Impurities colored

The cleanup of this oil is exactly like that which was done in Method 1. The oil is dissolved in about SOOmL of 3N HCl and the solution extracted with TOOmL of DCM. The chemist remembers that in this particular case the MDMA or meth is going to stay in the HCl/water but that unreacted, valuable MD-P2P or P2P is going to be in that DCM so it, of course, is saved. The HCl/MDMA solution is then basified with concentrated NaOH so that at around pH 9 the happy little beads of final, freebase product will appear in the solution. As usual, the oil is extracted with DCM, dried through Na2S04 and the DCM removed by distillation. The final product here is usually a little darker in color than the product achieved in Method 1, but it is still remarkably clean and may be crystallized as is with the crystallization process removing most of the color impurities. Of course the chemist may wish to vacuum distill to afford clear product. The average yield with this method is 60-70%. 

In kaolin (clay) processing, sulfur dioxide reduces colored impurities, eg, iron compounds. In the bromine industry, sulfur dioxide is used as an antioxidant in spent brine to be reinjected underground. In agriculture, especially in California, sulfur dioxide is used to increase water penetration and the avadabiHty of soil nutrients by virtue of its abiHty to acidulate saline—alkaH soils (327). It is also usefiil for cleaning ferric and manganese oxide deposits from tile drains (328). 

Alumina sufficient to adsorb the complete solution is added, then the solvent is removed under vacuum. While benz[a]anthracene, np 157-158°C, sufficiently pure for most purposes, can be obtained by crystallization of the crude product from ethanol-water, filtration" through alumina removes residual, colored impurities, affording a pure, white product. 

Regarding the color, we only see a need for colorless ionic liquids in very specific applications (see above). One easy treatment that often reduces coloration quite impressively, especially of imidazolium ionic liquids, is purification by column chromatography/filtration over silica 60. For this purification method, the ionic liquid is dissolved in a volatile solvent such as CFF2C12. Usually, most of the colored impurities stick to the silica, while the ionic liquid is eluted with the solvent. By repetition of the process several times, a seriously colored ionic liquid can be converted into an almost completely colorless material. 

This rapid filtration through alumina serves to eliminate minor colored impurities. 

Copper(I) iodide, purchased from Fisher Scientific Company, was purified by continuous extraction with anhydrous tetrahydrofuran in a Soxhlet extractor for approximately 12 hours in order to remove colored impurities. The residual copper(I) iodide was then dried under reduced pressure at 25° and stored under nitrogen in a desiccator. 

C-TMS protection of the alkyne provided acceptable yields of 3-substituted indole as long as the hydroxy group was protected with a stable group. Purple colored impurities, one of which has been identified as azulene 45, were seen in both coupling reactions using C-TMS-alkynes such as 36 and 40d (Scheme 4.9). The azulene was presumably formed through the dimerization of acetylenes... 

Colored impurities, if produced, can be removed by treatment of the solution, prior to cooling, with charcoal (Norit) followed by filtration. 

Colorless to brown oily liquid that is odorless when pure. Crude material may have a violet to purple color. Impurities give it an odor similar to geranium that is detectable at approximately 0.9 ppm. There are two configurational isomers of this agent that have been studied. 

Domestic consumption of selenium in 1981 exceeded 453,000 kg. About 50% was used in electronic and copier components, 22% in glass manufacturing, 20% in chemicals and pigments, and 8% miscellaneous (Cleveland et al. 1993). In 1987, world production of selenium was about 1.4 million kg (USPHS 1996). In 1986, 46% of the global selenium produced was used in the semiconductor and photoelectric industries 27% in the glass industry to counter coloration impurities from iron 14% in pigments and 13% in medicine, in antidandruff shampoos, as catalysts in... 

Boivan-Loiseau A process for purifying cane sugar. Calcium hydroxide is added to the syrup, and carbon dioxide passed through it. The precipitated calcium carbonate removes some of the coloring impurities. 

Talafloc A process for decolorizing cane sugar syrup by precipitating the coloring impurities with a long-chain quaternary ammonium salt. Invented in 1967 by M. C. Bennett at Tate and Lyle, United Kingdom. 

Isolation of the active component is carried out chro-matographically. Roth et al.9 used a magnesol (magnesium silicate) column to absorb colored impurities, followed by a Darco G-60 activated carbon column to eliminate sodium formate and inorganics. Elution with an alcohol/ammonia solvent was followed by rechromatographing in magnesol. 

The colored impurities normally enter the aqueous phase. 

The checkers found that it was important to use phenol free of colored impurities in a run in which phenol, m.p. 39.5-41°, with a slight rose tinge was used the yield of product was reduced to 56%. 

Digestion of the crude acid with about 50 ml of methanol (to remove some of the colored impurities) gave after cooling to 0-10° C and filtering an almost quantitative recovery of lighter colored acid. This material is suitable for conversion into LSD. 

Special Buchner funnel cleaning alert. The standard ceramic Buchner funnel is not transparent, and you can t see whether or not the bums who used the funnel the last time to collect a highly colored product, didn t clean the funnel properly. The first time you Buchner filter crystals from an alcohol solution, the colored impurity dissolves, bleeds up into your previously clean crystals, and you may have to redo your entire experiment. I d rinse the Buchner funnel with a bit of hot ethanol before I used it, just for insurance. 

Activated charcoal is ultrafinely divided carbon with lots of places to suck up big, huge, polar, colored impurity molecules. Unfortunately, if you use too much, it ll suck up your product And, if your product was white, or yellow, it ll have a funny gray color from the excess charcoal. Sometimes, the impurities are untouched and only the product gets absorbed. Again, it s a matter of trial and error. Try not to use too much. Suppose you ve got a hot solution of some solid, and the solution is highly colored. Well,... 

Sugar quality is enhanced by removal of colored impurities and by the extent and type of refining which is obtained. It is believed that this type of refining is the most valuable not only because of its extent but also because it is applied early in the process. This reduction of the impurity load near the forepart of the process avoids potential trouble... 

In addition to removing colored impurities and other colloids, ion exchange resins effectively remove the uncolored precursor of these colored substances. It has long been recognized that a small amount of 5-hydroxymethylfurfural (HMF), formed from dextrose by the action of acid catalysts, decomposes to form organic acids as well as pigments which polymerize to form highly colored bodies.23 Normal bone char... 

Slow precipitation tends to give large crystals with resulting inclusion of colored impurities. 

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