摘要:

AUGUST, 1905. Vol. XXX., No. 353. THE ANALYST. PROCEEDINGS OF THE SOCIETY OF PUBLIC ANALYSTS. NOTE ON THE SEPARATION OF STRYCHNINE AND BRUCINE. BY D. LLOYD HOWARD. (Read at t h e Meeting, June 7, 1905.) As a preliminary to the investigation of Gordin’s method for the separation of strychnine and brucine, and the determination of the former in presence of the latter, it appeared desirable to investigate Keller’s method, of which that of Gordin is a modification. It is the account of this preliminary investigation which I have the honour to submit to the Society. ‘( 0.2 to 0.4 gram of the dry mixture of alkaloids is dissolved in 10 C.C. of 10 per cent. sulphuric acid by heating on the water-bath. After complete cooling, 1 C.C. of nitric acid S.G. 1.40 to 1.42 is added, and the mixture shaken.The strych- nine sulphate, which usually separates from the solution, is redissolved on addition of the nitric acid, and at the same time the red brucine-nitric acid coloration is developed. After allowing the mixture to stand for an hour to an hour and a half, in order to complete the destruction of the brucine, 40 grams of chloroform, an equal quantity of ether, and 10 C.C. of 10 per cent. ammonia are added, and the whole shaken. Forty grams of the extract are filtered into a tared flask, from which the mixture of chloroform and ether are distilled. The residual strychnine is dried at 95” to 100” C. and weighed.” It has been stated that this process “only returns about 96 per cent. of the alkaloid,” but on experimenting with a mixture of strych- nine and brucine the results were found to be too high-e.g., 0.2486 gram strychnine with 0.19 gram brucine gave 0.2498 gram residue=10048 per cent.It should be mentioned that the acid solution was extracted three times with the solvent mixture, the latter washed with ammonia solution (which separates more easily than water), and the whole of the solvent distilled. Brucine similarly treated left a small residue (probably due to some impurity in the alkaloid used, as it gave no reaction for brucine), but not enough to account for the error in the strychnine determination described above. E.g., 0-412 gram brucine gave EL residue of 0.002 gram=0.5 per cent, A number of experiments were then made, using strychnine only. Using caustic soda solution to precipitate the alkaloid and to wash the solvent, 0.2434 gram strychnine gave 0.2473 gram residue = 101.6 per cent.Keller’s method is as follows :262 THE ANALYST. A large excess of caustic soda was then tried-viz., 30 C.C. of 10 per cent. solution-with the result that 0.4617 gram strychnine gave 0.4629 gram residue = 100.23 per cent. Discarding the nitric acid, and dissolving the strychnine in sulphuric acid, extracting, and washing the solvent with ammonia solution, 0.2776 gram strychnine gave 0-2795 gram residue = 100.7 per cent. Washing the solvent twice with ammonia solution, S.G. 0.959, 0.3311 gram gave 0.3358 gram residue = 101.4 per cent. On filtering the solvent after washing with ammonia the same result was obtained-via., 101.4 per cent. Drying the solvent with calcium chloride, 0.2909 gram strychnine gave 0.2948 gram residue = 101-3 per cent., but the residue contained a trace of chloride.An experiment was made with strychnine recrystallized from alcohol and dried at 50" C. till it ceased to .lose weight ; 0.3068 gram gave 0.3097 gram residue= 100.9 per cent. Using chloroform only as a solvent without treatment with acid, 0.3677 gram gave 0.3710=100.9 per cent. after drying for twelve hours at 100" C., and this was not reduced by further drying a t 110" C. A similar experiment, using ether (purified by washing with chromic acid, sodium bisulphite, and caustic soda, and then by distilling); 0.3802 gram gave 0.3831 gram residue = 100.7 per cent. A similar experiment, using a mixture of ether and chloroform, 0.2364 gram gave 0.2384 gram residue = 100.8 per cent.On the other hand, dissolving strychnine in alcohol, then distilling off the latter, produced no alteration in the weight ; also redissolving the residue from the ether or chloroform extractions in alcohol, and distilling off has little or no effect on the result. A mixture of benzene and amylic alcohol (which is an excellent solvent for cinchona alkaloids) was tried as a solvent, but proved unsatisfactory, the residue after distilling being a brown resinous body with strongly-marked odour, and the results being very high--e.g., 0.3217 gram gave 0.3365 gram residue = 104.6 per cent. As these results do not bear out the statement that Keller's method only returns about 96 per cent. of the alkaloid, some experiment8 were made to ascertain the effect of temperature on the reaction.0.1612 gram strychnine with 0.2017 gram brucine, left in contact with the nitric acid for three and a half hours at 21O C., gave only 0.1456 gram residue, or 90.32 per cent. 0.2256 gram strychnine with 0.1785 gram brucine, left in contact with the nitric acid for seventeen hours at 21" C., gave only 0.1821 residue, or 80.7 per cent. 0.2412 gram strychnine with 0.1452 gram bruoine, left in contact with the nitric acid for seventeen hours at 0" C., gave 0.2420 gram residue, or 100.3 per cent. 0.3436 gram strychnine with 0.1273 gram brucine, left in contact with the nitric acid for two hours at 0" C., gave 0-3460 gram residue=100-7 per cent., almost exactly the result obtained by dissolving strychnine in the chloroform and ether mixture, and then distilling without any treatment with acid,THE ANALYST.263 It appears, therefore, that at a sufficiently low temperature brucine can be completely destroyed in the presence of strychnine without injury to the latter, and that the defects of Keller’s method are simply those attendant on the use of chloroform and ether as a solvent. I feel that I owe some apology to the Society for submitting an account of this investigation at so early a stage, but as I may be unable to go further into the matter for some time, I offer these results in the hope that they may prove of some assistance (however slight) to others whose work lies in the same direction. I have to express my indebtedness to Mr. G. E. Shaw, B.Sc., F.I.C., etc., late senior assistant in the analytical laboratory of my firm, for his valuable help in carrying out the analyses described. DISCUSSION.Mr. CHAPMAN, who had read the paper in the author’s absence, added that Mr. Howard had been good enough to undertake this matter in connection with the Council’s investigation scheme. The object had been to ascertain whether Keller’s method could be modified with advantage, as had been stated to be the case by Gordin, who had published a modification of Keller’s method, involving the omission of the nitric acid and the substitution for it of a further quantity of much stronger sulphuric acid. The method as modified by Gordin gave, it was claimed, exact results, whereas Keller’s method was stated to yield only 96 per cent.of the total strychnine present. Mr. Howard’s results, however, went to show that Keller’s method was capable of giving not 96 per cent. of the strychnine, but, if anything, rather more than the actual quantity present, and consequently that its modifica- tion for the reasons given by Gordin was not necessary. The PRESIDENT (Mr. Bevan) said this seemed to be one of those cases in which very strict observance of time and temperature conditions was essential. Mr. F. C. J. BIRD said that the method laid down in the British Pharmacopceia for the determination of strychnine in preparations of nus vomica was not described in very full detail, a good deal being left to the judgment of the worker. As a matter of fact, the method was hedged around by conditions, not stated in the text, which it was absolutely necessary to observe in order to get correct results.In a recent case in his own experience several samples of nux vomica preparations had been condemned by certain analysts as containing excessive amounts of strychnine, whereas on further analysis they had been found to contain the correct amount only. Such errors were due simply to want of knowledge of the particular conditions under which the Pharmacopoeia process gave correct results. In the precipitation of the strychnine by ferrocyanide of potassium the prescribed strength of sulphuric acid must be strictly observed, and a certain definite amount of wash-water (at 70” F ) used, a correction being made for the amount of strychnine ferrocyanide dissolved by the wash-water.The temperature of the wash-water was also a most important factor. He had himself found that the same sample of a preparation of nux vomica yielded very different results when examined in summer and in winter respectively, the difference being due almost entirely to the variation in the temperature of the wash-water. At low temperatures--e.g., in winter-time-brucine ferrocyanide was264 THE ANALYST. precipitated with the strychnine ferrocyanide, and came out in the final weighiog as strychnine, making the result too high. In order, therefore, that the Pharmacopceia process might be properly understood, it was necessary that more detailed instruc- tions should be given with regard to it. The method in which the brucine was destroyed by means of nitric acid was a very promising one, and Mr. Howard had placed it on a sound basis in showing that at 0" C. it gave practically the exact amount of strychnine present. As a member of the committee of reference appointed by the Pharmacopoeia Committee of the General Medical Council, he could assure Mr. Howard that his results would be welcomed and greatly appreciated by those who were endeavouring to raise the analytical processes of the Pharmacopceia to that high level of accuracy and reliability on which it was most desirable that they should be placed.

ISSN:0003-2654    

DOI:10.1039/AN9053000261

出版商:RSC    

年代:1905

数据来源: RSC

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264 THE ANALYST. NOTE ON AN OBJECTIONABLE METHOD OF FINING WINES. BY R. BODMER. (Read at the Meeting, May 3, 1905.) ABOUT six months ago I was supplied with some Moselle (Zeltinger) by a firm of wine merchants. I n several bottles I noticed a blue sediment in the last glass poured out. I collected some of the sediment and examined it. I t proved to be a ferro- cyanide of iron, and also gave a distinct reaction for zinc. I was at a loss to under- stand how these substances could be introduced into wine, but on mentioning the matter to Mr. Hehner he showed me a note in the Zeitschrift fiir Untersz~chz~~zg der Nahrungs und Genussnzittel (1903, p. 452), by Dr. Karl Windisch on certain L L finings ” which he had examined. Heins Schnell-Kliirung,” and consisted of two solutions : They were sold as 1.A solution of zinc sulphate--ll*417 grams (cryst.) in 100 C.C. 2. A solution of potassium ferrocyanide-10.52 grains in 100 C.C. The solutions are supposed to be of exactly equivalent strength. No. 1 is first added to the wine-about 200 C.C. to 200 litres of wine-and then an equal volume of No. 2. A bulky precipitate of zinc ferrocyanide is formed, which, in settling out, rapidly and completely clarifies the wine. On further inquiry into the matter, I found that these solutions had actually been used by the importers of the wine under the impression that they contained nothing injurious to health and did not contravene the German wine laws. I may say that this preparation is patented in Germany and Sweden, and is advertised by the vendor as being safe and permissible, and the advertisement contains a certificate from a German analyst to the above effect.On further examining some of the wine, I detected ferrocyanide in solution after the blue precipitate had been filtered off. I next obtained some more wine of the same character from a totally differentTHE ANALYST. 265 source. I n this I could detect no ferrocyanide in solution nor mas there any blue sediment, but the wine contained zinc. I n order to corroborate me, Mr. Hehner kindly examined half of a mixture of two bottles of wine, and I examined the other half. Mr. Hehner found zinc in the proportion of 27.6 mgms. calculated as crystallized zinc sulphate per litre, and I obtained 28 mgms. The latter figure is equivalent to 1.96 grains per gallon, or 0.32 grains per bottle.Although this proportion of zinc sulphate is small, it is nevertheless decidedly objectionable in a light wine, of which some persons drink as much as two bottles a day. If the solutions do not exactly balance each other, the wine will contain either an excess of zinc sulphate or potassium ferrocyanide. I have proved by experiment that traces of hydrocyanic acid are evolved from a wine of the acid character of Moselle to which a little ferrocyanide of potassium has been added. Further, as shown by Dr. Windisch in the note above referred to, zinc ferro- cyanide is not entirely insoluble in an acid wine, so that some of the precipitate first formed may be redissolved. As a warning to wine merchants and importers, a letter signed by Sir Thomas Stevenson, Mr.Hehner, and myself was sent to four wine and spirit trade papers, pointing out the dangerous nature of this preparation. As to the method of analysis adopted: As a qualitative test, a few drops of ferrocyanide of potassium was added to some of the wine. A bluish-white preci- pitate was produced, which on further examination was found to contain zinc. This is, of course, not a conclusive test, as some wines which contain no zinc were found to give more or less precipitate with potassium ferrocyanide, no doubt due to the presence of a little albuminous matter in the wine (from isinglass, used as finings). Still, I noted that the quantity of this precipitate was more decided in wine containing zinc than when none was present. For the quantitative determina- tion 500 C.C.of the wine was evaporated, and the residue charred with nitric and sulphuric acid (as in the method for determining arsenic in beer). The residue was well extracted with boiling water and a little hydrochloric acid. Ammonia was added in excess (after the iron present had been oxidized by boiling with a little nitric acid) and the precipitate of ferric hydroxide, etc., filtered off. The filtrate was acidulated with acetic acid and a stream of SH, passed through for some time. The precipitated zinc sulphide, after washing with SH, water, was dissolved off the filter with dilute nitric acid and the solution evaporated, ignited, and the residue weighed as ZnO. In one experiment I ignited the precipitate of ZnS with the filter-paper, and there was a decided loss, owing, no doubt, to reduction of the ZnO to metallic zinc and volatilization. The ignited residue dissolved in dilute HC1 gave copious reaction for zinc with ferrocyanide of potassium in acetic acid solution and with ammonium sulphide in amrnoniacal solution.I have been informed by the wine importers froin which this wine was obtained Our results agreed very closely. This process of fining is a most dangerous one.266 THE ANALYST. that samples of this identical wine and others in which Mr. Hehner and Dr. Dyer also found zinc were sent to Germany for analysis, and that no zinc was detected in any of them. I ascertained, however, that the wines were incinerated and the ash examined for zinc. Dr. Windisch has pointed out that by this procedure a loss of zinc is likely to occur ; so this may perhaps account for the fact that the German chemists found no zinc, or else the samples could not have been identical with those examined by Mr.Hehner, Dr. Dyer, and myself. I have only succeeeded in finding ferrocyanide in solution in one sample-the one first referred to, in which the blue sediment was present, and where the use of these finings was admitted. A few drops of ferric chloride were added to the wine previously acidulated with The blue precipitate-much of which was probably tannate of iron-was filtered off, washed, and boiled with caustid soda solution. The ferric hydrate was filtered off, and the filtrate acidulated with HCI. On adding a drop of ferric chloride a bIue precipitate was again obtained. The mere fact that ferric chloride produces a bluish precipitate with a wine is not concluBive evidence of the presence of a, ferrocyanide, as the tannate of iron also has a decidedly bluish tint. Heins Schnell- Kliirung ” has been used in Germany to a very considerable extent, and not only for wines but for spirits and liqueurs. I believe, however, that the use of this prepara- tion is now prohibited in Germany, although patented there. few drops of hydrochloric acid. In the paper by Dr. Windisch already referred to he states that

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DOI:10.1039/AN9053000264

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年代:1905

数据来源: RSC

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266 THE ANALYST. AMMONIUM OXALATE, ITS FORMULA AND STABILITY. BY P. V. DUPRE. (Read at the Meeting, June 7, 1905.) THE introduction of the Act regulating the use of explosives in coal-mines rendered necessary the production of explosives which, while possessing sufficient power for practical purposes, could yet be used with safety, or at least with comparative safety, in coal-mines. In many instances this object was attained by the addition of some ingredient which had the effect of lowering the temperature produced by the explosion. Among such ingredients ammonium oxalate occupies a prominent position. In order to render possible the accurate analysis of explosives containing this ingredient, a knowledge, not only of its composition, but also of its beb.aviour under various conditions, became necessary, and as this information could not be obtained from available books of reference, the work which I now beg to lay before the members of this Society was undertaken.At the outset it appeared that even the composition of ammonium oxalate was given differently in different books ; for instance, although the majority gave it as containing one molecule only of water of crystallization, in Tilden’s edition of Watts’s (‘ Organic Chemistry,” published in 1886, it was stated to contain two molecules, while the first edition of Perkin and Kipping’s ‘‘ Organic Chemistry ”THE ANALYST+ 267 Time. omitted the water altogether, although this was given for oxalic acid (in the latest edition this has been corrected, one molecule being given).On this account, although the main object of the work was to determine the behaviour of ammonium oxalate under various conditions, it was considered advisable first to settle the question of its composition. For this purpose a sample of pure ammonium oxalate was taken and a portion further purified by recrystallization. Known portions were heated in a water-oven at a temperature of about 95' C. until they ceased to lose weight, when the mean of a large number of experiments which showed very slight variations gave a loss of 12-67 per cent. This is the exact value obtained by calculation on the assumption that the salt contains one molecule of water. In order to see whether the point at which the loss in weight ceased was really definite a portion was subjected to prolonged heating at 94" C.Table I. gives the figures obtained. TARLR I. Weight. HEATED IS WATER-OVEN AT 94" C. (SH,),C,O,. H,O. Name of (NH,),CIO,. No hours ... ... ... 'Iwo hours ... ... ... Seven hours ... ... Ten hours ... ... ... Sixteen hours ... ... Twenty-six hours . . . Twenty hours ... ... Estimated. 1.666 grams. 1.454 ,, 1.454 ,, 1.453 ,, 1.451 ,, 1.451 ,, 1.451 ,, Calcnla ted. Loss Per Cent. NH, .._ ... H2C,0, ... ... H,O ... ... - 12.72 12-72 12.78 12-90 12.90 12.90 23.94 63.38 12.67 It will be observed, bearing in mind that the theoretical loss of 12.67 per cent. is complete in about half an hour, that the salt suffers no further decomposition for seven hours, and even after twenty-six hours the further loss is very small. There was, however, the possibility that the loss might not be exclusively that of water.The analysis was therefore completed by the estimation of oxalic acid by means of a rarefdly standardized solution of potassium permanganate, and of ammonia by distillation, both in the original salt and in a portion of the dried salt. The results are given in the following table, which gives the mean of three closely concordant analyses : TABLE 11. Constituent. Calculated. I 99-99 I 23.94 63.38 12-67 27.42 72.58 - 99.99 I 100-00 Estimated. 27-33 72.58 - 100*00268 4 days 11 9 ) 16 s r THE - 2-23 5-35 ANALYST. 3 days 5 1 , 8 ) ? - The analysis thus agrees very closely indeed with the calculated value, and consequently the formula (NH,),C,O,.H,O may safely be assumed to be the correct one.Experiments were then made with a view to discovering whether under any conditions of crystallization a salt could be obtained with either more or less than one molecule of water. Crystals were prepared at the boiling temperature, at ordinary temperatures, and at a temperature near the freezing-point, the crystals formed being quickly dried by pressure between sheets of blotting-paper and the water estimated as before. I n no case were crystals obtained containing more or less than one molecule of water, and it seems certain that if a form with two molecules of water can exist, such a form must be extremely unstable. Having therefore settled the question of formula, the investigation as to the exact conditions under which the salt loses its water was begun, an accurate know- ledge of these conditions being necessary in order to render possible the estimation of moisture in an ammonium oxalate explosive.Weighed portions were put into an air- chamber, kept at constant temperature night and day, and weighed every twenty-four hours for from two to sixteen days, It was found that up to a temperature of 30" C. no loss of weight took place even in eight days; at 40" C. the loss was very small even in four or five days; while at 50" C. the loss in five days only amounted to 2.2 per cent. I t thus appears that when heated in ordinary air the oxalate remains stable up to a temperature of from 30" to 40" C., but above this temperature it begins to lose water very slowly. Weighed portions were then placed in a sulphuric acid desiccator, the whole being kept at constant temperature in an incubator.The following table gives the results : 1.44 2.94 4-75 - TABLE 111. TEMP. 12" C. - I - TEMP. 20" C. - I - TEMP. 30" C. Time. 1 day 3 days 4 9 9 5 $ 9 6 9 , 7 9 9 Loss. Per Cent. 2.51 7-62 10-13 11-59 12.40 12.64 TEMP. 40" C. I Thus it appears that in perfectly dry air ammonium oxalate loses water even at 12" C., although but slowly, while at 40" C. the loss is fairly rapid, being complete in two days. Since the percentage of moisture in explosives is often estimated by drying over sulphuric acid under reduced pressure, it was now necessary to find out the behaviour of ammonium oxalate under similar conditions. The last experiments were therefore repeated, with the difference that the desiccator was exhausted to about 1 millimetreTHE ANALYST. 269 before being placed in the incubator.The results showed that the percentage loss was the same as before, but took place much more rapidly, the salt losing all its moisture in three days at so low a, temperature as 44' F., or 6.7" C. These experiments, however, did not show whether the rate of loss was uniform, nor did they determine accurately the effect on the rate of loss caused by a definite rise of temperature, and in order to do this it was necessary to find some more convenient and accurate method: by which the loss could be observed. As it would be very difficult, if not impossible, to measure the water evolved volumetrically, and determination by weighing precluded the possibility of continuous observa- tion, it appeared that if the water vapour evolved could be converted into an equivalent quantity of some gas, measurement would be much more convenient.For this purpose calcium carbide seemed to possess the necessary qualities, and the following experiment was devised. A known weight of oxalate was placed in a small tube, and a quantity of calcium carbide mixed with it, the tube being connected with a nitrometer (see illustration) to measure the acetylene evolved by the action of the water vapour on the carbide, the tube being kept at the required temperature by im- mersion in an oil-bath. The first result was somewhat startling, for directly the tube was immersed in the oil-bath, which was at a temperature of 70" C., gas was rapidly evolved, the evolution ceasing in about half a minute, when the volume of gas corresponded fairly closely with the theoretical quantity obtainable from the water present in the quantity of ammonium oxalate taken.Obviously the carbide enormously increased the rate of decomposition. I n the next experiment, therefore, the carbide was separated from the ammonium oxalate by means of a thin layer of sand, the experiment being otherwise carried out in the same way. The results then obtained were very satisfactory, and are shown in the form of curves (Fig. 1). Experiments are now in hand to ascertain whether this method of estimating moisture can be applied to other substances. I t will be seen that the rate of decoinposition is very nearly constant for any given temperature, and approximately doubles for every rise of 10" C.As it was important in connection with the heat test to ascertain whether even minute traces of ammonia were lost with the water, a small quantity was submitted to the conditions of the heat test, the iodized starch-paper being replaced by moistened red litmus-paper. I t was found that after a few minutes the litmus-paper turned blue, showing that some ammonia, at any rate, was given off. This quantity was270 THE ANALYST, estimated by means of Nessler solution, and was found to be extremely small, and, as far as analysis is concerned, may be neglected. I t might, nevertheless, be supposed that the presence of ammonium oxalate in an explosive would materially affect the heat test. Experiments made tend to show, however, that, although in the case of an explosive giving a high heat test the effectTHE ANALYST.271 is very noticeable, it is of no practical importance in the case of samples giving low test. unless its vapour tension exceeds that of the water vapour present in the air, it was thought that the determination of the vapour tension of ammonium oxalate at various temperatures might give valuable indications of the stability of the salt under varying conditions of temperature. As a rather wide range of pressure-about 300 mm. of mercury-was re- quired, the apparatus used was as follows : As shown in the figure, it consisted of a U-tube, one limb of which was slightly longer than the maximum barometric height, the other about half as long, this latter being graduated in millimetres. The top of the long limb was closed by a stopper fitted with a tap, so that the tube could be exhausted by means of an air-pump or Sprengel pump, if desired.Such a quantityof mercury was put into the tube that, when the longer limb was completely exhausted, the mercury stood at or a little above the zero mark on the shorter limb. The upper half of the longer limb passed through a water-jacket, which could be kept at any desired temperature. For an experiment, the mercury was first forced up into the longer limb by means of an air-pump connected with the shorter limb to within a few centimetres of the stopper; a small quantity of ammonium oxalate-abaut 2 grams-was then introduced into the longer limb, the stopper replaced, and the tube completely exhausted by means of a vacuum- pump.The reading of the surface of the mercury in the shorter limb was then taken, and the temperature of the water-jacket slowly raised, readings being taken every 5" or 10". Curves for the tension of the aqueous vapour in air-when saturated, 70 per cent. saturated, which may be taken as the average hygrometric condition of the air, and 25 per cent. saturated- are also given; and, lastly, a vapour tension curve for sodium sulphate. The curves show that the vapour tension of ammonium oxalate does not reach that of water even at a temperature of 95" C., nor does it even reach the 70 per cent. curve; in fact, the salt will be stable at all temperatures up to at least 9 5 O C., provided the air is not less than half saturated with moisture.The curve for sodium sulphate, on the other hand, is always above the 70 per cent. curve, showing that the salt will effloresce at all temperatures in ordinary air-a fact proved by practical experience. It will be noticed that the 25 per cent. saturation curve cuts that of ammonium oxalate in two points bebeen 60a and 70" C.; hence, between these temperatures Lastly, as a salt containing water of crystallization does not effloresce in air These results are plotted in the form of a curve (Fig. 2).272 THE ANALYST. the salt would appear to be stable in air only 25 per cent. saturated, while outside these it would lose water. 0 10 20 30 40 50 60 170 80 90 100 TEMPEKATURES IN DEGREES C . Lastly, the curve for ammonium oxalate may be used to determine the tempera- ture t o which the salt must be heated in a water-oven in order that it may lose water. For the tension of the aqueous vapour inside the oven will probably be approximately the same as that outside; hence, this tension being known, it is simply necessary to find out at what temperature the oxalate curve reaches thisTHE ANALYST. 273 value. For example, take the temperature of 20' C., the average tension of aqueous vapour will be 9 millimetres, and the ammonium oxalate curve is found to reach this value at about 36" C. @ * * * + € +

ISSN:0003-2654    

DOI:10.1039/AN9053000266

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年代:1905

数据来源: RSC

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THE ANALYST. -4 j R 1.5 1.8 4.6 5.9 273 s . * G -- l o 1 0 0 0 20 25 ABSTRACTS OF PAPERS % z 1.5 2.2 5 6 PUBLISHED IN & * g z ? -- l o 1 0 0 0 20 25 OTHER 1 0 1 0 1.5 2 0 4.8 6 JOURNALS. 0 20 25 FOODS AND DRUGS ANALYSIS. The Determination of Ammonia in Milk, and its Value as a Test of Purity. A. Trillat and Sauton. (BUZZ. SOC. Chim., 1905, xxxiii., 719-723.)- The method of determining nitrogen, based upon the formation of nitrogen iodide (ANALYST, xxx., 218), can be applied to milk after separation of albuminoid matters, which would otherwise combine with the iodine. The simplest method is to treat the milk with iodine trichloride, which also reacts with traces of ammonia to form nitrogen iodide when the liquid is rendered alkaline. For this purpose 10 C.C. of the milk are treated with 10 C.C.of a 10 per cent. solution of iodine trichloride, and immediately filtered, and the filtrate treated little by little with pure milk of lime (2 to 3 parts of lime to 100 of water) until (in the presence of ammoniaj an intense black precipitate of nitrogen iodide, which disappears on adding an excess of the reagent, is formed, The method is capable of detecting 1 part of ammonia in 100,000 of milk, and a quantitative determination can be made by colorimetric com- parison with standard samples. I n determining the value of this reaction as a criterion of the purity of milk, the authors made experiments on samples of pure milk, whole, diluted, and sterilized, and on milk watered with impure water, and infected with different pathogenic and other organisms.It was found that no ammonia was produced by acetic or lactic bacteria, or by the bacilli of typhoid fever, anthrax, or tuberculosis. On the other hand, ammonia was produced by Micrococcus urea, certain species of tyrothriz, and Fliigge’s peptonizing bacillus, which is of frequent occurrence in milk. The following results are given to show the progress of the formation of ammonia in sterilized milk inoculated with different micro-organisms. In each case the acidity of the milk is expressed in terms of decinormtll sodium of milk and the ammonia in mgms. per litre. hydroxide solution per 10 C.C. Observations taken after Four hours . . . . Eight hours .. .. Sixteen hours . . .. Twenty-four hours . . Thirty-six hours . . Seventy-two hours . . CONTROL SAMPLE.hfICR0- COCCUY Umm. t; -- l o 1 0 1 trace 1.3 25 5.6 33 9 50 TYRO- TENIJIS. THRIX TYRO- FILI- THRIX FORMIS. FL~GGE’S BACILLUS. BACTERIA SEWAGE EFFLUENT. OF 1 1 *3 2.9 3.3 6‘4 12 2 z - 0 0 0 16 25 30 BACTERIA MEAT JUICS. OF DECOM- POSED - & z - 0 0 0 20 22 25 3ACTERIA POSED ~ D E C O M - URINE. 2 R - 0 0 0 20 22 33274 THE ANALYST. Two factors were found to play a part in the rate of formation of ammonia-the temperature and mode of inoculation. When the inoculation was made by means of a platinum wire, milks kept at 15"to 20" C. coagulated before the appearance of ammonia, while the reverse was the case when the same milks were kept at 35" C. But if the inoculation was on a larger scale the ammonia reaction was obtained long before the coagulation of the milk kept at the ordinary temperature.It was proved experi- mentally that milk watered with 10 per cent. of impure (Seine) water showed the reaction before coagulation, and that the amounts of ammonia often reached 20 to 25 mgms. per litre. These results were confirmed by the analysis of milks found to be watered in the Paris Municipal Laboratory. I n each case pronounced reactions for ammonia were obtained. Milks infected with sewage effluent (2 drops per litre) also gave the ammonia reaction before coagulation. The general conclusions drawn by the authors are that healthy cow's milk which has not been exposed to improper conditions-e.g., in badly ventilated stalls-ought not to contain ammonia, and that if it is present in any considerable quantity it should be regarded as raising a presumption of either pollution or watering.C. A. M. Determination of Free Sulphuric Acid in Vinegar. C. Rossi. (L'Indus- tria Chinz., 1904, vi., 253, 254 ; through Zeit. Untersuch. Nahr. und GenussrnitteJ, 1905, ix., 698, 699.)-Whilst acetic acid in aqueous solution has an acid reaction towards methyl orange, in the presence of alcohol or acetone it is quite indifferent to this indicator. Free sulphuric acid in vinegar can, therefore, be directly titrated if alcohol or acetone be previously added and methyl orange used as indicator. TO each 10 C.C. of vinegar at least 6.5 C.C. of alcohol or acetone should be added (cj. Schidrowitz, ANALYST, xxviii., 233). w. P. s. The Determination of Acetyl-Methyl-Carbinol in Vinegar. Pastureau.(Jounz. Pharm. Chim., 1905, xxi., 593-595.)-Several samples of vinegar examined by the author gave abundant precipitates on the addition of 95 per cent. alcohol, and strongly reduced Fehling's solution in the cold. From one of them, methyl ace tol, or ace t yl-methyl-carbinol, CH,.CO.CH(OH) .CH,, was isolated by neutralizing the vinegar with sodium carbonate and subsequently dis- tilling. The distillate gave an abundant precipitate of iodoform on treatment with iodine in an alkaline medium, and yielded with phenylhydrazine a yellow osazone melting at 243' C. The solution of this osazone gave a blood-red coloration on the addition of a trace of ferric chloride, and on evaporation yielded red acicular crystals. In the determination 50 C.C. of the vinegar were neutralized with sodium carbonate and distilled to dryness, superheating being avoided.The distillate was rendered alkaline and treated with 10 C.C. of a & solution of silver nitrate. After standing for twenty-four hours, it was diluted to 100 C.C. and filtered, and the residual silver determined by the cyanometric method. The amount of acetyl- methyl-carbinol was then calculated in accordance with the equation : S(CH,.CO.CHOH.CH,) + AgNO, = 3(CH,.C0.C0.CH3) + 3H20 + N + Ag.THE ANALYST. 275 I n one experiment 0.0674 gram of silver was found to have been reduced, and this corresponded to 0.1628 gram of acetyl-methyl-carbinol in the 50 C.C. of vinegar, or 3.256 grams per litre. The vinegars were grain products, and in the author's opinion the acetyl-methyl-carbinol was produced by the action of bacilli of the tartricus species on the carbohydrates.C. A. M. Determination of Vanillin, Coumarin, and Acetanilide in Vanilla Extract. A. L. Winton and E. Monroe Bailey. (Jounz. Anzer. Chem. SOC., 1905, xxvii., 719-724.)-The slight loss of cournarin which was found to take place during the determination of vanillin, etc., according to the method previously described by one of the authors (ANALYST, xxviii., 37), is obviated in the following modification of that method. The loss was sustained during the removal of the alcohol from the extract. Twenty-five grams of the latter are placed in a, beaker with marks showing volumes of 25 and 50 C.C. Water is added up to the 50 C.C. mark, and the mixture evaporated at a temperature below 70" C.to a volume of 25 C.C. This dilution and evaporation is once again repeated. Normal lead acetate solution is then added drop by drop, with stirring, until no further precipitate forms. The precipitate is collected on a moistened filter, and washed three times with hot water, taking care that the total filtrate does not exceed 50 C.C. The filtrate is cooled and shaken out four times with ether, using 15 C.C. each time. The combined ethereal extracts are now shaken out with four or five successive quantities of 2 per cent. ammonia, and the ammoniacal solutions set aside. After transferring the ether solution to a, weighed dish, it is allowed to evaporate at the ordinary temperature, dried in a desiccator, and weighed. The residue is stirred up three times with 15 C.C.of light petroleum (B.P. 30" to 40" C.) and decanted, thus removing the coumarin. The residue in the basin is dried and re-weighed, to obtain weight of the coumarin extracted, whilst the residue itself, if acetanilide, should have a melting-point of about 112O C., and respond to the qualitative tests for this substance. The light petroleum extract is allowed to evaporate at the ordinary temperature. If the residue be pure coumarin it should melt at 67" C. The ammoniacal solutions are now acidified with hydrochloric acid, cooled, and shaken out four times with ether, the ethereal extracts evaporated at the ordinary temperature in a weighed platinum dish, dried over sulphuric acid, and weighed. The residue, consisting of pure vanillin, should melt at about 80" C.If, however, acetanilide has previously been detected, this residue is dissolved in 15 C.C. of 10 per cent. ammonia and shaken out twice with an equal volume of ether. By evaporating the ethereal solutions and weighing the residue, the amount of acetanilide in the vanillin is obtained. The total quantity of acetanilide is found by adding the weight of this last extract to that of the residue previously obtained, and identified as acetanilide. Analyses of vanilla, extracts, containing known amounts of vanillin, conmarin, and acetanilide, show that the above process of separation is trustworthy, the error in no case exceeding 0-02 per cent, on the quantities taken. w. P. s. Detection of Antipyrin in Pyramidon. P. Bourcet. (Bzill. des Sci. Pharnz., vii., 318 ; through Pharm.Journ., 1905, lxxiv., 845.)-As little as 2 per cent.276 THE ANALYST, of antypyrin in pyramidon (dimethyl-amido-dimethyl-oxyquinizine) may be detected by the following reaction : About 0.02 gram of the sample is dissolved in 5 C.C. of cold water and shaken with 2 C.C. of sulphuric acid and 2 drops of saturated sodium nitrite solution (or a little of the salt). Pyramidon gives an intense bluish-violet coloration, which rapidly fades, leaving the solution colourless ; if antipyrin be present, a stable bluish-green colour is perceptible after the bluish-violet, due to the pyramidon, has faded away. w. P. s. Volumetric Determination of Mercury in Mereuric Salicylate. E. Ruff and P. Null. (Archiv. d. Plzarm., ccxliii., 1; through Pharm. Journ., 1905, lxxiv., 821.)-The following method, which is stated to be rapid and accurate, is also applicable to other organic mercurial compounds. 0.3 gram of the mercuric salicylate is heated with 4 grams of potassium sulphate and 5 C.C. of concentrated sulp’auric acid in a 150 C.C. flask, resting on wire gauze, and provided with a reflux tube about 50 centi- metres long. As soon as the mixture is clear and colourless, the reflux tube is rinsed out with from 5 to 10 C.C. of sulphuric acid; about 0.2 gram of potassium per- rnanganate is added to the contents of the flask, and the heating continued until the solution is again colourless. After diluting to 100 c.c., the solution is titrated with & sulphccyanide solution, using iron-alum as indicator, until a reddish brown colour appears. One C.C. of Fv sulphocyanide is equivalent to 0.010015 gram of mercury. w. P. s.

ISSN:0003-2654    

DOI:10.1039/AN9053000273

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年代:1905

数据来源: RSC

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276 THE ANALYST, ORGANIC ANALYSIS. A Test of the Purity of Cocoanut Oil. E. Milliau. (Comptes Rend., 1905, cxl., 1702, 1703.)-The presence of seed oils in cocoanut oil may be detected by the gooseberry-red colour produced by the simultaneous reaction of phloroglucinol and resorcinol in an acid medium. Four C.C. of the clear dry sample are shaken with 2 C.C. of a freshly-prepared saturated ethereal solution of phloroglucinol and then with 2 C.C. of a freshly-prepared saturated solution in benzene of resorcinol, and the tube cooled for a few moments in water at 10" C. The contents are then mixed with 4 C.C. of nitric acid S.G. 1.38, transferred to another tube, and vigorously shaken for five seconds. Pure cocoanut oil shows little or no alteration, while negligible traces of impurities give a very faint rose tint, which rapidly disappears.But if a seed oil or lard oil, oleonaphtha or resin oil, be present in the proportion of 5 per cent. or even less, the characteristic red coloration immediately appears. No notice is taken of reactions subsequently produced under the prolonged action of the nitric acid. C. A. M. The Characteristics of Sperm Oil. G. Fendler. (Chew Zeit., 1905, xxix., 555, 556.)-A specimen of undoubted purity yielded 15 per cent. of spermaceti, which, after purification, gave the following values: Specific gravity at 15' C., 0.942; melting-point, 42" C. ; saponification value, 134 ; iodine value (Hiibl), 9.3 ; un- saponifiable substances, 51.07 per cent., melting at 45" C. The oil separated from the spermaceti gave the following results: Specific gravity at 20" C., 0.8781 ; solidification-point, 15.5" C.; melting-point, 18.0" C. ;THE ANALYST. 277 Reichert-Meissl value, 0.60 ; saponification value, 150.3 ; iodine value, 62.2 ; and unsaponifiable matter (alcohols), 39.17 per cent. The fatty acids formed a brownish- yellow oily liquid with the following characteristics: Specific gravity at 15" C., 0.8999 ; solidification-point, 12.4" C. ; melting-point, 18-8" C. ; acid value (saponifica- tion value), 236.2 ; iodine value, 68.64 ; acetyl value, 17.9 ; acetyl acid value, 222.5 ; mean molecular equivalent, 237.7 ; liquid fatty acids, 85-78 per cent. ; solid fatty acids, 14-22 per cent. The solid fatty acids separated by the lead method melted at 38.2" C., and had acid value of 242.5, and mean molecular equivalent of 231.6; whilst the liquid fatty acids had an acid value of 228.7, a mean molecular equivalent of 245.6, and an iodine value of 75.6.The liquid acid distilled under reduced' pressure between 195" and 250" C. yielding fractions, of which the highest molecular equivalent was 287.4. The presence of physefoleic acid appeared doubtful in the light of these determinations. Contrary to the experience of Allen and Lewkowitsch, glycerin was found, 800 grams of the oil yielding 14.2 grams of thick brown syrup containing 74.33 of pure glycerin, corresponding to 1-32 per cent. in the original oil. According to Benedikt and Ulzer's assertion, this would represent adulteration with 13.2 per cent. of a fatty oil, whereas the purity of this sperm oil, obtained direct from the captain of the ship, was beyond question.C. A. M. Colour Reactions of Carbohydrates. R. and 0. Adler. ( A ? ~ z . Physiol., 1905, cvi., 323; Chenz. Zeit. Rep., 1905, xxix., l2l.)-The furfural test for pentoses can be simplified by decomposing them with acetic acid instead of employing the usual tedious distillation with hydrochloric acid. If a boiling mixture of equal parts of glacial acetic acid and aniline be treated with a few drops of a solution of a, pentose or a fragment of the solid sugar, the red coloration of furfural-aniline acetate soon appears. Methyl pentoses (rhamnose) react in an analogous manner, yielding the corresponding methyl furfural amines ; but carbohydrates, other than pentoses, do not yield the slightest trace of furfural within so short a time, with the exception of heptoses, which give the reaction. Other amines that form similar compounds with furfural may be used instead of aniline in this test.Certain phenols also give intense colorations when heated with sugars in the presence of acetic acid and some hydro- chloric acid. The resorcinol reaction for fructose is equally conclusive when acetic acid and one or two drops of hydrochloric acid are used ; whilst Tollens' tests for pentoses by means of orcinol and phloroglucinol give satisfactory reactions when carried out in this way, provided a few drops of hydrochloric acid be added to the acetic acid. Hexoses and di- and tri-saccharides that yield hexoses behave in quite a different manner. If a small quantity of dextrose be heated with the mixture of aniline and acetic acid, a reddish-brown colour is produced, which changes, on standing, to a bright green.This reaction is also given by the aldoses: mannose and galactose ; by the ketoses : fructose and sorbinose ; and by di-, tri-, and poly- saccharides after preliminary decomposition. Other amines can be used in place of aniline. The green colouring matter formed is insoluble in water, but dissolves in ether. C. A. M.278 THE ANALYST. Investigation of Tollens' Phloroglucinol Reaction for Pentoses. E. Pinoff. (Berichte, 1905, xxxviii., 766.)-If the test for pentoses by means of phloroglucinol and hydrochloric acid be made in an alcoholic instead of an aqueous solution, the coloration remains stable for a week if kept in diffused light and with the addition of ether.The spectrum shows one, two, or three adjacent absorption bands, according to the proportion of the three active agents in the test, and these bands are probably characteristic of three separate compounds. Evidence in support of this is that it is possible to prepare three distinct solutions, each of which shows only one of the bands. The band characteristic of pentoses is in the yellow part of the spectrum, and on heating the Rolutions showing the other bands with hydrochloric acid, they too yield liquids which also show only the pentose band. C. A. M. Colour Reactions of Pyruvic Acid with u- and @Naphthols in Sulphurie Acid Solution. P. Alvarez. (Bull. SOC. Chim., 1905, xxxiii., 716, 717.) -The reagents used are freshly prepared solutions of 0.02 to 0.05 gram of a- or &naphthol in 1 C.C.of sulphuric acid of specific gravity 1.83. One drop of the organic acid is added to 10 drops of the reagent in a porcelain crucible, which is then slightly warmed over a spirit-lamp. (i.) &Naphthol Reagent : A bright-red colour is immediately produced, and on gently warming the liquid it becomes a very intense blue, which changes to a fugitive yellow on the addition of water or concentrated alcohol. (ii.) u-Naphthol Reagent: The colour is yellow in the cold, becoming a very intense orange on heating. On shaking the liquid it adheres to the sides of the crucible like a coloured varnish. The colour does not change on the addition of water or alcohol. These reactions will distinguish pyruvic acid from citric, tartaric, malic acids, etc., and also afford an easy means of distinguishing between a- and @-naphthols.C. A. 111. The Valuation of Lubricants, with Special Reference to Cylinder Oils. F. W. Riehardson and H. Norman Hanson. (Journ. SOC. Chena. h d . , 1905, xxvii., 315.) -The paper is one which should be read in full, as it is almost impossible to give an adequate account of the work in a reasonable space. The following is a short summary of the main conclusions : The authors find that mechanical tests are of little value, a point with which the engineers who assisted in the investigations were compelled to agree. With regard to physical tests, the customary determinations of gravity, viscosity (usually at 210" F.), and flash-points (open and close tests) were not entirely satisfactory. The specific gravity is of rery little value, whilst the flash-points are chiefly useful for insurance purposes.With regard to the viscosity, the authors find that from 500" to 600" F. all cylinder oils have a practically identical value. On the other hand, the figures for 210" or 250" F. have little bearing on actual practice, owing to highly superheated steam being now generally employed. The authors therefore investigated more closely the value of the surface tension, or, as they suggest it may be termed, the wetting power " of the oil in thin films in hot air and in steam. Several methods were tried, but none were entirely satis-THE ANALYST. 279 factory. Finally, the authors determine the viscosity of the oil at 210" before and after exposing for four hours to the action of a current of hot air at 400" I?., in a special oven, the oil being spread out in a thin layer.For details of the experi- mental working, reference should be made to the original paper. The heating for four hours may seem excessive, but the authors point out that in the cylinder the oil makes a rapid succession of film surfaces, and the steam is not only at a very high temperature, but is under high pressure. They also find that much the same change is produced by steam at 400' as by air at the same temperature, and conclude that the changes are therefore due t o polymerization rather than oxidation. The relative viscosities before and after heating only are used; the absolute values are not calculated.An interesting point brought out by the experiments is the close relation between the viscometric and the refractometric changes. E. K. H. The Colorimetric Determination of Adrenaline. J. E. Abelous, L. A. Soulie, and G. Toujan. (Bull. SOC. Chim., 1905, xxxiii., 576.)-The method consists in matching the tint given by adrenalhe on the addition of a very dilute solution of iodine. The standard solution is prepared by mixing 10 C.C. of a solution of adrenaline (0.01 per cent.) with 5 C.C. of TG iodine solution, and allowing it to stand for fifteen minutes at the ordinary temperature, after which a few drops of starch paste are added, and the excess of iodine removed by means of TG sodium thiosulphate solution. The liquid is then diluted to 50 c.c.,.and furnishes a rose- coloured standard containing 1 mgm.of adrenaline. I n determining the adrenaline in suprarenal glands, 10 grams of the gample are ground up with sand, and the mixture treated little by little with salt water (7 per cent.) previously boiled, and then kept at a temperature of 40" to 50" C., until 100 C.C. in all have been added. The liquid is now slightly acidified with a few drops of a 10 per cent. solution of hydrochloric acid, boiled for a few moments, filtered, and the residue extracted with boiling water until the filtrate amounts in all to 150 C.C. Ten C.C. of the cooled liquid are now treated with iodine as above described, and the rose coloration compared with that of the standard solution. By this method the author found 1-47' mgm.of adrenaline in 1 gram of the suprarenal capsule of a sheep. As the standard solutions of iodized adrenaline lose their colour on keeping, it is advisable to prepare artificial standards of greater stability, such as, for example, tincture of turmeric, reddened by acid and diluted to match the original standard. C. A. M. Carbon Tetrachloride as a Solvent for Differentiating Bitumens. Clifford Richardson and C; N. Forrest. (Joum. SOC. Chem. I~zci., 1905, xxiv., 310.)-The *use of carbon tetrachloride RS a solvent has been facilitated by the introduction of a much purer commercial article. The authors used, in particular, carbon tetrachloride manufactured by the Acker Process Company, of Niagara Falls, New York, which is almost free from bisulphide.Carbon tetrachloride, as a general extractive agent, has many advantages. It280 THE ANALYST. has a high solvent power, mixes with all other solvents of its class, and dissolves only a trace of water. It is, moreover, non-inflammable and non-explosive, in marked contrast to carbon bisulphide, which ignites at 149' C., and has a considerable effect in making other inflammable solvents non-inflammable when mixed with them. It has, however, a high specific gravity, and, weight for weight, is not so economical as other solvents. As regards bitumens, though it is less rapid in its action than carbon bisulphide, it is valuable, since it exercises a selective action on the hydrocarbons and their derivatives which occur in native bitumens, whilst the true asphalts are dissolved by it to the same extent as by carbon bisulphide. I t can thus often show the extent to which a native bitumen has been weathered, and, further, the changes which may have been caused by the use of too high temperatures in the industrial preparation of pitches, etc. The authors recommend that for these purposes the carbon tetrachloride should be used at a temperature not exceeding 25' C., and should be quite free from carbon bisulphide. E. K. H. Note on Simplified Ultimate Analysis. E. Lippmann. (Chem. Zeit., 1905, xxix., 487.)_The author claims that his method of analysis in which the combustion is aided by copper oxide asbestos (Chenz. Zeit., 1903, xxvii., 810) is simpler and cheaper than that of Dennstedt, whilst equally accurate (vide ANALYST, this vol., p. 135). The author has succeeded in getting very accurate results even with such a substance as carbon bisulphide, the actual figures being: 0.1663 gram of carbon bisulphide yielded 0,0975 grain GO,, which corresponds to 15.98 per cent. of carbon, against the calculated 15-78 per cent. E. K. H.

ISSN:0003-2654    

DOI:10.1039/AN9053000276

出版商:RSC    

年代:1905

数据来源: RSC

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280 THE ANALYST. INORGANIC ANALYSIS. The Analysis of Cupric Ferrocyanide. A. Leuba. ( A m . de Clzim. aizal., 1905, x., 218, 219.)-When cupric ferrocyanide is boiled with a solution of sodium hydroxide, sodium ferrocyanide is formed and cupric oxide precipitated. This latter dissolves partially in the excess of alkali solution, and if the undissolved oxide be brought into solution by means of nitric acid, the two solutions cannot be mixed, hence the copper in each must be determined separately. This is obviated in the following method, based upon the reaction between cupric ferrocyanide and oxalic acid : Cu,Fe( CN), + 3H2C,0, = FeC,O, + 2CuC,04 + GHCN. From 0.3 to 0.5 gram of the finely powdered ferrocyanide is boiled for about two hours with a 5 per cent. solution of oxalic acid in B flask under a, reflux condenser.The resulting yellow precipitate of copper oxalate is washed and dissolved in dilute nitric acid, and the solution added to the filtrate. This is concentrated on the water-bath, and the copper and iron separated by the usual methods. The original solution contains the ferrous oxalate, which is soluble in excess of oxalic acid. It is easily decomposed by nitric acid, and the two nitric acid solutions can be mixedTHE ANALYST. 281 without fear of reprecipitating the original ferrocyanide. for the decomposition of other metallic ferrocyanides. Oxalic acid is not suitable C. A. M. A Method of Separating Arsenic. H. Cantoni and J. Chautems. (Ann. de Chim. anal., 1905, x., 213, 214.)-When a current of dry air at the ordinary temperature is passed over the surface of a solution of arsenious anhydride in con- centrated hydrochloric acid to which methyl alcohol has been added, the arsenic is completely volatilized, probably in the form of a methyl arsenious ester.Thus, if a current of air be drawn through a distillation flask, the outlet tube of which is connected with a condenser whose delivery tube is drawn out and dips into a solution of sodium hydroxide, no trace of arsenic is left in the flask. Antimony is not removed under the same conditions. The method should be particularly valuable in toxicological work, since all boiling is obviated. C . A. M. The Quantitative Determination of Antimony as Trisulphide, and its Separation from Tin. G. Vortmann and A. Metzl. (Listy Chemickk, 1905, xxix., 65; Chem.Zed. Rep., 1905, xxix., l2O.)-The method is based upon the fact that antimony trisulphide can be converted into the black crystalline modification by means of a current of hydrogen sulphide passed into the hot liquid containing a large amount of hydrochloric acid. The solution of the antimony salt is treated with hydrochloric acid (24 C.C. to 100 c.c.), heated on the water-bath, and frequently shaken while a current of hydrogen sulphide is passed through it. After thirty to thirty-five minutes the conversion of the sulphide into the black form will be complete, and the liquid is diluted with an equal volume of water, and the passage of the gas continued for another two or three minutes. The precipitate is collected in a Gooch's crucible, washed with water and alcohol, and dried at 270" to 280" C.in a current of carbon dioxide, The sulphide may also be converted into pentoxide by igniting it with a weighed quantity of a mixture of ferric oxide and ferric nitrate. Separation of Antimony from Tin.-The mixed sulphides are dissolved in hydro- chloric acid, the solution neutralized with sodium hydroxide, mixed with an equal volume of phosphoric acid (specific gravity 1-30), and after the addition of hydro- chloric acid (20 C.C. per 100 c.c.), heated to 100 c.c., and treated with a current of hydrogen sulphide, introduced at first rapidly, and then more slowly. I n this way the antimony is precipitated a8 the crystalline trisulphide, while the tin remains in solution. The filtrate from the precipitate is nearly neutralized with sodium hydroxide, diluted with water, and the tin precipitated from the hot solution by means of hydrogen sulphide.C. A. M. Determination of Manganese as the Green Sulphide. J. C. Olsen, E. S. Clowes, and Wm. 0. Weidmann. (Journ. Amer. Chem. SOL, 1904, xxvi., 1622.)- I n determining manganese, the authors have obtained very good results by precipita- ting and weighing it as the green sulphide. This sulphide may be obtained by proceeding as follows: 10 C.C. of the manganese solution, containing 0-15 gram of manganese, are poured into 90 C.C. of a boiling solution of 25 C.C. of ammonium sulphide and 10 C.C. of ammonium chloride solution (containing 2.75 grams ammoniumTHE ANALYST. 282 chloride per litre). The ammonium sulphide is prepared by diluting concentrated ammonia with twice its volume of water, saturating half of the liquid in the cold with hydrogen sulphida, and then adding the other half ; it must be free from the yellow sulphide.The precipitate is digested in the hot solution for thirty minutes, when i t will have been completely converted into the green sulphide. This is filtered off, washed with water containing ammonium sulphide and chloride, dried and ignited as for copper in Rose’s method. I n the above procedure, it is essential that the manganese solution be poured into the ammonium sulphide, and not vice wend, and that a large excess of ammonium sulphide be present, as otherwise conversion into the green sulphide may not be complete, if it take place at all. A. G.L. On the Solubility of Oxides of Iron in Hydrofluoric Acid. Ernst Deussen. (Zeits. angew. Chem., 1905, xviii., 813.)-A number of comparative determinations of the solubility of iron rust and scale in hydrochloric, hydrofluoric and oxalic acids showed that dilute hydrofluoric acid dissolves oxides of iron much more easily than do the other acids. The cleaning of rusty iron utensils was also most easily accomplished by means of hydrofluoric acid, the metal itself suffering very little. Iron stains could be easily removed from linen without injuring the fabric, and copper articles were very readily cleaned by dilute hydrofluoric acid, the metal itself being insoluble in the acid. To remove rust from iron it is recommended to first remove grease, if present, by hot sodium hydrate or carbonate, and then to immerse the vessel for from one to twelve hours in 2 to 5 per cent.hydrofluoric acid contained in wooden vats tarred on the inside. After removal from the acid the iron is to be washed with hot water and then immediately placed in soda solution or lime-water. The author mentions that it is possible to immerse one’s hands in 5 per cent. hydrofluoric acid for a considerable time without experiencing any ill effects. A rabbit into whose stomach 50 C.C. of 0.5 per cent. pure hydrogen fluoride was introduced showed no signs of poisoning. Any unrusted places may be protected by grease or varnish. A. G. L. Quantitive Determination of Iron and Aluminium in Ignited Mixtures containing large amounts of Al,O, and small amounts of Fe,O,.Ernst Deussen. (Zeits. angezo. Chem., 1905, xviii., 815.)-The finely divided oxides are intimately mixed with acid potassium fluoride in a platinum crucible. The mixture is fused over a small flame until, after a few minutes, it becomes solid. Dilute sulphuric acid is then added, and the greater part of the hydrofluoric acid expelled by heating for a short time. The sulphates are then dissolved in water in a platinum dish; the iron is reduced by sulphur dioxide, the excess of which is expelled by carbon dioxide, the liquid being then titrated with permanganate in a Jena, glass beaker. In one analysis by this method, in which 0.007 gram Fe20, was present in 0-094 gram of mixed oxides, 0.0065 gram Fe,O, was found. Some experiments are also given to show that the presence of considerable quantities of potassium hydrogen fluoride does not interfere with the titration.The advantages claimed for thisTHE ANALYST. 283 method over that of fusing with potassium bisulphate are that no platinum passes into solution, and thGt it requires less time. A. G. L. A Case of Iron Contamination in a Water-Supply due to Baeteria. A. Beythien. (Zeit. Untersuch. Nahr. Genussmittel, 1905, ix., 529-531.)-The water- supply of a small town in Saxony was found to contain a large quantity of ferruginous matter in suspension, although when drawn from the well the water was free from iron. Between the well and the town the water passed through about 2 kilometres of asphalted iron mains. An examination of the suspended matter showed that it consisted of a mass of threads similar to Crenothrix, incrusted with oxide of iron.These threads were in all probability Gallionella ferruginea, and the contamination of the water was due to their presence, aided by the large amount of free carbon dioxide naturally contained in the water. w. P. s. Method for the Analysis of Bauxite. H. Lienau. (Chem. Zeit., 1905, xxix., 584, 585.)-In view of the increasing manufacture of aluminium from bauxite, the following procedure for the analysis of this mineral is recommended : Moisture and Combined Water.-Several quantities of about 10 grams each of the same sample are dried at a temperature of 110' C. to obtain the moisture. The combined water is found by heating 1 gram of the dry sample in a platinum crucible in a muffle-furnace. The loss in weight should, more correctly, be termed the loss on ignition, as some specimens contain as much as 1 per cent.of organic matter. Silica.-One gram of the finely-powdered dry mineral is quickly mixed in a beaker with 8 C.C. of sulphuric acid (1 : 2). After again adding an equal quantity of the acid, the mixture is rapidly brought to boiling, and kept at this temperature until the colour changes from red to yellow or white. The solution is now evaporated until sulphuric acid fumes are evolved. If the latter do not appear before the mixture becomes dry, more acid must be added. Finally, the whole of the free acid is driven oft', and the residue, after cooling, boiled with 20 C.C. of dilute sulphuric acid (1 : 5 ) . If less than 10 per cent. of silica be present, this method of separation is sufficient.With more than 10 per cent., the silica found should be fused with potassium hydrogen sulphate. Titanic Acid.-The filtrate (or filtrates) from the silica is treated with about 500 C.C. of 3 per cent. sulphurous acid solution, then nearly neutralized with 10 per cent. sodium hydroxide solution, diluted to about 900 c.c., and heated to boiling for one hour. The precipitated titanic acid is collected on a filter, if necessary pouring the first 200 C.C. of filtrate once more through the filter, and washed with hot water containing ammonium chloride. Iron and AZu,mina.-Tfie filtrate from the titanic acid precipitate is concentrated over a naked flame and made up to a volume of 500 C.C. In 100 C.C. of this solution the iron is titrated in the usual manner with permanganate solution, after oxidizing and again reducing.A second quantity of 100 C.C. of the solution is oxidized, and The solution is diluted with water, and the silica filtered off. the iron and alumina precipitated as hydroxides. w. P. s.284 THE ANALYST. The Determination of Calcium and Magnesium. E. Maigret. (BUZZ. SOC. Chim., 1905, xxxiii., 631-634.)-The method is based upon the insolubility of magnesia in solutions of sodium chloride containing not less than 160 grams per litre in the presence of sodium hydroxide in the proportion of 0.8 gram per litre, and of the considerable solubility of lime in the same medium. Determination of Mag?zesium.-One hundred C.C. of the solution are mixed in a litre-flask with 10 C.C. of a solution of sodiunl hydroxide (80 grams per litre), previously freed from carbonic acid by the addition of barium chloride in slight excess, and standardized on bi-normal hydrochloric acid.After thorough shaking the liquid is made up to the mark with sodium chloride solution (160 grams per litre) and filtered, and 500 C.C. of the filtrate titrated with the standard acid, with phenol-phthalein as indicator. The difference between twice the amount consumed, and that required by the original 10 C.C. of sodium hydroxide solution, multiplied by 0.95, gives the amount of magnesium chloride per litre. Determination of Calcizim and Afag?zesiunz.--One hundred C.C. of the solution are mixed with 20 C.C. of a solution containing 100 grams of sodium carbonate and 20 grams of sodium hydroxide per litre, and standardized on bi-normal acid, using tropaeolin as indicator.The mixture is heated to the boiling-point, then cooled to the ordinary temperature, diluted to 200 C.C. with the sodium chloride solution and filtered, and 100 C.C. of the filtrate titrated with the standard acid, using the same indicator, The dif!€erence between twice the number of C.C. consumed and that required by the 20 C.C. of sodium hydroxide solution corresponds to the amount of calcium and magnesium. By deducting the amount of magnesium previously determined and multiplying the difference by 1.36 the amount of calcium sulphate in grams per litre is obtained. C. A. M. The Application of Bismuth Ammonium Molybdate to Gravimetric Analysis.Edmund H. Miller and Frederick Van Dyke Cruser. (Jozm. Arner. Chem. Soc., 1905, xxvii., 16.)-In this method the bismuth is precipitated as bismuth ammonium molybdate, as in Miller and Frank's method (Journ. Amer. Chem. Soc., 1903, xxv., 926), and the precipitate ignited and weighed as Bi,0s,4Mo0,. To carry out a determination, a large excess (four or five times the theoretical quantity) of ammonium molybdate is added to the bismuth nitrate solution. A few drops of congo red are added, and then dilute ammonia until the solution becomes pink. A little dilute nitric acid is then added until the colour changes to lilac ; the liquid is diluted to 150 or 200 c.c., and slowly heated, with occasional stirring. When the solution is at from 50" to 60" C., it is filtered through a platinum Gooch crucible, and the precipitate is washed with a 3 per cent.solution of ammonium nitrate until the volume of the filtrate is 400 to 500 C.C. The crucible with its cap on is next dried at 160" C. ; when thoroughly dry it is moistened with a few drops of concen- trated nitric acid, and heated at the tip of the flame of a Bunsen burner, so that the bottom is at not inore than a dull red heat. Treatment with nitric acid and ignition are repeated until the precipitate is very light yellow in colour and the weight becomes constant. Results obtained by this method show a maximum error ofTHE ANALYST. 285 -0*0011 gram on about 0.3 grain bismuth. They are as good as those given by Miller and Frank’s method (Zoc. cit.). Incidentally it was found that in the method for the determination of bismuth by evaporation of the solution with nitric acid and subsequent ignition to oxide, porcelain, and not platinum, vessels niust be used, as the latter cause low results owing to the passage of reducing gases through the red-hot vessel. A.G. L. The Oxidation of Sulphites by Iodine in Alkaline Solutions. R. Harmann Ashley. (Zeits. Anorg. Chem., 1905, xlv., 69.)-The author criticises Rupp’s method (Berichte, xxxv., 3694), in which sulphur dioxide and sulphites are determined by allowing their solution to stand for fifteen minutes with an excesB of iodine solution in the presence of 1 grzm of sodium bicarbonate, and then determining the excess of iodine with thiosulphate. He finds that with moderate quantities of sulphur dioxide good results may be obtained by this method, which, however, are due to the balancing of two errors, one arising from the incoinplete oxidation of the sulphite, the other from the fact that in alkaline solution a portion of the thiosulphate is oxidized further than to tetrathionate. With small amounts of sulphur dioxide the second error becomes very noticeable.A. G. L. Influence of Sulphurous Acid on the Determination of Boric Acid. W. Vaubel and E. Bartelt. (Chem. Zeit., 1905, xxix., 630, 631.) - Should sulphurous acid be present in a solution in which the boric acid is to be deter- mined by titration in the presence of glycerol, using phenolphthalein as indicator, a preliminary treatment of the solution to remove the sulphurous acid is necessary; otherwise too low results are obtained.The removal of the sulphurous acid is best attained by boiling the solution after the addition of a strong mineral acid. To prevent loss of boric acid, a funnel or short reflux condensing tube should be placed in the neck of the flask in which the operation is carried out. Oxidation of the sulphurous acid by means of potassium permanganate, nitric acid, or hydrogen peroxide is not to be recommended, It might be mentioned that preservatives containing boric and sulphurous acids are now on the market. w. P. s. Observations on the Use of Diphenylamine as a Reagent for Nitrites, Nitrates, and Chlorates. P. Alvarez. (BUZZ. SOC. Clzim., 1905, xxxiii., 717-719.) -Although nitrites invariably give the blue coloration with diphenylamine solutions, this is not the case with chlorates and nitrates. I n practice the colours most frequently obtained are reddish-brown, changing to green, and finally gray with chlorates ; and reddish-yellow, changing to green, and finally violet, with nitrates, the shades varying with the quantities of substances employed.The author therefore recommends a mixture of freshly prepared solutions in sulphuric acid of diphenylamine and resorcinol, or @-naphthol, as giving more permanent and distinctive tests. His reagent consists of 0.1 grain of crystalline diphenylamine and 0.1 gram of twice sublimed resorcinol in 10 C.C. of sulphuric acid (specific gravity 1.84). Five or six drops of this solution are added to 0.001 gram of the salt under examination in a small flat-bottomed crucible.ilTitmtcs give a very286 THE ANALYST. stable yellowish-green colour, and on diluting the liquid and blowing over the surface the edges of the stain become blue. The addition of alcohol changes the colour to orange. Nitrites give an intense bluish-violet colour, and on shaking the crucible the edges of the stain appear red. The liquid itself becomes red on the addition of alcohol. In the case of chlorates this reagent does not give satisfactory results, but if the resorcinol be replaced by an equal weight of ,@-naphthol in the reagent, and the test applied in the same manner, a dull green coloration is obtained, which changes to dark gray-almost black. On the addition of alcohol the liquid remains gray or black. As these reagents are extremely semitive, not more than 0.001 gram of the salts should be used in the test, especially in the case of chlorates and nitrites.C. A. M. The Determination of Iodine Cyanide in the Presence of Iodine. J. Mil- bauer and R. Hac. (Zed. anal. Chem., 1905, xliv., 286-292.)-The mixture of the two substances is thoroughly rubbed with concentrated sulphuric acid in a mortar, and the contents of the mortar washed by means of sulphuric acid into a Kjeldahl flask, and diluted with an equal volume of water. The flask is now gently heated SO that the iodine is expelled with the steam, after which the temperature is raised and the boiling continued for about an hour to convert the nitrogen into ammonium sulphate, and the ammonia distilled off and determined in the usual way.The results of the test experiments, described in detail, show that the method is extremely accurate. Nessler’s reagent can be used for the detection of iodine cyanide or other nitrogenous compounds in the presence of iodine. The substance is first heated with dilute sulphuric acid (1 : I), and the liquid after concentration to half its volume treated as in Kjeldahl’s method. The distillate containing the ammonia in dilute sulphuric acid is concentrated to a small volume, and after being rendered slightly alkaline is tested directly with Nessler’s reagent. All the samples of commercial iodine thus examined contained only insignificant traces of nitrogen. A solution of iodine cyanide in sulphuric acid is colourless, but becomes pink on standing, and on pouring water down the side of the tube a violet ring appears at the junction of the liquids.C. A. M. Standardization of Permanganate Solutions by Means of Silver. K. Hopfgartner. (Monntshefte f. Chem., 1905, xxvi., 469.)-The method used depends on the solution of silver by a ferric sulphate solution, the resulting ferrous sulphate being then titrated with the permanganate solution which is to be standardized. Since the reaction is reversible, a large excess of the ferric salt-pre- ferably ferric ammonium sulphate-is used. To diminish the hydrolytic dissociation of the ferric salt, which, owing to the colour of the dissociated salt, interferes with the titration, the solution is made strongly acid with sulphuric acid. The form of silver found best was the finely-divided precipitate obtained by heating a solution of ferrous sulphate with silver sulphate. Quantities up to 2.5 grams of this silver may be dissolved in about twenty minutes at the boiling-point. Solution and titration are carried out in an atmosphere of carbon dioxide, Suitable proportions for a test are 0.7 gram silver and 25 grams ammonia alum dissolved in 150 C.C. of water and287 THE ANALYST. 10 C.C. of sulphuric acid. When all the silver has dissolved, the liquid is cooled and diluted to about 600 C.C. with 10 per cent. (by volume) sulphuric acid. Two solutions, the iron values of which had been found to be 3,0222 and 28.300 grams respectively per litre by the hydrogen peroxide method, were found to have the iron values 3,0249 and 28.255 respectively. Since 1 gram of silver corresponds to 0.51773 gram of iron, and 1 gram of copper corresponds to 1.7573 grams of iron, silver-copper alloys may be analysed by dissolving a weighed amount in ferric sulphate solution and titrating with perman- ganate ; but solution takes a considerable time in this case. Thus, in a, silver-copper alloy containing 83.50 per cent. of silver, 83.57 per cent. of silver were found by this method. A. G. L.

ISSN:0003-2654    

DOI:10.1039/AN9053000280

出版商:RSC    

年代:1905

数据来源: RSC

摘要:

THE ANALYST. 287 APPARATUS. Apparatus for Evaluation of Coal-tar. A. Rispler. (Chem. Zeit., 1905, xxix., 488.)-The apparatus illustrated by the accompanying figure has been designed by the author to avoid the difficulty usually cxperienced from the boiling over of the tar on distillation. The apparatus consists of a still which is capable of holding 5 or 6 kilo- grams of tar. The top of the still has two short tubes, one of which is fitted with a glass T-piece carrying a ther- mometer and connected with a Liebig's condenser ; the other connected through a tap to a funnel-shaped vessel, which can contain about 13. kilograms of tar. There is another tap near the bottom of the still, and the still itself is heated by a large burner. For use, a quantity of 5 to 6 kilo- grams of tar is weighed out, and of this about 18 kilograms poured into the funnel-shaped vessel ; about half this quantity being let into the still.If the tar is very viscous, the funnel is heated by hot water or steam. The still is then heated and the tar begins to distil. When the thermometer reaches 110 to 120" C., the tap from the funnel is opened and tar run in at a rate that allows the temperature gradually to rise to 130°, which is then maintained n c throughout the operation by regulating the current of the incoming tar. In this288 THE ANALYST. A manner the whole 5 to 6 kilograms can be distilled within an hour, the funnel being, of course, filled up as required. This estimation of water and light oil being com- pleted, any further determination can be carried out in the ordinary manner.The apparatus lends itself to a number of successive determinations ; the tar deprived of water and light oil can be run off through the bottom tap, and the apparatus is then at once ready for a second experiment. The author states that five or siK such determinations can be made in this manner in one day. The apparatus can be obtained from the firm ‘‘ Vereinigte Fabriken fur Laboratoriumsbedarf,” Berlin, N. E. K. H. Gas-Holder with Constant Flow. Mario Betti. (Chzena. Zeit., 1905, xxix., 219.)-An improved form of Mitscherlich’s gasometer in which, by suitable construction of the water inlet-tube, a flow of gas at a constant pressure is obtained. Instead of the usual inlet-tube reaching to the bottom of the container, a double concentric tube is employed, of the shape shown in the figure.This forms a hydraulic valve, which allows water to flow into the container until the pressure of gas in this is equal to the weight of the column of water above the vessel (h). By varying the height of the upper reservoir, and maintaining the level of the water in this, the gas pressure may be kept at any desired point. H. A. T. Potash Apparatus for the Rapid Absorption of Carbon Dioxide. (Chem. Zed., 1905, xxix., 569, 570.)-The form of the apparatus is In the inner part of the apparatus ( I ) is placed a concentrated potassium hydroxide solution containing a little soap. As the gases bubble through the solution, a froth is formed which - greatly aids absorption of the carbon dioxide. The outer part (11) contains concentrated potassium hydroxide solution, to which has been added a small quantity of calcium chloride, or the solution may be made up with hard water.This destroys any of the froth which is carried over into this part of the apparatus, and prevents fouling of the calcium chloride drying-tube. The soap solution is prepared by dissolving 5 grams of ordinary yellow soap and 50 grams of potassium hydroxide in 150 C.C. of water The solution is warmed and filtered. For the second solution 100 grams of potassium hydroxide and 0.04 gram of calcium chloride are dissolved G. Seholer. shown in the accompaiying illustration.THE ANALYST. 289 in 100 C.C. of water. Filtration is not necessary. The combustion gases may be passed through the apparatus at the rate of ten bubbles per second, w.P. s. Apparatus for Determining the Melting-point of Organic Substances. A. Landsiedl. (Oesterr. Chent. Zeit., 1905, viii., 276, 277.)-The general form of the apparatus and its various parts are shown in the accompanying figures. A thermometer (T, Fig. 1) and a capillary tube (r) are placed in a tube (a) 25 cm. FIG. 2. FIG. 1. F1 n 3 . FIG. 4. FIG. 5 . long and 15 mrn. wide, closed at the bottom and provided with a cork at the top, through which the capillary tube and thermometer pass. This tube (a) is placed in the wider tube ( b ) , which is two-thirds filled with sulphuric acid. A small side-tube (Fig. 2) or hole (8, Fig. 3) prevents pressure being formed in the acid vessel (b). The latter stands on a, stout piece of wire-gauze, and may be surrounded by a glass jacket (c), placed on an asbestos ring (d).The substance290 THE ANALYST. of which the melting-point is to be determined is placed in a capillary tube, shaped as in Fig. 4. The widened top of this is held by the slightly constricted bottom of the capillary tube ( T ) , so that the substance ie brought close to the bulb of the thermometer. If ordinary cylindrical capillary tubes be used, a small cup-shaped support is placed on the tube (r, Fig. 5 ) to hold them in position. A screen (s) before the illuminating flame will be found useful. The apparatus gives a very steady rise in temperature. I n determining a melting-point, it is recommended that a preliminary experiment be made, and the actual melting-point then taken, com- mencing with the temperature a few degrees below the point thus roughly obtained.w. P. s. New Automatic Pipette. Von Greiner and Friedrichs. (Zeits. f. angezu, Chem., 1905, xviii., 465.)-In order to avoid contamination with rubber-which is a defect in the earlier automatic pipette brought out by one of the authors some twenty years ago-this new instrument is fitted with a closed cap, the neck of which is provided with a channel corresponding to an opening in the pipette. By rotating this cap the overflow of liquid can be easily let into the pipette again (Figs. 1 and 2). Fig. 3 shows a double automatic pipette, the tap of which is so arranged that one pipette is filled from the reservoir whilst the other is being emptied. Obviously the reservoir must also be provided with a tap by which the inflow can be regulated.E. K. H. Improved Suction Filter. J. Katz. (Chenz. Zeit., 1905, xxix., 489.)-As seen from the figure, the perforated plate, instead of being a fixture and occupying the whole width of the cylinder, is removable, and from 2 to 3 millimetres less in diameter, a rebate being provided to receive it, the height of which corresponds with the thickness of the plate, By this arrangement the filter-paper lies perfectly flat, and no wrinkles are formed at its edges through which a portion of the precipitate may escape. The funnel is readily taken in pieces to clean. A porcelain ring is also supplied, which may be placed inside the funnel to hold down the filter- paper, when it is necessary to pour off the liquid from above the precipitate.The funnel is manufactured in three sizes, for filter-papers 5J, 9, and 15 cm. in diameter respectively, by F. Hungershoff', of Leipsic. E. K. H. The Ashe-Finlayson Cornparascope.-This ingenious addition to the micro- scope may at times prove of considerable value to the analyst, for it enables him toTHE ANALYST. 291 visually place two objects in the same field of view, thus enabling an exact com- parison to be made between the two. As shown in the accompanying figures, the apparatus is attached to the nose of the microscope by an adaptor ( A ) , which takes two objectives, one being at a right angle with the other. To a horizontal arm fixed to the adaptor a fine- focussing stage, with clips (SS'), is provided, also a mirror (M), and for high powers a condenser (C) with iris diaphragm (I). The rays from the vertical objective and those from the horizontal one are divided into two series by a prism (P), so that in half the field the objects on the slide at S are seen, in the other half thoBe on the ordinary table of the microscope.A division ( E ) carried a short way up the tube serves to prevent confusion in the two half fields, The prism (P) can be turned out of position by the milled head b - - J (L), thus throwing the comparascope out of use when the instrument. acts as an ordinary microscope. The apparatus is manufactured by Messrs. R. and J. Beck, of London. W. J. S. Electrically Heated Carbon Tube Furnaces. R. s. Hutton and W. H. Patterson. (Chew. News, 1905, xci., 272, 285.)-The authors describe several forms of electrically heated furnaces, in all of which the heat is obtained by passing a current through a carbon tube. These carbon tubes may be bored from graphite; in this case the current is led in through copper connections fastened to graphite plates into which the ends of the carbon tube are screwed.I t is better, however, to use tubes of aggl-omerated carbon, which may be obtained from the makers of arc carbons. With these tubes connection is made by roughening the ends somewhat, plating them with copper, and then soft-soldering them to thick copper tubes just large enough to slip over them. The copper tube is water-jacketed for a:short distance to protect the joint; at its other end a copper clamp connects it to the flexible cable.Joints made in this way last exceedingly well. To prevent the carbon tubes from burning and to keep in the heat they are surrounded with magnesia, or, preferably, powdered carborundum, kept in place by suitably arranged brickwork. The carbon tubes are aIso extended by glass tubes inserted in the ends by means of asbestos string ; through the glass tubes hydrogen or other gas may be led through the carbon tube. A glass T-tube may conveniently292 THE ANALYST. be used at one end of the carbon tube to furnish a spy-hole through which the interior of the tube may be observed. I n order more thoroughly to exclude carbon monoxide and other oxygen gases, it is advisable to pass hydrogen outside as well as inside the carbon tube. This may be done by leading the gas into the whole space occupied by the carborundum.A better method consists in surrounding the carbon tube though which the current is passing with another carbon tube, also soldered to thick copper tubes at the ends. This outer carbon tube is surrounded with carborundum; the space between the two carbon tubes is filled with hydrogen. As regards dimensions and current required, a graphite tube 28 cm. long, 2 cm. external and 1.5 cm. internal diameter jacketed with carborundum, using a current of 320 amperes at 9.6 volts, melted nickel in thirteen and platinum in sixteen and a half minutes ; an agglomerated carbon tube, 27,cm. long, 2 cm. external and 1-5 internal diameter, jacketed with carborundum, using a current of 140 amperes at 7.7 volts, melted nickel in nineteen, and platinum in twenty-eight minutes; a larger agglomerated tube, 60 cm.long, 8.2 cm. external and 6.7 cm. internal diameter, using 600 amperes at 8.6 volts, gave a temperature of 1200" C. in thirty minutes ; with 850 ampAres at 13.0 volts it melted nickel in twelve and platinum in twenty and a half minutes. As may be seen, all these furnaces are designed to work with high-current densities at low pressures. I t will probably be possible to adapt them to high voltages by cutting a spiral in the tube, thus leaving a helix of much higher resistance (Eizg. Pat., 24,472, November 18, 1903). A. G. L. INSTITUTE OF CHEMISTRY OF GREAT BRITAIN AND IRELAND. PASS LIST OF THE JULY EXAMINATIOXS. OF nineteen candidates who entered for the Intermediate Examination, twelve passed : J. W. Agnew, H. G. Dale, James Dick, jun., W. P. Hayworth, I. M. Heilbron, R. F. Innes, S. Judd Lewis, A. J. C. Lickorish, F. L. Okell, R. P. Page, H. J. B. Rawlins, B.Sc. (Lond.), and D. R. Wood. In the Final Examination for the Associateship (A.I.C.), of five examined in the branch of Mineral Chemistry, three passed : J. B. Hoblyn, Assoc.R.C.Sc. (Lond.), G. W. James, B.A. (Oxon.), and H. H. Kingdon, B.A. (Oxon.) ; of six in Organic Chemistry, four passed : A. W. Bain, B.A., B.Sc. (Lond.), T. W. Cheke, J. Stuart Hills, and D. F. Twiss, M.Sc. (Birm.); and of nine who entered in the branch of the Analysis of Food and Drugs and of Water, including an Examination in Therapeutics, Pharmacology, and Micro- scopy, the following four passed : R. W. Blair, Assoc.R.C.Sc.,I., P. H. Carpenter, J. A. Goodson, and S. Summerson, B.Sc. (Lond.). One candidate passed an examina- tion for the Fellowship (F.I.C.) : E. F. Harrison, B.Sc. (Lond.). The examiners in Chemistry were Mr. W. W. Fisher, M.A., F.I.C., of Oxford, and Dr. G. G. Henderson, M.A., F.I.C., of Glasgow. The examination in Therapeutics, Pharma- cology, and Microscopy was conducted by Dr. 3’. Gowland Hopkins, M.A., M.B., F.R.S., F.I.C., of Cambridge.

ISSN:0003-2654    

DOI:10.1039/AN9053000287

出版商:RSC    

年代:1905

数据来源: RSC