Sciencemadness Discussion Board

Synth Of Iodic Acid W/out chlorine

DontHurtMe - 6-5-2008 at 13:36

Excuse me but in the prep of iodic acid can you use bromine instead of chlorine?

ShadowWarrior4444 - 6-5-2008 at 13:43

Originally posted by DontHurtMe
Excuse me but in the prep of iodic acid can you use bromine instead of chlorine?

Hmmm, as I recall, HI is not prepared using Chlorine, or any other halogen for that matter (aside from Iodine, obviously.) What method are you using? That may aid those who would provide answers.

[Edited on 5-6-2008 by ShadowWarrior4444]

Iodic, not hydriodic...

Bromide - 6-5-2008 at 14:05

Originally posted by ShadowWarrior4444
Originally posted by DontHurtMe
Excuse me but in the prep of iodic acid can you use bromine instead of chlorine?

Hmmm, as I recall, HI is not prepared using Chlorine, or any other halogen for that matter (aside from Iodine, obviously.) What method are you using? That may aid those who would provide answers.

[Edited on 5-6-2008 by ShadowWarrior4444]

For clarification, the question posed by DontHurtMe was regarding iodic acid (i.e., HIO<sub>3</sub>;), not hydriodic acid (the "HI" quoted in ShadowWarrior's e-mail).

Apologies to the original poster for not being able to provide an answer, however.

ShadowWarrior4444 - 6-5-2008 at 14:19

My apologies, wasn't paying enough attention. As for Iodic Acid, I am not entirely sure of a Cl-free way. As the traditional method is oxidizing I2 with Cl in an aq solution, perhaps something with a similar or greater oxidizing power. Electrolytic oxidation of iodide to iodate, then treatment with a mineral acid such as sulfuric may be effective.

[Edited on 5-6-2008 by ShadowWarrior4444]

DontHurtMe - 6-5-2008 at 14:39

Thank You!
Anyone Up For Selfcatalytic Oxidation Of HI with H<sub>2</sub>O<sub>2</sub>?

[Edited on 6-5-2008 by DontHurtMe]

roamingnome - 6-5-2008 at 18:21

Theres a good thread started here about its creation from the elements.

oh nevermind .. i fell into the IO3 Hi bit... still a good thread...

[Edited on 7-5-2008 by roamingnome]

not_important - 6-5-2008 at 19:21

Originally posted by DontHurtMe
Excuse me but in the prep of iodic acid can you use bromine instead of chlorine?

From A Dictionary of Chemistry and the Allied Branches of Other Sciences By Henry Watts 1871, page 298

Small quantities of iodic acid are conveniently prepared by heating iodine with the strongest nitric acid free from nitrous acid in a wide glass tube, and leaving the liquid to cool. Iodic acid is then deposited in crystals (Connel).
Jacqnelain (Ann. Ch. Phys. [3] xxx. 332) recommends this as the best mode of preparing iodic acid in all cases. He heats 5 grms. of dry iodine in a flask with 200 grms. nitric acid of specific gravity 1·5 to 60° for an hour; decants the supernatant liquid (the upper consisting of nitric acid containing pernitric oxide, the lower of a red-brown solution of iodine in nitric acid) from the separated iodic acid ; distills these liquids down to one-sixth ; and gently heats the residue, together with the crystallised iodic acid, in a vessel in which it is protected from dust ; iodic anhydride then separates in nacreous crystals.

The method with chlorine is stated as being preferred for more than a few grams.

Another, from Elements of Modern Chemistry by Adolfe Wurtz, 3rd ed. 1889

Iodic acid may be conveniently prepared by heating iodine and potassium chlorate with dilute nitric acid. The oxygen of the chlorate oxidizes the iodine to iodic acid, and on adding barium nitrate to the liquid, barium iodate is precipitated. The latter salt is decomposed by sulphuric acid ; iodic acid is set free in the solution, and barium sulphate is precipitated ; the filtered solution is concentrated by evaporation in vacuo.

DontHurtMe - 21-5-2008 at 10:54

Good! I:D Was Going To Make Barium Nitrate w/ it!

S.C. Wack - 21-5-2008 at 15:54

Since the question is the use of bromine I hesitated to post this, but I think that some detail could be added to the nitric acid procedure above. JACS 53, 44 (1931):

"10 g. of very finely divided iodine (resublimed, crystalline iodine is far less satisfactory than that recovered from an iodide solution by precipitation with an oxidizing agent, as chlorine, or hydrogen peroxide at high acid concentration) ; 10 ml. of concentrated nitric acid; 300-400 ml. of 3% hydrogen peroxide, which is 1.5 to 2 times the theoretical amount required.

Place the iodine, nitric acid and about 50 ml. of the peroxide solution in a 750 ml. flask and heat the mixture in a water-bath at about 70C. To minimize the loss of iodine vapor, place a loosely-fitting glass stopper or small funnel in the mouth of the flask. Shake the flask frequently when the solution does not show a deep color due to dissolved iodine. Observe when the reaction starts, as shown by the first decrease in color. Whenever the solution again becomes deeply colored, add more hydrogen peroxide. Continue until the solid iodine (or the hydrogen peroxide) is consumed. Evaporate the solution rapidly to a small volume.

To remove the nitric acid and the organic substances introduced with the peroxide, evaporate the solution to dryness in a small porcelain dish; heat the residue in a drying oven for at least two hours, at first at 140-150C and later at 170-180C; extract the iodic acid with boiling water, filter off and reject the dark-colored residue. Evaporate the solution to dryness, and partially dehydrate the solid by heating it in a drying oven at 150-200C, carefully avoiding overheating.

If the product is still dark-colored, add some concentrated nitric acid and treat the mixture again as described in the preceding paragraph, or proceed as follows.

To prepare crystalline iodic acid, HIO3, dissolve nearly all of the partially dehydrated solid in the minimum amount of hot water, filter, cool the filtrate, place the clear solution in a crystallizing dish in a vacuum desiccator over anhydrous calcium chloride and seed with a crystal of iodic acid if this is necessary. Finally, reject the mother liquor when only a small portion remains, and wash the crystals with a few drops of cold water.

While in 0.1 N acid at 25C the reaction between iodine and hydrogen peroxide will not start for several hours, it starts rapidly at a temperature of 70-80C when the acid concentration is molal or greater. When once started the reaction in the solution is rapid even at a low temperature, and the limiting factor is the rate of solution of the solid iodine. For this reason the high temperature is maintained, finely divided iodine is used, and the mixture is shaken frequently. Since hydrogen peroxide reacts also with iodic acid, catalytic decomposition is unavoidable; a 50% excess of peroxide is required in the procedure as here outlined, but much more may be used if the shaking is neglected.

The process would be much more satisfactory if hydrogen peroxide were available at higher concentration and free from preservative. The organic material is partially decomposed and rendered insoluble in the evaporation and subsequent heating, presumably on account of the presence of the nitric acid; but the product is not as white as that obtained with chloric acid.

The yield with respect to iodine is practically quantitative. There is danger of loss by decomposition during the heating of the solid product only if the temperature is not properly controlled, but the permissible temperatures are lower than for material prepared by the chloric acid method and our product is thus less completely dehydrated."

Via chloric acid, JACS 42, 1636 (1920):
Chloric acid.
The preparation was carried out in large earthenware crocks, and the quantities of materials used depended on the size of the crocks. The proportions were as follows. 625 g. of barium chlorate (90% Ba(ClO3)2) was dissolved in one liter of nearly boiling water and poured into the crock; the barium sulfate was precipitated by slowly adding, with stirring, the required quantity of hot sulfuric acid solution. The latter solution was prepared by adding 200 g. of H2SO4, sp. gr. 1.84, to 109 g. water, these quantities corresponding to equal parts by volume. It is necessary to have a very small excess of barium chlorate rather than of sulfuric acid, and the chloric acid solution should be tested for sulfate and for barium until the procedure is standardized. The mixture was allowed to stand until the barium sulfate settled out, which required at least one hour. About 2/3 of the chloric acid solution could then he removed by decantation or by a siphon, but filtration of this solution was sometimes necessary.

Iodic acid.
500 g. of commercial "resublimed" iodine was weighed into a 3 L glass flask, and to this was added an amount of chloric acid 3% in excess of the theoretical amount (one mol of chlorate per gram atom of iodine). The flask was connected with an absorption train of 3 wash bottles partly filled with a cold 20% solution of sodium hydroxide (or with milk of lime if bleaching powder was desired instead of sodium hypochlorite solution; the latter was used in another process in our laboratory). A slow current of air was passed through the apparatus after the reaction started. If the mixture was heated to start the reaction and again when only a small amount of iodine remained, a run could be completed in 20 minutes. When the initial heating was omitted the reaction started within 10 or 15 minutes.

The solution was then cooled, filtered to remove barium iodate or any foreign matter, transferred to a large evaporating dish, and evaporated just to dryness with frequent stirring. If during the evaporation a yellow-brown color appeared, a small amount of chloric acid was at once added. The material was heated in a hot-air oven at a temperature of 150-160C for 3 hours, and then removed from the evaporating dish for more complete dehydration.