Silver nitrate
Overview
Silver nitrate is an inorganic compound
Inorganic compound
Inorganic compounds have traditionally been considered to be of inanimate, non-biological origin. In contrast, organic compounds have an explicit biological origin. However, over the past century, the classification of inorganic vs organic compounds has become less important to scientists,...

 with chemical formula
Chemical formula
A chemical formula or molecular formula is a way of expressing information about the atoms that constitute a particular chemical compound....

 . This compound is a versatile precursor to many other silver
Silver
Silver is a metallic chemical element with the chemical symbol Ag and atomic number 47. A soft, white, lustrous transition metal, it has the highest electrical conductivity of any element and the highest thermal conductivity of any metal...

 compounds, such as those used in photography. It is far less sensitive to light than the halides
Silver halide
A silver halide is one of the compounds formed between silver and one of the halogens — silver bromide , chloride , iodide , and three forms of silver fluorides. As a group, they are often referred to as the silver halides, and are often given the pseudo-chemical notation AgX...

. It was once called lunar caustic because silver was called luna by the ancient alchemists, because they believed that silver was associated with the moon.

In solid silver nitrate
Nitrate
The nitrate ion is a polyatomic ion with the molecular formula NO and a molecular mass of 62.0049 g/mol. It is the conjugate base of nitric acid, consisting of one central nitrogen atom surrounded by three identically-bonded oxygen atoms in a trigonal planar arrangement. The nitrate ion carries a...

, the silver ions are three-coordinated in a trigonal planar arrangement.
Albertus Magnus
Albertus Magnus
Albertus Magnus, O.P. , also known as Albert the Great and Albert of Cologne, is a Catholic saint. He was a German Dominican friar and a bishop, who achieved fame for his comprehensive knowledge of and advocacy for the peaceful coexistence of science and religion. Those such as James A. Weisheipl...

, in the 13th century, documented the ability of nitric acid
Nitric acid
Nitric acid , also known as aqua fortis and spirit of nitre, is a highly corrosive and toxic strong acid.Colorless when pure, older samples tend to acquire a yellow cast due to the accumulation of oxides of nitrogen. If the solution contains more than 86% nitric acid, it is referred to as fuming...

 to separate gold
Gold
Gold is a chemical element with the symbol Au and an atomic number of 79. Gold is a dense, soft, shiny, malleable and ductile metal. Pure gold has a bright yellow color and luster traditionally considered attractive, which it maintains without oxidizing in air or water. Chemically, gold is a...

 and silver
Silver
Silver is a metallic chemical element with the chemical symbol Ag and atomic number 47. A soft, white, lustrous transition metal, it has the highest electrical conductivity of any element and the highest thermal conductivity of any metal...

 by dissolving the silver.
Encyclopedia
Silver nitrate is an inorganic compound
Inorganic compound
Inorganic compounds have traditionally been considered to be of inanimate, non-biological origin. In contrast, organic compounds have an explicit biological origin. However, over the past century, the classification of inorganic vs organic compounds has become less important to scientists,...

 with chemical formula
Chemical formula
A chemical formula or molecular formula is a way of expressing information about the atoms that constitute a particular chemical compound....

 . This compound is a versatile precursor to many other silver
Silver
Silver is a metallic chemical element with the chemical symbol Ag and atomic number 47. A soft, white, lustrous transition metal, it has the highest electrical conductivity of any element and the highest thermal conductivity of any metal...

 compounds, such as those used in photography. It is far less sensitive to light than the halides
Silver halide
A silver halide is one of the compounds formed between silver and one of the halogens — silver bromide , chloride , iodide , and three forms of silver fluorides. As a group, they are often referred to as the silver halides, and are often given the pseudo-chemical notation AgX...

. It was once called lunar caustic because silver was called luna by the ancient alchemists, because they believed that silver was associated with the moon.

In solid silver nitrate
Nitrate
The nitrate ion is a polyatomic ion with the molecular formula NO and a molecular mass of 62.0049 g/mol. It is the conjugate base of nitric acid, consisting of one central nitrogen atom surrounded by three identically-bonded oxygen atoms in a trigonal planar arrangement. The nitrate ion carries a...

, the silver ions are three-coordinated in a trigonal planar arrangement.

Discovery

Albertus Magnus
Albertus Magnus
Albertus Magnus, O.P. , also known as Albert the Great and Albert of Cologne, is a Catholic saint. He was a German Dominican friar and a bishop, who achieved fame for his comprehensive knowledge of and advocacy for the peaceful coexistence of science and religion. Those such as James A. Weisheipl...

, in the 13th century, documented the ability of nitric acid
Nitric acid
Nitric acid , also known as aqua fortis and spirit of nitre, is a highly corrosive and toxic strong acid.Colorless when pure, older samples tend to acquire a yellow cast due to the accumulation of oxides of nitrogen. If the solution contains more than 86% nitric acid, it is referred to as fuming...

 to separate gold
Gold
Gold is a chemical element with the symbol Au and an atomic number of 79. Gold is a dense, soft, shiny, malleable and ductile metal. Pure gold has a bright yellow color and luster traditionally considered attractive, which it maintains without oxidizing in air or water. Chemically, gold is a...

 and silver
Silver
Silver is a metallic chemical element with the chemical symbol Ag and atomic number 47. A soft, white, lustrous transition metal, it has the highest electrical conductivity of any element and the highest thermal conductivity of any metal...

 by dissolving the silver. Magnus noted that the resulting solution of silver nitrate could blacken skin. Its common name at the time was nitric acid silver.

Synthesis

Silver nitrate can be prepared by reacting silver, such as a silver bullion or silver foil, with nitric acid
Nitric acid
Nitric acid , also known as aqua fortis and spirit of nitre, is a highly corrosive and toxic strong acid.Colorless when pure, older samples tend to acquire a yellow cast due to the accumulation of oxides of nitrogen. If the solution contains more than 86% nitric acid, it is referred to as fuming...

:
3 Ag + 4 → 3 + 2 +


This is performed under a fume hood because of toxic nitrogen oxide given off in the reaction.

Reactions

A typical reaction with silver nitrate is to suspend a rod of copper
Copper
Copper is a chemical element with the symbol Cu and atomic number 29. It is a ductile metal with very high thermal and electrical conductivity. Pure copper is soft and malleable; an exposed surface has a reddish-orange tarnish...

 in a solution of silver nitrate and leave it for a few hours. The silver nitrate reacts with copper to form hairlike crystals of silver metal and a blue solution of copper nitrate:
2 AgNO3 + Cu → Cu(NO3)2 + 2 Ag


Silver nitrate also decomposes when heated:
2 AgNO3 → 2 Ag + O2 + 2 NO2


Most metal nitrates thermally decompose to the respective oxides, but silver oxide decomposes at a lower temperature than silver nitrate, so the decomposition of silver nitrate yields elemental silver instead.

Precursor to other silver compounds

Silver nitrate is the least expensive salt of silver; it offers several other advantages as well. It is non-hygroscopic, in contrast to silver fluoroborate and silver perchlorate
Silver perchlorate
Silver perchlorate is the chemical compound with the formula AgClO4. This white solid forms a monohydrate and is mildly deliquescent. It is a useful source of the Ag+ ion, although the presence of perchlorate presents risks.-Solubility:...

. It is relatively stable to light. Finally, it dissolves in numerous solvents, including water. The nitrate can be easily replaced by other ligands, rendering AgNO3 versatile. Treatment with solutions of halide ions gives a precipitate of AgX (X = Cl, Br, I). When making photographic film
Photographic film
Photographic film is a sheet of plastic coated with an emulsion containing light-sensitive silver halide salts with variable crystal sizes that determine the sensitivity, contrast and resolution of the film...

, silver nitrate is treated with halide
Halide
A halide is a binary compound, of which one part is a halogen atom and the other part is an element or radical that is less electronegative than the halogen, to make a fluoride, chloride, bromide, iodide, or astatide compound. Many salts are halides...

 salts of sodium or potassium to form insoluble silver halide
Silver halide
A silver halide is one of the compounds formed between silver and one of the halogens — silver bromide , chloride , iodide , and three forms of silver fluorides. As a group, they are often referred to as the silver halides, and are often given the pseudo-chemical notation AgX...

 in situ in photographic gelatin
Gelatin
Gelatin is a translucent, colorless, brittle , flavorless solid substance, derived from the collagen inside animals' skin and bones. It is commonly used as a gelling agent in food, pharmaceuticals, photography, and cosmetic manufacturing. Substances containing gelatin or functioning in a similar...

, which is then applied to strips of tri-acetate
Acetate
An acetate is a derivative of acetic acid. This term includes salts and esters, as well as the anion found in solution. Most of the approximately 5 billion kilograms of acetic acid produced annually in industry are used in the production of acetates, which usually take the form of polymers. In...

 or polyester
Polyester
Polyester is a category of polymers which contain the ester functional group in their main chain. Although there are many polyesters, the term "polyester" as a specific material most commonly refers to polyethylene terephthalate...

. Similarly, silver nitrate is used to prepare some silver-based explosives, such as the fulminate
Silver fulminate
Silver fulminate is an explosive, ionic, fulminic acid salt of silver.Silver fulminate is a primary explosive that has very little practical value due to its extreme sensitivity to impact, heat, pressure and electricity...

, azide
Silver azide
Silver azide is the chemical compound with the formula AgN3. This colorless solid is a well-known explosive.-Structure and chemistry:Silver azide can be prepared by treating an aqueous solution of silver nitrate with sodium azide...

, or acetylide
Silver acetylide
Silver acetylide is an inorganic chemical compound with the formula Ag2C2, a metal acetylide. The name is derived from the way it is synthesized, and emphasizes that the compound can be regarded as a salt of the weak acid, acetylene. Since acetylene is called "ethyne" in the modern IUPAC...

, through a precipitation reaction.

Treatment of silver nitrate with base gives dark grey silver oxide:
2 AgNO3 + 2 NaOH → Ag2O + 2 NaNO3 + H2O


Standard solution molarity = 0.05006 M, depends on solubility and concentration however.

Halide abstraction

The silver cation, , reacts quickly with halide sources to produce the insoluble silver halide, which is a cream precipitate if Br- is used, a white precipitate if Cl- is used and a yellow precipitate if I- is used. This reaction is commonly used in inorganic chemistry
Inorganic chemistry
Inorganic chemistry is the branch of chemistry concerned with the properties and behavior of inorganic compounds. This field covers all chemical compounds except the myriad organic compounds , which are the subjects of organic chemistry...

 to abstract halides:
+ (aq) → AgX


where = , , or .

Other silver salts with non-coordinating anions, namely silver tetrafluoroborate
Silver tetrafluoroborate
Silver tetrafluoroborate sometimes referred to "silver BF-4" is an inorganic compound commonly encountered in inorganic and organometallic chemistry. Similar to silver hexafluorophosphate, it is commonly used to replace halide anions or ligands with the weakly coordinating tetrafluoroborate anions...

 and silver hexafluorophosphate
Silver hexafluorophosphate
Silver hexafluorophosphate, sometimes referred to "silver PF-6," is an inorganic compound with the formula AgPF6.-Uses and reactions:Silver hexafluorophospate is a commonly encountered reagent in inorganic and organometallic chemistry...

 are used for more demanding applications.

Similarly, this reaction is used in analytical chemistry
Analytical chemistry
Analytical chemistry is the study of the separation, identification, and quantification of the chemical components of natural and artificial materials. Qualitative analysis gives an indication of the identity of the chemical species in the sample and quantitative analysis determines the amount of...

 to confirm the presence of chloride
Chloride
The chloride ion is formed when the element chlorine, a halogen, picks up one electron to form an anion Cl−. The salts of hydrochloric acid HCl contain chloride ions and can also be called chlorides. The chloride ion, and its salts such as sodium chloride, are very soluble in water...

, bromide
Bromide
A bromide is a chemical compound containing bromide ion, that is bromine atom with effective charge of −1. The class name can include ionic compounds such as caesium bromide or covalent compounds such as sulfur dibromide.-Natural occurrence:...

, or iodide
Iodide
An iodide ion is the ion I−. Compounds with iodine in formal oxidation state −1 are called iodides. This page is for the iodide ion and its salts. For information on organoiodides, see organohalides. In everyday life, iodide is most commonly encountered as a component of iodized salt,...

 ions can be tested by adding silver nitrate solution. Samples are typically acidified with dilute nitric acid to remove interfering ions, e.g. carbonate
Carbonate
In chemistry, a carbonate is a salt of carbonic acid, characterized by the presence of the carbonate ion, . The name may also mean an ester of carbonic acid, an organic compound containing the carbonate group C2....

 ions and sulfide
Sulfide
A sulfide is an anion of sulfur in its lowest oxidation state of 2-. Sulfide is also a slightly archaic term for thioethers, a common type of organosulfur compound that are well known for their bad odors.- Properties :...

 ions. This step avoids confusion of silver sulfide
Silver sulfide
Silver sulfide, Ag2S, is the sulfide of silver. This dense black solid constitutes the tarnish that forms over time on silverware and other silver objects. Silver sulfide is insoluble in all solvents, but is degraded by strong acids. Silver sulfide features a covalent bond, as it is made up of...

 or silver carbonate
Silver carbonate
Silver carbonate is the chemical compound with the formula Ag2CO3. Silver carbonate is yellow but typical samples are grayish due to the presence of elemental silver. It is poorly soluble in water, like most transition metal carbonates. Silver carbonate is used as a reagent in organic synthesis...

 precipitates with that of silver halides. The color of precipitate varies with the halide: white (silver chloride
Silver chloride
Silver chloride is a chemical compound with the chemical formula AgCl. This white crystalline solid is well known for its low solubility in water . Upon illumination or heating, silver chloride converts to silver , which is signalled by greyish or purplish coloration to some samples...

), pale yellow/cream (silver bromide
Silver bromide
Silver bromide , a soft, pale-yellow, water insoluble salt well known for its unusual sensitivity to light. This property has allowed silver halides to become the basis of modern photographic materials. AgBr is widely used in photographic films and is believed by some to have been used for making...

), yellow (silver iodide
Silver iodide
Silver iodide is a yellow, inorganic, photosensitive iodide of silver used in photography, in medicine as an antiseptic, and in rainmaking for cloud seeding.-Crystal structure:...

). AgBr and especially AgI photo-decompose
Photochemistry
Photochemistry, a sub-discipline of chemistry, is the study of chemical reactions that proceed with the absorption of light by atoms or molecules.. Everyday examples include photosynthesis, the degradation of plastics and the formation of vitamin D with sunlight.-Principles:Light is a type of...

 to the metal, as evidence by a grayish color on exposed samples.

Organic synthesis

Silver nitrate is used in many ways in organic synthesis
Organic synthesis
Organic synthesis is a special branch of chemical synthesis and is concerned with the construction of organic compounds via organic reactions. Organic molecules can often contain a higher level of complexity compared to purely inorganic compounds, so the synthesis of organic compounds has...

, e.g. for deprotection and oxidations. Ag+ binds alkene
Alkene
In organic chemistry, an alkene, olefin, or olefine is an unsaturated chemical compound containing at least one carbon-to-carbon double bond...

s reversibly, and silver nitrate has been used to separate mixtures of alkenes by selective absorption. The resulting adduct
Adduct
An adduct is a product of a direct addition of two or more distinct molecules, resulting in a single reaction product containing all atoms of all components. The resultant is considered a distinct molecular species...

 can be decomposed with ammonia
Ammonia
Ammonia is a compound of nitrogen and hydrogen with the formula . It is a colourless gas with a characteristic pungent odour. Ammonia contributes significantly to the nutritional needs of terrestrial organisms by serving as a precursor to food and fertilizers. Ammonia, either directly or...

 to release the free alkene.

Biology

In histology
Histology
Histology is the study of the microscopic anatomy of cells and tissues of plants and animals. It is performed by examining cells and tissues commonly by sectioning and staining; followed by examination under a light microscope or electron microscope...

, silver nitrate is used for silver stain
Silver stain
Silver staining is the use of silver to selectively alter the appearance of the target.-Use in medicine:It is used to stain histologic sections. This kind of staining is important especially to show proteins and DNA. It is used to show both substances inside and outside cells...

ing, for demonstrating reticular fibers, protein
Protein
Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...

s and nucleic acid
Nucleic acid
Nucleic acids are biological molecules essential for life, and include DNA and RNA . Together with proteins, nucleic acids make up the most important macromolecules; each is found in abundance in all living things, where they function in encoding, transmitting and expressing genetic information...

s. For this reason it is also used to demonstrate proteins in PAGE
Gel electrophoresis
Gel electrophoresis is a method used in clinical chemistry to separate proteins by charge and or size and in biochemistry and molecular biology to separate a mixed population of DNA and RNA fragments by length, to estimate the size of DNA and RNA fragments or to separate proteins by charge...

 gels. It is also used as a stain in scanning electron microscopy..

Antimicrobial uses

  • Water disinfection in hotels and hospitals
  • Postharvest cleaning of oysters and crabs
  • Inhibition of bacterial growth on chicken farms
  • Water recycling aboard space shuttles
  • Home purification of water in Europe and North America
  • Point of use disinfectant for water and vegetables in Mexico
  • Alternative to antibiotics (not recommended by the FDA)
  • Alternative to laundry detergent
  • Application to eyes of newborn babies to prevent infection
  • Coating on catheters to prevent infection

Medicine

Silver salts have antiseptic
Antiseptic
Antiseptics are antimicrobial substances that are applied to living tissue/skin to reduce the possibility of infection, sepsis, or putrefaction...

 properties. Until the development and widespread adoption of antibiotics, dilute solutions of AgNO3 used to be dropped into newborn babies' eyes at birth to prevent contraction of gonorrhea
Gonorrhea
Gonorrhea is a common sexually transmitted infection caused by the bacterium Neisseria gonorrhoeae. The usual symptoms in men are burning with urination and penile discharge. Women, on the other hand, are asymptomatic half the time or have vaginal discharge and pelvic pain...

 from the mother. Eye infections and blindness of newborns was reduced by this method; incorrect dosage, however, could cause blindness in extreme cases. This protection was first used by Credé
Carl Siegmund Franz Credé
Carl Siegmund Franz Credé was a German gynecologist and obstetrician who was a native of Berlin. In 1842 he received his doctorate from the University of Berlin. In 1852 he became director of the "Berlin School of Midwives" and chief physician of the maternity division at the Berlin Charité...

 in 1881. Fused silver nitrate, shaped into sticks, was traditionally called "lunar caustic". It is used as a cauterizing
Cauterization
The medical practice or technique of cauterization is the burning of part of a body to remove or close off a part of it in a process called cautery, which destroys some tissue, in an attempt to mitigate damage, remove an undesired growth, or minimize other potential medical harmful possibilities...

 agent, for example to remove granulation tissue
Granulation tissue
Granulation tissue is the perfused, fibrous connective tissue that replaces a fibrin clot in healing wounds. Granulation tissue typically grows from the base of a wound and is able to fill wounds of almost any size it heals...

 around a stoma
Stoma (medicine)
A stoma is an opening , either natural or surgically created, which connects a portion of the body cavity to the outside environment...

. Dentists sometimes use silver nitrate infused swabs to heal oral ulcers. Silver nitrate is also used by some podiatrists to kill cells located in the nail bed. Silver nitrate is also used to cauterize superficial blood vessels in the nose to help prevent nose bleeds.

The Canadian physician C. A. Douglas Ringrose researched the use of silver nitrate for sterilization procedures on women. A specialist in obstetrics and gynaecology, Ringrose believed that the corrosive properties of silver nitrate could be used to block and corrode the fallopian tubes, in a process that he called "office tubal sterilization". The technique was ineffective; in fact at least two women underwent abortions. Ringrose was sued for malpractice, although these suits were unsuccessful.

Disinfection

Much research has been done in evaluating the ability of the silver ion at inactivating E. coli
Escherichia coli
Escherichia coli is a Gram-negative, rod-shaped bacterium that is commonly found in the lower intestine of warm-blooded organisms . Most E. coli strains are harmless, but some serotypes can cause serious food poisoning in humans, and are occasionally responsible for product recalls...

, a microorganism commonly used as an indicator for fecal contamination and as a surrogate for pathogens in drinking water treatment. Concentrations of silver nitrate evaluated in inactivation experiments range from 10–200 micrograms per liter as Ag+. The antimicrobial properties of silver was first observed thousands of years ago when silver containers were used to store water for preservation. Its disinfection ability has been scientifically studied for over a century.

Silver's antimicrobial activity saw many applications prior to the discovery of pharmaceutical antibiotics, when it fell into near disuse. Its association with argyria
Argyria
Argyria is a condition caused by improper exposure to chemical forms of the element silver, silver dust, or silver compounds. The most dramatic symptom of argyria is that the skin becomes blue or bluish-grey colored. Argyria may be found as generalized argyria or local argyria...

 made consumers wary and led them to turn away from it when given an alternative. Since that time, as antibiotic-resistant microorganisms have emerged, interest in using the silver ion for anti-microbial purposes has resumed.

Kinetics

Before a disinfectant can be effectively used as a water disinfectant, its inactivation kinetics
Enzyme kinetics
Enzyme kinetics is the study of the chemical reactions that are catalysed by enzymes. In enzyme kinetics, the reaction rate is measured and the effects of varying the conditions of the reaction investigated...

 must be established. Kinetics generally depend on both the dosage of disinfectant and the time of application. It is important to understand the kinetics so that the minimum dosage of disinfectant can be applied for the minimum amount of time while still effectively inactivating any pathogens in the water. Because there are many microorganisms present in water, the inactivation kinetics of each one cannot be studied extensively. Therefore, indicator organisms generally more resistant to inactivation than others are used to estimate the kinetics of microorganisms as a whole. Escherichia coli, also referred to as E. coli, is a commonly used indicator organism.

It is well documented that the silver ion is effective in the inactivation of E. coli.
However, there are many inconsistencies in the literature regarding the kinetics of the inactivation of E. coli by the silver ion. With inconsistent data, it is impossible to tell what the true inactivation kinetics are, and therefore impossible to implement any sort of large-scale water treatment.

The inconsistencies may be due to several factors. First, the kinetics may depend on the source of the silver ion being used. In recent years, research has focused largely on electrolytically generated silver ions or colloidal silver. Most studies in which the inactivation kinetics of E. coli by silver nitrate were explored extensively date back several decades. Even within this smaller group of studies, vast inconsistencies exist, likely due to inaccurate analytical methods for measuring the concentration of silver in solution. Monitoring the decay of the silver ion in solution is imperative as silver tends to both adsorb readily to organic matter in the water and to be light reactive. Furthermore, silver tends to adsorb to glassware, which can lead not only to a decrease in the silver concentration within a given experiment but also to a release of the silver in subsequent experiments unless measures further than general glassware washing are taken for the removal of silver from the glassware surface. Therefore studies must both minimize the external factors effecting the concentration and to measure the changes in concentration that take place throughout the experiment.

Effects of various parameters

Despite the inconsistencies in the literature regarding the kinetics of the inactivation of E. coli by silver nitrate, important information can still be taken from the work. A study by Wuhrmann and Zobrist investigated the effect of various parameters upon the kinetics. First, they studied the effect of several ions in the water, including calcium, phosphates and chloride, all of which were found to decrease the bactericidal effect of silver. These effects are important to consider when designing an experiment. Because of the effect of phosphates, it is undesirable to use phosphate buffer to run experiments, as this creates a phosphate concentration much higher than that found in natural waters and will falsely slow the inactivation kinetics. Furthermore, it is important to avoid touching any glassware with bare hands, as chloride from sweat may contaminate the glassware, again slowing inactivation. Chambers, Proctor and Kabler established the importance of using an effective neutralizer solution made of a combination of sodium thioglycolate and sodium thiosulfate, rather than sodium thiosulfate alone, which though it is effective in neutralizing other disinfectants does not sufficiently stop the bactericidal action of silver nitrate. Both tested the effect of pH on the kinetics, finding that a higher pH increased the bactericidal action. Wuhrmann and Zobrist further established that at a higher temperature, inactivation occurs faster.

Kinetic models

A further complication of the inactivation kinetics by silver is the question of which model to use. With most disinfectants, the inactivation is effectively modeled using a first-order Chick-Watson model, which states that a certain level of disinfection will occur at a certain CT, or concentration *time value. According to this model, the same amount of inactivation should take place when a concentration of 0.2 mg/L is applied for 10 minutes as when 0.02 mg/L is applied for 100 minutes. Wuhrmann and Zobrist found rate kinetics that followed this model for all conditions, which agrees fairly well with a study by Chambers and Proctor, while another study by Renn and Chesney found curves that did not follow this law. It is therefore unclear whether this law sufficiently models inactivation by the silver ion.

Most recent papers regarding the disinfection of E. coli by silver nitrate have simply plotted the level of disinfection against time. While this method of data analysis does not risk making false assumptions about first-order kinetics, it does nothing to account for the applied concentration, which is essential to any kinetics. Therefore, different curves need to be generated for each concentration that might be applied. Furthermore, it does not account for changes in concentration that might take place during the experiment, and which may vary based on many factors.

A third model which has been suggested for the inactivation kinetics by silver nitrate is that of Cs*T, or chemisorbed silver onto the cell body times time. This model suggests that the rate of inactivation depends not on the concentration in the water at a given time, but rather on the silver that has been chemisorbed by the bacteria. It is assumed, according to this model that C0 = C1 + C2 + C3, where C0 is the initial concentration, C1 is the silver still in solution, C2 is the silver lost to adsorption to glassware or other factors in the solution, and C3 is the silver chemisorbed to the bacteria. C0 is measured at the beginning of the experiment, C1 is measured throughout the experiment, and C2 is determine in a control experiment without bacteria. C3, or the Cs value, is then determined to be C0-C1-C2. According to Hwang, et al., this model was successful in estimating inactivation of E. coli by silver nitrate. Although it is possible that this model does not sufficiently account for all of the possible fates of the initial silver nitrate added to the solution, it is certainly a compelling method of data analysis. Because it is a new model, it has not been extensively studied by various researchers.

Against warts

Repeated daily application of silver nitrate can induce adequate destruction of cutaneous warts, but occasionally pigmented scars may develop. In a placebo-controlled study of 70
patients, silver nitrate given over nine days resulted in clearance of all warts in 43% and improvement in warts in 26% one month after treatment compared to 11% and 14%, respectively, in the placebo group.

Safety

As an oxidant, silver nitrate should be properly stored away from organic compounds. Despite being used in low concentrations to prevent gonorrhea
Gonorrhea
Gonorrhea is a common sexually transmitted infection caused by the bacterium Neisseria gonorrhoeae. The usual symptoms in men are burning with urination and penile discharge. Women, on the other hand, are asymptomatic half the time or have vaginal discharge and pelvic pain...

 and control nose bleeds, silver nitrate is toxic and corrosive. Brief exposure to the chemical will not produce immediate or even any side effects other than the purple, brown or black skin stains; but with more exposure, side effects will become more noticeable, including burns. Long-term exposure may cause eye damage. Short contact can lead to deposition of black silver stains on the skin. Besides being very destructive of mucous membranes, it is a skin and eye irritant.

Although silver nitrate is currently not regulated in water sources by the Environmental Protection Agency, when between 1-5 g of silver have accumulated in the body, a condition called argyria
Argyria
Argyria is a condition caused by improper exposure to chemical forms of the element silver, silver dust, or silver compounds. The most dramatic symptom of argyria is that the skin becomes blue or bluish-grey colored. Argyria may be found as generalized argyria or local argyria...

 can develop. Argyria is a permanent cosmetic condition in which the skin and internal organs turn a blue-gray color. The United States Environmental Protection Agency had a maximum contaminant limit for silver in water until 1990, but upon determination that argyria did not impact the function of organs affected, removed the regulation. Argyria is more often associated with the consumption of colloidal silver
Colloidal silver
The medical uses of silver include its incorporation into wound dressings to treat external infections, and its use as an antiseptic and disinfectant in medical appliances...

solutions than with silver nitrate, especially at the extremely low concentrations present for the disinfection of water. However, it is still important to consider before ingesting any sort of silver-ion solution.

External links

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