102 British Association.-The President's Address. be regarded as in any way hostile to the literary studies,, and especially to the ancient classical studies, which have always been so carefully cherished at Oxford. If, indeed, there were any such risk, few would hesitate to exclaim― Let science shift elsewhere for herself, and let literature and philosophy find shelter in Oxford! But there is no ground for any such anxiety. Literature and science, philosophy and art, when properly cultivated, far from opposing, will mutually aid one another. There will be ample room for all, and, by judicious arrangements, all may receive the attention they deserve. A University, or Studium Generale, ought to embrace in its arrangements the whole circle of studies which involve the material interests of society, as well as those which cultivate intellectual refinement. The industries of the country should look to the Universities for the development of the principles of applied as well as of abstract science; and in this respect no institutions have ever had so grand a possession within easy reach as have the universities of England at this conjuncture, if only they have the courage to seize it. With their historic reputation, their collegiate endowments, their commanding influence, Oxford and Cambridge should continue to be all that they now are; but they should, moreover, attract to their lecture halls and working cabinets students in large numbers preparing for the higher industrial pursuits of the country. The great physical laboratory in Cambridge, founded and equipped by the noble representative of the House of Cavendish, has in this respect a peculiar significance, and is an important step in the direction I have indicated. But a small number only of those for whom this temple of science is designed are now to be found in Cambridge. It remains for the University to perform its part, and to widen its portals so that the nation at large may reap the advantage of this well-timed foundation. If the Universities, in accordance with the spirit of their statutes, or at least of ancient usage, would demand from the candidates for some of the higher degrees proof of original powers of investigation, they would give an important stimulus to the cultivation of science. The example of many Continental Universities, and among others of the venerable University of Leyden, may here be mentioned. Two proof essays recently written for the degree of Doctor of Science in Leyden, one by Van der Waals, the other by Lorenz, are works of unusual merit; and another pupil of Professor Rijke is now engaged in an elaborate experimental research as a qualification for the same degree. The endowment of a body of scientific men devoted exclusively to original research, without the duty of teaching or other occupation, has of late been strongly advocated in this country; and M. Fremy has given the weight of his high authority to a somewhat similar proposal for the encouragement of research in France. I will not attempt to discuss the subject as a national question, the more so as after having given the proposal the most careful consideration in my power, and turned it round on every side, I have failed to discover how it could be worked so as to secure the end in view. But whatever may be said in favour of the endowment of pure research as a national question, the Universities ought surely never to be asked to give their aid to a measure which would separate the higher intellects of the country from the flower of its youth. It is only through the influence of original minds that any great or enduring impression can be produced on the hopeful student. With out original power, and the habit of exercising it, you may have an able instructor, but you cannot have a great teacher. No man can be expected to train others in habits of observation and thought he has never acquired himself. In every age of the world the great schools of learning have, as in Athens of old, gathered around great and original minds, and never more conspicuously than in the modern schools of chemistry, which reflected the genius of Liebig, Wöhler, Bunsen, and Hofmann. These schools have been nurseries of original research as well as models CHEMICAL NEWS, of scientific teaching; and students attracted to them from Ipsa suis pollens opibus, nil indiga nostri? But while the Universities ought not to apply their resources in support of a measure which would render their teaching ineffective, and would at the same time dry up the springs of intellectual growth, they ought to admit freely to university positions men of high repute from other universities, and even without academic qualifications. An honorary degree does not necessarily imply a university education; but it if have any meaning at all, it implies that he who has obtained it is at least on a level with the ordinary graduate, and should be eligible to university positions of the highest trust. Not less important would it be for the encouragement of learning throughout the country that the English Universities, remembering that they were founded for the same objects, and derive their authority from a common source, should be prepared to recognise the ancient Universities of Scotland as freely as they have always recognised the Elizabethan University of Dublin. Such a measure would invigorate the whole university system of the country more than any other I can think of. It would lead to the strengthening of the literary element in the northern, and of the practical element in the southern universities, and it would bring the highest teaching of the country everywhere more fully into harmony with the requirements of the times in which we live. As an indirect result, it could not fail to give a powerful impulse to literary pursuits as well as to scientific investigations. Professors would be promoted from smaller positions in one university to higher positions in another, after they had given proofs of industry and ability; and stagnation, hurtful alike to professorial and professional life, would be effectually prevented. If this union were established among the old universities, and if at the same time a new university (as I myself ten years ago earnestly proposed) were founded on sound principles amidst the great populations of Lancashire and Yorkshire, the university system of the country would gradually receive a large and useful extension, and, without losing any of its present valuable characteristics, would become more intimately related than hitherto with those great industries upon which mainly depend the strength and wealth of the nation. It may perhaps appear to many a paradoxical assertion to maintain that the industries of the country should look to the calm and serene regions of Oxford and Cambridge for help in the troublous times of which we have now a sharp and severe note of warning. But I have not spoken on light grounds, nor without due consideration. If Great Britain is to retain the commanding position she has so long occupied in skilled manufacture, the easy ways which (owing partly to the high qualities of her people, partly to the advantages of her insular position and mineral wealth) have sufficed for the past will not be found to suffice for the future. The highest training which can be brought to bear on practical science will be imperatively required; and it will be a fatal policy if that training is to be sought for in foreign lands because it cannot be obtained at home. The country which depends unduly on the stranger for the education of its skilled men, or neglects in its highest places this primary duty, may expect to find the demand for such skill gradually to pass away, and along with it the industry for which it was wanted. I do not claim for scientific education more than it will accomplish, nor can it ever replace the after-training of the workshop or factory. Rare and powerful minds have, it is true, often been independent of it; but high education CHEMICAL NEWS, Sept. 8, 1876. British Association.-The President's Address. always gives an enormous advantage to the country where it prevails. Let no one suppose I am now referring to elementary instruction, and much less to the active work which is going on everywhere around us, in preparing for examinations of all kinds. These things are all very useful in their way, but it is not by them alone that the practical arts are to be sustained in the country. It is by education in its highest sense, based on a broad scientific foundation, and leading to the application of science to practical purposes-in itself one of the noblest pursuits of the human mind-that this result is to be reached. That education of this kind can be most effectively given in a university, or in an institution like the Polytechnic School of Zürich, which differs from the scientific side of a university only in name, and to a large extent supplements the teaching of an actual university, I am firmly convinced; and for this reason, among others, I have always deemed the establishment in this country of Examining Boards with the power of granting degrees, but with none of the higher and more important functions of a university, to have been a measure of questionable utility. It is to Oxford and Cambridge, widely extended as they can readily be, that the country should chiefly look for the development of practical science; they have abundant resources for the task, and if they wish to secure and strengthen their lofty position, they can do it in no way so effectually as by showing that in a green old age they preserve the vigour and elasticity of youth. | 103 been kept steadily in view by this Association, and the valuable Reports, which are a monument to the industry and zeal of its members, embrace every part of the domain of science. It is with the greater confidence, therefore, that I have ventured to suggest from this Chair that no partition-wall should anywhere be raised up between pure and applied science. The same sentiment animates our vigorous ally, the French Association for the Advancement of Science, which rivalling, as it already does, this Association in the high scientific character of its proceedings, bids fair in a few years to call forth the same interest in science and its results, throughout the great provincial towns of France, which the British Association may justly claim to have already effected in this country. No better proof can be given of the wide base upon which the French Association rests than the fact that it was presided over last year by an able representative of commerce and industry, and this year by one who has long held an exalted position in the world of science, and has now the rare distinction of representing in her historic Academies the literature as well as the science of France. Whatever be the result of our efforts to advance science and industry, it requires no gift of prophecy to declare that the boundless resources which the supreme Author and Upholder of the Universe has provided for the use of man will, as time rolls on, be more and more fully applied to the improvement of the physical-and, through the improvement of the physical, to the elevation af the moral-condition of the human family. Unless, however, the history of the future of our race be wholly at variance with the history of the past, the progress of mankind will be marked by alternate periods of activity and repose; nor will it be the work of any one nation or of any one race. To the erection of the edifice of civilised life, as it now exists, all the higher races of the world have contributed; and if the balance were accurately struck, the claims of Asia for her portion of the work would be immense, and those of Northern Africa not insignificant. Steam-power has of late years produced greater changes than probably ever occurred before in so short a time. But the resources of Nature are not confined to steam, nor to the combustion of coal. The steady water-wheel and the rapid turbine are more perfect machines than the stationary steam-engine; and glacier-fed rivers with natural reservoirs, if fully turned to account, would supply an unlimited and nearly constant source of power depending solely for its continuance upon solar heat. But no immediate dislocation of industry is to be feared, although the turbine is already at work on the Rhine and the Rhone. In the struggle to maintain their in-high position in science and its applications, the countrymen of Newton and Watt will have no ground for alarm so long as they hold fast to their old traditions, and remember that the greatest nations have fallen when they relaxed in those habits of intelligent and steady industry upon which all permanent success depends. If any are disposed to think that I have been carrying this meeting into dream-land, let them pause and listen to the result of similar efforts to those I have been advocating, undertaken by a neighbouring country when on the verge of ruin, and steadily pursued by the same country in the climax of its prosperity. "The University of Berlin," to use the words of Hofmann, "like her sister of Bonn, is a creation of our century. It was founded in the year 1810, at a period when the pressure of foreign domination weighed almost insupportably on Prussia; and it will ever remain significant of the direction of the German mind that the great men of that time should have hoped to develop, by high intellectual training, the forces necessary for the regeneration of their country." It is not for me, especially in this place, to dwell upon the great strides which Northern Germany has made of late years in some of the largest branches of industry, and particularly in those which give a free scope for the application of scientific skill. "Let us not suppose," says M. Wurtz in his recent Report on the Artificial Dyes, "that the distance is so great between theory and its industrial applications. This report would have been written in vain, if it had not brought clearly into view the immense influence of pure science upon the progress of dustry. If unfortunately the sacred flame of science should burn dimly or be extinguished, the practical arts would soon fall into rapid decay. The outlay which is incurred by any country for the promotion of science and of high instruction will yield a certain return; and Germany has not had long to wait for the ingathering of the fruits of her far-sighted policy. Thirty or forty years ago industry could scarcely be said to exist there; it is now widely spread and successful." As an illustration of the truth of these remarks I may refer to the newest of European industries, but one which in a short space of time has obtained considerable magnitude. It appears (and I make the statement on the authority of M. Wurtz) that the artificial dyes produced last year in Germany exceeded in value those of all the rest of Europe, including England and France. Yet Germany has no special advantage for this manufacture except the training of her practical chemists. We are not, it is true, to attach undue importance to a single case; but the rapid growth of other and larger industries points in the same direction, and will, I trust, secure some consideration for the suggestions I have ventured to make. The intimate relations which exist between abstract science and its applications to the uses of life have always At the conclusion of the Address the DUKE OF ARGYLL said-I rise for the purpose of asking you to record a vote of earnest and hearty thanks to our distinguished President for the most able and instructive Address which he has just delivered. The President has modestly called a great part of his Address a brief review of the recent triumphs of science. No one knows better than our distinguished President the utter impossibility, within the short space to which a presidential address is necessarily confined, of giving an adequate idea of the immense activities of modern science. But those who look carefully over this review, slight as the sketch may be held to be, will see that it is a sketch drawn by a master hand. It gave us a few points, but they are the salient points of recent discovery; they were told in close connection with each other, and above all they were told in that most valuable of all connections in relation to our duty as members of the 104 British Association.-Mr. Perkin's Address. British Association-in the connection between that which has been already done and that which it still remains to do. There was one very remarkable passage of our President's Address-I do not know whether it has attracted your attention as much as it attracted mine-in which he referred, lightly indeed, but significantly, to a notion that there is at present a danger of decline in the scientific activities of England, and, he added, that the periods of great intellectual activity in the human mind are almost always short. This may be true, and I am inclined to think that if the remark is applied to literature it is true, but my own impression is that as applied to science it is not true. We are at the present moment living in a golden age of scientific inquiry. As regards literature, it was only last week that I had the opportunity of conversing on the subject with a most distinguished man, who perhaps among many others was most able to appreciate the matter of which he spoke, and he gave it as his impression that as regards literature and philosophy there was a marked decline in eminence and ability, and certainly if we compare the state of literature now with the burst of genius which illustrated the close of last century and the first twenty-five years of the present we may be inclined to come to that conclusion, for where is the galaxy that will compare with Burns, Scott, Wordsworth, Southey, and Campbell? But when we come to science I rejoice to think that the contrast is remarkable indeed. Let me just remind this great assembly of the names of the living, and the men who have lately left us. In geology we have names-the grave has only just closed over them-the names of Murchison and Sedgwick, of a Lyell and Phillips; and I need hardly say that in those we have a group of names in whose powerful hands a branch of inquiry which but a few years ago was a ridicule and a discredit has risen to be one of the most popular and most certain sciences which illustrate the progress of the human mind. Then, again, physics. It is not very long ago that we had Faraday, and I rejoice to say we have still yourself, Mr. President. Again, in natural history we have Darwin and Walton, and even those who may not accept and I am one of those who do not accept the special theory of Mr. Darwin as a satisfactory explanation of the deepest mystery of nature,—namely, the history of creation. Even those who do not accept that theory must admit that Mr. Darwin stands Ar among the naturalists of the world. So, also, in comparative anatomy. On this platform, in all these departments of science we have assembled to-night men whom I do not name because they are present, and because they are personal friends of many of us, but whose names will be a household word in every home of science during generations which are yet unborn. Therefore, I repeat, we have no reason to fear any decline in intellectual activity so far as the discoveries and progress of science are concerned; and this brings me to another observation of the President's, to which I confess I attach special value. I thank you for the wise and weighty words which you have spoken upon the vexed question of the endowment of research. I sometimes wonder if those who call for the endowment of research have ever thought what real scientific research is. You may pay and pension men for the mere collecting and assorting of dry facts, but you cannot command by your pensions or emoluments that fire of genius, that intuition of the mind, which is the secret of all true and real scientific research. I should deeply deplore to see the day when scientific research was to depend for its appointments and the selection of its favourites upon any Minister or any Government. There is, indeed, another department of the endowment of research in which I think it may take a powerful and useful part, and I cannot illustrate that department better_than_ by referring to the fitting out of th: "Challenger" Expedition. You all know that my hon. friend and former colleague, Mr. Robert Lowe, was considered one of the hardest-fisted Chancellors of the Exchequer who ever filled the office, but he has a highly CHEMICAL NEWS, Sept. 8, 1876. educated mind. He knows as well as any man the things which private enterprise should be expected to undertake and what individual means cannot accomplish, and therefore he at once assented to the sending out of that great expedition, which, I believe, will be found to have added immensely to our knowledge of the secrets of nature. There is only one other observation in your Address, Mr. President, to which I would direct the attention of this meeting before I move the resolution of thanks, and it was that passage in which you spoke of there being no wall of partition between abstract and applied sciences-do not let us ever quit hold of the ground that the true spirit of science is to be found in the love of knowledge for its own sake. Applications are sure to follow applications infinitely greater in number and amount than any human imagination could conceive beforehand; but we pursue science for its own sake, thankful and grateful for the benefits to mankind which it scatters around with so lavish a hand. And let me say, Mr. President, you might have added, let there be no wall of partition between science strictly so-called and speculative philosophy. I am sure you will be inclined to agree with me when I say that one of the dangers of our modern science, arising from its very vitality and spirit and energy and growth, is the tendency to let speculation outrun knowledge. But the remedy for this is not to bar the way against abstract speculation of any kind, not to forbid or ostracise it in our halls of science, but rather to encourage it, and to remind scientific men, to remind ourselves, and to remind the world that after all our discoveries how very little our knowledge is; and where science has discovered this she will recognise her proper sphere, and philosophy will be chastened and subdued. The noble Duke concluded by moving the thanks of the Association to their distinguished President for his admirable Address. The motion was seconded by SIR WM. THOMSON, and was carried by acclamation. ADDRESS TO THE CHEMICAL SECTION BY WILLIAM HENRY PERKIN, F.R.S., President of the Section. THERE can be no doubt that chemistry and the allied sciences are now being recognised to a much greater extent in this country than in former years; and not only so, the workers at research, though still small in number, are more numerous than they were. In 1868 Dr. Frankland, in his Address to this Section at the Meeting at Norwich, commented upon the small amount of original research then being carried on in the United Kingdom; but, judging from the statistics of the Chemical Society, this state of things became even worse, for in 1868 there were forty-eight papers read before the Society, but in 1872 only twenty-two. Since then, however, there has been a considerable increase in the number; and at the Anniversary Meeting in March last it was shown that the number of communications for the Session had risen to sixty-six, or three times as many as in 1872. Of course these figures only refer to the Chemical Society, but I think they may be taken as a very safe criterion of the improved state of things, though it would be very gratifying to see much greater activity. It is also very pleasing to find that the aids to and opportunities for research are increasing, because it must be remembered that, in a pecuniary sense, science is far from being its own rewarder at the time its truths are being studied, although the results very often become eventually of the greatest practical value; hence the wisdom of a country encouraging scientific research. CHEMICAL NEWS, Sept. 8, 1876. British Association.—Mr. Perkin's Address. But little, however, has been done in this direction in past years the grants made for general science by this Association, and that of the Government of one thousand pounds annually to the Royal Society, being the most important. The Chemical Society has also been in the habit of giving small grants for the purpose of assisting those engaged in chemical research. In the future, however, it will be able to do much more than hitherto. One of the original members of the Society, Dr. Longstaff, offered in the early part of the year to give one thousand pounds provided a similar sum could be raised, the united amount to be invested and the interest applied for the encouragement of research. I am happy to say that rather more than the required sum has been raised, and it is hoped that it may be still further supplemented. In addition to the Royal Society grant, the Government have given this year a further annual sum of four thousand pounds. Of course this is for science generally. 105 It was in 1825 that Faraday published, in the Philosophical Transactions, his 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 Bicarburetted Hydrogen. Mitscherlich some years afterwards obtained the same substance 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 nitro-compound in 1841; and Hofmann and Muspratt obtained from this "toluidine," by the process used by Zinin to reduce nitrobenzol. Mr. T. J. Phillips Jodrell has also placed at the disposal of the Royal Society the munificent sum of six thousand pounds, to be applied in any manner that they may consider for the time being most conducive to the encourage-which were then practically useless, are the basis of the ment of research in physical sciences. When we consider how much of our science is of a physical nature we must be grateful for this bequest; and it is to be hoped that these helps will more and more stimulate research in the United Kingdom; and if we have any hope of keeping pace with the large amount of work now being carried on in other countries, we must indeed be energetic. The employment of well-trained chemists in chemical works is now becoming much more general than heretofore, especially on the Continent, where in some cases a considerable staff is employed and provided with suitable appliances, for the purpose not only of attending to and perfecting the ordinary operations which are in use, but to make investigations in relation to the class of manufacture they are engaged in. A conviction of the necessity of this is gaining strength in this country, though not so quickly as might be desired; nevertheless these things are encouraging. With reference to the progress of chemistry and what have been the fruits of research of late years, it will be impossible for me to give even a general outline, the amount of work being so large; in fact, to recount the list of investigations made during the past year would take up most of the time at my disposal. 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 extent and diversity, I propose to refer to some of the practical results which have already accrued from Organic Chemistry, as a plea for the encouragement of research; and those I intend to speak of are of special interest also on account of their close connection 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 purple; " and it may be of interest to state that it was in Scotland, in the autumn of the same year, that the first experiments upon the application of this dye to the arts of dyeing 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 colouring-matters capable of producing not only all the colours of the rainbow, but their combinations. I wish, however, to briefly refer to the date and origin of the products which have served to build up this great industry. I might mention other names in connection with these substances, such as Runge and Unverdorben; but I would now ask, Did any of these chemists make these investigations with the hope of gain? was it not rather from the love of research, and that alone? and now these products, 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, as in the cases 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 futher 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, had 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 anthracen, a coal-tar product differing from benzol and toluol in physical characters, inasmuch as it is a magnificent crystalline solid. The first colouring-matter derived from anthracen 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 naphthalin, inasmuch as phthalic acid can be produced from both of them; and many were the experiments made by chemists in this direction; it was not, however, until 1868 that this was proved to be a mistake, and its relationship to anthracen was discovered by Graebe and Liebermann, who succeeded in preparing this coal-tar product from the natural alizarin itself. Having obtained this important result, they turned their attention further to the subject, hoping to find some process by which alizarin could be produced from anthracen; in this they were soon successful. The discovery of the artificial formation of alizarin was of great interest, inasmuch as it was another of those instances which have of late years become so numerous, namely, the formation of a vegetable product artificially; but the process used by Graebe and Liebermann was of little practical value, because too expensive for practical purposes. 106 British Association.—Mr. Perkin's Address. Having previously worked on anthracen derivatives, it occurred to me to make some experiments on this subject, which resulted in the discovery of a process by which the colouring-matter could be economically produced on a large scale. Messrs. Caro, Graebe, and Liebermann about the same time obtained similar results in Germany; this was in 1869. Further investigation during that year yielded me a new process, by which "dichloranthracen" could be used in place of the more costly product anthraquinon, which was required by the original processes. I mention this, as most of the artificial alizarin used in this country up to the end of 1873, and a good deal since, has been prepared by this new process. It was observed that when commercial artificial alizarin prepared from anthraquinon, but more especially from dichloranthracen, was used for dyeing, the colours produced differed from those dyed with madder or pure alizarin; and many persons therefore concluded that the artificial colouring-matter was not alizarin at all. This question, however, was set at rest by separating out the pure artificial alizarin from the commercial product and comparing it with the natural alizarin, when it was found to produce exactly the same colours on mordanted fabrics, to have the same composition, to give the same reactions with reagents, and to yield the same products on oxidation. But whilst examining into this subject it was found that a second colouring-matter was present in the commercial product, and in somewhat large quantities, especially when dichloranthracen had been employed in its preparation; and to this was due the difference in shade of colour referred to. This substance, when investigated, was found to have the same composition as "purpurin," also a colouringmatter found in madder, but of very little value on account of the looseness and dulness of some of the colours it produces. This new substance, being derived from anthracen, was named anthrapurpurin; unlike its isomer purpurin, however, it is of great value as a colouringmatter. I do not think I shall be going beyond the results of experience if I say it is of as great importance as alizarin itself; with alumina mordants it produces reds of a more scarlet or fiery red than those from alizarin. In fact, so fine are the colours produced that, with ordinary alumina mordants on unoiled cotton, it gives results nearly equal in brilliancy to Turkey-red produced with madder or garancin; and I believe the rapid success of artificial alizarin was greatly due to its presence. Most of that consumed at first was for Turkey-red dyeing; and the colours were so clear that it was mostly used in combination with madder or garancin, to brighten up the colours produced by these natural products. The purple colours anthrapurpurin produces with iron mordants are bluer in shade than those of alizarin, and the blacks are very intense. Its application is practically the same as alizarin, so that they can be used in combina tion. As already noticed, the commercial product called "artificial alizarin "first supplied to the consumer was always a mixture of alizarin and anthrapurpurin; and various mixtures of these two colouring-matters are still sent into the market; but, owing to the investigations that have been made and the study and attention that has been given to it by manufacturers, nearly pure alizarin and anthrapurpurin are also sent into the market-the first being known as "blue-shade alizarin," and the second as red or "scarlet alizarin." The formation of anthrapurpurin in the manufacture of alizarin may to some extent be said to have arisen from a want of knowledge of the true conditions required for the production of the latter. It is now well known that alizarin is a dioxyanthraquinon, or, in other words, anthraquinon in which two atoms of hydrogen are replaced by hydroxyl. CHE MICAL NEWS, Sept. 8, 1876. If we want to introduce hydroxyl into a compound, there are several processes which can be used; but I will only refer to those connected with the history of this colouring-matter. The first process which I will refer to has been used by chemists for a long period. It consists in first replacing the hydrogen by bromine, and then treating the resulting body with potassic or other metallic hydrate; and according as one, two, or more atoms of hydrogen have been replaced by the bromine, so on its removal by the metal of the metallic hydrate, a compound containing a corresponding number of atoms of hydrogen replaced by hydroxyl is obtained. Graebe and Liebermann acted upon this principle in their experiments on the artificial formation of alizarin; and as it was necessary to replace two atoms of hydrogen in anthraquinon, they first of all prepared a dibrominated derivative, called dibromanthraquinon, C14H6Bг2O2. By decomposing this with potassic hydrate at a high temperature, they obtained a violet-coloured product, which, when acidified to remove the alkali, gave a yellow precipitate of alizarin, C14H6(HO)2O2. The second process I wish to speak of for the replacement of hydrogen by hydroxyl in a compound is by converting it into a sulpho-acid (usually by means of sulphuric acid) and subsequently decomposing this with potassic or other hydrate; and, according as a mono- or disulphoacid is employed, it yields on decomposition a compound with one or two atoms of hydrogen replaced by hydroxyl. The discovery of sulpho-acids of anthraquinon, and their use in place of the brominated derivative originally employed by Graebe and Liebermann, constituted the great improvement in the manufacture of alizarin already referred to. From what has just been stated, it was naturally supposed that a disulpho-acid of anthraquinon would be required to produce alizarin, and this was believed to be the case for some time; but further experiments have proved it to be a mistake, and shown that the mono-sulpho acid is required to produce alizarin, the disulpho-acid yielding anthrapurpurin. But how are we to explain this apparent anomaly? It would take up too much time to enter into a discussion respecting the constitution of the sulpho-acids of anthraquinon in reference to the position of the HSO3 groups. I will therefore confine my remarks to their decomposiMonosulphoanthraquinonic acid, tion. |