ANTLINE AND ANILINE DYES.—Manufacture of Aniline Blue. 231
Courier states that his toluidine, containing 95per cent, of a mixture of para- and meta- toluidine,furnishes from 45 to 50 per cent, of crystallizable red,whilst any admixture lessens the yield. IIoussillefinds that the tinctorial power of rosatoluidine is 140,that of rosaniliue being taken as 100 (Bull. Soc.Clam. Paris , [2] iv. 312).
Toluidine red gives to vegetable and animal fabricsa shade rather more blue than that communicated byfuchsine.
Xylidine Red. —A product has been introduced byCoupier under this name, derived from xylidineby the same processes as those by which rouge detoluene is got from Courier 's toluidine. The fol-lowing formulae are given by Coupier :—Xylidine,100 parts; arsenic acid at 75 per cent., 140 parts;commercial hydrochloric acid, 20 parts : heat for threehours to 130° to 140° C. Or heat to 200° C. xylidine,75 parts; and of the corresponding nitroxylidine,105 parts. This red dyes animal and vegetable fibresa more violet shade than fuchsine and rosatoluidine.Of the composition of this red, and its relation torosaniline and the other red dyes, nothing is known ;but without doubt its composition is analogous tothat of rosaniline. These results are entirely differentfrom those of Hofmann, who found that xylidinealone, or mixed with toluidine, gave no red; butthat a fine red could be formed from a mixture ofaniline and xylidine by the action of arsenic acid.The red derived from aniline and xylidine is notnecessarily identical with the “xylidine red” or“ rosaxylidine ” of Courier .
Ulrich's Scarlet. —Four parts of rosaniline acetateare dissolved in hot water, and mixed with a solutioncontaining 3 parts of lead nitrate ; the whole is thenevaporated to dryness, and heated to 150° to 200°C. until the whole mass is violet. After coolingthe mass is boiled for a long time with very dilutesulphuric acid; an excess of alkali is added to thehot liquor, and the whole filtered whilst hot. Thenew colouring matter is contained in the filtrate, andmay be precipitated by addition of salt. Perkin’smauve may also be used, and peroxide of hydrogenand other oxidizing agents can be employed with thesame result; it is therefore probable that this scarletis closely allied to Geranosine.
Geranosine. —LuTllRINGER gives the following pro-cess for the preparation of this dyestuff:—4£ kilos, ofbarium or calcium nitrite or dioxide are disseminatedthrough 25 litres of water, and 10 kilos, of strongsulphuric acid (at G6° B) are added; to this liquor isadded a solution of 1 kilo, of any rosaniline salt dis-solved in 1000 litres of water, and at a temperatureof 45° C.; the mixture becomes citron yellow andthen colourless. After filtration the temperature isgradually raised to 100° C. to separate barium sul-phate, when an intense red tint is developed ; aftertwo minutes’ boiling the liquor is cooled, and thedyestuff salted out and collected on filters. [
This dye is not decolorized by ammonia (alkaliesgreatly weaken or destroy the fuchsine tint by setting jfree the nearly colourless basis); it is soluble citherin water or alcohol.
Saffranine. —Mene gives the following process :—•Aniline nitrite is prepared by passing into anilinethe vapours evolved from a mixture of starch andnitric acid. The product is washed two or threetimes with water, and then heated with half its weightof arsenic acid to 80° to 120° G. for five minutes;the product is poured into boiling water, and limeadded until the acid is neutralized. The liquor isthen filtered through flannel, and the colouringmatter salted out from the clear red liquor by meansof common salt (5 parts to 1 of aniline nitrite).
The pasty mass is then drained, and pressed toremove the brine. In preparing the aniline nitritecare must be taken that the temperature does notrise too high, otherwise the aniline will be car-bonized ; the delivery pipe should dip pretty deeplyinto the oil, and the containing vessel should befrequently agitated and cooled by water. An excessof nitrous acid must also be avoided. Besidesarsenic acid, other oxidizing agents may be em-ployed, viz.: chromic acid, a mixture of sulphuricacid and potassium dichromate, stannic chloride, &c.
Of these potassium dichromate seems to be the mostsuitable. Simultaneously with saffranine, a violetcolouring matter is formed; this is precipitated bythe alkaline solution added, and is then separated.
Manufacture of Bleu de Lyons or Aniline Blue.—
The preparation of good aniline blue from fuchsineand aniline oils, by simply heating the ingredientstogether, is an operation of some delicacy, the resultdepending to a great extent upon circumstances whichat first sight would hardly seem to be important.
The original process patented by Girard and DeLaire was as follows:—Purified fuchsine is mixedwith its own weight of aniline oil, and the mixtureheated to a temperature as near 165° C. as possible(between 155° and 185°) for five or six hours: aviolet product is obtained, 1 part of which is boiledwith 10 to 12 parts of hydrochloric acid diluted withthe same quantity of water; unaltered fuchsine andaniline are dissolved out, and a violet dyestuff is left.
By further boiling this product with hydrochloricacid (10 of acid to 100 of water) several times suc-cessively, a pure blue colouring matter is left, whichis dissolved in acetic acid, alcohol, or wood spirit,and the solution used for dying.
According to Keimann, it is possible to get everyshade of violet in this way, but no true blue, unlessthe rosaniline salt of an organic acid be used, or whatamounts to the same thing, unless an organic sodiumor other metallic salt be added to the mass; more-over, a much larger proportion of aniline is desirable.
Levinstein’s process is worked as follows:—Threeparts of aniline and one of magenta are heated to
180° C. for three hours, when the red becomes violet;half a part of potassium acetate is then added, andthe temperature raised to 190° C. for one hour anda half, or until a sample taken out appears of a green-ish blue hue against a white background; the massis then treated with hydrochloric acid as before.
The blue thus obtained has a faint greenish tinge.
Passavant’s method was to heat 4 parts magenta,
8 of aniline, and 2 of sodium acetate to 200° C. for