Thus at room temperature about 1 part of "Cerelose" is soluble in 1
part of water. "Cerelose" is less soluble than sucrose and goes into solution
at a slower rate.
The solubility of dextrose limits its use in cookery to a certain extent.
Jellies average about 60 to 70 parts of sugar by weight and 30 to 40
parts of liquid or juice. Dextrose at room temperature is soluble in water
to the extent of 1 part of dextrose to 1 part of water. Since the finished
jellies average over 50 per cent of sugar, when dextrose alone is used
in jelly it soon begins to crystallize after the jelly is cooled. If the jelly is
not covered it crystallizes very rapidly.
Levulose. Levulose is very soluble. It has a greater solubility than
sucrose. Since it is very soluble it must be present in very large quantities
before it crystallizes and is therefore very hard to crystallize. The data in
the table for the solubility of levulose are obtained from the results of
Jackson, Silsbee and Proffitt. The data in the third column are computed
from the grams of levulose soluble in 100 grams of solution.
Properties of Solutions
A solute dissolved in a solvent affects the properties of the solvent or in
other words alters certain of its constant characteristics. No discussion of
osmotic pressure is given ; the effect on the freezing point is discussed in
the chapter on freezing. These characteristics may be listed as follows:
a. The vapor tension is lowered.
b. The boiling point is elevated.
c. The freezing point is lowered.
d. The osmotic pressure is increased.
EFFECT OF THE SOLUTE ON VAPOR TENSION 45
Vapor tension. Vapor tension may be defined as the vapor or gaseous
pressure of a liquid. The vapor tension of a liquid depends upon the amount
of vapor formed. Some liquids, like alcohol, evaporate rapidly and have a
high vapor tension. Others, like water, evaporate more slowly. This gaseous
pressure soon reaches a maximum at any given temperature. The maximum
pressure at a definite temperature represents the vapor tension of the liquid.
TABLE 9
Solubility of Levulose {Jackson, Silsbee and Proffitt)
Temperature,
degrees C.
Grams of levulose in 100
grams of solution, or
per cent
Grams of levulose dissolved
by 100 grams of water
20
78.94
374.8
25
80.29
407.3
30
81.64
444.6
35
82.98
487.5
40
84.34
538.5
45
85.64
596.3
50
86.90
663.3-
55
88.10
740.3
Effect of the solute on vapor tension. When a substance is dis-
solved in a liquid the vapor tension of the solvent is lowered, i.e., there is
less tendency to pass into the vapor state, hence the gaseous pressure is
decreased.
If water is the solvent, there is a tendency with a high concentration of
some substances for vapor from the air to enter the solution, thus increas-
ing the quantity of the solvent. This is particularly true of sugar solutions,
when the humidity of the air is high and the solutions are concentrated.
On damp, rainy days, fondant and similar candies have to be beaten for
a longer time to crystallize, unless they are cooked to a little higher tem-
perature so as to obtain a greater concentration.
Page 39
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Thus at room temperature about 1 part of "Cerelose" is soluble in 1
part of water. "Cerelose" is less soluble than sucrose and goes into solution
at a slower rate.
The solubility of dextrose limits its use in cookery to a certain extent.
Jellies average about 60 to 70 parts of sugar by weight and 30 to 40
parts of liquid or juice. Dextrose at room temperature is soluble in water
to the extent of 1 part of dextrose to 1 part of water. Since the finished
jellies average over 50 per cent of sugar, when dextrose alone is used
in jelly it soon begins to crystallize after the jelly is cooled. If the jelly is
not covered it crystallizes very rapidly.
Levulose. Levulose is very soluble. It has a greater solubility than
sucrose. Since it is very soluble it must be present in very large quantities
before it crystallizes and is therefore very hard to crystallize. The data in
the table for the solubility of levulose are obtained from the results of
Jackson, Silsbee and Proffitt. The data in the third column are computed
from the grams of levulose soluble in 100 grams of solution.
Properties of Solutions
A solute dissolved in a solvent affects the properties of the solvent or in
other words alters certain of its constant characteristics. No discussion of
osmotic pressure is given ; the effect on the freezing point is discussed in
the chapter on freezing. These characteristics may be listed as follows:
a. The vapor tension is lowered.
b. The boiling point is elevated.
c. The freezing point is lowered.
d. The osmotic pressure is increased.
EFFECT OF THE SOLUTE ON VAPOR TENSION 45
Vapor tension. Vapor tension may be defined as the vapor or gaseous
pressure of a liquid. The vapor tension of a liquid depends upon the amount
of vapor formed. Some liquids, like alcohol, evaporate rapidly and have a
high vapor tension. Others, like water, evaporate more slowly. This gaseous
pressure soon reaches a maximum at any given temperature. The maximum
pressure at a definite temperature represents the vapor tension of the liquid.
TABLE 9
Solubility of Levulose {Jackson, Silsbee and Proffitt)
Temperature,
degrees C.
Grams of levulose in 100
grams of solution, or
per cent
Grams of levulose dissolved
by 100 grams of water
20
78.94
374.8
25
80.29
407.3
30
81.64
444.6
35
82.98
487.5
40
84.34
538.5
45
85.64
596.3
50
86.90
663.3-
55
88.10
740.3
Effect of the solute on vapor tension. When a substance is dis-
solved in a liquid the vapor tension of the solvent is lowered, i.e., there is
less tendency to pass into the vapor state, hence the gaseous pressure is
decreased.
If water is the solvent, there is a tendency with a high concentration of
some substances for vapor from the air to enter the solution, thus increas-
ing the quantity of the solvent. This is particularly true of sugar solutions,
when the humidity of the air is high and the solutions are concentrated.
On damp, rainy days, fondant and similar candies have to be beaten for
a longer time to crystallize, unless they are cooked to a little higher tem-
perature so as to obtain a greater concentration.