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WHAT ARE NITRATES?
Chemical characteristic.
Nitrate is a chemical compound made up of nitric acid HNO3
and metal, oxide, hydroxide, salt (e.g.: NaNO3, KNO3,
NH4 NO3, Mg(NO3)2 etc).
Nearly all nitrates are water-soluble and stable at normal temperatures.
Normally nitrates smelt at relatively low temperatures (200-600°C),
often decomposing.
Nitrates of alkaline metals (potassium, sodium etc.) decompose to the
nitrites (NO2) with release of oxygen (at the protracted
heating step decompose on the oxide of metal, molecular nitrogen and
oxygen, because of what are good oxidants). Nitrates of metals of middle
activity (iron etc.) decompose at heating to the oxides of metals with
release of dioxide of nitrogen and oxygen. Nitrates of noble metals
(silvers etc.) decompose to the free metals with release of dioxide
of nitrogen and oxigen.
Nitrates are b enough oxidants in the hard state (usually as fusion),
but practically does not possess oxidizing properties in solution, unlike
an aquafortis.
Influence on an organism. Nitrates constantly intake into human body and directly are not poison for him. However, at a consumption in enhanceable amounts nitrates in a digestive tract are partly reducted to the nitrites (more toxic compounds), and last at a receipt in blood can cause a methemoglobinemia (bivalent iron in haemoglobin of blood oxidizes to trivalent and became metagemoglobin. He is not able to carry not oxygen O2 not carbon dioxide CO2). In addition, from nitrites in presence of amines can appear N-nitrozaminy, possessing carcinogenic activity (favour in formation of cancer tumours). At the reception of high doses of nitrates with a drinking-water or products nausea, shortbreathing, posinenie of skin covers and mucous membranes, diarrhoea, appear through 4-6 hours. All of it is accompanied by a general weakness, dizziness, by pains in cervical area, by palpitation.
Location in nature.
Plants use nitrogen from salt (nitrate) for the construction of cells
of organism, creation of chlorophyll. The maximal accumulation of nitrates
takes place in the period of growth of fruits (before the beginning
of harvesting), therefore not fully ripe not vegetables (vegetable marrows,
egg-plants) and potato, and also vegetables of the early ripening can
contain more nitrates, than attaining normal ripeness.
In plants nitrates are distributed unevenly. In a cabbage, nitrates
most accumulate in the head, in cucumbers and garden radish - in superficial
layers, in a carrot - in a center. On the average, at washing and peeling
of vegetables and potato 10-15% nitrates are lost. Yet more - at thermal
culinary treatment, especially at cooking, when lost from 40% (beet)
to 70% (cabbage, carrot) or 80% (potato) nitrates. As nitrates are enough
active compounds chemically, at storage of vegetables their content
diminishes after a few months on 30-50%. To weaken the concentration
of nitrates it is also possible by steeping of product or dilutions
of it in the large volume of products what are not containing nitrates.
Allowed levels. Daily allowed intake of nitrates is equal to 5 mg per kilogramme of human body. So, for the "ordinary" adult man with weight 70 kg this value is equal to 0,35 gramme. Maximum allowed concentrations of nitrates in some vegetables and fruit are resulted below in a table. These values are set coming from the "typical" diet (in other words - ration of feed) of man of central part of Eurasia.
| Product |
Content,
g/kg |
Leaf vegetables (lettuce, parsley, dill) |
2,00 |
| Radish | 1,50 |
| Beet | 1,40 |
| Early cabbage | 0,90 |
| Spring onion | 0,60 |
| Late cabbage | 0,50 |
| Early carrot, vegetable marrow | 0,40 |
| Aubergine | 0,30 |
| Late carrot, potato | 0,25 |
| Sweet pepper, banana | 0,20 |
| Tomatos | 0,15
/ 0,30 |
| Cucumber | 0,15
/ 0,40 |
| Strawberry | 0,10 |
| Melon | 0,09 |
| Onion | 0,08 |
| Watermelon, grape, apple, pear, apricot, mango, peach, ebony | 0,06 |