fuchsin are colored red; and fabrics dyed with fuchsin are likewise colored red. (2) Solid rliudainiiie shows no trace of fluorescence; its solutions are fluorescent; and silk dyed with rhodamine likewise shows distinct fluorescence. The fact that the same dyestuff may impart different colors to different fabrics is compared with the fact that iodine gives different colors in different solvents, and yet there is no reason for assuming that iodine forms chemical compounds with its ordinary solvents. Finally, in accordance with Witt"s theory, the function of mordants is explained by the assumption that solutions of these substances in fibres are much better solvents for the dyestuffs than are the pure fibres. However, while interesting because capable of development and quantitative verification, this physico-chemical theory is yet far from being definitely established or generally accepted by chemists.
Dyeing Processes. Cotton, silk, and wool are the textile fibres that are usually subjected to processes of dyeing. Occasionally the material is dyed before spinning, but usually in the state of yarn or thread, and sometimes as woven cloth. Before dyeing, the fibres are first cleaned so as completely to remove all natural and artificial impurities, such as grease and dirt, which tend to produce spots or uneven shades of color, in consequence of improper fixing of the mordant and color. Whenever light and delicate tints are to be dyed on the fibre, bleaching becomes necessary. The preliminary steps in the preparation of cotton consists in boiling the fibre in a weak solution of caustic lye, after which it is rinsed and then steeped in a solution of bleaching-powder and again rinsed. The third step consists in steeping it in dilute sulphuric acid, after which it is again cleansed by washing, and dried. Silk is boiled twice in soap in order to remove the natural silk glue which accompanies the crude fibre, and is then bleached by exposure to sulphurous acid fumes produced by burning sulphur. Wool is cleansed by washing and then steeped in soap and sodium carbonate, after which it is well rinsed in water, by means of which the natural grease of the fibre is removed. It is then bleached with sulphur dioxide. The dyeing of mixed cotton and woolen fabrics such as cashmere and delaines requires special treatment, and the processes must be selected so that the colors of the wool and the cotton shall be identical on the finished material. In dyeing with substantive colors, simple immersion of the fibre in a hot dye-bath and carefully working the material beneath the surface, to secure an even shade, is all that is necessary. The full quantity of the dye is not added at once to the bath, but in successive portions until the desired shade is obtained, the temperature of the bath being gradually raised. The use of mordants has already been noted above. In all dyeing processes, considerable attention must be paid to the permanency of the dyed color, and fast colors are those which withstand the action of air and sunlight. It is obvious that woolen goods and calicoes, which are worn frequently and may be washed, should l>e dyed with colors that are more fast than those which are used with silks.
Apparatus. The apparatus of the dyer is very simple, consisting of vats, kettles, and cisterns, which may l>e of wood, stone, or metal. In Europe the kettles are still heated over open fires, but in America a steam-coil is universally used. A jmre water-supply is absolutely essential to successful dyeing. When the available water-supply is contaminated by sewage or contains lime, magnesia, or other mineral matter, artificial purification must be employed. Suspended matter may sometimes be removed by sedimentation or filtration, or the two combined, but chemical treatment may be required to remove these and other impurities.
Bibliography. The literature of dyeing is very extensive, and reference should be had to the rrticli i in the various technical cyclopaedias, as well as to the following works: Crookes, A I'raclical Ilundhook of Vyeiitg and CalicoI'lintiiig (London. 1874); H>irst, Silk Dyeing, Printing, and Finishing ((ilasgow, 1892); Knecht, Rawson, and Lowonthal, A Manual of Dyeing, for the Use of I'ractieal Dyers, Manufaeturers, students, and All Interested in the Art of Dyeing (London. 18!t.3): Gardner, Wool Dyeing (Philadelphia, 1897); Dyer and ColorMaker's Companion (Philadelphia, 18!)S): and Recent Progress in the hidustries of Dyeing and Galico-Prinling, being a supplement to Sansone, The Printing of Cotton Fabrics Olanchester, 181)5); and. id., Dyeing (Manchester, 1897); Sadtler, Industrial Organic Chemistry (Philadelphia. 1900). See Textile Printing; Coai.Tar Colors; Mineral Colors; Mordants; and the special articles on the more important dyestuffs.
DY′ER, Alexandre Brydie (1817-74). An American soldier. He was born in Richmond, Va., graduated at West Point, and was assigned to the Third United States Artillery in 1837; served in the Florida War in 1837-38. and as lieutenant of ordnance in the War with Mexico in 1846-48, being brevetted captain for gallant conduct. At the beginning of the Civil War he did much to increase the efficiency of the Ordnance Department, and in 1864 was appointed chief of ordnance at Washington, with the rank of brigadier-general, a position which he held until his death. From 1861 to 1864 he had charge of the Springfield (Mass.) Armory, and in 1865 was brevetted major-general in the Regular Army.
DYER, Eliphalet (1721-1807). An American legislator and soldier. He was born at Windham. Conn.; graduated at Yale in 1740; and was admitted to the bar in 1746. He held several colonial offices, and was the original projector of the plan of establishing a Connecticut colony in the Susquehanna Valley, and was sent to England in 1763 as the agent of the company formed for that purpose. He was lieutenant-colonel of a Connecticut regiment in the French and Indian War; was the first commissioner sent by Connecticut to the Stamp Act Congress in 1705; and was a member of every Continental Congress excepting those of 1776 and 1779. From 1776 to 1703 he was a judge of the Superior Court, and for the last four years was Chief Justice.
DYER, George (1755-1841). An English antiquarian. He was born in London, and was educated at Emanuel College, Cambridge. He contributed 'all that was original' to Valpy's edition of the Classics (141 vols., 1809-31), and
