Rodolfo Amedeo Lanciani.

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present But on the other hand we must concede, that an entire
elimination of one or more of these constituents could only be
accomplished by such aa alteration in the physical and chemical
condition upon our planet, or in the nature of the disintegrating
agencies, as would create new affinities of sufficient power, to
alter the originally existing compounda The composition of
the present ocean, as compared with that of saline deposits of a
more ancient date, requires the assumption of such revolutioniz-
ing causes; causes, however, which may be looked upon as
merely a natural consequence of the lapse of time during the
history of our earth. The same agencies in fact, which are still
at work in effecting changes in the character of the saline com-
pounds of the present ocean, suffice to explain the gradual trans-
formation of the primitive ocean into that of the present day.
The mineral acids, the presence of which we had reason to
suspect in the primitive ocean, became neutralized by degrees,
and ceased to react upon the newly exposed rock ; and as the
temperature diminished, anew disintegrating agent, carbonic acid,
became active. This acid, then so abundant m the atmosphere,
aided by water and oxygen, and later by vegetable and animal
life, though a slower is by no means a less powerful agent in
effecting the decomposition of exposed rocKs ; it has enriched
and is still enriching the ocean with saline compounda Car-
bonates and silicates of alkalies and alkaline earths were in this
way introduced into the oceanic waters ; and thus a gradual
removal of metallic and earthy oxyds, and in some cases of
those of the alkaline earths also, was effected. The sulphuric
acid, exchanging the oxyds of the earths and the metals for
lime, formed a less soluble sulphate, so that the amount present
became dependent upon concentration and temperature. The
chlorine changed from its combinations with earths and metals,
only to the equally soluble compounds of the alkalies and
alkaline earths. Taking the chlorid of calcium, for example,
which thus far has been noticed in every salt deposit of ante-
tertiary date, and which must have been therefore one of the
original constituents of the ocean from which the salt originated,
we find it necessary to believe that the chlorids must have al-
ways exceeded the sulphates ; since an excess of any sulphate,
except sulphate of lime, would have caused the decomposition
of the chlorid of calcium.* An increase of the chlorids of the
alkaline earths, as of calcium and magnesium, and of the
alkalies, particularly of sodium, if we may judge from the
present composition of the ocean, was the final result of the

* The supposition that chlorid of calcium was one of the primitive constituents,
can only lose its force when some other general cause for its universal diffusion
can be pointed out



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C A, OoessTTKinn on the Ghemistry of Common Salt 81

changes now indicated. The agencies which produced these
changes are still at work ; and hence the oceanic waters of the
present day are liable to similar alteration in composition. There
are reasons to suppose that for some time past one of the main
changes has been the decomposition of the sulphate of lime by
carbonate of magnesia, forming carbonate of lime, sulphate of
soda and chlorid of magnesium. The latter compounds are
characteristic of the salt deposits of recent date, as well as of
the present marine waters ; they could make their appearance
only after the chlorid of calcium had been removed. There
are of course various other means, by which this result may
have been accomplished ; but I prefer to confine myself to the
one now given, as being of particular interest in view of the
fact, that chlorid of calcium is a characteristic constituent of the
ante-tertiary ocean. These changes in the oceanic waters ex-
tend apparently over long periods of time ; they are more likely
the resmt of a prolonged than of an intense action, — even from
the beginning. For these reasons it must always be quite dif-
ficult to point out with anything like a certainty, the condition,
and the composition of the ocean waters, during the successive
stages in the geological development of our planet. All we
can venture to assert upon that point may be summed up in the
following statements '.—first : the similarity of certain extensively
distributed metalliferous, and other deposits within the crevices
and fissures of primitive rocks, finds an apparently satisfactory
explanation in the assumption, that their K)rmation is due to a
more or less localized precipitation, under circumstances similar
to those we have supposed to exist in the primitive ocean;
second ; the saline compounds contained in the oceanic waters
of ante-tertiary date appear to differ essentially from those of
the present day ; the solutions of the primitive saline deposits
of oistinctly ante-tertiary date containing in every instance,
more or less chlorid of calcium, while the waters of our present
ocean are characterized, instead, by an excess of soluble sul-
phates, as sulphate of magnesia and of soda for instance,
which renders the existence there of chlorid of calcium impos-
sibla We do not hesitate on the strength of these observa-
tions, to speak in general terms of a primitive ocean, — of an
ante-tertiary or Silurian ocean, and of a Post-tertiary ocean, in-
cluding in the latter that of the present day.

Whenever during the various geological epochs a larger or a
smaller body of salt water was cut off from the main ocean, either
in consequence of a receding of the ocean, an infiltration into natu-
ral basins, or of changes in the level of the strata, and was
subsequently placed under favorable climatic conditions for its
evaporation and the subsequent preservation either in whole
or m part of its saline residue, then a salt deposit was pro-

Am. Jour. Sci.- Second Ssbibs, Vol. XJ^IX, No. 146.— Jaw., 1870.
6



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82 C A, Ghessmaain on the Ohemisiry of Common SoUt

duceA Such saline residues, commonly known as rock salt,
have been found in almost every geological horizon, from
the Silurian upward, and in many localities they are still
forming at the present time. Sometimes several independent
deposits occur one above the other, interstratified with the
rocks of the same geological basin.

Most of the foreign salts which accompanied the chlorid of
sodium in the marine waters, being more soluble than the
chlorid of sodium itself, accumulated during the evaporation
in the residual licjuid, commonly known as mother-liquor, which
covered, at least m part, the separated crystalline mass of chlorid
of sodium and sulphate of lima The amount of these salts
and the manner in which they overlie the solid saline mass, is
dependent on the form and the shape of the basin in which
the deposits accumulated. As these mother-liquors uniformly
contained a large number of deliquescent compounds, we must
assume very favorable climatic and meteorological conditions to
account for their evaporation, since the rate at which this took
place, must have exceeded by far that of the precipitation of
moisture. Whether such a state of the atmosphere was the
general rule in former ages, is of course quite uncertain. More-
over, although actual investigations have demonstrated the entire
absence not unfrequently of the upper layers of such saline de-
posits, this fact cannot be admitted as an argument against the
assumption of a common marine origin of all salt deposits.
Foi^ even granting that in former geological €^es, the extraor-
dinary state of the atmosphere did exist, which would be re-
quired to effect the solioij&cation of the entire saline mass —
mother-liquor and all — ^there remain numerous subsequent
influences, by which a part or the whole of the saline residue of the
original mother-liquors, even after their complete solidification,
could have been removed from a saline deposit In fact, c<m-
sidering the many casualties to which these saline accumula-
tions are liable in the course of time, it would be strange indeed,
if many entire and well preserved marine salt deposits should
be found.

We may assume then with some propriety, in cases
where salt deposits are foimd without their associated foreign
saline compounds, that these have been lost, either by oozing
out, never having been solidified, or after solidification, have
been removed by the percolation of surface waters, by sub-
terranean currents, by peculiar secondary chemical and physi-
cal reactions or by erosive action on the surface layers. In all
probability quite as many deposits have been modified in their
physical and chemical characters by the subsequent elevation
of their enclosing strata, a circumstance which must have favored
ihe percolation of surfEice moisture, as have been changed by



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C A. Goesamann on the Chemistry of Common Salt 88

denudation.* Indeed these changes have sometimes gone so
far as to leave nothing but the layers of gypsum which are the
substratum of all well investigated rock-salt deposits.

As the circumstances necessary for the preservation of entire
salt deposits, or saline marine residues can scarcely have been
the same, even throughout the same geological age, it is not sur-
prising, that these deposits so frequently differ in their physical
and chemical characters. In fact there is at present but one
salt deposit known, and its discovery is of quite recent date
(Stassrarth), where the entire saline mass of the ocean has been
preserved ; in this deposit the various saline compounds are
to a large extent arranged in lajers, which correspond closely
with the degree of their solubility ; yet even in this one instance
there are facts noticeable, which leave no doubt that portions of
the deposit have been exposed to peculiar disturbing influences
at a later date.

But not only may salt deposits be placed under conditions
which permit tneir re-solution, there may be in addition a re-evap-
oration of this solution, producing a secondary salt deposit
This requires only a repetition of the circumstances, which
fevored the formation and preservation of the original one.
A primary salt deposit may be dissolved entirely or only in
part ; in either case the solution may or may not be changed in
composition by filtering through the adjacent beds.. Both
primary and secondary salt deposits may occur in the same
geological {Post- Silurian) formation. Secondary reactions of a
physical as well as a chemical nature too may alter the character
of the surrounding geological formations, and thus may indirectly
affect the composition of a salt deposit, as is the case for instance
at StassfurtL The conditions which have now been given
may suffice to explain to us the great variations we notice in
the chemical composition both of rock salt and of brines ; they
may also serve as a suitable illustration of the great risk we
incur, when we assume to draw conclusions of an absolute
character from the geological formation in which the salt deposit
has been found, as to the chemical composition of the oceanic
waters of that geological age.

With these preliminary remarks upon the origin of chlorid of
0odium and its associated salts, I pass on to consider the main
sources of supply of common salt, with particular regard' to
those of this country.

The leading sources of supply for the manufacture of salt,
as already stated, are three in number. Bock sait^ Brines, and
Sea^vcUer. A. Bock salt : From what has been said it is manifest
that rock salt from different localities nuiy differ widely, both in

* As ^ rock salt deposit of Petit Anae, Louisiaiia, for example, and most likelT'
tibat whidi furnishes the brines of Onondaga.



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84 C. A. Ooessmann on the Chemistry of Common Salt

physical and chemical properties. Usually it occurs either in
densely aggregated masses of distinctly cubical crystals, or in
compact masses having a* conchoidal fracture ; it is frequently
colorless and transparent, yet is more often either red, yellow,
or blue, rarely green. Its most frequent saline admixtures are
1st, sulphate of lime, the chlorids of calcium, magnesium, and
potassium, and the bromid and iodid of magnesium ; or 2d, the
sulphates of lime, magnesia, and soda, the chlorid, bromid, and
iodid of magnesium, etc. A rock salt, which contains more
than from 2 to 3 per cent of these impurities is unfit for domestic
uses ; and a salt which contains carbonate, nitrate or borate of
soda, or similar foreign substances is, especially in its natural
state, frequently unfit even for many manufacturing purposes
also.

Eock salt deposits are frequently intercalated with layers of
gypsum and clay, a fact due to the successive periods of evap-
oration ; such conditions require especial care in mining the
salt Colorless and dry rock salt deposits having a fair composi-
tion and easy of access are mined directly with advantage ; the
salt obtained thereby, after being brought into a desirable form,
is directly applicable to most domestic purposes, particularly meat
packing. Colored salt deposits, or those which suffer from per-
colating waters, or which contain a large amount of foreign
saline admixture, or clay ; or finally, those which are located at
very great depths, if worked at all, are usually dissolved, and
their solutions treated like brines.

The northern part of this continent contains numerous salt
deposits ; some quite recently discovered, like that upon Petit
Anse Island, Vermilion Bay, Louisiana, the one in Canada
West, at Goderich on the shores of Lake Huron, and also that of
Neyba, St Domingo, West Indies, being of particular interest
Newspaper reports too tell of mountains of rock salt in Arizo-
na and Nevada. The salt deposit at Goderich is buried in the
shales of the upper Silurian (T. S. Hunt), at a depth of fix)m
eight to nine hundred feet ; it is about forty feet tnick, covers
so far as present indications show, dozens of square miles, and
is in close proximity to Lake Huron ; its solution famishes the
superior brmes at GodericL* The salt deposit of Petit Anse,
Louisiana, is apparently imbedded in Quaternary formations (E.
W. Hilgard), and is covered merely by a diluvial drift from 16
to 18 feet in thickness ; its extent is unknown, having been but
partially explored. It is accessible by sea and by land, and is
within 276 miles of the mouth of the Mississippi river. This
Petit Anse rock salt, so far as at present exposea, is one of the

* Report on the Salt BeaouroeB of Goderich, Canada West, by Ohas. A. Goeas-
mann; Syiaouse, N. Y., January, 1868.



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C. A. Ooessmann on the Chemistry of Common Sa,lL 85

purest on record.* At the present time there is but little rock
salt, as such, used in the United States. Natural solutions
of rock salt ftimish us with the brines of Saltville in North
Western Virginia, of Goderich, Canada West, and, as I believe,
of Onondaga, N. Y.

B. Brines, — ^Brines are either natural or artificial ; that is, they
are either natural solutions of saline deposits, or they are made
artificially by dissolving rock salt In regard to natural brines
we are quite fr^uentlv ignorant of the exact location, the
extent ana the nature oi the saline mass from which they ori-
ginate, while in the case of artificial brines, we are familiar at
least to some extent, with the nature of the sources from which
our supply is drawn.

Brines diflfer in strength and in composition, scarcely two of
them being alika In strength they vary fix)m three to twenty-
six per cent of saline matter, though weak brines are frequent-
ly strengthened for manufacturing purposes by adding rock
Bait Their composition depends on the peculiar nature of the
original source, and on the secondary influences to which they
are exposed in passing to the surface ; an intercepting stratum
often modifying materially their original composition, f More-
over brines from the same salt deposit frequently differ widely
in composition ; the upper parts of the deposit containing as a
general rule, more of the foreign salts than the lower portion ;
the exceptions being accounted for by extensive surface erosions
and percolating waters.^ Again, the upper layers of salt de-
posits being more exposed to surface action, as for instance, to
mfiltrations, which may cause chemical changes, are thus partic-
ularly liable to suffer from the accumulation of foreign admix-
tures, derived fix)m the disintegration of the overlying rocks.
Brines originating from the surface layers of a salt deposit are
therefore usually inferior in composition to those coming from
its lower portion.

The impurities of brines are those which are found in rook
salt, but in many instances they contain also the carbonates of
lime, magnesia, and protoxyd of iron, carbonic acid, and hy-
diosulphuric acid, besides organic matters. These last named
have found acce% to the brine in most cases during its passage
to the surface.

Brines are divided§ according to the character of the saline
admixture, into two classes ; those of the first class contain the

^^ See mj statement in a report of the American Bureau of Mines, On the rode
aUt deposit of Petit Anse, etc^ New Toric, 1867 ; and also Dr. E. W. Hilgard'a
statements in Proceedings of American Assoa for the Advanoement of Science,
A.ug«, 1868.

4 See my contribution to the Chemistry of Mineral waters, eta Syracuse, N. T.,
Feb., 1866, also this Jour., 1866.

1 See mj contribution to the Chemistry of Brines, this Jour., July, 1867.

g Ibid., p. 80.



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86 G, A. Ch>e89mann on the Chemistry of Common Salt

chlorids of calcium and magnesium, and sulphate of lime;
those of the second class contain no chlorid of calcium, but
only chlorid of magnesium, with the sulphates of lime, soda
ana magnesia ; the first class are supposed to originate chiefly
from the saline residue of the oceanic waters of ante-tertiary
date, while the second class represent most probably deriva-
tives of the former. All the brines found east of the Missis-
sippi river belong, so far as my own information extends, to the
first class, as they contain chlorid of calcium. The second
class of brines is largely represented west of that river ; for
instance in Nebraska, Kansas, and Arkansas.
L \st Class of brines and salt*

a eS




s=



im ^nS Sg| |g






I. II. I. IL

Sulphateoflime, 0-6433 0-574'? 0-0765 0-4887 008810 1060 traces 0*2978
Chlorid of calcium, 0-0216 0-1533 2-9422 0-4020 1-1360 0-6140 07009 11793
Ohl'dofmagne8H'>'0336 0-1440 1-2616 03710 0-4744 0-0409 0-7312 0*9587
** of8odlum,eta24-I433 16-5317 19*8595 126316 928 95*7 6*7684 9*8962
Water, 74-8 83- 76 86*0. 6-9 3*4 91* 87*

IL 2d Class of brines and salt ; it includes all kinds of salt
made fix)m oceanic waters.*

Nebraalut (brine), NebrMk* (ult). Kumm (ult).

Sulphate of lime, 0*1266 0-2475 11222

Sulphate of soda, 0*5808 0*3912 0*3511

" " magnesia, 01794

Chlorid of magnesium, 0*1542 0*0790 0*2400

Ohlorid of sodium, etcl, 0*3150 9812 93-06

Water, 90* 0*8 4*8

The value of a brine for manufacturing purposes does not
depend entirely either upon its density or upon the relative
percentage of chlorid of sodium and of foreign saline admix-
tures ; the hind of the impurity is of the greatest importance ;
for instance, the sulphate of lime and even the sulphate of
soda are considered far less objectionable, within proper limits,
than a corresponding amount of the deliquescent chlorids of
calcium and magnesium.

Saline springs are scattered all over the United States, their
number having been largely increased by the recent extensive
explorations for oil ; the amount of brine which they can yield
is apparently inexjiaustible. Foremost among them are the
brines of New York, (Onondaga co.), southeastern Ohio, western
Virginia, Michigan, Pennsylvania, and of late Nebraska and
Kansaa The brmes of New York, Ohio, Virginia, Pennsylvania,
Michigan, Tennessee, Kentucky, and Canada West, resem ole each

* These aaaljtical statements bj no means express the commeroial value and the
relative purity of the salts and brines, they daim merely to indicate their peculiar
dbaraoter.



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0. A. Gfoeesmann on the Chemiatry of Oommon Salt 87

other closely. They all belong to the first class of brines, and
all contain chlorid of calcium ; they differ merely in the relative
proportion of the impurities which they contain. The brines
of liincoln co., Nebraska, and of Smoky Hill river valley,
Kansas, etc, contain chlorid of magnesium, and the sulphates
of lime and soda, but no chlorid of calcium. They represent the
second class of brines. Most of the saline waters of this
country are, even in their natural state, strong enough to be
worked directly by artificial heat All our home mamSactured
salt, coarse as well as fine, with the exception of a small
quantity obtained fix)m sea-water, has thus far been made fix)m
natural brines; fully one half of the whole amount for a
number of years having been obtained from the brines of
Onondaga, New York State.

C. Sea-water, — The water of the ocean is a weak brine ; it
contains from three and one half to four per cent of saline matter,
of which three fourths is chlorid of sodium and one fourth is im-
purities ; it is free from chlorid of calciuin, and belongs pro-
perly to the second class of natural brines. Its impunties
consist mainly of chlorid of magnesium, the sulphates of lime,
magnesia and soda, besides smaller quantities of chlorid of
potassium, bibmid and iodid of magnesium, and carbonate of
lime, with traces of oxyd of iron, etc. Sea-water varies but
little in composition and concentration, except in localities
where either a limited body of water is prevented from unre-
stricted communication with the ocean, or where a large
influx of fresh water causes its dilution. It represents the
main source of supply for the manufacture of salt in France,
Portu^l, Spain, Italy, the West Indies, and Central and South
America ; it is used also largely for the production of salt in Eng-
land, Belgium and Holland, being frequently employed for the
solution of rock salt of inferior color. In the United States it
has been turned to advantage but to a very limited extent
Three hundred to three hundred and fifty thousand bushels
cover, in aU probability, our present production of salt fix)m sea-
water. The States of Massachusetts, North Carolina and
Florida on the Atlantic, and of CaUfomia on the Pacific
Ocean, have mainly been interested in this branch of industry.
The late increase in the production in Florida, and on the
Pacific coast, more than compensates for the falling off elsewhere.
In concluding this paper it may be well to re-state the fact,
that the comparative commercial value of various samples of salt,
80 far as their composition is concerned, does not always depend

rthe relative proportion of chlorid of sodium to foreign
xtura A mere analytical statement giving the percentage
of impurity, without specifjing its kind and nature, gives no
reliable standard by which to pronounce upon their commercial



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88 C. A. Ooeasmann on the Chemistry of Common Salt

value, since the various impurities, whicli the salt has retained,
are objectionable in quite different degrees ; thus a sample which
contains from one to one and a half per cent of foreign salts,
consisting almost exclusively of sulphate of lime, may claim to
be a verv fair article of common salt ; whilst if it contains but
one half of that amount of the chlorids of calcium and mag-
nesium or of the sulphates of soda and magnesia, together
with the chlorid of magnesium, or of the carbonates of lime
and magnesia, it would be considered quite objectionable, at
least for table and dairy purposes. Again, the superior
fitness of a sample of salt for many domestic purposes,
does not depend entirely on its chemical composition ;
its mechanical condition is quite frequently of not less impor-
tance. A well devised mode of manufacture, ought there-
fore, not only to aim at the most perfect removal of foreign
impurities, it must also secure to the salt the best mechanical
condition. The manufacturer in selecting a mode of working
is consequently limited in his choice ; he must often sacrifice
purity to mechanical condition, being obliged to adopt a method
which promises to secure most economically a desirable article
froxa his brine in the purest condition possible. So far as the



Online LibraryRodolfo Amedeo LancianiThe American journal of science and arts → online text (page 11 of 109)