Edwin Clarence Eckel.

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In most of the workable magnesite deposits noted below, however,
the first method of origin is the true explanation.

Distribution of magnesite deposits. — ^The magnesite deposits now
exploited on a sufficient scale to be of commercial interest occur in
Austria, Germany, Greece, Hungary, India, and the United States.
Workable deposits also occur in Canada, but as yet have not been suffi-
ciently opened up to determine their commerical importance.

Foreign localities. — ^The principal Austrian magnesite deposits are
near Mittendorf , in Styria, and near Tolsvar, in the province of Minsan,
Hungary. The Styrian magnesite averages about 88 per cent mag-
nesium carbonate with about 8 per cent of silica, alumina, and iron
oxide. The Hungarian product is a purer magnesite, carrying 92 to
95 per cent magnesium carbonate, with 3 or 4 per cent iron oxide.

In Germany the deposits now worked occur near Kosewitz and
Frankenstein, in Silesia, and are principally worked in connection with



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160 CEMENTS, LIMES, AND PLASTERS.

the manufacture of carbonic acid. The product will cany about 92
to 94 per cent magnesium carbonate, the principal impurity being
4 to 5 per cent of silica.

The principal Grecian deposits are on the island of Euboea, on the
east coast of Greece, and also near Corinth. The product is a very
pure magnesite, averaging 95 per cent magnesium carbonate. It is
low in clayey matter, the principal impurity being 3 to 5 per cent of

lime carbonate. The Grecian deposits are worked in primitive fashion
by pick and shovel. The mines, or quarries, are usually worked as
open cuts. As the rock is broken in the mines it is brought to the sur-
face, where the magnesite is sorted out. It is then loaded into small
carts and drawn to a narrow-gauge gravity railway, v.hen the mag-
nesite is loaded into one-ton cars and sent forward to the shipping port,
usually Kymassi or St. Theodore. The cost of producing the mineral
is about $3.50 per ton, transportation charges to the seaport about
$1.00, and freight to the United States about $2.50 per ton.

Magnesite is found in considerable quantity in southern India,
about two hundred miles from Madras. Deposits recently exploited
extend over 1500 acres. The railroad from Madras to Calicut runs
through these deposits, near the center of the magnesite area. The
material can be shipped, in any desired quantity, either from Madras
on the east coast or from Beypore on the west coast. As described
to the present writer by the owner, the magnesite occurs in beds or
veins of varying thickness, from a few inches up to several feet, the
magnesite beds being separated by bodies of disintegrated material.
An analysis o/ this magnesite is given in column 1, Table 63. This
was made on a 100-ton sample of crude rock. Another analysis of
Indian magnesite, quoted in column 2 of the same table, accompanied
a series of specimens exhibited at the St. Louis Exposition in 1904.

American localities. — ^The principal American magnesite deposits
are in California and in Quebec, Canada.

The California deposits are described* as foUows: "The principal
producing point in California is in the vicinity of Porterville, Tulare
Coimty, though a small quantity still comes from Chiles Valley and
Pope Valley, Napa County. At Porterville there are several deposits.
The main deposit at the opening carries a small vein, but at the end
of the 240-foot tunnel the deposit is 40 feet wide, and there are said
to be several million tons now in sight. At this place calcining furnaces
have been erected and are in operation. The mineral crops out boldly in

♦ Mineral Resources of the U. S. for 1903, pp. 1131-1135. 1904.



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SOURCES AND PREPARATION OP BIAGNESIA. 161

distinct veins, having a general strike northeast and southwest, and
there are spurs running in several instances at nearly right angles with
the primary veins. On the surface the veins are fom 2 inches to 10
feet wide. They cover an area of over 500 acres. In Pope and Chiles
valleys, Napa County, there are somewhat extensive deposits which
were formerly worked, but hauling by team to railroad made them
more expensive to operate than the mines at Porterville. In Placer
County there is a more extensive deposit than elsewhere in California,
but it is in an almost inaccessible mountain region where a very costly
road would be necessary to get the product out, and the deposit has
therefore not been utilized. Near Sanger, Fresno Coimty, 7 miles from
Centerville, another deposit is now being opened. A deposit has been
discovered also near Walkers Pass, Kern County, but it has never been
opened. There are also unutilized deposits near Morgan Hill, Santa
C3ara County.

"The extensive deposits of magnesite on Red Moimtain, at a point
where Stanislaus, Alameda, and Santa Clara counties join, are now
being opened by the American Magnesite Company, of Chicago, which
has obtained control of the numerous claims heretofore owned by
individuals. None of them have been at all thoroughly prospected
as yet, though there are numerous boulders or large croppings, some
from 30 to 150 feet wide, supposed to cover extensive beds beneath.
The parent company is the American Magnesite Company, organized
under the laws of the State of Maine, with Mr. G. Watson French, of
Chicago, as president and Mr. H. C. Stillwell, of Fruitvale, Alameda
County, Cal., as vice-president and Pacific coast agent; Mr. Charles
H. Spinks, of Berkeley, Cal., is to manage the mines. One of the sub-
sidiary companies is the Rose Brick Company, which is to manufac-
ture magnesite brick, at Oakland, Cal.; the American Carbonic Acid
Gas Company is another, of which Mr. John Deere is president and
Mr. George A. Wayman, manager. The third corporation is the Plastic
Construction Company, of which Mr. Edwin D. Weary, of Chicago,
is president. This company controls the American rights for making
a fire-proof construction material as well as a patent brick. This factory
will also be in Oakland.

"The mines of this company are nearly all in Santa Clara County,
with a few in Stanislaus, near the Alameda Coimty line. The Ala-
meda Coimty supervisors are building a wagon-road from the mines to
Livermore, where the railroad is met. There are twenty-seven mining
claims in the group, and several are at present being opened. Only
a few ear-loads for sample purposes have been shipped since the com



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152



CEMENTS, LIMES, AND PLASTERS.



pletion of the new organization, but it is expected that the properties
will shortly be opened on an extensive scale."

Recently several large deposits of magnesite have been discovered *
in the township of Grenville, Argenteuil County, in the province of
Quebec. Large boulders of the mineral were found, and finally the
magnesite was found in place. One of these deposits, which showed
an outcrop 90 feet long and 20 feet broad, is in the north half of the
eighteenth lot of the eleventh range of Grenville township. Another
outcrop, 100 feet wide and traceable for a quarter mile in length, is
on the north half of the sixteenth lot of the ninth range.

The following analyses of magnesite from these deposits were made
by G. C. Hoffmann, and are quoted from the report cited below.*

Table 60.
Analyses of Magnesite from Quebec, Canada.





1.


2. •


3.


4.


6.


6.


7.


Magnesium carbonate (MgCO,)
Calcium carbonate (CaCOj). . .
Magnesia (MgO) as silicate. . . .


77.62

16.07

3.50


74.68

18.89

3.71


78.08

15.67

4.18


77.16

10.78

6.14


76.09

16.00

4.29


76.97
13.14

5.87


49.71

30.14

9.17




8.


9.


10.


11.


12.


13.


Magnesium carbonate (MgCOj)

Calcium carbonate (CaCOj)


75.69

19.71

3.08


82.72

12.36

2.53


77.07

16.28

3.22


85.00
10.80
n. d.


95.50
tr.
n. d.


81.27
13 64


Magnesia (MgO) as silicate


3 66







It will be seen that this Canadian magnesite differs from all the
other magnesites known to commerce, in that it contains a comparatively
large percentage of lime carbonate as its principal impurity.

Production and imports of magnesite.— In the following tables (61
and 62) statistics regarding the domestic production and the imports
of magnesia and magnesite are given. It will be seen that in 1903 the
value of the United States production amounted to less than 3 per cent
of the total value of magnesia and magnesite used in this country.

Analyses of commercial magnesite. — As magnesite is simply mag-
nesium carbonate, a theoretically pure magnesite would consist of 47.6
per cent magnesia (MgO) and 52.4 per cent carbon dioxide (CO2). De-
posits of magnesite, however, rarely yield any considerable amount of
material of this degree of purity, and commercial magnesite may con-
tain as high as 10 per cent or thereabouts of lime carbonate, silica,
.alumina, iron oxide, etc.

* Ann. Rep. Canadian Geol. Survey, vol. 13, Report R, pp. 14-19. 1903.



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SOURCES AND PREPARATION OF MAGNESIA.



153



Table 61.
Quantity anJ) Value op Crude Magnesite Produced in the United States,

1891-1903.



Year.


Quantity.


Value.


Year.


Quantity.


Value.


1891


Short tons.

439
1,004

704
1,440
2,220 -.
1,500
1,143


$4,390
10,040
7,040
10,240
17,000
11,000
13,671


1898


Short tons.
1,263
1,280
2,252
3,500
2,830
3,744


$19,075


1892


1899


18,480


1893


1900


19,333


1894


1901


10,500


1895


1902


8,490


1896


1903


10,595


1897











Table 62.
Imports of Magnesite Int^ the United States in 1903.



Quantity.



Value.



Magnesia:

Calcined, medicinal

Carbonate of, medicinal. . .

Sulphate of, or Epsom salts.
Magnesite :

Calcined, not purified

Crude



Pounds.
34,586
10,569
2,392,831

73,534,690
36,017,637



$4,412

765

11,826

311.396
150,002



Table 63.
Analyses of Magnesite.



Silica (SiO.)

Alumina (ALO,)

Iron oxide (FejO,). . .

Lime (CaO)

Magnesia (MgO)

Carbon dioxide (CO J.
Water



2.20
^ 0.30

0.59
46.59
49.63

0.83



0.22
0.30

n. d.
47.35
51.44

0.27



0.30
1.62

n.d
46.00
51.23

n.d.



0.52
trace

2.25
45.28
51.61

0.34



0.52
0.08

2.46
44.96
51.44

0.54



Silica (SiO,)

Alumina (ALO,). . . . .
Iron oxide (FejO,). . ,

Lime (CaO)

Mainiesia (MgO)

Carbon dioxide (CO^)



1.0

} 3.0-6.0

0.28-1.12

42.84-45.70

n.d.



4.00

4.00

n. d.
41.89
n. d.



8.



0.8

{1:1}

0.06
45.12
49.72



4.5-5.25

1.5

0.6-0.7
46.0-48.0
46.0-50.0



1. 200 miles from Madras, British India. Private communication.

2. India. Indian Exhibit, World'** Fair, St. Louis. 1904.

3. Dept. of Ufa, Southern Urals, Russia. "Mineral Industry." vol. 10, p. 439.

4. Mondondi, Greece. U. S. Consular Reports. No. 168, 1900.
6. Eubcea. Greece. Proc. Inst. C. E., vol. 112. p. 381.

6. Styria, Austria. Proc. Inst. C. E.. vol. 112. p. 381.

7. Styria, Austria. Ens. and Minintr Journal, March 10, 1900.

8. Minsan. Hungary. Ensr. and Mining Journal. March 10. 1900.

9. Frankenstein, Silesia (Germany). Eng. and Mining Journal, March 10, 190a



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164 CEMENTS, LIMES, AND PLASTERS.

Effects of heating magnesite. — ^If magnesite (MgCOa) be strongly
heated, the effect (as with hme carbonate) is to drive off the carbon
dioxide (CO2), leaving magnesia (MgO) as a white soUd. A curious
and technologically important phenomenon connected with the tem-
perature employed is to be noted. If the calcination be carried on
quickly at a red heat, the magnesia resulting will have a specific gravity
of 3.00 to 3.07; while if the calcination is long continued or carried
on at a higher temperature the resulting magnesia will be much denser,
possessing a specific gravity of 3.61 to 3.80, -

The technologic importance of the two forms of magnesia lies in
the fact that the lightly burned magnesia will slake with water and
if then exposed to air will finally recarbonate and harden slowly, just
as lime does. The denser, higher-ljumed magnesia, however, will not
take up either water or carbon dioxide from the atmosphere. Another
difference of commercial interest lies in the fact that the light form
of magnesite possesses a certain amount of plasticity, so that it can
be molded into shape under heavy pressure, while the dense form of
magnesia is entirely devoid of plasticity.

Methods of burning magnesite. — For calcining magnesite at low
temperature, so as to obtain lightly burned magnesia, kilns closely similar
to ordinary lime-kilns are employed in California. The kilns in use at
one California magnesia-plant are built in the form of a frustum of a
cone, the broader part downwards. These kilns are about 19 feet in
height, 3 feet in diameter at the top, and 7 feet in diameter at the base.
Drawing-doors are placed at the base, while draft is obtained by suction,
air being drawn through a flue near the top of the kiln. These kilns are
charged with coke and magnesite mixed, in about the proportion of
300 lbs. magnesite to 20 lbs. of coke. The product is the light form
of magnesite, and is probably not entirely decarbonated. This fuel
consumption would amount to about 14 per cent on the weight of mag-
nesia produced.

When the dead-burnt or heavy magnesia is required, the burning
must take place at much higher temperatures. This kind of magnesia
may be prepared in reverberatory furnaces, in cupolas lined with siUcious
material, or in highly heated gas-kilns.*

The practice in Greece is described t as follows:

" At the Greek magnesite mines, until recently roughly built kilns
fired by wood were employed for catcining the ore, which required a

* Proc. Inst. Civil Engioeers, vol. 112, p. 381. 1893.
t Engineering and Mining Journal, Feb. 28, 1903



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SOURCES AND PREPARATION OF MAGNESIA.



155



large quantity of fuel. In recent years, however, modem shaft cal-
ciners have been built and a soft lignite coal is used. When calcined
magnesite falls into powder and is apt to choke the lower or cooler
portion of the kiln, preventing the access of air and heated gases to
the upper portion. The shaft furnaces are constructed to overcome
this result. The quantity of fuel required is from 15 to 20 per cent
of the weight of magnesite, equivalent to a fuel consumption of 30 to 40
per cent on the weight of magnesia produced. In some cases the cal-
cining is done in a double-hearth reverberatory furnace, where the flame
is brought into direct contact with the freshly charged magnesite on
the upper hearth, the operation being completed on the lower hearth,
which is the hotter of the two."

Composition of the product. — ^The analjrses given in Table 64 will
serve to show the composition of the burned product, which natiirally
varies according to that of the magnesite from which it is made.

Table 64.
Analyses of Calcined Magnesite (» Magnesia).





1.


2.


3.


4.


5.


6.


7.


Silica (SiO-)


0.98
0.10
6.70
1.88
91.10
n. d.


0.16
0.10
7.40
2.66
89. 3e
n. d.


0.17
2.38
5.02
1.50
90.42
0.46


0.50




1.2

}l3.0

7.3
77.6


0.73- 7.98


Alumina (A1,0,)

Iron oxide (KejO,)

Lime (CaO)




6.50
1.70
90.95
n. d.


6.90

91.50
n. d.


0.56- 3.54
83-10 92


Macnesia (MgO)

Carbon dioxide (00,). . .


82.46-95.36



1, 2. Burned Hungarian magnesite. Iron Age, Jan. 15, 1903, pp. 20, 21.
3, 4, 6. '* " *' Mineral Industry, vol. 10, p. 439.

6. *' Stjrrian (Austrian) magnesite. Proc. Inst. C. E., vol. 112, p. 381.

7. ** Grecian magnesite. Proc. Inst. C. £., vol. 112, p. 381.

Use of magnesite for preparation of carbonic acid, etc. — California
practice in the manufacture of carbonic acid from magpesite is de-
scribed as follows in a recent report:*

" In the manufacture of carbonic-acid gas, the gas is extracted from
the ;nagnesite by calcining and the remaining calcined material is sold
to the manufacturers of wood-pulp paper. The best English coke is
used for calcining the magnesite. From one short ton of magnesite,
after removing the gas, they obtain about 1200 lbs. of residue, w^hich
is partly calcined magnesite still carrying some 20 per cent of gas. In
the process about 500 lbs. of gas is obtained when finally compressed

♦ Mineral Resources of the U. S. for 1903, p. 1133. 1904.



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156 CEMENTS, LIMES, AND PLASTERS.

into liquid form. For every ton of magnesite about 500 lbs. of coke
is burned, and this, containing about 97 per cent of carbon, also fur-
nishes considerable gas. The steel cylinders for holding the liquid
gas are A inch thick and 5 by 49 inches long, and hold about 25 lbs.
The pressure on the cylinder at 60° F. is about 850 lbs., a three-stage
compressor being used. In shipping the liquid gas through the central
valleys and to Arizona the heat in the cars sometimes runs as high as
145°, the pressure being increased thereby. The cylinders containing
the liquefied gas are shipped to soda-water manufacturers, ice-fac-
tories, refrigerating-plants, breweries, bar-rooms, etc. The cylinders
with the liquid gas are shipped all over the Pacific coast- from San Fran-
cisco, even the British war vessels stationed at British Columbia using
the gas for their refrigerating-plants. The San Francisco carbonic-
acid-gas makers use about 1000 tons of crude magnesite annually.

As stated, the wood-pulp paper-mills of California and Oregon use
the calcined magnesite. They transform it into a sulphite of magnesia
and use it as a digester for the wood pulp. To make this sulphite they
put the material into a tank and pass sulphurous fumes through it.
Aiter being used as a digester they add a little lime and make the ' pearl
hardening ' of commerce to be used as a ' filler ' for the paper. "

Magnesian Limestones as Sources of Magnesia.

Highly magnesian limestones, approaching dolomite in composition,
may be regarded as possible sources of magnesia. The general char-
acters of such limestones are discussed in some detail in earlier chapters
of this volume, and reference should be made to pp. 90-91 for data
on these points.

Occurrence of magnesian limestones in the U. S. — Magnesian lime-
stones are so widely distributed throughout the United States that
no satisfactor}' sunmiary of their distribution can be given here. On
pp. 92-94 is given a list of reports on the limestones of the various
states and territories. Reference to these reports will furnish data
on the local distribution and composition of magnesian limestones, as
well as of other types.

Analyses of magnesian limestones. — In the following table analyses
of a number of highly magnesian limestones from various localities
in the United States are presented. It will be seen that these range
from 15 to over 22 per cent in magnesia (MgO), which is about
equivalent to a range of from 32 to 45 per cent magnesium carbonate
(MgCOa).



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SOURCES AND PREPARATION OF MAGNESIA.



157



Table 65.
Analyses of Highly Magnesian Limestones, U. S.



Silica (SiOg)

Alumina (Al^Oa) ,

Iron oxide (FejOj). . .

Lime (CaO). ,

Magnesia (MgO). •. . . .
Carbon dioxide (CO2).



1.



3.24

0.17

0.23

29.58

20.84

45.54



2.



7.75

1.48

31.00
16.46
42.47



10.02
31.01
21.79
47.35



4.



0.48

' 0.20

31.31
21.03
46.98



0.08

0.25

30.46
21.48
47.58



Silica (SiO,)

Alumina CALO3)

Iron doxie (FcjOa). . .

Lime (CaO)

Magnesia (MgO) ,

Carbon dioxide (COj).



6.



0.73

0.35

32.73
19.37
46.58



0.44

! 1.22

\ trace
30.73
20.87
45.85



8.



0.87
0.57
0.25
31.40
19.95
n. d.



9.



0.20

0.23

30.04
22.28
47.14



10.



0.70

ro.95

10.80
30.50
20.05
45.24



1. Morrisville. Calhoun Couoty, Ala. W, F. Hillebrand. analyst. Bulletin 60, U. S. Geol.

Survey, p. 159.

2. S. 16, T. 7. R. 7, E. Talladega County, Ala. J. B. Britton, analyst. Rep. Ala. Geol. Survey

for 1875. pp. 149. 150.

3. Inyo Marble Co.. Inyo, Calif. 20th Ann. Rep. U. S Geol. Survey, pt. 6, p. 359.

4. East Canaan, Conn. 20th Ann. Rep. U. S. Geol. Survey, pt. 6, p. 370.

6. Canaan, Conn. J. S. Adams, analyst. 20th Ann. Rep. U. S. Geol. Survey, pt. 6, p. 370.

6. Jasper, Ga. W. H. Emerson, analyst. Bulletin No. 1. Ga. Geol. Survey, p. 87.

7. Cockeysville, Md. J. E. Whitfield, analyst. Bulletin 60. U. S. Geol. Survey, p. 159.

8. Ossining, N. Y. H. Ries, analyst. Bulletin 44, N. Y. State Museum, p. 829.

9. Tuckahoe, N. Y. Ledoux, analyst. 20th Ann. Rep. U. S. Geol. Survey, pt. 6, p. 427.
10. Gates. Monroe County. N. Y. D. H. Newland, analyst. Bulletin 44, N. Y. Stete Museum,.

p. 796.

Extraction of magnesia from magnesian limestone. — ^Two principal
processes have been suggested for extracting magnesia from magnesian
limestone.

Scheibler process. — ^The mixture of lime and magnesia left by burn-
ing magnesian limestone is made into a thick milk by adding suffi-
cient water. Into this solution is poured water containing 10 to 15
per cent, by volume, of molasses, and the mixture is mechanically
stirred. In a few moments saccharate of lime is formed, which re-
mains in solution while the magnesia is precipitated. On putting:
through a filter-press the magnesia remains behind, while the saccha-
rate of lime passes through. The composition of the magnesia sa
obtained at a German plant was:

Silica (SiOj) ]

Alumina (ALOa) ■ 1 .47 per cent

Iron oxide (Fe-OJ J

Lime (CaO) '. 2.18" "

Magnesia (MgO) .- 95.99 " '*

The saccharate of lime which passed through the filters is now treated
for recovery of its constituents. Carbon dioxide precipitates the lime
as carbonate, after which it is filtered and the lime carbonate precipi-



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158 CEMENTS, LIMES, AND TLASTERS.

tate washed. The filtrate contains the molasses, which can be used
over again. In the course of the process a loss of 5 to 10 per cent of
molasses occurs.

. Closson process, — ^This process is based on the use of magnesium
chloride, and is therefore of value at points such as Stassfurt, where
that material is obtainable as a cheap by-product.

Twenty thousand pounds of magnesium chloride is mixed with the
lime-magnesia resulting from the calcination of 3000 lbs. of magnesian
limestone. Water is added to give a thick solution, and mechanical
agitation is employed. The result is the formation of lime chloridQ
and magnesia hydrate. On passing through a filter-press the magnesia
hydrate is caught on the filter, while the lime chloride passes through
in solution. The hydrate is washed and then burned, giving one ton
of magnesia, The magnesia obtained at Horde by this process gave
the following composition:

Silica (SiO,) ]

Alumina (ALO3) ■ 1 .05 per cent

Iron oxide (FcaOj) J

Lime (CaO) 1 .94 " ''

Magnesia (MgO) 96.90 '* *'

The lime-chloride solution is then treated for recovery. The mate-
rial is carried to receptacles like those in which blast-furnace gases
are washed, except that revolving wheels stir the chloride, making a
thorough mixture of the gases and the liquid. Two of these recepta-
cles are placed together back to back. A valve which can be reversed
sends the gases to either side and thus keeps up a continuous working.
Into these receptacles, together with the lime chloride, is put a quantity
of the lime-magnesia resulting from the calcination of magnesian lime-
stone. The blast-furnace gases passing through precipitate the lime
as carbonate, losing their carbon dioxide in the process, and are thus
rendered more combustible. They deposit, besides, a considerable
quantity of the solid materials mechanically carried by them and are
thus cleaned. • Magnesium chloride is reformed, remains in solution,
and is drawn off and filtered. The entire process shows a loss of 5 to
6 per cent of magnesium chloride.

Sea-water and Brines as Sources of Magnesia.

Sea-water contains small percentages of different magnesian salts.
In the manufacture of table salt from sea-water or salt brines, these
magnesian compounds are incidentally concentrated so as to be put in
more available form.



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SOURCES AND PREPARATION OF MAGNESIA. 159

Extraction of magnesia from sea-water.* — "Magnesia is mad©
out of sea-water, which contains about 4 lbs. magnesium chloride per
cubic yard of water, on a large scale at Aignes Morts, on the Mediter-
ranean coast of France.

"The sea-water is pumped into a tank made of masonry, and at
the same time milk of lime is pumped in, in the proportion of 1.5 per
cent of lime for every 1 per cent of magnesia. From this first tank



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