pared standard calibration disks are counted consecutively on the x-ray spectrometer using an aluminum mask with a S/s-inch diameter round opening ( 2 ) . The calibration standard disks of varying metal concentration are prepared by fusing weighed amounts of an oxide or salt of the metal in question with 2 grams of borax. By comparing the counts of the sample 1%-iththose of the calibration standards, a measure of the weight of trace metal is obtained
without having to go through the intermediate step of correcting for scattered background. To demonstrate the usefulness of the bora.; disk x-ray method in trace analysis, KBS Sample KO. 171 of magnesium base alloy has been analyzed for Fe and Ni. The Fe and S i were isolated from chloride solutions of 1gram samples of the alloy by double cupferron-chloroform and triple dimethylglo\ime-chloroform solvent e\-
tractions, respectively ( 1 ) . lnternal standardization was not used. The rcsultz obtained are shown in Table I. LITERATURE CITED
(1) l m . SOC.Testing Materials, Philadelphia, Pa., “,1STM Methods of Chemical hnalysis of lletals,” p 4i4,
11960).
121 Luke. C. L.. ANAL. CHEL 35. 36 (1963)’ C. I.. LUKE \
,
Bell Telephone Laboratories, Inc Murray Hill, N . J.
Spectrophotometric Determination of the Methyl Ether of Hydroquinone in Ethyl Acrylate in the Presence of Hydroquinone SIR. I n a previous publication ( I ) the determination of the methyl ether of hydroquinone (AIEHQ) in 1,3-butanediol dimethacrylate monomer by use of a modified 4-aminoantipyrine method was reported. The method required a preliminary aqueous 1 S sodium hydroxide extraction of the monomer to separate the phenol from the acrylate. However, the presence of hydroquinone (HQ) causes a yellowish-brown coloration of the basic extract, which is due to the air oxidation of hydroquinone to benzoquinone. To avoid any interference, it became necessary to investigate a method which nould completely remove the benzoquinone Recently, we developed a separation technique which enables the analysis of 10 p.p.m. MEHQ in the presence of 2000 p.p.m. HQ with no interference due to the quinone. The separation i b based on the partitioning of benzoquinone and MEHQ between water and benzene in which the N E H Q strongly favors the organic solvent. However, the conversion from H Q to benzoquinone must be quantitative since the column does not resolve HQ and MEHQ. As in our previous work, the phenol is eatracted from monomer with aqueous 1 S SaOH. The aqueous extract is then acidified with coned. HC1 which converts the sodium salt of the phenol back to PIIEHQ. This acidified solution is then placed on the partitioning column (Figure 1) which consists of water: Celite a t a 1.5:l.O ratio. The MEHQ is eluted from the column with benzene and the benzoquinone is retained on the column. The benzoquinone-free eluate is then extracted with 11%‘S a O H and analyzed using the modified 4-aminoantipyrine colorimetric method (1) rsing standard solution of XEHQ in ethyl acrylate (EA), with a concentra2000 tion range of 72.8 to 9.1 p.p.m. p.p.m HQ, our average per cent recovery was 85 =t270.
+
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ANALYTICAL CHEMISTRY
Figure 1. Partition column used to separate MEHQ from HQ EXPERIMENTAL
Preparation of Column. Thoroughly mix 150 ml. of distilled water
Table I.
Per Cent Recovery of
Sample 2000 p.p.m. 2000 p.p.m. 72.8 p.p.m. 72.8 p.p.m. 72.8 p.p.m. M E H ~ 72.8 p.p.m. X ~ E H C ~ 72.8 p.p.m. MEHQ 3 6 . 4 p.p.m. MEHQ 3 6 . 4 p.p.m. MEHQ 1 8 . 2 p.p.m. MEHQ 1 8 . 2 p.p.m. MEHQ 9 . 1 p.p.m. MEHQ 9 . 1 p,p.m. LlEHQ
+ 2000 p.p.m. p.p.m. ++ 2000 2000 p.p.m. + 2000 p.p.m. + 2000 p.p.m. + 2000 p.p.m. p.p.m. ++ 2000 2000 p.p.m. + 2000 p.p.m.
and 100 grams of Celite 545. Then add the mix t o the column jrvhich contains a plug of glass wool) n5th gentle tamping b e t w e n every 5 to 6 grams of mix added. When packed, the column should contain about 30 grams of mix and should fill ahout 6 inches of the column. Method. T o a 60-ml. separatory funnel, add 5 ml. of 1 S sodium hydroxide and 5 nil. of the acrylate sample. Shake vigorously for about 30 seconds and allow the layers t o separate. Drain the aqueous layer into a 50nil. beaker and then acidify with 0.6 i d . of concentrated hydrochloric acid. Place the acidified solution onto the partitioning column which contains 28 to 30 grams of 1.5: 1.0 distilled water: Celite. Rinse the beaker with 2 to 3 ml. of water and place the rinse on the column. Elute with benzene and collect 30 ml. of solvent. Pour the eluate into a BO-ml. separatory funnel which contains 5 ml. of 1 . O N sodium hydroside and shake vigorously for ahout 30 seconds. Allow the layers to separate completely. To a 50-ml. beaker, pipet 2 nil. of the clear basic extract, 18 mi. of a solution of 0.4M boric acid and 0.1.11 sodium hydroside, 0.1 ml. of 37, aminoantipyrine solution, and 0.2 nil. of 1Oyo potassium ferricyanide solution. I f t e r
MEHQ
in EA in the Presence of HQ p hsorbance % Recovery .IVP Rec 0 0 0 0 0 0 0 0 0 0 0 0 0
000 000 436 430
430 460 455 “30 230 120 120 053 06,5
82a 34 84 824 84 84 86 89 89 81 81
33
a The absorptivity obtained for this particular day of analysis was lower than usual. As a result, the apparent higher absorbance does not indicate a corresponding higher per
cent recovery.
a period of 15 minutes, the colored solution is measured in a suitable spectrophotometer at 520 mp. If the color is too intense, the basic aqueous extract is diluted to volume in a suitable volumetric flask with LON sodium hydroxide and a 2.0-ml. aliquot of the dilution is used for color development. Each day a reagent calibration should be done. This calibration is made by analyzing an HQ-free MEHQ standard solution directly by using the 4-aminoantipyrine procedure. RESULTS
Using the above described procedures, the results in Table I were obtained. I n all cases, a I-em. path length spectrophotometric cell was used with the reference solvent being water. The per cent recovery is based on the respective calibration for each particular day of analysis. DISCUSSION
The amount of eluate collected, between 30 and 60 ml., does not affect the per cent recovery. This was demonstrated hy running three standard solutions, 72.8 p.p.m. MEHQ, through
respective columns, and then collecting 30, 45, and 60 ml. of eluate. Upon analysis of each elute, we found that the per cent recovery for each sample was between84 to 86%. Since we are interested in the general field of acrylics, we scouted the feasibility of extending this technique to a methacrylate and another acrylate. During the analysis of a methacrylate sample, we found that the basic extract of the eluate exhibited the benzoquinone color. This indicates that either the column was not resolving properly or there was an incomplete conversion of HQ to benzoquinone due to an insufficient supply of oxygen. Apparently, the latter alternative is the case since a satisfactory separation is achieved by bubbling oxygen through the preliminary basic extraction of the monomer. Therefore, for systems other than ethyl acrylate (EA), it may he necessary to ensure complete conversion by the addition of oxygen to the preliminary extraction. Several samples of methyl acrylate (MA) which contained known amounts of MEHQ and 2000 p.p.m. HQ were
also analyzed. However, we were able to recover only about 50'% of the phenol. When a standard solution of MEHQ in MA, which was free of HQ, was analyzed directly without the column separation, about 65% of the phenol was recovered. Apparently, the base is consumed by hydrolysis of the ester and as a result only a portion of the phenol is extracted. During the extraction, we noticed that the volume of the monomer layer had decreased. We were able to alleviate this problem by diluting 1 part of MA with 4 parts of uninhibited EA. Several standards were run directly and in each case 100% recovery was achieved. Since the system is essentially EA, we have reason to assume the HQ can be effectively removed by the partitioning column. Also, the loss in sensitivity due to dilution can he re-established by using &em. cells instead of I-cm. cells. LITERATURE CITED
(1) Lacosta, R. J., Venablc, S. H., Stone, J. C., ANAL.CHEM.31,1246 (1959).
JACKC. STOXE Rohm & Haas Co. Philadelphia, Pa.
The Determination of Fine Metallic Filament Morphology by Ultramicrotomy Warren K. Tice and William R. Lasko, United Aircraft Corp., Research Laboratories, East Hartford, Conn. ULTRAMICROTOME has proved to be a valuable tool in cutting thin metal foils from both single and multiphase materials, However, these studies have been restricted to obtaining sections of continuous systems of metals and alloys. Application of ultramicrot-
TEE
omy recently has been made at these laboratories in which the size, cont i u i t y , and distribution of synthetically-encased filaments of lead in a matrix of aluminum or copper in wire form could be determined without severe deformation.
'.
Figure Micrograph Of Cu-Pb wire made reflected-'igh+ microscopy 1500X
Microscopy by reflected light was applied initially to the study of relatively large diameter (2 microns) lead filaments encased in 0.71-mm. diameter copper wire. A section of a typical drawn copper wire which contained 500 lead filaments is shown in Figure 1. However, as refinements were made in the wire-drawing process, the filament diameters were reduced and any further attempts at utiliaing the light technique proved unsuccessful. Replicas for electron metallography also were unsatisfactory, as shown by the micrograph in Figure 2. I n this instance, a negative carbon-platinum replica was prepared of a polished and etched aluminum wire (0.18 mm. in diameter) containing 2500 fine lead filaments. NO information concerning the morphology of the individual filaments could be gained by this method, as shown by the arrow, although, some background structure in the aluminum matrix is evident. This approach is largely ineffective because of reaction products formed during etching and smearing of the fine lead filaments into a mass during polishing. VOL. 35, NO. 10, SEPTEMBER 1963
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