HOFMANN’S VIOLET.

193

Fig. 18.

j 3S rft

Elevation and Section of the Apparatus.

a, b. Boiler and its cover. c. Steam-jacket, fed and emptied by the pipes d d.}. Pressure-gauge. g. Cylinder, with two taps for introducing matters into theapparatus without diminishing pressure. h. Screw- or valve-tap, to permit thevapours to enter a warm condenser. i. Pipe to run off the steam-jacket.

The mixture is heated to 115 0 to 130° C., for about two hours.For a blue violet, “ B ” shade, the mixture is—

Rosaniline ..

Alcohol.

Iodide of methylIodide of ethyl ..Potassa.

For a bluer shade, “ B.B. ”—Rosaniline ..

Iodide of methyl

Alcohol.

Potassa.

10 kilos.100 litres.5 kilos.5 »

10 kilos.20 ,,100 litres.10 kilos.

The alcoholic solutions of the iodides and of potassa are introduced in suc-cessive portions during the operation. When the required shade has beenobtained the contents of the still are drawn off and purified. For thispurpose the excess of alcohol is distilled off. The residue is then treatedwith an alcoholic solution of soda, in an apparatus fitted up with an agitatorand a cohobator. It is then washed with boiling water in the same apparatus,with constant agitation, in order to remove both the alkaline iodide formed andthe excess of soda. When thoroughly washed it is taken up in sulphuric,

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