Chlorides and chlorates

Kainite (KCl MgSOJ previously used occasionally for the control of cruiciferous weeds, is no longer used because of its weak action. 

In the USA sodium chloride is used in a restricted measure for postemergence treatment in table beet, and ammonium chloride (NH CI) is included as a component of cotton desiccation formulations. 

Calcium chloride (CaClj) and magnesium chloride (MgClj 6HjO) are sporadically used in the USA at rates of several hundred kg/ha as total weed killers for the sterilisation of soil on industrial sites, on the banks of highways and other non-crop areas. 

Two salts of chloric acid, sodium chlorate (NaCIOj) and magnesium chlorate (Mg(C10j)2 6HjO), have gained use in agriculture. 

Sodium chlorate is readily soluble in water (790 g/1 at 0°C) and is therefore applied as an aqueous solution. It is a strong oxidant. It reacts with organic materials in the presence of sunlight, creating a serious fire hazard when spray splashed on clothing forms deposits. Residual compound on wilted weeds has a tendency to self-ignite. To reduce the fire hazard, calcium chloride, sodium sulfite or trisodium phosphate is mixed with the sodium chlorate. 

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Thermal decomposition of perchlorate salts to chloride, followed by the gravimetric determination of the resulting chloride, is a standard method of determining quantitatively the concentration of perchlorates. Any chlorates that are present in the original sample also break down to chloride. Thus results are adjusted to eliminate errors introduced by the presence of any chlorides and chlorates in the original sample. 

Table 3. Mass Ratio of Crystalline Chloride and Chlorate Salts in Equilibrium with an Aqueous Solution...

A nanofiltration membrane will always allow the chloride and chlorate ions to pass... 

In 1815, L. G. Gilbert1 noticed that thoroughly dried calcium oxide or hydroxide does not react chemically with dry chlorine, and similarly, in 1879, J. K. Weisherg showed that the same remark applies to dry barium or strontium oxide. The case is very different if moisture he present. With barium hydroxide two gram-atoms of chlorine are absorbed per gram-atom of the bivalent barium, and barium chloride and chlorate are produced so that if barium hypochlorite is formed as the first product of the reaction, it is immediately decomposed 3Ba(0Cl)2=Ba(C103)2 +2BaCl2 with calcium and strontium hydroxides, the reaction appears to he much... 

In 1834, A. J. Balard 1 prepared solutions of salts of hypochlorous acid—the hypochlorites—by mixing the aq. acid with alkalies, magnesia, or with zinc or copper hydroxides, and avoiding an excess of the acid. If the liquids are not kept cold, the hypochlorites decompose into chlorides and chlorates. A. J. Balard said ... 

A. J. Balard found mercury immediately decomposes hypochlorous acid without the disengagement of any gas, but mercury oxychloride is formed. P. Grouvelle reported previously that when chlorine acts on mercuric oxide suspended in water, mercury oxychloride, very slightly soluble in cold water, is formed. L. J. Thenard found that the liquid contained both chloride and chlorate of mercury, also in soln. A. J. Balard, however, believed that these bodies are formed consecutively, and that their existence was preceded by that of a mercuric hypochlorite, as takes place with the salts of silver, and, as previously indicated, he prepared hypochlorous acid by the action of chlorine on mercuric oxide suspended in water. No mercury hypobromite has yet been isolated. There is a possible formation of mercury hypoiodite, or more probably of hypoiodous acid, when iodine is shaken up with... 

Perchlorates Since perchlorates arc not reduced by H2SOg, they will remain (if present) unchanged in the filtrate after removal of chlorides and chlorates. For a quantitative test, transfer that filtrate to a platinum crucible and evaporate to dryness on a steam bath. Add 5g of anhydrous Na2C03, mix and heat over a burner until a clear melt is obtd and then for 15—20 mins more. Cool the meit, dissolve in dilute HN03 and determine the chloride by pptn with AgN03 soln... 

If test is conducted starting wi th a 25 ml aliquot of original water extract, the wt of AgCl determines the sum of chloride, chlorate, and perchlorate. On subtracring chloride and chlorate from the sum, perchlorate is obtd Pierson s procedure D—6. Acid Extraction (Ref 11, ppl359-60 Ref 17, Methods D90-6,... 

Hypochlorite and chlorate production rely on reacting the anodically evolved chlorine in dissolved form with cathodically generated hydroxyl ions due to homogeneous reaction kinetics. In chlorate production the formation of hypochlorite is followed by disproportionation of the hypochlorite to chloride and chlorate. 

The standard potential of this reaction equals ept> ci-, 0107 = — 0.62 V. If we assume that the solution is neutral, and the activity a of both chloride and chlorate ions is unity, the following equation is valid at 25 °C according to Nernst s law ... 

Probably, the consumption of OH radicals in competing side reactions is lower. The same tendency was observed in experiments with chloride and chlorate (not shown here). 

On prolonged storage, the hypochlorite ions disproportionate gradually into chloride and chlorate. Hypochlorite solutions may also be decomposed to chloride and oxygen in the presence of heavy metal ions. When hypochlorite is reduced to chloride two oxidation equivalents are consumed. For example, 1 M hypochlorite solution contains 2 x 35.5 = 71 g/liter of active chlorine. 

In this process, the chlorine and caustic produced in the cell react immediately, and the cell liquor is kept hot in an additional vessel that provides sufficient residence time for all the hypochlorite to disproportionate into chloride and chlorate ... 

Several rubidium salts exhibit radioactivity,14 among them the sulphate,15 chloride, and chlorate.16 The action of the sulphate on the photographic plate is more powerful than that of potassium sulphate.17... 

Chlorine reacts with an aqueous solution of silver nitrate to form chloride and chlorate of silver, the hypochlorite being an intermediate product ... 

Silver hypochlorite, AgOCl.—A very unstable solution of the hypochlorite is formed by the action of chlorine-water on excess of silver monoxide. It soon decomposes into silver chloride and chlorate. 

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