499
ANALYTICAL EDITION
August, 1946
OTHERAPPLICATIUK OF TESTS. ilttempts to use purified pyridine homologs (boiling range 120” to 250” C.), isolated from the cracked pressure dist,illate, in place of pyridine in the Sommer test failed. This was due to the higher miscibility of these bases with the gasoline, and the failure of the mixture to separate into three phases on the addition of water. This is probably the desensitizing action of hydrocarbons on the test that was observed by Sommer. An attempt was made t o apply these different tests to detect free sulfur in crude shale oil, but alkali-soluble coloring matter in the oil masked any color reactions. ’
RESULTS
The results are expressed in sulfur concentration in parts per million by weight required t o give a definite, questionable, or negative test. With the standard solutions used, 1p.p.m. (TV/W) is equal to 0.7 microgram per cubic cent’imeter. Test Inverse doctor test Inverse, modified b y presence ofpyridine Sommer test Mercury test
Definite P.p.m. 20 15
4
Questionable P.p.m. 15
Negative P.p.m. 10
10 8 3 2 Positive even below 0.1 p.p.m.
The mcrciiry test is by far the most sensitive, but it is too sensitive for plant control. The inverted doctor test is posit’ive
to 15 p.p.m. of free sulfur, but the color of the lead mercaptide tends to make detection difficult near the limiting concentration; in the presence of pyridine, the modified test is ? a s h to observe and a shade more sensitive. The Sommer test is sensitive to 3 p.p.m. of free sulfur in the gasoline, being therefore about five times as sensitive as the inverted doctor test, and yet not too sensitive for plant control. With experience, a plant operator is able t o obtain an approximate estimate of the free sulfur content of the gasoline from any of the first three tests, but much more readily from the Sommcr test. The Sommer test has been found both quicker to operate and easier to observe than the inverse doctor test previously ured. If the gasoline being tested is highly aromatic, i t would br advisable to determine the optimum proportions of the reagents for the test before putting it into routine operation. ACKNOWLEDGMENTS
The author wishes to acknowledge with thanks the permission granted by the management of National Oil Pty., Ltd., to publish this paper and the assistance of -4.L. Kremer in carrying out the work. LITERATURE CITED
(1) Sommer, H., IND. ENG.CHEM.,AXAL.ED.,12,368-9 (1940).
Qualitative Test for Carbohydrate Material ROMAN DREYWOOD’, Paper Service Department, Eastman Kodak Company, Rochester, N. Y
A solution of anthrone in concentrated sulfuric acid gives a permanent green coloration ‘with carbohydrate material. The reaction is o f value as a qualitative test and for the preliminary classification of synthetic resins into a cellulose or noncellulose group.
A
LTHOUGH there are a large number of specific tests for certain types of saccharides (1, 2 ) , there are very few general tests for carbohydrate materials. The Molisch test, using 0naphthol, is well known and generally applicable to soluble carbohydrates. Anthrone, which is used for the determination of glycerol ( d ) , was found to give a green color with cellulose. Further experiments indicated that a positive test was obtained with all of a group of eighteen carbohydrate materials examined, including several cellulose derivatives. Furfural is the only noncarbohydrate material, thus far encountered, which gives a green color with anthrone. The test as given by furfural is, however, different from that given by carbohydrate materials. The green color given by a furfural test is rapidly obscured by a brqwn precipitate, and when the sample isdiluted with 50% sulfuric acid or glacial acetic acid, a heavy brown precipitate forms. Carbohydrate samples, on the other hand, may be diluted to any extent with these reagents, and the green color persists even a t extreme dilutions. Positive Test with A n t h r o n e Cellulose Ethvlcellulose (ether) Starch l I e t h \ lcellulose (ether) Dextrin Cellulose acetate Dextrose Cellulose acetate phthalate 1-Arabinose Cellulose acetate butyrate G u m arabic Cellulose acetate stearate Cellulose propionate G u m tragacanth Agar Cellulose nitrate Pectin Furfural (noncarbohydrate) Algin
A negative test was obtained by all of a large group of noncarbohydrate materials examined, which included a variety of noncellulose synthetic resins, organic acids, aldehydes, phenols, fats, terpenes, alkaloids, and proteins. PROCEDURE
One milliliter of water is placed in a small test tube containing approximately 1 mg. of the material to be tested, and 2 ml. of a 1
Present address, Tower Drug & Chemical Company, Rochester, N. Y.
0.2% solution of anthrone in concentrated sulfuric acid are then added. The final sulfuric acid concentration in the test solution should always be greater than 50%; otherwise the anthrone %rill come out of solution and produce a milky suspension. The heat produced by the dilution of the sulfuric acid is a necessary part of the test. I n the presence of carbohydrate material a clear green color iTill appear and rapidly increase in intensity until a dark blue-green solution result’s. The test solution can be diluted for comparison with glacial acetic or 50y0 sulfuric acid, I n the absence of carbohydrate material, but in the presence of other organic compounds, a brown color is often produced by t,he action of Dhe concentrated sulfuric acid. The anthrone, which is not a readily available chemical, can be prepared according to the directions of Schutz (4), or following the procedure given in Organic Syntheses (3). Care should be taken during the preparation to avoid contamination of the anthrone by carbohydrate material, especially filter paper pulp, which would cause a green color to develop in a blank test with the reagent. DISCUSSION AND APPLICATIONS
S o study ivas made of the mechanism of the reaction, but t lie appearance and deepening of the color seemed to be as rapid with a polysaccharide as with an equal weight of a monosaccharide. This would suggest t,hat hydrolysis may not be a neccssary stvp in the test. -1useful application of this reaction is the identification of synthetic resins. Even t,he most insoluble cellulose resins TTill give a poaitive test with anthrone, thus affording a preliminary classification into a cellulose or noncellulose group. However, many tic molding compositions contain n-ood flour and would giw a tive test for that reason. .-In attempt’ is now being made to apply this reaction to the qiiantitative colorimetric determination of small quantities of ccllulose in solution, particularly to the analysis of p- anti ycellulose. The anthrone test is extremely sensitive. I n tests with starch it proved t o be 10 to 40 times as sensitive as iodine for the detection of this carbohydrate. Approximately 1 part of starch in 900,000 parts of viater can be detected. LITERATURE CITED
(1) Browne, C. A., and Zerban, F. W., “Sugar Analysis”, p. 641, Sew York, John Wiley & Sons, 1941. (2) Degering, E. F., “An Outline of the Chemistry of Carbohydrates”, Chapter XVII, John S.Swift Co., 1943. (3) Gilman, H., and Blatt, A. H., editors, “Organic Syntheses”, Collective Vol. I, p. 60, New York, John Wiley & Sons, 1941. (4) Schutz, F..Papier-Fabr. (Tech. TI.,. 36,55 (1938).
