Chromium black material

In order to determine if the black material added to the autoclave was in fact chromium metal or a mixture of Cr(II) salts and potassium, the following experiments were carried out. The black material obtained from the reduction of CrCls BTHF with potassium in benzene was repeatedly extracted with THF to remove and to determine soluble chromium(ll) salts. Also the amount of unreacted potassium was determined by repeated extraction of the black material with alcohol and water and subsequent acidic titration of the extracts. From these two determinations, it was established that a minimum of 58% of the Cr(CO)e formed in the autoclave reaction originated from chromium(O). In a separate experiment, the black material was extracted repeatedly with THF to remove all the soluble chromium salts and was then treated with CO under the same conditions as in the previous reactions. The yield of Cr(CO)6 was 30% based on the material placed in the autoclave. Thus, it is clear that Cr(0) is produced in the reduction, and this Cr(0) will react with CO to yield Cr CO)e- It is difficult to determine the exact amount of Cr(CO)6 which originated from Cr(0) in the black powder due to its instability. Thus, excessive manipulations of the black powder even under argon or very long reduction times in the generation of the black powders seem to deactivate the Cr(0). 

Potassium (1.51 g, 0.0386 mol), CrCls-STHF (4.83g, 0.0129 mol), and KI (2.14g, 0.0129 mol) were heated in benzene (50 ml) at 90 C for 2h. The black material was filtered from the brown benzene solution, and the brown-black residue washed with benzene (3x10 ml) and then with THF (6 x 10 ml) until the THF was colorless. The combined benzene and THF extracts were evaporated, and the remaining brown crystals were dissolved in water, and the chromium content was determined as Cr20s, yielding 256 mg of Cr. Thus 38.1% of Cr remained only partially reduced in the form of chromium(II) salts. The black... 

Naphthalenediol. 1,5-Dihydroxynaphthalene or Asurol is a colorless material which darkens on exposure to air. It is manufactured by the fusion of disodium 1,5-naphthalenedisulfonate with sodium hydroxide at ca 320°C in high yield. 1,5-Naphthalenediol is an important coupling component, giving ortho-a2o dyes which form complexes with chromium. The metallised dyes produce fast black shades on wool. 1,5-Naphthalenediol can be aminated with ammonia under pressure to 1,5-naphthalenediamine. 

B. General Oxidation Procedure for Alcohols. A sufficient quantity of a 5% solution of dipyridine chromium (VI) oxide (Note 1) in anhydrous dichloromethane (Note 7) is prepared to provide a sixfold molar ratio of complex to alcohol. This excess is usually required for complete oxidation to the aldehyde. The freshly prepared, pure complex dissolves completely in dichloromethane at 25° at 5% concentration to give a deep red solution, but solutions usually contain small amounts of brown, insoluble material when prepared from crude complex (Note 8). The alcohol, either pure or as a solution in anhydrous methylene chloride, is added to the red solution in one portion with stirring at room temperature or lower. The oxidation of unhindered primary (and secondary) alcohols proceeds to completion within 5 minutes to 15 minutes at 25° with deposition of brownish-black, polymeric, reduced chromium-pyridine products (Note 9). When deposition of reduced chromium compounds is complete (monitoring the reaction by gas chromatography or thin-layer chromatography analysis is helpful), the supernatant liquid is decanted from the (usually tarry) precipitate and the precipitate is rinsed thoroughly with dichloromethane (Note 10). 

For commercial printing onto nonporous, hydrophobic materials such as plastics, metals, and glass, rapidly drying solvent inks which adhere to these substrates are needed. A typical solvent for these applications is methyl ethyl ketone (MEK). However, alternative alcoholic solvents tike ethanol and N-propanol have been introduced for ecological and safety reasons. The predominant color for industrial marking is black, and solvent soluble 2 1 azo chromium(m) complex, polyazo, Nigrosine, and sulfur dyes are used. Typical formulation of an... 

Bullet jacket materials include gilding metal cupronickel cupronickel-coated steel nickel zinc-, chromium-, or copper-coated steel lacquered steel brass nickel- or chromium-plated brass copper bronze aluminum/alumi-num alloy Nylon (Nyclad), Teflon- and cadmium-coated steel (rare). Black Talon bullets have a black molybdenum disulfide coating over the metal bullet jacket which acts as a dry lubricant. Steel jackets are frequently coated both inside and outside as an anticorrosion measure. Gilding metal is by far the most common bullet jacket material. Tin is claimed to have lubricating properties and is sometimes incorporated in bullet jacket material. The alloy is known as Lubaloy or Nobaloy and contains 90% copper, 8% zinc, and 2% tin. 

Acid etching can be used to treat types 301 and 302 of stainless. These processes result in a heavy black smut formation on the surface. This material must be removed if maximum adhesion is to be obtained. The acid etch process produces bonds with high peel and shear strengths. The 400 series of straight chromium stainless steels should be handled in the same manner as the plain carbon steels. The various types of precipitation hardening (PH) stainless steels each present an individual problem. Processes must be adopted or developed for each type. 

The high value of the potential 7t° = 1.8 V related to reaction (XXV-3) justifies in advance the assumption that the oxidation of trivalent chromium ions will be accompanied with an evolution of oxygen chiefly during the final stage of electrolysis, when the majority of Cr+++ ions has been oxidized to CrO ions. The material used for the anodes has a great influence upon the oxidation efficiency attained. It has been proved by experiments that oxidation will not ooeur on smooth platinum anodes at all. On platinum anodes coated with platinum black current efficiency is rather low, while with lead anodes which beoome coated with lead dioxide during eleotrolysis it is possible to reach... 

Regulated Colorants That Are FDA Approved. It often seems a contradiction that many of the colorants that are suitable for use in food contact applications must also appear on an MSDS as a reportable or hazardous material. Examples include zinc oxide and zinc sulfide, both zinc compounds chromium oxide green (pigment green 17), a chromium compound carbon black and cobalt aluminate blue (pigment blue 28), which is not only reportable because of its cobalt content but is also a suspected carcinogen. 

Perceived or Real Health and Safety Issues — There are a number of issues or perceived issues which customers encounter with the original MEK-based inks. The use of MEK has its share of concerns, based upon the smell and perception that it is a harmful material. Indeed, for this reason inks have been formulated with alternative solvents such as ethanol and methanol, as well as previously discussed acetone, and a variety of acetates, such as ethyl acetate. Some of these solvents have unpleasant odour, some more pleasant smell some have a lower toxicity level. That said, methanol is commonly used as a low odor replacement, but could probably be considered a more toxic ingredient Another component which is often replaced is the Solvent Black 29 dye, this dye does contain chromium as the counter ion and the toxicity concerns of having free Chromium 6 ions in an ink can be an issue for some applications or customers. Dyes with alternative counter ions or pigments have been chosen to replace this material. These requirements are often found in the food processing or pharmaceutical application areas, although they can occur with any customer. 

X-Ray diffraction powder patterns were developed by using a chromium source and a Phillips Debye-Sherrer camera. Due to their small size, the samples from the back of the halberd were irradiated for 12.5 h, and the green pseudomorph sample for 12.3 h. The black pseudomorph sample, larger, was irradiated for only 5 h. The exposed film was measured in accordance with standard procedures (8) and the resulting diffraction spacing values were compared to standard values of known materials (9). 

ARSENIC BLACK (7440-38-2) Finely divided material forms explosive mixture with air. Decomposes on contact with acids or acid fumes, emitting fumes of arsenic. Contact of dust or powder with strong oxidizers can cause ignition or explosion. Violent reaction with bromine azide, bromine pentafluoride, bromine trifluoride, dichlorine oxide, hypochlorous acid, nitrogen trichloride, tribromamine hexaammoniate, nitrogen oxyfluoride, potassium chlorate, potassium dioxide, powdered rubidium, silver fluoride. Incompatible with strong acids, cesium acetylene carbide, chromic acid, chromium trioxide, hafnium, halogens, lead monoxide, mercury oxide, nitryl fluoride, platinum, potassium nitrate, silver nitrate, sodium chlorate, powdered zinc. 

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