Although I agree with you that the Droitwich Springs are 'unique
worldwide' I have to dispute the figures for salt concentrations
that you quote.
You say that the concentration of sodium chloride in the water
at Droitwich is 25.926%, comparing well with:-
> 'The maximum amount of salts (all salts) that can be held in
>solution [which] is 26.395% at 60 degrees F (15.56 degreesC).'
Are you reproducing a regular typo here? Reference tables
show that a saturated solution of sodium chloride (the 'maximum
amount ...that can be held in solution') at freezing point, 32
degrees F, contains 35.7% w/w salt, rising to 39.2% w/w at
boiling point. The concentration at '60 degreesF' would be
between these two limits but much higher than the figure quoted
for the Droitwich brine. The latter indeed represents a very
concentrated solution of sodium chloride (and other salts) but,
on the figures quoted, falls short of being a solution that will not
dissolve further salt(s).
I urge you to check the analytical figures that you have been
Museum of London Specialist Services
From: [log in to unmask]
To: [log in to unmask]
Subject: Re: EH welcomes new UK industrial World
Date: 17 December 2001 16:54
I'm glad you asked. Thats exactly the point, the NATURAL brine
springs at Droitwich are unique worldwide. There are numerous brine
springs everywhere in the world. What is unusual is a set of phenomena
that combine to produce virtually PURE brine containing only sodium
chloride (which is an important economic aspect in the recovery of salt).
There are trace elements of one or two minerals that are usually
abundant in most springs, notably calcium carbonate, magnesium, ferric
oxide, sulfates (in volcanic areas)). The maximum amount of salts (all
salts) that can be held in solution is 26.395% at 60 degrees F (15.56C).
These brine springs contain 25.926% sodium chloride - and that is MOST
UNUSUAL worldwide. Salt is widely obtained from seawater which contains
2.9% sodium chloride out of a total dissolved solids of 3.7655% (high in
the magnesium and potassium bromides and chlorides). This means that 96%
water has to be evaporated to make salt, achieved more economically by
solar evaporation. But even then it takes a lot of refining to produce
salt fit for preserving different types of food (let alone its other
There are other factors: this brine lies only at 120-150 ft.deep.
Usually this concentration occurs only at greater depths. When springs
occur close to the surface they are usually diluted with fresh
groundwater and thus become brackish and uneconomic to exploit. This did
not happen at Droitwich.
Yet another factor was the brine flow. There are three sites where
brine springs of equal strength occur, but there was a huge difference in
brine flow and only one pit, Upwich, provided 92% of the salt for the
industry there (the other 4 pits/springs together supplied 8%). Two pits
at one site dried up in the 15th century. Drought being another factor
which affects brine flow. These three sites are only within a 1/4 mile
area, yet they differed significantly from the one principle pit. This
pit is 30 ft.deep
One would think that these conditions in natural springs must occur
somewhere else in the world, but so far in 30 years of searching I have
found none, from China to the Near East or in the New World that
duplicate these conditions. I am working with several specialists in an
attempt to account for this phenomena and there are two possible theories
we are looking into. Of course as technology advanced ways were found to
economically produce a pure salt, but even today it costs more to get it
to this stage of Droitwich purity.
On 12/15/01 11:05 PM Paul Barford writes:
>But then, is Droitwich a monument on a world scale? There are many other
>salt springs in western Europe, many of which have also long been in use
>some of continental significance, with authentic remains preserved. How
>Droitwich compete with these? To be on the WHL a monument does not simply
>have to be old but fulfil a mass of other criteria as laid down by the
>guidance notes of the Convention (which I understand are currently being
>modified). But you are right that the geology makes it a site which links
>the natural and historical heritage, which the World Heritage Committee
>seems to like at the moment.
>----- Original Message -----
>From: Bea Hopkinson <[log in to unmask]>
>To: <[log in to unmask]>
>Sent: Sunday, December 16, 2001 5:10 AM
>Subject: Re: EH welcomes new UK industrial World Heritage Sites
>> Although I am pleased to read the news below I still find it
>> that an industrial site as ancient as Droitwich has not been
>> Not only ancient, but continuously worked and a natural geological
>> phenomena. Yet not one word by the archaeological community to support
>> this British heritage unique worldwide.
Beatrice Hopkinson 73071,327@compuserve