December, 1930
I N D U S T R I A L A N D ENGINEERING CHEMISTRY
that the present industrial depression will emphasize everywhere the necessity of keeping such basic products ever within their chemical values. For agriculture the golden opportunity is at hand. Through closely interlocked chemical processes, as applied to agricultural staples, we shall unfold a new era in our food industries. The great strides in the automotive industry during the past decade will
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suffer indeed in comparison with these stupendous advances that lie just ahead in the development of new foods. The general result will be registered in a tremendous broadening of activities on the farm, and to this end we shall rejoice that both agriculturist and industrialist are at work hand in hand contributing to the fuller and richer enjoyment of life.
Freezing and Flow Points for Glycerol, Prestone, Denatured Alcohol, and Methanol' J. C. Qlsen, Austin S. Brunjes, a n d J. W. Qlsen THE POLYTECHNIC INSTITUTE,BROOKLYN, N. Y.
STUDY of the literature having shown considerable differences between the figures given for the freezing points of the liquids used as antifreeze materials, it was thought desirable to redetermine these values in the endeavor to establish the correct values. Commercial samples representing the material actually used for this purpose were obtained. Each sample was tested to establish its purity and commercial grade, with the following results:
A
Glycerol, a water-white, thick liquid. The sample was tested for purity and all the tests were found to correspond with U. S. P. glycerol. Eveready Prestone, a commercial grade of ethylene glycol. The liquid was colored deep green and contained an oily material which floated on the top. Thermal alcohol, completely denatured alcohol, formula No. 5, 188 proof, slightly cloudy. Synthetic methanol.
The specific gravity of each sample was determined at 20"/20° C., as follows: Methanol. ............................. Prestone.. 1.1095 ............................. 0.7968 0.8197 Denatured alcohol.. ..................... Glycerol.. .............................. 1.2548 (corresponding t o a glycerol content of 96.5 per cent)
these liquids would flow through the tubes of a radiator This temperature was called the "flow point." It could be defined as the temperature a t which the liquid would flow freely through an orifice of inch diameter. The flow poi@ was determined by cooling the liquid in a test tube until it had solidified and then allowing it to rise slowly until, on tilting the test tube, the liquid began to flow freely and observing the temperature. These determinations were checked by pouring the cold liquid, a t the temperature at which it flowed, through a Gooch funnel having a tube of '/4 inch internal diameter. The Gooch funnel was entirely enclosed in a second vessel containing a cooling mixture of approximately the temperature of the liquid to be tested. It was found that the flow point obtained in the test tube agreed very closely with the flow point as obtained in the Gooch funnel. As the test-tube experiment was very much simpler, this was used for most of the flow points reported. The flow point obtained in this way obviously depends upon the amount of solid material in the cold liquid as well as upon the viscosity of the liquid. At the higher temperature the viscosity was not sufficiently high to interfere with the test. At the lower temperature the flow point is prob-
D e t e r m i n a t i o n of Freezing Points
The freezing points were determined by cooling the liquid with constant stirring and observing the temperature at which crystals began to appear or the slowly decreasing temperature was arrested or rose to a constant point. Care was taken that the cooling bath was only a few degrees below the liquid in order to avoid supercooling. The freezing points were checked a number of times, in some cases by two independent obs e r v e r s . The check determinations usually .\ agreed within 0.1" or 0.2" C.
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D e t e r m i n a t i o n of Flow P o i n t s
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The freezing point obviously does not give 9 the minimum temperature a t which these liquids may be used as antifreeze materials in auto- Go mobile radiators. The few crystals present at this point would not interfere with the circula- -40 tion of the liquid. It seemed desirable to determine the minimum temperature a t which 1 Received August 9,1930. Presented before the Division of Industrial and Engineering Chemistry a t the 80th Meeting of the American Chemical Society, Cincinnati, Ohio, September 8 t o 12, 1930.
-so
Figure 1
I N D U S T R I A L A S D ESGIaISEERlh'G CHEMISTRY
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Vol. 22, No. 12
from the percentage composition obtained from the specific gravity. As glycerol is also sold in the form of a 60 per cent by weight solution, the volume per cent required to make the dilution tested was calculated and entered in the table for glycerol. The results are given in the accompanying table.
ably determined by the viscosity rather than the amount of crystals present. It is believed that the flow point gives the minimum temperature a t which these liquors may be used for cooling radiators. If the liquor will flow through a l/l-inch tube, it undoubtedly would be circulated by the pump installed for this purpose in the automobile. I n some cases the flow point is considerably lower than the freezing point; in other cases there is not much difference. Freezing Points and Flow Points of Prestone, Methanol, Denatured Alcohol, and Glycerol COMPOSITION FREEZIXG POINT FLOWPOINT
70b y
w1.
70 b y
801.
PRESTONE
OC.
-
3.3 7.8 -13.5 -17.1 -22.1 -26.7 -35.4 -41.7 -46
10 20 30 35 40 45 50 55 60
OC.
O F .
(ETHYLENE GLYCOL)
26.1 18.0 7.7 1.2 7.8 -16 -31.7 -43.0 -50.8
-
-
4.3 8.6 -14.0 -19.1 -24.5 -34.5 -43.9 -47 -53
O F .
24.3
+- 1266...468
-12.1 -30.1 -47.4 -52.6 -63.4
10
20
&men(
aa
by MkM
40
Figure 3
Curves drawn from the data given were in most cases very smooth, the deviation being in the order of uncertainty of the observed values. In the case of glycerol, there was considerably more difficulty in getting a smooth curve. There is reason to suppose that around 40 per cent by weight the eutectic is formed by a combination of glycerol with water, which seems to introduce some irregularity into the curve a t this point. The specific gravity table of glycerol shows irregularity in change of specific gravity with change of concentration a t this concentration.
SYNTHETIC M E T H A S O L
10 15 20 25 30 35 40
12,24 18.13 23.89 29.50 34.98 40.33 45.56
10 15 20 25 30 35 40 45 50 60
11.9 17.75 23.37 28.25 34.33 39,65 44.85 49 95 54.95 64.66
-
6.8 -10.5 -16.2 -21.2 -28 -35.2 -42
19.8 13.1 2 8 6 2 -18.4 -31.4 -43.6
-
DENATURED ALCOHOL
- 4.3 - 6.9 - 10
--18.1 14 -23.5 28 -31.6 -35.5 -42.0
-
24.26 19.58 14 6.8 0.2 -10.3 -18.4 -24.9 -31.9 -43.6
-
- 8,s
-13.9 -18.4 -24 -34 -40 -49.5
- 68 . 5 --14
-16 -21.4 -25.5 -34.5 -39.9 -42.4 -46.4
16.7 7.0 1.1 -11 2 -19 2 -40 -57.1
-
21.2 16.7 6.8 3 3 - 6 5 -13.9 -30.1 -39.9 -44.3 -52.5
GLYCEROL
96.5% 10 20 30 35 40 45 50 55 60 70 ~~
100% 9.65 19.30 28.95 33.78 38.60 43 43 48.25 53.08 57.90 67.55
96.5% 8.14 16,62 25 46 30.03 34.70 39.47 44.36 49.35 54.46 65.03
60 % 14.23 29.09 44.65 52.71 60.96 69.40 78,03 86.91 95.98
- 2.2 ---1 285. 4., 83
-17.2 -18.0 -21.4 -27.5 -34.0 -41.5
28.0 22.46 16.3 9.5 1.04 0.4 6.5 -17.5 -29.2 -42.7
-
- 3
- - ~ n -15.8 -18.9 -19.5 -20.5 28 -35.9 -41.9
-
26.6 15 8 3.5 - 2 0 3.1 - 4 9 -18 4 -32 6 -43.6
-
Dilutions of each of the samples were made by weighing measured volumes of the sample and water and noting the volume of the diluted sample. I n all cases concentrations were tested which gave freezing points of -40' E'. (-40" C.) or slightly lower. The percentage by volume of each sample was calculated from the percentage by weight using the specific gravity determinations a t 20" C. I n the case of glycerol the true percentage was calculated
Figure 4
The flow point is only a few degrees lower than the freezing point for temperatures down to about -25' C. for all materials except glycerol. Below -25' C. the difference tends to increase to about 7 degrees. Neither of the curves for glycerol is smooth, there being a maximum divergence of 6 to 7 degrees a t 30 to 35 per cent and a t 55 to 60 per cent. Comparison with Published Data
Comparison of these results with those of Curme and Young for Prestone (1) shows them to be in some cases several degrees higher. The results for methanol are in fair agreement with the figures published in International Critical Tables (Z), the
I.VDUSTRIAL A.VD EiVGINEERING CHEMISTRY
December, 1930
greatest divergence being found in the value for 40 per cent by xeight-namely, 4.4" F. The maximum difference shown with the figure published for glycerol in the same volume of the Critical Tables is 3 O F. a t 30 per cent by weight. Still greater differences are shown with the figures published by the Bureau of Standards (3) for denatured alcohol, the maximum being 9.40' F. a t 45 per cent by volume. It is not certain that the formula for denatured alcohol used in the Bureau of Standards test in 1921 or 1925 is the same as that used today. This may account for the large differences.
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Literature Cited -50
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(1) Curme and Young, IID. ENG.CHEM.,17, 1117 (1925).
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(2) International Critical Tables, Vol. IV, p. 262. (3) Standards, Bur. of, Letter Circ. 28.
Figure 5
Large-Scale Experiments in Sulfuring Apricots'" E. M. Chace, C. G. Church, and D. G. Sorber LABORATORY O F
HE dried-fruit industry of California is an important factor in the agricultural industry of the state. It is estimated that t h e t o n n a g e f o r 1929 a m o u n t e d to 390,000, of which 22,000 tons mere apricots. The districts in which the fruit is dried extend from R i v e r s i d e County on the south to Sacramento on the north; the largest part of the croD, however, comes from the- Santa Clara and San Joaquin Valleys. More than half of the dried apricots are exported.
T
FRUITA K D
VEGETABLE C H E M I S T R Y ,
BUREAU OF
CHEXIISTRY AND SOILS, L O S ASGELES, CALIF
The commercial process used for sulfuring apricots in California is described. Experiments were carried out in sulfuring fruit, with liquid sulfur dioxide in thermally controlled boxes. The concentration of the gas to which the fruit was exposed, the length of the exposure, and the temperature at which the treatment was carried out were varied, and the effect of these variations upon the retention of sulfur dioxide by the fruit and upon its grade have been studied. The system devised for grading the fruit is described. The results show that the appearance of dried fruit is correlated with the sulfur dioxide content, and that the concentration of gas and length of sulfuring period are important factors, good fruit resulting after 2 hours in 3 per cent of gas. Temperature was a minor factor, although the best results were obtained at 100-110"
F.
The Commercial Process
The treatment of apricots and peaches with sulfur dioxide gas before the fruit is dried in the sun is as old as the dried-
fruit industry. The treatment serves several purposes. It plasmolyzes the cells of the fruit, thus promoting rapid drying; it preserves the color by retarding the usual darkening of the fruit by enzyme action; it prevents the growth of mold and fermentation; and it keeps insects away from the exposed material while it is drying. Naturally some variation exists in the construction of the sulfuring houses used by fruit growers, but the type is usually the same. The greater number are built of tongueand-groove lumber, lined or covered, or sometimes both lined and covered, with roofing paper. Others are constructed of cement or tile. A tight framework is built on the front and a groove provided for a vertical, counterbalanced door. When down, this door is made tight with special door fasPresented under the title "Important Fac1 Received July 28, 1930. tors in Sulfuring -4pricots" before the Diiision of Agricultural and Food Chemistry at the 80th Meeting of the American Chemical Society, Cincinnati, Ohio, September S t o 12, 1930. Contribution No. 83 from Food Research Division, Bureau of Chemistry and Soils.
teners or by driving wedges b e t w e e n it and the outer framework of the groove. The houses haven capacity of from 1 to 2 tons of fruit, and are so constructed as to leave about 18inches between the front fruit truck and the door. This provides room for the sulfur burner, which usually consists of a cement pipe or hollow tile 8 to 10 inches in diameter set in the ground so as to afford clearance for the fruit trucks. A weighed or measured amount of sulfur is placed in these stoves and ignited by means of paper or splints. The amount of sulfur used varies greatly, but from 3 to 5 pounds per ton of fruit are used on most dry yards. No mechanical means of distributing the vapors are employed. The fruit is halved and pitted by the workers, after which it is placed cut side up on trays. These trays, usually about 3 by 6 feet, have sides and ends high enough to keep the halved fruits from being crushed by the trays above, when they are stacked on the trucks. From 20 to 24 trays are placed on each truck and stacked so that the alternate ends project about 6 inches beyond the tray beneath (Figure 1). As the sides fit rather closely, this staggering is necessary to permit the gas to have access to the fruit. I n some dry yards each tray of fruit is sprinkled with water before it is covered by the next one. This may be with the idea that is prevents surface evaporation and the formation of a layer of partly dried tissue, but the writers have not been able to detect differences in the absorption of sulfur dioxide or in the appearance of the fruit when thus treated if it is placed in the sulfuring chamber within a reasonable time after cutting. There is other evidence, however, t o the effect that this treatment may retard the retention of sulfur dioxide (3). The trucks loaded with fruit are handled on tracks and
