566 CONSIDERATION OF CARBON COMPOUNDS. 



sprinkled upon concentrated sulphuric acid produces a bright-red 

 color. 



Compound acetanilide powder, Pulvis acetanilidi compositus, is 

 a mixture of 70 parts of acetanilide, 10 parts of caffeine, and 20 parts of sodium 

 bicarbonate. It is one form of the numerous headache powders in the market, 

 in which acetanilide, the cheapest of the common antipyretics, is a common con- 

 stituent. Sodium bicarbonate increases the solubility of the acetanilide. 



Methyl acetanilide C 6 H 5 .N.CH 3 .C 2 H 3 0, (Exalgin], may be made by the 

 acetylating of monomethyl-aniline. It occurs as a crystalline powder or in 

 large crystalline needles ; it is tasteless and almost insoluble in water. 



Sulphanilic acid, Amline-para-sulphonic acid, C8H 4 .NH,.S0 3 H. Obtained 

 by heating 1 part of pure aniline oil with 2 parts of fuming sulphuric acid, 

 and purifying the product by crystallization. 



C 6 H 5 .NH 2 + H 2 SO, = C 6 H 4 .NH 2 .SO 3 H + H 2 O. 



It is a colorless crystalline substance, soluble in 182 parts of cold water. 

 When sulphanilic acid is acted upon by nitrous acid, it is converted into diazo- 

 benzol-sulphonic acid, C 6 H 4 N.N.SO 3 , which is of interest because it is used as a 

 reagent in Ehrlich's diazo-reaction in urinary analysis. 



Diphenyl-amine, (C 6 H 5 ) 2 NH, is obtained by the destructive distillation of 

 triphenyl-rosaniline (aniline-blue) as a grayish crystalline substance, slightly 

 soluble in water, more soluble in acids. A 0.2 per cent, solution in diluted 

 sulphuric acid (forming diphenylainine sulphuric acid) is colored intensely 

 blue by nitric acid; also, temporarily by nitrous acid and, somewhat less 

 intensely, by hypochlorous, bromic, and iodic acids, and a number of other 

 oxidizing agents. 



Diamino-benzene, Meta-phenylene-diamine, CgH^NHa^, is obtained by 

 the reduction of meta-dinitro-benzene as a grayish crystalline powder. It has 

 strongly basic properties, is somewhat soluble in water, readily soluble in alco- 

 hol or ether. It is a valuable reagent for nitrites, as it forms, with even traces 

 of nitrous acid, an intense yellow color. 



Methylthionine hydro chloride, Methylthioninae hydrochlori- 

 dum, C 16 H 18 N 3 SC1 = 317.36 (Methylene blue). This is a very complex 

 dye obtained by treating dimethyl-paraphenylene-diamine, C 6 H 4 .- 

 (NH 2 )N(CH 3 ) 2 , in hydrochloric acid solution with hydrogen sulphide 

 and subsequently with ferric chloride. It occurs as a dark-green 

 powder or in prismatic crystals having a bronze-like lustre, readily 

 soluble in water and somewhat less so in alcohol, giving solutions of 

 a deep-blue color. Alkalies change the color of the aqueous solution 

 to a purplish shade, and in excess cause a precipitate of a dull-violet 

 color. It is incompatible with potassium iodide, and reducing agents 

 decolorize it. 



