If you are interested in some other possibly "better" paths to Chlorate formation see the recent thread below and some of the cited references.
http://www.sciencemadness.org/talk/viewthread.php?tid=18452
I am currently looking at paths via Magnesium hypochlorite (add MgSO4, Epsom's salt, to bleach, NaClO), to which one adds HOCl (a must for Chlorate
formation in the reputedly superior non-alkaline approach) and an acid (to lower pH in 5.5 range) and warm the solution (around 70 C) and not boil.
Alternately, aqueous suspension of Magnesium hydroxide (or hypochlorite) and treat with Cl2 (or, Chlorine water which is basically, HCl and HOCl) and
warm. Add KCl and then cool to precipitate KClO3.
The thread focuses on ZnO with ostensibly higher yields, but Epsom's salt presents an easy path to Magnesium hypochlorite. See the reference below for
comments on Mg(ClO3)2 route.
Source: "The Manufacture of Sulphuric Acid and Alkali: Ammonia-soda, various ..." by Georg Lunge, an online googlebook. To quote from page 669:
"4. Magnesia Bleach-Liquor.
This can be made by decomposing a solution of bleachingpowder with Epsom salts and decanting from the gypsum formed. It has been proposed for
bleaching by Claussen, and again by Ramsay; it is said to bleach more rapidly, and not to turn straw, flax, hemp, etc., brown, as it is free from
lime; but it suffers decomposition more quickly than chloride of lime. The separated magnesia does not at all injure the fabrics (Bolley and Jokisch,
Schwciz. polyt. Zeit., 1866, p. 120). Such a liquor was patented by Oliver Grantham, Sinnock, and Leverson (B. P. 2351 of 1861), without adding
anything new. F. Hodges has shown that a liquor of the same kind (prepared from ordinary bleaching-powder and kieserite) can bleach linen fabrics
without exposure on grass, if they have previously been steeped in a hot solution of sodium carbonate.
Balard prepared a bleaching-liquor by dissolving magnesia in aqueous hypochlorous acid; Grouvelle by passing chlorine into magnesia suspended in
water.
None of these solutions had been properly investigated until Lunge and Landolt (Chem. Ind., 1855, p. 340) undertook this task. They tried first to
prepare a bleaching-magnesia, analogous to bleaching-powder, by treating solid magnesium hydroxide with chlorine, either in the dry or in the moist
state; but they did not obtain anything fit for use, viz., a. mass with only 0-15 available and 4-3 chloride-chlorine.
Now chlorine was passed into a milk of- magnesium hydroxide and water, at temperatures between o° and 100°. Even at 0°, together with magnesium
hypochlorite, much chlorate was formed, more than corresponding to half of the chlorine entering into the reaction. At 15° a little more chlorate was
formed, together with much hypochlorate, some of which was changed into chloride, with evolution of oxygen. In both solutions the hypochlorite is
easily converted into chlorate, not merely by heating to 50°, but even by prolonged agitation by a current of air at ordinary temperatures. At 70°
C, from the first mostly chlorate was formed, with a little chloride, produced by loss of oxygen. Hence magnesium hypochlorite in statu noscendi does
not possess much stability and is easily transformed into chlorate.
Very different from this is the behaviour of a product obtained by decomposing a solution of bleaching-powder with magnesium sulphate. Here no
conversion of hypochlorite into chlorate occurs, a very slight production of MgCl2 by loss of oxygen is observed, but no splitting off of free HOCl.
The stability of this bleaching-solution is almost equal to that of bleaching-powder solutions. Kept in closed vessels in the dark, it had lost only
1/60 of its available chlorine after keeping for thirty-three days; kept open in the dark, no change was observed after six days, and after
thirty-three days a loss of not quite 1/5 of bleaching-power. Kept in closed bottles in diffused daylight, the stability of this solution was superior
to that of all other bleach-liquors; after thirty-three days 9/10 of the available chlorine was still present. This is therefore a very good
bleaching-solution, if kept from the light.
M'Clelland and Lange (B. P. 27463 of 1907) render this solution more stable by adding during its preparation magnesium oxide, hydroxide, or carbonate,
stirring them properly in by means of an ebonite rod with india-rubber flaps, or allowing the liquor to trickle through the above-quoted magnesium
compounds."
LINK:
http://books.google.com/books?id=FnrTAAAAMAAJ&pg=PA670&a...
[Edited on 15-1-2012 by AJKOER] |
)