glucose on paper chromatograms (8) and compared (Table 111). A statistical analysis for comparison of averages (t test) (IO) shows no significant difference between the methods at the 5% probability level, and the standard deviation of the difference is 0.069.
to correlate hydrolytic glucose yields with molecular structure in the starch family of polysaccharides (‘7). Its practical application to similar studies with other polysaccharides-for example, cellulose and dextrans-should prove useful.
DISCUSSION
LITERATURE CITED
The microbiological assay of glucose
is easily adapted for large scale operations and results are obtained from a simple acid-base titration. Forty unknowns can be analyzed in a single working day with inoculum prepared from eight centrifuge tubes. The time required for titrating can be shortened considerably by use of an automatic titrator. Because of its sensitivity, the method has been used successfully
(1) Assoc. Offic. Agr. Chemists, “Official Methods of Analysis,” 8th ed., 1955. (2) Bloore, E. A,, L‘Applicationof Micro-
biological Asmy to Sugar Solutions,’J M.A. thesis, University of Toronto,
1950. (3) Dimler, R. J., Schaeffer,W. C., Wise, C. S., Rist, C. E., ANAL. CHEM.24, 1411 (1952). 4) Harris, D. A,, Zbid. 27, 1690 (1955). 15) Hassid, W. Z., ~ N D . ENG. CHEM., ANAL.ED.9, 228 (1937). (6) Hutner, S. H., Cur A., Baker, H., ANAL.CHEM. 30,849 0958).
(7) Kagan, J. J., “Studiee on the Acid
Hydro1 sia of Selected Starches and Starch %roducts,” Ph.D. thesis, University of Toronto, 1957. (8) Morris, D. L., Science 107, 254
(1948). (9) Strong, F. M., “Estimation of the Vitamins,” W. J. Dann G. H.Satter-
field, eds., Biological mposia, Vol. XII, p. 143, Jaques Battell Prese, Lancaster, Pa., 1947. (10) Youden, W. J., “Statistical Methods for Chemists,’! p. 24, Wiley, London, 1951.
RECEIVEDfor review October 29, 1959. Accepted January 8 1960. Based on a paper presented at the 41st Annual Conference and Exhibition of the Chemical Institute of Canada, Toronto, May 26, 1958. Research supported in grant from the Ontano Researc/%:ubnYd; tion through the Advisor Committee on Scientific Research, Bniversity of Toronto.
Determination of Chlorendic Acid in Fire-Retardant Paint G. G. ESPOSITO and
M. H. SWANN
Coating and Chemical Laboratory, Aberdeen Proving Ground, Md.
b Conventional methods of separating and measuring dicarboxylic acids in alkyd resins are unsuitable for determining chlorendic acid in alkyds used as vehicles for fire-retardant paints. A procedure is described that involves isolation ef chlorendic acid as the dipotassium salt by saponification in isopropyl alcohol, followed by acid treatment and extraction of the chlorendic acid with ethyl ether, washing free of other organic acids with water, and titration in a nonaqueous medium.
A-
made with chlorendic (3,6 endodichloromethylene -3,4,5,6 tetrachloro A4 tetrahydrophthalic) acid are used as vehicles for LKYD RESINS
-
II
GI-c
-
I
-
I C-C-OH
6
I
CI fire-retardant paints. Although a very limited number of such resins are commercially available, their durability, 680
ANALYTICAL CHEMISTRY
flexibility, rapid-drying properties, and shelf stability have attracted sufficient interest to tesult in issuance of specifications on paints incorporating this type of chlorinated binder. An analytical procedure for measuring the chlorendic acid in this class of paints was needed for quality control. Conventionally, the dicarboxylic acids in alkyd resins have been separated from other constituents as dipotassium salts obtained by saponification in anhydrous alcohol medium, followed by weighing or other means of measurement. If such a method (1-8) is applied to a chlorendic acid alkyd, some dipotassium chlorendate will precipitate, but the yield varies with sample size (Table I). If the sample size is increased sufficiently to obtain theoretical yields, the precipitated salts are contaminated with excessive entrained impurities. In addition, attempts to base the chlorendic acid content on these gravimetric fields would be affected by the presence of other dicarboxylic acids such as phthalic anhydride. Measurement of chlorendic acid by total chlorine content would make no distinction between the chlorinated alkyds and other chlorinated resins used in fire-retardant paints, but such an analysis can be useful for correlating different analytical schemes. In the method described, isopropyl
alcohol is substituted for ethyl alcohol t b obtain complete separation of chlorendic acid as the potassium salt from small samples of resin. It is then filtered, washed, dissolved in water, and transferred to a separatory funnel. After mineral acid treatment, the chlorendic acid is extracted with ethyl ether, washed free of mineral and organic acids with water, and titrated directly in nonaqueous medium (4). PROCEDURE
A sample of the isolated vehicle, representing 0.5 to 1.0 gram of nonvolatile material, is weighed into a 500ml. Erlenmeyer flask. It is dissolved in 100 ml. of benzene, and 50 ml. of IN potassium hydroxide in isopro yl alcohol (less than 1% water) are ad&d. A condenser is attached and the sample is refluxed in a water bath for 1 hour. On cooling, it is filtered through a Gooch crucible, using a mixture of 1 volume of isopropyl alcohol with 2 volumes of benzene for transferring and washing the precipitated salts. After a final washing with 25 ml. of ethyl ether, air is drawn through the crucible for 1 minute. The salts are dissolved from the crucible with a small amount of water, transferred to a 500-ml. separatory funnel, and diluted to 50 ml. Sulfuric acid (1 to 1) is added in small portions until a permanent cloud forms and then I-ml, excess is added.
got
40-
30-
2010-
4
3
5
6 Figure 1.
Table 1.
Analysis of Chlorendic-Type Alkyd Chlorendk Acid
Found (Gravimetric)
%
Found (new method), %
34.2 45.2
47.0, 4 7 . 3
Present, f+rnple 81% g. 3’% 47.2O
4
1 2 3 4
48.1 50.8
Obtained from total chlorine analysis.
The chlorendic acid is extracted with 7 5 , 50-, and 50-ml. consecutive volumes of ethyl ether, with vigorous shaking in each extraction. The ether extractions are collected and washed with 25ml. portions of water until acid-free. If phthalic acid is present, as many aa eight washings with 50-ml. portions of water may be necessary. The ether is withdrawn into a 500-ml. Erlenmeyer flask and 75 ml. of absolute ethyl alcohol are added. Five milliliters of m-cresol purple indicator (0.025 gram in 100 ml. of absolute ethyl alcohol) are added and the sample is titrated to a purple end point with 0.2N potassium hydroxide in absolute methanol.
yo chlorendic acid
=
ml. of alkali X normality X 19.45
sample weight
x nonvolatile vehicle fraction
DISCUSSION
The presence of potassium carbonate in the alcoholic alkali causes no interference and need not be removed. As
7
8
9
IO
II
12
13
14
MICRONS hfrored spectrum of chlwendic acid alkyd
the precipitated salts are not weighed, the filtration crucibles do not require drying or weighing, but if freshly prepared with filter asbestos, they should be rinsed with alcohol and benzene before using. If phthalate esters are known to be present along with the ehlorendic alkyd, a more thorough washing of the ether extracts will be necessary to remove phthalic acid, which is soluble in both ether and water. This separation is made possible by the near insolubility of chlorendic acid in water and its high solubility in ether. An infrared spectrum of the resin sample is useful, particularly if the material is of unknown origin, to detect other dicarboxylic acids and to establish the presence of chlorendic acid. The chlorendic acid alkyds do not show the strong, characteristic phthalate ester absorption bands at 7.8, 8.8, and 9.3 microns that are always exhibited by infrared spectra of phthalic alkyds. The medium to strong aromatic substitution bands in the 13.5- to 14.5 micron region are also missing. They are characterized by a strong band a t 8.45 microns arising from the aliphatic ester structure and a band of medium strength at 12.2 microns due to the - C C l r grouping as illustrated in Figure 1. This spectrum was obtained with a Perkin-Elmer Model 21 spectrophotometer. The resin film was dried on a sodium chloride plate in a vacuum oven a t 60’ C. for 1 hour. The limited analytical data are due to the scarcity of commercially available materials a t the present time. Although sources are limited, the chlorendic acid
alkyds have already attained considerable commercial importance. The authors feel confident that the analytical method will be applicable to other alkyds based on this dicarboxylic acid, as they become available. ACKNOWLEDGMENT
The advisory assistance of C. F. Pickett, director of the laboratory, is acknowledged and appreciated. LITERATURE CITED
(1) Am. Soc Testing Materials, Phil-
adelphia, “ASTM Standards,” Designation D 563-52, 597 (1958). (2) Zbid., D 1306-54T, 599. ( 3 ) Ibid., D 1307-54T, 602. (4) Esposito, G. G., Swann, M. H., ANAL.CHEM.32,49 (1960). RECEIVED for review September 29, 1959 Accepted February 9, 1960.
Correction Rapid Method for Semiquantitative Determination of Volatile Aldehydes, Ketones, and Acids I n this article by Jack W. Ralls [ANAL.CHEM.32, 332 (1960)], on page 336, the first line after the Literature Cited section should read Received for review, April 20, 1959.
VOL 32. NO. 6, M A Y 1960
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