Potassium+Dichromate

Burning sensation, sore throat, cough, wheezing, and labored breathing if inhaled Redness, pain, and skin burns if comes in contact with skin Redness, pain, blurred vision, severe deep burns if it comes in contact with the eyes Nausea, vomiting, abdominal pain, burning sensation, diarrhea, shock or collapse if ingested
 * Potassium Dichromate** can affect you when it is breathed in and may cause a skin allergy. It is a carcinogen and should be handled with extreme caution. Prolonged exposure to this chemical may cause a "hole" in the bone dividing the inner nose. This chemical, when it comes in contact with combustible material may cause a fire. According to the European Union classification this chemical by be mutagenic and may be toxic to the reproductive system. Potassium Dichromate is very toxic when it is inhaled, it may cause heritable genetic damage, and is harmful when it comes in contact with skin. This chemical is corrosive and causes burns, it may also cause sensitization by inhalation and skin contact and it is dangerous to the environment.
 * Possible Symptoms:**



Production
Potassium dichromate is usually prepared by the reaction of [|potassium chloride] on [|sodium dichromate]. Alternatively, it can be obtained from [|potassium chromate] by roasting [|chrome] ore with [|potassium hydroxide].

Reactions
Potassium dichromate is an oxidant (oxidising agent). The reduction half-equation can be seen: Cr2O72−(aq) + 14H+ + 6e− → 2Cr3+(aq) + 7H2O (E = +1.23 V)  In organic chemistry, potassium dichromate is a mild oxidizer compared with [|potassium permanganate]. It is used to [|oxidize] [|alcohols]. It converts primary alcohols into aldehydes, or into carboxylic acids if heated under [|reflux]. In contrast, with permanganate, carboxylic acids are the sole products. Secondary alcohols are converted into ketones — no further oxidation is possible. For example, [|menthone] may be prepared by oxidation of [|menthol] with acidified dichromate. [|[2]] Tertiary alcohols are not oxidized by potassium dichromate. In an aqueous solution the color change exhibited can be used to test whether an aldehyde or ketone is present. When an aldehyde is present the chromium ions will be reduced from the +6 to the +3 [|oxidation state], changing color from orange to green. This is because the aldehyde can be further oxidized to the corresponding carboxylic acid. A ketone will show no such change because it cannot be oxidized further, and so the solution will remain orange.

Cleaning
Like other [|chromium(VI)] compounds ( [|chromium trioxide], [|sodium dichromate] ), potassium dichromate may be used to prepare " [|chromic acid] ", which can be used for cleaning glassware and etching materials.

Construction
It is used as an ingredient in [|cement] in which it retards the setting of the mixture and improves its density and texture. This usage commonly causes [|contact dermatitis] in [|construction workers]. [|[3]]

Ethanol determination
The concentration of ethanol in a sample can be determined by [|back titration] with acidified potassium dichromate. Reacting the sample with an excess of potassium dichromate, all ethanol is oxidized to [|acetic acid] : C2H5OH + [O] → CH3COOH The excess dichromate is determined by titration against [|sodium thiosulfate]. Subtracting the amount of excess dichromate from the initial amount, gives the amount of ethanol present. Accuracy can be improved by calibrating the [|dichromate] solution against a blank. One major application for this [|reaction] is in old police [|breathalyzer] tests. When alcohol vapor makes contact with the yellow dichromate-coated crystals, the [|color] changes from yellow to green. The degree of the color change is directly related to the level of alcohol in the suspect's breath.

Leather
It is used to [|tan leather] which is used for [|footwear]. [|[4]]

Photography
Potassium dichromate has important uses in [|photography] and in photographic [|screen printing], where it is used as an oxidising agent together with a strong mineral acid. [|Gum bichromate] printing was one of the very first stable photographic printing processes, dating back to about 1850. A solution of [|gum arabic] and potassium dichromate, once applied to paper and dried, will harden when exposed to ultraviolet light. //Chromium intensification// or //Photochromos// uses potassium dichromate together with equal parts of concentrated [|hydrochloric acid] diluted down to approximately 10% v/v to treat weak and thin negatives of black and white photograph roll. This solution reconverts the elemental silver particles in the film to [|silver chloride]. After thorough washing and exposure to [|actinic] light, the film can be redeveloped to its end-point yielding a stronger negative which is able to produce a more satisfactory print. A potassium dichromate solution in [|sulfuric acid] can be used to produce a reversal negative (i.e., a positive transparency from a negative film). This is effected by developing a black and white film but allowing the development to proceed more or less to the end point. The development is then stopped by copious washing and the film then treated in the acid dichromate solution. This converts the [|silver] metal to [|silver sulfate], a compound that is insensitive to light. After thorough washing and exposure to actinic light, the film is developed again allowing the previously unexposed silver halide to be reduced to silver metal. The results obtained can be unpredictable, but sometimes excellent results are obtained producing images that would otherwise be unobtainable. This process can be coupled with [|solarisation] so that the end product resembles a negative and is suitable for printing in the normal way. CrVI compounds have the property of [|tanning] animal [|proteins] when exposed to strong light. This quality is used in photographic [|screen-printing]. In [|screen-printing] a fine screen of bolting silk or similar material is stretched taut onto a frame similar to the way canvas is prepared before painting. A [|colloid] sensitized with a dichromate is applied evenly to the taut screen. Once the dichromate mixture is dry, a full-size photographic negative is attached securely onto the surface of the screen, and the whole assembly exposed to strong light - typically about half an hour in bright sunlight - hardening the exposed colloid. When the negative is removed, the unexposed mixture on the screen can be washed off with warm water, leaving the hardened mixture intact, acting as a precise mask of the desired pattern, which can then be printed with the usual [|screen-printing] process.

Silver test
When dissolved in an approximately 35% [|nitric acid] solution it is called Schwerter's solution and is used to test for the presence of various metals, notably for determination of silver purity. Pure silver will turn the solution bright red, [|sterling silver] will turn it dark red, low grade [|coin silver] (0.800 fine) will turn brown (largely due to the presence of copper which turns the solution brown) and even green for 0.500 silver.

Sulfur dioxide test
Potassium dichromate paper can be used to test for [|sulfur dioxide], as it turns distinctively from orange to green. This is typical of all redox reactions where hexavalent chromium is reduced to the less harmful trivalent chromium. Therefore, it is not a conclusive test for sulfur dioxide.

Wood treatment
Potassium dichromate is used to stain certain types of wood by darkening the tannins in the wood. It produce deep, rich browns that cannot be achieved with modern color dyes. It is a particularly effective treatment on [|mahogany]. [|[5]]

Natural occurrence
A ~10 mm crystal of potassium dischromate in the same form as the mineral lopezite Potassium dichromate occurs naturally as the rare [|mineral] [|lopezite]. It has only been reported as [|vug] fillings in the [|nitrate] deposits of the [|Atacama desert] of [|Chile] and in the [|Bushveld igneous complex] of [|South Africa]. [|[6]]