

CHEMISTRY APPLIED TO THE ARTS. 



Reducing agents convert nitrobenzol and nitro- 

 toluol into 'aniline' and 'toluidine' respectively. 

 In practice, nascent hydrogen from iron and acetic 

 acid is used : 



C ? H S NO, + 



Nitrobenzol. 



C 7 H 7 NO, -I- 



NitrotoIuoL 



6H = 



6H = 



C 6 H 5 NH S 

 Aniline. 



2H a O. 



Water. 



C 7 H 7 NH, + 2H 2 O. 



Toluidine. Water. 



The mixture of aniline and toluidine obtained 

 from commercial nitrobenzol is known as 'aniline 

 oil.' It is an oily liquid, very slightly soluble in 

 water : from it a great number of colouring-matters 

 .are obtained we shall describe a few of them. 



Mauveine. When aniline is treated with a 

 mixture of bichromate of potash and sulphuric 

 acid, it is blackened, and from the black mass 

 there can be extracted by means of alcohol a 

 violet colouring-matter, called mauvetne, having 

 the composition C 27 H 24 N. 



Rosaniline. This substance, from which many 

 of the aniline colours are derived, is formed by the 

 -action of various oxidising agents on commercial 

 -aniline that is, upon a mixture of aniline and 

 toluidine, thus : 



C 8 H 7 N 



Aniline. 



Toluidine. 



3O = C M H 19 N 3 



Rosaniline. 



Water. 



The oxidising agent usually employed is arsenic 

 acid, which gives up part of its oxygen, and is 

 reduced to arsenious acid (see CHEMISTRY). 

 Hosaniline combines with water to form hydrate 

 of rosaniline, C 20 H 19 N 3 ,H a O, a colourless sub- 

 stance, which, when dissolved in acids, forms salts 

 of rosaniline, having an intense crimson colour. 

 The hydrochlorate and the acetate, C 20 H 19 N 3 HC1 

 and C 20 H 19 N 3 ,C 2 H 4 O 2 , are sold under the name 

 * fuchsin.' 



Violet Imperial, Aniline Blue, Bleu de Pan's ; 

 leu de Lyons, J f of mann' s Dahlia, Hof matin's Blue, 

 Aniline Green. These substances are all deriva- 

 tives of rosaniline. To understand their constitu- 

 tion, it is necessary that we should first consider 

 the constitution of rosaniline itself. Rosaniline may 

 be regarded as three molecules of ammonia, in 

 which six of the nine atoms of hydrogen have been 

 replaced by organic radicals derived from aniline 



C 6 H 4 

 .and toluidine, thus : C 20 H 19 N 3 = N 3 1 (C 7 H 6 ) 2 



Here C 6 H 4 and C 7 H 6 are dyad radicals (see 

 CHEMISTRY), derived from benzol (C 6 H 6 = 

 C 6 H 4 ,H 2 ) and toluol (C 7 H 8 = C 7 H 6 ,H 2 ), and 

 -each of these replaces two atoms of hydrogen, 

 so that C 6 H 4 and (C 7 Hg) 2 together replace six 

 atoms of hydrogen in 3NH 3 , leaving three atoms 

 of the hydrogen of the ammonia unreplaced. 

 Thus, in rosaniline, there are, in each molecule, 

 three atoms of hydrogen, occupying the same place 

 as the hydrogen in ammonia does, and similarly 

 related to the nitrogen. Now, it is possible to 

 replace these three atoms (or one, or two of them) 

 by hydrocarbon radicals. If the whole of these 

 are replaced by methyl (CH 3 ), ethyl (CjHg), amyl 

 <C 6 H n ), phenyl (C 6 H S ), or similar radicals, a blue 

 colouring-matter is produced. Thus, the ' aniline 



blue' of De Laire and Girard 



( C 8 H 4 

 isN 3 j(C T H 6 ) 2 

 t(C 8 H 6 ) 3 



triphenyl rosaniline, and is formed by heating a 



mixture of aniline and rosaniline. Hofmann's 



( C 6 H 4 ( C 6 H 4 



blues are N 3 \ (QH,), and N 3 \ (C 7 H 6 ), and are 



u l(.C 2 H 6 ) 3 ( (C 5 H U ) 



formed by heating rosaniline with iodide of ethyl 

 (C 2 H 5 I) or iodide of amyl (C 6 H U I). If one atom 

 of the hydrogen of rosaniline, which is in the same 

 position as the hydrogen of ammonia, is replaced 

 by a hydrocarbon radical, a reddish purple colour- 

 ing-matter is formed ; if two of them, the product 

 is bluish purple. Thus, for instance, we have 



( C 6 H 4 

 rosaniline, N 3 < (C 7 H 6 ) 2 the salts of which are red ; 



( QH 4 

 iline, N 3 } ^^ 2 the salts of which 



/ T_J / /- TT 



(. i! 2 ( C 6 H 4 



1 /A- TT \ 



are red-purple ; dimethyl rosaniline, N 3 ^ ^wr 1 



methyl rosaniline, 



the salts of which are blue-purple ; and trimethyl 



( C 6 H 4 

 rosaniline, N 3 < (C 7 H 6 ) 2 the salts of which are blue. 



( (CH 3 ) 8 



In all these cases the base itself is colourless ; the 

 colour makes its appearance when the base is 

 combined with an acid. 



The ' violet imperial ' consists of phenyl rosani- 

 line and diphenyl rosaniline ; ' Bleu de Paris,' or 

 ' Bleu de Lyons,' is triphenyl rosaniline ; Hof- 

 mann's dahlia is ethyl or amyl rosaniline, and 

 diethyl or diamyl rosaniline. 



Cherpin's aniline green is formed by heating 

 aldehyde (see CHEMISTRY) with sulphate of rosan- 

 iline ; its composition is represented by the formula 



^22^27 N 3 SjjO. 



Aniline yellow or aurine is the hydrochlorate 

 of a base called chrysaniline. The formula of the 

 base is C 20 H 17 N 3 ; it is obtained from the residues 

 of the manufacture of rosaniline. 



Phenol or carbolic acid is obtained from that 

 part of the oil of coal-tar which distils over after 

 the benzoL Commercial phenol is a mixture of 

 phenol (C 6 H 6 O) and cresol (C 7 H 8 O). It is a white 

 crystalline substance ; unites with a small quantity 

 of water to form an oily liquid heavier than water ; 

 it is slightly soluble in water, and smells like 

 creosote. 



The following colouring-matters have been 

 prepared from phenol : Picric acid. Strong nitric 

 acid converts phenol and cresol into trinitrophenol 

 (or picric acid) and trinitrocresol respectively 

 (C 6 H fl O + 3 .HN0 3 = C 6 H s (NO s )sO + 3H,O). 

 Picric acid is a bright yellow crystalline sub- 

 stance, and is used for dyeing wool and silk. The 

 picrates, such as picrate of potash, C H,K(NO,) 3 O, 

 are very explosive substances. When picric acid 

 is heated with cyanide of potassium,a purple-brown 

 substance (isopurpurate of potash] is formed, which 

 is used as a brown dye. 



When carbolic acid, oxalic acid, and sulphuric 

 acid are heated together, a scarlet colouring- 

 matter, coralline or rosolic add (C SO H 16 O 3 ), is pro- 

 duced. 



Naphthaline (C, Hg) is a crystalline solid ob- 

 tained from oil of coal-tar. When treated with 

 nitric acid it yields nitronaphthaline (Ci H 7 NO,), 

 which can be converted by nascent hydrogen into 

 naphthylamine (C 10 H 7 NH S ). These products cor- 

 respond perfectly with benzol, nitrobenzol, and 



Ml 



