1
I
CHEM. LIB.
AD
543
3651
B 397780
Blocher, J.M.
Osmotic press
ssure measurements of
levulose solutions at thirty degrees.
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JANSO 1917
543
B651
UNIV. OF MICH
OSMOTIC PRESSURE
MEASUREMENTS OF
LEVULOSE SOLUTIONS AT
THIRTY DEGREES
DISSERTATION
Submitted to the Board of University Studies of The
Johns Hopkins University in conformity with a
requirement for the Degree of Doctor
of Philosophy.
By
JOHN MILTON BLOCHER, JR.,
Baltimore, 1916.
OSMOTIC PRESSURE MEASUREMENTS OF
LEVULOSE SOLUTIONS AT
THIRTY DEGREES
DISSERTATION
Submitted to the Board of University Studies of The
}
Johns Hopkins University in conformity with a
requirement for the Degree of Doctor
of Philosophy.
By
JOHN MILTON BLOCHER, JR.,
Baltimore, 1916.
Gettysburg Compiler Print.
029 ge!?
TABLE OF CONTENTS
I. Acknowledgment
II. Levulose Solutions
III. Description of Apparatus
(a) The Cells
(b) Deposition of Membranes
(c) Recovery of Old Cells
4
5
8
Co
8
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It
(d) Manometers
12
(e) Regulation of Temperature
.16
IV. Measurements
19
V. Discussion of Tables
.36
VI. Conclusions
.39
VII. Biography
.40
I. ACKNOWLEDGMENT.
The author is glad to avail himself of this opportunity
to express his appreciation to Prof. Morse, the late Prof.
Jones, Dr. Lovelace, Dr. Reid, Dr. Frazer, Dr. Holland,
and Dr. Schwartz for their valuable instruction.
The author is especially grateful to Prof. Morse, at
whose suggestion and under whose guidance this investi-
gation was undertaken and carried out.
The author is under obligation to Dr. Holland for much
valuable advice and assistance.
The author is indebted to Dr. Frazer for much inspira-
tion, and for his kindly interest in the work.
THE OSMOTIC PRESSURE MEASURMENTS
OF LEVULOSE SOLUTIONS AT
THIRTY DEGREES
II. LEVULOSE SOLUTIONS.
The levulose, which was used in this investigation was
obtained in Germany. The repreliminary purification in
which the penta-acetate was made, giving the pure sugar
upon hydrolysis, was performed by Dr. C. S. Hudson, of
the Bureau of Chemistry at Washington, D. C. The au-
thor wishes to acknowledge his obligation to Dr. Hudson
and his co-workers for this valuable material.
There remained in the sugar some traces of acetic acid.
Our solute was freed from the traces of acetic acid by the
following method, depending upon the fact that levulose
is practically insoluble in cold absolute alcohol.
One hundred grams of the once recrystallized sugar
were dissolved in fifty cubic centimeters of 75% alcohol
which had been previously warmed on a steam bath.
Seventy-five cubic centimeters of absolute alcohol were
added to this solution. It was necessary, in some cases,
to add a little animal charcoal and a few cubic centimeters
of washed alumina to remove a slight turbidity. After
filtering the mixture, twenty-five cubic centimeters of
absolute alcohol were added to the clear filtrate. Upon
"seeding" the solution, the sugar was precipitated. The
crystallization was carried on in a dessicator with fre-
quent stirring. The yield was about 50% of the original
material used and the specific rotation was found to be
92°.0, the same value as the one assigned to pure levulose
by the Bureau of Chemistry at Washington.
Solutions of levulose are peculiar in that they exhibit
a change in specific rotation with change in temperature.
A solution which is taken from a cell after having given
6
Levulose Solutions.
a measurement, is examined in a saccharimeter to de-
termine whether or not it has undergone a change in con-
centration. It was found necessary, because of this
change in rotation with change in temperature, to retain
a sample of the original solution for the purpose of com-
paring its rotation, under the same conditions of tem-
perature, with the rotation of the solution which was
taken from the cell.
All solutions were made by dissolving a gram molecu-
lar weight of the sugar or a decimal part of the same in
one thousand grams of water. This weight normal sys-
tem of making up solutions is used in preference to the
volume normal method for the following reasons:¹
A volume normal solution, made by dissolving a gram
molecular weight of the substance, or a decimal part of
the same, in water and diluting to one litre is correct for
merely analytical purposes. It is "both disadvantageous
and illogical whenever any phenomenon is to be studied
in which the influence of the solvent upon the solute is
involved." "In cases of the latter kind, the true concen-
tration of the solution is determined by the numerical
ratio of the molecules of the solute to those of the solvent,
rather than by the number of solute molecules in a given
space."2
Difficulties are encountered when an attempt is made
to make up a less concentrated solution by diluting a more
concentrated one. For example, "Suppose a 0.1 volume
normal solution of cane sugar to be made up by diluting
100 cubic centimeters of a normal solution to 1000 cubic
centimeters. With respect to the relative numbers of
solute molecules contained in equal volumes, the new so-
lution is one-tenth as concentrated as that from which it
was made, but with respect to the ratio of solute to sol-
vent molecules, namely: 1:44.1 and 1:544.1, the concen-
tration of the diluted solution is not 0.1 but 0.081 nor-
mal.³
I For further discussion of the advantages of the weight nor-
mal system, reference is made to the Monograph by Prof. H. N.
Morse, Carnegie Publication, No. 198, Chap. V.
2 Ibid., Chap. V., p. 100.
3 Ibid., p. 100.
Levulose Solutions.
7
The numerical ratio of solute to solvent molecules in a
cane sugar volume normal solution at 30 degrees is about
1:44.1. At the same temperature, the numerical ratio
of solute to solvent molecules in a volume normal solu-
tion of glucose is 1:49.2. Thus we see that the cane sugar
solution is 11.5% more concentrated than the glucose
solution, although equal volumes of the two solutions con-
tain the same number of solute molecules. This differ-
ence would amount to 3.7 atmospheres when stated in
terms of osmotic pressure.
The practice of employing the volume of the solvent as
the standard for the computation of the gas pressure of
the solute made it necessary to make a correction corre-
sponding to the term "b" in the Van der Waals equation
for gas pressure. The weight normal system gives us a
means of correcting for the volume of the solute mole-
cules. However, the true volume of the solvent in solu-
tion cannot be known accurately until the extent of the
hydration of the solute is determined at all temperatures.
8
Description of Apparatus.
III. DESCRIPTION OF APPARATUS
A. THE CELLS.4
A cell, in which the true osmotic pressure of a solution
may be measured, must meet the following conditions:
(1) It must have a uniformly strong wall.
(2) It must be absolutely free from air blisters.
(3) It must have an excessively fine and perfectly
uniform texture of wall.
The high pressure, to which the cell is subjected in the
process of measuring, make the first requirement abso-
lutely imperative.
Air blisters, communicating with the interior of the
cell wall, would cause a local deposition of the membrane
in these regions. Experience has shown us that a mem-
brane, in order to be very strong, must be deposited just
within the mouths of the pores of the interior wall of the
cell.
The pores of the wall must be so fine that the more
mobile cation may pass nearly through them while the
slower anion is just entering the mouth of the pores on
the interior wall. In this way we secure an infinite num-
ber of plugs of the active membrane material supported
by the whole body of the cell wall. These plugs are
driven into the pores so tightly, by means of the electric
current, that no amount of pressure will dislodge them.
The electrolytic method of depositing membranes, devised
by Prof. Morse, is far superior to the old method of Pfef-
fer.
A mixture of equal parts by weight of the finest por-
tions of a fire clay, obtained from Dorsey, Md., and of a
ball clay from Edgar, Fla., was found to give the best re-
sults in cell making. The clays were first elutriated and
the finest portions were passed through No. 14 and No.
4 Ibid., Chap. I.
Description of Apparatus.
9
16 bolting cloth, containing 19,000 and 24,000 holes to the
square inch respectively. After the particles were filtered
and allowed to dry thoroughly, equal parts by weight
were mingled by sifting, and then by mixing with dis-
tilled water in large cylinders. The mixture of the two
clays and water was kept in constant agitation while the
particles were again passed through the No. 14 and then
through the No. 16 bolting cloth. The repeated bolting
insured a very intimate mixture of the clays and particles
of desired fineness were obtained.
Water was removed from the mixture of the clays until
it had the consistency of ordinary putty and cylinders
were formed under pressures of twenty tons to the square
inch. A cylinder, which is formed by any method em-
ploying a smaller pressure, produces a cell whose wall is
too porous. These cylinders were placed upon a lathe
and the cells of desired shape and size were turned out
with tools of special form. The cells were then baked at
the temperature of Seger cone No. 7 (1270°) and after-
wards rebaked at the temperature of cone No. 8 (1290°).
Before the upper end of the cell may be glazed it must be
ground to required form on a lathe. A small, rapidly ro-
tating carborundum wheel was used for this work.
Air must be entirely removed from the pores of the cell
before the membrane may be deposited. This is accom-
plished by electrolyzing a 0.005N solution of lithium sul-
phate in such a way that the cation, which always carries
a large "atmosphere" of water, is driven inwardly
through the wall of the cell. After the air has been re-
moved, the salt solution is replaced by pure distilled water
which is renewed frequently. This final electrolysis
serves to remove the lithium sulphate from the cell pores
and it is continued until the conductivity equals that of
distilled water. The cell is then placed in a saturated
solution of thymol water and kept there until required
for the process of depositing the membrane.
5 Ibid., Chap. I, p. 9.
10
Description of Apparatus.
B. DEPOSITION OF MEMBRANES.
The membranes of copper ferro-cyanide are deposited
in a constant temperature bath especially constructed for
that purpose. A circular anode of copper is placed in a
vessel containing a 0.01N solution of copper sulphate.
The cell is placed within the circular anode and is closed
by a rubber stopper carrying the cathode of platinum,
an overflow tube and a funnel whose stem nearly
reaches the bottom of the cell. A solution of 0.01N po-
tassium ferro-cyanide is placed within the cell by means
of the funnel and the membrane is deposited in the pores
of the cell wall under a pressure of 110 volts. The solu-
tion of potassium ferro-cyanide is replaced at intervals
of three minutes to prevent an accumulation of free
alkali, which acts disasterously upon the membrane. The
resistance of the membrane is noted from time to time by
means of a milliammeter. During the course of deposi-
tion a gradual increase in the resistance will be noticed.
The resistance will remain constant at its maximum for
a short time and then it will decline. The electrolysis is
interrupted just before the decline in resistance takes
place. The cell is then emptied, washed internally and
externally, and allowed to soak in thymol water for three
days.
Thymol is toxic toward a strain of pencillium glaucum, a
nitrogen consuming fungi, which readily infect the mem-
brane. After the soaking period, the cell is again sub-
jected to the membrane forming process. The subse-
quent "runnings" will cause the membrane to show an in-
crease in resistance.
When the resistance is thought to be sufficiently great,
the cell is "set up" with a concentrated cane sugar solu-
tion. This part of the cell's development is called, "sea-
soning under pressure," that is, the cell is filled with the
cane sugar solution which contains a little dissolved po-
tassium ferro-cyanide and is closed by a manometer. A
solution of copper sulphate, which is osmotically equiva-
6 Ibid., Chap. IV.
Description of Apparatus.
11
lent to the amount of dissolved potassium ferro-cyanide,
is placed on the outside of the cell. If there are any weak
places in the membrane, the pressure will cause a rupture
and the membrane formers will mend the broken places.
Very often one period of "seasoning under pressure" is
sufficient to produce a cell which will measure the true
osmotic pressure of a solution and which will not allow
the cell contents to become diluted. If this should not be
the case, the cell is again subjected to the "running" and
"soaking" process. During these operations, the cells
and the solutions of membrane formers are maintained at
the temperature at which the cells are subsequently used.
The cells must never be exposed to any great or rapid
changes in temperature.
C. RECOVERY OF OLD CELLS.
A cell will become intolerably slow in its action after
a time due to the fact that its membrane is old and per-
haps too thick, because of the repeated reinforcement.
It is then desirable to remove the old membrane and re-
place it by a new and more active one. The slowness
with which an old cell comes into equilibrium is the only
undesirable feature for a cell which has once "measured"
will continue to give good service while it is in existence
provided it is not injured in other ways.
Pfeffer recommends the following method for the re-
moval of membranes. The cell is allowed to soak in a so-
lution of potassium hydroxide to which a little Rochelle
salt has been added, and afterwards in water; then in
hydrochloric acid and again in water. This procedure
will remove the membranes with ease but we have not
been very successful in building a good membrane in a
cell after subjecting it to this treatment.
A modification of this method was tried in this labora-
tory in which the potassium hydroxide and the hydro-
chloric acid were omitted. The soluble salts which re-
mained in the cell wall after soaking in water were re-
7 "Osmotische Untersuchungen,” 12.
8 Ibid., Chap. V, p. 93.
12
Description of Apparatus.
moved by electrolysis. This method required a long
period of time, and, on the whole, was not very success-
ful. The method of grinding off the interior surface of
the cell wall, by means of a rapidly revolving carborun-
dum wheel, gave only fair results.
A very successful method was developed recently in
this laboratory. A one-fifth normal solution of potas-
sium acid tartrate is prepared and made alkaline by potas-
sium hydroxide. The old cells are soaked in this solu-
tion, which is frequently renewed, until the blue colora-
tion is no longer noticeable. The cells are then washed
and placed in a 5% solution of nitric acid until the slight
blue coloration again disappears. After the cells are
washed they are subjected to electrolysis in distilled
water until copper no longer deposits upon the cathode.
They are then reburned at the temperature of cone No. 7,
the air is removed by the lithium sulphate method, and
the new membrane is deposited in the usual manner.
Of the seventeen cells treated in this manner we se-
cured thirteen which are now giving measurements and
four which are giving promising results. These cells are
termed the "R" series and a number have been used suc-
cessfully in the measurement of the osmotic pressures of
levulose solution at thirty degrees.
D. MANOMETERS.9
The manometers, which were used for measuring the
pressures in the following experiments were made of
thick walled glass tubes having an external diameter of
about six millimeters. The diameter of the bore ranged
from 0.45 to 0.72 millimeters and the length of the cali-
brated portion was from 400 to 500 millimeters.
There are three reasons for using tubes of small bore.10
(1) After filling the manometer with nitrogen it is neces-
sary to enclose a small thread of mercury within the up-
permost portion of the tube because, in "sealing off" a
manometer, the caliber of the tube in the region of the
9 Ibid., Chap. II.
10 Ibid., p. 27.
Description of Apparatus.
13
seal is affected to an unknown extent. Should the bore
have a large diameter, this small thread of mercury
would become dislodged when the tube is subjected to
tapping during the determination of the volume of the en-
closed gas.
(2) The volume of the included gas is so
small that its compression does not produce a great dilu-
tion of the solution within the cell. (3) Small bore ma-
nometers require relatively small volumes of mercury.
Small bore manometers have these disadvantages.¹¹
(1) There is more difficulty in dealing with a meniscus
in a tube of small bore. (2) A tube of small bore has a
large capillary depression which varies greatly with
slight irregularities of bore. (3) The movement of the
mercury in such a tube is more liable to be influenced by
small irregularities or by impurities which may be fused
into the interior wall of the tube.
Two fine lines are etched upon the tube before the cali-
bration is begun. These lines extend completely around
the instrument and they are so fine that they may just be
seen by the naked eye. All subsequent readings are re-
ferred to these "scratches"12 for the tube is devoid of fur-
ther graduation. The "lower scratch" is placed near the
lower end of the calibrated portion of the tube and the
"upper scratch" is placed near the upper end and above
the widened section of the bore. The tube is placed in a
horizontal position upon a dividing engine, whose screw
has been carefully compared with the graduated meter
scales which are employed in the measuring of osmotic
pressures.
"The calibration is commenced at the lower scratch and
consists in setting the (short) thread of mercury exactly
end to end, and determining its length, until the thread
has passed the upper scratch. It is run out of the tube
and weighed. Then the whole of the calibrated portion
of the tube is filled with mercury, the thread measured
and again run out and weighed. From the length and
weight of the long thread, the mean diameter of the bore
may be estimated; and from the observations on the
II Ibid., Chap. II, p. 27.
12 Ibid., p. 29.
14
Description of Apparatus.
length of the short thread in the different parts of the
tube, a mean calibration unit is derived, and a curve of
corrections constructed. Finally, a mean value for the
double meniscus is obtained from the length and weight
relations of the long and short threads. If we multiply
the weight of the short thread by the number of times its
length is contained in that of the long thread, the differ-
ence is the weight of the mercury which would be re-
quired to fill the meniscus spaces which were left vacant
in setting the short thread end to end along the tube.
Converting this difference in weight into volume and di-
viding by the number of settings less one, we obtain a
mean correction for a double meniscus, which is the me-
niscus correction to be applied in all measurements of
pressure.
9713
The above method is used for manometers without the
widened portion in the bore. The method for large vol-
ume manometers differs in only one respect, the capacity
of the widened portion must be accurately determined as
a whole and afterwards in terms of the calibration unit.
The correctness of all previous work may be tested¹¹ in
two ways so that its accuracy can not be doubted.
A series of thick walled glass bulbs, three in number,
are sealed on to the calibrated tube. "The bulb nearest
the calibrated end serves as a reservoir in which the ni-
trogen, when under diminished pressure, may expand
without danger of escaping from the instrument." "The
bulbs nearest the cell serve as reservoirs for the mercury
which is to be driven forward in compressing the nitro-
gen, and their total capacity is therefore, to be regulated
by the volume of the gas under ordinary conditions and
the maximum pressure to be measured."15 The bulb next
to the cell is provided with a trap which prevents the
mingling of the sugar solution with the mercury in the
uncalibrated portions of the manometer.
The instrument is filled with mercury to a desired level
and is connected to a side tube, containing mercury, by
13 Ibid., Chap. II, pp. 31-33.
14 Ibid., Chap. II, p. 33.
15 Ibid., p. 37.
Description of Apparatus.
15
means of a flexible rubber tube. This system is placed
in a constant temperature bath and the capillary depres-
sion is determined at different points in the bore. A
curve is plotted, and, assuming that the change in capil-
lary depression between the points is regular, the values
for many points are secured. This procedure is of great
importance since the values obtained are used "in de-
termining the volume of the enclosed nitrogen under
standard conditions of temperature and pressure" and
also "in correcting its volume under an unknown pres-
sure, which, i. e., osmotic pressure is a quotient of the
two volumes."
Unusual care is taken in the purification16 of the mer-
cury which is used in the manometers and thermostats.
(1) The commercial product is allowed to run through a
few pin holes in a filter paper. This removes the coarse
dirt. (2) It is heated to its boiling point in a retort, to
which has been fused a long glass tube, while air is forced
through the metal. After four hours the metal is freed
from the scum of its oxides by filtration. (3) It is dis-
tilled in a partial vacuum. (4) The distillate is washed
by the method of Lother Meyer, modified by Hildebrand,
in which the very fine droplets of mercury are carried by
gravity through distilled water containing 2% nitric acid
and 2% mercurous nitrate. The washing is repeated
many times. (5) After it has been washed with distilled
water and thoroughly dried it is again distilled under di-
minished pressure but not in the still used for the first
distillation.
The gas employed in the manometers is pure nitrogen.
It is obtained by passing air through an alkaline solution
of para-gallol and then, in the order named over heated
copper oxide, heated copper, calcium chloride, potassium
hydroxide and resublimed phosphorus pent-oxide. A de-
tailed and interesting account of the process of filling ma-
nometers may be found on pace 46 in the Monograph by
Prof. Morse. The volume of gas in the manometer is then
determined under approximate atmospheric pressure and
16 Ibid., Chap. II, p. 28.
16
Description of Apparatus.
then reduced to standard conditions of temperature and
pressure. The instrument may now be used for the
measurement of osmotic pressures after being attached¹7
firmly to a cell containing the sugar solution of desired
concentration.
E. REGULATION OF TEMPERATURE.18
It is of utmost importance that the whole system, i. e.,
solution, solvent, cell and manometer be kept at constant
temperature during the process of measuring osmotic
pressure. A cell, filled with a solution of known concen-
tration and closed by a manometer is not unlike a ther-
mometer. Any slight fluctuation in temperature is always
followed by "thermometer effects"19 which are very detri-
mental to the success of an experiment because of three
facts: (1) "The capacity of the closed osmotic cell is
nearly a fixed quantity." (2) "Every change in the vol-
ume of the enclosed solution due to rise or fall in tem-
perature is followed by a discharge or intake of solvent
through the membrane, both of which acts also modify
the volume and the osmotic pressure of the solutions."
(3) "The passage of the solvent through the membrane,
in either direction, is usually a much slower process than
the changes in the volume of the cell contents which re-
sult from fluctuations in temperature."
The constant temperature baths used in this investiga-
tion were made to conform with the following principle: 20
"If all the water or air in a bath is made to pass rapidly
(1) over a continuously cooled surface which is capable
of reducing the temperature slightly below that which it
is desired to maintain, then (2) over a heated surface
which is more efficient than the cooling one but which is
under the control of a thermostat; and (3) again over the
cooled surface, etc., it should be practicable to maintain
17 Ibid., Chap. II, pp. 17-26.
18 Ibid., Chap. III.
19 For a discussion of the intricate phenomena concerned with
"thermometer effects," reference is made to the Monograph, pp.
51-55.
20 Monograph, p. 56.
Description of Apparatus.
17
in the bath any temperature for which the thermostat is
set, and the constancy of the temperature should depend
only upon the sensitiveness of the thermostat and the rate
of flow of the water or air."
The principle is the same whether the heating or the
cooling surface is under the control of the thermostat.
In the work at zero degrees, melting ice served both as a
cooling surface and as a thermostat.
The thermostats used at thirty degrees were suffici-
ently sensitive, when used in the baths made to conform
with the above principle, to maintain a constant tempera-
ture to within one-one-hundredth of a degree. This prin-
ciple is the last word in temperature regulation, for there
is a bath in this laboratory which will maintain a con-
stant temperature to within one-one-thousandths of a
degree. An especially sensitive thermostat is used.
The measurements of the osmotic pressures of levulose
solutions at thirty degrees were taken in the baths especi-
ally well suited for work at the higher temperatures.
They are made of heavy sheet brass. Each bath has an
outer shell and an inner compartment. Between these
two, water is kept in constant circulation in such a man-
ner and direction that it will first flow over a cooler sur-
face and then over a warmer surface of the bath. The
heating surface was provided for by a number of 60 watt
electric lamps in an equal number of compartments in-
serted within the water space. Each lamp, which serves
as a "stove," is under the control of a relay; the series of
relays is controlled by a master relay, which in turn is
controlled by the thermostat which is placed in the circu-
lating water and near the top of the bath. Sparking in
the thermostat and relays is prevented by introducing a
shunt of high resistance at the proper places.
The entrance to the inner bath is closed by (1) a plate
glass door and (2) a hollow, metal door in two sections,
the lower half of which is only opened when it is neces-
sary to introduce or remove cells. A space of 40 milli-
meters, between the doors, is occupied by (1) a metal
shield carrying on its upper half, a dozen smaller metal
18
Description of Apparatus.
strips or doors, anyone of which may be opened inde-
pendently of the others for the purpose of reading the
manometer.
The heat derived from the 60 watt lamps was sufficient
to keep the baths at thirty degrees. In the work at
higher temperatures, the gas burners beneath the bath
are put into use. However, the elevated temperature,
secured by means of these burners are kept a little lower
than the temperature at which the bath is maintained.
The difference or "temperature margin" is cared for by
the lamps under the control of the thermostat.
Measurements.
19
IV. MEASUREMENTS.
TABLE I.
0.1 Wt. normal solution. Expt. 1 at 30°; Cell D,. Re-
sistance, 35,400 ohms. Manometer 27. Calc. gas pres-
sure, 2.472 atms. Time of setting up cell Feb. 1, 1916.
Barometer during final record: max., 1.011; min., 0.984.
Total daily pressures:
Final Record.
Atms
Atms
Feb. 11. 3.554
Feb. 15, 3.537
Feb. 12, 3.540
Feb. 16, 3.537
Feb. 13, 3.517
Feb. 17, 3.534
Feb. 14, 3.517
Feb. 18, 3.519
(8 days)
3.532 atms
.1.002 atms
Mean total pressure Feb. 11, Feb. 18...
Mean barom. pressure Feb. 11, Feb. 18.
Mean osmotic pressure Feb. 11, Feb. 18 .....2.529 atms
TABLE II.
0.1 Wt. normal solution. Expt. 2 at 30°. Cell L. Re-
sistance 24,400 ohms. Manometer 27. Calc. gas pres-
sure, 2.472 atms. Time of setting up cell, Feb. 18, 1916.
Barometer during final record: max., 1.004; min., 0.972.
Total daily pressures:
Final Record.
Atms
Atms
Feb. 24, 3.523
Mar. 2, 3.489
Feb. 25, 3.505
Mar. 3, 3.480
Feb. 26, 3.494
1
Mar. 4, 3.476
Feb. 27, 3.483
Mar. 5, 3.473
Feb. 28, 3.486
Mar. 6. 3.481
Feb. 29, 3.492
Mar. 1, 3.497
Mean total pressure Feb. 24-Mar. 7
Mean barom. pressure Feb. 24-Mar. 7
Mean osmotic pressure Feb. 24-Mar. 7
Mar. 7, 3.487
(13 days)
3.489 atms
..0.991 atms
2.499 atms
20
Measurements.
TABLE III.
0.2 Wt. normal solution. Expt. 1 at 30°. Cell I,. Re-
sistance 23,400 ohms. Manometer 24. Calc. gas pres-
sure, 4.943 atms. Time of setting up cell, Feb. 10. 1916.
Barometer during final record: max., 1.012; min., 0.990.
Total daily pressures:
Final Record.
Atms
Feb. 16, 6.081
Feb. 17, 6.072
Feb. 18, 6.058
Atms
Feb. 19, 6.051
Feb. 20. 6.051
Feb. 21, 6.051
Mean total pressure Feb. 16-Feb.21
Mean barom. pressure Feb. 16-Feb. 21
(6 days)
.6.060 atms
..0.995 atms
Mean osmotic pressure Feb. 16-Feb. 21 .....5.065 atms
•
TABLE IV.
0.2 Wt. normal solution. Expt. 2 at 30°. Cell K,. Re-
sistance 25,000 ohms. Manometer 6. Calc. gas pressure
4.943 atms. Time of setting up cell, Feb. 10, 1916. Ba-
rometer during final record: max., 1.016; min., 0.984.
Total daily pressures:
Final Record.
Atms
Feb. 14, 6.044
Feb. 15, 6.043
Feb. 16, 6.040
Atms
Feb. 18, 6.023
Feb. 19, 6.019
Feb. 20, 6.002
Feb. 17, 6.035
Feb. 21, 6.017
(8 days)
Mean total pressure Feb. 14-Feb. 21
Mean barom. pressure Feb. 14-Feb. 21
Mean osmotic pressure Feb. 14-Feb. 21
..6.028 atms
.1.000 atms
..5.027 atms
Measurements.
TABLE V.
21
0.2 Wt. normal solution. Expt. 3 at 30°. Cell R15.
Resistance 78,500 ohms. Manometer 24. Calc. gas pres-
sure 4.943 atms. Time of setting up cell, Jan. 28, 1916.
Barometer during final record: max., 1.018; min., 0.994.
Total daily pressures:
Final Record.
Atms
Feb. 3, 6.008
Feb. 4, 6.022
Feb. 5, 6.015
Feb. 6, 6.009
1
Atms
Feb. 7, 6.029
Feb. 8, 6.022
Feb. 9, 6.030
Mean total pressure Feb. 3-Feb.10 .
Mean barom. pressure Feb. 3-Feb.10
Mean osmotic pressure Feb. 3-Feb. 10
Feb. 10, 6.028
•
(8 days)
6.021 atms
..1.006 atms
...5.014 atms
TABLE VI.
0.3 Wt. normal solution. Expt. 1 at 30°. Cell N.. Re-
sistance 30,600 ohms. Manometer 24.
Manometer 24. Calc. gas pres-
sure 7.415 atms. Time of setting up cell Jan. 13, 1916.
Barometer during final record: max., 1.015; min., 0.994.
Total daily pressures:
Final Record.
Atms
Jan. 15, 8.631
Jan. 16, 8.532
Jan. 17, 8.538
Jan. 18, 8.560
Atms
Jan. 19, 8.580
Jan. 20, 8.594
Jan. 21, 8.598
Mean total pressure Jan. 15-Jan21
Mean barom. pressure Jan. 15-Jan. 21.
Mean osmotic pressure Jan. 15-Jan.21
(7 days)
.8.576 atms
.1.007 atms
.7.569 atms
1
22
$
Measurements.
TABLE VII.
0.3 Wt. normal solution. Expt. 2 at 30°. Cell V,. Re-
sistance 47,000 ohms. Manometer 6. Calc. gas pressure
7.415 atms. Time of setting up cell, Jan. 13, 1916. Ba-
rometer during final record: max., 1.015; min., 0.997.
Total daily pressures:
Final Record.
Atms
Jan. 18, 8.509
Jan. 19, 8.564
Atms
Jan. 21, 8.598
Jan. 22, 8.594
Jan. 20, 8.590
Jan. 23, 8.512
Mean total pressure Jan. 18-Jan. 23
Mean barom. pressure Jan. 18-Jan. 23
Mean osmotic pressure Jan. 18-Jan. 23
•
(6 days)
..8.561 atms
.1.008 atms
..7.552 atms
TABLE VIII.
0.4 Wt. normal solution. Expt. 1 at 30°. Cell S,. Re-
sistance 29,000 ohms. Manometer 29. Calc. gas pres-
sure 9.886 atms. Time of setting up cell, Jan. 13, 1916.
Barometer during final record: max., 1.017; min., 0.997.
Total daily pressures:
Final Record.
Atms
Jan. 18, 11.014
Jan. 19, 11.034
Atms
Jan. 21, 11.020
Jan. 22, 11.024
Jan. 20, 11.030
Jan. 23, 11.031
Mean total pressure Jan. 18-Jan. 23
Mean. barom. pressure Jan. 18-Jan. 23
(6 days)
.11.025 atms
.. 1.009 atms
Mean osmotic pressure Jan. 18-Jan. 23 .....10.016 atms
Measurements.
TABLE IX.
23
0.4 Wt. normal solution. Expt. 2 at 30°. Cell R₁.
Resistance 91,600 ohms. Manometer (1). Calc. gas
pressure 9.886 atms. Time of setting up cell, Jan. 20,
1916. Barometer during final record: max., 1.016; min.,
0.999. Total daily pressures:
Final Record.
Atms
Jan. 27, 11.022
Jan. 28, 11.026
Jan. 29, 11.003
Atms
Jan. 31, 11.020
Feb. 1, 11.024
Feb. 2, 11.028
Jan. 30, 10.999
Mean total pressure Jan. 27-Feb. 2
Mean barom. pressure Jan. 27-Feb. 2
Mean osmotic pressure Jan. 27-Feb. 2
(7 days)
11.017 atms
1.006 atms
..10.011 atms
TABLE X.
0.5 Wt. normal solution. Expt. 1 at 30°.
Expt. 1 at 30°. Cell M,.
Resistance 47,800 ohms. Manometer 27. Calc. gas pres-
sure 12.358 atms. Time of setting up cell, Jan. 8, 1916.
Barometer during final record: max., 1.017; min., 0.997.
Total daily pressures:
Final Record.
Atms
Jan. 9, 13.736
Jan. 10, 13.676
Jan. 11, 13.676
•
Mean total pressure Jan. 9-Jan. 13
Mean barom. pressure Jan. 9-Jan. 13
Mean osmotic pressure Jan. 9-Jan. 13
Atms
Jan. 12, 13.677
Jan. 13, 13.681
(5 days)
.13.689 atms
1.004 atms
.12.685 atms
24
Measurements.
TABLE XI.
0.5 Wt. normal solution. Expt. 2 at 30°. Cell L..
Resistance 31,200 ohms. Manometer 24. Calc gas pres-
sure 12.358 atms. Time of setting up cell, Jan. 8, 1916.
Barometer during final record: max., 1.017; min., 0.997.
Total daily pressures:
Final Record.
Atms
Jan. 9, 13.695
Jan. 10, 13.655
Jan. 11, 13.628
•
Atms
Jan. 12, 13.628
Jan. 13, 13.617
Mean total pressure Jan. 9-Jan. 13
Mean barom. pressure Jan. 9-Jan. 13
Mean osmotic pressure Jan. 9-Jan. 13
(5 days)
13.644 atms
1.004 atms
..12.640 atms
+
TABLE XII.
0.5 Wt. normal solution. Expt. 3 at 30°. Cell Q,. Re-
sistance 55,000 ohms. Manometer 15. Calc gas pres-
sure 12.358 atms. Time of setting up cell, Jan. 13, 1916.
Barometer during final period: max., 1.015; min., 0.994.
Total daily pressures:
Final Record.
Atms
Jan. 15, 13.748
Jan. 16, 13.561
Atms
Jan. 18, 13.599
Jan. 19, 13.619
Jan. 17, 13.592
Jan. 20, 13.644
(6 days)
.13.628 atms
..... 1.007 atms
.....12.621 atms
Mean total pressure Jan. 15-Jan. 20
Mean barom. pressure Jan. 15-Jan. 20
Mean osmotic pressure Jan. 15-Jan. 20
Measurements.
TABLE XIII.
25
0.5 Wt. normal solution. Expt. 4 at 30°. Cell X,. Re-
sistance 55,000 ohms. Manometer 56. Calc. gas pres-
sure 12.358 atms. Time of setting up cell, Jan. 13, 1916.
Barometer during final record: max., 1.015; min., 0.994.
Total daily pressures:
Final Record.
Atms
Jan. 16, 13.549
Jan. 17, 13.509
Jan. 18, 13.524
Atms
Jan. 19, 13.530
Jan. 20, 13.475
Mean total pressure Jan. 16-Jan. 20
Mean barom. pressure Jan. 16-Jan. 20
Mean osmotic pressure Jan. 16-Jan. 20
(5 days)
.13.517 atms
... 1.005 atms
....12.512 atms
TABLE XIV.
0.6 Wt. normal solution. Expt. 1 at 30°. Cell A.. Re-
sistance 33,300 ohms. Manometer 29. Calc. gas pres-
sure 14.830 atms. Time of setting up cell, Jan. 6, 1916.
Barometer during final record: max., 1.018; min., 0.997.
Total daily pressures:
Final Record.
Atms
Atms
Jan. 8, 16.143
Jan. 9, 16.068
Jan. 11, 16.111
Jan. 12. 16.113
Jan. 10, 16.095
Jan. 13, 16.109
(6 days)
Mean total pressure Jan. 8-Jan. 13
Mean barom. pressure Jan. 8-Jan. 13.
16.104 atms
1.006 atms
Mean osmotic pressure Jan. 8-Jan. 13 .....15.098 atms
26
Measurements.
TABLE XV.
0.6 Wt. normal solution. Expt. 2 at 30°. Cell D,. Re-
sistance 34,300 ohms. Manometer (1). Calc. gas pres-
sure 14.830 atms. Time of setting up cell, Dec. 22, 1915.
Barometer during final record: max., 1.015; min., 0.987.
Total daily pressures:
Final Record.
Atms
Atms
Dec. 25, 15.985
Dec. 31,
16.082
Dec. 26, 16.053
Jan. 1, '16 16.061
Dec. 27, 16.078
Jan. 2,
16.104
Dec. 28, 16.104
Jan. 3,
16.100
Dec. 29, 15.998
Jan. 4.
4,
16.108
Dec. 30, 16.056
(11 days)
Mean total pressure Dec. 25, '15-Jan. 4, '16..16.066 atms
Mean barom. pressure Dec. 25, '15-Jan. 4, '16 0.998 atms
Mean osmotic pres. Dec. 24, '15-Jan. 4, '16 15.066 atms
TABLE XVI.
0.6 Wt. normal solution. Expt. 3 at 30°.
Expt. 3 at 30°. Cell S,. Re-
sistance 55,000 ohms. Manometer 27. Calc. gas pres-
sure 14.830 atms. Time of setting up cell, April 24, 1916.
Barometer during final record: max., 0.996; min., 0.992.
Total daily pressures:
Final Record.
Atms
May 1, 16.065
May 2, 16.048
May 3, 16.048
Atms
May 5, 16.048
May 5, 16.048
Mean total pressure May 1-May 5..
Mean barom. pressure May 1-May 5
Mean osmotic pressure May 1-May 5.
(5 days)
16.050 atms
.. 0.994 atms
....15.056 atms
Measurements.
TABLE XVII.
27
0.7 Wt. normal solution. Expt. 1 at 30°. Cell R. Re-
sistance 53,000 ohms. Manometer 6. Calc. gas pres-
sure 17.301 atms. Time of setting up cell, Dec. 20, 1915.
Barometer during final record: max., 1.015; min., 0.987.
Total daily pressures:
Final Record.
Atms
Atms
Dec. 24, 18.862
Dec. 30,
18.939
Dec. 25, 18.869
Dec. 31,
18.909
Dec. 26, 18.883
Jan. 1, '16 18.828
Dec. 27, 18.874
Jan. 2,
18.909
Dec. 28, 19.013
Jan. 3,
18.878
Dec. 29, 18.883
Jan. 4,
18.859
(12 days)
Mean total pressure Dec. 24, '15-Jan. 4, 16 ..18.817 atms
Mean barom. pressure Dec. 24, '15-Jan. 4, '16 0.998 atms
Mean osmotic pres. Dec. 24, '15-Jan. 4, '16 17.819 atms
TABLE XVIII.
0.7 Wt. normal solution. Expt. 2 at 30°. Cell B。. Re-
sistance 44,000 ohms. Manometer 6. Calc. gas pressure
17.301 atms. Time of setting up cell, Jan. 6, 1916. Ba-
rometer during final record: max., 1.018; min., 0.997.
Total daily pressures:
Final Record.
Atms
Jan. 7, 18.520
Jan. 8, 18.600
Jan. 9, 18.612
Atms
Jan. 11, 18.766
Jan. 12, 18.761
Jan. 10, 18.781
Jan. 13, 18.766
Mean total pressure, Jan. 7-Jan. 13
Mean barom. pressure Jan. 7-Jan. 13
Mean osmotic pressure, Jan. 7-Jan. 13
(7 days)
.18.686 atms
1.006 atms
.....17.679 atms
28
Measurements.
TABLE XIX.
0.7 Wt. normal solution. Expt. 3 at 30°. Cell R₂0.
Resistance 61,100 ohms. Manometer 53. Calc. gas pres-
sure 17.301 atms. Time of setting up cell, Dec. 20, 1915.
Barometer during final record: max., 1.015; min., 0.987.
Total daily pressures:
Final Record.
Atms
Atms
Dec. 22, 18.607
+
Dec. 29,
18.655
Dec. 23, 18.615
Dec. 30,
18.453
Dec. 24, 18.608
Dec. 31,
18.555
Dec. 25, 18.602
Jan. 1, '16 18.513
Dec. 26, 18.604
Jan. 2,
18.500
Dec. 27, 18.608
Jan. 3,
18.544
Dec. 28, 18.578
Jan. 4,
18.547
(14 days)
1
Mean total pressure Dec. 22, '15-Jan.4, '16 ..18.521 atms
Mean barom. pressure Dec. 22, '15-Jan. 4, '16 0.999 atms
Mean osmotic pres. Dec. 22, '15-Jan. 4, '16 17.562 atms
TABLE XX.
0.8 Wt. normal solution.
Resistance 137,500 ohms.
Expt. 1 at 30°. Cell R14.
Manometer 24. Calc. gas
pressure 19.773 atms. Time of setting up cell, Dec. 17,
Barometer during final record: max., 1.015; min.,
1915.
0.987. Total daily pressures:
Final Record.
Atms
Atms
Dec. 20, 21.424
Dec. 27,
21.344
Dec. 21, 21.381
Dec. 28,
21.362
Dec. 22, 21.265
Dec. 29,
21.234
Dec. 23, 21.265
Dec. 30,
21.221
Dec. 24, 21.226
Dec. 31,
21.439
Dec. 25, 21.353
Jan. 1, '16 21.205
Dec. 26, 21.300
Jan. 2,
21.186
(14 days)
Mean total pressure Dec. 20, '15-Jan. 2, '16 ..21.285 atms
Mean barom. pressure Dec. 20, '15-Jan. 2, '16 0.998 atms
Mean osmotic pres. Dec. 20, '15-Jan. 2, '16 20.301 atms
Measurements.
TABLE XXI.
29
0.8 Wt. normal solution. Expt. 2 at 30°. Cell R,. Re-
R₂.
sistance 91,600 ohms. Manometer 27. Calc. gas pres-
sure 19.773 atms. Time of setting up cell, Dec. 17, 1915.
Barometer during final record: max., 1.015; min., 0.978.
Total daily pressures:
Final Record.
Atms
Atms
Dec. 20, 21.172
Dec. 27,
21.261
Dec. 21, 21,172
Dec. 28,
21.164
Dec. 22, 21.202
Dec. 29,
21.098
Dec. 23, 21.208
Dec. 30,
21.196
Dec. 24, 21.237
Dec. 31,
21.125
Dec. 25, 21.237
Jan. 1, '16 21.050
Dec. 26, 21.237
Jan. 2, 21.073
(14 days)
Mean total pressure Dec. 20, '15-Jan. 2, '16 21.174 atms
Mean barom. pressure Dec. 20, '15-Jan. 2, '16 0.999 atms
Mean osmotic pres. Dec. 20, '15-Jan. 2, '16 20.176 atms
TABLE XXII.
0.8 Wt. normal solution. Expt. 3 at 30°. Cell B。. Re-
sistance 50,000 ohms. Manometer 5. Calc. gas pres-
sure 19.773 atms. Time of setting up cell Dec. 14, 1915.
Barometer during final record: max., 1.007; min., 0.975.
Total daily pressures:
Final Record.
Atms
Atms
Dec. 15, 20.959
Dec. 19, 21.044
Dec. 16, 21.025
Dec. 20, 21.187
Dec. 17, 21.072
Dec. 21, 21.199
Dec. 18, 21.149
Dec. 22, 21.255
Mean total pressure Dec. 15-Dec. 22
Mean barom. pressure Dec. 15-Dec. 22
(8 days)
.21.111 atms
..... 0.999 atms
Mean osmotic pressure Dec. 15-Dec. 22.....20.111 atms
30
Measurements.
TABLE XXIII.
0.8 Wt. normal solution. Expt. 4 at 30°. Cell R. Re-
sistance 157,000 ohms. Manometer 29. Calc. gas pres-
sure 19.773 atms. Time of setting up cell, Dec. 17, 1915.
Barometer during final record: max., 1.007; min., 0.995.
Total daily pressures:
Final Record.
Atms
Dec. 20, 21.222
Dec. 21, 20.998
Dec. 22, 21.042
Dec. 23, 21.050
Dec. 24, 21.057
Atms
Dec. 25, 21.054
Dec. 26, 20.927
Dec. 27, 20.994
Dec. 28, 21.034
(9 days)
Mean total pressure Dec. 20-Dec. 28 .......21.042 atms
Mean barom. pressure Dec. 20-Dec. 28 ... 1.000 atms
Mean osmotic pressure Dec. 20-Dec. 28.....20.042 atms
TABLE XXIV.
0.8 Wt. normal solution. Expt. 5 at 30°. Cell R₁g•
Resistance 84,000 ohms. Manometer 39. Calc. gas pres-
sure 19.773 atms. Time of setting up cell, Dec. 14, 1915.
Barometer during final record: max., 1.007; min., 0.975.
Total daily pressures:
Final Record.
Atms
Dec. 16, 21.546
Dec. 17, 21.086
Dec. 18, 20.908
Atms
Dec. 20, 20.940
Dec. 21, 20.926
Dec. 22, 20.959
Dec. 19, 20.808
Mean total pressure Dec. 16-Dec. 22
Mean barom. pressure Dec. 16-Dec. 22
(7 days)
.21.024 atms
..... 0.999 atms
Mean osmotic pressure Dec. 16-Dec. 22.....20.025 atms
Measurements.
TABLE XXV.
31
0.9 Wt. normal solution. Expt. 1 at 30°. Cell B。. Re-
sistance 61,100 ohms. Manometer 6. Calc. gas pres-
sure 22.244 atms. Time of setting up cell, Dec. 2, 1915.
Barometer during final record: max., 1.007; min., 0.983.
Total daily pressures:
Final Record.
Atms
Dec. 4, 23.800
Dec. 5, 23.887
Dec. 6, 23.899
Atms
Dec. 7, 23.854
Dec. 8, 23.810
Mean total pressure Dec. 4-Dec. 9
Mean barom. pressure Dec. 4-Dec. 9
Mean osmotic pressure Dec. 4-Dec. 9
Dec. 9, 23.799
(6 days)
.23.841 atms
. 0.998 atms
.....22.842 atms
TABLE XXVI.
0.9 Wt. normal solution. Expt. 2 at 30°. Cell G,. Re-
sistance 91,600 ohms. Manometer 27. Calc. gas pres-
sure 22.244 atms. Time of setting up cell, Dec. 7, 1915.
Barometer during final record: max., 1.004; min., 0.983.
Total daily pressures:
Final Record.
Atms
Dec. 8, 23.772
Dec. 9, 23.846
Dec. 10, 23.825
Dec. 11, 23.938
Atms
Dec. 13, 23.825
Dec. 14, 23.863
Dec. 15, 23.863
Dec. 16, 23.833
Dec. 12, 23.818
Mean total pressure Dec. 8-Dec. 16
Mean barom. pressure Dec. 8-Dec. 16
(9 days)
23.840 atms
... 0.995 atms
Mean osmotic pressure Dec. 8-Dec. 16......22.845 atms
32
Measurements.
TABLE XXVII.
0.9 Wt. normal solution. Expt. 3 at 30°. Cell R¸. Re-
sistance 137,100 ohms. Manometer 24. Calc. gas pres-
sure 22.244 atms. Time of setting up cell, Dec. 7, 1915.
Barometer during final record: max., 1.004; min., 0.989.
Total daily pressures:
Final Record.
Atms
Dec. 13, 23.814
Dec. 14, 23.820
Atms
Dec. 16, 23.813
Dec. 17, 23.770
Dec. 15, 23.835
Mean total pressure Dec. 13-Dec. 17
Mean barom. pressure Dec. 13-Dec. 17
(5 days)
23.810 atms
0.996 atms
Mean osmotic pressure Dec. 13-Dec. 17 ....22.814 atms
TABLE XXVIII.
1.0 Wt. normal solution. Expt. 1 at 30°. Cell R. Re-
sistance 183,300 ohms. Manometer 6. Calc. gas pres-
sure 24.716 atms. Time of setting up cell, Dec. 10, 1915.
Barometer during final record: max., 1.006; min., 0.975.
Total daily pressures:
Final Record.
Atms
Dec. 15, 26.301
Dec. 16, 26.327
Dec. 17, 26.327
Atms
Dec. 18, 26.287
Dec. 19, 26.394
Dec. 20, 26.354
(6 days)
Mean total pressure, Dec. 15-Dec. 20.......26.333 atms
Mean barom. pressure Dec. 15-Dec. 20 ..... 0.997 atms
Mean osmotic pressure Dec. 15-Dec. 20 .25.336 atms
Measurements.
TABLE XXIX.
33
1.0 Wt. normal solution. Expt. 2 at 30°. Cell R20. Re-
sistance 54,800 ohms. Manometer 39. Calc. gas pres-
sure 24.716 atms. Time of setting up cell, Dec. 6, 1915.
Barometer during final record: max., 1.004; min., 0.983.
Total daily pressures:
Final Record.
Atms
Dec. 8, 26.289
Dec. 9, 26.185
Dec. 10, 26.169
Dec. 11, 26.272
Mean total pressure Dec. 8-Dec. 14
Atms
Dec. 12, 26.186
Dec. 13,26.261
Dec. 14, 26.249
•
(7 days)
..26.226 atms
0.993 atms
Mean barom. pressure Dec. 8-Dec. 14
Mean osmotic pressure Dec. 8-Dec. 14 .....25.233 atms
TABLE XXX.
1.0 Wt. normal solution. Expt. 3 at 30°. Cell R12.
Resistance 78,500 ohms. Manometer 53. Calc. gas pres-
sure 24.716 atms. Time of setting up cell, Nov. 24, 1915.
Barometer during final record: max., 1.008; min., 0.989.
Total daily pressures:
Final Record.
Atms
Nov. 26, 25.288
Nov. 27, 26.211
Atms
Nov. 29, 26.145
Nov. 30, 26.167
Dec. 1, 26.197
Nov. 28, 26.081
Mean total pressure Nov. 26-Dec. 1
Mean barm. pressure Nov. 26-Dec. 1
(6 days)
.26.181 atms
0.998 atms
Mean osmotic pressure Nov. 26-Dec. 1 .....25.183 atms
1
34
Measurements.
TABLE XXXI.
1.0 Wt. normal solution. Expt. 4 at 30°. Cell R₁. Re-
sistance 100,000 ohms. Manometer 53. Calc. gas pres-
sure 24.716 atms. Time of setting up cell, Dec. 10, 1915.
Barometer during final record: max., 1.006; min., 0.975.
Total daily pressures:
Final Record.
Atms
Dec. 13, 26.040
Dec. 14, 26.065
Dec. 15, 26.050
Atms
Dec. 17, 26.090
Dec. 18, 26.098
Dec. 16, 26.073
Dec. 19, 26.171
Dec. 20, 26.150
(8 days)
.......26.092 atms
..... 0.995 atms
.....25.097 atms
Mean total pressure Dec. 13-Dec. 20
Mean barom. pressure Dec. 13-Dec. 20
Mean osmotic pressure Dec. 13-Dec. 20
Measurements.
35
TABLE XXXII.
Sol.
No.
ity
Weight Osmotic Calc gas Ration of Av. Ratio Deviation
Normal- Pressure Pressures O. P. to for each
C. G. P.
from av.
conc.
ratio for
all conc.
(1.019)
(1)
0.1
2.529
2.472 1.022
(2)
0.1
2.499
2.472
1.011 1.016
- .003
(3) 0.2
5.065
4.943
1,024
(4)
0.2
5.027
4.943 1.017
(5) 0.2
5.014
4.943
1.014
1.018
- .001
(6)
0.3
7.569
7.415
1.020
(7)
0.3 7.552
(8) 0.4 10.016
(9) 0.4 10.011
(10) 0.5 12.685
(11) 0.5 12.640
7.415 1.018 1.019
±.000
9.886
1.013
9.886
12.358 1.026
12.358 1.022
1.012 1.012
.007
(12) 0.5 12.621
12.358
1.021
24
(13) 0.5 12.512
12.358
1.012
1.02 +.001
(14) 0.6 15.098
14.830
1.018
(15) 0.6 15.067
14.830
1.015
(16) 0.6 15.056
14.830
1.015 1.016
- .003
(17) 0.7 17.819
17.301
1.034
(18) 0.7 17.679
17.301
1.021
(19) 0.7 17.562
17.301
1.014 1.023
+.004
(20) 0.8 20.301
19.773
1.026
(21) 0.8 20.176
(22) 0.8 20.112
19.773 1.020
19.773 1.015
(23) 0.8 20.042
19.773
1.014
(24) 0.8 20.025
19.773
1.011 1.017
- .002
(25) 0.9
22.842
22.244
1.027
(26) 0.9 22.845
22.244
1.027
(27) 0.9 22.814
22.244
1.025 1.026
+.007
(28) 1.0 25.336
24.716
1.025
24.716 1.021
24.716 1.018
(29) 1.0 25.233
(30) 1.0 25.183
(31) 1.0 25.097 24.716
1.016 1.020 +.001
Av. Ratio for all concentrations 1.019.
36
Discussion of Tables.
V. DISCUSSION OF TABLES.
Tables I to XXXI, inclusive, give a rather detailed ac-
count of the pressures developed in the cells after equi-
librium was reached; in other words, after the final
record was begun.
Table XXXII gives a summary of the osmotic pressures
developed by the various concentrations of levulose solu-
tions in the cells, and a comparison of these pressures
with the theoretical gas pressures, which are calculated
from the equation Pv Kt in which v is the volume of
the pure solvent at its maximum density.
It will be seen that the osmotic pressures are excessive,
i. e., they give a ratio with the theoretical gas pressures
which is greater than unity. This excessive pressure
would suggest that the solutions may have become con-
centrated before the final record was begun.
There are at least two ways in which the solutions
could have become concentrated to a slight degree:
(1) If a cell is "set up" at a temperature a little lower
than the temperature of the bath in which the measure-
ments are made, a well-known "thermometer effect" will
be noted. The cell contents and the liquids in the ma-
nometer upon expanding at this higher temperature, may
force some of the solvent through the membrane, thus
concentrating the enclosed solution.
(2) It is believed that certain sugars are capable of
uniting with part of the solvent to form hydrates, especi-
ally at the lower temperatures. Past experience in meas-
uring the osmotic pressures of cane sugar over wide
ranges of temperature, goes to prove the presence of hy-
drates at the lower temperatures. A concentration will
necessarily follow a union of the solvent molecules with
those of the solute.
The first explanation is untenable for special precau-
tions were taken to exert the initial mechanical pressure
quickly, and to keep the whole system at thirty degrees
Discussion of Tables.
37
in the process of setting up. The depositing bath served
for the latter purpose. The second explanation seems to
be more nearly correct. It is believed that the excessive
pressures, in the case of levulose solutions at thirty de-
grees, are due to the existence of hydrates in solution.
In almost every instance the solution which was taken
from the cell showed a loss in rotation. At first sight
this would appear to be due to dilution in the cell, brought
about by imperfections in the membrane. Such a dilu-
tion has always characterized a low pressure. However,
the greatest loss in rotation occurred in solutions which
gave the higher pressures. Four cases will serve to show
this strange behavior.
Sol. No.
Ratio of O. P.
to C. G. P.
Loss in rotation
(12)
1.022
-1.5 degrees
(17)
1.034
-0.7 degrees
1.027
-3.0 degrees
1.021
-3.1 degrees
(25)
(29)
The statement has been made on another page that a
fungus, a strain of penicillium glancum, creates much
mischief in osmotic pressure work, by attacking the mem-
branes. The measurements of levulose solutions were
made at a time when the cells were known to be slightly
infected by this pest. The solutions, when taken from
the cells were of a greenish blue color and solid matter of
the same color was found in suspension. In this way the
presence of the pest was detected for it is known by ex-
periment²¹ that a growth of penicillium will give this
coloration to a sugar solution in which there is placed
some membrane material.
Immediately, every effort was made to suppress and
destroy the pest by the usual and best method22 that of
soaking the cells in a saturated solution of thymol. The
pest was never quite eradicated. However, after the
21 Ibid., p. 95.
22 Statements regarding penicillium and the methods of com-
bating it will be found in the Monograph, pp. 94-95.
38
Discussion of Tables.
cells were treated in this way, the solutions which were
taken from them were clearer and more transparent.
Although no special harm seemed to come to the mem-
branes at this time, it is believed that the energies of the
penicillium were directed against the sugar solutions and
that the solute molecules were broken down into smaller
or part molecules.
This tentative conclusion, the result of a careful con-
sideration of the observed phenomena, serves to explain
the loss in rotation of a solution whose pressure has been
excessive. Furthermore, it led to believe that we could
not justly correct the observed osmotic pressures for the
seeming "dilution" as shown by the loss in rotation. These
measurements would, in all probability, have more au-
thority, if the penicillium had not been present and if the
solutions had shown no loss in rotation.
1
Conclusion.
39
VI. CONCLUSIONS.
The ratios of the osmotic pressures of levulose solu-
tions at thirty degrees, to the theoretical gas pressures
are fairly constant for the ten concentrations between
and including 0.1N and 1.0N.
The excessive pressures are due without a doubt to the
existence of hydrates in the solution at this temperature.
This view is supported by the fact that cane sugar solu-
tions exhibit like phenomena at this temperature.
The conclusion is further supported by the work per-
formed in this laboratory by Mr. C. C. Minter, upon the
freezing point lowerings of levulose solutions of the above
concentrations. He found the average of the molecular
lowerings to be 1°.92. This abnormal value seems to
prove23 that such solutions contain hydrates at the freez-
ing point. It is believed that these hydrates are not
broken down at thirty degrees.
23 Elements of Physical Chemistry, H. C. Jones, p. 237.
40
Biography.
VII. BIOGRAPHY.
{
John Milton Blocher, Jr., was born February 24, 1891,
in Gettysburg, Pa. He received his early education in
the public schools of that place, graduating from the
High School in 1908, after having completed a commercial
course of study. He received his preparation for col-
lege in the Gettysburg Academy during the school year
1908-1909. He graduated from Pennsylvania College,
Gettysburg, receiving the degree of Bachelor of Science
in 1913. In the fall of 1913 he entered the Johns Hop-
kins University, taking Chemistry as his major subject;
and Physical Chemistry and Mineralogy as his first and
second minors respectively. He assisted Dr. Gilpin in
the undergraduate laboratories during the school year
1914-1915.
fical Librant
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