摘要:

MARCH, 1909. Vol. XXXIV., No. 396. THE ANALYST. PROCEEDINGS QF 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. R. R. Tatlock, F.I.C., occupied the chair. The minutes of the previous annual general meeting were read and confirmed. Messrs. A. E. Parkes and G. Cecil Jones were appointed scrutators of the ballot papers for the election of Officers and Council for 1909. The HON. TREASURER presented the account8 of the Society for 1908. These were adopted, and votes of thanks were passed to the Eon. Treasurer, Auditors, and Hon. Secretaries. 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 past year.The PRESIDENT delivered his annual address. Mr. HEHNER moved that a hearty vote of thanks be accorded to the President for his address and for his services in the chair during the year, and that his permission be asked to print the address in the ANALYST, Dr. DYER seconded, and the motion was carried with acclamation. The PRESIDENT, having received the report of the scrutators, announced that the Officers and Council for 1909 had been elected in accordance with the nominations of the Council, the list being as follows : President.-R. R. Tatlock, F.I.C. Past-Presidents (limited by the Society’s Articles of Association to eight in nunzber).-M. A. Adams, F.R.C.S., F.I.C.; E. J.Bevan, F.I.C.; Bernard Dyer, D.Sc., F.I.C.; Thomas Fairley,F.I.C. ; W. W.Fisher, U.A., F.I.C.; Otto Hehner,F.I.C.; J. Augustus Voelcker, M.A., B.Sc., Ph.D., F. I.C. Vice-Presidents.-Bertram Blount, F.I.C. ; Cecil H. Cribb, B.Sc., F.I.C. ; H. Droop Richmond, F.I.C. Hon. Treasurer.-E. JV, Voelcker, A.R. S.M., F.I.C. Hon. Secretaries.-Alfred Chaston Chapman, F.I.C. ; P. A. Ellis Richards, F.T.C. Other Members of Cou~tcil.-W. J. A. Butterfield, M.A., F.I.C. ; H. C. H. Candy, B.A., B.Sc., F.I.C. ; Harold G. Colman, M.Sc., Ph.D., F.I.C. ; Arthur E. Ekins, F.I.C. ; John Golding, F.I.C. ; Arthur R. Ling, F.I.C. ; L. Myddelton Nash, F.I.C. ;82 THE ANALYST. James Nimmo, F.I.C. ; F. W. Richardson, F.I.C. ; F.G. Ruddock, F.I.C. ; G. E. Scott-Smith, F.I.C. ; Clarence A. Seyler, B.Sc., F.I.C. Messrs. E. R. Bolton and E. Hinks, B.Sc., were appointed auditors of the Society’s accounts for 1909. The monthly ordinary meeting of the Society followed the annual general meeting, the President occupying the chair. The minutes of the previous ordinary meeting were read and confirmed. Certificates of proposal for election to membership in favour of Messrs. S. 0. Richmond, F.I.C., and A. L. Scott, F.I.C., were read for the second time; and certificates in favour of Messrs. Morris Charles Lamb, analytical and consulting chemist, Director of the Leather Dyeing Department, Herold’s Institute, Bermondsey, S.E. ; and Francis Henry Tate, analytical and consulting chemist, 9, Hackins Hey, Liverpool, were read for the first time. Messrs. G. N. Huntly, B.Sc., A.R.C.Sc., F.I.C., S. J. Lewis, B.Sc., A.I.C., and W. H. Willcox, M.D., B.Sc., D.P.H., F.I.C., were elected members of the Society. The following paper was read : ‘‘ The Use of Quartz Combustion Tubes for the Direct Determination of Carbon in Steel,” by Bertram Blount, F.I.C., and Arthur G. Levy, B.Sc., F.I.C. A paper entitled “ Note on Some Commercial Samples of Monobrombenzene,” by J. H. Coste, F.I.C., was taken as read.

ISSN:0003-2654    

DOI:10.1039/AN9093400081

出版商:RSC    

年代:1909

数据来源: RSC

摘要:

82 THE ANALYST. ANNUAL ADDRESS OF THE PRESIDENT. (Delivered at the Annual General Meeting, February 3, 1909.) MY first duty at the beginning of a new session is to congratulate the Society on its continued, or rather increased, vigour and efficiency, and on the very satisfactory addition to its membership and finance. When my predecessor addressed you a year ago, the membership was 338. It stands now at 353, notwithstanding the losses we have sustained. Twenty-two new ordinary members have been admitted, and two new honorary members-Sir William Ramsay and Dr. F. Gowland Hopkins. Our roll of membership has been, indeed, impoverished by the irreparable loss we have sustained in the death of five members-Sir Thomas Stevenson, James Baynes, Robert Henry Harland, and Sidney Steel, regarding whom obituary notices have already appeared in the ANALYST, and of John Handby Ball.John Handby Ball, B.Sc., M.Sc., of Limerick, was much interested in the Society and in its official publication. EIis former work in the laboratories of Dr. J. Campbell Brown, of Liverpool, and of Dr. Jorgensen, of Copenhagen, fostered in him a spirit of research, and he has carried out some interesting investigations on LLBlown Condensed Milk,” ( ( The Composition of Butter during the Winter Months,” etc., while immedi- ately before his untimely death, he was engaged in a research on ‘‘ The Characteristic Glycerides of Butter.”THE ANALYST, 83 During the past session seven meetings have been held, at which the following thirty papers have been read : February 5, 1908.“ English Inks : their Composition and Differentiation in Handwriting.” “ The Constitution of Indicators.” By J. T. Eewitt, D.Sc., Ph.D., M.A. “ The Volumetric Determination of Reducing Sugars.” Part 11. : (‘ The Limits of Accuracy of the Method under Standard Conditions.” By Arthur R. Ling, F.I.C., and G. Cecil Jones, A.C.G.I., F.I.C. ; Part 111. : L c The Influence of Cane-Sugar.” By Arthur R. Ling, F.I.C., and Theodore Rendle. “ The Composition of Milk.” By H. Droop Richmond. ‘‘ An Apparatus for Quantitative Estimations involving Distillation.” By Gilbert By C. A. Mitchell, B.A., F.I.C. Harclz 4, 1908. T. Morgan, D.Sc., A.R.C.Sc., F.I.C., and Taylor Cook, B.Sc., A.R.C.Sc. ‘‘ Lead in Tartaric Acid, Cream of Tartar, and Baking Powder.” By the President.“ The Estimation of Nitrogen.” Part I. : ‘‘ The Nitrogen Factor for Casein ” ; The Recovery of Amy1 AIcohol from Waste Gerber Liquors.” By H. Droop By J. Lewkowitsch, Ph.D., F.I.C. April 1, 1908. Part 11. : Triazo Compounds.” By H. Droop Richmond, F.I.C. Richmond, F.I.C. ( ( Carapa Oil.” A Rapid Method for the Estimation of Mercuric Salts in Aqueous Solution.” By H. Droop Rich- By S. G. Liversedge. mond, F.I.C. ‘(Studies in Steam Distillation.” Part I. and Part 11. May 6, 1908. ‘‘ The Examination of Turpentine and Turpentine Substitutes.” By John The Estimation of Ferrocyanide in Crude Commercial Products : Commercial 6 ‘ A New Uethod for Milk-Testing, and Some Remarks on the Sydney Supply.” Henry Coste, F.I.C. Analysis of Ferrocyanides.” By Harold G. Colman, Ph.D., RI.Sc., F.I.C. By W.M. Doherty, F.I.C. June 3, 1908. 4 ‘ Studies in Steam Distillation.” Part 111. : ‘‘ The Fatty Acids.” By H. Droop By G. D. Lander, D.Sc., F.T.C., and Richmond, F.I.C. H. W, Winter. The Detection of Poisonous Metals.” (‘ Ochoco Fat.” ‘‘ The Detection of Small Quantities of Methyl Alcohol in the Presence of Ethyl By 5. Lewkowitsch, Ph.D., F.I.C. By L. E, Hinkel, F.I.C. November 4, 1908. 6 ‘ The Solvent Action of Carbonic Acid on the Carbonates of the Heavy Metals.” By Clarence A. Seyler, B.Sc., F.T.C.84 THE ANALYST. ‘‘ The Estimation of Cocoanut Oil in Butter.” By Raymond Ross, F.I.C. ‘‘ The Analysis of Camphorated Oil for Camphor Substitutes.” By F. W. Richard- son, F.I.C., and William K. Walton. ‘( The Separation and Estimation of Certain Volatile Fatty Acids by Extraction with Benzene or Toluene.” By T.R. Hodgson, B.A. ‘( The Gravimetric Estimation of Antimony and Tin.” ‘‘ The Oil from Carapa Guyanensis.” ‘ 6 The Detection and Estimation of Formaldehyde in Milk,” ‘( The Determination of Aldehydes in Oil of Lemon.” ( ( Some Analyses of Cream Cheese.” By Cecil H. Cribb, B.Sc., F.I.C. December 2, 1908. By Edward Cahen, ,4.R.C.Sc., A.I.C., and Gilbert T. Morgan, D.Sc., A.R.C.Sc., F.I.C. By J. Lewkowitsch, Ph.D., F.I.C. By Herbert S. Shrewsbury, F.I.C., and Arthur W. Knapp, B.Sc., F.I.C. By A. H. Bennett. I t affords me the greatest pleasure to report that the investigation scheme of the Society, 60 happily inaugurated a few years ago, is progressing even more favourably than was anticipated, and that the results are most gratifying.During the year twelve new investigations have been undertaken, of which three have been brought to a close and the results published in the ANALYST. An appeal was recently made to Analysts for suggestions in regard to subjects requiring investigation, and it is to be hoped that members will take an active interest in the scheme by suggesting subjects, if they cannot see their way to undertake actual investigations. Now, at the risk of being irksome, I should like to make a passing reference to a subject which has been a good deal before Analysts of late, and particularly Public Analysts, but as the matter has been most efficiently dealt with already by the con- joint action of the Institute of Chemistry and the Society of Public Analysts, I do so only for the purpose of keeping the reports and records of this Society in order.As you are aware, questions of a serious character, affecting their position, security of tenure of their office, of their work, and of their remuneration, have arisen between a number of Public Analysts and the Local Authorities under whom they serve. Some of them authorities interpreted the Food and Drugs Acts in such a way as to lead to great hardship to their official chemical officer, whom, although they could not dismiss, they could simply ignore and transfer his work and emoluments to a whole-time man in their exclusive employment and pay. They also made conditions with their Analyst prior to his appointment, restricting the term of his service to a year or other period at their pleasure, thus contracting themselves out of the terms of the Acts.With the view of having this undesirable state of matters remedied, this Society made representations to the Local Government Board in April last, requesting to be granted an interview between the officers of the Board and a deputation consisting of members of our Council. The President of the Board, the Right Hon. John Burns, replied to the effect that, as the matter had been, and still was, receiving the consideration of his department, he thought that a deputation was not necessary, but expressed himself ready to consider suggestions made to him in writing. ThisTHE ANALYST 85 was all that could be expected, and accordingly a joint letter on the subject, framed by the Councils of the Institute and this Society, dated July 15, 1908, was addressed to him.There can be no doubt that these representations have had the effect of securing the sympathy of the Board, as the latter in reply promised that they would have the best consideration in connection with any fresh legislation that might be proposed for the amendment of the 9cts. I n the meantime similar representations had been made to the Board of Agriculture and Fisheries, with regard to the undesirable position of Analysts under the Fertilisers and Feeding Stuffs Act, and a request was made for the reception of a joint deputation representing the Institute and the Society. The deputation was introduced by Sir William Ramsay, and, in the absence of the President, Lord Carrington, was received most sympathetically by Sir Thomas Elliot, who said, in reply to the address to the Board, presented by the leader of the deputation, that the Board recognised the weight of the arguments which had been submitted, and were disposed to do all in their power; at the same time he pointed out some difficulties in the way of his Department being able to take action which might be beyond its powers.I t is very gratifying to know that the Council of the Institute of Chemistry con- tinues to take an active interest in the welfare of Public Analysts, and one of the latest examples of its vigilance on their behalf is to be found in the action it has taken with regard to the procedure on the part of certain Local Authorities in filling the vacant post of Public Analyst.Two of these had advertised, inviting applica- tions from qualified Analysts, and asking the applicants to state the terms upon which they were prepared to accept the position-in fact, inviting them to tender for the post. A very appropriate letter was addressed to these Authorities by the Institute, pointing out the consequences, in lowering the status of the Analyst, or excluding applicants of high standing, with the inevitable result of impairing his efficiency in the public service. I t could hardly be expected that these Authorities would recognise or admit the censorship of the Institute: but it is satisfactory to know that in one of the cases, at least, the gentleman who put the lowest value on his own services was not appointed. I have no desire to harp upon the grievances of Public Analysts, but I am tempted to quote yet another instance of the manner in which their interests are menaced.A circular has recently been issued by the Local Government Board, to ‘‘ Counties and Boroughs,” dated December 8, 1908, in which, under the heading “ Informal Samples,” the following passage occurs : “ If, with a view to preliminary investigation, any informal samples have been collected and dealt with otherwise than by submission to the Public Analyst, the Board would be obliged if you would forward to them a short statement of the pro- cedure adopted in such cases.” We may safely trust the Council of the Institute to deal with this, if they deem it advisable, in their usual judicious way; but in the meantime there can be no harm in pointing out that this clause means either that the Board are simply seeking for information, or that they may take cognisance of samples which are purchased for the purposes of the Food and Drugs Acts, and analysed by some chemist other than This was granted, and the meeting took place on May 14.86 THE ANALYST.the Public Analyst. I t is scarcely necessary to point out that, if the latter is meant, the effect will be that the Public Analyst will receive only such samples as are likely to become the subjects of prosecution, the analysis of which mill require his highest skill and care, and will in inany instances involve preparation for his appearance as a witness, for which, of course, under the Acts, there is no remuneration.There is another little point affecting the interests of Public Analysts to which I would direct merely passing attention, as there is little prospect of any remedy being found for the consequences which it entails. I refer to the administration, by counties, of the Food and Drugs Acts, for boroughs who originally acted indepen- dently in this respect. The arrangement, if it has not been promoted, has been recognised and encouraged by the Board of Agriculture, no doubt for reasons which they consider adequate, and this applies also to the coalition of boroughs for the purpose of working the Acts. The effect of this, of course, is that Analysts are ousted from their posts, the centres in which the Acts are administered are fewer, but, being consequently larger, there is created the inducement to employ, as soon as the volume of work admits of it, a whole-time Analyst who is in the exclusive service and pay of the appointing body. I should now like to direct your attention to a matter which, although appar- ently trivial in itself, has given rise to a condition of matters, in one district in Scot- land, which is at once curious and interesting.The Sale of Milk Regulations, 1901, enjoins that a milk showing less than 8.5 per cent. of milk solids other than milk-fat is to be presumed to be not genuine. This provision seems to have worked fairly well, until there appeared the Annual Report of the Board of Agriculture for 1906, on Proceedings under the Food and Drugs Acts, etc., for that year, which (p. 17) con- tains the following paragraph : ‘‘ The Board were consulted by a Public Analyst as to the form of certificate to be issued in the case of samples of milk which on analysis showed the non-fatty solids to be less than 8.5, though the percentages of fat and of total solids were con- siderably in excess of the requirements of the Sale of Milk Regulations. In reply it was pointed out that in view of Section 4 (1) of the Sale of Food and Drugs Act, 1899, an Analyst would not apparently be justified in certifying such samples as genuine, but that it was open to him in such cases to confine his certificate to a mere statement of the constituent parts of the sample, and, if he considered it desirable, to give the opinion that the milk was abnormal, but not adulterated, and advise that no legal proceedings should be taken.” I presume that most Analysts have been in the habit of exercising their dis- cretion in giving their opinion with regard to a sample not being genuine which showed non-fatty solids slightly under this limit; but the paragraph in question clearly authorises the Analyst, in the event of the analysis showing the sum of the fat and non-fatty solids to be considerably in excess of the requirements of the Act, to describe it as “abnormal,” but not adulterated, and to advise that no legal proceedings be taken.The Analyst referred to in the paragraph quoted followed this course, as he was quite entitled to do if he thought proper, and by-and-by a representation was made by the sanitary inspector of the district to the Association of Public Analysts of Scotland, to the effect that the adoption of this suggestionTHE ANALYST.87 had resulted in the encouragement of systematic adulteration in the district on a wholesale scale. He supported his contention by a statement of the analysis of 108 samples purchased that year, 31 of which were returned as genuine, 28 adulter- ated, and 49 He further stated that in 26 instances of the latter he had tested the entire milk of the herds, or parts of herds, which had yielded the milk, and had in every instance found that it was of excellent quality in every respect, At the earnest request of the sanitary inspector referred to, the Secretary of the Association laid the whole matter before the Secretary of the Board of Agriculture, and was met in the most courteous and encouraging manner; and a good deal of correspondence has passed relative to suggestions for the remedy for this condition of matters, and even relating to proposals for material alterations in the terms of the Milk Regulations for 1901.I may be pardoned for making a slight digression here, in order to explain, in a word, the position of the Association of Public Analysts of Scotland. It was formed some five years ago as a local society, its object being to inculcate and promote a high standard of professional conduct, to render mutual assistance and advice in circumstances of difficulty arising in the course of practice, and particularly to foster a spirit of good-fellowship and camaraderie among its members, who consist of practically all the Public Analysts holding oftice in Scotland, some fifteen in number.Meetings are held several times a year, in Edinburgh and Glasgow alternately, to discuss topics of interest and to read short papers, which, however, are not published. There is no meeting without a dinner, which may partly account for the success of this little institution. I t was felt that in Scotland many minor questions arose which might be disposed of by a small local body, or discussed with the object of bringing them under the notice of the Institute of Chemistry and the Society of Public Analysts if they were deemed of sufficient importance; but the association does not in any way interfere with the functions of these two bodies; indeed, it may be regarded as entirely auxiliary to these.I t is a niatter of regret, to my mind, that there is not a more uniform condition of opinion and practice among Public Analysts with regard to the question of standards for the more important articles of food. This is not surprising, however, when we consider that some of our best authorities, those most competent to judge, are either averse to the principle of standards, unless in well-defined circumstances, or give only a half-hearted support to it. Much may and should be said on both sides of the question ; but one thing Public Analysts must recognise--namely, that the creation of a standard is a very serious matter, and one not to be decided upon without the gravest consideration; and I may be pardoned for expressing the opinion that we, as Analysts, should not accept standards from any outsiders, but only legalised ones, and those that we have decided upon after careful and mature deliberation. I hope to see this question made the subject of a field-night discussion at some meeting of this Society.A little commotion has taken place lately on the question of the rights and privileges of women chemists, particularly as regards their admission to the member- ship of our societies, and a considerable variety of opinion has been expressed--one, I think, to the effect that if women were accorded all these, they might become abnormal.”88 THE ANALYST. formidable rivals in an already overcrowded profession. It appears to me that this amounts not only to a confession of weakness on the part of the ‘‘ party in power,” but that it is an unconscious admission that the claims of the ladies rest on a firm and solid foundation.I t is not the first time, however, that men have been frightened by women. I t appears to me that, having granted women the right to join our Universities and educational institutions, to pay their fees, to compete with us, and, perchance, to beat us at examinations for diplomas, they are entitled to all the advantages which are, or ought to be, the natural consequence of their applica- tion and industry. My predecessor, in his presidential address a year ago, referred to the question of qualification for admission to the membership of our Society, and I was greatly pleased that he expressed the view that, although certain limitations were essential the question of eligibility otherwise should always be at the discretion of the Council and of the Society. Any attempt at a cast-iron definition of this would result in the members of the body being much of the same mould, and some of the best brains and best work of the country would be lost to the Society. The present system is, in my opinion, an excellent one, and the only qualification required on the part of the candidate ought to be that of securing the opinion of the Council and of the members that he is worthy of admission. I t has been mooted that certain Local Authorities are at present preparing superannuation schemes, and that some of these include proposals in favour of their Public Analysts. I t is devoutly to be wished that; something may come out of this ; but it seems difficult to believe that the same Local Authority who with one hand deprives the Public Analyst of his means of living while he is fit and capable will contribute to his support when he is disabled from age. I t only remains for me to remind you, if that is not superfluous, of the coming International Triennial Congress of Applied Chemistry, which is to be held in London at the end of May, and to ask you individually and collectively to do all in your power to promote its success, as opportunity offers. We are entitled to expect, and do expect, that some of the results will, among other benefits, prove of great service t o h a l y s t s and food experts.

ISSN:0003-2654    

DOI:10.1039/AN9093400082

出版商:RSC    

年代:1909

数据来源: RSC

摘要:

88 THE ANALYST. THE USE OF QUARTZ COMBUSTION TUBES ESPECIALLY FOR THE DIRECT DETERMINATION OF CARBON IN STEEL. BY BERTRAM BLOUNT F.I.C. AND ARTHUR GARFIELD LEVY B.Sc. F.I.C. (Read at tho Meeting Februcwy 3 1909.) DURING the last two years a new material fused quartz has come into use in analytical laboratories. The present paper deals with some applications of fused quartz tubes to high-temperature work for which their great resistance to sudden changes of temperature renders them very suitable. Quartz ware is obtainable in two varieties in the transparent fully fused state and in the opaque partly fuse THE ANALYST. 89 form. The first of these varieties is distinguished chiefly by the ease with which apparatus of any shape not too large can be made and by its high price.The second so-called " vitreous," variety is a much less costly material but possesses the disadvantage that particles flake off; hence it is not suitable for crucibles out of which precipitates are brushed before weighing. Analysis Organic of a sample of each kind of quartz tube gave the following results : Clear. Per Cent. Silica (by difference) . - > . 99.77 Alumina and iron oxide . . 0.12 Lime . . . . . nil Magnesia . . . . nil Sodium oxide . . . . 0.11 Vitreous. Per Cent. 99.77 0.15 0.04 trace 0.04 100-00 100~00 Combzistio?z.-The first use to which we put quartz was to replace the tubes commonly used for organic combustions. I t was found that tubes of clear silica were well suited to this purpose they being much longer-lived than glass tubes.The higher temperature possible also renders combustion of volatile liquids the vapours of which need rapid oxidation a much easier matter than with glass Unless an altogether excessive temperature i E reached silica withstands the action of the usual packing agents such as copper oxide and lead chromate very well-better in fact than does glass. It was found however that at about 900" C. copper oxide rapidly attacks and destroys quartz tubes so that some care is necessary in regulating the temperature. Determination of Oxygen in Copper.-We next proceeded to use quartz tubes for the determination of oxygen in copper by fusion in hydrogen. For this purpose a tube of clear silica 275 mm. long by 13 mm. bore joined at one end to a quartz tube 25 mm.long by 4 mm. bore is wound with very thin platinum foil obtained from Heraeus-a strip of foil about 1,500 rnm. long 4 mm. wide and 0.007 mm. thick being used. The resistance o€ this winding when cold is about 15 ohms and when heated to about 1,200' C. 26 ohms. The leads at the ends are made of stout platinum wire. The tube is supported by uralite discs in the centre of a fireclay cylinder 75 mni. in diameter with walls about 6 mm. in thickness. This cylinder is wrapped round with asbestos cloth. The furnace is constructed for a 200-volt circuit ; it is started in series with an adjustable resistance of not less than 25 ohms which is gradually lowered to about 7 ohms so as to keep the current constant at 6 ampBres. I n this apparatus a piece of copper weighing 10 to 15 grams ia completely fused in three to five minutes.As the furnace cools in about ten minutes successive determinations of oxygen in copper are easily carried out in twenty-five minutes each-a considerable saving in time as compared with older methods of heating. One such tube has now been in use for about eight months has not needed any repairs in that time and is still in good condition. Recently from experience gained by this earlier procedure a second furnace was constructed in which foil composed of 5 per cent. iridium-platinum alloy was used with leads of platinum foil 5 mm. wide by 0.03 mm. thick 90 THE ANALYST. soldered outside the fireclay cylinder to small silver forks. The iridium-platinum alloy withstands heating better than does platinum ; the new form of lead represents a considerable saving in precious metal.This second form of furnace will probably last even longer than the first. In passing it may be mentioned that the hydrogert generator used is of the form described by Browne and Brown (Journ. Amer. Chene. SOC. 1907 29 859 ; ANALYST 1907 32 344). This generator gives a constant stream of hydrogen for many hours though curiously enough it works badly when used for generating hydrogen sulphide. I t should be stated that a furnace similar to the above has been described by Professor S. A. Tucker (Joz~rn. rlqner. Clzem. SOC. 1907 29, 1442 ; ANALYST 1907 32 435) for low voltage currents. Determination of Curboiz in Steel.-It has been shown previously (B. Blount, ANALYST 1900 25 141) that even stout fragments of steel are completely oxidised when burnt in a stream of oxygen provided only that the temperature used is high enough and prima facie a furnace of the type described seems suitable for the direct.combustion of carbon in steel. The problem presented here is however essentially dieerent from the last-viz. the determination of oxygen in copper. Metals kept free from oxide by hydrogen do not attack silica howevzr high the temperature. The very nature of the process of combustion of steel involves the presence of metallic oxides which at the temperature used instantly and thoroughly destroy quartz. tubes. Steel when burning in oxygen at high temperature gives off sparks of incandescent material which are projected with considerable force for some distance.If air only is used a very large quantity of gases must be passed through the purifying. and absorbing apparatus and the time required by the process is correspondingly increased. Heating must be continued for a considerable time at a high temperature, thus subjecting the platinum resistance to a severe strain. During the burning of the steel a large quantity of oxygen is suddenly absorbed necessitating unless. special arrangements are made anxious manipulation of the oxygen supply to prevent entry of air at the wrotig end of the tube. To meet these difficulties the apparatus shown in the figure and photograph (p. 91) was evolved after preliminary experiments had shown that the foil used in Hemus furnaces is too thin to withstand the prolonged heating repeatedly ; that platinised quartz does not completely oxidise the carbon monoxide evolved unless supplementary oxgen is supplied to it ; and that combustion in air alone lengthens the process unduly.The apparatus described has now been, in use for some time and is used as a matter of routine to check the results obtained by the solution process. Referring to the figure combustion is carried out in a tube of clear silica E, 525 mm. long and 22 mm. in bore joined at one end to a clear silica tube 75 mm. long and 5 mm. in bore. At the drawn-out end of the wide tube a narrow silica, tube is sealed into it which terminates inside the wide tube at a point 175 mm. from this end and projects for 75 mm. outside the tube being joined by a rubber connec-tion to a glass tube I.Two sections of the wide tube each 150 mm. long 25 mm. apart and placed close to the drawn-out end of the tube are separately wound with iridium-platinum foil the portion nearest the open end G being wound with foil 3 to 3.5 mm. wide and 0.015 mm. thick whilst the other section H is wound with foil 4 mm. wide and of about the same thickness. The leads are made of stoute THE ANALYST. 91 92 THE ANALYST. platinum foil soldered to silver forks screwed to the three terminals. The sections are wired so that the main current of 200 volts can be sent through an adjustable outside resietance either through the farther section H only or through the two sections in series with each other. The relative resistance of the two windings is calculated so that when they are placed in series using a current of 5.5 ampires, section H is heated to a dull red heat and section G to a temperature of at least 1,050" C.Each section is enclosed in two fireclay semicylinders R S which fit tightly on the quartz tube and which are further protected by wrappings of asbestos cloth secured by copper wire. The section G serves for the actuhl heating of the boat containing the steel ; injury to the tube from sparks is prevented by surrounding the boat with a piece of iridium-platinum foil 150 nim. long 80 mm. wide and 0.03 mm. thick which is rolled into the form of a tube and inserted together with the boat. The latter itself is protected from the action of the burning steel by placing a layer of well-ignited alumina in the bottom. One boat usually lasts two or three times.The farther section H is packed with a mixture of platinised quartz and platinum scrap so as to form a sort of contact chamber ; oxidation of the carbon monoxide evolved is effected here by means of a stream of supplementary oxygen introduced through the narrow tube I. Most of the small quantity of ferric oxide projected from the boat collects harmlessly in the short comparatively cool space between the two sections. The (( contact mass '' is emptied out occasionally and cleaned by boiling with hydrochloric acid. A piece of silver foil F placed close to the boat section protects the rubber stopper from the intense radiation characteristic of quartz tubes. The spy-hole D is placed in alignment with a hole in the silver shield and enables the combustion to be watched to some extent.The supplementary oxygen is purified by the potash bulbs K and soda-lime tube L. The main stream of oxygen and the air used to sweep out the weighed bulbs are purified by a second set of bulbs B and soda-lime tube C. The oxygen passes to the bulbs through two arms of a Y-tube,T the third arm being joined to a trap A leading to the air outside the laboratory. The gases leaving the quartz tube are dried by passing through two sulphuric acid tubes M and N. They then pass through the weighed potash bulbs, 0 and sulphuric acid tube P to a sulphuric acid guard-tube connected to a water-pump. Coming to the actual process of combuotion 5 grams of steel are placed in the boat the latter is pushed into its iridium-platinum envelope and the whole inserted in the quartz tube by means of a rubber-tipped rod pressed against the foil.A current of about 7 ampires is sent through section H for about five minutes. The pump is started a slow current of supplementary oxygen is passed into the tube through I and the main cnrrent of oxygen supplied at such a rate that whilst about four bubbles pass through the potash bulbs B for every one through the bulbs K, about the same quantity of oxygen goes to waste thfough the trap A. The quantity of gases passing through the weighed potash bulbs is constant throughout the whole combustion being regulated only by the suction of the pump. As soon as the platinised quartz has attained a dull red heat the current is sent through both windings being kept at 5.5 to 6 ampires by means of the adjustable outside resistance.After about one minute this resistance is taken out. At this point th THE ANALYST. 93 boat section G is at a bright red heat and almost immediately after the steel begins to burn. As a large quantity of oxygen is required for the oxidation of the steel the oxygen which was bubbling to waste during the preliminary operations is sucked into the tube. After a short time air also enters through the trap A ; combustion slackens until most of the nitrogen has been sucked out of the tube and an atmosphere of oxygen restored. Violent oxidation then begins again and is again checked a6 before. As a rule there are three well-marked periods of energetic oxidation in each combustion lasting altogether five to ten minutes.The time during which the steel is heated in oxygen is twenty minutes for ordinary drillings or planings and thirty to forty minutes for stout fragments. At the end of this time both supplies of oxygen and the electric current are shut off and air is sucked into the combustion tube through the trap A for another twenty minutes after which the bulbs are placed on the balance for twenty minutes. I t will be seen that for ordinary samples of steel successive combustions require sixty-five minutes and that as the oxygen supply regulates itself automatically the operator need give attention to the combustion at four periods only for a few minutes at a time. The device of passing oxygen into a combustion tube from a Y-tube and applying suction at the other end of the tube has been in use for the combustion of volatile liquids for several years and there also works well.I n the table on p. 91 the results obtained on typical steels and pig-irons are compared with those obtained by the solution method a neutral solution of the double chlorides of copper and potassium being used. The results for steels differ by less than 0.02 per cent. from those given by the solution method and agree well with each other. Blanks also and combustion of diamond are satisfactory the blanks varying from 0.004 to 0.008 per cent. expressed as carbon on 5 grams of steel as against 0.005 to 0.009 per cent for the solution method. The blanks are complete in each case only the steel being omitted. The direct method compares favcurably with the solution method as regards length of time required and work involved.Drillings of any ordinary thickness may be handled ; thin drillings as required for the direct combustion methods of Johnson (JOZLTPZ. Amer. Chenz. SOC. 1908 30 773 ; ANALYST 1908 33 288) and Rosenhain (Journ IT072 mzd Steel I~zstitzite 1908 No. I. 96) are unnecessary. Stout drillings of steel are completely burnt if the time is moderately extended. Regarding source6 of error that due to the possible formation of sulphur dioxide is the most apparent. This gas would pass through the sulphuric acid tubes be absorbed in the potash bulbs and weighed as carbon dioxide. Chromic acid might be placed in one of the sulphuric acid tubes to stop this sulphur dioxide; but as a matter of fact it has been shown by repeatedly passing the gases from burning steel and pig-iron through a dilute solution of potassium permanganate acidified with nitric acid or through a solution of barium hydroxide immediately after leaving the combustion tube that neither sulphur trioxide nor dioxide leaves the tube.Incidentally it was found that a large proportion of the sulphur present is evolved from the burning metal and condenses in the form of minute drops of sulphuric acid inside the wide quartz tube at the point where it is joined to the narrow tube. The drawbacks of the method are these. Care is required not to spill the stee 94 THE ANALYSTo Sample. Solution Method. Per Cent. Carbon. Direet Method. Per Cent. Carbon. Difference. Diamond 0,0537 gram corre-sponding to 1.074 per cent.of carbon when 5 grams of steel are taken . . . Tram-rail . . . . y l plus 0.504 per cent. diamond . . 2 . . 2 . . . 2 . . 2 . . . 3 . . 4 . 4 . . 4 . . . 9 9 4 resampled . 5 . . 5 . . Y 5 . . 9 5 . . 9 s 5 . . 6 . 7 . . . 8 . . Boiler-plate 1 . . . . . . . 2 . 3 . . 2 . . . . . . . . . . Carriage-tyre 1 . . . Carriage-axle 1 . . . . 1 , 9 , . Y Y 9 s 9 ) 9 . 9 9 Y . . . . ) > 9 . . . . . Y . 7 , ,s . . 9 9 . 9 . . . Pig-iron 1 .,. Complete blank . . . 7, 9 , 9 , . . I . 9 9 * . * 9 9 . * - . . -0.571 E:} Z} 0.425 0.439 0.425) 0.393 -0,359 0.3401 0.341 0.343 0-335 0.339 0.315 0.334 0.344 0.168 0.141 0.100 3.987 3-802 i KE} -1 *089 0.535 1-034 0.573 0.575 1 0.572 j 0-432 0.407 1 0415 J 0.409 0.385 0.366 0.372 0.372 0.345 0.331 1 0.328, 0.322 0.328 0.331 0.164 0.138 0.107 4.058 3.758 0,008 0.004 0.007 -+ 0.015 - 0.017 - 0.023 + 0.002 + 0.002 + 0.007 - 0.021 + 0.016 + 0.016 + 0.013 - 0.006 -+ 0.007 - 0'006 - 0.013 - 0.004 - 0.003 + 0.007 + 0.071 - 0.044 in inserting the boat as this infallibly leads to speedy destruction of the quartz tube.The winding of the boat section although of iridium-platinum foil twice as stout as that used for the furnace for the determination of oxygen described in this paper, fails after about thirty combustions. Although a broken winding is easily patched, since the foil welds very easily yet after patching a few times failure becomes so frequent that it is best to remove the winding entirely and replace it by a new one.This operation takes about an hour. Apparently the high temperature used injures the foil in some way. The quartz tube itself lasts a long time if care is used but gradually becomes devitrified THE ANALYST. 95 For the solution method also the porcelain tubes used for the combustion of the separated carbon have been replaced by quartz tubes in this case of the ‘‘ vitreous ” or translucent variety. The tube is drawn out at the farther end thus doing away with the cap or stopper formerly used. Copper oxide is used as auxiliary oxidant; to protect the tube the copper oxide is enclosed in a sheet of iridium-platinum foil 0.03 mm.thick rolled into the form of a tube closely fitting the quartz tube. The column of copper oxide is kept in place by fragments of quartz placed at both ends. Combustion takes considerably less time than formerly as the burners may be at once turned up to their full extent. The plugs must however be washed free from copper chloride; if this is not done copper oxide may be deposited inside the quartz tube and will destroy it. The quartz tubes last much longer than porcelain tubes and stand rougher treatment. Marsh-Berzelius Test for Ammic.-Some years ago we constructed a small electric furnace at Dr. Bernard Dyer’s request for heating the glass tubes used in the Marsh-Berzelius test for arsenic. Although quartz does not enter into its construction this furnace may be described here.The problem of how to dispose of 200 volts in the short length available was finally solved by winding fine platinum wire (B.W.G. No. 40) forty times around a fireclay tube 37 mm. long and 27 mm. in external diameter packing this tube into a second fireclay tube of the same length, and with an external diameter of 35 mm. with kaolin and winding another twelve turns of the same platinum wire around the outer tube in series with the inner winding. The whole was then packed into a third fireclay tube 75 mm. in diameter, and held in place by uralite discs bound with copper wire the leads consisting of somewhat stouter platinum wire. The glass tube to be heated was supported by perforated sheets of mica placed at each end.As external resistance a 32 candle-power 100-volt incandescent lamp was used which was cut out when the furnace became hot. The current used was 1 amphre. The furnace worked well and is still in existence but has not yet superseded the Bunsen burner. Our thanks are due to Ur. H. E. Course for valuable help rendered in connection with the electrical part of the work. DISCUSSION. Mr. BLOUNT desired to add that the difficulties encountered in working out the details of this operation were considerable and had been entirely sustained by Mr. Levy. The regulation of the temperature in the oxidising part of the operation was the fundamental difficulty and when that was overcome by a difference in winding the difficulty presented itself of supplying the supplementary oxygen and supplying it at the proper rate as well as supplying oxygen for the combustion.It might not perhaps be generally realised that one of the chief difficulties was that oxygen must be supplied for the steel as well as for the carbon and when oxygen was passed in in the ordinary way it was taken up so quickly that no gas passed on, and therefore the present method of supplying supplementary air or oxygen was elaborated. The solution of these practical questions converted a process whic THE ANALYST. was not very difficult to design in principle into a working success and this fortunate result was due to Mr. Levy. Ah. ARCHBUTT said that while he congratulated the authors on the evolution of this piece of apparatus he was rather surprised (regarding more particularly the part relating to the determination of carbon in steel) at the ingenuity which seemed to have been expended in making the apparatus complicated.The apparatus which he used for the direct combustion process seemed to him to be very much simpler. In Mr. Blount's paper some years ago the necessity for a very high temperature was pointed out and at that time he (Mr. Archbutt) only used the direct method for checking purposes. Since then however he had found out how to make these direct determinations in an ordinary combustion furnace and now used no other method except for checking. The necessary temperature could not be obtained in the ordinary Erlenmeyer furnace but the Griffin furnace with a single radial burner answered excellently giving a temperature of 1,000" C.which was essential. He had begun by doing as some other workers had done-namely mixing the steel with small pieces of fireclay-but this was found later to be unnecessary it being sufficient to burn the steel without any admixture of red lead pieces of fireclay or anything else. The steel was introduced into small boats of what was known as " asbestos paper," shaped in wooden moulds These were found to be more suitable than porcelain boats because they held the steel better and spread it out better, being narrower and longer. The gases passing out of the furnace were very hot, which at first made it impossible to maintain the potash bulbs (which were Geissler bulbs not like those used by the authors) at constant weight moisture being driven off from them.This was prevented by attaching to the end of the combustion tube a narrow glass tube which was bent in the form of a U and placed in water with the result that the gases were cooled as they passed through the tube. With this arrangement a current of oxygen could be passed through the apparatus for four hours at the same speed at which the combustions were carried out without any gain or loss in the weight of the potash bulbs. A difficulty at first experienced was the liability of the ordinary porcelain tubes to breakage. This led him to try the Huxley furnace supplied by Messrs. Griffin in which the porcelain tube was surrounded by a fireclay tube so that the gas-flame impinged on the fireclay tube, the porcelain tube being heated by radiation.Used in that way the porcelain tubes lasted from twelve to fifteen months. About 34 inches of copper oxide was placed in the tube just inside the furnace and 2 inches of lead chromate in the thickness of the wall and just beyond it as it was not desirable to heat the chromate of lead too much; 2.727 grams of the steel were placed in the asbestos boat (which had been previously ignited in a muffle and cooled in a desiccator) and passed into the tube which had been already fully heated in the previous combustion. When carbon was being burnt it could not be run into a fully heated tube because the carbon would take fire and CO might be lost; but steel could be quite safely run into a red-hot tube. With the asbestos boat there was no risk of cracking the tube by undue chilling.As soon as the steel began to burn it was simply necessary for someone to stand by the apparatus and feed the oxygen as fast as the steel would take it consistently with its being properly purified. This lasted only a few minutes THE ANALYST. 97 and caused no difficulty; and when that stage was passed the speed of the current was reduced and the combustion continued. He had never experienced any difficulty through the potash in the bulbs sucking back. Before the steel was put in the potash bulbs were weighed full of oxygen at intervals of ten minutes until constant and when the combustion was finished they were weighed again at similar intervals until constant. The whole process was completed in from three-quarters of an hour to an hour. The results were much the same as the authors’ but the tcndency seemed for the direct method to give slightly higher results than the solution method owing he believed to the carbon being given a little more accurately.The difference however was generally only in the third decimal place. He had not been 60 successful as the authors in burning pig-iron owing to fusion taking place but he was continuing his experiments in this direction. Another advantage of the Huxley furnace might be mentioned-namely that it would accommodate as many as four tubes at once. This of course would be possible with the authors’ apparatus though at the expense probably of some further complication. Dr. DYER expressed his thanks to Mr. Levy for his care and ingenuity in making for him the small furnace for heating the tubes when testing for arsenic by the Marsh-Berzelius process.The furnace worked excellently-much better than the Bunsen burner In the electric furnace the heat could be well regulated but the great point was that it did away with the flicker of the Bunsen burner caused by draughts and with the consequent frequent annoyance caused by shifting or displacement of mirrors before the deposition was complete. The PRESIDENT remarked that he had been surprised lately to learn that quartz could be used for vessels of comparatively large size-e.g. basins up to 18 inches in diameter which could be used for concentrating sulphuric acid. He had never been able to understand why silica glass ( i e . the transparent material) should be so much more expensive than the opaque fused quartz.Mr. LEVY in reply said that although they were aware that composite tubes were being sold they had had no experience of them as yet having obtained a stock of the others before composite tubes were put on the market. The composite tubes would probably last very well though they had the disadvantage that one could not see so well what was going on or how far the tubes were attacked. I t might be mentioned that the electrical direct combustion process could be quite comfortably carried on in an ordinary room without any special ventilating devices which would certainly not be the caBe if a ,Griffin or Huxley furnace standing on an ordinary laboratory bench were used. He had made a good many determinations by direct combustion in a gas-furnace and had always experienced difficulty in supplying sufficient oxygen to the burning steel without getting air in at the other end unless some sort of trap were used.If four tubes were used in one furnace it would probably be worth while for an operator to give his whole attention to it ; but the process they had described only required attention for a very short time-about four times during the combus-tion and then only for about a minute each time. Otherwise it was as nearly auto-matic as one could make it. With four tubes in one furnace they would probably try cutting out the supplementary oxygen and platinised quartz and putting i 98 THE ANALYST, copper oxide protected by platinum as in the indirect method ; but with one tube only when the number of determinations was not very large this probably would not be 60 convenient as the present arrangement The diif'erence in cost between the vitreous quartz and the porcelain tubes was not great and probably Mr. Archbutt would find the superior lasting power of the quartz tubes to be an advantage even when using a gas-furnace for determining carbon in steel The chief advantage of the electrical heating wag that there was no inconvenience from fumes. They had generally found the direct method to give slightly lower results than the indirect The largest piece of quartz apparatus they had tried was a muffleof vitreous quart

ISSN:0003-2654    

DOI:10.1039/AN9093400088

出版商:RSC    

年代:1909

数据来源: RSC

摘要:

98 Volume of Distillate. THE ANALYST, Percentage by Volume. Refractive Index n E . NOTE ON SOME COMMERCIAL SAMPLES OF MONOBROMBENZENE. BY J. H. COSTE, F.1.C- MONOBROMBENZENE is a material which, from the fact that its boiling-point is so far from that of benzene on the one hand, and of either of the dibrom-derivatives on the other, should be easily obtained in a state of purity. Some time ago the author had occasion to calibrate some thermometers for temperatures near 150" C., and attempted to make use of a sample of monobrombenzene of German manufacture and supposed to be pure. I t was found to have a somewhat wide range of boiling- point, and to leave a crystalline residue when distilled to a temperature somewhat above the boiling-point of pure monobrombenzene (155' C.).A sample recently obtained from an English firm, but probably made in Germany, and also supposed to be pure, was found not to be of constant boiling- point. A portion measuring 300 C.C. was slowly distilled, using a 15-disc Young's rod and disc column. The following table gives the amounts and properties of the distillates obtained : Temperature. 1. Below 100' C. 2. 100-110" c. 3. 110-153" C. 4. 153-155" C. 5. 155-156" C. 6. 156-157" C. 7. 157-158" C. 8. 158-159" C. Total .._ ... 1 C.C. 9 C.C. 13 C.C. 99 C.C. 137 C.C. 19 C.C. 6 C.C. 3.5 C.C. 0-3 3.0 4.3 33.0 45.7 6.3 2.0 1-2 287.5 C.C. I 95.8 1.4975 1.5442 1 5502 1.5586 1.5590 1.5596 1.5596 1.5595 The residue in the flask was about 10 C.C. in volume, and on cooling solidified to a crystalline magma. The white crystals thus obtained weighed 10.0 grams, and melted at 83-84' C., and were This was broken up and pressed between filter-paper.THE ANALYST, 99 evidently crude dibrombenzene.The presence of unbrominated benzene was indicated by the odour of the first fraction, and the low refractive index of that and the two following fractions. Fractions 6, 7, and 8 were mixed and distilled from a small Ladenburg flask. A distillate of 25 C.C. was obtained between 1/54' and 156" C. This portion was mixed with fractions 4 and 5 , and yielded on distillation 239 C.C. of a liquid boiling between 153" and 154" C., at a pressure of 751.8 mm. of mercury, and having a refractive index at 20" n,=1*5589. Jahn and Moller found the refractive index at 13.2" C. to be i z D = 1.5635, and using the correction for 1" given in Landholt and Bornstein on the authority of Perkin-0.00054, this should equal 1.5598 at 20"-somewhat higher than the figure obtained by the author, who used an Abbe refractometer, and deter- mined the index at different temperatures below and above 20", and obtained a correction figure-0-00057-very close to Perkin's figure. Although monobrombenzene from the nature of things is a difficult material to prepare by direct bromination of benzene without obtaining some amount of the dibrom-compound, it should, in the opinion of the author, be carefully fractionated before sale, and certainly when sold as pure should contain no benzene, and much less than 3 per cent, of dibrombenzene.

ISSN:0003-2654    

DOI:10.1039/AN9093400098

出版商:RSC    

年代:1909

数据来源: RSC

摘要:

THE ANALYST, 99 ABSTRACTS OF PAPERS PUBLISHED IN OTHER JOURNALS. FOODS AND DRUGS ANALYSIS. The Estimation of Alkaloids in Coca Leaves. A. W. K. de Jong. ( A h . Tmv. Chim. Pays-Bas, 1908, 27, 419-421.)-The finely powdered leaves (12.5 grams) are mixed with 5 C.C. of 25 per cent. ammonia solution and extracted in a Soxhlet apparatus for ten to fifteen hours with petroleum spirit. The extract is transferred to a separating funnel, and the leaves extracted for three hours with a fresh portion of ether, to insure complete removal of the alkaloids. The united extracts are shaken, first with 50 C.C. and then with 25 C.C. of 0.5 per cent. hydrochloric acid, and the acid extracts filtered and shaken with ether. The ethereal layer is put aside, and the aqueous layer rendered alkaline with ammonia and again extracted, first with 50 C.C.and then with 25 c;c. of ether. The three ethereal extracts are distilled in a, tared flask, and the residue dried and weighed. The results of test experiments quoted show that this method gives results in close agreement with those of Keller’s method, and in a much shorter time. C. A. M. Metallic Salts of the Volatile Acids Present in Butter Fat and Cocoanut Oil, and the Detection of Cocoanut Oil in Butter. C. Paal and C. Amberger. (Zeits. Untersuch. Nuhr. Genzcssm., 1909, 17, 1-51.)-1n the first part of this investi- gation, experiments were carried out with the object of ascertaining whether the volatile acids obtained in the ordinary Reichert-Meissl distillate could be precipitated100 THE ANALYST.as their metallic salts, and the latter separated and weighed. Of the metals tried, zinc and cadmium gave the most promising results, and a cadmium salt was finally chosen as being the most satisfactory precipitant for the volatile fatty acids obtained from butter-fat and cocoanut oil. The cadmium salts of butyric acid and caproic acid, being quite soluble in water, do not come into account in the method described below for the detection of cocoanut oil in butter, the method mainly depending on the weight of cadmium salts of the higher and insoluble volatile fatty acids. The details of the method are as follows : 2.5 grams of the fat are saponified with sodium hydroxide and glycerol in the usual manner, the soap is dissolved in 50 C.C. of hot water, and the fatty acids are liberated by the addition of sulphuric acid.After standing for about ten hours, the solid fatty acids are collected on a filter, washed with 50 C.C. of cold water, and the filter-paper and fatty acids are transferred to the small flask D, shown in the accompanying illustration. Five C.C. of 1 per cent. sulphuric acid are added, and the flask is attached to the tube C. The large outer flask contains 800 C.C. of water and 1 gram of powdered pumice-stone; when the water is boiled, the steam passes down the tube E, through the small holes F, into the molten fatty acids; the steam and volatile acids then pass through the tube G into the still-head B, and thence into the condenser. The rate of distillation is so regulated that 200 C.C. of distillate are collected in from thirty-five to forty minutes ; the apparatus is then disconnected from the condenser and a small flask containing neutral alcohol is attached, and 50 C.C.of the alcohol are distilled over in order to rinse the solid fatty acids from the condenser. The total distillate (aqueous + alcoholic) is rendered alkaline with potassium hydroxide solution, using phenolphthalein as indicator, and the excess of alkali is neutralised by the addition of FG sulphuric acid. The titration with the alkali cannot be carried out directly, as a part of the acids is insoluble in the aqueous distillate. After the addition of an excess of 1 C.C. of the alkali solution, the mixture is evaporated to a volume of about 45 c.c., transferred to a graduated cylinder, diluted with water to 50 c.c., exactly neutralised with sulphuric acid, and the fatty acids pre- cipitated by the addition of a 20 per cent.cadmium sulphate solution; 2 C.C. of this solution are sufficient in the case of butters, but for cocoanut oil, or mixtures containing more than 40 per cent. of this oil, 4 C.C. are required. The voluminous precipitate is then collected on a Gooch filter, the portion of the precipitate clinging to the sides of the cylinder being rinsed on to the filter by means of portions of the filtrate, and the precipitate is washed with not inore than 50 C.C. of water after it has been pressed down on the filter by a glass rod. The filter and precipitate are next dried at a temperature of 102" C. for one hour, and weighed. The weight of the precipitate, expressed in milligrams, gives the '' cadmium value" of the fat.This value for pure butter lies between 70 and 90, whilst in the case of commercial cocoanut oils it varies from 441 to 470. pTHE ANALYST. 101 The addition of 10 per cent, of cocoanut oil to butter causes an average increase of 33 in the value. These limiting values were obtained as the result of experiments with butters yielded by cows receiving the usual kinds of fodder; but further experiments showed that when the cows were given unusually large quantities of either cocoanut cake (up to 10 lbs. per day) or beetroot leaves (up to 90 lbs. per day), or both, the butter fats gave higher cadmium values, figures of 100 and above being obtained. By taking into account the saponification value and the '' difference value " proposed by Juckenack and Pasternack (ANALYST, 1904, 29,156) in conjunction with the cadmium value, it is still possible to detect the presence of added cocoanut oil in butter, and the authors consider that a butter is adulterated with this oil if-(1) The cadmium value is over 100 and the difference value lies between +4.25 and -3.5; (2) the cadmium value exceeds 110, the saponifi- cation not higher than 235, and the difference value at the most - 8 ; (3) the cadmium value is 120, but the saponification value not higher than 235, and the difference value more than - 8 ; (4) the saponification value is over 235, and the cadmium value over 130.w. P. s. The Characteristics of Red-Currant-Seed Oil. R. Krzizan. (Chem. Rev. Fett- u..Ham-Ind., 1909, 16, 1-3.)-Air-dried seeds of Italian and Bohemian red currants yielded 16.0 and 18.5 per cent. of oil respectively on extraction with petroleum spirit. Both oils were of an orange-yellow colour, and had an odour recalling that of linseed oil. Exposed in thin layers on glass, they formed an elastic film in three to four days, and in Livache's test absorbed 9.24 and 8-78 per cent. of oxygen in seven days. The Italian oil gave the following values : Specific gravity at 15" C., 0.9265 ; acid value, 40.6 ; saponification value, 189.9 ; iodine value, 178.3 ; Reichert-Meissl value, 1.1. Insoluble fatty acids : Acetyl value, 13.2 ; iodine value, 178.7. Liquid fatty acids: Iodine value, 187.8. The Bohemian oil from freshly separated seeds gave similar values with the exception of the acid value, which was only 2.9.The high value of the other oil was possibly due to the presence of an enzyme. The Italian oil contained 0.14 per cent. of sulphur, but none was present in the Bohemian oil. The fatty acids in both oils consisted principally of linolic acid with smaller quantities of oleic, linolenic, and (probably) isolinolenic acids. About 5 per cent. of solid fatty acids (containing stearic and palmitic acids) was also present. The tetrahydroxystearic acid obtained by the oxidation of the linolic acid melted at 157O to 158" C., instead of at the usual melting-point of 173' to 174" C. (see also ANALYST, 1908, 33, 423). C. A. M. Estimation of Fat in Feeding-Stuffs. A. G. Palmqvist. (Landw. Versuchsstat., 1908, 69, 461; Chem.Zeit. Rep., 1909, 33, 37.)-Two grams of the sample are mixed with 20 C.C. of 0.5 per cent. hydrochloric acid in a flask, the neck of which has a graduated scale from 120 to 160 C.C. This flask is closed with a cork carrying a tube 0.5 metre in length, which acts as a reflux condenser, and is immersed for an hour in a boiling water-bath. Its contents are next neutralised with 0.5 gram of powdered marble and cooled, after which an addition of 20 C.C. of 92 to 93 per cent. alcohol and 40 C.C. of ether (specific gravity 0-72) is made. The flask is connected102 THE ANALYST. with a reflux condenser and stirring apparatus, and placed for thirty minutes in a water-bath at 45' to 50' C., and then in 500 C.C. of water at 1 3 O to 14' C., which will cool the contents to about 17" C.in fifteen minutes. Sixty C.C. of petroleum spirit boiling below 75" C. are now added, and the flask closed by a cork moistened with water, shaken several times, and allowed to stand until the separation of the layers is complete (at least one hour). Its contents should measure 140 C.C. if there has been no loss. From the clear upper layer containing the fat 51 C.C. are withdrawn, and evaporated in a tared beaker on the water-bath, and the residue dried for fifteen minutes on the water-bath, with the aid of blowing from time to time. The beaker is weighed after standing thirty minutes, and the increase in weight in centigrams c. L4. 31. gives the percentage of fat in the material. Deteetion of Bleaehed Flours. L. Weil. (Chem. Zcit., 1909, 33, 29.)- Flours bleached by ozonised air are liable to pass in a higher grade than that to which they really belong; in other words, the commercial claim that the yield of white flour is increased by the bleaching process is justified. But in countries where an export bounty is paid on flour according to its colour-grade, a rapid test which can be used for sorting out suspicious samples is a desideratum.Such a test may be based on the presence of nitrous acid as the result of the treatment with ozclnisedair. The Griess-Ilosvays test for nitrous acid, consisting in the formation of an amino-azo dyestuff from a mixture of naphthylamine acetate and sulphanilic acid, will show a red coloration in solutions containing less than 1 part of nitrous acid per 1,000,000,000.If bleached flour be treated with this reagent, a red coloration is immediately produced, whereas normal flours generally show no coloration until after half a hour, more or less according to the degree of exposure to the atmosphere, The author has found, however, that some normal flours, particularly that from a Russian wheat (Azima), respond immediately to the test, whilst several show a coloratioi; after five to twenty minutes. The test, therefore, is only a preliminary one, and though useful for sorting out samples, it cannot be used to afford reliable conclusions. The final test for bleached flours is based on the reversal of the bleaching process and the restoration of the original colour. I t is well known that bleached flours revert in colour during storage far more rapidly than normal flours.This reversion may be accelerated, so as to form the basis of a test, by aspirating a current of dry sulphuretted hydrogen through the sample in a closed vessel for one hour. In the case of bleached flours the difference in colour as compared with the ofiginal is very marked, whereas unbleached flours suffer no change when treated with sulphuretted hydrogen. J. F. B. Pharmaeopeia Tests for the Purity of Milk-Sugar. Hillringhaus and Heilmann. (Chem. Zeit., 1909, 33, 86.)-Difficulties are often encountered in satisfying the tests specified in the Pharmacopaia in various countries for the purity of preparations of milk-sugar; this is particularly the case in Japan. The German Pharmacopoeia specifies tlxt when 15 grams of the powdered sample are shaken with 50 c.c, of dilute spirit for half an hour, 10 C.C.of the filtered liquid should show no turbidity with an equal volume of absolute alcohol, nor leave, on evaporation, a residue exceeding 0.04 gram. The authors show that the solubility ofTHE ANALYST. 10 3 pure milk-sugar in dilute spirit depends very largely on the temperature, and that at temperatures of 20" C. and over, the amount dissolved exceeds the specified maximum. I t is shown also that the rasult of the test depends on the manner of shaking, and that the heat of the hand may raise the temperature beyond the correct limit, which the authors suggest should be 16" C. The solubility of the sugar is uninfluenced by the fineness of grinding. The Japanese Pharmacopccia, in addition to the above test, specifies that when 1 gram of the sample is dusted over the surface of strong sul- phuric acid in a flat dish, not more than a fuint coloration shoclcl be developed after one hour at 15" C.The authors show that if the tempcratuye be allowed to exceed 15" C., darkening rapidly occurs. Slso, a large surface shows less darkening than a small surface, owing to the fact that the particles of sugar, when crowded closely together, are more susceptible to the action of the acid. The presence of even 1 per cent. of cane-sugar is readily detected by this test, the cane-sugar particles showing up in a few minutes as small black specks. I t is desirable, in order to avoid mis- understanding, that these two tests should be more strictly defined.J. F. 13. The Distribution of Phosphorus in Certain Foods. W. Heubner and M. Reeb. (Che71t. Zciztmlbl., 1908, 2, 194S.)--Moisture was estimated by drying the substance at 85" C., and then reducing it to a fine powder, vhich was dried iiz w((czic, over sulphuric acid. The total phosphorus was estimated by Gregersen's modifica- tion of Neumann's method (Zeit. physiol. Cheiiz., 37, 115 ; 53, 453). That present in the form of compounds of the nature of lecithins mas estimated in the residue left on extracting a weighed portion of the dried Substance with 95 per cent. alcohol, and evaporatiug the extract. The portion insoluble in the alcohol was dried, weighed, and extracted with boiling water, the dried residue then containing the phosphorus in the form of nucleins or proteins containing phosphorus.The aqueous extract was treated with magnesia mixture to precipitate soluble phosphates, and the phosphorus in the form of soluble esters (inositol-phosphoric acid, etc.) esti- mated in the filtrate. The following percentage results, calculated on the dry substance, were thus obtained : Substance. Horseflesh . . . Cow's milk . . . White of egg . . . Bread ... ... Rice ... ... Bran ... . . Carrots ... Beetroot ... Green cabbage White cabbage Dry Substance. 26.0 12.6 12-6 70.1 87.8 98.8 13.6 14.6 12.3 8.3 Total Phosphorus. 0.74 0.84 0.12 0.14 0.11 1.47 0.40 0.19 0.48 0.31 Phosphorus :n the Form of Lecithin Compounds. 0.15 0-05 0 0.01 0.005 0.02 0.03 0.04 0.07 0.06 As Soluble Phosphate. 0.44 0.25 0.02 0-05 0.005 0.25 0.20 0.08 0.22 0.14 As Soluble Esters.0.04 0.05 0.02 0 0.35 0.11 0.05 (0.07) - (0.09) As Nucleins and Phosphor- proteins. 0.10 0.45 0.07 0.07 0.10 0.67 0.04 0.02 0.10 0.04 c. A. M.104 THE ANALYST. Estimation of Tartaric Acid in Wines. Mestrezat. (JOUY~L. Phamz. Chim., 1909, 29, 9-15.)-The author has always obtained better results with the evapora- tion methods (modifications of Pasteur's method) than with hhe precipitation methods, particularly in complex media like wines. He describes the procedure, which he finds most satisfactory: Fifty C.C. of wine are mixed with 2 C.C. of a 20 per cent. solution of potassium bromide, and evaporated to a syrupy consistency. This operation should not be pushed too far ; the mass should not solidify entirely on cooling, but should still possess the degree of semi-fluidity necessary for obtain- ing well-formed crystals which are easily washed. The capsules containing the evaporated liquid are allowed to remain in a cool place for four or five days, a period which has been proved to be both necessary and sufficient. The crystals of potassium bitartrate must then be washed with a saturated solution of this salt in 40 per cent. alcohol. Three or four quantities of 10 to 15 C.C. each of the washing solution should suffice. The liquid should not be passed through a filter, but decanted off the crystals, the washings being collected in a conical vessel and examined for crystals before being discarded. The purified bitartrate is then estimated by titration. Duplicate analyses are concordant to 0.5 per cent., and the presence of malic acid, succinic acid, and sugar has been proved to be without influence on the result. J. F. B.

ISSN:0003-2654    

DOI:10.1039/AN9093400099

出版商:RSC    

年代:1909

数据来源: RSC

摘要:

104 THE ANALYST. BACTERIOLOGICAL, PHYSIOLOGICAL, ETC. Methods for the Detection of Blood-Colouring Matters and Similar Substances. 0. Schumm. (Archiv Pharm., 1909, 247, 1-27.)-This paper con- tains in a collected form the various methods which have been proposed for the detection of blood-colouring matters (oxyhEmoglobin, methzmoglobin, and hzmo- globin) and similar substances, such as hmnatin, hzmatoporphyrin, and urobilin. When it is possible to obtain sufficient of the fluid suspected of containing blood, a spectroscopic examination yields most important information ; in the new forms of the instrument, where a layer of the solution 20 cm. in depth may be observed, it is possible to observe the absorption bands due to the oxyhamoglobin of the blood when the latter is present in a dilution of 1 in 25,000.In cases where the oxy- hEmoglobin has been converted into methzmoglobin or hEmoglobin, a, preliminary treatment with ammonium sulphide or oxygen respectively is necessary before the characteristic absorption bands can be observed. No other substance gives a similar spectrum; a very dilute ammoniacttl solution of carmine gives a spectrum which might possibly be confused with that of blood, but a comparison of the two would prevent any mistake being made. The detection of blood in a secretion by means of the microscope is, of course, only possible if unaltered red blood-corpuscles be present. The well-known guaiacum test for blood is extremely sensitive, being capable of detecting 1 part of blood in 100,000 ; but much depends on the kind of turpentine oil used, as well as on the absence of other organic colouring matters, enzymes, etc.The same remarks apply to the aloin test, in which guaiacum is replaced by aloin. A test, proposed originally by Weber, which may be employed for the detection of blood in fzces, consists in treating about 4 grams of the substance under examination with 60 C.C. of a mixture of equal parts of ether and alcohol, filtering, and washingTHE ANALYST. 105 the residue, firstly with alcohol-ether, and then with ether. The residue is well mixed with 4 C.C. of glacial acetic acid, filtered, and washed with a further 4 C.C. of glacial acetic acid. The filtrate is shaken with three times its volume of ether and half its volume of distilled water, the ethereal layer is separated, washed with a little water, and then tested with the guaiacum reagent, with the addition of old oil of turpentine.Faxes containing 0.1 per cent. of blood give a strong reaction, but it is pointed out that the administration of foods containing or consisting of blood preparations (haematogen, etc.) causes the faeces of the patient to give a positive reaction with the test. The benzidine reaction mentioned by Adler (ANALYST, 1904, 29, 227), whilst very sensitive in the case of blood, also gives a reaction with a whole series of other substances, both organic and mineral. A combined chemical and physical test may be employed for the examination of stains suspected to be blood. The stain (on a piece of linen, for instance) is cut out and moistened with a drop of potassium hydroxide solution.After the addition of a few drops of water, the solution is transferred to a small tube (absorption cylinder), a drop of hydrazine hydroxide solution is added, then a layer of ether, and the mixture is examined with the spectroscope, The hEmochromogen formed, if blood be present, exhibits two absorption bands, one between the lines 567 and 550, and the other between the lines 538 and 510. A similar test may be applied to the detection of blood in urine. One hundred C.C. of the latter are mixed with 10 C.C. of a 3 per cent. zinc acetate solution, and heated to a temperature of about 70' C. The precipitate formed, containing the blood-colouring matters, is collected on a filter, extracted with alcoholic ammonium chloride solution, and the extract transferred to an absorption cylinder.One drop of ferrous sulphate solution con- taining tartaric acid is added, and the mixture is examined with the spectroscope. If the urine contains as little as 1 part of blood in 20,000 parts, the spectrum of the hzmochromogen will be observed, The test may also be applied to sputum, stomach contents, bile, faeces, and similar materials. If a drop of blood be mixed with a few C.C. of concentrated sulphuric acid, a solution of hzmatoporphyrin is obtained which shows two absorption bands at the lines 608-509 and 566-544, respectively. Haematoporphyric urines are found after long-continued administration of sulphonal or trional ; these urines are red in colour, but may be readily distinguished from urine containing blood by means of the guaiacum reaction or by Weber's test, and the haematoporphyrin may be detected spectroscopically after treating the urine with zinc acetate as described above.Urobilin, a normal constituent of faeces and frequently occurring in urine, may be detected, in urine, by treating the latter with zinc chloride and an excess of ammonia, filtering the mixture, and observing the filtrate with the spectroscope ; the urobilin-zinc compound shows a band between the lines 519 and 475, and the solution has a green fluorescence. I n the case of faeces, the latter are treated with alcohol containing a few drops of a mineral acid, filtered, and the filtrate precipitated with zinc chloride, w. P. s. The Destruction of Organic Matter in Toxicological Analysis.Kerbosch. (Arclziu Pharm., 1908, 246, 617-620.)-1n testing for metallic poisons in animal106 THE ANALYST. organs, etc., the destruction of the organic matter is best attained by means of a, mixture of equal volumes of sulphuric and nitric acids. The substance to be examined should be ground with water to a paste, and transferred to a tubulated Jena-glass retort, which should have a capacity about four times greater than the volume of the paste introduced. A quantity of the acid mixture is then added, as many C.C. of the mixture being used as corresponds with the weight of the dry sub- stance in grams, and after the reaction has somewhat abated, the whole is heated gently, a further quantity of nitric acid being added drop by drop by means of a tapped funnel fitted in the tubulure of the retort.The stem of the funnel should reach within about 0.5 cm. of the bottom of the retort, and, if a small bulb is blown on the stem just below the tap, a sufficiently tight joint is formed at the tubulure. The temperature and the addition of the nitric acid must be so regulated that lumps of carbonised matter do not form, After a time a yellow solution is obtained with a, layer of fat floating on its surface ; on raising the temperature and continuing the addition of nitric acid, the fat is decomposed gradually, and the resulting dark- coloured liquid is further heated until colourless. If most of the excess of sulphuric acid be evaporated, the residual solution resulting from the destruction of 250 grams of flesh need not be more than a few C.C.w. P. s. Volumetric Estimation of Potassium in Liquids of Animal Origin. W. A. Drushel. (Zeits. Anorg. Chem., 1909, 61, 136-146.)-Animai liquids free from albumin (urine) are ashed by evaporating them to dryness and treating the residue with a mixture of 9 parts of nitric acid and 1 of sulphuric acid, at first in a covered and finally in an open dish. Other animal liquids (blood, serum, lymph, milk) are evaporated and treated first of all with bromine, or, cautiously, with nitric acid alone ; after further evaporation and charring of the residue, oxidation of the organic matter is completed by gentle ignition with sulphuric acid, In any case the inorganic residue is treated with a few drops of acetic acid and a little water.An excess of sodium cobaltic nitrite is added to the unfiltered solution, and the whole evaporated nearly to dryness. The cold residue is mixed with sufficient cold water to dissolve the excess of the reagent, filtered through asbestos, and washed with a saturated solution of sodium chloride diluted with its own volume of water. Filter and precipitate are transferred to a beaker and heated with an excess of a standard solution of potassium permanganate and a little sulphuric acid until the precipitate is completely oxidised. A small excess of oxalic acid is then added, and the excess titrated back with permanganate solution. As the formula of the precipitate is K,NaCo(NO,),, H20, 1 C.C. of a & solution of potassium pernianganate corresponds to 0.000857 gram K,O.The results obtained by the above method are practically identical with those given by the Lindo-Gladding method, the maximum difference being about 1 per cent. on the potassium oxide. A. G. L. The Use of Silver Salts in the Sterilisation of Water. F. Traetta-Mosca. (Gazz. Chim. Ittal., 1909, 39, 69-109.)-1n the author’s comparative experiments described in detail, 100 C.C. of sterile water were inoculated with 3 to 4 drops of an emulsion of a culture of various bacteria (Racillw szdtilis, B. coli, B. typhosus, etc.),THE ANALYST. 107 15 minutes ... 30 9 9 ... 1 hour ... ... 3 hours ... ... and 1 C.C. added to sterilised distilled water, containing a definite quantity of the silver salt. One C.C. was withdrawn at intervals, and cultivations made in Petri dishes.I n a typical experiment with B. coli, the following results were obtained after the addition of silver perchlorate in proportions of 1 in 10,000 to 1 in 500,000 : ~ 0 18 100 500 0 10 18 200 0 2 10 21 0 0 2 5 NUMBER OF COLONIES. 800 300 23 10 Duration of Action. 1 : 10,000 1 : 25,000 1 : 50,000 1: 100,000 1 1 1 1 800 ’i: ),,, 10 All the silver salts (fluoride, chlorate, perchlorate, 1 : 250,000 1 : 500,000 Control. I 1 sulphate) had pronounced bactericidal properties, and in the author’s opinion are suitable for sterilising water for drinking purposes. The bactericidal action is mainly due to the silver ions, and even when the silver is apparently precipitated completely by a chloride, it still retains a sterilising effect, which the author attributes to a minute quantity of the silver chloride remaining dissociated, or possibly to its remaining in suspension in a colloidal form, as Paterno and Cingolani (ANALYST, 1907, 32, 294) found to be the case with silver fluoride.According to D’Auna the acid radical is only of importance in so far as it reduces the amount of the metal, but the author’s experiments show that a certain bactericidal action must also be attributed to the acid radical. Thus silver chlorate (silver, 56.3 per cent.) and silver perchlorate (silver, 52 per cent.) had a much more energetic action than silver sulphate (silver, 69.2 per cent.). C. A. M. Determination of Total Sulphur in Urine. F. W. Gill and H. S. Grindley. (Journ. Anzer. C7zem. Sac., 1909, 31, 52-59.)-The authors have proved that in the Folin method (fusion with sodium peroxide) there is a loss of sulphur estimated at 10.3 per cent.of the total sulphur present, owing first to volatilisation during fusion, and secondly to the escape of sulphuretted hydrogen on acidification of the melt. If the Folin method be modified so that further small portions of the peroxide are added to the melt before the fusion is ended, the product contains no sulphide, and the second source of loss is eliminated. But even then the loss due to volatilisation is estimated at 6.2 per cent. of the total sulphur. The standard employed for estimating the losses by the fusion method was a method based on that of Konshegg, depending on the acid oxidation of the organic matters by a mixture of nitric acid and potassium nitrate : 25 C.C.of urine are measured into a 500-C.C. Kjeldahl flask, and 10 C.C. of a 20 per cent. solution of potassium nitrate and 25 C.C. of fuming nitric acid, specific gravity 1.53, are added. The flask is placed on asbestos-gauze and heated over an alcohol burner until its contents have evaporated nearly to dryness. The flask is then held in a, hand-clip and moved about over the naked flame until all108 THE ANALYST. brown fumes are expelled and the contents are fluid and colourless. During cooling the flask is rotated to avoid solidification in a mass ; the neck is then washed down with 25 to 50 C.C. of hot water, and 10 C.C. of hydrochloric acid (1 to 4) are added. The solution is transferred to a beaker and diluted to about 200 C.C. If now the sulphate be precipitated direct with barium chloride, the result is too high, owing to the influence of the potassium salt. I n order to counteract this influence, pure sodium chloride in the ratio of 4 parts to 1 part of potassium salt-ie., 8 to 10 grams -must be added; the precipitation is then effected with the usual precautions, forty-eight hours being allowed for the complete separation of the barium sulphate. The purity of the reagents must of course be controlled. The authors refer to the fact that a very large number of recorded analyses of the sulphur in foods and faxes have been based on the alkaline fusion method, and it thus becomes necessary to reinvestigate the question of their validity for purposes of comparison. J. F. B.

ISSN:0003-2654    

DOI:10.1039/AN9093400104

出版商:RSC    

年代:1909

数据来源: RSC

摘要:

108 THE ANALYST. ORGANIC ANALYSIS. Estimation of Alkaloids, Bitter Principles, and Glucosides by Means of Zeiss's Immersion Refractometer-I. Utz. (Chem. Zeit., 1909, 33, 47-49.)- When caffeine has been separated in an approximately pure condition from tea or coffee by one of the usual methods, its amount in aqueous solution may be estimated by means of Zeiss's immersion refractometer. The author gives a table showing that the amount of caffeine in grams per 100 C.C. in an aqueous solution corresponds with the readings on the scale of the refractometer at 17.5" C. Thus distilled water gives a reading of 15; 0.50 gram of caffeine a reading of 17.5; and 1.00 gram a reading of 20.0. I n the case of morphine the refractometer reading may be taken in hydrochloric acid solution, but it is better to convert the separated morphine into the hydrochloride by evaporation with hydrochloric acid, to expel all excess of acid by repeated evaporation with water and dry- ing at 100" C., and to dissolve the salt in water. A solution of 0.10 gram per 100 C.C.gave a, reading of 15-55 at 17.5" C. ; 0.50 gram, 17.75 ; 1.00 gram, 20.5 ; 2.0 grams, 26.00; and 4 grams, 37-00. Pure morphine may be estimated in a solution of methyl alcohol from the difference (N - 72) between the readings given by the methyl alcohol and the solution. This difference with 0.01 gram of pure morphine per 100 C.C. was 0.06; with 0.5 gram, 3.00 ; and with 1-00 gram, 6-00. In similar experiments with pure quinine the difference for 1 gram per 100 C.C. was 6.80, and for 2.0 grams 13.6. Quinine hydrochloride solutions gave similar readings, whilst with quinine sulphate the difference for 1 gram per 100 C.C.was 640. Pure brucine in methyl alcohol gave a difference for 0.50 gram of 3-10, and for 1.0 gram of 6.20. C . A. M. A Colour Reaction of Colophony, and Detection of that Resin in Other Substances. P. Foerster. (Artit. de Chim. Anal. AppZ., 1909, 14, 14-17.)-The following modifications of Halphen's method of detecting rosin oil in mineral oils enables traces of colophony to be detected in other substances. Halphen's reagent consists of (a), a solution of 1 part by volume of phenol in 2 parts of carbon tetra-THE ANALYST* 109 chloride ; and ( b ) , a solution of 1 part of bromine in 2 parts of carbon tetrachloride. On dissolving a little colophony in 2 C.C.of solution (a), and bringing the basin close to solution (b), the bromine vapours given off by the latter produce at the point of con- tact a blue coloration, changing to violet under the continued action of the bromine. The coloration is quite different from that given by rosin oil, which becomes violet at once. I n applying the test it is, as a rule, necessary to isolate the colophoriy beforehand. In the case of soap, a small quantity of the sample is dissolved in 80 per cent. alcohol, and the solution treated with an alcoholic solution of calcium chloride. The precipitate is filtered off, the filtrate acidified by the addition of a few drops of hydrochloric acid, and evaporated on the water-bath, and the residue tested with Halphen’s reagent.Colophony in shellac may be detected by pulverising 2 grams of the sample with sand, treating the powder with 10 to 15 C.C. of ether for five to ten minutes with occasional shaking, filtering the liquid, evaporating the filtrate, and testing the residue. Examination of Jalap Resin.-One to two per cent. of colophony may be detected in jalap resin by treating 0.2 to 0.5 gram of the substance with a few C.C. of petroleum spirit, evaporating the filtrate, and testing the residue. The reagent will also detect the presence of gum guaiacum in jalap. For this test a little of the resin is dissolved in a few drops of acetic acid or (preferably) acetic anhydride, and the solution spread over a basin and brought in contact with the vapours from solution (b). A blue coloration changed to green by excess of bromine indicates the presence of gum gusiacum.C. A. M. Combustion Analysis. J. Walker and T. Blackadder. (Chenz. News, 1909, 99, 5, 6.)-The authors have applied Dennstedt’s simplified apparatus for combustion analysis to the older method of working, with cupric oxide as the oxygen- carrier. The furnace, burners, absorption-tubes, and purifying apparatus for the oxygen, are practically all as described by Dennstedt. The combustion-tube is only 66 cm. long and 8 mm. bore, the length of the furnace being 60 cm., and three Bunsen burners being employed. The total charge of copper oxide including spirals weighs only 35 grams, the platinised quartz proposed by Dennstedt being omitted. The copper oxide, after ignition, is placed while still hot into a glass tube closed by a stopper carrying a calcium chloride tube; this oxide is used for mixing with the substance to be analysed and for filling the combustion-tube. The weighing and mixing of the substance is effected in a small stoppered weighing-bottle, the neck of which fits into the mouth of the copper oxide tube for mixing and into that of the combustion-tube for charging.washed out ” two or three times with copper oxide and the combustion-tube is ready. By taking precaution to expose the copper oxide as little as possible to the atmosphere, the combustion can be started at once. The operation is then similar to that described by Dennstedt, the copper oxide at the absorption end of the tube being kept at a dull red heat by two covered burners, whilst a third movable burner is manipulated so as to decompose the substance at a moderate rate.Liquid substances are weighed in bulbs with a capillary tube about 8 cm. long, the sealed end being broken when the bulb is intro- duced into the tube; the open capillary should point towards the cool end of the The bottle is110 THE ANALYST, combustion-tube, and the expulsion of the liquid is effected by manipulation of the free burner. Volatile liquids are weighed in bulbs with capillary tubes at both ends, one being closed by fusible metal and the other sealed after filling. By this method the entire operation can be completed in an hour, and the results are as good as those obtained by the older method. J. F. B. The Differentiation of Marine Animal Oils by Means of their Bromine Addition Compounds.H. Bull and J. C. F. Johannesen. (Chew$. Zeit., 1909, 23, 73,74.)-The method of estimating the amount of insoluble bromides from marine animal oils devised by Hehner and Mitchell (ANALYST, 1898, 23,310) has not proved satisfactory in the authors’ hands owing to the difficulty of filtration. They there- fore recommend the following modification of the method as applied to the fatty acids of the oils : A weighed quantity (0.9 to 1.1 gram) of the fatty acids is dissolved in 25 C.C. of a mixture of 100 C.C. of glacial acetic acid and 500 C.C. of anhydrous ether, and the flask (which holds about 75 c.c.) closed and cooled in ice-water. Bromine is next added from a burette, at the rate of about 1 drop per second, the flask being chilled and shaken after each addition. When 0.5 c.c, has been added, the flask is again closed and left for some minutes in the ice-water, after which it is allowed to stand for three hours at the ordinary temperature.The precipitate is then collected in a small tared filter-tube containing asbestos, filtration being aided by a filter-pump. The flask is washed with three successive portions of 5 C.C. of the solvent, and the washings passed through the filter, which is finally washed twice with 5 C.C. of ether, dried for two hours at 100’ C., and weighed. The yields of bromide from the fatty acids of ten samples of commercial medicinal cod-liver oil ranged from 27-08 to 37.53. I n no case did the results of duplicate estimations vary by its much as 1 per cent., and as a rule agreed within 0.5 per cent. C.A. M. On the Suitability of Carbon Tetrachloride as a Solvent in Fat Extrac- tions. (Clzenz. Zeit., 1909, 33, 93-94.) -Although carbon tetra- chloride has an advantage over ether in that it is non-inflammable, the author considers that it cannot be used for the quantitative estimation of fat in oily substances, as the results obtained are higher than those found by extraction with ether, and it is known that ether extracts matters other than fat or oil from such materials as oil- cakes, seeds, etc. Parallel estimations of oil in seeds, such as linseed, rape seed, etc., ether being the solvent in one case and carbon tetrachloride in the other, showed that the latter solvent extracted from about 1 to, in some instances, nearly 5 per cent., more oil from the seeds than did ether.The extractions were continued for five hours, the seeds being ground up previously with sand and dried; in the case of the extractions with ether, at the end of two and a half hours’ extraction, the seed was 0. Rainmstedt. again ground and the extraction continued. w, P. s. Quantitative Estimation of Formic Acid. G. Greve. (Chem. Zeit., 1909, 33, 51.)-The methods devised by Coutelle (Monatsh. Chem., 1893, 14, 750) and Lieben (Jounz. Prakt. Chem., 1906, 73, 67) require certain alterations for the estima- tion of small amounts of formic acid-e.g., in bacterial culture media. The concen-THE ANALYST. 111 tration of the formic acid may vary within wide limits, wbile the concentration of the mercuric chloride solution and the absolute amount of that salt may be reduced.For 1 part of formic acid fifteen times the quantity of mercuric chloride is sufficient instead of fifty times the quantity, as in the previous methods. The reaction is complete in two and a half hours, instead of the six to eight (and twelve) hours pre- scribed. The liquid is twice neutralised with normal sodium hydroxide solution during the reaction, and finally any mercurous oxide formed is reconverted into mercurous chloride by the addition of 10 to 20 C.C. of concentrated hydrochloric acid. The precipitate of mercurous chloride is then collected in a Gooch crucible, washed, and dried at 95' to 100" C. The results thus obtained in the estimation of both large and small quantities of formic acid are stated to be accurate, and to agree closely with those obtained after distillation of the formic acid.C. A. M. Determination of Halogens in Organic Compounds. C. W. Bacon. ( J o z ~ m . Amw. Chenz. SOC., 1909, 31,49-52.)-Stepanow has proposed (ANALYST, 1907, 32, 52) as an alternative to the Carius method for the estimation of halogens in organic compounds, a method based on the reduction of the compound by means of metallic sodium and alcohol. In the author's hands Stepanow's method failed to yield useful results ; he has consequently modified the original procedure, and gives the following directions for the improved method : Introduce about 0.2 gram of the halogen compound into a dry Kjeldahl flask. If w be the weight of substance taken, add 156 20 C.C.of alcohol (at least 98 per cent. strength) if the compound contains chlorine, or 68 w C.C. if the compound contains bromine, or 44 w C.C. if the compound contains iodine. Connect the flask with a reflux condenser, and heat over a wire gauze with a thin sheet of asbestos until the substance is dissolved. Then introduce very gradually through the condenser a total of 19-5 w grams of sodium for a chlorine compound, 8.5 w grams for a bromine compound, or 5-5 w grams for an iodine compound, The addition of the sodium should be extended over at least thirty minutes. Towards the end of the operation maintain the liquid at the boiling-point by the application of heat, and when all the sodiuln is added boil the solution gently for one hour longer. Then allow the liquid to cool to 50" to 60" C., dilute with cold water through the condenser, acidify with nisric acid, add an excess of standard silver nitrate, and when fully cold titrate back the excess with thiocyanate by Volhard's method.If the halogen be chlorine, filter off the silver chloride before titrating. I n the case of bromine or iodine, filtration is unnecessary. I t is not necessary to distil off the alcohol as recommended by Stepanow. Analyses of trichlorbenzoic acid, ethyl tribromben zoate, benzene hexachloride, and hexachlor- benzene, types of the most stable organic halogen compounds, are quoted to show that the results are as satisfactory as those obtained by the Carius method. J. F. B. Notes on the Guaiacum Test. C. L. Alsberg. (Arch. exp. Path.Phurnznkol., 1908, 39-53 ; Woch. fiir Brau, 1909, 26,26.)-The author states that many chlorides, including the alkali chlorides, give a blue coloration with guaiacum solution in presence of hydrogen peroxide ; sulphates and nitrates do not. Cupric chloride112 THE ANALYST, gives the blue coloration, as do also a number of other substances. The author therefore considers that the guaiacum test is quite unsuitable for the detection of oxydases and peroxydases, since catalytic changes, owing to the presence of some simple agent, such as iron, copper, manganese, aluminium, chlorine, etc., are very difficult to exclude. J. F. B. Viscosity of Indiarubber and Indiarubber Solutions. P. Schidrowitz and H. A. Goldsbrough. (Joz~rn. SOC. Chm. I d . , 1909, 28, 3-6.)-The authors have studied the relations existing between the tensile qualities or ( ( nerve " of crude indiarubber and the viscosity of its solutions.The '' nerve," however, is the resultant of at least two factors : (a) The minute mechanical structure or texture of the solid rubber material tested; ( b ) the internal qualities of the rubber substance itself considered as a particular form of matter. The viscosity of the solutions can only be expected to bear a relationship to the latter quality. The instrument employed was an Ostwald capillary double-bulb viscometer (see Fig.) ; height, 24 cm. ; capacity of bull, A, 11 C.C. ; capacity of bulb B, 10 C.C. ; length of capillary, 4.5 cm.; bore of capillary, 1 mm. So far, pure benzene is the only solvent which has been employed, and it has only been possible to investigate dilute solutions at maximum concentrations of 1 to 1.5 per cent.The solutions were filtered through a plug of glass-wool and tested in the viscometer at a A temperature of 20" C., the concentration being determined by the evaporation of a separate portion of the solution. I n plotting the curve illustrating the relations between viscosity and concen- tration, it was found that as the concentration rose t'he curves took an upward bend, at points depending on the particular sample under investiga- tion, and subsequently followed a straight line. This point at which the viscosity becomes proportional to the concentration is called the '' critical" point of the sample. Taking values above the critical point, it was possible to calculate the theoretical viscosity of a 100 per cent.solution-ie., of the rubber substance. Thebe values ranged from 1000 to 9940 (benzene = 1) for various qualities, that of a standard hard Pars rubber being 7253. Generally, the viscosities followed the tensile qualities (breaking strain, elongation, resiliency), but the latter are recognised as being of a highly complex nature, and the authors are content, at the present stage, to record the fact that the order of viscosities coincided with that of the relative '' nerve " or strength of the samples as valued by practical experts. J, F. B. A Method of Estimating Small Quantities of Impurities in Orthotoluidine and Orthonitrotoluidine. A. F. Holbeman. (Bee. Trav. Chinz. Pays-Bas, 1908, 27, 45S-462.)-A method of estimating p-toluidine in orthotoluidine is based upon the determination of the solidification-point of their acetyl derivatives.The solidifi- cation-point of pure ortho-acetotoluidide (109.15O C.) is lowered as follows by the addition of para-acetotoluidide : 1.12 per cent., 108-45" C.; 2.42 per cent., 107.75" C. ;THE ANALYST, 113 9-58 per cent., 103.2" C.; 13% per cent., 100*8° C. In making an estimation, 25.2 grams of oxalic acid are dissolved in 1,000 C.C. of hot water, and 42.8 grams of toluidine slowly added. The flask is cooled, finally in ice-water, and the toluidine omlate crystals are collected at 0" C. and washed once with a little water. The toluidine is next recovered both from the crystals and the mother-liquor by treat- ment with sodium hydroxide solution, and distillation of the extract in a current of stearn.To avoid loss it is necessary to extract the distillate twice with ether, after separation of the undissolved toluidine. A little of the recovered toluidine from both crystals and mother-liquor is separately converted into its acetyl derivative by adding to it 2 C.C. of glacial acetic acid and 1 C.C. of acetic anhydride per gram, evaporating the mixture on the water-bath, and distilling the residue in vacuo. The solidification- points of the two portions of acetotoluide are then determined, and the quantity of p-toluidine calculated from the results. A lowering of the solidification-point by 0.2" C. corresponds to a proportion oE 0-32 per cent. Since the p-toluidine is concen- trated by about four times in the mother-liquor, it is possible to estimate 0.08 per cent, I n examining o-nitrotoluidine, the substance is reduced with nascent hydrogen and converted into oxalate.I n a test experiment the acetotoluide from the crystals solidified at 109" C., whilst that from the mothar-liquors solidified at 108.1" C. The total quantity of the para, compound calculated from these results was 0.58 per cent. I n another commercial sample the amount of impurity was only 0.13 per cent. C. A. 11. A New Colour Reaction of Petroleum. C. Arragon. (Cizem. Zeit., 1909'33, 20, 21.)-Equal volumes of paraffin and nitric acid (specific gravity 1-4, freed from nitrous acid by treatment with urea) are shaken in a stoppered glass cylinder for thirty seconds. With pure American paraffin the oil acquireEt a violet colour, whilst the acid turns yellow.Austrian, Galician, and Russian paraffin, on the other hand, acquire a yellow colour, the acid becoming brown. A mixture of the two paraffins turns pale violet at first, and then, after another ten to fifteen seconds' shaking, becomes yellow. An admixture of 10 per cent. of the European oils may be recognised in this way in American paraffin. A. G. L. The Precipitation of Reducing Sugars with Basic Lead Acetate. A. H. Bryan. (Internat. Sugar Jourtb., 1908, 10,602-605.)-Cornparative experiments were made with solutions of dextrose and Iwulose containing magnesium sulphate and ammonium tartrate in the proportion of 1 gram of each to 5 grams of the sugar. Definite quantities of these solutions were diluted and treated with different lead salts, the excess of which was subsequently precipitated with potassium oxalate, and the sugar in the filtrate estimated by Allihn's method. I t was found that reducing sugars were not precipitated to any appreciable extent by normal lead acetate, but that basic lead acetate and basic lead nitrate, whether in the form of salt or in solution, precipitated a large amount of dextrose, and still more of levulose. For this reason the American Association of Official Agricultural Chemists now use only normal lead acetate solution. Analogous results were obtained in experiments in114 THE ANALYST. which solutions of sugars containing optically inactive substances were treated with various lead salts, and the proportion of reducing sugars in the filtrates estimated by means of the polarimeter. C. A. M.

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DOI:10.1039/AN9093400108

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年代:1909

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114 THE ANALYST. INORGANIC ANALYSIS. Volumetric Method for the Estimation of Barium. A. E. Hill and W. A. H. Zink. (Journ. Anzer. Chcm. SOC., 1909, 31, 43-49.)-To a cold, neutral, or filightly arnmoniacal solution containing about 0.1 gram of barium in 60 to 70 C.C. of liquid, a solution of potassium iodate is added in a fine stream, with continuous stirring, an excess of about 25 C.C. being used. The whole is stirred for one minute, allowed to stand, with frequent stirring, for five minutes, and filtered. The filter should be used dry or after moistening with potassium iodate solution, as barium iodate is appreciably soluble in water. The precipitate is transferred completely to the filter, using portions of the filtrate, and is then washed, first three times with concentrated ammonia solution, and then three or four times with 95 per cent.alcohol. I t is then washed with water into a flask, the filter-paper is added, and the whole treated with 50 C.C. of a 10 per cent. potassium iodide solution and 10 C.C. of hydrochloric acid. After standing for five minutes, with frequent shaking, the liberated iodine is titrated as usual. The method is applicable to all soluble barium salts, and is not affected by the presence of sodium salts, or of salts of magnesium, ammonium, or potassium, if their quantity does not exceed 0.5 gram. If larger quantities of these salts are present, precipitation is carried out in a hot solution, which is well stirred until cold. By proceeding in this way, occlusion of other iodates is avoided, but the barium iodate obtained does not dissolve so easily in hydrochloric acid as that precipitated in the cold.Calcium, strontium, and heavy metals must be absent. The limits of error of the method are given as 0.05 to 047 per cent., reckoned on the barium. A. G. L. Precipitation of Cobalt by Means of Potassium Nitrite. L. L. d e Koninck. (BUZZ. SOC. Chinz. Belg., 1909, 23, 11-13.)-1n precipitating cobalt a s potassium cobalt nitrite, the solution should be acidified before precipitation with nitric acid, according to the author, not with acetic acid, as is usual. The addition of nitric acid insures complete oxidation of the cobalt to the trivalent state. Suffi- cient potassium nitrite must be added to neutralise the free acid. A. G. L. Simplification of the Gravimetric Method of Estimating Halogens by Means of Silver Nitrate.E. Alefeld. (geeits. anal. Chem., 1909,48,79, 80.)- If 5 C.C. of ether are added to the solution of the halogen to be estimated, filtration of the liquid may be carried out immediately an excess of silver nitrate has been added, without heating or waiting for the precipitate to settle completely. The Gooch crucible used as filter should also be moistened with ether before filtration. The filtrate obtained is absolutely clear. A. G. L. Gravimetric Estimation of Nitric Acid. A. Hes. (Zeits. anal. Clze?n., 1909, 48, 81-98.)-The author’s experiments show that Busch’s nitron method forTHE ANALYST, 115 nitric acid yields accurate results (maximum error, 0.2 per cent.), if the solution contains about 0.1 per cent.of nitric acid. Ordinary weighed filter-papers may be used instead of Gooch or Neubauer crucibles. Solutions much more dilute than the above are not, or only incompletely, precipitated by nitron, but such solutions may be concentrated after the addition of the reagent. Dextrine and gelatine prevent the precipitation of nitron nitrate. The presence of aluminium sulphate, magnesium sulphate, ammonium sulphate, potassium phosphate, magnesium chloride, tartaric acid, citric acid, saccharose, and glucose does not interfere with the precipitation, but, if large quantities of these substances are present, the 10 C.C. of ice-cold water usually used may not suffice to wash the precipitate completely. I n presence of oxalic acid, high and very irregular results are obtained.Chloric acid is quanti- tatively precipitated by nitron from solutions containing about 0.25 per cent. of chloric acid, and the method can be used for the estimation of chloric acid, or of chloric and nitric acids together. Hydrobromic acid, if present, must be removed before precipitation by means of chlorine. Hydrogen iodide is destroyed by boiling with potassium iodate and acetic acid. Nitrous acid is removed by adding powdered hydrazine sulphate to the cooled liquid, or may be oxidised with hydrogen peroxide and sulphuric acid at 70" C. to nitric acid. Chromic acid is reduced with hydrazine sulphate. A. G. L. Action of Nitrogen on Commercial Barium Carbide. 0. Kuhling and 0. Berkold. (Zeits. Angew. Chem., 1909, 32, 193-196.)-Carbon present as carbide in barium and calcium cyanamide mixtures is estimated by evolution as acetylene, alcohol saturated with acetylene being used to decompose the substance, as, if water is used, explosions may occur.Twenty grams of the sample are treated first with 50 C.C. of 96 per cent. alcohol, and then with 100 C.C. of 80 per cent. alcohol. Cyanamide is estimated as previously described (Bericlzte, 1907, 40, 314). To estimate cyanide, 0.5 to 0.6 gram of the sample are distilled with 30 C.C. of a saturated solution of lead nitrate and 80 to 100 C.C. of water, the distillate being received in 25 C.C. of sodium hydroxide solution. An excess of ammoniacal silver nitrate solution is added to the distillate, and the silver acetylide filtered off after ten minutes' standing. The filtrate is gradually mixed in the cold with an excess of nitric acid, and the precipitated silver cyanide collected on a Gooch crucible, washed with cold water, and dried at, 100" to 110" C.This method was tested on solutions con- taining known amounts of cyanide and chloride, and proved accurate, the maximum error being 0.19 per cent. on the cyanide. A. G. L. Quantitative Estimation of Silver. F. Mawrow and G. Mollow. (Zeds. Anorg. Chem., 1909, 61 , 96-99.) - Hypophosphorous acid reduces solutions of silver nitrate instantly and completely on boiling, metallic silver, not silver hydride, being obtained. The precipitate is so finely divided that it passes through the filter on washing with water ; but it may be washed with 96 per cent. alcohol without loss. The results are accurate even in the presence of acetic and tartaric acids.Lead salts, treated in the same way, yield a precipitate of lead hypophosphite, difficultly soluble in cold water, more readily in hot water, and insoluble in alcohol. A. G. L.116 THE ANALYST, Colorimetric Estimation of Dissolved Oxygen in Water. G. B. Frank- forter, G. W. Walker, and A. D. Wilhoit. (Joz~rn. Anzcr. Chewz. SOC., 1909, 31, 35-43.)-The method depends on adding 2 C.C. of a solution of cuprous ammonium f- I colorinieter K, of 102 C.C. Capacity, is connected to G chloride to 100 C.C. of the sample of water, and com- paring the colour obtained with thatgiven by a known amount of cupric ammo- nium chloride suitably diluted. Air must be ex- cluded during the opera- tion. The process i s carried out in the ap- paratus shown : The bulb C contains copper wire introduced through the wide stop-cock B ; the bulb C is completely filled with a solution of cuprous chloride in hydrochloric acid. Burette A contains hydrochloric acid, and burette E ammonia.F is a bulb of 10 C.C. capacity, in which the reagent is prepared; it is initially filled with oxygen - free water from the inverted bottle H through the three-way tap G. The by a rubber tube leading to the tap I. The cork of the colorimeter carries a bent open tube M, and a short wide glass tube L, the lower end of which is closed by cementing on a glass disc. The colour of the liquid is observed through this tube L. K represents the com- parison colorimetier. In making a test, the bulb F is first filled with the reagent, by running in 2 C.C.of the liquid in C, after opening B, and then adding 8 C.C. of ammonia from E. The colorimeter K and the inverted bottle H, now containing the sample of water to be tested, are then connected to the apparatus, and the tube N, which reaches to the bottom of the bottle H, is joined to a hydrogen generator. The colorimeter is completely filled with the water, and 2 C.C. of the mixed reagent are added. For this purpose, the taps G, D, and B are manipulated so that 0-5 C.C. of liquid flows from C into F, and 1.5 C.C. of ammonia.from E into F. If the operation is carried out quickly, only water runs out of the bent tube M, and the colorimeter contains 1CO C.C. of water and 2 C.C. of reagent. Its colour is compared with that produced inTHE ANALYST.117 the second colorimeter by a known quantityof a solution of cupric chloride (contain- ing 1.1364 grams of copper per 1 litre of water), 1 C.C. of which corresponds to 0.1 C.C. of oxygen, and which is made up to 100 C.C. with ammonia and water. The standard is made up somewhat darker than the sample, and liquid drawn off through the stop-cock I’ until the tints are matched. The method is rapid; for waters con- taining up to 7 e . ~ . of dissolved oxygen per litre, the results obtained are generally about 0.1 C.C. higher than those given by Thresh’s method.* A. G. L. Estimation of Sulphide in Alkali Cyanide. T. Ewan ( J o z ~ m . SOC. Chm., I d . , 1909, 28, 10-13.)-0f the three methods studied, that of titration with lead nitrate, with lead paper as an external indicator, is the most rapid and convenient, and, if suitably performed and corrected, it is sufficiently accurate for technical purposes with quantities of potassium sulphide below 0.1 per cent. G.W. Williams’s modification of the colorimetric process (with sodium hydroxide and lead acetate) is more accurate but less rapid, and it is necessary to use boiled water and to check the strength of the standard solution very frequently. Lastly, Feld’s method, depending on the expulsion of sulphuretted hydrogen by distilling with magnesium chloride in an atmosphere of carbon dioxide, is the most accurate, but too laborious for technical purposes. The author describes the following procedure for performing the titration method with lead nitrate : 10 grams of the powdered cyanide are stirred quickly with 15 C.C.of ordinary water, any lumps being broken up with a glass rod. Any small undissolved residue will generally go into solution before the titration is finished. The lead nitrate solution (1 C.C. equivalent to 1 mgm. of potassium sulphide) is then run in quickly so long as it produces an increase in colour; after this it is added gradually, the solution being tested by placing drops of it in contact with drops of lead nitrate solution on thick blotting-paper. The author has carefully investigated the errors involved in the lead titration method, due to oxygen in the water, oxidation whilst the substance is being dissolved, and oxidation during titration. These errors are very considerable ; but if the procedure described above be adopted, one and a half to two and a half minutes being required for dissolving, and three to four minutes for titrating, the errors are sufficiently constant at from 18 to 26 per cent.of the sulphide present. If then the results be multiplied by the factor 1.25, or if, as is more convenient, a solution containing 2.4 grams of lead nitrate per litre be assumed to correspond with 0.01 per cent. of potassium sulphide per 1 C.C. used, the results are accurate to 2 or 3 units in the third place of decimals, and compare favourably with those obtained by Williams’s method. J. F. B. On the Titration of Sulphites with Permanganate. J. Milbauer (Zeits. ai2n.l. CZienz., 1909, 48, 17-24.)-The results of the experiments recorded show that correct results can only be obtained when the sulphite solution is added to a large excess of the permanganate solution acidified previously with sulphuric acid, and the excess of the permanganate then titrated.Ten times the quantity of per- manganate solution actually required for the oxidation of the sulphite is acidified with concentrated sulphuric acid (the amount added being such that the mixture * Dae probably to oxygen dissolved in the solution of ammonia.118 THE ANALYST. contains 20 per cent. by volume of sulphuric acid), and a very dilute solution of the sulphite is then added. The excess of permanganate is next titrated back with standardised oxalic acid, ferrous sulphate, or hydrogen peroxide solution. The excess of permanganate cannot be titrated with thiosulphate solution after the addition of potassium iodide.The permanganate solution should be of such strength that each C.C. is equivalent to 0.001 gram of sulphur dioxide. The addition of a mere trace of a catalytic agent, such as bromine or iodine, quickens the rate of the oxidation and renders the reaction more complete at low concentrations. w. P. s. Estimation of Sulphuric Acid as Barium Sulphate. E. Ruppin (Chen~. Zeit., 1909, 33, 17-18.)-The author quotes experiments to show that Treadwell's method, in which the boiling acid solution of the sulphate is precipitated with a dilute solution of barium chloride, added drop by drop, leads t o low results, only 96 per cent. of the theoretical amount being obtained. This is due to the occlusion of sulphates other than barium sulphate, especially of calcium and potassium.Correct results are obtained by modifying Hintz and Weber's procedure, a 50 per cent. excess of a 10 per cent. barium chloride solution being at once added to the boiling acid solution of the sulphate ; the precipitate should be repeatedly boiled out with water containing hydrochloric acid. Correct results are also obtained by pre- cipitating in a boiling solution made alkaline with sodium bicarbonate, acidifying with hydrochloric acid, and boiling for fifteen minutes. A. G. L. Estimation of Tin in Tin-plate. K. Meyer. (Zeits. mzgcw. Clze~n., 1909, 22, 68-69.)-Twenty to fifty grams of the tin-plate are freed from fat and dirt, cut into pieces of not more than 50 square cni. area, placed in a large dish or flask, and covered with water.After heating to 80" C., 1 gram of sodium peroxide for every 20 grams of sample is stirred into the liquid and the heating continued. As soon as the violent evolution of gas has ceased, another 1 grain of sodium peroxide is added and the liquid boiled. If any tin is still visible, a little more sodium peroxide is added, and the boiling repeated. The residual pieces of iron are removed from the liquid, washed first with water, then with alcohol, dried and weighed. The loss in weight corresponds to the tin present, not more than 0.009 per cent. of iron being removed. If lead and zinc are present, they will also pass into solution; in this case the dissolved tin must be actually estimated. A. G. I;. A New Reaction Distinguishing between Salts of Uranium and of Cadmium.P. Lemaire. (Ann. de Chim. 9naZ. Appl., 1909, 14, 6, 7.)-The reagent consists of a 5 per cent. solution of thiosinamine rendered alkaline, just before use, by the addition of 5 C.C. of 60 per cent. sodium hydroxide per 100 C.C. On adding to 2 or 3 C.C. of this alkaline reagent a few drops of the liquid under examination, and boiling and shaking the mixture, a permanent yellow precipitate is obtained in the presence of salts of cadmium or uranium. No yellow precipitate is obtained under the same conditions with arsenites, arsenates, or salts of lead, bismuth, antimony, copper, silver, mercury, tin, chromium, zinc, aluminium, iron, manganese, nickel, cobalt, alkalies or alkaline earth metals. When a yellow precipitate has been obtained, its nature is readily determined by the fact thatTHE ANALYST.119 hydrogen sulphide precipitates cadmium from a hydrochloric acid solution, whilst ammonium hydrosulphide precipitates uranyl salts, but not cadmium. In the case of mixtures of cadmium or uranium salts with other compounds, a preliminary separa- tion of the bases is usually necessary, since t.he thiosinamine precipitate may then be brown or black. C. A. M. Estimation of Zinc by Means of Ferrocyanide. E. Rupp. (Chern. Zeit., 1909, 33, 3, 4.)-The author shows that oxidation of potassium ferrocyanide to ferri- cyanide is effected quantitatively by allowing an excess of iodine to act on the neutral solution, to which 5 grams of Rochelle salt are added for a voluine of 50 to 100 C.C. At the end of one hour the excess of iodine is titrated with standard thiosulphate solution. To apply the method to the estimation of zinc, 10 C.C. of a neutral solution of zinc-sulphate, containing about 0-1 gram zinc, are added to 20 C.C. of a standard 5 per cent. potassium ferrocyanide solution after diluting the latter with 50 C.C. of water and adding 5 grams of Rochelle salt. The mixed solutions are allowed to stand for twenty to thirty minutes, to insure complete conversion of the zinc ferro- cyanide first precipitated into potassium zinc ferrocyanide, lC,Zn,Fe,C,,N,, ; 25 C.C. of a solution of iodine are then added, and the excess of iodine is estimated after another hour’s standing. Since iodine has no action on the precipitate, 2 atoms iodine correspond to 3 atoms zinc. The results vary between 99.9 and 100-2 per cent. of the zinc (Cf. ANALYST, 1902, 27, 291). A. G. L.

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DOI:10.1039/AN9093400114

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年代:1909

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THE ANALYST. 119 APPARATUS, ETC. An Apparatus for Simultaneously Extracting a Solid and Filtering the Solution so Obtained. F. Record. (C7~772. News, 1909, 99,53.)-The author has devised a modified and more simply constructed forni of extraction apparatus than that previously described (ANALYST, 1908, 33, 341). While the earlier form of extractor was con- structed wholly of glass, the modified appa- ratus, as seen from the figure, has its inner tube, A, held in position by means of a cork, H. The inner tube is contracted at its lower end, and has a pair of dianietrically opposite holes, C, in its walls, through which the vapour of the solvent passes from the outer tube, 13, into the condenser, when the condensed solvent drops back on to the mate- rial, G, in the inner tube, percolates it, and is filtered through the asbestos, F, placed on a layer of filter-paper over the filter- disc, E.A. R. T. G\ F\ / E i.4120 THE ANALYST. An Apparatus for Oxidations with Sodium Peroxide. E. Pozzi-Escot. (Ann. de Chinz. AnaZ. AppZ., 1909, 14, 5 , 6.)--For analyses in which the substance is first oxidised by means of sodium peroxide (AKALYST, 1904, 29, 220, 317; 1908, 33, 293, 337, 338), the author has devised a special crucible of nickel. This is provided with a cover, which can be fixed on to the crucible by mean8 of a bayonet joint, and in the centre of which is an open tube, 7 to 8 em. in length and 3 mm. in diameter. From 4 to 5 grams of sodium peroxide are mixed with about 0.2 gram of the substance to be analysed, and the covered crucible heated gently for a few seconds until the reaction takes place, after which it is kept at a bright red heat for ten minutes.I t is then allowed to cool, and its contents dissolved in warm water. Under these conditions carbon is converted into carbonate, and may be estimated in that form. C. A. M. An Apparatus for Testing Glue. E. Valenta. (Chem. Zed., 1909, 33, 94.) -The apparatus described is the same in principle as that of Lipowitz, and has been designed with the view of eliminating certain constructional errors, to which, in the author's opinion, are due the untrustworthy results obtained when Lipowitz's apparatus is employed for determining the resistance of glue-jellies. The modified apparatus is shown in the figure; the base plate is provided with levelling screws, and carries two vertical rods, one of which supports a mercury reservoir, whilst the other carries the piston-rod, St.The latter is square in section, and is fixed between the rollers, R, so that it can move freely. At the lower end of the rod is the convex piston, D, which is 14 mm. in diameter and about 4 mm. in depth. In using the apparatus, the glue-jelly (prepared by dissolving 5 grams of the glue in 45 C.C. of hot water) is placed in the beaker on the horizontal table, T, and allowed to set for at least twelve hours. The beaker is then placed in a water-bath at a, temperature of 15" C. until the jelly has attained this temperature ; it is again brought on to the table, the piston is lowered on to the surface of the jelly, and mercury is allowed to run into the beaker carriod on a plate at the top of the piston rod until the piston breaks the surface of the jelly. The tap admitting the mercury is then closed immediately, and the quantity of mercury admitted to the beaker is weighed. The weight in grams of the mercury, together with the combined weight of the beaker, rod, and piston, represents the '' resistance " of the 10 per cent. glue- jelly. w. P. s.

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DOI:10.1039/AN9093400119

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年代:1909

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THE ANALYST. 121 LOCAL GOVERNMENT BOARD REPORT. On the Presence of Tin in Certain Canned Goods. G. S. Buchanan and S. B. Schryver. (Reports of Inspector of Foods, No. 7, 1908, 1-30.)-1n July, 1906, the attention of the Local Government Board was directed to the condition of certain consignments of old tins of meat essence, which had been returned from the South African campaign. These were subjected to a detailed chemical examination, and, whilst no appreciable changes had taken place in the organic contents of tins, the sarriples were found to be highly contaminated with tin. Since that date a large number of samples of other tinned foods have been examined, and the results of the investigation are embodied in this Report. In order to ascertain whether there is a, liability of absorption of tin when com- paratively non-irritant, organic compounds are given by the mouth, Dr.Schryver himself for three weeks took quantities of a tin salt (sodium stannic tartrate) equiva- lent, during the first week, to 1 grain of tin per day; in the second week the quantity was increased to 2 grains of tin, and during the third week to 3 grains of tin per day. The quantity of tin excreted in the urine and fmes wag estimated, and from the results given it is seen that during the first fortnight there was no evidence of accumulation of tin in the system ; in the second week a small quantity of tin was found in the urine, showing that some of the metal had been absorbed from the alimentary tract. When 3 grains of tin were ingested daily, there was evidence of accumulation in the body, the amount being about 2 grains of tin during the week.No ill-effects were felt as a consequence of the doses taken. Whilst the urine con- tained but relatively small quantities of tin, experiments on dogs showed that when tin enters the body by a channel other than the alimentary tract, the metal is excreted in larger quantities in the urine than in the fmes. The canned goods examined consisted of flesh foods, fish, meat essences, extracts and soups, fruits, vegetables, puddings, and jams, the majority of the samples having been in the tins for from five to eight years. The meat samples appeared to have taken up into their substance a comparatively small proportion of tin, the quantity being generally less than 0.5 grain per pound ; only in one instance (canned tripe) did it reach 2 grains per pound.Meat extracts of similar age had absorbed larger quantities of the metal, 3.3 and 5.3 grains per pound being found in two samples respectipely ; the same was the case with the meat essences, but to a less degree. One sample of beef essence, however, contained 21.8 grains of tin per pound; this sample contained beads of solder, and it was found that a very conspicuous con- tamination by tin may take place in a short time if pieces of solder find their way into the contents of the can. Contamination by tin in this way is the more serious, as it is accompanied by risk of simultaneous contamination by lead. Only one of the three samples of soup examined contained tin in large quantities; in this instance the soup contained fruit acid derived from tomatoes, and was contaminated with 3.5 grains of tin to the pound.Canned lobster had absorbed as much as 2-4 grains of tin per pound, whilst two samples of canned vegetables (parsnips and122 THE ANALYST. carrots) showed 1.5 and 2.2 grains of tin per pound respectively. Apple and plum puddings and a sample of apricot jam contained about 3 grains of tin per pound. No samples of canned fruits most commonly consumed in this country were included in the South African samples, but samples of canned pears, apricots, and peaches, from a London importer, who specially selected them as old stock and stated them to be one or two years old, contained not more than 1 grain of tin per pound. The investigation brought out clearly that the tin, after solution in the liquid contents of the can, becomes in course of time absorbed in, or chemically combined with, the solid contents (meat, fruit, etc.) in such a way that the latter contain comparatively larger quantities than the liquid itself.Commenting on the results o€ the investigation, Dr. Buchanan says that they suggest that in the case of food contaminated with tin the larger portion of the tin does not become absorbed from the gastro-intestinal tract, and that accumulation of tin in the body in these circumstances takes place at a slow rate. Whilst it may be concluded that there is not a serious risk of chronic poisoning by the absorption of relatively small quantities of tin as a result of a diet which consists largely of canned foods continued over a lengthy period of time, it still remains necessary to consider the irritant action on the gastro-intestinal tract, which may result from the presence of considerable quantities of tin salts in the food.It appears to be well established (a comprehensive account of alleged cases of tin-poisoning and researches on the toxicity of tin by other workers is given in the Report) that such irritant action may take place, and the condition of the stomach, the susceptibility of the individual, and other circumstances must be taken into account. On the whole, it seems clear that in any kind of canned foods quantities of tin approximating to 2 grains to the pound are not only unusual and unnecessary, but also must be regarded with grave suspicion in consequence of the risk of irritant action of the tin they contain.I t is suggested that special attention should be directed by sanitary officers, with the co-operation of the Public Analyst, to canned foods which there is reason to suspect to be of unusual age--e.g., more than one or two years-and in particular to such canned goods as those in which the liability to act on tin is specially great. The presence of more than 2 grains of tin to the pound may be taken to signify that the food has become potentially dangerous to health, and calls for further examination of other samples with a view to dealing with the whole consignment in accordance with the results obtained. I t would be advantageous to be able to ascertain, from marks or labels on the cans, the date and place of preparation of canned goods.For the estimation of tin two processes were used, one colorimetric and the other gravimetric. I n both methods the organic matter of the sample was destroyed by hea,ting with sulphuric acid ; in most cases 50 grams of the material were employed for the estimation, this quantity being heated in a round-bottomed Jena flask with 50 grams of potassium hydrogen sulphate and 50 C.C. of concentrated sulphuric acid, further quantities of the acid being added, if necessary, to keep the contents of the flask in a fluid condition. When the solution had become perfectly colourless it was cooled, diluted with water to about 600 c.c., treated with hydrogen sulphide, and allowed to stand overnight. In some caseg, when large quantities of calcium salt are present in the foodstuff, calcium sulphate separates out when the acid solutionTHE ANALYST. 123 is diluted ; this must not be removed by filtration before precipitation with hydrogen sulphide, as it contains tin, possibly in the form of a double sulphate. The pre- cipitate of sulphide and sulphur was collected on a filter and washed a few times with water, and the tin then estimated either colorimetrically or gravimetrically as follows : C'olorimetric 1Method.-The filter and precipitate were transferred to a wide test- tube, boiled with 5 C.C.of concentrated hydrochloric acid, and the solution filtered through a small conical Buchner funnel, the residue being washed with 2.5 C.C. of hydrochloric acid. The test-tube was next closed with a cork carrying a tube, and carbon dioxide was passed into it.A piece of zinc foil was then added to the strongly acid solution while still hot; and as soon as the last trace of metal had dissolved, the reagent was added. The latter was prepared by dissolving 0.2 gram of dinitrodiphenylaminesulphoxide in 100 C.C. of & sodium hydroxide solution, and filtering. Two C.C. of the reagent were used in each test, and were introduced into the test-tube while the current of carbon dioxide was continued. After boiling for a few minutes, the solution was diluted to 100 C.C. with cold water, filtered, and the filtrate treated with a drop of dilute ferric chloride solution. The violet coloration produced was then compared with that yielded by known amounts of tin.The standard solutions were prepared from a solution containing such a quantity of stannous or stannic chloride that each 5 C.C. contained 14.28 milligrams of tin. This is a convenient amount, as 14-28 milligrams in 100 grams is equivalent to 1 grain per pound. One-quarter of a grain of tin per pound gives a marked coloration if 50 grams of the sample be taken for the estimation, and 0.1 grain per pound gives an appreciable colour. The colorimetric process was found to be useful for sorting purposes and for estimating less quantities of tin than 1 grain per pound, but for larger quantities the gravimetric method was preferred. The reagent used in the colorimetric process is prepared as follows : Ten parts of nitric acid of specific gravity 1-48 are mixed with an equal weight of nitric acid of specific gravity 1-40; the mixture is cooled with ice, and small quantities of thio- diphenylamine are added with continual stirring until 1 part by weight has been added altogether.The temperature must not rise above 5" C. during the addition, Aftier standing a few hours, the separated nitro-body is collected on an asbestos filter and washed, first with concentrated nitric acid, then with nitric acid of gradually diminished strength, and finally with water. I t is then extracted with hot alcohol, in which it is not appreciably soluble. Gravimetric Method.-In this method the washed precipitate of sulphide and sulphur obtained as described in the colorimetric process was dissolved in a small quantity of hot 10 per cent. sodium hydroxide solution, and the sulphide re- precipitated by the addition of glacial acetic acid. This treatment was necessary in order to remove sjlica derived from the flask. The sulphide was then collected on a filter, washed with hot water, dried, oxidised, and weighed in the form of oxide. w. P. s. Ferrosilicon and its Properties. Wilson. (Report of the Inspector of Factories, England, 1907.)-The poisonous action of certain samples of ferrosilicon is ascribed to the generation of arseniuretted and phosphorettsd hydrogen, owing124 THE ANALYST. to the action of moisture. The explosive properties of ferrosilicon are probably due to the formation of ferrous carbonate and spontaneously inflammable hydrogen silicide (SiH,), under the combined action of carbon dioxide and water. Other less probable theories attribute the explosions to the existence of the ferrosilicon in a strained condition (similar to that of Rupert’s drops), owing to rapid cooling; and to the freezing of contained water in winter. The quantity of ferrosilicon imported into England is about 4,000 tons per annum. A. G. L.

ISSN:0003-2654    

DOI:10.1039/AN9093400121

出版商:RSC    

年代:1909

数据来源: RSC