56 REPORT 18*6. 



Amongst the most interesting, perhaps, are those relating to isomerism, especially 

 in the aromatic series of organic bodies ; and it is probable that a more intimate 

 knowledge of this subject will be found of really practical value. 



As I am unable to give an account of the worK done during the past year on 

 account of its quantity and diversity, I propose to refer to some of the practical results 

 which have already accrued from Org-anic Chemistry, as a plea for the encourage- 

 ment of research ; and those I intend to speak of are of special interest also on 

 account of their close connexion with the textile manufactures of Great Britain. I 

 need scarcely say I refer to the colouring-matters which have been obtained from 

 the products found in tar. 



It was in 1856, now twenty years since, that this industry was commenced by 

 the discovery of the "mauve" or "aniline pm-ple;" and it may be of interest to 

 state that it was in Scotland, in the autumn of the same year, that the first experi- 

 ments upon the application of this dye to the arts of dj'eing and calico-printing 

 were made, at Perth and Maryhill. 



I need scarcely remind you of the wonderful development of this industry since 

 then, seeing we now have from the same source colourmg-matters capable of pro- 

 ducing not only all the colours of the rainbow, but their combinations. I wish, 

 however, to brieily refer to the date and origin of the products which have 

 served to build tip this great industrj\ 



It was in 1825 that Faraday published in the ' Philosophical Transactions ' hia 

 research on the oily products separated in compressing oil-gas, and described a 

 substance he obtained from it^a volatile colourless oil, which he called Bicar- 

 buretted Hydrogen. Mitscherlich some years afterwards obtained the same sub- 

 stance from benzoic acid, and gave it the name it bears, viz. " Benzol." This same 

 chemist further obtained from benzol nitrobenzol, by acting upon it with nitric 

 acid. Zinin afterwards studied the action of reducing agents upon nitrobenzol, and 

 obtained "aniline," which he at that time called Benzidam. 



Again, Pelletier and Walter discovered the hydrocarbon toluol in 1837. Deville 

 produced its uitro-compound in 1841 ; and Hofmann and Muspratt obtained from 

 this "toluidine," by the process used by Zinin to reduce nitrobenzol. 



I might mention other names in connexion with these substances, such as Eunge 

 and Unverdorben ; but I would now ask, did any of these chemists make these 

 investigations with the hope of gain ? was it not rather ti-om the love of research, 

 and that alone ? and now these products, which were then practically useless, are 

 the basis of the aniline colours. But to go further : Doebereiner a long while ago 

 obtained from alcohol a substance which he called "light oxygen ether," now 

 known as aldehyd. Gay-Lussac produced iodide of ethyl in 1815. Dumas and 

 Peligot discovered the corresponding substance iodide of methyl in 1835 ; but, aa 

 in the cases I have previously referred to, these bodies had no practical value and 

 were never prepared but in the laboratory. Hofmann, in his researches on the 

 molecular constitution of the volatile organic bases, discovered in 1850 the 

 replacement compounds of aniline containing alcohol radicals. 



All these compounds have now been manufactured on the large scale and used 

 in the further development of the industry of these artificial colouring-matters. 



Other substances might be mentioned ; but I think these are sufficient to show 

 how the products of research which, when first discovered and for a long period 

 afterwards, were of only scientific interest, at last became of great practical value ; 

 and it is evident that, liad not the investigations and discoveries I have referred to 

 been made as they were solely from a love of science, no aniline colours would 

 now be known. 



The colouring-matters I have hitherto spoken of are nitrogenous, and derived 

 from benzol and its homologues. There are a few others, however, of the same 

 origin which contain no nitrogen ; but they are of secondary importance. 



I now pass on to another class of colouring-matter, which is obtained from 

 anthracene, a coal-tar product diflering from benzol and toluol in physical cha- 

 racters, inasmuch as it is a magnificent crystalline solid. 



The first colouring-matter derived from anthracene which I wish to draw your 

 attention to is alizarin, the principal dyeing agent found in madder-root. This 

 substance was for a long time supposed to be related to naphthaline, inasmuch as 



