摘要:

FEBRUARY, 1906, Vol. XXXI., No. 359. THE ANALYST. PROCEEDINGS OF THE SOCIETY OF PUBLIC ANALYSTS. NOTE ON THE REMOVAL OF ARSENIC FROM HYDROCHLORIC ACID FOR USE IN THE MARSH-BERZELIUS METHOD. BY ARTHUR R. LIXG, F.I.C., AND THEODORE RENDLE. (Read at the Neetiq, December 6, 1905.) IT is a well-known fact that hydrochloric acid sufficiently free from arsenic for use in the Marsh-Berzelius method cannot be purchased, nor is this surprising, seeing that the acid acts on the glass bottle in which it is stored, and gla+s usually contains arsenic. Even the purest hydrochloric acid obtainable in commerce has therefore to be submitted to some preliminary purification before it can be used for any method of determining arsenic. The Joint Committee of the Society of Chemical Industry and of the Society of Public Analysts recommended a method for the purification of hydrochloric acid which depends in principle on the fact first pointed out by Rohmer (Ber., 1901, xxxiv., 31), that the presence of hydrogen bromide expedites the volatilization of arsenious oxide from a solution when it is distilled in a current of hydrogen chloride and sulphur dioxide.The Joint Committee’s method consists in diluting the hydro- chloric acid to be purified with water until it has B specific gravity of 1.10, adding about 5 C.C. per litre of bromine, and decolorizing the yellow solution with an excess of sulphurous acid. The acid, after standing for at least twelve hours, is boiled or distilled. The whole of the arsenic is contained in the first portion of the acid (one- fifth of the whole) which passes over.One of us employed this method regularly until about two years ago, when it was discarded in favour of distillation with metallic copper (the Reinsch method). The reasons for rejecting the Joint Committee’s method were threefold. In the first place, it was found very difficult to employ the method successfully with commercial hydro- chloric acid. The Committee’s instructions are that acid purchased as ‘( pure ” is to be treated. I n the second place, the yield of arsenic-free acid seldom, in practice, exceeds three-fifths of that originally taken ; and, lastly, the method is a lengthy one. The Fteinsch method was carried out under conditions devised by Dr. L. T. Thorne, who very kindly gave us complete details of his wzodus operandi. I n our experience, Dr.Thorne’s method is superior to that of the Joint Committee, as it can be used for the purification of commercial hydrochloric acid. When, however, the acid contains much arsenic the method is extremely slow.38 THE ANALYST. The method of separation of arsenic from non-volatile substances by distillation in presence of hydrochloric acid was considerably simplified and rendered much more exact by Emil Fischer’s proposal (Ber., 1880, xiii., 1778) to add ferrous chloride as a reducing agent before distillation. When, however, the residue as well as the distillate has to be examined, the addition of iron is obviously undesirable. In view of this, various other reducing agents have from time to time been proposed, and C. Friedheim and P.Michaelis (Bey., 1895, xxviii., 1414) proposed methyl alcohol for this purpose. A few months ago H. Cantoni and J. Chautems (Arch. Sc. phys. nat. Geneve (4), xix., 364) stated that when a current of air is passed through a solution of arsenious oxide in hydrochloric acid to which methyl alcohol has been added at the ordinary temperature the arsenic is volatilized, probably in the form of the ester methyl arsenite. As soon as this work became known to us we made numerous attempts to purify arsenical hydrochloric acid by making use of the principle just stated, but without success. It was found impossible to remove arsenic by this means at the ordinary temperature. We need not enter further into a description of the numerous preliminary experi- ments we carried out before finally adopting our present process.Briefly, the process consists in digesting a mixture of constant-boiling hydrochloric acid and methyl alcohol under diminished pressure in a flask furnished with a reflux condenser for some hours in presence of bright electrolytic copper free from arsenic, and then dis- tilling the acid over similar copper. Digesting with methyl alcohol alone has been found to be capable of removing all but the last traces of arsenic, but the purification is rendered complete and the process considerably expedited by the conjoint use of metallic copper. I t is our practice, before commencing the digestion, to add a trace of metallic zinc, and our experience has shown this to be an advantage. The details of the process are as follows : To 1,500 C.C.of commercial hydrochloric acid, slightly above 1.1 specific gravity, about 40 C.C. of redistilled commercial wood-spirit are added. The mixture is con- tained in a Wurtz flask of 2 litres capacity. About 5 to 10 grams of arsenic-free granulated zinc are then added. The flask is connected with the reflux condenser by an ordinary cork in which is fixed a glass rod supporting a coil of electrolytic copper foil, having a surface of about 120 square inches. The side tube of the Wurtz flask having been plugged, the, condenser is connected with an exhaust-pump, and the boiling commenced. With acid containing from 3; to 1 grain per gallon, about three hours’ gentle digestion is sufficient, the copper being withdrawn and cleaned at least once during this period. During the digestion a black, tarry, fuming liquid distils over, and the greater part of this is caught in a vessel intermediate between the condenser and the pump. I t is also advisable to interpose a second somewhat larger vessel containing water to absorb any hydrogen chloride which passes off. This water should be changed as often as necessary.

ISSN:0003-2654    

DOI:10.1039/AN9063100037

出版商:RSC    

年代:1906

数据来源: RSC

摘要:

THE ANALYST. 39 A SIMPLE ARRANGEMENT OF LENSES FOR READING THE GRADUATIONS OF CHEMICAL AND ASSAY BALANCES. BY G. T. HOLLOWAY, F.I.C. (Shown at the .Meeting, December 6 , 1905.) THE usual telescopic or portable lens arrangements are, as shown in the figure, replaced by lenses cemented ou the rising glass-front of the balance. Plano-convex lenses cemented with seccotine on the inside of the glass are preferred, but bi-convex lenses cemented at the edges in two or three places to small discs of cork, or other soft material cemented on the glass, may be used, as shown in the case of the upper lens in the accompanying figure. A 3-inch lens for the pointer reading is a convenient size, but 8 2-inch lens is sufficient for reading the beam graduations. A slight movement of the head suffices to bring any part of the beam into the field. The focal length of the lenses is of little importance, but they must not be powerful'enough to produce distortion, or thick enough to prevent the rise and fall of the balance-front on which they are fixed. There is always sufficient space for any ordinary lens, and as the lenses are fixed inside, they remain clean and require no attention or adjustment. As the lenses are not required except when the rider is being used, they are out of the way while the balance-front is 'raised. This arrangement is simple and cheap, and absolutely effective in saving &iia to the eye, and may be applied with advantage even to a rough balance.

ISSN:0003-2654    

DOI:10.1039/AN9063100039

出版商:RSC    

年代:1906

数据来源: RSC

摘要:

40 THE ANALYST. THE FACING OF RICE. BY CECIL H. CRIBB, B.Sc. LOND., F.I.C., AND P. A. ELLIS RICHARDS, F.I.C. (Read at the Meeting, February 7, 1906.) IT has been a matter of more or less general knowledge for some years that rice is faced, i.e., polished, with the aid of some extraneous substances, but we are not aware of any reEerences to the subject beyond a note in the ANALYST (vol. ii., p. 152) on t L waxed rice,” a statement in the Bdzsh Food Journal (1900, p. 46) that rice is finished with the aid of oil, paraffin oil being sometimes employed, and a paper by Matthes and Muller (Zeit. o f l e d . Chenz., 1905), abstracted in the ANALYST (vol. xxx., p. 206). These authors mention the use of ‘‘ talc ” as a coating material for various cereals, including rice. I t was formerly the custom in some retail businesses, and may be so now, to polish the rice by shaking in a bag of sheepskin or other suitable material, the process being known as “trouncing.” With the advent of machinery this simple method is no doubt a thing of the past ; but most of the earlier recorded analyses plainly show that, whatever the process employed, it did not as a rule involve the addition of any appreciable amount of mineral matter.The following figures for the total ash of rice are given by the authors named : Boussingault ... ... ... ... ... ... _ . I ... Poggiale ... ... ... 0 . . ... ... ... ... Cooley’s “ Encyclopaedia ” ... ... ... ... ... Jago (‘‘ Chemistry of Wheat Flour,” p. 233) ,.. ... Wynter Blyth (“ Foods : Composition and Analysis,” p. 214) ... Leffmann and Beam (“Food Analysis,” p.101) ... ... ... Leach (“ Food Inspection and Analysis,” p. 213) : Unhulled ... ... ... ... ... _.. ... Unpolished ... ... ... ... ... ... ... Polished ... Fresenius ... ... ... ... ... ... ... ... Polson ... ... ... ... ... ... ... ... ... ... Bell (“ Analysis and Adulteration of Foods,” p. 86) ... ... ... ... ... ... ... ... ... Total Ash. 0.5 per cent. 0.52 ,, 0.9 9 , 0.32 ,, 0.5 9 , 0.28 ,, 0.28 ,, 0.45 ,, 0.3 to 0.6 per cent. 4.09 per cent. 1.15 ,, 0.46 ,, Hassall, in a complete analysis of the ash, gives the silica as 3-35 and Leach as 6.14 per cent, of the total ash. We have recently had occslsion to examine a number of samples submitted to us under the provisions of the Sale of Food and Drugs Acts, and the very high proportion of ash in some of the samples, together with the presence of a substantial amount of mineral matter insoluble in hydrochloric acid, plainly indicated that some inorganic substance foreign to rice was present.Table I. gives the total ash, together with the soluble ash and the ash insoluble in hydrochloric acid, in the samples referred to, and it will be seen at a glance that in every case but one the polished samples exhibit an increased total ash and a largely increased insoluble ash, as compared with the unpolished samples, thus clearly establishing the connection between the polishing and the excess of mineral matterTHE ANALYST. 41 Also it may be mentioned that the sophisticated samples can be at once distinguished by the appearance of the ash as obtained in a muffle furnace.Genuine rice yields a fused glassy mass, whilst the ash of the polished samples exhibits a powdery appear- ance, and frequently retains, in skeleton form, the shape of the original granules. Further, it will be noticed that the variations in the total ash are almost entirely due to the substances insoluble in acid, the soluble ash being not only fairly constant in amount, but also almost always under 0.5 per cent.-ie., within the limits of variation of the ash of natural unpolished rice. TABLE I. Samples of iTnTcnown Ow@ii. 1. 2. 3. 4. 5 . 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 26. 27. 28. * 25. Price per lb. - lgd. l*d. 3d. - - - - - - -- 2d. - - 2d. Id. 2d. Id. 2d. 2d. l i d . 3d. 2id. 14d.2d. 24d. 2d. - Finish. Total Ash. 0.29 0.31 0.32 0.32 0.32 0.32 0.33 0.37 0.38 0.42 0.57 0.52 0.64 0.70 0.80 0.83 0.83 0.85 0.85 1.00 1.02 1-07 1.07 1.50 1.60 1.92 2.00 2.22 Insoluble Ash. trace 0*;05 trace 0.01 0.01 0-035 0.03 0.02 0.02 0.18 0.25 0.30 0 *40 0.41 0.40 0.44 0.39 0.48 0.53 0.71 0.66 1.10 1.10 1.46 1.55 1.65 ,, Residual Ash. 0.29 0.31 0.32 0.315 0.32 0.31 0.32 0-335 0.35 0.40 0.55 0.34 0.39 0.40 , 0.40 0.42 0.43 0.41 0.46 0-52 0.49 0.36 0.41 0.40 0.50 0.46 0.45 0.57 On further examination it was found that by agitating the rice with water and pouring off the turbid liquid, after the grains had' settled to the bottom, and repeating the operation two or three times, the fine particles thus removed from the surface contained practically the whole of the insoluble ash, while the residual grains had the ash of genuine unpolished samples.42 THE ANALYST.TABLE 11. Insoluble Ash. No. 25 ... ... ... Patna ... ... ... No. 12 ... ... No. 26 ... ... ... ... 1.10 0.73 0.18 1.46 Ash of Powder removed by Levigation. 1-05 0.68 0.25 1.52 More detailed analyses of the mineral matter in the samples will be found in Table V. It appears that, while the ash of the unpolished rice contains only a trace of insoluble matter, and from 9 to 11 per cent. of magnesia (MgO) in a soluble form, in the polished rice the insoluble portion almost invariably forms at least 40 per cent. of the total ash, and consists mainly of magnesia and silica. Although the substancs used in the polishing process apparently adds com- paratively little to the amount of soluMe ash, nevertheless, the latter invariably contains an increased amount of magnesium, the result, no doubt, of the partial decomposition of the silicate by fusion with the alkaline salts of the soluble ash, as the following figures show : TABLE 111. Percentage of MgO in portion of Ash Soluble in HC1.Rice. Carolina, unpolished ... ... ... 11.3 per cent. Patna, polished ... ... .I. ... 23.5 ,, Java, polished (A) ... ... ... 20.2 ,, 8 9 ‘2 (B> ... ... ... 21.2 ,, ,, polished ... ... ... 24.5 ,, I t may be taken for granted, therefore, that a compound of magnesia, and silica is largely, though not universally employed in the polishing process. To get further information we have examined a number of samples of known origin and of every price and quality, very kindly supplied to us by some of the largest wholesale and retail houses in the trade, and the analyses of these are set forth in Table IV., The conclusions already arrived at are fully borne out by the foregoing figures, for with the exception of the samples described as ‘‘ oil polished,” all the polished samples contain excess of mineral matter, showing itself almost exclusively in the insoluble ash.The absolute identification of the foreign substance is difficult, if not impossible. The powder washed off from the outside of the grains, when examined under the microscope, appears as transparent angular particles of irregular outline, which exhibit no particular characteristics, although they have a general resemblance to mica and talc. p.43.THE ANALYST. 43 Rice. Carolina .. .-. ... ... ... ... 9 ) 9 , ,Y .I. ..i ... ... .I. . ... Patna : Foreign cleaned ... 9 9 9 9 ... 2, ' a . ,? ..* ... Broken, London milled 9 , 9 9 9 , '.' English cleaned ... Japan ... ... ... Siam, Dutch cleaned ... Bassein : German cleaned ... ... 9 , ?, .*. 9 9 ,? * * . ... 9 , ... 9 , Java : Natural cleaned ... Foreign cleaned ... Indigo treated . .. ... 1.. Edklish cikmed * ' . . . $ 9 9 9 )) $ 9 $ 2 9 9 ... ... ... Dutch cleaned ... ... ... $ 9 9 ) * a . Burma ... ... ... Rangoon : Rice with hull ... Rice de-hulled in the laboratory . . . Oil-dressed, in Holland * Broken, London milled Antwerp milled ... TABLE IV. Samples of Known Origin. Price. 6d. 44d. 4d. 4d. 3d. to 4d 24d. 24d. 24d. 24d. 3d. 3d. 3d. to4a 3a.- 2d. 2d. 2id. 4d. 2d. 2+d. 24d. 24d. 3d. 3d. 3d. 3d. 3d. 14d. - 2ga. - - - - - Finish. Dull PoliLhed 99 Polished Polished (contains damaged grains) Dull Polished Brown Very dull Slightly polished Dull Polished Total Ash. 0.22 0.29 0.68 0.86 0.71 1.07 1-14 0.90 0.80 0.87 0.92 1-08 0.22 0.40 0.77 1.10 0.33 0.78 0.82 1-26 0.7 1 0.74 0.99 1-14 0.40 0.51 0.54 0.73 0.99 0.30 2.62 1-32 0.30 0.52 1.15 Insoluble Ash. 0.01 0.02 0.44 0-41 0.30 0.70 0.73 0.50 0.42 0.47 0.56 0.78 0.001 0.03 0.35 0-60 0.015 0.34 0.44 0.90 0.31 0.43 0.71 0.73 0.07 0.01 0.25 0.35 0.49 trace 1.421- 0.131- 0.01 0.17 0.82 Residual Ash. 0.21 0.27 0.24 0.45 0.41 0.37 0.41 0.40 0.38 0.40 0.36 0.30 0.219 0.37 0.42 0-50 0.315 0.44 0.38 0.36 0.40 0.31 0.28 0.41 0.33" 0.50 0.29 0.38 0.50 - 1.20 1-19 0.29 0.37 0.35 * Probably polished by oil or some other process.+ Practically all silica.44 THE ANALYST, Even the wholesale dealers appear to have no certain knowledge of the modus operandi of the polishing process, which seems to be a carefully-guarded trade secret, and no doubt differs slightly in different countries as regards both the method and the nature of the added substances. Steatite, French chalk, powdered talc, and mica are amongst the substances hinted at. We were informed that two of the Java samples had been treated with indigo in order to improve the colour, but we have so far been unable to verify the statement. The following table shows the composition of these, together with that of the insoluble matter actually found in the samples examined by ourselves : TABLE V.Polished Rice. Carolina ... ... Patna ... ... Java ... ... ... A. Unknown origin B. 9 , 9 , * * * C . 9 , 9 9 . * . French chalk ... Talc ... ... ... Steatite ... ... ..- ... ... ... ... ... ... ... ... ... 1.. Percentage Composition of Silicious Matter. SiO,. 6 1 56 58 62 62 62 58 61 61 57 62 MgO . 22 22 24 22 25 25 28 20 29 30 33 Fe,O, + A1,03. present" 5.8 present" present" 7-01 9.00 4.02 3-6 3 to 4 8.i Assuming that one or other of these substances is used, the difficult question which always confronts the Public Analyst in such matters at once arises-Is this method of treating rice to be regarded as adulteration ? On the one hand, it must be admitted that it is absolutely unnecessary, inas- much as there are other modes of polishing which are not open to the same objection ; and, moreover, there is no reason whatever, apart from the whims of certain purchasers, why the grains should not be left with their natural surface, as, indeed, is the practice of some of the chief rice-eating nations, notably Japan.The proportion of foreign matter present in some of the samples is quite sufficient to constitute a fraud, inappreciable, perhaps, by the individual purchaser, but ample to give to one unscrupulous vendor an pnfair advantage over his more honest rivals. Further, on the medical aspect of the case, it has been suggested to us that there is the possibility that even very small quantities of an insoluble mineral substance may be injurious to health, not, of course, owing to m y chemical action, but merely by the mechanical irritation it might set up, and because of the possible formation of faecal concretions. * Quantity not estimated.THE ANALYST. 45 On the other side, it has been urged that the proportion of foreign matter is at the worst small and at the best negligible; that the amount of irritation likely to be set up must be extremely slight, and would be quite as likely to be beneficial as other- wise by the promotion of peristalsis. As the alleged adulterant is more expensive than the rice itself, there could be no possible temptation to the manufacturer to adopt the process for the purpose of fraud, and in addition to this, it might also be urged that the foreign matter generally is, and always might be, largely removed during cooking. We understand this is the custom of native cooks in India, by whom the rice is always soaked and washed before use. Whatever may be the opinion in regard to the legal aspect of the question, it is somewhat startling to reflect that an article of diet of such common and widespread use, hitherto accepted as one of the purest forms of vegetable food, should so frequently contain a substance of a foreign nature.

ISSN:0003-2654    

DOI:10.1039/AN9063100040

出版商:RSC    

年代:1906

数据来源: RSC

摘要:

THE ANALYST. 45 ABSTRACTS OF PAPERS PUBLISHED IN OTHER JOURNALS. FOODS AND DRUGS ANALYSIS. The “Aldehyde” Value of Milk. R. Steinegger. (Zeit. Unters. Nahr. Genussm., 1905, x., 659-671.)-The addition of formaldehyde to milk causes an increase in the acidity of the latter, apart from that due to the acidity of the formaldehyde solution itself. The acidity increases with the quantity of formalde- hyde added until it reaches a maximum with the addition of 1.8 per cent., or about 5 per cent. of the ordinary 40 per cent. formalin solution. The difference between the original acidity of the milk (expressed in Soxhlet-Henkel degrees) and the acidity of the same after the addition of 5 or 6 C.C. of formalin is termed by the author the ‘‘ aldehyde ” value of the sample. This value for normal milks varies between 5.8 and 8.5.For the milk from single cows the value remains practically constant. In the case of colostrum the value rises as high as 17.3, but decreases as the milk becomes normal. The increase is observed with boiled milk, showing that the phenomenon is not due to the action of an oxidizing ferment. As the aldehyde value varies with the amount of casein and other proteids in the milk, the increase of acidity is undoubtedly caused by the chemical reaction between the formaldehyde and these proteids. The determination of the aldehyde value is ‘proposed as a means of detecting the presence of added water in milk, as this form of adulteration decreases the percentage of proteids in the milk, and, consequently, the aldehyde value.Abstraction of fat does not influence the value. w. P. 8. The Quantity of Water in .Canadian ‘‘ Domestic ” Butter. A. McGill. (Canadian Inland Revenue Department, Bull. 107, l-l2.)-By domestic butter is meant butter as found in the retail market, and intended for home consumption.46 THE ANALYST. Of 180 samples of this class of butter examined, only 1 contained an amount of water in excess of 16 per cent. Eight of the samples contained from 14 to 16 per cent., and in 144 samples the water was below 10 per cent. One of the samples con- tained borate preservative. w. P. s. Detection of Phytosterol in Lard in the Presence of Small Quantities of Paraffin, and the Determination of Small Amounts of Paraffin in Lard. E. Polenske. (Arbeit. Kaiserl. Gesmdheitsamte, 1905, vol.22, pp. 576-583.)-The sensitiveness of the phytosterol acetate test (ANALYST, 1902, xxvii., 94) is sometimes vitiated by the presence of traces of paraffin in the fat under examination. The paraffin becomes more and more concentrated as the acetate is recrystallized, until at last the melting-point obtained falls to that of the paraffin-that is, about 53" c. By taking advantage of the slight solubility of phytosterol in petroleum spirit, it is possible to remove the paraffin. The unsaponifiable residue obtained from 100 grams of fat in the usual manner is placed in a cylinder of about 8-C.C. capacity, and treated with 1 C.C. of petroleum spirit (boiling-point below 50° C.). After stirring up the residue with a glass rod, the cylinder is stoppered and placed aside for about twenty minutes.The whole is then poured on to a small pellet of cotton- wool placed in the stem of a funnel, and the residue and filter washed five times with petroIeum spirit, using 0.5 C.C. of the latter each time. The residue of phytos- terol is finally dissolved off the cotton-wool with a little ether, evaporated, and acetylated. Besides removing the paraffin, the above process concentrates the phytosterol in the residue, as cholesterol is considerably more soluble in petroleum spirit. For the determination of small quantities of parafin in fats the crude, un- saponifiable residue, from 100 grams of the fat is heated in a strong glass tube with 5 C.C. of concentrated sulphuric acid to a temperature of 105" C. for one hour (a mixture of 40 parts of glycerol and 60 parts of water boils at 104' to 105" C.).After cooling, the contents of the tube are shaken out three times with petroleum spirit, using 10 C.C. each time, and continuing the shaking for one minute. The extracts are united, washed a few times with a little water, the petroleum spirit is evaporated, and the residue weighed after being dried at 100" C. Should only traces of paraffin be present it is advisable to subject the residue to a second treatment with sulphuric acid. w. P. s. The Determination of Tannin in Wine. L. Kramszky. (&it. anal. Chenz., 1905, vol. 44, pp. 756-765.)-1t is shown that the method of Neubauer and Lowenthal gives not only the amount of tannin, but the sum of the tannin and colouring matters. Barth's colorimetric method has the same drawback, and is also not generally applicable.An amrnoniacal solution of zinc sulphate (or of nickel sulphate) yields quanfitafive results with solutions of pure tannin, which agree well with those obtained by the Neubauer-Lowenthal method, and at the same time does not pre- cipitate the colouring matter of wine. The reagent is prepared by dissolving about 25 grams of pure zinc sulphate in water, a2ding ammonia until the precipitate first formed redissolves, then an additional 300 C.C. of ammonia, and makingTHE ANALYST. 47 up the liquid to a litre. For the determination of the tannin 50 C.C. of a red wine or 100 C.C. of a white wine are rendered alkaline with ammonium hydroxide and heated, no notice being taken of any precipitate that may be formed.The liquid is then treated with 20 C.C. of the reagent and stirred until the zinc tannate separates, after which 300 C.C. of hot water are added, and the whole allowed to stand, The precipitate is repeatedly washed by decantation with hot, slightly ammoniacal water, and finally brought on to the filter (preferably a Gooch’s crucible containing asbestos), dried at 100” to 130” C., and weighed. It is then oxidized by means of a few drops of strong nitric acid, and ignited after evapora- tion of the acid. The diiference between the two weights gives the amount of tannin. The author gives a series of results thus obtained with solutions of pure tannin and with wines, including some to which had been added known quantities of tannin. Comparative determinations were made by the method of Neubauer and Lowenthal, the difference between the results in the case of red wines ranging from 0.02 to 0.08 gram.According to Neubauer, a deduction of 0.03 to 0.04 gram must be made for the colouring matters in dark-red wines when the permanganate method is used. As regards the question of gallic acid, the author considers tbat it is probably only present in traces in sound red wines, but that unsound wines may possibly contain considerably more. Experiments to determine the influence of gallic acid on the determination of the tannin by the zinc method have given the following results : (1) Gallic acid is not precipitated by ammoniacal zinc sulphate solution. (2) Wines to which a known quantity of gallic acid has been added give, on analysis by the method of Neubauer and Lowenthal, 0, higher value than corresponds to the sum of the tannin, colouring matter, and added gallic acid.(3) I n certain cases the presence of gallic acid prevents the precipitation of part of the tannin by ammoniaoal zinc sulphate solution, C. A. M. A Honey Substitute. G. Reiss. ( Arbeit. Kaiserl. Geszmdheitsamte, 1905, vol. 22, pp. 666-668.)-Under the name “Fruktin ” an article has recently been placed on sale as a honey substitute. I t consists of cane-sugar and a small quantity of tartaric acid, a little caramel being also present. According to the directions given with each packet of the article, 500 grams of the latter are heated to boiling with 150 grams of water, and the mixture then kept in a warm place for half an hour in o’rder to obtain a honey-like product. The author has himself prepared artificial honey by treating “Fruktin” in this way, and from it obtained the following analytical data : Specific gravity of a solution of 1 part in 2 parts of water, 1.11 ; invert sugar, 33.39 per cent.; cane-sugar, 41.63 per cent. ; ash, 0.024 per cent. ; polarization of a 10 per cent. solution observed in a 200-mm. tube, +4”35’; after inversion, -2’44’. The proportion of cane-sugar is, as will be seen from the above figures, about four times greater than is found in natural honey, whilst the percentage of ash is much lower. At the same time, a mixture of 1 part of ‘‘ Fruktin ” honey with 3 parts of pure honey would contain about 10 per cent. of cane-sugar, and such mixtures would only differ from natural honey in their low percentage of ash and in the presence of tartaric acid in them.w. P. s.48 THE ANALYST. Valuation of Saffron. A. Jonscher. (Zeit. byentl. Chem., 1905, xi., 444-447.)-The stigma of saffron possesses a considerably higher aromatic or spice value than the pistil, as it contains more ethereal oil and crocin. The stigma is also superior to the pistil as regards colouring power. An approximate method for determining the value of a sample of saffron consists in boiling 0.1 gram of the air- dried sample with 10 C.C. of 50 per cent. alcohol, at once cooling the mixture, and then allowing it to stand for one hour. The solution is then filtered, and 5 C.C. of the filtrate diluted to 100 C.C. with water. The coloration is then compared with that produced by a good specimen of saffron under similar treatment.W. P. S. Determination of Vanillin. J. Hanus. (Zeit. Unters. Nahr. Genussm., 1905, vol. 10, pp. 585-591.)-Vanillin is quantitatively precipitated from its aqueous solution by m-nitrobenzhydrazide. The presence of the ordinary adulterants of vanillin, such as acetanilide, benzoic acid, salicylic acid, and sugars, is without influence on the precipitation. For the determination of vanillin in vanilla the following method, based on the above-mentioned fact, is described : About 3 grams of the vanilla, in small pieces, are extracted for three hours with ether. The ethereal solution is evaporated at a temperature of 60" C., the residue is dissolved in a little ether and filtered into a small flask, the filter being washed with ether.The ether is again evaporated, the residue heated with 50 C.C. of water for thirty minutes on the water-bath, and the emulsion so obtained precipitated with a solution of 0.2 gram of m nitrobenzhydrazide in 10 C.C. of hot water. The flask and its contents are placed on the water-bath for thirty minutes, and then set aside for twenty-four hours. The mixture is now shaken out three times vith petroleum spirit to remove fat, the extracts, after separation, being filtered in a Gooch's crucible, and the precipitate itself then rinsed on to the filter, washed first with water, then with petroleum spirit, dried at a temperature of 100" to 105" C., and weighed. The weight of the precipitate mdtiplied by the factor 0.4829 gives the amount of vanillin present.The method is also applicable to the determination of vanillin in alcoholic extracts, but the alcohol must first be removed by evaporation at a low temperature. w. P. s. The Determination of Iodine in Iodated Thymols. H. Cormimboeuf. (Ann. de Chim. anaZ., 1905, vol. 10, pp. 453-454.)-Iodated thymols (aristols) contain from 15 to 45 per cent. of iodine, according to the mode of manufacture. Most of the commercial products are chlor-iodo- rather than di-iodo thymols, and there is a risk of the whole of the halogen present being determined as iodine if the ordinary methods of Carius, etc., be used. The following method is recommended as giving only the iodine and requiring but little material : 0.5 gram of the sample is thoroughly mixed in a mortar with 3 grams of dry sodium carbonate, and the mixture heated gradually in a platinum or nickel crucible until nearly complete combustion of the organic matter, after which it is fused.The mass, when cold, is treated with hot water, the solution filtered from any particles of unburnt carbon, the filtrate mixed with half its volume of ammonium hydroxide, and the iodine precipitatedTHE ANALYST. 49 with silver nitrate in the usual way. precipitate of silver chloride being obtained in the presence of chlorine. The filtrate is acidified with nitric acid, a C. A. M. Oil of False Savin. ' J. C. Umney and C. T. Bennett. (Pharm. Jozcrn., 1905, vol. 75, pp. 827-829.)-The oil of savin as distilled in this country, in Germany, and in the South of France, varies considerably.This is probably due to the fact that in the latter country the oil is distilled from false savin, Juniperus Phmzicia (the common Mediterranean Apecies), whilst in the former the distillers use Juniperus sabina. The following results were obtained with three specimens of the oil : Specific gravity Optical rotation Esters ... ... Total sabinol ... Solubility in 90 alcohol .,. Portion distilling : Below 155" C. ,, 165" C. ,, 175" c. 7 , 180" c. ,, 200" c. ,, 220" c. ,) 230" C. ... ... ... ... ... ... ... ... per cent. ... ... ... .., ... ... ... ... ... ... ... ... ... ... .*. ... English. From J. Sabinn. 0.909 + 68" 47.6 per cent. 52-1 ,, 1 in 1 nil. nil. 14 per cent. 23 9 9 48 7, 62 9 , 80 9 , German. Fro111 J . Subina.0.920 + 42" 36.5 per cent. 48.2 ,) 1 in 1 nil. nil, nil. 4 per cent. 29 9 7 49 9 7 60 $ 9 French. From J. Phceniciu. 0.892 + 4O30' 9.3 per cent. 17.1 ,) 1 in 5 The oil from J. Phcenicia contains over 75 per cent. of pinene, the hydrochloride of which melts at 125O C., and the nitrosochloride, after one recrystallization, at 1 0 7 O C. A sesquiterpene, cadenine, is also present in the oil. w. P. s. Examination and Assay of Aloes. L. v. Itallie. (Pharnz. Weekblad, xlii-, 553; through Pharm. Journ., 1905, vol. 75, p. 554.)-The author considers that Tschirch's method (ANALYST, 1905, xxx., 249) is open to objection, and modifies it as follows : Five grams of the powdered aloes are warmed with 5 C.C. of methyl alcohol until a homogeneous liquid is obtained; 30 C.C.of chloroform are then added, the mixture is shaken for five minutes, and allowed to stand until clear. The solution is decanted, evaporated to dryness, and the residue again dissolved in methyl alcohol and precipitated. By the use of this method Cape aloes mere found to contain from 18 to 43 per cent. of resin, and Curacao aloes from 11 to 21 per cent. Objection is also raised to Tschirsh's pro- posed colorimetric determination of aloin by Schouteten's reaction (green fluorescence with borax solution) on the ground that it is far too subjective, the author finding 100 per cent. of aloin in a sample of aloes, Determination of aloin by precipitation, as tri-bromo-aloin, succeeded with pure aloin, but indicated 71 per cent. of aloin in This treatment is repeated a third time.50 THE ANALYST.Cape aloes and 72 per cent. in Curacao, which results the author considers to be much too high. w. P. s. Analysis of Powdered Extract of Nux Vomica. W. H. Lenton. (Phar??~. Journ., 1905, vol. 75, p. 864.)-The following process is particularly applicable to the analysis of the powdered extract of nux vomica, and is similar to Bird’s method (Pharm. Jozcrn., xi., 4, 574), dilute alcohol being used as a solvent for the powder, and a mixture of ether and chloroform for the actual extraction. Ten C.C. each of ether and chloroform are placed in a dry separating funnel, 2 grams of the powder are introduced, then 5 C.C. of 90 per cent. alcohol and 3 C.C. of concentrated solution of ammonia, are added, and, finally, 5 C.C. of water. The whole is well shaken for about one minute, allowed to settle, and the ether-chloroform layer drawn off into another separating funnel, where it is shaken with 5 C.C. of 10 per cent. ammonium carbonate solution. After shaking the ether-chloroform once more with ammonium carbonate solution, the former is drawn off and placed aside. The alkaline mother- liquor is twice again shaken out with 20 C.C. of the ether-chloroform mixture, and the extract washed with the ammonium carbonate used for the first portion drawn off. The mixed ether-chloroform solutions are then treated as usual for the determination of strychnine. w. P. s.

ISSN:0003-2654    

DOI:10.1039/AN9063100045

出版商:RSC    

年代:1906

数据来源: RSC

摘要:

50 THE ANALYST. ORGANIC ANALYSIS. Studies on Formaldehyde in Aqueous Solution. F. Auerbaeh. (Arbeit. Kaiser2. Gesundheitsamte, 1905, vol. 22, pp. 1-46.)-The formaldehyde solutions employed in the experiments described were prepared by subliming tri-oxymethylene in an atmosphere of nitrogen, and collecting the vapours in water. For the deter- mination of formaldehyde the sulphite method of Lumihre and Seyewetz (ANALYST, 1904, xxix., 288) was found to be very useful, but for small quantities the iodine method was preferred. The results of determinations of the molecular weights of solutions containing varying amounts of formaldehyde lead the author to conclude that formaldehyde exists in aqueous solutions for the greater part in a hydrated or polymerized form. As the temperature is increased the simple molecule predominates.On distilling formaldehyde solutions of any strength whatsoever the distillate is always poorer and the residue richer in formaldehyde than the original solution. This fact should be taken into consideration in the detection and determination of formalde- hyde. I t is further shown that the boiling-point at normal pressure of formaldehyde solutions falls from 100" to 99" C. as the concentration increases. w. P. s. Distinction between Phenol and Cresols. C. Arnold and G. Werner. (Apoth. Zeit., xx., 925 ; through Phamz. Jouurm., 1905, vol. 75, p. 837.)-The following reactions are suitable for the identification of phenol and cresols : Phenol.-To 10 C.C. of the solution to be tested are added 10 C.C. each of potassium hydroxide solution and alcohol and 1 drop of aniline.After shaking the mixture, 5 drops of hydrogen peroxide and 10 drops of sodium hypochlorite are addedTHE ANALYST. 51 and the whole again shaken, Phenol gives a transient dirty red coloration, changing to yellow ; o-, m-, and tricresol, a violet, changing at once to green; p. cresol, a violet, which at once disappears. o-CresoL-With ferric chloride o. cresol gives a blue colour, rapidly changing to green ; phenol, m. cresol, and tricresol, a violet ; p. cresol, a blue colour. m-CresoL-On warming with a little phthalic acid and 5 drops of sulphuric acid m-cresol gives a cherry-red, phenol and tricresol a dark red, 0. cresol a cherry-red, p-cresol an orange colour. When diluted with water and rendered alkaline with sodium hydroxide phenol gives a magenta, o-cresol and tricresol a violet-red, m-cresol a bluish violet, and cresol a yellowish colour.CresoL-A dilute ammoniacal solution of cresol when boiled and treated with bromine water gives no coloration. Phenol and o-cresol treated in this way give a blue colour ; m-cresol and tricresol a bluish-green. If a trace of potassium nitrate be added to a solution of a little of the substance in sulphuric acid, a dark-red colour is obtained in the case of cresol, all the others giving an emerald-green coloration. When diluted with water and treated with an excess of ammonia, cresol gives a yellow colour, all the others a green. W. p. s. On the Inflammability of Celluloid Articles (according to experiments made by Fr.Gervais, director of the Laboratory of the Ministry of Finance, St. Peters- burg.) J. Bronn. (Zeeits. angezu. Chenz., 1905, xviii., 1976.)-It is shown that when heated to 100” C. (for instance, by contact with a steam-heater) articles made of celluloid decompose exothermically. Although the quantity of heat developed is not sufficient to set the celluloid itself on fire, it will cause the paper used for packing to smoulder, a slight draught of air being then sufficient to cause the whole mass to ignite. The temperature of ignition of celluloid appears to be fairly high, ranging from 355’ to 457’ C. in the case of four articles examined, that of pyroxylin being only 130’ C. White celluloid (imitation ivory) is more difficult to ignite than the other kinds, Celluloid articles may now only be sent to Russia when packed in wooden or metal cases.A. G. L. The Detection of “Blown” Fatty Oils in Mixtures with Mineral Oil. J. Marcusson. (Chem. Rev. Fett- ZL. Hnrx. Ind., 1905, xii., 290-293.)--“ Blown ” rape and cotton-seed oils are stated to be the two preparations of this kind most used in lubricating mixtures. Their presence cannot be detected by determination of the iodine value or molecular equivalent of the fatty acids. ‘‘ Blown ” cotton-seed oil does not give Halphen’s or Milliau’s reactions, though it gives the brown coloration with nitric acid. The latter reaction, however, is also given by “ blown ” rape oil. The author relies upon the following tests to distinguish between the two (( blown ” oils: (1) The odour of the mixture and of the fatty acids, recalling that of the unblown oils.(2) The consistency of the fatty acids-oily in the case of ‘‘ blown ” rape oil, semi-solid in that of ‘‘ blown ” cotton-seed oil. (3) The behaviour of the respective lead salts towards ether. Thus the amounts of fatty acids from the lead salts insoluble in ether ranged from 1.2 to 20.6 per cent. in the case of five ‘(blown ” rape oils, and 32.9 to 45.8 in the case of tws cotton-seed oils. The difference was52 THE ANALYST. more marked when the solubility of these Eatty acids in petroleum spirit was com- pared, the rape oils yielding 0 to 8-7 per cent. and the cotton-seed oils 23.3 to 32.5 per cent. The fatty acids from the insoluble salts of the (‘ blown ” cotton-seed oil’ melted at 5 4 O to 56” C., whilst those of the (( blown ” rape oil were oily or semi- solid.The following table gives results thus obtained, the amounts being calculated on the quantity of oil used in the preparation of the lead salts : Kind of Oil. Commercial (‘ blown ” rape oil ... Ditto ... ... ... ... Rape oil (( blown ” in laboratory.. . Commercial (( blown ” cotton-seed oil .. ... ... .. ... Cotton-seed oil blowu ” in labora2- tory ... ... ... ... On the Determination of Fatty Acids separated from Lead Salts insoluble in Ether. Total Fatty Acids. Per Cent. 1.2 14.5 20.6 32.9 45.8 Fatty Acids soluble in Petroleum Spirit. Per Cent. 1.2 5.7 8.7 23.3 32.5 Fatt Acids insoYuble in Petroleum Spirit. Per Cent. 0.0 8.8 11.9 9.6 13.3 C. A. M. Sulphur in Liquid Fuels (Petroleum, Oil, etc.).J. Matwin. (Zeits. angew. Chem., 1905, xviii., 1766.)-The author recom- mends a modification of Drehschmidt’s method in place of that of Goetzl (ANALYST, 1905, xxx., 376) for the determination of sulphur in liquid fuels, as much larger quantities (50 to 100 grams) may be used : The fuel is burnt in a small lamp pro- vided with a, wick, the products of combustion being led through a 5 per cent. solution of potassium hydroxide contained in three wash-bottles. The difference in weight of the lamp before and after the experiment gives the quantity of fuel burnt. No test analyses are given. A. G. L. Determination of Sulphur in Petroleum and Bituminous Minerals. F. C. Garrett and E. L. Lomax. (Journ. SOC. Chem. Ind., 1905, xxiv., 1212.)- A convenient quantity (0.7 to 1.5 gram) of the substance is intimately mixed in A small crucible with 3 or 4 grams of a mixture of 4 parts of pure lime with 1 of anhydrous sodium carbonate, and the crucible completely filled with this mixture.A larger platinum crucible is placed over the small one (mouth downward), the whole inverted, and the space between the two crucibles filled with the lime-soda mixture. The apparatus is then placed in a muffle furnace heated to bright redness, the mouth of the crucible being covered with a thick pad of asbestos board, which prevents distillation from the inner crucible before the mixture in the outer crucible is heated, due to radiation from the roof of the muffle, and the pad may be removed as soon as a flame appears. The roasting should be continued for two hours, after which the mixture is brought into water, any sulphide oxidized by bromine, andTHE ANALYST.53 the solution acidified, filtered, and precipitated by barium chloride in the usual way, the solution being allowed to stand on the water-bath for twenty-four hours before filtration, if the amount of sulphur is small. (Cf. ANALYST, 1905, xxx., 418.) W. H. S. Estimation of Tannin as Strychnine Tannate. S. R. Trotman and J. E. Hackford. (Joum. $06. Chem. Ind., 1905, xxiv., 1096.)-The present absorp- tion methods of determination are very unsatisfactory, even when the hide powder is replaced by Collin, and the authors have investigated a large number of bodies with the object of obtaining a compound of tannin which could be readily precipi- tated and weighed.Metallic salts proved useless, precipitation being incomplete, and after experimenting with many organic bases, including phenylhydrazine and various primary and secondary amines, the alkaloids were tried, and strychnine, one molecule of which combines with one molecule of tannin, finally adopted, as it does not precipitate gallic acid, and its tannate is highly insoluble in water. Sufficient material is4extracted with alcohol in a Soxhlet extractor to yield about 0.5 gram tannin, the solution evaporated to 50 c.c , transferred to a 100 C.C. flask, and made up to the mark with water, thus precipitating any resins and similar bodies. These are filtered off through a dry Gooch crucible, and the tannin estimated in the filtrate, 25 C.C. of which are placed in a 250 C.C.flask, diluted with water, the cooled strych- nine solution (prepared by dissolving 0.25 gram strychnine in 50 C.C. alcohol, and mixing with an equal volume of water) added, and the solution made up to 250 C.C. This method of treatment is essential, as otherwise the precipitate is difficult to filter. The contents of the flask are now filtered through a weighed Gooch crucible of platinum or porcelain, having a diameter a t the bottom of 1 to 2 inches, with a thin mat of asbestos over the bottom. After filtration the tannate is partly air- dried, and the dehydration completed in a vacuum oven heated to about 60". The soluble non-tannins are determined by evaporating 25 or 50 C.C. of the filtrate from the resinous matter. The amount of tannin found by the method is invariably less than that obtained by the use of hide powder or Collin.W. H. S. The Detection of Biliary Pigments in Urine. L. Grimbert. (Jouyfi. P h a ~ n . Chim., 1905, xxii., 487-492,)-The following method combines the principles of the methods of Hammarsten and Salkowski, but it is claimed that it is more simple than either: Ten C.C. of the urine are shaken with 5 C.C. of a 10 per cent. solution of barium chloride, and the mixture subjected to centrifugal force. The precipitate, consisting of the sulphate, phosphate, and bilirubinate of barium, is mixed with 4 C.C. of 90 per cent. alcohol containing 5 per cent. of hydrochloric acid, and heated for about a minute on the water-bath, after which the tube is allowed to stand. If the supernatant liquid over the deposit is bluish green or dark green the presence of biliary pigments is indicated, whilst in their absence the liquid is colourless.If there is a slight brownish tint the hydrochloric acid may have been insufficient to oxidize the barium bilirubinate, and in that case, and that case only, 2 drops of hydrogen peroxide (10 vol. solution) are added and the tube again heated on the water-bath, after which the green colour will appear, If the brown tint continues54 THE ANALYST. after the addition of the hydrogen peroxide the presence of certain altered products of biliary pigments is indicated. These are only met with in urines that have been allowed to stand for some time. In certain pathological urines the separation of the barium bilirubinate is promoted by the addition of a few drops of a 10 per cent.solution of sodium sulphate. C. A. M. Estimation of Naphthalene in Coal Gas. C. J. D. Gair. (Jourfi. SOL Chem Ind., 1905, xxiv., 1279.)-Three methods are described, the first a slight modification of Colman and Smith's, in which a measured volume of gas is passed through three Woulff's bottles, each containing exactly 500 C.C. of $G picric acid, the contents of the bottles mixed together in a 20-ounce flask, and heated on the water- bath at 60' C. until the precipitated naphthalene and naphthalene picrate have entirely dissolved, the flask being closed with a cork through which a glass tube dips into a beaker containing a small quantity of picric acid from the Wodff's bottles. This is afterwards returned to the flask and its contents cooled, when naphthalene picrate crystallizes out, is dried in vacuo or in a warm room.and weighed, whence the naphthalene may be calculated; or an aliquot part of the clear residual picric acid may be titrated with Tn sodium hydroxide, using lacmoid as indicator, showing the amount of picric acid taken up by the napthalene. 7 % ~ method, though devised for pure coal gas, is applicable to impure gas if the ammonia be first removed by passing the gas through oxalic acid before entering the picric acid solution, The second method, due to Somerville, consists in passing a known quantity of the gas through three glass tubes, 7 inches long and 1 inch wide, fitted UP 8s Woulffs bottles, and each containing 35 C.C. of 70 per cent. alcohol. The alcoholic solutions are then mixed in a flask, oxalic acid added if necessary, until the ammonia is neutralized, as shown by litmus-paper, and filtered, the filter-paper being thoroughly washed with dilute alcohol. About 500 C.C. of concentrated picric acid are then added, the liquid agitated, and allowed to stand for half an hour, when all the naphthalene picrate will have separated, and may be filtered, slowly dried, and weighed. A third method, devised by the author, depends on the solubility of naphthalene in acetic acid. A known volume of gas, usually not exceeding 3 to 6 cubic feet, is passed through 350 C.C. of acetic acid (specific gravity 1.044), contained in two Woulff's bottles, a small Woulff's bottle with 150 C.C. of picric acid being placed after the acetic acid to catch any unabsorbed naphthalene. The contents of all three bottles are mixed in a flask, and 500 C.C. of concentrated picric acid solution added, when the naphthalene picrate separates out at once in large flocculent masses, which are easily filtered off, dried, and weighed. W. H. S.

ISSN:0003-2654    

DOI:10.1039/AN9063100050

出版商:RSC    

年代:1906

数据来源: RSC

摘要:

54 THE ANALYST. INORGANIC ANALYSIS. The Determination of Bismuth, and its Separation from Copper, Cadmium, Mercury, and Silver. A. Staehler and W. Scharfenberg. (Berichte, 1905, xxxviii., 3862-3869.)-The method described is based upon the quantitative precipitation of bismuth by sodium phosphate, even in the presenceTHE ANALYST. 55 of hydrochloric acid. From 10 to 20 C.C. of the solution of the bismuth salt (0.1 to 0.2 gram of bismuth) are diluted to 300 or 400 c.c., and heated to boiling, any precipitate of basic salt being redissolved by the addition of the smallest possible quantity of nitric acid. The boiling liquid is treated with a boiling 10 per cent. solution of trisodium phosphate, the quantity required depending upon the amount of free acid present. I n the presence of much hydrochloric acid a larger addition of sodium phosphate is necessary.If the solution has become alkaline, it must again be rendered acid by means of a little nitric acid. After boiling for some time the precipitate is allowed to subside, the supernatant liquid tested with sodium phos- phate, and if the precipitation be complete, the precipitate is collected while hot in a Gooch's crucible, washed with hot 1 per cent. nitric acid containing a trace of ammonium nitrate, dried at 120' C., ignited for five or ten minutes over a Bunsen- burner, and weighed as BiPO,. The tabular results quoted agree within fractions of a mgm. with the theoretical amounts. Separation of Bismuth and Copper.-The bismuth is precipitated as above described, whilst the copper is precipitated from the filtrate by mcans of hydrogen sulphide, and weighed as cuprous sulphide (Cu 3S).Electrolytic determination is unsatisfactory in the presence of hydrochloric acid. Separation of Bismuth and Cudmiurn.-After separation of the bismuth as phosphate, the cadmium can be determined by electrolysis of the ammoniacal filtrate after the addition of potassium cyanide, provided hydrochloric acid be absent. In the presence of hydrochloric acid it is best to precipitate the cadmium as sulphide, which is then dissolved in'dilute nitric acid, and the solution electrolyzed after the addition of potassium hydroxide and potassium cyanide. Separation of Bismuth and Mercwy.-The filtrate from the bismuth phosphate is treated with a large amount of hydrochloric acid, and then with ammonia in excess, any precipitate formed being redissolved in hydrochloric acid, and the solution again rendered alkaline with ammonia.The liquid is next heated to the boiling-point, and immediately treated with hydrogen sulphide. After five to ten minutes the mercury sulphide separates out uncontaminated with free sulphur. I t is collected on a Gooch's filter, washed with hot water, alcohol, and ether, dried at 105" C., and weighed. Separation of Bismuth and Silver.-The bismuth can obviously only be separated in the absence of hydrochloric acid. The silver in the filtrate from the phosphate can be determined by the usual methods. Separation of Lead a d Bismuth.-It is suggested that a method of separation may be based on the precipitation of the two metals as phosphates, and the removal of the lead by boiling the precipitate with nitric acid (1 per cent.).Lead is quantitatively precipitated from a neutral solution by means of sodium phosphate ; but the precipitate consists of at least three different phosphates, which are con- verted, however, by long-continued boiling into the tertiary phosphate. C. A. M. On the Precipitation of Metallic Gold. P. E. Jameson. (Jozmz. Amer. Chem. SOL, 1905, xxvii., 1444.)-By the following method metallic gold may be56 THE ANALYST. precipitated in one or two minutes in a form resembling silver chloride, A stick of potassium nitrite weighing about 5 grams is placed in a solution of 1 gram of gold chloride in 30 C.C. of water, and 5 C.C. of concentrated sulphuric acid are at once added. As soon as the brisk reaction which takes place is over, another piece of potassium nitrite of the same size a5 the first is added, and the solution stirred until the reaction is over.The gold will then be found at the bottom of the clear liquid in the form of dark brown nodules, which, after drying, are more yellow than ignited cadmium oxide. A. G. L. Estimation of Platinum. Nordenskjold. (Chem. Zed. Rep., 1905, xxix., 293.) --Platinum is usually estimated as the metal by precipitating with sodium formate or with zinc. The former method can be carried out by treating the platinum solution with 2 grams sodium formate and a little ammonium acetate, diluting to 200 c.c., warming until the evolution of carbon dioxide slackens, and then heating €or twelve hours.The platinum is apt to pass through the filter-paper, but this can be prevented by adding a little nitric acid. The second method gives a granular precipitate of platinum. Magnesium is preferable to zinc. About 17 cm. of magnesium ribbon should be used per gram of platinum, and dilute solution used. Excess of magnesium is removed by hydrochloric acid ; any magnesium oxychloride is at the same time dissolved out. The two methods give concordant results. For iridium, ruthenium, and rhodium a slight modification is necessary, as these metals are sensibly attacked by acids in the precipitated form; only sufficient excess of magnesium to form oxychloride is used, the residue is heated, whereby the metals mentioned are rendered insoluble in acids, and the oxy chloride of magnesium dissolved out with acid.To estimate platinum in a mixture of this group, the heated metal powder 3s digested with aqua regia, when platinum (and palladium) go into solution. E. K. H, Note on an Antimonial Pigment for Enamels. P. Rasenack. (Arbeit. Kaiserl. Gesundheitsamte, 1905, vol. 22, pp. 653, 654.)-The author finds that a substance sold under the name of '' Leukonin " consists almost entirely of sodium metantimoniate, and that it is soluble to a considerable extent in water and in solutions of sodium chloride, sodium carbonate, tartaric acid, citric acid, etc., antimony in every case going into solution. The author suggests that enamels made with this substance may yield antimony to weak acid liquids. w. P. s. The Use of Potassium Periodate in the Detection of Manganese, Cobalt, and Zinc.S. R. Benedict. (Amer. Chem. Journ., 1905, vol. 34, pp. 581-585.) -On adding a solution of potassium periodate to a solution of a manganous salt a deep-red precipitate (or coloration with very dilute solutions) is immediately pro- duced. This precipitate is soluble in hydrochloric acid, and is converted by sodium peroxide into a black hydrated manganese dioxide. Tv solution of the potassium salt is capable of detecting 1 part of manganous chloride in 10,000, the test being more sensitive in %t warm ammoniacal solution than in a neutral warm As a reagent,THE ANALYST. 57 solution. Solutions of pure zinc salts yield a white periodate, but the presence of ammonium chloride and ammonium hydroxide prevent the formation of this, unless there is a very large amount of zinc.On boiling the filtrate from the precipitated manganese the zinc is precipitated. Conversely, a solution of manganese chloride may be used for the detection of periodate in the presence of iodate, iodide, etc. Iodates give no coloration with manganese in the presence of ammonium chloride and hydroxide. Solutions of pure nickel salts react with potassium periodate to give a light- green precipitate, which becomes slightly grey on boiling, whilst cobalt salts yield a dark-brown precipitate, which becomes greenish on adding an excess of the reagent, and dissolves, forming a greenish-black solution on heating. If cobalt and nickel are present together, the precipitate will become more or less olive green on boiling, and the test is capable of detecting as little as 0.1 per cent.of the former. It is advisable, however, to make a comparative test with a solution of a pure nickel salt of the same strength. If the precipitate turns black, either in the cold or on boiling, traces of manganese are present. Zinc does not interfere with the reaction, C. A. M. Separation of Iron and Zinc by Means of Ammonia. W. Funk. (Zeits. nngeiu. Chem., 1905, xviii., 1687.)-In the separation of iron and zinc by means of ammonia, the author shows that good results can be obtained if a large excess of ammonia is used in the presence of much ammonium chloride, the precipitate being washed with a 5 per cent. solution of ammonium chloride, and the precipitation being carried out twice.Practically the whole of the zinc.is then found in the two filtrates. A. G. L. Estimation of Metallic Iron in Presence of Ferrous and Ferric Oxides. B. Neumann. (Chem. Zeit. Rep., 1905, xsix., 310.)-Metallic iron can only be directly estimated in presence of ferrous oxide when no ferric oxide is present, otherwise the latter is reduced to ferrous oxide, using up hydrogen. The author therefore proposes the following indirect method : the substance is very finely powdered, and if only the content of metal is required, this is simply extracted with a magnet. In other cases the finely-divided substance is warmed with a measured quantity of a standard copper sulphate solution, and the precipitated copper directly estimated or, better, calculated from a determination of the copper left in the solution.This gives the metallic iron. Next the hydrogen given off on treatment with dilute sulphuric acid is measured. This represents only part of the hydrogen, some being used in reducing ferric oxide to ferrous oxide. The solution is then titrated with standard permanganate, which gives the original ferrous oxide dis- solved and the reduced oxide. From these figures the original content of ferrous oxide can be calculated. The total iron is then estimated in the usual manner, and the ferric oxide obtained by difference. E. K. H. Determination of Zinc in Zinc Aluminium Alloys. R. Seligman and F. J. Willott. (Journ. Soc. Chem. Ind., 1905, xxiv., 1278.)-A rapid method for the approximate determination of zinc (within 0.2 per cent.of the gravimetric result)58 THE ANALYST. consists in dissolving the alloy in caustic soda, precipitating the zinc as sulphide, redissolving in hydrochloric acid, and titrating the zinc with potassium ferrocyanide. Half a gram of the drilled alloy is dissolved in a 400 C.C. beaker in 25 C.C. of a 25 per cent. caustic soda solution, the liquid warmed till rapid evolution of gas takes place, and allowed to stand until solutioniis complete-usually five to ten minutes. The solution is then diluted to 300 C.C. with boiling water, any undissolved iron, copper, lead, tin, or nickel allowed to settle, and the clear liquid poured off, the residue being washed twice by decantation. This residue generally contains a small amount of zinc, which is removed by dissolving in a few drops of concentrated hydrochloric acid, diluting to 20 c.c., neutralizing with caustic sods, and adding 2 C.C.of the latter solution in excess. After warming the precipitated hydroxides are filtered off and washed, and the filtrate added to the main bulk of the zinc and aluminium solution. The zinc is DOW precipitated by sulp huretted hydrogen, which is passed till a skin forms at the point where the bubbles of gas burst, the precipi- tate allowed to settle, the clear liquid decanted, and the precipitate thrown upon a filter, whence it is dissolved in 8 C.C. hydrochloric acid, washed into the beaker used for precipitation, and diluted to 250 C.C. with boiling water. The presence of a small amount of alumina in the zinc is harmless, so that it is unnecessary to wash the precipitated sulphide.Five grams of ammonium chloride are then added, and the zinc titrated with a solution containing 22 grams of potassium ferrocyanide per litre, using uranium nitrate or acetate or ammonium molybdate as indicator. For the spot-tests a s1a.b of paraffin wax or a porcelain plate covered with a thin coat of wax is recommended. W. H. S. The Determination of Barium as Chromate, and its Separation from Strontium and Calcium. A. Skrabal and L. Neustadtl. (Zeit. anal. Chem., 1905, vol. 44, pp. 742-?55.)-The authors from a study of the different methods find that good results are obtained by precipitating the barium by means of ammonium bichromate from a neutral or slightly acid solution in the presence of ammonium acetate.The precipitation may be made from a hot or cold solution, but the filtration and washing of the precipitate must be done in the cold. Barium can be separated from calcium with approximately correct results by means of a single precipitation with ammonium bichromate from a cold, very dilute acetic acid solution in the presence of ammonium acetate. Better results are obtained, however, by a double precipitation. I t is impossible to effect a complete separation of barium from strontium by means of a single precipitation with ammonium bichromate. The following combined method is recommended for the separation of barium from calcium and strontium: The neutral or slightly acid solution of the salts (about 0.135 gram of the respective oxides) is mixed with ammonium acetate in excess (10 C.C.of a solution containing 300 grams per litre), brought to the boiling-point, and treated with ammonium bichromate solution (5 C.C. of a solution containing 100 grams per litre), added drop by drop, with continual shaking. The precipitate is allowed to subside, and when cold washed by decantation with a dilute solution of ammonium acetate (20 C.C. of the above solution diluted to a litre) until the washings passing through the filter are colourless. The small amount of the precipitate thatTHE ANALYST. 59 has been retained by the filter is dissolved in warm dilute nitric acid, the solution and washings returned to the original beaker, and sufficient nitric acid added to dissolve the whole of the precipitate. The clear solution is now treated drop by drop with ammonium hydroxide until the first signs of a permanent turbidity appear, after which ammonium acetate is added (10 C.C.of the strong solution), and the liquid boiled and allowed to cool gradually. The precipitate is washed by decanta- tion and on the filter with cold dilute ammonium acetate solution, then dried, ignited in a platinum crucible, and weighed. Strontium and calcium are then deter- mined in the united filtrates in the usual manner, C. A. M. The Determination of Titanium in Soil and the Ash of Plants. H. Pellet and C. Fribourg. (Ann. de Chim. anal., 1905, vol.10, p. 413-416.)-I. Direct Colori- metric Method-Half a gram of the dry earth, or 2.5 grams of ash, are introduced into a platinum crucible containing 15 grams of pure hydrofluoric acid and 1 C.C.of sulphuric acid, and evaporated to dryness. The residue is powdered, mixed with 5 grams of potassium bisulphate and fused, and the resulting product taken up with water containing 15 C.C. of sulphuric acid per 100 c.c., at a temperature not exceeding 60' C. The liquid is made up to 100 C.C. (there should be no insoluble residue), 1 to 10 C.C. taken and made up to 100 C.C. with distilled water, treated with 5 C.C. of hydrogen peroxide (12 volume solution), and compared colorimetrically with solutions of pure titanic acid containing 0.1 to 1.0 gram per litre. 11. Gruvimetric Methods.-In the case of soils containing about 2 per cent. of titanic acid, 3 grams of the dried and finely-powdered sample are introduced little by little into a, platinum crucible containing 30 grams of hydrofluoric acid, the mixture evaporated to dryness on the water-bath, after the addition of 3 C.C.of sulphuric acid, and the residue powdered and fused with 15 grams of potassium bisulphate. After cooling, the mass is powdered and dissolved in 200 to 250 C.C. of water at a temperature of about 60" C., and the solution, when cold, made up to 300 C.C. and filtered; 250 C.C. of the liquid is next transferred to a 400 C.C. beaker, and 40 C.C. of the remainder titrated with a solution of potassium hydroxide, 10 C.C. of which neutralize 5 grams of potassium bisulphate. From the result can be calculated the amount of potassium hydroxide solution to be added to the 250 c.c., so as to leave 5 grams of potassium bisulphate still unneutralized.After this addition, the liquid is treated with 50 C.C. of a freshly- prepared solution of sulphurous acid (1.020 to 1.025 specific gravity) and boiled for two hours, in the course of which two fresh additions of 50 C.C. each of the sulphurous acid solution are made. I t is then filtered, and the precipitate washed with boiling water and ignited, the residue being nearly pure titanic acid, with a little phosphoric acid. It is fused with pure potassium carbonate, the mass taken up with boiling water, and the insoluble portion washed with a 2 per cent. solution o potassium carbonate. The titanic acid remains behind in the form of an insoluble titanate, and the traces that pass into solution can be determined by a blank experiment with pure titanic acid.This titanate is ignited, fused with 1 gram of potassium bisulphate, and treated as above described, the residue of titanic acid being ignited and weighed,60 THE ANALYST. I n the case of soils containing less than 1 per cent. of titanic acid, 2 portions of 5 grams each of the finely-powdered and dry sample are ignited in separate platinum crucibles to destroy organic matter, and then fused with a mixture of 10 grams of sodium carbonate and 10 grams of potassium carbonate. The products of the fusion are taken up with very dilute hydrochloric acid, so as to form one solution, the silica separated by evaporating the liquid to dryness and igniting the residue, this being again taken up with dilute hydrochloric acid and the liquid filtered. The residual silica is treated with a mixture of hydrofluoric acid and sulphuric acid, which leaves a sulphated residue, whilst the filtrate is treated with ammonia, and the resulting precipitate separated from the filter and dried (the filter-paper being ignited alone).The united residue from the silica and ammonium precipitate is then fused with 15 to 20 grams of potassium bisulphate, and the titanic acid determined as described. I n the case of the ash of plants containing about 0.2 per cent. of titanic acid, 50 grams are treated with dilute hydrochloric acid, the silica separated, and the titanium determined in the filtrate. C. A. M. Rapid Method for the Valuation of Fluor-spar. A. W. Gregory. (Chem. News, 1905, vol. 92., pp. 184-185).-The following method may be found useful for the determination of calcium fluoride in fluor-spar when carbonates and silica are present in the mineral, all the determinations being carried out on the sample previously dried at 120" C.The carbon dioxide is determined by heating 2 grams of the sample to a red heat, until no further loss in weight takes place. Two grams of the sample are treated in a platinum basin with pure hydrofluoric acid, evaporated, ignited, and weighed. The calcium carbonate is thus converted into fluoride, and the loss in weight obtained is due to the silica present after allowance has been made for the quantity of carbonate previously found. (When the silica is present partly as silicate, this determination is not strictly accurate.) Another quantity of 2 grams of the sample are now heated in a platinum basin with concentrated sulphuric acid, hydrofluoric acid being first added if the amount of silica present be large.The excess of sulphuric acid is then driven off and the residue ignited and weighed. In this operation there will be an increase in weight, due to the conversion of calcium carbonate and fluoride into sulphate, and a loss of any silica present. The amounts of carbonate and silica being known, the fluoride may be calculated. w. P. s. Electrolytic Calcium. Joseph H. Goodwin. (Journ. Amer. Chem. SOC., 1905, xxvii., 1403.)-Metallic calcium can be easily and quickly prepared from calcium chloride by using the apparatus described. It consists essentially of a hollow cylinder of Acheson graphite, which is used as anode, the bottom being formed of a cooling copper coil, insulated from the graphite by asbestos.The cathode is a $-inch iron rod mounted on a, screw arrangement, by which it can be raised or lowered. The calcium separated at first acts as cathode during the remainder of the operation, and, by gradually raising the iron cathode, sticks of metallic calcium are easily obtained. The reaction is started by filling the anode with cold calcium chloride, andTHE ANALYST. 61 producing an arc between the cathode and anode ; a8 the calcium chloride melts, the cathode is lowered into it until electrolysis takes place, the heat generated being sufficient to keep the salt fused. The temperature must be kept within rather narrow limits, otherwise the calcium separates in a spongy instead of a coherent form.As, with the heavy currents used, the asbestos does not completely insulate the copper coil from the anode, a cell is inserted between the copper and the graphite so as to cause a, small current (0.04 amp8re) to flow in the other direction; this device effectually prevents contamination of the calcium by copper. In six experi- ments, with voltage varying from 14 to 22, and amperage from 105 to 185, a current efficiency of 21.5 to 41.9 per cent. was obtained, the average figures being: Volts, 17.7 ; ampAres, 163.0 ; efficiency, 26.6 per cent. I n six hours about 150 grams of calcium can be obtained. In one experiment the separated metal had the following composition: Ca, 98.00; Si, 0.03; Fe, 0.02; AI, 0.03; Mg, 0.11 ; C1, 0.90; and 0, by difference, 0.91 per cent. This sample had a conductivity of 3.43 microhms per C.C.at 0" C., the temperature coefficient being 0.00457, and a tensile strength of 8,710 lbs. per square inch, the elongation being 23.0 per cent. for 1 cm., 15 per cent. for 2 crn., 11.0 per cent. for 3 cm., and 6-6 per cent. for 5 cm. Calcium was found to be harder than sodium, lead, or tin, almost as hard as aluminium, but softer than zinc, cadmium, or magnesium. I t s specific gravity was found to be 1.5446 at 29.2" C. To clean the metal, after breaking off most of the calcium chloride, it is placed in 95 per cent, alcohol for some time, the loss owing to reaction with water and alcohol not being very great. The solid metal can be heated to a red-heat in air without igniting. I t is not hardened by quenching in water. At 300" to 400" C.it is as soft as lead. When cold, the bright surface of the metal rapidly dulls in air, but when hot its surface may be polished, and will keep bright as long as the metal remains hot. By placing the hot metal in a bottle heated to 150" C., and closing the bottle while at this temperature, the surface may be preserved quite bright. A number of the cylinders obtained were fused together in a closed iron tube and quickly cooled, when a mass of large reddish-violet cubical cystals was obtained, having the following composition : Ca, 91.28 ; gangue, 0.03 ; SiO,, 0.77 ; FelO,, 046; A1,0,, 0.77; &$g, 0.11; C1, 1.28; C, trace; N, trace; 0, by difference, 5.30. The specific gravity of the crystals was 1.5425 at 28.1" C ; they were quite soft, and could be hammered into sheets as thin as paper, often exploding with a slight flame under the impact of the hammer.A. G. L. Estimation of Percentage of Nitric Aeid in the Concentrated Acid by the Specific Gravity. Veley and Manley. (Chem. Zed. Rep., 1905, xxix., 1207.)-The authors publish some figures and details of their methods of purification, etc., in consequence of the divergence shown between the results published by Lunge and by Winteler. The authors come to the conclusion that Winteler's acid was not sufficiently pure. They purified their acid as follows : The purest commercial acid was distilled, and the distillate was redistilled over silver and barium nitrates to remove sul- phuric and hydrochloric acid. A current of ozonixed oxygen was then passed62 THE ANALYST.through, and finally the acid was fractionated in vacuo at the lowest possible tempera- ture. In this way an acid was obtained containing 99.8 per cent. ENO, with only 1 part per million of nitrous acid, 4 per million of sulphuric acid, and 3 per million of halogen acids. This acid was further freed from water by a special apparatus (Phil. Trans., 1890, A. 365)) and an acid finally obtained which contained 99.97 per cent. HNO,. The authors used for titrating the various dilutions of this acid a sodium hydroxide solution prepared from sodium and steam, and a N-sulphuric acid solution standardized against sodium carbonate. The following table shows the figures obtained by various observers : Specific gravity: 1,485 1.490 1.495 1.500 1.505 1510 1.615 1.520 Percentage according to- 1.Lunge and Rey ... ... 87.7 89.6 91'6 94.1 96'4 98.1 99'1 99.7 2. Vcley and Manley ... ... 87% 89.6 91.1 94'0 96.5 97'8 98 7 99'8 4. Mean of fisst three series ... 87.6 89.6 91.4 93.9 96'4 97.9 98.9 99.8 5. Winteler ... ... ... 86'3 88.2 90.2 91'8 93.6 95.6 97'3 99.7 8. Ferguson .. ... ... 87.6 89.7 91.4 93'7 - -. - I Difl'erence between 4 and 5 ...- 1'3 -1.4 -1.2 -2.1 -2.8 -2.3 -1'6 -- For further comments on these figures, reference should be made to the original ; but the authors express the view that the clearing up of the question lies with Winteler rather than with the other observers. E. K. H. Estimation of Percentage of Nitric Acid in the Concentrated Acid by the Specific Gravity.H. Putzer. (Chem. h i t . Rep., 1905, xxix.)-Compare paper by Veley and Manley, (see previous abstract). He adds his contribution to the figures already published. Great care was bestowed by the author on the purifica- tion of the acid. One hundred and fifty grams of this on evaporation in a platinum dish left a scarcely visible residue which was not weighable; the acid was quite free from nitrous acid (when diluted with water (5 : 1) and 1 drop of TG potassium per- manganate added it remained pink for an hour), sulphuric acid, hydrochloric acid, and iodine. The author having found the ordinary method of obtaining sodium carbonate from so-called chemically pure sodium bicarbonate unsatisfactory, he therefore pre- pared Na,CO,.H,O by boiling a solution of the bicarbonate and re-precipitating.This was then heated in a platinum dish by a burner whose flame-tip was about 5 cm. below the bottom of the dish. Na2C0, was used, with methyl orange, very dilute, as indicator. The specific gravity was determined by a hydrometer showing the first three decimal places exactly, and the fourth by estimation. The author's figures are : Specific Gravity $ (Vac.) Yc. HNO,. I Specific Gravity % (Vac.) Pc. HNO,. 1.4878 1.4908 1.4923 1 *4943 1.4958 1.4973 1.4988 1.4998 89-19 90.40 90.98 91.79 92.52 93.22 93.93 94.53 1.5018 1 -5033 1.5043 1.5058 1.5073 15103 1.5128 1.5163 95.51 96-13 96.59 97.21 97-76 98.62 99.20 99.75THE ANALYST. 63 By graphic interpolation these figures give results differing uniformly by 0.5 from those of Lunge and Rey.The author considers that these differences are due to the fact that his acid was even purer than that used by Lunge and Rey, whilst Winteler’s results may be rejected, as the acid used was, on his own showing, not pure. E. K. H. On the Determination of Sulphuric and Nitric Acids in 64Nitrous Vitriol.” G. Lunge and E. Berl. (Zeits. angew. Chem., 1905, xviii., 1681.)-As the result of determinations made, partly on a synthetic, partly on a commercial acid, the authors recommend that nitro-sulphuric acid should be examined for (a) total acidity, ( b ) permanganate consumed, (c) total nitrogen by means of nitro- meter, The nitric acid may then be calculated by subtracting (b) from (c), and the sulphuric acid by subtracting (c) from (a). Gravimetric determinations of sulphuric acid as barium sulphate tend to give high results; determinations of the nitric acid by the ‘ 4 nitron ” method easily lead to low values. ’ Evaporation of the nitric acid and titration of the residual sulphuric acid generally gives results slightly too low for the sulphuric acid, and consequently a little too high for the nitric acid. A. G. L. Modification of W. Winkler’s Method for the Determination of Oxygen in Waters. (Zeits. angew. Chem., 1905, xviii., 1767.)-The author believes that with ordinary waters Winkler’s method gives more exact results if the correction made by Winkler for the iodine consumed by the organic matter present is not made. When a, correction must be made, as in the case of sewage effluents, he proceeds as follows : A mixture of 2 C.C. of 40 per cent. sodium hydroxide solution, 2 C.C. of 50 per cent. manganous chloride solution, and 20 C.C. of distilled water is shaken in a large flask until it becomes brown in colour; 50 c.c of concentrated hydrochloric acid are then added, and the whole made up to 300 C.C. with distilled water. Of this solution, 20 C.C. are added to 100 C.C. of the water under examina- tion, and also to 100 C.C. of distilled water. After five minutes 10 C.C. of a 5 per cent. potassium iodide solution are added to each, and the iodine liberated is deter- mined with a solution of sodium thiosulphate, 1 C.C. of which corresponds to 0.1 C.C. of oxygen. The difference between the two values found gives the quantity of iodine taken up by the organic matter in the water, and may be applied as a correc- tion to the results found by Winkler’s method. Results obtained in this way on several waters agreed better with gasometric determinations of the oxygen in the waters than the values found using Winkler’s method of correction. Hermann Noll. A. G. L.

ISSN:0003-2654    

DOI:10.1039/AN9063100054

出版商:RSC    

年代:1906

数据来源: RSC

摘要:

THE ANALYST. 63 APPARATUS. Alternating Motion for Stirrers. (Chem. Zeit., 1905, xxix., 1208.)-Two stirring wheels are used, which rotate in opposite direction, and are so arranged that one of them is worked by the friction due to a projection on the main wheel during half a revolution of the latter, whilst the other is worked by a second projection on64 THE ANALYST the other half of the main wheel. the time of a half revolution. The two paddles, therefore, work each through The apparatus is protected, and can be obtained from Franz Hagershoff, Leipzig. E. K. H. Note on the Incandescent Mantle as a Catalyst, and its Application to Gas Analysis. J. E. Mason and J. Wilson. (Proc. Chenz. SOC., 1905, vol. 21, P. 296.)-Although less effective, the ordinary gas mantle may be used as a substitute for platinized asbestos in the preparation of formaldehyde from methyl alcohol vapour and air, and sulphur trioxide from sulphur dioxide and oxygen, Fragments of mantle in a hard glass or quartz tube may be employed in the place of palladium or palladium- asbestos for the determination of hydrogen and carbon monoxide by combustion with excess of air or oxygen. Methane and mixtures of methane and hydrogen may be determined similarly, the contraction being measured after combustion and subsequent treatment with potassium hydroxide solution.The results agree well with those obtained by the ordinary explosion methods. Good results may also be obtained by passing the gases mixed with oxygen over asbestos heated in a small quartz tube. Hydrogen, and less readily methane, may be determined by passing the gas mixed with oxygen through narrow tubes of heated Jena glass alone.w. P. s. INSTITUTE OF CHEMISTRY OF GREAT BRITAIN AND IRELAND. PAST LIST OF THE JANUARY EXBAIINATIONS. OF fourteen candidates who entered for the Intermediate Examination, ten passed A. P. Davson, F. W.IForeman, W. Gamed, T. R. Hodgson, B.A. (Cantab.), T. J. Kirk- land, A. Lathwood, B.Sc. (London), B. D. W. Luff, J. F. Reid, H. Stanley, B.Sc. (London), and F. Tattersfield. In the Final Examination for the Associateship (A.I.G.), of five examined in the branch of Mineral Chemistry, two passed: E. R. Bullock, Assoc.R.C.Sc. (London), and T. F. Cowie ; of four in Metallurgical Chemistry, two passed: H. J. B. Rawlins, B.Sc. (London), and Thomas Sten- house, B.Sc. (London), ABBOC.R.C.SC. (London), A.R.S.M. ; of four in Organic Chemistry, three passed: W. P. Hayworth, F. H. G. Horsman, B.Sc. (London), and D. Spence, Ph.D. (Jena) ; and of twelve who entered in the branch of the Analysis of Food and Drugs and of Water, including an Examinahion in Therapeutics, Pharmacology, and Microscopy, the following nine passed : J. T. Cart, B.Sc. (London), C. G. Gates, B.Sc. (London), A. G. Holborow, Miss E. S. Hooper, B.Sc. (London), S. J. Lewis, B.Sc. (London), A. J. C. Lickorish, S. G. Liversedge, Miss E. A. Macadam, F. E. Thompson, Assoc.R.C.Sc. (London). The Examiners in Chemistry were Mr. W. W. Fisher, M.A. (Oxon.), F.I.C., and Dr. G. G. Henderson, M.A., F.I.C. The Examination in Therapeutics, Pharmacology, and Microscopy was conducted by Dr. F. Gowland Hopkins, M.A., F.R.S., F.I.C.

ISSN:0003-2654    

DOI:10.1039/AN9063100063

出版商:RSC    

年代:1906

数据来源: RSC