Acid Acetic Arsenous

Redox titrants (mainly in acetic acid) are bromine, iodine monochloride, chlorine dioxide, iodine (for Karl Fischer reagent based on a methanolic solution of iodine and S02 with pyridine, and the alternatives, methyl-Cellosolve instead of methanol, or sodium acetate instead of pyridine (see pp. 204-205), and other oxidants, mostly compounds of metals of high valency such as potassium permanganate, chromic acid, lead(IV) or mercury(II) acetate or cerium(IV) salts reductants include sodium dithionate, pyrocatechol and oxalic acid, and compounds of metals at low valency such as iron(II) perchlorate, tin(II) chloride, vanadyl acetate, arsenic(IV) or titanium(III) chloride and chromium(II) chloride. 

The evidence for the formation of complex heteropoly-acids with tantalic acid is very comparable to that set forth in the case of niobic acid (see p. 165). Solutions of tantalates are readily hydrolysed in aqueous solution by boiling, and even more readily by the addition of mineral acids, acetic acid or succinic acid in the presence, however, of arsenious add, arsenic add, tartaric add or dtric add no precipitation of tantalic add takes place. Again, tincture of galls yields a yellow predpitate with solutions of tantalates which have been rendered feebly acid with sulphuric add this reaction does not, however, take place in the presence of ordinary tartaric add, racemic add or citric acid. Tartaric add also prevents the formation of the predpitates which are thrown down on the addition of potassium ferrocyanide or potassium ferricyanide to faintly acid solutions of tantalates, and hinders the precipitation of tantalic add from solutions in inorganic acids by the action of ammonia. In all these cases it is assumed that complex acids or their salts are produced, in consequence of which the usual reaction does not take place. 

Silver orthoarsenate dissolves in hydrochloric acid, forming arsenic trichloride,11 and in nitric acid with partial conversion to nitrato-arsenate,12 which may be separated by fractional crystallisation, silver orthoarsenate crystallising out first and then the nitrato-arsenate the latter, in contact with water, reverts to silver nitrate and silver orthoarsenate. The latter is also soluble in acetic acid, and in aqueous ammonia or ammonium carbonate. By crystallising the solution in ammonia over a mixture of quicklime and sal-ammoniac, colourless needles of silver tetrammino-orthoarsenate, Ag3As04.4NTI3, are obtained 13 these lose ammonia in the air and turn reddish-brown. 

Arsenic carbonate has not been prepared, but arsenic salts of several organic acids, including arsenic cyanide, thiocyanate, acetate and tartrate, are known. Arsenic chromithiocyanate, As[Cr(SCN)g], has also been described.5... 

Drum dryers potatoes, cereals, buttermilk, skim milk, dextrins, yeasts, instant oat meal, polyacylamides, sodium benzoate, propionates, acetates, phosphates, chelates, aluminum oxide, m-disulfuric acid, barium sulfate, calcium acetate-arsenate-carbonate-hydrate-phosphate, caustic, ferrous sulfate, glue, lead arsenate, sodium benzene sulfonate, and sodium chloride... 

Ammonium molybdate-benzidine test (DANGER THE REAGENT IS CARCINOGENIC.) Silicates react with molybdates in acid solution to form the complex silicomolybdic acid H4[SiMo12O40]. The ammonium salt, unlike the analogous phosphoric acid and arsenic acid compounds, is soluble in water and acids to give a yellow solution. The test depends upon the reaction between silicomolybdic acid and benzidine in acetic acid solution whereby molybdenum blue and a blue quinonoid oxidation compound of benzidine are produced. 

In solutions faintly acid with acetic acid, phosphate, arsenate, arsenite, and oxalate are precipitated by AgN03 solution. 

NIOSH REL (Chromium(VI)) TWA 0.025 mg(Cr(VI))/mh CL 0.05/15M SAFETY PROFILE Confirmed human carcinogen. Poison by subcutaneous route. Mutation data reported. A powerful oxidizer. A powerful irritant of skin, eyes, and mucous membranes. Can cause a dermatitis, bronchoasthma, chrome holes, damage to the eyes. Dangerously reactive. Incompatible with acetic acid, acetic anhydride, tetrahydronaphthalene, acetone, alcohols, alkali metals, ammonia, arsenic, bromine penta fluoride, butyric acid, n,n-dimethylformamide, hydrogen sulfide, peroxyformic acid, phosphorus, potassium hexacyanoferrate, pyridine, selenium. 

Explodes on contact with acetic acid, acetic anhydride, ammonium nitrate, dimethylformamide, formaldehyde, concentrated hydrochloric acid, potassium chloride + sulfuric acid, sulfuric acid + water. Forms sensitive explosive mixtures with aluminum powder + ammonium nitrate + glyceryl nitrate + nitrocellulose, ammonium perchlorate, arsenic, phosphorus, sulfur, slag wool, titanium. 

CHROMIUM TRIHYDROXIDE (308-14-1) CrH204 A powerful oxidizer. Violent reaction with many materials, including reducing agents (explosion) hydrides, nitrides, and sulfides acetic acid, acetic anhydride acetone, alcohols, alkalis, alkali metals, ammonia, anthracene, arsenic, combustible materials dimethylformamide, ethers, ethyl alcohol fumes (ignition) finely divided metals hydrogen sulfide sulfuric acid organic matter peroxyformic acid, phosphorus, pyridine, selenium, sodium, sulfur, and other oxidizable materials. 

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