Effect of Moisture on the Chromatographic Properties of a Synthetic Hydrated Magnesium Silicate M. L. WOLFROM, ALVA THOMPSON, T. T. GALKOWSKI, AND E. J. QUINN Department of Chemistry, T h e Ohio State Unioersity, Columbus 10, Ohio
AGKESOL is the trade name for a synthetic hydrated mag-
& nesium lsilicate manufactured by the Westvaco Chemical Di-
vision of Food Machinery and Chemical Corp., South Charleston, R . Va. I t has been used extensively in this laboratory for the chromatographic separation ( 4 )of sugar derivatives. It has been noted that procedures are often difficult to repeat, especially from season to season, even a h e n the same lot of adsorbent is used. It is known that the water content of alumina and silicic acid (1, S, 6, 7 ) has a marked effect upon their adsorptive strength. Trueblood and ;\lalmberg ( 7 ) found a simple relation between the adsorptive strength of silicic acid and its content of water removable by pren-ashing or mild heating; greater adsorptive strength was associated n i t h a IoM-er content of "free" water. For this reason experiments nere made to test the effect of the moisture content of Nagnesol upon its adsorptive strength. Samples of Nagnesol mixed with Celite [a siliceous filter-aid, a product of Johns-Manville Co., New York, IY.Y., which Trueblood and Malmberg ( 7 ) found had no appreciable water retaining capacity] were adjusted to varying water contents by storing the material in atmospheres of controlled humidity for several months. The content of loosely bound water was found by determining the weight loss upon heating for 24 hours a t 110°C. The samples were tested by making chromatographic separations of 8-gentiobiose octaacetate and 0-maltose octaacetate using as nearly identical conditions as possible; the developer was 0.8% tert-butyl alcohol in benzene. It was found that the adsorptive strength of the Magnesol-Celite mixture decreased as the moisture content increased. This loss in adsorptive strength was revealed by the fact that the zones moved further down the columns and were more diffuse and widely separated. Table I.
controlled by means of the following materials ( 2 , 6): water, relative humidity, ca. 100% ; saturated solution of ammonium chloride, 79%; saturated solution of sodium bromide dihydrate, 58%; saturated solution of potassium carbonate dihydrate, 44%: saturated solution of potassium acetate, 20%; and solid calcium sulfate (soluble anhydrite or Drierite, a product of the iJ7. 4. Hammond Drierite Co., Xenia, Ohio; thrice changed), ca. 0%. The samples were stirred from time to time. After standing 4 months in these atmospheres it was assumed that equilibrium had taken place. A second group of samples taken from different lots of Magnesol was mixed with Celite (5 to 1 by weight) and placed in the same desiccator over a saturated solution of sodium bromide dihydrate for 4 months with occasional stirring. The loosely bound water was determined by measuring the loss in weight by heating a t 110" C. for 24 hours. The adsorbent stored a t 58% relative humidity required 110 ml. of benzene to wet a column 175 X 35 mm., inside diameter; that dried a t 100" for 48 hours required 120 ml. The results are recorded in Figure 1 and Table I. X mixture of 1 gram each of &maltose octaacetate and 0gentiobiose octaacetate \vas dissolved in 500 ml. of benzene. .4 25-ml. aliquot of this solution contained 0.1 gram of an equal mixture of the acetates. The developing solution consisted of benzene-(tert-butyl alcohol) (125 to 1 by volume). The benzene was free of water and thiophene, p- Gentiobiose octooatqte
/ - I
Variation in Adsorptite S t r e n g t h of Different Lots of Magnesol"
@-MaltoseOcta~~i~~~~~ @-Gentiobiose Octaacetate Zone Content acetate Zone of Distance of Extent Distance of Extent Adsorbleading of leading of Sament, edge from Zone, edge from Zone, 70 top, mm. mm. top. mm. mm. de l b 13.5 30 22 90 30 2 9.2 21 8 78 25 3 9.1 11 7 59 28 4 11.8 10 6 43 24 a See experimental portion for details. bPlotted in Figure 1.
Interzone, Mm. 30 32 20 9
I
I
50
CQ
I
I
150
200
Position ot zones from top, mm
Figure 1. Relation between Moisture C o n t e n t a n d Adsorptive S t r e n g t h of Magnesol-Celite (5:l by weight) Mixtures at 25" C.
--.--. --
Leading edge of zone Trailing edge of zone Zone extent
After samples of four lots of Magnesol were stored for several months under the same controlled atmospheric conditions, they did not contain the same amounts of moisture nor did the chromatographic tests show a definite relation to the moi sture content. This indicates that some factors inherent in the manufacture of the product caused each lot t o be somewhat different. However, within a given lot, tests show that a definite relation exists between the moisture content and the adsorptive strength of the Magnesol. These tests also indicate that the optimum moisture content for practical use is over a range of from 10 to 20%. Below this range the zones lie too close together, and above it the zones are dispersed over too large a space on the column. The results of the measurements are recorded in Table I and Figure 1.
Procedure for Testing Samples. The Magnesol-Celite mixture was placed in a tube (175 X 35 mm., inside diameter). Benzene (20 ml.) was placed on the column followed by a 25-ml. aliquot of the mixed sugar acetate solution, followed again by 20 ml. of benzene. The developer (400 ml.) was then passed through the column. From the time the first benzene was added a constant pressure differential was maintained by means of a Cartesian manostat set a t 250 mm. in the vacuum line. The column was then extruded from the tube and streaked with alkaline permanganate indicator (1% potassium permanganate in 10% sodium hydroxide solution), and the position and size of the zones were measured in relation to the top of the column. The results of these measurements are recorded in Figure 1 and Table I.
EXPERIMENTAL
ACKNOWLEDGMENT
Materials. A sample of Magnesol (12.7% moisture) was mixed with Celite ( 5 t o 1 by weight). Portions of this mixture were placed in desiccators in which the relative humidity was
This work was supported by the Corn Industries Research Foundation.
1670
1671
V O L U M E 2 4 , NO, 10, O C T O B E R 1 9 5 2 LITERATURE CITED
(1) Brockmann, H., and Schodder, Helen, Ber., 74, 73 (1941). (2) Edgar, G., and Swan, W, O., J . Am. Chem. Soc., 44, 670 (1922). (3) RlcGavack, hl., Jr., and Patrick, W. A., Ibid.,42, 946 (1920). and Wolfrom, h1. L., Ibid., (4) *hlcNeely, W. H., Binkley, W.W., 67,527 (1945). ( 5 ) Obermiller, J., and Goertz, Martha, 2. physik. Chem., 109, 145 (1924).
(6) Patrick, W. A , , and Long, J. S., J . Phys. Chem., 29, 336 (1925). ANAL.CHEM.,21, (7) Trueblood, K. N., and Malmberg, E. W.,
1055 (1949).
RECEIVEDfor review April 2 5 , 1962. Accepted J u n e 27, 1962. Presented before t h e Division of Sugar Chemistry a t t h e 121st Meeting of the AMERICAN CHEMICAL SOCIETY,Sfilwaukee, Wis. Project 203 of T h e Ohio State University Research Foundation.
Viscometer for Dextrin Pastes W. R. FETZER, E. K. CROSBY, AND R. E. FULLICK Clinton Foods Inc., Clinton, Iowa ESPITE the wide use of dextrins and the large number of dextrins produced, very little attention has been given to standardization of the methods for the measurement of paste visrosities. There are several types of orifice funnels and tubes i n use for viscosity determination. Usually the orifice is of glass
