloration should he disregarded. tion of an emulsion is avoided. Replace the Erlenmeyer flask with a small beaker. Rinse the A simple gravimetric procedure n'as developed for the detercaent,rifuge bottle with 10 to 15 ml. of anhydrous ethyl alcohol, mination of phthalate in the presence of diglj-colate. It was transfer the contents to the separatory funnel containing the found that on being dried for 6 or 7 days over 95% sulfuric acid, interface left from centrifuging, and shake the separatory funnel. potassium glycolate loses ita retnined alcohol or water and Filt,er the whole mixture through the same funnel as was used reaches constaiit weight, \r.ith substantially no furt>herloss on liefore, and then repeat the operation of Tashing with alcohol.
V O L U M E 2 5 , N O . 8, A U G U S T 1 9 5 3
1231 _____
A C K S O W LEDG.\I EhT.
~
Determination of Phthalate in Dibutyl Phthalate Alone and in Dibutyl
Tahle \ - I .
Expt.
NU. 1
,
3
5 ii
Phthalate-Diglgcolic Acid lMixtures
Dibutyl Phthalste’J, Gram 0.4860 0.5063 0.5547
Diglycolic Acid. CI
0.3909 0.4127 0,4339
0.1373 0.1362 0.1422
... , . .
Decrease in Phthalic Anhydride, meight of ~ i ~ Amount ~ ~Calcd. ~ from~ precipitate .klnoilnt Decrease in Weight on Heating ~ ~ ~ i . . . ~ d Heating of Precipitate a t 15:‘ onC. a t 130’ C. froin for 3 Hrs. for 3 Hrs.*, Hainvlr, Grain Grain Grain 70 0.07.52 0.2.586 0.8418 93.5 0,0777 0.2694 0.2498 93.7 0.0833 0.29.53 0.2742 92.9 0.0379 0 0619 0.0633
0.2080 0.2196 0.230!1
0.1881
0,1990 0.2042
~
i
~
phthalate Dibutyl Correction Factor 1.070 1.079 1.076 Av, 1 . 0 7 3
...
...
...
...
,..
~
Folmdd,
%
... ... . ..
96.2 97.4 95.1 .I\..9 6 . 2
Specirnen lived was 100.2%opure as determined b y saponification nninber. b This is decrease t h a t occurred after preliminary treatment, which consisted i n heating 3 hours at 60” C. and drying in desiccator over 93% HnSOi for 6 days. 0 Decxbase in weight X ratio of molecular weights of phthalic anhydride and ethyl alcohol--i.e., decrease in weight X 3.215. d Result+ were calcrilated by using correction factor of 1.07.5. a
l
The authors are indebted to their colleagues, H. hi. Spurlin, for helpful suggestions during the course of this work and R. J. Langel, for most of the determinations of nitrate nitrogen by the ferrous-titanous method; and to the Parlin. N. J., laboratory for most of the nitrometer determinations. LITEHATURE CITED (1) ;im.
Soc. Testing Materials,
A.S.T.M. Standards, Part 4.“Standard Specifications and Testa for W u b l e Nitrocellulose,” pp. 361 -9,
D e s i g n a t i o n D 301-50 (1952). (2) Ibid.. “Phthalic Anhydride Content of Alkyd Resins and Resin Solutions,” pp. 332-3, heating s t 150” C. IVkieii sul)jrscted to a sirni1:tr treatment, poDesignation D 563-52 (1952), tassium phthalate :tl(!oholnte loses only a small fraction of its (3) Uecker, 15‘. &*.,ISD. E S G . C H E J I . , - 4 S . % L . ED.,5, 152--4 (1933). alcohol of crystallization. Therefore, after drying a mixture of (4) Carter, R , o,,j r , ,shuoy, FI, AI,, and 1viiljam8,J, mr,, iuni glycolatcs :tnd potassium phthalate alcoholate over 8. Xational Defense Research Council, Office of Scirntific Research and Development, Rept. 3876, U. S. Dept. of Comsulfuric acid, weighing, heating at 150’ C.. and weighing again, merce, OTS PB 30764 (1944). the final lorn in weight of alcohol can be calculated :is phthalate. ( 5 ) Dol&, C.. “hlethods of C’ellulose C‘heniistry,” 2 n d etl., p. 245, London, Chapman and Hall, Ltd., 1947. PROCEDURE FOR DETERJIINATIOS OF PHTHALATE I S PRESENCE (6) P. J.,~and .\lcElrW, .\s\L. OF nIGLYCOLATE. lxeat the crucible containing the ~ ~ ~ Elving, ~ 14, l -lv. It., ISD. EXf., ED.. 84-8 (1942). F., “Qualitative Analysis hy Spot Tests,” 3rd ed.,p. B94, ~ ~ 6 ~ ~ ~ : s , 1 e ~ ~ &~ ~ 17) Feigl, ~ Sew Tork, Elsevier~ I’rihlishing (.o.. 1946. a t 150” C. for 3 hours, anti weigh it again. (8) Goldberg. A. I., Asar.. (?HEM., 16, 198-200 (1944). (9) Kappelmeier, C . P.-L, Pnint, OiZ, C h ~ m Rw., . 99, KO. 12, 2 0 , _ _ in~ weight X 3.215 X 1.075 X 100 = %’,phthalicanhytlride Decrease 22, 24 (1937). Grams of sample (IO) Kappelnieier, C. P..4.,and vaii Goor, K. lt., T’eiilkrnriiek. 16, 8-10, 17-20 (1943). where 3.215 is the theoretival factor and 1.075 is a correction (11) Knecht. E.. and Ilibbert. E..“ S e w Redurtioii llrthod, in factor which needs to be applied under the prescribed rouditions Volumeti ic .inalysis,” 2nd ed.. Loiidon. Longmans, Green and (Table 1.1). Correct the foregoing result by taking into conCo.. 1925.. sideration the slight amount of precipitate removed for the (12) Lecler’cq, R., and Mathi., ,I., H u U . soc. chin!. H e i g c s . 60, 2!)& qualitative test for diglycolate. 300 (1951). (13) lluraour. H.. B d I . SOC. c h i m Prcrnce, 45, 1189-93 (1929), Tahle \-I shows the results found when phthalate \vas deter(14) Rhreve, 0. D., and H c e t h n . A I . R.. A S L I . . CHEM.,23, 441- 3 (1951). mined in admixt.ure Ivith a 1:trge amount of diglycolate. (15) Swann, 31. H., Ibl‘d., 21, 1443-53 (I94R). I t is obviously inipossil,le to distinguish between phthalate (16) Wagner, C. D., Smith, R. H., and Peters, E. D.,Ihid., 19, 982-4 derived from phthalate plasticizers and that, derived from alkyd (1947). resin3 if both of these sulmtances are present. The removal of R E C E I V EfDo r revic,w Ilcceinhrr 4 , 1931’. .icoepted 1Iay 20, I9;:j. I’rvphthahte plasticizers by c1irom:itography or by vacuum digtillasented in part a t the Delaware Ch?iiiical Syinpo.iiiii1. Univer,ity of l h l > ~ tion might be posail)lc. ware, S e w a r k , Drl., January 1953. -.
. .-..
2:;
~
tt
tl$tiii
Determination of Impurities in Titanium Metal J. 31. TIIOMPSO3P i g m e n t s D e p a r t m e n t , Chernicul Dirisiori, E. Z. diL Porct de Sernotirs & Co.. l r t r .. V e t c p o r t , D e l .
M
ETHODS are described for the determination of iron, nitrogen, magnesium, manganese, and chloride in titanium metal sponge. These coutaminants as well as orygen and hydrogen are present in all sponge produced by present da5- commercial processes. There is no suitable x e t chemical procedure for oxygen and hydrogen. These elements are best determined by the vacuum fusion mt+hod. Adaptations of the iron and riitrogen methods to cast and wrought forms are also included. iYo great amount of originality is required to adapt known methods for these elements to the analysis of titanium metal; however, the widespread activity of thie “new” metal appears to justify publication of these methods that have been proved in commercial operations over the past 5 years. Iron iq deterniiriecl hy the colored thiocyan:ite-iron complex
(2, 6 7 ) . T d ) k I givcxi :I ~ ~ ~ m p ~ iofi i i ~wod tn5 obtained I)> thls method verbui wpai:itioii of iioii its sulfide and titration rvith potassium dichromate 11epodueil)ility of the method is indicated by data in Tdble 11. Sitropen i 4 determined by a modified semimicro Kjeldahl method. .4 simple sulfuric acid digestion is sufficient to convert the nitrogen in sponge t o ammonium sulfate. Cast and wrought forms, hob ever, requirr treatment n i t h hydrogen peroxide to effect the conversion. This method was adapted from procedures received from the National Bureau of Standaids and Battelle Memorial Institute ($, 5). Table 111 indicates the reproducibility of the method. Separation of magnesium by precipitation u ith sodium hy-
