434 



NATURE 



\Sept. 14, 1876 



reducing action which has resulted in an increased yield of 

 colouring-matter, the percentage obtahied .being now not very 

 much below the theoretical quantity. _ _ 



When the process for making commercial artificial alizarm by 

 treating anthraquinone with sulphuric acid was first adopted, the 

 product from that treatment was a mixture of the mono- and 

 disulpho-acids of anthraquinone. Consequently the colouring- 

 matter prepared in this manner was a mixture of alizarin and 

 anthrapurpurin ; and the reason why dichloranthracene, when 

 used in place of anthraquinone, yields a product very rich in 

 anthrapurpurin, is on account of the readiness with which it 

 forms a disulpho-acid of dichloranthracene which afterwards 

 changes into the disulpho-acid of anthraquinone. 



At°first it was supposed by many that the quantity of coal-tar 

 produced would not yield a sufficient supply of anthracene for 

 the manufacture of artificial alizarin. Experience has, however, 

 proved that this supposition was groundless, as now the supply 

 is greater than the demand. 



Moreover some very interesting experiments have lately been 

 made, by which anthraquinone and its derivatives have been 

 obtained without the use of anthracene. The most interesting 

 are those in which phthalic anhydride is employed with benzolic 

 derivatives ; for example, this anhydride gives with hydroquinone 

 a colouring-matter having the same composition, as well as most 

 of the other properties of alizarin. It is called quinizarin, 

 Baeyer and Caro have also obtained from phthalic anhydride and 

 phenol oxyanthraquinone ; and by using pyrocatechin in place of 

 phenol they got alizarin itself. 



Although these products have not been obtained in sufficient 

 quantities by these processes to be of any practical value, we do 

 not know what further research may do. Already one of the 

 substances used is being prepared on the large scale for the manu- 

 facture of that beautiful colouring-matter "cosine;" I refer to 

 phthalic anhydride. 



Now with reference to the origin of the products which are 

 used for the manufacture of artificial alizarin. We find the first 

 researches made in reference to anthracene were by Dumas and 

 Laurent in 1832 ; subsequently Laurent further worked upon 

 this subject, and obtained, by the oxidation of this hydrocarbon, 

 a substance which he called anthracenuse ; he also obtained 

 dichloranthracene. Dr. Anderson also made an investigation on 

 anthracene and its compounds in 1 863, and assigned to it its 

 correct formula ; he re-examined its oxidation product, which 

 Laurent called anthracenuse, and named it oxyanthracene, this 

 substance we now know as anthraquinone. 



All these substances were without any practical value until 

 1868 ; but we now find them of the greatest importance, and 

 used in very large quantities. 



But to bring out more clearly the practical importance of these 

 fruits of research, it will be well perhaps to see what has been 

 their influence on the colouring-matters which were in use before 

 them, and also the extent of their present consumption. 



The influence of the so-called aniline colours on the old colouring 

 matters, has been remarkably small. It is true that at first magenta 

 had a depreciating influence upon cochineal ; but this has passed 

 away, and now the consumption of that dye is as great as ever ; 

 certainly its price is much lower than it used to be ; but this is 

 due to a variety of causes, especially the great increase in the 

 cultivation of the insect at Teneriffe. And perhaps this want of 

 influence is not so very remarkable, when we consider the aniline 

 colours are entirely new products, differing in composition and 

 properties from the old colouring-matters, &c., and therefore 

 could only displace them to a certain extent. 



But whilst this is the case the aniline colours have been more 

 and more used, until at present it is computed that their annual 

 sale in the United Kingdom and on the Continent exceeds 

 2,000,000/. This is probably due to new applications and in- 

 crease of trade. 



When, however, we come to consider the influence of the 

 anthracene colours alizarin and anthrapurpurin, more generally 

 known as " artificial alizarin," we find we have a very different 

 tale to tell. 



Here, in the case of alizarin, we have a competition not between 

 two colouring-matters, but the same from different sources ; the 

 old source being madder-root, the new one coal-tar. And 

 when we introduce the consideration of anthrapurpurin, which 

 produces such magnificent reds, much brighter than alizarin or 

 ordinary purpurin, we see we have not only a replacement but 

 an improvement, so that these new colouring-matters throw the 

 pld ones into the shade. The products being purer, the clear- 



ing processes for goods dyed with them are also necessarily easier 

 and simpler. 



It will be interesting to examine into the statistics of the 

 madder and garancine trade in a brief manner, to see what has 

 been the influence of artificial alizarin on their consumption. 

 The following figures are mostly calculated from the Board of 

 Trade returns. 



During the ten years immediately preceding the introduction 

 of artificial alizarin the average annual imports of madder into 

 the United Kingdom were 15,292 tons, and of garancine 2,278 

 tons, Estimating the value of the former at 2/. zs. 6d., and the 

 latter at 8/. per cwt., which were about the average prices during 

 that period, the annual value in round numbers was about one 

 million sterling. 



The introduction of artificial alizarin has, however, so influ- 

 enced the value of madder that its price is now less than one- 

 half ; and thus a saving of over half a million sterling per annum 

 has been effected to the manfacturers of the United Kingdom, one 

 half of which may be put down to Glasgow. 



So much for its effect in reducing prices ; but what has been 

 its influence on the consumption of these dye-stuffs ? 



I have already stated the average quantity of these substances 

 imported per annum prior to the discovery of the artificial pro- 

 duct, and will now compare it with tlie imports of last year and 

 this. That for the present year of course is an estimated quan- 

 tity, and calculated from the returns for the first seven months. 



Average annual imports. 

 1859-1868. 1875. 1876. 



tons. tons. tons. 



Madder 15,292 



Garancine 2, 278 



5.014 

 1,293 



3,653 

 813 



These numbers speak for themselves. 



The money value, which was formerly 1,000,000/. per 

 annum, is now, calculating from the estimated quantity for 

 this year, only 138, 105?., say 140,000/. taking garancine at 

 4/. per cwt. and madder at i/. per cwt., prices slightly in excess 

 of their present value. 



At the present prices the cultivation of madder-roots is unre- 

 munerative, so that it is to be expected that madder growing will 

 soon be a thing of the past, thousands of acres of land being at 

 the same time liberated for the growth of those products we can- 

 not produce artificially, and without which we cannot exist. The 

 quantity of madder grown in all the madder-growing countries 

 of the world prior to 1868 was estimated to be 70,000 tons per 

 annum, and at the present time the artificial colour is manu- 

 factured to an extent equivalent to 50,000 tons, or more than 

 two-thirds of the quantity grown when its cultivation had reached 

 its highest point. 



I might have referred to other subiects besides the coal-tar 

 colours which have resulted from scientific research ; but I know 

 of no other of such interest and magnitude. From the brief 

 history I have given we see that the origin of these colouring 

 matters is entirely the fruit of many researches made quite inde- 

 pendently by different chemists, who worked at them without 

 any knowledge of their future importance ; and on looking at 

 the researches which have thus culminated in this industry, it is 

 interesting to notice that many, if not most of them, were con- 

 ducted for the purpose of elucidating some theoretical point. 



These facts certainly ought to be a great encouragement to 

 chemists, and stimulate them to greater activity. It would be 

 very pleasing to see more work emanating from the chemical 

 schools of the United Kingdom ; and I think no student should 

 consider his chemical curriculum finished until he has conducted 

 an original research. The knowledge obtained by a general 

 course of instruction is of course of very great value, but a good 

 deal of it is carried on by rule ; in research, however, we have 

 to depend upon the exercise of our judgment, and in fact of 

 all our faculties ; and a student having once conducted even 

 one investigation, under the guidance of an efficient director, 

 will find that he has acquired an amount ot experience and 

 knowledge which will be of the greatest value _to him after- 

 wards. 



It is hoped these remarks will encourage young chemists 

 patiently and earnestly to work at whatever subject they may un- 

 dertake, knowing that their results, although sometimes appa- 

 rently only of small interest, may contain the germ of some- 

 thing of great scientific or practical importance, or may, like a 

 keystone in an arch, complete some subject which before was 

 fragmentary and useless. 



