摘要:

MARCH, 1915. Val. XL., No. 468. THE ANALYST. PROCEEDINGS OF THE SOCIETY OF PUBLIC ANALYSTS AND OTHER ANALYTICAL CHEMISTS. THE annual general meeting of the Society was held on Wednesday evening, February 3, in the Chemical Society’s Rooms, Burlington House. The President, Mr. A. Chaston Chapman, F.I.C., occupied the chair. The minutes of the previous annual meeting were read and confirmed. Dr.J. T. Hewitt, F.R.S., and Dr. G. D. Lander were appointed sorutators of the ballot papers for election of Officers and Council for 1915. The HON. TREASURER presented the accounts of the Society for the year 1914, and votes of thanks were passed to the Hon. Treasurer, Hon. Secretaries, and Auditors. On the motion of the PRESIDENT, a vote of thanks was passed to the President and Council of the Chemical Society for their kindness in allowing the Society the use of their rooms at Burlington House during the year.Dr. H. P. Stevens and Mr, J. F. H. Gilbard were appointed Auditors of the Society’s accounts for 1915. The PRESIDENT delivered his annual address. Mr. L. ARCHBUTT moved that a hearty vote of thanks be accorded to the President for his address, and that his permission be asked to print the address in the ANALYST.Dr. DYER seconded, and the motion was carried by acclamation. The PREBIDENT, having received the report of the scrutators, announced the election of Officers and Council for 1915 in accordance with the Council’s nomina- tions, the list being as follows : President.-A. Chaston Chapman, F.I.C. Past-Presidents serving on the Council (limited by t b Society’s Articles of Association to eight in nu,mber).-L.Archbutt, F.I.C. ; Edward J. Bevan, F.I.C. ; Bernard Dyer, D.Sc,, F.I.C. ; Thomas Fairley, F.I.C. ; Otto Hehner, F.I.C. ; R. R76 PROCEEDINGS OF THE SOCIETY OF PUBLIC ANALYSTS Tatlock, F.I.C. ; E. W. Voelcker, A.R.S.M., F.I.C. ; J. Augustus Voelcker, M.A., B.Sc., Ph.D., F.I.C. Vice-Presidents.-J.H. B. Jenkins ; H. Droop Richmond, F.I.C. ; R. T. Thomson, F.I.C. Hon. Treasurer.-Edward Hinks, B.Sc., F.I.C. Hon. Secretaries.-P. A. Ellis Richards, F.I.C. ; E. Richards Bolton. Other Members of Council.-E. M. Chaplin, Ph.D., F.I.C. ; J. H. Coste, F.I.C. ; J. A. Dewhirst, F.I.C.; P. V. DuprB, A.C.G.I., F.I.C.; G. H. Gemmell, F.I.C.; R. G. Grimwood, F.I.C.; E. M. Hawkins, F.I.C.; C.A. Keane, D.Sc., Ph.D., F.I.C.; R. Lessing, Ph.D. ; L. Myddelton Nash, F.I.C. ; Thomas Tickle, B.Sc., F.I.C. ; W. Collingwood Williams, B.Sc., F.I.C. An ordinary meeting followed the annual meeting, the President occupying the chair. The minutes of the previous ordinary meeting were read and confirmed. A certificate of proposal for election to membership in favour of Mr.D. Mitchell was read for the second time; and certificates in favour of Messrs. Christopher William McHugo, A.I.C., 35, Warrior Square, Southend-on-Sea, assistant to Mr. A. Chaston Chapman, F.I.C. ; Cyril Joseph Heath Stock, B.Sc. (Dun.), F.I.C., County Analyst’s Office, Darlington, Public Analyst for the County of Durham ; George Tate, Ph.D. (Wurzburg), F.I.C., Windsor Buildings, George Street, Liverpool, consulting and analytical chemist ; and Thomas Edward Wallis, B.Sc.(Lond.), F.I.C., 5, Hills- borough Avenue, Exeter, assistant to Mr. T. Tickle, B.Sc., F.I.C., were read for the first time. Messrs. H. S. Machin and F. Robinson, M.Sc., A.I.C., were elected members of the Society. The following papers were read : “ General Principles Governing the Complete Analysis of Minerals and Ores,” by W. R. Schoeller, Ph.D. ; and a ‘( Note on the Determination of Sulphates in Flour,” by G. D. Elsdon, B.Sc., A.I.C. A number of exhibits of glass and porcelain apparatus and of filter-paper, manufactured in this country, were shown by Messrs. Baird and Tatlock, Ltd., Messrs. W, and R. Balston, Ltd., Messrs. J. Powell and Son, and the British Laboratory Ware Association.

ISSN:0003-2654    

DOI:10.1039/AN9154000075

出版商:RSC    

年代:1915

数据来源: RSC

摘要:

ANNUAL ADDRESS OF THE PRESIDENT 77 ANNUAL ADDRESS OF THE PRESIDENT. THE TEACHING OF ANALYTICAL CHEMISTRY. (Delivered at the Annual General Meeting, February 3, 1915.) HAPPILY it has not fallen to the lot of any of your former Presidents to address you under circumstances such as those which exist to-day, and it is not to be supposed that such a terrible and widespread conflagration as that in which the greater part of the civilised world is now involved can leave even a peaceful scientific society entirely unaffected.I shall have occasion in the course of this address to refer to several connections in which the war has concerned us indirectly, and I may perhaps fittingly take this opportunity of tendering from the chair an expression of our deep and grateful appreciation to those of our members who have offered themselves for active service in the defence of their King and country.I ought, perhaps, to say that shortly after the outbreak of war I took upon myself to write to the President of the Local Government Board, informing him that, in common with other scientific and professional bodies, we were anxious to do any- thing in our power to assist the Government, should such help be needed.To this communication replies were received both from the Board of Education and from the War Office thanking the Society for their offer, and saying that, should the occasion arise later, the Government would inform us in what way the services of our members could be utilised. I t is my melancholy duty to record the death of two of our members-G. A.Abrines and John Mscallan. Although Mr. Abrines died during 1913, his death was not brought to the notice of the Secretaries until too late to be referred to in the last presidential address. Mr. Abrines, who died suddenly while on a visit to this country, studied chemistry at the Pharmaceutical Society, and also under our Past-President the late Dr. John Muter.He was for some years in private practice, and held, up to the time of his death, the position of Analyst to the Sanitary Commissioners of Gibraltar. Mr. Macallan, who joined the Society in 1900, studied chemistry under the late Sir Walter Noel Hartley, and was for many years professionally associated with Sir Charles Cameron, in conjunction with whom he held, to the time of his death, the position of Assistant Analyst to the Dublin Corporation.In addition, we have lost during the year four members, either by resignation or for non-payment of subscriptions. On the other hand, we have elected twenty new members, and our present membership therefore stands at 440 (including fourteen honorary members), as compared with 426 at the end of 1913. To our honorary member Sir James Dobbie we desire t o offer our hearty congratulations on the honour which has recently been conferred upon him.To none of his colleagues will the conferment of this dignity give greater pleasure than to those who, like ourselves, are specially interested in the snalytical branch of the ohemical profession.78 ANNUAL ADDRESS OF THE PRESIDENT Although the Society is steadily growing, the rate of growth is too small to be considered satisfactory, having regard to the great importance and diversity of the interests which it represents, and to the ever-increasing demands made by our journal on the Society’s income.Bearing in mind the unparalleled services which this Society has rendered during the thirty-eight years of its existence in promoting the study and development of analytical chemistry in all its branches, I feel most strongly that no chemist who is eligible for membership ought to remain outside our doors.I n saying this I wish it to be understood that I am less concerned with the financial aspect of the question, important as that is, than with the desire that our Society should receive from a greater number of our colleagues the personal support and encouragement to which We feel that its record entitles it, and that the important branch of chemistry which we represent in this country should obtain that full official recognition which is so clearly its due.Notwithstanding the expansion of our title, there can be little doubt that many chemists are under the impression that our activities are largely restricted to the consideration of analytical matters connected with the administration of the Sale of Food and Drugs Acts.A glance at a volume of the ANALYST would, however, suffice to make it clear that such is far from being the case, and that we are, in fact, concerned with nothing less than the whole field of analytical chemistry. I shall revert to this subject in another connection, and as the spoken is almost invariably more effective than the written word, I will content myself now with expressing the hope that our members will make a special point of impressing on those of their friends who are eligible for membership end who have not joined our ranks, the importance-I would even say the duty-of supporting a Society which has done so much for analytical chemistry and for those who practise it as a profession.During the past session twenty-nine papers have been read at our meetings, and forty-one original communications have been published in the ANALYST, an increase of no less than ten on the preceding year. To refer adequately to each of these communications would be impossible within the limits of this address, and to single any out for special mention might appear invidious ; but I may perhaps be permitted to say that not only have they dealt with a wide diversity of subjects, but that they have maintained the high level and-if I may use the expression-the workmanlike character which characterise the great majority of the communications made to this Society.To our Editor, Mr. Julian L.Baker, our warmest thanks are due for the great ability and energy which he has consistently displayed in the performance of the duties of his office. Few members, other than those who have served on the Publication Committee, can properly appreciate the vast amount of work involved in the monthly production of our journal, which, it should be remembered, is the only journal published in fhe English language and devoted solely to the interests of analytical chemistry.During the year, 669 abstracts of papers appearing in foreign journals have been published, as against 746 during 1913. This reduction is, of course, due to the fact that during the past five months no German or Austrian journals have rertched this country, but notwithstanding this disappearance of oneANNUAL ADDRESS OF THE PRESIDEST 79 of our most fruitful sources of supply, the ANALYST has practically maintained its size, being only twenty-six pages less than during the preceding year, Inasmuch as there is, unfortunately, every probability that for some time to come many important foreign journals will cease to appear, or, at least, to find their way into our hands, it has been necessary to consider in what way this shortage might be met.One suggestion, made by the Editorial Committee and approved by your Council, was that critical reviews of the progress made during recent years in certain branches of analytical chemistry should be prepared by members of the Society who have special knowledge and experience of those branches.Several of these reports, I am happy to say, are now in hand, and will be published in due course. I might, perhaps, under these special circumstances, express the hope that our members, in spite of all difficulties, will maintain their scientific activity during the present year, and will make a special effort to keep our meetings well supplied with original communications.The Analytical Chemistry Investigation Scheme is making slow but steady progress, and it may be of interest to recall that the results of thirty-seven investiga- tions, including three during the past year, have been published in our journal, and that others are still in hand. The following are the titles of the three papers in question, and I desire to take this opportunity of offering on behalf of the Society our thanks to the authors : “ The Determination of Iridium in Platinum-Iridium Alloys,” by C.0. Bannister and E. A. Du Vergier. “The Insoluble Bromide Value of Oils and its Determination,” by Alex. Gemmell. L L The Properties of Some Chlorhydrocarbons and their Uses in Chemical Analysis. Your Council have the success of this scheme very much at heart, but it is clear that if it is to be as fruitful as we all hope, it must receive more active support than has hitherto been the case from the great body of our members.I refer particularly to suggestions in regard to subjects, the investigation of which would be of realvalue to chemical practitioners, and, of course, to offers of active assistance. I do most earnestly hope that this matter will receive the really serious consideration of our members, and that they will communicate with the Secretaries, who will be only too happy to receive suggestions or to inform them of approved subjects awaiting investigation, and to supply them with any other information they may require.I am informed by our Treasurer that the fund which, as you are aware, has been established in connection with this Scheme, must be increased if, as ought obviously to be the case, we are in future to meet our expenditure out of income.Up to the present, owing largely to the very modest claims made by workers, there has been only a slight deficit, but with the increased activity for which we all hope, a substantial addition ought to be made to the fund. The present time, when so many claims are being made on us all, is scarcely a favourable one in which to appeal for money, but if any of our members, realising the value to the Society of this Scheme, can see their way to contribute, the Council will be grateful.The financial statement for the past year has been very clearly put before you Part 11. : The Estimation of the Chlorethanes,” by L.Gowing-Scopes.80 ANNUAL ADDRESS OF THE PRESIDENT by our honorary treasurer, and I think you will agree that it is, under the circum- stances, a very satisfactory one, the balance for the year being, if not large, at any rate well on the right side. I t is particularly interesting to note that our treasurer has not found it necessary to write down the value of our investments, which stand at the same figures as in last year’s balance-sheet.On the other hand, the statement discloses the disquieting fact that our income is nearly stationary, and that we are now spending on the ANALYST about as much as WB can properly afford. There is no office more important to the well-being of the Society than that which Mr. Hinks so ably fills, and I feel that I am only carrying out your wishes in placingon record in this address am expression of our indebtedness t o him and of our appreciation, AS I have already indicated, and as must always be the case in every healthy and vigorous society, our journal is making greater and ever greater demands on our purse.Fortunately, owing to the thrifty habits of our early years, and to the careful manner in which our resources have been husbanded by successive treasurers, we have not as yet felt any serious strain.I t would, however, be a matter for keen regret if, in the future, the full expansion of our activities as expressed by the ANALYST had to bs in any way limited by financial considerations, and the desirability of increasing our income must be added to the reasons I have already advanced for endeavouring to secure a considerable accession in our ranks.1 might, perhaps, take this opportunity of stating that a Decennial Index for the period 1906-1915 is in course of preparation, and will, it is expected, be issued early in 1916. During the past twelve months a number of matters of importance to our pro- fession have engaged the attention of your Counci1,and to a few of these I must now refer.The Bill to make further provision for securing the purity of articles of Food, presented by Mr. John Burns, and ordered to be printed by the House of Commons in August, 1913, was referred to by Mr. Archbutt in his last annual address. This Bil1,which was intended primarily to give to the Local Government Board the power to make regulations in defining the nature, substance, and quality of articles of food, after such inquiry as the Board might think necessary, was clearly of the highest interest to members of our Society, and for two main reasons-the one direct, the other indirect.I n the first place it proposed, and appeared to bring within measure- able distance, a procedure which the Society has in principle strongly and consistently advocated for nearly twenty years, and which had been made the subject of very definite recommendations by a number of Departmental and other committees.I n the second place, it was clear that if the Bill were to become law, it could not fail greatly to increase the amount of work devolving on the Public Analyst. Whilst your Council-and I believe the whole Society-was in entire sympathy with the priaciple of the Bill, they felt very strongly that it was in the highest degree undesirable to leave solely to a Government department, with or without inquiry, the settlement of the complicated questions involved in the laying down of standards of composition of food products.The formulation of such standards clearly demands the co-operation of the scientific men to whose activity our knowledge of the composi-ANNUAL ADDRESS O F THE PRESIDENT 81 tion of foodstuffs is chiefly due; and to have set about such a task without the help of the Public Analysts of this country-collectively represented by our Society- would not only have led to an unsatisfactory solution of the problem, but might not unreasonably have been regarded as a slur upon a body of.public officers, who since the passing of the Sale of Food and Drugs Act of 1875 have, without any thought of personal gain, done such invaluable work in increasing our knowledge of the com- position of all our ordinary food materials.I t may be noted, too, that notwithstanding the differences of opinion in regard to the precise constitution of a Board or Court of Reference, contained in the recommendations of the various Departmental and Select Committees, in no case did those recommendations contemplate the assignment of the task of formulating standards to a Government Department in the manner suggested in Mr.John Burns’ Bill. I n saying this I would not be thought to underestimate in the slightest degree the very valuable work done during recent years in the laboratory of the Local Government Board, and which has resulted in the publication of a number of reports which are in some respects unique, and which are of the highest value to all who are concerned in the chemistry of food products.A deputation consisting of Dr. Dyer, Mr. Hehner, and Mr. E. W.Voelcker, having had an informal interview with Dr. MacFadden at the Local Government Board, a small committee was appointed by the Council to prepare a statement embodying the views of the Society in reference to the proposals contained in the Bill, with the object of placing those views formally before the Board. A little later, however, the Bill disappeared as the result of the operation of certain Parliamentary procedure, and with it passed for the present, at least, both our hopes and our fears.The question of the increasing work and responsibility thrown on the shoulders of Public Analysts during recent years was also referred to by my predecessor in this chair, and it will perhaps suffice to say that the statement compiled jointly by representatives of the Institute of Chemistry and of this Society, for which we are largely indebted to the labours of Mr.Cribb and Mr. Hehner, has been issued as a separate publication, and that copies have been sent to the various local authorities concerned in the administration of the Sale of Food and Drugs Acts, together with a covering letter signed by the President of the Institute, and by myself as President of this Society.In an appendix to that statement no less than twenty instances of legislative enactments, Government Departmental regulations and recommendations issued during the past fifteen years are given, each of which has had the effect in one way or another of increasing the work and responsibility of the Public Analyst. Notwithstanding this, the tendency of local authorities has been to decrease rather than to increase the analysts’ remuneration, until the matter has become, in some cases, nothing less than a public scandal.Another piece of legislation in which we have taken some special interest is the Milk and Dairies Bill, which was passed during the year. In this Bill, as you are doubtless aware, reference is made to an officer who is to undertake the bacterio- logical examination of milk ; and there did not appear to be any reason, so far as the wording of the Bill was concerned, why the chemical analyses of milk should not be transferred from the hands of the Public Analyst to the officer in question.Your Council, therefore, instructed the secretaries to write to the secretary of the Local82 ANNUAL ADDRESS OF THE PRESIDENT Government Board on this point, and at the same time to inquire whether it was the intention of the Bill that the Public Analyst should be allowed, if he should so desire, to undertake the bacteriological examination of samples of milk taken under the provisions of the Act.The reply was of the lion-committal kind with which those of u8 who have had occasion to correspond in official capacities with Government departments are not altogether unfamiliar.I t was to the effect that ‘‘ the intention of the Bill is to require that satisfactory arrangements shall be made by local authorities for the bacteriological examination of milk”; and with that we had necessarily to be content. In EL circular recently issued by the Local Government Board, the date on which the Act comes into operation has been postponed until October 1 next ; and the Board has stated that before the Act comes into force they will issue an explanatory circular stating the principal duties of local authorities and their officers under the Act.Your Council also felt that the suggested amendment to the Sale of Food and Drugs Acts contained in one of the paragraphs of the Second Schedule of the Bill, with regard to the time-limit under which notice of intention to take proceedings under those Acts must be served, was quite impracticable.A representation to this effect was made to the Board, with the result that the paragraph in question was amended so as satisfactorily to meet the point to which we had called attention. Until the outbreak of the war, I doubt whether any of us realised the extent to which we had become dependent on Germany, and to a less degree on Austria for our daily scientific needs.With the economic and other causes of this dependence this is not the place to deal, and it will suffice to say that in the most convincing manner possible we were rapidly made aware that the bulk of our chemical reagents, most of our glass and porcelain apparatus, and tt good deal of our best filter-paper were of German manufacture.Necessity may or may not be the mother of invention, but it is frequently the origin of a good deal of hard work, and that was certainly so in this case. The need for ensuring to professional and technological chemists, as well as to professors and teachers of chemistry, a satisfactory supply of laboratory reagents, glass and porcelain apparatus and filter-paper of good quality, was so urgent, that immediate steps had to be taken to deal with the situation.It was felt that the desired end could be best attained by the co-operation of the Institute of Chemistry with this Society, and on September 22 a joint meeting of the two Councils was held, at which Lord Moulton of Bank was present.After a pre- liminary discussion two special Committees were formed : (1) To consider what steps should be taken to insure a satisfactory supply of laboratory reagents, and (2) to consider what steps should be taken to insure a satisfactory supply of glass and porcelain apparatus and filter-paper.At a meeting of the first of the above- mentioned Committees, it was resolved to appoint B Sub-Committee ‘‘ to prepare a list of reagents ordinarily required, indicating the standards of purity which would be necessary for analytical work, and giving, as far as possible, some information as to the quantities likely to be wanted; that the standards of purity be based on those adopted by a Committee appointed by the Eighth International Congress of Applied Chemistry, and that the Sub-Committee should indicate those substances which are regarded as indispensable.”ANNUAL ADDRESS OF THE PRESIDENT 83 The labours of the Sub-committee having been completed, and the required list of reagents having been prepared and approved by the two Councils, it was printed in pamphlet form and issued together with a covering letter to a number of firms of chemical manufacturers.I n the covering letter the firms in question were asked to indicate the substances which they would be prepared to manufacture in accordance with the specified standards of purity, and to state whether they would be willing to label the reagents guaranteed to comply with those standards in some distinctive manner.That many of Our British manu- facturers are as capable and as progressive as any of their German competitors admits of no shadow of doubt, and now that they are made clearly acquainted with the nature of our requirements in respect of pure chemical reagents suitable for analytical purposes, I for one have no doubt whatever that those requirements will be satisfactorily met.The Committee appointed to deal with the question of the supply of glass, porcelain, and filter-paper, has had a much more serious task, owing to the necessity for ascertaining the precise composition of the glass employed in Germany for the manufacture of chemical apparatus, such as beakers and flasks, or alternatively of arriving by experiment a t some other equally suitable formula.I n addition to this, it was necessary to find workmen who would be able to work the special glass in question, a matter which for various reasons has presented no little difficulty. The Institute of Chemistry in October last appointed an Advisory Committee to conduct, the necessary research on the composition of glass suitable for chemical purposes, and in doing so has established yet another claim on the gratitude of professional chemists.That Committee, consisting of the President of the Institute, Mr. Bertram Blount, Mr. Otto Hehner, and Professor Herbert Jackson, assisted by Rfessrs. Walter C. Hancock and T. R. Merton, has succeeded in producing certain formulas for glass which appear very promising indeed.These have been communicated freely to manufacturers throughout the country and some British laboratory ware recently produced has, I am informed, a composition very nearly approaching that of the Institute formula. We shall look forward with interest to further reports of the Glass Research Committee, and I am sure we shall all agree that this important work could not be in better hands.The problem of the supply of porcelain ware suitable for our requirements is making good progress towards solution, whilst, thanks very largely to the help rendered by Mr. Bevan and Mr. Bacon, there is no difficulty in obtaining home-made filter-paper of very good quality. In the course of the numerous discussions which have taken place in connection with the replacement of German goods by those of British make, it has been frequently pointed out in no uncertain language that if manufacturers in this country are to be expected suddenly to supply the needs of those who in the past have been content to rely exclusively on German supplies, they must be aEorded some guarantee of permanency for their enterprise. In many cases more or leas expensive plaut will have to be laid down, and costly experience will have to be gained, and it is only fair that our manufacturers should have Borne reasonable assurance that at the conclusion of the war the newly developed industries will not suffer from foreign competition, hitherto made possible, in some instances at least, I There for the moment the matter rests..84 ANNUAL ADDRESS OF THE PRESIDENT by economic conditions which do not prevail in this country.I am aware that I am nearing rather dangerous ground, but I may at least express the hope that all users of chemicals and of laboratory apparatus in this country will be patriotic enough, and shall I say far-sighted enough, to give their utmost support to the development of the new industries, even should such support involve for a time a slightly increased expenditure.Two publications which have appeared during the past year demand, I think, some notice. The first is Mr. Pilcher’s admirable “History of the Institute of Chemistry,” of wbich a most interesting review by Dr. Dyer appeared in a recent number of the ANALYST. Those who desire to know something of the ambitions, struggles, and development of the Institute in its passage from infancy to vigorous adolescence and its relations at various periods to our own Society, will find this little work, supplemented by Dr.Dyer’s discreet revelations, very fascinating indeed. I must also refer to the issue of a new edition of the British Pharmacopceia, the previous edition having made its appearance no less than sixteen years ago.Anything in the nature of a review of this important work would be out of place here, even if I were competent to attempt such a formidable task. Probably such a review will appear in due course in the columns of our Journal, and I must content myself with saying that so far as can be judged from a cursory survey, the new volume will be found to be free from a number of the objections which have from time to time been urged against its predecessor as a standard for drugs in connection with the administration of the Sale of Food and Drugs Acts.A very useful addition consists in a table showing the limits for lead and arsenic which are to be considered permissible as impurities in a large number of officinal substances, and the analytical processes and tests are carefully laid down and described, and appear likely to permit of a very much higher degree of accuracy than those given in the 1898 edit ion.A very cordial invitation wag recently extended to us to be present at a meeting of the Biochemical Society, at which a number of so-called ‘‘ micro-chemical ” methods of analysis were to be demonstrated. This meeting, which took place on December 8, was attended by a number of our members, and proved to be highly interesting.It is becoming increasingly clear to many of us that a number of the chemical problems with which we are almost daily concerned have a strongly marked biological aspect, and it has been felt that occasional co-operation and free discussion between those of us who are interested chiefly in the analytical side of a, question, and those who are more concerned in its biochemical bearing, could not fail $0 be productive of good results. As a first step in this direction, it has been decided to hold in May next a joint meeting with the Biochemical Society, the subject for discussion being ‘‘ Methods of Separating and Estimating the Nitrogenous Con- stituents of Meat Extracts and Other Foodstuffs, with Special Reference to the Interpretation of the Results.” A joint committee has been formed to make the necessary arrangements, and it is confidently anticipated that a most useful discussion will take place.In these days of extremely narrow specialisation, there is always the danger that in lookingANNUAL ADDRESS OF THE PRESIDENT 85 at an object from one point of view only we may gain a quite incorrect impression of its true form, and the only cure for this unfortunate, but unavoidable, state of affairs seems to lie in more frequent intercourse with our colleagues in other hranches of science, particularly with those whose scientific frontiers are conter- minous with our own.My review of the activities of our Society during the past year has been more lengthy than I expected when I commenced its preparation, but even at the risk of wearying you, I feel that there is one matter on which I must crave your permission to dwell for a brief space, as it is of the highest importance to our profession and has for long been uppermost in my mind and thoughts.I refer to the teaching of analytical chemistry in this country.At the commencement of this address I referred incidentally to tthe fact that many of our chemical colleagues, especially on the teaching side, are not members of our Society, although in our Articles of ,4ssociation ‘‘ professorial chemistry ” is specifically mentioned as a ground of eligibility. That many of them are but slightly acquainted with our work, and take very little interest in it, is unfortunately true, and yet this Society represents in this country a branch of chemistry which is not only of fundamental importance and the basis on which exact knowledge in almost every other branch of chemistry rests, but is admittedly a necessary part of every chemical curriculum, and when properly taught, a generally recognised instrument of the highest educational value.I allude to this want of recognition, not so much for the purpose of giving expression to a personal regret, as because I think that it is symptomatic of the attitude so widely adopted in this country towards analytical Chemistry, and so touches on a much wider question. Analytical chemistry has been often described as the handmaiden of the other branches of our science, a description which, however true in one sense, is a little unfortunate in that it carries with it a suggestion of inferiority.Now, whether regarded as an educational instrument, as a special branch of applied chemistry, or a s a subject of practical utility, I contend that analytical chemistry should stand on the same plane as the other departments of chemistry.I t is not necessary to labour this point, and it would not even be needful to refer to it were it not for the fact that in many quarters an impression appears to prevail that analytical chemistry is a useful art and little more, and that its practitioners are not much better than highly skilled labourers. That there are unfortunately here and there a few so-called analytical chemists to whom that description might be correctly applied is undoubtedly true.Some analytical opera- tions are of a more or less mechanical nature, and can be satisfactorily performed by almost any careful and sufficiently trained person. The same, we know, applies to certain simple procedures in surgery, but I am not aware that that fact has been allowed to detract from the high professional and scientific position which the highly trained surgeon properly takes, and it certainly has not been used as an argument for reducing surgery to a more lowly position in our medical schools than, say, physiology, or any other branch of medical study.There are a, few words in the introduction to the late Professor Dittmar’s admirable little work on Quali- tative Chemical Analysis,” which I cannot forbear to quote. Professor Dittmar-86 ANNUAL ADDRESS OF THE PRESIDENT -and there could be no better authority-said: “All we desire is, at the very outset, to make the student understand that analysis is not [the italics are Dittmar’s] an art which can be learned independently of chemistry itself, It is possible to be a fair theoretical chemist without being able to execute an analysis, but most assuredly no one can be an analyst without being a scientific chemist.” 9nd in the proper sense in which the word “analyst ” is here used, that is absolutely true.The enormous development of organic chemistry during the past fifty years, result- ing in the accomplishment of so many wonderful syntheses, has tended to monopolise the attention of chemists, and in large measure accounts for the dethronement of analytical chemistry from the high position which it occupied during the first half of last century, when almost every chemist of distinction devoted himself to the study of its problems.In the presence of this new field, in which almost every thrust of the spade served to bring to light some discovery of the highest import- ance and significance, it is not to be wondered at that so many chemists should have transferred their attention from an older branch of chemistry, the investigation of which was decidedly laborious, and which could not be expected to make the same appeal to the scientific imagination. An eminent chemist, who might possibly desire to-day to retract his words, is stated to have declared that “analytical chemistry presents no further problems.” A statement more wide of the mark could scarcely be imagined.So far from being a ‘‘ finished ” branch of knowledge (if such a thing exists), there is immense scope for research and development, due in great measure to the application of physical methods. I n fact, it may be said with truth that just as modern organic chemistry was responsible for the neglect of the study of analytical chemistry, so the still more modern physical chemistry is likely to be responsible for its vigorous revival.The application of spectroscopy in its modern development, electro-analysis, the use of physical instruments such as the refractomecer: the micro-balance, electrical conductivity apparatus, and appliances for measuring radio-activity, cannot fail to provide an immense amount of matter for research, and the same may be said of the many biological methods which are now being pressed into the service of analytical chemistry, and which seem likely LO lead to results of the very highest importance.On all sides the analyst of to-day is being faced with new problems, the solution of which frequently demands research qualities of as high an order as those exhibited by any of his colleagues in other branches of science.I am not exaggerating when I say that the really successful consulting and analytical chemist must not only have a good scientific training, a very extensive knowledge of general chemistry, and a genuine love for his work, but he must be mentally alert and adaptable and possess the faculty of research in a high degree.I t might perhaps surprise some of our professorial colleagues, who are a little disposed to look down upon the professional hemist if they could know the amount of true research work of a very high character carried out in analytical laboratories, but which cannot, for obvious reasons, receive the recognition of publication. For many of us life is one con- tinuous series of technical problems, and for the solution of each of them precisely those qualities are needed which are found to be necessary to make a successful investigator in the domain of pure chemistry.Not only must our solutions of theANNUAL ADDRESS OF THE PRESIDENT 87 problems entrusted to us be obtained in the minimum time, but they must be correct.Our results and conclusions are certain t'o be rigorously tested, often on a large scale, and any inaccuracy inevitably entails loss of reputation and of practice. I n this respect a t least our academic colleagues are working under less exacting conditions. Having very briefly touched on the nature and extent of the scientific equipment needed for the successful practice of analytical chemistry, we may reasonably inquire whether the training which our young professional chemists obtain is such as is calculated to insure the best results.Whilst there may possibly be some difference of opinion as to the precise position which a study of chemical analysis should take in the training of the chemical teacher, there can surely be none as to its supreme importance in the training of the professional chemist.In the great majority of cases it is the actual instrument by which, directly or indirectly, he is to earn his livelihood, and in every case it must tend to produce (if properly taught as a living subject, and not as a mass of tedious prescriptions and formulas) a deeper insight into the nature of chemical reactions, an appreciation of the influence of mass and other disturbing factors, and a recognition of the importance of attention to minute detail.In addition to this, it affords endless opportunity for the acquirement of dexterity in constructing and manipulating scientific appliances, and in all these ways renders invaluable service in the making of the successful technical chemist.Now, if all this be true-and I do not see how it can be denied-analytical chemistry ought clearly to take an outstanding position in our Universities and University colleges, as it is from them that, more often than not, the young chemist proceeds directly to the practice of his profession. Tjnfortunately, the position which it takes in those institutions is not, as a rule, a high one, nor one at all commensurate with its importance.I believe I am correct in saying that in no University in this country does a chair of Analytical Chemistry exist, and that a subject which is admittedly of such great importance is entrusted to teachers who, however well qualified and capable they may be, have as a rule to teach it, if I may use the expression, incidentally.That in some of our colleges it is well taught is happily the case, but that it is more often very imperfectly taught is unfortunately equally true. On this point I speak with knowledge and experience gained as an Examiner, as an employer, and as one whose professional work has for years brought him into contact with a great many of the young men who, after completing their college course, find their way into some chemical manufactory. I n saying this, nothing could be farther from niy desire than to cast the slightest reflection on the many highly qualified and exceedingly able men who deal with analytical chemistry in our Universities and colleges; I am rather concerned with calling attention to what I conceive to be the faulty conditions under which they are compelled to work.So large a subject, and one which is in constant process of development, might well, it seems to me, be entrusted to a specially appointed Professor, who would have the opportunity of keeping himself fully abreast of the developments of his subject, and who would have the time to deal with it in a manner practically impossible under the existing conditions.Such chairs of Analytical Chemistry exist in very many of the more important American and Continental Universities, and it can scarcely be88 ANNUAL ADDRESS O F THE PRESIDENT contended that what has been found desirable in so many other parts of the civilised world is unnecessary in Great Britain.Chairs of Analytical Chemistry, for example, exist in Yale, Virginia, Johns Hopkins, Cornell, and Columbia Universities, to name only those of which I know, and I believe I am correct in saying that in Columbia University there are no fewer than three such Professors. In many of the University prospectuses great emphasis is laid on the importance of analytical chemistry, and from one of the Yale Calendars I cannot refrain from quoting the following words : ‘‘ There is probably no branch of chemical study as important as qualitative analysis “in its use in developing the reasoning faculties, and enabling the student to “ generalise and to classify chemical phenomena.” I n Heidelberg, Munich, Leipzig, Wiirzburg, and other German Universities, in the Imperial Technical High Schools at Stuttgart, Vienna, and elsewhere, such chairs exist, as well as at Upsala, in most of the Swiss and Belgian Universities, and in some of the Italian.I n regard to France and one or two other countries I have no definite information, but 1 think I have said enough to establish my point, that in many of the world’s leading Universities the teaching of analytical chemistry is entrusted to a specially appointed Professor, who takes equal academic rank with his other chemical colleagues.Even when this is not the case, assistant professors or special assistants are frequently appointed to deal solely with this branch of chemistry. I t clearly cannot be objected that it has not been our custom in this country to appoint Professors to deal with special branches of chemistry, since in some of our colleges chairs exist devoted to Physical Chemistry, Biochemistry, Tinctorial Chemistry, Fuel Chemistry, Brewing Chemistry, Agricultural Chemistry, Technical Chemistry, and Metallurgy.I am not foolish enough to imagine that the establishment of chairs of Analytical Chemistry in all or any of our Universities and colleges would bring forth a new heaven or a new earth, but at least it is certain that this highly important branch of chemistry would be taught under better conditions than those which in many cases exist at present.The teachers, being in a position to devote themselves entirely to their special branch of instruction, would be able to give more time and attention to the student, and surely in no branch of chemistry is close and constant supervision of practical work so necessary.They would also have the time to make themselves thoroughly conversant with their subject, in both its theoretical and practical aspects, as well as to keep in touch with modern developments, and their laboratories might even become in process of time centres of original work in a department of our science in which research has been for so long neglected.There is still another useful purpose which such specially-appointed Professors might well serve. They might, by keeping in touch with consulting chemists, con- stitute a badly-needed link between the heads of the chemical departments of our teaching institutions and practising chemists, and so enable the former more easily to draw on the vast accumulation of practical knowledge and experience which the latter possess.Consulting chemists with large practices necessarily acquire a, large amount of experience of a kind which professorial chemists cannot-save perhaps in a few special casea-have gained, and that this would be freely placed at the disposal of our Universities I am confident.Something has, I believe, been done in this direction at the Royal School of Mines, and I have in addition reason to knowANNUAL ADDRESS OF THE PRESIDENT 89 that in one or two cases in which such assistance has been sought, it has proved of the utmost value both to the teachers and to their students. I am well aware of the vast amount of work which the chemical student of to-day is expected to do in his three or four years’ course, and the large and ever increasing extent of the field which he is expected to cover.It is, however, I think, certain that a thoroughly sound knowledge of analytical chemistry is about the best practical equipment a young professional chemist can have, and it seems to me that it should be taught in the most thorough manner possible, even if it should be necessary to devote rather less time to other portions of his studies.I t must be remembered that the student who, on the recommendation of his Professor, obtains an appointment in a works’ or other technical laboratory will, according to t h e nature of the work he does, bring either credit or discredit both on the institution in which he has been trained and to some extent on the science which he represents.The causes underlying the low esteem in whi,ch chemistry is held by not a few of our manufacturers, and the low value often placed upon the services of its prac- titioners, are so many and so varied that it would be impossible even to touch upon many of them in this address, but I am convinced, as the result of much experience, that one of those causes is the introduction into works’ laboratories of young men who, although quite ornamental in some respects, have not obtained a thorough grip of the fundamentals of the science, and who are incapable of performing even the simplest analytical operations in a cleanly and accurate manner. It may be that this is to some extent due to the fact that many of our colleges are tending to become factories for turning out University graduates, instead of centres for the production of, among other things, well trained chemists. I do not say that the two processes are incompatible, but that the one aim has certainly reacted very unfavourably on the other cannot be denied. That, however, is another story, and one which has been written by abler pens than mine. I have only sought to call attention to one respect in which I think that the training of the young professional chemist might be improved. For the rest, let all those of us who have the misfortune to be well advanced on the journey, strive to lose no opportunity of impressing on our younger brethren, by our practice as well as by our precept, the dignity of the profession of which we have the honour and the good fortune to be members. It is a young profession, and we cannot be surprised if it has not yet secured the same full public recognition that is accorded to Medicine or to the Law, but let every chemist realise at the outset of his career t’hat it is in his power to help to hasten or to delay the coming of the day when his profession will take the position to which it is from every point of view entitled. In bringing to a conclusion an address which I fear has been wearisomely lengthy, I desire to offer to members of the Council, and indeed to every member of the Society, my thanks for the help and for the many evidences of friendship which I have received during the past year. Above all, I would acknowledge with a deep sense of my personal obligation the invaluable assistance rendered to the Society by our Secretaries, upon whose shoulders the great bulk of the hard work must necessarily fall. This method may be slow, but it is a t least sure.

ISSN:0003-2654    

DOI:10.1039/AN9154000077

出版商:RSC    

年代:1915

数据来源: RSC

摘要:

90 W. R. SCHOELLER : GENERAL PRINCIPLES GOVERNING GENERAL PRINCIPLES GOVERNING THE COMPLETE ANALYSIS OF MINERALS AND ORES. BY W. R. SCHOELLER, PH.D., Assoc.1.M.M. (Read at the Meeting, February 3, 1915.) THIS paper is intended chiefly for the information of those acquainted with technical methods of assaying which they desire to apply to the complete analysis of raw materials and intermediate products of inorganic and metallurgical industries.While information on the determination of single constituents is easily available, little if anything is mentioned in the various textbooks regarding complete analysis. Descriptions of individual analyses may be found scattered throughout technical literature, but to my knowledge the subject has never been systematically treated in any manual or paper.Nor is the analyst’s preliminary training often adequate in this respect, with the result that he is frequently left to work out complete analyses as best he may, till he has acquired sufficient experience to satisfactorily carry out one of the most difficult tasks he may be called upon to undertake. I t is hoped that these notes, while a help to the learner, will call the experienced analyst’s attention to the lack of published information on the matter under dis- cussion; and that this first attempt at a systematic presentation may invite contributions which will form a fund of information for the guidance of all who are engaged in analytical work.I have endeavoured to confine myself as much as possible to considerations of general applicability to the great field of mineral analysis, and to omit details of analytical procedure ; the latter may be found in the standard books on technical analysis, to which reference is made in the bibliographical index, * I.Methods for Determiizing Elements.--In assaying for single constituents, a fairly considerable amount of the element to be determined is generally obtained by weighing out a suitable quantity of ore ; whereas in a complete analysis the same portion is used for estimating a number of constituents, some being present in large, others in minute, quantity.The method of estimation used will often depend on the amount present : a colorimetric process is frequently adopted for small quantities (e.g., bismuth, titanium) ; sometimes it is preferable to weigh small precipitates rather than use a volumetric method (e.g., zinc, antimony).We may therefore distinguish between methods more suitable for moderate to large, and others for minute, quantities. Table I. shows the different methods of estimating some of the commoner elements by way of illustration ; alumina, barium, silica, sulphur, and the alkalis have not been included, as they are practically always weighed.* The bracketed figures in small type refer to the bibliography.THE COMPLETE ANALYSIS OF MINERALS AND OEES 91 TABLE L(1) Abbreviations : G., gravimetric, V., volumetric, E., electrolytic, C., colorimetric, determination. Element. ~~ Antimony ... Arsenic ... Bismuth ... Calcium ... Cobalt ... Copper . . . Iron ...... Lead ... ... Magnesium . . . Manganese . . . Nickel ... Phosphorus . . . Silver ... Tin ... ... Zinc ... ... Moderate to Large Amounts. V. with permanganate, bromate, or V. with iodine, bromate, or sulpbo- G. as Bi,O, or BiOC1. V. with permanganate. V. with thiosulphate. V. with thiosulphate. iodine. E. as metal. cyana te. E. as metal. E. as metal G. as Cu,S. V. with permanganate or bichro- mate.V. with molybdate or thiosulphate. G. as PbSO,. V. by alkalimetry. V. with permanganate or oxalic acid and perm angana t e. E. as metal. V. with cyanide. V. by alkalimetry. V. with sulphocyanate or sodium chloride. E. as metal. G. as AgI. V. with iodine. V. with ferrocyanide or sodium sul- phide. G. as Mg,P,07. Minute Quantities. G. as SbO, V. with iodine. E.as metal. G. as CaSO, or CaO. G. as CoSO,. C. with ammonia or ferro- cyanide. V. with thio- sulphate. G. as Fe,O,. C. with thio- cyanate. V. with thiosulphate. C. with H,S. G. as Mg,P,07. G. as Mn,O,. C. as HMnO,. C. as BiI,. G. with dimet hy lglyoxime or as NiO. V. bypermanganate. G. as PbMoO,. Scorification or crucible fusion. V. with iodine. G. as ZnO. Speaking generally, a gravimetric process is preferable for small quantities to a volumetric where a certain excess of reagent is required to produce a good end-point, or still more to an indirect titration.Again, with still smaller quantities, the dis- advantage of gravimetric methods lies in the circumstance that a small alteration in the weight of a crucible several thousand times heavier than its contents causes a considerable relative error in the determination, and if available a colorimetric process is much to be preferred.11. Separation of Elements.-For the quantitative separation of the common elements into groups, the procedure is very similar to that followed in qualitative analysis, while that of the elements from one another often requires different methods in order to carry out their subsequent estimation.A subdivision into groups and quantitative separation of the common elements is given in Table 11.92 W. R . SCHOELLER : GENERAL PRINCIPLES GOVERNING I (b) Sulpho-acids Group. I Basic acetate pre- cipi t at e I Hydrogen sulphide group : (a) Sulpho-bases 4 I I Ammonium sulphide group i Alkaline earths 1 Alkalies I 1 TABLE II.(1) Separation of- Hg from Ag, Pb, Bi, Cd, Cu Bg 9 ) Pb, Bi, Cd, Cu Pb >, Bi, Cd, Cu As ,, Sb, Sn ...... Sb ,, Sn ... ... Cr ,, Fe, 1’,05, A1 ... Pe ,, P205, A1 ... p,o, 7, A1 ... Zn ,, Mn, Ni, Co ... Mn 9 , Ni, Co ... Ni 1 , C O ... Ba ,, Ca, Mg ... I ... Ca ,, Mg ... ... bfg 2 9 K, Na ... ... K ,, Na ... ... Method. Treatment of mixed sulphides Insolubility of AgI in dilute As PbSO, in 1 : 5 sulphuric As oxychloride.Insolubility of CdS in potas- Insolubility of As,S, in strong Insolubility of Sb2S, in oxalic Oxidation to chromic acid. As ferric hydrate in caustic soda. As ammonium phospho-molyb- date. As ZnS in faintly acid solu- tion with subsequent addi- tion of sodium acetate. Solubility of MnS in acetic acid. ,4s Ni(OH), in potassium cyanide; or as cobalt am- monium phosphate. As BaCrO,, As CaC204 or CaSO,.As MgNH,PO,or MgNH,AsO,. As K,PtCl,; or estimation of SO, in mixed sulphates. with 1 : 1 nitric acid. nitric acid, acid. sium cyanide. hydrochloric acid. acid. 111. Other Methods of Separation.-Besides the above general scheme, a number of special methods are available where only two elements have to be separated. As with the actual estimation, the best method for separation will frequently depend on the quantities present ; in making one’s choice one should, if possible, aim at leaving or obtaining the predominant element in solution and at precipitating the sub- ordinate, so as to avoid or minimise occlusion and co-precipitation and the washing of bulky precipitates; or a t producing a crystalline or heavy, rather than an amorphous or voluminous, precipitate.Table 111. is intended to illustrate this principle. The term “converse” may be applied to two methods if they can be used alternatively for the separation of two elements, subject to either element being predominant or subordinate in quantity. To facilitate the use of the table, the number of each method is followed by that of its converse in brackets.Some separations are not perfect because a small quantity of the predominant element isTABLE 111. (2) Arsenic. Large Quantities 0 f- Antimony. Tin. A. Arsenic ... Antimony . . . Tin ... ... Lead ... ... Coppcr ... Bismuth B. Iron ... ... Aluminium . . . Manganese . . . Zinc ._. ... Nickel.. . . . . Calcium ... From Small Quantities of- ti (1).H2S in stronl HC1. 11 (2). H,S in strong HCl. 16 (3). H2S0,. 21 (4). J3y ferric chloride and am- nionia. 26 (5). H,S in strong HCl. Iron. :i6 (31). NnOII. 4 1 (32). Zincoxide. 46 (33). Animonis. 51 (34). Ammonia. 56 (35). Ammonia. 1 (6). Ammonium carbonate. - 12 (7). H2S in oxalic acid. 17 (8). H,S04 and tartaric acid. 22 (9). Same as 21 ; or thiocyanatc and tartaric acid. 27 (10).As ROC1 in tartaric acid. Aliiniiriium. 31 (36). As phos- phate, or by ether. 42 (37). Zinc oxide 47 (38). Ammonia. 52 (39). Ammonia. 57 (40). Ammonia. 2 (11). Amrrionium carbonate. 7 (12). Metallic iron. - 18 (13). Nitric acid. 23 (14). Nitric acid. 28 (15). Metallic iron. Manganesc. 32 (41). Zinc oxide or by ether. 37 (42). NaOH. 48 (43). Bromine. 53 (44). Bromine. 58 (45).Bromine.' Lead. 3 (16). Sodium sul- phide. 8 (17). Potassium sulphide. 13 (18). Sodium sulphidc. - 24 (19). H,SO,; or electrolysis. 29 (20). As PbSO, in 1 : 5 H2S0,. Zinc. 33 (46). H2S in acetic acid, or by ether. 38 (47). H2S in acetic acid. 43 (48). H,S in acetic acid. 54 (49). H,S in faintly acid solu- tion followed by sodium acetate. i9 (50). Ammoniun: sulphide. 2 (21). Sodium sul- phide.9 ('22). Potassium sulphide. 14 (23). Sodium sulphide. 19 (24). H,SO,. 30 (25). Sulpho- cyanate. Nickel. 34 (51). Zinc oxide, barium carbonate, or by ether. 39 (52) NaOH. 14 (53) Ammoniun sulphide, followed by acetic acid. 49 (54). NaOH. 0 ( 5 5 ) . Ammoniun sulphide. 5 (26). Sodium sul- phide. 10 (27). Potassiuiii sulphidc. 15 (28). Sodiuni sulphide. 20 (29). As RiOCI. 25 (30).H,S and po tassiurii cyanide. Calcium. 35 (56). As calciurii osalate in oxalic acid. 40 (57). Same as 35. 45 (58). H,S04 and alcohol. 50 (59). Oxdate. 55 (60). Oxalate.94 W. R. SCHOELLER : GENERAL PRINCIPLES GOVERNING carried down with the precipitated subordinate; in this case the precipitate is subjected to a second treatment by the, same or the converse method, which is easily done on account of its small bulk.Thus in 18 (Table 111.) the insoluble tin oxide takes down a small quantity of lead as stannate, and is treated as in 13. Again, in 33, the zinc sulphide may be contaminated with iron, from which it is freed according to 46. These two separations are preferable to extraction of tin from lead sulphide by sodium sulphide, and the handling of a bulky precipitate of ferric hydrate.Examples of separations by repeating the same treatment are found under 20, 31, 36, etc. Most of these methods can be used for separating three or more elements (compare 7 and 28, 18 and 23, 41 and 42, 36, 37 and 39). 1V. Type Minerals.-In view of the widely varying nature of the various mineral products that may come under the analyst’s notice, the obvious plan for purposes of complete analysis is to subdivide them into groups and types, each of the latter requiring a suitable mode of procedure.A subdivision into classes, types and sub- types is outlined in Table IV. TABLE IV. CLASS A. Sulphide Ores of Common Metals. 1. Galena. 2. Blende. 2a. Lead-zinc ores. 3. Coppei. ores. 4 . Pyrites. 5. Mispickel. 6.Sulpharsenides of Ni, Co, etc. 6a. Speiss. 7. Stibnite. 7a. Crude anti- mony 8. Realgar, orpi- ment. 9. Bismuth ores. 10. Cinnabar. 11. Stannine. CLASS U. Oxide Ores of Common Illetals. ~ 1. Lead carbon- ate. 2. Smithsonite. B a . Calamine. 3. Oxidised coppei 4. Kickel silicates 5 . Antimony oxides. 6. Tin ores. 7, Iron oxides. 7a. Hydrated iron ores. 7 b . Siderite. 8. Ilmenite.9. Chromite. LO. Manganese ores. LOa. Earthly cobalt. Ll. Bauxite. ores. CLASS C. Ores of Rarer Metals. 1. Wolfram. la. Scheelite. 2. Rlolybdenite 3. Uranium ore 4. Tantalite. 5 . Monazite. 6. Platinum ore 7. Tellurides CLASS D. h’on-Metallic bliiiernls. 1. Silicate rocks. 2. Clay ; shale. 2a. Refractory ma- terials. 3. Quartzite. 4. Gypsum. 5 . 13arytes. 6. Limestone. 6a. Dolomite.7. I’hospliates. ia. Superphos- 8. Fluorides. 9. Rock-salt. 0. Nitrates. 1. Potassium salts 2 . Borates. 3. Coals. 3a. Coke. 4. Oil-bearing phates. rocks. CLAS5 E. Metallurgical Products. 1. Copper matte. l a . Kickel niatte. llr. Leady matte 2. Cement copper. 3 . Roasted ores (Pb, Zn). 4. Pyritic cinders. 5. Iron slag. 6. Lead and copper slags. 7. Thomas slag. 8. Flue dust. 9.Dross, ashes. LO. Silver (gold) izecipitates. 1. Portland cement. V. Preliminary Qualitative Bxamination. - The preliminary examination is obviously of the greatest importance, not only in that it establishes the qualitative composition of the material, but also because it should enable the operator to decide on the whole course of the subsequent operations. In the following general scheme of preliminary investigation I premise a knowledge of mineralogy ; non-metallic minerals (e.g., limestone, phosphates) do not require the elaborate examination necessary in the case of complex ores.(a) The lumps of material as received are first carefully examined, noting the1HE COMPLETE ANALYSIS O F MIXEKALS AND ORES 95 predominant mineral; the subordinate ones are recognised with the aid of a magni- fying glass.Weathered surfaces often give good indications of the presence of certain elements by the colour of their oxidised compounds. ( b ) Fresh surfaces are next exposed by breaking the lumps, and the fractures again examined. Blowpipe tests are made on small, clean lumps in doubtful cases ; a hand-magnet is useful for the distinction of magnetite and pyrrhotine.Hardness, streak, and cleavage are valuable means of identification, as is also the specific gravity using bromoform. (c) When everything possible has been done to ascertain the nature of the mineral as received, and not till then, the sample is crushed and screened throagh a 60 mesb, and 100 to 200 grms. weighed out. This is carefully panned, and the over- flow poured into a basin, in case it is desirable to repeat the mashing. Panning sometimes discloses some previously overlooked constituent, If a concentrate is obtained, it may be dried and weighed so as to gain a rough idea of the amount of heavy mineral, which it is best to submit to the ordinary process of qualitative analysis.The electro-magnet may be used with advantage for extracting weakly magnetic minerals-e.g., ilmenite, monazite, wolfram.((1) If an unusual constituent is suspected, it is made the object of a special test ; but to identify such common elements as silica, iron, alumina, lime, etc., is generally unnecessary-their presence is simply assumed beforehand. This also applies to elements the detection of which requires almost as much time and care as their estimation; the operator will combine the two by working on an accurately weighed sample-e.g., dry assay for noble metals.(c) A scheme of this kind, in which the presence of elements is inferred chiefly from the identification of their minerals, has two advantages over a qualitative analysis made on the original sample : it is much quicker than the latter, as less manipulation is required, and minute quantities are more easily detected.Thus a few flakes of muscovite indicate the presence of alkalis a t a glance; galena is a t once identified by its cleavage, colour, and high specific gravity. To enlarge upon this last example, the occurrence of galena renders the presence of commonly associated metals, such as silver, antimony, arsenic, or bismuth, highly probable, and they are accordingly put down for quantitative estimation.Similarly, in the case of iron pyrites, the presence of small quantities of arsenic and copper is a t once i 11 f er r e d . VI. Separation into Insoluble Residue and Soluble Fraction (3).-The usual acid treatment of minerals, etc., commonly results in a solution of the metals and an insoluble residue.Where the latter contains no metallic compounds such as oxides of tin or antimony, chromite, tungstic acid, silver chloride, etc., it consists of the insoluble part of the gangue, chiefly silica, barium sulphate, or silicates. The silica was either originally present as quartz or liberated from a silicate by the acid treat- ment. Most silicates and rocks, though termed insoluble, yield a small soluble fraction, the amount of which may vary with the size of grain and degree of weathering of the mineral, the nature and quantity of acids used, the time of contact, and the temperature of decomposition.Thus the insoluble is generally higher with sulphuric than with hydrochloric acid. Even when working under the same con-96 W. R. SCHOELLER : GENERAL PRINCIPLES GOVERNING ditions the results of duplicate trials may sometimes disagree ; of this the following is an example :+: 77.73 2.04 Successive Treatment with HC1 arid H,SO,.73.34 7.88 1. Soluble in hydrochloric acid ... ... 2. ,, sulphuric acid.. . ... ... 18-64 38.75 Muscovite. 17.80 41.80 Uiotite. Another source of error lies in the fact that silicic acid resulting from the decomposition of silicates is not quite insoluble even after careful dehydration, a few mgrms.being always recovered from the filtrate upon evaporation to dryness ; even then a small fraction still remains soluble, and part of this is precipitated along with alumina in the subsequent treatment. Generally speaking, hydrochloric is to be preferred to sulphuric acid in the separation of the insoluble.Barytes is more or less soluble in concentrated sulphuric acid, and reprecipitated on dilution ; the precipitate almost invariably carries down other sulphat’es, especially lead, which it tenaciously retains. Fluorite in the gangue will cause loss in silica if the usual acid treatment is applied, while glass or porcelain may be slightly attacked and yield soluble bases.The method of Berzelius is available for the determination of fluorine and silica in ores containing them. Unless the gangue is entirely composed of altogether insoluble material, such a s quartz or barytes, the insoluble figure gives no exact indication of the amount of gangue ; the weight is simply that of the unattacked portion, ~ Z Z L S any silica that may have separated.The distinction between, and separation into, a soluble and insoluble fraction is thus inore or less arbitrary and imperfect, and merely based upon the action of the common acids on minerals. Yet the errors to which the separation of the insoluble is liable make it one of great importance in complete analysis, for, if not taken into account and obviated, they will do more towards vitiating the final result than the small inaccuracies of the more scientific analytical methods.The following points should therefore be kept in mind : (a) The decomposition is done, wherever possible, with hydrochloric acid, with or without a nitric acid treatment; the assay is evaporated to complete dryness, preferably on a water-bath. ( b ) The filtrate from the insoluble is again evaporated to complete dryness to recover soluble silica. (c) Whether the insoluble ia subjected to further treatment or reported as such, the portion in which it is determined must also serve for the estimation of all the earths and silicate-forming bases, because silicates are not always attacked to the same extent.I The filtrate from the second evaporation ( 0 ) is treated with hydrogen * From H.Ries, “ Clays,” 1908, p. 69.THE COMPLETE ANALYSIS OF XINERALS AND ORES 97 sulphide, taking care to precipitate the whole of the arsenic if present. elements must, if present, be determined in the filtrate : The following Iron (total). (Alumina. I P,0,,Ti0,,Si02. Manganese. Lime. Bary t a. Magnesia. A1 kalies. The insoluble residue, in addition to some of the above elements, will contain the bulk of the silica, and possibly barytes, stannic oxide, tungstic acid, etc.( d ) It must not be forgotten that hydrated silicates may be present, which lose their water on ignition, Weighing the latter on a tared filter previous to igniting would not give the whole of the combined water, as some may have been lost through the partial decomposition of silicates in the acid treatment.(For estimation of combined water see S.) VII. Organic X u tter.-Many mineral products contain organic or carbonaceous matter, which remains with the insoluble residue. I n case hydrated silicates are present, the usual method of weighing the insoluble before and after ignition would produce erroneous results ; it is therefore best to treat the insoluble from another portion with hydrochloric and hydrofluoric acids to break up the silicates, and to collect on a tared filter after evaporating and taking up with dilute acid.After weighing, the filter is incinerated and the ash subtracted. VIII. Detemiiization 0.f Heavy XetaZs.-In order to rninimise chances of error in the analjsis of ores the decomposition of which is tedious or difficult, the heavy metals present should be determined in the same portion as the bases and insoluble residue.Thus, if a hydrogen sulphide precipitate is obtained in the filtrate from the insoluble [VI. (c)], it is subjected to further examination (Table 11.). The filtrate froin the basic acetate precipitate may contain the ammonium sulphide group, which is separated by adding ammonia and sufficient ammonium chloride to prevent precipitation of lime as carbonate, and passing hydrogen sulphide through the hot solution.This is preferable to using a stock solution of ammonium sulphide, which may be contaminated with sulphate, carbonate, etc. After filtering off the sulphide precipitate the solution is slightly acidified with acetic acid, concentrated by boiling, and filtered from separated sulphur, which may contain a little nickel, sometimes molylidenum.Concentration should be effected in any case before pr e ci pi t a t i n g m ag ne si a. Again, while the behaviour of silicates to acids may be uncertain, the decom- position of sulphides is in most cases a simple matter; therefore, where several heavy sulphide metals are present, the separation of which would entail much care and manipulation, it is legitimate, for the sake of expediency in technical work, to estimate some of them along with the lighter metals, and the remainder in a separate portion.( a ) If copper, antimony, and tin, are present in the hydrogen sulphide precipitate, it is convenient to determine the tin in the first portion after precipitating copper and antimony by means of metallic iron ; while in the other portion copper is separated by treating the sulphides with potassium sulphide, tin not interfering in the antimony assay.A few examples may here be given :98 W, R. SCHOELLER : GENERAL PRINCIPLES GOVERNING ( b ) If the filtrate from iron and alumina contains zinc, lime, and magnesia, the two latter are precipitated as usual, zinc not interfering ; in another portion the same filtrate is used for the volumetric assay of zinc.( c ) With ores containing lead, antimony, or arsenic as principal or important constituents, the decomposition by strong sulphuric acid alone presents advantages as regards separation and estimation of these metals. Lead is converted into sul- phate, which is filtered off and dissolved in ammonium acetate.For the most exact work I prefer to weigh the lead as sulphate, after filtering from the gangue, re- precipitating with sulphuric acid, and concentrating by evaporation. The original sulphate precipitate is apt to include small quantities of antimony, bismuth, iron, or lime, which remain dissolved in the liquor on re-precipitating the lead.Arsenic is converted into arsenious acid, which is separated from antimony according to Table 11. by diluting the filtrate from the lead sulphate with twice its volume of strong hydrochloric acid and passing in hydrogen sulphide. The filtrate is partially neutralised for the precipitation of the antimony sulphide, to which is added the small quantity found in the filtrate from the rs-precipitated lead sulphate.The simultaneous determination of the insoluble residue and all the soluble metals may also be carried out by taking 2.5 grms. of ore and making up the volume of the filtrate from the insoluble to 250 C.C. Two 100 C.C. portions are then measured off, and worked upon separately for different metals as explained above. IX.Separate Determination of Certain Co-rzstitueizts.-In addition to the general method outlined in Paragraphs VI. and VIII., special trials will be required for elements present in very minute quantity, or determinations necessitating the use of certain apparatus and reagents undesirable in the combination scheme. Elements present in small quantities : The most important and common example is the gold and silver amay, which is always done by crucible fusion or scorification.The rarer elements occasionally form the object of a special trial (e.g., tellurium), but almost any element may at times have to be looked for separately according to the case in hand, especially where it occurs as an objectionable impurity. The other assays of this class include : (a) Sulfhw.-Whether the assay involves a fusion or not, sulphur is always estimated separately. I t should not be determined in solutions having undergone treatment with hydrogen sulphide, as small quantities of sulphuric acid may have formed in presence of oxidising compounds.(b) Bksion assays, such as : Potassium cyanide for tin (in presence of tungsten).Sodium hydroxide or peroxide, for tin or antimony. Sodium carbonate and potassium nitrate, for arsenic or antimony. Sodium carbonate and sulphur, for arsenic or antimony. Calcium carbonate and ammonium chloride, for alkalis. ( c ) Distillation assays, for mercury, arsenic, fluorine, boric acid. ( d ) Gasontetric methods : Nitric acid, carbonic acid. (e) Deconzpositions by means of hydrofluoric acid.X. Ozidised Minerals. -The composition of clean sulphide ores is established by With oxidised minerals, however, there means of the operations so far described.THE COMPLETE ANALYSIS OF MINERALS AND ORES 99 Element. will be a deficiency due to unestimated combined water, carbonic acid, or oxygen present in various forms of combination. Thus oxides, peroxides, hydroxides, car- bonates, sulphates or hydrated silicates may be present.The analysis is carried out as follows : 1. Silica and total metals are determined in one portion, or two if more con- venient. 2. Total combined water (in hydroxides, hydrated sulphates, and silicates, etc.) ; direct estimation by Penfield’s method (4). 3. Carbonic anhydride: This is most conveniently estimated in a Geissler or similar apparatus by decomposition with an acid.For Clem carbonates, fusion with borax answers well. (5) 4. Sulphuric anhydride : Sulphates of barium and strontium require fusion with sodium carbonate; those of lead and lime are opened up by boiling with ammonium carbonate ; basic sulphates dissolve in dilute acids. The determination differs from that of sulphur in that no oxidising agent is used.The following commoner elements occur in ores in different states of oxidation : 5. Differentiation between higher and lower oxides. Lowest. Highest. Intermediate. Iron ... ... ... Chromium ... ... Arsenic ... ... Manganese . . . ... Ancimony ... ... FeO MnO Cr203 Sb203 As,O, Fe304 &ln,O, ; Mn203 Sb02 - I - Therefore, if found to be present, it will be necessary to ascertain their state of oxidation.Iron : Ferrous oxide is usually determined by decomposing the ore in an atmos- phere of carbonic acid, and titrating with permanganate, ferric oxide being found by difference. Chalybite and vivianite are soluble in dilute sulphuric acid ; magnetite and ilmenite are opened up by fusion with bisulphate, silicates by hydrofluoric acid.( 6 ) Manganese: The intermediate oxides act like mixtures of the proto- and the peroxide, which latter is determined by oxalic acid, or ferrous ammonium sulphate, and permanganate. The higher oxides of manganese interfere with the determina- tion of ferrous oxide, and vice versa; they react upon one another with formation of ferric and manganous salts, though the amount of excess oxygen can, of course, be correctly ascertained.Chromium: Chromic oxide is found in some bauxites; combined with ferrous oxide it occurs a6 chromite, which always contains inore or less ferric iron. I know of no really reliable method for the estimation of the two oxides of iron in this mineral. Chromates are only found in a few localities, and will not be discussed in this paper. The same applies to antimoniates, arsenates, and arsenites.Antimony : Oxidised ores may contain tri- and tetroxide, the former being soluble in tartaric or dilute hydrochloric acid. Total antimony is determined by100 W. R. SCHOELLER : GENERAL PRINCIPLES GOVERKING fusion with sodium carbonate and sulphur, and the insoluble oxide found by difference.XI. Mixed Oxide and Szdphide Ores.-If the sample under examination contains both oxidised minerals and sulphides, the latter will interfere with the determination of combined water and carbonic acid described under Paragraph X. I t also becomes necessary to estimate the metals present as oxides. (1) Combined water: Direct estimation in a Penfield tube by adding ignited litharge or bismuth oxide, as a retainer for sulphur.In presence of fluorides ignited lime is mixed with the substance (*). (2) Carbonic anhydride: The ore is decomposed by a mineral (but not hydro- chloric) acid and sufficient potassium chromate to oxidise the sulphides, or an organic acid, such as tartaric acid, may be used. Calcite is decomposed by bichromate solution alone, without the addition of an acid.(3) Sulphur as sulphides and sulphates : Minerals containing sulphur may be classified as follows according to their solubilities : (a) Sulphates soluble in water (" vitriols "). ( b ) Sulphates of calcium and lead, and basic sulphates (e.g., brochantite), soluble (c) Sulphides soluble in hydrochloric acid (e.q., galena, blende). ( d ) Sulphides insoluble in hydrochloric acid (e.q., pyrites, sulphides of copper). (e) Insoluble Rulphates (of barium and strontium).Extraction with ammonium carbonate solution yields a solution of sulphur frioxide from ( a ) and ( b ) ; nitric acid and potassium chlorate dissolve the sulphur from (c) and ( d ) ; the sulphuric anhydride in the insoluble residue from this treat- ment is determined after fusion with sodium carbonate.Barium (or strontium) carbonate, which forms an occasional gangue mineral of sulphide ores, interferes with the determination of sulphide sulphur by being con- verted into insoluble sulphate. I n such a case the alkaline earth carbonate is removed by a preliminary treatment with acetic acid. (4) Differentiation between oxides, sulphides, etc. : In estimating oxides of metals in presence of their sulphides, advantage is taken of the different behaviour of minerals towards certain reagents which dissolve some while leaving others unaffected.The same principle is applied in separating various oxidised minerals from one another. The percentage of total metals, sulphur, silica, etc., having been determined as described in the preceding paragraphs, a fresh portion of sample is attacked with a suitable solvent and the resulting solution examined for metals by the usual methods, while the residue is subjected to extraction by another solvent if necessary.A scheme for the separation of the more important minerals of the common metals is outlined in Table V., in which the vertical columns indicate the order in which the reagents are used; these are distinguished by lettering (A, B).The horizontal lines show the order of solution of the minerals. Some are soluble in reagents placed in successive vertical columns ; this is indicated by arrows inserted between the names. in hydrochloric acid, or decomposed by boiling ammonium carbonate solution.TABLE V. Lead ... Copper . . . Silver .. . Antimony Tin ... Iron ... Zinc ... ... ... ... ... ... ... ... Nickel:(cobalt). . . Manganese . . . Cdcium ... Barium.. . , . . 1. Water. - Sulphate. - - - Sulphate. Sulph ate. Sulphates. - Sulphate. T[ - 2. A. Acetic, or B. Tartaric Acid. L. Carbonate. k. Carbonates, Oxides, Basic sulphates Oxychloride. B. Trioxide 3 A, B. Carbonate, Carbcmate (in 5~ per cent. acetic- acid).Carbonates. Crtrbonate. Carbonate. Carbonate. 3. L. Caustic Soda, 01 5. Ammonia. A. Sulphate. B. Chloride. A. Trioxide, Sulphide. - A. Carbonate, S.ilicat e. - 4. Hydrochloric Acid. A. Dilute. B. Strong. I i, B. Sulphide. 3 B. Silicates. A, B. Sulphide.3 B. Oxides.$ \ A, B.: - H y dr oxr des, Pyrrhotine. 3 k, B. Sulphide. 3 B. Ni-silicate. Sulphide, 11 Peroxides. A, Phosphate. - 5 .Nitric Acid. Sulphide. Sulphides, Antimonides. Sulphide, Arsenides, etc. Native. Sulphide. * Su1phide.t - Pyrites, Arsenides, Pyrrhotine. Sulphide. Sulphides. Arsenides. Sulphide. { 6. I 7. Fusion with Sodium- A. Bisulphate, or B. Carbonate. - A. Ilmenite, B. Silicates. A , B : Zinc spinels. $ A, B. Ni-silicate. B. Silicates. B. Silicates. B. Sulphate. Magnetite, Chromite. 3 * Separation of sulphide from tetroxide by hydrochloric or nitro-tartaric acid.t Stannine : dissolve in aqua regia. $ Some oxide ores are difficultly soluble in h drochloric acid : fuse with bisulphate. 0 Addition of borax glass advisable when so&m carbonate is used. 11 In zinc blende. T[ If much sulphate is present, extract with sodium sulphate or chloride solution. l. Hydroxide, or B.Peroxide. - - A. Tetroxide. B. Oxide. R. Chromite.102 W. R. SCHOELLER : GENERAL PRINCIPLES GOVERNING Hydrochloric acid. The procedure outlined in this table separates the ore into an c‘insoluble residue ” and L L soluble fraction ” much in the same manner as does hydrochloric acid or aqua regia in the determination, described in paragraph VI., of the insoluble gangue and total metals; but what has been said there with regard to the behaviour of silicates towards acids applies to a much greater extent to the separation of minerals by selective decomposition. Not only does the degree of decomposition vary with the temperature, quantity, and concentration of solvent used, the time of contact, and the degree of comminution, but the dissolved constituents themselves may exert a slight solvent kction.Moreover, crystalline varieties are often less soluble than amorphous ones. The solubility may also be affected by impurities or isomorphous replacements. In this manner, a small amount may escape solution, or be dissolved, by a reagent contrary’to the ordinary behaviour of the mineral. If thereby metals present as sulphides are calculated to oxides, or vice wersa, the final summation will be affected.I t should, therefore, be borne in mind that separations by fractional decomposition, while quantitative in many cases, are far from satisfactory in others. At times it is almost impossible to establish the exact composition of a complex ore by direct analysis, in which case it is legitimate to compute the quantity of one or more oxides present by calculation on the assay results, which is facilitated by the use of tables.(’) The mineralogical examination is the most valuable help where chemical methods fail.Where hydrochloric acid dissolves both the sulphides and oxides of the same metal, the order of the reagents in columns 4 and 5 of the table may be inverted, thus : A. Sod.bisulphate. B. ,, carbonate. Iron ... ... Manganese . . 4. Nitric acid. Pyrites, arsenides, Sulp hide. p yrrho t ine. 5. 6. _- I Hydroxides, oxides. 1 A. Oxides. Peroxides. B. Silicates. Pyrrhotine may also be separated magnetically from pyrites, limonite, etc. (8) XII. Determinations by Diference ; Loss on Ignition.-When making determina- tions by difference, the following rule is observed wherever possible : After the sum of the constituents has been ascertained, the subordinate is estimated direct and the predominant found by difference.If the reverse is done, though this may not affect the final result, the experimental error is all thrown on the side of the subordinate element, and the smaller its amount the less reliable will be the figure so obtained, To take one constituent by difference, by subtracting the sum of all the others from 100*00, is an objectionable practice in mineral analysis ; it is admissible only in the case of refined metals, the fineness of which is ascertained by determining the impurities.TEE COMPLETE ANALYSIS OF MINERALS AND ORES 103 The ‘ I loss on ignition method I’ for the estimation of combined water can only be used occasionally, as with some minerals belonging to classes B and D, Table IV.(e.g., bauxite, limonite, certain silicates). Organic matter, carbonates, sulphides, sulpharsenides, etc., cause high results, while ferrous oompounds lower them. With a little practice, Penfield’s direct determination of combined water is almost as simple as that by loss on ignition.In a few cases carbonic acid and combined water can be estimated together by loss on ignition-viz., with oxidised ores free from sulphur, consisting of carbonates of copper, zinc, or lead, with or without ferric oxides or hydroxides. This is done at a gentle heat in a porcelain crucible, avoiding reduction of its contents by the burner gases. XIII. Choice of Methods ; Purity of Reagents.-A great deal of work in metal- lurgical chemistry has to be carried out abroad, very often in remote districts where working facilities are inadequate, and supplies in chemicals and glassware difficult to procure.In view of this, the analyst who intends to go abroad should become thoroughly familiar with methods involving the use of the most easily procurable and stable chemicals and the simplest form of apparatus.The following examples of alternate methods illustrate this point : Element. Arsenic ... Copper ... Manganese . . . Nickel and co- balt ... ... Simpler Method. Separation as sulphide in strong hy- Iodide titration. Oxalic acid : permanganate, or Vol- hard’s method. Separation by cyanide and bromine. Titration with cyanide (Ni) ; thio- sulphate (Co).drochloric acid. Other Method. Distillation assay. Electrolysis. Bismuthate, persslphate, hydrogen peroxide. Electrolysis; separation by dimethylglyoxime or ni- troso-P-naphthol. The ‘‘ simpler” methods can be carried out with the aid of flasks, funnels, burettes, crucibles, and general reagents. I know from personal experience that work of very varied description can be done with little more than the apparatus just mentioned, and in a laboratory not supplied with gas or water.Charcoal is a good substitute for gas, but a spirit blast lamp is required in gravimetric work; electro- lytic methods are almost a luxury, as involving the use of platinum, though this is indispensable in opening up the If the number of reagents can be restricted, they must, nevertheless, be of known purity.The most frequent metallio impurities in salts are iron and lead. They are readilyremoved by ammonium sulphide, the small excess of precipitant being destroyed by exposure to air or boiling. Sulphuric acid containing lead may be purified by dilution and decan- tation. Volatile reagents-e.g., ammonia, ammonium salts, sulphur, mercuric oxide- must be tested for fixed residue, and blank tests made on all doubtful reagents in general and fusion mixtures in particular.XIV.. Accuracy. Traces.” Statement of Results.-Concerning the degree of accuracy to be attained, a final error of k0-50 per cent. should not be greatly insoluble residue ” or silicates.104 We Re SCHOELLER : GENERAL PRINCIPLES GOVERNING exceeded, and a complete analysis which sums up to between 99.50 and 100*50 is very satisfactory.Clean sulphide ores are moat easily accounted for, oxidised ones less so, while the calculation of mixed ores is likely to be more troublesome. The results are calculated to the second decimal place. To go beyond this is useless in ore analysis. The use of the term b b trace ” may here be considered, as opinions differ regard- ing the amount to which it should be applied.However, from the point of view of complete analysis, we may define 8s b b trace ” a quantiby that does not affect the final result-ie., less than 0.01 per cent, This does not, of course, apply to noble metals, which are calculated to ounces per ton. Complete Analysis of Complex Copper Carbonate and SdphLide Ore.Sample dried at 105O C. Per Cent. Per Cent. ... Copper oxide (CuO) ... 221:fE}Tot~1 copper ... ... 19-40 Ferric oxide ... ... .-. 16.36}Equivalent to ferrous oxide 24.86 Copper, as sulphide ... Iron, as sulphide ... 7-88 Total iron ... ... 19.33 ... Alumina ... ... 2-05 Lime ... ... ... ... 0.28 Lead ... ... ... ... 2.15 Zinc ... ... ... ... 3-11 Arsenic ... ... .. 0.18 Silver and gold (approximate) 0*04{ Gold Bismuth ...... 0.02 Magnesia ... ... ... 0.07 Silver ... 11-63 oz. per ton of 4.20 dwt .} 2,240 Ibs. ... ... Sulphur ... ... ... 10.33 Silica (SiO,) ... ... ... 21-01 Titanic acid (TiO,) ... ... 0.07 Carbon dioxide ... ... 6.80 Combined water .. , ... 5.18 99.48 Manganese, antimony ... traces. Nickel, barium sulphate ... nil. A few concluding remarks, illustrated in this analysis, may be devoted to the mode of reporting complete analyses.For technical and commercial purposes the analyst’s report, in addition to the percentage composition of the material, includes the necessary information regarding its economic value. The left-hand side column gives the list of constituents. Oxides are reported as such, while sulphides and ternary compounds (e.g., carbonates) are returned separately, the former as elements, the latter as oxides and anhydrides.If a metal occurs in the two forms of com- bination, the quantities of oxide and of “metal as sulphide” are given. The description ‘‘ silica ” must be restricted to actual SiO,. To obviate any doubt as to the meaning of a term, it may be followed by the chemical formula in brackets. The residue from the acid treatment, if not subjected to fusion, is described asTHE COMPLETE ANALYSIS OF MINERALS AND ORES 105 “ insoluble ” or ‘‘ insoluble gangue.” Any alumina found in the filtrate from the insoluble is then returned as 6‘ soluble,” which implies that the gangue may contain some more.For the sake of clearness, elements found to be absent and those occurring in traces are best reported below, not included in, the list of constituents. An element not mentioned in the report is understood not to have been specially looked for.The data given in the right-hand side column refer to the valuation of the product. Thus a metal forming one of the values in the ore, if present as oxide, or oxide p l m sulphide, is calculated to b L total metal,” and to another form of com- bination if such information is of use.In this connection the reporting of gold and silver deserves special mention. Many chemists do not include them in the summation, on the ground that noble metals are reported in ounces, etc., per ton. This is no doubt indispensable, but it seems illogical to omit from the general list any element the quantity of which exceeds 0.01 per cent.The following procedure seem8 to me to be free from objections : The ‘‘ approxi- mate” sum of noble metals ( i e . , calculated to the nearest second decimal place) is given in the list of constituents, and the exact figure for eaoh is reproduced in ounces or pennyweights per ton in the opposite column. XV. Bibliography.Tables I. and 11.-(1) Most of these methods will be found in Low’s ‘( Technical Text-Book of Assaying,” f- or Treadwell- Methods of Ore Analysis,” * Beringer’s Hall’s Analytical Chemistry,” vol. ii.,f except the following : Antimony, iodide titration : Classen,$ 146. Arsenic, bromate titration : Classen.sl25. Cobalt, thiosulphate titration : Crookes,ll 255-256. Copper, colorimetric by ferrocyanide : Sutton,T 204. Phosphorus, gravimetric, as PbMoO, : Ohm. News, vol. 82, 55. Silver, separation and estimation as AgI : Classen,§ 23. Table III.-(2) The methods are numbered as in the table. 1, 2 : Seamon, 6‘ Manual for Assayers and Chemists ” (1910), 12.-3, 4, 5,8, 9, 10, 13,14,15 : Tread- well, 235.-6, 11, 26 : Low, 28.-7, 28 : Low, 251.-12 : Low, 30 ; Treadwell, 248.- 16, 19 : Treadwell, 193.-17 : Classen, 179.-18, 23 : Treadwell, 193.-20 : Low, 56. -21, 22 : Furman, sixth edition, 428.-22 (KCNS).: Treadwell, 186.-24 : Treadwell, 193 ; electrolysis, Treadwell, 198.- 25 : Low, 52.-27 : Treadwell, vol. i. (1905), 164, 202.-29 : Low, 52.-30 : Treadwell, 186.-31, 32, 33, 34 (ether) : Treadwell, 313.- 31 (AlPO,) : Low, 22.-32, 34, 41, 42 (ZnO) : Low, 167.--33, 38, 43 (H,S) : Tread- well, 158 ; Classen, 350.-34 (BaCO,) : Treadwell, 149.--35,40 : Low, 73.-36,37,39 : Treadwell, 107.-44 : Treadwell, 161.-45 : Classen, 835.-46, 47, 51, 52, 56, 57 : * Fifth edition, 1911. 8 AusgewiiitEte Mkthoden der AnaZytischen Chnzie, 1901. 11 “ Select Methods of Chemical Analysis,” fourth edition, 1905. B “ Volumetric Analysis,” tenth edition, 1911. t Twelfth edition, 1910. 1 Third edition, 1912106 J. S. JAMTESON: NOTE ON VINEGAR Classen, 462.-48, 53, 58: Low, 163.-49; Low, 189.-50, 55: Beringer, 321.- 54 : Treadwell, 158.-59, 60 : Treadwell, 147. VI. Insoluble Residue and Soluble Fraction.-(3) For the fusion and examination of the insoluble residue and the complete analysis of silicates and rocks, the following books should be consulted : Hillebrand, I‘ United States Geological Survey Bulletin,” 422 ; Washington, X. Oxidised Ores.-(4) ( ( Combined Water ” : Penfield, Amer. J. Science, 1894, 48, 30. (I) Borax Fusion for Carbonates ’’ : Fresenius, ( ( Quantitative Chemical Analysis,” seventh edition (1876), 336. (6) (( Titration of Ferrous Oxide in Silicates ”: J . Soc. Chem. Ind., 1912, 185. XI. Nixed Oxide and Xui’phide Ores.-(’) “Tables for Calculating the Com- position of Minerals ”: Holloway : Trans. Inst. Min. and Met., vol. 21, 576. (8) Magnetic Separation of Pyrrhotine ” : Lunge-Keane, vol. i., Part I., 289. Manual of the Chemical Analysis of Rocks ” (1904).

ISSN:0003-2654    

DOI:10.1039/AN9154000090

出版商:RSC    

年代:1915

数据来源: RSC

摘要:

106 J. S. JAMTESON: NOTE ON VINEGAR NOTE ON VINEGAR. D TRING a re nt BY J. S. JAMIESON, F.I.C. (Read at the Meeting, November 4, 1914.) xamination of a vinegar factory, and the analysis of the vinegar made from malted maize, the following figures were obtained : Sample No. 1 was a vinegar prepared from germinated maize and pasteurised ; Sample No. 2, the same vinegar before pasteurisrttion ; and Sample No, 3, an ordinary barley malt vinegar : 2.3. SP. gr. ... ... ... Total ~lolidg . . . ... .a Ash ... ... ... ... Nitrogen ... ... ... ... Phosphoric acid.. . ... ... Aoetic acid ... ... ... Original solids . . . ... ... 1.019 3-66 per cent. 0.36 ,) 0.009 ,, 0.02 ,, 4-20 ,, 9-96 ,, 1.020 3.28 per cent. 0.34 ,, 0.014 ), 0.02 ,, 0.50 ,, 10.03 ,, 1-013 1.64 per cent.0.36 ,, 0.06 ), 0.05 ), 4.59 ,, 8.52 ,, The analysis and examination were carried out for the purpose of comparing vinegar prepared from malted barley with that prepared from malted maize. The manufacture of the above vinegar was carried out on the same principle as that used for the manufacture of malted barley vinegar. I t will be seen that the figures for nitrogen and phosphoric acid in the vinegar made from malted maize are muchANALYSIS OF CELLWLOSE AND CELLULOSE DERIVATIVES 107 below those generally accepted for a genuine malt (barley) vinegar, and that the: figures for the extract and original solids are a good deal higher. The conclusion is that the proteins and phosphates from malted maize are not so readily extracted by an aqueous infusion as that of malted barley,

ISSN:0003-2654    

DOI:10.1039/AN9154000106

出版商:RSC    

年代:1915

数据来源: RSC

摘要:

ANALYSIS OF CELLWLOSE AND CELLULOSE DERIVATIVES 107 RECENT PROGRESS IN THE ANALYSIS OF CELLULOSE AND CELLULOSE DERIVATIVES. * COMPILED BY J. F. BRIGGS. GENERAL. THE study of cellulose as a chemical entity has attracted numerous new workers within the last decade. This increased attention is to be ascribed mainly to the enormous development in recent years of the plastic cellulose industries, which manipulate this material in virtue of its chemical and colloidal functions, as distin- guished from its anatomical or structural features, which form the basis of the older cellulose industry.Until quite recently the only comprehensive textbook in any language dealing systematically with the chemistry of cellulose and members of allied groups was Gross and Bevan’s ‘( Cellulose ” (Longmans, Green, 1893), with quinquennial appendices, (‘ Researches on Gellulose,” issued at intervals to bring the main sections of the original up to date.Latterly, however, we have to record the publication of a more ambitious work in German by Carl Schwalbe, I ‘ Die Chemie der Cellulose ” (Borntraeger, Berlin, 1911). Schwalbe has done for the chemistry of’ cellulose what von Lippmann did for that of the sugars-he has collected and systematically classified the principal results of all the accessible research literature of the subject. Besides forming a co-ordinated and exhaustive textbook of cellulose chemistry, Schwalbe’s book eerves the useful function of an historical starting-point in original work by saving the search for previous publications through the scientific.journals prior to 1911. In addition, the analytical section of the subject receives in Schwalbe’s book its first systematic exposition. This branch of analytical work consists to a large extent in the establishment of so-called ‘(values ” by the rigid standardisation of reactions already well known in their qualitative aspect, and many of the methods owe their origin and operative details to the investigations of the author himself.ESTIMATION OF CELLULOSE IN RAW MATERIALS. Foremost among the analytical operations in connection with cellulose stands the problem of the estimation of cellulose in raw and semi-raw plant materials. The operations here concerned have for their object the preparation under quantitative conditions of purified cellulose in the form of a residue, after the elimination of all work.* This is the first of a series of articles dealing with recent advances in certain branches of analytical Others will follow at intervals. -EDITOH.108 J. F. BRIGGS: RECENT PROGRESS IN THE other matters by methods of selective extraction, oxidation and hydrolysis, combined in some cases with the formation of specific chemical derivatives of non-cellulose groups, which thus become soluble in the extracting media employed.The cellulose is the residue from a series of carefully regulated processes of attrition, and the results embody all the errors, pZzu and minus, caused by the chemical and mechanical deficiencies of the methods of purification employed. No new advance has to be recorded in the principles of cellulose estimation.The methods so generally applicable in analytical chemistry have hitherto proved of no service here ; none of the physical or chemical “ constants ” of cellulose have as yet been made available for its quantitative estimation, and it has yielded no speci- fically characterised derivatives from which its percentage may be calculated in the ratio of combining weights.In discussing the question of the estimation of cellulose in plant materials, the subject may be approached from two main points of view, differing widely in their objects and conceptions-that of agricultural Chemistry, and that of the cellulose- manufacturing industries. With the first aspect the present review has no concern, sxoept to remark that it falls mainly within the domain of foodstuff chemistry.In this connection the word cellulose ” has sometimes been loosely used, and the term The object of the I‘ crude fibre ” methods of analysis is to estimate, by processes of extraction and mild hydrolysis, the residuum of plant substance which might be expected to resist the digestive processes of the herbivora.These methods include the old-established Henneberg-Weende method and the more recent glycerol-sulphuric acid method of hydrolysis of J. Konig ; the products comprise, and rightly so, other resistant matters besides cellulose, notably most of the Ugnin. The industrial methods for the estima- tion of cellulose in plant materials have for their principal object the establishment of an analytical basis for the control of the processes of production, by affording a, comparison between the total amount of cellulose actually present and that prac- tically realisable on the large scale under the limitations imposed by commercial conditions.In analytical operations of this order the presence of lignin, even as traces, in the product is fundamentally inadmissible, and the product of analysis must preserve reasonably unimpaired the chemical and physical properties recognised as characteristic of the particular species of cellulose at the optimum.The same proviso applies equally to the estimation of cellulose in plants for purely scientific purposes, from a botanical or biochemical point of view, and the operations involved are not essentially different. As a starting-point for the study of the recent literature of the subject, the dissertation by Max Renker, “ Ueber Bestimmungsmethoden der Cellulose ” (Berlin University, 1909; AKALYST, 1910, 36, 71), forms an outstanding mark. In the course of a complete r6sum4 of the methods hitherto published for the estimation of cellulose in lignified tiswes, Renker subjected to a searching critical and experimental revision all those which appeared to possess any claim to serious consideration.Renker’s work is of the highest value ; it embodies a vast number of laborious estimations, and preserves throughout the correct perspective necessary in treating ao complex a subject. He worked with a series of typical materials : raw cotton, crude fibre ” more appropriately represents the conception implied.ANALYSIS OF CELLULOSE AND CELLULOSE DERIVATIVES 109 sulphite wood pulp, boiled jute halfstuff, and dealwood shavings, representing a range of increasing degrees of lignification.The materials were previously extracted with water and organic solvents, and all the methods in question then applied to each so as to obtain strictly comparable results.The net outcome of this research was to confirm experimentally what had long been recognised on CL priori grounds-namely, that for the estimation of cellulose in lignified materials, the classical chlorine-gas method of Cross and Bevan is the only one capable of general employment with any satisfaction. The suitability of any method depends on the complete removal of the lignin with the minimum attack on the cellulose proper.This aspect of the question was systematically dealt with by Renker. The cellulose produced by each process was tested for its freedom from residual lignin and for its chemical integrity. In addition, the inherent severity of each process, its tendency to reduce the yield .of cellulose while removing the lignin, was tested by repeating the treatment on the purified cellulose obtained in the first instance.None of the methods available could be described as perfect in all respects; some of them-e.g., permanganate in presence of 5 N-acetic acid-were sufficient for the purification of such nearly pure materials as cotton and sulphite wood pulp, but failed to remove the lignin from jute and wood.As a matter of fact, Cross and Bevan’s reaction stands alone, although Renker classifies it among the methods of oxidation.” Lignin, as an unsaturated body of cyclic configuration, is susceptible both to halogenation and to oxidation; but whereas the former reaction is perfectly specific, the latter is only selective, and the purely oxidation methods all fail. Cross and Bevan’s method is satisfactory only in so far as the conditions favourable to oxidation can be controlled.The action of the gas at low temperatures (0’ C.) and st maximum concentration, the restriction of the duration of the action to the shortest time sufficient to obtain penetration, and the immediate immersion in sulphurous acid when the treatment is finished-all of them precautions endorsed by Renker-have precisely the object of restricting oxidation.The deficiencies of the method are nearly all referable to mechanical imperfec- tions, mainly to the difficulty of penetrating with the gas a colloid material of dense formation. I n the case of a loose fibre like jute, the purification may, with due precautions, be carried out in a, single cycle of operations without sensible modifica- tion of the cellulose proper; but in the case of woody structures no mechanical preparation is sufficiently perfect to expose all the fibres uniformly to the immediate action of the chlorine gas, and the chemical operations are called upon to supplement the deficiencies of the preliminary mechanical treatment.The dense structure has to be opened up by chemical attrition by removing successive portions of the lignin in order to make the rest accessible; the cellulose residue is thus subjected to very excessive treatment, and the yield is accordingly lowered.Renker’s description of the procedure required for the preparation of pure celluloso from the finest dealwood shavings illustrates the difficulty. In this case a single exposure to chlorine gas for m e hour, and elimination of the chlorinated products with sodium sulphite, were totally inadequate for the preparation of a lignin-free cellulose ; a second chlorination of thirty minutes, followed by four more of fifteen minutes each, with intermediate extractions with sulphite, were neoessary110 J.F. BRIGGS: RECENT PROGRESS IN THE before the final traces of lignin were removed from the denser tissues.This necessity of attacking the lignin of woody structures piecemeal by a succession of chlorination treatments is confirmed by all other authors who have studied the question, and the prejudicial effect on the yield of cellulose is incontestible. By careful mechanical preparation to overcome the cohesion of the tissues, the number of successive chlorinations may be reduced to four, or perhaps three; but certain workers (Dean and Tower, J .Amer. Chem. Soc., 1907, 29, 1119) have been content with two chlorinations only, balancing the ptus and minus errors by accepting a. cellulose not perfectly free from traces of lignin. In carrying out the estimation of cellulose by Cross and Bevan’s method, Renker recommends the omission of the preparatory digestion of the material with boiling caustic soda, also the omission of the caustic soda from the sodium sulphite bath employed for the extraction of the chlorinated products.These omissions do not prevent the complete elimination of the lignin, and a higher yield of cellulose i s obtained. For instance, sulphite wood pulp yielded 9495 per cent.of cellulose by Cross and Bevan’s original process, 95-5 per cent. when the caustic soda was omitted from the sulphite bath, but used in the preparatory treatment, and 97.9 per cent, when it was omitted at both stages. The omission of the caustic soda from the sulphite bath may be readily accepted as an improvement on the original process; the alkali is not necessary, although helpful, for the extraction of the chlorinated lignin, and since the cellulose, after exposure to the chlorine, is likely, owing to oxidation, to be highly sensitive to the action of alkali, the loss caused thereby should be avoided.On the other hand, the preparatory digestion with caustic soda cannot be dispensed with in any general sense, although in many cases the severity of the treatment might be modified, according to the chemical and physical constitution of the material and the experience of the analyst, 80 as to combine a legitimate conservation of the cellulose with sufficient purification.No raw plant material, however, consists of lignin and cellulose alone, and an alkaline digestion is necessary to insure the removal of matters such as proteins, pectins, gums, etc., which would otherwise be only partially eliminated.In certain materials-e.g., flax, hemp, straw, grasses, etc., not taken into account by Renker-these other constituents assume a greater importance than the lignin itself. Moreover, although Renker has proved that the alkaline digestion is not necessary for the removal of the lignin by the chlorination process, it certainly contributes towards opening up and softening the denser structures, and in such cases may even preserve the cellulose by reducing the number of chlorinations required.Closely following the appearance of Renker’s review, Dmochowski and Tollens (J. fiir Landw., 1910, 58, 1; ANALYST, 1910, 35, 408) published a process for the estimation of cellulose in cc crude fibre ” and industrial materials.I t is substantially a revival of Cross and Bevan’s nitric acid process, which had been practically abandoned by those chemists in favour of the more controllable chlorination process. Renker had included the nitric acid method in his experimental survey, but it shares the defects of all the “wet ” acid processes of the same class, in that the cellulose is severely modified both by oxidation and hydrolysis while the lignin is being attacked.It may be conceded that complete elimination of the lignin isANALYSIS OF CELLULOSE AND CELLULOSE DERIVATIVES 11.1 attainable by this process, and that the numerical results are fairly satisfactory in the case of materials not highly lignified (e.g. chemical wood pulps); but in the case of raw lignocelluloses, such as jute or wood, the attack is too general and the 108s of cellulose substance too high (compare table in Renker’s article, Zoc.cit.). Dmochowski and Tollens, and later, Rao and Tollens (J. fur Landw., 1913, 61, 237; ANALYST, 1913, 38, 509), recognising the effect of the hot acid upon the cellulose, proposed corrections to meet the case; but it is difficult to see what advantages the nitric acid process offers over the chlorination method, either for general or special purposes, while the defects common to both are far more pronounced in the former, where the cellulose is exposed for a considerable time to the action of a hot oxidising and hydrolysing acid.The only serious opposition to the supremacy of the chlorination process has been raised by J.Konig and Huhn in a series of articles in the Zeitsch. Farben-Id., 1911-12 (ANALYST, 1912, 37, 268). These authors made a most elaborate com- parative research on the principal methods for the estimation of cellulose in woods and textile fibres. Their experimental work is of the highest order, and their critical examination of the products more thorough even than that followed by Renker ; but the theoretical and practical conceptions upon which the investigation and its conclusions are based are so extraordinary that the utility and validity of the whole laborious research are imperilled.According to the authors, a raw plant material, freed from adventitious 6‘extractives,” consists substantially of “ true cellulose,” hemihexosans, pentosans, lignin, and, in the case of bark tissues, cutin.Cross and Bevan’s method removes the lignin, but leaves those other bodies which are not readily soluble in boiling 1 per cent. caustic soda stiil in union with the cellulose, which consequently contains methoxyl, furfuroid, and possibly carboxylic groups. Aocording to Konig’s method (ANALYST, 1908, 33, 98) the material is first hydrolysed by heating for one hour at 135OC.with a 2 per cent. solution of sulphuric acid in glycerol, in order to attack these pseudocellulose groups, and subsequently treated with ammoniacal hydrogen peroxide to oxidise the lignin ; the residue should then be true cellulose,” pZus cutin, if any. This is a scheme which naturally appeals to the analytical chemist, but unfortunately the residue is certainly not true cellulose.It is a disintegrated fibrous debris which cannot be recognised as cellulose, either in the scientific or industrial sense of the word. Cellulose is not simply a particular arrangement of atomic groupings of carbohydrate organic matters (as, for instance, sugar, which can be crystallised and recrystallised without change of identity) ; it is a physico-chemical complex bearing the impress of the vital evolu- tion of the plant from which it is derived.Thus it cannot be chemically described in terms of certain percentages of 66 true ” cellulose and pseudocellulose. The removal of even the humbler members of tbe complex destroys the integrity of the whole organism, just as the elimination of the lower classes would destroy the fabric of human society.true cellulose” as a common denominator is doomed to dissipation in the act of realisation. The chemical organisation of the various natural celluloses must differ according to the vital conditions under which they are elaborated, and they may be classified according to the degree of chemical resistance, or otherwise, which characterises the species.The idea of the isolation of112 J. F. BRIGGS: RECENT PROGRESS IN THB The analytical problem, defined on the plane of practical utility, is to determine the maximum yield with the optimum chemical and physical qualities obtainable from the species. The results recorded by Konig and Huhn by their method of estima- tion are a sufficient refutation of their outlook.Pure cotton is reported to contain only 88.27 per cent. of “ true cell~lose,~~ while sulphite wood cellulose, for all prac- tical purposes of 95 per cent. purity, ig reported to contain less (( true cellulose” than the raw wood of the same species ! These extraordinary results become in a manner intelligible when the method is viewed in its true perspective, It is not a method for the estimation of cellulose, but rather an empirical measure of the degree of resistance of the material to acid hydrolysis under specific conditions, unnecessarily complicated by the subsequent oxidation with peroxide.Of two soft, isolated celluloses, both equally penetrable and exposed to attack, the ootton loses less weight by hydrolysis than the more sensitive wood cellulose; but the raw wood itself is protected both mechanically and chemically by the presence of the lignin, so that the total loss of substance, including the latter, is actually less than that suffered by the unprotected wood fibre previously freed from lignin.However attractive the conception of a residuum of “true cellulose” as a common com- ponent of all natural celluloses may be, it is practically untenable, and no amount of so-called “ purification ” could ever raise a true cellulose ” derived from wood to the chemical level of a cotton cellulose in its natural condition.The validity of Konig and Huhn’s conceptions was contested by Cross and Bevan (ANALYST, 1912, 37, 501), and the reply of the German authors (ibid.) left the controversy very much in the same position, It is obvious, however, that any analytical definition of 4 6 cellulose ” must conform to some ideal of technical utility, and that a method which reports 88 per cent.of cellulose in a material which in all its technical applications has a value of 100 per cent. purity would lead to serious confusion. The discussion on the value of the various methods was completed by a com- parative investigation by €3.Matthes and F. Konig (Arch. Pharm., 1913, 251, 223, 244 ; ANALYST, 1913, 38, 415), who, operating on filter-paper and cinchona bark, pronounced definitely in favour of Cross and Bevan’s chlorination process. The chemistry of the reaction has recently been studied by E. Heuser and R. Sisber in a paper on the action of chlorine on spruce wood (Zeitsch. angew.Chem., 1913, 26, Sol), from which it would appear that in the case of wood the action of the chlorine is twofold, part of the lignin being chlorinated, and part directly oxidised; four successive chlorinations (total exposure two hours) are sufficient to yield a cellulose free from lignin, and the formation of oxycellulose is not such a serious source of error as might be feared. The utility of the systematic application of analytical methods in industrial research in this field is ably illustrated in a report by W.Raitt on “Bamboo” (Indian Forest Records, 1912, 3, Part 111.). REtitt adopts a simple scheme of extractions and classifies the constituents of the raw plant as follows: (a) Starch group-matters extracted by water at looo C.; (b) fat-wax group-matters extracted by organic solvents (ether-alcohol) ; (c) pectose group-extracted by 1 per cent. sodium hydroxide at 100” C.; (d) lignin, extracted by 4 per cent. sodium hydroxideANALYSIS 04' CELLULOSE AND CELLULOSE DERIVATIVES 11 3 above 130" C., with simultaneous loss of cellulose, preferably estimated by Cross and Bevan's chlorination process ; (e) cellulose, as residue from d.He recognises the extreme importance, in all operations of this order, whether analytical or industrial, of the mechanical and physical condition of the material submitted to treatment. Three factors are inimical to thorough penetration and extraction : resistance due to mass or density of structure ; resistance due to imprisoned air ; colloidal resistance due to the partial gelatinisation of the structures through which free interchange is desired.In the case of bamboo, the opening of the tissues by severe roller-crushing is recommended. NATURE OF LIGNOCELLULOSE. For many years the nature of lignocellulose was a subject of discussion, the prevalent opinion-that favoured by Cross and Bevan-being that lignocellulose was a chemical compound, ester or ether, of lignin and cellulose. This view was founded chiefly on the difficulty of separating the two bodies, except by reactions involving chemical decomposition.The development of colloid chemistry in recent years has, however, led Wislicenus and Kleinstiick (Zeitsch. Chem. Ind. Kolloide, 1910, 6,17, 87) to formulate, on the basis of some synthetic experiments, the theory that ligno- cellulose is an adsorption compound of interpenetrating colloids, and that the process of lignification in plants is one of deposition of colloids from the sap in the form of gel-membranes under the surface-action of the cellulose.This view now appears to be generally acceptable, and receives some support by the recent isolation of lignin as a definite residue, preserving the form and structure of the original cell-membrane by reactions which dissolve and hydrolise the cellulose.Thus, J. Konig (Chern. Zeit., 1912, 36,1101) has isolated 31 per cent. of lignin from spruce wood by hydrolysing the cellulose according to the method of Ost and Wilkening with 72 per cent. sulphuric acid, whilst Willstatter and Zechmeister (Ber., 1913, 46, 2401) have obtained a similar result more satisfactorily by the use of fuming hydrochloric acid (41 per cent.HCI). These observations might form the basis of a simple direct method for the estimation of lignin. Richter (Wochenbl. Papierfab., 1912, 43, 1631) has applied a, modification of Seidel's process for the estimation of lignin in raw materials and impure commercial sulphite wood pulps.I t depends on the action of 13 per cent. nitric acid at 98" C., and titration of the nitrous acid produced by the oxidation of the lignin. Five grms. of the sample are heated with 100 C.C. of the acid in a special distillation flask, cmd the yield of nitrous acid is standardised in terms of lignin by an estimation made with spruce wood on the assumption that the latter contains 28 per cent.of lignin ; all materials must be previously freed from resin and other reducing substances by extraction with ether, alcohol, and water. In a later communication (ANALYST, 1912,37, 511) Richter described a colorimetric application of the same reaction. MODIFIED CELLULOSE. d large section of the analytical chemistry of cellulose is concerned with the determination of what may be called the '' chemical condition " of cellulose.Interest in this aspect grew up with the development of the chemical industries employing114 J. F. BRIGGS: RECENT PROGRESS IN THE purified cellulose as their raw material, as it became recognised that two specimens of cellulose of similar origin, and purified apparently in a similar manner, are not necessarily chemically equivalent.This branch of the subject is still largely in the empirical stage, with particular tests for each industry, and still awaits the systematic co-ordination of the factors involved. Thus, we find methods for determining the 4 4 degree of mercerisation ” and the ‘‘ degree of bleaching,” which are really of far wider general significance.Owing to its complexity, cellulose is a very sensitive organism, and its integrity is liable to modification by the cumulative eil’ect of almost every agency to which it has been exposed. The problem is to determine in what sense, and to what degree such modification has taken place. The results may be used for comparing a modified cellulose with a normal specimen of the same type, or various types of cellulose with a standard type, for which cotton cellulose is adopted by general consent ; but in all cases it must be remembered that the chemical processes used for the isolation of pure celluloses may have had a very pronounced effect on the integrity of the original.The chief modifications to be recognised are those due to hydration, oxidation, acid hydrolysis, and (( depolymerisation.” (a) Hydrated CeZZulose.-It was formerly held that cellulose formed loose com- binations with water, constituting definite hydrates analogous to the hydrates of sulphuric acid or of crystallised salts, and it was attempted to describe the hydrates of cellulose in terms of molecular formulae.A distinction wa8 made between hygro- scopic moisture and water of hydration, which were supposed to be expelled at different hemperatures corresponding to a difference in the nature of the union.These views, however, have not been maintained, and it is necessary now to regard the phenomenon of hygroscopicity merely as a manifestation of hydration, both belonging to the same ord& of adsorption phenomena common to the colloidal condition (see Briggs, Papierfabrikant Festheft, 1910 ; J.SOC. Chem. Ind., 1910, 29, 874). In presence of an excess of moisture, whether in the form of atmospheric aqueous vapour or of liquid water, an adsorption equilibrium is set up and water is solidified in the substance of the cellulose in proportions depending on the surface development of the internal structure. In this sense all celluloses, even the normal cotton cellulose, are hydrated, but the degree of hydration is capable of modification over a very wide range by chemical or mechanical treatments.The analytical methods originally devised for the estimation of the degree of mercerisation ” are applicable in a general sense for the comparative estimation of the degree of hydra- tion, however produced. Since hydration is a- colloidal adsorption phenomenon, all these methods are based on the estimation of the relative adsorption capacity of the cellulose for various substances under strictly empirical conditions.Thus, we have methods proposed by Hubner (J. SOC. Chem. Id., 1908, 27, 105), based on the adsorption of iodine ; by Knecht (J. SOC. Dyers and CoZ., 1908, 24, 68), on the adsorp- tion of substantive dyestuffs ; by Schwalbe (Die Chemie der CeZZuZose, p.634), on the adsorption of cupric hydroxide from Fehling’s solution ; by Vieweg (Chem. Zeit., 1908, 32, 329), on the adsorption of sodium hydroxide. In all these methods the assump- tion is that increased adsorption capacity indicates, and is proportional to, increased hydration or mercerisation ; in other words, that the colloidal distention’ or gelatinisa-ANALYSIS OF CELLULOSE AND CELLULOSE DERIVATIVES 11 5 tion in presence of water, which is the outward sign of hydration, is accompanied by an increase in those activities which are attributed to the surface development of the colloid particles, ( b ) Ozycelldose and ~~droceEZzLZose.-Cellulose modified by oxidising agents or hydrolysing acids acquires cupric reducing properties owing to the formation or opening up of free carbonyl groups.Little has been added in recent years to our knowledge on the theoretical side as to the nature of these modifications, much of it being based on assumption and analogy. Neither oxycellulose nor hydrocellulose can be described in terms of definite compounds ; they merely indicate the sense in which the cellulose complex has suffered modification, in degrees which appear capable of infinite variation.Attempts to describe these modified products a8 mixtures of percentages of (‘ true ” oxycellulose or hydrocellulose and unaltered cellulose have not been sustained; it is true that the portions containing the free carbonyl groups can be split off in the form of soluble products by the continued action of boiling alkalis, but the residue is not unaltered cellulose.Oxycellulose and hydrocellulose must be assumed to differ in the mode of formation of the open carbonyl groups which characterise them. In the case of oxycellulose, there appears to be definite oxidation of alcoholic hydroxyls into aldehydic carbonyl radicals ; in the case of hydrocellulose, it may be inferred that the closed carbonyls of the cellulose are opened by hydrolytic fission in a manner analogous to the production of amylodextrin from starch.In the action of acid oxidising agents, both effect8 may be supposed to take place simultaneously. The well-known methylene blue test for oxycellulose may be assumed to depend on an increase of the balance of acidity in the groups of the cellulose complex through the oxidation, resulting in an increased combination with dyestuff bases, whereas the opening up of aldose groups by simple hydrolytic fission is not accompanied by an increase in acidity.Oxycellulose and hydrocellulose, like the cupric reducing sugars, are readily attacked by boiling alkali hydroxides, and the residue ultimately loses its reducing property, but the cellulose still remains modified.Vieweg (Papier Zeit., 1909,34, 1352) proposed to measure the degree of chemical modification by estimating the amount of alkali neutralised by boiling under standard conditions; but since the action of the alkali is not confined to the carbonyl groups, and is continued indefinitely on the cellulose residue, the method has not been widely adopted.Parker (J. Phys. Chem., 1913, 17, 219; ANALYST, 1913, 38, 331) recommended a, boiling alkali method for estimating, by loss of weight, the percentage of normal cellulose in bleached cotton (surgical cotton-wool) ; but his assumption that a final point is ever reached, indicating a line of demarcation between resistant and non- resistant cellulose, cannot be accepted on grounds of general experience.Never- theless, the rate of hydrolysis of the carbonyl groups by alkalis is far more rapid than that of the complex as a whole, and the loss of weight in boiling alkali under rigidly standardised conditions takes a legitimate place among the empirical tests for the chemical integrity and purity of cellulose.The degree of chemical modifioation of cellulose by oxidising or hydrolysing agents may range from a barely perceptible weakening of the fibre to a profound structural breakdown. I t is frequently called, not very appropriately, the ‘( degree116 J. F. BRIGGS: RECENT PROGRESS IN THE of bleaching,” and is generally measured by the estimation of the cupric reducing power (copper value) of the sample.The details of the method have been most elaborately worked out by Schwalbe, and the minute precautions and special apparatus required to obtain concordant and strictly comparable results are the only obstacles to its perfectly general utility. A full description of the procedure is given in Schwalbe’s book (p. 625), also in Zeitsch.angew. Chem., 1910, 23, 924; ANALYST, 1910, 35, 318; further sources of error have recently been noted in Zeitsch. angew. Chem., 1914, 27, 567. The estimation of the copper value is the most definite measure available for the diagnosis of the chemical condition of cellulose, and is particularly useful in the nitrocellulose industry; in other applications it is employed to detect weakness due to chemical damage in bleached textiles, and consequent instability of colour.The term (6 copper value ” denotes the weight of metallic copper in grms. reduced from Zehling’s solution by 100 grms. of cellulose. The purest bleached cotton of highest commercial quality shows a copper value considerably less than 1, but commercial specimens with copper values between 1 and 2 are fairly common. Modification of the cellulose by oxidation produces a higher copper value than modification, to an externally equivalent degree, by acid hydrolysis.Specimens which have suffered profound modification in the sense of oxycellulose may show copper values of 16 or more. In addition to the direct determination of the cupric reducing value of cellulose, Schwalbe has described other applications of the reaction with Fehling’s solution.The ‘6 hydrate copper value ” represents in terms of metallic copper the amount of cupric hydroxide adsorbed by the cellulose from Fehling’s solution in the cold, without reduction (see above, under Cellulose Hydrate). This value is considerable in the case of specimens of pronounced degree of hydration-q., mercerised cellu- lose-and a correction must be made for it in arriving at the true cupric reducing value ; it is low (0.5) for ordinary cotton cellulose, and still lower for hydrocellulose.The hygroscopic moisture in these three types also shows differences in the same sense. Another application of the reaction with Fehling’s solution is the ‘‘ hydrolysis difference value ” which represents the difference between the original cupric reducing value and the increased value obtained after boiling the sample for fifteen minutes with 5 per cent.sulphuric acid. This difference affords a measure of those portions of the cellulose, whether adventitious or pertaining to the complex, which are more readily susceptible to hydrolysis by acids. Cellulose of high degree of hydration is hydrolysed more rapidly and shows greater difference values than ordinary cellulose, while hydrocellulose, having already undergone acid hydrolysis, shows smaller differences.An important comparative study of the various copper values and other analytical factors, as applied to bleached cotton for use in the manufacture of guncotton, was published by C.Piest (Zeitsch. angew. Chem., 1912, 25, 2518). (c) Solubility in Caustic AZkaZi.-The matter soluble in cold caustic soda solution varies largely according to the concentration of the alkali; the nature of the sub- stances dissolved must also be very variable, according to the nature of the cellulose investigated. Thus the test is somewhat deficient in specific significance, but is oapable, when applied empirically, of affording valuable indications of purity andANALYSIS OF CELLULOSE AND CELLULOSE DERIVATIVES 11 7 chemical condition.The concentrations of sodium hydroxide most generally employed are 5 per cent. (Schwalbe, p. 636) and 17-5 per cent. (Jentgen, Kunststofe, 1911, 1, 165) ; the matters soluble in alkali are separated on neutralisation or acidification, sometimes with the addition of alcohol, into two groups-(a) reprecipitated as colloid, and ( b ) permanently soluble.The matters extracted by the alkali may be partly pre-existent in the raw cellulose-e.g., pentosans, hemi-celluloses, resins, etc. ; hence the designation ‘( wood-gum value ” applied by Schwalbe and others to this test-but they may consist also partially of substances formed by the chemical modification of the cellulose itself.Thus celluloses, otherwise pure but modified by hydration, oxidation, or hydrolysis, are all sensitive to caustic alkalis, and suffer more or less loss of weight according to the conditions adopted. With concentrated (17.5 per cent.) alkali the more highly hydrated modifications of cellulose are con- siderably gelatinised, yielding large proportions of soluble matters, and some difficulty is experienced in the filtration.This process finds an application in the characterisa- tion of the various types of artificial silks ; it may be noted also that wood cellulose prepared by the soda process yields to concentrated alkali a larger proportion of soluble and reprecipitable ‘‘ hemicellulose ” than pulp prepared by the sulphite process.(d) Viscosity of Solutions,-The viscosity of cellulose solutions is capable of affording a most valuable measure of the chemical condition of the complex. Unfor- tunately, the test is hedged about by many experimental difficulties, and a really satisfactory standardisation has hardly yet been attained. The interfering factors are : (1) Chemical modification of the cellulose during the treatment necessary for bringing it into solution-this excludes the use of the ordinary cellulose esters (nitrates, acetates) as a basis for the test ; and (a), since none of the direct solvents of cellulose are of simple composition, the influence of slight variations in the com- position of the solvent upon the viscosity of the solution.Cuprammonium appears to be the only comparatively indifferent solvent available, and its use forms the basis of a method developed by H. Ost (Zeitsch. angew. Chem., 1911, 24, 1892). The solvent employed must be of strictly standard composition, both as to cupric hydroxide and ammonia. Changes, imperfectly understood, take place in the viscosity of the solutions on standing, which seem to indicate that the solvent is not perfectly inert, and it is sometimes difficult to obtain concordant results in successive observations.Piest (Zeitsch. ungew. Chm., 1912, 25, 2518) has studied the applica- tions of this test, and demonstrated its importance in the valuation of cotton for the nitrating industry. H e has also extended his investigations (Zeitsch.angew. Chem., 1913, 26, 24) to the study of the viscosity of solutions of nitrocellulose in organic solvents, leading to similar general conclusions. A paper by B. Baker (J. Clzem. SOC., 1913, 103, 1653) should also be noted. According to Ost, cellulose modified in the sense of oxycellulose and hydro- cellulose gives solutions of low viscosity. The viscosity diminishes rapidly at first, according to the degree of modification, but in both cases a point is soon reached at which further modification produces only small decreases in viscosity, which, in fact, almost becomes constant. The fall in viscosity is not a direct measure of the degree of modification, nor of the sense in which it has taken place; it is provisionally118 J. F.BRIGGS: RECENT PROGRESS IN THE assumed to indicate a certain L L depolymerisation ” of the cellulose complex, and affords a sharp diff’erentiation between normal and modified cellulose, which is independent of the cupric-reducing power.Thus the residue from the alkaline digestion of oxycellulose or hydrocellulose may show little or no reduction of Fehling’s solution, but the depolymerisation which accompanies the original modifi- cation will still be indicated by low viscosity of solutions.Ost states that cellulose mercerised by short treatment with concentrated alkali suffers no diminution in viscosity, whence it would appear that simple hydration, as such, involves no hydrolysis or depolymerisation of the complex ; this, however, is disputed by Baker (Zoc. cit.). On the other hand, the prolonged action of concentrated alkali on cellulose causes a progressive dacrease in the viscosity of the solutions similar to that produced by the action of acids.Thus we have an analogous range of hydrated hydrocelluloses which do not reduce Fehling’s solution. SPECIFICATION OF cc NORMAL COTTON ” FOR NITRATING. For the manufacture of stable explosives from cellulose the demands as to purity and chemical quality are somewhat severe, and the specifications are framed so as to insure the use only of new (is., unworn) material, consisting mainly of mature, long-staple fibres, perfectly freed from seed residues (“ motes ”) and care- fully bleached.According to the chemical clauses of the specification (O.F., No. 72 J, March 20, 1908) issued by the Royal Gunpowder Factory, the material must not show more than the following percentages, calculated on the dry substance : Moisture, 7.0; oily matter, 0.6 ; loss on boiling for one hour in 3 per cent.caustic soda solution, 5.0; reduction of Fehling’s solution (1 vol. to 2 vols. of water), on heating at 100” C. for fifteen minutes, 1.0 (as Cu20) ; mineral matter, 0.5.On dyeing with a basic dyestuff such as fuchsin, the fixation of colour must be slight and uniform and show no deeply dyed particles [seed residues] or fibres [oxycellulose]. C. Piest (Papisrfabrikant, 1914, 12, 860), in describing the methods and precautions to be followed in the purification of cotton waste for gun-cotton, states that the copper value by Schwalbe’s test must not exceed 1.0 [as Cu] per cent.; fatty and waxy matters extracted by absolute alcohol, 0.5 per cent.; and ‘‘ wood gum value ” (soluble in cold 5 per cent. caustic soda, and reprecipitated by alcohol after neutralisation), 2.0 per cent. The chemical qualities of cotton and wood celluloses for other industrial purposes [celluloid, artificial silk, acetate, varnishes, etc.] are alrco noted.ESTIMATION OF MOISTURE. The question of the estimation of moisture in cellulose and raw cellulose materials was very fully discussed in Renker’s dissertation (Berlin, 1909), already cited. When cellulose is heated in dry air at increasing temperatures there appears to be no sharply defined temperature limit between the expulsion of hygroscopic moisture and the loss of weight by decomposition.Material [sulphite pulp] which has arrived at constant weight at any given temperature suffers a further small loss at a higher temperature. The difference between drying in presence of ordinary moist air and artificially dried air becomes only small at temperatures aboveANALYSIS OF CELLULOSE AND CELLULOSE DERIVATIVES 1 19 100' C. For all practical purposes, '6 dry" cellulose may be obtained without appreciable loss of weight by decomposition by heating in dry air at 105" to 107' C.to constant weight. Between this temperature and 125" C. the losses are small, but above 125" C. the decomposition becomes appreciable. The question of loss of weight other than hygroscopic moisture on heating depends on the purity and chemical condition of the cellulose, and was studied by Renker with materials which had arrived at constant weight in vacm over phosphorus pentoxide. Pure normal cotton thus dried at 35' C., and then heated under the same conditions, remained constant in weight up to a temperature of 125' C., suffering no further loss either of hygroscopic or constitutional moisture ; above 125" C.small losses by decomposi- tion were recorded.With materials other than pure normal cotton (e.g., boiled jute and sulphite wood pulp) continuous small losses were found with increase of temperature, becoming serious above 125" C. Although Renker could detect no chemical alteration of sulphite cellulose after drying at 105" to 107' C., such as increased acid-hydrolysis value or abnormal loss in chlorination, it has nevertheless been recorded (Ost, Zoc.cit.) that a slight modi- fication of pure cellulose is produced by prolonged heating alone, indicated by a progressive decrease in the viscosity of its solutions. It is therefore necessary that all chemical analytical operations be carried out on samples which have not been exposed to the action of heat for any considerable length of time, especially in the case of materials other than pure normal cellulose.Taking sulphite cellulose dried to constant weight at 105' to 107' C. as representing absolutely dry cellulose, Renker studied some alternative practical methods of drying at reduced tempera- tures, yielding equivalent gravimetric results without the danger of chemical modi- fication. Cellulose exposed over phosphorus pentoxide in a vacuum desiccator at 3 5 O C.becomes absolutely dry in twenty hours, and the values are constant to 0.5 mgrm. In a current of previously dried hot air at 90' C., at the rate of 30 litres per hour, the same result is attained in four hours; but this method, in spite of its rapidity, is less satisfactory than the vacuum method, and the results are easily influenced by variations in the speed and temperature of the air-current. 0 s t and Weathoff (Chem.Zeit., 1909, 33, 197) consider that a temperature of about 125O C. is necessary for the expulsion of the last traces of hygroscopic moisture, and recommend the gradual heating to this temperature in a current of dry hydrogen or carbon dioxide. Renker's results at 105' to 107" C., controlled by those obtained in vacuo over phosphorus pentoxide, appear, however, to be beyond criticism, and the difference of opinion must be referred to some secondary cause possibly connected with the conditions of heating or the structural density of the material.I n an investigation by the officials of the Kon. Materialpriifungsamt (Yer. der Zellstof. und Papier Chemiker, Hau,ptversammE.zcng, 1909, 133) on the effect of various conditions of drying on the dry weight of wood pulp for commercial purposes, it was concluded that the results obtained by drying at temperatures between 90" and 1 0 5 O C.were technically equivalent, and no sensible gravimetric error was recorded even at 120'C. The usual method of drying at 105' C. is therefore unobjectionable.An important study of the conditions of equilibrium between cellulose and120 ANALYSIS OF CELLULOSE AND CELLULOSE DERIVATIVES atmospheric moisture has been made by K. Fenchel and K. Comely (Wochnbl. Papierfab., 1913, 44, 4323). According to these observations, cellulose absorbs moisture from a humid atmosphere more rapidly than it parts with it to a dry one.Between certain limits of moderate degrees of humidity, the hygroscopic moisture in the cellulose is directly proportional to the relative atmospheric humidity, but the absolute values depend on the nature of the oellulose and its previoue treatment. Cellulose which has previously been dried at 100" C. contains, under identical conditions of atmospheric humidity, less hygroscopic moisture than cellulose which has not been dried by heat.CELLULOSE AND ALCOHOL. It is a common analytical practice, after chemical operations with cellulose, to displace the water by washing with alcohol previous to drying in the oven. Renker made the surprising observation that alcohol so introduced cannot be completely expelled by heating, and that the dried cellulose obstinately retains traces of alcohol. This observation was subsequently confirmed by Richter, but a full investigation will be necessary before it can be definitely accepted. ANALYSIS OF CELLULOSE ESTERS. The analysis of the cellulose esters of organic acids by alkaline saponification or acid liydrolysis is considerably complicated by the fact that the majority of the commercial products are esters of chemically modified cellulose (hydrocellulose), which is itself sensitive to the agents employed for the decomposition of the ester. Volatile fatty acids (acetic and formic) may thus be derived from the cellulose portim of the ester, and seriously interfere with the accuracy of the estimation. I n most cases the difficulty may be met by saponification at the ordinary temperature-e.g., with equal volumes of $-aqueous sodium hydroxide and 95 per cent. alcohol, which gives satisfactory results for cellulose fatty acid esters on standing for about forty- eight hours, or with an alcoholic solution of sodium ethylate, which is sometimes employed for the less readily saponifiable cellulose benzoates. For the analysis of esters of profoundly modified cellulose, when alkaline saponification, even in the old, cannot safely be employed, A. Stein (Zeitsch. anyew. Chem., 1913,26, 673) recommends hydrolysis with slightly diluted sulphuric acid at the ordinary temperature for forty- eight hours and subsequent distillation of the volatile acid. A correction is made for the acid derived from the cellulose, on the assumption that this acid is produced at a constant rate during the whole period of distillation, and continues to come over at the same rate after all the esterified acid has been distilled. An article by H. Ambron (XoZZoid. Zeitsch., 1913,13, 200 ; ANALYST, 1914,39, 94) describes the use of the polarising microscope for the examination of nitrocellulose, principally for the determination of the uniformity of nitration. For the estimation of traces of sulphuric acid in cellulose, nitrocellulose, and other cellulose esters, C. Piest (Zeitsch. angew. Chenz., 1913,26, 661; ANALYST, 1914, 39, 45) decomposes the sample with nitric acid (sp. gr. 1.4) and potassium nitrate by drying and incinerating, then estimates the sulphate in the ash. Von Hottenroth (Chem. Zeit., 1914, 38, 515) recommends the digestion of the sample with hot ?on- centrated hydrochloric acid for several hours, until the solution can be diluted without the formation of a precipitate of hydrocellulose

ISSN:0003-2654    

DOI:10.1039/AN9154000107

出版商:RSC    

年代:1915

数据来源: RSC

摘要:

FOOD AND DRUGS ANALYSTS 121 ABSTRACTS OF PAPERS PUBLISHED IN OTHER JOURNALS. FOOD AND DRUGS ANALYSIS. Sensitive Reaction of Apomorphine. L, Grimbert and A. Lecldre. (J. Pharm. Chim., 1915, 11, 23-24.)-When 5 C.C. of apomorphine hydrochloride solution are boiled with the addition of 5 drops of a saturated mercuric chloride solution and 5 drops of 10 per cent. sodium acetate solution, then cooled, and shaken with 2 C.C.of amyl alcohol, the latter is coloured blue. This coloration may be obtained with a solution containing 0-002 grm. of apomorphine hydrochloride per litre; with stronger solutions a blue precipitate forms which is soluble in amyl alcohol. The blue coloration appears to be characteristic of apomorphine. w. P. s. Reports on the Determination of the Original Gravity of Beers by the Distillation Process.Parts I. and 11. : Memoranda and Tables. T. E. Thorpe and H. T. Brown. (J. Inst. Brew., 1914, 20, 569-605.)-The “Table to be used for Determining the Original Specific Gravity of Worts of Beer ” cootained in the first schedule of the Inland Revenue Act, 1880, having been found to give inaccurate results, the Commissioners of Customs and Excise, in 1909, instructed Sir Edward Thorpe to co-operate with Dr.Horace Brown (nominated on behalf of the brewing trade by the Institute of Brewing) in making an investigation with a view to obtain data for the construction of a more correct table. The final outcome of this investigation was a new table, which now has the force of law, having been incorporated in the Finance Act, 1914 (Session 2).This table is reproduced below. In the memoranda under review, the authors of the table explain in detail how they collected the data on which it was based. After conducting some fermentations in the laboratory, under such conditions that no loss of alcohol was possible, the investigators transferred their operations to a number of breweries, selected as representative of the various systems of brewing practised in this country.An initial difficulty lay in the fact that it is customary to pitch the first or strongest worts with yeast as they run into the fermenting vessel, so that some portions of the wort may have been fermenting for several hours before the filling of the vessel is complete. The method adopted for determining the true original gravity of the contents of the vessel in such cases was to take samples at regular intervals of time from the pipe filling the vessel, noting also the ‘(dry dip ” of the wort in the vessel a t instants midway between those at which samples were taken. Finally, portions of the samples were mixed in proportion to the bulks which the (( dry dip ” nieasure- ments showed that each represented, the result being a (( miniature collection.” This method was shown to be thoroughly trustworthy by checking its results against the actual gravity of the whole contents of the fermenting vessel in one or two brewings where the wort was not pitched with yeast until collection was122 ABSTRACTS OF CHEMICAL PAPERS complete. The true original gravity having been thus determined, samples of the well-mixed beer were withdrawn at intervals throughout the fermentation and submitted to distillation, distillate and residue being subsequently made up to the volume of beer taken for the experiment, and their specific gravity taken.The values for spirit indication and corresponding degrees of gravity lost were then plotted on a system of rectangular co-ordinates, and smooth curves drawn. Owing to the impossibility of obtaining samples containing the true average proportion of yeast, except in the early stages of fermentation, all worts were filtered before distillation.NEW ORIGINAL GRAVITY TABLE. Spirit Indica- tion. 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 0.0 0.00 4.25 8.50 12.90 17.30 21.85 26.40 31-00 35.65 40.30 45.00 49.85 54.85 59.95 65.10 70.30 75.60 0.1 0.42 4.67 8094 13.34 17.75 22.30 26.86 31.46 36-11 40.77 45-48 50.35 55-36 60.46 65.62 70.83 - 0.2 Corresponding Degrees of Gravity Lost.Tenths. 0 85 5.10 9.38 13-78 18.21 22-76 27.32 31.93 36.58 41.24 45.97 50.85 55-87 60.97 66-14 71.36 - 0.3 1.27 5.52 9-82 14.22 18.66 23.21 27.78 32.39 37.04 41-71 46-45 51.35 56.38 61-48 66.66 7 1 *89 - 0'4 1.70 5-95 10.26 14.66 19.12 23-67 28.24 32-86 37.51 42.18 46.94 51-05 56.89 61.99 67.18 72-42 - 0.5 2.12 6-37 10.70 15.10 19-57 24.12 28.70 33-32 37.97 42-65 47.42 52-35 57-40 62 51 67.70 72.95 - 0.6 2.55 6.80 11.14 15-54 20.03 24-58 29.16 33.79 38.44 43.12 47.91 52.85 57-91 63.01 68-22 73.48 - 0-7 2-97 7.22 11.58 16-98 20.48 25.03 29-62 34.25 38.90 43.59 48-39 53.35 58.42 63-52 68.74 74-01 - 0.8 3.40 7.65 12.02 16.42 20.94 25-49 30.08 34.72 39.37 44.06 48.88 53-05 58.93 64-03 69.26 74-54 I 0.9 3.82 8.07 12-46 16.86 21-39 25.94 30.54 35.18 39.83 44.53 49.36 54.35 59,044 64.54 69.78 75.07 - The new Statutory Table represents the mean of all the results obtained from thirty-four brewings in ten breweries.Having regard to the number of breweries visited and the care taken to include every well-defined type of brewery and of beer, it is reasonable to suppose that the application of this tabls to beer, at any stage of fermentation and manufacture up to racking, will on the average give a true indica- tion of original gravity, The individual brewery data in this Report suggest that it will more often underestimate than overestimate original gravity, but the extreme error should be k0.5'.The authors suggest that where it can be shown, as in the case of a brewery designated by them as L, that the use of the new table leads to overestimation, an allowance might be made by the Board of Customs and Excise. The Finance Act, 1914 (Session 2), actually provides a, general allowance of 0.75". When cane sugar is used as a, brewing adjunct, inversion takes place in the early stages of fermentation, and, since inversion per se increases the gravity, it is evidentFOOD AND DRUGS ANALYSIS 123 that, in order to arrive at the true original gravity of such cane-sugar wort, some correction becomes necessary in the interests of the brewer.If the whole of the invert sugar derived from the cane sugar were present at every stage of the fermenta- tion, such a correction would be very simple. For every 10 pounds of cane sugar in 100 gallons of wort, the gravity would be increased about 0*23.Though the whole of the invert sugar corresponding to the cane sugar is never found at any stage, the processes of inversion and fermentation proceeding simultaneously, the authors express the opinion that the above full correction should be made in all cane-sugar worts which at the time of distillation have not reached a spirit indication of 5.Their experiments show that by the time fermentation has proceeded thus far, and indeed usually by the time a spirit indication of 4 is reached, the whole of the invert sugar will have disappeared, and no correction should be necessary.Part 11. describes the results of analysis of samples of beer of known history after more or less prolonged periods of storage. When beer brewed at a gravity of 80' or under is taken after prolonged (the experiments extended to eighteen months) storage, but whilst still sound, submitted to the distillation process, and its original gravity calculated with the aid of the new Statutory Table, without any correction for acidity, the result will, on the average, be a little over 1" low, and will in no case be so much as 2" in error.The error is mainly due to loss of alcohol on storage. There is also a small but sensible absorption of the beer into the wood of the cask immediately after filling, or, in the case of a freshly-washed cask, an interchange of beer and water.There is finally a loss of water through the wood of the cask, this tending to reduce the error due to loss of alcohol. In rare cases the loss of water may be so great that the spirit indication may actually increase somewhat on storage. These cases occur under exceptionally dry storage conditions, which favour loss of water, whereas the rate of loss of alcohol appears to be independent of the hygro- metric state of the cellar atmosphere.When analysed as described, the original gravity of a beer brewed at 90' or above will, on the average, be underestimated by 2.4". In only two cases did the error exceed 30, and in these cases the beers were sensibly acid. Had the estimate of original gravity been corrected for the volatile acid present, the error would have been reduced nearly a degree.The opinion is expressed that, when beer is exported on drawback, sn allow- ance of 2" on the declared gravity is a sufhient margin to cover all losses during storage due to differences between the true original gravity of the beer and that calculated from the new table in the case of all beers of an original gravity not exceeding 90".For beers of a higher original gravity a margin of 3' might be allowed. Incidentally, the authors point out that the amount of acetic acid in worts and beers appears to have been very much overstated. Experiment showed that fresh worts contain practically no acetic or other volatile acid, and that the amount produced during fermentation and storage is negligibly small so long as the beer remains sound.Only in the two cases above referred to-of strong ales which had beoome markedly acid-was there sufficient volatile acid present to make its estima- Heavy beers, as might be expected, show greater losses on storage.124 ABSTRACTS OF CHEMICAL PAPERS tion worth while, and in general the process may be omitted with all sound beers, I n cases such as those referred to, however, the acidity must be estimated and allowed for, and the authors point out that the official method of direct titration and subtraction of 0.1 per cent.from the acidity so found is unsatisfactory. The best method is by distillation in 5t current of steam and titration of the distillate. A more convenient but somewhat less accurate method is to determine the volatile acid, calculated as acetic acid, by the loss of acidity of a sample of the beer after evaporating to dryness over an open steam bath.Nom-The correction for acidity, where necessary, will coil tinue to be made as before by estimating the percentage of acetic acid in the beer and by reference to the table which was in use with the original gravity table, which has now been superseded.-EuIToE.G. C. J. Reports on the Determination of the Original Gravity of Beers by the Distillation Process. Parts III., IV., and V. H. T. Brown. (J. Inst. Brew., 1914, 20, 606-713J-Part 111. covers the same ground as Parts I. and II., but goes more closely into the detail of the experimental methods adopted. One of these methods, which afforded data necessary to the calculations in Part V., relates to the estimation of yeast reproduction.Essentially, the method consists in determining in the first instance the average number of yeast cells per unit volume of the wort, introduced with the pitching yeast, and in making a series of cell counts at various stages of the fermentation. A haemacytometer is employed, and the unit of volume selected is 7& c.mm. Experiment showed that a cell count of 1 corresponded to 0.022 grm.dry yeast substance per 100 C.C. Since the average solution density of the wort solids contributing to yeast growth certainly approximates 4, it follows that the loss of gravity due to yeast increase is approximately given by multiplying the increase in cell count by the factor 0.088.Part IV. is a history of previous tables of original gravity, and a comparison of these with the new Statutory Table. The most important section of this part is an examination of the report of Graham, Hofmann and Redwood, in which they described the methods adopted by them in constructing their original gravity table in 1852. This is the table which was embodied in the Inland Revenue Act, 1880, and which remained in force until the promulgation of the new table, the subject of the reports now under review.The differences between the new table and that of Graham, Hofmann and Redwood-differences which exceed lo over a great part of the table-are almost wholly explained by the fact that Graham, Hofmann and Redwood employed about six times as much yeast in their laboratory brewings as is used on the average in real brewery practice.Under these conditions very little yeast reproduction can have occurred, SO that the loss of extract by assimilation must have been abnormally low, and, moreover, an appreciable amount of alcohol must have been added to the wort with the yeast. Part V. deals with the scientific principles underlying the empirical method of determining original gravity, and includes a proof that a more rational method is available.The method devised is more troublesome and probably less accurate than the empirical method, using the new table; but the fact that a rational method giving closely approximate results has been devised is interesting, in view of theFOOD AND DRUGS ANALYSIS 125 expressed opinion of Graham, Hofmann and Redwood that such a thing was, by the nature of the case, impossible.I t is shown that the original gravity is closely given by the expression R + 3.912 A.S. + Y, where R is the residue gravity, A the: percentage of alcohol (grams per 100 c.c.), S a factor the exact value of which (1*795-1*941) depends on the alcohol percentage, being highest when this is high, and Y represents the loss of gravity due to yeast reproduction.Y increases with the per- centage of alcohol until this reaches 3 per cent., when Y = 1.6. At this stage of the fermentation yeast reproduction substantially ceases. Values of Y corresponding to. smaller percentages of alcohol are given in the report, which also includes a descrip- tion of the experiments on which the values are based.Finally, the method of determining original gravity by the evaporation method is discussed. Experiment showed that when the attempt is made to estimate the spirit indication by subtracting the present gravity of the beer from that of the evaporated residue made up to the volume of the beer taken for the test, the spirit indication is on the average underestimated by 0*16", the variations from the average being very small.With an addition of 0.16O to the spirit indication found, the method is therefore a practicable one. The difference of 0-16O is explained by the fact, known to Graham, Hofmann and Redwood, that a sensibly greater contraction occurs when spirit is mixed with sugar solutions than when it is mixed with water.G. C. J. Characteristics of Flour Bleached with Chlorine. C. A. A. Utt. (J. Ind. and Eng. Chem., 1914,5,908-09.)-Since the American Government ruled against flour treated with the oxides of nitrogen, chlorine-bleached flour has made its appearance. The following figures were obtained on analysing a number of bleached and unbleached flours, the chlorine being expressed in parts per million : Number of examined.Samples Highest. Lowest. Average. Bleached ... ... 21 1,056 260 775 Unbleached . . . ... 21 576 348 489 Chlorine-bleached flours show an increased acidity, and are not improved a8 regards their breadmaking qualities, loaves made from bleached flours having an objectionable colour and texture. H. F. E. H. Rate of Liberation of Hydrocyanic Acid from Commercial Kinds of Linseed. S.H. Collins and H. Blair. (Chem. News, 1915, 111, 19-20),-The variations in the amount and rate of evolution of hydrocyanic acid due to variations in the place of origin of the linseed are recorded. The authors have shown pre- viously (ANALYST, 1914, 39, 70) that the amount and rate of evolution are also governed by other conditions. All the specimens of seed tested were the first year's seeds grown in Essex from foreign seeds.The seeds of Oriental origin-Calcutta, Bombay, Japan-were all high in total hydrocyanic acid (from 0.21 to 0.27 part per 1,000) and rich in enzymic activity. Moroccan seed was low in both hydrocyanic acid (0.112 part per 1,000) and enzymic activity, The general result of growing126 ABSTRACTS OF CHEMICAL PAPERS linseed in England is to reduce the total amount of hydrocyanic acid and to increase the enzymic activity; that is, the differences are caused by changing the seed from hot and dry to cool and damp conditions of growth.w. P. s. Estimation of Cane Sugar in Beet Molasses. Inversion Method by Double Polarisation in Neutral Solution. E. Saillard. (Comptes rend., 1915, 160, 31-34.)-The principal sources of error in the application of Clerget's method to beet molasses are-The influence of the mineral salts on the rotatory power of the cane sugar, and the difference in the rotatory power of the nitrogenous matters in neutral and acid solutions. Consequently, the results for cane sugar are always too low.The following procedure has been devised to correct these errors : Four times the (French) normal weight of molasses is dissolved, clarified with basic lead acetate, made up to 200 c.c., and the solution filtered.To 50 C.C. of the filtrate a quantity of potassium chloride, equivalent to that of the acid to be employed for inversion, is added, the liquid made up to 100 c.c., treated with animal charcoal, filtered, and polarised at 20" C.(polarisation A). Another 50 C.C. portion of the solution is inverted with 6.8 C.C. of hydrochloric acid, sp. gr. 1.17, neutralised with potash, made up to 100" c.c., decolorised, filtered, and polarised aft 20" C . (polarisa- To determine the coefficient 100 (A + B) coeff. of inversion - 0*5t tion B). Then, cane sugar= -- - of inversion, the quantity of hydrochloric acid, equivalent to the sulphuric acid in the sulphated ash, is first calculated, This may be assumed to be 1.8 C.C.of hydrochloric acid, sp. gr. 1.17, for the normal weight of molasses. A solution of pure cane sugar, having the same polarisation as the original clarified molasses solution (double norrual strength), is prepared. To 50 C.C. of this pure solution, potassium chloride, equivalent to 8.6 C.C.of hydrochloric acid, are added, and the liquid is made up to 100 C.C. and polarised (polarisation A), Another 50 C.C. portion is inverted with 5 C.C. of hydrochlorio acid, cooled, treated with a further 3.6 C.C. of acid or an equivalent quantity of potassium chloride, neutralised with potash, made up to 100 c.c., and polarised (polarisation B').A third portion of 50 C.C. of the pure solution is diluted to 100 c.c., and polarised direct (polarisation A ) . The coefficient of inversion (X) is then calculated from the formula A"= loo ( A + B ) , and the value of X is utilised in the calculation of the results for the molasses. For the inversion of the molasses 6.8 C.C. of hydrochloric acid are employed, instead of the customary 5 c.c., because it is assumed that 1.8 C.C.of the acid are required to decompose the salts of the molasses ; there exist, therefore, in the neutralised inverted molasses solution salts equivalent to the pre-existing salts and to 6.8 C.C. of added acid-in all, 8.6 C.C. of hydrochloric acid. In a, series of analyses, the results obtained by the above method agreed well with those obtained by cupric reduotion after inversion, and were, on an average, 1.4 per cent.higher than the results of the ordinary Clerget method. J. F. €3. X - 0*5t Melting and Solidification Points of Spermaceti. R. Meldrum. (Chem. News, 1915, 111, 37-39.)-To elucidate the erratic results frequently obtained inFOOD AND DRUGS. ANALYSIS 127 determining the melting-point of fats and waxes, comparative determinations were made by different methods upon spermaceti.Notwithstanding the crystalline character of the sample, the same melting-points were obtained by Dalican's method (45.75' C., with a, rise of 0-05'C.) after repeated melting and remelting, and rapid or slow cooling. Nor did the size of the test-tube (14 inch to 8 inch) or the mode of stirring influence the results.The point to which the temperature fell and remained stationary for some time appeared to be due to the solidified layers of the wax increasing the non-conductivity of the glass, and not to the rate of crystallisation, or to any change in the viscosity or density of the substance. The critical temperature at which opacity began on cooling and ceased on heating varied from 45.8" to 45.9' C. The melting-points determined by the thermometer-bulb method (45.3' to 45.5' C.) and the open capillary tube method (45*1° to 45.4' C.) were lower than the solidification-point, whilst the results obtained by the closed capillary-tube method ranged from 45.9' to 46.0" C., and by the opacity method from 46.0' to 46.4' C. The presence of 0.1 per cent. of water, glycerol, or oleic acid as impurities in the spermaceti had no influence upon the melting or solidification points. The addition of 20 per cent. of sperm oil lowered the melting-point of the wax by 1 . 6 5 O C., and no variations were produced by repeated melting or cooling, or by heating the mixture for a long time above its melting-point. A mixture containing 5 per cent. of sperm oil showed a melting-point only 0.2" C. below the normal. With 95 per cent. of oil no stationary solidification-point was found when the mixture was cooled to 14%" C., but by the opacity method the solidification-point was 26-5O C., and the melting-point 23' C. The fact that no stationary solidification- point seems to occur with mixtures of such extreme dilution explains the discordant results obtained in examining mixtures malting at a low temperature. C. A. M.

ISSN:0003-2654    

DOI:10.1039/AN9154000121

出版商:RSC    

年代:1915

数据来源: RSC

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FOOD AND DRUGS. ANALYSIS 127 BACTERIOLOGICAL, PHYSIOLOGICAL, ETC. Estimation of Allantoin in Urine in the Presence of Dextrose. R. H. A. Plimmer and R. F. Skelton. (Biochem. J., 1014, 8, 641-649.)-The presence of dextrose in urine affects the determination of allantoin by Folin’s magnesium chloride method, and it is therefore essential to remove the sugar before this method is applied. A number of experiments were made to determine the conditions neces- sary for the removal of dextrose by fermentation.I t was found that the rate of fermentation was unreliable, probably due to the variations in the acidity of the urine. With zymin and yeast dried according to Von Lebedeffs method the fermen- tation was much slower, and a still greater correction for the amount of nitrogen introduced in the preparation had to be made.Attempts were also made to remove dextrose by benzoylation according to the Schotten-Baumann method. In only one experiment out of eleven was the sugar completely removed. Experiments were also made on the removal of dextrose by precipitation with cupric hydroxide and sodium hydroxide. I t was found that, though dextrose can be completely removed by this method if the exact quantity of alkali is employed, yet, owing to the solu- bility of the precipitate in a slight excess of alkali and to the loss of ammonia,128 ABSTRACTS OF CHEMICAL PAPER6 during filtration, the method is not applicable to urine.Experiments were then made on the removal of dextrose by lead hydroxide and sodium hydroxide. It was found that the dextrose is completely precipitated if the reagents are employed in the proportions : 2C,H1,0, : 5(Pb(OH),.PbAX) : NaOH.The precipitation is not SO sensitive to excess of alkali as that with copper hydroxide. A slight excess of sodium hydroxide may be added, and in many experiments as much as 2.5 mole- cules of sodium hydroxide were used, and the whole of the dextrose removed.A larger excess of sodium hydroxide leads to solution of the precipitate. It was also found that allantoin is not precipitated by the basic lead acetate and sodium hydroxide or by the dextrose lead hydroxide compound. This method can therefore be applied to the estimation of allantoin in urine containing sugar. The experi- mental details are as follows: Twenty-five C.C.of urine are treated with 1 grm. of sodium carbonate and the ammonia estimated by Folin’s method. I t is not necessary to use paraffin or toluene to prevent frothing if tall cylinders are employed. The solution is washed int6 a, 250-C.C. measuring-flask, and the sodium carbonate neutralised by carefully adding glacial acetic acid from a burette and warming. To the neutral solution 25 C.C.of basic lead acetate + 14 C.C. of basic lead acetate for every per cent. of dextrose are added. These quantities require 6*2+3.4 C.C. of 2N sodium hydroxide to precipitate the dextrose and to remove any excess of lead acetate. It is advisable to determine the exact amount of 2N sodium hydroxide which is required to precipitate the lead hydroxide from the basic lead acetate by a special experiment, as in making up solutions of the basic lead acetate and 2N sodium hydroxide the solutions have never quite the same concentration, The caustic soda is added slowly from a burette with constant shaking.The solution is made up to 250 C.C. and*the precipitate filtered off. Fifty C.C. of the filtrate should be tested for dextrose before proceeding to the allantoin estimation, as it occasionally happens that the sugar is not completely removed.A slight reduction has no effect upon the result. If there is considerable reduction, the removal of dextrose must be repeated in another sample. The incomplete precipitation of the dextrose is probably due to incomplete neutralisation of the sodium carbonate. Fifty C.C. of the filtrate (= 5 C.C.of urine) are used for the estimation of the urea + allantoin by Folin’s magnesium chloride method. E. W. Estimation of Carbohydrates. IV. The Presenee of Free Pentoses in Plant Extracts and the Influence of Other Sugars on their Estimation. W. A. Davis and G. C. Sawyer. (J. Agric. Sci., 1914, 6, 406-412.)-Substances exist in plant material which are soluble in 80 per cent.alcohol, are not precipitated by basic lead acetate, are unfermentable by ordinary yeasts, and reduce Fehling’s solution after other sugars present have been fermented. From the fact that the reducing power of such substances when calculated as a mixture of arabinose and xylose correeponds with a proportion of pentose nearly identical with that calculated from the Krober-Tollens phloroglucide distillation, it is assumed that free pentoses are actually present, and that the furfural formed on acid distillation does not arise from gums, pentosans, or other sugars present.From the results of nearly 400 fermentation experiments made with extracts of leaves, the amount of the residualBACTERIOLOGICAL, PHYSIOLOGICAL, ETC. 129 reducing power after fermentation with pure cultures of distiller’s yeast has been found to be proportional to the pentoses present as estimated by the Krober method.When only small quantities of other sugars are present, the direct distillation method, with subsequent weighing of the phloroglucide is quite accurate ; but in presence of large quantities of other sugars, these should first be fermented away before applying Krober’s process.The maltase-free yeasts (S. Marxianas, S. exiguus, and S. ano- malus) gradually but slowly destroy the pentoses, and cannot be used in their presence (cf. Davis and Daish, ANALYST, 1913, 38, 504, and Daish, ibid., 1914, 39, 555). H. F. E. H. Cholesterol of the Brain. 11. The Presence of 660xycholeste~ol” and its Esters. M. C. Rosenheim. (Biochem.J., 1914, 8, 74-82.)-The examination of the whole human brain by means of Windaus’ method has shown the complete absence of cholesterol esters. Human brain contains oxycholesterol esters to the extent of at least 0.01 per cent. Free oxycholesterol seems to be present in adult human brain, but not in the brain of young children. E. W. Cholesterol of the Brain. 111. Note on the Cholesterol Contents of the Human and Animal Brain.M. C. Rosenheim. (Riochem. J., 1914, 8, 82-84.)- The following estimations were made by a method based on 0. Rosenheim’s process for the preparation of cholesterol and Windaus’ method for its quantitative estima- tion. In some cases search was made for the presence of cholesterol esters, but with negative results. The figures must be taken to express the sum of the quantities of cholesterol and oxycholesterol present.Except in the case of human brain, oxycholesterol was not tested for. Description of Brain. Man ... ... ... Faetus aged thirty-six weeks ... Child aged three months ... Child aged five days ... Dog Cat o x ... ... ... Sheep ... ... ... Rabbit ... ... ... Fowl 0 . . ... ... Codfish ... ... ... ...... ... ... ... ... MTster Percentage 78-86, 78.90 90-29 85.80 89 -99 76-18 76.53 78.83, 78-32 79-50 77.86, 79.15 80.34 84-03, 84.94 I Cholesterol Percentage. c .- - In Moist Brain. 1.95, 1.91 0.39 0-69 0.53 2.76 2.35 2.39, 2.61 2-13 1.45 1.92, 1-79 2-12, 1.90 In Dry Brain. 9-22, 9.01 4.07 4-89 5-29 11 059 9.99 11.28, 12-04 10.37 9-57, 9.11 7-40 12.02, 11.89 E. W. Studies on Enzyme Action.XII. The Enterase and Lipase of Castor Beans. K. G. Falk and K. Swgiura. (J. Amer. Chem. SOC., 1915, 37, 217-230.)- The authors draw distinction between two types of hydrolytic action towards130 ABSTRACTS OF CHEMICAL PAPERS esters met with in castor bean extracts, and for convenience call the enzyme which is soluble in water and exhibits the greater activity towards ethyl butyrate ‘( enterase,” while reserving the term (‘ lipase ” for the insoluble substance or substances which show greater activity towards triacetin than towards ethyl hutyrate.Enterase can undoubtedly hydrolyse complex esters such as the fats, and lipase hydrolyses simple esters to a certain extent. Cold pressed castor beans were used for the preparation of the enzymes, toluene being employed throughout to prevent bacterial growth. The general procedure adopted was the same as in previous work on the castor bean (ANALYST, 1912, 37, 316), and the aation of the extract was investigated on triacetin in the presence of some neutral salts, and after drying and heating under different conditions.An esterase preparation active towards ethyl butyrate was separated by extraction with water, and its properties studied in solution and in the solid form.I t appears to have many properties in common with, and to resemble strongly glycerophosphatase. A lipase preparation active towards triacetin was separated by extraction with 1.5 N sodium chloride and its properties studied. The different preparations were investigated with regard to their nitrogenous compo- sition, eight different compounds being identified, and the probable protein character of esterase and lipase are discussed, H.F. E. H. Enzymes of Washed Zymin and Dried Yeast (LebedefQ. 11. Reductase. A. Harden and R. V. Norris. (Biochem. J., 1914, 8, 100-106.)-The presence of a fermentable sugar favours the reduction of selenite by living yeast, but has little influence on the reducing power of zymin unless the sugar is present in high concentration, when inhibition occurs.Sodium selenite in concentration of 0-5 grms. per 100 C.C. almost totally inhibits the fermentation of dextrose by zymin and dried yeast (10 grms. per 100 C.C. of 10 per cent. dextrose solution). When dried yeast or zymin is washed with cold water it loses its power of reducing methylene blue and sodium selenite.Such washed preparations reduce methylene blue in presence of many aldehydes and of bouillon, but these do not restore to it the power of producing alcoholic fermentation. Addition of the boiled washings to these washed preparations restores both the power of reducing methylene blue and of producing alcoholic fermentation. E. W. Total Amino-Nitrogen in the Seedlings of the Alaska Pea. T. G. Thompson, (J. Amer. Chem. SOC., 1915, 37, 230-235.)--The method employed for the determination of amino-nitrogen was a modification of Van Slyke’s (ANALYST, 1911, 36, 17 and 457). for seedlings from one to seven days old was found to rise steadily from 6.6 to 28.3, while the same ratio for seven-day seedlings was determined for the plumule, cotyledon, and root, the values being 36, 12.5, and 32 respectively. There is a decrease in both total and amino-nitrogen, calculated on dry-leaf material, as the plant increases in age, and the same is true of the stems both near the top and bottom of the plant. It would appear that there is less amino-nitrogen in root material than in the stems, and less in the extreme ends of the roots than in the portions nearer the stem. The ratio total H. 3’. E. H.

ISSN:0003-2654    

DOI:10.1039/AN9154000127

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年代:1915

数据来源: RSC

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ORGANIC ANALYSIS 131 ORGANIC ANALYSIS. Estimation of Cineol (Eucalyptol) in Eucalyptus Oil. J. L. Turner and R. C. Holmes. (Pharm. J., 1915, 94, 60-62.)-Arsenic acid forms an additive product with cineol, and the reaction affords a method of estimating the latter ; the compound is more stable than the similar one formed with phosphoric acid. Ten C.C. of eucalyptus oil, cooled to 0" C., are mixed with 10 C.C.of 85 per cent. arsenic acid solution, the mixture is stirred until precipitation is complete, and then main- tained a t 0' C. for ten minutes. If at this point the mixture forms a hard mass, indicating an oil rich in cineol, 5 C.C. of petroleum spirit are added. The mixture is then pressed between filter-paper until the cineol arsenate is dry, and separates readily when touched; the pressing is not complete while the mass remains hard.The cineol arsenate is now decomposed by heating it with water in a flask provided with a graduated neck, and the volume of the cineole is read. In the case of eucalyptus oils containing less than 25 per cent. of cineol, the separation of the cineol arsenate is not quantitative, and it is necessary to add 5 C.C.of pure cineol to the 5 C.C. of oil taken for the estimation. The results of the method are accurate within 2 per cent. The authors criticise other methods which have been proposed for the estimation of cineol. The phosphoric acid method invariably gives low results owing to the readiness with which the additive compound is decomposed by moisture. The hydrobromic acid method has the same drawback, whilst the resorcinol method and its modification (cj.ANALYST, 1908, 33, 15; 1914, 39, 475) are untrustworthy, owing to the fact that substances other than cineol are soluble in resorcinol solution, that water dissolves from 4 to 5 per cent. of its weight of. eucalyptus oil, and that the fraction of eucalyptus oil boiling between 1'70' and 190' C . does not always contain the whole of the cineol present.w. P. s. Blue Hydrocarbon Occupring in Some Essential Oils. A. E. Sherndal. (J. Amer. Chem. SOC., 1915, 37, 167-171.)-1t is found that the blue compound which gives a marked colour to certain oils, such as those of cbamornile, wormwood, and cubebs, and which may be detected in selected fractions of other oils, is an un- saturated hydrocarbon, which can be isolated by taking advantage of the fact that it is readily soluble in 60 per cent. sulphuric acid, from which solution it is again thrown out by dilution with water.Analysis and cryoscopic measurements point to its possessing the formula C,,H,,. It is a slightly viscid liquid, intensely blue in thin layers, appearing black in quantity, with a weak phenolic odour not unlike that of thymol. Its density at 25' C.is 0.9738. The substance resinifies somewhat rapidly on exposure to light and air. G. C. J. Action of Hydrazine Hydrate on Fats. P. Falciola and A. Mannino. (Annali Chim. AppZic,, 1914, 2, 351-356.)-0n adding a concentrated (90 per cent.) solution of hydrazine hydrate to olive oil a turbidity is produced, and, after a few hours, a solid mass of higher melting-point is obtained, without any appreciable evolution of heat.The solidity of the product will depend upon the proportion of132 ABSTRACTS OF CHEMICAL PAPERS reaggnt added. The solid product obtained by the author melted (after twice recrystsllising from alcohol) at 110" to 112" C., whilst the crystalline product separating from acetone melted at 65" to 67' C.Other oils treated in the same way yielded products which, when twice recrystallised from alcohol, had the following melting-points : Tung oil, 106" to 107" C. ; crude linseed oil, 102" to 105" C. ; arachis oil, looo C. ; nut oil, 103" to 104' C.; and chrysalis oil, 101' C. I t is suggested that a, technical process of hardening fats may be based on this reaction.Triolein (5 grms.), when treated with hydrazine hydrate yielded about 6 grms. of a crystalline white product, which melted, after recrystallisation from alcohol, at 110" to 112" C., and had an iodine value of 166, and the composition-Carbon, 74.32 ; hydrogen, 13.06; and nitrogen, 9.07 per cent. When crystallised from acetone it gave a product melting at about 76" C., but this, when again crystallised from alcohol, melted at 106' to 108' C.Under similar conditions tristearin yielded a crystalline mass melting at 112" to 114' C. and containing-Carbon, 73.1 ; hydrogen, 13.4 ; and nitrogen, 9.1 per cent. Tripalmitin gave a product melting at 108O to 109" C. C. A. M. Hydrolysis of Maltose by Hydrochlorio Acid. W. A. Davis. (J. of Agric. Sci., 1914, 6, 413-416.-A.J. Kluyver (Bio. Suiker. Boek. E. J. Brill. Leiden, 1914, p. 223) has published a protest against the statement of Davis and Daiah (ANALYST, 1913, 38, 504) that during the inversion of cane sugar by hydrochloric acid under Herzfeld's conditions there is a danger of maltose undergoing hydrolysis if present. Davis adduces further evidence that such decomposition does, in fact, occur to the extent of about 2 per cent.when 1 per cent. solutions of maltose are used. That this slight hydrolysis of maltose escaped the notice of Kluyver and Jalowitz (Zeitsch. ungew. Chem., 1895,8,208) is probably due to their method of estimating the reducing power not being sufficiently delicate, the former worker having estimated the residual copper volumetrically by the.iodimetric method. It is, therefore, preferable when estimating cane sugar in plant extracts in presence of maltose to employ either invertase or 10 per cent. citric acid under the conditions laid down (Zoc. cit.). Cf. also ANALYST, 1909, 34, 233. H. F. E. H. Analysis of Tanning Materials. H. G. Bennett. (J. Soc. Chem. Ind., 1914, 33,1182.)-I. Improved Basic Chloride Shake Method.-The author proposes that the basic chloride shake method should be modified as follows : (1) Hide powder to be exactly neutralised before chroming.(2) Instead of 6.5 grms. of hide powder, 5 grms. to be used. (3) To 100 C.C. of infusion of ordinary strength 100 C.C. of water to be added before the hide powder, and the total brought to 220 c.c., of which 110 C.C. are evaporated for weighing.(4) The chroming liquor to be a solution of Cr,(OH)& and not Cr,(OH),Cl,. In this way less tannin and more non-tannin material is found, and the method is easier to work than the official method. Analyses of a number of tanning materials by the two methods show differences in the tan percentage varying from 1.5 for sumach to 12.3 for quebracho (sulphited), the new method giving the lower result in each case.11. Tannery Liquors.-The filtered solution is made up to standard volume, to contain from 0.17 to 0.23 perORGANIC ANALYSIS 133 cent. tannin. The total soluble matter is determined by evaporating 50 C.C. or less with 5 C.C. of 0-5 per cent. tartaric acid, added to prevent the formation of oxidisable salts of tannins. The residue, not exceeding 0-25 grm., is dried for one hour in the steam-bsth ; 25 mgrms., for the tartaric acid added, are deducted.111. Non-Tannin Matters.-Air-dry hide powder, equivalent to 2.5 grms. dry powder, is neutralised with sodium hydroxide, chromed with 2 per cent. of its weight of chromic chloride, and made basic to correspond with the formula Cr,CI,(OH), by the addition of sodium carbonate.After it has been churned for one hour, the powder is washed and added to 100 C.C. of the liquor ; the whole is made up to 112.5 c.c., and agitated for fifteen minutes. The solution is filtered, and 55 C.C. or less evaporated to dryness with 5 C.C. of 0-5 per cent. tartaric acid, and the residue dried and weighed as usual. The method is more accurate, easier, and cheaper than the official method. 0. E. M. Melting-Point of 1.2.4.6-Trinitrotoluene. W. Rintoul. (J. SOC. Chem. Id., 1915, 34, 60-61.)-The melting-point of this substance, for whioh widely varying values have been published in the past, is found to be between 80.8O and 80.85' C. The elaborate methods adopted for preparation and purification is described in detail, as is the manner of determining the melting-point. Incidentally the melting interval of p-nitrotoluene is established as 51.6' to 51.9" C., and that of 1.2.4-dinitrotoluene as 69.9' to 7 0 * 2 O C. Concerning these constants also there is eonsiderable discrepancy among the earlier published records. G. C. J.

ISSN:0003-2654    

DOI:10.1039/AN9154000131

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年代:1915

数据来源: RSC

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ORGANIC ANALYSIS 133 INORGANIC ANALYSIS. Electrolysis of Solutions of the Rare Earths. L. M. Dennis and B. J. Lemon. (J. Amer. Chem. Soc., 1915, 37, 131-137.)-Experiments are described which show that fractional electrolysis of mixtures of the rare earths yields quite rapid separations in some cases, and that these separations can be effected with far less expenditure of time and labour than by the customary methods of fractional crystallisation or fractional precipitation. The method adopted was the electrolysis of somewhat concentrated (50 grm s.oxides per litre) neutral solutions of salts of the rare earths, using a mercury cathode, kept clean by violent agitation with air, and a platinum anode. The most notable result was the complete separation of lanthanum from praseodymium by a very small number (6) of fractional electrolyses.About twice a8 many (10) operations suffice to separate lanthanum from admixture with praseo- dymium, neodymium, and samarium, the lanthanum-the stronger base-being in each case the last to come out of solution. Yttrium can be almost completely freed from erbium in five operations, but it is much less easy to obtain erbium free from yttrium.G. C. J. Rapid Estimation of Iron in its Alloys with Cerium Metals. I. Bellucci. (AnnaZi Chim. AppZic., 1914, 2, 366-369.)-From 0*2 to 0.3 grm. of the alloy is dissolved in a small quantity of cold hydrochloric acid, and the solution (without134 ABSTRACTS OF CHEMICAL PAPERS separation from the insoluble carbon and silica) diluted, slightly heated, and treated with hydrogen sulphide to precipitate copper, lead, etc.It is then filtered, and the filtrate heated on the water-bath until a11 hydrogen sulphide is expelled, after which 5 to 10 C.C. of 3 per cent. hydrogen peroxide are added, and the evaporation con- tinued to dryness. The residue is taken up with very dilute hydrochloric acid, and the iron in the solution estimated by an iodimetric method.C. A. M. Lime-Sulphur Sprays : Their Composition and Analysis. A. A. Ramsay, (J. Agric. Sci., 1914, 6, 476-483.)-1n a former paper (J. Agric. Sci., 1914,6, 194), the author stated the solution of lime-sulphur appeared to consist of calcium hydroxy- hydrosulphide (CaHSOH), calcium thiosulphate, with sulphur held in solution. This he now amends by including calcium disulphide.The following method of analysis is recommended : Fifty C.C. of the concentrated material are diluted to 500 C.C. with water. (1) 25 C.C. of the diluted mixture are titrated with TG iodine till the yellow colour is discharged, and the number of C.C. of iodine solution used x 0-0016 =sulphur (1) and x 0.0028 = lime (1). (2) To the 25 C.C. diluted mixture used for (1) the addition of & iodine is continued till a tinge of yellow colour obtains.The number of C.C. of iodine added x 0.0064 = sulphur as thiosulphate, and x 0.0056 = lime (CaO) in combination as thiosulphate. Starch indicator may be used in (l), but should be avoided in (2) as interfering with filtration when proceeding to (3). (3) The fluid used in (2) is filtered and washed with cold water.To the filtrate barium chloride and a few drops of hydrochloric acid are added, and the whole allowed to stand overnight in the cold. Barium sulphate is filtered off, dried, and weighed. The weight obtained x 0-1373 = sulphur present as sulphate and sulphite. The sulphur x 1.75 = lime oquivalent as sulphate and sulphite. (4) Ten C.C. of the diluted mixture are diluted with about 25 C.C.of water, and shaken up in a separating funnel with 10 C.C. of carbon disulphide, and allowed to separate. The carbon disulphide is drawn off into a tared flask. The mixture in the funnel is again extracted, once with 10 C.C. and twice with 5 C.C. of carbon disulphide, and the total extract (= free sulphur) is dried and weighed. ( 5 ) To 10 C.C.of the diluted mixture are added about 6 or 8 grms. aodium peroxide, and the whole allowed to stand for a few minutes; 50 to 75 C.C. of water are added, and then hydrochloric acid cautiously till the mixture clears. A few drops of 15 per cent. potassium iodide solution are added to reduce the higher oxides of chlorine, the excess of iodine boiled off, and the whole diluted with water to about 200 c.c., and the sulphur precipitated as BaSO,.(6) To another 10 C.C. of the diluted mixture is added cc iodine till sulphides and thiosulphates are decorn- posed as in (1) and (2). The sulphur is filtered off, and the filtrate made ammoniacal, and the lime precipitated with ammonium oxalate; this gives total lime. The calculations are as follows : (a) Sulphur obtained at (5) minus [sulphur (4) + sulphur (3) + sulphur (2)] = sulphur as hydroxyhydrosulphide and disulphide = (a).(b) lime obtained in (6) minus [lime (3) + lime (2)] = lime as hydroxyhydrosulphide and disulphide = (b). Then if x = lime in combination as hydroxyhydrosulphide, ( b ) - x =lime in combination as disulphide. Further, x x 0.5714 will be the sulphur in From this the total sulphur can be calculated.INORGANIC ANALYSIS 135 combination with x lime as hydroxyhydrosulphide and (b) - x x 1.1428, the sulphur with (b) - x lime as disulphide.Then- x x 0.5714 + [(b) - X] x 1.1428 = (a) [(b) x 1.14281 - a 0.5714, The analysie of a typical lime-sulphur spray, sp. gr. 1.3735, was as follows, the x=. from which (b) -x is found. results being expressed in grms.per 100 C.C. Hydroxyhydrosulphide, con- Associated with calcium equiva- ... ... ... 1.653 Disulphide . . . containing 14-716 ,, 12.877 Sulphur. Lime. taining ... ... ... 0.944 lent to ... 9 9 1, - Free sulphur . . . t t 23.11 Thiosulphate . . . 9 , 0.99 9, 9 9 ? 9 0.86 Sulphate and sulphite ,, 0.07 9 , 9 , 9 , 0.11 39-83 15-50 H. F. E. H. Estimation of Minute Quantities of Phosphorus.H. S. Raper. (Biochem. J., 1914, 8, 649-656.)-The method described for the gravimetric estimation of fractions of a milligram of phosphorus is a modification of Brearley and Ibbotson’s method for the estimation of phosphorus in steel (“Analysis of Steel Works Materials,” p. 55). After preliminary oxidation to phosphoric acid the phosphorus is precipitated as ammonium phosphomolybdate, and the molybdenum in this precipitate estimated as lead molybdate.The substance is oxidised with nitric and sulphuric acids in a Kjeldahl flask. The volume of acid left after the oxidation is estimated by pouring water from a measuring cylinder into a similar Kjeldahl flask. The contents of the flask are rinsed into a 500 C.C. conical flask, which has been marked at the 100 C.C.level, Fifteen C.C. of a 50 per cent. ammonium nitrate solution are added, and for every C.C. of acid left after the oxidation, 0.75 C.C. of ammonia (sp. gr. 0*880) in addition. Ten C.C. of a 10 per cent. ammonium molybdate solution are added, and the contents of the flask agitated for a minute and a half. If precipitation of the phosphomolybdate has not begun, less than 1 mgrm.of P,O, is present, and 5 C.C. of a standard phosphate solution (0.3833 grm. KH,PO, per litre ; 5 C.C. = 1 mgrm. P,O,) should be added, or precipita tion will be too slow. The contents of the flask are again shaken, then maintained at 80’ C. for twenty minutes, shaking twice during this period, each time for a minute. The precipitate is filtered off by suction on a pulp filter.The precipitate is now dis- solved in 6 c . ~ , of dilute ammonia (10 per cent,), which is allowed to filter through into the rinsed-out precipitation flask, and the pulp washed with water. The filtrate and washings, which should measure rather less than 100 c.c., are acidified by adding 11 C.C. of concentrated nitric acid and 8 C.C. ammonium nitrate solution (50 per cent.).The liquid is heated to 80” C. and the phosphorus again precipitated as phosphomolybdate by adding 7 to 8 C.C. of ammonium molybdate solution. The The solution is diluted to 100 C.C. and heated to 80’ C.136 ABSTRACTS OF CHEMICAL PAPER8 precipitate is collected, washed, and dissolved in ammonia as before, and the solution treated with 11 C.C. concentrated hydrochloric acid and 10 C.C.of a 4 per cent. lead acetate solution, and then heated almost to boiling. The hot liquid is then poured into a boiling hot mixture of 50 C.C. of a 20 per cent, ammonium chloride solution and 50 C.C. of a 50 per cent. ammonium acetate solution, and the precipitation of the lead molybdate facilitated by shaking. The precipitate is filtered off on a Gooch crucible, washed with hot water, dried, ignited, and weighed.The weight of the precipitate multiplied by 0.0069 gives the weight of phosphorus. The factor 0.0159 gives the weight of P20,. The factors theoretically are 0.00703 and 0.0161. Since the results are on an average 2 per cent, too high, the amended factors have been used when reprecipitation is necessary. When this is not the case, the theoretical factors may be used.In the author’s work the incineration method for the pre- liminary oxidation was not convenient, but when a substance can be incinerated the reprecipitation of the ammonium phosphomolybdate is not necessary. The substance to which a few drops of a saturated sodium carbonate solution have been added is dried in a platinum dish and ignited, The mass is dissolved in a solution of 8.5 per cent.nitric acid, containing 6.5 per cent. ammonium nitrate, and after Precipitation with ammonium molybdate the phosphorus is determined by the lead molybdate method. I t is necessary to know approximately the amount of phosphorus present. For each tenth of a mgrm. of phosphorus about 25 C.C. of the ammonium nitrate- nitric acid mixture must be used for dissolving the mass after ignition.The solu- tions used in the precipitation of the lead molybdate must be taken in about the same relative proportions--i,e., 25 C.C. of the ammonium chloride and ammonium acetate mixture, 2.5 C.C. of concentrated hydrochloric acid, and 2.5 C.C. of 4 per cent. lead acetate solution. E. W. Titanium Trichloride in Qualitative Analysis.A. Monnier. (Ann. C J Z ~ anal., 1915, 20, l-4.)-Owing to its strong reduoing properties titanium trichloride yields a number of reactions with inorganic substances and with certain organic acids. Platinum chloride, iridium chloride, and palladium chloride are reduced when heated with titanium trichloride solution, the metals forming black pre- cipitates ; gold chloride is reduced immediately in the cold, the solution appearing blue by transmitted light, and red by reflected light.Alkali tungstrtte solutions, slightly acidified with hydrochloric acid, yield a blue coloration with titanium trichloride ; molybdates, under similar conditions, give a brown coloration which changes to green or blue on heating; vanadate solutions are at first decolorised, and become blue when heated. Chromates and bichromates are reduced to green chromium compounds, selenious acid yields a red precipitate of selenium, and telluric acid is reduced rapidly when heated, giving a black precipitate of tellurium.Sulphur is deposited when sulphurous acid, sulphites, or thiosulphates are boiled with titanium chloride solution. The following reactions are obtained when the sodium, potassium, or ammonium salts of various organic acids are heated with titanium trichloride solution; the solution of the salt under examination should not be too dilute : Formates and acetates, violet-black precipitate, which becomes white when separated and exposed to the air ; oxalates, yellowish-brown precipitate ; succinates,APPARATUS, ETC.137 violet-grey precipitate ; tartrates, bluish-grey precipitate ; lactates, blue coloration, but no precipitate ; benzoates, brownish-green precipitate ; sslicylates, yellow, slightly green precipitate ; tannin, red-orange precipitate.Citrates yield a character- istic reaction, an intense violet coloration being obtained when a citrate solution is heated to boiling and treated, drop by drop, with titanium trichloride solution ; the coloration is stable for some hours, but the surface of the solution may become decolorised owing to atmospheric oxidation. This reaction is given by citric acid in the presence of formic, acetie, lactic, succinic, and benzoic acids ; citric acid prevents the formation of a precipitate by these acids, but, on the other hand, oxalic and salicylic acids inhibit the reaction given by citric acid. w. P. s. Estimation of Moisture in Zinc Ashes. E. A. Lewis ( J . SOC. Chem. Ind., 1914, 33, 1119-1120.)-1t is not possible to remove all water from zinc ashes by drying at 100" C., especially when chlorides are present ; heating for four hours at 200" C., however, removes practically all the moisture. When the heating is prolonged for more than four hours, the weight tends to increase, probably owing to oxidation of metallic zinc. w. P. s.

ISSN:0003-2654    

DOI:10.1039/AN9154000133

出版商:RSC    

年代:1915

数据来源: RSC

摘要:

APPARATUS, ETC. 137 APPARATUS, ETC. Standard Loop for Use in Bacteriological Tests of Disinfectants. A. D. St. John. ( J . Ind. and Eng. Chem., 1914, 6, 940.)-The objections to the ordinary “standard loop” are-(1) that it transfers too small a quantity of the liquid, viz., about 0.003 c.c., and (2) the quantity conveyed may vary by as much as 80 per cent. from the average. The author recommends the employment of a platinum wire ‘‘ loop ” of the form of a cage, having the appearance of the outline of a cube supported by a wire from one corner, and measuring about 3 mm.on an edge. Such a loop holds a drop varying in weight from 0.019 to 0.021 grm., the maximum variation being 6 per oent. The corners should be welded rather than twisted. H. F. E. H. New Thermochemical Method for Subdividing Accurately a Given Interval on the Thermometer Scale.T. W. Richards and T. Thorvaldsen. (J. Amer. Chem. SOC., 1915, 37, 81-86.)-The method described in the paper depends upon the execution of a given simple reaction, step by step, over the range in question, somewhat analogously to the calibration of a burette with the Ostwald calibrator. The reaction chosen by the authors is the dilution of hydrochloric acid, the heat capacity problem involved in this case being comparatively simple.Allowance must be made, of course, for the temperature co-efficient of the reaction and other details depending on changing heat capacity, but this more difficult part of the work can be carried out once for all with great accuracy, and the figures thus obtained can be used by anyone in any part of the world for the computation of his results. The work required for the verification of any thermometer will then consist simply in a series of dilutions, some sixteen experiments being necessary to calibrate138 REVIEWS satisfactorily a range of 4" in a thermometer scale.This experimental work is easily carried out, and with an adiabatic calorimeter is capable of great accuracy.The method was suggested by the fact thttt inconsistencies exceeding 0.5 per cent. were frequently encountered in careful calorimetric work with thermometers of the best make, calibrated with every care by other methods. The inconsistencies were such as to point to the fact that the 18" point on the thermometers was not exactly half-way thermodynamically between the 16' and the 20" point.The new method of calibration served to confirm this suspicion and to supply corrections, the application of which in subsequent work led to the almost complete disappearance of the irregularities formerly noticed. G. C. J. Vacuum and Pressure Stopcocks. M. Randall and F. R. von Bichowsky. (J. Amer. Chem. Soc., 1915, 37, 137-14P.)-Common faults in glass stopcock design are discussed, several illustrations are given of well-designed stopcocks, and detailed specifications for thirty different sizes and types of stopcock are also supplied. G. C. J.

ISSN:0003-2654    

DOI:10.1039/AN9154000137

出版商:RSC    

年代:1915

数据来源: RSC