Preparation of Iodic Acid

Preparation of Iodic Acid. Perform the experiment in a fume cupboard/) Weigh 1 g of iodine in a porcelain bowl, carefully add the 

Heat the bowl with its contents until the iodine dissolves completely. Heat the bath up to boiling and evaporate the solution until dry only after the colour of iodine vanishes. Acquaint yourself with the properties of iodic acid (see p. 101). 

Transfer the iodine trichloride from the flask into a weighed drawn out test tube. Cool the tube with dry ice and rapidly seal it wear eye protection ). Weigh the test tube with the substance and the remaining fragments of the tube. Calculate the yield in per cent. Write the equation of the reaction. Use the prepared iodine trichloride in the following syntheses. 

Preparation of Potassium Tetrachloroiodate Dihydrate. Dissolve 18 g of iodine trichloride in 20 ml of concentrated hydrochloric acid with vigorous stirring in a round-bottomed flask with a ground-glass stopper. Cool the solution to 0 °C and add to it a mixture of 5 g of potassium chloride and 12 ml of a concentrated hydrochloric acid solution. Dilute the reaction mixture to twice its volume with concentrated hydrochloric acid cooled to 0 °C. 

After 30-40 min, rapidly filter off the formed potassium tetrachloroiodate crystals on a filter No. 2 and wash them two or three times with concentrated hydrochloric acid cooled to 0 °C. Dry the crystals in a desiccator over sulphuric acid. Weigh the substance and seal it in an ampoule. Calculate the yield in per cent. 

---

III A) 1931 Bray, W. C., Caulkins, A. L. Reactions Involving Hydrogen Peroxide, Iodine and Iodate Ion II. The Preparation of Iodic Acid. Preliminary Rate Measurements. J. Amer. Chem. Soc. vol. 53, 44-48... 

The third paper is by Gay-Lussac and was read by him to the Institut on 20 December 1813. It describes the preparation of iodic acid by precipitating a solution of potassium iodate as barium iodate and decomposing this with sulphuric acid. A detonating salt (potassium iodate) was formed by dissolving iodine in caustic potash solution, but Gay-Lussac says this had been announced by Davy (j etais parvenu de mon cote a la connaissance de ce sel detonnant de I iode mais M. Davy I a annonce avant moi) (see p. 89). Iodine pentoxide is not mentioned. 

Preparation ofpure potassium hydrogeniodate. Dissolve 27 g of potassium iodate in 125 mL of boiling water, and add a solution of 22 g of iodic acid in 45 mL of warm water acidified with six drops of concentrated hydrochloric acid. Potassium hydrogeniodate separates on cooling. Filter on a sintered-glass funnel, and wash with cold water. Recrystallise three times from hot water use 3 parts of water for 1 part of the salt and stir continuously during each cooling. Dry the crystals at 100 °C for several hours. The purity exceeds 99.95 per cent. 

Iodine pentoxide is prepared by dehydration of iodic acid at 240°C. 

W. Harrison 1 prepared unstable hydrosols of iodine by adding hydriodic acid to a dil. soln. of iodic acid and by adding alcohol to soln. of iodine in glycerol. The hydrosol is at first blue, but it quickly flocculates forming a grey aggregate which, if the cone, be small, can scarcely be recognized. J. Amann has prepared soln. in sulphuric acid and in propylamine. The relation between the colour and the nature of the solvent has already been discussed. 

The preparation Of iodine dioxide.—N. A. E. Millon s method of preparation by the reduction of iodic acid, modified by M. M. P. Muir, is as follows ... 

H. Landolt s reaction can be demonstrated in the following manner Dissolve 1 8 grm. of iodic acid in a litre of water also prepare a litre of an aq. soln. of 0 9 grm. of sodium sulphite, Na2ROa.7HaO lOper cent, sulphuric acid, and 9 5 grms. of starch made into a paste with hot water. Add 100 c.c. of each soln. to separate beakers and mix the two. Note the time when the soln. are mixed. Count the seconds which pass before the starch blue appears. Dil. each soln. to 0 8, 0 6, 0 4, 0 2th of its former concentration, and repeat the experiments with the dil. soln. Plot the results as has been done in Fig. 12. If the concentration and temp, be constant, the same results can always be reproduced. 

Prepare a solution of iodic acid (see p. 109) and pour it into two test tubes. Pour a potassium iodide solution into one tube. What substance evolves Pour an iron(II) sulphate solution into the other tube. What do you observe Write the equations of the reactions. What properties of iodic acid do the above experiments indicate Write the formulas of the iodine oxyacids. What oxygen compounds of iodine are known How are they prepared ... 

Of the older methods for the preparation of periodic acid, the most satisfactory for obtaining large quantities is the electrolytic oxidation of iodic acid at an anode of platinum plated with lead dioxide, the cathode solution being dilute nitric acid.1 The iodic acid for this preparation is conveniently prepared by the electrolytic oxidation of iodine.1 However, periodic acid prepared in this way often contains... 

The most extensively studied oxide of iodine is I2O5. It is prepared by the dehydration of iodic acid,... 

Cupric iodate, Cu(I03)2.—Solution of cupric hydroxide or carbonate in a solution of iodic acid yields the iodate, which is known in the anhydrous form,1 and as monohydrate,2 and dihydrate.3 From excess of a solution of potassium iodate, cupric nitrate precipitates the pale-blue monohydrate. At 25° C. its solubility is 3-3 X 10-3 gram-molecules per litre of water.4 A basic iodate, Cu(I03)2,Cu(0H)2, has also been prepared.5... 

---