Iron colors

Eisen-erz, n. iron ore. -fallung, /. iron precipitation. -finger, m. iron trap, farbe, /. iron color. 

Cerium is a grayish/iron-colored, very reactive metallic element that is attacked by both acids and alkalies. Pure cerium will ignite if scratched with a knife, but it can be combined safely with many other elements and materials. It is relatively soft and both malleable and ductile. 

Color pigments, inorganic Ferric oxide pigments Iron blue pigments Iron colors Iron oxide, black Iron oxide, magnetic Iron oxide, yellow Lamp black Lead oxide pigments Lead pigments... 

The sodium amide (20 mols) is prepared in 5 1. of liqmd ammonia in a 12-1. flask by the procedure described in synthesis 38, then acetylene is introduced exactly as in part B. No gas is evolved through the condenser, and the reaction mixture becomes milky with insoluble disodium acetylide, which masks the dark color imparted by colloidal iron. The milkiness persists until the theoretical amount of acetylene has been added, when the original deep-brownish or black iron color appears. Acetylene is absorbed for a few minutes longer, to saturate the ammonia solution, and is then discharged through the condenser as a final indication that the reaction is complete. 

The urochromes dissolved in water are precipitated by coprecipitation with aluminium hydroxide. The precipitate is decanted or centrifuged off and dissolved in formic acid. After adding phosphoric acid to eliminate iron coloration, the urochrome content is determined by measurement of the extinction at 380 nm. If humic acids are present, a second extinction measurement is taken at 530 nm and taken into account in the calculation. Instead of calibration with a urochrome reference solution, the urochrome content is calculated by multiplying the "colour value" by an empirical factor. 

Because both apparatus and reagents may contribute silica, avoid using glassware as much as possible and use reagents low in silica. Also, make a blank determination to correct for silica so introduced. In this method, tarmin, large amoimts of iron, color, turbidity, sulfide, and phosphate interfere. Treatment with oxalic acid eliminates interference from phosphate and decreases interference from tannin. If necessary, use photometric compensation to cancel interference from color or turbidity. 

Dissolve a small portion of the sodium derivative in a few mi. of water in a test-tube, and add one drop of ferric chloride solution. A deep red coloration is produced, but rapidly disappears as the iron is precipitated as ferric hydroxide. The sodium (derivative (A) of the nitromethane wh dissolved in water undergoes partial hydrolysis,... 

It is essential to use an excess of sodium, otherwise if sulphur and nitrogen are both present sodium thiocyanate, NaCNS, may be produced in the test for nitrogen it may give a red coloration with ferric iron but no Prussian blue since there will be no free cyanide ions. With excess of sodium the thiocyanate, if formed, will be decomposed ... 

Acetic acid, fp 16.635°C ((1), bp 117.87°C at 101.3 kPa (2), is a clear, colorless Hquid. Water is the chief impurity in acetic acid although other materials such as acetaldehyde, acetic anhydride, formic acid, biacetyl, methyl acetate, ethyl acetoacetate, iron, and mercury are also sometimes found. Water significantly lowers the freezing point of glacial acetic acid as do acetic anhydride and methyl acetate (3). The presence of acetaldehyde [75-07-0] or formic acid [64-18-6] is commonly revealed by permanganate tests biacetyl [431-03-8] and iron are indicated by color. Ethyl acetoacetate [141-97-9] may cause slight color in acetic acid and is often mistaken for formic acid because it reduces mercuric chloride to calomel. Traces of mercury provoke catastrophic corrosion of aluminum metal, often employed in shipping the acid. 

Mild steel is a suitable material of constmction for storage and handling of DMAC at ambient temperatures. Aluminum or stainless steel is recommended for cases involving very stringent color or iron contamination requirements. Mild steel is not recommended for high temperature service or handling aqueous solutions of less than 50 mol % (82.86 wt %) DMAC. 

Analytical Procedures. Standard methods for analysis of food-grade adipic acid are described ia the Food Chemicals Codex (see Refs, ia Table 8). Classical methods are used for assay (titration), trace metals (As, heavy metals as Pb), and total ash. Water is determined by Kad-Fisher titration of a methanol solution of the acid. Determination of color ia methanol solution (APHA, Hazen equivalent, max. 10), as well as iron and other metals, are also described elsewhere (175). Other analyses frequendy are required for resia-grade acid. For example, hydrolyzable nitrogen (NH, amides, nitriles, etc) is determined by distillation of ammonia from an alkaline solution. Reducible nitrogen (nitrates and nitroorganics) may then be determined by adding DeVarda s alloy and continuing the distillation. Hydrocarbon oil contaminants may be determined by ir analysis of halocarbon extracts of alkaline solutions of the acid. 

Textile dyes were, until the nineteenth century invention of aniline dyes, derived from biological sources plants or animals, eg, insects or, as in the case of the highly prized classical dyestuff Tyrian purple, a shellfish. Some of these natural dyes are so-caUed vat dyes, eg, indigo and Tyrian purple, in which a chemical modification after binding to the fiber results in the intended color. Some others are direct dyes, eg, walnut sheU and safflower, that can be apphed directly to the fiber. The majority, however, are mordant dyes a metal salt precipitated onto the fiber facUitates the binding of the dyestuff Aluminum, iron, and tin salts ate the most common historical mordants. The color of the dyed textile depends on the mordant used for example, cochineal is crimson when mordanted with aluminum, purple with iron, and scarlet with tin (see Dyes AND DYE INTERMEDIATES). 

Anhydrous iron(II) fluoride [7789-28-8] white soHd. The off-white to buff-colored appearance of the material is attributed to the partial... 

Iron(III) fluoride [7783-50-8] most widely known fluoride of iron. It is light greenish (lime green) in color and the crystals have a rhombic... 

Anhydrous FeF is prepared by the action of Hquid or gaseous hydrogen fluoride on anhydrous FeCl (see Iron compounds). FeF is insoluble in alcohol, ether, and ben2ene, and sparingly soluble in anhydrous HF and water. The pH of a saturated solution in water varies between 3.5 and 4.0. Low pH indicates the presence of residual amounts of HF. The light gray color of the material is attributed to iron oxide or free iron impurities in the product. 

Procedures for determining the quaUty of formaldehyde solutions ate outlined by ASTM (120). Analytical methods relevant to Table 5 foUow formaldehyde by the sodium sulfite method (D2194) methanol by specific gravity (D2380) acidity as formic acid by titration with sodium hydroxide (D2379) iron by colorimetry (D2087) and color (APHA) by comparison to platinum—cobalt color standards (D1209). 

Methanol can be converted to a dye after oxidation to formaldehyde and subsequent reaction with chromatropic acid [148-25-4]. The dye formed can be deterruined photometrically. However, gc methods are more convenient. Ammonium formate [540-69-2] is converted thermally to formic acid and ammonia. The latter is trapped by formaldehyde, which makes it possible to titrate the residual acid by conventional methods. The water content can be determined by standard Kad Eischer titration. In order to determine iron, it has to be reduced to the iron(II) form and converted to its bipyridyl complex. This compound is red and can be determined photometrically. Contamination with iron and impurities with polymeric hydrocyanic acid are mainly responsible for the color number of the merchandized formamide (<20 APHA). Hydrocyanic acid is detected by converting it to a blue dye that is analyzed and deterruined photometrically. 

Inorganic Color Pigments. Iron blue is made in several shades, such as Mdori blue and Pmssian blue. It is economical, but has poor alkaH resistance. It is also used as a toner in some black inks. 

Alkali or alkaline-earth salts of both complexes are soluble in water (except for Ba2[Fe(CN)g]) but are insoluble in alcohol. The salts of hexakiscyanoferrate(4—) are yellow and those of hexakiscyanoferrate(3—) are mby red. A large variety of complexes arise when one or more cations of the alkah or alkaline-earth salts is replaced by a complex cation, a representative metal, or a transition metal. Many salts have commercial appHcations, although the majority of industrial production of iron cyanide complexes is of iron blues such as Pmssian Blue, used as pigments (see Pigments, inorganic). Many transition-metal salts of [Fe(CN)g] have characteristic colors. Addition of [Fe(CN)g] to an unknown metal salt solution has been used as a quaUtative test for those transition metals. 

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