摘要:

THE ANALYST. OCTOBER, 1904. THE DETERMINATION OF BORIC ACID IN CIDER, FRUITS, ETC. BY (THE LATE) ALFRED H. ALLEN AND ARNOLD R. TANKARD. (Read at the British Pharmaceutical Conference at Shejkld, August 10, 1904.) THE natural occurrence of traces of boric acid in certain plants, trees, fruits, etc., has been pointed out by various observers,* and the presence of this acid in wine, cider, and allied products follows as a natural consequence. These facts were confirmed at the outset of our experiments upon the presence of preservatives in cider. All the eiders examined were found to contain a small but distinct amount of boric acid, and st similar result was obtained .by the examination of various fruits, such as apples, pears, quinces, grapes, and pomegranates. Hence boric acid in cider, Perry, wine, etc., cannot be regarded as an adulteration unless the amount ig materially greater than can be fairly ascribed to natural causes. Our experiments have been chiefly made on cider and apples, and the following observations have special reference to these substances.The detection of boric acid in cider and fruits can be readily effected by evapor- ating 20 C.C. of cider or apple-juice to dryness and igniting the residue, or by directly igniting 25 grsmmes of apple or other fruit. The ash is rendered distinctly acid to litmus with dilute hydrochloric acid, a piece of turmeric paper partially immersed in the liquid, and the whole evaporated to dryness on the water-bath in a flat porcelain dish. The residue is further dried in the water-oven for a short time.In the presence of boric acid the turmeric paper will acquire a brownish-red colour, which, on being moistened with a drop of caustic soda solution, is changed into a variety of colours, chiefly green and purple, The quantitative determination of boric acid in cider and fruits, etc., we have found very troublesome, and this has been the subject of numerous experiments. The English references only are given : Boric acid in trees and lants, E. Bcchi, J. C. S., lviii., 656 ; J. C. S. I., ix., 635 ; in hops and (therefore) beer, but not in mart or barley, J. Brand, ASALYST, xviii., 135 ; in all parts of the vine, Baumert, Rising (reference not known) ; in peach-trees and peaches, Knorr (reference not known) ; in grapes and wine, apples, pears, radishes and lettuce, M.Gassend, Phurm. Journ., xxiii., 6 ; J. C. S., lxii., 93 ; in various fruits, A. Hebebrand, ANALYST, 1903, xsviii., 37 ; in fruits generally, E. Hotter, J. C. S., 1890, lviii., 1338 ; in the ash of fruits and vine-leaves, H. Jay, J. C. S., lxx., ii., 327 ; in wine, water-melon, etc., C. A. Crampton, J. S. C. I., viii., 569 ; in wines, cider, perr and fruits, day and Dupasquier, J. C. S., lxx., ii., 76, 327 ; absent from- natural wines, Villicrs and %ayolle, J. C. S., lxx., ii., 75. * The following is a summary of the chief papers on this subject.302 THE ANALYST. The difficulty of the analysis is enhanced owing to the minute quantity of boric acid present, and the determination is further complicated by the presence of phosphates. These salts render inapplicable the direct employment of R.T. Thomson’s well- known process ( J . S. C. I,, 1893, p. 433), in which the solution is first made neutral to methyl orange and then titrated with standard caustic soda solution and phenol- phthalein in presence of glycerin, the end-point of the titration corresponding to the formation of NaBO,. The unsuitability of Thornson’s method without modification in the presence of phosphates is due to the fact that while phosphates of the formula, M.H,PO, are neutral to methyl orange, they are acid to phenolphthalein. We have made a number of experiments with a view of overcoming the difficulty caused by the presence of phosphates in quantity, but without success. I t does not seem possible to make an allowance for the disturbing action of the phosphates ; nor does the addition of glycerin after the aqueous liquid has been rendered neutral to phenol- phthalein overcome the difficulty, owing to the fact that boric acid is distinctly, but indefinitely, acid to phenolphthalein, even in the absence of glycerin.F. Parmentier (Comptes renc7., 1891, cxiii., 41 ; abst. J. C . S., Ix., 1551) has devised a process for the determination of small quantities of boric acid, based on the solubility of borates in a solution of ammonium nitrate. The method has been found quite useless for our special purpose, owing to the fact that it is impossible to titrate boric acid with alkalies in the presence of large quantities of ammonium nitrate, since ammonia is set free during the titration.Boric acid is, moreover, more or less volatile when heated with ammonia or ammonium nitrate. After a large number of experiments, the following method for the determination of boric acid in cider, etc., based on the moderate solubility of calcium borate in water, was devised : About 100 C.C. of cider or other liquid is evaporated to dryness with a few cubic centimetres of a 10 per cent. solution of calcium chloride ; or, in the case of fruits, about 50 grammes weight is cut up into small pieces, and the solution of calcium chloride poured over the mass, which is then evaporated to dryness. The dry residue is well charred, boiled with about 150 C.C. of distilled water, and the liquid filtered. The carbonaceous residue is thoroughly incinerated at a moderate temperature, and when cold boiled with a further quantity of 150 C.C.of water, and allowed to stand in the cold for some hours, or preferably overnight. The liquid is then filtered cold, and the filtrate added to the first extract.* The mixed aqueous extracts are next evaporated to a volume of 25 or 30 c.c., and after cooling neutralized by decinormal acid, ueing methyl orange as indicet0r.i An equal volume of glycerin is next added, and the liquid titrated with phenolphthalein and 2; caustic soda solution (free from carbonate). About 10 C.C. more glycerin should now be added, when, if the titration is complete, the red coloration will remain. Each C.C. of the ;G normal solution of caustic soda, required represents 0.00175 gramme of boric anhydride, B203 ; 0.0031 gramme of crystallized boric acid, H,B03 ; or 0.004775 gramme of crystallized borax, Na2B,0, + lOH,O.The above process gives good results when the amount of boric acid present in the sample taken is not less than 0.005 gramme. to stand for some time hefore filtration. found to be free from boric acid. ’ It is desirable to extract the rcsidue for a third time with hot water, allowing the liquid when cold This third extract, when titrated sepnratcly, wyill generally be t Care should be taken that all the borate is in solution before the titration is begun. If not, tlie amount found must be added to that alrcady extracted.THE ANALYST. 303 We have also examined the well-known method for the determination of boric acid based on the volatility of methyl borate, and find the following to be the best method of operating : X suitable quantity of the substance under examination is treated with calcium chloride solution as already described, and well charred, and the main portion of the salts extracted with about 50 C.C.of water. This aqueous extract is transferred to a distillation flask of about 100 C.C. capacity, and cautiously evaporated nearly to dryness over a naked flame. Meanwhile the charred residue is incinerated, the ash (nearly white) moistened with 2 C.C. of strong sulphuric acid, and the mixture warmed. When the evolution of hydrochloric.acid gas is nearly ht an end, the acidified residue is transferred to the distilling-flask containing the evaporated aqueous extracts. The last portions are washed in with 10 c..c.of methyl alcohol,* the flask immersed in a boiling water-bath, and the liquid distilled almost t o dryness. A further addition of 10 C.C. of methyl alcohol is then made, and the distillation repeated. Between each distillation the residue in the flask should be allowed to cool before the next addition of methyl alcohol is made. The residue finally contained in the distilling flask should be tested by the flame reaction with alcohol to insure that the whole of the boric acid has been volatilized. If this is not found to be the case, the distil- lation should be repeated once or twice more. The alcoholic vapours are passed into 25 C.C. of water contained in a flask, the end of the condenser-tube dipping into the liquid. When the process is completed, hhe distillate is evaporated over a water-bath until free from alcohol.By this treat- ment the methyl borate is hydrolysed, and the boric acid left in a free state. The residual liquid is diluted with a little water and rendered exactly neutral to methyl orange. An equal volume of glycerin is then added, and the liquid titrated with $G normal caustic soda and phenolphthalein as already described. The glycerin used in these processes should be rendered neutral to phenolphthalein just before use, as it is generally slightly acid in reaction. I n many of the processes already in use for the separation of boric acid by distillation the methyl borate is distilled into a solution of caustic soda, and after evaporation of the alcohol the aqueous liquid is titrated in the usual way.I n our experience, however, when an alkali was used, the results were always above the fruth, even when specially purified methyl alcohol was employed. For this reagon the use of caustic soda is not to be recommended, and, as previous experiments have shown, is quite unnecessary (see Allen’s ‘‘ Commercial Organic Analysis,” vol. iv., footnote to p. 178). The following result8 were obtained in a series of experiments made to test the accuracy of the processes here described. A known weight of crystallized borax was added either to a mixture of calcium chloride, magnesium sulphate and sodium Phosphate, 01: to a known weight of apple. In the latter c.ase, an exactIy similar Portion and weight of the same apple was treated with calcium chloride, and the boric acid determined and deducted from that found in the other portion to which borax had been added : * Ordinary mood-spirit of good quality, purified by redistillation over caustic potash, is suitable for this purpose.As many as six such treatments are usually required.304 lalcium chloride, magnesium sul- phate, and sodium phosphate 50 grctmmes of apple None None Sodium phosphate Sodium phosphate THE ANALYST. Gramme. 0.200 { 0.200 0.200 0.020 0.200 0.020 Extraction method Fruits, etc. < Boric Acid, H,BOR. Distillation method - ... ... ... ... ... ... ... ... ... ... ... ... Number of Experiment. _____._ _ _ __ - -. -~ 0.009 per cent. 0.013 ,, 0.011 ,, 0.007 ,, 0.016 ,, 0.016 ,, 0.005 ,, 0,004 ,, 0.009 gramme per 100 C.C. 0.017 ,, $ 9 $ 8 0.004 ,, ,, ,, 0.004 ,, ,) ,, ... } ...5. ... 6. ... 7. ... 8. ... Substances Added t o the Borax. Borax Taken. Borax Found. Gramnie. 0.198 0.204 0.019 0-020 0-197 0.022 0.201 0-023 Richmond and Harrison’s method (ANALYST, 1902, xxvii., 197) for the determina- tion of boric acid in butter is rapid and accurate for its intended purpose, but the presence of phosphates in fruits and fruit products renders the process unsuitable for the determination of boric acid in these substances. A colorimetric method for the determination of boric acid in milk and other foods has been devised by Cassal and Gerrcbns (British Food JozmzaZ, October, 1902)- The process is based upon the fact that in the presence of oxalic acid the colouring- matter of turmeric forms with boric acid an intense magenta-red colour more delicate than the ordinary turmeric reaction (that is, when obtained in the absence of oxalic acid), and permanent for many hours.The alcoholic solution of the colour formed in the reaction is compared with that from a known weight of boric acid. The method is said to be reliable and accurate, but appears to be rather lengthy and tedious. The two processes described at the beginning of this paper are obviously applicable to a considerable number of other substances besides cider and fruits; and their employment will, we believe, be found to result in a large saving of time, while the accuracy attained will at least equal that of other more tedious metbods now in use. The following table shows the proportion of boric acid contained in various fruite and ciders, etc., examined by us : 1. Apple (Norfolk) ... ... 2. Apple (Fox Whelp) 3. Apple (Old Fox Whelp)” 4. Pear, No. 1 ... ... 5. Pear, No. 2 ... ... 6. Quince ... ... . I . 7. Pomegranate ... ... 8. Grapes ... ... ... 9. Norfolk Cider .... ... 10. Hereford Cider , . . ... 11. Devonshire Cider ... 12. Apple Juice (Devon) I ... ... ... ... ... ... ... ... ... ... ..- ... ... ... ... ... ... ... ... ... ... ... ... ... ... N0Tx-h Mr. Allen’s paper on ‘( Cider ” (ANALYST, xxvii, p. 183) the quantities of boric acid are stated in terms of B203, and not H,BO,, as might be supposed.

ISSN:0003-2654    

DOI:10.1039/AN9042900301

出版商:RSC    

年代:1904

数据来源: RSC

摘要:

THE ANALYST. 305 ABSTRACTS OF PAPERS PUBLISHED IN OTHER JOURNALS. FOODS AND DRUGS ANALYSIS. Distinction between Raw and Heated Milk. Ute. (Oesterr. Chem. Zeit., 1904, vii., 389-391 .)-The author finds that the p-phenylenediamine tost gives a coloration with milk which has been heated at a temperature of 71' C. for one and a quarter hours. When the hydrogen peroxide is too concentrated the coloration is obtained even with boiled milk. The test, however, when properly performed, will detect 5 per cent. of mw milk in boiled milk. There is no advantage in using the reaction as a, zone test. Schardinger's test (methylene blue-formalin solution) is considered untrustworthy, w. P. s. The Composition of Dutch Butter. Grossmann and Meinhard. (Zeit. Untersuch. Nahr. Genussmittel, 1904, viii., 237-243.)-1n order to ascertain whether Dutch butters as a whole give abnormally low Reichert-Meissl values, the authors purchased in the open market (in Holland) fifteen samples of butter.The bulk of the butter was bought by large dealers for export to Germany. These fitteen samples were analysed, and gave Reichert-Meissl values from 29.5 to 33.4. The other analytical results also corresponded with those yielded by genuine bntters. It being the usual practice for dealers to " salt " the butter bought in the market before exporting it to Germany, samples were a few days afterwards taken in the latter country from consignments imported by the dealers mentioned above. These samples (fifteen) would correepond to the first fifteen samples. On analysis, how- ever, the Reichert-Meissl values obtained were considerably lower in every case- from 21.8 to 25.8.In some cases, the actual presencg of vegetable oil was proved by means of the phytosterol acetate test, and, from the results obtained in the other analytical determinations, all the samples might be considered as adulterated ones. From this it will be seen that Dutch butters do not always give low Reichert-Meissl values (Van Rijn, ANALYST, 1902, 136)' and that. exported Dutch butters are mixed with foreign fats at the same time that they are (' salted." w. P. s. Improvements in Gerber's Process for Fat Determination in Cheese. P. Wieske. (MilchrZeit., 1904, xxxiii., 353 ; through Chem. Zeit. Rep., 1904, xvii., 196.)-The improvement consists essentially in shaking the cheese (finely divided) with hot sulphuric acid.Four to five grammes of cheese are introduced into the butyrometer, and dilute sulphuric acid (specific gravity 1-500) added to about the 60 mark. The butyrometer is then placed in a water-bath at 70" to 80" C, and, on attaining that temperature, is taken out and well shaken. Repeated heating may be necessary for complete solution of the albuminoids. After cooling to 60" amyl alcohol is added, and the subsequent manipulation is as in the usual process. H. A. T.306 THE ANALYST. Detection of Rancid Fat in Edible Fats. F. Wiedmann. ( h i t . Untersuch. Nahr. Genussmittel, 1904, viii., 136-139.)-1t has been recognisd for some time that the rancidity of a fat or oil bears no relation to the amount of free fatty acid in the same.An oil with a high acid value may still be pleasant to the taste, or, in other words, be free from rancidity, whilst rancid oils may contain little free acid. Rancidity being due to the presence of products of decomposition possessing an aldehydic nature, the author proposes various tests for detecting these substances. On shaking 5 C.C. of melted fat with 5 C.C. of a 1 per cent. solution of phloroglucinol in acetone and 2 to 3 drops of concentrated sulphuric acid, the mixture is coloured red should even 1 per cent. of a rancid fat be present. It is thus possible to detect admixture of old and rancid lard with fresh lard. The coloration produced increases in intensity with the rancidity of the sample. Other substances, such as pyrogallol, p-phenylenediamine, guaiacum resin in the presence of acetic anhydride, etc., also give characteristic colorations with rancid fats.All the tests fail, however, with fats and oils which have been heated above 200° C. (see ANALYST, 1902, 363). w. P. s. The Dextrins occurring in Pine Honey. A. Hilger. (Zeit. Untersuch. Nahr. Genussmittel, 1904, viii, 110-126.)-These dextrins are readily precipitated from the honey by means of a mixture of methyl and ethyl alcohol, and have the character of achroodextrin. Each kind of pine honey contains a dextrin peculiar to itself, and having a constant specific rotation. The author has isolated the dextrins from four typical sorts of pine honey, and determined the rotatory power of each. The results obtained were : [aID = + 157.00 ; + 131.28 ; + 125.59 ; and + 119.90 respectively.The dextrin with [a],157 had the empirical formula C,HI,O,, exhibited true dextrin properties, and was scarcely attacked by dilute acids. Hydrochloric acid alone effected complete inversion. The remaining three dextrins were more closely allied to the sugars, and were readily hydrolysed by weak acids. Neither Fehling’s nor Ost’s solutions nor Soldiani’s reagent were reduced by the dextrins. After boiling for some time hydrolysis by the alkali took place, with a consequent reduction of the copper salts. The dextrin with [a],157 was not fermentable, and the others only with difficulty, little gas being evolved. Top and bottom fermenting beer yeasts, as well as certain wild species (Succharomyces and Sc hizosacchuromyces), acted more energetically on these dextrins than did the majority of the wine yeasts employed in the experiments. No osazone was obtained with any of the dextrins.w. P. s. Detection of Maize Flour in Bread. D. Ottolenghi. (Zed. Untersuch. Nuhr. Genussmittel, 1904, viii., 189-193.)-Although the detection of maize flour in wheat flour is a, comparatively simple matter, it is difficult to prove the presence of maize iu cooked materials, such as pastry, macaroni, bread, etc. For the latter purpose the following method is proposed, being based upon the separation of the proteids peculiar to maize, and recently investigated by Donard and Labbd : One hundred grammes of the bread (crumb) dried at a temperature of 4G0 C.THE ANALYST. 307 and finely powdered are treated for twelve hours with 500 C.C. of 0.3 per cent.potassium hydroxide solution, with frequent shaking. The liquid portion is then filtered through gauze, and the residue again extracted with the alkali solution. After three hours the whole is poured on the gauze, and the residue well pressed. The filtrate is evaporahed at a temperature not exceeding 70” C. When dry, the residue is broken up as finely as possible, transferred to a flask, and treated with 35 to 40 C.C. of absolute iso-amyl alcohol. The flask is attached to a, reflux condenser, and its contents boiled over an oil-bath for eix hours. After this time the amyl alcohol is passed through a filter while still hot, and the filtrate allowed to COO]. If the bread contains no maize, the yellowish-brown filtrate remains quite clear, or only slightly opalescent, buf in the presence of maize it becomes more or lese turbid.The addition to the filtrate of three times its volume of pure benzene causes no turbidity in the case of wheat bread, but accentuates the turbidity should maize flour be present. After allowing the filtrate to stand for twelve hours, the super- natant liquid may be decanted, and any precipitate redissolved in 2 C.C. of hot iso-amyl alcohol. On cooling, the solution becomes strongly opalescent, but not turbid if the bread consists of wheat flour, and very milky if maize be present. By adding 6 C.C. of benzene, iihe substance causing the milkiness is precipitated as yellowish flakes. w. P. s. Composition of Ducks’ Eggs. H. Liihrig. (Zed.Untersuch. Nahr. Genziss- mzttel, 1904, viii., 181-1$8.)-With a view to detecting the presence of ducks’ eggs in pastry, and also to ascertain the differences in composition between ducks’ and hens’ eggs, the authcr has carried out a, number of analyses, the results of which are given in this paper. Attention was principally paid to the determination of the lecithin- phosphoric acid contained in these two kinds of eggs (see ANALYST, this volume, p. 117). One hundred grammes of the yolk of ducks’ eggs were found to contain : Total phosphoric acid . . . . .. ... 1. Soluble in boiling alcohol ... ... Consisting of : ( a ) Directly soluble in efher . . . ( b ) Soluble in alcohol after extrac- tion with ether ... ... 2. Insoluble in boiling alcohol . . . ... (a) As nuclein ...... ... (b) As insoluble phosphates or compounds of phosphogly- ceric acid ... ... ... 1.255 grammes. 0.861 gramme (tot a1 dist earyllecit hin). 0.643 ,, (free dist earyllecithin). (disteary llecit hin com- 0.218 ,, { bined with vitellin). 0.394 ,, 0.178 ,, 0.216 ,, The chief differences between the above results and those yielded by hens’ eggs lie in the figures for free lecithin and that combined with vitellin. The average amount of ether extract obtained from ducks’ eggs (ten) was found to be: Total egg, 12.2 per cent. ; total egg, without shell, 13.7 per cent. ; and the yolk, 33.8 per cent. w. P. s.808 THE ANALYST. Determination of Xanthine Bases in Meat, Yeast, and other Extracts. 11. In Yeast Extracts (continued). K. Micko. (.&it: Untersuch. Nahr.Genuss mittel, 1904, viii., 227-237.)-Methods are given for the further purification of the fractions obtained by the process previously described (ANALYST, this volume, p. 158), the treatment employed following the lines of that given for isolating the bases contained in meat extracts (ANALYST, 1903, 315). The author has again investigated the alleged occurrence of carnine in meat extracts. In no instance was this base detected, the conclusion being that meat extracts do not contain it, or that it is of a transitory nature. Hypoxanthine was found to crystallize in two forms, one apparently as quadratic octahedra containing no water of crystallization. The other crystallizes as needles, which contain water, are unstable, and spontaneously change into the anhydrous form.w. P. s. Composition of Commercial Substitutes for Coffee. F. Duchacek. (Ann. de Chim. a?utZ., 1904, ix., 292-303.)-The following results were obtained in the analysis of three coffee substitutes manufactured in Austria, and of a sampIe of freshly roasted Ceylon coffee : Moisture ... ... ... Substances soluble in water Nitrogen soh ble in water ... Total nitrogen ... ... Sugars ... ... Dextrins ... ... Caffeine ... ... Ash ... ... ... Fat ... ... ... Cellulose ... ... Pentosans , . . ... Potassium oxide ... Sodium oxide ... Calcium oxide ... Phosphoric acid (P20s) Sulphuric acid (SO,) Silica (SiO,) ... ... Chlorine ... ... Lignin ... ... ... ... ... ... ~ .. ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ...... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... Ceylon Coffee. Per Cent, 1.96 26.02 1.74 1-10 1.43 0.90 1-12 3.65 15-05 20.92 7.18 16.27 2.22 0.06 0.22 0.49 0.15 0.01 0.04 Ma1 t Coffee. Per Cent. 2.07 41-93 1.86 0-36 1.73 15-82 3.19 5.24 7-50 2.108 8.35 0.38 0.06 0.12 1.09 0.07 0.84 0.03 - Fig Coffee. Per Cent. 7.83 70.99 1.19 0.71 35.70 2-30 4.47 3.07 0.91 5-17 2.13 0-44 0-53 0.68 0.17 0.08 0.05 - 5.a7 Chicory Coffee. Per Cent- 5.99 69.67 1.08 1.08 18.23 1-40 5988 2.23 8.13 4-21 9.21 3-08 0.41 0.25 0.48 0.05 0.89 0.16 - C. A. M. The Occurrence of Coffearine in Coffee. L. Graf. (Zeit. fur ofentl. Chem., 1904, x., 279-281.)-Paladino was the first to recogniae this new alkaloid (Berzchte, 1894, 406), and Forster and Riechelmann (ANALYST, 1897, 189) have also separatedTHE ANALYST.309 substance which they believe to be identical with coffearine. Doubt having been thrown by other observers on its actual occurrence in coffee berries, the author has repeated Paladino’s experiments, and obtained a substance having undoubted alkaloidal properties. It had the formula C,,H,,N20, and its hydrochloride crystallized from dilute alcohol in the form of needles, which contained one molecule of water of crystallization. The alkaloid was obtained from raw coffee beans, even when treat- ment with calcium hydroxide was dispensed with, showing that coffearine is not a, product of the reaction of the alkali on caffeine. It is present in the beans in very small amounts, and is not extracted from the decoction by chloroform, as is caffeine.w. P. s. The Composition of Chocolate Varnish. F. Jean. (Ann. de Chim. anal., 1904, ix., 258.)-A liquid preparation used in Spain for hardening chocolate and preventing it becoming white on keeping was found to consist of 25.6 grammes of gum benzoin, and 6.4 grammes of an unidentified resin in 100 C.C. of alcohol. C. A. M. A Fictitious Pepper. E. Collin. (Rdpertoire [3], xvi, 289; through Pham. Journ., 1904, lxxiii., 379.)-An ingenious fraud, consisting in the treatment of the seeds of a species of Pisum or Lathyrus to resemble black pepper-corns, is exposed by the author. The peas are apparently soaked in an aqueous extract of capsicums, and then treated with a dilute solution of an iron salt to give them a black colour.When mixed with pepper-corns the fictitious seeds are not readily detected by a cursory examination. The treated peas are also sold in the ground condition, powdered capsicum and olive stones being also frequently added. w. P. s. The Testing of Quinine Sulphate. B. H. Paul. (Chemist and Druggist, 1904, lxv., 428-430.)-The author takes exception to the British Pharmacopaeia test for cinchonidine in quinine, and suggests a method of procedure carefully worked out on the solubility limits, and depending on the appearance or non-appearance of crystals in the ether under precise conditions. The influence of quinine on the solubility of cinchoni- dine is also dealt with. The details of the method are as follows : 1 gramme of the quinine sulphate is dissolved in 100 C.C.of boiling water. After cooling the solution is filtered from the crystals of quinine sulphate and the filtrate evaporated to a bulk of 30 C.C. ; any further crystals separating are removed by filtration through a small plug of cotton-wool, and the filtrate made up to exactly 30 C.C. with water ; 5 C.C. of this solution are then treated with 5 drops of ammonia, and shaken in a corked tube with 1 c.c of ether. If at the end of one hour no crystals be formed in the solution, the quantity of cinchonidine in the 5 C.C. of solution would be less than 0.004 gramme, and consequently in original quinine sulphate less than 3.24 per cent. I n the more probable case of crystals being formed, less quantities (4.5, 4.0, 3.5 c.c.) are shaken out with ether and ammonia, until a difference amounting to 0.5 C.C.of solution corresponds to an entire absence of crystals in the one instance and a slight formation of crystals in the other after twelve hours’ standing. The mean of these310 THE ANALYST. two quantities is then. taken as containing 0.004 gramme of cinchonidine, and the percentage calculated on that basis. When shaken out from aqueous solutions, the ethereal solution becomes supersaturated, but deposits crystals on standing. A 'solution of quinine in ether is a better solvent for cinchonidine than ether itself, and coneequently the above method is so devised that the quantity of the quinine preeent is considerably reduced before applying the test. Cinchonidine has an abnormal solubility in ether. W. P. S.~ ~~ A Morphine Reaction, C. Reichard. (Phrm. Zeit., 1904, xLix., 523 ; through Chm. Zeit. Rep., 1904, xvii., 195.)-A small quantity of morphine, or one of its salts added to a mixture of formaldoxime sulphate with concentrated sulphuric acid, gives, on heating, an intense blue colour, even with quite minute traces of the substance. Atropine gives a brownish-black colour, disappearing on addition of water. H. A. T. The Identification of Colouring Matters in Absinthes. P. Onfioy. (Journ. Phamn. Chim., 1904, xx., 99-104.) The three principal colouring matters in genuine absinthe are chlorophyll, a vegetable yellow, and glycyrrhizin. In testing whether a sample contains only these colouring matters derived from the plants used in the manufacture, 200 C.C. of the liquid are evaporated until the alcohol is expelled.The residue should be turbid, and of a greenish-yellow colour. A clear aqueous residue indicates the absence of chlorophyll. The cold neutral liquid is twice shaken with amyl alcohol, which extracts the chlorophyll. The residual aqueous layer (which should be yellow) may contain glycyrrhizin. I t is concentrated to about 15 c.c., and treated with a few drops of sulphuric acid. This precipitates the glycyrrhizin in brown flakes, which are soluble in ammonium hydroxide, yielding a yellow solution. Many of the commercial samples of absinthe are weak in alcohol (35 to 40 per cent.), and hence cannot be coloured with chlorophyll, which is only stable in strong solutions of alcohol. I t is therefore replaced by artificial coal-tar colours, of which the most commonly employed are: soluble indigo carmine, solid yellow S, and a ponceau.The following dye-stuffs are also met with, though less frequently: Victoria blue, indulin blue, naphthol yellow, and Orange 11. In testing an absinthe containing a mixture of vegetable and coal-tar colours, 200 C.C. of the liquid are evaporated to dryness, the residue taken up with water, and the liquid filtered from the insoluble chlorophyll. If the filtrate has a blue or green shade, the presence of an artificial colour may be regarded as certain. This liquid is then extracted with amyl alcohol, giving an extract, A, and a residue, B. The extract A, which ought to be yellow (if blue, Victoria, blue), is evaporated to dryness, the residue taken up with water, and the liquid treated with a few drops of sulphuric acid, and again extracted with amyl-alcohol.The alcoholic extract is evaporated with a little unmordanted wool, the liquid being neutralized as exactly as possible with a few drops of ammonium hydroxide before complete evaporation. The residue, B, is evaporated in like manner with a little unmordanted silk. All colours that distinctly dye unmordanted wool may be regarded as coal-tar products. The following table gives the characteristic reactions of the different colours met with in commercial absinthe8 :Colouring Matters. Chlorophyll . . . Vegetable yellow Indigo carmine.. . Indulin blue ... Victoria blue ... Solid yellow S . . . Naphthol yellow Ponceau 3 R ... Orange 11. ... Glycyrrhizin .. . Solubility. Water. nsoluble soluble soluble soluble very soluble soh b 10 soluble soluble soluble soluble Ethyl Alcohol. very soluble soluble soluble soluble very soluble soluble soluble soluble soluble soluble Amy1 Alcohol Extract. Neutral. -______ rapid extraction, green slow extraction not extracted not extracted rapid extraction, blue extracted with difficulty extracted extracted with difficulty extracted not extracted -- Acid. yellow extract rapid ex traction greenish extract extracted rapid extraction blue extracted extracted extracted extracted not ex tract ed ~ _ _ _ Alkaline. -- yello w extract very slow extract ion not extracted not extracted rapid extraction red very slow extraction very slow extraction not extracted extracted not extracted Colour Reactions, Sulphuric Acid.._ - - brownish black violet blue reddish brown yellowish brown yellowish brown cerise red - Addition of Water. - - blue violet green, ;hen bluc orange dirty yellow reddish yellow yello wid brown - Hydro- chloric Acid. - yellow no change blue greenish yellow & brown orange makes colour paler no change irownisl yellow I Immonia. I yellow yellow rownisl violet red yellow yellow no change dark brown - A. Does not dye wool except when mordanted (alum 10 per cent., tartrate 5 per cent.). B. Dyes unmordanted wool. Sodium Iydroxide. yellow yellow rownish violet red no change yellow no change dark brown Sxtract. - A B B B k E C. A. M312 THE ANALYST, The Chemical and Physiological Assay of Digitalis Tinctures. G. Barger and W. V. Shaw.(Pharm. Jozmz., 1904, lxxiii., 249-254.)-1n the course of an examination of various digitalis tinctures prepared according to the directions of the British Pharmacopaeia, the authors made a comparative study of the two methods, chemical and physiological. The chemical part was limited to a determination of the digitoxin by Keller’s method (Bey., 1897,125). I n the physiological determina- tion of the activity of the tinctures and of the digitoxin obtained from them, frogs were used, the species being Rana tevzporaria. Comparative experiments were limited to frogs of approximately the same weight. The tinctures employed had an average of 3.4 per cent. of total solids and 0.0485 per cent. of “crude” digitoxin (Keller), or 0.031 per cent. of “pure” digitoxin. By making up a tincture containing a known amount of digitoxin (Merck), it was found that Keller’s method yielded less than one-half the digitoxin actually present.The minimum lethal dose of pure digitoxin (Merck) for frogs of 23 to 26 grammes in weight was 0.3 milligramme. By determining the minimum lethal close of the various tinctures, the actual amount of digitoxin in them was ascertained. The authors consider that at present the physiological method is the only reliable one for this kind of tincture. Digitalin and digitaleln were found to be much less toxic than digitoxin. w. P. s. The Distribution of Fat and Strychnine in Nux Vomica Seeds. H. W. Gadd and S. C. Gadd. (Paper read before the Brit. Pharnz. Co72j, Shefield, 1904.)-As Some trouble occurs in making the official liquid extract of nux vomica, on account of the fat which the seeds contain, the authors carried out a series of experiments to ascertain what portion of the seeds contains the most fat. For this purpose the seeds were freed from hairs, and analyses made both of the seeds and the hairy portion. The following results were obtained : Hairs ... ... ... ... ... 7.0 ... ... 0.5 Remainder of seeds ... ... 2.0 ... ... 1.5 FAT. STRPCHNIKE. Per cent. Per cent. Whole seeds (calculated) ... ... 2.25 ... ... 1.4 As the weight of the hairs amounted to about 5 per cent. of the whole, no material loss of strychnine would be caused by their rejection in making the liquid extract, whilst at the same time a considerable portion of the fat would be removed. The skins of the seeds were found to contain little fat, and there is therefore no advantage in rejecting them. I n making extracts from the hairs and the inner portions of the seeds, it was ascertained that the fat is more readily removed by alcohol (70 per cent.) from the hairs than from the denser portions. IT. P. s.

ISSN:0003-2654    

DOI:10.1039/AN9042900305

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年代:1904

数据来源: RSC

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THE ANALYST. 313 ORGANIC ANALYSIS. The Determination of Methyl Alcohol by the Iodide method. M. J. Stritar and H. Zeidler. (Zcit. anal Chem., 1904, xliii., 387-400.)-The method employed by the authors is practically identical with that devised by Zeisel and Fanto for the determination of glycerin (ANALYST, xxvii., 300; xxviii., 222). In test experiments 5 C.C. of an aqueous solution containing 0.0385 gramme of methyl alcohol were mixed in the small flask of the apparatus with 13.5 C.C. of pure hydriodic acid of specific gravity 1-96, and the following amounts of silver iodide obtained : (I) 0-2800 gramme, and (2) 0.2797 gramme ( = 0.0382 and 0.0381 gramme of methyl alcohol). In no case did the operation take longer than one hour from the time boiling commenced. It is essential that the concentration of the methyl alcohol solution should not exceed 1 per cent., and if possible not be less than 0.5 per cent.Obviously the absence of other substances that yield silver iodide or interfere with the process must be ascertained, such as, c.g., sulphur compounds, large amounts of chlorides, nitrates, etc. Dcterirnhtation of Methyl Alcohol in the Products of the Distillation of Wood.- Experiments are described in detail to show the influence of the different products on the results of the iodide method. The only substances that it is necessary to take into account are alcohols (allyl alcohol) and esters (methyl acetate). To obtain the correction for allyl alcohol, an aliquot portion (25 c.c.) of the solution is acidified with 5 C.C. of dilute sulphuric acid, and titrated with a solution containing 1.186 grammes of potassium bromate and 4.224 grammes of potassium bromide per litre, which is introduced with continual shaking, 0.2 C.C.at a time, at intervals of a minute, until the liquid becomes yellow. The number of C.C. of the bromide-bromate solution used gives the number of niilligrammes to be deducted from the weight of silver iodide in the methyl alcohol determination. The necessary correction for methyl acetate is obtained by determining the ester value of the solution in the usual manner. Crude wood spirit is prepared for the determination by diluting 5 C.C. of known specific gravity to 500 C.C. and using 5 C.C. of this solution. The weight of silver iodide obtained, multiplied by the factor 272.94, gives the amount of methyl alcohol in grammes per 100 C.C.Crude aqueous zooocl! spirit (Rohholzgeistwasser).-From 5 to 10 c.c., according t o the strength, are diluted with 40 C.C. of water, shaken for fifteen minutes with animal charcoal, filtered, and the filtrate and washings made up to 100 C.C. If an error of 2 per cent. is permissible, the treatment with animal cliarcoal may be omitted. Crzide pyroligwous acid.-Fifty C.C. are neutralized with sodium carbonate, and the liquid diluted to 250 C.C. and filtered, 100 C.C. of the still dark filtrate are rendered strongly alkaline with sodium hydroxide and distilled until 50 C.C. of the distillate have been collected, this is then treated with animal charcoal as above described. C. A. M.314 THE ANALYST.The Determination of Methyl Alcohol in Commercial Formaldehyde. M. J. Stritar. (Zeit. anal. Chenz., 1904, xliii., 401-403.)--Five C.C. of the formalin are diluted with 100 C.C. of water, treated with ammonium hydroxide in excess (about 10 C.C. of a 12 per cent. solution of ammonia are generally sufficient) and distilled, the first 50 C.C. of the distillate are rendered slightly acid with strong acetic acid and made up to 100 C.C. Five C.C. of this solution are then analysed by the iodide method (see preceding abstract), and the amount of silver iodide multiplied by the factor 54.57 to obtain the grammcs of methyl alcohol in 100 C.C. of the formalin. Formaldehyde itself acts upon hydriodic acid, yielding silver iodide as a, final product ; but the reaction takes place very slowly, and as only traces of formalde- hyde are left in the distillate obtained as described above, the results of the iodide method are not affected.Two samples of commercial formalin thus examined contained 16.5 and 15.14 grammes of methyl alcohol per 100 C.C. respectively. C. A. M. On the Quantitative Determination of Methoxyl. Wilhelm Kropatschek. (Mo?zatshefte f. Chew., xxv., 583.)--Tn Gregor’s modification (Monatshefte f. Chem., xix., 116) of the Zeisel method a solution of potassium arsenite in potassium carbonate is substituted for the mixture of amorphous phosphorus and water generally used as washing liquid, in order to prevent the formation of silver phosphide, supposed to be due to mechanically carried over phosphorus. It has since been shown that this may lead to serious errors, a crystalline precipitate containing iodine being deposited from the arsenite solution.The author now finds that a deposit of the formula KI+As,O, is indeed produced if the concentration of the washing liquid recom- mended by Gregor in his paper, but not actually used by him, is employed, but that exact results are obtained if the concentration does not exceed 1 to 2 per cent. By means of experiments on pure hydrogen iodide, prepared by the action of iodine OD formic acid-ie., from phosphorus-free materials-he also shows that the formation of the silver phosphide is due not to the mechanical carrying over of amorphous phosphorus, but to the presence of hydrogen phosphide in most ordinary samples of “ pure ” hydrogen iodide made from iodine and phosphorus. This hydrogen phosphide is completely absorbed by Gregor’s washing liquid. A.G. L. The Hydration of Alcohols by Calcium and Barium Oxides. L. Crismer (BUZZ. Xoc. Chiim. BcZg., 1904, xviii., 128, 129.)-If anhydrous methyl alcohol be heated with calcium oxide freshly prepared from marble and then distilled, the dis- tillates show critical temperatures of solution (in a suitable solvent, such as paraffin oil or petroleum spirit), corresponding to amounts of water ranging from 0-12 to 2 per cent. Hence the author concludes that the ordinary method of distilling methyl alcohol with lime ought to be abandoned. I n like manner ethyl alcohol is hydrated by barium oxide, though not by calcium oxide. The author has prepared pure methyl, ethyl, and propyl alcohols by utilizing their different critical temperatures of solution.He shows that the difference between the three values is a constant. Thus, the fol-THE ANALYST. 315 lowing critical temperatures were obtained with paraffin oil as the solvent : Methyl alcohol, 166" C. ; ethyl alcohol, 89.7"C. ; and propyl alcohol, 13.5" C, ; difference, 76.3" and 76.2O C. C. A. M. Notes on the Determination of the 100" Point on Ventzke'rJ Saccharimeter Scale. Schoenrock. (Zeits. Zt&e&td. ; through Chenz. Zeit. Rep., 1904, xii., 177.)- The author, in a very exhaustive paper, comes to the following conclusions : (1) To obviate the effect of various sources of light on different observers, the light should be purified by passing through a 1-5-centimetre film of 6 per cent.potassium bichromate solution. (2) According to Herzfeld's observations, a plate of quartz of 100" Vent& gives a rotation, at 20" C., of 34.657 scale degrees with pure sodium light. substance giving different values for different lights has not the same dispersion as quartz. (4) Increase of rotation value z1 is causgd by risihg temperature, according to the formula : (5) In the case of quartz, v is independent of t when the temperature of both quartz- plate and apparatus coincide. (6) If the rotation of an approximately normal sugar solution (this and the apparatus at 2Oo)=S,,,Ventzke, and at to=&, then s20 = S, + S,O*O00609 ( t - 20). (7) The rotation of a normal sugar solution at 20" with spectrally purified sodium light is 0.010 scale degrees greater than the corresponding angle of the normal quartz-plate of 100" Ventzke.(8) For accurate analyses observn- tion tubes, which can be filled after both cover-plates are in position, should be used. ( 3 ) vt = ~~~o + ~,,0*000148 ( t - 20). H. A. T. On the Reaction of Lard from Cotton-seed Meal-fed Hogs with Halphen's Reagent. Elton Fulmer. (JOZLY72. Amcr. ChCY72. Soc., sxvi., 837.)-The author finds that lard from hogs fed even for short periods on cotton-seed meal will give a coloration with Halphen's reagent, equivalent to an apparent content of cotton-seed oil of 0.4 to 15 per cent. The colour is given by lard rendered from all parts of the body of the hog, the strongest colour being given by kidney fat and the faintest by intestinal fat.The colour-producing substance is very persistent when once deposited, a reaction being given by fat from animals killed five months after receiving their last ration of cotton-seed meal. A, G. L. A Comparison of the Halogen Absorption of Oils by the Hubl, Wijs, Hanus, and McIlhiney Methods. L. M. Tolman. (Jozmz. Amer. Chent. xoc., xxvi., 896.)-Froni a. number of comparative determinations, the author comes to the conclusion that much better results are obtained by the Wijs and Hanus solutions than by the Hiibl. With the Hanus solution an excess of 60 to 70 per cent. is necessary to ensure rapid absorption ; the Wijs solution works well with an excess of 35 per cent., but gives higher results. I n either case thirty minutes is sufficient time for the absorption.For ordinary work, a solution of iodine chloride in carbon tetrachloride is best, when a determination of substitution is to be made ; otherwise acetic acid is the better solvent. Bromine solutions are not generally satisfactory. A. G. L.316 THE ANALYST, Contributions to the Analysis of Rose Oil. P. Jeancard and C. Satie. (BzdZ. Xoc. Chim., 1904, xxxi., 934-937.)-A green oil distilled from rose flowers after removal of the petals (Le., from the calices, pistils, stamens, etc.) had the following characteristics : Freezing-point, +So C. ; specific gravity at 15" C., 0.8704 ; optical rotation at 15" C., - 41" ; acid value, 6.12 ; saponification value, 22.4 ; stearoptene, 51.13 per cent. ; total alcohols, 13.99 per cent. ; and citronellal 13.56 per cent, The stearoptene consisted, in the main, of a substance melting at about 14" C.A specimen of oil obtained horn the tea-rose had a characteristic odour, and contained 72 to 74 per cent. of stearoptene, although its freezing-point was only 23.5" C. This stearoptene consisted of two bodies, one of which melted at about 14" C., and the other at 40" C., and apparently contained the same constituents as the oil from the calices. The authors point out that these facts show that it is not rational to base a judgment as to the purity of rose oil solely on the freezing-point, since the latter does not necessarily correspond with the proportion of stearoptene. In their opinion, it is best to make a determination of stearoptene and citronellal in the following manner : Ten grammes of the rose oil are mixed with 50 C.C.of acetone and cooled to about -loo, without shaking. The stearoptene is collected on a weighed filter, which is kept cool by a freezing mixture, and after being washed several times with acetone, is dried in vacuo and weighed. The filtrate, which should yield no further deposit on chilling, is distilled in a weighed flask, the distillation being finished under diminished pressure, and the residue of eleoptene weighed and submitted to further tests. Ten samples of Eastern oil of known purity thus examined gave results ranging between the following limits : Oil.-Freezing-point, 19" to 21" C. ; stearoptene, 18 to 23 per cent. EZeoptene.-Specific gravity at 15" C., 0.886 to 0.888; optical rotation at 15" C., - 1" to -3" ; solubility in 70 per cent.alcohol, 1.5; acid value, 1 to 2 ; saponification value, 10 to 12 ; total alcohols, 84 to 88 per cent. ; and citronellal, 30 to 40 per cent. In practice the authors have adopted provisionally the following limits : Provence Oil. Bulgarian Oil. Stearoptene, per cent. ... ... ... 30 to 35 18 to 23 Citronella1 in the eleoptene, per cent. . . 20 to 23 30 to 40 The limits for Provence rose oil are thus v e y similar to those given by Schimmel and Co. for Saxony rose oil. C. A. M. Testing Colloids. Edmund J. Mills and Archibald Gray. (Jourqz. SOC. Chenz. Iqzcl., xxiii. 526.)-This paper contains a preliminary account of a physical method for testing colloids-namely, the determination of the modulus of elasticity- which, while capable of giving comparative results of practical value, is not claimed to be entirely successful, The method consists in coating a standard cotton thread with a given colloid, drying the thread, and determining the modulus of elasticity of the coating, which is directly related to the stiffening power of the colloid.Brook's No. 12 white cotton thread is suitable on account of its freedom from finishing ingredients. The thread is first slightly singed to burn away the projectingTHE ANALYST. 317 ends surrounding it, and is then immersed in a standard solution or paste of the colloid, such as gum arabic, potato starch, etc. About a metre of this coated thread is then drawn repeatedly through a german-silver nozzle (Fig. l), the narrow bore of which is 0-5 millimetre in diameter.The thread is finally hung up to dry in the air with a weight of 18 grammes attached to its lower end. The dried threads are cut into about 0.2 metre lengths, and kept in closed tubes until required for testing. For the determination of the modulus the piece of thread is placed with its ends in the glass tubes carried by the two blocks (Fig. 2), which can be moved nearer to or further away f r o m e a c h other by means of t h e r i g h t FIG. 1, and left hand screw working in a bed beneath them. FIG. 2. The exposed lengthof the thread is next measured by a millimetre scale. The lowering of the thread, produced by hanging on it small S-shaped copper wires weighing 0.03 gramme, is determined by measurement with a cathetometer, or by using a low-power microscope with a micrometer eye- piece, the measurements being made through a screen of thin glass.Then, if E is the modulus, P the weight in kilogrammes, 1 the exposed Iength (rnillimetres) of thread, s the deflection produced by the weight, and r the radius of the thread, 13 E = x x --( = kilogrammes per square millimetre of section). 12 s rr4 The value of .the modulus for the thread alone was found by the authors to be 86.9, a quantity to be deducted from all the observations. Two independent effects take place in the coating of the thread with these colloids. The cotton in contact with the gum arabic, for instance, takes up the lime or gum, which becomes com- bined, and the modulus comes out too low. When this has ceased, only a stiffening effect takes place, and thus the results obtained on the stronger solutions are more nearly normal.The authors found the comparative values of potato starch, maize starch, and gum arabic by the modulus of elasticity to be as 3 : 4 : 7 (35.7 : 48.4 : SZ-S), and the prices of the two first-named were strictly in this ratio, Maize starch is too variable in price to admit of m y comparison. A. R. T. The Use of Sodium Peroxide i n the Qualitative Analysis of Organic Sub- stances. (D. Chenz. Ges. Bey.: 1904, xxxvii., 2155; through Chem. Zeit. Rep., 1904, xviii., 206.)-Advantage is taken of the oxidizing action of sodium peroxide for the identification of S, C1, Br, I, P, As, in organic compounds. The peroxide is mixed with one-twenty-fifth of its weight of a substance con- taining much C and H (naphthalene, cinnamic acid, etc.) and kept in well-stoppered bottles. H. H. Pringsheim.318 THE ANALYST. A small quantity of this oxidizing mixture with a few drops or grains of the substance to be tested is heated in a Bunsan flame. The cooled mass is dissolved in water and divided into two portions. One, rendered acid with HNO,, serves for the determination of halogens and phosphorus, in the other ; acid with HCI, sulphur and arsenic are determined. H. A. T. The Use of Pumice-Stone in the Incineration of Organic Matter. M. Duyk. ( A m . de Chim. anal., 1904, ix., 252-254.).-It is possible to obtain rapid and complete incineration of even the most refractory substances, such as albumin, yeast, wool, etc., by mixing them with an equal weight of coarsely powdered, recently ignited pumice-stone, and heating the mixture at it moderate heat in a muffle or over a gas flame. C. A. M.

ISSN:0003-2654    

DOI:10.1039/AN9042900313

出版商:RSC    

年代:1904

数据来源: RSC

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318 THE ANALYST. INORGANIC ANALYSIS. The Separation of Mercury from Molybdenum and Tungsten by Hydra- zine. (D. Chem. Ges. Ber., 1904, xxxvii., 2210; through Chem. Zeit. Rep., 1904, xviii., 205.)-Mercury can be separated from molyb- denum by the addition ol hydrazine sulphate to a hot ammoniacal solution of the mixture. The precipitation of molybdenum is prevented by the addition of tartaric or citric acid. In the separation of mercury from tungsten the addition of citric acid is unnecessary, and tungsten is finally precipitated by heating with fuming nitric acid to destroy the hydrazine sulphate. P. Jannasch and W. Bettges. H. A. T. The Determination of Palladium by Hydrazine. P. Jannasch and W. Bettges. (D. Chem. Ges. Ber., 1904, xxxvii., 2210; through Chem. Zeit. Rep., 1904, xviii., 205.)-To a hot, slightly acid solution of palladium aqueous solution of hydrazine sulphate is added.Reduction takes place very rapidly, with evolution of nitrogen, and palladium is precipitated. The washed and dried precipitate is ignited in a current of hydrogen. Palladium has thus been separated from K, Na, Mg, Zn, Fe. H. A. T. Determination of Palladium, H. Erdmann and 0. Makowka. (Berichte, xxxvii., No. 11; through Chem. News, xc., S9.)-By means of acetylene, either in aqueous solution or as a gas, palladium may be readily separated in cold, strongly acid solutions from platinum, iridium, rhodium, and gold. The yellowish-brown precipitate obtained is non-explosive; it is readily soluble in ammonia, and on ignition with a little ammonium nitrate in a current of hydrogen yields the pure metal.The presence of copper does not hinder the reaction, as is the case when hydraeine is used as the precipitating agent, A. G. L. The Microchemical Detection of Gold b y Means of the Colloidal Coloration of Silk Fibre. Julius Donau. (Momtshefte f. Chem., xxv., 545.)-The test depends on the red colour developed in a silk thread previously treated with a, reducing agentTHE ANALYST. 319 when dipped into a solution of auric chloride and exposed to the air. Cotton threads similarly treated may also be used; the reaction in this case, however, is not so sensitive, and the colour produced may be blue instead of red. The silk threads used are best prepared from raw silk by soaking it in 10 per cent. sodium or potassium hydroxide for three or four hours, well washing, and then soaking for several hours in either a solution of tannin or of a mixture of stannous chloride and pyrogallol. To carry out the test a pellet of wax is fastened to one end of the prepared thread, which is then cut off so as to leave a length of 1 centimetre.It is then dipped in a vertical position into a drop of the gold solution and examined under a microscope, using a magnification of 200. Using a silk thread treated with stannous chloride and pyrogallol, 0.000002 milligramme of gold may be recognised ; tannin threads are somewhat less sensitive. The presence of other metals, except iron, arsenic, and antimony, does not prevent the reaction ; silver gives a yellow colour, which is hidden, however, by the red of the gold, and may in a6y case be removed by treating the thread with nitric acid.Silicic acid and strong mineral acids prevent the reaction. To isolate the gold for the purpose of the test, the following procedure is recommended : The suspected solution is evaporated almost to dryness with lead filings; the residue is washed with water by decantation, and treated with aqua regia; a little sulphuric acid is then added to the decanted aqua regia solution, which is next evaporated to fuming, diluted, and filtered to remove lead ; the filtrate is evaporated nearly to dryness, and a drop tested as above. Gold could be detected in this way on 5 or 10 grammes of a mixture of iron and copper oxides with sand to which one ten-millionth part its weight of gold had been added.A. G. L. On the Examination of Tinned Wares. Utz. (Oesterr. Chem. Zeit., vii., 271.) -The tinning used is examined for lead by heating 0-5 gramrne of the scrapings with 7 to 8 C.C. of. strong sulphuric acid in a small flask for a short time. If the sample dissolves completely, no lead is present ; the solution obtained is occasionally dark in colour from the presence of organic matter. If lead is present, a white precipitate of lead sulphate is formed, which is filtered off and determined after diluting the sulphuric acid with 20 C.C. of a 5 per cent. ammonium oxalate solution, a little water, and an equal volume of alcohol. A. G. L. Determination of Minute Quantities of Arsenic in Copper Ores and Metallurgical Products. (Journ. SOC. Chem. Ind., xxiii., 524.)- The author uses a modification of the Marsh apparatus described by Chittenden and Donaldson (Amer. Chem.Journ. ; ChenzicaZ Pews, January 14, 1881). The low results always obtained by the presence of iron in the solution introduced into the apparatus are obviated by the use of sufficient copper to form a ‘‘ couple ” with the zinc. Forty grammes of zinc and 0-05 to 0.08 gramme copper are employed in each experiment. Two grammes of the finely ground sample are treated with 20 to 30 drops of T. C. Cloud. The arsenic deposited in the tube is finally weighed.320 THE ANALYST. sulphuric acid, then a sufficient quantity of nitric acid, and the mixture digested on the water-bath until decomposed. The excess of sulphuric acid is largely evaporated, the cooled residue.dissolved in water, boiled and filtered.The liquid is then electrolysed, using a platinum cone or cylinder as the cathode. The amount of copper being known by a previous determination, the electrolysis can be stopped when the solution contains the small amount of copper above specified. The anode is heated with the liquid until all deposit has dissolved, when the solution is evaporated down to 5 or 10 C.C. For quantities of arsenic up to 0.002 gramme, the timeataken for the experiment is two hours, and an additional hour for each 0.001 gramme. After the experiment the tuba containing the arsenical mirror is cut off, wiped clean, and weighed after being kept in a desiccator for twenty minutes. The arsenic is then dissolved out of the tube with nitric acid, and the clean and dry tube again weighed. A balance turning easily with 0.05 milligramme is required.A. R. T. Determination of Manganese in Drinking-Water. G. Baumert and p. Holdefleiss. (Zeit. Untersuch. Nahr. Genussmittel, 1904, viii., 177-181.)-The following method is proposed for the estimation of the small quantities of manganese occurring in some well waters (ANALYST, 1904, 201). The process is an iodometric one : From 250 to 1,000 C.C. of the water, according to the quantity of manganese present, are evaporated to a volume of 80 c.c., after adding 1 C.C. of concentrated hydrochloric acid. To separate any iron occurring in the water, a little zinc oxide or barium carbonate is added towards the end of the evaporation. The mixture is passed through a filter, and washed until the filtrate measures 100 c.c.; 5 C.C.of a 10 per cent. sodium hydroxide solution are then added to the filtrate, and the latter well shaken in a stoppered flask, the stopper being removed from time to time to admit air. Any manganous salts are oxidized. Five C.C. of a 10 per cent. potassium iodide solution are now added, and suficient concentrated hydrochloric acid, drop by drop, to completely dissolve the brownish precipitate, and leave a, clear yellow solution. After adding starch solution, the liberated iodine is titrated with a sodium thio-sulphate solution (0.30 gramme per litre) which has been pre- viously standardized on a solution containing a known amount of pure manganous chloride, and to which the above process has been applied.w. P. s. A New Separation of Thorium from Cerium, Lanthanum, and Didymium by Metanitrobenzoic Acid. (Journ. Amer. Chem. Soc., xxvi., 780.)-The author finds that metanitrobenzoic acid precipitates thorium quanti- tatively from neutral solutions 01 the nitrate, whilst cerium, lanthanum, and didymium are not precipitated. A quantitative separation of the thorium from these elements can be effected by two precipitations with this reagent from dilute solutions. The impure thorium metanitrobenzoate obtained by the first precipitation is best dissolved in dilute nitric acid, the thorium precipitated as hydroxide by an excess of potassium hydroxide, this precipitate dissolved in nitric acid, and the solution Arthur C. Neish.TRE ANALYST. 333: evaporated to remove free nitric acid, after which the precipitation with metanitro- benzoic acid is repeated.The reagent itself is readily prepared from benzoic acid ; as the ortho- and para-acids react similarly, though not so completely, the direct product of nitrating benzoic acid, containing about 75 per cent. of the meta-acid, may be used. The method gives good results in the analysis of monazite sands, and is more expeditious than Metzger's fumaric acid method, besides avoiding the use of alcohol. A. G. L. On the Separation of Calcium and Magnesium. Carl Stolberg. (Zeit. f- angew. Chern., xvii.., 741.) -According to the author, the separation of calcium from magnesium by means of the oxalate method is complete only if the calcium is precipitated twice from dilute slightly ammoniacal solutions containing sufficient ammonium chloride, a large excess of ammonium oxalate being used, and the pre- cipitate being allowed to stand for twelve hours in each case before filtering.As a, more rapid method he recommends conversion of the mixed calcium and magnesium salts into anhydrous sulphates by evaporation to dryness with sulphuric acid ; enough water is then added to the residue to form the hydrate MgSO, + 7H,O, after which the mass is treated with methyl alcohol containing 10 per cent. of absolute ethyl alcohol, which dissolves the magnesium sulphate and leaves the calcium sulphate undissolved. The residue is washed with methyl alcohol containing 5 per cent. of ethyl alcohol, and ignited and weighed as usual. The method gives excellent results. The addition of a slight excess of water does not appear to be injurious, but the whole should be heated on the water-bath for one minute with constant stirring to insure complete conversion of the magnesium salt into the hydrate. A.G. L. Chloride in Barium Sulphate precipitated by Barium Chloride. G. A. Hulett and L. H. Duschak. (Zeit. Anorg. Chern., XI., 196.)-The authors concur with the opinion of Richards that the chlorine present in barium sulphate precipi- tated by means of barium chloride should be determined, as it may amount to 1 per cent. of the precipitate. For this purpose the barium sulphate should be ignited at a temperature not exceeding 700" C. After weighing, it is dissolved in concentrated sulphuric acid, and the hydrogen chloride formed removed from the warmed solution by means of a current of dry air into a vessel containing silver nitrate.A. G. I;. The Determination of Sulphur in Iron. Allen P. Ford and Ogden G. Willey, (Journ. Amer. Clieuz. SOC., xxvi., 801.)-The authors believe that the different results often obtained by different analysts for the sulphur in the same sample of steel are due, not so much to differences in the methods used-provided that some form of the ordinary oxidation method is used-as to the want of skill of the operators. In their experience works chemists generally obtain correct values, whilst commercial chemists usually report low results. Too rapid solution appears to be one of the chief causes of error leading to loss of sulphur. The authors recommend covering the sample in a dish with a small inverted watch-glass before adding the acid.In322 THE ANALYST. this way the evolved gases are forced to remain in contact with the oxidizing liquid for some time; or else solution may be effected in an Erlenmeyer flask, covered with a small funnel. Instead of the ordinary oxidation method, they prefer to use Bamber’s method (Journ. Arner. Chem. Soc., xix., 114), in which the nitric acid solution of the steel is evaporated to dryness, the residue ignited after adding potassium nitrate, and the mass obtained extracted with dilute sodium carbonate. The solution is then evaporated to dryness with hydrochloric acid, the residue taken up’in dilute hydrochloric acid, and sulphuric acid precipitated as usual. The authors state that with this method accurate results are obtained even by analysts who have had no previous experience of the method.A. G. L. A Rapid Method for the Determination of Total Sulphur in Iron by Evolution. (Amer. Chem. Journ., xxxii., 84.)-The method, which is a modification of that of Walters and Miller, obviates the necessity for the expensive and unusual apparatus required in that method, and also materially reduces the time required for the operation. Two grammes of the sample are mixed with 1 gramme of the purest iron dust obtained by reducing the oxide in hydrogen, and the mixture is placed in a small porcelain crucible, and covered with 1 gramme of the iron dust. On top of this is placed a disc of ash-free filter-paper ; the lid is put on, and the crucible heated for ten minutes at the highest temperature of the blast-lamp.The contents of the crucible are then allowed to cool partially and placed in an ordinary evolution flask, after which the determination is finished as usual. The results obtained are said to be excellent, and a complete determination requires less than thirty minutes. The sulphur in the iron dust used must, of course, be determined. A. G. L. S. S. Knight. The Action of Acetic Acid on Portland Cement and Blast-furnace Slag. F. Hart. (Tonniizd. Zeit., xxviii., 809 ; through Chem. Zeit. Rep., xxviii., 241.)-Port- land cement and blast-furnace slag may be readily differentiated by means of alcoholic acetic acid solution as follows : 1 gramme of the finely-powdered sample is vigorously shaken for ten minutes in a closed flask with 100 C.C. of a 10 per cent.solution of acetic acid in absolute alcohol. After allowing the whole to settle for a few minutes the difficultly soluble slag may be recognised as light-coloured, glass- like particles ; any undecomposed Portland >cement remains as dark grains, whilst the precipitated silica is flocculent. I t is stated that 5 per cent. of slag may be recognised in Portland cement by this method. A. G. L. Determination of Nitrites in the Absence of Air. I. K. Phelps. (Amer. Journ. Science, xvii., No. 99; through Chenz. News. 1904, xc., 114, 115.)-The method proposed is based upon the interaction of nitrous and hydriodic acids. Nitric oxide and free iodine are liberated, the latter being subsequently indirectly titrated.The apparatus employed is the same as that described in the determination Qf nitric acid (ANALYST, 1903, 125). An amount of standard arsenious acid solutionTHE ANALYST. 323 slightly in excess of that required to take up the iodine set free later by the nitrous acid, and 25 C.C. of concentrated sodium carbonate solution, are placed in the flask, and boiled to expel air. The flame is then removed, the exit tube is lowered well into the mercury, and 7 C.C. of sulphuric acid (1 : 4) passed into the flask through the tapped funnel. This amount of acid is sufficient to liberate enough carbon dioxide to fill the flask, but still leave its contents alkaline. After the acid has been washed in and the mixture in the flask is quite cold, the nitrite solution to be analysed, con- taining 2 grammes of potassium iodide, is introduced, followed by sufficient sulphuric acid (1 : 4) to render the contents of the flask acid in reaction.A saturated potassium hydrogen carbonate solution is now added until the free iodine is taken up, and the mixture boiled for about five minutes to expel the nitrogen dioxide. After cooling, the solution is titrated with & iodine solution, using starch as indicator. In making the various additions to the flask, care must be taken that no air is allowed to, enter ; it is also necessary to expel the nitrogen dioxide before titrating. w. P. s. Analysis of Liquid Carbon Dioxide. R. Wog. (Zeit. ofeelztl. Chenz., 1904, x., 295-297.)-Anslyses are given of liquid carbon dioxide, the principal object of the investigation being a determination cjf the air in the carbon dioxide and also of the rate at which the air is liberated from the liquid. I t was found that the latter phenomenon takes place very gradually.For instance, the first 0-5 kilogramme taken from a cylinder gave 5.2 per cent. as the volume of air present. The next 0.5 kilogramme yielded 11.3 per cent. by volume of air. In the succeeding quantities taken from the cylinder the amount of air gradually diminished until, after with- drawing 5.0 kilogramrnes, only 1.1 per cent, was present. After standing overnight, the liquid remaining in the cylinder was again analysed, and found to contain 0-5 per cent. by volume of air. The average of all the results (fifteen) gave the amount of air as 5 per cent. by volume, a figure closely agreeing with that yielded by the first 0.5 kilogramme drawn from the cylinder.I t should be stated that the air mentioned above was the residue of gas unabsorbed by potassium hydroxide. I t contained only from 1-87 to 3-25 per cent. by volume of oxygen, and was therefore almost pure nitrogen, and not atmospheric air. w. P. s. Sources of Error in the Analysis of Coal. E. Goutal. (dim. d e Chint. anal. 1904, ix., 242-246.)-The calculation of the calorific power of coal by means of the author’s formula (ANALYST, xxviii., 128) may give erroneous results when the sample contains a high proportion of ash, owing to the influence of the volatile substances yielded by the schists themselves. This may be obviated by treating the powdered mineral with a mixture of methylene iodide with a third of its volume of benzene, and washing the separated fractions with pure benzene. Coal or anthracite thus treated is shown to give calculated calorific values in close agreement with those actaally determined. Another source of errm is introduced if oxygen prepared by electrolytic processes be used for the combastion in calorimeters. I n the author’s experience324 THE ANALYST. such oxygen sometimes contains as much as 2 per cent. and seldom less than 1 per cent. of hydrogen, with the result that the calorimetrical determinations are much too high. The oxygen should therefore be tested by calorimetrical determinations of naphthalene or other organic substance of known calorific value, purified if necessary by a preliminary combustion in Berthelot’s apparatus. C. A. M.

ISSN:0003-2654    

DOI:10.1039/AN9042900318

出版商:RSC    

年代:1904

数据来源: RSC

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324 THE ANALYST. APPARATUS. An ApparGtus for the Direct Determination of the Specific Gravity of Cement. Daniel D. Jackson. (Jozwn. Soc. Chem. Ind., xxiii., 593.)-By the t use of the author’s apparatus it is claimed that a determination of specific gravity accurate to 0.01 can be obtained in about ten minutes. The apparatus consists of a specially graduated burette having a bulb at the top, the bulb holding exactly 180 C.C. from 8 mark on the neck to a mark on the burette just below the bulb. The flask is of heavy glass, and has a capacity of 200 C.C. up to a mark on the neck of its hollow ground-glass stopper. To make a determina- tion 50 grammes of the dry sample are poured into the unstoppered flask, and the bulbed burette is filled with kerosene up to the mark on the neck of the bulb.About half the kerosene is then allowed to run into the flask, and then a further quantity to wash down any cement adhering to the neck of the flask, which should now be nearly full, and the contents free from air bubbles. The ground stopper is next inserted into position, when more kerosene is run into the flask from the burette until the level of the liquid reaches the mark on the neck of the flask stopper. The specific gravity may now be read off directly on the burette stem. Thus, if the kerosene has been run out exactly to the 180 C.C. mark below the bulb, the specific gravity of the sample will be 2.50, since- 200 - 180 = 20 ( = volume displaced by 50 gramrnes of sample), and ,=2.50. 50 2u The author gives tables of temperature correc- tions, and by observing the temperature of the kero- .sene before and after the determination increased accuracy may be obtained. Good samples of Portland The apparatus is made by Emil cemenb have a specific gravity of 3.05 or over. Greiner, 78, John Street, New York City. A, R. T.THE ANALYST. 325 On the Use of Bunsen Burners and Combustion Apparatus without Coal Gas. H. D. Gibbs. (Journ. Amer. Chem. SOC., xxvi., 760.)-In places where coal- gas is not obtainable, the author proposes to use the vapours of ethyl and methyl alcohol (95 per cent.) as a substitute. The alcohol is heated to boiling by means of an alcohol lamp, or other convenient source of heat, in a 4-litre boiler, from which sufficient gas is obtained to run several combustion furnaces at the same time. Under each section of the burners of the furnace an alcohol lamp is placed to avoid condensation. The pressure in the boiler does not exceed 10 millimetres. The same arrangement is used to supply gas to ordinary Bunsen burners. In this case it is well to have one burner alight in addition to those actually required, as this allows of more easy regulation of the size of the flame. A. G. L.

ISSN:0003-2654    

DOI:10.1039/AN9042900324

出版商:RSC    

年代:1904

数据来源: RSC

摘要:

THE ANALYST. 325 REVIEWS. A COMPENDIUM OF CHEMISTRY, INCLUDING GENERAL, INORGANIC, AND ORG~NIC CHEMISTRY. By Dr. CARL ARNOLD. Translated by Dr. J. A. MANDEL. (London : Chapman and Hall. This work, which is a translation of Professor Arnold’s ‘( Repetitorium der Chemie,” contains some 570 pages of reading matter, in which the author has contrived to embody a large mass of information probably in as satisfactory a manner as is possible in, for such a wide subject, so limited a space. The information given is accurate, also well up to date, as is especially shown in the chapters devoted to physical chemistry. The book is well printed, commendably free from typo- graphical errors, and contains a copious index. The work has had a large circulation in Germany, having reached its eighth edition, hence it must have a large sphere of usefulness.The information given is, however, hardly detailed enough for the advanced chemist, and the book would be by no means easy reading for the novice. The translator has done his part admirably. Price 15s. net,) W. J. S. THE OCCURREKCE OF ALUMINIUM IN VEGETABLE AND ANIMAL PRODUCTS, AND IN NATURAL WATEBS. By Drs. C. F. LANGWORTHY and P. T. AUSTIN. (London : Chapman and Hall.) This is an exhaustive compilation and reproduction in a condensed form of the numerous articles which have appeared for some years past in the various chemical and food journals, official reports, etc., and certainly is a monument to the authors’ patience and perseverance. The book cannot fail to be extremely useful to those interested in the subjecli on which it treats.The printing is good, the work has been carefully revised, and is furnished with an index occupying a fifth of the whole volume. W. J. S.326 THE ANALYST. THERMODYNAMICS AND CHEMISTRY. By P. DUHERI. Translated by GEORGE K. BURGESS. (London: Chapman and Hall, Ltd. 1903.) Price 17s. net. Pp. xxi + 445. The day of rule-of-thumb methods and empirical reactions in analytical chemistry fast drawing to a close; the modern analyst is not satisfied wit,h the knowledge that a reaction takes place, but must needs find out under what conditions it is complete, and how it is eEected by the presence of (‘ inert ” bodies. Thermodynamics, therefore, is a st.udy which should not be neglected. As this science concerns change of state, it has usually been treated of by that branch of mathematics which enables change to be expressed in a simple manner-the infinitesimal calculus ; and a want of training in higher mathematics has deterred many from familiarizing themselves with modern thermodynamic theories.This work is written for the non-mathematical student; in fact, the author states in the preface that he has supposed on the part of the reader no knowledge beyond that possessed by the graduate of a good high-school. I t is a little doubtful wh‘ether the author can be considered to have achieved entire success in his en- deavour to free the ideas of thermodynamics from all mathematical complications, for not only does the work bristle with formullfit, but these are used to define terms used.The differential calculus is not used, but the idea of a diflerential is brought in as a tangent to a curve, and it is not made quite plain why the tangent is introduced. If a page or two at the commencement of the work had been devoted to explaining the first principles of the differential calculus, and especially that if a law is ex- pressed by an equation or a curve, the differential expresses rate of change, many points would have been simplified. The author has assumed that the reader has a knowledge of co-ordinate geometry of three dimensions, which is not always taught at gnglish high-schools. The reader must therefore be prepared to use a certain amount of math em at ic s . The first five chapters are introductory; the first treats of work, energy, and equilibrium, while in the second the ideas are applied to heat; the next three are on chemical calorimetry and equilibrium and the principles of chemical statics.The sixth chapter is on the phase rule of J . Willard Gibbs, which treats of the relation between the number of components and the number of phases of a system; this rule, which is purely mathematical, is treated of with a minimum of mathematics, and in a manner which makes it plain to the careful reader. In succeeding chapters the various kinds of systems are described and illustrated by examples ; thus multi- variant systems-ic., those in which there are more components than phases-are illustrated by ternary alloys and solutions of several salts ; monovariant systems, those which have one phase more than there are components, by, among other illus- trations, the variation of fusing point with pressure ; triple points--i.c., points whero a substance csn exist in equilibrium in three phases-are explained, as well as the analogous multiple points of systems containing more than one component.Considerable space is devoted to mixed crystals, eutectic points, and critical states, and the chemical mechanics of perfect gases is discussed. The chapters on false equilibrium, and on chemical dynamics and explosions, which conclude the work,THE ANALYST. 327 are of considerable interest and importance, and should have practical bearing on analytical work, I t is annoying to constantly find letters dropped out in the printing, and to meet with so much repetition ; for instance, the heading of Section 322 is ‘‘ Every state of false equilibrium which is not limiting is indifferent,” a self-evident proposition ; yet this is discussed and explained by putting it into other words, and, finally, the proposition is again stated; all this takes up nearly half a page.The author uses the value 2.325 in many of his formulif?, as well as its reciprocal 0.4301 ; these are evidently the value of log. 10 and the modulus of common logarithms, which should be 2,3026 and 0.4343 respectively. The spelling of some chemical names-e.g., butric acid, propionitrite, benzine, and methylethylcetone-is not in accord with the usual methods. While the book is unnecessarily tedious, and requires very careful study and constant reference to formuk given in the earlier chapters, it is one that will repay the time spent in mastering its contents, and the earnest student will gain much valuable information and have his mind widened by reading it.H. D. R. THE EXAMINATION OF WATERS AND WATEIC-SUPPLIES. By J. C. THRESH, D.Sc, The interpretation of the results of water analyses is not to be undertaken lightly or without patient study, and the work now under review will be found very helpful to young practitioners, while most analysts of riper experience will find in its four hundred odd pages much to interest them, and will be glad to possess it as a book of reference, if only for the sake of the many illustrative analyses of waters from different sources which are here brought together. The work is divided into three parts, of which the first deals with the sources from which water is derived.Without undervaluing the information yielded by the mere analysis or examination of the water itself, the author strongly urges that the examination of its source is even of greater importance, and is sometimes absolutely essential to a right interpretation of the results obtained in the laboratory. This portion of the work deals with the geology of water-bearing strata, and discusses deep and shallow wells, surface-water supplies, rivers and streams, and includes a chapter on storage and distribution, written from a sanitary rather than from an analytical standpoint, The second part deals with the interpretation of the results of physical, chemical, microscopical, and bacteriological examinations ; while the third part is devoted to a detailed discussion of the collection of samples and of the various methods of analysis, whether for ordinary sanitary purposes or of a more complete character, including the determination of gaseous as well as saline contents.I n this section considerable space is given to methods of bacteriological and microscopical examination. Under the heading of “Nitratcs” two reduction methods by the copper-zinc couple are described-namely, reduction in slightly acid and in alkaline solution respectively. The indigo process is described, but the author only gives it half-hearted commendation, saying that he prefers the copper-zinc couple process. When the (Lond.), M.D. (Vict.), D.P.H. (Camb.). (London : J. and A. Churchill.)328 THE ANALYST.accurate determination of very minute quantities of nitrate is concerned, the author is probably right. I t should be observed, however, that the instructions given both for standardizing the indigo solution and for applying it seem insufficient for working the process with the simplicity, rapidity, and degree of accuracy of which it is capable. The phenol-sulphonic method of converting nitric acid into picric acid is described, but not recommended. The Crum process, singularly enough, is not given. The author mentions various modifications introduced from time to time in Forcham'mer's method for (' oxygen absorbed by oxidizable organic matter." Prob- ably most analysts in this country are in the habit of keeping the water, after adding the permanganate, for four hours at a temperature of 80" F., in accordance with the recommendation of the Water Committee of the Society of Public Analysts in 1881 (see ANALYST, vol.vi., 1881). Dr. Thresh prefers a temperature of 98" F., because that is the temperature of the ordinary warm incubator now found in most laboratories. Where, however, temperature is a purely arbitrary matter, but where uniformity is essentially desirable for the comparison of results, it seems a pity, on the mere ground of slight extra convenience, to introduce yet another alteration. The author only casually alludes to the fifteen minutes' period. Probably most public analysts, still following the recommendations of the Water Committee of 1881, are in the habit of making two determinations of oxygen absorbed-one after a period of four hours, and the other after a period of only fifteen minutes-attaching considerable significance to the ratio between the matter so readily oxidizable as to consume oxygen in the shorter period as compared with that oxidized during the main period of four hours. Referring to the opinion now largely held that a bacteriological examination is more important than a chemical analysis, the author observes that this is undoubtedly true in certain cases, but not in all, and that, while a properly made bacteriological examination may often afford indications of pollution which no chemical analysis can detect, yet the inferences drawn from the results of many so-called bacteriological examinations are often as fallacious as those derived from the results of chemical analyses.He observes that when we find that waters used for long periods by large communities are condemned by bacteriologists as being dangerously polluted, and that the results obtained from the same water by different bacteriologists differ to an extent that is impossible in a chemical analysis, our -faith in bacteriological examina- tions is somewhat shaken ; and that in any case a proper bacteriological examination is far more tedious and troublesome to perform than a chemical analysis, while the results are even more difficult to correctly interpret. The book is well printed in large, clear type, and is copiously illustrated. B. D. JUST before going to press we have received the painful intelligence that our esteemed colleague, Mr. William Chattaway, died suddenly on Friday night, Oct. 7, after a surgical operation. This sad announcement will, me feel sure, be read with universal regret.

ISSN:0003-2654    

DOI:10.1039/AN9042900325

出版商:RSC    

年代:1904

数据来源: RSC