Yellow iron oxides

Penniman-Zoph A process for making a yellow iron oxide pigment. Hydrated ferric oxide seed is added to a solution of ferrous sulfate and the suspension circulated over scrap iron, with air being passed through. Hydrated ferric oxide deposits on the seed crystals, giving a finely divided, yellow pigment ... 

Methylparaben, Propylparaben preservative magnesium trisilicate, talc, tragacanth, sodium alginate, essential oils, sorbitol and atropine, yellow iron oxide, and ultramarine blue... 

Parabens are approved for use in oral solution and suspensions at a concentration of 0.015% to 0.2% w/v. Due to their low solubility, the sodium salts of parabens are often used in aqueous formulations. The parabens are most effective in the pH range of 2 to 6, and their antimicrobial activity decreases with increasing pH. Additionally, they are very unstable at pH 8 or above in solution. Methyl paraben has also demonstrated incompatibility with sorbitol and may show some discoloration in the presence of iron. The absorption of methylparaben by plastics has been reported with the amount absorbed being dependent upon the type of plastic and vehicle. However, no absorption has been reported for low density polyethylene (LDPE) or high density polyethylene (HDPE) containers. Certain coloring agents such as yellow iron oxide, ultramarine blue, and aluminum silicate can extensively absorb ethyl paraben in simple aqueous systems, thus reducing its preservative efficacy. 

Oxides and oxide -hydroxides Iron oxide pigments Chromium oxide pigments Mixed metal oxide pigments chromium oxide cob chromium oxide hydrate green alt green and b lue iron oxide red iron oxide orange chromium rutile orange iron oxide yellow nickel rutile yellow, chromium rutile yellow iron oxide brown zinc iron spinell, Mn-Fe-brown... 

Figure 2. Standard deviation ellipses of a logarithmic normal distribution (yellow iron oxide pigment)...

The calcination of yellow iron oxide produces pure red iron oxide pigments with a high tinting strength. Further processing is similar to that of calcined black pigments. 

The solutions of the iron salts are first mixed with alkali in open reaction vessels (Fig. 23, Route A) and oxidized, usually with air. The quantity of alkali used is such that the pH remains acidic. The reaction time (ca. 10-100 h) depends on the temperature (10—90 °C) and on the desired particle size of the pigment. This method yields yellow pigments (a-FeOOH) [3.16], [3.17]. If yellow nuclei are produced in a separate reaction (Fig. 23, Route A, tank c), highly consistent yellow iron oxide pigments with a pure color can be obtained [3.18],... 

Figure 23. Production of yellow iron oxide by the precipitation (A) and Penniman (B) processes a) Tank b) Pigment reactor c) Seed reactor d) Pigment reactor with scrap basket e) Filter f) Dryer g) Mill...

The Penniman process is probably the most widely used production method for yellow iron oxide pigments [3.26], [3.27], This method considerably reduces the quantity of neutral salts formed as byproducts. The raw materials are iron(II) sulfate, sodium hydroxide solution, and scrap iron. If the sulfate contains appreciable quantities of salt impurities, these must be removed by partial precipitation. The iron must be free of alloying components. The process usually consists of two stages (Fig. 23, Route B). 

Transparent yellow iron oxide has the a-FeO(OH) (goethite) structure on heating it is converted into transparent red iron oxide with the a-Fe203 (hematite) structure. Differential thermogravimetric analysis shows a weight loss at 275 °C. Orange hues develop after brief thermal treatment of yellow iron oxide and can also be obtained by blending directly the yellow and red iron oxide powders. 

Production. Transparent yellow iron oxide [51274-00-1], C.I. Pigment Yellow 42 77492, is obtained by the precipitation of iron(II) hydroxide or carbonate... 

X Red iron oxide paste, yellow iron oxide paste, and black ink... 

Fortovasc Saquinavir X X X Red ttrtd yellow iron oxide... 

Ocher is a weak tinting agent and is often replaced by synthetic hydrated yellow iron oxides for brighter color and better uniformity. 

Hot springs may contain lots of different minerals in solution. Upon reaching the surface, these waters cool off and the compounds held in solution will precipitate around vents or pools. The most common deposits around hot springs are composed of calcite or common opal. Both of these minerals are colorless when pure, but are often colored by other materials in the water. Oxides of iron are the most common pigments in these situations. In shades of brown, red, and yellow, iron oxide may color an entire deposit, or appear episodically, dyeing some layers and not others. 

Burnt siennas are reddish brown in masstone with a salmon-colored tint. The difference in hue between raw and burnt sienna results from the conversion of yellow iron oxide to red iron oxide during calcination, during which the water of crystallization is driven off. Burnt siennas typically contain 55-80% Fe203. 

Yellow iron oxides are produced by one of three methods ... 

Red and yellow iron oxides have excellent weathering characteristics both absorb ultraviolet radiation. They offer good opacity and excellent value in use. Their chroma and saturation, however, are limited. 

In contrast, yellow iron oxide begins to lose its water of hydration above 177°C and converts to Fe203. Consequently, its use in plastics is limited to low-temperature processes. It is well suited for weatherable flexible vinyl applications. At one time, truckloads of yellow iron oxides were used in the coloration of low-density polyethylene disposable green garbage bags. 

An increasing number of colored inorganic pigments are FDA-compliant. Historically, yellow iron oxide, red iron oxide, black iron oxide, zinc ferrite, burnt umber, raw and burnt sienna, channel carbon black, chromium oxide green, ultramarine blue, cobalt blue and copper chrome black have enjoyed FDA—compliant status, under 21 CFR 178.3297, Colorants for Polymers . More recently, the FDA has been successfully petitioned with regard to nickel titanium yellow, chrome titanium yellow, and cobalt green under 21 CFR 170.39, Threshold of Regulation for Substances Used in Food-Contact Articles . 

The simultaneous influences of aluminium silicate and yellow iron oxide on the antistatic properties of PVC-based composites were analysed. Antistatic properties were estimated in terms of electrostatic potential values, its halving time and surface electrical resistivity. Two optimal antistatic composites were established using the second order programme method. 14 refs. 

Oxides and oxide-hydroxides Iron oxide pigments iron oxide red iron oxide orange iron oxide yellow iron oxide brown... 

Fig. l.n Determination of the hiding power of a yellow iron oxide pigment. 

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