Methyl orange crystals

Detection of alkali and acid residues, including formation of methyl orange crystals... 

Whilst the solution is still hot, add dilute hydrochloric acid until the stirred solution is just acid to litmus, and then distil off as much ethanol as possible, using the water-bath. Now add more dilute hydrochloric acid to the residual hot solution until it is just acid to methyl-orange. The 5,5-dimethyl-cyclohexan-1,3-dione separates as an oil which solidifies on cooling. Filter the product at the pump, wash it with ice-cold water, and dry it in a desiccator. Yield of the pale cream-coloured crystals, 12 g. m.p. 136-145 (preliminary softening). 

A solution of 10 g. of ethyl 2-(D-ara ino-tetrahydroxybutyl)-5-methyl-4-furoate in 20 ml. of 10% aqueous sodium hydroxide is kept81 at 37° for 15 hours and then heated under reflux, in a bath of boiling water, for one hour. After cooling, the solution is acidified with phosphoric acid, Congo Red or Methyl Orange being used as indicator. A mass of crystals is formed this is collected by means of a little cold water and fil-... 

By contrast, alkylation of the 1,2,4-triphospholide ion by bis(trimethylsilyl)bromomethane takes place at P-1 and affords a stable 1,2,4-triphosphole (192) which is isolated as orange crystals <95CC1661>. It gives a t-PtCl2PEt3 complex in which the triphosphole is attached via P-4 (molecular structures of the triphosphole and its complex in Table 6). By reaction with methyl iodide the triphosphole is converted to a homopentaprismane-structured phosphonium iodide (193) <94CCRl >. 

Cresol red Crystal Violet Malachite Green Methanil Yellow Thymol Blue Orange IV -2,4-Dinitrophenol -Erythrosin, Na2 salt -Dimethyl Yellow Cl 11020 Bromophenol Blue Congo Red Cl 22120 Methyl Orange Bromocresol Green Alizarin Red S Cl 42750 Methyl Red Cl 13020 -Bromocresol Purple Chlorophenol Red p-Nitrophenol Alizarin Bromothymol Blue Brillant Yellow Phenol Red Neutral Red Cl 50040 -m-NItrophenol -Cresol Red Metacresol Purple Phenolphthalein -Thymolphthalein -P-Naphthyl Violet Alizarin Yellow R 2,4,6-T rinitrotoluene... 

Rubidium Dihydrogen Orthoarsenate, RbH2As04, is obtained in the anhydrous form by fusing together equal parts of arsenious oxide and rubidium nitrate, or by neutralising rubidium carbonate solution with arsenic acid using methyl orange as indicator in the former method it yields tabular crystals and in the latter silky needles. At a dull red heat it forms the metarsenate. 

A solution of 8.65 g 2,5-dimethoxy-4-methylbenzaldehyde in 30 g nitromethane was treated with 1.1 g anhydrous ammonium acetate and heated for 50 min on the steam bath. Stripping off the excess nitromethane under vacuum yielded orange crystals which weighed 12.2 g. These were recrystallized from 100 mL IPA providing yellow crystals of 2,5-dimethoxy-4-methyl-6-nitrostyrene which weighed, when dry, 7.70 g. The mp was 117-118 °C, and this was increased to 118-119 °C upon recrystallization from benzene/heptane 1 2. 

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