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What makes nitric acid the most effective way to test silver?
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+ Acids
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+ Nitric acid
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Mohamad Bawa
What makes nitric acid the most effective way to test silver?
You cannot convert concentrated nitric acid into anhydrous nitric acid by distillation, because the standard concentration is an azeotrope.
The anhydrous acid is known commercially as white fuming nitric acid WFNA and is used as an oxidant with rocket fuel. It is also available for laboratories.
In order to manufacture it, you have to make it without water, by swapping the sulfate bit of H2SO4 with the nitrate from KNO3. That is, heat these two compounds together and condense the vapors which come off, since HNO3 has a lower boiling point (83°C) than H2SO4 (337°C). Further purification using a great deal of skill to get to the assay you require.
It is recommended that you do not do this at home!
While at school, I came across an exam question which was why anhydrous copper nitrate could not be prepared (because the hydrated form decomposes when you try to remove the water). So as a project I prepared it by dissolving copper metal in N2O4. This taught me a lot about working with dry materials. It was furiously hygroscopic.
You cannot convert concentrated nitric acid into anhydrous nitric acid by distillation, because the standard concentration is an azeotrope.
The anhydrous acid is known commercially as white fuming nitric acid WFNA and is used as an oxidant with rocket fuel. It is also available for laboratories.
In order to manufacture it, you have to make it without water, by swapping the sulfate bit of H2SO4 with the nitrate from KNO3. That is, heat these two compounds together and condense the vapors which come off, since HNO3 has a lower boiling point (83°C) than H2SO4 (337°C). Further purification using a great deal of skill to get to the assay you require.
It is recommended that you do not do this at home!
While at school, I came across an exam question which was why anhydrous copper nitrate could not be prepared (because the hydrated form decomposes when you try to remove the water). So as a project I prepared it by dissolving copper metal in N2O4. This taught me a lot about working with dry materials. It was furiously hygroscopic.
As I did a little Google research, I have concluded that the “old-school” approach of testing silver with concentrated nitric acid, while quite excellent in the hands of an experienced tester because of the rather distinct color-changes of the applied (to the silver surface) nitric acid that depend on the alloying metal that will cause a silver item to be classified as 100% silver, Sterling silver, or an item containing a lesser percentage of silver, may need to be supplemented with additional testing techniques that deal with common forgers’ approaches to counterfeiting silver and take into account the damage the acid will do to the piece being tested.
China is a famous source of counterfeit coins, flatware, jewelry, and other “silver” items that involve the masquerading use of stainless steel, ferrous metals that are magnetic, or simply plating a base (relatively worthless) metal with 100% silver that will test positive for silver when using nitric acid in the hands of an untutored tester when all that is being tested in the last example is the silver plating.
Since silver is paramagnetic (exhibits a slight attraction to an externally applied magnetic field) some knowledge of how a magnet will react is required as the magnet will not be attracted strongly to real silver, will not be attracted to some stainless steels, and will be only slightly attracted to real bar silver. Again, employing the services of an experienced tester is to be preferred for making definitive conclusions.
When valuable silver items are tested with concentrated nitric acid, and depending on the test method employed, it is imperative to keep in mind that the test (for instance, of a proof coin if the acid is applied to its surface) may so damage the surface of the piece as to cause its monetary value to be drastically altered.
All the foregoing considered, nitric acid may NOT be the most effective way to test silver. There are, however, other test procedures that used in combination will function as good and effective second choices.
As I did a little Google research, I have concluded that the “old-school” approach of testing silver with concentrated nitric acid, while quite excellent in the hands of an experienced tester because of the rather distinct color-changes of the applied (to the silver surface) nitric acid that depend on the alloying metal that will cause a silver item to be classified as 100% silver, Sterling silver, or an item containing a lesser percentage of silver, may need to be supplemented with additional testing techniques that deal with common forgers’ approaches to counterfeiting silver and take into account the damage the acid will do to the piece being tested.
China is a famous source of counterfeit coins, flatware, jewelry, and other “silver” items that involve the masquerading use of stainless steel, ferrous metals that are magnetic, or simply plating a base (relatively worthless) metal with 100% silver that will test positive for silver when using nitric acid in the hands of an untutored tester when all that is being tested in the last example is the silver plating.
Since silver is paramagnetic (exhibits a slight attraction to an externally applied magnetic field) some knowledge of how a magnet will react is required as the magnet will not be attracted strongly to real silver, will not be attracted to some stainless steels, and will be only slightly attracted to real bar silver. Again, employing the services of an experienced tester is to be preferred for making definitive conclusions.
When valuable silver items are tested with concentrated nitric acid, and depending on the test method employed, it is imperative to keep in mind that the test (for instance, of a proof coin if the acid is applied to its surface) may so damage the surface of the piece as to cause its monetary value to be drastically altered.
All the foregoing considered, nitric acid may NOT be the most effective way to test silver. There are, however, other test procedures that used in combination will function as good and effective second choices.
You cannot convert concentrated nitric acid into anhydrous nitric acid by distillation, because the standard concentration is an azeotrope.
The anhydrous acid is known commercially as white fuming nitric acid WFNA and is used as an oxidant with rocket fuel. It is also available for laboratories.
In order to manufacture it, you have to make it without water, by swapping the sulfate bit of H2SO4 with the nitrate from KNO3. That is, heat these two compounds together and condense the vapors which come off, since HNO3 has a lower boiling point (83°C) than H2SO4 (337°C). Further purification using a great deal of skill to get to the assay you require.
It is recommended that you do not do this at home!
While at school, I came across an exam question which was why anhydrous copper nitrate could not be prepared (because the hydrated form decomposes when you try to remove the water). So as a project I prepared it by dissolving copper metal in N2O4. This taught me a lot about working with dry materials. It was furiously hygroscopic.
You cannot convert concentrated nitric acid into anhydrous nitric acid by distillation, because the standard concentration is an azeotrope.
The anhydrous acid is known commercially as white fuming nitric acid WFNA and is used as an oxidant with rocket fuel. It is also available for laboratories.
In order to manufacture it, you have to make it without water, by swapping the sulfate bit of H2SO4 with the nitrate from KNO3. That is, heat these two compounds together and condense the vapors which come off, since HNO3 has a lower boiling point (83°C) than H2SO4 (337°C). Further purification using a great deal of skill to get to the assay you require.
It is recommended that you do not do this at home!
While at school, I came across an exam question which was why anhydrous copper nitrate could not be prepared (because the hydrated form decomposes when you try to remove the water). So as a project I prepared it by dissolving copper metal in N2O4. This taught me a lot about working with dry materials. It was furiously hygroscopic.
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As I did a little Google research, I have concluded that the “old-school” approach of testing silver with concentrated nitric acid, while quite excellent in the hands of an experienced tester because of the rather distinct color-changes of the applied (to the silver surface) nitric acid that depend on the alloying metal that will cause a silver item to be classified as 100% silver, Sterling silver, or an item containing a lesser percentage of silver, may need to be supplemented with additional testing techniques that deal with common forgers’ approaches to counterfeiting silver and take into account the damage the acid will do to the piece being tested.
China is a famous source of counterfeit coins, flatware, jewelry, and other “silver” items that involve the masquerading use of stainless steel, ferrous metals that are magnetic, or simply plating a base (relatively worthless) metal with 100% silver that will test positive for silver when using nitric acid in the hands of an untutored tester when all that is being tested in the last example is the silver plating.
Since silver is paramagnetic (exhibits a slight attraction to an externally applied magnetic field) some knowledge of how a magnet will react is required as the magnet will not be attracted strongly to real silver, will not be attracted to some stainless steels, and will be only slightly attracted to real bar silver. Again, employing the services of an experienced tester is to be preferred for making definitive conclusions.
When valuable silver items are tested with concentrated nitric acid, and depending on the test method employed, it is imperative to keep in mind that the test (for instance, of a proof coin if the acid is applied to its surface) may so damage the surface of the piece as to cause its monetary value to be drastically altered.
All the foregoing considered, nitric acid may NOT be the most effective way to test silver. There are, however, other test procedures that used in combination will function as good and effective second choices.
As I did a little Google research, I have concluded that the “old-school” approach of testing silver with concentrated nitric acid, while quite excellent in the hands of an experienced tester because of the rather distinct color-changes of the applied (to the silver surface) nitric acid that depend on the alloying metal that will cause a silver item to be classified as 100% silver, Sterling silver, or an item containing a lesser percentage of silver, may need to be supplemented with additional testing techniques that deal with common forgers’ approaches to counterfeiting silver and take into account the damage the acid will do to the piece being tested.
China is a famous source of counterfeit coins, flatware, jewelry, and other “silver” items that involve the masquerading use of stainless steel, ferrous metals that are magnetic, or simply plating a base (relatively worthless) metal with 100% silver that will test positive for silver when using nitric acid in the hands of an untutored tester when all that is being tested in the last example is the silver plating.
Since silver is paramagnetic (exhibits a slight attraction to an externally applied magnetic field) some knowledge of how a magnet will react is required as the magnet will not be attracted strongly to real silver, will not be attracted to some stainless steels, and will be only slightly attracted to real bar silver. Again, employing the services of an experienced tester is to be preferred for making definitive conclusions.
When valuable silver items are tested with concentrated nitric acid, and depending on the test method employed, it is imperative to keep in mind that the test (for instance, of a proof coin if the acid is applied to its surface) may so damage the surface of the piece as to cause its monetary value to be drastically altered.
All the foregoing considered, nitric acid may NOT be the most effective way to test silver. There are, however, other test procedures that used in combination will function as good and effective second choices.
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VOTE