Metaphenylenediamine Hydrochloride

Nitrites.—To the solution of 1 gm. of ammonium nitrate in 20 cc. of water are added 1 cc. of 16 per cent sulphuric acid and 1 cc. of a freshly prepared (0.5 100 ) colorless solution of metaphenylenediamine hydrochloride no yellow or yellowish-brown color should develop. 

Should the solution of metaphenylenediamine hydrochloride already-have a color it is to be decolorized before use by warming with ignited, animal charcoal. 

A white, or slightly reddish-white, crystalline powder, easily soluble in water. Metaphenylenediamine hydrochloride is used as a reagent in the form of a 1 200 solution. Should... 

Should the solution of metaphenylenediamine hydrochloride have a color, it is to he decolorized before using by wanning with previously ignited animal charcoal. 

Metaphenylenediamine reaction (Windisch). To 10 c.c. of the spirit in a porcelain dish is added, drop by drop, 1 c.c. of fresh 10% metaphenylenediamine hydrochloride solution, mixing of the two liquids being avoided. In presence of small amounts of aldehydes, after 2-4 minutes there forms at the surface of contact of the two liquids a more or less intense yellow or orange-red coloration, while later there appears a green fluorescence, which is shown more especially on heating. 

Pure alcohol. Pure alcohol of commerce of at least 96% strength is neutralised exactly, boiled for an hour in a reflux apparatus with 1-2% of metaphenylenediamine hydrochloride and then distilled, the first and last portions of the distillate being discarded. The sp. gr. of the alcohol thus obtained is determined and the strength adjusted to 90% or 50% (see Tables XXV and XXVII). This alcohol should not colour either with Schiff s reagent or when heated for an hour with an equal volume of concentrated sulphuric acid in a bath at 120°. 

Detection of the Aldehydes.—This is effected with Schiff s reagent (General Method, No. 10) on about 2 c.c. of the oil dissolved in pure alcohol in presence of aldehydes a magenta-red coloration is obtained immediately. Also when 2-3 c.c. of the oil, dissolved in 10-15 c.c. of ure alcohol, are heated with a small quantity of metaphenylenediamine hydrochloride, a yellowish-brown coloration (faint yellowing is allowable) is formed in presence of aldehydes. 

Whenever aldehydes are present in excess of 15 parts per 100,000, add to the distillate 0.5 g. of metaphenylenediamine hydrochloride, boil under a reflux condenser for an hour, distil 100 cc., add 25 cc. of H2O, and continue the distillation until an additional 25 cc. is collected. 

Triamidoazobenzene is formed along with other azo-compounds, on treating metaphenylenediamine with nitrous acid. Its hydrochloride forms the principal constituent of the dyestuffs known under the above names. (A more recent view is that Bismark brown consists partly at least of a compound of the formula... 

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