Qualitative Test for Distinguishing Tris(1 -aziridinyl)Phosphine Oxide (APO) and Tetrakis(hydroxymethy I) Phos pho nium ChIo ride THOMAS D. MILES and ARMAND0 C. DELASANTA Textile, Clothing, and Footwear Division, Quartermaster Research & Engineering Command, Research & Engineering Center, Natick, Mass.
A qualitative paper chromatographic test for distinguishing two flame-retardant compounds, tris( 1 aziridiny1)phosphine oxide (APO) and tetrakis(hydroxymethy1)phosphonium chloride (THPC), was developed. Using butanol-hydrochloric acid as an elutent, and placing the paper in ammonia fumes, APO develops a yellow color at R, 0.8 and THPC develops a blue color at R, 0.4. The method is also suitable for identifying the compounds when present in typical formulations used for impregnating textiles. Test results for APO-, APO-THPC-, and THPC-treated fabrics after curing are described and the last two compared to results obtained with other phosphorus-containing flame-resistant finishes.
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RIS( ~-AZIRIDINYL)PHOSPHIXE oside,
(Cs$)3P=0
( I ) , and tetrakis-
(hydroxymethy1)phosphonium chloride, (HOCH2),PC1 (S), are used in textile finishes. The latter, known as T H P C , is used as a flame retardant in combination with either methylol melamine or with tris( 1-aziridiny1)phosphine oxide, known as rlP0 ( 5 ) . APO is also used to to impart wrinkle resistance to cotton fabrics ( 2 ) . I n evaluating the uses of these two compounds in flame-resistant treatments for military fabrics, an analytical method \yas developed to distinguish the two when present either in typical finishing bath formulations or on treated fabric. T h e test, a horizontal paper chromatographic method, consists of spotting the paper with a sample of the compound, the bath formulation, or the acid extract from treated fabric. Distinguishing colors are developed with ammonium molybdate. REAGENTS
T h e elutent was a solution of 20% 6N HCI and 80% butanol (by volume). The ammonium molybdate solution for color development was prepared as follows: A solution of 117 grams of 85%
molybdic acid, 300 ml. of water, and 120 ml. of concentrated ammonium hydroxide n-as diluted to a total volume of 800 ml. and allowed to cool. This was added to a solution of 500 ml. of concentrated nitric acid which had been diluted to 1200 ml. Three or four drops of 10% sodium phosphate solution were added and allowed to settle. The solution was filtered before use. The ammonium molybdate solution is the same as that used in phosphorus determinations. PROCEDURE
A circle of filter paper (Whatman KO. 3 for paper chromatography) slightly larger in diameter than the Petri dish (approximately 6-inch diameter) n a s used. The paper had a l / d inch wide nick cut to the center. The solution being tested was transferred to the paper with a niicropipet using approximately 126 p1. K i t h its wick immersed in the elutent, the spotted paper was placed in the Petri dish and covered with another Petri dish. iifter the elutent had covered approximately two thirds of the area of the Petri dish, the paper was removed and the outside edge of the solvent was marked n i t h a pencil. The paper was air-dried. A few milliliters of the ammonium molybdate solution were poured onto the paper, which was then placed in ammonia fumes from concentrated ammonium hydroxide. The resulting color reactions and R, values are listed in Table I. The values shown are a n average of 10 determinations and the average deviation. When treated fabric was t o be tested, a n acid extract was made. T o do this, approximately 5 to 10 grams of the fabric were placed in a 400-ml. beaker and 300 ml. of lyGhydrochloric acid were added. The solution was boiled until the volume was reduced t o approximately 50 ml. This was used to spot the paper. DISCUSSION OF RESULTS
A T H P C flame-resistant formulation for treating textiles contains, in addition t o T H P C , triethanolamine, urea, a wetting agent such as isooctylphenoxy(po1yethoxy)ethanol and methylol melamine
Table I. R, Values and Color Reactions of APO and THPC with Molybdate Solution
Compound Ri Color hlonomer or Its Finishing Bath Formulation APO 0.77 f 0.02 Yellow THPC 0.44 f 0 . 0 3 Blue Acid Extract. (lye HC1) of Treated Fabric APO 0.76 f 0.02 Yellow APO-THPC 0.76 f 0 . 0 2 Yellow ... No color THPC
resin. An APO-THPC formulation contains triethanolamine and a wetting agent such as benzyldimethylstearylammonium chloride. None of these other compounds present in the bath formulation interferes with the test. HoIvever, there are other phosphates that would give a yellow ring at R/ 0.8. Ammonium phosphate, sodium phosphate, and hexamethyl phosphoramide, for example, will give a yellow ring a t R, 0.8. On the other hand, tris(p-chloroethyl)phosphate, dimethyl hydrogen phosphite, tricresyl phosphate, tris(2ethylhexyl)phosphate, and trioctyl phos phate produce no color reaction by the test method. The above compounds that do give a yellow ring a t RJ 0.8are not usually encountered in durable flame-resistant finishes. T h e blue color t h a t forms with the THPC may be due t o t h e reaction product of T H P C with ammonia, a white water-insoluble compound. T o demonstrate this, T H P C was placed in a solution of ammonium hydroxide and the water-insoluble precipitate was filtered and washed. This compound gave the blue color with ammonium molybdate without the necessity of placing the paper in ammonia fumes. The compound did not migrate in the test procedure using the butanol-acid solvent, but remained at the point of origin. Heating the APO-THPC bath formulation to 50' C. for 1 hour producea no change in the position or color of the two compounds in the chromatogram. VOL. 31, NO. 12, DECEMBER 1959
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However, heating the bath formulation to 100" C. made a difference. No color developed a t 0.4 but a blue color appeared at the point of origin on the paper. This spot a t the origin also gave the molybdenum blue color before the paper was placed in the ammonia fumes. This suggests that in the APOT H P C formulations used for treating cotton the T H P C is converted into an insoluble polymer only when heated but remains in the bath formulation as THPC. In regard to the yellow color with ,4PO, the addition of APO to an ammonium molybdate solution forms a yellow precipitate. The reaction is highly exothermic and the addition of concentrated solutions of APO to ammonium molybdate should be avoided. The APO molybdate was filtered and titrated with sodium hydroxide according to the usual procedure for a phosphorus determination. Each mole of APO took 5.5 to 5.9 moles of sodium hydroxide. The infrared spectra of the precipitate differ from those of the molybdate formed b y sodium phosphate, in that an intense absorption at
7.25 microns in the spectra of the latter is absent in the APO molybdate spectra. On standing, the color of the precipitate changes from yellow to green, which is the same type of color change produced by mixing a reducing agent with ammonium phosphomolybdate. The infrared spectrum of the molybdate that forms from the acid-extracted APO-THPC-treated fabric is the same as for ammonium phosphomolybdate. The completely polymerized APO, a white water-insoluble solid, does not form a molybdate and does not migrate during the chromatographic test described. However, when the polymerized APO is boiled in 1% hydrochloric acid, it dissolves and the solution will form a yellow ring at Rr 0.8 in the test. Other phosphorus-containing flameresistant cotton fabrics were extracted with 1% hydrochloric acid and chromatograms were run. These included phosphorylated cotton and cotton treated with diallylcyanoethane phosphonate, the bromoform adduct of triallyl phosphate in combination with T H P C , and chloroethylene (vinyl chlo-
ride)-antimony oxide in combination with THPC. Of these, only phosphorylated cotton gives the same yellow ring at R, 0.8. However, phosphorylated (urea phosphate) cotton can be distinguished from APO-treated fabric by the following test (4): A small piece of fabric from which any wax finish has been removed by solvent extraction is spotted with ammonium molybdate solution. Phosphorylated cotton will immediately turn yellow; APO-THPCtreated cotton does not. LITERATURE CITED
(1) Bestian, H., :4nn. Chem. Liebigs 566,
210 (1950). (2) Drake, G. L., Jr., Cuthrie, J . D., Textile Research J . 29, 155-64 (1959). ( 3 ) Hoffman, A., J . Am. Chew SOC. 52, 2995 (1930). ( 4 ) Nuessle, A . C., Ford, F. M., Hall, WT.P., Lippert, .4.I.., Yertiie Research J . 2 6 , 32-9 (1956). (5) Reeves, W. A,, Drake, G. L., Chance, L. H.. Guthrie. J. D.. Ibid.. 27. 260-8 RECEIVEDfor review June 22, 1959. Accepted September 8, 1959.
Determination of Arsenic in Petroleum Stocks and Catalysts by Evolution as Arsine DAVID LIEDERMAN, J. E. BOWEN, and 0.1. MILNER Research Department, P oulsboro Laboratory, Socony Mobil Oil Co., Inc., Paulsboro,
,An improved method has been deveioped to determine arsenic in reforming charge stocks and catalysts. The range of the method for charge stocks is from zero to several hundred parts per billion, and for catalysts from zero to several thousand parts per million. The arsenic is extracted from the naphtha and separated as arsine which is measured spectrophotometrically after reaction with silver diethyldithiocarbamate in pyridine. Catalysts are fused before the arsine separation and spectrophotometric determination. The method has been applied to a wide variety of reforming samples.
A
contained i r reforming charge stocks poisons platinumbearing petroleum reforming catalysts. To study this poisoning process and to find ways to minimize it, a sensitive, rapid, and precise method was needed to determine from 1 to 100 p.p.b. of arsenic in charge stocks. A method was also needed for determining 1 to RSENIC
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rn
ANALYTICAL CHEMISTRY
5000 p.p.m. of arsenic in reforming and pretreating catalysts, generally cobalt oxide-molybdena-alumina. Previous chemical methods for the determination of traces of arsenic in petroleum and catalysts have been based on the separation of arsenic by arsine evolution and final determination by a modification of the Gutzeit method (3, 6),or distillation as the trichloride and formation of the arsenic-molybdeniim blue complex ( 4 ) . A method using neutron activation has been presented (8). The authors' previous method (d), although sensitive and precise, was lengthy. T o develop a more rapid method, a colorimetric procedure introduced by Vasak and Sedivek (9) was adapted. The method involves the reaction of arsine with a pyridine solution of silver diethyldithiocarbamate (AgDDC). After the work included in this paper was completed, other studies based on the use of AgDDC were reported ( I , 6). However, these mrthods are applicable only to liquid petroleum products. In t,he present method as applied to
N. 1. liquid stocks, the arsenic is extracted and simultaneously oxidized by a mixture of sulfuric acid and hydrogen peroxide. Catalysts are solubilized by a sodium peroxide fusion. If platinum is present in the catalyst, it is largely removed by a basic filtration; last traces are removed by extraction as the platinum-stannous chloridr complex. The arsenic is then determined by a modification of the Vasak and Sedivek procedure. Quantities of arsenic d o w i to 0.03 y can be detected. APPARATUS
Evolution apparhtus (Figure 1). Separatory funnels. Although ordinary separatory funnels can be used, the specially designed one shown in Figure 2 is much more convenient. Spectrophotometer cells, special 70mm. ( 4 ) . REAGENTS
The water was treated by passing it through a mixed-bed ion exchange
