Nephrol Dial Transplant (1996) 11: 969-975
Special Feature
Nephrology
Dialysis
Transplantation
The history of salt—aspects of interest to the nephrologist
E. Ritz
Department of Internal Medicine, Ruperto Carola University, Heidelberg, Germany
neophyte as a symbol that wisdom is acquired. This
habit goes back to a pre-Christian Roman custom.
The stimulating flavour of salt was metaphorically
When one reads current literature on salt, one is
amazed by the emotional energies released by this applied to a tale or discourse. To be without 'salt' was
issue. Why is this so? Undoubtedly much of the meant to indicate that something was insipid—based
controversy is simply due to the fact that there is much on the concept that salt was an essential element, so
poor science in this field. Some of it may also be that to be insipid and without salt indicated that
explained, however, by the fact that in the past salt something essential was lacking.
It was claimed, not without some justification, that
profoundly influenced human thinking and life style in
a way which is no longer properly appreciated today, salt promoted libido and potency. According to the
now that salt has become an easily available commod- legend Venus was born in the salty sea (Venus saligena)
ity. Even today, perhaps subconsciously, salt has not as depicted in the painting of Sandro Boticelli
yet become an emotionally 'neutral' substance—no (Figure 1). There may be an even more amusing
doubt a remnant of the profound symbolic significance explanation, however, for this specific custom of
attached to salt for millenia.
depicting Venus riding on a clam in the sea: the female
vulva was considered to be impure and consequently
called 'porcella', derived from 'porcus', the Latin word
for pig. For obvious reasons, clams were called porThe symbolic value of salt
cella. This usage explains also the origin of the word
Salt had both positive and negative symbolic connota- porcelain. When Chinese porcelain was introduced into
tions from time immemorial. Salt is white, immaculate, Northern Italy, a parallel was drawn between the
uncorruptible and imperishable, according to an iridescent hue of porcelain vessels and that of clams.
Arabian proverb 'salt is not worm-eaten'. As a con- This led to their designation as porcellano.
sequence it was a symbol of immutability. It played a Nevertheless, for folklore salt is strongly linked to
role in the rites of ratifying compacts and sealing sexuality. This is illustrated for instance by a custom
covenants (e.g. Num. 18 19; 2 Chr. 13, 5). Its durability of Bavarians (who are never too subtle) to put salt
and its immunity to decay made it an emblem of into the bride's bed. And in Shakespeare's The Merry
immortality. Salt was also a symbol of immutable Wives of Windsor we read 'We have some salt of our
loyalty, as illustrated by the ancient custom, particu- youth in us'.
larly in Slavic countries, to share bread and salt with
Salt was said to promote health. The Latin words
the guest.
for health and healthy, salus and salubris, are actually
As a reflection of its bacteriostatic properties related derived from sal (salt). Today few Frenchmen will
to osmolality and ionic strength, salt was considered think of salt when greeting each other—but the word
to have healing properties. The prophet Elisha made 'salut' is derived from salt as well.
Although salt was felt to be indispensible for health,
the foul water of Jericho potable by using salt (2 Kings
2, 19-22). Salt was felt to be indispensible for life: the wise ancient Chinese remained sceptical. The
according to the East Gothic king Theoderich (6th famous Yellow Emperor wrote approximately 3000 BC
century) 'one can do without gold, but not without 'If too much salt is used in food, the pulse hardens,
salt'. Salt was therefore added to the sacrificial offerings tears make their appearance and the complexion
as repeatedly alluded to in the Old Testament (Lev. 2, changes'.
13; Ex. 30, 35; Ezek. 43, 24). In the New Testament,
Salt was a precious commodity. In many cultures it
Christ when referring to his apostles stated (Mt 5, 13, was the equivalent of money. In ancient Rome, soldiers
14) 'Ye are the salt of the earth: but if the salt has lost and officials were reimbursed in the form of a 'salarium'
his savour, wherewith shall it be salted?. Salt was, and i.e. salt money—from which our word salary is derived.
still is, used by the Catholic church during the cere- Salt was a symbol for exquisite value; St Jerome
mony of baptism: salt is put upon the tongue of the referred to Christ as the 'true salt'.
Introduction
© 1996 European Dialysis and Transplant Association-European Renal Association
970
E. Ritz
Fig. 2. The last supper (Cenacolo) by Leonardo da Vinci
(1452-1519). Detail reproduced from a copy (Norbertijenenabdij,
Tongerlo/Antwerpen), which shows the knocked-over salt shaker as
a symbol of imminent disaster. After B. Loffler, in ref [5]. (By
permission, Da Vinci Museum, Norbertijnenabdij, Tongerlo,
Belgium.)
Fig. 1. Primavera by Sandro Boticelli (1445-1510). The painting is
an example of the motif of 'Venus Saligena' (see text).
The symbolism of salt had also negative connotations. In biblical times salt was sown over the territory
of defeated and destroyed cities. Salt was felt 'to belong
to the realm of the evil, the deadly desert, the land of
sin, i.e. Sodom and Gomorrah'—one of the justifications for the custom of the church to subject salt to
exorcism, i.e. expelling the devil prior to its liturgical
use. Even in this century Bavarian farmers still put
salt into the hat brim to ward off evil. On the other
hand, spilling salt at the table was considered a bad
omen. In the famous 'Cenacolo' by Leonardo da Vinci
(1496/97) in Santa Maria della Grazia (Milano) the
knocked-over salt shaker symbolizes the imminent
treason of Judas and the suffering of Jesus Christ
(Figure 2). Ambivalence towards salt is also reflected
by the statement 'take it with a grain of salt', indicating
that something is to be taken with a healthy dose of
scepticism.
How did societies cope with lack of salt?
Salt hunger is well known in the animal kingdom. As
early as 1884, Manley wrote: The 'universal existence
of an appetite for salt surely indicates that the sub-
stance serves more important functions than that of
merely gratifying the palate'. With very good arguments it has been assumed that one of the reasons why
some species could be bred as domestic animals was
that their ancestors living in the wild were attracted to
human settlements by the salt content of human urine.
This notion is also supported by some amusing observations, e.g. from British Columbia, where porcupines
gnawed at the veranda posts of cottages which had
been soaked with urine after they had been misused as
substitutes for urinals; or reports from Australia where
rabbits and kangaroos chewed away pales impregnated
with salt. Every mountaineer knows that mountain
goats are attracted by sweat soaked, i.e. saltimpregnated, pullovers which they will lick. Monkeys
groom not to hunt for fleas, but rather to search for
skin secretions containing salt. Grooming becomes
more intense when salt is put on the fur.
It is also of note that in the past many mineral
springs were discovered by animals. In Germany,
examples include the famous stag of the 'Teinacher
Hirschquelle' or the pig (Salzsau) which discovered the
salt water fountain of Liineburg upon which the
immense wealth of this city was based. Salt deposits
in Hall/Tirol were discovered when hunters noted that
saline rock was used as salt licks by chamois.
Is there evidence of salt deficiency in animals? Salt
deficiency occurs usually in regions remote from the
sea. It is not noted in carnivorous animals (which have
a supply of sodium from the extracellular fluid of their
prey), but occurs in herbivores. Lack of additional salt
is not a physical handicap under normal conditions;
nevertheless it can lead to a severe sodium deficit,
The history of salt
when additional stress such as diarrhoea, vomiting, or
profuse sweating supervenes. Salt deficiency imposes a
handicap in selection: speed and endurance are diminished when animals are hunted by predators; thermoregulation is disturbed and fertility is reduced. The
relation between salt intake and fertility in herbivorous
animals was well known to our ancestors. Compared
to 5-7 g/day of salt intake that is recommended for
the human diet, the recommended diet for a heifer is
25 g and that for a lactating cow no less than 90 g.
This fact explains the very high salt demand in alpine
countries, e.g. Switzerland, in the middle ages—a
problem which had important implications for trade
and politics.
Do salt deficiency and salt appetite also occur in
humans?
It is very illuminating to note the desperate efforts
humans made to acquire salt when they hade to live
under conditions conducive to salt deficiency. The
Venetian Ca de Mosto explored the West African coast
in 1455/56 and wrote: 'At certain times in the year
heat is there so oppressive that blood decomposes and
starts to rot, so that (the natives) would die without
salt' and a little later Valentin Fernandez, who explored
the Senegal in 1506, wrote 'The chiefs trade more gold
for salt than for anything else. They need salt for their
cattle and for themselves. They state that without salt
neither they nor their cattle will survive and prosper'.
In Africa salt was traded for gold on the basis of 1:1.
Lack of salt was also one element contributing to the
development of the slave trade. In the interior of the
continent children were sold into slavery for salt; in
Sierra Leone and in Central Africa it has been documented that the natives even gave their wives and
children away for salt. Enormous efforts were made to
transport salt across thousands of kilometers by caravans into the interior of the continent. Some investigators ascribed cannibalism, at least in part, to the drive
to satisfy the salt appetite.
When did the need arise to add salt to food?
Addition of salt to food was unknown to huntergatherers and this notion is well supported by more
recent anthropological studies in New Guinea. The
need to add salt arose when agriculture was introduced
in the fertile crescent and Anatolia, leading to a largely
vegetarian diet. In agreement with this idea linguistic
studies provide further evidence that the use of salt
was unknown to hunter-gatherers prior to the introduction of agriculture; for example ancient Asian languages do not have a word for salt.
Sources of salt throughout history
How was the needfor salt met?
Some populations satisfied their need for salt by cannibalism (see above), others by drinking milk (e.g. the
Kirgises and Numidians), others by drinking from
971
saline sources (e.g. Arabian Bedouins) or by drinking
animal blood and animal urine (e.g. the Massai in East
Africa). Such unaesthetic and uneconomical procedures illustrate the lengths to which humans may be
prepared to go in order to gain access to salt.
The intensity of salt hunger in some primitive societies is also illustrated by several laborious low-yield
techniques of salt production, e.g. burning of saliferous
herbs (in Neolithic England, contemporaneously documented in New Guinea and the Amazon basin), and
drying and burning of seaweed (Faroe Islands) etc.
The poorer classes burned plants or wood in 'pots' in
order to obtain plant ash, i.e. potash (Potasche in
German) as an alternative to the expensive salt. The
word 'potassium' for the element K is derived from
potash.
Apart from such minor techniques of salt production, the three main sources of salt were:
(i) sea salt obtained through evaporation of salt water
in salt pans
(ii) mining of rock salt, and
(in) heating of the brine of salterns (this procedure
gave rise to the German word 'Kochsalz').
The important role of salt production and salt trade
is well illustrated by linguistic studies.
In Indogermanic languages two roots for the word
salt exist: one is equivalent to the Latin 'sal', sel in
French, sale in Italian, sal in Spanish, Salz in German,
salt in English and in the Scandinavian languages, soli
in old Slavic. This word was also adopted in the nonIndo-European languages of Hungarian and Finnish.
The other is represented by Greek 'hal' (ok)—which is
of course going back to the same root—hall in
Protokeltic, halen, haloin and holen in the Gaelic
languages, al in Iranian, alt in Armenien and halicz in
Ukrainian.
The extreme value of salt is illustrated by the fact
that many city names are derived from the radical
'sal': Salzburg in Austria (whose founder, Sant Rupert,
is depicted with the salt vat), Salzkotten in Prussia,
Salzuflen in Westfalia, Langensalza in Thuringia,
Saltcotes in Scotland, Sulz/Neckar, Sulzbach,
Sulzbrunn, Sulztal (from sulze, the Germanic word
for brine).
The name of the city Hall (today Schwabisch Hall)
is derived from Celtic hal. Hall, an independent imperial city (Freie Reichsstadt) was so prosperous that it
had the privilege of minting its own coinage, the
so-called 'Heller', which was accepted throughout the
German empire and is still well known in folklore.
Further examples include Friedrichshall/Kocher,
Hall/Tirol, Halle/Saale (a University town also called
'Salt-Athens'), Hallstatt/Salzburg (after which an
entire prehistoric period is called: 'the Hallstatt
period'), Hallein/Salzburg, Reichenhall/Bavaria. The
distinction between Hallein (the diminutive) in
Salzburg and Reichenhall (the rich Hall) in Bavaria,
is evidence of medieval marketing techniques: one tried
to create the impression that the salt of Hallein was of
inferior quality compared to the rich salt of
Reichenhall.
The river Halys (famous through the prophecy of
the Pythia to Croesus) also derives its name from hal.
972
English towns linked to salterns can be recognized
by the suffix 'wich', e.g. Sandwich, Ipswich, etc.
Similarly Soden Germany and Solnice in
Czechoslovakia derive their the names from 'sot',
to 'boil'.
Tuzla in Bosnia (of dubious fame in recent years)
also derives its name from tuz, the Turkish word
for salt.
The high commercial value of salt is reflected by the
fact that enormous efforts were made to transport it
to the customer. Ancient Rome had special salt streets
(via salaria) which were taken care of by salt officials
(salarii). The city of Munich owes its origin to salt
trading: the bishop of Freising was collecting duty on
salt transports in Fohringen; Henry the Lion (Heinrich
der Lowe), then Duke of Bavaria, destroyed the
Fohringen bridge and founded Munich a few miles
upstream in order to collect duty from salt for his
treasury. Another example is the 'golden staircase'
(Goldene Steig), a path along which large quantities
of salt were laboriously transported by mule tracks
from Passau/Bavaria across the mountains of the
Bohmer Wald to Prachatice/Bohemia. The first tunnel
in the Alps, Monte Viso, was built in 1480 to transport
salt from Provence into Savoy. Even earlier, in 1298,
the Elbe-Trave canal with 17 locks and covering a
distance of 94 km was built to ship salt from Liineburg
to Liibeck in order to meet the high demand for salt
in Liibeck and the Hanseatic League to produce pickled
herring. The Latin word for herring, alecium, is said
to be derived from hal.
Let us return to the issue of salt production. In more
southern countries, Mediterranean and Southern
Atlantic, salt was produced by evaporation of sea
water in salt pans: sea water was run into basins, the
salt concentration increased by evaporation and finally
salt would precipitate in crystalline form.
In Northern countries, heat from the sun was not
sufficient for this process. Salt production required
heating brine or seawater, e.g. sel de briquetage in
Normandy or brenna-salt in Scandinavia. An alternative was the burning of peat soaked in sea water. The
'peaty' taste of Dutch herrings was a sales-promoting
gimmick similar to the 'peaty' taste of some whiskies
from West Scotland.
Until the 17th century, in central Europe salt was
almost exclusively produced in salterns e.g. in
Luneburg, Hall/Kocher, Reichenhall etc. Brine, with a
salt content of 10-25% (compared to 3.5% in sea
water) was heated in pans until salt precipitated and
could be collected. This process required enormous
quantities of wood.
Mining of rock salt was known in the early Iron
Age. In 1846 graves with rich gifts ranging from Baltic
amber to Egyptian fayence, were discovered in
Hallstatt close to Salzburg—an impressive documentation of the high market value of salt in those days.
The mining shafts extended over a length of several
kilometres and penetrated to a depth of 300 m into
the mountain. In Roman times mining of rock salt
was abandoned because the salt pans in the
E. Ritz
Mediterranean supplied sufficient salt for the entire
Roman empire. Salt from Palestine was one of the
sources of wealth of King Herod. It was only after the
collapse of the Roman empire that salt became a scarce
item again, and the market value of salt increased
dramatically. In ancient Rome salt had been a necessary but not exorbitantly expensive item: a lazy slave
was referred to as 'bought with salt', i.e. for next
to nothing.
It was not until the 16th century that mining of salt
was resumed, when exploitation of the rich salt deposits
in Wieliczka (close to Cracow in Poland) began.
Massive expansion of mining occurred under August
the Strong (August der Starke) of Saxony, then also
king of Poland, with the help of Saxon miners.
The regions of salt production and of high salt
demand did not coincide. As a consequence salt trading
became important. Salt, the 'white gold' was an object
of high politics, comparable to oil in present times.
In the early Middle Ages, Venice monopolized salt
trading for a long time. Large amounts of salt were
produced in the salt pans of Chioggia and Cervia in
the Adriatic sea, but it was also imported from
Alexandria, Cyprus, and the Balearic islands. Salt trade
with Alexandria is illustrated by the legend of St Mark,
today the local Saint of Venice, who gave his name to
the Duomo San Marco (St Marc Cathedral) and
Piazza San Marco (St Marc Square). In the 4th century
his bones had been stolen from Alexandria and
smuggled through customs, according to the legend
'hidden under salt and salt meat'. Pisa and Genoa
imported their salt from Sardinia and Provence and
delivered it across the Alpine passes into Switzerland.
With the beginning of the 14th century salt was also
produced South of the Bretagne on the Atlantic coast.
This so-called bay salt was of inferior quality.
Nevertheless, enormous quantities, up to 100000 tons
per year, were bought by Dutch herring fishers. Until
the 14th century the German Hanseatic League had
monopolized trade in herrings, which were cured with
salt from Luneburg. After the treaty of Straalsund
(1372) Denmark opened the Sund and the cheaper
though qualitatively inferior bay salt of Dutch merchants penetrated into the Baltic, and contributed to
the decline of the Hanseatic League. Bay salt was first
used for preservation of herring, but from the 16th
century onward large quantities were also needed for
the curing of cod caught in the rich Newfoundland
fishing grounds.
It is ironic that production of herring and cod was
mainly restricted to the protestant countries of the
North, while salted fish was predominantly consumed
in the catholic countries of the South, where the
catholic church insisted on abstinence from animal
meat on Friday. In 1350 horsemen still had to transport
fish on ice at a gallop from the Mediterranean to
Avignon to allow the Pope to have his Friday fish
meal. From the 16th century onward, even lesser
catholics had ready access to (salted) fish, which unfortunately had to be supplied by the hostile protestants—
according to Bergier 'trade between fools and dimwits'.
The history of salt
973
/*/£/W
Fig. 3. a Plans of a graduation house, and b view of a graduation house still in existence (after ref [7]). Brine was put on top of brushwoodcovered beams and gradually trickled downward. Water evaporated and the salt concentration was increased.
174
E. Ritz
A great demand for salt resulted not only from
fishing, predominantly in Holland and Scandinavia,
but also from cattle breeding in the Alpine countries.
Salt was needed for maximal yield of milk (which is
sodium-containing extracellular fluid, if you wish), for
the preservation of butter and cheese, for curing meat
and for tanning hides. It is important to remember
that in those days it was not possible to feed animals
during winter. Animals had to be slaughtered in late
autumn and their meat salted.
Very early on the Swiss developed the art of doing
business peacefully, while others bloodied their noses
in wars. Food supplies for European armies, and from
the 16th century onward of fleets as well, were dependent on the supply of salted meat and cheese from
Switzerland. Switzerland imported salt from Venice,
Salzburg, Bavaria, and Franche Comte. It was thus
able to play off one supplier against the other and to
achieve optimal prices—undoubtedly one important
element in the origin of the dreaded Swiss business
acumen.
Production of salt—its role in the beginnings of
modern industry and capitalism
Salterns were forerunners of industrial production and
capitalistic organization. They are therefore of great
interest with respect to the history of economics and
social sciences.
At the end of the 16th century, salterns were confronted with an economic and an ecological crisis.
Wood firing became uneconomical (i) because wood
had to be transported over increasingly long distances,
and (ii) because wages became prohibitive. An ecological crisis arose because gradually the forests in the
vicinity of salterns had been cleared. This is not
surprising since the production of one ton of salt
required 1.5 tons of wood. The heath around Liineburg
(Liineburger Heide), for romantic German poets the
incarnation of untouched nature, is mainly the result
of wood cutting to satisfy the voracious needs of the
Ltineburg salterns.
What measures led to a solution?
Admirable technological efforts were made to rationalize salt production. The brine was transported to the
wood instead of vice versa. After the forests around
Reichenhall had been cut down, a pipeline was built
to bring brine from Reichenhall to Traunstein which
was then still surrounded by dense forests. The pipeline
(Figure 4a) covered a distance of 33 km and with the
use of sophisticated pumps (Figure 4b) elevations of
more than 300 m were overcome.
Fig. 4. a Part of a pipeline, built by Reiffenstuel and operating
in 1619, that delivered brine from Reichenhall to the factory in
Traunstein, 33 km distant, b Sophisticated water pump used on the
pipeline. (After Ref [5].)
975
The history of salt
The second technological advance concerned concentration of brine by evaporation in graduation
houses. The ecologically compatible cost-free energies
of sun and wind were harnessed to increase the salt
concentration of brine from 20 to 60%, thus lowering
wood consumption by 80%. Figure 4 shows a typical
construction, 6-10 m in height and 100 m in length.
The third technological advance concerned substitution of cheap coal for wood. This was introduced in
Liverpool in 1770-71 after the saline sources of
Cheshire had been discovered. This was one of the
triggers of the industrial revolution in the Midlands.
, Salt as a source of revenue and its role in the
French revolution
For peasants salt was indispensible because they were
forced to use it for curing food and raising cattle. This
state of affairs was a golden opportunity for taxation.
It is little known that the salt tax, the so-called gabelle,
was one of the factors that led to the French revolution
in 1789. In India late as 1929-31, this tax still gave
rise to a civil disobedience campaign under Mahatma
Ghandi against the British.
The word gabelle is related to Arabian quabala,
hebraic gab, and Latin gabellum, the term for tax—
equally unpleasant in all languages. Saracens in Sicily
'invented' the salt tax and in 1320 Philip le Bel was
quick to introduce the gabelle as an indirect tax for
the salt produced in the salt pans of Peccais, which
were run as a royal monopoly. In this respect France
was certainly not unique. Salt production for instance
was also a royal monopoly in Bavaria, and in 1596
income from the salt tax amounted to two-fifths of the
royal revenue and two-thirds of the revenue from
customs. Before the French revolution, the salt price
to the customer was 20 times higher than the production cost. Because of the gabelle no less than oneeighth of the yearly income of a peasant's family was
spent on salt. Some regions in France were forced not
only to pay the tax, but also to consume 9 kg of salt
per head from the Royal salt stores (sel de devoir).
The gabelle was particularly oppressive because it was
so arbitrary: the gabelle was levied only in some regions
of France, and not in others, for instance when Brittany
joined France in 1550 it insisted on remaining exempt
from the gabelle forever. This situation was bound to
give rise to salt smuggling, which became so much of
a problem that a special police force, the hated gabelous, was created to stop it. The force was entitled to
enter and search private property for hidden salt and
even undertook military action against the smugglers.
The degree of oppression is illustrated by the fact that
in the last year before the French revolution, 3500
citizens were sentenced to death or the galleys for salt
smuggling. The French government had the wisdom
to use not only police and military action, but also to
summon the spiritual assistance of the church. In 1674,
Collet in his treatise on moral theology wrote that 'for
all Christians, smuggling of salt is a mortal sin'. He
stated that 'flagrant injustice is done to the Faith by
the licentiousness of salt smuggling, an accursed trade,
which leads to neglect of the church and disregard of
the holy sacraments'. Today the internal revenue office
has less painful, but more efficient means of indirect
taxation to extract money from citizens—undoubtedly
an admirable testimony to continuous human progress.
What salt intake is optimal?
This historical survey shows that salt deficiency may
undoubtedly exist in humans. The potential dangers
of salt excess that have been recognized more recently
must be balanced against it.
In this contextfigureson salt consumption in historical times are of definite interest. What evidence is
available? According to Pliny the Elder and Columella
among ancient Romans 25 g salt per day were used in
the cuisine of the patricians (in whose houses salt was
kept in a salt box, the so called patella). Not all of the
salt was consumed, however, since part of it was
discarded with the cooking water. In France where salt
was heavily taxed very detailed records are available
from revenue offices. For instance in 1725 daily salt
consumption in different districts subjected to the
gabelle varied between 13 and 15 g. In regions with
less taxation, consumption was presumably higher, but
the evidence is somewhat conflicting. For instance,
according to J. Waser, daily salt consumption in
Baden (Switzerland), a region without cattle raising,
was approximately 15.5 g. Similarly, in Zurich
(Switzerland) 8.5 kg of salt per capita were consumed
annually. In contrast, considerably higher salt consumption is documented in Scandinavian countries.
According to Astrup as much as 50 g per person per
day was consumed in Denmark, and Nils Alwall even
estimated that in the 16th century daily consumption
of salt in Sweden approached 100 g, mainly from salted
fish and cured meat.
What all these considerations show is that there is
little room for fanaticism when making recommendations concerning optimal salt intake in healthy individuals. Furthermore, for the nephrologist, who is
often forced to recommend reduced dietary intake of
salt, it may be useful to consider that a long history
has charged salt with emotional and symbolic connotations beyond what is supported by scientific evidence.
References
1. Denton D. The Hunger for Salt. An anthropological, physiological
and medical analysis. Springer-Verlag, Berlin, 1984
2. Hocquet 3C. Le Sel el le Pouvoir. De Van mil a la Revolution
francaise. Editions Albin Michel S.A., Paris, 1985
3. Astrup P, Bie P, Engell HCH. Salt and Water in Culture and
Medicine. Munksgaard, Copenhagen, 1993
4. Bergier JF. Die Geschichte vom Salz. Campus Verlag,
Frankfurt, 1989
5. Trend, M, Jahn W, Brockhoff E. Salzmacht Geschichte. Aufsatze
Haus der Bayerischen Geschichte. Verlag Dietrich Pustet,
Regensburg, 1995
6. Adshead SAM. Salt and Civilisation. MacMillan, London, 1992
7. Mager J. Johann Gottfried Borlach. Technisches Halloren- und
Salinemuseum, Heft 1, 1990