摘要:

APRIL, 1906. VoI. XXXI., No. 361. THE ANALYST. PROCEEDINGS OF THE SOCIETY OF PUBLIC ANALYSTS. THE PURIFICATION OF ZINC AND HYDROCHLORIC ACID FROM ARSENIC. BY L. T. THORNE, PH.D., AND E. H. JEFFERS. (Read at the Meeting, February 7, 1906.) 1. Zinc.-Hehner first suggested (ANALYST, 1902, 261) the treatment of zinc with sodium for the purpose of removing traces of arsenic, but the method was some- what uncertain, owing to the exact conditions necessary not being ascertained. Later we described before this Society conditions of this treatment under which we obtained reliable results; but as the manipulation we then used was complicated, we delayed printing the details, in order, if possible, to simplify it. After long trials and use we now lay before the Society the simplest conditions which we find reliable.Commercially pure zinc is melted in a, crucible in a gas furnace, and when at or only just above its melting-point sodium is mixed with it in the proportion of about 1 gram to each pound of zinc. This is best effected by adding the sodium in pieces of 1 to 2 grams weight which have not been dried from the adhering petroleum in which the sodium is stored. If the zinc be at the right temperature (ie., not too hot) the sodium is dissolved without either it or the petroleum vapour becoming ignited. After all the sodium has been added, it is preferable to add a small piece of zinc to insure the temperature being reduced to about the melting-point. The crucible is heated for a few minutes till the zinc is completely fluid, and the zinc is then poured into a second previously heated crucible, and back again once or twice to insure thorough melting.If the temperature is not allowed to get too high practically no oxidation takes place during this transference. The crucible, with the lid on, is then put back into the furnace and heated to a dull red heat, when the furnace and crucible lids are both removed, and the heating is continued for at least half an hour (preferably for an hour), care being taken that the temperature should not rise much. A scum (or alloy) gradually rises to the top and forms a hard, dark gray crust on the surface about & inch thick. This crust contains practically all the arsenic and the greater part of the sodium in combination with zinc. The crucible is allowed to cool slightly, the crust is pierced at one side, and the molten mass is poured into a second previously heated crucible and skimmed if necessary.This crucible is then heated to bright redness, any slight scum removed, then allowed to cool, and the zinc granulated just before the solidifying-point is reached.102 THE ANALYST. The essential points for success appear to be to get as thorough mixing as possible at a low temperature, and to avoid material rise in temperature whilst the scum or alloy is forming and rising. The arsenic sodium and zinc compound seems to be most stable at somewhere near the melting-point of zinc, and to be partially broken up at high temperatures. The temperature, before the scum is removed, should not be hot enough for the zinc or scum to take fire when the crucible lid is removed.In this way zinc absolutely free from arsenic is obtained, which gives in the Marsh-Berzelius apparatus a perfect blank with the solution of 15 to 20 grams of zinc, and is yet so sensitive as to give a definite and reliable result with 0.000002 grams of arsenious oxide, and the sensitiveness is always the same. The yield is about 95 per cent. of the zinc taken. 2. Hyd~ochloric Acid.-In 1902 we described (Proc. Chem. SOC., 1902, 118) a method for the freeing of hydrochloric acid from arsenic by a modification of the Reinsch test. I n use we found the presence of a little stannous chloride (i.e., of a strong reducing agent) greatly facilitated the deposition of the arsenic on the copper gauze, lessened the amount of copper dissolved, and shortened the process, but it still remained somewhat tedious.Noticing the great effect of the tin, we then tried the employment of a copper-tin couple with complete success. Redistilled hydrochloric acid is diluted to rather under a specific gravity of 1,100 (water = l,OOO), and is then poured on to a copper-tin couple, prepared by reducing with zinc a mixture of copper and tin chlorides in hydrochloric acid and washing the precipitated spongy couple. The metals are used in about the propor- tion of 1 part by weight of tin to 4 to 8 parts by weight of copper. A convenient mode of preparing the couple is as follows : Cuprous chloride is dissolved in excess of hydrochloric acid, and a small quantity of granulated tin added. The tin rapidly dissolves, at the same time reducing some copper in a spongy form.Zinc dust, or the smaller portions of granulated zinc, is then added, and this reduces the remainder of the copper together with the tin in the form of a dark gray spongy couple, which is washed by decantation. Ordinarily pure cuprous chloride and tin may be used, as traces of arsenic which may be present are eliminated, and do not affect the fins1 result. The couple may also be readily obtained by reducing with zinc the residual liquor in the distilling flask, which consists of the mixed chlorides. The couple should be gray in colour; if it is nearly black the copper is in too great excess. About 2 or 3 grammes of the couple are used to each litre of the diluted acid. The acid containing the couple is gradually heated, a strong reaction taking place at about 70" C., and kept on the boil for about a quarter to half an hour.During this time most of the tin and a part of the copper is dissolved, and practically the whole of the arsenic is evolved. The acid may then be distilled direct, or be cooled and kept under a layer of petroleum (to prevent absorption of oxygen) ; but in the latter case it must be distilled within twenty-four hours, or partial oxidation will occur. In the distilling-flask a small quantity of the couple should be placed, and also a small piece of 100-mesh copper gauze, This latter determines the pre- cipitation of any minute traces of arsenic which may have escaped elimination by the preceding treatment, and also prevents bumping.The distilled acid is perfectly free from arsenic.THE ANALYST. 103 Good commercial muriatic acid may also be used, but in this case the first treat- ment must be repeated twice, as, owing to the traces of iron chloride and other impurities contained in the acid, the first lot of couple is generally completely dissolved, and does not fully eliminate the arsenic, The residue in the distilling-flask serves conveniently for the preparation of fresh copper-tin couple, as the proportion in which these two metals are present in the couple is not important. DISCUSSION. The PRESIDENT (Mr. Bevan) having invited discussion, Mr. HEHNER desired personally to thank the authors for laying down the conditions under which the sodium treatment was fully successful. As he had explained a few years ago, he had often succeeded in purifying satisfactorily very bad zinc by treatment with sodium, but he had often failed to improve materially even .comparatively pure zinc.He had not, however, had so much patience as the authors, and so had never ascertained the exact conditions that were necessary. He was very glad now to find that the authors had brought what was formerly an entirely rule-of- khumb process into something like law and order. Mr. CHAPMAN said that his own experience was that it was now rarely necessary t o purify zinc from arsenic, the great difficulty at the present time being to get zinc fhat would give out the full amount of arsenic that was put in. Consequently, the problem was not quite SO urgent a one as it was when Mr.Hehner took the matter up a few years ago. There could, he thought, be no doubt whatever that the sodium method, if properly applied, was capable of removing the arsenic. He himself had gometimes been unsuccessful with it, but that was probably because he had not known the precise conditions necessary for success. The many experiments he had made, however, went to show that, unless the sodium mas entirely removed, the zinc obtained was distinctly ‘‘ insensitive.” He thought that that was proved by the mirrors which the authors had shown. For example, their mirror for the mgm. .of arsenic was not more than half that which he was in the habit of getting, and which he had every reason to believe to be correct. The same applied to the other mirrors. Through the kindness of Dr.Thorne, he had had the opportunity of examining some of this sodium-treated zinc with his own materials, and the conclusion he came to was that it was distinctly insensitive. If, therefore, the sodium treatment was to be employed, it must be with very great care, and the operator must recognise the possibility, or even probability, of the resulting zinc being more or less insensitive. The method for the purification of hydrochloric acid recommended by the joint committee of the Society of Chemical Industry and the Society of Public Analysts (treatment with bromine and sulphurous acid and distillation) in some cases worked well, but in others did not. He had, however, for some time been invariably successful in purifying the most impure acid by a slight modification of that method.The only modification was that the strong acid was distilled, instead of being first diluted down to constant boiling-point strength. The pure acid obtained amounted to about three-fifths of the total quantity treated. The only failure he had had was due to the mechanical carrying over of a little iron into the distillate from a very104 THE ANALYST, impure acid. This, as had been recently shown, caused diminished Sensitiveness, but it was easily obviated by a suitable arrangement of the distilling apparatus. Dr. DYER said that Mr. Chapman had anticipated a, remark that he had been about to make regarding the faintness of the authors’ mirrors. Their mirror from mgm. appeared to be less than the mirror obtained in his laboratory from half that quantity of arsenic, working with acid which gave a good blank, and using tubes of approximately the same size as those shown.That seemed to point to slight insensitiveness of the authors’ zinc. Mr. H. D. LAW said that, from the results of the investigation recently corn-, municated to the Society by Mr. Chapman and himself, it was evident that sodium was one of those metals which seriously interfered with the sensitiveness of zinc. He had since made some experiments to find out the particular reducing efficiency of hydrogen liberated by sodium and potassium. By passing an electric current through a solution of sodium hydroxide or potassium hydroxide, a deposit of sodium or potassium was obtained. This dissolved in the water, with liberation of hydrogen at the potential of the metal.The reducing power of this hydrogen had been compared with that of the hydrogen liberated by various metals of different potentials. Camphor wa,s very readily reduced with lead electrodes, but when he tried to reduce camphor with the hydrogen liberated by sodium or potassium, he found that he was quite unable to do so. This showed that the potential of the sodium or potassium was very much lower than that of zinc or lead. He then took different materials which were capable of being readily reduced, such as benzaldehyde, in order to find out, by lowering the reducing potential, at what point a degree of reduction was obtained corresponding with that produced by sodium hydrogen. With lead elec- trodes benzaldehyde yielded a very sticky mass quite characteristic of high-potential reduction, while with metals of lower potential the sticky masses produced were very much less in quantity.Finally, he took refined copper electrodes, which yielded no sticky substance at all, but a crystalline, brittle hydrobenzoin corresponding to that obtained by reduction in sodium and potassium solutions, This proved conclusively, he thought, that the potential of sodium and potassium was about the same as that of copper, which was extremely low. Dr. THORNE said that he was inclined to think that, if there was any diminution a t all in the sensitiveness of the zinc, it was but very slight. Personally, he was strongly of opinion that in many cases where zinc was said to be highly sensitive either it or the acid was not absolutely free from arsenic.He had certainly not had the same success as Mr. Chapman in obtaining zinc that would give an absolutely clear blank without repurification, though there had undoubtedly been a great improvement in commercial zinc during recent years. As a test of the absolute purity of the zinc, they ran blank determinations for an hour and a half. A twenty- minutes’ blank might to a certain extent be satisfactory, but they had found after a large experience that the very small traces of arsenic which were present in most commercial zincs tended to cause irregular results, giving undue prominence to small quantities as compared with larger quantities of arsenic in the material under examination. They found the sensitiveness of each successive batch of zinc purified to be practically the same, and although he was quite prepared to admit that theTHE ANALYST.105 mirrors they obtained might be slightly less intense than the small-quantity mirrors obtained with other zincs, he thought that the continuous concordance of the mirrors after repeated treatments with sodium showed that they were truly representative, and that the danger of loss of sensitiveness by the treatment was practically nil. The more strongly marked character of the low-quantity mirrors in other cases was probably due, in part at any rate, to traces of arsenic in the other materials. With reference to Mr. Hehner’s remarks, he should like to say that a good deal of the patience expended on this matter had been that of his collaborator, Mr.Seffers. With regard to hydrochloric acid, they also had found that the method first proposed by the joint committee did not answer in all cases. They did not say that the method they had described was a better one than the committee’s method as now modified, but it had been found reliable with ordinary impure acid as well as with acid of good quality, and was a simple and convenient method. In answer to a question put by Dr. DYER, Dr. THORNE said that they had not tried Mr. Chapman’s device of introducing cadmium sulphate into the flask. Mr. CHAPMAN said that he could put forward in support of his own contention exactly the same argument which Dr. Thorne had used. The mirrors he obtained were perfectly concordant, whatever the method or materials were. Sometimes he put cane-sugar, soluble starch, etc., into the flask, sometimes he left it out ; but the mirrors in either case were always of the same intensity within the very narrow limits of experimental error. He asked what evidence there was that the appearance of a bright surface on the zinc coincided with the disappearance of the whole of the sodium. Mr. JEFFERS said that he did not think it could exist alongside the zinc at that temperature. Mr. CHAPMAN said that it might quite well exist in very small quantity as an alloy dissolved in the zinc. Mr. JEFFERS said there was no room for doubt as to the complete removal of the sodium. If the sodium were not entirely removed, it was impossible to get a bright surface on the zinc at a red heat.

ISSN:0003-2654    

DOI:10.1039/AN9063100101

出版商:RSC    

年代:1906

数据来源: RSC

摘要:

THE ANALYST. 105 NOTE ON DUTCH CHEESE. BY CECIL H. CRIBB, B.Sc., F.I.C. (Read at the Meeting, February 7, 1906,) IN the earlier part of last year I received, amongst a number of other samples of Dutch cheese submitted to me under the Sale of Food and Drugs Acts, some which contained extremely minute proportions of fat. In view of the general recognition of the fact that Dutch cheese is not made, except in the case of certain well-defined brands, from whole milk, it became necessary to consider*whether the sale of such samples brought the vendors within the provisions of the Act-Le., whether they should be regarded as genuine or adulterated.106 THE ANALYST. On looking up the literature of the subject, the question seemed fairly simple. Practically all the published analyses give proportions of fat far exceeding those in the samples I have just referred to, the figures given in every case but one ranging from 19 to 33 per cent.The sole exception to this occurred in a paper by Messrs. Pearmain and Moor (ANALYST, xix., 145), where a fat content of 10.6 per cent. is recorded. I also found that during the last four or five years there have been several prosecutions for selling, either as Dutch cheese or as cheese, samples which were more or less deficient in fat (British Food Journal, 1900, p. 47 ; 1901, p. 202 ; 1903, pp. 90, 159, 164, 229) ; and in those cases in which Dutch cheese had been specifically asked for, and in which the proportion of fat was at all comparable with that in the cheeses examined by myself, a, penalty was inflicted. I felt justified under these circumstances in certifying adulteration, and proceedings were instituted against the vendors.Counsel appeared €or both sides, and after a somewhat protracted trial the magistrate decided that there was no standard, and that the pro- secutor had therefore been supplied with cheese which was of the nature, substance, and quality demanded. As during the hearing of some of the cases referred to above, somewhat widelyvarying opinions had been expressed as to the amount of fat Dutch cheese should contain, I thought it desirable to get some idea as to the range of fat content in the Dutch cheese which was actually being imported into the country at the time, and by the kindness of two of the largest firmsin the wholesale trade I obtained a series of samples which fairly represent every price and quality coming over at that particular date, the results of analysis of which, together with those of the official samples submitted to me, are given in the following table : I.FROM WHOLESALE HOUSES. 1. Gouda ... 2. Edam ... 3. 9 , ... 4. Gouda ... 3. ? 9 ... 6. 29 ... 7. 9 , ... 8. 9 9 ... 9. Derby shape.. . 10. Gcuda ... 11. 9 , ... 12. 9 9 ... 13. ? 2 ... 14. ... 15. Dliby ... 16. Edam ... 17. Edam (full cream) ... 18. '' Case " cheese Wholesale Price per Cwt. 28s. 30s. 34s. 28s. 28s. 32s. 34s. 34s. 36s. 38s. 42s. 44s. 42s. 42s. 46s. 52s. 58s. 65s. 4d. Approximate Retail Price per Pound. 4d. to 5d. 9 7 9 , 7 ) 5d. 6d. 7 7 G. ¶, Y, ,9 2 9 7d. t'; 8d. 9 , 8d. 10d. to 1s. Fat. 1.64 3.83 4.04 5.01 5.02 5.36 4.56 4.73 4.75 13.6 12.45 13.2 15.3 18.37 1695 15-12 24.4 27.9 N 6-33.- 25.34 31.92 28.53 24.89 22.05 34.22 25.34 31-92 23.91 26.67 25-34 23.90 24.54 24.37 24.00 26.05 21.89 Ash. 5.71 5.81 7.33 5.29 7.30 5.30 6.10 6.26 5.67 5.48 5.43 4.26 5-15 4.48 5.27 5.54 5.58 4.28 Water. 55.22 60.38 53.66 54-26 58.26 59-28 54.83 60.17 54.10 56-15 50.46 50.63 50-96 52.45 49-45 52-50 41 -70 46.2THE ANALYST. 11. OFFICIAL SAMPLES. 107 ___- --__ 19. 20. 21. 22. 23. 24. 25. Fat. 1 -89 2.75 5.20 2.65 6.62 15.40 27.12 N 6.33. 36.24 31-02 31.37 38.46 26-85 - Ash. 747 8.82 7.15 6.47 6.07 5.94 10.8 Water. 56-89 55.40 53.80 51.90 58-80 50.14 43.70 The most striking thing about these figures is the vast difference between the proportions of fat occurring in my samples and that found by the various authors to whom I have previously referred.For, excepting Messrs. Pearmain and Moor, all previous observers seem to have found what, judging from my analyses, must be regarded as the maximum figures for fat. I t seems clear that a great change had taken place in the composition of Dutch cheese since the earlier analyses were made. I was informed that the great bulk of the trade is concerned with cheese of the quality represented by the samples numbered 10 to 16, and that at the time the samples were given to me the total bulk of this quality which was sold amounted to fifty times as much as that of the poorer kinds represented by numbers 1 to 9. I was also told that the greater part of the latter was imported into England for one large retail firm, with branches all over the country, who, by selling this inferior article, were gradually forcing their poorer competitors to deal in goods which they would formerly have refused to touch, and thus the whole trade was gradually becoming demoralized. It is quite obvious from the proportions of fat they contain that the samples numbered 1 to 9 really represent a class of product altogether different from numbers 10 to 16, and are plainly made entirely from separated milk.Considering that the cheeses were valued almost entirely by the unaided senses, it is remarkable how closely the proportions of fat run parallel with the price ; and although in many cases a larger percentage of fat was expected than actually turned out to be present, there is no reason to suppose that an expert buyer would be under the slightest delusion as to what he was getting if he came across any of the first nine samples on the list.On the other hand, the ordinary householder would probably fail to see any difference between members of the first and second groups. As the main point in the defence was the absence of an official standard for cheese, the local authority for whom I acted addressed the Board of Agriculture on the subject, and requested that they would consider the advisability of fixing such a standard. Similar action was at the same time taken by a large number of county and borough councils throughout the country, namely, a t the instigation of the Council for the County Borough of Bournemouth. In response to these communications a letter was received from the Board of Agriculture, saying that “there were difficulties in the way of framing suitableTHE ANALYST.regulations of the nature desired,” owing to the existence of so many different vmieties of cheese, and that it was not clear in what way such regulations ‘‘ would assist consumers in obtaining the article they desire.” They state that, on con- sideration of all the circumstances,” they did not feel that ‘‘ any advantage would be gained by the attempt to deal with cheese by the issue of regulations under the Act.” This decidedly unsatisfactory document entirely fails to answer the question to which 1 want to direct attention in the present communication-namely, Should the sale of these separated-milk Dutch cheeses be held to constitute adulteration ? The question is not merely the academic one of clerical procedure, but involves a matter of much greater importance.If the Board of Agriculture, having power to fix standards, do not use it, their failure to do so is likely to prove a most serious hindrance to the proper administration of the Acts. Before the 1899 Act came into force the magistrate relied almost entirely on the Public Analysts for information as to what constituted adulteration, but now the first question he asks ’is usually, What is the Government standard? And if there is not one, he in many cases at once concludes that the Government have refrained from fixing one because they were unable, and not because they had never tried, the obvious conclusion being that, if they had failed, no one else could succeed.I t is quite plain that now the reply of the Board of Agriculture has become more or less public property, the analyst who attempts to support a prosecution in the case of a separated-milk Dutch cheese will be in a much more difficult position than he would have been in before that reply was issued. Whatever the law may have to say on the subject, the Public Analyst is bound to report the sample as either genuine or adulterated, as the Act recognises no halfway house between the two. Put quite briefly, I personally think that such samples as those referred to should be returned as adulterated for the following reasons : Dutch cheese has been known for a very large number of years, and its reputation was built up during a period when such products as some of the worst samples were practically unknown, or, if they existed, were openly sold as skimmed or separated milk cheese.I t is used, not as a condiment, but as a cheap and convenient source of nourishment, mainly by the poorer classes, and in probably the greater number of cases without butter being taken at the same time, so that the almost complete absence of fat interferes seriously with its digestibility, Apart altogether from this, the great deficiency of fat carries with it other defects, which are most distinctly to the prejudice of the purchaser. The most important of these is the fact that the presence of so little fat enables the cheese to retain a much larger amount of water without betraying the fact in any way, and as a further result it dries much more rapidly, and in a short time gets so hard that it can only be cut with a hammer and chisel.The obvious explanation of the poor quality of much of the Dutch cheese now on the market is to be found in the use of separated instead of skimmed milk. As far as my information goes, all the reputable kinds of Dutch cheese were formerly made either from whole milk or from the whole morning milk mixed with the skimmed milk of the previous evening. Now that cheese is mainly the product of a factory instead of a farm, it is not likely that the old and inefficient process of hand-THE ANALYST. 109 skimming is employed at all, so that even if the old traditions were adhered to as regards the cheeses other than those made from whole milk, there would be a lowering of the fat content to at least the extent shown by my analyses.As these facts are not known to the public, it seems to me that this is a case, if ever there was one, in which the Board of Agriculture should exercise its powers, especially as the objections it advances to fixing standards are by no means con- vincing, and, so far as Dutch cheese is concerned, have but little force. DISCUSSION. The PRESIDENT (Mr. Bevan), in inviting discussion, said that, personally, he lthought that the justice of the case would be met if cheese made from skimmed milk were required to be so labelled. Dr. VAN RIJN said that, as Mr. Cribb had already very clearly explained, a good deal of cheese had been sent over from Holland lately-during the last year or so- which contained only a very small proportion of fat.The reason for this was that i n some parts of Holland, where several years ago no cheese at all used to be made, all the separated milk was now used for making cheese, A market was found for it over there at the price it was worth, but, of course, the people who made it could not be responsible for what was done with it later on. He personally thought that it was not fair to sell this ‘( separated cheese,” as he would call it, simply under the name of Dutch cheese. I t was, however, very diflicult-he thought almost im- possible-to fix a, legal standard for cheese generally. Something in that direction had been attempted in Holland, and now combinations of cheesemakers were being formed for the purpose of doing what had been done with regard to butter control- namely, to fix st standard for themselves and to establish stamps or marks for their cheeses. For instance, it would not be permissible to make a gheese of the ordinary Gouda or Edam shape containing less than about 15 per cent.of fat (25 per cent. fat in the dry residue). He thought that the majority of the cheesemakers at the moment were in favour of such a limit. It would not have any legal force, but would be a commercial standard. If it were adopted it would naturally strengthen greatly the position of the authorities in such prosecutions as had been lately instituted in this country. He should like to explain why so low a limit as about 15 per cent. was suggested. For Edam cheese it was the custom to mix the evening milk, after the cream had been taken off, with the full-cream morning milk, and to make the cheese from this mixture, which contained, especially at some seasons of the year, a, some- what low proportion of fat.From experiments made with normal milk of varying degrees of richness at a Government station in Holland, the lowest proportion of fat in cheese made in this way was found to be 20 per cent. The lower limit of 15 per cent. was proposed in order that a margin might be allowed to cover possible abnor- malities in the milk used. I t was, moreover, possible to make good cheese containing this amount of fat. With a much smaller quantity of fat the quality of the cheese was quite different. He did not know much about the digestibility of cheese containing only a few per cent.of fat, but it certainly was not a first-class commercial product.110 THE ANALYST. The question of the estimation of fat in cheese had been already mentioned in the ANALYST about a year ago. He had just had an opportunity of discussing it with one or two colleagues, whose opinion had been that the same results would be ob- tained whichever of the ordinary methods might be used. This was, practically speaking, correct in the case of full-cream cheese containing from 30 to 40 per cent. of fat, but it had been stated very clearly in Holland by several analysts that, with cheese containing a low percentage of fat (below 22 per cent.), the method of extrac- tion with ether always yielded 2 or 3 per cent. less fat than was actually present.He might perhaps later on have something to add in reference to this. Mr. HEHNER said that many years ago he had called attention to this problem, because it seemed to him very anomalous that, while a man was allowed to sell cheese made from milk from which the fat had been taken, as soon as he tried to confer a benefit on the purchaser by filling up the cheese with other fat he was punished. He thought it unreasonable to punish the vendor of margarine cheese while leaving the vendor of skimmed-milk cheese free. He had never found any difficulty in distinguishing by taste and appearance between skimmed-milk cheese and full-cream cheese, but a ‘‘ filled ” cheese was very difficult to distinguish without chemical analysis. At one time cheese might fairly be considered to be, roughly,, one-third water, one-third fat, and one-third other things.But times had since changed considerably. Cheese was now one of those manufactured products which, allowed the maker a good deal of scope; and the courts had laid down-he thought rightly-that the manufacturer had a right to exercise his ingenuity in the manufac- ture and composition of a manufactured product. A food material that was virtually sold as Nature furnished it must be as Nature gave it, but as soon as the question of manufacture came in there must necessarily be a certain latitude. That was the case with cheese and with many other things. I t was, however, very difficult in a case, like that of cheese to give a notice consistently. * I t was imaginable that boxes should1 be branded, but it was almost impossible to mark each piece of cheese sold.If,. however, some means could be introduced for distinguishing at once-say, by colour ---between full-cream cheese and skimmed-milk cheese it would probably be a boonl to the consumer. But the Dutch manufacturers were very scientific, and understood very well how to sell both butter and cheese at the same time at a good price, and it would be much better that they should, in the way that Dr. van Rijn had mentioned, themselves take steps to guard against the mischief resulting from too acute competition. He thought that everybody must agree with Sir Thomas Elliott that it was exceedingly difficult to lay down a general law. Several kinds of cheese had, by common consent, been allowed to be made from skimmed milk-for example, Parmesan, Dutch, and some Dorset cheeses-and, after all, what one person had the right to do could not well be denied to another.I n fact, he had gradually come to consider that cheese was now one of those products which were entirely manufac- tured, and that the question was one in which the public and not the analyst must be the final arbiter. Mr. JOHN WHITE thought that all that Mr. Cribb wanted was what he himself had wanted when he was concerned in a similar campaign which had resulted disastrously-namely, not to stop the sale of the article, but to let it be sold for wbatTHE ANALYST. 111 it was, viz., skim-milk cheese. It was right that the skill of the manufacturer should be taken into account, provided that the article made was being improved; but here the skill of the manufacturer had been employed to produce, not an improved article, but one of diminished value, With regard to the position of the public as the ultimate arbiter, he could not conceive that anybody would buy this stuff a second time.After being kept for two or three days it became exceedingly hard. Per- sonally, he considered it a gross fraud to sell as cheese, or as Dutch cheese, an article containing only 1.6 per cent. of fat. As to the estimation of the fat, he had found that such small quantities could only be accurately determined by what was practically the Werner-Schmidt process-namely, by boiling with water and hydro- chloric acid, cooling, and shaking out with ether.Mr. FISHEX drew attention to the results shown by a sample purchased as Dutch cheese, which he had analysed in 1903. It contained only 1.6 per cent. of fat, with 57.1 per cent. of water and the vendor was in consequence fined $10. Mr. CRIBB, in reply, said that he had adopted practically the same method of fat estimation as Mr. White. He could confirm what Dr. van Rijn had said as to direct extraction with ether. When the quantity of fat was large the error was, for prac- tical purposes, of no consequence, but with a small percentage of fat the error, which was still about the same in absolute weight, bore a larger proportion to the total. It seemed to him that if the manufacturer of cheese were to have an entirely free hand he might make an article containing nothing but casein, water, and a little mineral matter, but nobody would pretend that to the consumer that was Dutch cheese as ordinarily understood. As to the suggested difficulty of notification, he could not see any difference between the case of cheese and that of butter and margarine, with regard to which provisions as to labelling were already in existence. If the Sale of Food and Drugs Acts were carried out properly, any radical change in a well-known article of food would be discovered at once. Under the present conditions any such change was, as a rule, not found out until it had been so long in operation as to become an established trade custom, which could not be altered without incon- venience and ioss to many. All this pointed to the necessity for a, more thorough application of the Sale of Food and Drugs Acts, and for the taking of much larger numbers of samples than were taken November 22, 1906.

ISSN:0003-2654    

DOI:10.1039/AN9063100105

出版商:RSC    

年代:1906

数据来源: RSC

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THE ANALYST. 111 ORDINARY MEETING OF THE SOCIETY. THIS was held on Wednesday evening, March 7, in the Chemical Society’s Rooms, Burlington House. The President, Mr. E. J. Bevan, occupied the chair. The minutes of the previous meeting were read and confirmed. Certificates of proposal for election to membership in favour of Messrs. G. Craig, J. B. Gall, H. N. Hanson, B. W. Methley, F. D. Ratcliff, and F. Robertson, were read €or the second time ; and certificates in favour of Messrs. Ernest Quant, 2, Park112 THE ANALYST. Crescent, Torquay, analytical chemist ; Frederick Wilson Montrose ROSS, 21, Soh0 Square, London, W., analyst to Messrs. Crosse and Blackwsll, Ltd.; and Frank Ernest Thompson, A.R.C.Sc., A.I.C., the Laboratory, Walsall, analytical and consulting chemist, were read for the first time. Messrs. S. Dickson, J. Evans, F. Hughes, G. Patterson, and H. Thompson, were elected members of the Society. The following papers were read : A Simple and Rapid Method for the approxi- mate Estimation of Boric Acid,” by Cecil H. Cribb, B.Sc., and F. W. F. Arnaud ; (‘ Analysis of a Sample of Air extinguishing Flame,” by Bertram Blount ; “ The Detection of Cocoanut Oil in Butter,” by Arthur W. Thorp ; and (( The Composition of Milk,” by H. Droop Richmond.

ISSN:0003-2654    

DOI:10.1039/AN9063100111

出版商:RSC    

年代:1906

数据来源: RSC

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112 THE ANALYST. ABSTRACTS OF PAPERS PUBLISHED IN OTHER JOURNALS. FOODS AND DRUGS ANALYSIS. A New Centrifugal Method for Determining Fat in Milk - Wendlep’s Method. Von Kuttner and Ulrich. (Zeit. ofentL Chem., 1906, xii., 41-58.)-The process consists in mixing the milk with a saline solution, adding a little isobutyl alcohol, and subjecting the mixture to centrifugal action, the procedure being similar to that of Gerber’s method. The saline solution employed contains tartrates, sodium chloride, and sodium hydroxide (proportions not given). Eleven C.C. of this solution, 10 C.C. of the milk to be tested, and 0.6 C.C. of isobutyl alcohol are successively intro- duced into a butyrometer tube and the latter then closed with an indiarubber stopper. The contents of the tube are mixed, the tube is immersed for two or three minutes in water at a temperature of 45” C., and then submitted to centrifugal action in the usual way.The surface separating the fat from the saline solution is quite horizontal, rendering the reading of the volume of the fat an easy matter. If the contents of the tube have been well mixed, no flocculent layer ever occurs between the fatty and aqueous layers. The results obtained, as shown by 360 comparative determinations, agree with those yielded by Gerber’s method. w. P. s. A Rapid Method for the Detection of Traces of Zinc in Wort, Beer, Wine, etc. J. Brand. (Ztschr. ges Brauw., 1905, xxviii., 440; through Chem. Zed. Rep., 1906, xxx., 25.)-The liquid to be examined is acidulated with hydrochloric acid, and a few drops of potassium ferrocyanide solution are added.The presence of even a, trace of zinc will cause a flocculent precipitate of zinc ferrocyanide to be produced, which, being mixed with much albumin, settles rapidly, and may be readily filtered after decanting the bulk of the liquid. The washed precipitate is ignited, and theTHE ANALYST. 113 residue treated with acetic acid; in the solution obtained zinc is identified with hydrogen sulphide. As little as 1 part of zinc in 500,000 parts of beer, etc., can be readily detected by this method. A. G. L. Hordenine: A New Alkaloid extracted from the Germ of Barley. E. Leger. (Journ. Pharm. Chim., 1906, xxiii., 177-181.)--A crystalline alkaloid has been separated by the author from the dried germs of malted barley.It was first obtained in ethereal solution by meam of Stas' method, and the residue left on evaporation purified by repeated crystallization from alcohol and decolorized with animal charcoal. The yield of hordenine appears to vary with the temperature at which the malt was dried, and the author has obtained from 0.22 to 0.45 or 0.5 per cent. from different germs. The alkaloid crystallizes in orthorhombic prisms, which show double refraction. They are anhydrous, colourless, and almost tasteless, and melt at 117.8' C. (corr.) to a colourless liquid. Hordenine slowly sublimes at its melting-point and rapidly at 140' to 150'. It is readily soluble in alcohol, chloroform, and ether, less soluble in benzene, only slightly soluble in water, and almost insoluble in cold petroleum hydrocarbons. It dissolves easily in hot carbon tetrachloride, but separates out almost quantitatively on cooling.It acts as a, strong base, giving a red coloration with phenolphthalein and displacing ammonium from its salts in the cold. It gives no coloration with strong sulphuric acid, and is hardly attacked by a hot concentrated solution of potassium hydroxide. On the other hand, it reduces potassium permanganate in acid solution, hot silver nitrate solution, and iodic acid solution, yielding a precipitate of iodine. Its formula, calculated from the composi- tion of its salts, is C,,H,,NO. I t is a tertiary monoacid base, and thus forms only a, single series of salts, all of which are very soluble in water. C. A. M. Determination of Chloral Hydrate.T. E. Wallis. (Pharm. Journ., 1906, vol. 76, 162, 163.)-The method proposed consists in heating the chloral hydrate with sodium hydroxide in alcoholic solution and titrating the sodium chloride formed. The determination of the amount of sodium hydroxide absorbed gives untrustworthy results (cf. ANALYST, 1903, xxviii., 189), unless strict conditions be adhered to. The details of the method are as follows : A weighed portion of from 0.1 to 0.4 gram of the chloral hydrate is dissolved in about 10 C.C. of the alcohol, and introduced into a, thick-walled bottle. A measured volume of $ sodium hydroxide solution is added, the bottle is closed by an indiarubber stopper, which is tied down, and the bottle with its contents heated for three hours in a water-bath. After cooling, the solution is neutralized with sulphuric acid, using phenolphthalein as indicator, and then titrated with & silver nitrate solution.The reaction is represented by the equation, CCl,CH(OH), + 5NaOH = 3NaC1+ 2HCOONa + 3H20. I t is important that the contents of the bottle during the heating contain at least 50 per cent. of alcohol by volume. w. P. s.114 THE ANALYST. The Determination of Traces of Chloroform. M. Nicloux. (Comptes Rendus, 1906, cxlii., 163-165.)-Chloroform when present in alcoholic solution in a quantity not exceeding 0.1 gram can be determined by diluting the liquid to 60 C.C. with alcohol, and boiling it for an hour under a reflux condenser with 10 C.C. of a 10 per cent. alcoholic solution of pure potassium hydroxide. When cold, the contents of the flask are mixed with 15 C.C.of water, exactly neutralized with phenolphthalein as indicator, and treated with potassium chromate, and the chlorine titrated with standard silver nitrate solution (8.535 grams per litre), each C.C. required representing 2 mgms. of chloroform. Air containing chloroform is analysed by being drawn through alcohol (95 per cent. strength), contained in two absorption vessels, at the rate of 1 litre in half an hour, and the absorbed chloroform is then determined as above described, In the case of blood and aqueous liquids it is necessary to add strong alcohol (80 to 95 per cent.), acidified with 0.25 gram of tartaric acid in the proportion of 5 parts to 1 of the sample, and to distil the mixture in a fractionating flask until about third has passed over.The distillate is received in 10 C.C. of 95 per cent, alcohol, and the chloroform determined as before. The results thus obtained are invariably 1-5 to 2 per cent. too low. C. A. M. The Constituents of Myrrh. A. Tschirch and W. Bergmann. (Archiv. Pharm., ccxliii., 641 ; through Pharm. Journ., 1906, vol. 76, 128.)-Picked Somali myrrh was found to have the following composition : Soluble in alcohol (resin and oil), 28 to 30 per cent, ; insoluble in alcohol (gum and enzyme), 61 per cent. ; im- purities, 3 to 4 per cent. ; moisture, 5 per cent. Part of the substances soluble in alcohol was insoluble in ether, the remainder (about 21 per cent. of the myrrh) being soluble. The portion insoluble in ether was redissolved in alcohol, and separated by precipitation with lead acetate into a-heerabo-myrrholol and P-heerabo-myrrholol, the latter remaining in solution. These substances were obtained in the form of yellowish-brown and grayish-brown amorphous powders respectively.The portion of the alcoholic extract soluble in ether was dissolved in this solvent, and treated with potassium hydroxide to remove a-and 6-heerabo-myrrhol, which were afterwards separated by means of lead acetate, when they were obtained as grayish-yellow powders, The ethereal solution was next evaporated and distilled in a current of steam. By this means a residue of heerabo-resene was obtained in the retort, whilst the distillate consisted of yellow oil. The latter had a specific gravity of 1.046, rapidly resinified, and bore no relation to the resin acids, resinotannols, resinols, etc., found in other resins.The substances insoluble in alcohol, consisting of the gum and enzyme, could not be separated from one another. In addition to these substances, myrrh also contains a bitter principle, but all attempts to isolate it failed. The gum yielded arabinose on hydrolysis. w. P. s. Determination of Cinnamic Acid in Storax. D. Hooper. (Pharm. Journ., 1906, vol. 76, 107.)-The determination of the amount of cinnamic acid in storax is proposed as a method of detecting the presence of adulterants in this balsam.THE ANALYST. 115 Tschirch and Itallie have shown that true Oriental storax contains 23 per cent. of cinnamic acid, and other investigators have concluded that the percentage of the acid should not fall below 20.A weighed quantity of the storax is saponified in alcoholic solution with potassium hydroxide, evaporated to remove the alcohol, the residue dissolved in water, and the solution shaken out with ether to remove unsaponifiable substances. The solution is then treated with sulphuric acid in excess, and the voluminous precipitate collected on a filter and washed. The precipitate is next dissolved in hot water, and the crystals which separate on cooling are collected, dried, and weighed. w. P. s. Adulterated Santal-Wood Oil. E. J. Parry. (Chemist alzd Druggist, 1906, lxviii., 211.)-The low price of large parcels of this oil imported from Germany caused suspicions to arise as to the purity of the oil, and the author has recently examined a sample which enabled him to definitely decide the nature of at least one of the adulterants present.The oil had a specific gravity of 0.970 a t 15' C., an optical rotation of - 14' in a 100 mm. tube, was soluble in 5 volumes of 70 per cent. alcohol, and had an apparent santalol value (free) of 93.5. By repeated fractionation under reduced pressure a small amount (about 5 per cent.) was obtained, which boiled at 220' C. at ordinary pressure. The specific gravity of this fraction was 0,943, and the refractive index 1.4823 a t 20' C. The odour left no doubt as to its being terpineol. This was confirmed by the melting-point (115' C.) of the nitroso- chloride yielded by the fraction. w. P, s. The Purity of Balsam of Peru, Utz. (Phar?n. Post,, xxxix., 21 ; through Pharm.Jouriz., vol. 76,129.)-Adulteration of this balsam is, according to the author, the rule rather than the exception. Turpentine and gurjun balsam appear to be the favourite adulterants, and the usual tests often fail to detect them. Such adulterated balsams may show a cinnamein content of 50 to 60 per cent. The physical characters of the cinnamein obtained sometimes indicate sophistication. It should be brown and homogeneous, whereas with turpentine it is often granular or even solid. The refractive index gives more satisfactory results, as for pure balsam the value varies from 1,5862 to 1,5878 at 15' C. ; whilst the refractive index of gurjun balsam is 1.5142; of castor oil, 1.4809; and of paraffin oil, 1.4821. On the other hand, perugen, which is a factitious substitute for balsam of Peru, possesses a refractive index of 1.5863. Perugen, however, gives an intense olive-green coloration with Ccesar and Loretx's nitric acid test, instead of the golden yellow yielded by pure balsam of Peru. TOXICOLOGICAL ANALYSIS. Toxicity of Cyanogen Compounds towards Fish. J. Hasenbaumer. (Zed. Uutersuch. Nahr. @eizussn%., 1906, vol. 11, 97-101.)-The author has carried out a considerable number of experiments regarding the action on fish of certain cyanogen compounds when the latter were added to the water in which the fish lived, The investigation was in connection with an inquiry regarding the discharge of effluent containing traces of these compounds. Potassium cyanide was found to be extremely w. P. s.116 THE ANALYST. poisonous to fish, 0.0018 gram per litre of water killing tench and goldfish in a very short time The following quantities per litre of other cyanogen compounds also killed fish of these species : Potassium ferrocyanide, from 1-5 to 3.0 grams ; potassium ferricyanide, from about 1.7 grain ; potassium or ammonium thiocyanate, about 1.5 gram. w. P. s.

ISSN:0003-2654    

DOI:10.1039/AN9063100112

出版商:RSC    

年代:1906

数据来源: RSC

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116 THE ANALYST, ORGANIC ANALYSIS. Temperature of Combustion of Methane in presence of Palladiumized Asbestos. (Journ. SOC. Chem. Ind., 1905, xxiv., 1202.)-An investigation undertaken to ascertain to what extent methane is burnt when passed over palladiumized asbestos in presence of oxygen has shown that (1) the tempera- ture of combustion of a mixture of 1 volume of methane with 2 volumes of oxygen lies between 514' and 546'; (2) an increase in the speed at which the gases are passed through the tube causes a decided increase in the temperature of combus- tion; (3) a variation in the volumes of the gases influences the temperature of com- bustion, tending to raise it beyond the above-mentioned range ; and (4) the addition of hydrogen, even in large quantities, does not cause the methane to burn at a lower temperature.I t is concluded, therefore, that the usual method of fractional com- bustion of hydrogen gives reliable results, if the temperature does not exceed 500" to 550'. The catalytic action of the metal does not appear to be due to superficial oxidation, and in no case has anything approaching complete combustion been observed, even when the gas was 100' above its combustion temperature. H. J. Denham, W. H. S. The Volumetric Determination of Pentoses. A. Jolles. (Berichte, 1906, xxxix., 96, 97.)-From 0.2 to 1.0 gram of the substance under examination is treated with 200 C.C. of hydrochloric acid (specific gravity 1*06), and distilled in a current of steam until Bids reagent shows that no more furfural is formed, an additional 100 C.C.of the hydrochloric acid being introduced into the flask during the distillation. The furfural is now determined in an aliquot part of the distillate by treating it, after neutralization, with a known excess of standard potassium bisulphite solution, and titrating the excess with standard iodine solution after the mixture bas stood for two hours : C,H,O.COE + EKSO, = C,H,O.CH(OH)SO,K. Each C.C. of normal bisulphite solution is equivalent to 0.07505 gram of pentose. C. A. M. The Detection of Olive Oil extracted by Means of Carbon Bisulphide in Soap. J. Vamvakas. (Ann. de Chim. Anal., 1906, vol. 11, 53, !%.)--The soap manufactured in Crete is prepared almost exclusively from olive oil, and the author has long used the following simple method for determining whether the original oil had been extracted by means of carbon bisulphide: 2 grams of the soap are dissolved in 100 C.C.of 95 per cent. alcohol, the solution filtered, and its colour noted. If colourless or gray the oil was obtained by mechanical expression, whilst a yellow colour (with green fluorescence) indicates soap prepared from anTHE ANALYST. Specific Gravity. -- 0.9126 (21" C. 0.9120 (21" C. 0.9140 (l8O C. 0.9134 (18" C. - - 3,9389 (19" c. 3.9384 (18" c. 3.9160 (20" C. 1.9230 (23" C., 1.9130 (20° C. )'9120 (21' C.; - - - - - - 1.9136 (15' C.) )*910d (21" C.) 1.9108 (18" C.) 1.9604 (20" C.; 1.9596 (18" C.) 1'9161 (19O C.) ,09144 (22" C.) - - - - .I - - 0.9247 (14" C.) 0.9250 (15" C.) 0.9206 (20" 0.) - 117 extracted oil. The addition of a green or yellow dye-stuff, soluble in alcohol, to the soap is stated not to interfere with the test, since in that case the green fluorescence of the solution is even more pronounced (cf.ANBLYST, xxx., 313). C. A. M. On the Behaviour of the most Important Vegetable Oils towards Polarized Light. M. A. Rakusin. (Chem. Ztg., 1906, XXX., 143.)-The author suggests that animal and vegetable oils may be distinguished from mineral oils by means of polarized light, and has compiled the following table : OIL. A. LIQUID OILS. 1. Nowdrying Oils. Olive oil (Ob. olivarum) ,, (church use) .. ,, (gallipoli) .. Earth-nut oil ... .. 9 7 ... .. 9 9 ... .., Croton oil ... .. A1&6d oil (swkk't) . . ,, (Persian) ... 9 ) ,.. ..a ... ... olivi 'oil ... ... ,, (Provence oil) <.. oil (Prenci j .. . ,, (Japanese) ... $ 9 ... ... 9 9 ... ... ,, (01. raparum) ,, (refined) ... . . . Castor oil (Italian) 9 , 9 9 9 ... ... ... . . 4 ... ... Musiard oil (Sarepta) . . . ,, (black) ... Sesame oil (cold pressed) ,, (hot pressed) ,, 1878 ... ,, 1882 ... ,, 1882 ... ,, (Indian) ... ,, (01. sesame Gallicum) ,, 11. ... ... ... ... Must&d oil (white). Colour, etc. Yellow. Yellowish green. Y , 7 9 - - Dark 1 yellow. Light * yellow. I - - - Light yellow. j - - - Light yellow. - - Dark yellow. - - - - - - - Light yellow. - Ventzke with a Tube of Mm. 200 -- + 0-6 + 0.2 Opaque., -I- 0.2 - 0.4 - 0.31 ;o + 1-15 + 14-5 + 43 - 0'1 <- 0.1 - 0.7 + 0-6 + 0.2 f 0'3 - 2.1 - 1.6 - 0'23 D - 0'46 - 0.2 - 0.1 - 0.2 + 8.0 + 8.4 c+ 8-65 + 40.7 - 0.5 Opaque. + 3.1 + 7.2 + 4% -t 3.9 + 9.0 + 7.7 + 1.9 + 2-4 + 2.3 - 0.43 Analyst.i R* B. c. L. P. B. B. R. R. B. B. c. L. 1 R. I R. t R. w. P. - R. - B. - R. c. L. Remarks. Dark, with 200 mm. tube. - 7' to +24', with a Laurent. Benzene is with- out influence. Huil d'olive surfine. -5' to -10' with a Laurent, Belgian Go., Odessa. J. K. Glitschin, Sarepta. -9' with a Laurent. * B., Bischop ; C. L., Crossley and Le Sueur ; R., Rakusin ; W., Walden.THE ANALYST OIL. A. LIQUID OILS (continued). 2. Drging Oils. Cotton-seed oil ... Garden cress oil .. . Hemp-seed oil (raw) . . . Linseed oil (raw) > > > 7 ... ... Canieline oil ... Poppy-seed oil ... > > 9 9 a * * > > 9 7 - * a Niger-seed oil ... Walnut oil ... ... ' 6 Saiiior ' 9 oil ... Sunflower oil . . . ... ...a . . ... ... . .. ... ... ... ... ... P,. SEMI-SOLID ASD SOLID 011,s. Cocoanut oil ... .., 1 . Visco us 0% Is. Cocoanut oil in 50 pel cent. benzene solution Palm oil ... .., Palm oil in 50 per cent. benzene solution. 2. Solid Oils. 'Coca0 butter ... .. Cocno butter in 50 pel cent. benzene solution OTHER OILS. Laurel oil ... .. Laurel oil in 25 per cent Jasmine oil (01. jasstin Wild seed oil (01. resccla ether solution. pingue). pinpe). Colour, etc. -- Light yellow. bark green Dark - yellow. - - Dark yellow. - - Light yellow. - Almost :olourless. - - Light yellow. Nhite anc viscons. 2olourless Yellow paste. Light yellow. Pale yellow. Light yellow. Green paste. Green. Almost eolourless Yellow. Specific Gravity. -- 1.9220 (22" C.) 1.9256 (22" C. I 1'9314 (21" C.) - - - 0.9'230 (21" C.: - - 0.9219 (20" c.; - 0.9238 (18" C.: - - 0'9195 (22" C.: 0'9264 (20" C.- 0.9508 (18" C. - 0.9702 (20" C. - 0.9335 (19" C. - 0'9054 (IS" c. 0.9122 (18" C. O Veritzkc with a Tube of Mm. 2 00 -- - 0'1 0 0 paq ae . 7 9 - 0'3 + 0'28 - 0'1 0 to 0.17 0 + 0.1 0 to 0.86 + 0.15 - 0.3 -I- 0.17 to 0.66 + 0.1 Not exan + 0'19 x 5 Not exan 0.1 x 2 Not exan 0'1 x 2 Not exan - + 0.9 + 0.6 malyst. R. c. L. R. R. 3. c . L. R. c. L. B. R. c. L. R. B. c. L. R. - R. R. R. R. R. R. Remarks. -- !otton oil (OE. GossypX) . nactive oil. piltered. t 6 ' with a Lauren t. I" to + 4 with a Laurent. nactive. 1" to + 18' with a Laurent. -4' to +14' with a Laurent. 3- ystalline structure. Tasteless. A. G. L.THE ANALYST. 119 Detection of Artificial Colouring Matter in Fats.A. Olig and J. Tillmans. (Zed Untersuch. Nuhr. Genussm., 1906, vol. 11,94.)--If, during the rendering of a fat, the proteid matter be charred through over-heating, the fat becomes more or less tinted, and imparts a yellow colour to the acetic acid .ased in the test described by Sprinkmeyer and Wagner (cf. ANALYST, 1905, 244). I n case a coloration is obtained, the fat should be extracted with alcohol (which is also coloured by the oharred proteid matter), and the solution further tested for the presence of coal-tar dyes, etc. w. P. s. On the Detection and Determination of Paraffin Wax in Mixtures with Ceresin. F. Ulzer and F. Sommer. (Chem. Zeitg., 1906, xxx., 142.)-Various methods of examining mixtures of paraffin wax and ceresin are discussed. The best appears to be the determination of the refractive index at 90" C., the refractive index of paraffin wax with solidifying points varying from 50" to 60" C.lying between 2.0 and 4.0, whilst the values for ceresins solidifying between 68" C. and 71" C. vary from 11.5 to 13. A sample of German paraffin, however, with a solidifying point of 38" C. gave the high refractive index of 6-81. If only a small quantity of paraffin is present, it may be concentrated by boiling 5 grams of the sample for ten minutes with 100 C.C. of 95 per cent. alcohol, filtering hot, and evaporating, the refractive index of the residue obtained being compared with that of the original. Conversely, if only a small quantity of ceresin is present, 5 grams of the sample are dissolved in 50 C.C.of carbon bisulphide, and 100 C.C. of ether are added. Alcohol is then slowly added, the temperature being kept at 25" C. until a copious precipitate is obtained, which is washed with alcohol and ether, dried, and examined for ceresin. Good indications are also obtained by using Crismer and Motton's method of determining the critical temperature of solution in various solvents, ethyl alcohol being preferred. The critical temperature of solution of various paraffins was found to be, in ethyl alcohol, 155.5" to 158 ; amyl alcohol, 47" to 54" ; acetone, 67.5" to 77" ; and acetic anhydride, 163" to 176" ; whilst some samples of ceresin gaxe the values 68" to 71°, 174" to 177O, '73*5" to 76", 95" to 98", and 191" for the same solvents. A differentiation may also be made by capillarity, ceresin rising much less in filter-paper than does paraffin (6 cm.as against 10 cm. in one hour at 100" C. in the case of two samples compared), A. G. L. Determination of Fatty Acids in Textile Soap. Gerhard Kruger. (Chem. Zeit., 1906, xxx., 123.)-Ten grams of the cut-up soap are weighed out into a tared porcelain crucible of 150 C.C. capacity, dissolved in water, and heated with 20 C.C. of dilute (1 : 10) sulphuric acid on a water-bath until the fatty acids have become clear, From 5 to 10 grams of beeswax are then stirred into the fatty acids, and the whole allowed to cool. The solidified fatty cake is then lifted out of the crucible, the acid is poured out, and the cake treated with successive quantities of water until the latter ceases to show an acid reaction.The crucible and fat are then dried for one hour at 70" C., moistened with alcohol and dried for another hour at 10.0" C., after which they are weighed. The error due to any fatty acid passing into solution in the acid liquid120 THE ANALYST. may be neglected, since even for palm-nut oil soaps it is quite small, whilst cocoanut oil is not used for making textile soaps. A. G. L. Note on Commercial Oil of Turpentine. W. Vaubel. (Zed Ofensaztl. Chem., 1905, xi., 429-432.)-The author recommends the determination of the bromine absorbing power as a means of distinguishing between genuine oil of turpentine and its adulterants. American oil of turpentine was found to have a bromine value of 110 to 115 ; Russian, 72 to 97 ; resin '' essence " (a product of the distillation of resin), 89.The figures express the grams of bromine required per 100 grams of oil. Russian oil of turpentine is distilled from the roots of the trees, and is an unsatis- factory substitute for the genuine oil. w. P. s. The Physical Characteristics of Certain Copals. Bottler. (Chem. Rev. Fett a. Harx. Ind., 1906, xiii., 1-5.)-A comparative examination has been made of the characteristics of all the more important copals met with in commerce, many of the results being in tabular form. The physical properties included the appearance of the surface, the colour, transparency, lustre, appearance on fracture, specific gravity, hardness, fusibility and solubility. The specific gravities of the copals in most demand ranged from 1.03 to 1-07 for the substance containing air-bubbles, a higher value being obtained after removal of the air. Speaking generally, the smaller the difference between the densities determined before and after removal of the air, the more valuable the copal.Thus the following differences were observed : Lindi copal, 0.001 ; Zanzibar copal, 0.0015 ; red Angola copal, 0.014 ; Brazil copal, 0-014 ; Cameroon copal, 0.015 ; Manila copal, 0.059 ; Hymenea (South-American) copal, 0.0615; and Kauri copal, 0.064. In the author's opinion the Brazil copal is really a West African and not an American copal. The degree of hardness is an important factor for distinguishing between the different kinds of copals. The hardest is Zanzibar copal, and the other important kinds can be ranged in the following scale : Hard- Mozambique, Lindi, red Angola, Sierra Leone (Kiesel), yellow Benguela, white Benguela, Cameroon, and Congo copals ; Medium-Manila, white Angola, and Kauri copals ; Soft-Sierra Leone (new), Hymenea, and Brazil copals.The melting-points of copals range between 90" and 360" C. The following results were obtained by the author: Hymenea, 95" C.; Cameroon, 108" C.; Manila, 112" C. ; Manila (yellow, hard), 135" C. ; Kauri, 126" C. ; Kauri, 140" C. ; yellow Benguela, 170" C. ; white Benguela, 175' C. ; Congo, 180" C. ; Sierra Leone, 185' C. ; Kiesel, 220' C. ; white Angola, 245" C. ; Lindi, 246' C. ; Zanzibar, (a) 259" C., ( b ) 265" C.; and red Angola, 305" C. The solvents tried included chlorhydrin, terpineol, and carbon tetrachloride, in addition to the older solvents.A rapid method of dissolving copals (e.g., West African varieties) consists in heating them for forty-eight hours at 100" C., mixing them with sand or glass powder, digesting the mixture for twenty-four hours with anhydrous ether, and finally adding an equal quantity of hot alcohol. Turpentine oil has usually only a solvent action on copals when it contains ozone. The different copals can be arranged in the following order as regards their solubility in the solvents most commonly employed : White Angola,THE ANALYST. 121 Manila, Kauri, Brazil, Congo, Sierra Leone, yellow Benguela, red Angola, white Benguela, Kiesel, Cameroon, Lindi, and Zanzibar copals. C. A. M. Recovery of Iodine from the Residues obtained in Hubl's Method. A. olig and J.Tillmans. (Zeits. Untersuch. Nahr. Genussm., 1906, vol. 11, 95-97.) -The solutions obtained after the final titration in determinations of the iodine value of fats by Hubl's method are collected until a, good quantity is obtained. After removing the chloroform by means of a separating funnel, the aqueous portion is rendered strongly alkaline with sodium hydroxide, and evaporated as far as possible. The mercury compounds (oxide, basic carbonate, and some metal) are filtered 0% washed, and the filtrate again evaporated to dryness and ignited. A little mercury will still be present, and care must be taken during the ignition. The residue is dissolved in water, filtered from any insoluble matter, and the solution then rendered strongly acid with hydrochloric acid.The mixture is now warmed, and a concen- trated potassium bichromate solution is added until all the iodine has been precipi- tated. The liquid is then decanted, the iodine is washed with a small quantity of water, and distilled from a retort in a current of steam. The distilled iodine is collected in a well-cooled receiver, from which it may be readily removed in its wet state, and then dried or sublimed. w. P. s. Notes on the Determination of Calorific Values by means of the Bomb. I). Aufhauser. (Zeits. angew. Chem., 1906, xix., 89.)-In order to make the temperature corrections as small as possible, the water used should be initially as much below the normal temperature as it is finally above it. The temperature of the water in the calorimeter may be most conveniently adjusted for this purpose by putting colder water into the calorimeter, placing the bomb in position, starting the stirrer, and then warming the whole to the required temperature by means of a small electric heater, preferably a cylindrical electrical lamp.The lamp should be wetted before it is plunged into the water in order to obviate the error due to adhering water when it is taken out. A. G. L. The Volumetric Determination of Organic Hydrosulphides and Thio Acids. P. Klason and T. Carlson. (Berichte; 1906, xxxix., 738-742.)-Titration of organic hydrosulphides with an aqueous solution of iodine gives under suitable conditions quantitative results in accordance with the equation : 2R. SH + I, = R,S, + 2HI. Thiocyanic acid, however, does not react in this way.The presence of bicarbonate is not only unnecessary, but may lead to further oxidation. The weighed quantity of the hydrosulphide is dissolved in alcohol and titrated with N-iodine solution until a faint yellow colour appears. I t is essential that there shall be sufficient alcohol present to keep the bisulphide formed in solution, since otherwise it too can absorb iodine, and the results will be too high. The resulhs of test experiments with different classes of thio compounds, such as p-thiocresol, methyl and ethyl hydrosulphides,122 THE ANALYST. thioglycollic, and thioacetic acid, show that the method is capable of great accuracy. Rosenheim and Davidson found that the reaction between thioglycollic acid and iodine in sodium bicarbonate solution gave a, quantitative yield of dithioglycollic acid; but the author finds that the results thus obtained are not constant, and are invariably too high owing to further oxidation with the formation of thioacetic acid. This latter acid, too, also undergoes further oxidation in a bicarbonate solution, acetyl- bisulphide being produced.Aromatic hydrosulphides--e.g., thiophenol, P-thionaphthol, and p-thiocresol- are so strongly acid that they form salts with alkalies in neutral solutions, and can therefore be titrated with standard alkali solution, phenolphthalein being used as indicator. The more carbon the molecule of the compound contains, the greater the accuracy of the results. With alipathic hydrosulphides the end reaction is not sharp, and thioglycollic acid cannot be titrated with alkali.either in aqueous or alcoholic solution. C. A. M. On Quantitative Determination by Means of the Immersion Refracto- meter. H. Matthes. (Chem. Ztg., 1906, xxx., 101.)-The author severely criticises some applications of the use of the immersion refractometer made by Wagner (Ztschr. ofentl. Chem., 1905, xi., 404), especially in the case of sugar analysis. For legitimate uses of the instrument, such as the control of beer, wine, etc., prepared in the same way and under the same conditions, and the control of the strength of standard solutions, he refers to his own work (Ztschzr. arzalyt. Chem., 1904, xliii., 83). A. G. L. Simplified Ultimate Organic Analysis for Scientific Purposes. M. Denn- stedt. (Chem. Zeit. Rep., 1905, xxix., 390.)-In the use of the simplified method (see ANALYST, xxx., 135) of the author a diiliculty arises from the fact that, as some substances require different treatment in the combustion, these must be burnt in succession.The chief point of the “quick” method is that the boat containing the sub- stance is not placed directly in the combustion tube, but in a, narrow, hard glass tube, which may take any of three forms : (1) The form open at both ends, a, ’Fig. 1 ; The author now suggests some improvements. FIG. 1. (2) that with the hinder end closed, b, Fig. 1; or (3) that with a double current of oxygen, Fig. 2. The last named is fitted with a capillary and a bubble counting arrangement through which the oxygen enters the inside of the tube. AT-piece of somewhat wider bore fits over the capillary, and is provided with a cork to fit into the main combustion tube. The main current of oxygen passes through the calcium chlorideTHE ANALYST. 123 tube and the side tube of the T-piece. The bubbling apparatus and the calcium chloride tube are each connected to the ordinary drying apparatus by rubber tubing, which allows the tube to be withdrawn with one hand for introduction of the boat, etc. Form a is suitable for the combustion of substances which decompose slowly, with formation of much carbon difficult to burn--e.g., sugar, albumin; form b is for use with easily volatile or moderately volatile substances, which do not give a separation of difficultly combustible carbon-e.g., alcohols, benzol, aniline, etc. The third kind of tube is serviceable for all substances without exception. The regulation of the combustion is especially easy, as this can be effected not only by the flame, but also by increasing or diminishing the rate of the inner current of oxygen. The tubes can be obtained from Emil Dittrnar and Vierth, Hamburg. E. K. H.

ISSN:0003-2654    

DOI:10.1039/AN9063100116

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年代:1906

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THE ANALYST. 123 INORGANIC ANALYSIS. The Estimation of Opalescent Silver Chloride Precipitates. Roger Clark Wells. (Amer. Chem. Joz~rn., 1906, vol. 35, 99.)-A number of small pre- cautions are described, which must be used in connection with the nephelometer (ANALYST, 1905, xxix., 203). It is found that ground-glass standards are to be preferred, and that for every concentration a suitable solution and excess of pre- cipitant are required. It is also shown that the presence of electrolytes both augments the maximum opalescence and hastens its dissppearance through coagulation. The best procedures in a number of special cases are also described. A. G. L. The Volumetric Determination of Copper. G. Denigbs. ( A m . de C h h . anal., 1906, vol. 11, pp. 10-12.)-Ammoniacal solutions of cupric salts form double colourless compounds with alkali cyanides, thus : CUSO, + 4NH4CN = (NHJ,SO, + Cu(CN),.2(NH),CN.The double cyanide thus formed is very stable, but gives up a, portion of its cyanogen on treatment with silver ritrate, the amount varying, e.g., with the degree of alkalinity of the liquid. The author has found that when the quantity of the copper salts taken contains from 1 to 50 mgms. of the metal, whilst 20 C.C. of & potassium cyanide solution and 2.6 grams of ammonia are used, the total amount124 THE ANALYST. of liquid being 120 c.c., each cgm. of copper gives up to the silver an amount of cyanogen equal to 2.5 C.C. of the potassium cyanide solution, or in other words each C.C. of cyanide solution is equivalent to 4 mgms.of copper. In making a determina- tion, a quantity v of the solution of the cupric salt containing not more than 50 mgms. of copper is treated with a volume w’ of ammonia solution containing 2.6 grams of ammonia, and with 20 C.C. of -& potassium cyanide solution (standardized on the silver nitrate solution). Then, after the addition of 1 C.C. of a 10 per cent. solution of potassium iodide, and 99 - (v + w’) C.C. of water, the liquid is titrated with & silver nitrate until there is a faint but persistent turbidity. If n C.C. be used, the value (20 - n) C.C. represents the cyanide taken up by the silver, and (20 - 72) x 0.004 gram gives the amount of metallic copper in the amount, v, of solution taken. I n order to obtain concordant results it is necessary that the volume of w + v’ should not exceed 100.In testing cupric sulphate by this method the presence of zinc does not inter- fere with the results unless it amounts to 40 to 50 per cent, of the quantity of the copper salt. Volumetric Determination of Copper and Mercu~y in Admixture with Each Other.- A quantity v (not exceeding 100 c.c.) of the solution, which should not contain more than 0.5 gram of mercury and 0.1 gram of copper, is treated with 5 C.C. of hydro- chloric acid (specific gravity 1-18>, and 5 C.C. of a solution (1 : 5) of cystallized sodium phosphite, and boiled for five minutes with continual agitation, after which it is filtered, and the filtrate and wastings made up to 150 C.C. The copper is then deter- mined in 75 C.C. of this liquid in the manner described above, with the difference that it is necessary t o add a constant of 0.8 C.C.to the volume of silver nitrate, n, con- sumed, to make up for the modification in the reaction caused by the added salts. The precipitate (containing the mercury) left on the filter is detached with the aid of a fine jet, and treated with 5 C.C. of water, 5 C.C. of hydrochloric acid, and 0.25 gram of potassium chlorate, the whole being heated until solution is complete, and the liquid then cooled and made up to 100 C.C. An aliquot portion (a c.c.) of the solution is now mixed with 12 C.C. of ammonia solution (25’ BQ., S.G. 09), 10 C.C. of TG potassium cyanide solution, 100-n C.C. of water, and 1 C.C. of a 10 per cent. solution of potassium iodide, and titrated with TG silver nitrate solution. If q C.C.be used, (10 - q ) = n represents the amount of cyanogen in terms of TG potassium cyanide solution given up by the mercury to the silver. This figure must be corrected by multiplying by the factor 0.96 if it lies between 0 and 5.5, or by the factor 1.04 and subtraction of 0.45 of the product if it lies between 5.5 and 9.5. The corrected value, c, multiplied by 0.02 gram (one ten-thousandth of the atomic weight of mercury) gives the quantity of that metal in the amount of solution, a, taken. C. A. M. The Separation of Metals of the Arsenic Group. 0. Materne. (Bz~ll. Xoc. Chirn. BeZg., 1905, xix., 241.)-The mixed sulphides of arsenic, antimony, and tin are boiled with a 2 per cent, solution of borax containing some ammonium chloride (amount not stated), and the liquid allowed to cool and filtered.The filtrate contains the arsenic, which is precipitated by means of tartaric acid. The residue of the two other sulphides is treated with a boiling 5 per cent. solution of sodium carbonate (containing some ammonium chloride), which dissolves the antimony sulphide andTHE ANALYST. 125 leaves the stannous sulphide. On treating the filtrate with tartaric acid the antimony sulphide is re-precipitated, whilst the residue of stannous sulphide can be brought into solution by means of a 10 per cent. solution of sodium hydroxide. C. A. M. Determination of Carbon in Steel by Direct Ignition with Red Lead. Charles Morris Johnson. (Proc. Eng . SOC. West. Pen?zsyEvania, 1906, xxi., 586.)- The author has found that for molybdenum and chromium steels the ordinary potas- sium cupric chloride method of determining carbon gives very discordant results, as the carbide obtained appears to oxidize rapidly if exposed to air, or, in some cases a t least, to acid.He therefore burns such steels directly with red lead in a current of oxygen, the resulting carbon dioxide being absorbed in barium hydrate, and the barium carbonate formed filtered off and weighed. The baryta is contained in two large test-tubes, through which the carbon dioxide bubbles. The steel used should pass a 20-mesh sieve and be retained by a 30-mesh, or else it may be in the form of fine drillings. For high carbon steels, 0.5 to 1 gram is taken ; for low carbon steels, 2 or 3 grams may be used.The sample is placed in a weighing-bottle with 4 grams of red lead, and well mixed by shaking; the mixture is then transferred to a porcelain boat and covered over with asbestos, which prevents creeping. The highest heat obtainable should be used for the combustion. Old boats may be cleaned with nitric acid. A combustion by this method takes in all only seventy-five minutes from start to reporting, and results obtained on ordinary steels check exceedingly well with those given by the usual method. A. G. L. Determination of Sulphur in Roasted Zinciferous Ores and Similar Materials. G. Lunge and R. Stierlin. (Zeits. ungew. Chem., 1906, xix., 21.)- The authors show that the Watson-Lunge method is not applicable to materials containing zinc, and recommend the following : Exactly 2 grams of sodium bicar- bonate, the alkali content of which is accurately determined, is mixed in a small nickel crucible with 3.206 grams of the finel? powdered sample and 2 grams of potassium chlorate. The crucible is covered and heated for one hour, for the greater part of the time very gently, but finally to dull redness, without, however, allowing the mixture to fuse.The mixture is then extracted with water to which 25 C.C. of sodium chloride solution, absolutely neutral and free from magnesium salts, have been added. The whole is boiled until sodium chloride commences to separate out, when tihe insoluble residue is filtered off and washed with sodium chloride solution (to prevent iron oxide from passing through the filter). The filtrate is then titrated with hydrochloric acid, using methyl orange as indicator. The difference between the alkali value of the sodium bicarbonate taken and that found corresponds to the sulphur.If more than 6 per cent. of sulphur is present, only 1.603 grams of substance should be taken, and 2 grams of ferric oxide added, to prevent fusion of the mixture. A. G. L. Titanium Chloride in Volumetric Analysis. E. Knecht and E. Hibbert. (Clzem. Zeit. Rep., 1905, xxix., 380.)-The authors have successfully used the strong126 THE ANALYST. reducing action of titanium chloride for the volumetric analysis of other substances, especially coloured organic compounds which form colourless (‘ leuco-” bodies. This is usually effected by the addition of 2 atoms of hydrogen to the molecule.The colouring matter acts as its own indicator in the titration, as the end of the reaction is marked by the solution becoming colourless. The experiments must be conducted in absence of air, owing to the ease with which the “leuco-” bodies are oxidized. The authors also succeeded in accurately estimating inorganic substances by the. same reagent. E. K. H. Analysis of Incandescence Mantles. T. B. Stillman. (Chem. Zeit., 1906, XXX., 60.)-The following scheme of procedure is given : Five mantles are burnt off, broken into small pieces, weighed, and evaporated with sulphuric acid in a platinum basin to dryness. This digestion is repeated four times. When cold, the mass is extracted with cold water, and the solution filtered, if necessary. The residue, if any, is fused with potassium hydrogen sulphate, diluted with water, and added to the main solution.Ammonium sulphide is now added in slight excess, and the precipitate collected on a filter and washed with water containing ammonium sul- phide. The filtrate contains the calcium and magnesium, which are separated in the usual manner, after boiling the solution to drive off hydrogen sulphide, and filtering to remove separated sulphur. The precipitate contains the hydroxides of cerium, thorium, lanthanum, zirconium, aluminium, didymium, and yttrium. I t is dissolved in hydrochloric acid, diluted with water, boiled; a dilute solution of sodium thio- sulphate is added, the whole boiled for one hour, then allowed to stand for twelve hours and filtered, giving precipitate ‘‘ A ” and filtrate ‘ 6 B.” Precipitate ‘( A ” contains the oxides of thorium, zirconium, and aluminium.These are dissolved in hydrochloric acid filtered from precipitated sulphates ; the latter are dried, ignited, fused with potassium hydrogen sulphate ; the melt dissolved in cold water, precipitated with ammonia, filtered, and the precipitate dissolved in hydrochloric acid and added to the main hydrochloric acid solution. The latter is treated with an excess of sodium thiosulphate, boiled, filtered, treated with ammonia, in slight excess, Itgain filtered, and washed with water. The precipitate is dissolved in hydrochloric acid, supersaturated with oxalic acid, boiled for five minutes, allowed to stand for twelve hours, and filtered. Precipitate. Wash with cold water, dry, ignite, and weigh as Tho,.Gives no ab- sorption spectrum. Tho,. Filtrate. Treat with excess of sodium hydroxide, boil for ten minutes, filter, and wash with hot water. Precipitate. Dry, ignite, and weigh as Zr0,. Gives no absorption spectrum. ZrO,. Filtrate. Acidify with hydro- chloric acid, render feebly alkaline with ammonia; boil, filter, wash, and weigh as A1,0,. No absorp- tion spectrum. A1,0,. Filtrate ‘( B ” contains the oxides of cerium, yttrium, lanthanum, didymium, and thorium. The solution is rendered alkaline with ammonia, filtered, washed withTHE ANALYST. 127 cold water, the precipitate dissolved in hydrochloric acid, and the solution treated with dilute sodium thiosulphate solution to precipitate any .thoria, present, Any precipitate obtained is dissolved in hydrochloric acid and added to the hydrochloric acid solution of precipitate ‘‘ A.” The filtrate is precipitated with ammonia, filtered, washed, the precipitate dissolved in sulphuric acid; the excess of the latter is ignited, and the residue dissolved in cold water.The solution is now treated with a saturated solution of potassium sulphate, and the precipitate collected on a filter after standing for four hours, and washed with a, solution of potassium sulphate. Precipitate. Dissolve in dilute hydrochloric acid, add oxalic acid, filter, dry, and ignite. Dissolve the residue in hydro- chloric acid, precipitate with sodium hydroxide, saturate with ohlorine gas, filter, and wash well. Precipitate. Dry, ignite, and weigh as CeO,. Gives no absorption spec- trum. Ce02.Filtrate. Acidify with hydrochloric acid, boil, precipitate with oxslic acid, filter, wash, dry, and ignite. The residue is dissolved in nitric acid, and divided into two parts : Test for Di with the spectroscope. A dark band shows that Di is present. Di,O,. Add ammonium acetate, then am- monia, and filter. Treat the precipi- tate with solid iodine. Lathanurn gives a blue colour, but no spectrum. La,O,. Filtrate. Add a dilute solution of sodium hydroxide ; filter off the pre- cipi t a t e, wash, dry, and weigh as Y,O,. Gives no absorp- tion spectrum. The didymium may consist of praseodymium and neodymium; the salts of the former are green and of the latter rose-red. w. P. s. The Separation of Iodine from Chlorine and Bromine by Means of Hydrogen Peroxide.J. Jannasch and F. Zimmermann. (Berichte, 1906, xxxix., 196, 197.)-The aqueous solution of the mixed halogens (120 to 150 c.c.) is treated with 15 c.c, of glacial acetic acid, and 3 C.C. of hydrogen peroxide (30 per cent.), which effects a quantitive separation of the iodine from the chlorine and bromine. The iodine thus liberated is distilled by means of a current of steam into three connected vessels containing respectively (a) 10 grams of hydrazine sulphate, and 10 C.C. of ammonium hydroxide in 80 to 100 C.C. of water, and (b) and ( c ) 0.5 gram of hydrazine sulphate, and 2 C.C. of ammonium hydroxide in 25 C.C. of water. After the whole of the iodine has passed over, the contents of the absorption vessels are cooled, mixed, and acidified with 30 to 40 C.C.of strong sulphuric acid, and the iodine determined as silver iodide. C . A. M,128 THE ANALYST. triangle or on a piece of platinum foil placed on the bottom of the furnace. The lid of the furnace is also covered with platinum foil. After passing a The Detection and Determination of Chlorate in Sodium Nitrate. L. Grimbert. (Jourrt. Pharm. Chim., 1906, xxiii., 98-100.)- A few C.C. of a, solution of the sodium nitrate are shaken with one drop of aniline, and a little strong sulphuric acid then poured down the side of the tube. In the presence of a chlorate an intense blue zone appears at the junction of the liquids. For the determination of the chlorate a given weight of the sodium nitrate is ignited with a, little cane sugar to effect reduction, the mass extracted with water, and the chloride determined by titration in the usual manner.In this way the author found a sample of sodium nitrate to contain 0.692 per cent. of sodium chlorate. Three other samples of sodium nitxate free from chloride also contained chlorate, but different samples of potassium nitrate examined were found to be quite pure. C. A. M. Use of the Electric Furnace for Burning Magnesium Phosphate Precipi- tates. F. Haussding. (Chzem. Zed., 1906, xxx., 60, 61.)-The construction of the furnace is shown in the illus- ‘I injurious action of ordinary gas-flames on The Determination of Carbon Nonoxide in Air. A. Levy and A. PBcoul. Conzptes Rendus, 1906, cxlii., 162.)-The method is based upon the fact, recorded by Gautier, that carbon monoxide, even when only present in traces in air, reduces iodic anhydride, and also on the colorimetric determination in a chloroform solution of the iodine thus liberated.Acetylene has a similar reducing action, but to a much smaller extent. Thus, air containing 4 parts per 10,000 of acetylene causes only a very slight reduction of the iodic anhydride, whereas with 1 part of carbon monoxide in 10,000 a large amount of iodine is liberated. Hence in testing ordinary air for carbon monoxide no special precautions are necessary, but in the case of industrial gas-products any acetylene, hydrogen sulphide, etc., must be absorbedTHE ANALYST. 129 before making a determination. a solution of potassium hydroxide for the absorption of the iodine. The most accurate results are obtained by using C.A. M. Determination of Water in Superphosphates and in Silicofluorides. Ludwig Schucht. (Zeits. angew. Chem., 1906, xix., 183.)-To determine moisture, as distinct from chemically combined water, in superphosphate, 2 grams of the sample are rubbed up in a glass dish with 20 C.C. of absolute alcohol. After one hour the liquid is decanted through a weighed filter-paper ; the insoluble material is brought on to the filter with more alcohol, washed with ether, dried at 40° C., and weighed. The filtrate is evaporated to dryness, and the residue dried at 120" C. to constant weight. The weighings must be made as quickly as possible. The difference between the original 2 grams and the sum of the two residues gives the moisture. For the determination of free acid, the author recommends the use of his oxalate method, and answers some objections which have been brought against it. TO determine the free acid in commercial siZico-fluoric acid, 50 C.C.are weighed Out, diluted with water to 1 litre, and 50 C.C. of this solution titrated hot with If free hydrofluoric acid is also present, the total acid is determined in this way, and the precipitate produced by potassium chloride and ethyl alcohol by Stolba's method is also weighed. The precipitate may also be titrated with sodium hydroxide. I n the analysis of commercial sodium silico-juoride, moisture is determined by heating 2 grams of the substance for three hours at 100" C. in a current of dry air which has to bubble through sodium hydroxide after passing over the substance, any volatilized acid being thus retained and allowed for.To determine free acid, 3 grams of the sample are moistened with methyl orange in a glass dish, and titrated with To determine the sodium silico-fluoride, 3 grams of the sample are dissolved in 450 C.C. of water, and the solution is titrated hot with 4 sodium hydroxide, using phenolphthalein as indicator. The free acid previously found must be deducted from the result, and the proportion of sample to water should always be that stated, otherwise errors due to hydrolysis will be made. sodium hydroxide, using phenolphthalein as indicator. sodium hydroxide. A. G. L. Determination of Available Plant Food in Soil by Use of Weak Acid Solvents. A. D. Hall and A. Amos. (Proc. Chem. XOC., 1906, xxii., 11.)-Repeated extraction, with water charged with carbon dioxide or with a 1 per cent.solution of citric acid, of soils of known history has shown that the first extraction does not remove the whole of the soluble phosphates, the reaction being a reversible one. With carbon dioxide and water the position of equilibrium is approximately constant for succegsive extractions, but with dilute acetic acid the amount of phosphoric acid dissolved falls for the first four or five extractions, then becoming nearly constant. No support is found for the theory that all soils establish in the soil-water a solution of phosphoric acid of approximately the same composition, and independent of the fertilizers the soil receives. W. H. S. Mechanical Analysis of Soils.J. A. Murray. (Chem. News, 1906, vol. 93, p. 40.)-The author has worked out the following scheme for the mechanical analysis130 THE ANALYST of soils : Five grams of the air-dried fine soil (passed through a 100-mesh sievej were disintegrated in weak ammonia solution and allowed to stand for fifteen minutes, after which the water containing the finer material in suspension was poured off. The coarser material was then introduced into a 200 C.C. Erlenmeyer flask, which was filled with water and attached by a rubber joint to a wide glass-tube of exactly the same diameter as the neck of the flask, from which the flange had previously been removed. The tube used was 147 cm. long and 2.3 cm. internal diameter. Water was next poured gently down the side of the tube so as to fill it, after which it was closed by a cork and inverted in a large glass basin full of water.The cork was then immediately removed and a small weighed porcelain dish placed under the open end of the tube under the water. The particles descending the tube were collected in a, series of fractions, the first porcelain dish being removed and another one substituted five minutes after the first particle had reached the bottom, the second dish being removed after another ten minutes, and the third after another twenty minutes (or else, after another twenty-five minutes, the times as given not corresponding exactly with each other). Nearly the whole of the remainder of the material was deposited in another hour. This last fraction was returned to the beaker containing the quantity of fine material originally poured off, well mixed with it, and the whole then placed in the flask and allowed to fall through the tube as before, the same water being used so as to avoid loss of material.In this way three more fractions were collected, after one, three, and seven hours respectively. The liquid remaining in the flask and tube was then measured and an aliquot part evaporated to dryness so as to give a, seventh and last fraction of finest material. The other fractions collected were also dried and weighed. The preliminary separation into finer and coarser material is necessary to prevent some of the fine particles being dragged down with the coarse material. The method enables a soil to be separated into a number of fractions con- taining particles of nearly uniform size; duplicate analyses made by it are in good agreement with each other.A. G. L. A Rapid Method for the Determination of Moisture in Fuels, especially Coal. E. Graefe. (Braunkohle, 1906, iv., 581; through Chem. Zeit. Rep,. 1906, xxx., 23.)-Ten grams of the coal are heated with 50 C.C. of solar oil or petroleum in EL 75 C.C. distilling flask until 25 C.C. of oil have been distilled off, which should require about five minutes. The distillate is caught in a 25 C.C. measuring cylinder, the amount of condensed water being read off directly; each & C.C. corresponds to 1 per cent. of moisture in the coal. The neck of the distilling flask should onlyreach a short distance above the side-tube, and a narrow condenser tube (above 5 mm.diameter) should be used. The method is stated to give serviceable results. A. G. L. Standardization of Chemieal Disinfectants. (Chem. Trade Joz~rrt., 1906, xxxviii., 4.)-The large variety of tbese now on the market renders desirable their classification according to their efficiency, and since they are sold for germicidal purposes, any comparison should be on this basis. The need for standardization is emphasized by the following table, taken from the Public HeaZth Eagiizeer.THE ANALYST. 131 - Sample. A. B. C. D. E. F. G. H. I. J. K. L. M. Carbolic Acid Coefficient. Price per Gallon, or 10% lbs. 0.02 0.30 8.00 1.00 2.50 1.40 0.30 0.10 0.10 0.90 2.50 0.03 11.00 6 8. d. 0 3 6 0 5 6 0 4 0 0 1 0 0 8 0 0 2 6 7 1 7 6 0 1 8 9 0 1 5 0 1 0 7 6 I 0 3 6 2 0 0 Cost of Disinfectant equivalent to 1 Gallon of Carbolic Acid. 6 s. d. 815 0 018 4 0 0 6 0 1 0 0 3 2 0 1 9 26 5 0 9 7 6 7 1 0 0 0 8 4 0 1 5 66 13 4 0 0 4 W. H. S. Determination of Turbidity of Water. J. F. Liverseege. (Journ. Sot. Chem. Id., 1906, xxv., 45.)-Test type as used by oculists, mounted on a board and attached to a cord running on a pulley, ig viewed through a 2-foot tube, filled with the water under examination, and placed with its end about 6 inches from the type, which is raised or lowered till a set is found that can be easily read. The turbidity figure is obtained by subtracting 2.5 feet from the normal range in feet for the particular type, and is recorded as ( ( turbidity expressed in feet of distance required to read standard type.” If a water is so turbid that 2 feet of it obscures the type entirely, a I-foot tube may be used, still reading at 2-5 feet from the type, but the results cannot be calculated from one tube to the other. W. H. S. Filtration of Finely Divided Precipitates. C. S. Palmer. (Chem. Zeit. Rep., 1905, xxix., 342.)-The author proposes to add 1 or 2 drops of albumen to the liquid to be filtered, and, after stirring, to quickly raise to boiling. The coagulated albumen enables the precipitate to be easily filtered, washed, and burnt. The trace of ash from the albumen is quite negligible. E. K. H.

ISSN:0003-2654    

DOI:10.1039/AN9063100123

出版商:RSC    

年代:1906

数据来源: RSC

摘要:

THE ANALYST. 131 APPARATUS. A Form of Burette for avoiding Errors in Titration at the Boiling- point. H. Gockel. (Chem. Zeit., 1905, xxix., 1208.)-A modification of Koninck’s burette, in which the exit-tube comes out at right angles to the main tube. In the present type the side tube is not horizontal, but curves up somewhat and then down again. This avoids the necessity of placing the burette at a high level. The burette can be obtained from Dr. H. Gookel, Berlin, W. E. K. H.132 THE ANALYST. Heating under Reduced Pressure by the Aid of an Electric Oven. E. Haagn. (Chem. Zeit., 1905, xxix., 1209.)-The accompanying figure shows a very useful form of electric oven, furnished with an arrangement for giving a partial vacuum. The bottom portion of the appa- ratus is made with a double wall, between which water circulates, being admitted by the aperture B, and running off by aperture A.In consequence of this cooling, the top can be safely provided with a rubber fitting, which insures an air-tight joint. The oven is exhausted by means of the tube C, connected to a water-pump. The oven itself is a modification of that designed by W. C. Herams, of Hanover, but, in contrast to the earlier models, the heating resistance is within the mass of the oven body. This gives greater heat economy in working, and causes the highest temperature to be more quickly attained. A temperature of l l O O o C. can be obtained, and this is reached in about twenty to twenty-five minutes. About 8 kilowatt is used. For ordinary purposes a good water-pump gives a sufficiently reduced pressure ; but, of course, any desired reduction can be obtained by the ordinary means.The advantages of heating in a partial vacuum are often very great. Thus marble, which requires a good half-hour in a gas furnace for complete conversion to lime, is, in the present apparatus, completely converted in three minutes after the full temperature is attained. By first exhausting and then admitting any gas, it is easy to use this apparatus for heating substances in an atmosphere of any desired gas. The advantages of electric heating are also obtained by this oven. The influence of gas flames on platinum crucibles is especially bad, and the avoidance of this evil is almost a sufficient recommendation. E. K. H. An Improved Pattern of Gooch Crucible.H. Vollers. (Chem. Zeit., 1905, xxix., 1088.)-The principle of this form of crucible is clearly indicated in the accompanying figure. In place of the usual perforated bottom, there is a raised cylinder with the holes passing through the wall, the direction of the holes being parallel to the bottom. By this device the author claims to have removed the defect shown by an ordinary Gooch crucible, that the pores get blocked up by the asbestos; the asbestos can be pressed down very firmly, and, if the filtration is then too slow, some of the holes, usually only a, few, can be cleared by means of a bent needle. The crucible is supplied by the firm of C. Gerhardt, Bonn a. Rh. E, K. H.THE ANALYST. 133 A Constant Temperature Bath for Low Temperatures. A.Given. (Journ. Amw. Chem. SOC., 1905, xxvii., 1519.)-The bath shown in Fig. 1 was FIG. 1. designed originally to keep pyk- nometers at a constant tempera- ture of 15.6" C.; but it has since been found to work well at other moderately low temperatures. In principle it consists essentially of a bath of distilled water, in which the greater part of the pyknorneter is immersed, and which is cooled by an ice-box, and heated by a Bunsen burner (not shown) fitted with a gas-regulator. The bath itself is double-walled, the space between the outer galvanized iron wall and the inner copper wall being packed with asbestos. The ice-box I is of copper, and fitted with a wooden cover. I t is raised 14 inches above the bath, so as to leave space for an overflow-pipe, and it extends to within 14 inches from the bottom of the bath.A gentle current of air is introduced close to the bottom of the ice-box, and serves to stir the water in the outer bath, The pyknometers stand on the perforated shelf P, supported on hangers, which also carry the narrow shelf S for the thermometer and gas-regulator. This last is shown in Fig. 2, and consists of a large bulb, A , 5 inches long and 1 inch in diameter, filled with methyl alcohol (toluol might be even better), M represents the mercury seal, R being a rod of glass to strengthen the apparatus. The gas enters at I and leaves at 0 ; at P there is a hole for the pilot-flame I n using the bath, the pyknometers are first of all cooled to about 14" C., and then only placed in the bath, in which they may remain for any reasonable time, A 50 pounds of ice in seven hours in the hottest weather, but less than 1 pound of ice in it will keep the temperature of the bath constant.d -- supply* bath, 18 inches square and 12 inches deep, consumes about &-- FIG. 2. A. G. L.134 THE ANALYST. A Modification of Gintl's Pyknometer. M. Raukusin. (Chew. Zeit., 1905, xxix., 1087.)-The author brings forward a modified form of apparatus, the design of which is seen in the accompanying figure. The sample of fat is contained in the cylinder a, which in this form is open at both ends. The lower end of this pyknometer tube is ground to fit the glass cap k, which is ground on the inside, and thus a tight joint closes the tube. On the upper edge of the pyknometer tube a glass cover, b, is laid, which closes the tube 3 dl K C , tube fits exactlv with the canal in the cover.The whole tightly through receiving the wall of the tube in a small annular canal. The apparatus is used as follows : The three portions of the instrument are carefully cleaned and dried. The tube a is then placed in the cap k, and filled with the melted fat. The cover b is then laid on the tube, so that the wall of the .I instrument is then placed in a metal clamp, shown in the figure, and the excess of fat removed by pressure from the screwf, and the instru- ment then washed with petroleum ether and cleaned with chamois leather. The fat can be removed from the cylinder by a glass rod, the last traces being h got rid of with ether, etc. A New Crucible Triangle. A. Kette.(Chem. Zeit., 1905, xxix., 1208.)-The author points out the failings of the ordinary pipeclay triangle and the platinum triangle. In particular all forms suffer from the defect that the flame is broken on the bottom of the crucible, and its further heat- ing power is thus lost. To remedy this defect, the author brings forward the arrangement shown in the figure. The crucible rests on the angles of the three prisms, and the flame touches only fire-resisting material. The ring surrounding these pieces can be tightened and loosened by means of the small screw, and the opening thus altered to 5 t various-sized crucibles. Finally, the effective heating of any given flame is much increased, as very little of its power is lost. The author states that a platinum crucible can be easily and quickly raised to L temperature of 1300" C.This apparatus can be obtained from the firm of Bender and Hobein, Munich. E. K. H. E. K. H.THE ANALYST. 135 A New Vacuum Filter for Laboratory and Domestic Use and a wholly Novel Method of Cleaning the Filtering Material. (Zeits. angew. Chem., 1906, xix., 95.)-In the vacuum filter described the filtering material may be easily cleaned by evacuating the upper part of the ap- paratus by means of the pump p , as shown in Fig. 1, air being sucked in through the opening F below the filter. As soon as the filter is thoroughly clean, the liquid in A will become filled with small air - bubbles. The air admitted through F may be previously sterilized in any convenient way. Fig. 2 shows the normal way of working the apparatus as a filter.I t may be obtained of the following firms : Warmbriinn, Quilitz and Co., Berlin, N.W., Haidestrasse 55 to 57 ; Albert Dettloff, Berlin, N.W., Luisenstrasse 59 ; Franz Hugershoff, Leipzig. FIG. 1. FIG. 2. A. G. L. Apparatus for Continuous Extraction of Liquids with Ether, Benzene, or other Solvent. R. S. Bow- man. (Proc. Ch-em. Soc., 1906, xxii., 24.)-The apparatus described obviated the use of numerous corks and rubber joints, and may be easily constructed in the laboratory. The flask A, which may frequently be replaced by a wide test-tube, is filled almost to the neck with the liquid to be extracted, one-eighth to one-fifth of this volume of solvent being placed in the flask B, which is suitably heated. The vapour passes up the tube C, is condensed, and falling back, collects in the inner tube D, forming a column of liquid which in time becomes long enough to force its way through the liquid in A, and small drops of solvent, ascending in A, collect on the surface of the liquid, and finally overflowing at F, return to the flask B.On completion of the extrac- tion, the solvent is run off from the neck of the flask by opening the stop-cock E. W. H. S. ETHE ANALYST. 136 La ID Apparatus for Removing Gases from Aerated Liquids before Determining the Specifie Gravity of the Latter. K, Ulrich. (Chem. Zed., 1906, xxx., 90.)-The liquid is filled into the cylinder A and drawn into the bulb B by attaching the pipe L to an air-pump, the taps C and D being turned to give the necessary connections. The tap C is then closed, and the action of the pump allowed to proceed until the gases have been com- pletely removed from the liquid in B. Air is now admitted by turning the tap D, and the liquid allowed to flow back again through the tap C into the cylinder A, where its specific gravity is taken by means of a hydrometer. The short tube below the Note on a Combined Wash-Bottle and Pipette, J. W. Hogarth. (Chem. News, 1906, vol. 93, p. 71.)-By inserting the apparatus shown in an ordinary wash - bottle flask, a, measured volume of solution may be delivered from the jet of the wash-bottle. The measuring vessel a, which is fitted with a jet and the mouth-piece f, is filled by raising the rod d, which closes the lower orifice, d’, of a, and by blowing into the wash-bottle flask through the rubber-tube h. As soon as a i s filled to the desired extent, the rod d is released, when the rubber-tube e, which connects d and the short piece of glass-tubing in the stopper through which it passes, forces the rod back into position, so as to close the lower opening of a. The vessel a is capable of holding 15 c.c., and of delivering any less quantity with an error of only + C.C. A. G. L.

ISSN:0003-2654    

DOI:10.1039/AN9063100131

出版商:RSC    

年代:1906

数据来源: RSC