ANALYSIS. Boil twice for one minute with 5 per cent. acetic acid. A. Much color is stripped-Basic dyestuff. On boiling with hydrosulphite A decolorized and color does not return on exposure to air or on oxidation with persulphate. Azo Group No. 1— Bismarck Brown. B. Little or no color is stripped-Acid, Salt or Mordant dyestuff. Boil twice for one minute with dilute ammonia. X. Much color is stripped-Acid dyestuff. On boiling with hydrosulphite A decolorized, and color does not return on exposure to air or on oxidation with persulphate. Azo Group No. 2— Acid Brown R, Fast Brown O, &c. Y. Little or no color is stripped-Salt or Mordant dyestuff. Boil for two to three minutes with 5 per cent. sodium acetate and white cotton. Cotton is stained-Salt dyestuff. Boil with hydrosulphite A. Decolorized, but color not restored by air or by persulphate. Azo Group No. 3. Test ashfer chromium to ascertain if chromed. Diamine Browns, Benzo Browns, Toluylene Browns, &c. Decolorized, but color returns slowly on exposure to air, or quickly on oxidation with persulphate. Stilbene Group No. 4-Mikado Browns. Cotton remains white-Mordant dyestuff. Confirm by testing for metallic mordants in ash. Color not changed. Boil with dilute hydrochloric acid (1:10). Color is stripped-No. 5 Anthragallol (anthracene Color is not stripped-No. 6 Cutch. Decolorized, or changed to pale buff or light brown. Color returns slowly on exposure to air, or Color not restored either by air or persulphate. EXAMINATION OF BLACKS AND GREYS. TABLE VII. The fibre may be dyed with one of the following: 1. A basic black or grey, such as Diazine Black, Janus Black, Methylene Grey, &c. 2. An acid black, such as Naphthol Black, Naphthylamine Black, Palatine Black, Nerol, Anthracene Black, Azo Acid Black, Azo Merino Black, &c. 3. A salt dyestuff, such as Union Black, Half-wool Black, Columbia Black, Diamine Blacks, Dianil Blacks, Carbide Blacks, &c. 4. A mordant azo dyestuff, such as Anthracene Chrome Blacks, Palatine Chrome Blacks, Chromotropes, Chromate Black, Acid Chrome Blacks, &c. 5. A" vatted" black (indigo and logwood). 6. Logwood black on chromium mordant. 7. Logwood black on iron mordant or Bonsor's Black. 8. Naphthazarine, Alizarine Blacks, or Alizarine Blue Black SW (naphthoquinone group). 9. Diamond Blacks. 10. Alizarine Cyanine Black (anthraquinone group). 11. Aniline Black. ANALYSIS. Boil for one minute with 5 per cent. acetic acid. A. Much color is stripped-Basic dyestuff. No. 1 Diazine Black, Janus Black, Methylene Gray, &c. B. Color is not stripped-Acid, Salt or Mordant dyestuff. Boil twice for one minute with aqueous alcoholic ammonia and small piece of white cotton. X. Much color is stripped but the cotton remains white— Acid dyestuff. On boiling with hydrosulphite A the color is permanently discharged. No. 2 Naphthol Black, Naphthylamine Black, Palatine Black, &c. Y. Color is not stripped-Salt and Mordant dyestuffs. Boil with 5 per cent. sodium acetate and a small piece of white cotton. Z. Cotton is stained-Salt and Azo Mordant dyestuff. Chromium is absent-Salt dyestuffs. No. 3 Union Cotton remains white. Mordant dyestuffs. Confirm by testing ash for mordant. Boil with dilute hydrochloric acid (1:10). Test for indigo by boiling with a little aniline; blue Fibre and solution crimson-No. 6 Logwood on Cr. Not affected. Boil with hydrosulphite A. Becomes brown. Original color returns on exposure to air. No. 8 Naphthazarine, Alizarine Black S, Alizarine Blue Black SW. Decolorized. Color is not restored by exposure to air or by persulphate. No. 9 Diamond Blacks. Unaffected. Treat fibre with conc. H2S04. Blue solution No. 10 Alizarine Cyanine Black. Although it is not intended, in the present paper, to deal fully with the detection of mixtures, a few general principles may be mentioned here which will be found useful by those who wish to extend the scheme to such cases. If a mixture consists of two or more dyestuffs of the same chemical and dyeing group, it will behave as a whole similarly to a single dyestuff, though sufficient differences will usually exist in the rate of solution or of attack by the group reagents to render it possible to distinguish or even to separate the constituents. Thus a green consisting of a mix ture of an acid azo yellow with an acid azo blue will be distinguishable upon careful reduction with hydrosulphite, since the azo blue will be reduced first, and the shade will therefore change from green to yellow before it is decolorized. Neither color will return on oxidation. Further, if such a compound shade be extracted fractionally with dilute ammonia, the yellow is generally stripped first, and may be transferred to another piece of wool for subsequent tests. Mixtures of colors belonging to different groups will usually exhibit at once their diverse composition. For example, a navy blue shade dyed with patent blue-and an azo orange will, upon reduction, first change to bright blue, then become colorless; and upon reoxidation with persulphate the blue alone will return. If a mixture of an azine, oxazine, or thiazine dyestuff with a triphenylmethane color has been employed, only the first will return upon exposure of the leuco compound to air, the latter being also restored upon treatment with persulphate. Fractional extraction of the fibre with dilute alcohol or dilute acetic acid can also be employed in many cases to effect a separation or partial separation of the dyestuffs, the extracted color being then transferred to fresh wool or silk, and separately tested. This paper which is taken from the "Journal of the Society of Dyers and Colorists" is the most systematic work on the subject which has yet appeared. Owing to the necessities of the pages it has been necessary to change the form of the tables but the matter is exactly that of the original.-ED. |