Colour Developers

The two main colour developers are both substituted 1,4-phenylenediamines. The more active of the two (2.81) is used in the colour negative C-41 process, whilst the less toxic and more brilliant dye-producing compound, the sulfonamide (2.82) is used in the colour reversal E-6 process. 

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SchifT s reagent A solution of rosaniline in water decolorized with sulphurous acid. Aliphatic aldehydes and aldose sugars give a magenta colour with this reagent with aromatic aldehydes and aliphatic ketones the colour develops more slowly aromatic ketones do not react. 

To a few drops of the ester, add 0 2 g. of hydroxylamine hydrochloride and about 5 ml. of 10% NaOH solution and gently boil the mixture for 1-2 minutes. Cool and acidify with HCl, cool again and then add a few drops of FeClj solution. A violet or deep red-brown colour develops immediately. 

Sodamide should never be stored in a stoppered bottle from which samples are to be removed intermittently, since dangerous mixtures may result when the substance is exposed for 2-3 days to even limited amounts of air at the ordinary temperature. As a safe practice, sodamide should be used immediately after preparation, and should not be kept longer than 12-24 hours unless it be under an inert solvent. Even small amounts of unused sodamide should be removed from the apparatus in which it was made by washing with methyl or ethyl alcohol. In all cases where a yellowish or brownish colour develops, due to the formation of oxidation... 

It is advisable to test a small portion of the filtrate for platinum by acidifying with hydrochloric acid and adding a few drops of stannous chloride solution a yellow or brown colour develops according to the quantity of platinum pVesent. The yellow colour is soluble in ether, thus rendering the t t more sensitive. If platinum is found, treat the filtrate with excess of formaldehyde and sodium iQrdroxide solution and heat,- platinum black septarates on standing and may be filtered and worked up with other platinum residues (see Method 3). 

Prepare the reagent by dissolving 7 -5 g. of sodium iodide in 50 ml. of A.R. acetone. The colourless solution gradually acquires a yellow colour. Keep it in a dark bottle. When a red-brown colour develops, it should be discarded. 

As the result of the performed investigations was offered to make direct photometric determination of Nd microgram quantities in the presence of 500-fold and 1100-fold quantities of Mo and Pb correspondingly. The rare earth determination procedure involves sample dissolution in HCI, molybdenum reduction to Mo (V) by hydrazine and lead and Mo (V) masking by EDTA. The maximal colour development of Nd-arsenazo III complex was obtained at pH 2,7-2,8. The optimal condition of Nd determination that was established permit to estimate Nd without separation in solution after sample decomposition. Relative standard deviations at determination of 5-20 p.g of Nd from 0,1 g PbMoO are 0,1-0,03. The received data allow to use the offered procedure for solving of wide circle of analytical problems. 

A general method for purifying chlorohydrocarbons uses repeated shaking with concentrated sulfuric acid [CARE] until no further colour develops in the acid, then washing with water then a solution of sodium bicarbonate, followed by water again. After drying with calcium chloride, the chlorohydrocarbon is fractionally redistilled to constant boiling point. 

K. S. Hikncr has devised n, process depending on ihe vellow colour developed when oitral reacts with. iie/ i-phenvlcno-diamine. Tile process 13 best carried out as iollowa —... 

With most woods, new surfaces first of all darken when exposed to light, particularly with teak and afrormosia, where any masking of portions of the surfaces of furniture can give blemishes. After full colour development, strong sunshine bleaches most woods to a common brown colour. 

Procedure. Dissolve 0.0393 g of pure copper(II) sulphate pentahydrate in 1 L of water in a graduated flask. Pipette 10.0 mL of this solution (containing about 100 jug Cu) into a beaker, add 5.0 mL of 25 per cent aqueous citric acid solution, render slightly alkaline with dilute ammonia solution and boil off the excess of ammonia alternatively, adjust to pH 8.5 using a pH meter. Add 15.0mL of 4 per cent EDTA solution and cool to room temperature. Transfer to a separatory funnel, add lOmL of 0.2 per cent aqueous sodium diethyldithiocarbamate solution, and shake for 45 seconds. A yellow-brown colour develops in the solution. Pipette 20 mL of butyl acetate (ethanoate) into the funnel and shake for 30 seconds. The organic layer acquires a yellow colour. Cool, shake for 15 seconds and allow the phases to separate. Remove the lower aqueous... 

Pipette 25 mL nickel solution (0.01 M) into a conical flask and dilute to 100mL with de-ionised water. Add the solid indicator mixture (50mg) and 10 mL of the 1M ammonium chloride solution, and then add concentrated ammonia solution dropwise until the pH is about 7 as shown by the yellow colour of the solution. Titrate with standard (0.01 M) EDTA solution until the end point is approached, then render the solution strongly alkaline by the addition of 10 mL of concentrated ammonia solution, and continue the titration until the colour changes from yellow to violet. The pH of the final solution must be 10 at lower pH values an orange-yellow colour develops and more ammonia solution must be added until the colour is clear yellow. Nickel complexes rather slowly with EDTA, and consequently the EDTA solution must be added dropwise near the end point. 

B. Duplication method. This is usually applied as the so-called colorimetric titration in which a known volume (x mL) of the test solution is treated in a Nessler cylinder with a measured volume (y mL) of appropriate reagent so that a colour is developed. Distilled water (x mL) is placed in a second Nessler cylinder together with y mL of reagent. A standard solution of the substance under test is now added to the second cylinder from a microburette until the colour developed matches that in the first tube the concentration of the test solution can then be calculated. The standard solution should be of such concentration that it amounts to no more than 2 per cent of the final solution. This method is only approximate but has the merit that only the simplest apparatus is required it will not be discussed further. 

Sugars are estimated with reducing DNS reagent, based on the colorimetric method developed in an earlier module. Die samples are determined by colour developed, which is detected by a spectrophotometer at a wavelength of 540 nm. In large-scale operations, mycelia are separated by a rotary drum filter. 

When undiluted 2-vinylfuran was added to metallic sodium (mirror or particles) an orange colour developed and some resinous material was deposited on the metal surface. On prolonged contact much of the monomer was converted into a partly-insoluble reddish resin with spectra unrelated to those of standard poly(2-vinyl-furan). Reaction of diluted monomer with sodium gave a milder interaction, but no evidence of living anionic polymerization. 

Free formalin. Inactivation of bacterial toxins with formalin may lead to the presence of small amounts of tree formalin in the final product. The concentration, as estimated by colour development with acetylacetone, must not exceed 0.02%. 

Gaseous sterilization Ethylene oxide (EO) Reactive chemical Indicator paper impregnated with a reactive chemical which undergoes a distinct colour change on reaction with EO in the presence of heat and moisture. With some devices rate of colour development varies with temperature and EO concentration Gas concentration, temperature, time (selected devices) NB a minimum relative humidity (rh) is required for device to function... 

Gonzalez-Aguilar GA, Buta JG and Wang CY. 2001. Methyl jasmonate reduces chilling injury symptoms and enhances colour development of Kent mangoes. J Sci Food Agric 81 (13) 1244—1249. 

The interference from amino acids was investigated and found to be negligible as reported by Solorzano [37] and Haywood and Huyser [43], who employed no heating for the indophenol blue colour development. Solutions containing 50 xg N/l of urea, histidine, lycine, glycine, and alanine were analysed. The NH4-N detected ranged between 0.4% (for urea) and 2.2% (for alanine) of the nitrogen added. 

Antia et al. [96] proposed a colorimetric method comprising a concentration step and a reaction with 2,7-dihydroxynaphthalene. This method has a detection limit of 0.1 mg/1. Methods comprising concentration by adsorption on alumina, followed by elution and colour development, yielded a detection limit of 5 ng/1 [97,98]. These methods have not been too successful in hands other than those of the original authors, possibly because of the amount of manipulation necessary in the analysis. 

Stradomskaya and Goncharova [99] have developed an extraction and colour development method for formic acid which should work in seawater. The sample is acidified to pH 2 and extracted with diethyl ether. After removal of the ether, the formic acid is reduced to formaldehyde and determined spectrophotometrically with chromotropic acid. A sensitivity of 1 ig/l with a normal range of 0.9 pg/1 is claimed. 

Phenolic substances can be measured directly, without colour development, by the difference in their ultraviolet absorption in acidic and basic... 

The electronic spectrum of the complex consists of a combination of the spectra of the parent compounds plus one or more higher wavelength transitions, responsible for the colour. Charge transfer is promoted by a low ionization energy of the donor and high electron affinity of the acceptor. A potential barrier to charge transfer of Va = Id — Ea is predicted. The width of the barrier is related to the intermolecular distance. Since the same colour develops in the crystal and in solution a single donor-acceptor pair should be adequate to model the interaction. A simple potential box with the shape... 

A more recent development is a technique known as flow injection analysis, in which a discrete volume of a liquid sample is injected into a carrier stream. Reagents required for the development of the analytical property of the analyte, e g. colour developing reagents for spectrophotometry, are already present in the stream. The stream then flows straight to the detector and the technique depends upon the controlled and reproducible dispersion of the sample as it passes through the reaction zone. Thus the reaction does not necessarily need to develop to completion,... 

Block diagram of a remote spectrophotometric, flow injection based monitor for the determination of nitrate in river water. Reduction to nitrate by copperized cadmium followed by colour development with sulphanilimide and N-I-naphthylmethylenediamine dihydrochloride. 

Van Urk s reaction (24) Bromocriptine mesilate is dissolved in methanol. After addition of van Urk s reagent and vigorous shaking a blue colour develops slowly, which is substantially weaker than with 2-H-ergot alcaloids. 

Thus, transitions such as 2p -> Is, 3p -> Is, 3d -> 2p are allowed, whereas 2s - Is, 3d-> Is, 3d -> 3d are strictly forbidden. As discussed in Chapter 5, however, transitions within the J-orbitals (so-called d-d band transitions) do occur, and are important in the consideration of the colour developed by transition metals in solution. Other forbidden transitions also occur. 

These products, which have been copied by other manufacturers under various tradenames, are designed specifically for printing applications. Azoic dyeing applications were catered for in 1967 when Hoechst introduced the Azanil salts, a limited range of mixtures of substantive triazenes and Naphtols that can be absorbed onto the fabric and the colour developed by acidification of the dyebath. 

Phenylephrine (27) is a low-potency sympathomimetic amine used as a decongestant. Solutions become coloured due to an auto-oxidation accelerated by light. In a series of experiments, aqueous solutions of the hydrochloride were left under a UV lamp until a tan colour developed. HPLC analysis showed four main products of which one was identified as adrenaline (19). Even after prolonged irradiation, there was never more than 2% adrenaline in the solution. It was assumed that the catecholamine was removed as it formed by further reaction to adrenochrome and melanine, which accounted for the colour [34],... 

A major effort in this field was made by Jordan and Treloar [14]. They showed that a yellow colour developed in the following systems ... 

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