摘要:

THE ANALYST. OCTOBER 1900. PROCEEDINGS OF THE SOCIETY OF PUBLIC ANALYSTS THE DETERMINATION OF OXYGEN I N COPPER BY IGNITION I N HYDROGEN. B Y L. BRCHBUTT F.I.C. (IZec~tl at the Meetiny June 6 1900.) IN consequence of some anomalous results obtained during the autumn of 1893 in determining oxygen in commercial copper by Abel’s silver nitrate method which I had up to that time employed with confidence my attention became directed to a paper on “The Analysis of Copper,” by W. Hampe (Zeits. fiir anal. Clmn. 1874, pp. 176-234) in which the estimation of oxygen is directed to be made by heating the copper to redness in a current of hydrogen. The unfavourable results previously obtained by Abel (JozLrn. Chem. SOC. 1864 pp. 166-172) which led him to conclude “ t h a t correct indications of the proportion of oxygen existing in a specimen of copper cannot be obtained by treatment of the metal with hydrogen,” did not encourage further experiment in the same direction ; but the experimental results reported by Hampe in his paper were so satisfactory that I determined to make a careful trial of his method of which the following is a description : ESTIMATION OF OXYGEN (Rampe).The clean copper is converted into filings with a not too coarse file the filings are passed through a hair sieve in order to separate any coarse particles fragments of iron are removed by a magnet and the powdered copper is washed either with a dilute solution of caustic potash followed by water or with pure alcohol or ether in order to remove grease. For the reduction a bulb-tube of Bohemian glass is used drawn out at both ends This is connected with a drying apparatus through which a current oi air is passed from a gasometer.The empty bulb-tube ia first heated in the stream of air allowed to cool and at once closed with indiarubber stoppers. The tube having been weighed 30 to 50 grammes of the prepared copper are placed in the bulb the tube is again weighed and a current of dry air-free CO is passed through it. This CO is prepared from marble and hydro-chloric acid and is purified by passing through vessels containing sodium carbonate The purified copper is dried 254 THE ANALYST. and silver nitrate and dried by passing over sulphuric acid and calciuiii chloride. The apparatus is set in action two hours previous to use in order to drive all air out of the purifying train.After the stream of CO has passed over the copper for about five minutes a very moderate heat is applied in order to expel every trace of superficial moisture. With many coppers which contain arsenic too strong heating will result in the formation iii the bulb or just beyond it of a sublimate of As,O,. After cooling in CO, a stream of dry air is immediately passed through the bulb-tube to displace this gas and the tube is again stoppered and weighed. The weight is usually only a few milligrammes less than the previous weight. A very slow stream of hydrogen is now conducted over the copper which is heated at first gently and afterwards to a red heat which temperature is maintained for about fifteen minutes.During the heating water is formed and by impure copper there is also formed a black sublimate containing arsenic antimony and lead so that the end of the tube must be long enough and the stream of hydrogen slow enough, to insure the whole of this sublimate being retained within the tube. During the formation of water there is noticed with commercial copper an evolution of H,S. The formation of this gas already observed by Dick but not explained can be accounted for in the author’s (Hampe’s) opinion only by the presence in the copper of sulphur dioxide a part of the sulphur of which is converted into H,S. Cuprous sulphide cannot exist in copper along with oxygen compounds, and would not be decomposed by heating in hydrogen. To retain the escaping H,S, the bulb-tube must be connected with several small flasks containing silver solution or alkaline lead solution and the sulphur can then be estimated by known methods.Arsenic and antimony cannot be found in the precipitate. After the copper has corn-pletely cooled in the stream of hydrogen and this gas has been displaced by dry air, the tube and copper are again weighed. As control a duplicate experiment is desirable. The mean loss of weight less the weight of volatile sulphur is oxygen. The correction for sulphur seldom exceeds 0.002 per cent. in refined copper. The following results were obtained by Hampe : i\. SYNTHETICALLY PREPARED SAMPLES. Oxygen Oxygen Prevent Found (per cent.). (per cent.). 1. Copper containing copper oxide . . . . . 0.247 0.237 2. Copper containing (‘ copper mica ” .. . . . 0.262 0-2G7 3. Copper containing bismuth antimonate of which the oxygen content must have been from . . . . . . 0.141 to 0.170 0.159 B. COPPER FROM OKER. OXYGEN PER CENT. APTER CORRECTING FOR VOLATILE SULPHUR. / . Mean. First Second Third Experiment. Experiment. Experiment. 1. Tough copper . 0.117 0,117 - 0.117 3. Dry copper . 0.806 - - 0.806 2. ? 9 . 0.154 0,153 0.165 0.15 THE ANALYST. 355 Mean. I. “ Black copper ” . . . . . 0.443 - .- 0.443 2. Dry refined copper . . . . . 0.737 0.765 - 0.746 3. Tough (‘‘ dichtgepoltes ”) copper . . . 0.147 0.162 - 0.155 4. Tough (‘‘ ziihe gepoltes ’ I ) copper . 0.077 0072 0.077 0.075 5. Overpoled copper . . . . . 0.045 0.044 - 0.045 In connection with the above analyses of dry copper it is interesting to note that Dick in 1856 found about 1-4 per cent.of oxygen in a specimen of copper “ in the driest state,” which Percy had procured specially for experiment. This result of Dick’s was obtained by rolling the copper as thin as possible cutting the rolled metal into small pieces exposing these to a current of dry hydrogen at a red heat and weighing in a calcium chloride tube the water formed. Ilampe refers to Dick’s experiments but apparently makes no inention of Abel’s work in the same direction, which is strange as Abel tried for a long time to estiniate the oxygen in copper by a method similar to the above-mentioned process used by Dick and came to the con-clusion ‘‘ that although the larger proportion of the oxygen contained in a specimen of copper may perhaps be abstracted during the first two or three hours’ treatment its complete removal from the metal in the form of water requires very long continued exposure to the action of hydrogen.” In several experiments a continuous increase in the weight of the calcium chloride tube was observed which ‘‘ appeared likely to continue for an indefinite period,” and which was attributed partly to traces of atmospheric oxygen obstinately retained by the copper.After numerous failures to obtain satisfactory results Abel finally abandoned the method as impracticable. Blount much more recently (Analyst 1896 pp. 57-61) came to the conclusion that the action of hydrogen on copper at any temperature below the softening-point of a glass combustion tube is only superficial and he has described a method in which the copper is actually fused in a current of hydrogen.Blount found as Dick had done, that the reduction is accompanied by such violent spirting of the molten copper that an estimation by loss of weight is impracticable; but by conducting the operation in a porcelain tube and absorbing the water formed in a sulphuric acid drying tube he has worked out an elegant and successful process. My own experiments however, and several years’ subsequent experience have convinced me that the reduction takes place easily and completely at a red heat and that Ilampe’s process is accurate as well as when certain unnecessary details are omitted extremely simple. By the courtesy of Mr. Blount an opportunity has recently been afforded of proving that the results obtained by the two methods are practically identical.:In account of my experiments and of the results obtained may therefore be of interest to the Society. I commenced by following Harnpe’s directions closely but arrangements were made for absorbing and weighing the water formed as a check on the loss of weight undergone by the copper. An apparatus for the supply of dry oxygen-free hydrogen was therefore fitted up which consisted of (a) Kipp generator containing Leclanchb First Second Third E:.ulterimeiit. lS\periment. Experiment 256 THE ANALYST. _ _ _ _ - considerable admixture of steel from the teeth of the file which must be carefully picked out by a magnet and they must be very well washed with ether to remove grease and dirt.There does not appear to be the least necessity to pass the filings through a hair sieve as Hampe directs. Very convenient bulb-tubes for containing the copper are made for me of Jena glass of the shape and dimensions shown in Fig. 1. They are suspended for weighing by means of a j t I’ \’ platinum wire hanger with sufficiently large loops at either end to slip easily off and on the tube. These tubes can be used -3’- drp. s s without serious alteration of shape for a large number of opera-tions in fact until the glass becomes opaque. During the com-bustion a black deposit of lead arsenic etc. usually forms near the exit end but is easily cleaned off afterwards with a solution of bromine in hydrochloric acid. The tube is then thoroughly the weights in grammes of three different tubes after being used for three successive combustions : (2) (3) 48.654 (1) 53.593 48.155 - _ _ 53.593 48-155 48.654 The clean dry tube when cold is wiped outside and allowed to remain supported across a beaker not in a desiccator for te THE ANALYST.257 as before. The weight of copper taken for assay is thus ascertained. I prefer to weigh the tube open at the ends as I have found that indiarubber stoppers are not only unnecessary but they are apt to cause errors in the weighings. FIG. 2. The bulb-tube containing the copper is supported on a sheet-iron tray lined with asbestos millboard a piece of perforated sheet asbestos is bent over the top and kept in shape by an iron-wire frame and flat pieces of asbestos perforated in the centre to receive the ends of the bulb-tube are placed at the sides (see Fig.2). The bulb thu 258 THE ANALYST. __________ - ~ I ~ Weight of copper taken . . . . ~ 29.7526 ~ ~ 35.0023 ~ 33.5010 By Loss of Weight By Weight of of Copper. Water formed. Experiment 1 . . . . 0.161 0.167 t ? 2 . . . . 0,167 0.170 9 3 . . . . 0.169 0.165 Mean . . 0.166 0.167 The copper remaining after Experiment 1 was transferred to another tube (the first having developed a minute crack) and reheated with the following results : Fourth Experiment. Weight of copper and tube before heating . . . . 58,2991 , after heating in CO . . 58.3001 . 7 9 . 9 9 , after heating in hydrogen to full redness for half an hour . . . . 58.3000 Loss of weight in hydrogen .. . *0001 This experiment shows how easily 8 constant weight i n hydrogen is obtained. I n fact by watching the progress of an experiment one soon acquires confidence in the method. As soon as the copper reaches a dull red heat water begins to condense rapidly in the first cool place and has to be chased along by a small flame; after heating for about half an hour it ceases to condense. I n the above experiments the heating was continued for about two hours longer the current of hydrogen being at the rate of 200 to 300 C.C. per hour. The following experiments were made with two other firebox-plate coppers, '' B " containing 0.031 per cent. and " C " 0.485 per cent'. of arsenic. I n Experi THE ANALYST. 259 1 Fifth 1 Experiment. I 1 - - _ - __-_____-___ Weight of copper taken .. . . Weight of copper and tube before heating . 1. 1 ;::;;:; 9 1 9 , after heating in hydrogen . I 60.6305 Loss of weight in hydrogen . I . . I 40440 9 9 9 9 , after heating in CO . I 60.6745 Water absorption tube after . . . ' 49,4910 - ~-I . ,> Y9 . . 1: 49-4427 Weight of water formed . . . . a0483 - _. , before Containing oxygen . . . . . . * ' 1 -0429 . ~ - _ _ _ _ _ _ ~ ~ _ ~ ~ __ ____ ment 7 the heating in GO was carried to rather too high a temperature and a sublimate of As,O formed in the end of the bulb-tube. In Experiment 8 no sublimate was formed. COPPER FIBEBOX PLATE B. Sixth Experiment. . _ -35.1397 62.8178 62.8140 62 -7657 *0483 - _ _ ~ ~ -. . -0555 -. . . . By Loss of Weight By Weight'of of Copper.Water formed. Experiment 5 . . . . 0.133 0.130 6 . . . . 0.137 Mean . . 0.135 7 ) -COPPEB FIREBOX PLATE C. a0554 46.9477 46.8869 ~-Seventh Eighth ~ Experiment. ~ Experiment. _____ -. . . . _ 1 34.5900 1 34.4244 Weight of copper and tube before heating . . 59.7740 ' 67.2730 9 , , after heating in hydrogen . 1 59.7158 1 672171 I I Weight of' copper taken i J J 9 9 , after heating in CO . I 59.7713 j 67.2725 Loss of weight in hydrogen . . Water absorption tube after . I) I) ,) before . Weight of water formed . . . Containing oxygen . . . . . _ _ - _ ~ - __ ____ . . Experiment 7 . 9 9 8 . . . Mean . . . . . -0608 *0540 PERCENTAGE or OXYGEN FOUND. * ,-Hy Loss of Weight Ry Weight of of Copper.Water formed. . 0.160 . 0.161 0.157 . 0.1605 0-157 -260 THE ANALYST. From the foregoing experiments it appears that practically the same results are obtained whether the oxygen be estimated from the loss of weight of the copper or from the weight of water formed. It seemB hardly necessary to go to the trouble of recovering the trace of sulphur which passes off as H,S. I t can only influence the result in the third decimal place and such accuracy is not required in the present state of our knowledge. If the water formed in the combustion is not weighed there is no need to purify the hydrogen from traces of oxygen. This was not done in Experiment 7 whilst in Experiment 8 it was and it will be observed that the loss of weight of the copper is practically the same in each case.The tube containing the red-hot copper gauze The former method is much the simpler. RESULTS OBTAINED 131- ASSAY FOR OXYGEN OF TWENTY-THREE SAMPLES OF COMMERCIAL COPPER. . - - -_ . - __-_-_____ _ _ ~ Exper'- Description 1 of Copper. No. ~ -9 /Tube . 10 9 . 11 I . 13 i 1 . 12 ~ &I3 . 14 ' Firebox plate 15n 15b 16 17 1 18 i 19 20 21 22 23 24 25 26n 26b 27 28n 2% 2'3 30 I I 31 1 Loss of ' in CO,. Weight I Weight taken. Grammes. 39.1339 35.8081 35.2848 32.9537 30.4792 33-9440 33.5455 , ~ 32.0803 I ' 31.6886 32.3282 34.6286 32.0084 33.5971 35.0629 36.7553 37.7511 36.5867 , 35.6362 , 36.6247 ) 35.1720 , 35.8049 I , 37.6476 , ' 40-0071 Grammes.0~0000 0*0005 0.0004 0 a0004 0-0003 0.0001 0.0005 0.0005 0.0006 0.0006 0-0006 0.0006 0.0005 0-0006 0.0001 0~0009 0 *0806 L ~ ) ~ ~ of ~ ~ ~ ~ i ~ ~ - Other Particulars. Weight lent to A \ Phos- I I -1-Grammes. Per cent. ,Percent. Percent.1 in 13. Oxygen. j Arsenic.! phorus. 1 Remarks. 0*0028=0.007 trace 0.099 1 0.0032=0-009 nil I 0.033 I 0.0018=0-005 I nil I 0-026 I 0*0337=0-072 1 0.377 nil 0.0220 = 0.072 0.0269 = 0.079 0.0383 = 0.114 0.0370 = 0.115 0.0498 = 0.157 0.0230 = 0.071 0.0579 = 0.167 0.0464 = 0.145 0.0380 = 0.113 0.0471 = 0.134 0.0331 = 0.090 0.0733 = 0.194 0.0576 = 0.157 0.0008 0.0530 = 0.137 0.0011 0.0494 = 0.135 0.0021 0.0469 = 0-133 0.074; nil j 0.037 ~ ),.,, -I 0-268 0.218 0463, 0.034 0.215' 0.172 0.013 0.2001 0.0211 0.181: 1 }0-148! -I Duplicate tests of the same I sample.Duplicate tests of the same sample. Duplicate i 1 1 r 0.0413 = 0.110 0.0435 = 0.109 0.0738 = 0.207 0.0442 = 0.122 0.0386 = 0.103 ~- THE ANALYST. 261 spiral was therefore removed from the purifying train and the twenty-three samples of copper included in the table on the opposite page were assayed for oxygen thus : 1. The prepared copper was heated in purified dry CO for half an hour during which time 500 C.C. of the gas were passed through the bulb the tempera-ture being high enough to expel moisture but not high enough to sublime As,O from the copper. 2. The dry copper was heated to redness in hydrogen which had been purified from acid vapours and water but not from traces of oxygen.The tempera-ture was maintained at a red heat for one hour about 1 litre of gas being passed through the bulb. I have included in the table the percentages of arsenic and phosphorus found in F I G . 3. these coppers. Copper containing phosphorus is invariably free from oxygen or contains only traces of that element and a considerable proportion of the loss on ignition in hydrogen of such copper is probably made up of the traces of oily hydro-carbons which usually distil from copper when heated however carefully it has been washed with ether. The loss of weight in carbon dioxide is seen to have been very trifling in all these experiments except one (No. 26b). In fact it was so small that I have now abandoned this part of Hampe’s proceBs and merely wash the copper with ether and dry it well in the water-oven before heating in hydrogen.Although the water resulting from the combustion in hydrogen is not weighed a trap of some kind beyond the bulb-tube is necessary and may conveniently consist of a U-tube containing pieces of glass rod and sufficient sulphuric acid to fill the bend. Fig. 3 is from a photo of the complet 262 THE ANALYST. apparatus which I now employ for the combustion in hydrogen. It comprises (1) Kipp generator ; (2) washing-bottle containing caustic soda solution ; (3) tower, containing stick soda; (4) U-tube containing re-fused dry caustic potash in small pieces ; ( 5 ) bulb-tube containing the prepared dry copper ; (6) U-tube containing strong sulphuric acid; and (7) pipettes for measuring the rate of flow of hydrogen.Process.-The copper (30 to 40 grammes) which must be free from superficial oxide is thoroughly cleansed with ether carefully dried introduced into the dry bulb-tube and weighed as already described. The apparatus is joined up and a current of hydrogen (about 1 litre per hour) is passed through it until the issuing gas burns quietly which is usually the case after fifteen minutes have elapsed. The current of hydrogen is then reduced by about one-half and if much arsenic is present in the copper it is still further reduced; the copper is then heated up with a flame just touching the iron support until water begins to condense beyond the bulb-tube. If any sublimate of As,O be observed the current of hydrogen is made very slow, and the tube is heated more strongly so as to reduce the oxide to a mirror of arsenic within the tube.Any water condensing between the bulb and the U-tube is chased along by a small flame. Gradually the copper is raised to full redness and when water ceases to condense the current of hydrogen is increased to 1 litre per hour. After continuing to heat the copper thus for one hour the gas is turned out but the current of hydrogen is kept up until the copper is quite cold. The bulb-tube is then disconnected the hydrogen is displaced by aspirating a current of dry air through the tube and the latter is weighed and the loss calculated as oxygen per cent. of the copper taken. The following results were obtained by Mr.Blount and myself working inde-pendently on the same specimens of copper. Mr. Blount’s determinations were made by fusion of the copper in hydrogen and weighing the water produced; my results were obtained by simply heating to redness in hydrogen and observing the loss in weight of the copper as described above. The agreement is sufficiently close to show that both methods give practically identical results. The compara-tively large discrepancy in the case of No. 3 sample may be due Mr. Blount thinks, to the fact that the copper was in rather coarse pieces for his process and he had to work on comparatively small quantities the small constant plus error due to the almost inevitable gain of an absorption tube would therefore have a larger effect on the final result in this case than it would under the normal conditions ol working when the copper is large.The results in the second column were obtained by my assistant Mr. P. G. Jackson A.I.C. Sample Number. Oxygen per cent. determined by 1 . . . . 0.18 . . . 0.17 2 . . . 0.22 . . . 0.21 3 . . . 0.05 . . . . . 0.003 4 . , . 0.03 . . . 0.03 5 . . _ 0.13 . _ . . . 0.12 6 . . . . . . . 05% . . . 0.2 THE ANALYST. 263 DISCUSSION. Mr. BLOUNT said he was glad to find that processes of the same class as the old silver nitrate process might be reckoned as deleted. There was in fact only one method of determining the oxygen in copper-namely by reduction in hydrogen. The only point upon which it was possible to base a discussion was the fact that there was some doubt-or had been until that occasion-as to the practicability at a temperature short of the fusing-point of copper of determining by reduction in hydrogen the whole of the oxygen present.I n his own experiments he had doubted this so much that he was ultimately led to abandon the notion of reducing at a temperature lower than fusing-point. He felt bound to say however that the reduction in hydrogen of the oxides present in copper when the copper had to be fused was not an altogether convenient proceeding and if it were possible as Mr. Archbutt had shown it to be to reduce the oxides without raising the copper to its fusing-point a great step would have been taken in advance. Nevertheless he (Mr. Blount) could not help thinking that there were certain reasons which would lead one to prefer the method he had ventured to recommend of fusing the copper in hydrogen and weighing not the copper remaining but the water produced.I t seemed evident that the determination of an impurity occurring in small proportion such as oxygen in copper must be made more or less by determining the difference between two comparatively large weights-e.g. of the vessel in which the impurity was con-tained. When the substance constituting the impurity was isolated-as for instance, in the case of bismuth the proportion of which in commercial copper was generally under 0.01 per cent.-the errors would be quite tangible; and in the same manner the increase in the weight of the absorption tube in determining the oxygen by fusion of the copper in hydrogen was so small that any error would assume relatively large proportions.But the method of determining the oxygen by difference between the weights of the copper before and after reduction in hydrogen was still more open to error rendering necessary not only the most minute accuracy in weighing the original mass in the tube and the final mass but also many precautions against the escape of volatile constituents other than oxygen. There could be no guarantee that arsenic for example would remain unvolatilized. The fact that such admirable results were obtained by the author was a testimony to his skill and that of those whom he had trained rather than to the excellence of the process. I n the prepara-tion of the copper for the determination of oxygen by this method it was necessary to subdivide it ; and although the author had succeeded in overcoming the difficulties due to contamination from files drills etc.it was really unnecessary to face them when one could work satisfactorily upon lumps of copper obtained without any risk of such contamination. From a purely utilitarian point of view the question of speed was of considerable moment and it might be mentioned that the method which he had described in 1896 enabled as many as twelve determinations of oxygen in copper to be made in a working day with the Bame apparatus and by one operator. Mr. JENKINS said that he was personally indebted to the author for having introduced this method to his notice several years previously. He thought that Mr. Blount had altogether overemphasized the objections which may be brough 264 THE ANALYST.against the method. The machining of the metal into small fragments was easily done without any contamination with oil etc. not only in the case of copper but of steel and other materials. It was shown by the figures given in the paper that the results obtained by absorption of the water were practically the same as those obtained by difference. It would certainly in many cases be more convenient to make the determination by Mr. Archbutt’s method than by Mr. Blount’s method, seeing that the former did not involve working at so high a temperature and it was highly satisfactory that Mr. Archbutt and Nr. Blount working a t considerable differences of temperature should get such closely-agreeing results.Mr. ALLEN said that he had an extensive experience of the burning of metals in oxygen which was a process somewhat analogous to the one now under considera-tion and he must say that he would give preference to a method in which drillings or finely-divided particles of metal were used. He altogether deprecated the sugges-tion that there would be contamination by oil from the drill or other tool. There was no difficulty in getting drillings free from oil in the case of steel and it would be still easier in the case of copper. Mr. Blount however had given good reasons for believing the fusion process to be quicker and equally accurate and therefore the matter was one of convenience rather than of accuracy He had heard with some surprise that where a sample of copper contained arsenic it was devoid of phosphorus, and vice versd.He would like to hear whether the author could suggest any possible explanation of this very curious fact, Mr. ,~RCHBUTT in reply said that after all it did not matter whether the deter-mination was made by fusion or by loss of weight at a red heat ; the material point which he had sought to establish was that both methods gave practically the total percentage of oxygen present. Every sample of copper in which he determined the oxygen and which he also completely analysed for other elements was in the form of turnings from a test-bar which was subjected to mechanical tests. I t seemed to him that this was a necessity if any information was to be obtained as to the extent to which the chemical composition bore upon the mechanical qualities of the metal.I n obtaining them as far as possible anything in the way of grease was excluded but neverthe-less the precautions were taken of washing the turnings with ether and of picking out any iron with a magnet. He was glad to gather from Mr. Blount’s remark as to the importance of speed that engineers and purchasers of copper take so large an interest in the bearing of the chemical composition upon the wearing qualities of the metal as this would afford the means of obtaining information which really did not exist at present He did not know that he was in a position to state exactly why phosphorus and arsenic never occurred together in copper but that was his experience. He had never met with a firebox plate containing phosphorus but phosphorus was generally present in copper used for making tubes ; such copper was practically free from oxygen and was he believed deoxidized by adding phosphorus to it.E e had so frequently found phosphorus absent when arsenic was present that he had ceased to test for it in such cases. Arsenical copper always contained oxygen and such copper could not contain phosphorus. Mr. BLOUNT entirely endorsed Mr. Archbutt’s view that the sample for analysis He had found these turnings very convenient to work upon THE ANALYST. 265 should come from the actual test bar though it did not follow necessarily that it should consist of turnings. Dr. DYER said he believed that small variations in the proportion of oxygen present had considerable effect upon the electrical conductivity of the copper. He would like to ask the author what quantity of oxygen would be expected in good electrical copper and more especially how far variations in the proportion of oxygen affected the strength and durability of the copper for mechanical purposes. Mr. ARCHBUTT said that he had no experience of the composition of copper for electrical purposes but there seemed to he a definite relationship necessary between the proportions of oxygen lead arsenic etc. in order to yield a good tough copper though exactly what that relationship was he could not at present say. He had a number of figures showing a remarkable relationship between the cuprous oxide determined by Abel’s method and the arsenic and lead but exactly what that meant was not yet clear

ISSN:0003-2654    

DOI:10.1039/AN9002500253

出版商:RSC    

年代:1900

数据来源: RSC

摘要:

THE ANALYST. 265 A NEW COLOUR REACTION FOR CITRAL AND CERTAIN OTHER AROMATIC COMPOUNDS. BY HERBERT E. BURGESS. (Bead at the Meetiyzg, 1cfc~y 2 , 1900.) IN various endeavours I have made to discover a quantitative reaction which could be used for the estimation of citral (especially in oil of lemon), I was led to try the action of mercury salts on aldehydes, with a view to determine the amount of reduc- tion, or, if possible, to weigh the compound so formed. Up to the present time I have been unable to base any satisfactory quantitative method on my results, owing to the fact that many other allied aromatic compounds form salts with the reagent I employ, and also that these mercury compounds are not easily crystallizable, and are probably of indefinite composition and transitory. I have, however, noticed well-defined colour reactions with many of the aldehydes, alcohols, and other constituents found in various essential oils, and it is to these reactions that I wish t o draw attention now.The reagent mentioned above is prepared as follows : Ten grammes of mercuric sulphate are dissolved in and made up to 100 C.C. with 25 per cent. pure sulphuric acid. Then 2 C.C. of the substance to be examined are placed in a small phial fitted with a cork, and 5 C.C. of the reagent added. The whole is then vigorously shaken, any change in colour noted, and again examined after standing for about ten minutes. A porcelain tile will be found useful when only small quantities of an oil can be obtained. The sensitiveness of the colour reaction is not in any way impaired by the use of such small quantities.One drop of the oil is placed on the tile and 3 to 4 drops of the reagent added, and well stirred with a glass rod. Twenty-five per cent. sulphuric acid itself gives no reaction with the substances I have examined.266 THE ANALYST. The following reactions are characteristic : Citra1.-Bright red colour forms on shaking, which rapidly disappears, and at the same time a, whitish compound is formed, which floats on top of aqueous portion. Citronella1.-A bright yellow colour forms on shaking. The compound formed retains the yellow colour for some time. Limonene.-A very faint flesh colour at first forms, but almost instantly dis- appears, leaving a white compound. Linalyl Acetate.-A brilliant violet colour, which remains permanent, increasing slightly in depth.Limlol. --Quickly gives a deep violet colour. Carophylhze.-A yellowish compound, but not any violet colour. Eugeno1.-A slight violet colour on standing for some time. Cinnamic Aldehyde.-No reaction. Terpineol.-Flesh colour and precipitate. Poymic Aldehyde.-No reaction. Acetic Aldehyde.-No reaction. Benza1dehyde.-No reaction. A.lzisic Aldehyde.-No reaction. The following essential oils have also been examined : Oil of Cassia.-Yellowish compound formed, floating on the oil. No reduction Oil of Cinwmon.-Brown compound formed and slight violet-coloured aqueous Oil of C1owes.-On shaking and standing for some time, a violet colour is foimed on shaking. portion. in the aqueous portion, and increases on standing. On standing, the whole becomes a black, solid mass. DISCUSSION. The PRESIDENT having invited discussion, Mr. CHAPMAN said that it would be interesting to know something of the nature of the compounds which the author had observed to be formed with the mercuric sulphate. A great deal of interest attached to many colour reactions, and more especially to those which afforded means of readily identifying some of the con- stituents of essential oils. But their general usefulness was to a, great extent limited by the fact that they were, more than any other reactions, subject to the disturbing influence of impurities. The compounds existing in essential oils were very often extremely difficult to separate in a state of purity, when working with small quantities of material, and consequently it was possible that these colour reactions might on that account have a somewhat limited application,

ISSN:0003-2654    

DOI:10.1039/AN9002500265

出版商:RSC    

年代:1900

数据来源: RSC

摘要:

THE ANALYST. 267 ABSTRACTS OF PAPERS PUBLISHED IN OTHER JOURNALS. FOODS AND DRUGS ANALYSIS. Examination of Brown and Taylor's 0fficia)l Method of identifying Butter. J. A. Hummel. (JOUTIZ. Amer. Chenz. SOC., 1900, xxii., 327.)-10 the manufacture of renovated butter, the butter-fat is melted and then cooled rather rapidly in a stream of cold water. This melting and rapid cooling induces a semi-crystallization of the fat. Samples of genuine and renovated butter were examined with a polarizing microscope magnifying 120 diameters having a selenite plate below the slide. Normal butters gave a uniformly blue field. Renovated butters gave a blue field mottled with yellow. A. &I. New Method for the Determination of Essential Oils i n Drugs and Spices. Neumann- Wender and G. Gregor.(Oest. Chcm Zeit., 1900, iii., 233-235.)-The method depends upon the fact that petroleum ether, of specific gravity 0.640 to 0.670, does not mix with alcohol of 40 to GO per cent. strength (Hefelmann, Pharrn. CentraZhaZZe, 1896, 683), whereas essential oils can be readily shaken out of alcoholic solutions by means of the petroleum ether. Ten to 20 grammes of the coarsely-powdered substance are heated for six hours with 70 C.C. of 96 per cent. alcohol. The residue is again treated for six hours with 25 C.C. more of the alcohol. The extracts are united and made up to 100 C.C. ; 50 C.C. of this are then taken and distilled with steam until the distillate is no longer milky. A distillate of 95 C.C. is generally sufficient. This is made up to 100 c.c., 50 C.C.of it are introduced into the apparatus shown in the illustration, and are made up to the 100 C.C. mark with water acidified with a few drops of sulphuric acid; 25 C.C. of petroleum spirit are then introduced, and the apparatus is well shaken and allowed to stand some hours. The decrease in volume of the alcoholic solution gives the quantity of ethereal oil. A, M. The Gluten Constituents of Wheat and Flour and their Relation to Bread- making Qualities. H. A. Guess. (Joum. Anzer. Cl~e??z. Soc., 1900, xxii., 263.)- The analytical work was performed as follows : ( a ) Five grammes of the finely-ground wheat meal or flour mere placed in a 250 C.C. flask, which was then filled to the mark with 1 per cent. salt solution,shaken at intervals for an hour, and allowed to settle for two hours.The liquid was then decanted through a filter, 100 C.C. of it taken, and the proteids precipitated with a few C.C. of 1Qper cent. solution of phosphotungstic acid. The precipitate mas allowed to settle, 50 C.C. of the clear filtrate were evaporated with sulphuric acid, and the amide nitrogen determined.268 THE ANALYST. ( b ) One gramme of sample was put into a 500 C.C. flask with 100 C.C. alcohol (specific gravity 0.90), shaken thoroughly, and heated with occasional shaking for one hour just below the boiling-point. I t was then allowed to settle for one hour, and the clear liquid decanted off. Twenty-five C.C. fresh hot alcohol were added, allowed to settle for twenty minutes, decanted, and the operation repeated three times. I n the extract the alcohol was distilled off, and the nitrogen in the residue determined, the amide nitrogen (a) subtracted, and the remainder calculated as gliadin (N x 5.7).(c) To the residue from the alcohol extraction, after cooling, 250 C.C. of 1 per cent. salt solution were added. I t was allowed to settle for one hour, and decanted through a filter. Two hundred and fifty C.C. fresh salt solution were added, shaken at intervals for one hour, allowed to settle two hours, and decanted through the same filter. The filter and contents were added to the residue in the flask, and the nitrogen determined and calculated to glutenin. The author found that the quality of the gluten depends upon the ratio in which its two constituents are present. The higher the ratio of gliadin to glutenin, the more elastic is the gluten, and consequently the better is the result of a baking test.The author publishes the result of the analysis of eighty wheats from the Canadian North-West. The glutenin varies from 3.30 to 5.64, and the ratio from 0.70 to 2.90. A number of flours were also examined. The results show that, whilst the gliadin remains fairly constant, the glutenin increases as one goes through the different grades in descending scale. Thus, in Keewatin flour the gliadin was always about 8 per cent., but the glutenin varied from about 2 per cent. in the patent grade to over 5 per cent. in the Glenwood grade. As an aid in grading wheats and flours for commercial purposes, the author proposes a cccompo~ite factor,”” which is the product obtained by niultiplying the percentage of gluten (ie., gliadin + glutenin) by the ratio of gliadin to glutenin. I n the case of the Keewatin flours, the factor comes out at 37 to 58 for patent grades, and 15 to 21 for Glenwood grade, the intermediate grades giving intermediat,e figures.The gliadin in these varies from 3.65 to 9.21 per cent. A. M. Detection of Cherry Syrup in Raspberry Syrup. 0. Langkopf. (Phar??z. C. H., 1900, xl., 421 ; through Chem. Zeit. Rep., 1900, 219.)-The author’s process depends on the presence of hydrocyanic acid in cherry syrup. If one drop of an alcoholic solution of guaiacurn is mixed with a little 1 : 10,000 copper sulphate solu- tion, a milky liquid is produced which turns blue with an exceedingly minute trace of HCN. From 50 or 100 C.C.of the syrup to be examined 2 C.C. are distilled, and the distillate collected in some of the reagent, when 5 per cent. of cherry syrup in rasp- berry causes the appearance of the blue tint. F. H. L. The Examination of Gum Acacia. R. G. Shoults. (Amcr. Jozbrn. %‘harm., 1900, lxxii., 267-270.)-According to the United States Pharmacopceia (lS90), pure gum acacia does not reduce Fehling’s solution. The author, however, shows thatTHE ANALYST. 269 this statement is not correct. He found that powdered samples which caused only a slight reduction at the temperature of the water-bath, yielded much heavier precipitates when the supernatant liquid was filtered and again boiled; and that samples which yielded no deposit at first gave a marked reduction after being dried at 130” C.and then boiled with the Fehling’s solution. In fact, this phenomenon was observed after simple powdering of the gum without drying. He considers that if dextrin were used as an adulterant, a white sample would be liable to contain unconverted starch, which would be detected by means of iodine. A high specific rotatory power, in combination with the detection of starch, would certainly indicate dextrin. On the other hand, a dextrin free from starch would be more or less yellow in colour. For the calculation of the amount of dextrin (specific rotatory power = 198) the author subtracts the specific rotatory power of pure acacia (18) from the observed specific rotatory power of the sample, and divides the results by the increase in the rotatory power produced by an addition of 1 per cent.of dextrin (viz., 1.8). Thus, if a specimen of powdered acacia had a specific rotatory power of 126, this would correspond to 126 - 18 = 108 ; 108 + 1.8 = 60 per cent. of dextrin. C. A. M. Euquinine. Zimmer and Co. (Special pamphlet ; through Chem Zeit. Rep., 1900, 159.)-Euquinine, or euchinine (“ quininE ethyl-carbonas ”), is quinine ethylic carbonate. I t forms hard, white, needle-shaped crystals, melting at 95” C., sparingly soluble in water, easily in alcohol and ether. It has a basic reaction, and yields crystalline salts. Like quinine, euquinine shows a blue fluorescence in sulphuric acid solution, gives the thalleioquin reaction, but not the Herapathite (iodo-sulphate) test. I t possesses only a faint bitter taste, and is more permanent when exposed to light than the compounds of quinine itself. F. H. L. Determination of Bismuth in Organic Preparations. C. Gaebler. (Pharm. Zeit., 1900, xlv., 567 ; through Chem. Zeit. Rep., 1900, 919.)-In ‘‘ Airol ” (bismuth oxyiodogallate) the metal cannot be determined by incineration, as the bismuth volatilizes. By precipitation as oxalate, however, useful results may be obtained. ‘‘ Orphol” (the P-naphtholate) can be safely ignited ; according to the formula, it should contain 80.3 per cent. of Bi,O,. With bismuth salicylate, incineration, extrac- tion of the residue with nitric acid, and ignition is quite accurate. “Xeroform” (bismuth tribromophenol) can neither be analysed by ignition nor by the oxalate process ; it should be treated with strong nitric acid, thrown down with ammonium carbonate, and the precipitate converted into Bi,O,. I?. H. L.

ISSN:0003-2654    

DOI:10.1039/AN9002500267

出版商:RSC    

年代:1900

数据来源: RSC

摘要:

270 THE ANALYST. ORGANIC ANALYSIS. Influence of Temperature on the Speciflc Rotatory Power of Saccharose. F. G . Wiechmann. (Special pamphlet, 1900.)--In this paper the author quotes and discusses the discordant statements which have been made by different observers as to the effect of varying temperature upon the opticity of cane-sugar solutions, records numerous results obtained by himself and his assistants, and finally comes to the conclusion that, under the practical working conditions existing in technical sugar analysis, the specific rotatory power of saccharose may be regarded as constant. F. H. L. The Halphen Reaction for Cotton Oil. P. N. Raikow. (Chenz. Zeit., 1900, xxiv., 562, 583. )-This article contains an account of some incomplete investigations of the mechanism of the Halphen reaction, as well as sundry speculations upon the true cause of the colour.Tortelli and Ruggeri have proved that the active substance in the Becchi test must be of the nature of an unsaturated acid; Raikow has demon- strated that the active substances in the Becchi and Halphen tests are so much alike as regards their removal from or destruction in the oil, that the latter may well be an unsaturated acid also, while his previous work suggested that the two substances might even be one and the same. When, however, 10 C.C. of cotton oil are shakenin a stoppered tube for two hours with dilute sulphuric acid, and increasing quantities of potassium permanganate are added by degrees, if the residual oil is collected by means of ether, filtered, and the solvent removed, apoint is soon reached (5 grammes of permanganate) where the product gives a normal Becchi test but fails to yield the Halphen reaction entirely. This shows that the active substances are not the same, and also that the body which produces the Halphen colour is far more easily attacked by nascent oxygen than the substance responsible for the Becchi colour.Raikow has mentioned (ANALYST, this vol., 106) that a Halphen red appears when the usual mixture of cotton oil, carbon bisulphide, sulphur, and amylic alcohol is simply exposed to sunlight. If such a mixture, after becoming red, is left in the light, it gradually and slowly loses its colour, turning yellow almost as at first, similar changes occurring in a sealed tube. If the original mixture, before becoming red, is kept in the dark in an open tube, it does not turn red even in eight months ; and if the red insolated mixture is placed in the dark before it loses its colourit remains red indefinitely.If the red colour is produced by heating on the water-bath, further heating does not destroy it. A mixture which has been insolated till it has become yellow again may be heated on the water-bath without effect; and if more amylic alcohol, carbon bisdphide, and sulphur are added, further heating only produces an insignificant tint, such as is exhibited by olive oil containing 0-5 per cent. of cotton oil. These experiments indicate that the red body is neither produced nor destroyed in the dark; in sunlight it is first produced, and then decomposed into something different from the original active substance of the oil.Three closed tubes were exposed to south light for seven winter months, ( a ) containing cotton oil alone, ( b ) cotton oil and carbon bisulphide without free sulphur, and ( c ) cotton oil and flowers of sulphur. Tubes b and c were then tested with arnylic alcohol, bisulphide,T E E ANALYST. 271 and sulphur ; they gave no reaction ; tube u gave both Halphen and Becchi tests normally. Light alone, therefore, does not render cotton oil indifferent to the Halphen test, but in presence of sulphur and carbon bisulphide the active substance is destroyed. Part of the contents of tube b were freed from bisulphide by means of a current of warm air ; the residual oil gave a reaction of sulphur with phloroglucinol and vanillin. There is no evidence to show whether this sulphur existed in the free state, as a compound of bisulphide with some constituent of the oil, or as a compound of sulphur and cotton oil; the latter supposition is the more likely, explaining well why carbon bisulphide ultimately makes cotton oil fail to respond to the Halphen test.In sunlight free sulphur renders the oil inactive more rapidly than bisulphide; presence of amylic alcohol hastens either process notably. The Halphen reaction is always accompanied by the evolution of sulphuretted hydrogen, and this evolution is more marked in the presence of amylic alcohol than in its absence. This liberation of gas, indeed, may be employed as a check on the intensity of the Halphen red. When two similar tubes are charged with equal volumes of the Halphen mixture, if the colours in both develop equally, moist lead papers placed over the mouths of the tubes show identical brownish-black tints ; if the reds are different] parallel differences are to be seen in the stains of lead sulphide.All the foregoing observations give the active substance the character of an Unsaturated fatty acid. Yet; 95.8 per cent. of the acids of cotton oil are solid, saturated bodies, and, according to Hazura and Grussner, the 4.2 per cent. of liquid acids are composed of linolic and oleic, which occur in nearly all vegetable oils, and which do not give the Ralphen reaction. Therefore it may be asserted that the red colour depends on some unsaturated acid not hitherto isolated, which is only present in a very small proportion.Finally, Raikow calls attention to Barbaglist’s work upon valeraldehyde and benzaldehyde when heated with sulphur, and to Gattermann’s statement that the thiocarbonyl group is a chromophore, whence it seems not improbable that the action of sulphur upon the unsaturated acid of cotton oil may be either to convert a CH, group into CHS, or a CH group into CS. When, accordingly, the Halphen colour is produced by heat alone, the thiocarbonyl group suffers no further change ; but if the reaction proceeds in sunlight, or if the heated red mixture is insolated, a second stage of the reaction occurs in which the thioaldehyde or thioketone is altered or polymerized, liberating H,S, and losing its red colour [cj: the reactions of benzalde- hyde, ,Jozim.Chem Xoc., Abs., 1891, p. 1049, and of valeraldehyde, Zoc. cit., 1885, p. 1361. Thus the thiocarbonyl group is wholly broken up, yielding a derivative indifferent to sulphur, and this explains why cotton oil which has lost its Halphen red will not give the test a second time. Cotton oil never yields so strong a red in sunlight as on the water-bath, because in the former case production of the CS group is accompanied by its almost simultaneous destruction. It is rather curious, in spite of the extremely small quantity of the active substance present in the oil, that so large an amount of permanganate should be required to decompose it. This may be explained by the hypothesis that the active body is less susceptible of oxidation than at least part of the other msaturated acids, whence it follows that the said active substance must be no less nearly saturated than oleic and linolic acids.F. H. L.272 THE ANALYST. Maize Oil (Corn Oil). H. T. Vulte and H. W. Gibson. (Jouriz. Arner. C'hem. SOC., 1900, xxii., 453.)-Three samples were examined. No. I. was six or seven years old. No. 11. was a sampIe freshly prepared by hydraulic pressure, and was of undoubted purity. No. 111. was a, product of the mash of distilleries : Specific gravity at 15.5" C. ... 9 , ,, 100" c. ... Viscosity (water= 1) 20" C. . , Index of refraction at 15" C. 9 , ) ) 20" c. ,, (rape oil= 100) 20" C. Ash per cent. ... ... ... Iodine absorption ... ... Saponification value ... ... Hehner value ... ... Reichert value ...... Acetyl value ... ... ... Glycerol per cent. ... ... Acid value ... ... ... Unsaponifiable matter per cent. MaumenB-rise in temperature ), -specific ,, Bromine thermal value ... Valenta's test ... ... Livache test-per cent. gain ... ... ... ... ... ... ... ... ... ... ... ... ... ... *.. -.. ... ... ... ... ... ... ... . . I ... ... ... . . I ... ... ... ... ... ... ... ... ... ... ... I. 11. 0-9213 0.9213 0-8716 0.8711 9-79 10.57 70.42 73.89 1.4767 1.4766 1.4761 - 0.065 - 3.70 2.25 119.7 118.6 192.7 192-6 92.8 92.2 4.3 4.2 11.1 11.5 10.55 10.35 1-39 1-43 75" c. 74" c. 21.9" C. 21.8" C. 74" c. 80" C. 179 176 5.97 in seven 5.19 in ten days 111. 0.9255 0.8756 - - - 1.4765 0.0655 20.65 113.3 191.8 88.2 9.9 - - __ - - - 65" C. - The fatty acids gave the following results : Specific gravity at 100" C., 0.8529 ; melting-point, 22.4" C.; iodine absorption, 121.0 ; saponification value, 199.1 ; bromine thermal value, 21-6" C. The iodine values were determined by Hubl's method, using an excess of 100 per cent. and allowing to stand twenty-four hours. A. M. The Composition and Analysis of Artificial Turpentine. G. Fabris. (Aiznali del Laboratorio delle Gabelk, 1900, iv., 143-150.)-The substitutes for turpentine which have been on the market for some time consist, according to the author, of mixtures of rosin oil, colophony, and oil of turpentine. Their colour and consistency depend on the relative proportion of these constituents, and they usually have a mingled odour of colophony and rosin oil. Six commercial samples examined by the author were all completely soluble in 95 per cent.alcohol, and on distillation yielded volatile compounds (turpentine oil) below 250" C. On analysis they gave the following results : Substance volatile below 250" C., 6.5 to 13 per cent. ; acid value, 105 to 113.8; saponification value 113.6 to 119.2 ; difference between saponification and acid values 5.3 to 9.2. From these figures the author calculated approximately the composition of the samples from the data that the rosin oil used boiled above 300" C. and had no appreci- able acidity ; that oil of turpentine boils at 151 to 170" C., and is not acid whenpure; and calculated below 250" cent.; and - - THE ANALYST. 273 that colophony commonly has an acid value of 161 to 170. They were to have the following composition : Turpentine oil (substance volatile C.), 6.0 to 13 per cent. ; colophony (from acid value) 65.2 to 67.9 per rosin oil (by difference) 19.1 to 28.8 per cent.I n addition to the distinct difference in appearance and odour, natural turpentine (French or American) contains more than 15 per cent. of constituents volatile below 200" C., whilst the highest amount found by the author was 13 per cent. in one sample, the others yielding only 6 or 7 per cent. The artificial products also contain rosin oil, which is readily recognisable. Larch or Venetian turpentine might possibly be confounded with the artificial preparations, but it invariably contains more than 15 per cent. of oil of turpentine. According to Dieterich, the acid value of Venetian turpentine varies from 65 to 75, and the saponification value from 110 to 125.In three commercial samples the author found 20 to 25 per cent. of oil of turpentine and acid values of 90.1, 90.2, and 96.8. The difference between the acid and saponification values is thus much greater than in the artificial products. I n order to detect rosin oil, 5 grammes of the turpentine are dissolved in 20 C.C. of 95 per cent. alcohol, a fern drops of phenol-phthalein added, and the solution rendered just alkaline with potassium hydroxide. I n the case of artificial turpentine the liquid becomes turbid, and, on standing, oily drops of rosin oil separate out, whereas Venetian turpentine tested in the same way gives a perfectly clear solution. C. A. AT. Oil of Bitter Orange. G. Fabris.(Amuli del Laboratorio delle Gubelle, 1900, iv., 139, 140.)-Oil of bitter orange, which is also known as Essence d'04'a;Zge bignradc, is extracted from the peel of the bitter orange. Having only a very limited use, it is not, according to the author, easily obtained pure in commerce. It is a yellow liquid, with a bitter aromatic taste, and an odour of orange rather more delicate than oil of sweet orange. Its rotatory power varies within far wider limits than that of the sweet oil (+92" to 98"), but it does not differ much from tho latter in its other properties. Two pure specimens examined by the author gave the following results : Specific gravity at 15" C., 0.853 and 0.852 ; and rotation at 20" C., 92O.40' and 92O.O'. On account of the greater variation in the rotatory power, this oil can be ingre easily adulterated than oil of sweet orange.But the author considers that the rotation considered in conjunction with a fractional distillation should be sufficient to detect tbe inore common and grosser forms o€ adulteration. C. A. 1% Detection of Salicylic Acid in Presence of Citric Acid. A. Klett. (P7~ar~z. C. H., 1900, xli., 452 ; through Chem. Z e i t . R e p . , 1900, 238.)-The following test, due to Jorissen, will indicate the presence of salicylic acid in lemon-juice by giving a blood-red colour : 10 C.C. of the liquid are mixed with 4 drops of a 10 per cent. solution of potassium or sodium nitrite, 4 drops of acetic acid, and 1 drop of 10 per cent. copper sulphate, the whole being heated to the boiling point.(C'. this vol., p. 238.) F. H. L.274 THE ANALYST, Detection of Salicylic Acid and Vegetable Albumin by Means of Millon’s Reagent. C. J. Lintner. (Zeds. nngezo. Chem., 1900, 707.)-When prepared in the usual manner, by dissolving mercury in nitric acid, Millon’s reagent tends to give somewhat uncertain results ; the author therefore prefers to use solutions of mercuric nitrate and sodium nitrite, keeping them separately and adding them in succession to the substance under examination. For the detection of salicylic acid, the sample should be boiled for two minutes with a few drops of 10 per cent. mercuic nitrate, then 2 or 3 drops of dilute sulphuric acid and a very small quantity of 1 per cent. sodium nitrite solution, avoiding excess, should be added. The red colour appears usually with the first drops of nitrite, and generally becomes more intense as the mixture cools. Dilute nitric acid can be employed to acidify the liquid, but it gives a yellow instead of a blue shade of red to the reaction, and thus diminishes the delicacy of the test.This limit of delicacy, both with Millon’s reagent and the above modification, is at about 1 part of salicylic acid per 500,000 ; the modified test yields rather brighter and more permanent tints. To detect vegetable albumin in seeds, etc., a combined reagent should be pre- pared of the mercuric nitrate solution, 5 vols. ; the sodium nitrite, 1 vol. ; and dilute sulphuric or nitric acid, 1 vol. If, for example, longitudinal sections of barley grains are placed in this liquid, the cut surfaces gradually turn red-violet, which renders the glutinous layer and the embryo very conspicuous; the husk becomes a dark brownish-red.F. H. L. It will remain unaltered for a day. Detection of Indican in Pathological Urine. A. Klett. (Clzena. Zed., 1900, xxiv., 690.)-The ordinary calcium hypochlorite test for indican is very apt to fail, especially if the reagent be added in excess; and it is better to use ammonium persulphate, which gives a blue coloration unaffecr;ed by excess. To 10 C.C. of urine are added 5 C.C. of 25 per cent. hydrochloric acid, some persulphate, and then chloroform. Klett calls attention to Xtrzyowski’s test for albumin and bile pigments (ANALYST, 1899, xxiv., 49), and observes that ammonium persulphate is a most service- able reagent in the examination of urine.3’. H. L. The Relation of the Reducing Power of Normal Urine to the Amount of certain Eitrogen Compounds Present. J. H. Long. (Journ. dmer. Clzem. Soc., 1900, xxii., 309.)-Normal urine contains only a small proportion of sugar (see Allen, ANALYST, 1894, 178.) Among the other substances present which have the power of reducing copper, the most important are uric acid and creatinine. The author has determined their reducing power, and has estimated the amount present in a number oi normal urines. For this work a, sensitive copper solution was required. It was found that the oxidizing power increases with the amount of caustic soda and ammonia present. The solution adopted had the following composition : Copper sulphate, 8.166 grammes ; sodium hydroxide (100 per cent.), 15 grammes ; glycerol, 25 C.C.; ammonia (specific gravity 0-9), 350 c.c.; water to make 1 litre. One C.C. of this oxidizes 1 milligramme of sugar in 0-2 per cent. solution ; 50 C.C. of the solution are taken, diluted to 100 C.C. ; solid paraffin is added, which when melted covers theTHE ANALYST. 275 surface. slowly ; 1 molecule of dextrose = 5-88 molecules of CuO. and 1 molecule of uric acid, C,H,N,O,, almost 3. urine, obtained mostly from young men : The liquid is boiled gently and the solution under examination is added I t was found that 1 molecule of creatinine, C,H,N,O, reduces 2 molecules, CuO, The following table gives the results of the examination of 24 samples of healthy Minimum. (a) Excretion in twenty-four hours ...... 765 C.C. ( b ) Specific gravity at 20“ C. ... ... ... 1.018 (c) NH,, milligrammes per litre ... ... 227.7 ( d ) Uric acid, milligrammes per litre ... 423.7 ( e ) Creatinine ,, ... 653 (f) Urea, grammes per litre ... ... ... 14.83 ( h ) Reducing power of uric acid ... ... 0.592 (4 (m) Ratio of I to g ... ... ... ... 0.328 ’ 1 (g) Total reducing power, grammes CuO per litre ... ... ... ... ... 2.245 creatinine ... ... 0.920 <z> sum’bf h and’k ... ... ... ... 1.897 Maximum. 1920 C.C. 1.035 1001.0 1020Q 1930 37.27 8.738 1.381 3.133 4,023 0.631 Mean. 1167 C.C. 1.025 620.0 658.7 1392 24.37 6.204 0.935 1.961 2.896 0.466 The reducing power, which remains unaccounted for, is probably due principally Calculation shows that the quantity of the latter present The value (??a) was A man The same individual some The urea figures given above were determined by the Knop-Hufner process.The ratio of urea to to saccharine matter. amounts in the mean t o about 1.4 grammes dextrose per litre. found to be highest for men of strong physique with a diet containing meat. consuming a diet largely meat gave values 0.63 and 0.60. weeks later, after a change to bread and vegetables largely, gave a value 0.3. Higher results were naturally obtained by the Liebig process. uric acid is 36.9. A. Rill. Artificial Silks. C. Hassac. (Oest. C h e m Zeit., 1900, 235-237, 267-269, 1. Chardonnet silk (made from collodion) from PrAs de Vaux, near Besancon. 2- 9 , ,, from Fismes, in North France. 3- , I ,, from Walston, in England. 4. Silk made from collodion by Lehner’s process at Glattbrugg, near Zurich.5 . Cellulose silk made with ammoniacal copper oxide, by Dr. Pauly’s process, 6. Gelatin silk. Nos. 1, 2, and 4 are very similar in appecwance. 297-299.)-The materials examined were : at Oberbruch, near Aix-la-Chapelle. They excel real silk in lustre, but they are stiffer and have not the characteristic feel of the real material. No. 3 feels rough and appears hairy. I t reminds one of mohair rather than of silk. No. 5 resembles Nos. 1 and 2 in appearance, but its lustre is even better, and when made up it has also the characteristic feel of real silk.c W I. - - . ". ITEE ANALYST. 277 Under the wzicroscope the Chardonnet silks much resemble one another, except that the Fismes product is grooved more.They can, however, be distinguished by their cross-sections (see Figs. 1, 2, 3). Lehner silk (Fig. 4) is characterized by deep grooves running lengthwise along the fibres and by small air-bubbles. Cellulose silk (Fig. 5 ) is regular in cross-section. On the surface are fine grooves running lengthwise ( s t ) , and in the centre of the fibres are fine lines running across ( q j. Gelatin silk (Fig. 6) is almost circular in section and free from grooves or bubbles. The fracture is even and the thick- ness constant. The figures represent the materials swollen by immersion in water and magnified 150 diameters. I n polarized light all the artificial silks show double refraction, except gelatin silk, which is singly refracting. I n this they resemble natural silk.I n No. 5 the interference colours are even over considerable lengths of the fibres, whereas in the collodion silks great play of colours is observed in consequence of the variations in thickness. Beha.L;iow w i t h Reagents. - The collodion silks, Nos. 1 to 4, always contain a small amount of nitro-compound, and consequently give a fine blue with a solution of di$heizyZami?ze in sulphuric acid. When immersed in water, all artificial silks swell. If placed in absolute alcohol or glycerin, the fibres contract again. In co7tceiztrated sulphwic acid the collodion silks swell rapidly and dissolve. Cellulose silk becomes gradually thinner and dissolves away. Gelatin silk only dissolves on strongly heating. Co?zcentrated hydrochloric acid has not much action on artificial silks in the cold.When warmed it dissolves gelatin silk rapidly. Acetic acid only causes a slight swelling, except in the case of gelatin silk, which on boiling dissolves almost completely. Half-saturated chromic acid solution in the cold rapidly dissolves all artificial silks, Real silk takes longer. Cotton, flax, and other vegetable fibres are not dissolved. Collodion and cellulose silks swell, but do not dissolve, even on boiling; but the liquid assumes a yellow colour. Real silk (white) is dissolved on boiling, but does not colour the liquid. Sclzzoeizer's reagent (ammoniacal copper oxide) causes the collodion silks to swell rapidly and then dissolve. Cellulose silk swells less rapidly. Gelatin silk does not dissolve, but is coloured bright violet.Real silk dissolves immediately on warming to 80". Tussah silk dissolves on boiling about a minute, as also does gelatin silk. Solution of iodine a7zd potassizm iodide colours artificial silks an intense red or GELATIN SILK BY PROFESSOR HAMMEL'S PROCESS. sp, Splits in a bent fibre. 13, Cross- section. ( x 150.) Forty per cent. potash lye dissolves gelatin silk rapidly. -4 Zknline copper-qZyce?.in solution is a very useful reagent. The other artificial silks are in no way affected.278 THE ANALYST. reddish-brown. When washed with water the colour disappears, and collodion silks show a transient grayish-blue. Solution of iodine and dilute szdphe~~ic acid (v. Hahmel’s paper reagent) colours real silk yellow, gelatin silk yellowish-brown to reddish-brown, collodiou silks deep blue with a shade of violet, cellulose silk pure blue.Solution of zinc chloride and iocliize colours collodion silks bluish-violet, cellulose silk grayish-blue to grayish-violet ; gelatin silk, like real silk, becomes yellow and disintegrates. As regards inflammability, the artificial silks, with the exception of gelatin silk, behave like cotton. Gelatin silk behaves in this respect like real silk. I n the following table the first column shows the moisture in the air-dry material. The second column the moisture after standing twenty-four hours in an atmosphere saturated with water vapour. The third shows the specific gravity, determined by weighing in benzene, air-bubbles being removed by manipulation under the receiver of a vacuum pump. The fourth column shows the number of elementary fibres which go to 1 square millirnetre after soaking in water. This was determined by measuring the sectional area under the microscope. The fifth column shows the number of fibres in the air-dry state which go to 1 square rniliimetre. This was calculated from the previous figures and the known coeEcients of swelling, as satisfactory sections could not be cut dry. The tensile strengths mere measured on the instrument of .Teclu (C~IZ~TCL~OY~CL’IZ f. SVktZ. 21. Technlg., i., 200). Cellulose silk does not show this blue coloration. Real silk 1. Chard Moisture Air-dry. Saturated. Per cent. Per cent. -7 ... 8-71 20.11 .onnet 11.11 27.46 2. Fismes ... 10.92 27-12 3. Walston ... 11.32 28.94 4. Lehner ... 10.45 26.45 5. Cellulose ... 9.20 23.08 6. Gelatin ... 1398 45.56 Specific Gravity. 1.36 1.52 1-52 1-53 1.51 1.50 1.37 No. of Fibres to 1 sq. mm. 7+ wet. Dry. 9,710 9,710 640 1,135 370 656 683 1,620 413 1,180 742 1,550 265 945 Tensile Strength. Kg. per sq. iiim. 7’-. Wet. Dry. 37.0 37.0 2-54 12.0 1.6 7.8 1.0 22.3 1.5 16.9 3.2 19.1 ni 1 6.6 Ex tension. Per cent. Dry. 21.6 8.0 81.6 7.9 7.5 12.5 3.8 I t will be seen that the cellulose silk made by Dr. Pauly’s process is the most satisfactory. A. M.

ISSN:0003-2654    

DOI:10.1039/AN9002500270

出版商:RSC    

年代:1900

数据来源: RSC

摘要:

278 THE ANALYST. I N O R G A N I C A N A L Y S I S . J. J. Norton. (Zeits. cznorg. Chenz., 1900, xxiv., 411.)-Sherer having stated (cf. Sutton's " Volumetric Analysis") that mercurous nitrate, mercuric nitrate, and mercuric chloride can be accurately determined by titration with standard thiosulphate, the present article is a study of the processes suggested. Norton finds that neither mercurous nor mercuric nitrate can be analysed by Sherer's method ; but that mercuric chloride is amenable to the process if the following directions are followed closely : The solution, containing up to about 0.2 gramme of metallic mercury, is brought into a 1-litre flask, diluted to 100 c.c., heated to 60" C., and a & solution of thiosulphate is run in till the pre- cipitate, which is at first white, becomes brownish.The liquid is then diluted with Titration of Mercury Salts with Thiosulphate.THE ANALYST. 279 cold water, some asbestos fibres added to assist filtration, and the whole filtered through asbestos with the aid of the pump. After thorough washing, the filtrate is made up to a definite volume, treated with 3 grammes of potassium iodide, and the excess of thiosulphate is titrated with iodine and starch. The process should not occupy more than fifteen minutes. Addition of hydrochloric acid is not necessary. F. H. L. Test for Tin. A. Rogers (Jozim. Anzer. Chern. XOC., 1900, xxii., 220) and J. P. Longstaff ( i b ~ d . , 450).-The separation of the tin is conducted in the usual way with zinc, and the black flakes dissolved in hydrochloric acid.To a few drops of this solution a little water is added, and then ammoniuni molybdate. A blue colour shows the presence of tin. Longstaff points out that he published the method last year in the Cliem. News (lxxix., 282). The zinc which is used for reduction must be quite free from tin. With dilute solutions the niolybdate should be added at once, before the tin can hecome oxidized. One part of stannous chloride can thus be readily detected in 100,000 parts of solution. By using the special precautions described in the C'hem. News, it is possible to detect 1 in 1,500,000. A. M. Valuation of Zinc Dust. A. Fraenkel. (Xittlz. Teclm. Gew. MZLS. W i c n , 1900, x., 161 ; through Chenz. Zed. Rep., l900,219.)-0ne gramme of the sample is weighed into a dry stoppered 200 C.C.flask, mixed with 100 C.C. of potassium bichromate solution (30 gramnies per litre) and 10 C.C. of 1 : 3 sulphuric acid, and agitated for five minutes. Another 10 C.C. of acid are then added, and the shaking continued for ten or fifteen minutes, when everything, except a small earthy residue, should be dissolved. The liquid is diluted to 500 c.c., and in 50 C.C. thereof the excess of bichromate is estimated by introducing 10 C.C. of 10 per cent. potassium iodide and 5 C.C. of sulphuric acid, titrating the liberated iodine with decinorrnal thiosulphate. F. H. L. Estimation of Cobalt in New Caledonian Ores. T. Moore. (Chenz,. Nezos, 1900, lxxxii., 66.)-These ores consist mainly of the hydroxides of manganese, iron, aluminium, cobalt, and nickel, with small quantities of calcium, magnesium, zinc, and lithium ; occasionally also barium and copper. The proportion of cobalt may reach 8 per cent., averaging 5 per cent., and the ores are sold simply upon the amount of that metal.To estimate the cobalt, 2.5 grammes are dissolved in strong hydrochloric acid, and evaporated to a syrup; the soluble matter is taken up in water, and the Fe and A1 precipitated by the basic process. To the filtrate 20 C.C. of saturated sodium acetate and 10 C.C. of acetic acid are added, and the whole heated nearly to boiling. A current of sulphuretted hydrogen is next passed through the solution till it is almost cold, when the sulphides of cobalt, nickel, and zinc are collected, washed with H,S-water, dried, and ignited. The ignited oxides and any sulphide adhering to the walls of the flask are dissolved in strong HC1 and a few drops of HNO,, evaporated twice t'o dryness with more HC1, and the chlorides dissolved in 5 or 10 C.C. of water. To remove any traces of iron which280 TEE ANALYST. may have escaped precipitation, this solution is treated with a cream of zinc oxide. The filtrate, diluted to about 50 c.c., is mixed with 10 or 15 C.C. of 10 per cent. hydrogen peroxide and 10 C.C. of 10 per cent. sodium hydroxide. The precipitate of cobalt sesquioxide and nickel monoxide is boiled for a minute, cooled, and treated in a stoppered bottle with excess of potassium iodide and HCl until the decomposition is complete, titrating the liberated iodine with thiosulphate (I x 0.46511 = Co). The caustic soda, employed must be examined for impurities capable of liberating iodine, as samples containing nitrites are nat uncommon. The examples quoted are satis- fact or y. F. H. L.

ISSN:0003-2654    

DOI:10.1039/AN9002500278

出版商:RSC    

年代:1900

数据来源: RSC

摘要:

280 THE ANALYST. APPARATUS. Kreitling. ( Z e d s . ungew. Chem., 1900, 829.) -This is a lengthy article on the behaviour of an Erdmann float in a graduated burette, and the author’s conclusions are as follows: I t is advisable never to use a float in a burette, for the readings obtained with this device vary considerably at different times and with different observers. I n etched burettes graduated without a float, the device should on no account be adopted, for it is liable to cause errors the magnitude of which cannot be predicted. The Use of Floats in Burettes. F. H. L. The Distilration of Ammonia in the Determination of Nitrogen. F. G. Benedict. (Jo.ur.12. Amer. Chenz. SOC., 1900, xsii., 259.)--Ammonia is entirely removed from an alkaline liquid after boiling for quite a short time.If a condenser be used, part of the ammonia condenses in it, and requires a large amount of distillate to wash it through-not less than 150 C.C. If, on the other hand, the condenser be done away with, and the steam be led directly into a beaker containing standard acid, the latter becomes very hot, and must be cooled before titrating. Some of the acid may be lost also. The advantages of both these methods are combined in the following : A condenser is used, the tube of which dips below the surface of the acid in the receiver. After boiling for fifteen minutes, the water is gradually run out of the condenser, and steam is allowed to pass through for five minutes. By that time all the ammonia is distilled from the interior of the con- denser. _I. 11. R E V I E W . Foou AND DRUGS. A Manual for Traders and others, being a Consolidation of the Sale of Food and Drugs Act, 1875, the Sale of Food and Drugs Act Amendment Act, 1879, Nargarine Act, 1887, and Sale of Food and Drugs Act, 1899. By CHARLES JAMES HIGGINSON. London : Effingharn Wilson, 11, Royal Exchange, 1900. Price 2s. 6d. THIS is a, useful little work, which contains, besides the text of the four statiites above cited as chief conr;ents, those clauses of the four Acts which are concurrentlyin force, consolidated in such a manner that one can see at a glance in how far they modify or enlarge each other. The more important of the many High Court decisions which interpret the clauses of the Acts of Parliament are also shortly and clearly referred to. 0. H.

ISSN:0003-2654    

DOI:10.1039/AN9002500280

出版商:RSC    

年代:1900

数据来源: RSC