Ferric chloride, reactions with neutral solution

Ferric chloride solution sometimes contains a large excess of HCl which would interfere with the following reactions. If it is very markedly acidic add dil. NaOH solution, drop by drop, to the ferric chloride solution until a small but permanent precipitate of ferric hydroxide is obtained. Filter this off through a small fluted filter paper, and use the clear filtrate. The latter is still not quite neutral owing to hydrolysis, but this feeble acidity does not interfere with the tests given below. 

Colorations or coloured precipitates are frequently given by the reaction of ferric chloride solution with.(i) solutions of neutral salts of acids, (ii) phenols and many of their derivatives, (iii) a few amines. If a free acid is under investigation it must first be neutralised as follows Place about 01 g. of the acid in a boiling-tube and add a slight excess of ammonia solution, i,e., until the solution is just alkaline to litmus-paper. Add a piece of unglazed porcelain and boil until the odour of ammonia is completely removed, and then cool. To the solution so obtained add a few drops of the "neutralised ferric chloride solution. Perform this test with the following acids and note the result ... 

Aqueous solutions give with ferric chloride the characteristic reactions of the neutral salt of the acid (p. 348). Identify the carboxylic acids by the tests already given (Section 14, p. 347), or by the preparation of one of the crystalline derivatives below. 

Addition of chlorine to the residua ethylene contained in the effluent resulting from the absorption of vinyl chloride, by passage through a solution of ferric chloride in ethylene dichloride. The temperature is maintained at between 50 and 70°C, under pressure between 0.4 and 0.5.10 Pa absolute. The chlorine is injected in sub-stoichiometric quantities in relation to ethylene (96 to 98 per cent) to eliminate the risks of explosive reactions due to the presence of hydrogen. The ethylene dichloride produced is rid of the catalyst by extraction with water. Added to that employed as a solvent in the previous stage, it is neutralized with caustic soda, filtered, washed with water, separated frojn the light components (especially water)hnd heavy components by azeotropic or conventional distillation. 

Directions a) Determine by testing with litmus paper whether solutions of the following salts show a neutral, acidic, or basic reaction sodium chloride, potassium nitrate, sodium sulphate, calcium chloiide, sodium sulphide, copper sulphate, ferric chloride, sodium carbonate, and sodium acetate. (1) Tabulate the results and state in the case of each salt the strength (weak or strong) of the acid and the base from which the salt is derived. 

III was acidic, decomposing sodium carbonate in the cold, and giving a red colour with ferric chloride, a reaction regarded by W. Wislicenus as characteristic of enolic forms (containing OH groups) in many cases the colour is violet-blue. IV, shown to have the same mol. wt. as III, was neutral and did not react with sodium carbonate it dissolved only slowly in potassium hydroxide solution, and on acidifying III was precipitated. Ill dissolved in hot dilute alcohol IV crystallised on cooling. Formylphenylacetic ester was shown by W. Wislicenus to exist in two forms ... 

When neutral solutions of uranyl-, ferric-, or bismuth nitrate (chloride) are shaken with a benzene solution of Rhodamine B, the benzene layer turns red and exhibits an intense orange fluorescence in ultraviolet light. This effect is surprisingly heightened if a little benzoic acid or some other benzene-soluble carboxylic acid is added to the benzene solution. In the case of uranyl salts, the color (fluorescence) reaction is so marked that a sensitive... 

Amino acids give deep red colorations with ferric chloride and, as would be expected from their relation to ammonia, give a deep blue color with solutions of cupric salts. The simple a-amino acids are practically neutral in reaction they may be considered as inner salts. 

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