1242
C. J.
TRESSLER, W. I. ZIhlhlERMAX .4ND C. 0. WILLITS
BOILISG-POIKT ELEVATION OF SUCROSE SOLUTIONS' C. J. TRESSLER, W. I . ZIMIIERMAS,
AND
C. 0. WILLITS
Sew Y o r k State Agrzcultural Experzment Stataon, Geneva, Xew Y O T ~ Received M a y 3, 1941
In the maple syrup industry it is commonly acknowledged that a syrup of standard density, weighing eleven pounds per gallon, will be obtained when the boiling-point elevation of the syrup solution is 7°F. or 3.9"C. When an attempt was made to obtain this value from the data on boilingpoint elevations of sucrose solutions as presented in the literature (1, 2, 3), it was found that various observers gave values, which, if interpolated to give the boiling-point rise for a 65.46 per cent sucrose solution (eleven pounds per gallon), varied from 3.9" to 4.8"C. Since such wide deviations were observed, it was decided to re-investigate the boiling-point elevation of sucrose solutions, using the purest sucrose available and modern apparatus. Ten pounds of chemically pure sucrose was kindly supplied by the Sational Sugar Refining Company. Two Washburn-Cottrell boilingpoint assemblies fitted with Beckman thermometers were used for determining the elevation of the boiling points. The procedure employed consisted in placing distilled water (140 cc.) in one assembly and the sucrose solution (140 cc.) in the other, and the boiling-point elevation of the sucrose solution was read directly by noting the difference in reading on the two thermometers. The two Beckman thermometers were previously standardized against each other in boiling distilled water. Two complete boiling-point assemblies were used, in order to avoid the necessity of making observations and subsequent corrections for slight fluctuations in barometric pressure. The sucrose solutions used in the present study were prepared by slowly heating, with rapid mechanical stirring, a carefully weighed amount of sucrose and water. Care mas taken that no discoloration of the sugar solutions took place during preparation. The sucrose solution (140 cc.) was then slowly heated to boiling in the boiling-point apparatus, while a t the same time distilled water was maintained a t a constant boil in the other. All equipment was shielded from air currents during the observations. After boiling equilibrium had been reached and the temperatures of the boiling water and sucrose solution noted, a sample of the sucrose solution was quickly withdrawn in a small vial which was immediately stoppered and cooled to 20°C. Care was taken t o incorporate condensed moisture clinging to the sides of the vial with the sample. The sucrose concentration of the sample was determined 1 Approved by the Director of the S e w York State Agricultural Experiment Station for publication as Journal Paper KO. 433, March 1, 1941.
1243
BOILISG POIKTS OF SCCHOSE SOLCTIOXS
T.%BLE 1 Data showing relation between boiling-point elevation, refractive i n d e x , and sucrose concentration BOILING-POINT ELEVATION
'
REFRACTIPE INDEX A T
20°C.
CONCENTRATION OF SUCROSE . .
per cent
0°C.
0.000 0.071 0.245 0.490 0.690 0.817
I
I
I
0,954
1,220 1.405 1.602 1.827 2.018 2 146 2.202 2,244 2.701 3.213 3.813 4.469 4.853 5.140 5,809
I
1 3333 1 3100 1 3549 1 3712 1 3821) 1 3890 1 394s 1 4045 1 4102 1 4161 1 4218 1 4253 1 4290 1 4308 1 4315 1 4100 1 4475 1 4546 1 4610 1 4649 1 4663 1 4698
II I
I
0 0 4 8 14 5 24 4 31 0 34 4 37 4 42 4 45 3 48 4 50 8 52 5 542 55 0 55 4 59 2 62 5 65 6 68 3 69 9 70 5 71 9
I
~
I
I
I
6
5 4
3 2 I
' 0
IO
20
30
40 50
60
70
80
PER CENT SUCROSE
FIG. 1. Boiling-point elevation of sucrose solutions
by taking the refractive index, using an Abbe refractometer. It was found that there was a slight but continuous loss of moisture from the apparatus, so that the concentration of the sucr0.e solution gained constantly. For
1244
C. J. TRESSLER, W. I. ZIMMERMAN A N D C. 0. WILLITS
this reason it was futile to weigh the sucrose for each solution but preferable t o rely on the values obtained from the measurement of the refractive index for determining the sucrose concentration of the boiling solution. If the thermometer was removed from the boiling-point apparatus for a few minutes, enough moisture evaporated so that, after boiling equilibrium was again reached, a higher elevation of the boiling point could be recorded. In this way the same sugar solution could be used for obtaining several boiling points. However, in order to avoid any decomposition of the sucrose, it WM found necessary to use freshly prepared solutions after a few determinations had been made.
TABLE 2 Boiling-point elevations for pure sucrose solutions CONCENTBATlON QP BOLUT3ON, P E B CENT
WJLIDLI
30 40 50 55
60 65
65.46t 70 75 80 85
90
08
reported by various investigators
BOILING-POINT ELIVATION, I N
. C . T.t >laMan Kahlenberg --- : and H‘ 0.95 1.45 2.14 2.62 3.23 4.10 4.21 5.443 7.16 9.66 13.55 19.95
0.70 1.10 1.90 2.50
3.25 4.20 4.3 5.5 7.3
0.6 1.06 1.8 2.3 3.0 3.8 3.9 5.1 7.0 9.4 13.0 19.6
0.7 1.45 2.00 2.50 3.20 4.2 4.3 5.55 7.2
- - - --
* Values baaed on carbon and hydrogen
‘c.
‘reutkel Permsn
1.0
1.5
2 .o
-
3.0 4.8 4.94
6.6 8.8 12.0 17.1
27.0
-
0.6 1.1 1.9 2.4 3.1 3.9 4.0 5.3 7.4 10.3 14.5 22.6
- -- 1.0 0.66 1.9 2.6 3.4 4.5 4.62 6.3 9.2 14.8
1.5 2.0 2.5
1.09 1.75 2.21
terminations appear to average about 0.3OC. higher than thorn reported by Claseen. The cauae of this small but rather consistent difference hae not yet been aacertained. t International Critical Tables. $ Sugar content of “standard” maple syrup.
A summary of our results is presented in table 1, and figure 1 shows this material in graphic form, while table 2 shows a summary of the results of other investigators a compiled by Holven (2), with interpolated values for a 65.46 per cent solution, which is defined as a “standard” maple syrup solution. CONCLUSIONS
It may be concluded from the present work that the values obtained for the boiling-point elevation of sucrose solutions vary considerably according to the method used in the determination, For the type of apparatus used the values presented are somewhat lower than those of other investigators,
ADSORPTION FROM NON-AQUEOUS MEDIA
1245
the boiling-point elevation for “standard” syrup being 3.80”C. or 6.845’. I n the actual preparation of maple syrup, deviations from this standard value may be expected, owing for the most part to the fact that the thermometer is customarily read while it is dipping into the superheated boiling solution, and also to the presence of certain amounts of invert sugar and substances other than sugar. REFERENCES (1) CLAASSEN, H.: Centr. Zuckerind. 44, 444 (1936). (2) HOLVEN,A. L.: Xnd. Eng. Chem. 28, 452 (1936). (3) KAHLENBERG, I..: J. Phys. Chem. 6, 377 (1901).
USE OF SMALL GLASS SPHERES I N ADSORPTION FROM XON-AQUEOUS MEDIA. I
ADSORPTIONOF IODINEFROM CARBONTETRACHLORIDE A. J. URBANIC
AND
V. R. DAMERELL
Department of Chemistry, Western Reserve University, Cleveland, Ohio Received April 1.9, 1941
Most adsorption results obtained by using solid adsorbents have been difficult to interpret, because of the complex nature of the surface and because of the indefinite extent of its area. A relatively simple surface can be prepared by passing powdered glass through a flame (1). The resulting spheres may then be separated into fractions and their surface area determined microscopically. It occurred t o the authors that this adsorbent should be of particular value in the study of adsorption from non-aqueous media, because of the stability of glass in the presence of many such liquids. Furthermore, results on a spherical surface are easier to interpret than those on the simplest crystal, berauE in the former there is no problem of possible selective adsorption on corners, edges, or faces (3). Aso, errom due to an adsorbed film of air will be at a minimum, as the hot freshly formed spheres are projected directly into the liquid and kept submerged throughout the adsorption experiment. The authors accordingly undertook a study of the adsorption of iodine in carbon tetrachloride. The former is soluble in the latter, positively adsorbed, and readily determined by analysis. Carbon tetrachloride, on the other hand, is not inflammable and is probably without significant effect on glass.
