PERKIN ON THE ACTION OF CHLORIDE ETC. JV,-Nobe 011 the Action of Chloride of Lime on Aniline. By W. H. PERKIN, F.R.S. ABOUTtwelve years ago when studying the process of con-verting aniline into aniline purple by means of bichromate of potassium I very naturally made experiments also upon the oxidation of aniline by means of chloride of lime to see if the colour of the reaction pointed out by Runge was really due to aniline purple or not; but the result,s I obtained were of so decidedly negative a character t,hat I did not pursue t.he inquiry very far especially as my time was then much occupied. Two or three years after the aniline purple had been intro- duced commercially French manufacturers began to experiment upon this colouring matter and succeeded in preparing it by oxidizing aniline with chloride of lime.PERKIN ON THE ACTION OF This hct puzzled me very considerably but by following their process I found that they were correct and that aniline purple could be produced by iiieaiis of a salt of aniline and chloride of lime; but I was at that time uiialole to look more fully into the matter though I could not believe that my prc-vious conclusions were erroneous. Lat’elyI had the curiosity to repeat my original experiments and was pleased to find they gave confirmatory results. R uiig e it will be remembered designated aniline lqaiiol or blue oil on account of the blue reaction it gave wit’h chloride of lime. If this reaction be performed properly Run ge’s state- ment is found to be perfectly correct ; bnt if too much chloride of lime be employed brown products are likewise produced arid these when mixed with the blue give an impure purple colour.In makiiig thip experiment it is best to me a solution of hydrocli’lorate of aniline and a very dilute solution of chloride of lime adding the latter reagent in small quantities at a time ; by this mettiis a dark slightly opaque indigo coloured solution is obtained. The dull appearaiice of this solution is due to tlie presence of suspended colouring matter and if it be niixed with about its own bulk of alcohol it becomes perfectly clear and of a bright blue COIOU~’ like that of ammoniacnl sulpliate of copper but in no way similar to that of aniline purple. I have made a few experiments for the purpose of isolating this blue colouring matter and have succeeded tolerably well.If a large qiiantity of a cold dilute solution of liydroclilorate of aniline be treated with a very dilute solution of chloride of lime so as to produce as much of the blue product as possible and then saturated with chloride of sodium the colouring matter is precipitated and may be collected upon a filter. This product is of a black colour and very impure; when pressed it forms it soft pitchy mass. It may be purified however by treatment with cold ether or benzol which removes brown resinous bodies. The product thus obtained dissolves in alcohol producing a very fine blue solution. I therefore propose to call it Runge’s blue. Its solution when evaporated on a glass plate leaves the colouring matter with a coppery coloured surf‘we.Runge’s Flue is the salt of an organic base possessing properties quite different from thoae of mauveine The blue CHLORIDE OF LIME ON ANILINE. alcoholic solution when mixed with hydrate of potassium changes to a reddish brown colour but is reconverted into blue by the addition of an acid. An alcoholic solutioii of a salt of mauveine when treated with caustic alkali gives a violet reaction. The sulphate of this blue colouring matter appears to be difficultly soluble in water. The instability of this product has prevented me from getting it into a aufficiently pure state for analysis. Runge’s blue dyes silk of a blue or blue violet shade but does not possess such an affinity for this material as a salt of mauveine.It will be asked-if a solution of hpdrochlorate of aniline produce Ittunge’s blue with chloride of lime how is it that manufacturers produce aniline purple with the same reagent? The answer to this is that the manufacturer goes a step fur- ther and boils his product. I find that an alcoholic solution of Runge’s blue when heated rapidly decomposes with formation of aniline purple which may be obtained in crystals upon the addition of a little sulphuric acid. This change likewise takes place in the cold after the lapse of twenty-four hours. This decomposition can very well be shown by dyeing a piece of woven silk with Runge’s blue and then exposing it in parts to the action of steam when the parts so treated will change in colour from blue to that of aniline purple. Exposure to heat will also produce the same result. Therefore Rung e’s reaction does not produce aniline purple but a blue colouring matter which decomposes when heated yielding a salt of mauveine.