Can anyone explain what happens when i try to grow (large) crystals using solution that contains mix of salts. Magnesium sulphate and copper sulphate for example. Do i get separate crystals of both compounds or something else?

it`s considerably easier to grow large crystals if you do do them chem at a time rather than a mix

 

don`t get me wrong, they will all grow, but at different times depending on solubility of each, and each will be pure, as no 2 crystals will mix, but for larger specimens, do them one at a time and remove all impurities

yeah, they should separate pretty easily since magnesium sulfate is so much less soluble than copper sulfate (f for americans, i guess) you should get colorless (white) crystals in a blue solution, if it gets cloudy, then try adding a little more water (but not too much) to dissolve the MgSO4 back up (if you want larger crystals)

when i make crystals with metal oxides and acids i do this for larger crystals: (an eg for copper sulphate)

 

1. add copper oxide to hot sulphuric acid until it is not soluble anymore, then add exess copper oxide.

 

2. filter off the exess into a watch glass.

 

3. heat the filtrate GENTLY in a water bath for the largest crystals then take out and let evaperate.

 

can someone tell me what metal oxide to use to make the green crystals ive forgot. i think its a chlorate so its done with hydrochloric acid.

hmm , most chromium salts are green (or blue) don't know about the oxides, but i think that chromates are usually green or yellow (or orange, pot. dichromate), i think CrO3 is yellow

 

nickel salts are usually green too, don't know about the oxides

i made some big fat crystals of nickelocene one time (20 electron complex) and they were a nice hunter green

 

copper nitrate is green too

 

???

ohh sorry the only growing technique ive been tought is by using an acid and metal oxide .

Thanks to all for info about crystals & mixed solutions!

 

I do not know if this helps but Cr2O3 (that is used as polishing powder) is green in color, but does anyone know, will it react with any acids? Only reaction that i know with this substance is aluminothermic extraction of chrome metal.

 

regards,

Raivo

you could gently heat it in sulphuric acid to make Cr2(SO4)3, this will have different colors at degrees of dryness, as the hydrated crystal Cr2(SO4)3.18H2O will be a violet/blue color and without the water of crystalisation it becomes a Violet/Red color

 

Cobalt Chloride exhibits similar properties also

it`s considerably easier to grow large crystals if you do do them chem at a time rather than a mix

 

don`t get me wrong' date=' they will all grow, but at different times depending on solubility of each, and each will be pure, as no 2 crystals will mix, but for larger specimens, do them one at a time and remove all impurities [/quote']

 

How about the solubilities are the same?

then both will form at exactly the same time, but each will still be an idividual crystal made of just one substance each

Can somebody teach me how to produce a pure sample of nickel nitrate crystals? And any factors that i should take note that affect the crystal growing...

Sure, there is a whole thread on it here:-

 

http://www.scienceforums.net/forums/showthread.php?t=5445

 

Although I suspect it should be in homework help.

Can somebody teach me how to produce a pure sample of nickel nitrate crystals? And any factors that i should take note that affect the crystal growing...

nice choice it`s such a lovely green color too!

 

as with any other recipe, the key to purity is start with pure ingedients (shocker!) LOL

 

as for growth, the slower they grow, the larger they become, although storage has to be perfectly dry and airtight.