摘要:

NOVEMBER, 1916. Vol. XL., No. 476. THE ANALYST. ABSTRACTS OF PAPERS PUBLISHED IN OTHER JOURNALS. FOOD AND DRUGS ANALYSIS. New Silicotungstic Acid Method for the Estimation of Alkaloids. A. Ferencz and L. David. (Pharm. Post., 1914, 47, 559-563; through J. Chem. SOC., 1915, 108, ii., 600.)-Ten C.C. of a solution containing the salt of the alkaloid are treated with 5 C.C. of 10 per cent. silicotungstic acid solution; the precipitate is collected on a filter, and washed with 10 C.C.of very dilute hydrochloric acid. The precipitate is then transferred to a flask, and shaken for five minutes with 5 C.C. of water and 10 C.C. of 20 per cent. sodium hydroxide solution ; after the addition of 15 grms. of sodium chloride and 100 C.C. of ether (in the case of nicotine, 50 C.C.of a mixture of ether and light petroleum are used), the mixture is shaken for ten minutes, allowed to separate, and one-half of the ethereal solution is drawn off and titrated with & hydrochloric acid, using iodoeosin as indicator. Estimation of Sulphates in Bread. C. D. Howard. (J. Ind. and Eng. Chem., 1915, 7, 807.)-O’Sullivan (ANALYST, 1914, 39, 425) and Cripps and Wright (ibid., 429) have shown that sulphuric anhydride tends to be lost under certain conditions when organic matter is destroyed by incineration.The latter authors and also Elsdon (ibid., 1915, 142) have described methods depending on extraction of the bread, flour, and the like, with acids without previous incineration. The method now described differs from that of Elsdon in the use of dilute instead of con- centrated hydrochloric acid, which the author has found to give rise bo trouble, due to progressive precipitation of protein substances.The air-dried bread (25 grms.) is digested with 200 C.C. of 5 per cent. hydrochloric acid for three or four hours on the water-bath at a gentle heat,” the cooled extract is filtered, the residue washed with warm water, and sulphate in the filtrate is precipitated by means of barium chloride.As a rule the precipitate is clean ; when otherwise, as shown by charring on ignition, the ignited precipitate is extracted on the Gooch crucible with acidulated hot water and reignited. G. C. J. Estimation of Fat in Ice Cream by the Babcock Method. C. A. A. Utt. (J. Ind. and Eng. Chem., 1915, 7, 773.)--The hydrochloric-aoetic acid method is not satisfactory if much gum thickener, gelatin, or condensed milk has been added, a,462 ABSTRACTS OF CHEMICAL PAPERS white precipitate tending to risein theneck of the bottle and obscure the fat column.A mixture in equal parts by volume of sulphuric acid (sp. gr. 1.83) and glacial acetic acid (99-5 per cent.) gives excellent results.The sample is warmed to 40' C., and, if the fat has separated, a little powdered sodium hydroxide is added to aid emulsification. Of the well-mixed sample, 9 grms. are weighed into a 10 per cent, Babcockmilk bottle, 12 to 15 C.C. of the acid mixture are added, the whole shaken, and then heated in a, hot water-bath, with occasional shaking, until of a dark chocolate colour. The bottles are centrifuged for ten minutes, shaken again, filled to the neck with hot water, the contents mixed, and centrifuged again for three minutes.Boiling water is added to bring the fat column into the graduated neck, and the tubes are centrifuged again for two minutes. The author reads from the bottom of the fat to the extreme top of the meniscus, The Babcock reading, multiplied by two, gives the percentage of fat in the sample.The extreme error of the method, with ice cream of 12 to 17 per cent. fat content, is 0.15 per cent. on the sample. G. C. J. Estimation of Hgdrastine in Plants and in Extracts of EVdrast8s Cunud ensis by the Methods prescribed in the Various Pharmacopaeias, and a New Method for the Estimation of Berberine in Extracts. L. David.(Pharm. Post., 1915, 48, 1-4; through J. Chem. Soc., 1915, 108, ii., 601.)-The author has determined the solubility of hydrastine in various solvents; 1 grm. of the substance is dissolved by 227.27 grms. of ether at 20° C., by 22727027 grms. of light petroleum (boiling-point 40° to 60' C.) at 15' C., by 11627.88 grms. of light petroleum (boiling-point 50" to 85" C.) at 15* C., and by 1791 grms.of benzene at 15' C. Hydrastine is soluble in chloroform. The methods given in the German and Belgian pharmacopoeias are the most trustworthy for the estimation of hydras- tine ; then follows that of the Austrian pharmacopoeia, whilst the French, Dutch, Swiss, and U.S.A. methods are untrustworthy, as the hydrastine obtained by their use is very impure. The U.S.A. method may be improved by removing the alcohol before the hydrastine is extracted with ether.I n the estimation of hydrastine, alcohol must be removed previously, berberine should be separated by precipitation with potassium iodide or hydrochloric acid, and the ethereal extract must be mixed with light petroleum, and the mixed solution treated with tragacanth. A method proposed for the estimation of berberine in hydrastine extracts depends on the precipitation of berberine and hydrastine by potassium bismuth iodide, and the separation of the hydrastine by extraction with ethyl acetate.The precipitate is then treated with 10 per cent. sodium hydroxide solution, and the berberine sxtracted with a mixture of equal parts of ether and chloroform. Estimation of the Quantity of Meat Extract in Soup Tablets.T. Sudendorf and 0. Lahrmann. (Zeitsch. Urtters. Nahr. Genussm., 1914, 29, 1; through J. SOC. Chm. Ind., l915,34,1027.)-Ten grms. of the sample are dissolved in water, the solution diluted to 100 c.c., filtered, and 20 C.C. of the filtrate is mixed with 10 C.C. of 1 hydrochloric acid and the mixture evaporated to dryness. The brown-black residue is treated with water, neutrslised with alkali solution, d o gFOOD AND DRUGS ANALYSIS 463 litmus as indicator, then diluted to about 75 c.c., and 1 per cent. permanganate solu- tion containing 2.5 per cent.of sodium chloride is added, drop by drop, until a slight excess is present. The excess of permanganate is destroyed by the addition of 3 per cent. hydrogen peroxide solution containing 1 per cent.of glacial acetic acid, the mixture heated for ten minutes on a water-bath, filtered, and the filter washed with hot water. The filtrate is evaporated to a small volume, transferred to a 50 C.C. flask, diluted to about 20 c.c., 10 C.C. of 10 per cent. sodium hydroxide solution and 20 C.C. of saturated picric acid solution are added, the mixture is diluted to 50 C.C.after the lapse of five minutes, and the coloration compared with that of a standard dichromate solution in the usual way. (See ANALYST, 1909, 34, 475.) Oil of Pistncia Lentiscus. E. Sernagiotto and N. Vita. (,d?zn. C h h . anal., 1915, 4, 92-93.)-The cold-drawn oil, freed from substances volatile with steam, ha.d the following characteristics : Sp. gr. at 15' C., 0.9188 ; butyrorefracto- meter reading (Zeiss), 66.0 ; acid value, 15.92 ; saponification value, 165.58 ; saponification value after acetyl'ation, 203.03 ; Hehner value, 94-82 ; iodine value, 83.61 ; and iodine value of fatty acids, 85.96.The fatty acids consisted of palmitic and oleic acids. C. A. M. Theory of Wetting Power and the Determination of the Wetting Power of Dipping and Spraying Fluids containing a Soap Basis. W.F* Cooper and W. H. Nuttall. (J. Agric. Sci., 1915, 7, 219-239).--It is recognised that the efficiency of sheep-dips or agricultural sprays does not depend solely on the strength of the toxic constituent, but that its ability to wet and spread over the greasy surface to be treated is a matter of the greatest importance. This wetting power cannot be estimated by chemical analysis, and the factors which operate form the subject of a lengthy theoretical discussion in the present paper.To a, certain extent the wetting power of a liquid towards a solid depends on the condition that the surface tension of the solid be greater than the sum of the surface tension of the liquid and the interfacial tension. This latter is a function which comes into play, for example, when a drop of oil is suspended in dilute alcohol of the same density, and is the tension existing at the interface between the two immiscible liquids.A liquid having a good wetting power should have a low surface tension and a low interfacial tension in relation to a greasy or waxy surface, but the latter tension is the more important in determining the wetting power, since a low inter- facial tension enables the liquid to spread over the whole surface, even if its own surface tension be fairly high.But the general problem is complicated by secondary factors-viz. , the solvent properties of the wetting liquid, which ensure actual contact between the liquid and the solid, and the phenomenon known as surface concentration (capillary adsorption).This last has a curious effect on the physical surface properties of liquids containing saponin or gdatin, causing them to '' run " very readily, forming liquid planes the high surface viscosity of which prevents rupture and formation of globules. On account of these and other complications,464 ABSTRACTS OF CHEMICAL PAPERS no perfectly general and satisfactory method for the determination of wetting power has yet been evolved, but in the case of liquids prepared with a soap basis, the surface tensions of which are substantially constant, comparative valuations may be obtained in a simple manner by an estimation of the interfaqial tensions towards a thick neutral oil (liquid vaseline) taken to represent the greasy solid to be treated.The method employed is a modification of Donnan’s drop-pipette method. The standard oil is run from a pipette, the end of which is bent round so as to point upwards, immersed in a column of aqueous liquid containing the fluid to be tested at a concentration similar to that recommended for practical use. For com- parative purposes the interfacial tension may be taken as inversely proportional to the drop number, and the wetting power as directly proportional to the same.The aperture of the pipette is somewhat restricted, and ground perfectly level ; the walls of the aperture should be fairly thin. The portion of the pipette above the bulb has a side branch for filling by suction, and both side branch and upper vertical limb are controlled by stopcocks; in addition, a piece of fine capillary tubing is attached to the top of the pipette to regulate the flow of oil so as to allow about ten seconds between the drops when immersed in water.The capacity of the pipette may be 25 c.c., and the diameter of the aperture 2.7 mm. After adjusting the charged pipette in a cylinder containing the liquid to be tested, the stopcock is opened and the number of drops counted as the oil passes from the upper mark to the lower mark.If streaming occurs, as with liquids of very low interfacial tensions, a pipette with smaller orifice must be used. The value of the standard vaseline should be determined against distilled water at 20’ C., and the wetting power of the solution expressed as the ratio of its drop number to that of pure water x100.Quite useful results may be obtained by this method with most of the commercial fluids, but it must only be applied to soap solutions, and is valueless for saponin and similar preparations. J. F. B. Occurrence and Estimationof Citric Acid in Wine. (R. Kuna. Arch. Chem. Mikrosk., 1914 ; through J. Chzem. SOC., 1915, 108, ii., 595-596.)-Stahr’s reaction is recommended for the detection of citric acid; the reaction depends on the formation of a white precipitate of pentabromacetone, when bromine and potas- sium permanganate act on citric acid.The author prefers to use potassium bromide in place of bromine ; 10 C.C. of the solution to be tested are treated with 1 C.C. of sulphuric acid (1 : 1) and 0.3 C.C. of 37.5 per cent.potassium bromide solution; 1 C.C. of 5 per cent. permanganate solution is then added, the mix- ture heated for five minutes at 45’ C., and any traces of manganese dioxide are removed by addition of a drop of ferrous sulphate solution containing sulphurio acid. A distinct turbidity is obtained with 1 mgrm. of citric acid. Wines usually give a precipitate with bromine done, and in this case the test is modified by evaporating 50 C.C.of the wine to 10 c.c., adding 2 C.C. of dilute sulphuric acid, then 10 C.C. or more of saturated bromine water, diluting the mixture to 50 c.c., and filtering it through kieselguhr. The filtrate is then tested as described. Red and white wines examined all yielded a reaction for citric acid, although the quantity present was usually very small.TJsing a larger quantity of the wine (100FOOD AND DRUGS ANALYSIS 465 c.c.) the pentabromoacetone formed may be collected, dried over sulphuric acid, then washed with very dilute sulphuric acid, again dried, and weighed. For the detection of citric acid in milk, the latter is warmed with dilute sulphuric acid, the serum treated with tannin to remove soluble proteins, filtered, and the test applied to the filtrate. Fresh milk appears to contain more citric acid than does old and curdled milk. In the case of jams, a portion of the sample is diluted with water, acidified with a few drops of sulphuric acid, the solution is mixed with about twice its volume of alcohol, and filtered.The filtrate is neutralised with ammonia, evaporated to expel alcohol, again filtered after the addition of dilute sulphuric acid, and the filtrate used for the test.If the filtrate gives a precipitate with bromine, it is treated i s described under wine. Fruit juices also require a similar treatment before being tested. Colorimetric Determination of Pentoses and Methylpentoses in Wine. F. Schaffer. (Jahresversamml. Schweiz.Vereiizs. anal. Chem., Zurich, June 5, 1915 ; through J. SOC. Chem. Ind., 1915, 34, 1025.)-The following method is much more expeditious than that of Tollens, but requires strict adherence to the procedure described. Wines containing more than 3 per cent. of sugar must first be fermented. One hundred C.C. of the sample are evaporated to one-third of its volume, made up to 50 c.c., and heated under a reflux condenser for two hours with 22 C.C.of hydrochloric acid of sp. gr. 1.19. The liquid is next diluted to 100 c.c., and 92 to 93 C.C. are rapidly distilled (cork connections should not be used) and made up to 100 C.C. Five C.C. is transferred to a wide test-tube containing at least 0.2 grm. of resorcinol, 10 C.C. of hydrochloric acid of ap. gr. 1.19 are added, and after a rubber stopper, carrying a vertical tube of 6 mm.diameter, has been inserted, the test-tube is heated for ten minutes in boiling water. The liquid is then quickly cooled and compared with a standard solution which may be prepared by operating as above with a solution of arabinose of known titre, or with a wine containing a known amount of pentoses and methyl-pentoses, or a solution of (‘ Paper Red E ” (SOC.Chim. Ind., Basle) may be employed (0.01 per cent. solution diluted 7.5 times before use; this corresponds in colour to a 0.01 per cent. solution of pentose). The apparent pentose-content thus found must be corrected as described below for the influence of methylpentoses (rhamnose). To determine the latter, 5 C.C. of distillate (see above) is transferred to the test-tube, which contains sufficient pure vanillin to cover the tip of a knife-blade ; 10 C.C.of hydrochloric acid are added, and the tube is heated as before, but only for five minutes. The liquid is quickly cooled without agitation, and compared with a standard which may consist of a 0.01 per cent. solution of Merck’s indigocarmin. sicc. puZv. diluted 5.5 times before use, and treated, if necessary, with a trace of Chinese ink.The content of methylpentoses of the wine so found, multiplied by 0.6, must be subtracted from the apparent pentose content obtained by using resorcinol, to arrive at the true pentoee-con tent. In 200 natural wines (Naturwezne) examined, the ratio arabinose : rhamnose was never less than 2 : 1, whilst in ( ( marc ” wines, yeast wines, and raisin wines, it frequently ranged between 0.5 : 1 and 1 : 1.Alkaloids of Tobacco Extract. E. Noga. (Fachlich Mitt. osterr. Tabakregie, 1914; through J. Chem. SOC., 1915, 108, i., 711.)-Residues from Turkish tobacco466 ABSTRACTS OF CHEMICAL PAPERS were extracted systematically with water, and the extract evaporated in a vacuum. By the use of benzene, a small quantity of alkaloid, which was not volatile with steam, was obtained from this extract, and was separated by distillation into four fractions : (1) Nicotoine, C,H,,N, colourless, mobile liquid, with a peculiar intense odour resembling that of pyridine; boiling-point 208' C.; sp. gr. at 21'/4O C. 0.9545, ny = 1.5105. It gives the usual alkaloidal reactions.With hydrochloric, sulphuric, and picric acids, mercuric and platinic chlorides, it yields, in part, well-crystallised salts of definite melting-point. (2) Nicoteine. (3) Isonicoteine, Cl0HI2N2, colour- less, viscous, oily liquid, with a rather powerful, very persistent odour. I t is optically inactive, and has boiling-point 293" C. (darkening), sp. gr. a t 20"/4" C. 1.0984, & = 15749.With hydrochloric, sulphuric, and picric acids, mercuric, platinic, and auric chlorides, it yields, in part, well-crystallised salts. It forms a methiodide. I t is converted by oxidation into nicotinic acid, gives the pine-shaving reaction, and immediately decolorises potassium permanganate. It probably has the following constitution : CH--CH, CHQCR*CH \ c.c B I \N=CH/ \N ( CHJ .C H ~ (4) Nicotelline, CIOHsN2, melting-point 148" C., boiling-point above 300" C. (Zoc. cit.). Method for the Determination of Tobacco Resin and its Application to Various Tobaccos. J. von Degrazia. (Fachliclze Mitt. osterr. Tabakrcgie, 1914, 1-4; through J . Chem. Soc., 1915, 108, ii., 603-604.)-Two portions of 60 grms. each of the dry powdered tobacco are extracted in a Soxhlet apparatus with ether, about 100 grms.of ether being used for each portion. One of the ethereal solutions is then washed with water containing a small quantity of acid to remove nicotine, the ether evaporated, the residue dissolved in 90 per cent. alcohol, and the solution strongly cooled. After the separated wax has been removed, the alcoholic solution is boiled with the addition of 150 C.C.of 2 per cent. potassium hydroxide solution, and the mixture is extracted with ether ; the ethereal solution contains the tobacco resin, together with small quantities of ethereal oils. The solution usually has a reddish-brown colour, but in the case of Cserbel tobacco it has a green colour. After the ether has been evaporated, the residue of tobacco resin is weighed.The alkaline solution contains the resin acids and the resin alcohol ; the latter is in suspension, and is separated and weighed, whilst the resin acids are separated by extraction with ether in the usual way, the ethereal solution evaporated, the residue weighed, the acids dissolved in alcohol, and the tobaccic acid precipitated by the addition of alcoholic lead acetate solution.The lead salt is separated by filtration, and the filtrate mixed with ten times its volume of water acidified with nitric acid ; the B-tobacco acid which separates in flecks is collected, dissolved in ether, the solution evaporated, and the residue weighed. The y-tobacco acid is found by difference. The other portion of the ethereal solution is evaporated, and the residue extracted with alcohol to dissolve the u-tobacco acid; the alcoholic solution, which contains tannin and nicotine in addition to the acid, is evaporated,BACTERIOLOGICAL, PHYSIOLOGICAL, ETC. 467 the residue heated with very dilute potassium hydroxide solution, cooled, filtered, the filtrate neutralised, and the separated a-acid collected. The following table shows the composition of the reains from various tobaccos expressed as percentages of the latter ; the figures indicate that it is possible to differentiate between different kinds of tobacco : Wax. -- 0.59 9.55 0.55 0.77 1.32 0.69 1-48 1.00 Kind of Tobacco. Resin. 2.64 1-97 1-37 5.75 3-41 3.46 5.88 3-80 Havana ... ... ... ... Brazilian . . . ... ... ... Java ... ... ... ... Virginian . . . ... ... ... Hungarian . . . ... 1.. Cserbel (Nicotiana rustica) ... Dalmatian . . . ... ... Turkish ... ... ... . .. Total Besin. 4-65 3.36 4.45 7.59 5-15 4.57 7.86 7.00 Acids. Resin Alcohol. -_I__ -- 1.44 0.93 0.96 0.86 0.83 1.04 1-22 2.02 0.18 0.12 0.27 0.43 0.24 0.03 0-26 0.32 I 9.38 0.32 1 -75 0.44 0.65 0.04 0.45 0.81 0.01 0.02 0.10 0.02 0.02 None 0.05 0.07 (Cf. ANALYST, 1914, 39, 220.)

ISSN:0003-2654    

DOI:10.1039/AN9154000461

出版商:RSC    

年代:1915

数据来源: RSC

摘要:

BACTERIOLOGICAL, PHYSIOLOGICAL, ETC. 467 BACTERIOLOGICAL, PHYSIOLOGICAL, ETC. Culture Media employed for the Bacteriologieal Examination of Water. 111. Composition of the Gases formed in Lactose-Peptone Fermentation Tubes. E. M. Chamot, C. M. Sherwood, and R. C. Lowary. ( J . Amer. CFkm. Xoc., 1915, 37, 2198-2204.)-The gases formed by faecal bacteria in lactose-peptone media increase in volume with an increase in peptone concentration.The propor- tion of carbon dioxide in the gases increases with an increase in peptone, meat, or liver, until an equivalent of about 4 per cent. of peptone is reached, after which the amount of carbon dioxide remains substantially constant at 30 per cent. Hydrogen decreases with an inorease in the peptone concentration until 4 to 5 per cent. of peptone is reached, after which the quantity of this gas remains constant at about 60 per cent.The ratio of carbon dioxide to hydrogen (together with other gases not absorbed by potassium hydroxide) varies with the concentration of the nitrogenous substances present in the medium. The gases do not contain methane unless the inoculated medium stands for over twenty-four hours in free contact with oxygen (air), but a small quantity (2 to 3 per cent.of nitrogen) is always present. An excess of oxygen retards gas formation, and tends to increase the quantity of carbon dioxide. The total volume of gas formed is proportional to the volume of the liquid contained in the fermentation tube. The authors used a fermentation tube consisting of a cylindrical vessel of about 300 C.C.capacity; a short stem at the bottom of the vessel was provided with a tap and connected with a reservoir, whilst the top of the vessel was drawn out to form a capillary, through which the gases were passed to a, Hempel burette for analysis. The presence of such substances as bile, bile-salt, or468 ABSTRACTS OF CHEMICAL PAPERS phenol, in the medium retards gas formation, but does not materially alter the composition or total volume of the gas formed. (See also ANALYST, 1915, 351, 446.) w.P. s. Reaction of the Pancreas. J. H. Long and F. Fenger. (J. Amer. Chem. Soc., 1915,37,2213-2219.)-All authorities agree that the pancreatic juice is distinctly or even strongly alkaline in reaction; but this applies to the juice as a secretion alone, and is not necessarily the reaction of the organ itself or of the juice pressed from it.If a pancreas be cut open, even before it has been removed from the animal, and tested with litmus paper, a well-defined acid reaction is always observed. By subjecting minced pancreas to centrifugal action, the mass may be separated into three layers-namely, a lower layer which is largely protein, a middle layer of clear liquid, and an upper fatty layer.The liquid layer has a distinctly acid reaction, the ionisation constant being represented by the expression CH = 29 x 10-7. The liquid is rich in phosphates, the acid reaction seems to be due to acid phosphates. w. P. s. Comparison of Methods for Determining Putrescibility or Oxygen Demand. F. E. Hale and T.W. Melia. (J. Ind. and Eng. Chem., 1915, 7, 760- 764.)-As the result of experiments described in the paper, the authors arrive at the conclusion that the dilution method of Jackson and Horton, using methylene green (J. Id. and Eng. ChLsm., 1909,1, 328) or methylene blue, as suggested by Lederer (Am, J. Pub. Health, 1914, 4, 241), is the only trustworthy method for determining oxygen required to prevent putrescibility.I t is said that " the English method " as at present practised is subject to grave and uncertain errors, among them loss of oxygen, and is therefore quite untrustworthy. G. C. J. Note by Abstractor.-The English method referred to is presumably that formu- lated in the Eighth Report of the Royal Commission on Sewage Disposal, but no reference is given to this report, nor is the method described in detail in the paper.Estimation T. S. Harding. diagram indicates of Ramnose by Enzymic Hydrolysis. C. S. Hudson and (J. Amer. Chem. SOC., 1915, 37, 2193-2198.)-The following the various steps in the hydrolysis of rafinose by enzymes : Raffinose. I (1) I (BY invertase) (3) I (BY emulsin) \L Melibiose + Laevulose I \L Cane Sugar + Galactose (2) I (By melibiase) Galactose + Dextrose (4) j (BY invertase) & Dextrose + Laevulose 4BACTERIOLOGICAL, PHY STOLOGICAL, ETC.469 According to the method proposed, the raffinose is estimated by the measure- ment of step (2) in the hydrolysis. The melibiase employed for the inversion is prepared from bottom yeast as described previously by the authors (ANALYST, 1914, 39, 443).This product is free from maltase, cellase, Iactase, trehalese, inulase, and diastase, but it contains a very powerful invertase ; the presence of this enzyme is not, however, of importance, since top yeast yields an extract rich in invertase amd quite free from melibiase, and this top yeast extract can be used to complete step (I), whereupon an accurate measure- ment of step (2) may be carried out.The only interfering substance is melibiose itself, which would be estimated as raffinose by the method. Since melibiose reduces Fehling's solution, whilst raffinose does not, it is possible to exclude the former from consideration in certain cases. Thus, an aqueous extract of cottonseed meal contains a very small quantity of reducing sugars, but much raffinose.Low- grade beet sugars are nearly free from reducing sugars, but often contain raffinose. The method appears to be sufficiently conclusive, therefore, for the estimation of raffinose in these products. I n the analysis of plant material and sugar mixtures in general, the method serves for the estimation of raffinose and melibiose, but does not distinguish them.The solution in which the raffinose is to be estimated is clarified with neutral lead acetate, end the excess of lead is removed as oxalate or sulphide; it is then neutralised, acidified with a few drops of acetic acid, and diluted to 100 C.C. Not more than 13 per cent, of total sugars should be present. To 95 C.C. of the solution are added 5 C.C. invertase solution prepared from top yeast (Zoc. cit.) and a few C.C.of toluene. The mixture is shaken and kept at the ordinary temperature until its rotation becomes constant ; this usually takes from eighteen to twenty-four hours. At this stage all the cane sugar present has been inverted, and all the rafinose has been hydrolysed into melibiose and lavulose. All the polariscopic readings should be taken at 20" C.To 95 C.C. of the solution which has been hydrolysed by invertase are now added 5 C.C. of bottom yeast extract (prepared as described), and the rotation is observed immediately after mixing ; the reading should correspond with that calculated from those of the bottom yeast exbract and the solution to which it has been added. The solution is kept at ordinary temperature, and its rotation measured from day to day.A change of rotation in the IEVO direction indicates the hydrolysis of melibiose. The specific rotation of this sugar is +143", and since 1 grm. of it yields 0.527 grm. of dextrose and the same quantity of galactose, which have specific rotations of + 52.5" and + 81" respectively, the specific rotation of melibiose changes from +143O to + 70.4' on hydrolysis.If the readings are observed in a 200 mm. tube, a solution containing 1 grm. of melibiose per 100 C.C. will change in rotation during hydrolysis 0.347" or 4.18" Ventzke. Each degree Ventzke change of rotation indicates, tnerefore, 0.239 grm. of melibiose in the final solution, a quantity which corresponds with 0.352 grm. of anhydrous raffinose, and the amount of the latter in the original solution may be calculated. Results of estimations of raffinose in admixture with cane sugar, dextrose, Iavulose, invert sugar, lactose, maltose, cellose, and trehalose, are recorded.When 1.5 per cent. of raffinose was present, from 1.45 to 1.53 per cent. was found by the method. w. P. s.470 ABSTRACTS OF CHEMICAL PAPERS Toxins and Antitoxins.IV. : New Reaction for Characterising Toxins. I. I. Ostromisslensk. (J. Russ. Phys. Chern. SOC., 1915, 47, 313-317; through J. Chem. SOL, 1915, 108, i., 752-753.)--In order to ascertain if there exists an antitoxin corresponding with a given toxin, or if a particular poison represents a toxin, the following method may be employed. I n a mixture of 3 C.C. of the toxin or poison with about 3 C.C. of normal serum, 0.36 grm. of pure sodium chloride is dissolved, the liquid being maintained at 37Oto 37.5" C. for three to thirty-six hours. In these conditions the globulin of the serum will undergo transformation into the corresponding antitoxin. Consequently, if the antitoxin sought really exists, the mixture should become atoxic after this treatment. With the toxins of tetanus, diphtheria, and botulismus, positive results were obtained, but the treatment with normal serum and sodium chloride is without effect on the toxicity of morphine and strychnine.

ISSN:0003-2654    

DOI:10.1039/AN9154000467

出版商:RSC    

年代:1915

数据来源: RSC

摘要:

470 ABSTRACTS OF CHEMICAL PAPERS ORGANIC ANALYSIS. Salting Out of Amino-Acids, and their Separation by Means of Neutral Salts. P. Pfeiffer and F. Wittka. (Bw., 1915, 48, 1041-48; through J. &c- Chem. I d . , 1915,34,976.)-0n addition of saturated solutions of neutral salts to satu- rated solutions of amino-acids, glycocoll, tyrosine, and aspartic acid gave no precipi- tate ; alanine was only precipitated by ammonium sulphate, whereas d,Z-leucine and d,Z-phenylalanine were precipitated by sodium and potassium chlorides, potassium oxalate, magnesium and sodium sulphates, sodium and potassium acetates, but best by ammonium sulphate.In these precipitates, the amino-acids are not combined with the salts, but are in the free, crystalline condition. Phenylalanine did not give a precipitate with potassium or aluminium sulphete, ammonium, calcium, barium, magnesium or aluminium chloride, or with barium bromide.The results afford further confirmation of the view that proteins are com- plexes of amino-acids, the salting out of which can no longer be accepted as a criterion of their colloidal character. Phenylalanine and I-leucine may be separated from glycocoll by means of ammonium sulphate.The calcium chloride compounds of glycocoll and d-alanine have been separated by the difference in their solubility in aqueous alcohol. Disturbing Factor in Barfoed's Test. W. H. Welker. (J. Amer. Chm. SOC., 1915, 37, 2227'-2230.)-Barfoed's cupric acetate solution has been used exten- sively in bio-chemistry for the detection of reducing monosaccharides, and since it does not reduce disaccharides such as maltose, it has been employed to show the difference between the products obtained by the action of diastase and of dilute acids respectively on starch pastes.The author finds that when starch is boiled with hydrochloric acid the solution at that stage, when the iodine reaction vanishes, does not reduce Barfoed's reagent, but that a greenish-white precipitate is formed.The cause was traced to the presence of sodium chloride (the solutions had been neutralised with sodium hydroxide and acidified with acetic acid), a very small quantity of which interferes with the reaction. The precipitate contains copper, sodium, chlorine, and acetic wid, but its exact composition has not been determined.w. P. s.ORGANIC ANALYSIS 471 Estimation of Formic Acid in the Presence of Acetic Acid. R. Lauff- mann. (Chem. Zeit., 1915, 39, 575; through J. SOC. Chem. Ind., 1915, 34, 1008.) -A method described recently by Heermann (Chem. Zeit., 1915, 39, 124) depends on the fact that formic acid is capable of expelling acetic acid from acetates. A mixture of sodium formate and sodium acetate is dried at 125' C., and weighed, then treated with formic acid, evaporated, the residue again dried at 125' C., and weighed, the quantity of acatic acid being calculated from the loss in weight, and the amount of formic acid present originally being ascertained indirectly.Investigation of this method showed that it yields results which are only approximately correct.Solu- tions containing about 1 per cent. of formic and acetic acids together, the quantity of formic acid varying from 0.3 to 0.7 per cent,, were neutralised, evaporated, and the residues dried and weighed. The latter were then twice evaporated with the addition of formic acid, followed by four evaporations with the addition of water. The quantity of formic acid found was about 0.02 per cent.too high, whilst that of the acetic acid was too low. Analytical Distillation of Petroleum.-11. W. F. Rittman and E. W. Dean. (J. Ind. and Eng. Chern., 1915, 7, 754-760.)-1n continuation of their work (ANALYST, 1915, 249), the authors have now examined the merits for their particular purpose of every type of fractionating column hitherto described. A Hempel column is finally recommended.The only columns giving more perfect fractionation were the evaporator still-head of Young and an 18-inch rod and disc column, but the latter is unsuited for work above 225" C., as it floods owing to excessive reflux condensation, whilst the evaporator still-head is fragile, complicated, and only very slightly more efficient than a simple Hempel column. The sole disadvantage of the latter, on which Young laid stress, is the comparatively large amount of liquid trapped by it at the end of a, distillation, but with quantities of 200 c.c.under examination this is less important than when smaller quantities must be taken.An advantage of the Hempel column is that it can be constructed in one piece with the distilling flask. The form of apparatus finally recommended is a distilling flask with a bulb of 300 C.C. capacity, and a neck 1 inch in diameter and 6 inches long from the bulb to the side tube.A copper wire with a hook at the top, to facilitate withdrawal, and bent into a spiral near the bottom of the neck of the flask, Berves to support 5 inches of aluminium beads, which fit together less closely than glass beads, and are therefore less liable to be flooded at high temperatures by excessive reflux condensation.If the neck of the flask is as narrow as Q inch, the results are not materially different. The length, however, should closely approximate 6 inches and the height of the column of beads 5 inches to obtain strictly comparable results. A longer column gives slightly better fractionation, but is unwieldy and leads to excessive condensation at high temperatures.The reduction of cracking is desirable in the analytical distillation of petro- leum, but it is shown that the importance of this factor has been overestimated in the past. The simpler hydrocarbons are stable at much higher temperatures than those of higher molecular weight, and the tendency for the products of reflux action to be cracked by superheating is negligibly small.It is the residual hydrocarbons in472 ABSTRACTS OF ,CHEMICAL PAPER,R the still that tend to become cracked, and the extent of the action is a function of time and temperature. I t is shown that when vapour at 300" C. was passing from a Hempel column, as described, to the condenser, the temperature of the liquid in the still approximated 340" C., against 310" C.when no fractionating column was used, so that simple distillation can only be carried about 30" C. higher than distillation in- volving efficient fractionation, with the same possibility of cracking in each case. In the apparatus described, the authors distil 200 C.C. of petroleum at the rate of 2 to 2.5 C.C. per minute.G. C. J. Estimation of Solid Matter in Smoke. A. Gautier. (Bull. SOC. Chim., 1915, 17, 273-278.)--For the estimation of soot, tarry matters, etc., in smoke, an iron tube closed at one end is inserted through a hole in the chimney, where it reaches to the opposite wall. In this tube are two slits directed downwards, and a second narrower tube of nickel with open end is fitted into it.The other end of the narrow tube is connected with an absorption vessel consisting of two superposed bulbs cooled in a tank of water. The smoke is drawn into the space between the iron and nickel tubes by means of a suitable aspirator, and then passes upwards through the bulbs, which contain water and small glass balls to retain the bulk of the soot, etc. It is next drawn through a vertical filter composed of three pieces of filter-paper fixed between platinum cones, having a lateral tube which is heated to 100" C. to prevent condensation of steam. The fine particles of solid matter are retained by the filter, and the gas leaving it is finally drawn through a gas meter. The filter- papers, which have previously been dried stti 100" C. and weighed, are then trans- ferred to a funnel, the contents of the bulbs collected upon them, and the papers washed with ether and hot alcohol, to remove tar, etc., dried at 100" C., and weighed. The amount of solid matter i n coal smoke usually averages 0.003 to 0*008 grm., but may reach 0.890 grm. or more per cubic metre. C. A. M.

ISSN:0003-2654    

DOI:10.1039/AN9154000470

出版商:RSC    

年代:1915

数据来源: RSC

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472 ABSTRACTS OF ,CHEMICAL PAPER,R INORGANIC ANALYSIS. Estimation of Aluminium Oxide and Total Aluminium in Steel. F. 0. Kichline. (J. Ind. and Eng. Chcm., 1915, 7, 806-807.)-1t is shown that alumina that has been heated to 1,000' C. for an hour, dissolves to the extent of only 3 per cent. when digested for an hour with dilute (1 : 1) hydrochloric acid, whilst alumina which has been heated to 2;OOOO C.is practicably insoluble. I t is held, therefore, that alumina, present in steel, which must have been subjected to a temperature of 1,600' C., is not likely to yield more than 1 or 2 per cent. of its weight to dilute hydrochloric acid, and a, 2 per cent. error in estimating the small quantity of alumina in steel is certainly negligible. That the alumina in steel is substantially insoluble has been shown directly by adding only just enough aluminium to deoxidise the steel, avoiding an excess.No aluminium was found in the solution of the steel in hydro- chloric acid. On these facts the following method of estimating alumina, in steel is based. The drillings (50 grms.) are dissolved in a mixture of 200 C.C. hydrochloric acid and 300 C.C. water.The insoluble matter is filtered off, washed with hot dilute (1 : 2) hydrochloric acid, and finally with hot water. The ashless filter and itsINORGANIC ANALYSIS 473 contents are incinerated, the residue fused first with 0.5 grm. sodium borate and, when in solution, with 5 grms. sodium carbonate. The alumina in the melt is then estimated in any convenient manner. Without the use of sodium borate, it is often impossible to decompose the alumina completely.I n the iron filtrate, aluminium originally present as metal is precipitated as phosphate by Blair’s modification of Wohler’s method. The precipitate is dissolved in nitric acid, any chromium oxidised by boiling with permanganate, and the aluminium precipitated from the chromium, copper, etc., by means of ammonia.This precipitate is dissolved in hydrochloric acid, the solution evaporated to separate silica, and in the filtrate aluminium is re-precipitated as phosphate. G. C. J. Application of Stock’s Reaction to the Volumetrie Estimation of Aluminium. T. V. Kovseharova. ( J . Russ. Plzys. Chem. Soc., 1915, 47, 616-624 ; through J. Ohm. Soc., 1915, 108, ii., 582-583.)-The author has examined Stock’a method for the volumetric estimation of aluminium (J.Chem. SOC., 1900, 78, ii., 247, 315). To a definite volume of potash alum solution are added a mixture in equal volumes of 25 per cent. potassium iodide and 6 per cent. potassium iodate solutions, and an excess of & sodium thiosulphate solution. The liquid is then heated to boiling, and the excess of thiosulphate titrated with iodine solution. A large number of estimations, carried out under different conditions, shows that trustworthy results are obtained when (1) the excess of sodium thio- sulphate solution is small, (2) the solution is as nearly neutral as possible, and (3) the heating on the water-bath is not continued for longer than twenty to thirty minutes.Arsenic Acid as an Alkalimetrie Standard.A. W. C. Menzies and F. N. McCarthy. (J. dmer. Chem. Soc., 1915, 37, 2021-2024.)-1t has been shown by Menzies and Trotter (ANALYST, 1912, 37, 580) that arsenic acid can be titrated with sodium hydroxide solution, using phenolphthalein as indicator, and that the end-point of the titration is quite sharp. The authors now give a method for pre- paring pure arsenious acid and for the conversion of the latter into arsenic acid.A 6 by I inch test-tube is constricted to about one-fourth its diameter at a point 2 inches from the closed end, and the end pocket thus formed is filled with com- mercial arsenious acid of good quality; the tube is then clamped horizontally with its pocket over, but not touching, a Bunsen flame. The arsenious acid collects as a sublimate in the other end of the tube; the sublimate is removed by cutting the tube at the constriction, dried by heating, and bottled while hot.To prepare 500 C.C. of & arsenic acid solution, a quantity of about 2.47 grms. of the sublimed arsenious aoid is weighed into a 75 C.C. conical flask, 5 C.C. of chloride-free concentrated nitric acid are added, then 5 C.C.of water, a suitable tube is placed in the neck of the flask to prevent loss by splashing, and the mixture is heated, gently at first, and then more strongly. When the arsenious acid has dissolved, 5 C.C. more of nitric acid are added through the above mentioned tube, the latter is removed, and the solution evaporated to dryness. The evaporation is acclerated by blowing a current of cotton-filtered, ammonia-free air into the flask.The dry residue is474 ABSTRACTS OF CHEMICAL PAPERS then dissolved in water, the solution evaporated to dryness, water is again added, and the evaporation repeated. These operations are necessary in order to remove the last traces of nitric acid. The final residue, consisting of arsenic acid, is dis- solved in water and diluted to the required weight or volume of solution.An approximately FG alkali solution, when standardised against pure bensoic acid, WBS found to have a factor of 1.0040; against standard hydrochloric acid, 1.0037 to 1.0039 ; against arsenic acid, 1.0036. w. P. s. Titration of Nitrates with Ferrous Sulphate. F. C. Bowman and W. Scott. (J. Ind. and Eng. Chem., 1915,7,766-769.)-The method depends on titration with a concentrated solution of ferrous sulphate in strong sulphuric acid solution, the acid strength of which must not fall below 75 per cent.at the end of the titration. Under these conditions, provided the temperature is not allowed to exceed GO" c., nitric acid is not reduced to NO, but only to N20,. The ferrous solution is made by dissolving 176 grms. crystallised ferrous sulphate in 400 C.C.water, stirring the solution into a cooled mixture of 250 C.C. water and 250 C.C. sulphuric acid, cooling and diluting to 1,000 C.C. One C.C. of this solution contains 0.8 C.C. water, and is approximately equivalent to 0.02 grm. HNO,. Its exact titre is best determined by titration with nitric acid, made from pure acid and standardised by titration with alkali.To 100 C.C. of sulphuric acid a measured quantity (10 c.c.) of nitric acid is added by means of a pipette the contents of which to the mark are known. The pipette is used to stir the liquid and its contents are delivered near to the bottom of the vessel containing the acid. The pipette is rinsed by sucking up sulphuric acid into it and letting this flow back.The ferrous solution is then added from a burette, with constant agitation of the liquid, until the appearance of a delicate pinkish-brown colour. From the con- sumption of ferrous solution, 0-2 C.C. is deducted, this being the excess required to give a pronounced coloration. In conducting sn analysis, as much of the sample as will require about 30 C.C. of ferrous solution is dissolved in such a quantity of water that the final acid con- centration will not fall below 75 per cent., and added to 100 C.C.of sulphuric acid and titrated as described, deducting 0.2 C.C. from the apparent consumption of ferrous solution. The method is not suited for the estimation of traces of nitrate, and gives only approximate results when applied to commercial nitrate of soda, the impurities in which interfere.The method has been used successfully for estimating nitric acid in fuming sulphuric acid of American manufacture, which appears always to contain 2 per cent. and often 3.5 per cent. of nitric acid. I t is also useful for mixtures of sulphuric and nitric acids, such as may have to be assayed in explosives works. In such mixtures nitric acid can be estimated with an error not exceeding 1 part in 300, Chlorates and chlorides interfere, but nitrites do not.G. C . J. Assay of Platinum. F. Mylius and A. Mazzwcchelli. (Chem News, 1915, 112, 88-91, 104-107, 125-126, 134-135, 144-146, 155-156 ; from Xeitsch. anal. Chem., 1914, 89, 1-38.)-The authors ignore the rarer constituents of commercial platinum, but deal with the detection and estimation of all the ordinary ones inINORGANIC ANALYSIS 475 great detail.Fourteen qualitative reactions of each of the six platinum metals in 0.1 per cent. solution are tabulated, the method of carrying out colorimetric estima- tions with solutions of the chlorides in presence of hydrogen chloride is described, and a simple process for the analysis by precipitation of dissolved platinum alloys is recommended. The behaviour of ruthenium chloride towards ammonium chloride is explained by means of new experiments, and the existence of iridium mercaptide proved. Methods of separating the platinum metals from one another have been tested and improved, and a, special method is proposed and described in detail for the quantitative analysis of technical platinum.Finally, for the detection of impurities in high-grade platinum a, method is described as a supplement to that recommended by Finkener and tested by Mylius and Forster for the purification of the metal. G. C. J. Estimation of Traces of Silver by the Cyanimetric Method. G. Rebikre. (Bull. SOC. Chznz., 1915, 17, 306-309.)--In DenigBs’ method of estimating silver by means of potassium cyanide in’ammoniacal solution the end-point of the reaction is shown by the use of potassium iodide as indicator. As the opalescence due to silver iodide is not readily perceptible, the author detects its formation by directing 6 beam of light through the flask.One hundred C.C. of the silver solution are shaken with 10 C.C. of standard cyanide solution containing 10 C.C.of i% potassium cyanide solu- tion and 20 C.C. of ammonia solution in 100 c.c., and the excess of cyanide titrated with i& silver‘nitrate solution, with a, drop of potassium iodide solution as indi- cator, until a bluish opalescence is rendered visible by the first excess of 0.05 C.C. of the silver solution. C. A. M. Effect of Grinding Soil on its Reaction as Determined by Veitch’s Method.P. E. Brown and H. W. Johnson. (J. Iyzd. and Eng. Chem., 1915, 7, 776-777.)-1t is shown that, when acid soils are ground before being tested by Veitch’s method, the acidity is reduced and frequently the reaction becomes basic, owing to the basic reaction of finely ground silicates. As the weathering of coarse granular silicates is much too slow to remedy acid conditions in the soil, soils should not be ground previous to testing their reaction by Veitch’s method.G. C. J. Probable Error of Sampling in Soil Surveys. G. W. Robinson and W. E. Lloyd. (J. Agric. Sci., 1915, 7, 144-153.)-The usual method of sampling for survey purposes is to select a field uniform in itself and representative of the type; borings are taken at various points, and the samples mixed for analysis, representing the top soil and subsoil respectively. The total probable error (P) of a, single boring is a function of the laboratory error (pJ and the field error ( p J , due to the normal variation from point to point of the Geld.Each of these has a different value for the various items. The experiments recorded illustrate the operation of these errors ( A ) in the case of a field not sufficiently uniform for survey purposes; (23) in that of a suitable field, a complete mechanical analysis and determinations of hygroscopic moisture, organic matter, and phosphoric acid being made separately on each boring.I n the mechanical analysis the value for fine gravel is subject to the476 ABSTRACTS OF CHEMICAL PAPERS largest errors of both classes, but this item is of relatively small importance.Excluding this, the experiments showed an average laboratory error of +2*5 per cent., and a probable field error of round about 210 per cent. for the mechanical determinations, and +, 13.4 per cent. for the phosphoric acid in the case of field A . For the more uniform field B, the field errors in mechanical analyses were small, and in the estimation of phosphoric acid were k7.3 per cent.For survey work gene- rally, & maximum field error in a single boring of rtl0 per cent. may be taken as a fair basis for the chemical analyses, and k 5 per cent. for the mechanical. The total probable error can then be reduced by increasing the number of borings and the number of determinations.The total probable error is represented by the expression P= J*22, and if borings are made and analysed separately, this would be divided by &. On the other hand, if IZ borings are mixed and analysed as a single sample, only the field error is divided by J< while the laboratory error remains. Thus, when the field error is comparatively large, there is little advantage in analysing the borings separately.In a suitable field ( B ) the errors may be reduced sufficiently for general survey purposes by taking six borings and making duplicate determinations on the mixed sample. The expression for the probable -2F5 error then becomes +, 2/( j a y+($y= -L 2.7 per cent. for a mechanical analysis, and 2 2/(z)2+ (%r = * 4.4 per cent.for a, chemical analysis. JJ J6 Calculating thence the probabilities, it would appear that an accuracy of 5 per cent. may be expected with a probability of 4 to 1 in the case of a mechanical analysis, but in a chemical anaIysis the same degree of probability only covers an error of k 8-3 per cent. J. F. B. Effect of Changes in the Viscosity of Water on the Results of Mechanical Analyses conducted at Varying Temperatures.G. W. Robinson. ( J . Agric. Sci., 1915, 7, 142-143.)-1n the mechanical analysis of soils by practical sedimentation discordant results will be obtained if the experiments are performed at widely divergent temperatures owing to the change in the viscosity of the water. According to Thorpe and Rodger's formula, the increase in viscosity over the range of 10°.C., corresponding to a fall in temperature from 15' to 5" C., amounts to 33 per cent., in comparison with which the changes in the densities of the solid and liquid are quite negligible. This increase in viscosity affects the limiting diameter of the particles remaining in suspension in the ratio of the square root of the viscosity, so that the limiting diameter of the particles in suspension is 15 per cent. greater at 5' C. than it is at 15" C., and if there is a large proportion of particles at or about this limiting diameter the effect on the sedimentation fractions may be very con- siderable. This eflect has been shown in the separation of samples of mixtures of fine sand and silt made at different temperatures. Taking the fine sand fraction at 6" C. as equal to 100, the amount collected at 11" C. was 105.7 and at 16" C. 108.1. These analyses should therefore always be conducted at a constant temperature, preferably 12" to 14' C. J. F. B.

ISSN:0003-2654    

DOI:10.1039/AN9154000472

出版商:RSC    

年代:1915

数据来源: RSC

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APPARATUS, ETC. 477 APPARATUS, ETC. Apparatus for the Rapid Testing of Substanees used for Newtralising Noxious Gases. E. Kohn-Abrest. (Compt. rend., 1915, 161, 310-313.)-The apparatus employed for testing the efficacy of respirator charges consists of a, bottle, F, of about 4 litres capacity containing the gas to be tested at a known dilution. This is connected with the tube T, containing cotton-wool impregnated with the absorbing substance.The tube T i g also connected with a glass bulb, A , of about 250 C.C. capacity, having three tubulures, each controlled by a, stopcock. The bulb A is evacuated by means of a pump through the stopcock 5, until the mercury in the manometer M indicates a vacuum of 10 to 12 mm. The gas is then aspirated, at a rate corresponding to that of moderate breathing, by opening the taps.2 and 3, the gas passing through the charge in the tube 57, and being collected in the bulb A. The connections are closed while a slightly reduced pressure still exists in the bulb. Reagents are then introduced into A to determine the efficiency of the absorption. Working with chlorine, it was found that at a dilution of 1 per 1,000.the cotton-wool alqne was sufficient to remove all the chlorine, and no appreciable difference could be detected in the behaviour of the varioue absorbing chemicals at concentrations below 1 per cent. of chlorine. With higher concentrations, a, saturated solution of sodium carbonate was considerably more effective than one of478 ABSTRACTS OF CHEMICAL PAPERS bicarbonate, and the former should be used in preference to the latter, in conjunction with sodium thiosulphate. A 30 per cent.solution of potassium iodide is a very effective agent for absorbing chlorine gas at high concentrations. Glycerol is used for preventing evaporation ; it also tends to make the absorption of chlorine more regular. J. F. B. Mano-nitrometer for the Analysis of Nitrocellu- lose, Nitrating Acids, etc.V. Planchon. (Ann. Chim. anal., 1915, 20, 189-197.)-The estimation of nitrates with the ordinary nitrometer is subject to errors which can scarcely be reduced below 1 per cent.; among the incon- veniences attending the method may be mentioned : The very small quantity of sample taken for the estimation; the difficulty of adjnsting the gas to atmospheric pressure for reading ; the uncertainty of the temperature of the gas inside the tube ; the necessity for an arbitrary correction for the solubility of the gas in the sulphuric acid; the presence of air dissolved in the acid at the same time as the nitro- cellulose; the effect of the violence and duration of the shaking on the results obtained. These difficulties are avoided or rninimised by the use of the ‘‘ mano-nitrometer ” (see Fig.), in which the gas is developed in an evacuated vessel from a larger quantity of the sample and measured by the increase of pressure recorded.The apparatus consists of a reaction bottle, P, with a stopper, B, bored so as to communicate with two delivery tubes; one of these has a tap, P, and is connected with a vacuum pump- the other is connected with the upper end of the barometric tube T by the rubber tube X ; the bottle and stopper are held in close contact by the clamp ‘v and a rubber washer.A millimetre scale and vernier, moved by the milled head C, and fixed in any position by the screw S, are fitted to the support of the barometric tube. The reaction bottle is charged with mercury, sulphuric acid and the substance to be analysed, and the whole apparatus evacuated by connecting with the pump.The scale is clamped with the zero adjusted to the height of the mercury in the tube and the pump-connection closed. The bottle is shaken until no further fall in the column oE mercury is noticed, and is then immersed in a vessel of cold water until the position of the mercury is steady.This is read off by means of the vernier, and the tempsrature, t, of the water-bath is noted. If F = the fall of the column of mercury in mm., C = the total gas-space in the apparatus at the time of reading, and P = the weight of substance taken, the number of C.C. of gas 760 (1 + 0*00366S). evolved per 1 grm. of substance is expressed by the formula - p x CXF 1 The capacity of the apparatus is found from the difference in weight of the bottle, clamp and connecting tubes empty and filled with water, plus the capacity of the barometric tube down to its lowest measure.A table can then be constructedAPPARATUS, ETC. 479 showing the capacity for any position of the mercury in the tube, and the volume of the reagents used is deducted. For the analysis of nitrocellulose in an apparatus of about 700 C.C.capacity, the usual quantities of reagents taken are: 50 C.C. of sulphuric acid (measured), 15 C.C. of mercury (weighed, 204 grms.), and 2.5 grms. of nitrocellulose (sp. gr. 1.5). Sulphuric acid of commercial strength (93 to 97 per cent.) should b9 used, variations within these limits having no appreciable effect. All the sources of error noted with the ordinary nitrometer are considerably reduced by working under vacuum ; the air is removed from the solution before the reaction and the solubility of the nitric oxide in the per cent.is attainable with ordinary care. acid is negligible. An accuracy of 0.5 J. F. B. Receivers for Fractional Distillation under Dimin- ished Pressure. M. T. Bogert. (J.I d . and Eng. Chem., 1915, 7, 785-786.)-Two slightly different pieces of apparatus are figured in the original. The single illustra- tion reproduced here is nearly self-explanatory. The receiver is graduated in c.cs. The connection to the con- denser is at B, that to the pump at P. F and Hare plain cocks, but D is a three-way cock, by means of which the ultimate receiver (a, flask, separator, or other convenient vessel attached to E by means of a, rubber bung) can be put into connec.tion with the pump or with the outer air.Connection with the pump is neccessary when drawing off fractions from A . To prevent liquid being drawn over to the pump from the outlet stem of the receiver, the latter is jacketed, liquid falling through the inner tube G, and air being exhausted by the outer tube E. G. C. J. Weighing Pipette. F. Hall.. ( J . Amer. Chem. SOL, 1915, 37, 2062-2063.)- The pipette consists of a cylindrical body having a short tube provided with a tap at its lower end. The upper stem of the pipette is made of a short length of thick- walled glaw tubing with a bulb blown in it. This bulb fits into a slotted metal hook attached to the arm of the balance. If desired, the pipette may be graduated, and glass caps may be provided for closing the ends when dealing with volatile liquids. w. P. s.

ISSN:0003-2654    

DOI:10.1039/AN9154000477

出版商:RSC    

年代:1915

数据来源: RSC

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480 ERRATUM.-Page 443, fourth line from bottom should read : “ Analysis of €’WE& 37th CompositzCs {Gregory’s Powder). G. D. Elsdon and R. Hawley.”

ISSN:0003-2654    

DOI:10.1039/AN915400480b

出版商:RSC    

年代:1915

数据来源: RSC