摘要:

NOVEMBER, 1909, Vol. XXXiV., No. 404. THE ANALYST. PROCEEDINGS OF THE SOCIETY OF PUBLIC ANALYSTS AND OTHER ANALYTICAL CHEMISTS. ON JAFFE’S COLORIMETRIC METHOD FOR THE ESTIMATION OF CREATININE. BY A. CHASTON CHAPMAN, F.I.C. (Rend at the Meeting, June 9, 1909.) IN 1886 Jaffh called attention to the fact that when a solution of creatinine is added to a solution of sodium or potassium picrate containing an excess of alkali, a deep orange-red colour results. I n the communication in which this test was first described (Zeit. physio7. Chenz., 1886, 10, 391), Jaffii refers incidentally to the reaction as being due to the reduction of the picric acid, and it is therefore a little curious that this should have been so generally overlooked, and that the formation of the red coloration should have been ascribed to the formation of creatinine picrate.Creatinine picrate, it may be mentioned, is a yellow substance, as is also the double picrate of creatinine and potassium. It may be of interest to quote the actual words in which the reaction was described by Jaffii : (6 Versetzt man eine Losung von Kreatinin mit etwae wassriger Pikrinsaurelosung und einigen Tropfen verdiinnter Kali- und Natronlauge, so farbt sie sich sofort und zwar schon in der Kalte intensiv roth. Die Intensitat der Farbe, die je nach der Concentration der Losung von rothorange bis dunkelblutroth varirt, nimmt in einigen Minuten noch erheblich zu und bleibt stundenlang unverandert; nur wenn ein Ueberschuss von Alkalilauge angewendet war, wird die Liisung, zumal dem Lichte ausgesetzt, nach einiger Zeit gelb.Ansauern mit Essigsgure oder Salzsiiure wandelt die rothe Farbe in wenigen Minuten in gelb um.” The above statement as to the stability of the red coloration is incorrect, but it has to be borne in mind that Jaffb’s experiments were of a qualitative character, and did not, so far as one can see, involve any exact measurements. The statement, moreover, that the solution becomes yellow when an excess of alkali is present is not476 THE ANALYST. in accordance with facts ; but in other respects the above description of the reaction is clear and accurate. In the concluding paragraph of his paper Jaff6 also calls attention to the fact that acetone, dextrose, and other substances are capable of producing the same coloration. Inasmuch as the formation of the red colour is clearly due to the reduction of the picric acid, I have thought it of interest to ascertain how other reducing substances would behave.The following were tried : Substances. Remacrks. Titanium trichloride.. . Acetone ... ... Hydroxylamine . . . Dextrose ... ... Lwulose ... ... Maltose 1.. ... Aldehyde ... ... Formaldehyde . . . Urea ... ... ... Benzaldeb yde ... Tannic acid ... ... Gallic acid ... ... Ammonium sulphide.. . . . . Reduces instantaneously and completely in . . . Reduces quickly in the cold. ... Reduces immediately in the cold. ... Reduces immediately in the cold. Reduces slowly in the cold, but the action 1:: 1 takes place readily on warming. . . . Reduces almost immediately on warming, but less actively than dextrose or lsevulose. .. . Reduces on warming. ... Reduces on warming. ... Reduces on warming. ... Reduces in the cold, but must be used in considerable excess. ... Reduces more readily than tannic acid. . . . Reduces very readily. the cold. Nascent Hydrogen : These were used in acid solution, the alkali Charged palladium ... I being added afterwards. I n both cases Tin and hydrochloric acid.. . the orange-red coloration was readily Aluminium powder ... Reduces readily. I produced. On reference to the above table, it will be seen that the action on the acid of the substances experimented with is, as a rule, proportional to their general reducing activities, as evidenced in other reactions. The reduction of picric acid may, of course, take place in three stages : Arnino- dinitro-phenol (picramic acid) being formed first, then di-amino-nitro-phenol, and finally tri-amino-phenol.Attempts to match the colour produced by the action of creatinine on the alkaline picrate solution with an alkaline picramate solution, showed that the colour produced in the ordinary test was not due to the presence of that substance alone, the colour dilution ratios and the absorption spectra being very different in the two cases. Thus, a picramate solution which had the same colour as a creatinine- reduced solution, when viewed through a column of 10 cm., was very much less intense when the depth of the columns of liquid was reduced to 5 cm. Further, when each of the two solutions was diluted with an equal volume of watsr, the creatinine-reduced solution was very much the darker of the two.THE ANALYST.477 Preoisely similar results were obtained when using other reducing agents than creatinine, the picric acid being, of course, always kept in excess. The reducing agents employed were charged palladium, titanium trichloride, dextrose, formal- dehyde, and aluminium powder, and in all cases (with the single exception of aluminium, which gave a colour containing more yellow) the colour, although capable of being matched with a sodium picramate solution, followed the same colour ratio on dilution as that observed in the case of creatinine-reduced picric acid. From this it was evident that some other colouring body than picramic acid was present in the solutions reduced by creatinine, or, in other words, that the reduction had proceeded beyond the picramic acid stage.I n order to ascertain the influence of the potash salt of di-amino-nitro-phenol on the colour dilution ratio of a solution of sodium picramate, a quantity of that substance was prspared by the method of Griess (Liebig’s Annalen, 1870, 153, 202). The substance was recrystallised from hot water, and was found to possess the properties stated by Griess. Thus, in a weakly ammoniacal solution, silver nitrate gave a reddish-yellow precipitate which turned black on standing, whilst the picramate gave under similar circumstances a brick-red precipitate which did not darken. Solutions of the sodium salt of this di-amino-nitro-phenol have an intense blood-red colour, whilst solutions of potassium picramate are less intense and of an orange colour. Experiments made with mixtures of the alkaline salts of the two compounds showed that solutions could be obtained which possessed very nearly the same colour properties as the creatinine-reduced solution.I t is therefore clear that in the Jaffk test, under the conditions laid down by Folin and adopted by subsequent authors, the picric acid is reduced by the creatinine, partly to the rnon-amino and partly to the di-amino compounds. Under the conditions of the test as carried out in practice, the picric acid is always in excess, and it became interesting to ascertain whether, if the creatinine were in excess, the reduction could be carried still farther. This was found to be the case, for on adding an excess of creatinine to a solution of the alkaline picrate, the colour, after having reached the maximum intensity, gradually faded, the solution finally becoming almost colourless, owing to the complete reduction of the picric acid to tri-amino-phenol.This substance is well known to be highly unstable, but by working rapidly it was found possible to obtain the characteristic ferric chloride reaction, an olive-green colour being of course observed, instead of the deep blue, I n its action upon an alkaline solution of picric acid, creatinine therefore behaves as a very powerful reducing agent, which is in accordance with its behaviour in regard to other substances (potassium ferri-cyanide, mercuric chloride, alkaline copper salts, etc.), but which is not easily explained by its structural formula,, On alkaline picrate solutions, creatinine exercises, in fact, a reducing action almost comparable with that of ammonium sulphide, or nascent hydrogen (tin and hydrochloride acid).The intensity of the reducing properties of crestinine being somewhat difficult to understand, experiments were made with a few substances containing groups, such as might be expected in the splitting products of the creatinine molecule, but no478 THE ANALYSTc light was thrown upon the matter. Thus, guanidine nitrate, glycollic acid, and swcosine produced no red coloration with alkaline picrate solutions, and glycocoll showed only a very slight tendency to bring about any reduction. On acidifying picrate solutions which had been reduced by means of an excess of creatinine, a disengagement of carbon dioxide was always observed, showing that some of the available oxygen of the picric acid is used for the oxidation of the GO group in the creatinine molecule.I t was also noticed that on acidifying the reduced picrate solution in a closed vessel with sulphuric acid, and introducing a test-paper which had been treated with an alcoholic solution of guaiacum resin and copper sulphate, a faint blue colour was developed, indicating the presence of a trace of hydrogen cyanide. I t would appear, therefore, that hydrogen cyanide is formed in the course of the reaction, but as that substance itself readily reduces alkaline picrate solutions, it is clear that one could not expect to obtain evidence of the presence of more than traces.I t seems, therefore, that in the breaking down of the creatinine molecule, hydrogen cyanide is formed, and it is not improbable that the reducing action is intensified in virtue of its formation. Having established the fact that the colour on which the colorimetric estimation of creatinine by Jaffh’s method is based is due to a complex reducing action, it became of interest to repeat some of the experiments of Emmett and Grindley (J. BioZ. Chent., 1907, 3, 491; ANALYST, 1908, 33, 51) in regard to the influence on the results of variations in time and temperature, and also to ascertain to what extent the presence of a commonly occurring reducing agent, such as dextrose, might% be expected to interfere. Further, inasmuch as the colour dilution ratio of the reduced picric acid solution, differs materially from that of a solution of potassium bichromate (which is frequently used for purposes of comparison), it was thought advisable to devote a little con- sideration to the best method of effecting the colour comparison.Dealing with the last point first, it will be clear, from what has been said above, that it is impossible LO make use of a standard solution of sodium picramate, and it will only be necessary to consider two methods-namely, matching with standard bichromate solution under well-defined conditions, or matching against the colour produced by known weights of pure creatinine. The former method was, I believe, originally suggested by Folin. in a paper entitled Beitrag zur Chemie des Kreatinins und Kreatins im Harne ’’ (Zeit.f. physiol. Chem., 1904, 41, 223). In this paper, the conditions necessary for obtaining correct results are very fully and very carefully detailed, and in view of the explanation which I have given above of the general nature of the process, it is interesting to note that the author endeavoured, unsuccessfully, to prevent the red, coloration from fading, and so to render the colour comparisons possible after a considerable lapse of time. Folin rightly calls attention to the fact that colour comparisons can orly be made against a constant bichromate value-that is to say, a fixed bichromate coloration corresponding with a known weight of creatinine must be adopted as a standard, and with this all solutions under examination must be compared. Using a Duboscq colorimeter, or some similar instrument, Folin has suggested a colour intensity represented by a depth of 8 mm.of a semi-normalTHE ANALYST. 479 potassium bichromate solution (24.54 grm. per litre) as a practically convenient one, corresponding with 8.1 mm. of a solution containing 10 mgm. of creatinine in 500 C.C. of liquid, the colour being, of course, developed under the conditions specified. If, however, some other colour intensity is adopted, then it is necessary to ascertain its creatinine value by direct experiment. In this communication, Folin (loc. cit.) quotes an experiment in which a certain creatinine solution was treated with alkaline picrate in the usual way, and the colour compared against 8 mm. of the bichromate solution. When, however, the same solution was matched against 25 mm.of the same bichromate solution, it was found that the reading was 20-3 mm. instead of 28-2 mm. This experiment can be easily repeated in the following manner with a Duboscq colorimeter : Put some of the standard bichromate solution into one cylinder of the instru- ment, and in the other a creatinine-reduced picric acid solution of such a strength that it is equal in intensity to the bichromate solution when both are set at 8 mm. If, now, both scales are set to read at 4 mm., it will be found that the bichromate solution is considerably the darker of the two; whilst if both scales are set to read at 16 mm., the bichromate solution will be distinctly the lighter. I have carefully checked Folin’s number (8 mm.), using the purest creatin and creatinine obtainable, and working with a Duboscq colorimeter, and find it to be correct.It may be well to point out here that crystalliaed creatin contains 1 mole- cule of water of crystallisation, and usually a little moisture. As a matter of fact, the creatin ordinarily purchased as pure does not contain more than 85 to 86 per cent. of the pure a?ahydrozis substance. Having regard to the fact that the red coloration is due to the presence of several reduction substances, and that it is not easy to insure that in any two experiments the picric acid shall have been reduced to precisely the same extent, it will, I think, be clear that the employment of a fixed standard, such as the bichromate standard, has a great advantage in respect of accuracy over the method involving comparison with the coloration produced in solutions containing known weights of creatinine.I have made a number of experiments with the object of ascertaining what influence variations in the proportions of alkali and picric acid have on the results obtained, and I have been able to confirm the conclusions arrived at by Emmett and Grindley (Zoc. cit.). In the great majority of cases, 15 C.C. of saturated picric acid solution are quite sufficient, but inasmuch as there is some evidence that in certain cases a larger quantity than this gives slightly more accurate results, there is no objection to increasing the volume to 30 C.C. For the benefit of those who are not familiar with the method, the following details, showing its application to the estimation of creatin and creatinine in a substance such as meat-extract, may be of interest : A 10 per cent.solution of the meat-extract in distilled water is first prepared. Several 10 C.C. quantities of this solution are then pipetted into small beakers, and to each 10 C.C. of normal hydrochloric acid are added, after which the beakers are I n this way, a reading of 9 mm. was obtained.480 THE ANALYST, placed in an autoclave and heated for half an hour at a temperature of 120' C. I n this manner, the whole of the creatin present is converted into creatinine, with the minimum formation of colour, and with the least possible amount of decom- position. TO the contents of one of these beakers, cooled to 20' C., 30 C.C. of the saturated picric acid solution, and 15 C.C.of a 10 per cent. sodium hydroxide solution, are added. After standing for five minutes, the coloured liquid is made up to 500 C.C. This solution is then matched against 8 mm. of the standard bichromate in the cylinders of a Duboscq colorimeter. From the reading obtained, a simple calcula- tion will show approximately the volume to which a second 10 C.C. of the meat- extract solution must be diluted in order to give a reading in the colorimeter of between 7 and 10 mm. From this, the proportion of total creatinine present can be readily ascertained. The creatinine present as such in the meat-extract may be determined by ascertain- ing the dilution necessary for matching, by means of a preliminary reading, with an aqueous solution purposely made too strong.This method is, in my opinion, by far the most accurate for the estimation of creatin and creatinine, but as an alternative the colour may be matched in ordinary Nessler tubes against that given by standard creatinine solution. The necessity for obtaining the exact dilution of the meat-extract necessary to give readings in the colorimeter of between 7 and 10 mm. is, of course, a slight objection, and to avoid this, Mellanby ( J . of Physiol., 1908, 36, 447) has suggested the construction of a curve of such a nature that the amount of creatinine corresponding with known colour intensities can be directly read off. It will be seen that, in a sense, Jaffe's method is analogous to Fehling's method for the estimation of sugars. I n both it is essential that the experimental conditiona shall be accurately defined and closely observed.I n both cases, moreover, the chemical reactions on which the estimations depend are of a general character, and, just as the analyst, when determining dextrose in a given substance, must take steps to assure himself that the copper reduction is due to that carbohydrate alone, so it behoves the analyst, when reporting creatinine percentages as determined by this method, to assure himself that other substances capable of exerting a reducing action on alkaline picrate solutions are absent. INFLUENCE OF TEMPERATURE. Having regard to the general nature of the reaction which I have described above, it might be expected that the temperature at which the creatinine solution and the reagents are allowed to interact would have a considerable effect on the result.This, in fact, was found to be the case, as the following experiment shows. Three equal volumes of creatinine solution were treated with the same volumes of picric acid solution and of caustic soda solution, the temperature being maintained in the one case at 100 C., in the second at 30" C., and in the third at 500 C. On comparing the colours at the end of five minutes, it was found that No. 2 was darkerTHE ANALYST. 481 than No. 1 to the extent of about 15 per cent., whilst No. 3 waB lighter to the extent of about 10 per cent. I t will be seen, then, that this factor is of considerable importance, for, up to a certain point, the colour is intensified with rise of temperature, after which there is a, reduction due to the formation of tri-amino-phenol. The necessity for working at a constant temperature has already been pointed out by Folin and also by Mellanby (Zoc.cit.), and I suggest that in carrying out this test the reacting solutions should be maintained at 20° C., which is a convenient temperature to adopt. INFLUENCE OF TIME. Experiments were also made with the object of ascertaining to what extent the results are influenced by varying the time during which the creatinine and the alkaline picrate solution are allowed to interact. It was found that slight variations have no appreciable influence on the results, the tendency being, however, in the same direction as in the case of the temperature factor-that is to say, up to a certain point there is an increase, and then a reduction of the colour intensity.Inasmuch as dextrose is capable of exerting a reducing action on the alkaline picrate solution, and since this substance might possibly be present in certain commercial creatinine-containing products, such as meat-extracts, etc., experiments were made with the object of ascertaining to what extent the results for the crestinine estimations would be influenced by its presence. A solution was made containing a known weight of yeast-extract (free from creatinine) to which a weighed quantity of creatinine was added. This was divided into two equal portions, a, quantity of commercial glucose being added to the one equal to 10 per cent. of the weight of the yeast-extract taken; whilst the other was used as a control.Estimations of creatinine in these two solutions gave results which were almost identica.1, showing that under the conditions of the experiment, the glucose was without appreciable effect. Provided that the Holutions eniployed in determining the creatinine in meat- extracts, urine, and other substances are sufficiently dilute, the colouring bodies present do not exercise any appreciable effect upon the results. If, however, stronger solutions are examined, the disturbhg effect of the natural colour may be very considerable, and high results inay be obtained, as has been pointed out by Van Hoogenhuyze and Verploegh ( h i t . f. Plzysiol. Chem., 1908, 57, 161). These authors have found, moreover, when estimating the combined creatin and creatinine in urine, that if the heating of the urine on the water-bath with hydrochloric acid is continued for more than three hours, a proportion of the creatinine is destroyed. They therefore recommend for the conversion of the creatin the method of Benedict and Meyers (Anzei..J. Physiol., 1907, 18, 397), a recommendation in which I concur. This method consists in heating the solution to be examined with 10 C.C. of normal hydrochloric acid for thirty minutes in an autoclave, at a temperature of 117' C. to 120" C.482 THE ANALYST. I have much pleasure in expressing my best thanks to my assistant, Mr. Fredk. T. Harry, for much valuable help in connection with the experimental portion of this communication. DISCUSSION. MR. F. C. COOK said that in the course of a considerable amount of work which he had done on the application of Jaffk’s method to meat-extracts and meat-products in general he had found it absolutely necessary, if the results were to be accurate, to conform strictly to standard conditions.In a paper on the subject which he had just prepared, and which would shortly be published, some of the factors influencing this reaction were dealt with. He had not as yet done much work with regard to the temperature factor, which undoubtedly was very important. Among other important factors was that of dilution. Folin originally applied the test to 10 C.C. of urine, whereas other chemists, both in this country and in the United States, had used 150 or 200 C.C. of solution from meat-extract or similar product, the result of the increased dilution being an error of some 25 or 30 per cent.in the figures obtained for creatinine. The error due to dilution averaged of a mgm. of creatinine for every 10 c.c., and it was therefore necessary either to concentrate the product or to use some correction factor. The influence, too, of coagulable proteins, and also of proteoses and peptones, was important. Working with solutions of pure creatinine, and also of meat-extract, t o which egg albumen, proteoses, or peptone products such as somatose had been added, he had found that all these additions had the effect of lowering the oreatinine results. Continued standing seemed to lower the results, while alkali, when present in excess, tended to destroy the creatinine compound. With regard to the quantity of picric acid to be used, which had been disoussed by a number of authors, he had come to the conclusion that at least 30 C.C.was required to give accurate results, and that the results were not materially affected by the use of a larger quantity. To sum up, the factors which he had studied were (1) The influence of alkali, an excess of which he had found to destroy the creatinine compound; (2) the influence of the picric acid, of which he considered the best quantity to use was 30 C.C. ; (3) the influence of coagulable proteids, proteoses, and peptones in excess, which tended to cause the results to be too low ; (4) the error due to dilution, which must be carefully watched ; (5) the effect of standing, which seemed to make the results become lower as the period became longer.I t followed that all the work must be carried out under exactly uniform conditions if the results were to be of any value. He had also compared some methods in use in America for the estimation of creatin and creatinine -for example, those of Emmett and Grindley, and of Benedict and Meyers. The latter used an autoclave, in which the creatin was converted into creatinine in fifteen or twenty minutes-a plan which he (Mr. Cook) would recommend, the other methods being all evaporation methods, which required several hours to carry out. MR. A. R. LING asked if the results had been confirmed by taking the absorption spectra of the solutions and comparing them with those of the nitrophenols supposed to be present both alone and in mixtures.He should also like to hear whether the effect of using different alkalis (for example, potash, soda, baryta) had been studied. As those who had worked with nitrophenols were aware, the different salts wereTHE ANALYST. 483 of somewhat different colour. The alkali salts of ortho-nitrophenol derivatives were, a rule, red, whilst those of para-nitrophenol derivatives were yellow. He had tried Jaffgs method on the lines hitherto laid down, and had found the results to be unsatisfactory; and he could quite confirm what Mr. Chapman had said as to the difficulty of matching with bichromate solution. MR. CHAPMAN, in reply, said he trusted that when Mr. Cook’s paper was published it would be found that their results were satisfactorily concordant. He was rather sorry that Mr. Cook had spoken of destruction of the creatinine compound,” by excess of alkali, because what he (Mr. Chapman) had been trying to explain was lthat there was no such compound, and that what really happened was that the alkali tended to break up the creatinine, so that the reduction was more readily brought about. He did not know to what extent the question of concentra- tion was dealt with in Mr. Cook’s work, but the important influence of the colour of the substance under examination must not be overlooked. I n the case of a substance like meat-extract or urine, the colour of the solution after boiling with hydrochloric acid was a very important factor indeed, and one which, until the paper of Van Hoogenhuyze and Verploegh, seemed to have been largely overlooked. Mr. Ling’s suggestion as to absorption spectra had been in his mind, but he had been unable t o carry it out owing to lack of time.* So far as he knew, it made no difference whether soda or potash was used. As to the use of baryta, there were certain difficulties in the way. * * * * ? I ?

ISSN:0003-2654    

DOI:10.1039/AN9093400475

出版商:RSC    

年代:1909

数据来源: RSC

摘要:

THE ANALYST. 483 ABSTRACTS OF PAPERS PUBLISHED IN OTHER JOURNALS. FOODS AND DRUGS ANALYSIS. The Carbohydrates of Asparagus. G. Tanret. (BUZZ. SOC. Chim., 1909, 5, $89-895.)-The author has investigated the carbohydrate reserve materials of the roots of asparagus before the shoots begin to grow, and has isolated, besides sa,ccharose and invert sugar, two new carbohydrates of the inulin group, which he terms ‘( asparagose ” and (‘ pseudo-asparagose.” These were separated from the juice by precipitation in combination with barium hydroxide by means of .alcohol. They are laevo-rotatory bodies, and do not reduce Fehling’s solution. On hydrolysis they both yield laevulose, together with small quantities of dextrose. They differ from inulin in being slowly hydrolysed by invertase. They give no coloration with iodine.The author has also made analyses of the roots, shoots, and berries of .the asparagus. The violet tips of the shoots contain 93 per cent., the white portions contain 90 per cent. of water. The analysis of the whole shoots showed- Per Cent. Water ... ... ... ... ... ... ... 92.03 Cellulose skeleton ... ... ... ... ... 2.65 Other soluble matters.. . ... ... ... ... 2.51 ... Carbohydrates ... ... ... ... ... 2.81 * This has since been done.-A. C. C.THE ANALYST. 484 Africa (S samples). The carbohydrates constitute 55.5 per cent. of the dry substance of the juice ; they are present almost entirely in the form of reducing sugars, the polysaccharides having been hydrolysed in the course of vegetation. A juice obtained in June, con- taining 5.2 per cent.of dry solids, showed- Per Cent. of Per Cent. of Juice. Dry Solids. ... Water ..- ... ... ... 94.80 - Reducing sugars ... 263 50.5 Non-reducing sugars ... 0.26 5.0 Protein.. . ... ... ... ... 0.53 10.2 Asparagine ... . . I ... 0.11 2.1 Ash ... ... ... 0-42 8.1 Pectin and bodies not estimated ... 1.25 24.1 ... ... ... ... ... ... ... J. F. B. Australia (1 Sample) The Amount of Caffeine in Coffee, and the Loss of Caffeine during the Roasting of Coffee. K. Lendrich and E. Nottbohm. (Zeit. Untersuclz. Nahr. Geimssm., 1909, 18, 299-308.)-Results of estimations of caffeine in twenty different sorts of commercial coffee are given. The coffees came from various countries, as mentioned below, and the caffeine was estimated both in the raw and in the roasted article.I n the following table are given the lowest and highest results obtained : Per Cent. 1-05 to 2.83 1-09 to 2.95 Origin. Per Cent. 1.35 1-42 Raw.. . ... Roasted ... South America (8 Samples). Per Cent. 1.08 to 1-35 1-11 to 1-45 Central America (9 Samples). Per Cent. 1-11 to 1.68 1-15 to 1.70 Asia (6 Samples). Per Cent. 1-10 to 1-65 1-12 to 1-68 The percentages are calculated on the dry substance in each case. I t will be seen that the quantity of caffeine in these coffees varies, roughly, from 1 to 3 per cent., and that the amount; in the roasted coffees is only slightly higher than in the. corresponding raw samples. The total loss in the weight of the berries caused by the roasting process amounted to from 14.67 to 18.33 per cent.; the loss of caffeine during the roasting varied from 1.5 to 8.53 per cent.of the total caffeine present. The skins and husks of the berries contain considerably less caffeine than do the berries themselves. The method employed for the estimation of the caffeine mas that described previously by the authors (ANALYST, 1909, 214). w. P. s. Estimation of Camphor in Spirit of' Camphor. E. Deussen. (Archiv P~zcY,~~., 1909,247,307-313.)-Whi1st natural camphor is destro-rotatory and synthetic camphor optically inactive, it is not possible to say, in the case of a sample exhibiting 8 lower rotation than usual, whether the low reading is due t o the presence of synthetic camphor or to deficiency in the quantity of natural camphor. The following process is described for the estimation of the total camphor, and consists in pre- cipitating the latter by the addition of saturated ammonium sulphate solution, theTHE ANALYST, 485 precipitate being then separated, dried, and weighed.Five grm. of the spirit of camphor are weighed into a small flask, 20 grrbs. of cold saturated ammonium( sulphate solution and 30 C.C. of water are added, the flask is closed with a cork, and, after its contents have been mixed, is placed in an ice-chest for a period of at least twelve hours. The precipitated camphor is then collected on a small filter, and washed with ice-water until free from sulphates; about 90 C.C. of water will be required for this purpose, and it is advisable to cover the funnel with a clock-glass during the washing process. When the water has drained off, the mass of crystals is removed from the filter and spread in a thin layer on a porous tile, where it is covered with a clock-glass and allowed to dry for one minute.The crystals are then transferred to a tared card, covered with 'a tared watch-glass, and weighed. The method yields within 4 to 6 per cent. of the quantity of camphor present. On oxidation with nitric acid, natural camphor yields d-camphoric acid melting a t 187' C., whilst synthetic camphor gives i-camphoric acid melting at 204" to 205" C. w. P. s. Sulphite Preservatives in Cider and Perry. H. E. Durham. (J. of Hygiene, 1909, 9, 17-32.)-The author discusses the question of sulphite preservatives in cider and Perry, and gives the results of estimations of sulphur dioxide in twenty- three samples of these beverages.Seven of the samples were practically free from the preservative ; one contained 10.6 mgm. of sulphur dioxide per litr e ; four con- tained from 42 to 97 mgm.; and the remainder contained from 123 to 599 mgm. Most of the samples yielded negative results when tested for salicylic acid, but one of the samples, which mas free from sulphur dioxide, owed its sweetness to the presence of saccharin. The author is of the opinion that the practice of adding sulphite preservatives to beverages is in need of regulation. w. P. s. Chemistry of Hops. R. Siller. (Zeit. Unterszic7~. Nahr. Genussm., 1909, 18, 241-271.)-The author has investigated the processes dealing with the separation of the bitter principles of hops, and describes a method of procedure for the estimation of these substances ; the chemical properties of the bitter principles are also described. I n the method recommended, the hops are extracted with ether, and the extract is dissolved in methyl alcohol ; a portion of this solution is evaporated to give the total quantity of resins, and another portion is precipitated with lead acetate in order to separate the a-resin.The y-resin, being insoluble in petroleum spirit, is determined by difference, the hops being extracted with this spirit to separate the a- and /3-resins together. The details of the method are as follows: Ten grm. of the finely-divided hops are extracted in a Soxhlet apparatus, with ether, for about ten hours, or until the ether extracts no more colouring matter.The dark- green ethereal solution is evaporated under reduced pressure at a temperature of about 40' C., the residue is taken up with methyl alcohol, the solution filtered to remove a quantity of white wax, and the filtrate is diluted to a volume of 100 C.C. with methyl alcohol. Ten C.C. of this methyl alcohol solution are placed in a small beaker, diluted with methyl alcohol, heated to a temperature of about 55' C., and 1 per cent. lead acetate solution (prepared with methyl alcohol) is added, drop by486 THE ANALYST. I drop, until a drop of the supernatant liquid gives a coloration with a drop of potassium sulphide solution on a filter paper. From 10 to 15 C.C. of the lead solution are usually required. The precipitation of the a-acid is dependent on the absence of any excess of lead acetate, and, to avoid any but the slightest excess, it is advisable, when the amount of lead required has been ascertained as just described, to take a fresh portion of 10 C.C.of the hop solution, and to add 5 C.C. of the lead solution directly, and the remainder very cautiously, until the faintest reaction for lead is detected. The mixture is then kept at 50" to 60" C. for five minutes, cooled to the ordinary temperature, and the precipitate collected on a weighed asbestos filter. After being washed with methyl alcohol, the filter and precipitate are dried at 100" to 105" C., and weighed. The weight of the residue, multiplied by 0.6319, gives the amount of a-acid. Another portion of 10 C.C. of the methyl alcohol solution is placed in a flask, and heated in an oven at a temperature of 80° C.for from four to five hours; after cooling, the residue is weighed. The weight gives the total amount of resins present. Ten grm. of the finely-divided hops are next extracted with petroleum spirit (boiling-point 30" to 40" C.) for about ten hours, and the extract is evaporated under reduced pressure at a temperature of about 40' C . The residue is then taken up with methyl alcohol, filtered, and the filtrate diluted with methyl alcohol to a volume of 100 C.C. On evaporating 10 C.C. of this solution to dryness, at a temperature of about 80" C., the weight of the a- and p-resins may be obtained. The quantity of these resins may also be obtained by titration by Lintner's process (ANALYST, 1898, 23, 331). The following results were obtained on the analysis of various samples of hops by the above described process, duplicate estimations agreeing with each other within 0.3 per cent.: Number. Water. 1. 2. 3. 4. 5. Per Cent. 10.98 10 -78 10.47 10.88 10.01 Total Resins ( a +P +Y). Per Cent. 17.74 17.85 13.93 18 49 16-73 Bitter Principles (a +PI. Per Cent. 14.79 15-75 9 86 16-07 14.55 a- Acid. Per Cent. 5.65 5.86 1.61 4.31 6.39 @-Acid. Per Cent. 9.14 9-89 8.25 11.76 8.16 y-Acid. Per Cent. 2.95 2.10 4.07 2.42 2.18 The lead salt of the a-resin contains 36.65 per cent. of lead, and most probably has the formula C,oH,o05Pb. It is soluble in an excess of the alcoholic lead acetate solution, with the formation of a basic salt. If only traces of the a-resin be present, the addition of the lead reagent produces a characteristic yellow coloration, but no precipitate. The pure a-resin may be obtained by recrystallising the lead salt from glacial acetic acid, removing the lead by means of sulphuric acid, and extracting the resin with ether.The a-resin is fairly stable at ordinary temperatures, but absorbs oxygen when heated for a long time. The p-resin absorbs oxygen at theTHE ANALYST. 487 The y-resin appears to be a mixture of at least two different Each molecule of the ordinary temperature. resins, which can be fractionated from their ethereal solution. a-resin absorbs 4 atoms of bromine to give the addition product C,,H,,O,Br,. w. P. s. Diastatic Catalysis of Hydrogen Peroxide applied to Malt Analysis. H. Van Laer. (J. Inst. Brezuiizg, 1909, 5, 553-569.)-After an extended review condemning the existing methods of estimating the diastatic capacity of malts, the author describes his method ( J .lizst. Brewing, 1906, 12, 313-338) for the estiniation of the catalytic activity of malts-that is, the power they possess of bringing about the change 2H,O, = 2H,O + 0,. Six grm. of malt are allowed to act for exactly ten seconds on 25 C.C. of a 0.85 per cent. solution of H20, in a 500 C.C. Erlenmeyer flask of thick glass, and the oxygen liberated is measured in a, graduated burette. Six duplicate determinstions of one sample of malt gave figures varying from 21.8 to 23 C.C. of oxygen. Examples are given of the variations in the results obtained on the same malt by different methods of kilning; thus a final kiln temperature of 100" C.gave a malt yielding 37.7 C.C. of oxygen, while, when dried to 112" C., 19.5 C.C. were obtained. Variations in the draught supplied to the kilns also cause differences in the yield of oxygen obtainable. Speaking generally, any series of friable malts classed according to Lintner's diastatic activity will also be found to be classed according to their catalytic activities, though it is not possible to use one determination as an exact measure of the other. Catalase reaches its optimum activity in the neighbourhood of neutrality with phenolphthaleln.. Malt extract which is alkaline to methyl orange and acid to phenolphthaleln shows an increased diastatic activity when, by the addition of H' ions, the extract approaches neutrality to methyl orange, and a diminished activity with increasing quantities of (OH)' ions.Catalytic activity is the reverse of this, and is at its optimum when the mixture of H202 and malt flour is nearly neutral to phenolphthalein, and falls off on the addition of H' ions. In about half the malts examined the specific rotatory power of the hot mash agreed fairly well with the catalytic activity. The author considers that the diastatic activity of a malt can also be measured to some extent by the specific rotatory power of the wort, Examples of discrepancies between the relations of these three factors are discussed. H. F. E. H. Cholesterol Content of Eggs as a Means of Estimating the Quantity of Egg-substanee in Pastry. H. Cappenberg. (Chenz. Zeit., 1909, 33, 985.)- The fatty oil of eggs contains on an average 3 per cent.of cholesterol, and conse- quently an egg weighing 50 grm., and containing 12 per cent. of oil, will yield 0-18 grm. of cholesterol. An estimation of this substance will therefore afford a means of ascertaining the amount of egg-substance in a sample of pastry. For the estimation 500 grm. of the finely divided sample are extracted with anhydrous ether, the solution is filtered, and the ether evaporated. The fatty residue obtained is saponified with potassium hydroxide, the soap solution is evaporated to dryness, and the dry, powdered soap is extracted with ether. The ethereal extract is now filtered, evaporated, and the residue is dissolved in hot methyl alcohol. The hot solution is488 THE ANALYST.filtered, and the filtrate, after the addition of 20 per cent. of water, is evaporated until crystallisation commences. The whole of the cholesterol crystallises out when the solution is cooled to a temperature of Oo C., and is collected on a weighed filter, washed first with 50 per cent. methyl alcohol, then with hot water, and dried at tt temperature of 100" C. until constant in weight. w. P. s. The "Gemme" [Crude Turpentine] of the Aleppo Pine. M. Vezes. (BzdZ. Xoc. Chim., 1909, 5, 931-933.)-The author has analysed various samples of '' gemme " obtained from the Aleppo pine ( P i m s halepiisis) in Algeria. The corn- position of three typical samples showed : No. 1. No. 2 . No. 3. Per Cent. Per Cent. Per Cent. Oil of turpentine ... ... 27.0 17.3 14.7 Water and loss .. , ... ... 5.5 4.2 2.1 Dry resin ... ... ... 66.7 71.9 78-3 Solid impurities.. . ... ... 0.8 6.6 4.9 No, 1 was exceptionally clean and soft, and had been carefully collected. The others were harder, dirty, and dark in colour. The physical constants of the oils of turpentine obtained from the above and two other samples of '' gemme " ranged between the following extreme values : Sp. gr. at 25' C., 0.8552 to 0.8568 ; rotatory power, [ a ] ~ = + 46.6" to + 47.6" ; refractive index, '1213 at 25" C. = 1.4638 to 14652. On fractional distillation the oil of turpentine of the Aleppo pine shows only a very, small range of 'boiling-points; over 80 per cent. of the oil distils between 155" C. and 156" C. This fraction consists of nearly pure d-pinene, having sp.gr. at 2 5 O C. 0-8541 to 0.8547 ; [ a ] ~ = + 47.4" to + 48.4", and YZD at 25' C. = 1.4833 to 1.4639. This oil of turpentine constitutes a far more satisfactory source for the preparation of d-pinene and its derivatives than the American oil of turpentine. J. F. B. Assay of Hyoscyamus Extracts. E. H. Gane and M. H. Webster. (Merclc's Report, 1909, 142.)-The authors prefer the following method for the assay of hyoscyamus extract to that of the United States Pharmacopoeia (belladonna extract process) : A cylindrical separator of 150 C.C. capacity is tightly plugged at its lower end with a small piece of lint, and a thin glass rod placed in the separator, of such length that when pressed against the lint its upper end touches the bottom of the cork closing the separator.Thirty grm. of finely powdered pumice, 75 C.C. of ether- chloroform mixture (1 : a), 25 C.C. of the fluid extract of hyoscyamus, and 1 C.C. of strong ammonia solution, are placed in the separator. After shaking and settling, the ether-chloroform is drawn off and extracted with 20 C.C. of seminormal sulphuric acid in another separator. The extracted ether-chloroform may again be used for further extracting the fluid extract in the first apparatus, when it is separated, extracted by means of the acid in the second separator, and re-extracted with 10. C.C. of acid in a third separator. Twenty C.C. of chloroform is finally used for extracting the fluid extract, and this chloroform is then extracted with the acid in the two separators as previously. The mixed acid liquids are filtered and made alkaline withTHE ANALYST. 489 ammonia, and extracted with chloroform in small quantities at a time.The chloroform extract is then evaporated at a low temperature. A. R. T. The Separation of Inosite from Natural Wines. G. Meillhe. (J. Pharm. Chim., 1909,30, 247-249.)-1n the separation and identification of inosite as a means of distinguishing natural from artificial wines, for which the author claims priority Over Perrin (ANALYST, 1909, 247), the use of a solution of acid bismuth nitrate and lead nitrate is advocated for the defecation in place of basic lead acetate. The reagent is nearly neutralised by baryta, water before it is added to the wine, previously concentrated to a fourth of its volume. After separation of this first precipitate with the aid of a centrifuge, the filtrate is rendered faintly alkaline with ammonia, and treated with basic lead acetate so long as a precipitate forms.The flask is heated for some minutes on the water-bath and then cooled, and the precipitate, which contains the whole of the inosite, separated. After decomposition of this precipitate with hydrogen sulphide, the liquid is evaporated to 1 or 2 c.c., and mixed with 5 C.C. of methyl alcohol, 20 C.C. of absolute alcohol, and finally 5 C.C. of anhydrous ether. The precipitated inosite may be identified by the tests already described (ANALYST, 1906, 31, 344). C. A. M. Estimation of Dirt in Milk. H. Weller. (Zed. Untersuch. Nahr. Genussm., 1909,18,309-313.)-The treatment of the sediment obtained from milk by centrifugal action with ammonia, alcohol, and ether, as recommended by Fendler and Kuhn (ANALYST, 1909, 322), is considered by the author to be open to objection.These reagents may dissolve appreciable quantities of the dirt found in milk, particularly if this dirt consist of cow-dung, and the quantitative results obtained are likely to be erroneous. He emphasises the fact that the character of the dirt is, within limits, of more importance than its actual quantity (cf. C. Revis, ANALYST, 1909, 403). w. P. s. Adulteration of Mustard. G. Jorgensen, (Annales Falsq., 1909, 12, 372-375.)-A microscopic examination of a sample of mustard, and an estimation of the amount of mustard-oil in the latter, do not always supply sufficient information as to the genuineness of the sample.It is difficult to distinguish microscopically the different species of Brassica, and many of these seeds yield mustard-oil when distilled in the presence of Siizapis alha. The mustard-oils yielded by the Brassica, however, contain less nitrogen than does true mustard-oil, ally1 thiocyanate, the thiocinnamine of which yields 24.14 per cent. of nitrogen, The following percentage quantities of mustard-oil are yielded by various seeds of the above-mentioned group of cruciferous seeds, the figures in parentheses being the amount of nitrogen in the thiocinnamine : Brassicn dichotoma, 0.43 (20.52 per cent. of nitrogen) ; B. glauca, 043 (20.34 per cent. nitrogen) ; B. ramosa, 0.43 (18.36 per cent. nitrogen) ; B. Napzu, 0.22 (21.21 per cent. nitrogen); B. rapa, 0.14 (20.33 per cent. nitrogen). It is there- fore recommended that the sample under examination be distilled after the addition of a quantity of Xinapis alba, and that the nitrogen be estimated. The mustard-oil being collected in a receiver containing ammonia, the ammoniacal solution is490 THE ANALYST, evaporated, and the thiocinnamine weighed. The nitrogen in the thiocinnainiue is then estimated by Kjeldahl’s process. w. P. s Chemical Composition of Soup Tablets (Desiccated Soups). H. Wagner and J. Clement. (Zeit. Untersuch. Nalzr. Genussnz., 1909,18, 314-319.)-Analyses are given of 101 samples of desiccated soups prepared by five leading German manufacturers. The analyses show the percentage quantities of water, proteins, fat, crude fibre, ash, salt, phosphoric acid, and nitrogen-free extractives in the samples, and the refractometer number of the fats extracted from the soups is @en. w. P. s.

ISSN:0003-2654    

DOI:10.1039/AN9093400483

出版商:RSC    

年代:1909

数据来源: RSC

摘要:

490 THE ANALYST, BACTERIOLOGICAL, PHYSIOLOGICAL, ETC. On the Transmission of Air and Micro-Organisms through Berkefeld Filters. W. Bulloch and J. A. Craw. (J. of Hygiene, 1909, 9, 35-45.)- Previously-published results of experiments showing the inefficiency of Berkefeld filters having been the subject of a.dverse criticism, particularly by A. Wilson, who states ( J . of Hygiene, 1909, 9, 33-34) that the unsatisfactory results were due to injury to the filters during the sterilisation, the authors now give the results of further experiments with the filter. They find that the passage of air through the joint and wall of the Berkefeld filter does not seem to be materially affected by boiling in water, by autoclaving at 120" C., or by soaking new and used filters in water for twenty-four hours.The filters leaked, in general, at the neck or joint at lower pressure than at the wall: the joint at from 0.5 to 6 pounds, the wall at from 4 to 7 pounds per square inch. Simple immersion of a dry Berkefeld filter may give rise to a pressure of over 6 pounds per square inch, and this causes immediate leakage at the joint. With autoclaved, comparatively moist filters, a pressure of 3 pounds per square inch was obtained with leakage at the joint. At the pressure used in the experiments-viz., 0.9 pounds per square inch-the large filters gave a yield of filtrate approximating to 0.4 gallons per hour ; this was an exceptionally lenient test for a filter which it is considered should give a yield of about 6 gallons per hour. Of two Berkefeld filters with porcelain nipples, one gave a contaminated filtrate from ordinary London tap-water immediately, the other likewise after three hours and forty minutes. Of three filters with metal nipples, two gave immediate contamination with tap-water, and the third after two hours and forty minutes.Two dried filters, one with metal and the other with porcelain ends, on immersion of a portion of their walls in a water culture of B. prodigiosus, allowed this organism to pass into the interior of the filters. w. P. s. These were new filters, which had been merely boiled for one hour. Observations on the Differentiation of Lactose-Fermenting Bacilli, with Special Reference to those of Intestinal Origin. A. MacConkey. (J. of Hygiene, 1909, 9, 86-103.)-1t is shown that the tests at present in general use do not allow the lactose-fermenting bacilli to be adequately differentiated from each other.Certain tests are, however, described which, in conjunction withTHE ANALYST. 491 those already employed, enable the observer to pick out those organisms which are most closely associated with €axes ; at the same time the bacteriological examination of water-supplies is placed upon a firmer basis than that upon which it stands at present. The author has previously suggested that certain tests should be omitted- namely, (1) The characters of the growth on gelatine ; (2) action on milk ; (3) action on glucose ; (4) action on neutral red; and (5) the indole test, and that the following should be used in place of them: (1) The action on dulcite; (2) the action on adonite; (3) the action on inulin; and (4) Vosges’ and Proskauer’s reaction. Further experience has confirmed this opinion of these tests, and the method of procedure now recommended for the examination of lactose-fermenting organisms is as follows : A sloped agar tube should be inoculated from a single colony on a plate, the growth being rubbed all over the surface of the medium and in the water of condensation.After four to six hours’ growth at 37’ C., a drop of the condensation water can be examined to ascertain the presence or absence of motility. After twenty-four hours’incubation at 37” C., a good loopful of the growth is put into tubes of gelatine, lactose, saccharose, dulcite, adonite, and inulin. The agar tube is returned to the incubator, together with the rest of the tubes, and is used later for the indole test, An inosite tube and a glucose tube (for Vosges and Proskauer’s reaction) may be inoculated at the same time as the others, or these two may be used as confirmatory tests. Vosges’ and Proskauer’s reaction may be tested for at the end of four days.The other tubes should be kept under observation as long as there is no change in the reaction of the medium. The tests must be considered together, no one test being of much value by itself. w. P. s. Method for the Rapid Estimation of Albumin in Urine. Braungard. (Chem. Zeit., 1909, 33, 942.)-The method is a modification of that proposed by Esbach. A solution containing 20 grm. of citric acid and 10 grm. of picric acid per litre of water is employed to precipitate the albumin, the precipitation being carried out in a tube similar to the Esbach tube, the narrow portion of the tube, however, being graduated into an arbitrary scale, showing tenths of a gram of precipitate.Marks on the tube indicate the volumes of the urine and reagent to be introduced, and, when this has been done, the tube and its contents are subjected to centrifugal action for two minutes. Thevolume of the precipitate is then read on the scale, and the quantity of albumin present is thus obtained. The author has made some hundreds of estimations by the method, and in the majority of cases the results agreed with those obtained by the ordinary gravimetric process. w. P. s. Estimation of Urea in Urine. F. W. Gill, F. G. Allison, and H.S. Grindley. (J. Amer. Chem. Soc., 1909, 31, 1078-1093.)-The authors show that the Benedict-Gephart method for determining urea (ANALYST, 1909, 27) gives high results, because-( 1) creatinine and hippuric acid are decomposed to some extent into ammonia by distillation with fixed alkalis ; (2) uric acid is also partially decomposed both by the autoclave treatment with acid and by the subsequent distillation with fixed alkali. These decompositions are gradual, and depend upon the length of time of heating, distillation, etc. Folin’s method (ANALYST, 1902, 27, 20, 21 ; 1903, 28,492 THE ANALYST. 155) gives accurate results in the hands of skilled workers, but requires much attention. The method proposed by the authors is a combination of Benedict and Gephart’s autoclave process, with Folin’s method for the determination of ammonia in urine.Five C.C. of the urine are measured into a hard-glass test-tube, followed by 5 C.C. of 1 : 4 hydrochloric acid, After thoroughly mixing, the tube and its contents are heated in the autoclave at 142’ to 145O C. for ninety minutes. When quite cold the contents of the tube receive an addition of 3 drops of 1 per cent. alizarin-red solution and 3 to 4 drops of pure cotton-seed oil. The tube is then closed with a rubber stopper carrying wash-bottle tubes (one dipping into the liquid), the short tube being connected at its outer end to a Folin absorption-tube contained in a wide-mouthed bottle holding 25 C.C. of sulphuric acid and 130 C.C. of ammonia- free water. The end of the Folin tube is connected to a pump, by means of which air is drawn through the test-tube, and the ammonia evolved caught in the standard acid in the bottle. A piece of sodium carbonate, weighing 2 to 3 grm., is dropped into the testdtube, and the stopper is not replaced until the effervescence has almost ceased. The tube is then shaken until the contents are alkaline (red). A rapid aeration is kept up for five hour8, when the excess of acid in the bottle is determined, using congo-red as indicator. The above method yields results showing a, percentage of 99-45 to 101.94 of the Folin method (loo), or an average of 100-43 par cent. (for twenty-five analyses). It would appear that urines containing ammonium magnesium phosphate may fail to yield all of the ammonia resulting from the urea hydrolysis (cj. Steel and Gies, J . Biol. Chenz., 1908, 5, 71). A. R. T.

ISSN:0003-2654    

DOI:10.1039/AN9093400490

出版商:RSC    

年代:1909

数据来源: RSC

摘要:

492 THE ANALYST. ORGANIC ANALYSIS. Method of Identifying Allyl Alcohol and its Derivatives. G. Denigks. (Bull. SOC. Chinz., 1909, 5, 878-879.)-Since the derivatives of allyl alcohol are fairly numerous among vegetable products, some characteristic test is desirable for their identification in small quantities. Allyl alcohol absorbs bromine with the production of glycerol dibromhydrin. 0.1 C.C. of the allyl alcohol is treated in the cold with bromine water (0.6 C.C. of bromine per 100 c.c.) until a slight yellow coloration persists. The liquid, after being heated to boiling to expel the excess of bromine, is ready for the characteristic tests. 0.4 C.C. of this product is placed in four different test-tubes, together with 0.1 C.C. of 5 per cent. alcoholic solutions of codeine, resorcinol, thymol, and ,&naphthol respectively ; 2 C.C.of concentrated sulphuric acid are added to each, and the tubes are heated in a boiling water-bath for three or four minutes. In this way thymol and code'ine show a violet-red coloration, resorcinol a wine-red, and 6-naphthol a yellow coloration, with strong green fluorescence. These reactions are due to the formation of glyceric aldehyde and its condensation with the various reagents. A further test depends on the conversion of the dibromhydrin into dihydroxy-acetone. 2.5 C.C. of the brominated product are treated with a further 5 C.C. of bromine water, and the liquid is heated for twenty minutes in a boiling water-bath; the excess of bromine is expelled by boiling, and the product should then show the properties of dihydroxy-acetone.This may be detected by means of codeine, thymol, resorcinol, salioylic derivatives,THE ANALYST. 493 guaiacol, phenylhydrazine acetate, Fehling’s solution, and Nessler’s solution, as in testing for glycerol. J. F. B. Analysis of Calcareous Asphaltum and Asphalt Paving Mixtures. Prettner. (Cheyn. &it., 1909, 33, 917-918, 926-927.)-The ordinary method of estimating gypsuni in asphaltum, by burning off the organic matter, is shown to give incorrect results, owing to the interaction of the ‘‘ organic ” sulphur and the calcium carbonate to form calcium sulphide, which is subsequently oxidised to calcium sulphate. Thus, in the case of a sample which by this method was found to contain 4.3 per cent. of gypsum, subsequent examination by other methods proved the absence of that salt.The following method is therefore recommended for the rapid estimation of ‘gypsum : Two grms. (or 1 grm. when more than 20 per cent. of bitumen is present) of the sample, previously dried at 105” C., are mixed by means of a flattened glass rod in a 150-C.C. flask with 15 C.C. of a mixture of ether and hydrochloric acid, which is gradually introduced in three to four portions. This solvent is prepared by saturating 200 C.C. of hydrochloric acid (sp. gr. 1-19> with ether (about 300 c.c.), the liquid being meanwhile continually shaken and cooled. After the asphaltum has been thoroughly mixed with the reagent, an additional 5 C.C. are added to replace that evaporated, and 10 to 15 C.C. of water are then introduced.From 40 to 50 C.C. of hot water are next added, and the flask immersed in hot water to complete the evaporation of the ether. The contents of the flask are now cooled and filtered, the residue of bitumen, which adheres to the flask, washed two or three times with very dilute hydrochloric acid, and the sulphate in the filtrate estimated in the usual manner. The total amount of sulphur is estimated by cautiously heating 0.5 to 1 grm. of the sample with 7 grm. of sodium peroxide in a loosely-covered nickel crucible until reaction occurs, after which the crucible is’ strongly heated for five minutes, and then cooled. The fused mass is dissolved in hot water, the liquid boiled for about ten minutes to decompose the excess of sodium peroxide, and then treated with hydrochloric acid, and the sulphate precipitated with barium chloride.Silicates do not interfere with the estimation. The difference between the result and the amount of ‘( inorganic ’’ sulphur previously obtained in the estimation of the gypsum gives the quantity of “ bitumenous sulphur.’’ For the estimation of the bitumen, two portions (1 to 2 grm.) of the sample are treated as described above for the estimation of gypsum, so as to obtain two solutions of the inorganic matter. One of these, (a), is filtered through an Allihn’s filter-tube containing asbestos, whilst the other, (b), is filtered through a paper filter, which is then washed and dried at l l O o C. The bitumen on this paper is now washed by means of six or seven successive portions of 2 to 3 C.C.of chloroform into a weighed platinum basin, the solution evaporated, and the residue dried at 105’ to 110’ C. The weight, less the amount of ash subsequently estimated, gives the quantity of “ total bitumen.” The residue in the other flask and filter-tube, (a), is dried, and the amount of ‘‘ bitumen soluble in chloroform ” estimated by digestion with successive quantities of chloro- form, evaporation of the solution, and deduction of the weight of the residue (less ash) from the quantity of ‘( total bitumen.” The ash should always be treated with a few drops of sulphuric acid to convert calcium oxide into sulphate, and the494 THE ANALYST, increase in weight of SO, calculated into the corresponding amount of CO,, The following results were thus obtained in the analysis of different samples of asphaltum : Sicilian asphaltum- “Bonelli” ....,. Sicilian paving mix- ture-“ Cocotesta ” German paving mix- ture ... ... Dalmatian asphaltum -“ Adris ” ... Gypsum by Igni- tion Method. Per Cent. 1 -05 1 ’01 1.99 4.20 True GYP- sum. Per Cent. 0.23 0.27 0.25 0.00 I ‘ Inor,; ganic Sulphur. Per Cent. 0.054 0.063 0.065 0~000 Total Sul- phur. Per Cent. 0’46 0’44 0.66 3.37 “ Bitu-,, menous Sulphur. Per Cent. 0 ‘42 0 -36 0.60 3 - 3 i Total 3itumen. Per Cent. 11.62 11.25 12-57 33.15 Chlcro. form- Soluble 3itumen. Per Cent. 9.45 9 -58 11-12 23.35 Aah in Chloro- form- Soluble Bitumen. Per Cent. 0.31 0.32 0.27 0.37 Ash ob- tained by Extrac- tion Method. Per Cent. 0.09 - 0.79 0.64 C. A. M. Calorimetry, and the Determination of the Calorific Value of Philippine and Other Coals from the Results of Proximate Analysis.A. J. Cox. (Philippine J . of Science, 1909, 4, 171-203.)-As the result of experiment with 150 American coalg, the author finds the following values for a in Goutal’s formula (ANALYST, 1903, 28, 128) for deriving the calorific value of fuel from the results of proximate analysis : Ratio of Volatile Combustible to Total Combustible. 25 30 35 40 45 50 55 Corresponding Value of a. 102 92 82 72 63 58 56 A chart is given which greatly simplifies the calculation of the calorific value of American coals. The above values for a and the chart based on them can be applied to Australian coals, with an error averaging 1.5 per cent., and in no case reaching 3 per cent., compared with direct determinations by the Berthelot-Mahler bomb as the standard. Philippine coals are of the type in which the percentage of volatile combustible matter is approximately equal to that of fixed carbon.In the eighty-seven analyses given, the ratio of volatile combustible to total combustible ranges between 41 and 59. The American official method for determining volatile matter (seven minutes exposure to a full Bunsen flame) cannot be applied to them, as it leads to mechanical loss. The author employs his ‘( smoking-off” method (ANALYST, 1907, 32, 298). Goutal’s formula is not applicable to Philippine coals, but the following modification of it, P = 81C + 53*6V., is shown to give results agreeing closely with those obtained by the bomb calorimeter. G. C . J.THE ANALYST.4 95 Pure beeswax ... Wax with 2% stearin ,> 5% 9 , 9 ) 10% ?, $ 7 20% 9 9 Rapid Method of Detecting Stearin and Other Glycerides in Beeswax. A. Ostrogovich and S. Petrisov. (BUZZ. SOC. Sciences de Bucarest, 1909, 18, 127- 130.)-Zinc chloride has the property of hydrolysing glycerides, and of simultaneously converting the liberated glycerin into acrolein. The latter may then be detected by means of Barbet and Jandrier's reagent (a solution of phloroglucinol in concentrated sulphuric acid, in the proportion of 0.3 grm. per c.c.). The coloration, which is rendered more intense by the presence of alcohol, ranges from yellow to reddish- violet, according to the amount of acrolein. In testing beeswax, from 6 to 7 grm. of fused zinc chloride are melted in a porcelain crucible, 1 grm.of the sample then introduced, and the crucible immediately covered with the lid, on the inside of which a few drops of the reagent have previously been distributed. After about forty seconds the lid is removed, a few drops of alcohol added to the exposed reagent, and the colour noted. In the case of pure wax there will be a brown coloration, without any tint of red, whilst beeswax adulterated with stearin gives a coloration varying with the amount of the foreign body. The results thus obtained with mixtures of known composition were as follows : 19.04 19-01 18.90 17.66 16.65 Coloration. Wax. Acid Value. Ester Value. Light brown, without any red Yellow, inclining to red ... Deep red, with violet tint ... Orange red ... ... ... Light red ...... ... 73.05 73-77 77.98 82.75 94-20 The method will thus detect the presence of 5 per cent. of stearin in a mixture which gives analytical values not differing widely from those of a normal wax. C. A. M. Estimation of Carbon Monoxide in Mine Gases. F. H. Weiskopf. (Zeit. f. d. ges. Schiess- und Sprengstofwesen, 1909, 4, 352; from J. Chem. Met. and Min. SOC. S. Africa, 1909, 9, 258.)-The literature dealing with the estimation of carbon monoxide in gases is examined in detail, and the conclusion reached that the most accurate method is the conversion of the carbon monoxide into CO, by means of iodine pentoxide (first observed by Ditte, Bull. SOC. Chim., 1870, [II.] 13, 318; cj. also J. Thth, Chem. Zeit,, 1907, 31, 98, and Morgan and McWhorter, ANALYST, 1908, 33, 30), and absorption of the CO, in weighed potash bulbs.In the author's apparatus, devised in collaboration with Cullen, the gases pass in succession through a three-way cock, a T-tube communicating with a manometer, a dust and moisture intercepting U-tube packed with glass wool and pumice soaked with sulphuric acid, acetylene-absorption bulbs containing 99 per cent, sulphuric acid at 165' C., a sulphuric acid spiral, GO,-absorption potash bulbs, a sulphuric acid spiral and U-tube packed with pumice saturated with sulphuric acid, the iodine pentoxide spiral in an oil-bath at 150" C., an iodine-absorption tube containing 15 per cent. potassium iodide solution, a drying tube, and the weighed potash bulbs. An aspirator placed at the end helps to overcome the resistance to the passage of the gases.If H,S is present in the sample, a tube containing acidulated lead acetate solution or copper sulphate pumice is placed before the first sulphuric acid bulbs.496 THE ANALYST. Methane is estimated by combustion in a heated porcelain tube packed with copper oxide placed between the apparatus and the aspirator. The apparatus is swept out before and after an analysis with air, introduced through the three-way cock, which has been passed through calcium chloride, palladium chloride solution, caustic potash solution, and soda-lime. An artificial gas mixture containing 0,999 per cent. CO and 4.00 per cent. GO, gave 0.97 per cent. CO and 4.11 per cent. GO,. Very accurate results were obtained. 0. E. M. Chitin. D. H. Wester. (Archiv Pharm., 1909, 247, 282-307.)-An account is given of the distribution of chitin in the animal and vegetable kingdoms, and a, full bibliography of researches on the substance since the year 1811 is appended to the paper.I t may be obtained from shrimp-shells by treating the latter with cold 5 per cent. acetic acid, then with 5 per cent. hydrochloric acid for three hours, and afterwards on the water-bath for fifteen minutes with a fresh portion of hydro- chloric acid. The mass is next extracted with hot alcohol to remove colouring matters, and then heated under a reflux condenser for five hours with several successive portions of 5 per cent. potassium hydroxide, and, finally, for one hour with 10 per cent. potassium hydroxide. The residue is now collected, washed, dried, extracted with ether, and treated with dilute acid to remove chitosan.The chitin thus prepared is fairly pure; the author finds that chitin obtained from different sources is one and the same substance. I t is converted by the action of alkalis into chitosan, and is slowly attacked by dilute mineral acids ; concentrated sulphuric acid destroys it within thirty minutes in the cold. When heated to temperatures between 160' and 250' C. with potassium hydroxide, chitin yields a number of decomposition products, including chitosan, ammonia, acetic, oxalic, formic, butyric, and other organic acids. Analyses by various investigators show that chitin contains : Carbon, 46.55 ; hydrogen, 6.57 ; and nitrogen, 6-64 per cent. Chitosan, C,,H,,N,O,o, is best prepared by heating chitin for about one hour at a temperature of 160" C.with eight times its quantity of 50 per cent. potassiua hydroxide. The mass is then dissolved in 3.5 per cent. acetic acid, and the chitosen reprecipitated by the addition of a slight excess of alkali. I t is soluble in organic acids, but is precipitated from such solutions by concentrated mineral acids. I n the presence of 1 per cent. sulphuric acid and 0.5 per cent. iodine solution, chitosan gives a violet coloration. w. P. s. Estimation of Nitrogen in Explosive Powders. 0. Poppenberg and E. Stephan. (Zeit. f. d. ges. Schiess- und Sprengstofwesen, 1909, 4, 350.)-The existing methods of estimating the nitrogen in powders, involving its conversion into nitric oxide, which is then measured, insure neither the exclusion of all gaseous decomposition products except nitric oxide from the measuring vessel, nor the inclusion in it of all the nitrogen as nitric peroxide.The authors prefer to subject the powder to coniplete combustion, and to measure the nitrogen in the free state. About 1 grm. of the powder, mixed with 1 to 1.5 grm. of copper oxide, and con- tained in a, thin-walled iron test-tube perforated at the bottom, is placed in a small steel bomb. A special arrangement of the electric firing device is necessary to secure accurate results, One of the copper firing wires is attached to a firing pinTHE ANALYST. 497 Powder gelatinised with ether-alcohol . -. ... Nitro-glycerine powder . . . Tubular powder . . . ... Flake powder . . . ... passing through an insulating sleeve in the axis of the screw-plug which closes the bomb, and is prevented from short-circuiting against. the tube containing the powder by means of a thin glass tube slipped over it.The second firing wire makes contact with the wall of the bomb, passes up through the hole in the iron test-tube, and is connected to the first by a bridge of platinum wire 0.1 to 0.15 mm. thick embedded in the charge. The air having been expelled by alternate sweeping out with dry GO, and evacuating, both valves are closed and the powder fired. The gases are then allowed to pass slowly over hot copper oxide-no reduced copper spiral is necessary, as no oxides of nitrogen are formed-and into a nitrometer containing caustic potash solution. The transference of the nitrogen is completed by means of a stream of GO,. The bomb has two side tubes closed by valves.Sample analyses are appended : {ii::: 12.53 -( 14.84 14-88 14.72 12.40 12-48 Sample. Percentage of Nitrogen by- 7 Lunge-Lubarsch Method. Schlosing Method. 12.05 11-99 11.97 Bomb Method. 12-69 12-68 12.69 12-92 12.84 12.70 15.02 12.85 12.37 0. E. M. Heat of Combustion and Explosion Temperature of Explosives. 0. Pop- penberg and E. Stephan. (Zeit. f. d. p s . Schiess- und Spreiigstqfzvcseiz, 1909, 4, 281 and 305.j-In order to obtain the true explosion temperature and heat of combustion, it is necessary to know the composition of the explosion gases at the moment of completion of the explosion in the closed vessel. This differs considerably from that found on analysis, on account of the reactions taking place during cooling.The authors show that if A.= GO,, B = the hydrogen, C = the GO plus three times the methane, D = the water less the methane, all expressed froin the analysis as gram-molecules per grm. of explosive fired, then- For temperatures about 2,000°, K = 6.6 (Langen), or 5.5 (Mallard and Le Chatelier). The composition of the gases before cooling is thus obtained by deducting x from the number of gram-molecules of GO, and H,, determined analytically, per grin. of explosive, and the addition of x to those of GO and El2. The true heat of combustion is calculated from that determined experimentally by deducting 50,600 calories for each gram-molecule of methane found, and 10,000 (Ostwald) or 10,100 (Berthelot) calories for each gram-molecule of GO, formed during cooling.In order to obtain more accurate results, gravirnetric methods are substituted498 THE ANALYST. for the usual gas analysis by absorption and measurement of volume. The sample is placed in the bomb described in the preceding abstract, usually 1 to 1.5 grm. of dry powder in a bomb of 10.1 C.C. content, or 10 grm. of other explosive in a bomb of 750 C.C. After sweeping out with dry C0,-free air and closing the valves, the charge is fired, the bomb allowed to cool, and the gases-consisting of H,O, CO,, CO, CH,, H,, and N,-passed slowly through a weighed CaCl, tube and potash bulbs. The mixture of CO, CH,, H,, and N, is then led over hot copper oxide in a hard glass tube 25 to 50 cm. long, connected to a CaCl, tube and potash bulbs.The CH, and (by difference) the CO are determined in a fresh analysis by leading the gases issuing from the first potash bulbs into an absorption apparatus containing cuprous chloride solution, which is renewed several times during an analysis from a vessel at a higher level, through towers containing dilute sulphuric acid (to absorb ammonia), concentrated sulphuric acid (to keep back moisture), and thence to the combustion tube. The CO,, weighed in the second potash bulbs, will now be due to the CH, alone. If the two firings are carried out under exactly similar conditions, the results of the two analyses will be directly comparable. The gases are finally swept out of the bomb, CaCl, tube, and potash bulbs by a stream of dry C0,-free air, which, to avoid oxidation of the CO absorbed in the cuprous chloride, has been passed through alkaline pyrogallol, and the rubber connection leading to the cuprous chloride apparatus closed with a pinch-cock.By raising the level of the cuprous chloride solution the gases are driven over into the sulphuric acid towers, and thence, with a stream of dry C0,-free air, into the combustion tube and bulbs. By means of a pump with a drying tube interposed, the CaC1, tube and bomb, which is warmed to 50’ C., are evacuated, and the water remaining in the bomb thus transferred. The nitrogen is determined as described in the preceding abstract. 0. E. M. Measurement of the Coneentration of Hydrogen Ions. S. P. L. Sorensen. (Comptcs Rend. Trav. Lub. de Carlsberg, 1909, 8, 1-168.)-It is well known that the kinetics of enzyme actions are considerably influenced by the reaction of the medium.This is not a question of the relative acidity or alkalinity, but of the absolute con- centration of the hydrogen ions. This concentration cannot be determined by any process involving a change of concentration in the course of its performance, so that ordinary acidimetric titrations are not available. The author first defines the terminology used : the concentrations of hydrogen ions is expressed in terms of normal solutions in powers of - 10, so that, for instance, iEs concentration would be 10-2, and the (‘ exponent ” of the concentration of hydrogen ions, p&, would be 2. The author has investigated in very considerable detail two methods for determining this exponent for any given liquid.The first method is an absolute one, depending on the measurement of the electromotive force of a cell having one electrode of calomel immersed in a 10 per cent. solution of potassium chloride, and the other electrode of hydrogen (platinised platinum) immersed in the liquid to be tested. The cell was prepared according to the directions contained in Ostwald-Luther’s <‘ Physiko-Chemische Messungen,” and the measurements were made by Poggen- dorff’s method of compensation. The connection between the E.M.F.’s and the corresponding exponents of the concentration of hydrogen ions is expressed by a formula and curve. This electrical method is extremely accurate, but somewhatTHE ANALYST, 4139 laborious. The author has therefore worked out a simple rapid method for general use, based on the use of a large number of indicators and standard solutions of substances, readily obtained in a state of perfect purity.Suitable substances for this pur2ose are tho primary and secondary phosphates. By mixing solutions of these salts in various proportions, it is possible to prepare standards having " exponents " ranging from p& = 1 t o 13. Other substances, such as citrates, borates, and glycocoll, together with hydrochloric acid and sodium hydroxide, are also used in preparing some of the standards. The standard solutions have been standardised by the electrical method, and the exponents corresponding to various mixtures art? tabulated. I n performing the test, the liquid to be examined is tested as to its behaviour towards various indicators, until one is found towards which it is approximately I( neutral." A series of standard mixtures is then prepared in test-tubes, so that some of the standards will possess exponents above and others below that of the liquid to be tested.The selected indicator is then added to each, and the position of the test-liquid on the scale of standards is estimated colori- metrically by comparison. A large number of precautions have to be taken and circumstances taken into account, for the details of which reference must be made to the original. The authm recommends twenty different indicators, the limits of sensibility of which, expressed as '( exponents," are given in the following table : Limiting 6 6 Expoileiits, ' J p + Indicator.H. Methyl violet ... ... . . I ... ... ... Diphenylamino-azobenzene ... ... ... ... Diphenylamino-azo-p-benzene bulphonic acid ... Diphenylamino-azo-m-benzene sulphonic acid ... Benzylanilino-azobenzene ... ... ... ... Benzylanilino-azo-21-benzene sulphonic acid ... ... m-Chlordiethylanilino-azo-p-benzene sulphonic acid ... Dimethylanilino-azolenzene ... ... ... ... Dimethylanilino-azobenzene sulphonic acid ... ... a-Naphthylamioo-azobenzene ... ... ... ... a-Naphthylamino-azo-21-benzene sulphonic acid ... 23-Nitrophenol . . , ... ... ... ... a-Naphthol-azo-23-benzene sulphonic acid , . . ... Phenol-phthalein ... ... ... ... ... ... Thgmol-phthalein ... ... ... ... ... p-Nitrobenzene-azo-salicylic acid ... ... Resorcinol-azo-p-ben zene sulphonic acid ...... Mauveine .. ... ... ... ... ... ... Neutral red . . r ... ... ... ... ... Rosolic .acid ... ... ... ... ... ... Analysis of Brewery Pitch. J. Brand. (Zeit. ges. 0.1- 3.2 0.1- 2.9 1.2- 2-1 1.4- 2.6 1.2- 2.3 2.3- 3.3 1.9- 3.3 2-6- 4.0 2.9- 4.0 3.1- 4.4 3.7- 5.0 3.5- 5.7 5.0- 7.0 6.8- 8.0 6.9- 8.0 8*3-10*0 9.3-10.5 10.1-12.1 11.1-12.7 7.6- 8.9 J. F. B. Brauzu., 1909, 32, 265-267; J. Inst. Brewiizg, 1909, 15, 608-610.)-The author finds that the purer a sample of pitch, the lower is the acidity of its distillation products, and bases his analysis on a careful estimation of the acidity of the bodies distilled from the pitch in a current of air. One hundred grm. of the pitch are heated in a 180 C.C. retort,500 THE ANALYST. a d the volatile products collected in a weighed U-tube, anything passing beyond this being trapped in a flask of water.The degree of acidity of the pitch is defined as the number of milligrams of potassium hydroxide required to saturate 1 grm. of the distillation products. A number of pitches examined by this method showed degrees of acidity ranging from 4 to 102. The so-called transparent pitches from colophony and resin oil which have not been further purified show an acidity of from 20 to 40; superheated pitches, from 4 to 15. A rapid method for the rough valuation of pitches consists of heating in an iron pot full of sand, test-tubes, each containing 3 grm. of the samples to be tested. The whole is heated to 200° C., and the flame then removed. In the mouths of the test-tubes are placed strips of litmus-paper moistened with glycerine, to prevent their drying up.Control tubes containing purified and unpurified pitches of known acidity are used, Whilst with unpurified pitches the paper is often reddened before 200” C. is reached, a purified sample will not show any colour till much later. The proceas may advantageously be used for controlling on the large scale the heating of transparent pitchea to 200° C. in open boilers, to remove volatilo objectionable bodies. The overheating and consequent spoiling of the material can be prevented if the treatment is controlled by watching the acidity developed in the manner already described. €€. F. E. H. Analysis of Galactose. A. Fernau. (Zeit. physioZ. Chenz., 1909, 61, 284; through Chem. Zeit.Rep., 1909, 33, 461.)-The following modification of Tollens’s method is recommended: 5 grm. of the sample are mixed in a tared beaker with 60 C.C. of nitric acid of sp. gr. 1-15, and the mixture is evaporated. After cooling, the magma is diluted with 40 C.C. of water, set aside for twelve hours, aud the precipitate (mucic acid) then collected on a weighed filter, washed with 50 C.C. of water, and dried at 100” C. until constant in weight. One grm. of galactose under these conditions yields 0.7 grm. of mucic acid. w. P. s. Estimation of Lactose in Milk by Means of the “Iron Method” of Michaelis and Rona. K. Oppenheim. (Clzem. &it., 1909, 33, 927-928.)- Michaelis and Rona have devised a method of removing albumin from diluted blood- serum by the addition of colloidal iron hydroxide, so as to obtain a filtrate which can be examined polarimetrically after suitable concentration (Biochem.Zeit., 1908, 7, 329; 13, 121; 14, 476; 1909, 16, 60). The author has applied the method to milk in the following manner : 10 C.C. of the milk are diluted with 13 C.C. of distilled water, and treated, drop by drop, with continual shaking, with 7 C.C. of colloidal iron hydroxide. The resulting precipitate is filtered off, and the lactose in the clear filtrate estimated polarimetrically. The results are invariably about 0.3 per cent. higher than those obtained by gravimetric estimation, the difforence possibly being due to the presence of a dextro-rotatory substance other than lactose. C. A. M. New Procedure for the Estimation of Sugars by Bonnan’s Method.( A m . CtLinz. anal,., 1909, 14, 342-348.)--The sources of discrepancies P. Maillard.THE ANALYST. 501 in the estimation of sugars by Bonnan’s method [A. J. Salm, ‘‘ Estimation of Sugar in Urine” (Chem. Weekblad., 1903,1,12 ; Centralb., 1903, ii., 1150) describes the estima- tion of sugar in urine by Bonnan’s solution, which he states is used in clinical practice in Bordeaux] may be divided into four heads: Variations in the alkalinity of the reagent, variations in the quantity of ferrocyanide, the duration of the titration, and the greater or less intensity of ebullition. The two first may be avoided by making up the solutions most carefully according to the standard prescription. The influence of the time has been studied by the author, who finds that cupric reduction factor is constant for titrations made in the same time.Lastly, the reducing power of the sugar increases with the intensity of ebullition. The author describes a procedure designed to insure constant conditions of ebullition, and has compiled a table in which the influecce of the time taken for the titration is taken into account. The reagents, prepared carefully according to Bonnan’s prescription, consisting of 10 C.C. of copper solution, 10 C.C. of alkaline tartrate solution, and 5 C.C. of ferrocyanide solution, are measured into a flask with a flat bottom and short neck, having a capacity of 100 to 150 C.C. About 0.25 to 0.30 grm. of finely granulated pumice are added, and the flask is placed on a wire gauze? fixed at a height of 5 cm. over a Bunsen burner, and heated in such a manner that ebullition commences after two and a quarter minutes and is in full course after two and a half minutes. This means a dull red disc on the wire gauze of about 2 cm.in diameter, but the exact size of the flame is Boon found by practice. As soon as the liquid begins to boil the point of the burette containing the sugar solution is brought to a height of 1 cm. above the mouth of the flask, and when ebullition is well established, the tap is opened so that the sugar solutiou runs out at the rate of 2 to 6 C.C. per minute. Immediately the first drop enters the liquid the time is noted, and the titration must proceed at a uniform rate with uniform ebullition until finished. When the liquid turns yellow, the fingers are placed on the tap of the burette and when, shortly afterwards, a brown coloration and precipitate are formed, the tap is at once turned and the time noted again. The rate at which the liquid flows from the burette is important ; if at less than 2 C.C.per minute, the operation lasts too long and the reagent boils too vigorously and becomes concentrated; if more than 6 C.C. of the cold liquid is run in per minute, the ebullition becomes too feeble. The rate of titration must not be changed in the course of an experiment, and care must be taken that the rubber band does not turn the tap after it has been set ; if the rate has been miscalculated, the titration must be repeated. With solutions containing 4 t o 8 grm. of dextrose per litre the end point is sharp, and the results of different observers coincide to a single drop.With more dilute solutions the final point consists of a brown coloration resembling that of caramel which succeeds the yellow. Its formation is not instantaneous, and there is a tendency to stop the titration too soon; it is necessary to continue until the whole liquid is dark and begins to show a cloudiness. A turbidity marks the end point with solutions containing 1.5 grm. or more of dextrose per litre. A correction must be made in the case of dilute solutions : When more than 12 C.C. of the sugar solution are required, the readings of the burette must be diminished by 0.1 C.C. for every 1 C.C. in excess of 12 C.C. used. When the solution contains less than 1-5 grm. of dextrose per litre, it is desirable to increase its concentration by the addition of a502 THE ANALYST, known quantity of pure dextrose.The following table gives the figures which must be divided by the corrected number of C.C. of dextrose solution used in order to calcu- late the concentration of anhydrous dextrose per litre, the first column indicating the time occupied in the titration : Duration of Ti tra tion. Mins. 1 1 1 1 1 1 2 2 2 2 3 3 3 4 4 5 5 6 6 7 Secs. 10 20 30 40 50 0 15 30 45 0 15 30 0 30 0 30 0 30 0 0 Bonnan’s Factor. 0.88 0.87 0.86 0.85 0.84 0.83 0.82 0.81 0.80 0.79 0.78 0-77 0.76 0.75 0-74 0.73 0.72 0.7 1 0.70 0.69 Figure to be divided to obtain the Grams of Dex- trose per Litre. 44.0 43.5 43.0 42.5 42.0 41.5 41.0 40.5 40.0 39.5 39-0 38.5 38.0 37.5 37.0 36.5 36.0 35.5 35.0 34.5 J.F. B. Volumetric Estimation of Thiocyanic Acid by Means of Permanganate. K. Schroder. (Zeits. ofeiztl. Chem., 1909, 15, 321 -336.)-Grossmann and Holter have shown (ANALYST, 1909, 244) that thiocyanic acid is not quantitatively oxidised to hydrocyanic and sulphuric acids by potassium permanganate, but that the consumption of perinanganate is less than is required by theory. I n the present communication, experimental evidence is adduced in support of the view that the low consumption of permanganate is due to two disturbing factors, namely, to (a) the formation, to a greater or less extent, depending on the conditions of the titration, of a feebly dissociated complex, and ( b ) to oxidation by atmospheric oxygen activated by the principal reaction itself.In relatively concentrated (decinormal) solutions, the influence of factor CL greatly outweighs that of b, in more dilute (TC) solutions, that of b predominates. Thiocyanic acid can be estimated accurately by means of permanganate if the latter be added very quickly until no longer decolourised, the manganese in solution precipitated by means of sodium carbonate, and, without filtering, the precipitateTHE ANALYST. 503 redissolved in hydrochloric acid. The titration is then continued, when, in decinormal solutions, quite accurate results are obtained. Weaker solutions must be titrated in an atmosphere of carbon dioxide. I n the absence of chlorides, the following method gives accurate results: 5 C.C. of phosphoric acid (sp. gr. 1*7), 20 C.C.of sulphuric acid (1 : 1) and 50 C.C. of water are heated to boiling, 50 C.C. of permanganate added, and then the thiocyanate solution in such quantity that the permanganate remains in excess. This excess j s then determined by means of hydrogen peroxide solution of known strength. G. C. J. Preparation and Estimation of Pure Urobilin and Urobilinogen. 0. V. Fiirth. (Chem. Zeit., 1909, 33, 1016.)-Urobilin is so sensitive to the action not only of acids and alkalis, but also of solvents, such as alcohol and chloroform, that but little reliance can be placed upon the ordinary spectro-photometric method of estimating it. The only means yet found of obtaining it in a pure condition, and of estimating it quantitatively, is by way of its chromogen, urobilinogen.The best method of preparing this from the urobilin of urine is by reduction with sodium amalgam in sodium hydroxide solution, and in a current of carbon dioxide. The conversion may also be readily effected by fermentation of the alkaline urine at incubating temperature, the whole of the urobilin being converted into urobilinogen in about twenty-four hours. Then, by acidifying the urine with tartaric acid, extraction with ether, and removal of foreign colouring matters by means of petroleum spirit, completely colourless solutions of urobilinogen may be obtained. Froiii these solutions pure urobilin may be prepared by a method of exposure to light, (‘ salting out,” treatment with alcohol at a low temperature, and concentra- tion in a cathode vacuum. For the estimation of urobilinogen a spectro-photometric method may be based upon Ehrlich’s colour-reaction with dimethyl-amidobenzalde- hyde, and the results controlled by a gravimetric estimation of the urobilin obtained by the method described above.C. A. M. Estimation of Water in Tar. H. Beck. (Chem. Zeit., 1909,33, 951-952.)- In the estimation of water in tar by the ordinary method of distillation, the tar is very apt to froth over, even when the most careful attention is paid to the distilla- tion. The author describes a simple and rapid method whereby this difficulty is overcome. The retort consists of a spherical iron vessel of 2 litres capacity, with a tubulure for a thermometer, and a short neck for the connection to the condenser. This connection consists of a wide tube, open at the top, with a side branch to the condenser. I n the top opening is fitted a large metal dropping-funnel, capable of holding 200 grni. of the tar. Into the spherical retort, 500 grm. of perfectly dry tar or heavy tar oil are introduced, and 200 grm. of the wet tar to be analysed are weighed out into the dropping funnel, The temperature of the oil in the iron retort is raised to 250° to 270’ C., and then the aqueous tar is allowed to enter, drop by drop. The water is immediately volatilised, and passes over into the condenser, to be collected in a measuring cylinder. The rate at which the tar may be allowed to enter the still depends on the amount of water it contains, but the distillation of a mixture containing as much as 50 per cent. of water may be completed in about504 THE ANALYST. thirty-five minutes. After all the tar has been introduced, the oil in the still is heated at 300" C. for a short time; the drops of water remaining in tihe condenser are then washed down into the measuring cylinder with a little xylene, and the volume may be read off when separation is complete. If this be difficult, on account of the presence of naphthalene, the distillate is poured on a small folded filter previously wetted with xylene. When the light oil has passed through, the point of the filter is pricked, and the water is collected in another measuring cylinder. J. F. B.

ISSN:0003-2654    

DOI:10.1039/AN9093400492

出版商:RSC    

年代:1909

数据来源: RSC

摘要:

504 THE ANALYST. INORGANIC ANALYSIS. New Method of Estimating Antimony. Coolbaugh and Betterton. (Eng. and ~11212. J., 1909, 88, 209; Chem. Zeit. Rep., 1909, 33, 480.)-The ore is fused for fifteen minutes at a low temperature (in a glass flask) with eight to ten times its weight of ammonium persulphate, and the melt boiled out with 30 C.C. of hydrochloric acid (sp. gr. l*l), and diluted to 100 C.C. with hot water. Hydrogen sulphide is passed through the solution for fifteen minutes, and the precipitate filtered off, and dissolved in 40 C.C. concentrated hydrochloric acid with the addition of potassium chlorate. The solution is filtered from undissolved sulphur, and tinted by addition of a small, measured quantity of ferric chloride solution of known strength. It is then heated to 90" C., and stannous chloride added until the yellow colour of ferric chloride is discharged.All the antimony but none of the arsenic present is reduced by stannous chloride before the iron. The excess of stannous chloride is decomposed by mercuric chloride,.tbe solution diluted to 500 to 600 c.c., and titrated with permanganate. Copper, if present in the ore, must be separated; but neither silver, l e d , bismuth, nor arsenic, interfere. Close attention to detail is necessary to secure accurate results. G. C. J. Estimation of Carbonates in Presence of Nitrites, Sulphides, or Sul- phites by Means of Potassium Bichromate. E. R. Maple. ( J . Chem. SOC. 1909, 95, 1491-1497.)-Soluble carbonates are completely decomposed when boiled for two or three minutes with a 5 per cent.aqueous solution of potassium bichromate, whilst insoluble carbonates in a fine state of division are decomposed when boiled for five to ten minutes, provided that the resulting chromate is soluble in water ; other- wise the decomposition is not complete. The apparatus used by the author was a conical 300 C.C. flask, through the cork of which passed a funnel with a tap and the end of a reflux condenser. The top of this was connected with a series of drying- tubes, follomed by potash bulbs and a calcium chloride tube communicating with an aspirator. When nitrites are present, the nitrous acid produced is condensed, and only negligible traces of nitric oxide (from the decomposition of the nitrous acid) are carried forward by the carbon dioxide.In the presence of sulphides or sulphites there is produced a basic chromium carbonate, for the complete decomposition of which it is necessary to add dilute sulphuric acid after boiling the liquid. No hydrogen sulphide or sulphur dioxide are liberated by the action of the bichromate. The test analyses quoted show that the method gives accurate results. C. A. M.THE ANALYST, 505 Separation of Cerium from the other Cerium Earths. 0. Hauser and F. Wirth. (Zeits. anal. Chenz., 1909, 48, 679-692.)-Existing methods are criticised with regard to their accuracy and difficulty, and the conditions defined which must be secured in order to obtain the best results of which each is capable. Dennis and Magee’s modification ( J . Amer. Chem. SOC., 1894, 16, 649) of Debray’s method separates most of the ceria in pure condition, but the other earths cannot, by repeti- tion of the operation, be freed from the remainder of the ceria.Mcyer and KOSS’S modification (ANALYST, 1902, 27, 232) of Witt and Theel’s persulphate methsd separates in one operation the whole of the ceria, but this is contaminated to the extent of 8 per cent. of its weight by the other earths. Meyer and Schweitzer’s modification (ANALYST, 1907, 32,305) of the permanganate method is less satisfactory than the persulphate method. For the separation of the whole of the ceria from quantities up to 100 grm. of the mixed earths, the following new modification of Mosander’s original chlorine method is recommended. I t does not involve the use of any non-volatile reagent, and as regards accuracy is about equal to the persulphate method.To the solution containing the earths as nitrates, ammonia is first added to precipitate them as hydroxides, and then a 3 per cent. solution of hydrogen peroxide in proportion not greatlyexceeding35 C.C. for each 10 grm. of Cs,O, present. ,4n excess of ammonia is of no consequence, but a large excess of peroxide is to be avoiaed. The failure of the hydroxides to deepen in colour on further addition of hydrogen peroxide is an indication when enough has been added. h current of chlorine is then passed through the mixture at such a, rate that the bubbles can just be counted. If excess of hydrogen peroxide has been avoided, no trace of ceria will be dissolved, but five minutes sufices to dissolve 5 grm.of lanthana, and by prolonging the treatment the whole of the neo- and praseo-dymia can be dissolved. These latter oxides, however, when precipitated in presence of hydrogen peroxide, are so much more slowly re-dissolved by chlorine that the authors hope to found on this behaviour a method for their separation from lanthana. G. C. J. Titration of Cobalt. C. D. Test. (Evzg. and fMiiz. J., 1909, 88, 256; Chem. Zed. Rep., 1909, 33, 480.)-The cobalt is separated from nickel by means of sodium nitrite as usual, and the precipitate washed with a 10 per cent, solution of potassium nitrate, of which from 50 to 100 C.C. suffice. Precipitate and filter are then transferred to a, flask, dispersed in 200 C.C. of water, an excess of permanganate and some sulphuric acid added, the mixture heated, aud the excess of permanganate determined by titration with oxalic acid.If manganese dioxide separates out, excess of oxalic acid is added, and then permanganate drop by drop. The cobalt titer of the permanganato solution is taken as being equal to the iron titer x 0,877. The limits of accuracy of the method are not stated, but the results are said to be a trifle low. G. C. J. Assay of Cyanide Solutions for Gold Content. W. F. Boericke. (Chenz. Trade J., 1909, 45, 290.)-Four assay tons (118 c.c.) of solution are treated with506 THE ANALYST, 10 C.C. of lead acetate solutim in a small flask. A few drops of 1 per cent.potassiuin cyanide solution are then added to insure the subsequent complete precipitation of the gold, followed by a f e a drops of 1-37 per cent.silver nitrate solution to increase the proportion of silver and cause the gold to part easily. A small quantity of zinc dust is then added, the flask shaken, and its contents boiled, and the excess of zinc dissolved by the cautious addition of 15 C.C. of hydrochloric acid. When cool the liquid is decanted, the precipitate washed, and the spongy lead and gold pressed together with the finger into a small firm ball. This is finally wrapped in test lead foil and cupelled in the usual manner. The method is especially adapted to assaying zinc tailings where the gold content is low, the lead acetate being added to collect the gold and give a larger button to assay. A. R. T. Gravimetric Estimation of Free Iodine by Means of Metallic Silver.F. A. Gooch and C. C. Perkins. (Zeit. anorg. Chem., 1909, 63, 318-324.)-Free iodine dissolved in a solution of potassium iodide may be accurately estimated by shaking the liquid with finely-divided silver in a closed flask in which the air has been replaced by hydrogen, and determining the increase in the weight of the silver. The silver may be prepared by reducing a silver salt with zinc, or by reduction of silver sulphide with hydrogen, provided it be shaken with potassium iodide solution (to convert any unreduced chloride, sulphide, etc., into silver iodide), and then washed and dried. Silver reduced from silver oxide by means of hydrogen is also suitable for the purpose; but the best form of the metal is that electrolytically deposited upon a small oscillating platinum cathode (the anode being enclosed in a porous cell). The shaking of the flask is continued until the iodine coloration disappears, after which the liquid is diluted with water, and the deposit collected in a Gooch crucible, washed, dried at 130°C.to 140" C., and weighed. From fifteen to twenty-five minutes are required for the absorption of about 0.65 grm. of iodine in 50 C.C. of liquid. The mean error in eleven estimations with electrolytic silver wm - 0.0001 grm., the extremes being +0*0005 and -0*0004 grm. I n experiments in which air instead of hydrogen was in the flask, the results were too high, owing to liberation of iodine from the potassium iodide solution. C. A. M. Presence of Iodate in Commercial Potassium Iodide. L. W. Andrew. ( J . Amer.Chem. SOC., 1909, 31, 1035-1039.)-The production of a blue colour when a solution of potassium iodide is mixed with starch-water and acidified with hydrochloric acid is not necessarily due to iodate, but more likely to be caused by the presence of traces of ferric oxide or cuprous iodide. Acidification of the liquid by means of potassium acid tartrate will suffice if iron oxide be the impurity, and any blue colour then produced may be said, in the absence of cuprous salt, to be due to an iodate. To determine an iodate in the presence of a, cuprous salt with certainty, the test should be carried out in the absence of free oxygen as follows : Fifty C.C. of a 10 per cent. solution of the sample, contained in a 100 C.C. flask, is boiled down to half the bulk, the flask meanwhile being closed with a rubber stopper carrying a bent narrow tube, dipping into a beaker containing 75 C.C.ofTHE ANALYST. 507 distilled water, 1 grm. of pure potassium acid tartrate, and a little starch-water. The contents of the beaker are simultaneously boiled, and kept boiling while the contents of the flask are allowed to cool somewhat, a pinchcock being placed on the end of the tube in the beaker at the time of withdrawing the flame from the flask. The pinchcock is next slightly released to allow half or more of the solution in the beaker to flow into the flask, when it is again closed. The flask is cooled, and if iodate is present a blue colour will be produced. The test is capable of detecting about 1 part of iodate in 47,000 parts of iodide. Incidentally, the author found that the concentration of iodide solutions for the maximum sensitiveness of the iodine-blue reaction was less than A.R. T. Estimation of Phosphorus in Organic Substances. A. Neumann. (Zeit- anaZ. Chem., 1909, 48, 612-617.)-The method described consists, briefly, in decom- posing the organic substance with sulphuric and nitric acids, precipitating the phosphoric acid from the solution by means of molybdic acid, dissolving the pre- cipitate in a definite volume of standard alkali solution, and titrating the excess of the latter after the ammonia has been expelled by boiling the mixture. A weighed quantity of the substance under examination (excreta, animal organs, foods, vegetable seeds, etc.), containing not more than 0.01 grm.of phosphoric acid, is heated in a round-bottomed flask with from 10 to 25 C.C. of a mixture of equal parts of con- centrated sulphuric and nitric acids. The heating is continued until a clear and colourless or faint yellow solution is obtained, and practically all the nitric acid has been boiled off. After cooling, the solution is diluted with 30 C.C. of water, boiled, filtered into a 500 C.C. flask, and the residue (generally a small quantity of fatty acid and silica remains undissolved) is washed with water until the filtrate and washings together amount to 100 C.C. From 25 to 50 C.C. of 50 per cent. ammonium nitrate are then added, the mixture is heated, and from 25 to 40 C.C. of 10 per cent. ammonium molybdate solution are added drop by drop while the mixture is shaken.After standing for eighteen hours at a temperature of 60' C., the precipitate is collected on an asbestos filter, washed, and dissolved in a definite volume of sodium hydroxide solution. This solution is boiled to expel the ammonia, and the loss of alkali due to removal of the ammonia is estimated by titration. Each C.C. of sodium hydroxide corresponds with 0-001368 grm. of phosphoric acid (P205), or with 0*0005536 grm. of phosphorus. As a rule, 1 grm. of flesh or animal organ, 0.5 grm. of vegetable needs, or 5 C.C. of blood, will be found to be convenient quantities to take for the estimation. Fluids should be evaporated in the flask to a volume of about 5 C.C. before the acid mixture is added. w. P. s. Quantitative Volatilisation of Phosphoric Acid from Metallic Phosphates. P.Jannasch and W. Jilke. ( J . pr. Chem., 1909, 80, 113-127.)-The whole of the phosphorus contained in the phosphates of iron, chromium, uranium, cobalt, nickel, manganese and zinc, but not aluminium, can be volatilised by heating in a current of carbon tetrachloride vapour. The substance (0.3 grm.) is mixed with powdered quartz and placed in a silica boat in a combustion-tube, which is drawn out508 THE ANALYST. at the forward end and connected to a tube which reaches almost to the level of some water contained in a flask. The vapours escaping from this flask are subsequently washed in a bulb apparatus. Within the combustion-tube, and near its forward end, is placed a plug of glass wool. The substance is first heated to about 200' C.in a current of dry carbon dioxide until all moisture has been expelled from it and from the combusticn-tube. Vapour of carbon tetrachloride is then passed through the tube, which, in the neighbourhood of the boat, is raised to dull redness. One hour at this temperature is sufficient to decompose ferric phosphate, but the phosphates of the other metals require an additional hour and a half at a bright-red heat. The current of carbon tetrachloride vapour is again replaced by one of carbon dioxide, whilst the glass-wool plug is gently heated to drive forward any phosphoryl compound which may have condensed on it. The glass-wool plug serves to hold back the metallic chlorides which are volatilised at the high temperature prevailing round the boat, It is supposed that the phos- phorus volatilises mainly, but not entirely, as phosphoryl chloride.Whatever its state of combintttion, it can all be volatilised and collected in the water contaimd in the receiver and washing-bulbs, aud ultimately estimated as magnesium pyrophosphate (cf. ANALYST, 1907, 32, 430). G. C. J. Estimation of Tantalum and Niobium in Minerals, Steel, and Alloys. W. E. von John. (Chenz. News, l909,100,154.)--Minerals are fused with potassium bisulphste, and the residue insoluble in boiling water thoroughly washed successively with hot water, hot yellow ammonium sulphide, hot water and dilute sulphuric acid, and finally hot water, If tin be present, the mineral should be ignited before fusion. The residue, which consists of silica, and tantalic and niobic acids, is ignited and weighed.The separation of the two last named from silica is based on the solubility of potassium hexatantalate and niobate in water and in potassium hydroxide, while the corresponding sodium salts are soluble in water, but insoluble in sodium hydroxide. The ignited residue is fused with caustic soda in a silver crucible, the melt dissolved in cold diiute caustic soda, and the liquid filtered through a Gooch crucible, the residue being washed several times with dilute caustic soda, solution. The filtrate contains the sodium silicate. The insoluble residue of sodium tantalate and niobate is now washed with lukewarm water till no precipitate is obtained on adding dilute sulphuric acid to the washings, and this second filtrate is collected separately.Dilute sulphuric acid is added to this filtrate, the solution boiled for a few minutes, the liquid filtered, and the washed precipitate (Ta,O, + Nb,O,) ignited and weighed. The residue is re-fused with potassium hydroxide, and the aqueous solution of the melt precipitated with sulphuric acid and boiled. The separated precipitate is dissolved in hydrofluoric acid, and boiled after addition of some potassium fluoride, when the liquid is diluted and again boiled. The tantalum separates as an insoluble oxy-fluoride (K,Ta,O,FI4), the more soluble niobium salt remaining in solution. The method furnishes a meam of detecting traces of tantalum in presence of niobium. The precipitate is washed with cold water till no reddish precipitate is obtainedTHE ANALYST 509 when tincture of galls is added to the washings ; the residue is then heated with strong sulphuric acid until all hydrofluoric acid is expelled.The liquid is cooled, diluted, a d filtered, and the residual Ta,O, washed till free from sulphate, then ignited and weighed. Steel is dissolved in hydrochloric acid, the solution evaporated to dryness, and taken up in dilute sulphuric acid. The residue is ignited, and fused with sodium hydroxide as before. Ferro-tantalum and alloys containing as much as 45 per cent. of tantalum are treated similarly. If a larger proportion of tantalum is present, the finely-powdered alloy should be previously ignited. The methods are stated to give satisfactory results, and are rapid in working. A. R. T. Quantitative Precipitation of Tellurium, and its Application to the Separation of Tellurium from Selenium.P. E. Browning and W. R. Flint. (Zeit. anorg. Chem., 1909, 64, 104-lll.)-The material is dissolved in 10 per cent. caustic potash, of which about 1 C.C. is taken for each 0.1 grm. tellurium dioxide supposed to be present, the solution is made faintly acid with hydrochloric acid, and diluted to 200 C.C. (or more if the tellurium present exceeds 0.4 grm.) with boiling water. Dilute ammonia in slight excess is then cautiously added, though addition of so much that the precipitate at first formed is just redissolved introduces but a, small error. Acetic acid is nest added, in quantity just sufficient to restore the acid reaction, and, on cooling, the whole of the tellurium will have separated out in an easily filterable condition, selenium remaining in solution. After half an hour the precipitate is filtered off in a Gooch crucible, washed with cold water, and dried a t any temperature above 105" C., and below a dull-red heat.With 0.2 grm. tellurium dioxide present, the results are usually 0-5 mgm. low, the worst of thirty recorded being 1 mgm. low. G. C. J. Electrolytic Estimation of Thallium. G. W. Morden. ( J . Anzer. Chem. SOC., 1909, 31, 1045-1048.)--The author used in his experiments the apparatus described in Smith's '' Electro-Analysis " (fourth edition, p. 44) and Myers' mercury-cup cathode (ANALYST, 1905, 30, 1903). Fairly good results were obtained with the first-mentioned apparatus when a protective coating of zinc (to prevent oxidation) was deposited on the thallium; but owing to the uncertainty of obtaining a non-porous coating of zinc in this way, the author tried a mercury cathode in order to obtain a thallium amalgam.It wag found, however, impossible to dry this amalgam without oxidation, and loss was entailed if the coating was again washed with water, while alcohol and ether dissolved out thallium. The best results were finally obtained by producing a dilute zinc amalgam by electrolysing a zinc sulphate solution in the ordinary mercury cup with a rotating anode, followed by depositing on this amalgam (the cathode) the metallic thallium. This zinc- thallium-mercury alloy can be repeatedly washed with water, and dried by alcohol and ether without loss. The minimal amount of zinc necessary to prevent oxidation of the thallium was found to be 0.0007 grm.zinc for 0.1143 grm. of thallium. Good results were also obtained with a cadmium-thallium amalgam. A. R. T.510 THE ANALYST, Quantitative Volatilisation of Vanadic Acid from its Compounds by heating in a Current of Carbon Tetrachloride Vapour. P. Jannaseh and H. F. Harwood. (J. pr. Chem., 1909, 80, 127-134.)-The mineral is treated like the phosphates in the analogous process for volatilising phosphoric acid (see p. 507), with the difference that the receiver is charged with dilute nitric acid. The distillate is evaporated to dryness, the residue dissolved in dilute sulphuric acid, any arsenic present separated as sulphide, and the vanadium estimated volumetrically by reduc- tion by sulphur dioxide and reoxidation by permanganale in the usual manner. A moderate red heat suffices to volatilise the vanadic acid from its ammonium and sodium salts, and from vanadinite, endlichite, and carnotite. I n presence of sodium phosphate, the vanadium of sodium vanadate cannot be completely volatilised. I t was found, however, that though sodium phosphate did not yield up its phosphorus when heated alone in a current of carbon tetrachloride vapour, yet admixture with four times its weight of salt caused it to give up the whole of its phosphorus under such treatment. For the estimation of vanadic acid in presence of alkali phosphates, therefore, admixture with salt is resorted to, when the whole of the vanadic and phosphoric acid can be volatilised at the highest tempera- ture an ordinary combustion-tube can stand without distortion. After estimation of the vanadium in the distillate by permanganate as described, phos- phoric acid can be determined in the same solution. G. C. J.

ISSN:0003-2654    

DOI:10.1039/AN9093400504

出版商:RSC    

年代:1909

数据来源: RSC

摘要:

510 THE ANALYST, APPARATUS, ETC. Apparatus for the Estimation of Mineral Oil in Oil of Turpentine. J. Marcusson and G. Winterfield. (Chenz. Xeit., 1909, 33, 987.)-The apparatus is shown in the figure, the mode of using it being as follows : Thirty C.C. of fuming nitric acid (sp. gr. 1.52) are placed in the bulb, a, and cooled to a temperature of - 10" C. by immersing the bulb in a freezing mixture. Ten C.C. of the oil of turpentine under examination are then placed in the stoppered funnel, and allowed to fall drop by drop into the nitric acid. During the addition, which should take from thirty minutes to one hour, the mixture is agitated continually. When all the turpentine has been introduced, the contents of the bulb are kept at a temperature of -10' C. for fifteen minutes; the stoppered funnel is then removed, and ordinary concentrated nitric acid, cooled previously to -10' C., is added until the oily portion in the bulb is brought up into the graduated neck, c ; its volume is read off when it has attained the ordinary temperature, the bulb meanwhile being kept in the freezing mixture.The petroleum- oil portion may then be removed by means of a pipette, and its boiling-point and specific gravity determined. w. P. s.THE ANALYST. New Shape of Boat for Combustions. M. Delgpine. (Bull. Sac. Chem., 1909, 5, 876-877.)-1n the ordinary form of boat, when a liquid or fusible substance has to be burnt, there is a tendency for the substance to flow away from the source of heat and to collect in a small space at the coldest end of the boat.Combustion is then liable to be incomplete, or at least very slow. This defect is avoided in the new form of boat, which is cut out of a strip of platinum 14 mm. wide, of the shape illustrated in the figure, In this strip four small cavities are hammered, each 7 mm. wide, 20 mm. long, and 3 mm. deep. The total length of the strip is 15 cm. In using this boat each of the cavities is charged about equally, and the boat is inserted in the combustion-tube between the copper oxide in front and the spiral of oxidised copper behind. The small portion of the substance in each compartment is heated, and either volatilised or carbonised separately, so that there is no fear of any sudden excessive development of gas. Further, it is impossible for the space between the boat and the tube to become choked with charcoal, since the widened ends of the strip hold the boat away from the bottom of the tube, and allow a free circulation of oxygen round all sides of the boat, J.F. B. Double Measuring Pipette. W. Nagels. (Zeit. aizgew. Chem., 511 ~ 1909, 22, 1806.)-The tap controlling this double pipette is pierced with four openings, two of which communicate with the measuring chambers, and the others with the inlet and outlet tubes shown in the figure. Glass floats, which rise into the upper constricted portions of the pipettes, prevent the overflowing of the liquid. The apparatus is made by Strohlein and Co., Diisseldorf. C. A. M.512 THE ANALYST. Simple Fat Extraction Apparatus. L. T. Bowser. (J. Anzer. Chem. XOG., 1909, 31, 947-949.)-The apparatus described is of the kind in which a rriercury seal is employed instead of the usual cork for connecting the flask to the extraction cylinder ; the general arrangement of the apparatus is shown in the figure. A flat cork is used to fix the mercury cup to the neck of the flask. The extraction-tube used is shown at E, the tube employed for collecting the ether differing from it only in that there is no hole at the bottom. It is dented in on two sides sufficiently to allow the ether vapours to pass upwards. The filtering medium is cotton-wool, on which are placed sniall circles of filter-paper, the perforated plates being of aluminium, w. P. s.

ISSN:0003-2654    

DOI:10.1039/AN9093400510

出版商:RSC    

年代:1909

数据来源: RSC

摘要:

512 THE ANALYST. NEW BOOKS. THE VEGETABLE PROTEINS. By T. B. OSBORNE. 8vo. 125 pp. The present volume is another of the valuable series of mono- graphs on biochemistry edited by R. H. Plimmer and F. G. Hopkins (ANALYST, 1909, 343). The contents comprise : Historical Review ; Occurrence of Proteins in the different Parts of Plants, and their General Characteristics ; Isolation and Preparation of Seed Proteins ; Basic and Acid Properties of Proteins ; Solubility of Vegetable Proteins ; Precipitation of Vegetable Proteins ; Denaturing of Vegetable Proteins ; Physical Constants of Vegetable Proteins ; Products of Hydrolysis of Vegetable Proteins ; Classification of Vegetable Proteins ; Sonie Physiological Bela- tions of Vegetable Proteins to the Animal Organism and the Biological Relations of Seed Proteins to one another.There is also a very complete Bibliography and an Index. THE PERIODIC LAW. By A. E. GARRETT. International Scientific Series. Crown 8vo. 294 pp. Illustrated. London : Kegan Paul, Trench, Triibner and Co. Price 5s. The contents comprise : Introduction ; The Methods of Finding the Atomic Weights of the Elements ; Early Attempts at Classification ; De Chancourtois and Newlands ; MendelBeff and Lothar Meyer ; The Work of Carmelley ; Other Methods of Arranging the Elements ; Other Applications of the Periodic Law ; Formuls to express the Relationship between the Atomic Weights ; The Stom and the Periodic Law; Index. CHEIIISTRY (PART 11.) INOBGBNIC AND OXGANIC. Catechism Series. Small 8vo. 73 pp. The matter is arranged in catechism form, followed by an alphabetical index, London : Longmans, Green & Co. Price 3s. 6d. net. Edinburgh : E. and S. Livingstone. Price 1s. net. THE PRACTICAL MANAGEMENT OF SEWAGE-DISPOSAL WORKS. By W. C. EASDALE. Small 8vo. 56 pp. London : The Sanitary Publishing Go., Ltd. Price 2s. net. The contents consist of : Introduction ; Preliminary Processes ; Contact Beds and Filters ; Final Processes ; Tests and Records ; General Remarks ; Index.

ISSN:0003-2654    

DOI:10.1039/AN9093400512

出版商:RSC    

年代:1909

数据来源: RSC