I N D U S T R I A L A N D E N G I N E E R I N G CHEMISTRY
200 Table
VI. Titration of Dipotassium Phthalate with Perchloric Acid
Wei h t of Ci"(8OOK)a Taken A Grams 0.928 0.986 1,154
in Glacial A c e t i c A c i d Calod. Wei ht of Weight CsHi CO%K)a of KC104 from Litration Found C B Grams Grams 0.935 1.061 1.131 0.995 1.162 1.329
Calcd. Weight of CsH4(COOK)r from KClOn D Grama 0.929 0,990 1. I60
requirements is based on the use of sfeebly basic solvent to increase the basicity of the phthalate ion. Hall and Werner (7) have shown that perchloric acid is the most suitable of the common acids for titrimetric purposes in a glacial acetic acid solvent. The use of indicators in titrating amines with perchloric acid in glacial acetic has been reported (a). The titration of dipotassium phthalate or its alcoholate can be followed with several indicators-for example, bromophenol blue, bromocresol purple, and methyl violet-the latter was very satisfactory (1, 4). It is necessary to remove the water present in the solutions to secure quantitative results (6). The addition of acetic anhydride converts the water to acetic acid; excess acetic anhydride has no effect on the titration ( l a ) . The anhydrous perchloric acid solution was standardized by the use of sodium carbonate as a primary standard ( d ) , the end point being taken a t the green-yellow stage. The perchloric acid presents a little danger in handling. The 0.1 N solution should be prepared carefully as indicated below, Once the perchloric acid is present in the dilute solution it is relatively harmless. The glacial acetic solutions are most conveniently used in a wellventilated hood. The standard solution of approximately 0.1 N perchloric acid in glacial acetic acid was prepared by adding 9 ml. of 60% perchloric acid dropwise to 36 ml. of acetic anhydride kept in a chilled glass-stoppered liter Erlenmeyer ( 7 ) . The resultant solution was then diluted with 720 ml. of glacial acetic acid and 24 ml. of acetic anhydride and allowed to stand 2 weeks until the reaction with water was completed (IS). To standardize the solution a definite quantity of sodium carbonate was dissolved u-ith gentle warming in a solution of 20 ml. of glacial acetic acid and 2 ml. of acetic anhydride and brought to boiling (hood) in order to react with any water. Upon cooling, this solution was titrated with the above perchloric acid solution using methyl violet indicator, 2 drops per 10 cc. of 0.2yomethyl violet in glacial acetic acid. The results obtained by titrating dipotassium phthalate isolated by the modified Kappelmeier procedure are given in Table VI. A comparison of columns A and B shows that the volumetric procedure gives results that are 0.8% high. A white precipitate, formed upon addition of the perchloric acid, contained potassium and was soluble in hot water and insoluble in cold water. The precipitation of potassium perchlorate under these conditions has been noted ( 7 ) . The precipitate was filtered off, dried to constant weight, and used as a basis for calculating the weight of dipotassium phthalate. A comparison of columns A and D indicates that precipitation is quantitative. Sodium perchlorate is soluble in glacial acetic acid while the potassium salt is insoluble. A procedure for determining both potassium and sodium simultaneously under certain limited conditions is indicated. Semiquantitative results were secured on mixtures of potassium acetate and sodium carbonate. ACKNOWLEDGMENT
The author wishes to express his gratitude to the Paint and Automotive Chemical Laboratory of the Army Ordnance Department now located in the Proving Center, Aberdeen Proving Ground, Md., where the laboratory work was performed. LITERATURE CITED
(1) Adams, E. Q., and Rosenstein, L., J . Am. Chem. SOC.,36, 1452 (1914).
Vol. 16, No. 3
(2) Blumrich and Bandel, Angew. Chem., 54, 374-5 (1941). (3) Brown, A. E. G., Oil Colour Trades J., 89, 1489 (1936). (4) Conant, J. B., and Werner, T. H., J . Am. Chem. Soc., 52, 4436 (1930). (5) Fonrobert, E., and Munchmeyer, A , , Farben-Ztg., 41, 747-8 (1936). (6) Hall, N. F., and Conant, J. B., J. Am. Chem. SOC.,49, 3065 (1927). (7) Hall, N. F., and Werner, T. H., Zbid., 50, 2367 (1928). (8) Kappelmeier, C. P. A., Farben-Ztg., 40, 1141-3 (1935); 41, 161 (1936). (9) I b i d . , 42,561-3 (1937). (10) Kavanaugh, F., IND.ENG.CHEM.,ANAL.ED., 8, 397-8 (1936). (11) Kerckow, F. W., Farben-Ztg., 44, 33 (1939). (12) Kilpi, S., 2. physik. Chem., A177, 116 (1936). (13) Mitchell, Smith, and Bryant, J . Am. Chem. Sac., 58, H 5 2 (1936). (14) Ruff and Krynicki, Farben-Ztg., 41, 111 (1936). (15) Sanderson, J. McE., A.S.T.M. Bull. 107, 15-16 (December, 1940). (16) Wolff and Zeidler, Farben-Ztg., 41, 1009, 1035 (1936). CONDENBED from a thesis presented to the Department of Chemistry, Brooklyn College, Brooklyn, N. Y . , in partial fulfillment of the requirements for the master of arts degree, June, 1943.
Determination of Total Phthalic Anhydride in Modified A l k y d Resins C. D. DOYLE, Resin and Insulation Meterials Division, General Electric Company, Schenectady, N. Y.
T
HIS paper presents confirmatory evidence of the modified Kappelmeier method ( 3 ) described in the preceding paper
(d), independently obtained during the spring of 1942 by a simi-
lar modification which is used in this laboratory. This modification, which also eliminates the tedious drying of the residual crystals over sulfuric acid, consists in removing the alcohol of crystallization by heating a t 210OC. for one hour. The work done here indicates that the modification is applicable also to alkyd resins complicated by maleic anhydride or fumaric acid.
Table
1. Alkyd Resin Analysis Phthalic Anhydride Btandard Modified method A method B C
RePiin
Other Acids Present Maleic anhydride
1
2 3 4 5 6 7 8 9
Maleic anhydride Maleic anhydride Maleic anhydride Rosin Fumaric acid Fumaric acid
10
11
70
70
70
34.10 35.09 34.80 42.05 35,42 34.78 25.95 17.94 28.78 34.32 36.08
34.06 35.17 34.78 42.01 35.43 34.84 25.87 17.87 28.80 34.30 36.06
34.06 35.05 34.80 42.55 36.45 34.65 25.63 17.87 28.88 34.68 35.72
PROCEDURE. The standard Kappelmeier procedure ( 1 ) is followed up to the point of drying the filtration residues over concentrated sulfuric acid in vacuum. The crucibles containing the residues are transferred from the low-temperature oven to a 250" C. oven for one hour. They are then cooled over Dehydrite, weighed, and converted to phthalic anhydride, assuming dipotassium phthalate as the weighing form. Table I lists representative results on the basis of which the two methods may be compared. LITERATURE CITED
(1) Am. Soo. Testing Materials, D563-40T, B.S., 11, p. 1362. (2) Goldberg, A. I., IND. ENQ.CEEM.,ANAL.ED., 16, 198 (1944). (3) Kappelmeier, C. P. A., Farben-Ztg., 40, 1141-3 (1935); 41, 161
(1936).
