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3D model (JSmol) | |
| ChemSpider | |
| ECHA InfoCard | 100.030.221 |
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| Properties | |
| NH4MnP2O7 | |
| Molar mass | 246.885 |
| Appearance | violet solid |
Except where otherwise noted, data are given for materials in theirstandard state (at 25 °C [77 °F], 100 kPa). | |
Manganese violet is theinorganic compound with the formula NH4MnP2O7.[1] As implied by its name and composition, it is a purple,inorganicpigment.[2] Because it is often impure, the pigment's hue is varied.[3] Notable artists who have used the pigment includeClaude Monet, who relied on manganese violet in hisRouen Cathedral series to further his exploration of shadows.[4] Beyond the artistic community, manganese violet has been used in cosmetics to color products like lipstick and eyeshadow.[5]
The pigment was originally named Nurnberg violet, and little is known about its early history beyond its creation in 1866 by E. Leykeuf. The first documented production of the pigment was in 1890 by Messers Winsor and Newton (currently known asWinsor & Newton).[6]: 128–29 In theWinsor & Newton 1892 catalog, both permanent violet and permanent mauve were listed. The two were distinguished by the company in 1896 when permanent mauve was described as phosphate of Manganese (which is another name for manganese violet).[7]: 257 In 1898, the paint supplier Reeves listed permanent violet and permanent mauve as the same color.[7]: 257
The compound can be generated by combiningmanganese dioxide,phosphoric acid, andammonium dihydrogenphosphate.[2][8][9] For the synthesis from Mn(III) oxide, an idealized equation follows:
The pigment has twopolymorphs: α- and β-forms. Both are stable to about 340 °C.[10] The optical properties of manganese violet arise from the distortedoctahedral sites.[10] Theinfrared spectroscopy,reflectance spectrum, andfluorescence spectroscopy can be found on ColourLex.[11]
According theX-ray crystallography, both polymorphs of manganese violet have similar structures. The feature octahedral Mn(III) centers, which are distorted byJahn-Teller effect, as expected for a high spin (quintet state) d4 ions.[10]
Manganese violet is a fine, vibrant purple pigment that is synthetically generated.[12] It exhibits exceptional permanence and highlightfastness.[13][14]
Some artists historically avoided manganese violet because of they found its color to be dull.[6]: 128 Variances in visual characteristics can arise fromimpurities.[3]: 178 The visual characteristics of manganese violet remain a source of contention among the artistic community. Some sources claim that manganese violet is actually a more accurateviolet hue than previous pigments likecobalt violet, which has a redder tone.[12] Conversely, some sources assert that manganese violet (as well ascobalt violet) should not be categorized asviolet according to modern color measurements.[15]
The manganese violet pigment is compatible with many artistic techniques; however, it is incompatible withfresco andstereochromy.[13] The pigments' popularity was short lived within the artistic community because of its dullness and poor hiding power.[6]
A number of nineteenth-century artists used the pigment when representing shadows. InÉdouard Manet'sThe Waitress, manganese violet was used to create the red or purple colors.[16]Claude Monet was an avid proponent of manganese violet's usage for shadows.Monet was quoted saying "I have finally discovered the true color of the atmosphere. It's violet. Fresh air is violet. Three years from now, everyone will work in violet."[4]Impressionists used violet in place of black, which they argued was not found in nature.[4] InMonet'sRouen Cathedral series, he utilized diverse colors to display how the perception of the same cathedral changes based on the lighting during the course of the day. InThe Rouen Cathedral, West Facade, Sunlight andThe Portal of Rouen Cathedral in the Morning Light,Monet manipulated the shadows through using manganese violet and other pigments to represent the time of the day.[4]
Georges Seurat also employed manganese violet in his paintings, though he used it sparingly because he saw it as impure.[17] He tended to use what he regarded as pure pigments, such ascobalt blue,French ultramarine, andlead white.[18] For many of his works,Seurat would combine other pure pigments to create a violet hue and, consequently, he would only utilize impure pigments like manganese violet for specific purposes.[16] InSeurat's paintingChannel of Gravelines, Grand Fort-Philippe, for example, manganese violet was used in the border.[18] There is speculation thatSeurat utilized manganese violet in the border because of its low tinting power. In comparison to manganese violet, pure pigments and their mixtures have high tinting powers, which may have been undesirable in this case; therefore,Seurat opted to use manganese violet for this painting.[18]
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Beyond the artistic community, manganese violet is used various cosmetics such as lipstick and eye products.[5] The United States categorizes it as a safe compound for products used around the eyes such as eyeshadow.[19] Additionally, the pigment is often used in lipstick to counter brighter pigments.[5] Health concerns have been raised about manganese violet and other metal pigments in cosmetics.[20]