[HP]

Hi,
Can enybody tell me easy method for the laboratory preparation potasium per-iodate (KIO4). The only procedure i found at google describe preparation of per0iodic acid by reaction HClO4 and iodine:
HClO4 + I2 --> HIO4 + Cl2,
But no detail procedure of this reaction was given..If someone have experience this reaction pls share his know-how 
I have some potasium iodate (KIO3) at the lab, so do you think its possible to prepare KIO4 from this reagent 
Any help grateful !

[Alberto_Kravina]

I have some potasium iodate (KIO3) at the lab, so do you think its possible to prepare KIO4 from this reagent  Huh
Any help grateful !

I think that you could oxidize iodate to periodate with a stronger oxidizing agent. KMnO₄ is not strong enough though...

[HP]

Yah, it seems hard to obtain per-iodate from iodate with common oxidizers..may be it's possible electrochemical oxidation but this make troubles too. It's better to purchase it as it's not very cost reactive, but the time untill it be delivered i'll try to synthesize it by some way  Again if someone can suggest me easy synthetic procedure be welcome.Thanks for the reply

[Will]

One of my old chem books says you can make NaClO₄ from NaClO₃ by "heating very carefully". I don't know how good that reaction is though.
Maybe heating KIO₃ in O₂ might yield some KIO₄ .

Have you tried adding iodine to HClO₄ yet?

[Alberto_Kravina]

One of my old chem books says you can make NaClO4 from NaClO3 by "heating very carefully"

Really? I think that even if you heat Sodium chlorate you'll get Sodium chloride and Oxygen.
However, trying to heat sodium chlorate in oxygen is a smart idea

[HP]

It seems possible to heat NaClO4 carefully but may be and some dangerous as we know the properties KClO4 in the match. Of course if no organic material near NaClO4 it seems not so dangerous to heat it so i'll try with small demands. I may try the same and with KIO3 but its about sure this is not the proper way to convert it with reasonable yeld to per-iodate i think I've still not tried the reaction HClO4 with I2 because i dont know how much water need to delute my anhydrous HClO4 i have and it seems dangerous to use it for that purpose without some delution...If you have any suggestion how deluted HClO4 to use pls tell me i'll do the experiment
Regards,

[woelen]

I'm quite sure that you should not dilute the HClO4. I have 60% HClO4, and even when this is mixed with potassium iodide, no iodine is formed, so forget about the periodate with dilute HClO4. HClO4 only works as a strong oxidizer, when its concentration is very high, and even 70% HClO4 only is a very slow oxidizer, even towards easily oxidized compounds like KI.

KMnO4 indeed is not a strong enough oxidizer to make KIO4. It is even the other way around. Periodate is capable of oxidizing Mn(2+) ions to permanganate quantitatively at reasonable speed and only slight heating (50 C or something like that). This is really amazing, I know no other aqueous oxidizer, which can oxidize Mn(2+) to permanganate so easily as periodate can do.

Also keep in mind that KIO4 is only VERY slightly soluble. I have NaIO4, which is soluble much better. KIO4 hardly can be used in aqueous solutions, unless a slow release oxidizer is needed of good strength.

One way to make periodate probably is electrolysis of an iodate solution. In a similar way, perchlorate can be made from chlorate. I have no practical experience, however, with making periodate. I just purchased it for a few bucks for 100 gram (from an old GDR lab). Yes, even home-chemists can find this stuff 

[HP]

I agree KIO4 is slightly soluble in water - its one of the few K-salts which have little solubility in water and is sometimes periodates are used for improving K+ ions, though in alkaline media its solubility is much better...Its really a very power oxidant thats and the purpose i'm thinking to use it at one synthesis. Also i have K2S2O8 at the lab and i'll try this reagent as posible oxidant of NaIO3 i have to., will see With anhydrous HClO4 and I2 i'm still not fully aware but may try with mini experiment..

[Organishe]

Anyone else scared right now? Not insulting anyone's lab safety, but I personally find perchloric acid/perchlorates scary as hell, especially when there is high concentration and heat involved 

Best of luck in your synthesis.

[HP]

Well the perchloric acid i use is 73%, so its my mistake to call it anhydrous..Anhydrous HClO4 is really very dangerous reagent which should be worked with best caution! But when talking for 73 and 85 % perchloric acids the work up with them is not from such big danger as you describe, if the precautious steps known from any professional chemist take in mind: the most hazardous is not contact these acids (73% HClO4 boils at 260C) as they are strong oxidizing agents with any organic matter and some methals which is really  from great danger!!! By the way in my proposed synthesis where external heat involved mentioned? And for last theres nothing much pitty and much dangerous by ignorant chemist scared from not knowing how to do safety some synthesis - from making soap to making TNT...Who scares from bears don't go in the wood
P.S. I tried this synthesis with 2ml 73% HClO4 and I2 and it works fine with the only safety problem some Cl2 released in the hood. In fact i am not very fond this synthesis because its always some warm when working with strong acids be it conc H2SO4, HNO3 or this HClO4, sonow i am thinking for this possible route KIO4:
KClO4  + I2/KI water(Lugol)--> KIO4 , as KIO4 is less soluble in water it shouls settle i think 

[woelen]

Forget about the KClO4 + I2 synthesis. In water, perchlorate ion (without acid) is even less reactive than sulfate ion. Perchlorate is remarkably inert in aqueous solution.

If you can't get the reaction to start with 60% HClO4, then how would you expect KClO4 to do the job. KClO4 also is soluble in water VERY sparingly, unless the water is boiling hot. Just try for fun. Take 0.5 ml of your HClO4, mix with 0.5 ml of water and add a solution of KCl. You'll see immediate formation of a milky precipitate of KClO4.

[Alberto_Kravina]

Also, If you want to have more fun , you could watch the crystals with a mycroscope. They have a beautiful rectangular shape

[HP]

Yah, woelen you are right the idea with KClO4 is stupid    What do you think for the same reaction with the much soluble NH4ClO4 insted ? The system I2/KI is interesting because it makes the elemental iodine soluble in water - i'm not very familiar with this reaction but may be some I3- formed...My tought was about posible substitution of Cl athom in ClO4- with I-one do you think this is theoreticaly possible  And Alberto i have alredy watched perchlorate crystals with my home microscope - they are pretty nice looking - Art is everywhere 
P.S. It's a week my KIO4 delivered and i sugest know experiments untill then so the lab will safe )

[HP]

Cool, i alredy recieved my reagent 
For the fellows who still interested in synthesis KIO4 problem here what i found in one yellow book (book with yellowish papers :
Its synthesis of NaIO4 but may be the same and for K one:
NaIO3(NaOH/water solution) + Cl2 --> NaIO4 + NaCl..
Txs for the good discussion