white powder which turned red

[amit]

recently in gravimetric experiment i made nickel dmg complex which was red coloured. i left it in dessicator for week. i turned white(yellowish). while trying to wash the crucible(filter used in gravimetry) as soon as i poured water it turned red again. whats happening

[insane_alien]

well, obviously the hydrate of the complex is red and the anhydrate is white.

 

in the dessicatior the water is removed turning the red hydrate into the white anhydrate. when washing the crucible water was reintriduced and the hydrate was fromed again.

[amit]

actually i also thougt the same but vogel practical manual doesn't mention it besides won't it bring error in gravimetric analysis if any compoun can exist in hydrated state as well as the other

[YT2095]

that`s why water of crystalisation is usually specified, ie/ CuSO4.5H2O

[hermanntrude]

actually i also thougt the same but vogel practical manual doesn't mention it besides won't it bring error in gravimetric analysis if any compoun can exist in hydrated state as well as the other

 

which is why you put it in a dessicator

[amit]

i think i got the answer guys. go to the following link

http://books.google.co.in/books?id=LpJPWKT3PNcC&pg=PA342&lpg=PA342&dq=nickel+dmg+complex+and+water+of+hydration&source=web&ots=Drx3vBIkpK&sig=eHLrs7Uxsl3lPl7uXPiNvN7WfU8&hl=en&ei=LyCUSc2SDpKwkAWq-4CjCw&sa=X&oi=book_result&resnum=1&ct=result

 

 

or book introduction to modern inorganic chemistry by mackay

on page 343 this structure is given. now water removed is from the oxime. hence it wasn't mentioned in vogel etc as it is not co ordinated from solvent but its there in the oximehttp://books.google.co.in/books?id=LpJPWKT3PNcC&pg=PA342&lpg=PA342&dq=nickel+dmg+complex+and+water+of+hydration&source=web&ots=Drx3vBIkpK&sig=eHLrs7Uxsl3lPl7uXPiNvN7WfU8&hl=en&ei=LyCUSc2SDpKwkAWq-4CjCw&sa=X&oi=book_result&resnum=1&ct=result

[John Cuthber]

There is no water in the diagram 14.30 of that book.

What was the drying agent in the dessicator?

[vedmecum]

we used CaCl2 as a drying agent .

[amit]

well i have tried and uploaded the pic. and circled the water molecules that may have removed according to me. as a latest update that white powder turned green

[hermanntrude]

amit, water is [ce]H2O[/ce] NOT [ce]O2H[/ce]!

[John Cuthber]

I wonder if there's something in the air in the dessicator-(as an outright guess with no supporting evidence, perhaps HCl from hydrolysis of CaCl2) that reacts with the nickel DMG.

[vedmecum]

me and my friend amit performed this exp. in same lab . now we are trying to relate these abnormal color shift with CFSE (crystal field stablisation energy ) . we noticed that color shifted from high wavelength to low wavelength region i.e. with passage of time energy required to excite electron from low energy level to high energy level decreases . these will only happen if any other chemical species (may me O2 or any other ) attack on complex or the extent of bonding b/n Ni and DMG decreases . BUT THESE IS COMPLETELY AN APPARENT GUESS .

 

waiting for comments .........

[amit]

damn it .:doh::doh::doh::embarass::mad:

second blunder in 2 days. anyways we are back to original problem that what went white?