Organic analysis

 

作者:

 

期刊: Analyst  (RSC Available online 1908)
卷期: Volume 33, issue 392  

页码: 431-437

 

ISSN:0003-2654

 

年代: 1908

 

DOI:10.1039/AN9083300431

 

出版商: RSC

 

数据来源: RSC

 

摘要:

THE ANALYST. 432 ORGANIC ANALYSIS. The Detection and Estimation of Cotton in Kapok. M. Greshoff. (Chew. Zentrbl., 1908, 2, 642.) -The fibres from the fruit of Eriodendron anfractuosum, known commercially as Kapok, are used as a material for filling cushions, life-belts, etc. They are sometimes adulterated with cotton, which is rodily detected, however, by a microscopical examination and by chemical tests. Thus, cotton treated with Schultze’s zinc chloride and iodine reagent is coloured reddish-blue, whilst kapok becomes yellow. Again, kapok is dyed bright red, while cotton remains practically colourless, after being immersed for an hour in a solution of 0.01 part of magenta in 30 parts of alcohol and 30 parts of water. The approximate proportion of cotton in an adulterated sample may be calculated from the amount of pentosans estimated by Tollen’s method of distillation with dilute hydrochloric acid and precipitation of the furfural in the distillate by means of phloroglucinol.The amount of pentosans in cotton does not exceed about 3 per cent., whereas in kapok they amount to 23 to 25 per cent. C. A. M. Estimation of the Yield of Coke from Coal. F. W. Hinrichsen and S. Taczak. (Stahl. u. Eisen, 1908, 28, 1277-1279.)-From 4 to 5 grams of the finely powdered sample contained in a 40 or 50 C.C. Ro~e’s crucible are heated in a current of hydrogen. All air is first removed by passage of the current of gas for at432 THE ANALYST, Iodine Value (Hanhs). least ten minutes, after which the crucible is heated gently for two minutes, then strongly for five minutes, and allowed to cool in the current of hydrogen.In this way all loss by oxidation is prevented, and results are obtained in close agreement with the technical yields of coke. C. A. M. Saponification Value. Effect of Heat upon the Physical and Chemical Constants of Cotton- seed Oil. E. Fulmer and T. C. Manchester. (Jounz. Anze~. Chenz. SOL, 1908, 30, 1477-1478.)-1t is well known that, if cottonseed oil be heated to 250" to 270" C., it fails to give the Halphen sulphur-reaction, and gives no reduction with Bechi's test if it has been subjected to a temperature of 245" C. The following table shows the results of the authors' investigation into the effect of similar temperatures upon the physical and chemical constants of this oil : .Specific Gravity at 1 5 . 3 C. 191.5 7'- Heated f m - 10 rnins. YO iilinb 190 9 190 s 190.7 190.2 190.3 190.6 190 6 190'1 190.7 190.9 Norniul uillieated \ oil ... ... 0.9221 Temperature (C.) : 1 SO" 220" 2-10" 250" 270" 7 Heated for- 10 mills. 3U Inins. 0.9267 09228 0.9229 0.9229 0'9229 0'9236 0'923ti 0*0210 0.9234 0'9218 1lefr;rctirc Index at W C. Frec Fatty Acids (calcukttcd a s Oleic Acid). 1 .A7509 Heated f w - 10 mills. 30 inins. 110.1 7; r-*- Iiented for- 10 inins. 30 rnins z /' 110'0 108'1 108.8 108.5 108.4 10s 5 10s-3 107 h 106'9 l o t i 3 I n general, the results show that the specific gravity, refractive index, and free acid, increase, and the iodine value decreases, as the temperature of heating rises. The saponification value remains fairly constant throughout.The changes are not very marked, and a cottonseed oil subjected to temperatures such as these will still give constants within the normal limits of variation for this oil, and the fact of such heating cannot, therefore, be detected from the above figures. A. R. T. New Constants for the Valuation of Mineral Lubricating Oils. R. Kissling. (Chem. Zeit., 1908, 32, 938-940.)-As some mineral lubricating oils become more '( tarry" and carbonised in use than do others, the author proposes a method in which these changes are determined. The oils are heated for fifty hours at tempera- tures of 150" and 250" C., and the tarry matters formed are then estimated by heating 50 grams of the oil to a temperature of about 80" C. with 50 C.C. of a mixture consisting of 50 parts by weight of alcohol and 50 parts of 7-5 per cent.sodium hydroxide solution, The mixture is well shaken, and the aqueous portion is then separated, filtered, and extracted with benzene. The residue obtained on evaporating the benzene extract is weighed, and represents the amount of tarry matter formed by heating the oil. The oily portion is next diluted with benzene, filtered through a weighed filter, and the carbonised matter thus collected is weighed. PennsylvanianTHE ANALYST. 433 oils are but little altered by the continued heating, the sum of the tarry and carbonised matters increasing by about 0.1 per cent., whilst Texan oils show an increase of about 1 per cent. w. P. s. Detection of Small Quantities of Turpentine in Lemon Oil. E. M. Chace.(Jounz. Arner. Chcm. Xoc., 1908, 30, 1475-1477.)-The methods of Schimmel and Co. and of Soldaini and Bert6 for the detection of this adulterant are stated to be open to several objections, chief of which are the variations produced owing to the differing sizes of the apparatus used by different workers, and also the variable optical rotation of the oil of turpentine added; while the adulterant itself is not actually identified in either method. The author prefers to isolate the nitrosochlorides from 50 C.C. of the suspected sample, and then to examine microscopically the crystalline compounds obtained for pinene nitrosochloride, which is of characteristic appearance, and can readily be distinguished from the limonene nitrosochloride in admixture with it. The amount of lemon oil employed is insufficient to cause the minute quantity of naturally-occurring pinene to interfere with the accuracy of the test.Ten to 15 per cent. of turpentine oil in oil of lemon can be detected without distillation, while if distilled by means of a fractionating column, less than 1 per cent. of the adulterant can be definitely identified. The method for the preparation of the nitrosochlorides is substantially that of Wallach. Fifty C.C. of the sample are distilled in a Ladenburg three-bulb flask or in an ordinary flask fitted with a Glinsky three-bead fractionating column. The first 5 C.C. of distillate are mixed with an equal volume of glacial acetic acid, cooled in a freezing-mixture, and, when cold, a similar quantity of ethyl nitrite is added; the solution is mixed thoroughly, and, while still cold, 2 C.C.of concentrated hydrochloric acid is run in drop by drop, and the mixture kept at 0” C. for fifteen minutes, when the solution is filtered under diminished pressure on a Buchner funnel. The filtrate is again placed in the freezing mixture for twenty minutes, and the second crop of crystals added to the first quantity, when the whole is washed with alcohol (95 per cent. by volume). I t is often advantageous to add alcohol or acetic acid to aid crys- tallisation. The dry crystals are dissolved in the smallest possible quantity of chloro- form, and then hot methyl alcohol is added until recrystallisation begins, when the liquid is cooled, more methyl alcohol added, the crystals filtered off and mounted in olive oil for microscopical examination.A. R, T. Examination of Turpentine Oil and ‘‘ Reduced Turpentine.” A. K. Turner. (Oil and CoZozLr Trades Jouwz., 1908, August 15, 503-506.)-Notwithstanding recent statements as to the accuracy of Armstrong’s polymerisation method for the estima- .tion of petroleum in oil of turpentine (cj. J. H. Coste, ANALYST, 1908, 219), in the author’s experience the method is unreliable and frequently gives results 20 per cent. below the truth, while the residue in the distillation-flask invariably gives a red colour with a solution of commercial picric acid in benzene, indicating the presence of non-volatile petroleum. The author, therefore, prefers to polymerise the turpentine oil with an equal volume of concentrated sulphuric acid, and then measure directly the residual petroleum without steam-distillation.The following are the details of434 THE ANALYST. the method : One hundred C.C. of turpentine oil, or of reduced turpentine” (Le., a mixture of turpentine oil with petroleum), is gradually shaken in a separator with an equal volume of strong sulphuric acid, in quantities of 5 C.C. at a time, avoiding any great rise of temperature by frequently cooling the mixture in a stream of cold water. When all the acid has been added, and the mixture thoroughly agitated, it is allowed to stand overnight to separate. If petroleum be present, it separates com- pletely, forming an upper insoluble layer, from which the dark acid layer may be drawn off, and the petroleum residue repeatedly washed with water until free from acid.As a precaution, this residue may be further shaken with an equal volume of strong sulphuric acid, and this process repeated until no rise of temperature takes place and the acid is only slightly coloured. The method appears to be capable of considerable accuracy, the results cited being within 2 to 5 per cent. of the actual proportion of adulterant in samples containing from 50 to 90 per cent. of petroleum. As a qualitative test, the author places considerable reliance on the behaviour of the samples on shaking. When vigorously agitated and then allowed to stand, the “ beads” so formed break up instantaneously in the case of turpentine oil ; while if petroleum be present (e.g., ‘‘ reduced turpentine ”), the (( beads ” last for some time.The ‘( aniline oil ’’ test is condemned as unsatisfactory, and the nitric acid polymerisation process as too dangerous for ordinary use. The amount of adulterant is then measured. A. R. T. Analysis of Oil Varnishes. P. C. McIlhiney. (Clzem. Engi?zccr, 1908, 8, 70-73.)-While the proportion of volatile oil (solvent) in varnishes may be readily determined by steam-distillation, and the distilled oil measured or weighed, the separa- tion of the “ gum ” from the resin in the varnish presents many difficulties. I t is im- possible to dissolve out, by any solvent, either ingredient after they have been heated together, as is the case in the manufacture of these varnishes. The author’s method consists in saponifying the mixture of gum ” and resin, and precipitating and separating the fatty and resin acids, thus leaving the gummy matters insoluble in petroleum-ether.The process is carried out as follows : From 2 to 10 grams of the varnish are saponified with a considerable excess of appropriately semi-normal caustic alkali (of known strength) in strong or, preferably, absolute alcohol, and the greater portion of the solvent then distilled and the residue dissolved in neutral absolute alcohol. The excess of alkali found by titretion with semi-normal acetic acid in absolute alcohol gives the Koettstorfer figure of the mixture. A further quantity of the standard acetic acid is now added in amount exactly sufficient to neutralise the total quantity of alkali originally added, which liberates the fatty and resin acids, and which remain in solution in the alcohol.A quantity of petroleum- ether is then added, followed by sufficient water to strongly dilute the alcoholic liquid, when the fatty and resin acids are obtained in solution in the pstroleum- ether, and the ‘‘ gum ” is precipitated from the aqueous solution. The two liquids are separated in the usual way, the fatty and resin acids being weighed, and the mixture examined qualitatively, and also by Twitchell’s method for the proportion of resin acids. The amount of fatty acids is equal to about 92.5 per cent. of the linseed oil present. Occasionally the nature of the fatty acids, whether from linseed oil orTHE ANALYST, 435 China-wood oil, may be ascertained. If the varnish contains non-volatile petroleum or other unsaponifiable matter, it will be found in the petroleum-ether extract, and may be separated in alkaline solution by petroleum-ether as usual.The aqueous liquid containing the (‘ gum,” which adheres largely to the sides of the vessel in which it is precipitated, is filtered on to a tared filter in such a manner that most of the precipitated ‘( gum ” remains behind, and the filtrate evaporated until free from alcohol, when any further precipitate of “gum” is added to the main quantity. If the weight of the vessel in which the precipitation is carried out be known, the “gum ” is best dried and weighed in this vessel, and the weight of ‘( gum ” on the filter-paper added. The odour, physical characters, acidity and Koettstorfer figures serve to identify the “ gum ” in Borne cases, The aqueous filtrate from the “gum” contains the glycerin, which may be estimated by means of Hehner’s bichromate method.I n the case of varnishes prepared with ( ( blown ” linseed oil, the oxidised fatty acids have a considerable lessened solubility in petroleum-ether, and they will there- fore be precipitated with the ( ( gum,” from which, however, they may be extracted by digesting the freshly precipitated gummy matters for some time with a moderate quantity of cold 85 per cent. alcohol. The matter thus dissolved out is weighed separately and further examined. The solubility of the acids of linseed oil thickened by heat only is scarcely altered, and any slight error in such cases is usually negligible. The resin in varnishes is usually combined with about 5 per cent.of its weight of lime, so that it is important to examine the mineral constituents of the varnish. These may be readily extracted by thinning the varnish somewhat with petroleum- spirit and treating the liquid with strong hydrochloric acid. A. R. T. New Method for the Examination of Leather. W. Fahrion. (Chem. Zeit., 1908, 32, 888-889.)-The author recommends the following ‘‘ hot-water test ” as a ready method for ascertaining the completeness of tanning experiments carried out in the laboratory : One gram of the finely divided sample is treated for ten hours wiGh 70 to 80 C.C. of water in a boiling water-bath ; the whole is shaken from time to time, and the water lost by evaporation replaced. The liquid is then allowed to cool to 75” to 80” C.made up to 100 C.C. with water, and filtered through a dry linen cloth iuto a dry beaker; 50 C.C. of the filtrate are at once evaporated to dryness in a tared platinum dish, the residue dried at 105” to 110’ C., weighed, ashed, and again weighed. On another portion of the sample moisture and ash are estimated, and the organic matter insoluble in hot water is calculated on the sample free from moisture and ash. For an ideal leather the matter insoluble in water would be 100 per cent. ; for com- mercial leather it varies from 31 to 90 per cent., according to the degree of tanning and the quantity of tanning material left in the leather. A. G. L. The Detection of Pentoses by Means of Orcinol and Hydrochloric Acid. J. Pieraerts. (BUZZ. Assoc. Chim. Sucr. et Dist., 1908, 26, 46-62.)-The author’s method of applying the orcinol hydrochloric acid teat for pentoses is to mix 5 C.C.of a 1 to 5per cent. solution of the sugar with three drops of a freshly prepared solution of orcinol (1 gram in 200 C.C. of 94 per cent. alcohol) and with 5 C.C. of strong436 THE ANALYST. hydrochloric acid, and to heat the mixture for thirty minutes on a boiling water-bath. I n the presence of a pentose a bluish-green coloration (with sometimes a blue deposit dissolving in amyl alcohol to form a bright blue solution) is obtained ; but if l=vulose, or a compound yielding Izvulose on hydrolysis be also present, a brown coloration is produced. Hence, for the detection of pentoses by this test it is necessary first to decompose by fermentation, sugars that interfere.Tollen's modification of the reagent (0-5 gram of orcinol in 30 C.C. of hydrochloric acid, with the subsequent addition of 30 C.C. of water) gives good results in the case of solid substances ; but in testing solutions for pentoses 5 c.C. of strong hydrochloric acid should be added to the mixture of 5 C.C. of the reagent with 5 C.C. of the sugar solution. The presence of dextrose has but little e.ft'ect upon the test, especially when an alcoholic solution of orcinol is used. Other aldose sugars of natural occurrence are practically without influence upon the reaction between orcinol and pentoses. C. A. M. This is attributed to the influence of the ketonic group. Detection and Identification of certain Reducing Sugars by Condensation with p-Brombenzyl Hydrazide.E. C. Kendall and H. C. Sherman. (Journ. A w r . Chem. SOL, 1908, 30, 1451-1455.)-The authors have developed certain observations of Kahl on the condensation of reducing sugars with p-brombenzyl hydrazide. This reagent is prepared by heating ethyl p-brombenzoate in alcoholic soIution with hydrazine hydrate, For condensing with the sugar, 30 mgm. of sugar, 60 mgm. of the hydrazide, and 10 to 15 C.C. of alcohol are evaporated to dryness in a test-tube in a boiling water-bath, Addition of alcohol and evaporation to dryness are repeated three or four times. In order to dissolve the uncombined sugar and hydrazide, 5 or G C.C. of chloroform and 4 or 5 drops of water are added to the residue in the tube, and heated with thorough agitation until the chloroform boils ; the hydrazone remains suspended in the hot liquid. Dextrose, galactose, mannose and arabinose give flakes or crusts of hydrazone ; lawdose gives only a milky turbidity ; whilst maltose and lactose give clear solutions.The non-reacting sugars interfere with the formation of the hydrazones of the sugars which do react, and reduce the delicacy of the test. When the conditions and quantities of reagents approximate fairly closely to those given above, the reacting sugars may be identified by the different solubilities of their hydrazones in alcohol, 20 C.C. being added to the evaporated residue in the tube and boiled. Galactose hydrazone is insoluble under those conditions, that of dextrose is soluble, and those of mannose and arabinose are partially soluble.The liquid is filtered, the alcohol is evaporated off, and the residue is taken up with chloroform and water. Alcohol is then added until the solvents mix and the mixture is boiled; arabinose hydrazone is insoluble, mannose hydrazone partially soluble, and dextrose hydrazone completely soluble. J. F. B. Determination of Reducing Sugars. F. Zerban and W. P. Naquin. (Joz~nz. Anter. Chem. Soc., 1908, 30, 145G-l4Gl.)-Munson and Walker have published tables for the estimation of reducing sugars by weighing the cuprous oxide after drying for half an hour at 100" C. in a Gooch crucible. The authors find that ifTHE ANALYST. 437 the precipitate be filtered off in a Munroe-Neubauer crucible (a platinum crucible with a filter-bed of spongy platinum) and converted into cupric oxide by ignition, the analysis may be made in half the time. In order to prevent contact with reducing gases the crucible may be placed in a, platinum dish during ignition. The copper calculated from the cupric oxide was constantly 0.0017 gram lower than that calculated from the cuprous oxide dried in the water-oven. This is probably due to residual moisture in the latter case, but in order to make Munson and Walker’s tables available, this quantity must be added as a correction to the weight of copper calculated as metal. In the analysis of low-grade products, the Neubauer crucible possesses no advantage over the Gooch, as the precipitate must be dissolved, owing to its contamination with mineral and organic impurities ; with such products the volumetric method is really preferable. It is always best to clarify low-grade solutions with just sufficient neutral lead acetate, in order to remove the reducing non-sugar constituents; basic lead acetate is not to be recommended. J. F. B.

 

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