摘要:

MAY, 1905. Vol. XXX., No. 360. THE DETERMINATION OF OXYGEN IN COPPER. BY S. DICKSON. (Read at the Meeting, March 1, 1905.) THE processes for the determination of oxygen in copper in use at the present time, and on which reliance can be placed, are two in number : 1. That devised by Mr. Bertram Blount. 2. That devised by Mr. Leonard Archbutt. The first process is based on the complete fusion of the metal in a current of dry hydrogen, and the water formed collected in a U-tube containing pumice saturated with sulphuric acid. The second process consists in heating the metal (in a fine state of division) to146 THE ANALYST. redness in hydrogen, and the loss in weight is taken as representing the amount of oxygen present. In considering the above processes, and assuming both methods of equal accuracy, the analyst would most probably select that which would be more easily conducted, and for which the apparatus necessary is to be found in everyday use in the laboratory.There is, however, one objection which limits the usefulness of the latter process, and that is, the pieces of metal must be of very small dimensions. The first process, on the other hand, has no such drawback; the size of the pieces is immaterial, and a lump may be and is used. The only objections are the high temperature required for the fusion of the copper, to attain which special apparatus is necessary, and, when using a blast furnace, the heating of the absorption apparatus by radiation, it being by no means easy to insulate it thoroughly. The somewhat lower results obtained by this method, when compared with those given by the process to be described, are, I think, due to such heating.The use of an electrically heated furnace, as described in the February number of this journal by the same author, would no doubt obviate the defect. I n considering the objections to the foregoing methods, and in an attempt to overcome the same, it occurred to me that the property of combination (or solution) of a high melting-point metal with one of low melting-point, at or about the fusing- point of the latter, would probably give the desired result-viz., complete fusion at a. comparatively low temperature, The following experiments were conducted to ascertain if oxygen could be determined accurately in this manner. Ten grams of copper in one piece, and 20 grams of tin (previously fused in hydrogen), were placed in a boat and heated in a porcelain tube until complete fusiora had taken place, dry hydrogen passing through the apparatus as in the fusion process.The water formed caught in the ordinary sulphuric acid and pumice U-tube. Comparative determinations on the same samples were also made by the fusion method, and two by a modified Archbutt method, the gain in weight of the U-tube, and not the loss in weight of the metal, being taken as representing the The method adopted was as follows : oxygen present. Sample I. ... ... 0.15 0.140 ,, 111. ... ... 0.163 0.174 Blast Furnace Method : Heating Fusion Lump Small Piece only ,, IA. ... ... prolonged heating. 0.166 ,, 11. ... ,, IV. ... ...0.132 - 1 I v. ,, VI. ... ... 0.021 ... 0.107 - ... ... 0.161 - - Copper and Tin Lunips. 0.166 0.115 0.188 0.146 0.194 0.022 I A blank experiment was made, using 10.9 grams of copper previously fused by the blast in hydrogen, and 24.1 grams of tin, also fused in hydrogen: the gain in weight of the U-tube amounted to 0.0001 gram. To ascertain the limit of size permitted by the Archbutt method, an experiment was conducted on strips of copper, the dimensions of which were & inch by & inch by 1 inch. The metal was heated in a glass combustion-tube at as high a tempera- ture as possible without undue softening of the glass.THE ANALYST. 147 The amount of oxygen found was 0.061 per cent. The heating was then The original amount found was 0*115 per cent. (No.11) ; therefore a deficit Twenty grammes of tin were then added to the metal used in the above experi- continued for thirty minutes, but there was no increase in the weight of the U-tube. or' 0-054 remains unaccounted for. ment and the whole fused ; the amount of oxygen remaining was : Oxygen ... ... ... ... 0.050 per cent, -or a total of 0.111 per cent., instead of 0-115 per cent. obtained by the tin solution method. A reasonably close agreement. A further experiment was made on copper wire of 0.035 inch diameter. Ten grams were heated in the furnace to a red heat for two and st half hours, at as high a temperature as the glass tube would stand. The gain in weight amounted to 0.00'75 gram. It was reheated for another period of one hour, and when weighed A, Hydrogen generator ; B, wash-bottle ; C, C, sulphuric acid and pumice drying-tubes ; D, platinized asbestos heated with Bunsen burner ; E, furnace with porcelain tube ; F, weighed absorption-tube ; G, guard-tube.the increase amounted to 0*0008 gram. Again, after a further heating for one hour no increase occurred. The amount found by the copper-tin solution method being 0.0100 gram, or a deficit by the heating method of 0.0017 gram. The apparatus consists of a hydrogen generator, drying-tube, platinized asbestos bulb tube heated by Bunsen burner €or the elimination of oxygen, drying-tube, con- nected with the porcelain tube, 1; inch external diameter, in which is placed the porcelain boat containing the copper and tin. The furnace consists of a section of Fletcher, Russell and Coo's tube furnace, which is heated by a battery of five Bunsen burners.The absorption apparatus is a U-tube containing pumice saturated with sulphuric acid, and a similar one as a guard-tube. In conclusion, I have to thank Mr. R. H. Stanger, in whose laboratories the work has been carried out, and Mr. R. Doresa for the care he has taken in making the determinations.148 THE ANALYST. DISCUSSION. The PRESIDENT (Mr. Bevan) having invited discussion, Mr. ARCHBUTT said that it was not altogether correct to speak of the “Archbutt method ” for the determination of oxygen in copper. The method referred to was originally devised by Professor Hampe. He (Mr. Archbutt) had tested it, and, having found it to be a good method, had adopted it for his own use.H e might claim also to have shown that it gave the whole of the oxygen without the trouble of fusing the copper, which was necessary in Mr. Blount’s method. As he had mentioned in describing the method before the Society, comparisons of the two methods had been made, with the kind assistance of Mr. Blount; and with one exception, for which an explanation was given, the results had agreed very well. He was therefore not prepared to find that an increased quantity of oxygen was obtained as the result of adding tin to the copper. He did not understand why, in the experiment in which 0.061 per cent. of oxygen was obtained after one hour’s simple heating of the copper in hydrogen, more was not obtained after heating for a further thirty minutes, if the copper contained more.The action certainly com- menced on the outside, but he thought it gradually penetrated to the interior ; and although he could quite understand that the oxygen might be given up slowly if the piece of copper were thick, he thought it would have been all given up eventually. He had not, however, experimented on the subject, and therefore could only express surprise at the result of Mr. Dickson’s experiment. Since his paper was read he had used some specially-made silica glass bulbs, which could be heated to a very high temperature. He had found, however, that this was not really necessary, for practically the same results were obtained by heating to a good red heat in an ordinary Bohemian glass bulb. Sometimes a trifling amount more oxygen was obtained at the high temperature.Mr. Dickson seemed only to have noted the increase in the weight of the U-tube. He (Mr. Archbutt) took the loss of weight of the copper, and he thought it would have been more satisfactory if Mr. Dickson had done this as well as weighing the U-tube, because the one would have checked the other. The method which he used was, of course, more suitable for copper in very small turnings, which he could obtain without difticulty. If he had to deal with copper in large lumps, he should probably prefer such a me,thod as Mr. Dick- son’s. His remarks had been called forth mainly by the discrepancies, which he should not have expected, in the analytical figures. Mr. BLOUNT said that the author’s process was certainly a very ingenious one. The only objection he could urge against it was that he did not like adding unnecessary materials in large quantity in any process of analysis.Mr. J. H. B. JENKINS said that, in connection with the method used by Mr. Archbutt, the concave surface of the fine copper turnings was full of fissures and minute cracks, so that the surface actually exposed to the reducing action of the hydrogen was very great ; and this fact should be borne in mind in comparing the behaviour of these small pieces of turnings with that of a solid block. Mr. DIUKSON, in reply, said that the whole question of the suitability of the different processes turned upon the state of division in which the metal was obtain- able. Drillinge or turnings were composed of very fine scrapings, agglomerated,THE ANALYST.149 perhaps, by the action of the tool, but still in a very fine state of division; and he quite agreed that, where it was possible to get the copper so finely divided, the whole of the oxygen could be estimated by a simple heating process. With a wire, however, it was difficult, if not impossible, to get the copper into such a fine state of division, and in that case a process of mere heating would fail. His reason for not weighing the copper was simply one of convenience, the experiments having been conducted in tubes. He had started with the idea that the heating method was quite a good one when the particles were fine, and had not considered it necessary to go any farther under those conditions. As to the effect of heating when the pieces of copper were larger, he showed a tube in which some pieces of copper wire had been heated to the highest temperature available, and, although the severity of the treatment was apparent, the attempt to obtain the whole of the oxygen in that way had distinctly failed. Mr. ARCHBUTT said that it would probably have been better had the heating not been so severe. M i . DICKSON, however, thought that the higher the temperature the better the results would be. The PRESIDENT said that the fact that Mr. Dickson had obtained a larger pro- portion of oxygen than either of the other processes yielded seemed to be in his favour, as he had shown that practically nothing was obtained in the blank experiment. + 3 * @ * + € +

ISSN:0003-2654    

DOI:10.1039/AN905300145b

出版商:RSC    

年代:1905

数据来源: RSC

摘要:

THE ANALYST. 149 SOME CONDITIONS AFFECTING THE ETHER VALUE OF BRANDY. BY PHILIP SCHIDROWITZ, PH.D., F.C.S., AND FREDERICK KAYE, A.R.C.Sc. (Read at the Neeting, March 1, 1905.) SOME little while ago we analysed a brandy which showed an ether values of 98.8, the alcoholic strength of the sample was 54.2. This sample, we were informed, was unreduced, and had been drawn direct from bond. At the same time we examined a sample which was stated to be the same brandy from duty paid stock, and reduced in strength to 44-5. To our surprise, the ether value of the latter was found to be only 66-5. At first we were inclined to doubt whether the two samples actually represented the same brandy originally, but our subsequent investigations lead us to say that we believe this to have really been the case.We were further informed that the spirit had been ‘‘ broken down” with New River main water, the object of using this instead of distilled water being, according to our informants, to avoid the slightly mawkish taste that distilled water occasionally imparts to brandy. The cellar operations, which consist substantially in pumping the spirit into a vat, reducing therein with water, with subsequent filtration through paper pulp, and finally bottling, were carried out in the presence of one of us, and samples were drawn at various stages in order to ascertain, if possible, whether any of the operations or vessels were responsible for the falling off of the ether value recorded. In order to avoid needless repetition, we may say that throughout this paper secondary products will be expressed in those terms, and alcoholic strength in per cent.by volume. * Expressed in grams per 100 litres of absolute alcohol.150 THE ANALYST. As a result, we found that none of the operations or vessels-apart from the “breaking down ” with New River tap water, and disregarding for the moment the condition of the bottles-had any material influence in tliis direction. An examina- tion of the influence of the reducing medium, however, afforded evidence that this factor must be taken into serious consideration by shippers and merchants. I n addition, we are satisfied thah the condition, or, rather, quality, of the glass bottles employed in bottling is a question deserving the serious attention of those interested. We propose briefly to allude to the latter point first.The bottles examined by us were of clear white glass, stated to be of excellent quality, and guaranteed to be well cleaned before delivery. Half a dozen of these bottles were filled by us with distilled water, and a few drops of phenolphthalein solution were then added to the contents of each, I n two cases a very pronounced pink coloration was produced at the point of contact of the fluid with the glass, but on shaking up this disappeared. After standing, however, for a few days,‘:’ the two bottles were observed to have developed a distinct pink colour throughout the liquid. After ten days the contents of the various bottles were titrated with acid, using methyl orange as indicator. The two bottles affected required 1-2 C.C.each for neutralization, the others only 0.3 to 0.4 C.C. It is fairly obvious, therefore, that bottles which display the slightest alkaline reaction should be rejected. With regard to the influence of the nature of the water used for reducing, we were able to obtain direct evidence that the ether value is seriously aEected thereby. The results of the experiments were as follows : Number of Sample. 1. Same as 1. 3. Same as 3. 5. Same as 5. 7. Fame as 7. Alcoholic Strength. 44.37 45.40 39-14 39.09 33.15 33-12 24-13 23.62 Alcoholic Strength of Original. 55-46 do. 55-88 do. 55-60 do. 48.27 do. N.B.-The time refers t o the number of Water Used for Dilution. New River main do. do. distilled New River main distilled New River main distilled Ether Value. 66.9 67-0 87-4 98.4 55.2 62.7 51.7 57.3 Ether Value of Original.78-2 do. 100.6 do. 69-3 do. 57.3 do. Time in Da.ys. 7 do. 1 2 do. 2 d 0. 4 do. avs the mixtures of brandv and water were allowed to stand betore being analysed. From the above it will be seen that distilled water exercises very little, if any, influence on the ether value, but that an undistilled water (of otherwise excellent quality) may cause a falling off of nearly 15 per cent., if not more. The figures given at the commencement of this paper indicate that a loss of as much as 30 per cent- may arise from this cause. We found also, as might have been expected, that the use of New River tap water appreciably affected the acid value of brandies. The following results illustrate the differences obtained in this regard, using distilled and tap water respectivily as diluents.* We need scarcely say that all the bottles mere kept tightly corked and completely filled throughout.THE ANALYST. 151 Distilled water ... 125.0 ,New River main water 80.6 [Original brandy] . . . 46.6 Distilled water ... 58-6 N( 3. 5. [Original brandy ... ... 43.7 Distilled water . . . ... 55.3 New River main water . . . 13.3 4. separate tables. TOTAL ACID. No. of Experiment. 1. 2. 3. 4. 5. 6. 6a4:. 7. 8, 8a*. 9. 9a*. 10. IOU". 11. Ha::. 12, 120':'. Acid in Each Sample before Blending. Theoretical Mean. 55.25 39.1 76-7 58.25 74.0 81.6 do. 27.1 91.9 do. 99.5 do. 86.75 do. 53-55 do. 45.5 do. Found in Blend. 45.4 40.0 90.5 62.7 61.2 103.1 41.9 89.6 112.0 66.0 52.7 47.2 1 47-21 [ncrease or Decreasc Per Cent.- 17.8 + 2.3 + 15.2 + 7.0 - 17.2 - 0.24 + 20.8 + 35.3 - 15.1 - 2-3 - 0.4 + 11.1 - 25.1 - 23.9 - 6.6 - 1.5 + 8.7 * Same sample after three weeks.152 THE ANALYST, Looking at the above figures, it is clear that the total acid in a blend is by no means necessarily equivalent to the theoretical mean of the constituents. I t also seems that time plays a not unimportant r61e in the changes that take place-that is to say, time quite apart from any actual maturing-as the above samples were kept in glass bottles full to the neck. The deviation from the mean in the case of the non-volatile acid is not so marked as with the total acid, if we restrict this remark to the figures obtained immediately after blending, for in several cases very remarkable differences were observed after the lapse of three weeks-differences which we certainly cannot explain at present.Omitting the general table, which, as we have indicated, is of no particular interest, we subjoin figures in this connection which we believe to be worthy of attention : NON-VOLATILE ACID. No. of Experiment. 6. 6a*. 8. 8a*. 9. get;:::(. Acid in Each Sample before Blending. Theoretical Mean. 63.0) 4.2 [ do. 12-51 do. 36.8 j ;;:I} do. 33-6 do. 24-65 do. 37.7 do. Pound in Blend. Increase or Decrease Per Cent. 51.6 44.7 28'5 t 33*7 64.6 t + 9-1 + 34.8 + 15.6 + 80-9 - 13.3 + 71.3 With regard to the ethers, the deviations from the mean produced by blending were in a few cases found to be appreciable, and certainly larger than we have found the experimental error to be.At the same time, the results in this regard are not as striking as in the case of the acids. The following figures show the maximum deviations observed : No. of Experiment. Ethers in each Sample before Blending. 3. 8. 8a*, 11. Ha*. 12. 12a*. Theore tical Mean. 117.45 79.7 do. 91-6 do, 76.65 do. Found in Blend. 124.4 73.0 70.9 99.6 93.5 82.5 87.0 Increase or Decrease Per Cent. + 5.8 - 8.5 - 11.0 + 8.7 4- 2.0 + 7.5 + 13-5 * After three weeks.THE ANALYST+ 153 DISCUSSION. The PRESIDENT (Mr. Bevan), referring to the alteration in acidity which accorn- panied the use of New River water, said that this would obviously be accounted for by the fact that that water was alkaline. I t was remarkable, however, that the ethers also should have decreased on the addition of water, unless, indeed, the water contained a good deal of carbonate of soda.He had made one or two small experi- ments in this direction by mixing with alcohol small quantities of ethyl acetate and adding water containing in one case sodium bicarbonate and in another case calcium bicarbonate. Contrary, however, to the author’s experience, he had not found any alteration to take place after several days. Obviously, a man might use any reasonable water-supply that he chose, and if in some cases the ether content was reduced, a very grave question was opened for the magisterial mind to consider. Mr. FISHER said that he had recently had a sample of strong spirit from the Midi, which was said to be pure grape spirit, and which contained a high proportion of ethers, and it had occurred to him that if such a spirit mere mixed with distilled water some of the ethers would hydrolyse, and that, in view of this possibility, it would be desirable to ascertain whether the acidity of the spirit was altered.Accord- ingly, he had diluted it with an equal volume of distilled water and redistilled the mixture, but had found that the acidity that came over was entirely unaffected; so that apparently there had been no hydrolysis that could be attributed to the addition of distilled water and subsequent distillation. That, in so far, was rather against the authors’ conclusions. Dr. J. T. HEWITT said that he was very glad this matter had been brought forward, because there were several things that must affect the ether value to a certain extent.For his own part, he was rather surprised that, on breaking down the brandy with a high ether value, so slight a diminution in the ether content had resulted. Re should like to ask whether the authors had made any attempt to ascertain whether any constant value was obtainable for such an expression as- Number of molecules of ethers x number of molecules of water Number of molecules of acid x number of molecules of alcohol, He had been wondering whether the authors were going to say anything about the flasks in which the estimations were made. This was really a very important point, and if thoroughly reliable flasks were not available, the only thing wits to make a control determination, either beforehand or afterwards, with the same materials.He should also like to ask whether the author’s ether estimations were made on the original samples or on the spirit after the removal of aldehydes. The latter mode of procedure was perhaps the more scientifically correct, but, as far as one could judge, most of the published results were obtained on the original samples, and any potash used in resinifying or effecting any other changes in the aldehydes had always been counted as ethers, so that for his own part he was rather inclined to take the total value obtained by working on the original sample. Moreover, it was difficult to eEect the removal of the aldehydes satisfactorily, because nearly all the reagents available for the purpose were of such a nature that one could not quite say whether they would or would not have any eBect on the ethers.One had to take into account154 THE ANALYST. the presence of hydrogen or hydroxyl ions which might affect the saponification and cause a low ether value to be obtained; and, again, certain reagents might act on the ethers and keep back part of their acids in the form of anilides or similarly constituted compounds. Dr. DYER suggested that these changes might conceivably be due to some biological influence, if the water were used straight from the tap and not filtered through a Pasteur filter. Mr. CHAPMAN said that Dr. and Mrs. Veley had some years ago described an organism which was capable of living and developing in tolerably strong rum, and it was not impossible that something of the same sort might occur, as Dr. Dyer had suggested, in the case of brandy.The question of the composition of the glass of the distilling flasks, which had been raised by Dr. Hewitt, was, however, a matter of much greater importance, and in his own laboratory he was in the habit of using carefully selected Jena glass for the purpose. The results which Dr. Schidrowitz had brought before them that evening were exceedingly interesting and curious, but he (Mr. Chapman) must confess that he would have liked to have seen a greater number of results with other kinds of water, such, for example, as the soft alkaline waters from the chalk underlying the London clay, and also with artificially prepared waters. Owing to its practical bearing, the statement made by Dr. Schidrowitz was a serious one, and it was obviously very desirable that further experiments should be made.He was rather surprised to hear that any spirit-merchant employed New River water for the purpose of breaking down brandy, as he should have thought that+ turbidity would have resulted. Mr. CRIBR said that he was somewhat inclined to question the possibility of these changes being entirely accounted for by the saponifying action of New River water. New River water contained about 18 parts per 100,000 of calcium carbonate, and, supposing a brandy to be diluted with half its volume of New River water, about a third of that amount, or 6 parts of calcium carbonate per 100,000, would be avail- able for first neutralizing the acidity and then saponifying the esters. That would represent 12 parts of calcium carbonate per 100,000 parts of alcohol if the brandy contained 50 per cent.of absolute alcohol, and the quantity of acetic acid it could neutralize would only be a trifle greater. As the average amount of acidity was far greater than this, the possibility of the esters being attacked at all seemed to him to be very remote. Mr. W. T. BURGESS inquired whether the artificial waters used by the President were made up so that they contained what might be termed an excess of carbonic acid-for instance, by putting sodium carbonate or calcium carbonate into the water and passing carbon dioxide through it. The PRESIDENT said that he had taken a saturated solution of sodium bicarbonate, estimated the soda, and diluted it down; and had then used a rather large quantity, representing about 70 parts of sodium carbonate per 100,000.I n the case of the calcium carbonate he had simply passed an excess of carbon dioxide through water containing calcium carbonate in suspension. He did not, however, lay much stress on these experiments. Dr. DYER observed that one could not argue necessarily from ethyl acetate to the esters in brandy. The esters were calculated in terms of ethyl acetate, but thatTHE ANALYST. 155 might under some circumstances be a very stable thing, whereas some esters might be very unstable. The PRESIDENT said that it had merely occurred to him that, if there were any action, it would serve as confirmatory evidence. I t did not, of course, follow that because there was no action on ethyl acetate there would be Done in the case of actual brandy.Dr. SCHIDROWITZ, in reply, said that, although it might be anticipated that the acidity should be diminished somewhat on the addition of New River water, it was remarkable that there should be such a diminution in mixed brandies. They had not as yet found any constant of the nature mentioned by Dr. Hewitt. H e quite agreed with what had been said in reference in flasks. They were very careful as to this, and the experiments had been practically all made in the same flasks and under the same conditions. The aldehydes had not been removed previous to the estimation of the ethers. He had found in practice that the difference in the results due to the removal of aldehydes was, practically speaking, inappreciable. They had used the New River tap-water direct from the main, as it had been used in the case in question. With regard to Mr. Cribb’s remarks, he could only say that the results of their experiments were purely matters of fact, and he might point out that they had not advanced the theory that the changes recorded were due to the alkalinity of the water. Possibly the explanation suggested by Dr. Dyer might be the correct one. The PRESIDENT asked, as bearing on Dr. Dyer’s suggestion, how long the blended brandies had been left to stand. Dr. SCHIDROWITZ said that the mixed samples were examined immediately, and the same brandies were then left to stand for periods of three weeks, when the examination was repeated. In the experiments with water, the examinations were made after periods of two to twelve days had elapsed subsequent to the dilution.

ISSN:0003-2654    

DOI:10.1039/AN9053000149

出版商:RSC    

年代:1905

数据来源: RSC

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THE ANALYST. 155 ABSTRACTS OF PAPERS PUBLISHED IN OTHER JOURNALS. FOODS AND DRUGS ANALYSIS. The Examination of Butters for Adulteration by Coeoanut Oil. A. Muentz and H. Coudon. (Ann. d. Z'Inst. Agron., 1904, iii., Part 1.)-It is well known that the proportion of volatile soluble to the volatile insoluble fatty acids is much higher in butter than in cocoanut oil, and the authors have based on this difference a process for the approximate determination of the latter substance in butter. Ten grams of the fat, melted and weighed at 60" C., are weighed into a cylindrical vessel, and 5 C.C. of potash solution (120 grams KOH dissolved in water and made up to 100 c.c.) are added and stirred for ten minutes, when a hard The method is as follows :156 THE ANALYST, soap is obtained.Saponification is then completed by heating to 70" to 80" C. for a further period of twenty minutes. The saponified fat is washed into a distilling-flask with 200 C.C. of water and gently warmed until solution is complete. The fatty acids are then liberated by the addition of 30 C.C. of phosphoric acid (specific gravity 1-15), and any GO, given off is removed by connecting the flask to a pump for ten minutes. It is important, in order to obtain comparative results, that the dimensions and general arrangement of the distilling apparatus should not vary. The flask, of Bohemian glass, has a capacity of 500 c.c., measured to the bottom of the neck. A fractionating tube is interposed between the flask and the ordinary condenser, and has a total length of 1 metre, with an internal diameter of 14 millimetres.Toreduce the space required it is bent into a zigzag or serpentine form. This tube is connected a (One-tenth the actual size of the apparatus.) to the condenser by a short lateral tube at the upper end, and its total available length from the top of the flask to the lateral tube is about 92 centimetres. The flask, resting upon a copper ring 6 centimetres in diameter, is heated by an ordinary BunBen flame, regulated so as to complete the distillation in one and a half hours. Exactly 200 C.C. are distilled over, and allowed to stand until the following day before filtering through a wet paper. The flask is washed with water (5 c.c.), which is then poured through the filter, and the soluble fatty acids are titrated with lime- water, using phenolphthalein as indicator, the end-point being taken when a pink colour remains permanent for a few seconds.The results are expressed as butyric acid.THE ANALYST. 157 The filter is then washed with four lots of 5 C.C. each of alcohol, poured on drop by drop, the washings being collected in the flask originally used for receiving the distillate. Twenty C.C. of alcohol are introduced into the condenser, the bottom orifice of which has been previously closed ; the alcohol should entirely fill the inner tube, and, after remaining for a few minutes, is run into the distillate flask, and the condenser rinsed with a further 5 C.C. of alcohol. All the insoluble fatty acids are now in the flask, and are titrated in this with lime-water, taking as end-point the formation of a permanent pink colour.The result is again expressed as butyric acid. In forty analyses of pure butters of known origin the volatile insoluble acids averaged 0.65 per cent., and the ratio of these to the soluble fatty acids, according to Insol. acids the formula x i c i a i - - x 100, gave a value of 10 to 15. Cocoanut oil, on the other hand, gave a mean percentage of insoluble fatty acids of 3.405, or, according to the above formula, a value of 250 to 280. The mean value for butter-fat was found to be 12.04, and it is suggested that this should be taken as the standard number. Analyses of various mixtures of butter with cocoanut oil gave the following figures : Insoluble Acids Soluble Acids Butter containing 50 per cent. cocoanut oil ...... ... 73.1 ¶ Y 9 7 20 $ 7 $ 7 7 7 .'. ... ... 27.0 7 , ,? 15 7 ) 9 9 7, - a - ... ... 24.1 ? 7 9 , 12.5 Y 7 9 7 , T ..' . . I ... 22.9 9 , ,> 10 $ 7 7 7 7 9 ..- ... ... 19.8 The authors claim that by the employment of this method it is possible to detect with certainty as little as 5 per cent. of cocoanut oil in butter (cf. ANALYST, xxix., 154). HI. A. T. The Analysis of Vioform and Vioform Gauze. W. Freseniws and L. Grunhut. (Zeit. anal. Chem., 1905, xliv., 25-28.)--Vioform7 which has recently been introduced as an antiseptic bandage dressing, is a bulky powder, with a com- position corresponding to the formula C,H,N.(OH)ClI (chloriodohydroxyquinoline). I t dissolves readily in cold alcoholic potassium hydroxide, and the solution remains clear when diluted with a considerable quantity of water.The addition of nitric acid precipitates the vioform, and if the exact amount required to neutralize the alkali be added, the precipitation is quantitative. I n an analysis the precipitate is collected on a weighed filter, which is then thoroughly washed with cold water, and dried a t 100" C. until constant in weight, Test experiments showed that there was a loss averaging 2-62 per cent. during the drying. 'Vi'oform Gauze.-From 6 to 8 grams of the sample are made into a roll and placed in a Soxhlet's extractor with sufficient potassium hydroxide solution to just cover it, whilst 75 C.C. of alcohol are introduced into the flask beneath. After standing for two hours, heat is applied to the flask, and the extraction with alcohol continued for several hours. The contents of the flask are then diluted with ten158 THE ANALYST. times the amount of water, and the vioform precipitated with nitric acid, dried, and weighed as above described. Finally a determination of the total amount of halogen is made, in order to prove the identity of the powder. Theoretically, vioform requires 70.69 per cent. of silver to combine with the halogens, whilst the author found 67.01 per cent. in a, test experiment. C. A. M.

ISSN:0003-2654    

DOI:10.1039/AN9053000155

出版商:RSC    

年代:1905

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158 THE ANALYST. ORGANIC ANALYSIS. The Determination of Aleohol by the Freezing-point Method. R. Gaunt. (&A. ana2. Chem., 1905, xliv., 106-108.)-The author's experiments have been made with the object of determing to what extent Raoult's method can be used as a practical means of determining alcohol in aqueous solutions. For this purpose Beckmann's apparatus was used, and the freezing mixture of ice-water and salt kept at about - 8" C. The following results were obtained : Amount of Alcohol in 100 Grams of Solution. Lowering of Freezing-point comnared with that of Water. I. 11. Grammes. 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 10.0 12.0 O c. 0.428 0.853 1.271 1.692 2.120 2.554 3.010 3.510 4.525 5.590 C. 0.420 0.845 1-267 1.690 2-135 2'570 3.020 3.520 4.530 5.600 Calculated Decrease for each 1 per Cent.of Alcohol. I. 11. A c- \ c. 0.428 0.426 0.424 0.423 0.424 0-425 0.430 0.439 0452 0.466 c. 0.420 0.422 0.422 0.422 0.427 0.428 0-431 0.440 0.453 0.467 Thus, up to 7 per cent. of alcohol the lowering of the freezing-point is proportional to the amount of alcohol, but at higher strengths it becomes greater. The error of determination corresponds to only about 0.25 per cent. of alcohol, which is negligible for most practical purposes. C. A. M. A Source of Error in the Estimation of Acetone by the Iodoform Method. W. Vaubel and 0. Seheuer. (2eits.f. angew. Chem., 1905, xviii., 214.)-The method of determining acetone as iodoform, due originally to G. Kraerner, was modified by J. Messinger, who treated the solution containing acetone with solution of potash (5 to 6 per cent.), then added excess of a btandardized iodine solution, and, after two minutes' standing, estimated the excess of iodine in the usual way with thiosulphate.Messinger's method, however, does not satisfy all requirements, and the authors have noticed for some time a source of error of especial importance, and the present communication is the outcome of their observations. The principle involved has been worked out by Foerster and Gyr, whose workTHE ANALYST. 169 was not known to the authors at the commencement of their researches. A quotation from areference to Foerster and Gyr’s paper, ‘( The Action of Iodine on Alkalies,” in the Chemisches CentraZbZatt is given, of which the substance is as follows : When iodine is treated with alkalies, hypo-iodite is formed, but the reaction is incomplete, and free iodine exists concurrently with free alkali.The quantity of free iodine compared to a definite amount of hydroxyl ion is, in accordance with the require- ments of the Law of Mass Action, being greater the more iodine ions the solution contains. If bicarbonate is added to a solution of hypo-iodite, the quantity of free iodine is diminished, since the quantity of hydroxyl is decreased. There remains always a certain amount of hypo-iodous acid, as Foerster and Gyr deduce from the fact that the solution requires less thiosulphate than it does arsenious acid. They consider that free iodine converts thiosulphate into tetrathionate, whereas hypo-iodous acid oxidizes it directly to sulphate.Arsenious acid is not oxidized by free iodine, but only by hypo- iodous acid. Dissolved hypo-iodite gradually pmses entirely into iodate. This takes place with very great velocity, but the more slowly the greater the excess of free alkali there is. Rise of temperature accelerates the reaction ; increase in the amount ol potassium iodide present also accelerates the formation of iodate. In consequence of the iodate being formed at the expense of the hypo-iodous acid, thaquantity of free iodine (which is in equilibrium with the hypo-iodite) must also diminish. The authors examined this action further, with the following result : If 20 C.C. of Fo NaOH solution and 20 C.C. of F, iodine solution were mixed, and then titrated back with thiosulphate, 4.0 C.C. TG thiosulphate were used u p ; and if acetic acid were then added, 13-2 C.C.more were required-in all, 17.2 C.C. Thus, there was still an amount of 2.8 C.C. of thiosulphate wanting, which should have been required if the iodine and alkali had reacted, to give one molecule of iodide and one molecule of hypoiodite. Similar results were obtained with other mixtures by using thiosulphate, but when arsenious acid was used, after first acidifying and subsequent addition of bicarbonate, the correct result was obtained. The conclusion of the authors is that, in order to avoid the error in Messinger’s method, it is necessary to titrate back with arsenious acid, and not with thiosulphate. The method suggested by Martz, of standardizing the thiosulphate solution by means of a known amount of iodine dissolved in sodium hydroxide, and again liberated by means of acid, does not completely effect the purpose, as the extent of the error varies with the proportion of iodine to alkali.Further communications will follow. E. K. H. A New Method of Distinguishing between Primary, Secondary, and Tertiary Alcohols. P. Sabatier and J. B. Senderens. (BUZZ. SOC. Chim., 1905, xxxiii., 263, 264.)-The vapours of the alcohol are brought in contact with reduced copper heated to 300” C. and the products of the reaction examined. In the case of a p rimary alcohol, conversion into hydrogen and the corresponding aldehyde takes place. Secondary alcohols yield hydrogen and acetone, while tertiary alcohols are transformed into water and an ethylenic carbide (carbure ithyldnique) which is usually liquid (gaseous in the case of trimethyl-carbinol).In making the test, the tube containing the reduced160 THE ANALYST. copper is closed at one end by a cork, through which passes a capillary tube com- municating with an open tube containing the alcohol, whilst the other end is connected with a condensing vessel. The apparatus is first swept out by means of a current of hydrogen, the copper then brought to about, 300" C., and the alcohol introduced through the capillary tube. The condensed liquids are examined for the respective products. If a coloration is given with Schiff's reagent (a solution of fuchsin exactly decolorized with sulphurous acid), the alcohol is primary. If no coloration is obtained, 1 gram of semicarbazide hydrochloride niixed with 1 gram of potas- sium acetate and 6 C.C.of water are added, and the formation of a precipitate immediately or after a few seconds indicates acetone and that the alcohol is secondary. The non-formation of a precipitate shows that the alcohol was tertiary, and the presence of an ethylenic carbide can be identified by the addition of a drop of bromine, which is immediately decolorized. C. A. M. The Origin of Fusel Oils. 0. Emmerling. (Berichte, 1904, xxxvii., 3535- 3538.)-Under the ordinary conditions of alcoholic fermentation of pure worts con taining different carbohydrates, only traces of fusel oil are produced by different kinds of yeasts. The author finds, however, that numerous anaerobic bacteria, are capable of converting carbohydrates, notably starch and cane-sugar, into higher alcohols, especially propyl, butyl and amy 1 alcohols.Typical micro-organisms possessing this property are Granulobacter butyliczm and B. orthobzctylicus, and certain species of bacteria invariably present on the skins of potatoes. Fusel oil is only produced under anaerobic conditions, and much larger yields are obtained by the use of non-hydrolysed material, leaving the bacteria to effect the hydrolysis themselves. Hydrogen, carbon dioxide, butyric acid and traces of ethyl alcohol are also formed during the fermentation, which proceeds well at 37" C. The addition of nitrogenous compounds does not increase the yield of fusel oil. C. A. &I. A Direet Method of Estimating Glycerin. A. A. Shukoff and P. J. Schestakoff.( Z e d s . f . aizgew. Chem., 1905, xviii., 294.) - Most processes in present use in analytical practice for estimating glycerin depend on indirect methods, based on its oxidation products (Benedikt and Zsigmondy, Hehner), or saponification of its esters (Acetin method). The difficulty in employing a direct method of extraction by shaking up an aqueous solution with any organic solvent lies partly in the limited solubility of glycerin in organic solvents, and partly in the great avidity with which it is retained by the water. The authors have, however, succeeded in overcoming this difficulty, and in working out a practical method for the direct estimation of glycerin. Their method consists in mixing the glycerin-containing solution with powdered anhydrous sodium sulphate, and extracting the mass so obtained with dry acetone. The process, in detail, is as follows : If the solution to be analysed is alkaline, it is first made slightly acid with sulphuric acid, and any precipitate filtered off.The filtrate is then made slightly alkaline with potash ; if the solution is originally acid, the potash can be added directly. The solution so obtained is then concentrated to a syrup at a temperature notTHE ANALYST, 161 exceeding 80" (to prevent loss of glycerin) ; solutions which precipitate salts on con- centration are evaporated to a semi-solid consistency. A quantity of material should be taken which will yield not more than 1 gram of pure glycerin. Thus there is obtained a nearly dry powdery mass on mixing the evaporated liquid with 20 grams of ignited powdered sodium sulphate, which can be easily transferred to a paper thimble for the Soxhlet extraction apparatus. The form of Soxhlet used must be such that all joints are of glass ground to fit, as acetone attacks cork and rubber.The acetone used for extraction should be well dried over ignited potassium carbonate, and distilled. The extraction takes about four hours. If, after distilling off the acetone, the glycerin shows oil-drops on the surface, these can be got rid of by washing with low-boiling petroleum spirit. The glycerin is now dried in an air-bath at 75" to BOO, till the weight is constant (usual time four to five hours). The temperature must not exceed this limit, and the bulb of the thermometer should be placed close to the side of the flask, which is closed by a well-fitting stopper for weighing. Solutions containing more than 40 per cent.of glycerin do not need concentration, but can be treated with sodium sulphate at once. The authors give figures which show comparative results by three methods : direct extraction as above, specific gravity, and Hehner's method. The figures indicate that the new method is quite equal in accuracy to the old. E. K. H. Detection of Dextrose by Barfoed's Cupric Acetate Method. H. C. Sher- man. (American SchooZ of Mines Quarter&, 1905, xxvi., 159, 160.)-This method* is useful for distinguishing between dextrose (or other monosaccharide) and those disaccharides which also reduce Fehling's solution. The solution employed is prepared by dissolving 45 grams of neutral crystallized cupric acetate in 900 C.C.of water, filtering if necessary, adding 1.2 C.C. of 50 per cent. acetic acid, and diluting to 1 litre. A portion of this solution when heated in a water-bath must show no change. Five C.C. of the solution to be tested are mixed in a test-tube with 5 C.C. of the reagent, and heated in a water-bath for three and a half minutes. The contents of the tube are then examined for cuprous oxide, viewing the tube against a black background in a good light. If no evidence of reduction be found the tube is kept at the ordinary room temperature for ten minutes and again examined. Under these conditions maltose and lactose do not reduce the reagent, but longer heating or the use of a more acid solution causes a reduction, owing to the hydrolysis of the disaccharide.In order to prevent this, the solution may be heated to 40" C. only. At this temperature, however, dextrose itself reduces so slowly that the heating must be continued for several hours. The test is capable of distinguishing between dextrose and maltose in aqueous solutions containing less than 0.02 per cent, of the former and 0.2 per cent. of the latter, provided that the results are controlled by check experiments with solutions of known amounts of dextrose and maltose. Dextrin does not interfere, but if proteids are present in the solution to be tested they are precipitated by the copper, and render the test slightly less delicate. w. P. s. * This old process is given because exact directions for working it are now so rarely t o be found.162 THE ANALYST.Determination of Sugar in Urine. J. Bilinski. (Monatshef t Chem., 1905, xxvi., 133-141.)-Varying quantities of the urine are heated in a series of test-tubes, each tube containing 6 C.C. of Fehling’s solution. To determine in which tube the volume of urine added has exactly reduced the Fehling’s solution, a few drops of uranium nitrate solution are added, and the tubes again heated. In those tubes containing the slightest excess of sugar above the quantity necessary to reduce Fehling’s solution, the uranium nitrate is also reduced, and a greenish or brownish coloration is produced. The details of the process are as follows : 50 C.C. of the urine are treated with so much 4 per cent. uranium nitrate solution that a drop of the mixture gives a brown-red colour with a little powdered potassium ferrocyanide.The solution is then diluted to 100 C.C. and filtered. A series of preliminary tests are now made to ascertain how much of this solution is approximately required to reduce 6 C.C. of Fehling’s solution. According to the quantity of sugar thus found, the urine solution is diluted to five, seven, or ten times its volume, and quantities of it differing from each other by 0.1 C.C. and about equal to the volume required to effect complete reduction are mixed in test-tubes with 6 C.C. of Fehling’s solution and a few drops of uranium nitrate solution. The tubes are then heated almost to boiling and allowed to settle. Should one tube exhibit a yellow coloration and the next one, containing 0.1 C.C.more urine solution, a, green colour, the first contains the exact amount of sugar (in the urine) to reduce the 6 C.C. of Fehling’s solution- that is, the volume of urine in this tube contains 0.03 gram of sugar. The method works well with urines containing more than 0.6 per cent. of sugar. With smaller quantities, a little solid sodium hydroxide must be added to each tube, as, with the necessarily large volumes of urine added, the dilute alkaline solution fails t o give a satisfactory coloration. Exactly known weights of grape sugar may also be added to urines containing little sugar, in order to obtain a satisfactory colora- tion, the amount of added sugar being afterwards subtracted from the quantity found. IT-. 9. s. A New Method of Esterifying Organic Acids.A. Werner and W. Seybold. (Berichte, 1904, xxxvii., 3658-3661.)- This is based upon the fact that dimethyl sul- phate reacts upon the alkali salts of organic acids to form the methyl ester of the acid in question. Thus- R.COOK + (CH3),S0, = R.COOCH, + CH,KSO,. Five grams of the acid are dissolved in a slight excess of N-potassium hydroxide solution, and the liquid well shaken for thirty minutes with twice the molecular pro- portion of dimethyl sulphate. It is next heated for thirty minutes on the water-bath to destroy the excess of the reagent, after which it is cooled and an excess of potassium hydroxide added to separate the ester from the free acid. Experimental results are given to show that satisfactory yields are obtained by this method with acetic, iso-valeric, stearic acids, etc.The method can also be used for the methylation of acids, such as 2.4.6 tribromo-benzoic acid and 2.4.6 trinitro-benzoic acid, where the usual method of esterification is impracticable. C. A. M. The Determination of Sulphuric Acid in Malt Worts and the Ash of (Wochens. Brauerei, 1905, xxii., 1 7 ; through Chem. Zeit. Beer. W. Windisch.THE ANALYST+ 163 aep., 1905, xxix., 49.)-The author calls attention to the well-known fact that the amount of sulphuric acid found in the ash of malt worts or beer is much lower than that actually present, unless the ignition took place in the presence of a base as sodium or barium hydrate. The loss of sulphur by reduction is considerably greater than has hitherto been assumed.A series of analyses are quoted, showing that if an alkali is used in the ignition the amount of sulphuric acid found is very materially higher than would ordinarily be the case when no alkali had been employed. H. A. T. Determination of the Viscosity of Lubricating Oils. R. Hackel. (Mitt. kaiserl. konigl. tech. Gewerbe-Museum in Wien, 1905, xv., 44-51.)-Experimental determinations are given showing that determinations made with a ring burner in Engler's vicosimeter involve smaller possible errors at 50" C. and 100" C. than those made without such a burner. The difficulties in the latter case are obviated in an apparatus devised by the author, in which the viscosimeter is connected with two other vessels containing oil. One of these is heated by means of a Bunsen burner, while the oil in the other is cooled by a, cold-water coil, so that the contents of the viscosimeter can be brought to any required temperature by the admission of either hot or cold oil to the heating chamber, which is ring-shaped, and is provided with an additional outlet-tap for drawing off oil that has been made too hot or too cold.C. A. M. The Determination of the Solidification-point of Lubricating Oils. R. Hackel. (Mitt. kaiserl. konigl. tech. Gewerbe Museum in Wien, 1905, xv., 38-43.) -The rapid method of determining the solidification-point of oils by immersing the tube in a mixture of ice and salt is shown to involve errors due to too rapid cooling, and the amount of these is too variable to admit of the use of any factor of correc- tion.The most exact method is to keep the tube of oil immersed for at least an hour in successive freezing mixtures, consisting of ice and water with the following salts in solution, and contained in a vessel of at least 100 mm. in diameter : Parts by Weight in 100 Parts of Water. Salt. - 3 Potassium nitrate . . , ... ... 13.0 - 5 Potassium nitrate and sodium chloride 13.0 and 3.3 - 9 Barium chloride ... ... ... 35.8 - 10 Potassium chloride ... ... ... 22.5 - 15 Ammonium chloride ... ... ... 25.0 - 18 Sodium nitrate ... ... ... ... 50.0 - 21 Sodium chloride ... ... ..* 33.0 For more rapid determinations the author has devised an apparatus in which the oil is cooled by ice and salt much more slowly than in the ordinary method, SO that the results agree more nearly with those obtained by use of the above solutions, I n this apparatus the test-tube of oil is fixed in a larger tube, and both are clamped in a vessel with an exterior chamber containing the ice and salt; so that there is a, double intervening air-spare between the oil and freezirg mixture.The tube is To Produce an Approxi- mate Temperature of- O c.164 THE ANALYST. closed by a rubber cork through which a thermometer passes, and an observation- slit in the outer vessel enables the behaviour of the oil to be watched, whilst the tubes can be raised and shaken in the clamp without coming in contact with the hand. C. A. M. The Determination of Rosin in Shellac. A. C. Langmuir. (Jourrz. Xoc. Chem. Ind., 1905, xxiv., 12.)-The petroleum-ether extract of shellacs gives no reliable quantitative indication of the rosin present, while the test based on the formation of a green colour on shaking the petroleum-ether extract with dilute copper acetate solution fails to show a less proportion than 15 per cent.of rosin. The well-known Storch-Morawski reaction may be made to detect as little as 2 to 3 per cent. of rosin in shellac by treating 1 gram of the sample with 15 C.C. of acetic anhydride, and warming the mixture until solution is complete. On cooling the liquid the rosin remains in solution, and may be filtered from the gelatinous shellac, Two drops of strong sulphuric acid are then allowed to flow down the side of the tube containing the acetic anhydride solution of the rosin, end the liquid gently shaken. An evanes- cent coloration is produced in the presence of even 2 per cent.of rosin. Pure shellacs give no colour if charring has been avoided. According to the author, the Wijs’ metlhod of determining the iodine absorption is the best process for the examination of shellac, since it provides both a qualitative and quantitative test for rosin. Shellac has no effect on the colour of the Wijs’ iodine chloride solution except after long standing ; while rosin, even when mixed with shellac, gives a characteristic red-brown colour in proportion to its amount, and by means of standards a rough colorimetric determination may be made. The well-known difference between the iodine values of rosin (high) and shellac (low) has caused a determination of the iodine absorption to be considered the most valuable as a test of purity of the latter.The author prefers Wijs’ modification, which he works as follows : 0.2 gram of ground shellac is treated with 20 C.C. of glacial acetic acid in a 250 C.C. stoppered bottle, and the liquid warmed somewhat until solution takes place (the wax remains insoluble). Solution takes place more quickly in proportion to the amount of rosin present, shellac being only difEcultly soluble. Ten C.C. of chloroform are added, the solution cooled to 21’ to 24” C,, and kept at that temperature during the determination. Twenty C.C. of the Wijs’ solution are next run in from a pipette having a fine orifice, and the stoppered bottle then laid aside in the dark for exactly one hour. The process is then carried out in the usual way.I n the case of bleached shellac, 0.4 gram is used in the determination, while for rosin 0.15 gram of sample and 40 C.C. of Wijs’ solution are the best quantities. The temperature and time of reaction shouldbe constant, since the author has found very large differences in the results obtained when variations in these conditions are introduced. The effect of the shellac-wax (iodine value 4.5) is small, and may be ignored. The author regards 18 as the maximum iodine value (Wijs’) of a pure shellac examined under the above conditions, and the value 228 as an average for the very variable rosin figures. Shellacs giving 18 to 23 iodine absorption may be regarded as 6‘ fair ” ; at 23 the various qualitative tests show the presence of rosin, while samples giving 23 to 28 are ‘‘ poor.” A liberal excess of Wijs’ solution should be added.THE ANALYST.165 A close connection is traceable between the iodine absorption of a sample of shellac and the quantity of bleaching agent required to bleach it properly. Rosin is bleached only with difficulty and by the addition of a much larger quantity of sodium hypochlorite solution. The colour of the " varnish " obtained by dissolving the bleached and washed shellac, separated from its solution by acid in alcohol in the proportion of 4 pounds shellac to 1 gallon of the spirit, should be compared with that obtained from a sample of known purity. Bleached shellacs have a lower iodine value than unbleached samples, the average figure being about 8 per cent. A figure much exceeding 10 points to adulteration, and for bleached shellacs the figures used in the formula for calculating the proportion of rosin should be 10 and 228.The strength or '' body " of the varnish may be determined by weighing the solid matter obtained on evaporation of the solvent, while an examination of the latter will show its character (wood-spirit, grain-spirit, petroleum spirit, etc.). Rosin may be detected by the iodine value of the solid residue, which should be about 10 to 15. I n the case of a large proportion of rosin, the iodine value of the residue will scarcely give a reliable figure, since the iodine absorption of rosin is materially lowered on heating. It should also be noted that other alcohol-soluble resins, such as sandarac, copd, and kauri, may be present ax adulterants in shellac-varnish.The following is ai simple and reliable colorimetric test for the presence of adulterants in shellac-varnish ; and the test may be readily applied to shellac by dissolving it in alcohol. Five C.C. of gracial acetic acid and 5 C.C. of Wijs' solution are added to 5 drops of the varnish. With pure shellac-varnish the liquid will remain light yellow with a shade of red, while an impure varnish will almost immediately develop a reddish-brown colour, proportional to the rosin, etc., present. Sandarac, copal, kauri, and acaroid resins act like rosin in this test, while their iodine values (Wijs) range from about 120 to 175. A. R. T. ATote by Abstractoy.--E. J. Parry, in the Chemist and Druggist, April 7, 1905, has replied to some of the criticisms in Langmuir's paper, and pointed out certain advantages of the Hiibl method over the Wijs' modification of the iodine absorption in the case of shellacs. Much adulteration is practised in the preparation of shellac-varnish. The Gum of Feronia Elephantum. P. Eemeland. (Jouryz. Pharm. C?L~?IZ., 1905, xxi., 289-295.)-The Feronia el&phantanz, which belongs to the family of Auriantiacis, is indigenous to the East Indies, hut is also cultivated for the sake of its fruit and gum in Ceylon and Java. The gum is sold in the bazaars of Madras under various titles, such as wood -apple gum, Icatbdl - Ici - go.rzd, velampishin, kupithawia ~ ~ S C . Z L W Z , etc. I t is also sold in England, where it is stated to be frequently adulterated with gum arabic. The sample examined by the author was in the form of sinall brilliant translucent particles of about the size of a small pea, some colour- less, and others yellow or reddish-amber. I t contained 17.75 per cent. of moisture, and 6.4 per cent. of substances insoluble in water. The optical rotation of the soluble portion a t 15.5" C. was [aD] = -6O.41'. It yielded 3.61 per cent. of ash containing calcium, potassium, and phosphoric acid, but not iron or manganese. It was found to contain an indirect oxidizing enzyme. It yielded on hydrolysis 35.56 per cent. of pentoses and 42-67 of d-galactose, and thus closely resemble the gum of Cochlosper- mum gossypium in composition. C. A. M.

ISSN:0003-2654    

DOI:10.1039/AN9053000158

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年代:1905

数据来源: RSC

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166 THE ANALYST. INORGANIC ANALYSIS. The Separation of Silver from Lead. H. Lidholm. (Berichte, 1905, xxxviii. , 566-568.)-Silver is reduced from its solutions by various organic compounds, and notably by phenols, whereas lead forms sparingly soluble phenates with many of these. Hydroquinone gives no precipitate with lead, but precipitates silver quantita- tively, provided the solution does not contain free mineral acid, a condition that can be insured by the addition of sodium acetate. The substance is dissolved, with the aid of tartaric acid if necessary, and the solution neutralized, treated with ammonium acetate, and brought to the boiling-point, any precipitated basic lead acetate being brought into solution again by the addition of acetic acid. It is then treated with a solution of hydroquinone in the proportion of 2 C.C.of a 4 per cent. solution to each 0.1 gram of silver, and the resulting precipitate of metallic silver collected, washed with water containing 5 per cent. of ammonium nitrate, dried, ignited, and weighed. If copper or bismuth are present, they too will be partially precipitated, and the ignited precipitate must then be dissolved in nitric acid, and the silver precipitated as chloride, the precipitate being freed from any bismuth by means of nitric acid, as directed by Fresenius, The presence of cadmium does not interfere with the results. C. A. M. The Prevention of Poisoning by Mercury Vapour. N. Tarugi. (Gaxxetta, January 14, 1905 ; through Pharm. Joum., 1905, lxxiv., 367.)-Finely-divided aluminium completely absorbs mercury vapour at the ordinary temperature, even when the vapour is largely diluted with air.On this fact the author bases a delicate test for the detection of mercary, and the action of the aluminium has been utilized (in the form of a respirator) as a preventive measure against poisoning by mercury vapour. A. R. T. The Electrolytic Determination of Small Quantities of Arsenic. C. Mai and H. Hurt. (Zeit. Untersuch. Nahr. Genussmittel, 1905, ix., 193-199.)-The authors employ the apparatus described below, in which the electrodes consist of pure sheet lead (see ANALYST, 1904,268), and the liberated arseniuretted hydrogen is absorbed in silver nitrate solution. The decomposition vessel, A , is connected with the absorption bulbs, B, by means of the short tube, g, which contains pumice stone soaked in alkaline lead solution.The pointed upper ends of the cathode, e, and the anode, a, are cemented into glass tubes, b, passing through the stoppers of the apparatus. The funnel, d, has a capacity of 25 c.c., and the bore of its capillary stem is of such diameter that the solution under examination enters the apparatus drop by drop. A 12 per cent. solution of pure sul- phuric acid is placed in A up to the height indicated in the illustration, and 10 C.C. of && silver nitrate solution are introduced into the absorption bulbs, B. The current may be obtained from the main, and regulated by a suitable resistance. After working the apparatus for some time, to prove that the acid and electrodes are free from arsenic, the solution to be tested is allowed to enter, without interrupting the current.Should The safetg-tube, c, is filled with water. The quantity of solution used should not exceed 10 C.C.167 THE ANALYST. arsenic be present, the silver solution is darkened within a few minutes, and after two, or at the most three, hours the reduction is completed. The contents of the bulbs are then filtered, the filter is washed with a, little water, and the excess of silver in the filtrate titrated with T& thiocyanate solution as usual. One c . ~ f of +ia. silver nitrate solution is equivalent to 0.125 mgm. of arsenic or 0.1655 mgm. of arsenic trioxide. When the quantity of arsenic present is less than 0.02 mgm., the titration method fails, and the reduced silver must be determined colorimetrically. For minute traces of arsenic, down to 0.0005 mgm., the absorption bulbs may be replaced by the combustion tube of a Marsh apparatus and an arsenical mirror obtained in the usual manner.w. P. s. Electrolytic Analysis of Cobalt and Nickel. F. M. Perkin and W. C. Prebble. (Chewz. News, 1904, xc., 307.)-Cobalt and nickel were deposited electro- lytically from various solutions. With cobalt, solutions containing sodium hypophos- phite gave very high results, the deposit containing about 5 per cent. of phosphorus. Ammonium oxalate and tartrate also gave somewhat high results, due to the presence of carbon in the deposit. Similar results were obtained with ammonium borate. The best results were given by solutions containing an alkali phosphate and a small quantity of free phosphoric acid.The procedure used was as follows: About 1 gram of CoSO;(NH,),80;6H,O (containing 14.94 per cent. of cobalt) was dis- solved in 50 c . ~ . of water; 5 c . ~ . of a 5 per cent. solution of phosphoric acid and 25 C.C. of a 10 per cent. solution of ammonium, or, better, sodium dihydrogen phos- phate, were then added, and the solution was made up to 130 C.C. and electrolysed, using a gauze-flag cathode. After about thirty minutes, 0.5 gram of hydroxylamineTHE ANALYST. 168 sulphate or chloride is added to dissolve a brown deposit which forms on the anode, and after the bulk of the cobalt has been deposited, it is advisable to add a few drops of ammonia to neutralize the acid liberated. With a current density of 0.3 to 1.8 ampere per 100 square centimetres the operation is complete in from three to three and a half hours at about 55" C.; it is best to start with a low current density, and to increase this after about one hour. The deposit obtained is brilliant ; the error varies from about 0.14 to 0.45 per cent. on the cobalt. Solutions con- taining ammonia and ammonium borate, on the other hand, gave very good results. With ammonium tartrate solutions good results can be obtained if care is exercised, but they are apt to be erratic. With ~zickeZ, phosphate solutions gave unsatisfactory results. A. G. L. The Analysis of Iron Sesquioxides. H. Cormimbeuf. (Ann. de Chiqn. anal., 1905, 95, 96.)-About 0-5 gram of the sample is treated with an excess of hydrochloric acid to which are added a few crystals of potassium iodide to act as a reducing agent.After applying heat for a few moments, complete solution of all the iron is obtained, even in the case of the most refractory colcothars. The liquid is diluted with water, oxidized with nitric acid or bromine-water, and filtered from the residue of sand, etc. The iron in the filtrate is precipitated by means of ammonia, and the calcium and sulphuric acid subsequently determined in the usual manner. C. A. M. Determination of Phosphorus in Iron Ores. J. S. Rowland and Llewellyn J. Davies. (Jo7cm. Xoc. Chem. Ind., 1904, xxiii., ll86.)-By incineration of the ore with magnesia, and subsequent treatment with dilute nitric acid, a solution is obtained which contains all the phosphorus, and the yellow molybdate precipitate can be subsequently titrated with a standard caustic soda solution, 1 C.C.of which is equivalent to 0.0001 gram of phosphorus. A quantity of pure yellow molybdate precipitate, dried at 100" C., and preserved in a stoppered bottle, is required. One or two grams of the dry, finely-ground sample are well mixed with 2 gram of calcined magnesia free from phosphorus, and the mixture heated in a shallow porcelain dish to bright redness in a muffle-furnace. After cooling, the mixture is dissolved in 25 C.C. of nitric acid (equal parts acid of 1-42 specific gravity and water) by boiling the liquid for ten minutes. After standing, the clear liquid is filtered into a flask. Twenty-five C.C. of water are added to the residue, boiled for five minutes, and filtered through the same filter, washing the residue until free from acid.Five C.C. of ammonia are next added and the solution boiled, and then 50 C.C. of ammonium molybdate solution (E. F. Woods' 1888 formula), and the mixture shaken for ten minutes. The liquid is immediately filtered, the precipitate washed five times, each with 1 per cent. nitric acid and potassium nitrate solution (1 gram per litre), and then until free from acid. The filter-paper and precipitate are transferred again t o the flask, a known quantity of standard caustic soda added (10 to 20 c.c.), and the liquid shaken, when the precipitate will readily dissolve. After diluting the liquid with water to about 50 c.c., the excess of caustic soda is titrated back with standard nitric acid solution, using phenolphthalein as indicator.From the number of c.c.'s of caustic soda required the amount of phosphorus present can be deduced.THE ANALYST. 169 For the preparation of the standard solution of alkali, 7.2 grams of caustic soda are dissolved in 100 C.C. of water, a saturated solution of baryta-water added until no further precipitation takes place, the liquid filtered, and the solution made up to 2 litres. The standard nitric acid solution is made by diluting 10 C.C. of 1.42 nitric acid to 2 litres with water. The acid and alkali are then titrated against each other, and the stronger one diluted until they are of the same relative strength. The phosphorus equivalent of the caustic soda is next determined by titrating it against 0.100 gram of the pure yellow rnolybdate precipitate ( = 0.00163 gram phosphorus). If the caustic soda solution is too strong, it should be diluted with water until 1 c.c.=O.OOOl gram phosphorus.A similar quantity of water should then be added to the standard acid solution to make it exactly equivalent to the caustic soda solution. The presence of silica in the yellow precipitate does not affect the results, which are stated to be very accurate, while the process only requires forty minutes. A. R. T. Estimation of Sulphur in Iron Ores, Slags, Limestone, ete. H. Hart- wigsson. (Chzem. Zeit. Rep., 1905, xxix., 4.)-The method employed is founded on the fact that some sulphur-containing iron ores, when heated in a current of hydrogen, give off their sulphur as sulphuretted hydrogen, and though others do not, in all cases any sulphur not so converted is left in such a condition that sulphuretted hydrogen is evolved on treatment with hydrochloric acid.The analysis is conducted as follows: 1 to 5 grams of the finely powdered sample are introduced in a porcelain boat into a combustion tube. After air has been expelled from the apparatus the tube is raised to a red heat and maintained so for three-quarters to one hour. A stream of hydrogen, purified in the usual way, is then passed through the tube, and the issuing gas passed through two Erlenmeyer flasks of 200 C.C. capacity, containing 30 to 40 C.C. of a cadmium acetate solution, prepared by dissolving 25 grams cadmium acetate in a mixture of 200 C.C. concentrated acetic acid and 800 C.C. water.A yellow precipitate of cadmium sul- phide is usually obtained. The tube is then cooled in a current of hydrogen, the residue transferred from the boat to a filter paper ; the filter paper is carefully rolled up, and placed in a flask, provided with a reflux condenser, to which are connected the two Erlenmeyers used before. The air is expelled by carbon dioxide, and 150 C.C. hydrochloric acid (1 : 2) let in through a dropping funnel; the flask is heated, and, after the evolution of sulphuretted hydrogen has ceased, the contents of the two Erlenmeyers are mixed. An excess of an iodine solution (3.97 grams iodine and 10 to 15 grams potassium iodide in 1,000 c.c., 1 C.C. =0*0005 gram sulphur) is added, the cadmium sulphide then decomposed by the addition of 10 t o 20 C.C.hydrochloric acid, and the excess of iodine over that required to act with the liberated sulphuretted hydrogen found by titration with thiosulphate of soda (7.77 grams in 1,000 c.c., 1 C.C. = 1 C.C. of iodine solution used). The whole process requires' about two hours, and the trial analysis made by the author gave results agreeing well with those obtained by the direct oxidation method. E. K. H.170 THE ANALYST. Determination of Sulphur in Pyrites by Lunge's Method. H. Salvin Pattinson. (Journ. Soc. Chem. Ind., 1905, xxiv., 7.)-Lunge's method is easier and less expensive to work than that of Silloerberger, but the latter gives accurate results when carefully carried out. The author has made experiments with a view to overcoming the following sources of error which may arise in Lunge's process : (1) Retention of iron by the barium sulphate precipitate ; (2) solubility of barium sulphate in the filtrate and washing water ; (3) co-precipitation of barium chloride with the barium sulphate. Lunge avoids (1) by first precipitating the iron with ammonia and filtering off the precipitated ferric hydroxide, but this procedure introduces the possibility of carrying down sulphur in the form of basic ferric sulphate.The author finds that the quantity of hydrochloric acid present in the sulphate solution not only influences the physical character of the barium precipitate, but also affects the proportion of barium chloride carried down with it. Further, the amount of ammonia to be added in excess, to precipitate the iron, decides the formation of the basic ferric sulphate.The following mode of operating is recom- mended: After the oxidation of the pyrites as directed by Lunge, and subsequent separation of the silica, etc., the liquid is heated to 70" C., and the ferric hydroxide precipitated by ammonia, an excess of 5 C.C. of 0.880 ammonia being employed. The liquid is kept a t 70" C. for ten minutes and then filtered, and the precipitate washed in the usual manner. The washing requires from a half to one hour, and the filtrate and washings then measure about 350 to 400 C.C. Without; concentration the liquid is made neutral to methyl-orange by hydrochloric acid, an excess of 1 C.C. of hydrochloric acid of 1.17 specific gravity added, and the sulphate precipitated from the boiling solution by the addition of 20 C.C.of boiling barium chloride solution (10 per cent.). A blank experiment should be made with the materials employed, and the amount of barium sulphate found deducted, in which case the necessity of determining the proportion of sulphate lost in the wash-waters is avoided, since the same error operates both in the blank experiment and the actual deter- mination. Lunge agrees with the author's detailed method of working. A. R. T. The Estimation of Sulphur or Sulphuric Acid in Pyrites by Means of Benzidine Hydrochloride. G. v. Knorre. (Chem. Ind., 1905, xxviii., 2 ; through Chem. Zeit. Rep., 1905, xxix., 29.)-The author finds that the method suggeEited by &fuller (Berichte, 1902, xxxv., 1587) and further elaborated by Raschig (Zed.Angew. Chem., 1903, xvi., 617), in which the sulphuric acid in the benxidine compound. formed is directly titrated, gives excellent results in the analysis of pyrites. The presence of ferric compounds, especially ferric chloride, was observed to oxidize the benzidine compound, discolouring the solution and rendering titration difficult. The iron should therefore first be reduced or separat,ed. Hydrazine hydrochloride and sulphurous acid are satisfactory reducing agents ; whilst tartaric and citric acids and their salts give unreliable results. H. A. T. Determination of Zinc in Blendes, etc. H. Salvin Pattinson and George C. Redpath. (Journ. Xoc. Chem. Ind., 1905, xxiv., 228.)-The authors have ex- amined the three following methods: (1) Von Schulz and Low's Method (Journ.THE ANALYST. 171 Soc.Chem. Ind., 1892, p. 846); (2) Von Berg’s Method (Dittmar’s “Quantitative Analysis”); and (3) Lewis’s Method (ANALYST, xxviii., 93), and consider that the three methods give closely-agreeing results, the most rapid and convenient being the first. Of the two others, Von Berg’s is preferable, since the sulphide precipitate is denser and can be more readily washed; and if cobalt is present, it is completely separated in Method 2, while the presence of this element renders Method 3 inaccurate. Method 1 may be employed in the separation of zinc from iron ores, and is more rapid than the acetate method. A. R. T. Use of Tannie Aeid in the Determination of Alumina. Robert E. Divine. (Jourrt. Xoc. Chem. Ind., 1905, xxiv., 11.)-Owing to the difficulty of filtering and washing alumina precipitates free from chlorides, the author has employed tannic acid and ammonia to separate alumina from its solutions.To a solution containing about 0.1 gram of alumina, 2 C.C. of a 24 per cent. solution of tannic acid, some ammonium chloride, and ammonia in slight excess, are added, and the liquidhboiled until nearly all the ammonia is expelled. By this method the alumina is obtained in a form which allows of its rapid filtration, especiaily if suction be used; whilst it may be freed from chlorides by washing somewhat, redissolving in hydrochloric acid, reprecipitating with ammonia, and well washing the pre- cipitate. The slight trace of alumina sometimes obtained on evaporating the filtrate and rendering alkaline with ammonia may be added to the a a i n quantity, although its amount is practically negligible.Even in the presence of considerable quantities of lime, magnesia, and chlorides of the alkali metals, the separation of alumina by this method is very complete and satisfactory, whilst the presence of tannic acid does not interfere with the subsequent determination of the lime and magnesia in the filtrate. Large quantities of ferric hydroxide with the alumina do not prevent the ready filtration of the precipitate, although pure ferric hydroxide does not filter well in presence of tannic acid. A. R. T. A New Method of Determining Molybdenum Trioxide and Vanadium Pentoxide in the Presence of each other. B. Glasmann. (Berichte, 1905, xxxviii., 600-603,)- A solution of molybdium trioxide in hydrochloric acid is reduced by either zinc or magnesium to molybdenum sesquioxide, whereas vanadium pent- oxide under the same conditions is reduced by zinc to the dioxide, but by magnesium to the trioxide.Hence, if a solution containing the mixed oxides he divided into two parts, one of which is boiled in a flask fitted with a Bunsen valve, with zinc and hydrochloric acid, and the other with magnesium and hydrochloric acid, a subsequent titration of the two solutions with permanganate solution will give the amounts of vanadium and molybdenum. The difference between the amounts of permanganate consumed in the two titrations thus gives the amount required to convert the vanadium from the dioxide into the trioxide (2KMn04=5V,0,).I n the analysis from 0.25 to 0.5 gram of the substance is boiled for one to one and a half hours with 40 to 45 C.C. of hydro chloric acid (specific gravity 1-19> and zinc and magnesium respectively, The solutions are subsequently poured into large basins containing 300 C.C. of water with172 THE ANALYST. 10 grams of manganese sulphate in solution, and titrated with manganate solution with continual agitation. potassium per- C. A. M. The Reduction of Molybdenum Compounds in Sulphuric Acid Solution by Means of Magnesium. B. Glasmann. (Berichte, 1905, xxxviii., 604, 605.)- Molybdenum trioxide can be reduced by means of magnesium, and the molybdenum then determined by titration with standard permanganate solution. For this purpose the substance is heated for thirty to forty-five minutes with magnesium and dilute sulphuric acid (1 : 5) in a flask fitted with a Bunsen valve.The contents are then transferred to a large basin, diluted with about 300 C.C. of water acidulated with sulphuric acid, and titrated with & permanganate solution at a temperature of 30" to 40" C. C. A. M. The Quantitative Estimation of Tellurium. A. Gutbier. (Sitz Bey. of the SOC. Phys. Med., Erlangen ; through Chem Zed. Rep., 1904, xxviii., 353.)-The author discusses the conditions necessary for successful reduction and precipitation of tellurium by means of hgdrazine, and considers that the solution should be as concentrated as possible. It should contain no nitric acid, and recently precipitated tellurium must also be avoided.Hydrazine hydrate was found to be the best general precipitant. H. A. T. Note on the Quantitative Estimation of Tellurium. A. Gutbier and W. Wagenknecht. (Joura. Pract. Chem., 1905, lxxi., 54; through Chem. Zeit. Rep., 1905, xxix., 28.)-Frerichs (Jourrz. Pract. Chem., 1905, lxvi,. 54) suggests a process for the estimation of tellurium by means of potassium iodide and sulphurous acid in the presence of sulphuric or hydrochloric acid. From a number of experiments the authors conclude that this method is quite unreliable, owing to the fact that some tellurium tetra-iodide is always formed. H. A. T. Practical Hints for the Performance of an Easy and Convenient Estimation of Potassium. Friedrich Klinkerfues. (Chem. Zeit., 1905, xxix., 77.)-The author disclaims any fresh principle in his method, which is simply a modification of the process based on the reduction of potassium platinichloride to platinum by formic acid.The modification consists in reducing to platinum in a weighed platinum dish and washing by decantation without transferring the pre- cipitated platinum to a filter, as the author finds it adheres to the dish sufficiently to prevent any loss. The modified process is carried out as follows: From 0.5 to 1.0 gram of substance, according to its potassium content, is dissolved in water, excess of platinic chloride solution added, and the whole evaporated to dryness on the water-bath. A little water is added to the residue, which is then rubbed up with a stirring rod, and extracted with alcohol until all matter soluble in that menstruum is removed, the alcoholic washings being passed through a filter in order to retain any particles of potassium salt which may be carried over.The residue in the dish is then dissolved in boiling hot water, and passed through the before-mentioned filter into a tared platinum dish, a couple of drops of formic acid added, the whole evaporated to dry-THE ANALYST. 173 ness, and the residue repeatedly extracted with hot water until no more chloride or sulphate occurs in the washings-in some cases it may be necessary to first digest with 5 per cent. HC1 for half an hour. The platinum basin is then gently ignited, allowed to cool in a vacuum desiccator and weighed, and the platinum calculated to K,O. The author finds this method accurate with an error of less than 0.3 per cent. He recommends it especially for cases where potassium is to be estimated in super- phosphate, etc.Experiments are in hand to determine whether any cheaper material can be substituted for the platinum basin. E. K. H. Eschka’s Method of Estimating Sulphur. C. Bender. (Zeits. f. ayzgew. Chem., 1905, xviii., 293.)-The author has made experiments with a view to comparing the merits of Sauer’s method for determining sulphur in coal with that of Eschka, and has obtained identical results, even when Eschka’s method was conducted over a gas-flame. The author modified Sauer’s pro- cess by using platinum foil in place of a combustion-tube for the com- bustion. Eachka’s method, which was also modified so as to prevent the com- bustion gases from coming into contact with the heated mixture of coal and soda-magnesia, is conducted as follows : The mixture is placed towards the closed end of a tube of difficultly fusible glass, about 18 centimetres long and 2.3 to 3 centimetres in diameter, which is left open at the other end.Having been completely dried in an air-bath, it is clamped horizontally in a stand (see figure), and is heated by a Bunsen burner capable of giving a powerful fiame. Heat is first applied to the border of the mixture, and the flame gradually moved along the tube, which is rotated from time to time, and the heating continued until the mass is white, On the completion of the combustion the holder is lowered, the tube somewhat inclined, and a porcelain dish placed directly under it.On cooling, the tube usually breaks up and falls into the dish. The residue is treated as in the original process of Eschka. The author recommends that the tubes should be obtained from a professional glass-blower . E. K. H. A New Iodometric Method of Determining Alkali Heptamolybdates. (Berichte, 1905, xxxviii., 193, 194.)-Iodine is precipitated from an B. Glasmann.174 THE ANALYST. aqueous solution of potassium iodide and iodate, through the conversion of the heptamolybdate into a neutrd salt and free molybdic acid, which then reacts with the mixture. Thus- (a) 3(NH4),M~702, + 12H20 = 9(NH4),MoO, + 12H,llI00, ; I n the analysis from 0.2 to 0.3 gram is mixed with 0-5 gram of potassium iodide, 0.1 gram of potassium iodate, and distilled water in the distillation flask of Bunsen’s iodine apparatus.The mixture is then distilled, and the iodine collected in the receiver and titrated with standard thiosulphate solution. One part by weight of ammonium heptamolybdate, (NH4),Mo7O2, + 4H,O, is equivalent to 0.822 part of iodine. ( b ) 20KI + 4KI0, + 12H,MoO, = 12K,Mo04 + 121, + 12H20. The analytical results show that this method is very accurate. C. A. M. Some Sources of Error in Sulphur Determinations. John Pattinson and J. T. Dunn. (Jourrz. Xoc. Chenz. Ind., 1905, xxiv., 10.)-Some of the red indiarubber stoppers used for wash-bottles are acted upon to a, serious extent by boiling water or steam, yielding sulphuric acid to the water. This sulphuric acid has its source in the oxidation of the sulphur in the rubber or in the metallic sul- phides, such as antimony sulphide, added to the rubber.Such stoppers may introduce a serious error in the determination of sulphur in iron and steel. Soluble unoxidized sulphur compounds are sometimes present in commercial barium chloride, due no doubt to the fact of its being prepared from heavy spar by reduction to sulphide and treatment with hydrochloric acid. Many samples of barium chloride, when dis- solved in water and oxidized with nitric acid or bromine and boiled, yield a precipitate of barium sulphate. A. R. T. The Diphenylamine Test for Nitric Acid. G. Frerichs. ( A ~ c h . Phamn., 1905, ccxliii., 80; through Cham. Z e d . Rep., 1905, xxix., 84.)-Ferric salts and chromates react with diphenylamine in a similar manner to nitric acid, and these compounds, if present, must be eliminated from the substance to be tested before applying the reaction.The substance is shaken in a test-tube with about 10 C.C. of dilute sulphuric acid and 20 C.C. of ether; any precipitate is allowed to settle, and 2 to 3 C.C. of the ethereal solution filtered through a dry paper. Five to ten C.C. of concentrated sulphuric acid are then carefully added, when any nitric acid present will give the characteristic reaction, Should the ethereal solution contain iodine, bromine, or chromic acid, it will be yellow in colour. Iodine and bromine do not affect the test. Chromic acid is eliminated by shaking with a little aqueous sulphurous acid, filtering the ether solution, and testing as before. This is best carried out by extraction with ether.H. A. T. The Differentiation of Nitric and Nitrous Aeids by Means of Diphenyl- amine. P. Raikow. (Oest. Chenz. &it., 1904, vii., 557.)-An exhaustive paper, in which the various methods for the identification of nitrates in the presence of nitrites are discussed. The author considers that diphenylamine is the only satisfactory reagent, and suggests an improved method of applying this reaction. 0.5 C.C. of a 2 per cent. solution of diphenylamine in sulphuric acid (specificTHE ANALYST. 175 gravity, 1.78) is introduced into a flat-bottomed porcelain dish, and a single drop of the solution to be examined is allowed just to come into contact with the reagent. Nitrate solutions, in strength from twice normal to &, give a blue colour, becoming brown or black on standing.Weaker solutions, down to i&m, give no immediate colour, but a blue appears in from four to ninety seconds, according to the extent of dilution of the solution, and, after increasing for a few minutes, slowly disappears. Nitrite solutions, in strength from normal to TG, react similarly to nitrates weaker solutions ; give an immediate violet colour, rapidly becoming blue and disappearing. This violet colour is distinct with solutions as weak as These reactions are suggested as affording a certain indication as to whether nitric or nitrous acid, or both, are present. With a suitably dilute solution contain- ing nitrate only, no immediate reaction is obtained, but a blue colour, gradually increasing in intenaity, shows after a few seconds, A nitrite, on the other hand, gives a violet colour immediately, which rapidly becomes blue, and disappears in from two to ten minutes. A sufficiently dilute mixture of both acids gives an immediate violet colour (nitrite), becoming pale blue, which quickly disappears. A blue colour is then gradually formed, which becomes more intense, and only slowly vanishes (nitrate). The exact degree of dilution necessary to give a satisfactory reaction must be found by experiment. Dilution of a solution containing only nitrate or nitrite mainly affects the intensity, etc., of the reaction, by progressive dilution of a mixed solution, a point is finally reached at which the two reactions are quite distinct. Using phosphoric acid as solvent for the diphenylamine, the reaction for nitrites is unaltered. Nitrates acquire a quite characteristic reaction. At the point of con- tact, numerous black points are observed, the solution itself remaining colourless. These points gradually expand and merge, a blue solution being formed. This reaction however, is only noticed in strong solutions (normal to 4 normal KN03). The smallest quantity of KNO, which can be detected by the phosphoric acid solution is 0.0025 gram. The reaction with NaNO, is definite when as little as 0.00006 mgm. is present. Any colour, therefore, after sufficient dilution is a sure indication of nitrous acid. A solution of diphenylamine in acetic or formic acid proved quite unsuitable for the purpose. H. A. T. (NaNO,). The colour disappears slowly. Preparation of Volumetric Solutions. E. C. Worden and John Motion. (Journ. Xoc. Chem. Ind., 1905, xxiv., 178.)-The paper consists of a number of valuable tables showing the relation of specific gravity to composition in the cases of sulphuric, hydrochloric, and oxalic acids, for use in the preparation of volumetric solutions. A. R. T.

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DOI:10.1039/AN9053000166

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年代:1905

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176 THE ANALYST. APPARATUS. A Comparative Refractometer Scale for use with Fats and Oils. A. E. Leach and H. C. Lythgoe. (Jmu. Amer. Chem. Xoc., 1904, xxvi., 1193-1195.)--The Zeiss butyro-refractometer has an arbitrary scale from 0 to 100, covering tho indices of refraction from 14220 to 14895, which scale is not uniform with the values of n,. Thus the difference from 0 to 10 in indices of refraction is 0*0080, and from 90 to 100 is 0.0055, whilst the variation for 1" C. on the refractometer is 0-46 for readings between 0 and 10, and 0.66 for readings from 90 to 100. The best method of obtaining scale readings at different temperatures is to convert them into indices of refraction, apply the cor- rection (0.000365 for each degree), so obtaining the indices at the required temperature, and then to recalculate the figures into scale readings.To avoid this long calculation, the authors have devised the slide rule illustrated. By the use of this instrument readings may be obtained on the butyro-refractometer scale at different temperatures, without first transforming them into indices of refraction ; readings of the latter may be obtained at difierent tempera tures without calculation, and values on either scale can be readily transformed into values on the other. The authors are making arrangements for the manufacture of the in- strument, but pending this prints of the scale may be obtained by applying to the authors at Room 501, State House, Boston, U.S.A. These can be cut and used like a slide rule. w. P. s. A Simple Bunsen Burner.F. Allihn. (Chem. Zeit., 1905, xxix. , 34, 35.) -This burner is the same iu principle as that previously described by the author (ANALYST, 1900,138). The vertical tube of the burner is open at the bottom, and the jet is done away with. A gauze cover is pro- vided at the top, so that a uni- formly hot flame is obtained. This flame is particularly suitable for heating platinum vessels, as the objectionable '' inner cone " of the ordinary Bunsen flame is absent. The small upright arm shown in the illustration at the left of the base is the handle of the air-THE ANALYST. 177 regulator, but the burner is also made without this device. The burner may be obtained from Warmbrunn, Quilitz, and Co., Berlin, N. W. w. P. s. a b e FIG. 1. @ @ FIG. 2. A New Form of Eggertz Tube for the Determination of Carbon in Steel and Iron.H. Schumacher. (Chem. Zeit., 1905, xxix., 35.)- The tube shown in Fig. 1 really consists of two tubes separated by a milk-glass partition. Each is graduated, and has a capacity of 20 C.C. The tube b holds the standard steel solution, and is closed by a cork; whilst the tube a contains the steel solution under examination. When it is necessary to dilute this, the tube is closed by means of the finger and shaken. The milk-glass partition prevents the coloration in one tube in- fluencing that in the other. Another form of tube is shown in Fig. 2, and is suitable for other colorimetric determina- tions. The tubes are sold in sets, and have one side flattened. In each set one tube has its flat side made of milk-glass, and is intended to hold the standard solution. By reason of their flat sides the tubes may be brought close together, and the comparison of the colour of their contents is rendered more easy. The tubes are sold by A. Eberhard, Berlin. w. P. s. A Practical Mechanical Mortar. (Chem. ,Yeit., 1905, xxix., 56.)-The instrument as illus- trated is supplied by the ‘‘ Vereinigten Fabriken fur Laboratoriumsbedarf,” Berlin, N. I t consists of an agate mortar fixed into a wooden stand, which also has an upper portion, in which is a socket for the wooden handle, in which is set the agate pestle. The arrangement thus allows both hands to be used for the grinding. A slide on the upper guiding place allows more or less lateral play as required. %. K. H.

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DOI:10.1039/AN9053000176

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年代:1905

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78 THE ANALYST. REVIEWS. CHEMICAL TECHNOLOGY AND ANALYSIS OF OILS, FATS, AND WAXES. By DR. J. LEWKO- WITSCH, M.A., F.I.C. Third Edition. (London: Macmillan and Co. Two vols. Price 36s. net.) For many years the subject of oils and fats was one of the most neglected branches of analytical chemistry, for the problems it presented were looked upon as almost incapable of solution. Now the reverse is the case, and every month sees the publication of papers dealing with different processes or with the characteristics of individual fats and oils. And so important are the industrial applications of these products that it is essential for the analytical chemist to keep in touch with the new facts recorded about each of them. Hence it is not surprising that the present work, which in its first edition was contained in one volume of moderate size, has now expanded into two volumes containing 1,152 pages, and has only been kept within even these limits by the rigorous exclusion of matter which the author regarded as possessing only historical interest.This was, doubtless, an inevitable necessity, but at the same time it detracts from the completeness of the work, even from the practical point of view, since many methods that we have abandoned as apparently useless may yet form the starting-point for new researches introducing other principles. The value of the book has been considerably enhanced by the introduction of chapters dealing with the technology of the subject ; but here again the virtue of compression has been carried too far, and insufficient space has been given to the description of apparatus and manufacturing processes.The arrangement of the book differs somewhat from that of the earlier editions. The first three chapters deal with the general properties and composition of oils and fats and the theory of saponification, and are followed by chapters describing the general physical and chemical methods of examination. The second volume opens with a chapter on the commercial preparation of oils and fats, which is followed by a systematic description of the individual products and two chapters dealing with the technology of every description of fat, and the work concludes with a good index. The book bas been brought thoroughly up to date, and is a most valuable text- book for the analyticalTaboratory. Perhaps Chap. XIV. will still be found the most useful to the analyst, for the excellent tables of values, which formed a striking feature of the first edition, have been greatly enlarged and extended so as to include all known fats. The book is well printed and is singularly free from errors, although there is one slip that is constantly repeated. The author, in writing about the insoluble bromide8 given by certain oils, describes them as ‘‘ hexabromides,” whereas it has been shown that they do not contain the percentage of bromine required by the hexabromide of linolenin, and all the evidence points to their being bromides of mixed glycerides containing as one of their constituents the glyceride of linolenic or jecoric acid. C. A. M. 1

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DOI:10.1039/AN9053000178

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年代:1905

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摘要:

THE ANALYST. 179 HIGH COURT OF JUSTICE. KING’S BENCH DIVISION. (Fro?n the “ Times ” of Thursday, April 13, 1905.) (Before the LORD CHIEF JUSTICE OF ENGLAND, MR. JUSTICE KENNEDY, m d MR. JUSTICE R’IDLEY.) SMITH v. SAVAGE. THIS was a case stated by the justices of Wiltshire sitting a t Narlborough, and raised a question under the Food and Drugs Act. The respondent, Henry Edward Savage, a grocer, was charged at the instance of the appellant, an inspector under the Food and Drugs Act, with having, on August 9, 1904, unlawfully sold to the appellant, to his prejudice as the purchaser thereof, four penny packets of cream of tartar, which were not of the nature, substance, and quality of the article demanded, such cream of tartar containing lead in the proportion of 2 grain per pound, contrary to Section 6 of the Food and Drugs Act.On August 9, 1904, the appellant visited the respondent’s shop, and saw there some packets of creani of tartar. He asked the respondent if he sold cream of tartar, where- upon the respondent produced a box containing packets labelled “Finest cream of tartar, 98 per cent. bitartarate of potassium, B.P., 1898.” The appellant asked for four packets, which were all similar in size and outward appearance and label, and were taken from the same box. He paid fourpence for them, and told the respondent that the purchase had been made for the purpose of analysis. The appellant emptied the contents of the four packets into one place, and then divided the whole of the contents or matter into three parts, and sealed them up. One of these three packets was sent to the county analyst, another handed to the respondent, and the third packet was retained and produced to the justices by the appellant.The appellant said that cream of tartar mixed with bicarbonate of soda was used in baking-powder, and also in the preparation of cakes, etc. The result of the analysis as above stated was proved, where- upon the appellant asked for a conviction. The respondent’s solicitor contended that the appellant made four separate purchases, each packet being an article, and that the appellant did not by mixing together the contents of the four packets, and then dividing the substance SO mixed into three parts, comply with Section 14 of the Food and Drugs Act, 1875, and, in support of this argument, the case of Mason o.Cowdary (16 The Times L.R., 434 ; 1900, 2 Q.B., 419) was cited. For the appellant it was contended that the facts were not similar to those in Mason v. Cowdary, and that Section 14 had been properly complied with, inasmuch as the entire purchase had been properly divided into three parts as the Act directed. I t was also pointed out that in Mason v. Cowdary there was no mixing and division of the entire purchase. The justices dismissed the summons, and the question for the opinion of the Court was whether they were right in so doing. Mr. HOLMAN GREGORY, for the appellant, submitted that the justices were wrong in dismissing the summons. All the packets were labelled in the same manner, and given to the appellant as cream of tartar, not as four packets.Making up the article in packets was only a, means of measuring the quantity. No question could have arisen if the appellant had asked for fourpennyworth of cream of tartar. That was a case in which six bottles of camphorated oil were bought ; there was no division of the contents of any one bottle, but two bottles were sent to the analyst, two given back to the seller, and two retained by the inspector. That was held not to be a compliance with Section 14, but it was obvious that the oil might be of quite different quality in the different bottles. That was not the case as to the packets of cream of tartar, which were all labelled in the same way and taken from the same box. The case of Mason o. Cowdary was not in point.180 THE ANALYST. Mr.BONSEY, for the respondent, contended that the justices were right. There had been four separate purchases, and not one purchase. Suppose a person were to purchase several loaves of bread, one of the loaves would have to be divided into three parts in order to comply with the Act. Mason 21. Cowdary was directly in point ; in that case Mr. Justice Darling said that ‘‘ six bottles are six articles.” I n that case it might, with equal force, have been contended that oil, and not six bottles of oil, had been asked for by the inspector ; so here it could not be said that merely cream of tartar was demanded ; the request was for four packets of it, There was no reason why one of the packets should not have been divided into three parts. I t had been suggested that one packet was too small to permit this being done; that was not so, and, moreover, whatever the quantity might be could make no difference, as the Act, which required division into three parts, must be complied with.The LORD CHIEF JUSTICE, in giving judgment, said that on the whole he thought the appeal must succeed. Some question, he thought, might arise in the case of different articles not of a similar name or articles coming from different people being mixed together in the shop ; that, however, was not the case with which they had to deal. I n the case before them the appellant asked for cream of tartar, which, for the purpose of measurement, was put up in penny packets. He said he would take four packets, and they had t o say whether because four packets of the same article, labelled in the same way, and sold at the same time as cream of tartar, were mixed together and then divided into three parts was a good objection to the analysis that followed.He was of opinion that it was not a good objection. The case was different from Mason w. Gowdary; it must, therefore, go back to the justices to proceed in the matter. Mr. JUSTICE KENNEDY and Mr. JUSTICE RIDLEY concurred. INSTITUTE OF CHEMISTRY OF GREAT BRITAIN AND IRELAND. PASS LIST OF THE APRIL EXAMINATIOXS. OF six candidates who entered for the Intermediate Examination, three passed : J . D. Kettle, B.Sc. (Lond.), Elison A. Macadam, and R. Simmons. I n the Final Examination for the Associateship (A.I.C.), of seven examined in the branch of Mineral Chemistry, three passed : J. Alexander, B. O’Shaughnessy, Ass0c.R. C.Sc. (Lond.), and E. Rhodes, B.Sc. (Vict.) ; of five in Organic Chemistry, three passed : S. J. M. Auld, Ph.D. (Wurzburg), H. W. Goodwin, and R. Robison; and of eight who entered in the branch of the Analysis of Food and Drugs and of Water, including an examination in Therapeutics, Pharmacology, and Microscopy, the following six passed: J. H. Barnes, B.Sc. (Birm.), J. W. Brisbane, D. Gair, B.Sc. (Lond.), H. G. Harrison, B.A. (Cantab.), K. Park, and J. Race. One candidate passed an examination for the Fellowship (F.I.C.): A. E. Brown, B.Sc. (Lond.). The examiners in chemistry were Mr. W. W. Fisher, M.A. (Oxon.), F.I.C., and Dr. G. G. Henderson, M.A., F.I.C. The examination in Therapeutics, Pharmacology, and Microscopy was conducted by Dr. F. Gowland Hopkins, M.A,, F.I.C. @ * + € + + 5 * THE LATE PROFESSOR TICHBORNE. WITH regret we have to announce the death of an old and distinguished member o l the Society, Professor C. B. C. Tichborne, which took place on May 1. A full notice of his scientific career will appear in our next issue.

ISSN:0003-2654    

DOI:10.1039/AN9053000179

出版商:RSC    

年代:1905

数据来源: RSC

摘要:

180 THE ANALYST. ERRATUM.-Page 110, eighth line from bottom, for February 1 read (( March 1.”

ISSN:0003-2654    

DOI:10.1039/AN9053000180

出版商:RSC    

年代:1905

数据来源: RSC