Purples

There are thousands of available pesticides broad-based to combat a large number of pests or narrowly focused to combat individual species and leave others unharmed. They include a range of chemicals, almost all of which are toxic to both the pest and humans, including  

Pesticides may be solid, liquid, or gaseous. They may be applied to crops, soils, seeds and grain, fabrics, etc., as dust, smoke, dispersions, emulsions, or solutions. Fumigants are gases, volatile chemicals, or mixtures of pesticides in a volatile liquid, often petroleum or coal tar distillates. They are most effective in enclosed environments where penetration to all points is assured. Fumigants include hydrogen cyanide, methyl bromide, carbolic acid, hydrocyanic acid, and chloropicrin. 

Historically, almost every chemical or compound known to be toxic has been tried and used to inhibit the action of wood-destroying pests. Among the many chemicals used as wood preservatives are compounds based on creosote, mercury, arsenic, thallium, borate, cyanide, chromium, copper, zinc, nickel, fluorides, and pentachlorophenol. The majority fall into 3 classes  

Petroleum distillates play an extensive role in wood preservation as solvents and diluents for the active ingredient but appear to have little or no preservative value. Many light petroleum solvents and gases deliver the preservative and help it penetrate into the wood before evaporating. 

Related Terms Aerosol, see Aerosols, p.3 Alkaloids, see Alkaloids, p.7 Compounds, see Terminology, Compound, p.234 

---

Dissolves in alkaline solutions to give purple-red solutions which are precipitated as lakes by heavy metal salts. Occurs naturally as a glucoside in madder but produced synthetically by fusing anthraquinone-2-sulphonic acid with NaOH and some KCIO3. Applied to the mordanted fibre. Al(OH)3 gives a bright red lake, Cr(OH)3 a red lake, FefOH) ... 

Manganates V f), [MnOJ", permanganates. Dark purple tetrahedral anion (electrolyte oxidation of [Mn04]. Powerful oxidizing agent... 

Manganese(llf) fluoride. MnFj, formed from F2 on, e.g., MnCl2. Purple-red, forms complexes, e.g. K2MnF s.H20, K MnFg, hydrolysed by water. 

An intense purple crystalline solid m.p. 219-220 C. One of the few monomeric cyclo-pentadienone derivatives, most of which spontaneously undergo self Diels-Alder type dimerization. Used as a diene in many studies of various aspects of the Diels-Alder reaction. ... 

Breton J, Martin J-L, Fleming G R and Lambry J-C 1988 Low-temperature femtosecond spectroscopy of the initial step of electron transfer in reaction centers from photosynthetic purple bacteria Biochemistry 27 8276... 

Pullerits T, Visscher K J, Hess S, Sundstrom V, Freiberg A, Timpmann K and Van Grondelle R 1994 Energy-transfer in the inhomogeneously broadened core antenna of purple bacteria-a simultaneous fit of low-intensity picosecond absorption and fluorescence kinetics Biophys. J. 66 236-48... 

Chaohisvilis M and Sundstrom V 1996 Femtoseoond vibrational dynamios and relaxation in the oore light-harvesting oomplex of photosynthetio purple baoteria Chem. Rhys. Lett. 261 165-74... 

The pure tribromide and triodide are unknown but their ammoniates have been prepared by the action of the appropriate halogen on ammonia. The tribromide, NBr bNUj, is a purple solid which decomposes explosively above 200K. The iodide, Nl3. NH3, is a black explosive crystalline solid, readily hydrolysed by water. 

Like bromine, iodine is soluble in organic solvents, for example chloroform, which can be used to extract it from an aqueous solution. The iodine imparts a characteristic purple colour to the organic layer this is used as a test for iodine (p. 349). NB Brown solutions are formed when iodine dissolves in ether, alcohol, and acetone. In chloroform and benzene a purple solution is formed, whilst a violet solution is produced in carbon disulphide and some hydrocarbons. These colours arise due to charge transfer (p. 60) to and from the iodine and the solvent organic molecules. 

Addition of an oxidising agent to a solution of an iodide (for example concentrated sulphuric acid, hydrogen peroxide, potassium dichromate) yields iodine the iodine can be recognised by extracting the solution with carbon tetrachloride which gives a purple solution of iodine. 

The purple colour of this ion alone is a sufficient test for its presence addition of sulphuric acid and hydrogen peroxide discharges ihe colour. 

Olle Edholm, Oliver Berger, and Fritz Jahnig. Structure and fluctuations of bacteriorhodopsin in the purple membrane. J. Mol. Biol., 250 94 111, 1995. 

Both these acids are colourless, but the spots of each acid on a filter-paper strip show up in ultraviolet light as intense blue fluorescent zones. They can also be detected, but considerably less sensitively, by spraying with ethanolic ferric chloride solution, which gives with N-methylanthranilic acid a purple-brown coloration. 

Finally spray the paper with neutral 1% ethanolic ferric chloride solution the methylanthranilic acid spot develops a purple-brown coloration, whereas the anthranilic acid gives only a very faint pink coloration. 

If a solution of potassium permanganate containing dilute sulphuric acid is used, the purple colour disappears and the solution ultimately becomes... 

Reactions of Aspirin, (i) Distinction from Salicylic acid. Shake up with water in two clean test-tubes a few crystals of a) salicylic acid, (0) aspirin, a very dilute aqueous solution of each substance being thus obtained. Note that the addition of i drop of ferric chloride solution to (a) gives an immediate purple coloration, due to the free —OH group, whereas (b) gives no coloration if the aspirin is pure. 

Dissolve 5 g. of benzii in 15 ml. of boiling ethanol in a conical flask fitted with a reflux water-condenser. Then add a solution of 5 g. of potassium hydroxide in 10 ml. of water, and heat the mixture (which rapidly develops a purple colour) on a boiling water-bath for about 15 minutes. Cool and stir the solution, from which the potassium benzii ate separates in fine cr> stals. 

Filter the product at the pump, using an alkali-resisting filter-paper, or a sintered glass filter-funnel. Wash the crystals on the filter with a small quantity of ethanol to remove the purple colour, and then drain thoroughly. 

Dissolve ca. 0 2 g. of product (I) in cold ethanol, and add with shaking 1-2 drops of dilute sulphuric acid. A deep purple coloration appears at once. This shows that salt formation has occurred on the quinoline nitrogen atom to form the cation (Ha), which will form a resonance hybrid with the quinonoid form tils). [Note that the forms (IIa) and (11b) differ only in electron position, and they are not therefore tautomeric.] If, hoAvever, salt formation had occurred on the dimethylaniino group to give the cation (III), thrs charge separiition could not occur, and the deep colour would be absent. 

Sulphur. THE LASSAIGNE SODIUM TEST. The sodium fusion will have converted any sulphur present in the original compounds to sodium sulphide. Dissolve a few crystals of sodium nitroprusside, Na8[Fe(CN)5NO],zH20, in water, and add the solution to the third portion of the filtrate obtained from the sodium fusion. A brilliant purple coloration (resembling permanganate) indicates sulphur the coloration slowly fades on standing. Note, (i) Sodium nitroprusside is unstable in aqueous solution and therefore the solution should be freshly prepared on each occasion, (ii) This is a very delicate test for sulphides, and it is essential therefore that all apparatus, particularly test-tubes, should be quite clean. 

NH2CONH2 = NH2CONHCONH2 + NH3 Dissolve the solid residue in a few ml. of warm 10% NaOH solution, cool and add i drop of very dilute copper sulphate solution. A purple coloration is obtained. ... 

A purple or rose pink coloration i produced when sodium hydroxide and dilute copper sulphate solution are added to compounds containing two -CONH- groups attached either to one another, or to the same nitrogen atom, or to the same carbon atom. It is therefore also given by oxamide, NHjCO CONH, malonamide, NHtCO-CH, CONH, and by proteins and peptides. In fact the -COKH - is often spoken of as the peptide linkage. 

Alizarin dissolves in aqueous NaOH solution giving a purple solu tion. Calcium hydroxide will precipitate a blue sdt from this solution. Anthraquinone is unaffected by NaOH solution. 

---