Powder mixing colouring

Other Coloured Flames.—The following salts, if finely powdered, mixed with spirits of wine and set fire to will communicate to the flame their peculiar... 

Normally they are dried and ground to a powder, mixed with fillers (e.g. mica, glass fibres, sawdust), colourants and hardeners, and then cured (i.e. crosslinked) in a hot mould. Hexamethylenetetramine, with magnesium or calcium oxide as a catalyst, usually is employed as the hardener to facilitate crosslinking reactions. Most of the crosslinks formed are methylene bridges, though some dimethylene amine links can be produced. The fillers are added to improve the electrical or mechanical properties of the resin. 

The effect of the nature of the synthesis medium has also been considered through the replacement of both titanium precursor and solvent. An organic medium has therefore been used containing titanium isopropoxide as precursor and isopropanol as solvent. In these conditions, two different R = [HF]/[Ti] molar ratios have been studied, i.e. 3 and 4. The corresponding X-ray diffraction powder patterns (not shown) are similar to those obtained from the aqueous medium with a broadening of the X-ray peaks suggesting smaller particle size. Here, the salient point is that the recovered powders are coloured, which is consistent with mixed-valency Ti. Such a point will be discussed later. 

A colouring material mixed with rubber to give the desired colour in the product. The term has been used in the sense of any powdered compounding ingredient. 

A similar RP-HPLC method has been employed for the determination of the effect of reduced glutathion (GLT) and hydroxypropyL/Tcyclodcxtrin (HP-/LCD) on the stability of the colour pigments of paprika. Samples were prepared by mixing 5 per cent GLT (w/w) and 5 per cent HP-/TCD (w/w) with paprika powder and stored at room temperature (22 1°C) in diffuse light in Petri dishes covered by glass plates. Samples without additives served as a control, lg of paprika was taken after 14, 28, 42 and 56 days of storage... 

Bis[dimethylthienol]l,4,6,8-tetratellurafulvalene. 3,4-Dibromo-2,5 dimethylthiophene in tetrahydrofuran is treated at -78°C with 2 equiv of ferf-butyllithium. After 2 h, 1 equiv of tellurium powder is added. The mixture is slowly warmed to 0°C and kept at 0°C until all the tellurium has dissolved. The mixture is cooled again to -78°C, treated with tert-butyllithium and then with tellurium at 0°C. The ditellurolate solution is cooled to -78°C, mixed with 0.5 equiv of tetrachloroethene, stirred for 18 h and allowed to warm to 20°C. The brown solid is isolated by filtration and extracted with carbon disulphide. The extract is evaporated and the residue recrystallized from 1,1,2-trichloroethane to give bronze-coloured crystals. Yield 75% m.p. 295-298°C. 

Ives et al. (79) tended to reject our hypothesis that brown colours of mixed oxides (and in particular less pure NdaOs) are due to traces of praseodymium. However, these authors noted the interesting effect that such dark colours (also of Pro,oaTho.9802) bleach in the reflection spectrum at higher T. It was noted that mantles of NdaOa alone rapidly hydrate to a pinkish powder (carbonate ) in humid air. It is weU-known that -type sesquioxides are far more reactive, and for instance dissolve almost instantaneously in aqueous acid, than cubic C-type samples. Ives et al. 19) also studied the broad continuous spectrum of the orange light emitted from Thi- 11 0 2+2/ where the oxidation state of uranium is rather uncertain. 

Some of the most highly acclaimed displays commenced around 1865 at the Crystal Palace where Mr C. T. Brock set a standard for brilliance and colour which was said to defy competition. This improvement was due, in no small part, to the introduction of metal powders and chlorates into the pyrotechnic mixes, an innovation which is used even today. 

The bromide separates in prismatic needles which are reddish in colour and less soluble than the chloride. The mercury double salt with mercuric iodide is produced by mixing the chloride with mercuric iodide and hydriodie acid. The salt is very sparingly soluble in water and separates as an orange-coloured powder.1... 

For free anthraquinones, powdered plant material is mixed with organic solvent and filtered, and an aqueous base, e.g. NaOH or NH4OH solution, is added to it. A pink or violet colour in the base layer indicates the presence of anthraquinones in the plant sample. 

This results from the transformation of starch by means of heat or by the action of dilute acid or diastase. It is prepared principally from potato, wheat or maize starch and rarely from rice or other exotic starches. Many varieties of dextrin, made in diverse ways, are sold under different names. It occurs as a fine powder, either wliite, dirty white, yellowish or light brown as granules, similar in appearance to gum arabic and as a thick syrup, more or less highly coloured and opaque. In general dextrin has a special odour and taste, which are particularly marked in the pulverulent varieties. It is soluble in water, but insoluble in alcohol. Its solution is strongly dextro-rotatory the value of [a]D varies from 173° to 2250,but is mostly about 200°. With iodine different dextrins give bluish violet to brownish red colorations (the colour is observed by adding the iodine solution drop by drop if the mass is mixed after the first drops are added, the colour disappears). 

English red consists essentially of anhydrous ferric oxide in very fine powder, more or less deep red in colour. It usually contains small quantities of silica and silicates, alumina, lime and magnesia, and often sulphates, chlorides and free sulphuric acid it may also contain manganese and copper. It is often sold mixed with considerable proportions of gypsum (Venetian red), barium sulphate and chalk sometimes its colour is heightened or modified by addition of artificial organic colours. 

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