Barium ferricyanide

Barium ferricyanide, Ba3[Fe(CN)6]2.20H2O, is prepared by neutralising ferricyanic acid with barium carbonate and evaporating to crystallisation in vacuo.2. It also results on boiling a solution of barium ferrocyanide with lead dioxide.4 It yields reddish brown crystals. These are soluble in water without decomposition. The salt is decomposed on warming with acids. The compound Ba3[Fe(CN)6]2.2BaBr2. 20H2O, has been obtained.5... 

Barium potassium ferricyanide, BaKFe(CN)6.4H20, first isolated by Bette,6 who regarded it as a trihydratc, is conveniently prepared by addition of the requisite quantity of potassium sulphate to a solution of barium ferricyanide and allowing the filtered liquid to evaporate.7... 

Chromium Chromate. Chromium chromate treatment baths are acidic and made up from sources of hexavalent chromium and complex fluoride, fluorosiHcate, fluorozirconate, fluorotitanate, and siHcofluorides. Optional additional components added to accelerate coating rate are free fluoride, ferricyanide, and other metal salts such as barium nitrate. Conversion coating on aluminum precedes by the following reactions (2,3,17) ... 

A similar accelerating effect is exerted by other substances, such as potassium ferricyanide, potassium permanganate, potassium chromate,6 sodium peroxide,6 barium peroxide,7 cyanogen bromide,8 cyanogen chloride,9 persulphates, and certain organic compounds.10 The best method of reducing the proportion of the other metals is to maintain the cyanide solution dilute. 

Barium sodium ferricyanide, BaNaFe(CN)6.3H20, and Barium ammonium ferricyanide, BaNH4,Fe(CN)6.4H20, have also been prepared. 

Magnesium ferricyanide, Mg3[Fe(CN)6]2.10H2O, is prepared in an analogous manner to the barium salt, and dried over sulphuric acid. The aqueous solution decomposes when warmed.4... 

Hydrogen nitroso ferricyanide or nitroprussic acid, H2[Fe(CN)5NOJ, is obtained by decomposition of the silver salt with hydrochloric acid or by the action of dilute sulphuric acid upon the barium salt. It is also formed when nitric oxide is bubbled through an acidified solution of potassium ferrocyanide.4 The reaction proceeds in two stages, namely, (a) oxidation to the ferricyanide, and (b) substitution of the cyanogen radicle by NO —... 

Chromium Chlorate, Cr(C10g)3, which is obtained by the double decomposition of barium chlorate and chrome alum, forms a violet solution which becomes green at 65° C. and decomposes on boiling, yielding chromium hydroxide and oxides of chlorine. Tire dcconr-position is facilitated by potassium ferricyanide. The salt is used iir calico printing and for increasing the permanence of aniline black. 

Vanadium compounds (vanadic acid and vanadium chloride) have been proposed as substitutes for copper sulphide, but without much practical success. Potassium ferrocyanide and ferricyanide are also used to a certain extent. A mixture of these salts with aniline salt and potassium chlorate is printed, and the goods aged. The probable action is that the ferricyanide oxidises the aniline, and is continually regenerated from the ferrocyanide formed by the chloric acid present. Thus these salts play the part of oxygen carriers in a similar manner to the copper and vanadium compounds. In the opinion of technologists, the hlack produced by this process differs somewhat in its properties from that obtained with copper, but this may be ascribed to the presence of prussiaii blue in the former. In place of the aniline hydrochloride and potassium chlorate, a mixture of aniline sulphate and barium chlorate has recently been employed in black-printing. 

Potassiuiii ferricyanid. Potassium sulfoeyanate. Potassium carbonate. Potassium chromate, Barium chlorid,... 

Made green ferrocyanide of Beryllium by precipitating barium salt with BeSO. Made ferricyanide by oxidia-ing ferrocyanide with Cl, olive green. Could not separate the sulphocyanate and nitroprusside. 

Butyl hydroperoxide, barium chlorate,or potassium ferricyanide can also be used as oxidants in catalytic procedures. Scheme 12.6 provides some examples of oxidations of alkenes to glycols by permanganate and by osmium tetroxide. 

White silver cyanide, thiocyanate, ferro- and yellow ferricyanide are decomposed with production of ignition-resistant silver. All metal ferro- and ferricyanides of the base metals leave a residue of ferric oxide and the particular metal oxide. For instance, the colorless ferrocyanides of zinc, cadmium, magnesium, calcium, barium, strontium, thorium etc. become yellow-brown Prussian blue and Turnbull s blue become dark (Fe304) and, later, brown (FegOg). Cupric ferricyanide (brown) and cupric ferrocyanide (violet-brown) are blackened when ignited because of the formation of cupric oxide. 

---