conducted by the method of Hilgard, depends largely for its practical
value on an intelligible tabulation. The method of collating results is
illustrated in the table of analyses of Mississippi soils shown on page
237.
The character of the soils entering into the given analyses is as
follows:
Nos. 248, 206, 209, 397, 219, belong to the end of the drift period.
No. 230 is one of the two chief varieties of soils occurring in what is
known as the flat-woods, a level surface bordering on the cretaceous
area, having lower tertiary clays near the surface.
No. 165 is a light soil which occurs in the former in irregular strips
and patches, is easily tilled, absorbs rain water readily, but is
subject to drought and does not hold manure.
SILT ANALYSES OF MISSISSIPPI SOILS AND SUBSOILS.
──┬─────────────┬────────────┬───────────┬──────────
│ Designation │ Diameter. │ Velocity │ DRIFT
│of Materials.│Millimeters.│(Hydraulic │
│ │ │ value). │
│ │ │Millimeters│
│ │ │per second.│
──┼─────────────┼────────────┼───────────┼──────────
│ „ │ „ │ „ │ „
──┼─────────────┼────────────┼───────────┼──────────
│ „ │ „ │ „ │ „
──┼─────────────┼────────────┼───────────┼──────────
│ „ │ „ │ „ │ 238
│ │ │ │ White
│ │ │ │pipeclay.
│ │ │ │Tishomingo
│ │ │ │ Co.
│ │ │ │
──┼─────────────┼────────────┼───────────┼──────────
1│Coarse grits │ 1.0 to 3.0│ │
2│Fine „ │ 0.5 to 1.0│ │
3│Coarse sand │ 0.40│ 6│ 0.06
4│Medium „ │ 0.30│ 32│ „
5│Fine „ │ 0.16│ 16│ „
6│Finest „ │ 0.12│ 8│ 0.08
7│Dust „ │ 0.072│ 4│ 0.02
8│Coarsest silt│ 0.047│ 2│ 0.04
9│Coarse „ │ 0.036│ 1│ 0.08
10│Medium „ │ 0.025│ 0.5│ 0.08
11│Fine „ │ 0.015│ 0.25│ 2.00
12│Finest „ │ 0.008│ <0.25│ 21.15
13│Clay │ 0.0001│ <0.0023│ 74.65
──┴─────────────┴────────────┴───────────┼──────────
│ 98.16
Compactness (resistance to tillage) │ 97.80
Porosity │ 0.36
Hygroscopic Moisture (+7° to +21°) │ 9.09
Ferric Oxide │ 0.13
─────────────────────────────────────────┴──────────
──┬─────────────┬─────────────────────────────────────────────────────
│ Designation │ UPLAND.
│of Materials.│
│ │
│ │
│ │
──┼─────────────┼─────────────────────────────────────────────────────
│ „ │ YELLOW LOAM.
──┼─────────────┼─────────────────────────┬───────────────────────────
│ „ │ SANDY. │ LOAM.
──┼─────────────┼─────────┬─────────┬─────┼────────┬─────────┬────────
│ „ │ 248 │ 165 │ 206 │ 209 │ 397 │ 219
│ │Tallahoma│ Lt. │Pine │ Pine │ Oxford │ Table
│ │ subsoil │Flatwoods│Hill │ Hill │subsoil. │ Land
│ │ Jasper │ soil. │soil.│subsoil.│Lafayette│subsoil.
│ │ Co. │Chickasaw│Smith│ Smith │ Co. │ Benton
│ │ │ Co. │ Co. │ Co. │ │ Co.
──┼─────────────┼─────────┼─────────┼─────┼────────┼─────────┼────────
1│Coarse grits │ 6.94│ 2.90│ 0.36│ 0.36│ │ 0.23
2│Fine „ │ 17.65│ 6.96│ 2.98│ 0.83│ │ „
3│Coarse sand │ 18.81│ 2.81│ 6.62│ 6.21│ 0.79│ 1.47
4│Medium „ │ 10.16│ 4.41│ 7.75│ 3.38│ „ │ 2.33
5│Fine „ │ 2.66│ 3.13│ 3.01│ 3.85│ „ │ 1.17
6│Finest „ │ 1.66│ 2.02│ 1.59│ 1.49│ 0.18│ 0.78
7│Dust „ │ 1.02│ 2.23│ 1.19│ 0.64│ 0.78│ 0.76
8│Coarsest silt│ 0.88│ 5.06│ 3.56│ 2.63│ 3.56│ 9.79
9│Coarse „ │ 1.96│ 9.67│ 6.50│ 5.40│ 13.12│ 7.26
10│Medium „ │ 7.89│ 14.18│13.97│ 7.77│ 16.64│ 13.14
11│Fine „ │ 8.40│ 22.03│14.20│ 16.65│ 27.28│ 15.07
12│Finest „ │ 15.53│ 15.62│29.36│ 37.75│ 18.87│ 26.50
13│Clay │ 8.63│ 7.86│ 4.58│ 10.70│ 17.23│ 19.19
──┴─────────────┼─────────┼─────────┼─────┼────────┼─────────┼────────
│ 99.28│ 98.68│95.67│ 97.77│ 98.35│ 97.65
Compactness (res│ 32.56│ 45.33│48.14│ 45.10│ 63.38│ 60.82
Porosity │ 59.55│ 40.40│37.89│ 47.13│ 20.23│ 26.04
Hygroscopic Mois│ 1.80│ 3.36│ 2.48│ 7.69│ 8.79│ 7.21
Ferric Oxide │ 1.10│ 1.45[G]│ 1.25│ 4.15│ 2.53│ 5.11
────────────────┴─────────┴─────────┴─────┴────────┴─────────┴────────
──┬─────────────┬────────────────────────────────────
│ Designation │ UPLAND.
│of Materials.│
│ │
│ │
│ │
──┼─────────────┼────────┬───────────────────────────
│ „ │ YELLOW │ TERTIARY.
│ │ LOAM. │
──┼─────────────┼────────┴───────────────────────────
│ „ │ CLAY.
──┼─────────────┼────────┬─────────┬────────┬────────
│ „ │ 173 │ 230 │ 246 │ 196
│ │Prairie │ High │ Red │ Hog
│ │subsoil.│Flatwoods│ Hills │ Wallow
│ │ Monroe │ soil. │subsoil.│subsoil.
│ │ Co. │Pontotoc │ Attala │ Jasper
│ │ │ Co. │ Co. │ Co.
──┼─────────────┼────────┼─────────┼────────┼────────
1│Coarse grits │ 2.10│ 0.33│ 1.97│ 0.83
2│Fine „ │ „ │ 0.35│ „ │ 1.19
3│Coarse sand │ 0.62│ │ 0.72│ 1.96
4│Medium „ │ „ │ │ 2.32│ 1.64
5│Fine „ │ „ │ │ 2.09│ 0.88
6│Finest „ │ 0.20│ 0.23│ 0.70│ 0.26
7│Dust „ │ 1.26│ 0.18│ 1.29│ 0.19
8│Coarsest silt│ 2.92│ 1.61│ 1.81│ 2.49
9│Coarse „ │ 7.36│ 2.66│ 3.60│ 3.67
10│Medium „ │ 8.81│ 9.13│ 2.73│ 5.39
11│Fine „ │ 7.85│ 26.64│ 13.30│ 10.31
12│Finest „ │ 35.22│ 32.35│ 25.33│ 24.18
13│Clay │ 33.16│ 25.48│ 40.25│ 47.03
──┴─────────────┼────────┼─────────┼────────┼────────
│ 99.50│ 97.87│ 96.11│ 100.00
Compactness (res│ 69.77│ 84.47│ 78.88│ 81.52
Porosity │ 17.04│ 6.40│ 39.18│ 10.12
Hygroscopic Mois│ 11.35│ 9.33│ 18.60│ 14.48
Ferric Oxide │ 5.42│ 5.90[G]│ 10.50│ 4.00
────────────────┴────────┴─────────┴────────┴────────
──┬─────────────┬────────────────────────────────────────────────────────────────────────
│ Designation │ MISSISSIPPI BOTTOM.
│of Materials.│
│ │
│ │
│ │
──┼─────────────┼───────────────────┬────────────────────────────────────────────────────
│ „ │ Champlain. │ MODERN.
──┼─────────────┼───────────────────┼──────────────────────────────┬─────────────────────
│ „ │ Swamp River. │ RIVER DEPOSIT. │ DELTA.
──┼─────────────┼─────────┬─────────┼────────────┬─────────┬───────┼──────────┬──────────
│ „ │ 390 │ 237 │ 365 │ 377 │ 395 │ Southwest│ Southwest
│ │Buckshot │ Loess. │Tallahatchie│Frontland│Dogwood│ Pass.│ mudlump.
│ │ soil. │Claiborne│soil. Panola│subsoil. │ ridge │Plaquemine│Plaquemine
│ │Issaquena│ Co. │ Co. │Sunflower│ soil. │ Par.│ Par.
│ │ Co. │ │ │ Co. │Coahoma│ │
│ │ │ │ │ │ Co. │ │
──┼─────────────┼─────────┼─────────┼────────────┼─────────┼───────┼──────────┼──────────
1│Coarse grits │ 0.09│ 0.24│ 0.09│ │ │ │
2│Fine „ │ 0.05│ „ │ „ │ │ │ │
3│Coarse sand │ │ 0.37│ 0.04│ 0.32│ 0.15│ 0.18│ 0.10
4│Medium „ │ 0.36│ 0.61│ 0.05│ „ │ │ „ │ „
5│Fine „ │ │ 0.93│ 0.21│ 2.97│ │ 0.47│ 5.02
6│Finest „ │ 0.31│ 1.65│ 1.30│ 2.41│ 3.74│ 7.03│ 3.68
7│Dust „ │ 0.27│ 1.95│ 2.68│ 16.90│ 21.49│ 12.38│ 5.34
8│Coarsest silt│ 1.56│ 14.25│ 9.38│ 19.79│ 21.83│ 13.27│ 10.09
9│Coarse „ │ 2.23│ 16.20│ 9.88│ 13.90│ 14.01│ 15.87│ 5.58
10│Medium „ │ 3.68│ 20.08│ 20.37│ 4.27│ 9.93│ 8.25│ 9.54
11│Fine „ │ 8.97│ 5.59│ 19.79│ 1.89│ 9.58│ 7.26│ 8.01
12│Finest „ │ 38.19│ 33.38│ 25.30│ 30.08│ 8.65│ 19.67│ 34.46
13│Clay │ 44.30│ 2.51│ 9.64│ 5.51│ 10.35│ 12.20│ 18.18
──┴─────────────┼─────────┼─────────┼────────────┼─────────┼───────┼──────────┼──────────
│ 100.01│ 97.74│ 98.73│ 98.04│ 99.72│ 96.58│ 100.00
Compactness (res│ 89.46│ 41.48│ 54.63│ 37.48│ 28.57│ 39.13│ 60.65
Porosity │ 4.87│ 38.44│ 23.63│ 58.25│ 61.50│ 49.20│ 28.81
Hygroscopic Mois│ 14.31│ 4.18│ 6.12│ 5.68│ 3.95│ │
Ferric Oxide │ 5.82[G]│ 3.27│ 2.58│ 2.31│ 2.69│ │
────────────────┴─────────┴─────────┴────────────┴─────────┴───────┴──────────┴──────────
Footnote G:
Bog ore.
No. 248 is from a soil stratum three feet thick. The soil is so light
that the finer particles of it are carried away by high winds.
Nos. 206 and 209 are typical of the soils producing the long-leaf pine.
This soil is much improved by an admixture of the subsoil No. 209, which
enables it to hold manure.
No. 219 is a cotton upland soil of the best quality, found in Western
Mississippi and Tennessee.
No. 397 is the same soil of a second rate quality. These lands are
easily washed into gullies on account of their lack of perviousness to
water. They also easily swell up in contact with water, and become
thereby readily diffused. The denudations produced by heavy rains are
rapidly destroying the lands covered by these soils.
No. 173 is a sedimentary or residual subsoil of the cretaceous prairies
of Northeastern Mississippi, forming a stratum from three to seven feet
thick.
No. 230 is a residual soil which is formed by the disintegration of the
old tertiary clays. It yields good crops only in very favorable years,
and is easily injured both by wet and dry seasons.
No. 246 is a soil of the same origin, but is more easily tilled than the
foregoing, does not crack, but becomes very hard when dried slowly. Its
superiority to the former soil as regards tillage consists in the
presence of the large amount of iron and lime.
No. 196 is a typical heavy clay soil; is better suited for the potter
than the farmer. It cracks on drying, whence its popular name. On the
accession of rain the edges of these cracks crumble and fall, until
finally the lumpy surface is produced which is locally known as hog
wallows.
No. 390, the richest soil of the Yazoo Bottom, seems to have a physical
composition like the preceding one. Its superiority is due not only to
the increased quantity of plant food which it contains, but to its
property of crumbling on rapid drying. Even when plowed wet, on drying
each clod crumbles into a loose pile resembling buck-shot; whence its
name. It is strongly calcareous.
As comparative data, are added the soils 365, 377, and 395, representing
alluvial deposits, and two deposits from the Delta of the Mississippi.
=235. Comparison of Osborne’s Method with Hilgard’s Method.=[154]—The
comparative results obtained by Osborne’s method, beaker elutriation,
and Hilgard’s method, churn elutriation, are given in the following
tables:
SOIL FROM EXPERIMENT STATION GARDEN, NEW HAVEN, CONN.
SURFACE SOIL, BOILED TWENTY-THREE HOURS.
Beaker
elutriation.
Average of
four
Churn elutriation. analyses.
Diameter in
millimeters. per cent. per cent. per cent.
Removed by sieves 47.77 47.77 47.77
0.25–0.05 22.06 21.95 20.75
0.05–0.01 11.20 11.62 11.18
<0.01 9.82 9.14 10.72
Clay (difference) 2.32 2.69 2.75
Loss on ignition 6.83 6.83 6.83
—————— —————— ——————
100.00 100.00 100.00
SUBSOIL, BOILED TWENTY-THREE HOURS.
Churn elutriation. Beaker elutriation.
Diameter in
millimeters. per cent. per cent. per cent. per cent.
Removed by sieve 39.33 39.33 39.33 39.33
0.25–0.05 33.61 30.83 32.35 32.95
0.05–0.01 10.91 12.25 10.32 10.37
<0.01 7.05 8.11 8.29 7.64
Clay 5.02 5.40 5.63 5.63
Loss on ignition 4.08 4.08 4.08 4.08
—————— —————— —————— ——————
100.00 100.00 100.00 100.00
These analyses agree quite as well as could be expected from two such
different methods.
_Elutriation of Clayey Soils._—Hilgard found that by churn elutriation
no satisfactory results could be obtained on clay without long boiling
and subsequent kneading of the finer sediments. Osborne examined a
sample of clay by his method after previous boiling for twenty-three
hours. When the sediments were examined by the microscope they were
found to contain many aggregations of particles which broke into dust
under the pressure of the thin glass slide-cover. These sediments were
then gently crushed in the beaker with the help of a soft rubber stopper
with a glass rod for a handle, the grinding together of the particles
being, as much as possible, avoided. This pestling was continued with
clear water as long as it occasioned turbidity. Comparison of the
analyses shows that practically identical results were obtained on this
soil whether it was boiled or not and indicates that the sediments are
reduced to their elements by gentle pestling alone. For such soils,
therefore, it is demonstrated that pestling is a much safer treatment
than boiling. The same remark may be applied to the fertile prairie soil
of Mercer County, Illinois, where boiling proved quite insufficient and
in which the pestling process proved completely successful. The general
conclusions arrived at from the results obtained by Osborne are as
follows:
1. On sands and silts of pure quartz or similar resistant material
Hilgard’s method and beaker elutriation give practically identical
results.
2. With coarse sands and silts upon whose grains finer matter has been
cemented by silicates, etc., and with soils containing soft slaty
detritus, the churn elutriator with preliminary boiling may give results
too low for the coarse and too high for the finer grades. In these cases
beaker elutriation with pestling yields more correct figures.
3. Some loamy soils containing no large amount of clay or of extremely
fine silt, as well as prairie soils rich in humus, cannot be suitably
disintegrated by twenty-four hours’ boiling, but are readily reduced by
pestling.
4. Beaker elutriation preceded by sifting, gives results in five or six
hours with use of two to three gallons of pure water, which, in churn
elutriation, require several days and consume eight to ten gallons of
pure water.
5. Hilgard found that practically 0.25 millimeter is about the lowest
velocity of water current per second available within reasonable limits
of time in his elutriator. Such a current carries over particles up to
0.015 millimeter diameter and hence the silts of less dimensions cannot
be conveniently separated by churn elutriation. In beaker elutriation
there is no difficulty in making good separations at 0.01 millimeter and
at 0.005 millimeter.
6. Beaker elutriation requires no tedious boiling or preliminary
treatment and with careful pestling of the sediments gives, we believe,
as nearly as possible, a good separation of adhering particles and at
every stage of the process carries with it, in the constant use of the
microscope, the means of testing the accuracy of its work and of
observing every visible peculiarity of the soil. It is not claimed that
pestling may not easily go too far, but in any case a good judgment may
be formed of its effects and of the extent to which it is desirable to
carry it.
7. In beaker elutriation the flocculation of particles occasions little
inconvenience and does not impair the accuracy of the results.
=236. Comparison of the Osborne with the Schloesing
Method.=—Schloesing’s method has been compared by Osborne[155] with the
beaker method of elutriation with the following results:
SCHLOESING’S METHOD.
Per cent.
Calcium carbonate 4.20
Sand 64.91
Clay 22.65
Humus none
Loss on ignition 6.60
BY THE DIRECT BEAKER METHOD.
Per cent.
Above 0.25 millimeter diameter 1.02
0.25–0.05 millimeter diameter 0.76
0.05–0.01 millimeter diameter 20.95
Below 0.01 millimeter diameter 71.01
Loss on ignition 6.60
It is seen by the above that there is little agreement between the
results of the two methods.
With the prairie soil from Mercer County, Ill., the following results
were obtained working on the original sample and the sand separated by
the Schloesing process:
SCHLOESING’S METHOD.
Per cent.
Calcium carbonate 0.88
Humus 1.57
Loss at 150° C. 4.42
Sand 82.86
Clay 7.86
—————
97.59
BEAKER METHOD.
Original
Schloesing’s sand. soil.
Dried at
150°C., Ignited, Ignited,
per cent. per cent. per cent.
Above 0.25 millimeter diameter 0.12 0.10 0.92
0.25–0.05 millimeter diameter 3.58 3.55 2.89
0.05–0.01 millimeter diameter 42.69 41.87 42.86
0.01–0 millimeter diameter 23.66 20.47 } 31.44
Clay 12.81 10.14 }
Clay 7.40
Loss on ignition 6.73 14.49
————— ————— ——————
82.86 82.86 100.00
Osborne says the above figures indicate that the treatment with acid has
disintegrated the particles of less than 0.01 millimeter diameter so
that one-third of this portion appears as clay, according to the Hilgard
method of estimating clay, which is the one employed.
As to the humus it may be noted that loss in the analysis by
Schloesing’s method; _viz._, 2.41 per cent, plus loss at 150° = 4.42 per
cent, plus humus found = 1.57 per cent, plus carbon dioxid (⁴⁴⁄₅₆ of
0.88 =) 0.69 per cent amounts to 9.09 per cent, while the loss on
ignition which represents humus, carbon dioxid and water is 14.49 Per
cent. The 5.40 per cent difference must evidently be, for the most part,
humus which has escaped estimation by the Schloesing method, having been
distributed among the sand and clay.
=237. The Mechanical Determination of Clay.=—Schloesing’s method for the
separation of the clay as stated by Osborne[156] is essentially one of
subsidence for twenty hours from a volume of from 200 to 250 cubic
centimeters of water, but of no specified height. Hilgard’s conventional
method requires the same time and a height of solution of 200
millimeters.
Such methods of separation assume, first, that most of the sand and,
second, that little of the clay shall settle within the fixed time. That
both of these assumptions are fallacious, the following experiments
show. The clay obtained by twenty hours subsidence from thirty grams of
brick clay is suspended in four liters of distilled water and allowed to
settle out completely, which requires several days. The water is then
decanted so as to remove all soluble matters, the jar again filled with
distilled water, and the clay and fine sand allowed to settle again for
several days. The upper three-quarters of the liquid are then decanted
and made up to a volume of four liters, and this is allowed to stand
several days, when a considerable sediment forms. A decantation is again
made as before. The operations are repeated until the clay water has
been so far freed from the clay as to become opalescent; then it first
ceases to deposit any appreciable sediment. A microscopic examination of
the several sediments thus collected shows them all to contain particles
of sand. It appears, therefore, that only after the liquid containing
the clay has become opalescent does it cease to deposit fine particles
of sand as well as of clay.
Furthermore, the character of the true clay itself is so changed under
certain conditions that it loses the property of remaining in prolonged
suspension in water.
A sample of clay which has been freed from particles of sand exceeding
0.005 millimeter diameter is suspended in water and precipitated from it
by freezing. It is then washed by decantation with alcohol and dried in
the air. A portion of this clay is shaken with water and allowed to
stand a few hours, during which time the greater part of it has settled.
After decanting the water and suspended clay and repeating this process
a few times, a very considerable part of the clay is left which will
subside completely through 100 millimeters in a few hours. After
standing under water for several months, only a small part of the clay
has regained the quality of prolonged suspension. It has been found,
however, that if this clay be pestled, this quality of prolonged
suspension is restored to it to a very considerable degree.
It is evident, therefore, that conventional methods depending on simple
subsidence can give no accurate results because the ever varying amounts
of finest sand and clay in different soils yield variable mixtures of
the two when subjected to any simple course of treatment by elutriation
and subsidence.
The method of persistent pestling and repeated subsidences and
decantations continued until no further separation can be effected,
although extremely tedious, is the only one which has so far yielded
even approximately good separations on any of the clayey soils examined
by Osborne.
A single subsidence of the clay water for twenty-four hours will free it
from all particles of sand having a diameter greater than 0.005
millimeter, but in many cases a considerable amount of finer sand will
remain in suspension for many hours or days.
On the other hand, the sediment formed during the twenty-four hours
subsidence will not be free from clay, as may be easily seen by
suspending it in water a second time and allowing it to stand again for
twenty-four hours. Both Hilgard and Schloesing direct attention to these
defects, but assume that they do not usually influence the results to a
sufficient extent to deprive them of value. In many cases this is
undoubtedly true, as, for example, in such soils as that from the garden
of the Experiment Station, at New Haven, in which there is but little
clay and fine sand; but in soils of the opposite character, as in the
North Haven brick clay where exact separations are most desirable, a
very considerable error is thus inevitably encountered.
=238. Effect of Boiling on the Texture of Clayey Soils.=—Most
investigators who have worked upon mechanical soil analysis advise
boiling with water in order to detach clay and sand from each other and
make a good separation of the several mechanical elements practicable or
possible. In general, however, the instructions as to the time and
manner of boiling are rather indefinite, and no definite research as to
the effects of this treatment has been undertaken.
The practice of Hilgard, to boil twenty-four hours or even longer in
case of adhesive clays, according to Osborne[157] appears to be
objectionable in view of the dehydration and change of physical
properties known to occur in case of many hydroxids, especially those of
iron and aluminum, which may be present in the soil. It is a familiar
fact that the hydroxids above named and many other amorphous substances
when precipitated from cold solutions are more bulky and less easily
washed upon a filter than when thrown down hot. It is also well known
that their properties are considerably changed by warming or boiling
with water. Heating with water to boiling for some hours or days
gradually converts the bulky brown-red ferric hydroxid, which when
precipitated cold and air-dried for eighteen days, contains thirty-eight
per cent of water, into a much denser, bright red substance containing
but two per cent of water. St. Gilles has also observed the partial
dehydration of aluminum hydroxid from Al₂O₃.5H₂O to Al₂O₃.2H₂O by
prolonged boiling.
The hydrate of silica and the highly hydrated silicates are most
probably affected in a similar manner, and if such be the case, boiling
would evidently change the constitution of clay in a very essential
degree.
The following experiments throw light on this subject:
Ten grams of North Haven brick clay were boiled continuously for nine
days with about 700 cubic centimeters of distilled water, in a glass
flask of one liter capacity and furnished with a reflux condenser.
Fifteen grams were boiled in the same manner for eight and one-half
days. When the boiling was concluded, the soil was found to have assumed
a granular condition, the clay and fine sand being collected into a mass
of small grains resembling coarse sand and settling rapidly. One portion
thus boiled was elutriated by the beaker method, the other by Hilgard’s.
The pestle was not used on either of those portions as it was desired to
determine simply the effect of prolonged boiling. The separations thus
accomplished are here compared with the elutriations of the same soil
boiled twenty-three hours and of the pestled but unboiled soil.
Hilgard elutriation. Beaker elutriation.
Not pestled. Not pestled. Not Pestled. Pestled.
Boiled Boiled eight
twenty-three Boiled nine and a half
hours, days, days. Not boiled.
Diameter of
particles. per cent. per cent. per cent. per cent.
By sieves 3.36 3.24 3.63 3.49
0.25–0.05 1.21 1.11 1.91 1.29
0.05–0.01 28.27 33.04 33.61 27.02
0.01–0 56.29 48.85 54.78 52.21
Clay 4.92 3.05 1.97 10.15
Loss on
ignition 5.95 5.95 5.95 5.95
—————— —————— —————— ——————
100.00 95.24 101.85 100.11
Here it is observed that the eight to nine days boiling diminished the
clay as determined by Hilgard’s conventional method by seven to eight
per cent, increasing the dust by two to three per cent, and the silt by
about six per cent.
Under the microscope small, rounded, opaque, brown granules were seen in
large numbers, which when pressed under the cover glass, broke up into a
multitude of very fine particles.
From these experiments it would appear to be conclusively proved that
too long boiling precipitates clay and thereby defeats the very object
of the operation.