Use of Magnesium Oxide in Determination of Cahon and Hydrogen In Fluoro-organic Compounds W. H. THROCKMORTON AND GLENNA H. HUTTON Research Laboratories, Tennessee Eastman Co., Kingsport, Tenn. T H E determination of carbon and hydrogen in fluororganic compounds, difficulties are encountered because the fluorine-containing combustion products react with the silica of combustion tubes to form silicon tetrafluoride (8). A preliminary report of a method which appears to Overcome these difficulties is presented here. Although metallic silver reacts with any hydrogen fluoride present to remove its fluorine, it has no effect on the silicon tetrafluoride. Belcher and Goulden ( 2 ) successfully used sodium fluoride at 2700 c. to the latter compound. Carbon analyses on fluoro-organic compounds containing no hydrogen were 1 to 2% low, hon-ever, unless hydrogen was supplied by the addition of a known weight of a pure substance, such as benzoic acid. It also appeared that correctcarbon could be obtained when water vapor was introduced into the system. Most of the procedures described in the literature do not permit the simultaneous determination of carbon and hydrogen. Teston and AIcKenna ( 1 1 ) determined carbon, fluorine, and chlorine in completely halogenat'ed hydrocarbons. Other procedures deal with the determination of carbon and fluorine ( I O ) , hydrogen only ( 5 , 8 ) ,or carbon only (6). For the determination of carbon in uranium tetrafluoride, Warf (9, 1 2 ) mixed the sample with an equal weight of ignited magnesium oxide and covered the sample with additional oxide. The results, corrected by a blank determination, RTyere stated to be from to high, as determined from added amounts of uranium carbide. Methods for the determination of fluorine in biological materials make use of magnesium acetate or peroxide t o prevent loss of fluorine during the ashing procedure ( 3 , 1 4 ) . The Procedure des~ribed makes use of Pellets of magnesium oxide as p:trt of the combustion tube filling. The results obtained with a limited number and type of compounds ranging in fluorine content from 15 to 30% indicate that this filling reacts effectively with all the fluorine-containing combustion products, including the silicon tetrafluoride.
atures were checked in an empty tube with a thermocouple a t the mid-points Of the furnaces. Materials. COMPOUNDS ANALYZED.The sample of 1,132~ r ~ c ~ ~ o r o ~ 3 , 3 , 3 ~ ~ r ~was ~ u oobtained r o p r o from ~ e n ethe Columbia Organic Chemicals Co. The other samples were obtained from the Hooker Electrochemical CO. All materials were redistilled before use. The boiling points and refractive indices of the fractions analyzed and the types of distilling columns used are shown in Table 1. hfAGNEsruhf OXIDEPELLETS. Reagent grade magnesium oxide Powder was mixed with water t o form a creamy Paste. This The was poured into a flat-bottomed dish and dried a t 110" dry cake was cut into 8- to 20-mesh pellets which were then ignited for 1 hour a t 800" C. in a muffle furnace to convert any carbonate present t o oxide. Procedure. The customary techniques of sample weighing, and Of absorption tubes fo110V7ed ('7). The sample capillaries contained potassium chlorate. The sample furnace was set for automatic drive a t a rate of 4 mm. per minute and with a 5-minute burning time directly over the sample boat. The COmbuStion was repeated at a rate of 12 mm. per minute but without stopping the furnace Over the sample boat. ~ ] was determined ~ ~ by parr ~ bomb i combustion ~ ~using potassium chlorate as the accelerator. The combustion was followed by the volumetric lead chlorofluoride method essentially and Lundell ( 4 ) . as described by Experiments. The first trials with magnesium oxide consisted of covering the sample, contained in a sample capillary in a long platinum boat, with magnesium oxide powder and using the, "combination" filling described by Niederl and Niederl ( 7 ) . The results were rather poor, although somen-hat better results were obtained on a solid sample contained in a boat and covered with the oside. The oxide powder was next placed in a platinum boat 45 mm. long which was then positioned SO that it was about half covered by the long furnace. An improvement in results mas noted, especially after the magnesium oxide became scattered about in the tube because of the flashing of a rather volatile sample. This in&cated that better contact between the gases and the oxide was needed.
c.
:k :&$
E: :
f i l ~ ~ ~ o $ ~ pei;r"," ~ ~~ ~$ ~~ a~ ~' ~~ ~ the pellets in analyzing five fluoro-organic compounds are sented in Table 11. Fluorine analyses of these compounds are also included in the table.
EXPERIMENTAL DISCUSSION OF RESULTS
Apparatus. The apparatus used was essentially that described by Siederl and Xiederl(7). The "combination" filling for the combustion tube was modified only by replacing 3.5 to 4.0 cm. of t'he coPPer oxide in the front end of the quartz tube with magnesium oxide pellets. The Sargent micro combustion apparatus was used with the temperature of the long furnace set a t 775" C. ( I S ) and that of the sample furnace a t 800' C. Temper-
The data of Table I1 indicate that the carbon and hydrogen values obtained are TTithin the generally acceptable limits, a]though there does appear to be a tendency for both to be slight]y high* The indication of some hydrogen for the completely halogenated hydrocarbons is possibly due to the dehydration of the lead peroxide used in the filling. _. This appears to be confirmed by the correct reT a b l e I. C o m p o u n d s Analyzed sults obtained with the compounds not containing Boiling Point nitrogen when the lead peroxide was replaced by Distillationa, hficro ' Refractive silver wool. (The results obtained with this filling Compound C. (uncor.)/mm. C. (cor.))mm. Index, n%o 201 0 / 7 3 1 . 2 1.4726 will be discussed in a subsequent article.) I t was m-Nitrobenzotrifluoride 199-200/730b-, m-Chlorobenzotrifluoride 136.6-136.l/137-Sc 136.6/732.8 1.4467 necessary in this case to deduct a small blank 1.1,2,2,3-Pentachloro-3,3difluoropropane 166.5-166 0/730. S b 166.6/731.2 1,4618 from the m-eight of the water absorption tube. 1,1,2,2-Tetrachloro-l,2The blank was determined by following all the difluoroethsne 89.0/731 92.0/i34 (250 c,) 1,1,2-Trichloro-3,3,3steps of the procedure without using any sample. trifluoropropene 86.8-86.9/725.8d 87.3/732.8 1.4095 It was of the order of 0.09 mg. of which approxiAlthough distillation d a t a indicate boiling ranges of t h e fractions used, temperatures mately 0.06 mg. found to be due to the nre uncorrected. Therefore micro boiling points which are corrected, are included. b 22-mm. X 18-inch Podbielniak Heligrid distilljng column. opening of the combustion tube for the introduc8-mm. X 72-inch Podbielnisk Nichrome wire-spiral distilling column, d 7-mm. X 36-inch Podbielniak Xichrome wire-spiral distilling column. tion of the sample boat. [While the manuscript was in preparation, Backeberg and Israelstam
2003
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2004
ANALYTICAL CHEMISTRY
Table 11. Results of Analyses Compound
Analyses Hydrogen
Carbon
n-Nitrobenzotrifluoride
Calcd. Found (14)
m-Chlorobenzotrifluoride Calcd. Found 1,1,2,2,3-PentachloroCalcd. chloro-3,3-diAuoroFound propane
43.99 44.22 + 0.078bv
C
46.56 (8) 46.69 =t0.11932 d 14,28 14.43
Fluorine“
2.11 0 . 0 6 1 b ~C
29,83 29.74
2.23 2 . 3 7 + 0.0843, d 0.40 0.46
31.57 31.59 15.06 14.96
2.23
f
14.41 14.35 14.44
0.50 0.46 0.43
1,1,2,2-Tetrachloro-1,2- Calcd.
Found
11.78 11.84 11.85
None 0.22 0.12
18.$4
1,1,2-Trichloro-3,3,3trifluoropropene
Calcd. Found
18.07 17.86 18.05
h-one
0.08
28.59 28.75
difluoroethane
0.20
...
values with compounds which contain little or no hydrogen. A more detailed study is in progress. The study will include the determination of the optimum temperature for the magnesium oxide, its position in the combustion tube, and its physical form; the use of an external absorbent for the oxides of nitrogen: and the application of the procedure t o a wider variety of fluoroorganic compounds. This preliminary report is offered a t this time in the hope that others may find the suggested procedure helpful and make improvements upon it. LITERATURE CITED
Calcd. 71.09 6.70 ... Found (8) 7 1 . 1 8 i 0,0943, f 6 . 7 2 * 0.040bt f Average found by P a r r honib combustion followed b y volumetric lead chlorofluoride method ( 4 ) . b Averages with * limits a t 96% confidence level for number of determinations indicated in parentheses. Acetanilide (KBS)
(1) Backeberg. 0. G., and Israelstam,
S. S.,dxaL.
CHEM.,24, 1209--14(1952).
(2) Belcher, R., and Coulden, R., .~fikrochernieT e T . Mikrochim. Acta, 36/37,679-89 (1951). (3) Crutchfield, IT,E., Jr., IND.EXG.CHEM.,ASAL. ED.,14, 57-8 (1942). ‘z(2 - a ) 2 for carbon = 0.135% C and for hydrogen = c Standard deviation (4) Hillebrand. TI-. F., and Lundell, G. E. F., “Ap0.106% H. plied Inorganic Analysis,” pp. 604-5, Kern d Standard deviation for carbon = 0.142% C and for hydrogen = 0.101 % H. l o r k . John Wiley & Sons, 1929. 8 Obtained only 88 t o ’20% of calculated value. (5) Miller, J. F., Hunt, H., Hass. H. B., and RIcBee, f Standard deviation for carbon = 0.112% C and for hydrogen = 0.048% H. E. T.. ASAL. CHEX.19,146-4i (1947). (6) Miller, J. F., and McBee, E. T., “Quantitative Determination of Carbon in Polyfluorocompounds,” “hIonthly Technical Report on Research at Purdue L-niversity for October 1944.” by McBee, (1) reported their findings concerning this water blank. The E. T.. Rept. A-1515,pp. 25-9. reader is referred t o their article for a more complete discussion.] (7) Xiederl, J. B., and Niederl, J., “Micromethods of Quantitative K i t h a tube containing lead peroxide it is obviously impossible to Organic Analysis,” 2nd ed., pp. 101-23, S e w York, John V’iley determine a blank that will apply correctly to compounds which &Sons, 1942. (8) Pearlson, W. H., Brice, T. J., and Simons, J. H., IXD. ENG. contain hydrogen as well as to those which do not. KO blank CHEM., A N A L . ED.,18, 330-1 (1946). was used with the analyses given in Table 11. The results ob(9) Rodden, C. J., et al., “dnalytical Chemistry of the Manhattan tained viith acetanilide indicate that none was required with this Project,” p. 279. Sew York, McGraw-Hill Book Co., 1950. particular apparatus to obtain correct hydrogen values x i t h (10) Simons, J. H., and Rlork, L. P., J . Am. Chem. SOC.,61, 2964 (1939). compounds containing considerable hydrogen. (11) Teston, R. O., and NcKenna, F. E., AXAL. CHEM., 19, 193-6
(t.-i->
(1947).
SUMMARY AND CONCLUSIONS
The addition of magnesium oxide to the combustion tube filling appears to offer promise as a simple means of overcoming the difficulties encountered in the determination of carbon and hydrogen in fluoro-organic compounds. There are indications that dehydration of the lead peroxide leads to high hydrogen
(12) TTarf, J. C., L-, 8. Atomic Energy Comm., Rept. CC-433 (Jan. 26, 1943). (13) ’Killits, C. O., and Ogg, C. L., J . Assoc. Ofic. Agr. Chemists, 34, 609 (1951). (14) Winter, 0. B., I b i d . , 19, 359-65 (1936). RECEIVED for review July 10, 1952. Accepted September 6, 1952.
Quantitative Determination of Pentoses with Anthrone ROBERT ROY BRIDGES Masonite Corp., Laurel, Miss. 1946 Dreywood reported that anthrone in concentrated I Nsulfuric acid gives a permanent green coloration with carbo( 1 ) . Morris later shoned that the green color
hydrate material intensity obeyed Beer’s lam- a t 620 mp for such carbohydrates as glucose, lactose, glycogen, and maltose ( 2 ) . Other investigators have successfully used the reagent for the quantitative determination of minute amounts of sucrose, cellulose, and starch with a sensitivity exceeding that of previously used tests for these materials (5,6). Sattler and Zerban, as a result of a study of the reaction, concluded that the color was due to the formation of furfural compounds in strong sulfuric acid (4). This was confirmed when Shriver, Webb, and Slvanson revealed that the spectral curves for glucose and xylose with the reagent were almost identical with those given by hydroxymethyl furfural and furfural, respectively, nyith the reagent ( 5 ) . They further confirmed a minimum a t 620 mp and the validity of Beer’s Ian- for hexoses and methyl pentoses (fucose and rhamnose) a t this rrave length. With
pentoses such as arabinose and xylose, hoTvever, the blue-green color responsible for the minimum a t 620 mp appeared too transient to permit transmittance readings. The blue-green color was observed to form, but to change rapidly to an amber color having a spectral curve with no distinct minimum a t 620 mp and for which Beer’s law is not obeyed a t any wave length. It n-as found that the blue-green color m-ith pmtoses remains stable long enough to make accurate, reproducible transmittance readings, provided the reaction mixture is cooled in an ice bath immediately after mixing the sample with the reagent. EXPERIMENTAL PROCEDURE
A 2.00-ml. sample of sugar solution in water from 0 001 t o O.Ol%, t o be analyzed in a 16 x 144 mm. test tube has added to it carefully as a lox-er layer, 4.00 ml. of a 0.05yo ( ~ - . / ~ ~ . ) - s o l u tion of anthrone in concentrated sulfuric acid. The acid is added with a pipet so as not to mix with the aqueous layer. The two layers are then quickly mixed using an oscillating motion of
