Iron pigment properties

In general, all iron pigments are characteri2ed by low chroma and excellent Hghtfastness. They are nontoxic, nonbleeding, and inexpensive. They do not react with weak acids and alkaHes, and if they are not contaminated with manganese, do not react with organic solvents. However, properties vary from one oxide to another. 

At the completion of the reaction, the aniline is separated from the iron oxides by steam distillation and the umeacted iron removed. The pigment is washed, filtered and dried, or calcined in rotary kilns to hematite (Plate 20.1, see p. XXXIX). Considerable control over pigment properties can be achieved in this process by varying the nature and concentration of the additives and the reaction rate the latter depends on pH, the rate of addition of iron and nitrobenzene and the type and particle size of the iron particles. Two advantages of this method are that a saleable byproduct, aniline, is produced and that there are no environmentally, harmful waste products. 

Bismuth vanadate shows a sharp increase in reflection at 450 nm and considerably higher chroma than iron yellow or nickel titanium yellow. It has very good weather resistance both in full shade and in combination with Ti02. General pigment properties are ... 

The presence of coordinative water is essential for stabiUzation of the crystal structure. Removal of this water, however carefully carried out, destroys the pigment properties. Many investigations helped to elucidate the structure of iron blue [3.172-3.175]. 

Sodium or potassium hexacyanoferrate(II) or mixtures of these salts are used in most cases. When the pure sodium salt or a calcium hexacyanoferrate(II) solution is used, the pigment properties are obtained by adding a potassium or ammonium salt during the precipitation of the white paste product or prior to the oxidation stage. The iron(II) salt used is crystalline iron(II) sulfate or iron(II) chloride solution. 

Natural and synthetic iron oxides not possessing pigment properties are used as raw materials in the production of hard and soft ferrites (see Section 5.5.5.2, Electro- and Magneto-Ceramics) for radio, television and telephone technology, for adhesive magnets, for rotors in dynamos, for low-loss magnetic layers, for DC-motors, for transformer cores, for electronic calculators and high frequency furnaces. This amounts to an annual worldwide production of more than 300 10 t/a. 

Definition Sienna, siderite and umber are natural iron oxide ores used as brn. pigments Properties Reddish-brn. powd. sol. in acids insol. in water and alcohol... 

The final product of all the above processes is iron(III) oxide, a-Fe202, but its properties are deterrnined by the method of preparation. Thermal dehydration of goethite yields a pigment of lowest (4.5 g/cm ) density. The highest (5.2 g/cm ) density pigment is one prepared by two-stage calcination. The particle si2e varies from 0.3 to 4 p.m the refractive index varies from 2.94 to 3.22. 

Consumer articles often use colorants (qv), reodorants, or finishing agents. Carbon black (qv) provides the best technological properties for industrial appHcations, so most mbber articles are black. Red iron oxide or other inorganic pigments are used to color mineral-filled articles. Organic... 

The exceUent adhesion to primed films of polyester combined with good dielectric properties and good surface properties makes the vinyhdene chloride copolymers very suitable as binders for iron oxide pigmented coatings for magnetic tapes (168—170). They perform very weU in audio, video, and computer tapes. 

The white cast irons and their low alloys have good abrasion resistance properties [2,3]. White cast irons are used for grinding balls, segments for mill liners and slurry pumps. In the ceramic industry they are used for muller tyres and augers in the pulp and paper industry for attrition mill plates and chip feeders and in the paint industry for balls for grinding pigments. 

The compounds of the t/block elements show a wide range of interesting properties. Some are vital to life. Iron is an essential component of mammalian blood. Compounds of cobalt, molybdenum, and zinc are found in vitamins and essential enzymes. Other compounds simply make life more interesting and colorful. The beautiful color of cobalt blue glass, the brilliant greens and blues of kiln-baked pottery, and many pigments used by artists make use of d-block compounds. 

Some inorganic compounds are used as food additives and food colorants. They include titanium dioxide, carbon black, iron oxides, ultramarin, and calcium carbonate. Some of them are important for properties other than the ability to impart color. Titanium is the most commonly used inorganic pigment in food and will be briefly discussed below. ° "°... 

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