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Topic: Dichromate

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	Chromate - Wikipedia, the free encyclopedia
		Chromates and Dichromates are salts of chromic acid and dichromic acid, respectively.
		The chromium atoms are in oxidation state +6 in both, and the chromate and dichromate ions are fairly strong oxidizing agents.
		Most chromate and dichromate salts of heavy metals, lanthanides or alkaline earth metals are only very slightly soluble in water and are thus of much less usefulness.
	en.wikipedia.org /wiki/Dichromate (237 words)

	Potassium dichromate - Wikipedia, the free encyclopedia
		Chromium intensification uses potassium dichromate together with equal parts of concentrated hydrochloric acid diluted down to approximately 10% vol to vol to treat weak and thin negatives of fl and white film.
		All the gelatine exposed to sun-light will have been hardened by the dichromate and will be retained on the screen leaving a precise mask of the required design which can be printed in the usual way.
		Potassium dichromate is one of the most common culprits in causing chromium dermatitis.
	en.wikipedia.org /wiki/Potassium_dichromate (575 words)

	Potassium dichromate -- Facts, Info, and Encyclopedia article (Site not responding. Last check: 2007-08-07)
		Chromium intensification uses Potassium dichromate together with equal parts of concentrated (An aqueous solution of hydrogen chloride; a strongly corrosive acid) hydrochloric acid diluted down to approximately 10% vol to vol to treat weak and thin negatives of fl and white film.
		This converts the (A soft white precious univalent metallic element having the highest electrical and thermal conductivity of any metal; occurs in argentite and in free form; used in coins and jewelry and tableware and photography) silver metal to silver sulphate, a compound that is insensitive to light.
		Potassium dichromate is one of the most common culprits in causing chromium (Inflammation of the skin; skin becomes itchy and may develop blisters) dermatitis.
	www.absoluteastronomy.com /encyclopedia/p/po/potassium_dichromate.htm (652 words)

	Potassium dichromate (Site not responding. Last check: 2007-08-07)
		A Potassium dichromate solution with sulphuric acid can be used to produce a reversal negative (i.e,.
		This converts the silver metal to silver sulphate, a compound that is insensitive to light.
		Dichromate can also drive the oxidation of organic compounds as in Alcohol --> Aldehyde --> Ketone.
	potassium-dichromate.area51.ipupdater.com (541 words)

	[No title]
		Measure the absorbance of the potassium dichromate at 350 nm.
		The potassium dichromate contaminant was dissolved from the sample in water.
		The accuracy of the determination was checked by measuring the percent potassium dichromate in a synthetic mixture of potassium dichromate, sand and sodium chloride.
	www.augustana.edu /users/Chwanke/CH200/labs/analytrpt.html (760 words)

	Encyclopedia: Potassium dichromate
		Girl Arranging Flowers, Serigraphy by Angel Botello (1985) Screen-printing, also known as silkscreening or serigraphy, is a printmaking technique that creates a sharp-edged single-color image using a stencil and a porous fabric.
		Gelatin (also gelatine) is a translucent brittle solid, colorless or slightly yellow, nearly tasteless and odorless, that is created by prolonged boiling of animal connective tissue.
		Dichromate can also drive the oxidation of organic compounds as in Alcohol â’ Aldehyde â’ Ketone.
	www.nationmaster.com /encyclopedia/Potassium-dichromate (1732 words)

	Iron-dichromate Titration
		After all the Fe ion has been oxidized, the endpoint of the titration can be recognized by the color change when excess dichromate ion now oxidizes the indicator, sodium diphenylamine sulfonate.
		The normality of the dichromate solution is six times its molarity.
		The end-point is indicated by a sudden change in color of the solution from the green of the chromic ions to the purple color of the indicator.
	www.sonoma.edu /chemistry/chem115b/dichromate.html (432 words)

	Chemistry Film Studio
		Working in a fume cupboard, place a conical pile of about 10g of ammonium dichromate on a heat-proof mat standing on a tray to collect the chromium oxide that shoots into the air.
		As the wick burns down into the ammonium dichromate, the compound begins to spark and decompose leaving behind a cone of green chromium (III) oxide that has a considerably larger volume than the original compound.
		The reaction may also be started by pointing a roaring Bunsen flame at the top of the pile of ammonium dichromate.
	neon.chem.ox.ac.uk /vrchemistry/FilmStudio/volcano/HTML/page01.htm (170 words)

	dichromate disposal FAQ (Site not responding. Last check: 2007-08-07)
		Ingestion and inhalation of dichromate dust is toxic and should be avoided.
		Putting bare skin in dichromate solutions can contribute to the development of an allergic sensitivity and should be avoided.
		- If the dichromate has been used in conjunction with a silver process (not an issue with gun printing, but with bleach and intensification processes it is) then you need to go the extra step of adding table salt (sodium chloride) after neutralizing the acidity but before filtering.
	duke.usask.ca /~holtsg/photo/dichromate_disp_faq.html (480 words)

	John Stevenson Gallery: The Fresson Process
		The dichromate is light-sensitive and hardens with exposure.
		He found that the dichromated colloid hardened in proportion to its exposure to sunlight, and applied this principle to an early photogravure process.
		Their works inspired other photographers, and great use was made of the gum dichromate process as a way of creating the painterly images so characteristic of turn-of-the-century art photography.
	www.johnstevenson-gallery.com /gum.html (387 words)

	The Influence of Dichromate Ions on Al Dissolution Kinetics in Artificial Crevice Electrode Cells (Site not responding. Last check: 2007-08-07)
		In an attempt to understand the dissolution kinetics for pits and crevices in aluminum and the effect of dichromate ions on the dissolution kinetics, the electrochemical behavior of aluminum thin foil electrodes in chloride-containing solutions with and without dichromate ions was investigated in the present work.
		The effect of dichromate ions on the dissolution kinetics is not direct but it may affect the condition of the crevice by influencing hydrogen evolution.
		The dissolution kinetics of aluminum in crevice in chloride-containing solutions and the effect of dichromate ions on the crevice growth were investigated by the artificial crevice electrode technique.
	mse-gsf1.eng.ohio-state.edu /fcc/papers/ArtCrevice/ACE.html (4028 words)

	APUG - dichromate in developer
		Just curious, what is the advantage of using dichromate in potassium oxalate in addition to Na2 in the coating.
		I've been considering the dichromate method but having that many bottles of dev seems to be a pita.
		The dichromate method allows slightly finer contrast adjustments and keeps the warm tones of palladium but gives poor results (grainy prints) with low contrast negatives.
	www.apug.org /forums/printthread.php?t=9787 (1237 words)

	PowerLabs Vesuvian Volcano demo
		The Ammonium Dichromate self decomposition demonstration, commonly called the "Vesuvian volcano", is a classic High School chemistry example of how chemicals can undergo spectacular expansion during decomposition.
		The Ammonium Dichromate decomposition becomes self sustaining at 225C, and the product combusts quietly with the evolution of some sparks and Cromium Trioxide (Cr), a greenish powder which is lifted up in part by the rising hot Nitrogen gas.
		Within a short time the entire Dichromate sample has decomposed and a volume of Cr many times larger than the original sample volume is left behind.
	www.powerlabs.org /chemlabs/volcano.htm (305 words)

	Chemical Oxygen Demand (Site not responding. Last check: 2007-08-07)
		Potassium dichromate is a strong oxidizing agent under acidic conditions.
		Most commonly, a 0.25 N solution of potassium dichromate is used for COD determination, although for samples with COD below 50 mg/L, a lower concentration of potassium dichromate is preferred.
		To do so, the excess potassium dichromate is titrated with ferrous ammonium sulfate (FAS) until all of the excess oxidizing agent has been reduced to Cr Typically, the oxidation-reduction indicator Ferroin is added during this titration step as well.
	www.wikiverse.org /chemical-oxygen-demand (1034 words)

	The alternative photographic process FAQ (Site not responding. Last check: 2007-08-07)
		Pottasium dichromate and ammonium dichromate are moderately irritating to skin and highly irritating by inhalation.
		The dichromate causes the gelatin to harden where it is exposed to light.
		Potassium dichromate and potassium bromide are moderately irritating to skin and highly irritating by inhalation.
	duke.usask.ca /~holtsg/photo/faq.html (6419 words)

	FIELD TECHNIQUES--Return of Spent Mercury and Dichromate Ampoules to the National Water Quality Laboratory
		The NWQL uses disposal procedures that are approved by the U.S. Environmental Protection Agency, and that conform to regulations required by permitting agencies in the State of Colorado, Fruitdale Sanitation District, and the Denver Metropolitan Wastewater Reclamation District.
		This NWQL ampoule-disposal service pertains only to spent ampoules that contain mercuric chloride or potassium dichromate residuals; ampoules containing other chemical preservatives are to be disposed of by WRD District personnel.
		The minute preservative residual remaining on the inner walls of the spent mercuric chloride or potassium dichromate ampoule is considered hazardous by definition of 40CFR Part 261.
	water.usgs.gov /admin/memo/QW/qw92.11.html (921 words)

	Norma Clamps
		The clamp and the screw are custom-plated in corrosion resistant zinc dichromate (yellow zinc) to match the factory look.Price each.
		These clamps have the original 9mm bandwidth and are plated in corrosion resistant zinc dichromate (yellow zinc) to provide the correct factory look.
		These clamps have the original 9mm bandwidth and are custom-plated in corrosion resistant zinc dichromate (yellow zinc) to provide the correct factory look.
	www.eagleday.com /normaclamps.html (330 words)

	Science in Pictures: The Oxidation of Ammonium Dichromate
		the dichromate ion, is rich in oxygen, so the bonded metal is said to be in an unstable and high oxidation state.
		Soon the dichromate ions will oxidize the ammonium within the orange powder, and the chromium atoms will be reduced to ions of a lower oxidation state:
		There is no orange dichromate left over; all that remains is Cr Although it weighs less than the starting material (because, after all, we have “lost” the mass of the escaping gases), it seems more voluminous than the starting material, creating the illusion that our mountain has grown like a true volcano.
	www.emsb.qc.ca /laurenhill/science/oxidation.html (561 words)

	Induction by Iron(II) of the Oxidation of Iodine by Dichromate (Site not responding. Last check: 2007-08-07)
		Induction by Iron(II) of the Oxidation of Iodine by Dichromate
		When acidic dichromate and iodide solutions are mixed, no immediate reaction takes place, even though the electrochemical potentials predict that chromium(VI) should oxidize iodide to triiodide ion.
		A reasonable hypothesis for the mechanism is that dichromate oxidizes iron(II) to iron(III), and that iron(III) then oxidizes iodide to triiodide.
	jchemed.chem.wisc.edu /JCESoft/CCA/CCA2/MAIN/INDUCT/CD2R1.HTM (181 words)

	Ammonium Dichromate Volcano
		An alcohol-soaked fuse is placed upon a small mound of ammonium dichromate and ignited.
		The orange ammonium dichromate decomposes to form nitrogen, water vapor, and fluffy greenish-fl chromium(III) oxide.
		When a wick soaked in alcohol is placed into the ammonium dichromate and ignited with a match the higher temperature causes the ammonium dichromate to start reacting.
	jchemed.chem.wisc.edu /JCESoft/CCA/CCA3/MAIN/VOLCANO/PAGE1.HTM (233 words)

	Chromate-Dichromate Equilibrium (Site not responding. Last check: 2007-08-07)
		Wear a respirator (an air filtering mask like a surgeon's mask) when working with the chromate powder so as not to inhale any solid aerosol that may form when the bottles are opened.
		Barium chromate stains can be removed by converting them to soluble barium dichromate by the addition of a weak acid such as vinegar.
		The net effect is that chromate is produced, dichromate is used up, and the orange solution turns yellow.
	129.93.84.115 /Chemistry/DoChem/DoChem110.html (1036 words)

	25258. How to make up Sodium Dichromate seal [Florida]
		I want to install a small 185 gallon Sodium Dichromate seal tank for MIL-A-8625 TY IB and TY II anodized parts.
		I have found two makeup plans, but I am uncertain as to how to calculate the amount of sodium dichromate to add to DI water.
		Water weighs 1 gram per ml, a liter is 1,000 ml, so 4 -6% would be 40 to 60 grams of dichromate.
	www.finishing.com /252/58.shtml (243 words)

	Volcano Demonstration (Site not responding. Last check: 2007-08-07)
		The ammonium dichromate will burn fiercely while producing large volumes of a grayish green ash.
		Place the ammonium dichromate in the fire resistant cup at the top of the volcano, and light it.
		While the risk is extremely low for a one time exposure, many public schools have banned this demonstration for fear of lawsuits.
	www.west.net /~science/volcano.htm (288 words)

	Demonstrations - Ammonium Dichromate Volcano
		While the ammonium dichromate decomposes, it gives off orange sparks and throws the green chromium(III) oxide crystals into the air, producing an effect that looks like a miniature volcanic eruption.
		The chromium(III) oxide crystals that are produced are "fluffier" than the original ammonium dichromate crystals, and even though a lot of the mass of the starting materials escapes as vapor, the product looks like a larger amount of material.
		In the following demonstrations, a pile of ammonium dichromate is ignited with a Bunsen burner, producing the "volcano" effect.
	www.angelo.edu /faculty/kboudrea/demos/volcano/volcano.htm (264 words)

	Is potassium dichromate worth the risk? (Site not responding. Last check: 2007-08-07)
		I've heard that potassium dichromate, used as a treatment for mahogany, brings out the color and grain to a very deep, rich appearance.
		Because it is a chemical reaction (oxidizing agent) it does not have the same effect as a wiping stain.
		As for concentration: try 3 grams of potassium dichromate for 1 litre of water (warm is better).
	www.woodweb.com /knowledge_base/Is_potassium_dichromate_worth_the_risk.html?printfriendly (657 words)

	29926. Dichromate Seal Finish is Greenish [Florida]
		Switch to a nickel based seal and you should have good results and a fl finish with both dyes, plus you have eliminated a source of hex chrome which makes many tree huggers happy.
		Dichromate Seals are ALWAYS yellow-greenish tint if properly applied.
		Dichromate Seals should never be used on dyed work: not just because it changes the color of the dye but also because Dichromate Seals are for maximum corrosion protection and ALL dye slightly lowers corrosion protection.
	www.finishing.com /299/26.shtml (243 words)

	The Tutte Dichromate and Whitney Homology of Matroids - Wagner (ResearchIndex) (Site not responding. Last check: 2007-08-07)
		The Tutte Dichromate and Whitney Homology of Matroids - Wagner (ResearchIndex)
		We consider a specialization YM (q; t) of the Tutte polynomial of a matroid M which is inspired by analogy with the Potts model from statistical mechanics.
		Wagner, The Tutte dichromate and Whitney homology of matroids, preprint.
	citeseer.ist.psu.edu /wagner97tutte.html (758 words)

	Kinetics: Decomposition of Hydrogen Peroxide by Dichromate
		0.1, 0.15, 0.2 and 0.3 molar dichromate solutions are prepared by diluting appropriate aliquots of the 0.4 molar stock potassium dichromate solution.
		Potassium dichromate: Hexavalent chromium compounds are generally more toxic than trivalent chromium compounds.
		In addition the experiment is carried out using a 0.2 and a 0.32 molar solution of potassium dichromate.
	www.uni-regensburg.de /Fakultaeten/nat_Fak_IV/Organische_Chemie/Didaktik/Keusch/chembox_per_di_T-e.htm (395 words)

	Potassuim Dichromate Reference for Absorbance/Linearity in the Ultraviolet (Site not responding. Last check: 2007-08-07)
		Potassium dichromate in perchloric acid sealed in a quartz cell
		Potassium Dichromate solvated in dilute (0.001N) perchlorate acid has been found to be the best method for testing the absorbance scale and linearity of spectrophotometers in the UV.
		Measure the absorbance of the potassium dichromate cells at the four wavelengths specified by NIST.
	www.starna.com /d_ref/d_abs/PDC.html (363 words)

	RE: Potassium Dichromate solutions in Sulphuric and Perchloric Acid
		We prepare this solution our selves by drying the dichromate to constant mass at 130 °C and then dissolving 60 mg ± 3.0 mg dichromate in 0.005 M sulphuric acid (1000-ml) The acceptance criteria for the absorbance at different wavelengths is given in the table below.
		From personal experience, countless laboratories also experience the problems associated with the use of these sulphuric acid based dichromate solutions, not least in the actual preparation of the solution as detailed in the E.P. The main two advantages of sulphuric acid, availability and safer handling are cancelled out by using sealed reference materials.
		In your brochure, you state that the use of potassium dichromate solvated in dilute perchloric acid is an established and well recognised method.
	www.optiglass.com /ukhome/d_tech/tech07.html (2857 words)

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