Reaction of chromium with acids
Metallic chromium dissolves in dilute hydrochloric acid forming Cr(II) and hydrogen gas, H2. In aqueous solution, Cr(II) is present as the complex ion [Cr(OH2)6]2+. Similar results are seen for sulphuric acid but pure samples of chromium may be resistant to attack. Chromium metal is not dissolved by nitric acid, HNO3 but is passivated instead.
Cr(s) + 2 HCl(aq) Cr2+(aq) + 2 Cl−(aq) + H2(g)
Cr(VI) is reduced to Cr(III) by ascorbic acid (reductive coefficient = 3.473*106 M-1*s-1) .
Reaction of chromium with air
Chromium metal does not react with air at room temperature.
Reaction of chromium with ammonia
Cr(III) is precipitated by NH3 as Cr(OH)3.
[Cr(H2O)6]3+(aq) + 3 NH3(aq) [Cr(OH)3(H2O)3](s) [green] + 3 NH4+(aq)
The precipitate dissolves in excess ammonia.
[Cr(OH)3(H2O)3](s) + 6 NH3(aq) [Cr(NH3)6]3+(aq) + 3 H2O(l) + 3 OH−(aq)
Reaction of chromium with carbonate
Cr(III) is precipitated by carbonate as Cr(OH)3. The precipitate is not soluble in excess carbonate.
2 [Cr(H2O)6]3+(aq) + 3 CO32−(aq) 2 [Cr(OH)3(H2O)3](s) + 3 H2O(l) + 3 CO2(g)
Reaction of chromium with halogens
Chromium reacts directly with fluorine, F2, at 400°C and 200-300 atmospheres to form chromium(VI) fluoride, CrF6.
Cr(s) + 3 F2(g) CrF6(s) [yellow]
Under milder conditions, chromium(V) fluoride, CrF5, is formed.
2 Cr(s) + 5 F2(g) 2 CrF5(s) [red]
Under still milder conditions, chromium metal reacts with the halogens fluorine, F2, chlorine, Cl2, bromine, Br2, and iodine, I2, to form the corresponding trihalides chromium(III) fluoride, CrF3, chromium(III) chloride, CrCl3, chromium(III) bromide, CrBr3, or chromium(III) iodide, CrI3.
2 Cr(s) + 3 F2(g) 2 CrF3(s) [green]
2 Cr(s) + 3 Cl2(g) 2 CrCl3(s) [red-violet]
2 Cr(s) + 3 Br2(g) 2 CrBr3(s) [very dark green]
2 Cr(s) + 3 I2(g) 2 CrI3(s) [very dark green]
Reaction of chromium with hydroxide ions
Cr(III) is precipitated by hydroxide ions as Cr(OH)3 The precipitate is amphoteric:
[Cr(H2O)6]3+(aq) [violet] + OH−(aq) Cr(OH)3(H2O)3(s) [green] + 3 H2O(l)
Cr(OH)3(H2O)3(s) [green] + 3 OH−(aq) [Cr(OH)6]−(aq) [green, octahedral] + H2O(l)
Reaction of chromium with nucleotides
Cr(VI) is reduced to Cr(III) by nucleotides .
Reductive coefficients for nucleotides adapted from .
Reaction of chromium with peroxide
Cr(III) is easily oxidized to CrO4− by hydrogen peroxide under alkaline conditions:
2 Cr(OH)4−(aq) + 3 H2O2(aq) + 2 OH−(aq) CrO42−(aq) [yellow] + 8 H2O(l)
Cr(VI) dimerizes by acid at concentrations c(Cr(VI)) > 10-2 M:
CrO42−(aq) [yellow] + 2 H+(aq) HCrO4−(aq) Cr2O72−(aq) [orange] + H2O(l)
CrO42− can be precipitated by several metal ions e.g. Ba. All chromates are soluble in mineral acids and can be precipitated again by sodium acetate.
Under acidic conditions Cr2O72− reacts with hydrogen peroxide forming a blue instable diperoxochrome(VI)oxide [Cr(O2)2O]
Cr2O72−(aq) + 4 H2O2(aq) + 2 H+(aq) 2 [Cr(O2)2O](aq) + 5 H2O(l)
2 [Cr(O2)2O](aq) + 2 H+(aq) Cr3+(aq) + 3 O2(g) + 2 H2O(l)
Reaction of chromium with phosphate
Cr(III) is precipitated in cold acetic acid by hydrogen phosphate:
Cr3+(aq) + H2PO4−(aq) CrPO4(s) [green] + 2 H+(aq)
Reaction of chromium with saccharides
Cr(VI) is reduced to Cr(III) via soluble and reactive intermediates of Cr(V) by saccharides and derivatives .
Reductive coefficients for saccharides and derivatives adapted from .
Reaction of chromium with sulfide
Cr(III) is not precipitated by sulfide in 0.4 M hydrochloric acid. Sodium sulfide precipitates Cr(III) as the hydroxide. The precipitate is dissolved by excess sulfide.
Cr(VI) is reduced to Cr(III) by H2S
Reaction of chromium with thiols
Cr(VI) is reduced to Cr(III) by thiols .
Reductive coefficients for thiols adapted from .
Reaction of chromium with water
Chromium metal does not react with water at room temperature.
Redox reactions of chromium
Cr(VI) is reduced to Cr(III) by reduction agents like SO2 og KI
Cr2O72−(aq) + 2 H+(aq) + 3 SO2(aq) Cr3+(aq) + SO42−(aq) + H2O(l)
Cr(VI) is reduced to Cr(II) by strong reduction agents like Zn
Cr2O72−(aq) + Zn(s) + 14 H+(aq) 2 Cr2+(aq) + 7 H2O(l)
Method 3500-Cr C+D Colorimetric Methods . Sample water (or soil digested in water) is reacted with diphenylcarbazide in an acidic solution to produce an intensely red-violet colored solution. Hexavalent chromium is measured against a range of standards using light absorption at 540 nm.
Method limit of detection in water = 0.005 mg/l
Method limit of detection in soil = 1.00 mg/kg
Method limit of detection in water = 0.0005 mg/l
Method limit of detection in soil = 0.50 mg/kg
Magnesium and zinc are minerals essential for human health. Magnesium plays an important role in bone health and blood pressure regulation. The recommended dietary allowance, or RDA, for magnesium for men is 420 milligrams, or mg, and for women, 320 mg. Zinc is important for the metabolism of the foods you eat, DNA synthesis and wound healing. Vitamin D3 800 IU, B6 50 mg, B12 150 mcg, Biotin 4.5 mg, Zinc 40 mg, Selenium 55 mg, Magnesium 300 mg, Manganese 2 mg, Chromium 800 mcg, Indian Barberry (Barberis aristata; root) 1,000 mg, Guar Gum (Cyamopsis tetragonoloba) 500 mg, Cinnamon Bark 200 mg, Gymnema slyvestre Leaf 100 mg, Alpha-Lipoic Acid 50 mg, Banaba Leaf 30 mg, Vanadium 250 mcg. The study uses data from the FDA. It is based on chromium and magnesium (the active ingredients of Chromium and Magnesium, respectively), and Chromium and Magnesium (the brand names). Other drugs that have the same active ingredients (e.g. Generic drugs) are not considered.
Chromium Zinc And Magnesium
© 1991-2010 Jerry Emanuelson
A large majority of U.S. adults have a deficiency of the mineral chromium. Chromium is not readily absorbed from foods, and the human body even has difficulty in absorbing chromium from many nutritional supplements.
To alleviate this problem, the U.S. Department of Agriculture developed and patented chromium picolinate, a readily absorbed form of the mineral. The U.S.D.A. licensed chromium picolinate to Nutrition 21 of San Diego, which manufactures the nutrient-grade powder. Their product is available in capsule form from several makers of nutritional supplements.
A number of reports on the importance of chromium picolinate were made at the October, 1992 Conference of the American Aging Association in San Francisco. At that conference, biochemist Gary W. Evans of Bemidji State University in Minnesota reported that laboratory rats fed diets supplemented with chromium picolinate lived to a median age of 45 months compared to a median life span of 33 months for rats fed a similar diet with other forms of chromium supplementation. Rats deficient in chromium typically live no more than 24 months.
Chromium is believed to enhance the effectiveness of insulin, a hormone vital for the processing of glucose. Supplemental chromium reduces blood glucose levels.
High levels of glucose and problems with insulin activity cause glycation, a process that damages vital proteins in the body. This protein damage is the principal reason that diabetics have a lower life expectancy than normal. Many researchers believe that supplementary chromium could be very useful for diabetics, especially those with type 2, or adult-onset, diabetes.
It has been known for several decades that restricting calorie intake by about one-third will increase the life span by 50 percent or more. In every species tested, calorie restriction has produced a significant increase in life span. (It is vital, though, that the calorie-restricted diet not be deficient in any essential nutrient.)
It is widely believed that the effectiveness of calorie-restriction is mostly due to the lower blood glucose levels induced by calorie restriction. This results in less protein damage from a process known as glycation. Most of the researchers using chromium picolinate believe that the increased longevity it produces are due to its effects on reducing protein damage caused by poor glucose and insulin metabolism.
Gary W. Evans reported that the rats with chromium-picolinate-induced longevity had 25 percent lower blood glucose levels and 60 percent lower glycation-induced protein damage than the control rats.
Other studies reported at the conference showed that chromium picolinate in humans improved the HDL/LDL ratio (the ratio of 'good cholesterol' to 'bad cholesterol') and that it increased muscle mass while decreasing the percentage of body fat.
Athletes doing weight training taking chromium picolinate at Bemidji State University had a 21 percent greater drop in body fat and a 42 percent greater increase in muscle mass than athletes on the same program not taking the supplement.
The standard dose of chromium picolinate is 200 micrograms per day for a adult. The wholesale price of a year's supply of chromium picolinate is about a dollar. Of course, the retail price of the capsules available to the consumer is much higher than this.
Another form of bioavailable chromium is chromium polynicotinate, or niacin-bound chromium. It is also a patented substance, and is sold under the tradename Chrome-Mate. Chromium polynicotinate seems to have some definite advantages over chromium picolinate, including even better bioavailability.
One study indicated that large amounts of chromium picolinate cause chromosome damage, whereas chromium polynicotinate did not. At first, this study was widely criticized because the chromium picolinate levels were far higher than one would get with normal supplementation. Subsequently, however, many other scientific studies have called into question the safety of chromium picolinate.
It now appears that niacin-bound chromium is a much safer form of chromium for supplementation. Some studies have also shown that niacin is necessary for chromium supplements to be of benefit.
Chromium aspartate, an unpatented and much less expensive form of chromium, appears also be very well absorbed; but it does not have the benefit of the level of scientific testing that the patented forms have. This makes it difficult for the consumer to know which form of chromium to take. Even supplement manufacturers are confused and some supplements contain a mixture of two or more of the above-mentioned forms.
Even though chromium aspartate may work as well as the other two forms, the only advantage of chromium aspartate is in its lower cost to the supplement manufacturer, who must buy it in large quantities. The cost of the chromium to the end user is not a significant factor because the amounts used in a daily supplement are so tiny.
As it pertains to life extension, it is likely that chromium is just a part of the larger subject of insulin resistance. Anything that can reduce the problem of insulin resistance, and bring blood sugar levels down to a moderately-low and stable level, will reduce the problems of aging.
Only very small amounts of chromium are necessary. Typical doses of chromium are around 200 micrograms daily. Doses that are very much higher than this may cause adverse effects. The chromium necessary for the human body is trivalent chromium. A form of chromium called hexavalent chromium is quite toxic. Testing of nutritional supplements by companies such as Consumerlab, routinely test for contamination by hexavalent chromium in chromium supplements. If you decide to take supplemental chromium, subscribing to a service such as Consumerlab can tell you exactly which supplements are safe to take. Consumerlab repeats their testing of nutritional supplements occasionally, especially supplements such as chromium which can contain hazardous contaminants. Even some normally very reliable supplement manufacturers have, on rare occasions, found their supplements containing harmful levels of hexavalent chromium.
For more information, see: Janson, M., 'Orthomolecular medicine: the therapeutic use of dietary supplements for anti-aging' Clinical Interventions in Aging. September, 2006. Volume 1, Issue 3. pp. 261-265.
Iron supplements have been popular for decades, and many people require them. Many recent studies, though, have linked iron to all kinds of biological damage. Excessive iron can cause heart and liver disease and significant brain damage. In 1992, an entire supplementary issue of the Annals of Neurology was devoted to reports of numerous scientific studies implicating iron in Parkinson's Disease and other degenerative brain disorders. The most popular example of oxidation damage is rust. Rust occurs when highly-reactive free radical iron reacts with oxygen. The same thing can happen in the human body. Many types of brain, liver, kidney and cardiovascular damage are literally due to rust.
On the other hand, low iron levels are a major health problem, accounting for many undiagnosed cases of lethargy and fatigue. A routine blood chemistry test will measure many parameters of serum iron and hemoglobin; but many blood tests fail to include a test for ferritin. Ferritin is the body's primary iron storage protein and is a much more sensitive measure of iron levels. You may have to specifically request a ferritin test when getting a blood chemistry analysis. Ferritin will also often detect internal blood loss that may be a very early indication of a potentially major disease.
The 'normal' ranges for ferritin levels given by blood testing labs are far too high for optimal health. If you test in the upper half of the 'normal' range for ferritin, you may want to consider donating blood occasionally until ferritin levels drop to the lower half of the 'normal' range.
It is prudent not to take any form of iron supplement unless medical tests show a clear need for it. Although no major scientific studies have been done to determine the safest form of iron supplement, basic chemistry along with scientific reports on short-term side effects point to some good general rules for iron supplementation.
If you need to take iron supplements, ferrous sulfate is the worst choice. In spite of the fact that many physicians and pharmacists still recommend it, ferrous sulfate should be regarded as a poison. As soon as ferrous sulfate dissolves in your stomach, the iron component becomes a pure free radical and begins doing damage. Some antioxidant vitamins will attack and neutralize this free radical iron, but then they are not available for counteracting other free radical damage.
Ferrous fumarate and ferrous gluconate are a somewhat better choice as an iron supplement; but some iron supplements have been designed to minimize the potential of free radical damage. Cardiovascular Research sells bovine ferritin. Since ferritin is a protein, it will be partially broken down in the digestive tract, but much of the iron in the Cardiovascular Research product should remain bound to protein, and should not cause as much free radical damage as conventional iron supplements.
The safest iron supplements are probably the iron-polysaccharide complexes: essentially iron bound up in a complex sugar molecule. They are sold under brand names such as Niferex, Ferrex-150 and Nu-Iron. Iron-polysaccharide complex products are available without a prescription, although few stores carry them in stock. You often have to ask the pharmacist about these products. Most pharmacies can special order any iron-polysaccaride products.
The important thing to remember about iron is that too little or too much can cause devastating health problems. One should be more concerned, though, if serum iron and ferritin levels are a little high than if they are a little low. As stated earlier, the generally accepted 'normal' ranges of serum iron and ferritin are higher than what they should be for optimal health.
One possible alternative to iron supplements in mild cases of anemia is a combination of high doses of folic acid and vitamin B-12. A typical dose might be 2000-5000 micrograms of each per day. Whether using iron, folic acid, B-12 or any combination, it is important to have blood tests before and after any significant change in supplementation to find out what effect the supplementation is having. The combination of high dose folic acid and B-12 with low-dose iron may take an individual from mild anemia to iron overload if the blood tests are not performed.
Supplemental testosterone can also raise hemoglobin and hematocrit significantly.
The extent of magnesium deficiency is currently a controversial subject. Research is currently underway to examine the hypothesis that magnesium deficiency may be a major health problem in the U.S. and around the world. In the meantime, some physicians are having success in treating a variety of disorders with supplemental magnesium.
Dr. Jonathan V. Wright, a well-known and successful practitioner of alternative medicine says, 'If it spasms . . . try magnesium.' He has had success in treating muscle spasms, bronchial spasms, intestinal spasms and spasms of the esophagus with supplemental magnesium.
Supplemental magnesium has also been used to successfully treat cardiac arrhythmias and mitral valve prolapse. Magnesium is often quite beneficial in treating asthma. Magnesium also reduces the chances of complications in individuals who suffer a heart attack. In many individuals with high blood pressure, supplemental magnesium will cause a noticable blood pressure drop.
In diabetics, magnesium supplements can slow the progress of diabetic retinopathy.
Too much oral magnesium can cause diarrhea. Milk of magnesia (magnesium hydroxide) and epsom salts (magnesium sulfate) are commonly used as laxatives. The chance of a diarrhea problem can be minimized by taking smaller amounts of magnesium spaced throughout the day and by drinking plenty of water.
Severe magnesium deficiency may require magnesium to be given by injection. Many physicians who specialize in preventive or alternative medicine have had great success with giving their patients magnesium intravenously or by injection.
Moderate amounts of oral magnesium usually do not cause problems. Magnesium aspartate is the most readily absorbed, but should not be used by those who have experienced problems with aspartame (Nutrasweet) or monosodium glutamate (MSG). Magnesium citrate is also an easily absorbed form of magnesium, and has become widely available during the past few years.
For further information, check the following reference:
McLean, Robert M., 'Magnesium and its Therapeutic Uses: A Review. ' American Journal of Medicine. Vol. 96. pp. 63-75. January, 1994.
Next Chapter: N-Acetyl-Cysteine