Ecology of knowledge: How does sea salt differ from ordinary salt and how much does water pollution affect its quality? Interesting chemical experiments and refutation of popular myths about the usefulness of sea salt.

How does sea salt differ from regular salt and how much does water pollution affect its quality? Interesting chemical experiments and refutation of popular myths about the usefulness of sea salt.

Origin of sea salt and methods of its extraction:

In fact, by and large, all the salt mined on the planet comes from sea water - it is from it that halite crystals precipitate, and it doesn’t matter whether it is modern water or the water that covered our planet millions of years ago. But a generally accepted division still exists. The Codex Alimentaris defines salt “as a crystalline product consisting of at least 97% sodium chloride on a dry matter basis (this is important) and is obtained from the sea, from underground salt mines and natural brines.”

However, the efforts of modern marketers aimed specifically at sea salt have already formed a whole set of cliches and have given rise to modern mythology based on them. Let's figure out which of these myths is reality and which is violet smoke. :)

This is my current collection of table salt, which is sold as “sea salt”.

Top row from left to right: Swedish pyramidal salt flakes (1), gray salt (2) and fleur de salt (3) from Guerande (France)

In the center from left to right: Crimean pink salt (4), fine sea salt noname (5), Dead Sea salt from Israel (6).

Bottom row from left to right: Hawaiian red (7) and green salt (8), “fleur de salt” from Lake Baskunchak (9), and sea bath salt from the USSR (10).

How not to get confused in this variety, and choose what is truly a natural product, and which of these can be put in quotation marks?

Let's figure it out.

And at the same time, let’s face the facts of “usefulness”, “naturalness” and other persistent clichés that are full of pseudo-scientific and pseudo-popular articles about sea salt. :)

I. MYTH FIRST

Sea salt is of natural origin or the economy must be economical.

In modern salt production, it is not the source that is important, but the method of its production - scale, manufacturability, costs and all sorts of prosaic matter in the form of additional buns - obtaining associated minerals from production waste. And sometimes the salt itself acts as a waste byproduct.

It’s easier and cheaper to open an underground or underwater salt dome formed millions of years ago and draw salt from there, either with combines or pumps. And it is this salt, rock, mined in a mine or lake, self-planted - that is what nature has worked on and is working on today. Our task is to take and not lose in the final product what already exists.

The method of artificial crystallization of halite in pools of sea water, and this is exactly what all marine fisheries do, is called “salt settling” and is, in fact, the formation of salt crystals under certain conditions. That is, yes, natural factors are certainly present - water, wind, wooden rakes, clay soil, that's all... But most often, salt pools are complex hydraulic structures, which are also used seasonally. Sea water is pumped into multi-stage “salt cages” with a complex system of flows and channels and goes through several stages of evaporation and concentration of the salt brine - purification from mechanical impurities and silt, precipitation of “associated” dissolved elements in the form of gypsum, dolomite, calcite, mirabilite, etc. . etc. and only penultimately is halite deposited. All this complex pool management requires care, remarkable staff skills, and in some places even manual labor. The order in which salts are deposited from the brine is the important “secret” of each fishery, since it depends on the weather, climate and the skill of the salinier. And somewhere else you need to put the remaining water and the minerals remaining in it, the solubility of which is better than halite - these are borates, sulfates, magnesium and other tables of the grandfather of modern chemistry. (As far as I know, in Crimea there was even a plant for the production of liquid bromine and magnesium salts, which most likely gave an extra penny to the fishery).

In the photo - this is approximately how salt is obtained from sea water - grains of sand, particles of clay and various other things, which will be discussed below. Therefore, after the “harvest”, halite goes through several more stages of maturation - purification, now from the “earth” or “human” factor, washing, drying. Where the volumes of salt extraction by sea are quite large, separate precipitation is not used; the salt is simply collected by combines and purified (USA, Italy, Turkey, Cyprus). Or they use modern technologies - deep-sea pumps, artificial pools under canopies with controlled air supply (Hawaii). This or that part of the salt is subjected to conventional refining - dissolution and crystallization in vacuum devices.

And here lies the first boundary of naturalness, that is, “naturalness.” Well, partly subjective, of course:

Salt, which is precipitated from sea water and perhaps washed with concentrated brine, is obtained in a few places. This is salt:

Salt that is precipitated from seawater using high-tech equipment or subjected to various types of refining or modification. This is salt

And the world economy has long understood everything about sea salt - its artisanal or semi-artisanal extraction hardly makes up a percentage of the entire world production, since objectively, even for large producers, the costs are much higher than for the extraction of rock or self-planted salt, and the volumes obtained are much smaller. The costs are even higher for traditional enterprises, where everything is done using old-fashioned methods and is kept afloat thanks to tourism and the accepted practice of “protecting the traditional name.”

Hence its increased price, which needs to be justified somehow.

About microminerals contained in salt, their benefits and harms:

While still on the shore, I would like to clarify a couple of points that I took as starting points.

1. The prefixes “macro-” “micro-” in relation to chemical elements as components of food have recently been actively replaced by the prefix “oligo-”, which actually literally means “insignificant” and indicates a deviation from the norm towards a decrease in something .

Meanwhile, these are completely scientific terms, as encyclopedias explain to us. Food macroelements are chemical elements contained in food products, the daily requirement for which is measured in at least tenths of a gram, these are: Na, K, Ca, Mg, P, etc. That is, these are two decimal places.

Micronutrients are elements contained in food products in low concentrations and necessary for normal life. Metals (Al, Fe, Cu, Mn, Zn, Mo, Co, Ni, Sr, etc.) and non-metals (I, Se, Br, F, As, B). They are usually measured in thousandths of a percent and below - these are three or four decimal places.

Anything less than these quantities are so-called “trace” quantities, that is, those that are at the limit of measurement accuracy using existing methods.

2. Standards for salt (GOST), adopted in our country, do not in any way distinguish sea salt from the rest, regulating the difference in indicators only by the degree of purification. Plus sanitary standards for the content of harmful substances. Actually, the same standards apply all over the world, differing only in details.

3. I took data and figures from salt packages, manufacturers’ certificates of analysis (reputable manufacturers keep them in the public domain) and analysis data performed on orders from manufacturers and independent studies. Links - along the way.

So.

II. MYTH SECOND

Sea salt - contains less sodium chloride and more iodine than “regular” salt.

Salt from the first photo is involved in comparisons and experiments.

Here are its characteristics.

Whether this is actually so can be seen from the table. According to the Codex Alimentaris, in order for salt to receive the prefix “food”, it must contain at least 97% sodium chloride in the dry residue. All salt that does not fit into this standard belongs to the category of agricultural (for animals) or technical (cosmetics, lamps and stoves, etc.)

Here are reservoirs of different sizes and different geographical locations. Obviously, the composition of the salt must be different. But in fact, this great diversity allows us to distinguish only two groups - salt from the industrial and traditional production methods. Let us first compare the available indicators of industrially produced salt with the standard adopted in our country.

It is clearly seen that in terms of sodium chloride content, the salt of these brands corresponds to refined salt of the highest quality, that is, that same “ordinary” salt, which in any case contains all the same macroelements and all within the same limits. And this is understandable. Any industrial method of salt extraction includes its purification in one way or another, resulting in refined salt of ordinary quality, which does not have any advantages over other types of salt. For example, for an Israeli company, the main activity is the production of chemical fertilizers, and table salt is only a by-product. In addition, the mineral composition of the Dead Sea water simply does not allow us to directly obtain food-grade salt from it.

If you look at the iodine content... Do you see it? So I don’t see it. Simply because all iodine compounds are volatile and unstable, and by the time the salt is packaged in packs, they have safely disintegrated. The commercially available “iodized” sea salt is refined sea salt with the addition of iodine. Iodine, by the way, is added exclusively to refined salt simply because other macroelements, which are more abundant in unrefined salt, are able to displace iodine from its potassium compounds - and as a result, it will fly away again.

And, like any fine salt, an anti-caking agent is added to sea salt.

Thus, the content of macroelements in the examined samples clearly demonstrates that the imaginary “advantages” of industrially produced sea salt disappear in a lilac mist, like the iodine evaporating right on the seashore. That is, from the name “sea” all that remains is sea water as the source of its production.

An important indicator of the naturalness of sea salt and evidence that the salt has not been processed are indicators 8 and 9. “Insoluble residue” is impurities, and “Moisture” is water built into the salt crystal lattice. We’ll talk about them a little later, when we have something to talk about, but for now the data doesn’t even hint at their presence.

And this fact tells us that all sea salt from large producers is no better than other types of salt - rock or evaporated salt, which means that we pay the entire amount above the regular price for marketing.

And further. Whatever you want, these distorted Latin words in the names, in my opinion, put the brands on the same level as “Panassonik”, “Abibas” and similar artifacts.

OK. But maybe natural salt mined by hand in a traditional way really has an advantage and is worth the money?

At the same time, let’s dispel another myth.

III. MYTH THIRD

Sea salt is a source of valuable minerals or deposits of “precious stones and golden sand in the depths of the body.”

Let's take a look at another table that compares the raw sea salt that is currently available to me with the standards.

What do we see here? There is no iodine here either, or it is in such an insignificant amount that it does not even have a preventive value. But it has marketing. :) Backed up to the wall, manufacturers and retailers reluctantly admit that the iodine content in their product is so low that their salt cannot be recommended even for preventive purposes.

Speaking about the macromineral composition, we are again convinced that natural sea salt does not go beyond the usual content for unrefined first and second grade salt, which, by the way, includes most varieties of natural rock salt.

What about microminerals? Wanting to show how unique their products are, some manufacturers and retailers order independent studies of their samples for the presence of microminerals using all existing physical and chemical methods.

The lower part of the table reflects only those elements for which maximum permissible concentrations in food products have been introduced, and the table helps to understand what and how much. I did not present here the tails of the tables with complete data, but the research results reflect 4/5 of the entire periodic table, including heavy metals, rare, rare earth, transuranium, radioactive elements. They are not found in nature in their pure form, but are part of some minerals and sea water. All of them are found in the samples in the so-called “trace” quantities that sea salt marketers are so proud of.

Why is all this math important? Part of this chemical compote are strong poisons and kill, have an effect immediately or after some time, having the ability to accumulate in the body - it all depends on the dose. So a strong mineral composition is a controversial benefit, in my opinion...

However, the effect of “trace” elements is much less pronounced than the effect of macro-elements. And the most important thing here is sodium. And all sea salt manufacturers talk about the reduced amount of sodium in sea salt. But if we add up the first two lines of the table, we almost always get the required 97-98%. Only one salt, Seltic Salt, shows a decrease in the total indicator - 83%, but the decrease in sodium is not at all that great compared to the others. This means, according to the law of conservation of the same grandfather Mendeleev, there is more of something else in it. And this is another thing - sulfides, carbonates, etc. have been little studied from the point of view of nutritional value.

However, many note that sea salt still tastes less salty than “regular” salt. By the way, this is a term that means nothing if you look at it. It’s better to compare refined and unrefined salt. And here, yes, salt tasters or sensitive people can detect the difference.

The fact is that aqueous minerals crystallize mainly in the form of crystalline hydrates, which is why there is such an indicator as “water content,” which determines the content of bound water. Perhaps its presence in the crystal lattice explains the “less salty” taste of unrefined sea salt that some experience.

The generally accepted standard prescribes that the sodium chloride content should be at least 97% in the “dry matter”. That is, to carry out the analysis, water is first removed from the salt, and then measurements are taken. Natural salt salt, as standards allow, may contain 4-5 even up to 12 percent water (France), so taking into account the insoluble residue (impurities), less than 95% sodium chloride is obtained, which means the salty taste is weakened. However, in order to “replenish” the usual sensations, it may simply have to be added in larger quantities.

Let me make a reservation once again - we are talking only about unprocessed natural sea salt. Each other contains less water or does not contain it at all. Water is removed from sea salt in different ways. Over millions of years, processes of recrystallization, formation of new compounds, etc., occur in the thickness of the earth’s crust under monstrous pressure, so the composition of rock salt, for example, is quite different from sea salt. Another natural process is storing salt in piles on the seashore: precipitation, wind and sun also contribute to chemical and physical transformations and the removal of excess moisture from the salt. Large sea salt production plants cannot waste as much time drying the salt naturally. Therefore, excess water is removed from it by some industrial method.

Whether such bound water exists in salt can be determined by a fairly simple physical experiment. I took 30g of different salts and heated it in a dry, tightly sealed container in a sand bath for 10-15 minutes.

The rest of the heated salt did not give any residue on the foil, which is quite adequate to the lack of moisture in it.

The fact is that “when heated above 100°C,” well, you understand... Crystalline hydrates give up water, the water begins to evaporate, the carriage turns into a pumpkin, and already at 150°C sea salt loses all its advertised properties.

But that's not all. There is one more indicator of naturalness, which would also be nice to highlight. And this will be an “insoluble residue”, which is not in refined salt, but which is in natural salt.

IV. MYTH FOUR

“Water is the source of life” - millions of bacteria cannot be wrong.

Until now, we have all been looking for benefits dissolved in sea water. But. There is another interesting indicator - the insoluble residue. These are all kinds of pollution - natural or not. Obviously, it will only be contained in unrefined salt; it does not matter whether it is rock salt or cage salt. In order for salt to be classified as food grade, this insoluble residue must be less than 1%.

Water-soluble compounds that “sit” together with salt

Organic remains of marine flora and fauna, etc.

Silt, clay, sand, rocks

Petroleum products, metal or concrete chips, rust, etc.

On the Internet you can find very beautiful romantic pink-red panoramas of salt pools. This “blooming” of salt water gives rise to the prosaic vital activity of about a hundred species of so-called “halophilic” flora and fauna - these are small crustaceans, algae and bacteria that have adapted to live in strong brines. The basis of their life activity is not chlorophyll, but the orange dye beta-carotene, which has recently been ranked as an important antioxidant. In a certain way, these products can be extracted along with salt, and then it acquires a pinkish-orange color, but such salt is not a food product, but can be used in cosmetic products or as a source of beta-carotene.

And this is not all the types of bacteria that exist in sea water - pathogenic bacilli and cocci survive quite well in salt water at a concentration of 10-15% for up to three months. And if the salt is not subjected to any heat treatment above 70°C. They feel quite comfortable in it and are waiting in the wings.

Since there are strict standards for the content of bacteria in food products, each batch of organic French salt undergoes bacteriological control. For comparison, refined sea salt produced in the USA undergoes such control once a year.

If the first three pollution can be classified as natural, then the fourth point is added by industrial mining. That is why most of the cage sea salt mined in the open pit is subjected to some kind of purification.

Well, now let's take a closer look.

The presence of sediment is easier to detect, and everyone encounters this when preparing, for example, pickle for cucumbers. If you take unboiled cold water and rock salt, for example.

From left to right: red Hawaiian salt, gray salt, Crimean salt, Dead Sea salt. The naked eye can see that the color of the solutions is slightly different.

True, red “Hawaiian” salt and black Cretan salt are not natural salts, since they contain artificial additives: activated carbon and “purified” red clay. I almost said “food grade clay.” :) It is worth saying that the initially cloudy solution became more transparent after a day; during the settling process, both solutions cleared, almost everything that was added to them settled to the bottom. That is, no artificial coloring components, everything is natural and mineral.

The same cannot be said about the trendy “green Hawaiian salt.” As a supplement, it contains “organic green bamboo extract” produced in China. In the photo there is a bag of this very fashionable salt. During storage, the faint odor, of course, had long since disappeared, and everything that served as a carrier of the extract left a mark not only on the salt crystals, but also on the environmentally friendly paper bag. :)

As a result, let’s compare what we end up getting on store shelves under the name “Sea Salt”. In fact, all the cracking trade names are the same two large categories of salt - refined and unrefined. Each of them has its own advantages and disadvantages that arise from their characteristics. published

Obtaining table salt from Black Sea water and studying its properties (Author: Alexandra Borisenko, Municipal Educational Institution “Technical and Economic Lyceum”, Novorossiysk, Krasnodar Territory. Supervisor N.P. Kozlova)

For a long time, residents of Kuban have been looking for the opportunity to obtain local salt due to the high cost of imported salt. The body of primitive man received the necessary salt from food of animal origin. Salt has had a strong influence on many human languages. Until recently, salt was so expensive that wars were fought over it, and sometimes a lack of salt caused “salt riots.” Now the problem of salt extraction in Kuban has not been solved, and I decided to study ways to obtain it.

Target: Obtaining table salt (NaCl) from Black Sea water and the possibility of its use for residents of the Caucasian coast.

To achieve the goal I set the following tasks:

1. Study methods of extraction and properties of table salt.

2. Study the areas of use of table salt in human life.

3. Conduct an experiment to obtain sodium chloride from Black Sea water and determine its salinity in Tsemes Bay.

4. Assess the economic efficiency of obtaining salt from sea water.

Methods: To conduct the experiment, I used the combined method of the ancient Pomors of sequential freezing and evaporation.

Hypothesis: Table salt obtained from the water of the Black Sea has all the properties and qualities of commercially available salt.

Table salt has weak antiseptic properties; The 10–15% salt content prevents the development of putrefactive bacteria, which leads to its widespread use as a preservative, and in the past in the processing of leather and fur raw materials. They used to say: “One eye is on the police (where the bread is), the other is on the solonitsa (salt shaker)”, “Without bread it’s not satisfying, without salt it’s not sweet.”

In nature, sodium chloride occurs in dissolved form in seawater and in the form of the mineral halite - rock salt. The word "halite" comes from the Greek "halos", meaning both "salt" and "sea". Halite is rarely pure white. More often it is brownish or yellowish due to impurities of iron compounds.

In modern industry, salt is mainly mined three ways:

1. Open method - development of salt layers reaching the surface (Artyomovskoye field)

2. Mine method - development of underground deposits (Iletsksol, Tyretsky salt mine, etc.)

3. Freezing or evaporation of salt from salty reservoirs (Baskunchak deposit, Lake Elton, etc.)

Salt sold in stores is approximately 97% NaCl; the remaining share comes from various natural impurities and special additives (iodides, carbonates, fluorides).

I placed the container with pre-filtered sea water in the freezer, where it was kept at a temperature of -18°C for 7 hours. The resulting fresh ice after opening the plastic container was removed, and 120 g of the remaining liquid or brine was poured into a steel container. The brine was evaporated on a gas burner for 19 minutes. After evaporation, crystals formed in the form of an uneven, porous, fragile white crust along the entire bottom of the container. The crystal size ranges from 0.5 to 5 mm. Almost all of them do not have a regular shape, and only individual specimens approach the cube. When you try to separate from the crust, the crystals are destroyed, turning into a white powder. The distribution of impurities of various salts in seawater can fluctuate under the influence of various factors over a wide range (emergency discharges from industrial enterprises, pesticide pollution, etc.).

The monetary costs in the experiment to determine salinity consist of payment for electricity consumption for operating the freezer and gas consumption. Electricity consumption according to the electric meter was 4.7 kW/h. Due to the lack of a gas meter, the payment for operating a gas burner was taken to be 0.7 rubles. The total costs for evaporating salts from sea water amounted to 4.7 x 1.97 + 0.7 = 9.96 rubles. The commercial cost of table salt in the retail network is 10 rubles. for 1 kg.

I studied the basic properties, methods of extraction and production of sodium chloride and conducted an experiment, during which it turned out:

1. The salinity of sea water in laboratory and field conditions can be determined by freezing and evaporation.

2. When using the technology of freezing and evaporation from sea water, the final product produces sodium chloride with admixtures of other salts in a mass volume of up to 20-25%.

3. The data obtained during the experiment on the monetary costs of freezing and evaporating salts from sea water can be used when planning similar educational work in school laboratories.

Extracting minerals from sea water

Despite the fact that at least 60 elements are now known to be dissolved in seawater, only four are extracted on an industrial scale. These are sodium, chlorine (common table salt), magnesium and some of its compounds, as well as bromine. Some calcium and potassium compounds are extracted as by-products during the production of table salt or during the extraction of magnesium. Typically, these products are obtained either by extraction from seawater or by processing algae, which concentrate calcium and potassium. It should be noted, however, that the industrial extraction of the listed elements directly from sea water has not yet been developed. Numerous attempts have been made to extract other mineral compounds from seawater, but commercial extraction has been unsuccessful. Many methods have also been patented for extracting table salt, magnesium and its compounds, bromine, iodine, potassium, calcium sulfate, gold and silver from sea water (Baudin, 1916; Cernik, 1926; Niccali, 1925; S. O. Petterson, 1928; Vienne , 1949).

Table salt extraction

The systematic extraction of salt from seawater began in China much earlier than 2200 BC. e. For centuries, many peoples were dependent on the sea as a source of salt (Armstrong, Miall, 1946). And now salt, extracted from seawater by simple evaporation by the sun's rays, occupies a significant share in the total balance of salt consumption in countries such as China, India, Japan, Turkey and the Philippines. Every year, about 6 million tons of salt are produced worldwide. Typically, producing salt by evaporation from seawater requires a hot climate with dry winds. However, in addition to the proximity of the sea and a hot climate, a number of other conditions must be met: low permeability of the soil of evaporation pools, the presence of vast low-lying areas lying below sea level or flooded by sea tides, low precipitation during months of active evaporation, the absence of the diluting influence of river fresh waters and, finally, due to the low cost of salt extraction - the availability of cheap vehicles or the proximity of sales markets.

About 5% of all salt consumed in the United States is produced by evaporation, primarily in the San Francisco Bay area, where the fishery began in 1852. Figure 5 shows artificial evaporation ponds near the southern end of San Francisco Bay. Here, with a total area of ​​about 80 sq. miles "Leslie Salt Company" annually produces approximately 1.2 million tons of salt. Similar salt pans are also found in the upper reaches of Newport and San Diego Bays in Southern California; their annual productivity is 100 thousand tons (Emery, 1960). The release of sea water into the evaporation basins near San Francisco Bay is carried out during periods of high water through the sluice gates in the dam that protects the basin from the sea. Sea water is kept here until a significant part of it evaporates and the salts contained in it settle down.

Rice. 6. Mechanical scrapers are used to remove the top layer of crystallized salt. By the time the salt harvest occurs, the thickness of the salt layer usually reaches 4-6 inches.

Calcium sulfate is one of the first to crystallize from solution. After the calcium sulfate salts have settled to the bottom, the remaining brine is carefully transferred to the cage basin, where, due to evaporation, the solution is further thickened until sodium chloride begins to precipitate. Evaporation of brine continues until it reaches a specific gravity of about 1.28, that is, until the addition of magnesium salts begins. At this stage, the brine solution is called bitter mother brine. The brine is removed from the cage pond and transported to other plants, where various magnesium compounds, bromine and other salts are obtained from it. After removing the brine, fresh brine is again poured into the cage basin and the entire cycle of producing sodium chloride is repeated. By August 1, a 4-6 inch thick layer of sodium chloride has accumulated at the bottom of these pools. Salt is sampled using mechanical scrapers and loaders (Fig. 6); then the salt is washed from various impurities with sea water and stored in the form of large cone-shaped mounds (Fig. 7). Salt used for industrial use in most cases is not further purified. However, it is additionally purified if it is intended for food consumption by the population. The NaCl content in the refined product exceeds 99.9%. The cost of salt obtained by free evaporation of sea water under the influence of the sun ranges in the USA from $10 per 1 ton of raw product near the extraction site to $150 per ton of purified and packaged table salt.

The procedure for extracting salt from seawater is approximately the same all over the world, however, in a number of countries, cheap labor makes it possible to modify this process.

In countries with other climates, such as Sweden and the Soviet Union, salt is obtained by freezing sea water. Brine ice, consisting of almost pure water, is filtered from the residual brine, which is then subjected to a series of successive operations to freeze it out before the concentration of the residual portions becomes high enough to begin evaporation to dryness under the influence of artificial heat (Armstrong, Miall, 1946) .

The concentrated brine remaining after the separation of sodium chloride is subjected to further special processing in order to extract the compounds present in them. Thus, adding calcium chloride to a solution causes the precipitation of calcium sulfate (gypsum), which is then sold. With further concentration of the brine, magnesium, potassium and other salts precipitate. In the final stages of the process, magnesium chloride and bromine are extracted from the residual solution.

Extraction of bromine from sea water

Bromine can be considered almost a marine element, since the ocean contains 99% of the total bromine content in the earth's crust (see Table 2). Bromine was discovered in 1825 by the French researcher A. J. Balard in concentrated solutions obtained after precipitation of salt from the water of salt marshes near Montpellier. Bromine was later discovered in potash deposits in Strasfurt and in brines from drilling wells in Michigan, Ohio, and West Virginia. Bromine was first isolated from seawater in 1926 in California during the processing of mother brines obtained during the extraction of salt in artificial evaporation tanks. Industrial consumption of bromine was relatively limited before the production of high-compression internal combustion engines, so market demand was met by quantities obtained from well brines and salt deposits. But then the situation changed dramatically. Ethylene dibromide was added to anti-knock gasoline containing tetraethyl lead additive to prevent lead deposits on cylinder walls, valves, pistons and spark plugs. With such an increased need for bromine, brines pumped from boreholes turned out to be insufficient. The production of bromine as a by-product in the production of salt did not satisfy demand either. There was an urgent need for another source of bromine.

In an extensive search for additional sources of bromine, the Ethyl Corporation developed a process for direct precipitation of bromine directly from seawater that had not been pre-concentrated. According to this scheme, bromine is precipitated in the form of an insoluble compound - tribromoaniline - when seawater is treated with aniline and chlorine. To avoid hydrolysis of chlorine, seawater is first acidified with sulfuric acid. Later this process was expanded to industrial scale. The plant was installed on a ship, which was then converted into a bromine recovery plant. Operating 25 days a month, such a floating plant produces about 75 thousand pounds of bromine. During the same period, the plant consumes reagents: 250 tons of concentrated sulfuric acid, 25 tons of aniline, 66 tons of chlorine, stored between the upper and lower decks. The efficiency of extracting bromine from seawater, which contains only 0.1 lb per ton, is approximately 70%. The vessel has protective measures taken to avoid dilution of seawater by waste water discharged after completion of the process. Later it was found that to prevent mixing, along-shore sea currents that exist off many coasts can be successfully used. At the moment, it is believed that from a technical point of view, the process of extracting bromine on board a floating plant has been solved successfully, but working in the open sea with highly corrosive reagents is much more difficult than on land.

The choice of location for the construction of a bromine extraction plant should be made with particular care. In this case, it is necessary to exclude in advance the possibility of diluting the sea water consumed by the plant with rainfall, waste water, as well as water from which bromine has already been extracted. In addition, sea water must have a high and constant salinity, a relatively high temperature and must not be contaminated with organic waste, which wastes chlorine. Such a place that satisfies all of the above requirements was found near Cure Beach (North Carolina). Here the Ethyl Dow Chemical Company built a plant with a capacity of 3 thousand tons of bromine per year. In 1938, the capacity of this enterprise was increased to 20 thousand tons of bromine per year (Shigley, 1951).

Another plant of this type was built near Freeport, where the conditions for extracting bromine from sea water meet all technological requirements to a greater extent than near Cure Beach. The design capacity of this plant is 15 thousand tons of bromine per year. In 1943, another plant of equal capacity was built there. The enterprise near Cure Beach was closed at the end of the Second World War. Thus, the Freeport plants currently produce about 80% of the bromine consumed annually by the United States. In Fig. Figure 8 shows a flow diagram of the bromine extraction process of the Ethyl Dow Chemical Company.

At the Cure Beach plant, according to previously developed technology, a mixture of seawater with acid and chlorine was poured into the top of a brick tower with wooden gratings built inside it. Bromine dissolved in seawater was reduced by chlorine to relatively volatile elemental bromine, and the acid present in the mixture prevented the hydrolysis of chlorine. As the mixture of seawater and bromine drained from the top of the tower, air was blown from the bottom up. The passing air carried the free bromine out of the seawater and carried it into an absorption tower filled with soda ash, after which the bromine-free seawater was discharged back into the sea. A solution of soda ash saturated with bromine was treated with sulfuric acid in order to convert sodium bromates and bromides into free bromine. The mixture was then pumped into an evaporation column, where bromine was distilled off and recondensed into glass or ceramic vessels. Further purification of bromine by distillation made it possible to ultimately obtain a product with a bromine content of up to 99.7%.

In 1937, this process was slightly modified. Thus, during the initial distillation of bromine, sulfur dioxide and air were used as transfer agents. As a result, bromine was released in the form of hydrobromic acid, which made it possible to significantly improve its subsequent purification. Although bromine recovery efficiency in both processes exceeds 90%, the direct extraction of bromine from seawater using sulfur dioxide is now used almost exclusively in the United States (Shigley, 1951).

Extraction of magnesium from sea water

Magnesium is the lightest metal used in construction. Its specific gravity is 1.74, while that of aluminum is 2.70, and that of iron is 7.87. This metal is most widely used in the construction of vehicles. In addition, magnesium is used as a component of alloys with aluminum, in systems of anodic and cathodic protective coatings, in pulsed photo lamps and in many other fields of technology. By 1964, annual world production of magnesium was about 150 thousand tons.

Sea water contains approximately 0.13% magnesium. Although this concentration is only 1/300th the amount found in magnesium ore mined on land, the main source of this metal for the United States is seawater. Magnesium was first obtained from seawater in England (Armstrong, Miall, 1946), but the first large enterprise for extracting magnesium from seawater was built near Freeport in early 1941 by the Ethyl Dow Chemical Company. Until this time, magnesium in the United States was obtained from well brines and from magnesite deposits.

The choice of a site for building a plant near Freeport was dictated by the following very favorable circumstances. The availability of cheap natural gas allows it to be used effectively to generate heat and electricity. The geographical location of the plant makes it possible to discharge wastewater back into the Gulf of Mexico, with an extremely negligible possibility of diluting the consumed seawater. Very cheap lime can be obtained from lime shells mined from the bottom of the Gulf of Mexico, just a few miles from the magnesium plant. In Fig. Figure 9 shows a flow diagram for magnesium extraction at a plant near Freeport, and one of the sections of this plant is shown in Fig. 10.

Rice. 10. General view of the magnesium processing plant at the Ethyl Dow Chemical Company plant, Freeport (Texac). Dorr thickeners are visible in the foreground, into which a mixture of seawater and lime is pumped in order to accelerate the precipitation of magnesium chloride.

Seawater enters the facility at a rate of about 1 million gallons per hour through the underwater sluice gates of a canal connected to the Gulf of Mexico. The advantage of this supply system is that the lower layers of water have a significantly higher salinity than the surface water in the plant area. In an artificial pool, the water is continuously treated with lime milk (it was mentioned above that lime is obtained by calcining oyster shells). As a result of the reaction of lime milk with magnesium compounds, a liquid sludge-like precipitate of insoluble magnesium hydroxide is formed, which is then pumped into settling tanks. The sediment makes up approximately 2% of the total volume of sea water consumed in this production, in other words, already at the first stage of the technological process, a 100-fold concentration of the useful component is carried out. The waste water is discharged into the Brasos River, which flows into the Gulf of Mexico at a considerable distance from the plant.

Filtered magnesium hydroxide is dissolved in hydrochloric acid. The resulting solution of magnesium chloride is concentrated by evaporation in order to partially get rid of the salts captured from sea water. Calcium is precipitated as insoluble sulfate or gypsum by adding magnesium sulfate to the solution, after which the solution is filtered again to separate the gypsum and other salts, and then concentrated by evaporation. When the magnesium chloride concentration reaches approximately 50% and the temperature of the solution rises to approximately 170°, it is sprayed onto the previously dried solid MgCl 2 . The solvent instantly turns into steam, and magnesium chloride precipitates. The dried solid residue is then placed in an electrolytic chamber where it decomposes into magnesium metal and chlorine gas. Chlorine is converted to hydrochloric acid, which is successfully used in subsequent cycles of the process. Magnesium metal is scooped out of the electrolytic chamber and formed into ingots. Their metal content exceeds 99.8% (Shigley, 1951).

Man began to obtain salt from sea water from time immemorial, and more specifically, when plant foods appeared in his diet. The production technology was quite simple: areas in the form of lagoons were separated from the sea, in which, under the influence of the sun, the water evaporated, and the salt crystallized and settled to the bottom. It was collected and eaten.

The main disadvantage of such salt is a large amount of impurities “unnecessary” for the human body: gypsum, anshdrit, calcium sulfate. However, as this technology developed, it was noticed that the salts contained in seawater could be precipitated separately. For this purpose, in some basins (preparatory) the specified impurities are deposited, and in others (sedimentary) salt is deposited. Table salt obtained in this way is much cleaner and more pleasant to the taste.

Modern solepractitioners work according to the above principle. In Ukraine these are the Genichesky, Heroic saltworks and the Solyanoye saltworks.

How is table salt obtained from sea water?

Enterprises for the production of table salt consist of two sections: 1) extraction and 2) salt processing.

The first section - the basin farm - includes pools with dams and sluices, feeding bypass ditches and ditches for removing mother brine, as well as areas for storing freshly mined salt. Pools are divided according to their purpose into preparatory, reserve and cage.

Table salt from sea water. The technological process for extracting table salt includes the following stages: preparation of the pool system for the evaporation season, preparation of cage brine and its storage, cage, harvesting and storage of salt.

In Crimea, pools are prepared at the end of November. To do this, the remaining salt is dissolved with seawater, which is then, after dissolving the salt, pumped into reserve pools.

Next, the bottom of the cage pools is leveled using a massive metal trowel, which is a welded frame with knives and moved by a salt combine. After ironing, the bottom of the pool is dried, filled with a small layer of water and left until spring.

In the spring, the pools are emptied, the bottom is leveled with rollers and filled with appropriately prepared cage brine obtained from sea water by natural concentration by evaporation either in preparation pools or in natural lakes (where they exist). The cage wound is stored in reserve pools, the distinguishing feature of which, from the preparatory and cage basins, is their greater depth (about 3 m).

The evaporation season in the south of Ukraine and Crimea begins in April. As water evaporates from the cage basins, they are replenished. At the same time, salt is released at the bottom of the pools in the form of a layer, the thickness of which reaches 80 mm by the end of the evaporation season. The accumulated brine is dumped into the sea or lakes. The salt is harvested using combines and stored here, on the shore, in the form of mounds. Salt is not only stored in the mounds, but is also washed away by precipitation.

Salt from the hillocks, as needed, is supplied to the processing workshop using vehicles or rail. In this workshop, it is washed several times with cage brine in order to wash solutions of magnesium salts from the surface of its particles. The washed salt is dehydrated in centrifuges and sent for drying, and after drying, it is crushed to the required grinding in roller mills and supplied for packaging. The finished product is packaged in paper packs (weighing 1 kg) using special machines and sent to consumers.

On the packs of salt it is indicated at which salt plant it was made, its grinding, and the method of production.

Dissolving and evaporating salt

Target: Integration of experimental and research activities within a single educational space for children to master educational fields. Increasing productive cooperation between teacher and children.

Integration of educational areas.

Educational field "Cognitive development"

Continue to introduce children to the properties of salt (smell, taste, color, solubility);

Develop cognitive initiative

To develop the ability and skills of research activities;

Exercise children in basic experimentation with salt

Practice working with magnifying glasses,

Educational field "Speech development"

Improve dialogical speech: learn to participate in a conversation, it is clear for listeners to ask and answer questions.

Develop curiosity. Expand children's ideas about objects and phenomena that did not occur in their own experience.

Educational field "Physical development"

Continue to introduce children to physical exercises to strengthen body systems (finger exercises for speech development); visual gymnastics – for the prevention of myopia).

Form correct posture.

Material and equipment:

Magnifying glasses according to the number of children, salt, containers with water (according to the number of children, spoons, napkins, video slides on making salt.

Progress of the lesson.

1. - Guys, I again invite you to our laboratory. We will conduct an experiment. But first, let's play.

Game "Say the other way around"

Game "Logic chain"

1. - What is experience? (methods that scientists use when studying science; scientific experiment).

Experience is a scientific experiment. To do science, you need to be smart, be able to think, and draw conclusions. And we want to become like that. To do this, let's do some brain exercises.

Exercise 1

I.p. Stand with your feet shoulder-width apart. We carry shoulder to hip, not elbow to knee! The head turns slightly as it moves. The body seems to be folded, and the arms and legs are only exposed. Do not close your mouth. Lips are free.

This exercise increases a person’s activity and energizes him.

Exercise 2

We take ourselves by the ears - by the upper part of the ear: thumb behind, index finger in front. And gently massage the ears, as if slightly stretching them back and turning them inside out. We massage each point on the edge of the auricle several times from top to bottom.

There is clarity in your head, you can quickly gather your thoughts.

Exercise 3

We bend one arm at the elbow and put it forward, thumb up, on which we fix our gaze. The thumb is on the midline of the body. We mentally imagine a circle in front of us, in which we draw an infinity sign - a lazy figure eight, the main thing is that it is round.

The left arm hangs freely along the body. With our right hand we calmly and freely draw: up along the midline of the body, to the left - down-right to the midline of the case and along it up to the middle and in the other direction: up-right-down-left-midline up.

We change hands. And we draw with our left hand. Start left up.

Vision improves.

3. – Let’s go to our laboratory. Sit down at the tables.

Before conducting experiments, listen and remember the rules of the laboratory:

Answer each other;

Don't interrupt each other;

Listen to your friend’s answers to the end;

Answer with a complete sentence.

What's on your tables? (a cup of salt, a glass of water).

Repeat safety rules!

Consider the water. What is she like?(liquid, transparent, odorless, has no shape, fresh, colorless).

Examine the substance in the cup. What is this? Riddle - hint: I'm not so tasty on my own, but everyone needs it as food. (Salt.) What salt? You can also try. (white, crystals).

Salt is the only mineral that people consume in its pure form. Salt is a food product, and we know it as small white crystals. In fact, naturally occurring salt has a grayish tint. Salt is produced in different types: unrefined (rock) and purified (table), coarse and fine, sea salt.

Where do we meet salt? (in the kitchen, at sea).

Right. The water in the sea and ocean is salty. There are lakes in the world with salt water, salt lakes, in which the water is even saltier than in the sea. Look. Here are the salt lakes.

4. - Now let’s carry out the experiment. Pour salt into the water. What happened? (salt has dissolved)

What was the water like? (salty)

Where did the salt go? (she dissolved)

Is there any salt left in the water? (yes, the salt has changed its state)

And now the main question. Children, do you think it is possible to separate salt from water? Is it really impossible? How?

(pour into another glass, filter. Any assumption of children must be tested experimentally)

5. Experiment - evaporating salt in a spoon.

What's left in the spoon? (salt)

The spoon is still hot, so I'll try the taste myself - is it really salt? Yes, children, this is salt. This means that the assumption turned out to be correct: after heating, salt remained.