Vhin
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What are the best salts to keep?
I know that a lot of salts tend to be pretty "malleable", in that they can easily be changed into a different (but related) salt. So, keeping in mind
the widest variety of cations and anions, ease of turning them into other salts, and ease of storage, what are the "best" salts to keep on hand?
If I'm unclear, I mean in terms of the fact that it's silly to have like five Copper salts, or five Sulfates, instead of just one and making what you
need.
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AndersHoveland
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No, actually it can be useful to keep all different types of chemicals for available access, even if you think you are never going to use them. There
are always new things to learn, and (very frequently) unexpected uses for old chemicals.
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Vhin
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While, yes, it would be best to buy reagent grade versions of all the salts, this isn't really possible due to the cost.
If they're fairly easy to make, I'd rather make them for my purposes then spend the money to buy them.
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DJF90
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I guess its quite dependent on the metal salts you wish to deal with. For example, making salts of the first row transitions metals would be
considered fairly facile (assuming no need for anhydrous) as they all form insoluble oxides or carbonates which can be precipitated, thoroughly
washed, and dissolved in the acid which corresponds to the anion you want. If you dont have the requisite acid, things get a bit trickier in that you
generally have to resort to a metathesis reaction.
These work best when both starting materials are readily soluble, and one of the products is insoluble. Precipitation of the transition metal
oxides/carbonates is an example of this. Another example is in the formation of alkali metal salts containing an anion which is readily procured as
the barium salt. Metathesis with the alkali metal sulfate precipitates barium sulfate, leaving the desired compound in solution. Careful not to
over-add the sulfate solution otherwise you'll contaminate your product. An example which springs to mind is hypophosphite. Ba(OH)2.8H2O is treated
with (white?) phosphorus to afford phosphine gas (waste) and barium hypophosphite. Metathesis with either dil. H2SO4 or metal sulfate solution yields
barium sulfate (ppt) and either H3PO2 or Mx(H2PO2)y in solution.
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woelen
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Indeed, selecting a well-chosen set of chemicals is the best thing you can do. If for instance you want to experiment with copper salts, then you
should take one or maybe two copper salts with a non-reactive anion. I would like copper sulfate or coper nitrate for such experiments. E.g. copper
dichromate would be a bad choice, because the anion in that latter case has very specific properties which certainly would interfere mostly with the
properties of the copper salt.
I have written a webpage about what chemicals to buy and where to start. It may be helpful for you. Keep in mind that the webpage is written with
inorganic home chemistry in mind. If you want to do a lot of organics, then you need to find other info.
http://woelen.homescience.net/science/chem/misc/chemicals.ht...
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AndersHoveland
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Quote: Originally posted by Vhin  | it would be best to buy reagent grade versions of all the salts, this isn't really possible due to the cost.
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Usually the carbonates or hydroxides are best. You can always mix with acids to obtain the respective salts.
For example, copper sulfate by reacting coppric oxide with sulfuric acid.
In some cases (not with the transition metals) certain salts can be prepared by boiling the hydroxide or (carbonate) with the respective ammonium
salt. For example, calcium nitrate from calcium carbonate and ammonium nitrate.
This thread should be moved to 'beginnings'...
[Edited on 25-5-2012 by AndersHoveland]
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Bot0nist
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I find calcium chloride handy often, as it is an easily available and cheap source of water soluble calcium. This question is a bit subjective.What
kind of chemistry do you plan on focusing on? Many here love to have a nitrate and nitrite salt handy, as they are very useful in a lot of amateur
energetic research.
IMO, The usefulness of the salt is in the eye of the beholder(chemist).
[Edited on 25-5-2012 by Bot0nist]
U.T.F.S.E. and learn the joys of autodidacticism!
Don't judge each day only by the harvest you reap, but also by the seeds you sow.
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Rosco Bodine
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nitrates, carbonates, hydroxides, sulfates, chlorides in that order generally are the economical salts which you can manipulate changeably from one of
those salts into another one of those salts by some relatively easy and economical method. Often it is the relative consumer demand mass production
market for a particular salt which will make that particular salt the most economical form supplied commercially as a standard item while another
less in demand salt will be many times more expensive as a special order item.
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longtermmadscientist
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If you’re intending on using those compounds for general- purpose experiments later on, you’ll be looking for a salt which is stable against both
hygroscopy and efflorescence. For example, if you choose chlorides as a storage medium for many metals, then you may find that your “dry” compound
will gain weight over time, even when stored in “airtight” containers, meaning you may have to go to the trouble of drying your compound by
heating (assuming that you don't have a dessicator) before you use it. This wouldn’t be a problem for alkali- and alkaline earth- metals, but may be
tricky with the chlorides of the f and d block elements (the former especially), which may partly hydrolyse in the process. And if you choose a
compound which is known to lose some water of crystallisation at ambient temperature and humidity, then cobalt chloride and copper sulphate hydrates
are not good choices, either. All this isn’t likely to be a problem, or hardly at all, if you have air-tight containers, but it has been an issue
for me, which is why I mention it.
Also, obviously, if you want to do wet chemistry experiments with these chemicals at some point, you will want a water soluble compound, like others
have mentioned here. Having a compound with no strongly oxidising or reducing properties in particular may be wise, especially if you’re not sure
what experiments you’re likely to be doing.
Overall, I’d say sulphates are a good all- round choice, but you need to do research on the individual sulphate you’re thinking of storing.
If, however, you’re thinking of not using the salts for future experiments, but rather as an example of a particular element in a particular
oxidation state, then I’d opt for orthophosphates, as these are on the whole insoluble or comparatively insoluble, and rather chemically stable.
It all depends on what you want to use the salts for, and it’s always best, I find, to do individual research on the individual compound you’re
contemplating.
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