Speaking of “nitrate”, I am afraid that many people will immediately think of what corrosive nitric acid is encountered, of Nobel’s glycerol nitrate explosives, of the ammonium nitrate that caused the Beirut Port explosion in Lebanon some time ago, and of the battlefield filled with smoke… In short, yes. Give people a terrible feeling. In fact, “nitrate” is indispensable in daily life.
Glauber’s salt
The ancients called some mineral salts nitrate or saltpeter. In fact, nitrate or saltpeter includes two different types of compounds, that is, two different types of mineral salts, one is sulfate, such as sodium sulfate, and the other is nitrate, such as potassium nitrate.
Natural sodium sulfate is often called Glauber’s salt, and there are abundant Glauber’s salt resources in some inland lake deposits. Long ago, people used Glauber’s salt to tan fur. People first put on “clothes” by directly putting animal fur on their bodies. The untanned animal fur is smelly, hard and easy to rot. Therefore, the method of tanning fur with nitrate should have been invented a long time ago, and it is difficult to verify how early it is.
The action of nitrocellulose with leather changes the structure of collagen in the leather, and the leather not only becomes soft, but also can avoid decay. Now, the folks still retain the ancient method of tanning fur, commonly known as “tanning”. It is also precisely because the ancients believed that nitrate can make fur soft and eliminate the ingredients that make fur hard, so this substance is called “elimination” or “elimination of stone.” Since this is a naturally occurring mineral, the word “nitrate” was later created to replace “elimination”. However, in older documents, it is often called “elimination” or “elimination of stone”.
The most common crystals of natural Glauber’s salt (sodium sulfate containing 10 crystal water) are as sharp as thorns, so it is called Glauber’s salt. Impure Glauber’s salt, which contains more impurities, is sometimes called nitrate, and because it is often used to tan fur and leather, it is also called dermatophyte.
Sodium sulfate is easy to absorb water. External use has the effect of sterilizing and reducing swelling. Oral use can cause diarrhea and can be used as a laxative. Glauber’s salt is still used as a topical medicine. For example, nitrate alum lotion is an auxiliary medicine for the treatment of herpes zoster, hemorrhoids and other diseases. Alum is a mixture of 50% Glauber’s salt (sodium sulfate), 30% borax (sodium borate) and 20% alum (potassium aluminum sulfate). These three compounds all have drying and water absorption and antibacterial effects.
There is also a medicine for external use, the ingredients of which are “cold water stone”, realgar, cinnabar, stone cassia (calcined), etc., which are also used to treat diseases such as herpes. “Cold water stone” is Glauber’s salt, which is sodium sulfate, which has water absorption and drying effect; realgar is tetraarsenic tetrasulfide and cinnabar is mercury sulfide. They are both poisons. Heavy metal ions can bind to the sulfhydryl groups in the organism and have a good poisoning effect. The role of microorganisms; Shijue Ming is a shellfish, after calcination, the organic matter is burned out, and the remaining calcium oxide (lime) also has the effect of sterilization and drying. Putting these several medicines together has obvious sterilization and drying effects, which is beneficial to the regeneration of the body.
Fire nitrate
The main component of another type of saltpeter is potassium nitrate. Potassium nitrate can also be used to “nitrate”. When it is put together with combustible materials, it will easily catch fire, so it is called nitrate.
In ancient times, there were not many places where potassium nitrate mines could be found. People mostly obtained them from the soil in the roots of old houses, toilets, pig pens, etc. Soil with a lot of nitrogen elements, due to the action of bacteria and other microorganisms, oxidize nitrogen-containing organic compounds into nitric acid, and the cations in the soil generally include calcium, magnesium, sodium, potassium, etc., thus forming nitrate. Soil that contains more nitrates is called nitrate soil. The ancients used plant ash water (rich in potassium carbonate) to soak this kind of nitrate, let potassium carbonate react with calcium nitrate, magnesium nitrate, sodium nitrate, etc. to obtain a solution rich in potassium nitrate, and evaporate the water to obtain saltpeter (potassium nitrate crystals) . Since such saltpeter is obtained from soil, it is also called soil saltpetre.
Because Glauber’s salt can also be obtained from alkaline soil, it is sometimes called soil salt; both kinds of glauber’s salt can be used to tan fur. Therefore, it is easy to confuse Glauber’s salt with sodium sulfate as the main component and sulphur salt with potassium nitrate as the main component in the ancients.
Relatively speaking, it is more difficult to obtain fire salter, and fire salter has the magical function of “fire”. Therefore, ancient alchemists believed that fire salter should be “real saltpeter” and that true saltpeter should emit a purple flame. . Just as Tao Hongjing of the Southern Dynasties recorded in “The Annotation of Materia Medica”: “Burn it with fire, purple and green smoke will rise, and clouds are real saltpeter.”
The knowledge of these alchemists is really amazing. Now we know that the flame reaction of potassium ions (reflecting the characteristics of its emission spectrum) is purple, and only pure potassium nitrate can emit a purple flame reaction. If some sodium ions are mixed in, the orange produced by its combustion The yellow flame will be more conspicuous.
Combining sulfur and charcoal with fire smelt, that is black gunpowder, which is used to make firecrackers in the folk.
Nitrate, including potassium nitrate and ammonium nitrate, is also a very good fertilizer. After the invention of the synthetic ammonia process, they have been used on a large scale. Since nitrate is an oxidant, it is easy to catch fire when it encounters flammable substances. Therefore, the nitrogen fertilizers we actually use are mainly urea, and potash fertilizers are mainly potassium chloride. This is important for the transportation, storage, sales and users of chemical fertilizers. That said, it’s much safer.
Nitroso
A long time ago, people discovered that when processing meat (such as making sauce, ham, meat, sausage, etc.), adding a small amount of “nitrate” (sodium salt of nitric acid or nitrous acid) will make the meat bright red and beautiful , Delicious and not easy to spoil.
Studies have found that under the action of bacteria, nitrate will be reduced to nitrite, and then react with the lactic acid in the meat to become nitrous acid, followed by a disproportionation reaction to produce nitric acid and nitroso groups. Nitroso groups combine with meat myoglobin to produce bright red nitroso myoglobin, which makes cured meats appear bright red. Moreover, nitrite has a certain effect on inhibiting the growth of microorganisms, so that the cured meat can avoid rot. In this process, a special good taste is also produced.
People have been using this method for thousands of years. However, this method also has a great risk, that is, nitrous acid can react with amines commonly found in the human body, such as dimethylamine, to produce nitrosodimethylamine, which is a strong carcinogen.
Although most countries in the world still allow the use of nitric acid and sodium nitrous acid as preservatives (antimicrobial agents) and coloring agents in meat processing, they have strict regulations on their dosage. Some small workshops often use excessive amounts of nitrate in order to make meat products look better, taste better, and keep them longer. We must pay special attention to this.
Sodium nitrite can oxidize the divalent iron ions in hemoglobin into trivalent iron ions in the human body, so that hemoglobin loses the ability to carry oxygen, resulting in hypoxia of human tissues, especially brain tissue, and even death.
Of course, the possibility of acute sodium nitrite poisoning caused by the addition of nitrate in meat processing is relatively small. The biggest danger of adding nitrate in meat processing is carcinogenesis. The main danger of acute sodium nitrite poisoning is accidental ingestion. The appearance of sodium nitrite is very similar to that of table salt (sodium chloride), and it also has a salty taste, which often causes poisoning by accidentally ingesting sodium nitrite.
Nitroglycerin
Finally, let me talk about nitroglycerin. Yes, it is the famous explosive in history, but now it is even more famous as an emergency medicine. Nitroglycerin is used as a vasodilator in medicine. It is made into tablets and administered sublingually. It has a rapid effect and is used to treat angina pectoris caused by coronary artery stenosis. Nitroglycerin tablets must be taken under the tongue. This is because the swallowed nitroglycerin must pass through the liver during the absorption process, the effect is too slow, and most of the nitroglycerin in the liver will be broken down. When contained under the tongue, the dissolved medicine can quickly pass through the blood vessels under the tongue and directly enter the blood system. Nitroglycerin generates nitric oxide during metabolism, which is a messenger molecule that can dilate blood vessels and expand blood vessels so that the heart muscle can be supplied with blood in time to avoid necrosis. Therefore, it is good for us to know some of this knowledge, and sometimes it can even save lives.
