Table I.
,%me analytical results are shown in Table I.
Analysis of Some Nitrocellulose Lacquers
yitrocellulose Other Components
Present, 70
Alkyd and tricresyl phosphate
29.3
Alkyd and dibutyl phthalate
30.1
Alkyd and dioctyl phthalate
31.0
Sitrocellulose Found (Separate Determinations), yo Colorimetric Gravimetric 29.4 29.1 29.1 30.0 29.9 30.1 31.2 31.2 31.1
29.7 28.9 31 . 0 29.5 31 . 4 31.5
LITERATURE CITED
(1) Bost, R . W., Nicholson. F., IND. ENG. CHEX, A N ~ L ED. . 7 , 190 (1935). (2) Shaefer, W, E., Becker, JF7. W., ASIL. CHEM.25, 1226 (1953). Lwann '11. H., .%dams, hf. L., Espo( 3 ) iito,'d. G., I b i d . , 27, 1426 (1955).
'
RECEIVED for review Febriiary 11, 1957 Accepted >fay 18, 1957.
Determination of CeIIuIose Resins in Coatings by Colorimetric Cellulose Analysis M. H. S W A N N Coating and Chemical Laboratory, Aberdeen Proving Ground,
b Anthrone reagent was investigated for application to the specific determination of cellulose resins in coatings in general. In the absence of nitrocellulose, the cellulose esters and ethers can b e determined in coatings without interference from other resins or plasticizers.
C
ethers (methyl and ethylcellulose) and cellulose esters (cellulose acetate, propionate, acetatebutyrate, and nitrate) are nidely used in coatings. With the exception of nitrocelluloqe. there are no analytical methodc for determining these resins in coating materials in general. The reagent anthrone (9,lO-dihydro9-ouoanthracene) was investigated for application to the detection and determination of cellulose resins without interference from other materials t h a t may be present, such as plasticizers or other resins. Anthrone is a nonspecific reagent used mostly for carbohydrates in general (2-6) and for cellulose and carboxymethylcellulose ( 1 ) . I n the field of coating resins, however, the nonspecific nature of the reagent is not objectionable, as color is developed only with the cellulose resins. The bluegreen color that forms is very intense and highly reproducible, and extremely small amounts of hoth sample and reagent are used. Color derelopment is influenced only by the cellulose content of these resins, consequently all cellulose ethers and esters \Till not yield the same amount of color. The ethoxyl content of ethvlELLULOSE
Md.
cellulose, for e u m p l e , will vary from -23 to 5OY0, although coating types usually have a more limited variation of 47.5 to 49.070. Cellulose acetate contains approximately the same amount of cellulose as the ethylcellulose, while cellulose acetate-propionate and acetate-butyrate will run slightly loner. This variation in cellulose content indicates that any precise measure of a resin b y its cellulose content will require some knonledge of its type and if unknown, some tests are available for qualitative use. If the cellulose ester or ether cannot be identified, it can be estimated in coatings with fair accuracy. Sitrocellulose interferes and cannot be measured by this method, b u t other methods are available (6, 7 ) and this ester is not usually blended with other cellulose resins. PROCEDURE
A very small sample of the coating material is carefully and accurately weighed, dissolved in acetone, and diluted to volume in such a manner that a n aliquot of 1 to 3 nil. represents not more than 0.5 mg. of nonvolatile resin. If incompletely soluble in acetone, sufficient dioxane may be used to di+ solve the sample, so that acetone may be used as the main diluent. Aliquots are withdrawn into large test tubes, approximately 200 by 25 mm., and dried in a n oven a t 105" C. A large quantity of 3 to 1 sulfuric acid is prepared and cooled to room temperature. Exactly 10 ml. of the acid are added to the sample and to an additional tube as blank. Exactly 0.5 ml. of a 0 5yo solution of anthrone
(in absolute ethyl alcohol) is added to saniple and blank and the tubes are stoppered, agitated, and placed in a water bath at 90" C. for exactly 20 minutes with occasional agitation. Upon removal, the tubes are cooled t o room temperature and the absorbance is measured a t 625 nip; the color solution is compared againqt the prepared blank.
Table
I.
Analysis of Some cellulose Blends
Ethyl-
Ethylcellulose Present, Found7 Other Component Tricresyl phosphate Dibutyl phthalate Raw castor oil Tricresyl phosphate hlaleic modified ester gum and dibutyl phthalate
C'
/C
c /O
80 80 80 90
80.9 79 0 80 6 90 5
45 5
46 3
Cellulose content is calculated from a working curve prepared from any knowi cellulose resin or from pure cellulose, If cellulose is desired as a standard, an analytical grade filter paper pulp may be used and solution can be effected directly in 3 to 1 sulfuric acid with slight warming in a bath. Appropriate aliquots are n ithdrawn and acid is added so that the final volume is exactly 10 ml. The reagent solution in ethyl alcohol is prepared by warming to about 70" C. in a water bath with considerable agitation, and is stable for approximately 12 hours. Some typical resin analyses are shown in Tables I and I1 and some typical VOL. 29, NO. 10, OCTOBER 1957
1505
7 -
0.4
F
working curves in Figure 1. Attempts to extend the range by using larger acid volumes were not entirely satisfactory.
Table II.
q
Analysis of Some Strippable Protective Coatings
Cellulose -4cetate-Butyrate Present, Found,
E
E0.2
Other Components 70 Polyglycol di-2-ethylhexoate, 47.6% 42.8 PIlineral oil, 8.9 Antioxidant, 0.5 Pour-point depressant, 0.2 Polystyrene, 35.3% 40.0 Dioctyl phthalate, 17.0 Butyl stearate, 5.5 Rust-preventive oil, 1.2 Bntioxidant and stabilizers, 1.0
0.11
70
LITERATURE CITED
43.7
39.2
ABS O R B AN CE
Figure 1. A. 6. C. D. E.
Color developed, measured a t 625 mp
Pure cellulose Cellulose acetate Ethylcellulose, 49% ethoxy, 100 c.p.5. Ethylcellulose, 49% ethoxy, 19 C.P.S. Cellulose acetate-butyrate
rately measured volumes of concentrated acid and water, the original working tuxes can be used continually. The temperature of the water bath, reaction time, and size and quality of test tubes should be uniform and carefully controlled. K i t h simple precautions the method is highly reproducible. The color appears to be stable for 2 1 hours, but this has not been thoroughly investigated.
DISCUSSION
The color developed is affected b y time, temperature, and concentration of acid. If the 3 to 1 sulfuric acid is carefully made b y mixing together accu-
Black, H. C., Jr., A N ~ LCHEW 23, 1792 (1951). Bloom, W. L., Wilcox, 11. L., Proc. SOC. Exptl. Biol. J f e d 76, 3-4 (1951). Drevn-ood, R., IND. ESG CHEM., A ~ A LED. . 18, 499 (1946). Durham, W. F., Bloom, W. L., Lewis, G. T., blandel, E. E., U . S. Publzc Health Serv., Publzc Health Repts. 6 5 , 670 (1950). Koehler, L. H., ANAL.CHEJI.24, 1576 (1952). Shaefer, W. E., Becker, IT. W., Ibzd., 2 5 , 1226 (1953). Swam, M. H., Adams, 11. L , Esposito, G. G., Ibid., 27, 1426 (1955). RECEIVEDfor review January 15, 1957, Accepted Bprill7, 1957.
Ion Exchange Micromethods for Separation of Fermentation Acids Determination of Fumaric Acid in Fermentation Broth CECIL H. VanETTEN and CLARA E. McGREW Northern Utilization Research and Developmenf Division, Agricultural Research Service, U. S. Deparfmenf of Agriculfure, Peoria, 111.
b The use of ion exchange resins to separate fermentation acids prior to titration appeared to offer simple rapid methods for acid determination. Experiments using a micro ion exchange column and samples of the order of 0.1 5 meq. of total acids led to the development of a rapid method for the determination of fumaric acid in fermentation broths. Recovery of added fumaric acid was 98.27& with a standard deviation of 1.52. The method also gave information concerning the total acidity of fermentation broth and the nature of the remaining acids present. Ion exchange resins may also b e used to separate other fermentation acids from mixtures prior to determination.
I
where the production of an organic acid is studied,
N FERMENTATIOKS
1506
ANALYTICAL CHEMISTRY
rapid, accurate methods of analysis are essential. Semiquantitative information concerning the nature of all the organic acids the microorganism produces is also important. Rapid and inexpensive analytical methods are of value in following a fermentation proce5s in production. Chromatographic methods with anion exchange resins have been used for the separation of fermentation acids ( 2 , 7 , 8). Although these methods are very valuable for separation and determination of each acid present in a mixture, they are not suited for the routine determination of a single fermentation acid. This report is concerned v,-ith a study of the exchange behavior on anion resins of a number of organic acids. A simple method for determination of fumaric acid was developed, and information concerning the nature of other organic acids present was obtained.
EQUIPMENT AND REAGENTS
Cation exchange resin Dowex 50 X 2 and anion exchange resins Don-ex 1 X 1 and X 8 (all 50- to 100-mesh) lvere prepared in convenient batches, sufficient for a number of columns, by recycling with aqueous sodium hydroxide and hydrochloric acid. The recycled cation resin was kept in the acid form; the anion resins, in the chloride form. Micro ion exchange columns of the type previously described (10) had the following approximate resin column diameter and height in distilled water: Dowex 50 X 2 , 6 by 70 mm.; Dowex 1 X 1, 6 by 60 mm.; Dowex 1 X 8, 6 by 30 mm. Reagents prepared from analytical reagent chemicals, unless otherwise specified, were: tert-butyl alcohol, 90%, made by diluting 100% technical grade. Formic acid, 0.35N in 90% tert-butyl alcohol. Acetic acid, 0.35N. Sodium hydroxide and hydrochloric acid, 1N. Phenolphthalein indicator solution.
