Sodium Hydroxide-Chromic Acid

Immerse for 5—10 min at 63—79 °C in a solution of 12 parts by weight water and 1 part sodium hydroxide (commercial grade) 

Immerse for 5—15 min at room temperature in the solution described in Table 6.13 

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ASTM D 2651 sodium hydroxide-chromic acid etch... 

ARSENOLITE or ARSENOUS ACID or ARSENOUS ACID ANHYDRIDE or ARSENOUS ANHYDRIDE (1327-53-3) AS2O3 Noncombustible solid. Reacts, possibly violently, with acids, aluminum, aluminum chloride, chlorine trifluoride, chromic oxide, fluorine, fluorides, halogens, hydrogen fluoride, mercury, oxygen fluoride, phosphorus pentoxide, rubidium acetylide, sodium chlorate, sodium hydroxide, sulfiiric acid, tannic acid, zinc iron in solution. Contact with acids or acid mists releases toxic and flammable arsine gas. The aqueous... 

Conversion coatings are not as protective as anodized coatings. In most cases, conversion coated surfaces are subsequently primed or painted. Xraditionally, pretreatment of Al has relied on chromate-based systems. Xhere are two general classes of chromate conversion processes the activated acidic formulations such as the chromium chromate processes that use a sodium fluoride-chromic acid chemistry, and alkaline oxide processes based on a sodium chromate-sodium hydroxide or carbonate chemistry. 

Oxidation of saligenin with chromic acid or silver oxide yields saUcyladehyde as the first product. Further oxidation results in the formation of sahcyhc acid, which is also obtained when saligenin is heated with sodium hydroxide at 200—240°C. Chlorination of an aqueous solution of the alcohol gives 2,4,6-trichlorophenol, and bromination in an alkaline medium yields 2,4,6-tribromophenol and tribromosaligenin. When saligenin is heated with one mole of resorcinol in the presence of anhydrous zinc chloride, 3-hydroxyxanthene forms. 

When a potential is appHed across the ceU, the sodum and other cations are transported across the membrane to the catholyte compartment. Sodium hydroxide is formed in the catholyte compartment, because of the rise in pH caused by the reduction of water. Any polyvalent cations are precipitated and removed. The purified NaOH may be combined with the sodium bicarbonate from the sodium dichromate process to produce soda ash for the roasting operation. In the anolyte compartment, the pH falls because of the oxidation of water. The increase in acidity results in the formation of chromic acid. When an appropriate concentration of the acid is obtained, the Hquid from the anolyte is sent to the crystallizer, the crystals are removed, and the mother Hquor is recycled to the anolyte compartment of the ceU. The electrolysis is not allowed to completely convert sodium dichromate to chromic acid (76). Patents have been granted for more electrolytic membrane processes for chromic acid and dichromates manufacture (86). 

Skin Inorganic acids (chromic, nitric) organic acids (acetic, butyric) inorganic alkalis (sodium hydroxide, sodium carbonate) organic bases (amines) organic solvents. Dusts Detergents salts (nickel sulphate, zinc chloride) acids, alkalis, chromates. ... 

While keeping the collected deuterioammonia at dry ice-isopropyl alcohol temperature, lithium wire (10 mg) is added, followed by a solution of 3/3-hydroxy-5a-cholest-7-en-6-one (161 50 mg) in anhydrous tetrahydrofuran (4 ml). The reaction mixture is stirred for 20 min, the cooling bath is then removed and the ammonia is allowed to boil under reflux for 40 min. A saturated solution of ammonium chloride in tetrahydrofuran is added dropwise until the deep blue color disappears and then the ammonia is allowed to evaporate. The residue is extracted with ether and the organic layer washed with dilute hydrochloric acid and sodium bicarbonate solution and then with water. Drying and evaporation of the solvent gives a semicrystalline residue which is dissolved in acetone and oxidized with 8 N chromic acid solution. After the usual workup the residue is dissolved in methanol containing sodium hydroxide (0.2 g) and heated under reflux for 1 hr to remove any deuterium introduced at C-5 or C-7. (For workup, see section II-B). 

The theoretical aspects of molybdenum s corrosion behaviour are complex and there is as yet no clear cut, generally applicable picture. There are, however, a large number of literature references which include data on polarisation, passivation and potential of molybdenum under widely assorted conditions. The electrode potential of molybdenum depends on its surface condition. For example, some tests showed an of -t-0-66V when the molybdenum was passivated by treatment with concentrated chromic acid and —0-74 V after activation by cathodic treatment in sodium hydroxide. 

Tetrachromate electrolytes The alkaline tetrachromate baths are used to a small extent chiefly for the direct chromium plating of zinc die-castings, brass or aluminium, since the solutions do not attack these metals . The original bath was developed by Bornhauser (German Pat. 608 757) and contained 300 g/1 of chromic acid, 60g/l of sodium hydroxide, 0-6-0-8g/l of sulphuric acid and 1 ml/l of alcohol. 

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