ANILINE 177 



ANHYDRIDES. A name now given by chemists to the so-called oxygen acids, 

 or those which are clearly results of a combination of an element with oxygen. 



Thus, the gaseous compound of sulphur and oxygon, commonly called sulphurous 

 acid (SO 2 ), is now termed sulphurous anhydride ; indeed, in its anhydrous state, tho 

 gas does not exhibit any of the characteristic reactions of an acid, and hence in 

 modern chemistry the term sulphurous acid is restricted to tho combination of tho 

 anhydride with water (SO 2 . HO, or H 2 SO 3 ). 



ANHYDRITE. A mineral consisting of anhydrous sulphate of lime. It occurs 

 in granular masses ; in crystals belonging to tho orthorhombic system ; in crystalline 

 masses presenting cleavage in three rectangular directions, and hence termed dice- 

 spar ; and in certain curiously contorted forms known as tripe-stone. Anhydrite is 

 frequently found in , beds of rock-salt, where it is often associated with gypsum, or 

 hydrous sulphate of lime ; indeed, anhydrite may readily pass into gypsum by 

 combination with water, and in certain localities as at Bex, in Switzerland exten- 

 sive beds of anhydrite have been thus hydrated. The compact and granular varieties 

 of anhydrite are often worked into ornamental forms, and the coarser kinds, when 

 occurring in sufficient quantity, have been used for building purposes. The mineral 

 is also useful to the agriculturist, like gypsum, for improving certain soils. 



AXSTIIi. The name of the American species of the Indigo plant (Indigofera). It 

 is a shrubby plant, growing from 2 to 3 feet high. From it the name Aniline is 

 derived. See ANILINE and INDIGO. 

 ANIItEINE. See ANILINE-VIOLET. 



ANIX.XNE. (C 12 H'N, or Unitary System, C 8 H s , RHHT,* Phenylamine.) This 

 organic base having of late years met with an important application in the arts, in 

 the production of beautiful dye-colours, a description of the methods of preparing it, 

 and of some of its characters, becomes necessary ; though for details of its more 

 interesting relations in scientific chemistry, we must refer to Watts's ' Dictionary of 

 Chemistry.' 



Preparation, There are few bodies which admit of being prepared in a greater 

 variety of ways all of them interesting in tracing the chemical history of this most 

 curious body; and wo proceed to describe Dr. Hofmann's original mode of procuring 

 it from the basic oil of coal-tar, although this method is no longer resorted to for the 

 manufacture of aniline. 



The oil is.agitated with hydrochloric acid, which seizes upon the basic oils ; after 

 decanting the clear liquor, which contains the hydrochlorates of these oils, it is 

 evaporated over an open fire until it begins to disengage acrid fumes, which indicate a 

 commencement of decomposition, and is then filtered, to separate any adhering neutral 

 compounds. The clear liquor is then decomposed with potash or milk of lime, which 

 liberates the bases themselves in the form of a brown oil, consisting chiefly of a 

 mixture of aniline (C 8 H' N), and leucol or quinoleine (C 9 H" N). This mixture is 

 submitted to distillation, and the aniline is chiefly found in that portion which passes 

 over at or about 360 F. (182 C.) : repeated rectification and collection of the product 

 distilling at this temperature purifies the aniline ; but to complete the purification, it is 

 well to treat tho partially purified aniline once more with hydrochloric acid, to 

 separate the bases again by an alkali, and then to rectify carefully. 



The violet reaction of aniline with solution of bleaching-powder enables the 

 operator to test the distillate from time to time, to ascertain when aniline ceases to 

 pass over, since leucol does not possess this property. Hqfmann. 

 Aniline may also be obtained from indigo. 



When indigo-blue is dissolved by the aid of heat in a strong solution of potash, 

 and the mass, after evaporation to dryness, submitted to destructive distillation, 

 it intumesces considerably, and aniline is liberated, which condenses in tho re- 

 ceiver in the form of a brown oil, together with a little water and ammonia disengaged 

 with it. The aniline is purified by rectification, as in the method before described. 

 By this process, the quantity of aniline obtained is about 18 to 20 per cent, of the 

 indigo used. Fritzsche. (See INDIGO.) 



By treatment with potash, the indigo-blue (C 8 H s NO) is converted into chrysa- 

 nilic acid and anthranilic acid (C 7 H 7 NO 2 ), and it is this latter body which, by 

 destructive distillation, yields carbonic acid and aniline. 



Nitrobenzol may bo converted into aniline, either by the action of sulphuretted 

 hydrogen, or, more conveniently, as has been shown by M. B6champ, by the action 

 of a basic acetate of iron. 



* The formulae employed throughout this article, and in tho following articles on aniline colours, 

 arc constructed With the modern atomic weights, although not printed in black type. 

 VOL. L N 



