摘要:

JANUARY. 1817 . Vot . XLII. No . 490 . Aluminium Antimony . Argon . Arsenic . Barium . Bismuth . Boron . Bromine . Cadmium . Caesium . Calclium . Carbon . Cerium . Chlorine . Chromium Cobalt . Columbium Copper . Dysprosium Erbium . Europium . Fluorine . Gadolinium Gallium . Germanium Glucinum . Gold . Helium . Holmium . Indium . Iodine . Iridium . Iron . Hydrogsn . Krypton . Lenthanum Lead . Lithium . Lutecium . Magnesium Manganese Mercury . THE ANALYST . ~~ INTERNATIONAL ATOMIC WEIGHTS . 1917 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Atomic Symbol. Weight . . A2 27.1 . Sb 120.2 .A 39-88 . As 74.96 . Ba 137.37 . Bi 208.0 . El 11.0 . Br 79.92 . Cd 112.40 . Cs 132.81 . Ca 40.07 . C 12.005 . Ce 140.25 . C1 35.46 . Cr 52.0 . Co 58.97 . Cb 93.1 . Cu 63.57 . Dy 162.5 . Er 167.7 . Eu 152.0 . F 194 . Gd 157.3 . G.8 69.9 . Ge 72.5 . G1 9.1 . Au 197.2 . He 4-00 . Ho 163.5 . El 1.008 . In 114.8 . I 126.92 . Ir 193.1 . F0 55.84 . Kr 82.92 . La 139.0 . Pb 207.20 . Li 6.94 . Lu 175.0 . N n 54493 . Mg 24.32 . Hg 200.6 Atomic Symbol . Weight . Molybdenum . . Mo 96.0 Neodymium . . Nd 144.3 Neon . . . Ne 20.2 Nickel . Ni 58-68 Niton frad'i;;m emanation) Nt 222.4 Nitrogin . . Oxygen . . Osmium . . Prtllrtdium . Phosphorus . Platinum . . Potassium . Praseodymium . Radium- . Rhodium .Rubidium Ruthenium Samarium Scandium Selenium . Silicon . Silver . Sodium . Strontium Sulphur . Tantalum Tellurium Terbium . Thallium . Thorium . Thulium . Tin . Titanium . Tungsten . Uranium . Vanadium Xenon . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . N 14.01 0 s 190.9 0 16.00 Pd 106.7 P 31-04 Pt 195.2 K 39.10 Pr 140-9 Ra 226.0 Rh 102.9 Rb 85-45 Ru 101.7 Sa 1504 SC 44-1 Se 79.2 Si 28.3 Ag 107-88 Na 23-00 Sr 87.63 S 32.06 Ta 181.5 Te 127.5 Tb 159.2 T1 204.0 Th 232.4 Tm 168.5 Sn 118.7 Ti 48.1 W 184.0 U 238.2 V 51.0 Xe 130.2 Ytterbium-(Neoytterbiurn) Y b 173.5 Yttrium . . . Yt 88.7 Zinc . . Zn 65-37 Zirconium . . Zr 90-6

ISSN:0003-2654    

DOI:10.1039/AN9174200001

出版商:RSC    

年代:1917

数据来源: RSC

摘要:

2 PROCEEDINQS OF THE SOCIETY OF PUBLIC ANALYSTS PROCEEDINGS OF THE SOCIETY OF PUBLIC ANALYSTS AND OTHER ANALYTICAL CHEMISTS. AN ordinary meeting of the Society was held on Wednesday evening, December 6, in the Chemical Society’s Rooms, Burlington House. The President, Mr. G). Embrey, F.I.C., occupied the chair. The minutes of the previous ordinary meeting were read and confirmed. A certificate of proposal for election to membership in favour of Mr.(3. W. Baker was read for the second time; and a certiiicate in favour of Professor Alfred Francis Joseph, D.Sc., A.R.C.Sc. (Lond.), F.I.C., 296, Willesden Lane, N.W., Pro- fessor of Chemistry, Ceylon Medical College, was read for the fist time. The President announced that the Decennial Index of the ANALYST, 1906-1915, ww now ready, and could be obtained from Messrs.Billing and Sons, Ltd., Railway Esplanade, Gddford, the price being one guinea. He hoped that all members of the Society would make a point of purchasing it. The fallowing papers were read: “ Copying-Ink Pencils and the Examination of their Pigments in Writing,” by C. A. Mitchell, M.A., F.I.C. ; “ Braziljan Oil Seeds,” by E. Richards Bolton, F.I.C., and Dorothy G.Hewer, B.Sc.; ‘‘ Army Sanitation,” by Captain C. 0. Moor, M.A., F.I.C.; and “ The Analysis of Honey and Other Sub- stances containing Laevulose,” by W. R-. G. Atkins, Sc.D. The list of the Council’s nominations of Officers and Council for 1917 was read as follows : President.-G. Embrey, F.I.C. Past-Presidents serving on the Council (limited by the Society’s Articles of Amo- ckti& to eight in number).-L.Archbutt, F.I.C. ; Edward Bevan, F.I.C. ; A. Chaston Chapman, F.I.C.; Bernard Dyer, D.Sc., P.I.C.; Otto Hehner, 3.1 C.; R. R. Tatlock, F.I.C.; E. W. Voelcker, A.R.S.M., F.I.C.; J. Auguetus Voe?cker, M.A., B.Sc., Ph.D., F.I.C. ~ice-Presidents.-Harold G. Colman, D.Sc., Ph.D., F.I.C.; J. T. Dunn, D.Sc., F.I.C.; C. A. Hill, B.Sc., F.I.C. Hon. T9.easurer.E. Hinks, B .Sc . , F.1.C . Actiw Hon. Treasurer.-E. W. Voelcker, A.R.S.M., F.I.C. H m . Secretaries.-P. A. Ellis Richards, F.I.C., and E. Richards Bolton, F.I.C. Other iffember8 of Counci1.W. T. Burgess, F.I.C.; T. W‘. Glass, B.Sc., F.I.C.; €I. G. Harrison, M.A., F.I.C.; C. N. Huntly, B.Sc., A.R.C.Sc., F.I.C. ; P. H. Kirkaldy, F.I.C.; S. J. C. G. Macadam, F.I.C.; W. Macnab, F.I.C.; W. Partridge, F.I.C.; W. H. Roberta, M.Sc., F.I.C.; E. Russell, B.Sc., F.I.C.; H. L. Smith, B.Sc., F.I.C.; J. webster, F.I.C.

ISSN:0003-2654    

DOI:10.1039/AN9174200002

出版商:RSC    

年代:1917

数据来源: RSC

摘要:

COPYING-INK PENCILS 3 COPYING-INK PENCILS AND THE EXAMINATION OF THEIR PIGMENTS IN WRITING. BY C. A. MITCHELL, B.A., F.T.C. (Read at the Meeting, December 6,1916.) THE nature of the pigments in copying-ink pencils might seem, on first thoughts, to be of little interest to anyone except the manufacturer and the consumer, who naturally would not buy an unsuitable article; but when I pention that during the last few years I have had to examine these pigments in connection with two criminal trials and one civil action, the importance of the subject in forensic chemistry will be recognised.One of the earliest applications of aniline dyestuffs was in the preparation of inks which could be used for copying purposes. Unlike iron-gall copying inks, which form an insoluble pigment on oxidation, and so will only xield good copies for a short time after writing, concentrated solutions of aniline dyestuffs will pro- duce writing which does not undergo any material alteration on exposure to the air for a relatively long period, and from which, therefore, a copy may be taken at any subsequent time.Most of the commercial inks of thia type contain sugar, glycerol, or deliquescent salts, to give consistency, and to prevent their drying up in open bottles.Methyl violet has long been the favourite dyestuff for this purpose, and is given as the main constituent in the earlier formuls for such inks. This copying quality of solutions of aniline dyestuffs suggested the incorporation of the pigment with the graphite of a lead pencil, which would then Be capable of producing charactera from which one or more copies could be taken on damp paper in a copying press.The earliest reference to copying-ink pencils which I have been able to discover is a description of their composition by Viedt in 1875 (Diagler’s poZyt. J., 1875, 216, 96). It is there stated that the pigment consists of a, mixture of kaolin clay, graphite, and methyl violet, and that gum arabic is not a suitable binding material.A year previouely a patent was taken out by Petit (Eng. Pat., 4090, 1874) for the manufacture of pencils of thia type, but it was abandoned before completion. It is probable that at the preeent time such pencils are but seldom employed for copying purpoees, but are commonly used for producing writing which cannot be erased so readily as the marks of a lead pencil.Hence they are also frequently termed “ indelible pencils,” although the description is only relatively correct. Lehner (Eng. trans. from 8th Germ. Ed. Ink Manufacture, 1902, p 125) gives the composition of the pigments in four kinds of ink pencils then being made by Faber in Bavaria. 1 have calculated his figures into the corresponding percentage amounts : Aniline Dyestuff.Graphite. Kaolin Clay. 1 .. .. .. . . . . 50.0 37-5 12-5 2 .. .. * . .. .. 44.2 32-6 23.2 3 . * .. .. .. . . 30.0 30.0 40.0 4 *. .. .. .. . a 26.6 24.6 50.04 MITCHELL : COPYING-INK PENCILS AND The pencil containing No. 1 is stated to be very soft, that containing No. 4 very hard. Neither of the specimens of Faber’s pencils which I examined gave results corresponding with any of these formulae (vide infra).Pencils containing methyl violet are still the most popular, although those con- taining blue and red pigments are also made by most manufaoturers. Two examples of blue copying-ink pencils are included in the subjoined table of analyses. The following is an outline of the methods I used to estimate the constituents of these pigments : Moisture.--From 0-25 to 0.3 grm.of the finely powdered pigment was dried in the water-oven until constant in weight. Dymtufl.-The dried pigment was treated with successive small quantities of warm 95 per cent. alcohol, each extract being decanted on to a small filter until no further colour waa extracted. In gome instances the combined alcoholic filtrates were evaporated, and the residue dried in the water-oven, but in most cases the amount of dyestuff was estimated by Merence. A colorimetric method was also tried, an aliquot portion of the alcoholic ex- tract being compared with a solution of 0-05 grm.of methyl violet in 50 C.C. of alcohol diluted to the required extent. The objection to a ~olorimetric method is that neither the standard dyestuff nor that in the pigment of the pencil are necessarily of the same degree of purity.Substam Insoluble in AZcohol.-The f3 ter-paper through which the alcoholic extracts had been filtered was lightly brushed with a camel’s-hair brush dipped in alcohol, so as to remove all fine particles of graphite and kaolin clay. These brush- ing~ were added to the insolubIe residue in the basin, which was then heated in the water-oven until constant in weight.Carbon.-!She dried residue was heated in a wide platinum basin covered with a flat lid. Occasionally the graphite burned away quite readily, but more often it was necessary to accelerate the ignition by introducing small quantities of am- monium nitrate from time to time. By keeping the basin covered it wa-s possible to avoid all loss during the deflagration. T78e Residue from the Ignition.-This was boiled with hydrochloric acid, and any iron or aluminium present in the solution was estimated in the usual way. The results thus obtained with the pipents of twenty-one pencils typical of those on the market since 1907 to the present year are giveh in the following table : From these results it appears that the proportion of dyestuff used in these pencil pigments ranges from less than 25 per cent.(Nos. 13 and 17) to about 50 per cent. (Nos. 12 and 19). As part of the ash is derived from impurities in the original graphite, it is only possible to make an approximate estimation of the relative proportions of graphite and kaolin clay from these figures. Impure graphite may conbin only about 60 to 70 per cent.of carbon, but the better kinds used for pencils generally contain not more than 3 or 4 per cent. of impurities (iron oxide, silica, etc.). When the amount of aah is less than 5 per cent., as in the case of Nos. 4, 12,13, 16, 17, 20 and 21, it is probable that the mineral matter was derived solely from the graphite.The ash of No. 14 (8.76 per cent.), consisting largely of ferric oxide, was also probably due to the graphite.COMPOSITION OF PIGMENTS OF COPYINGI-INK PENUILS . - - 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 - Descitption. American Pencil Co., Duplex, Blue Do. Duplex, Violet Do. Ink Ertu,” No. 160 Do. Venus, No. 167 Eagle Pencil Co., Atlas, No. 823 Do.Copying Eagle Ink, No. 1522 Do. Do. No. 824 Do. Leads, No. 119 Faber, Copying .. .. .. Do. x .. . I Do. Blue, No. 2251 Hardmuth, “ Mephisto ” . , .. “ Ink and Copying ” .. .. Hessin, Copying Ink, No. 74 . . Kurz .. .. .. .. Lapis Tinta, No. 180 . , .. Rowney .. * . .. .. Swan Copying, No. 1039 , . .. Do. No. 1039 ,, .. WolfE’s c‘6‘ British Preference ” . . Do. Royctl Sovereign ” ..Origin. ---- U.S.A. U.S.A. U.S.A. U.S.A. London U.S.A. U.S.A. U.S.A. Bavaria Bavaria Bavaria Austria Bavaria U.S.A. Bavaria - Britain Bavaria Bavaria London London Date. --- 191 1 1916 1916 1916 1907 1911 1911 1911 1907 1911 1907 1907 1911 1911 1907 1911 1911 1907 1911 1916 1916 - Per Cent. 2.35 3-96 7.48 2.30 4.86 4-53 3.75 3.55 3.72 2.64 1.82 3.56 3.74 5-36 3.83 2.04 4-53 6.33 2.05 2-72 2291 - Per Cent.76-45 59.28 51.53 60-89 66.69 67-77 63.95 57.14 64.48 71.27 58.68 47-14 72-92 61 *40 57.59 69.36 73.05 59.83 46-43 65.48 65.35 7 9 .o FI --- Per Cent. 21.20 36.76 40.99 36.81 28.45 27.70 32.30 36.84 31-80 26.09 39-50 49.94 23.34 33.24 38.58 28.60 22.42 33.84 51-52 31 40 32.74 Ic 3 -- Per Cent. 27.09 27-36 25-48 56-84 35.78 11.66 13.90 22-18 11.86 23.50 29-34 44.14 68.12 52.64 40.01 64.86 69.17 7.61 5.50 62-08 62.56 --- Y Per Cent.47-36 31.92 26.36 4.05 30.91 56.1 1 50.05 34.96 3.2.86 47.77 29.34 3.00 4-80 8.76 17.58 4.50 3.88 52.22 40.93 3.40 2.79 _.__ Remarks. Red ash, F%03 = 14054% White ash, Al2O3=2-19%. Trace Fe M20, and Fe203 = 0.5970 Slight iron reaction Buff-coloured ash, Al,03 = 1*210/,. Traceof Fe White ash, A1,O3=2*52%.Trace of Fe White ash Putty-coloured ash, Fe203= 3.00/, A1&+ Fe203=5*31% A1203+ Fe203 = 13.27% Ash, mairily Fe203 Trace of Fe Red ash. Good Fe reaction Ash, mainly Fe20, Trace of Fe Buff-coloured ash. Good Fe reaction Reddish ash. Good Fe reaction White ash, A1,0,=19*370/,. Trwe of Fe - Red ash, mainly Fe2O3 DO. Do.MITCHELL : COPYING-INK PENCILS AND The total amounts of mineral matter range from 2-79 per cent.in No. 21 to 56.11 per cent. in No. 6. By attributing about 5 per cent. (calculated on the entire pigment) to the graphite, and adding this to the loss on ignition, a result approximat- ing to the proportion of impure graphite originally used would be obtained. These pigments may therefore be classified into four main groups-viz. (1) those composed of graphite and dyestuff only; (2) those in which the dyestuff hw been incorporated with approximately equal proportions of kaolin and graphite (Nos.2, 3, 5 and 8); (3) those in which the kaolin is largely in excess (Nos. 1, 6, 7, 9, 10, 18 and 19); and (4) one case (No. 15) where the graphite predominates. The amount of iron oxide left on igniting the pigment ranged from nit to 14.54 per cent.in No. 1, in which it constituted about a third of the total ash. The alumina extracted from the ash by means of hydrochloric acid ranged from 0.59 per cent. in the case of No. 3 to 19.37 per cent. in No. 18. Where alumina was present in quantity it wted as a mordant, so that about 5 per cent. of the total dyestuff was not extracted by alcohol, and the residue was of a pale mauve colour.Its presence:affeched the behaviour of the pigment in the solution tests, and prob- ably accounted for the inferior copying properties of some of the pencils (notably Nos. 18 and 19). The variations in the pigments in pencils of the same type made by the same manufacturers at difEerent periods are shown in Nos. 10 and 11 and 18 and 19. Making allowance for the variations in the grades of graphite, the two pencils manu- factured by Faber were probably made from the same formula.But there is a pronounced difference in the proportions of dyestuff in the two Swan pencils, made in 1907 and 1911 respectively. COPYING PROPERTIES.-TWO consecutive copies on moist paper were taken of writing done with moat of these pencils. The best results were obtained with No.3 ‘’ Ink Eau ” and No. 12 HaTdmuth’s; the worst with No. 16 “ Lapis Tinta ” and NOII. 18 and 19 (Swan). The copying properties thus appear to depend not only on the proportion of dyestuff, but also on the influence of the substratum on the solution of the dyestuff in water. For instance, No. 19 (Swan), which contained a larger proportion of dye- stuff than any of the other pencils, but had a large amount of alumina in its pigment, gave only a very faint copy, whereas No.14, with a medium proportion of dyestuff, but no alumina, gave a fairly good copy. The nature of the graphite in the pigment also appears to have an influence on the copying properties. For example, No. 4 f“ Venus ”), in which the substratum was mainly graphite, gave a relatively poor copy compared with No.2 (“ Duplex ”), which contained about the same amount of dyestuff incorporated with a mixture of graphite and kaolin; while one of the best copies waa given by No. 12, in which the basis was graphite only. The behaviour of the written characters on treatment with a drop of water, or, in other words, their copying properties in miniature, may thus be used as one of the tests for distinguishing between the pigments of different pencils in writing.D~RENTLATION OF THE PIGMENTS IN WRITINGL-I~ is possible to distinguish between many of these pigments by the difference in the colours of the writing. For example, pigments which contain a large proportion of kaolin clay are of a muchTHE EXAMINA.!I!ION OF THEIR PIGMENTS IN WRITING 7 brighter tint than those in which graphite predominates, and even the intermediate cohurs may be differentiated to some extent with the aid of the microscope.For such colour comparisons, and also for following the parallel action of re- agents upon. two specimens of writing, the comparison microscope devised by Mr. A. S. Osborn, of New York, will be found of the greatest use.This instrument, which is made by Messrs. Bausch and Lomb, has two separate body-tubes, the upper ends of which are fitted into a prism-box containing a double prism. The objects to be compared are placed side by side below the respective objectives, and when viewed through the single eyepiece each appears to occupy one-half of the field, owing to the effect of the double prism.In each tube is a slot with a movable shutter intended for the introduction of Lovibond’s tintometer glmsea, so that it is possible to obtain a numerical record of the colour of any pigment placed under either objective. SOLUTION TEsTs.-Tht: behaviour of the pigments on treatment with different solvents is frequently characteristic. If a drop of water be placed on part of the writing and allowed to remain un- disturbed for a, few minutes, pronounced differences will be observed with different pigments.In some cases (e.g., Nos. 2, 3’4, 5, 6 and 12) there is immediate solution of the dyestuff, while in others (e.g., Nos. 10, 11, 17, 18 and 19) the drop remains colourless, or practically so, for five minutes or longer. As has been mentioned already, the amount of dyestuff which can be absorbed by applying filter-paper to the drop affords a rough indication of the copying capacity of the pigment. Again, the behsviour of ether may prove distinctive.There is usually a, pronounced centri- fugal action, but in some cases the dyestuff is diffused over the whole area, (Nos. 4, 5, 8 and 13), while in others the core is left much paler or nearly colourless, and dark zone is formed (Nos.9, 12 and 15). A similar test with a drop of acetic acid will sometimes distinguish between two cloeely similar pigments. The residue left after removal of the dyestuff by means of acetic acid should be examined microscopically. When much graphite is present, the carbon particles will be seen scattered plentifully all over the field, while pigments poor in graphite will show only a scanty sprinkling of carbon.The difference between Nos. 13 and 18 in this respect was quite pronounced. CHEMICAL TESTS.-A consideration of the analytical results given in the table indicates that chemical tests of differentiation may be based on the nature and quantity of the dyestuff, on the influence of the graphite or kaolin clay on the course of colour reactions given by the dyestuff, and on the presence of iron, alumina, or other mineral impurities in the pigments.The DyestzlfS.-The dyestuff in these pigments may be readily extracted by placing a drop of acetic acid or alcohol on a portion of the writing, and then applying filter-paper. To prevent any chance of reduction, the solvent should be allowed to evaporate spontaneously.The colour reactions of violet dyestuffs thus transferred as spots to filter-paper differ somewhat from those given by the same dyestuffs on sized paper, owing to the more rapid diffusion of the reagent in &he former case. The influence of any impurities in the dyestuff an the course of the reaction is much more pronounced in the tests on the non-absorbent paper.8 MITCHELL COPYING-INK PENCILS AND Methyl Violet Extra 1 Methyl Violet 111.h'. For example, I obtained the following results with samples of methyl violet and with crystal violet: ' REACTIONS OF METHYL VIOLETS ON SIXED PUER. Strong nitric acid . . Sulphuric mid (50%) Stannouschlmide . . Sodium nitrite with acetic acid Titanous chloride . .sodium hypochhrite with acetic acid Methyl Violet Extra 1 Methyl Violet 0. IIr. N. (B.A.s.F.). (B.A.s.F.). Bright yellow with green zone, c h q - ing to green Bright yellow, paler in centre Grass-green with dark green centre Blue with dark blue zone, subsequently bleached Bright yellow with green zone Blue - green centre, dark blue zone, be- fore bleaching Yellow to brownish- yellow, changing*to dark green mth purple core Yellow to greenish- yellow or brown Bluish-green Blue with dark blue zone Dirty yellow with faint green zone Blue core, white inner zone, dark blue outer zone Cryatal Violet (B.A.S.F.).Bright yellow, thin green zone Bright yellow Pale green, darker zone Violet blue centre, light blue and dark blue zones Bright yellow, thin green zone Pale blue, dark blue zone, before bleach- ing REACS~ONS OF METHYL VIOLETS ON FILTER-PAPER.Nitricacid . . .. Sulphuricacid .. H~dm~hloricacid . . Sfannouschloride . . sodiwn nitrite with Tifanouschloride . . acetic acid ! -- Greenwith orange zone Darkgreenwithorange i zone Bright yellow Bright yellow Deep green with Blue with darker Yellow, darkening darker centre zone Dull yellow Dull yellow Deep green, forming plum-coloured centre Blue with darker zone Dirty yellow Crystal Violet.--_ Bright yellow, then green with yellow zone Bright yellow Bright yellow, darken- * Grass-green with Violet-blue with Deep yellow darker centre darker zone _ _ -~ -_-- - _ _ ~ _ _ _ _ _____ ~ _ _ __ _ _ _ The sodium nitrite was applied in the form of 8 minute particle of the salt, which was then moistened with 80 per cent.acetic acid. The titanourr chloride waa the ordinary commercial solution, which had been kept for some years, and did not react as strongly as when fresh. In the tests applied to the filter-paper stains the differences in the coloratione given by Methyl Tiolet Extra, 111. N. and 0. were mainly in the brilliancy of the former, and they were hardly sufficiently distinctive to diff ereatiate between the two dyestuffa. The alcoholic extrwts from most of the pencil pigments left stains which gave very similar colour reactions.THE EXAMINATION OF THEIR PIGMENTS IN WRITING 9 In the case of the two blue pencil pigments, however, there was a pronounced difference.The blue Duplex pencil (No. 1) contained a, water-soluble blue aniline dyestuff, while in Faber’s blue pencil (No.11) the soluble dyestuff to which it owed its copying properties was methyl violet, and its blue colour was due to Prussian blue. In applying these reagents to the pigments of the pencils in writing, the course of the colour reactions should be followed under the microscope. Speaking generally, they will resemble the reactions of the residues from the extracts, but will vary in their speed and intensity with the proportion of the dyestuff, while the purity of the colour will be affected by the other constituents of the pigment.Another useful reagent is 5 per cent. potassium ferrocyanide solution, which is applied to the spot from which the pigment has been extracted by means of acetic acid. I n some cases (e.g., No.21) a pronounced green coloration was obtained immediately, while in others there was only the faintest indication of iron after a long period (e.g., No. 5 ) . I attempted to adapt F. Atack’s alizarine red test (ANALYST, 1915,40,511) for alumina, using a specimen of the dyestuff which he kindly placed a t my disposal. Unfortunately, the test was unsuitable for this purpose, as a blood-red coloration was obtained with certain papers to which no pigment had been applied, apparently owing to the presence of alum in the paper.Silver nitrate solution may be employed as an additional. test, a drop being applied to the writing either before or after treatment with acetic acid. The pre- sence of chloride is shown by the growing opalescence of the drop, as seen under the microscope.In this way i t was possible to distinguish between the pigments in the two violet pencils made by Faber (Nos. 9 and 10). By way of illustration,the case of Rex v. Wood, tried in 1907, may be cited. Some fragments of partially burned paper, on which were words written in copying- ink pencil, were found in the grate of a room where a woman had been murdered.The resemblance of the writing to that upon a postcard led to the arrest of the man Wood, and in his pocket was found a Swan copying-ink pencil. The question was thus raised whether the pigment of this pencil could have been used in writing the words on the fragments. The colour of the pigment when applied to paper matched exactly, both in light and dark portions, the colour of writing on the fragments. It was a very deep purple, quite distinct from the colour of the ordinary Swan copying-ink pencil (No.1039). The colour somewhat resembled that of the pigments in some of the pencils made by the Eagle Pencil Co., but the Eolutjon test with a drop of water sharply differ- entiated between the two pigments. The writing on the fragments and that pro- duced by Wood’s pencil repelled the water for a long time, and the drops remained practically oolourless for five minutes. Ether produced a fairly uniform stain with very little centrifugal effect, while acetic acid acted rapidly, producing zones and extracting much dyestuff. Two good copies could be taken on filter-paper of the acetic acid stains, while the residue still retained colour.This residue showed a, larger proportion of graphite particles10 MITCHELL : COPYTXG-INK PEXCILS AND than the Swan pencil (No. 1039), although these were scanty as compared with results given by pencils rich in graphite. The ferrocyanide test applied to the residue from the acetic acid treatment showed no indications of green coloration at first, and only a elight green tint after drying.In this respect the pigment resembled that of the Swan pencil (No 1039). The following coloup reactions were given by this pigment in comparison with certain other pencil pigments : Nitricacid .. StaMous chlor- ide sodium nitrite with acetic acid Titanous chlor- ide Sodium hypo- chlorite with acetic acid Wood’s Pencil, and Writing on Fragments. Yellow to deep orange, accord- ing to amount of pigment.Greenish zone with tendency to form OllteI pale zone. Dried w i t h dirty mauve orgreen- ish centre Dirty green Deep bluish - green, leaving pale green core, and dark blue narrow zone Deep yellow, slowly bleached. Left pale green core, deep blue zone Rapidly bleached. Deep violet-blue zone Swan Pencil 1039 (No. 18). Very faint yellow, bleached Light dirty &reen Rapidly bleached, leaving narrow pale blue zone Bright yellow, quickly bleached.Left very pale green core, with wide blue green zone Rapidly deaehed. Light violet-blue zone _______ Hessin’s Pencil (Xo. 13). -_____- Very pale green, slowly darkened to olive-green Faint lemon- yellow Bleached, leaving pale blue zone Yellow, then bleached Bleached, leaving pale blue zone __-____ Faber’s Pencil (No.9). --- Pale green drop, with light- yellow zone Faint straw tint Deep blue zone, neasly colourless core Bright yellow, bleached elowly Slowly bleached. Colourless P U d Eagle Pencil (No. 5 ) . I_ Pale green, darkening to olive-green Faint straw tint Deep blue zone, pale-blue corn Dirty yellow Rapidly bleached. Colourless am8 The general course of the reactions of the pigment of Wood’s pencil and of the writing on the fragments was similar to those given by the Swan pencil, but they c auld be readily distinguished when compared under the microscope.After having denied that he had written the words on the fragments, Wood subsequently admitted that he had done so. In another criminal case (Rez v. Seddon) the question was raised whether the entries of payments in a, note-book over a period of fourteen months had been made on the corresponding data.The pigment of the copying-ink pencil was of the sameTHE EXAMINATION OF THELR PIGMENTS IN WRITING 11 character throughout the whole period, but it was, of course, impossible to express any opinion as to the age of my part of the writing.The degree of permanence of methyl violet in association with graphite and kaolin clay has not been ascertained, although the dyestuff by itself is well known t o be fugitive. It is possible that under certain conditions the degree of fading might enable an estimate of the age of writing to be formed. In the case of Macbeth v. King, which was tried in July of this year (1916), the question of the fastness of copying pencils was raised.The steamship Membland was presumably lost a t sea eerly in 1915. Two months later the stave of a wooden ’bucket was washed ashore near Hornsea, and on this was written in copying-ink pencil the words cT Membland *torpedoed engine-room port-side. Good-bye, dear.” If this were genuine, it would show that the vessel had been sunk by war risks, -and one get of underwriters would be liable. Otherwise it was contended that the ship had fallen a victim to ord.inary marine risks. At the Board of Trade inquiry in 1915 it had been suggested that a copying- ’ink pencil pigment would not withstand the action of sea-water for two months. To determine this point I wrote words on pieces of oak with four kinds of copying-ink pencil, and placed these in a strong solution of salt and water in a glass basid, which was shaken a t frequent intervals and exposed to strong sunlight. The writing on these slips remained quite legible after eight weeks, although the writing done with Hardmuth’s pencil was less smudged than that done with the Eagle or Atlas pencil. The pigment from Faber’s pencil was most affected by the treatment. There would therefore seem to be little doubt as to the possibility of writing done with a. copying-ink pencil remaining relatively anaff ected when immersed in sea-water for a long period. In giving his decision, the judge held that conceivably the stave waa genuine, but he was not convinced on the point; he decided, however, upon other grounds that the vessel had been lost by war risks. (See Times Law Reports, 1916,32,SSl.) In conclusion, I would thank Messrs. Wolff and Sons for their kindness in supplying me with specimens of their pencils and details as to their manufacture; and the Bausch and Lomb Optioal Company for the loan of instruments and infor- mation with regard to the construction of the comparison microscope.

ISSN:0003-2654    

DOI:10.1039/AN9174200003

出版商:RSC    

年代:1917

数据来源: RSC

摘要:

12 ATKINB: THE ANALYSIS OF HONEY THE ANALYSIS OF HONEY AND OTHER SUBSTANCES CONTAINING LJEVULOSE. BY W. R. G. ATKINS, Sc.D. (Red at the Meeting, December 6,1916.) IN the course of some work on mixtures of the three reducing sugars, dextrose bvulose, and maltose, met with in plant tissues, it was found necessary to devise means for the estimation of each. If maltose is hydrolysed by prolonged boiling with acid, so much laevulose is destroyed as to render the estimation worthlem The oxidising action of bromine in removing aldehydic sugars while leaving the ketonic sugar lzevulose untouched, was finally made use of for the purpose of estimat ing one constituent of the mixture of the three sugars. While the work was in progress the researches of Davis and Daish (ANALYST, 1913,38,504) were published These workers obtained very accurate results, but the preparation of cultures of pure yeasts is troublesome, and the length of time, about twenty-one days, required for complete fermentation is a drawback to the general usefulness of the method for technical analyses.The bromine method of Wilson and Atkins (ANALYST, 1917, 19) does not give as accurate results as those obtained by Davis and Daish, but it is rapid.If a mixture containing dextrose, laevulose, and maltose, to which has been added excess of bromine and enough sulphuric acid to render the solution deci- normal, be allowed to remain for forty-two hours at room temperature, the laevulose only is unoxidised. To insure completion of the reaction the reaction flask must be ahaken continuously during the period.This may be effected by causing it to rotate slowly with the long axis of the bottle a t a small angle to the horizontal Glms beads in the solution may also be used to assist shaking. The maltose leaves a mere trace of reducing power, dextrose leaves approximately 1 per- cent. of the original reducing power? and laevulose falls off in reducing power approximately 1 to 2 per cent., owing to its decomposition, even in the cold, by the & acid i n d by the hydrobromic acid formed during the oxidation of the other pugare The slight loss in the quantity of laevulose is roughly balanced by the reducing power remaining after the destruction of the dextrot3e and maltose. The excess o bromine is cautiously removed by gaseous sulphur dioxide, and finally by titratio] with dolution of t,he gas in water.The acidity is just removed by the addition o potassium carbonate, care being taken to leave the liquid neutral or faintly acid, bu not alkaline. Fo this we found Kendall’s solution (ANALYST, 1912,37, 205) suitable, as it does no dissolve the cuprous oxide. Kendall did not give a, table for laevulose, so one wa constructed by the author (ANALYST, 1916,41,285).By this means laevulose may be estimated readily and with tolerable accurac in the presbnce of dextrose and maltose, or either of them. If only dextrose an lmvulose are pregent, as in natural honey, which contains about 36 per cent. of th latter, it is sufficient to determine the reducing power before and after oxidatio The reducing power of an aliquot portion is then determined.AND OTHER SUBSTAXCES CONTAINING LLEVUJIQSE 13 with bromine. The cane-sugar in the honey musf be estimated separately by determining the reducing power before and after inversion.Oxidation should be effected on the inverted solution, due allowance being afterwards made for the dextrose and laevu1,ose resulting from the inversion.It is, of course, possible to estimate dextrose and lsvulose in a mixture of the two by obtaining the total reducing power and the optical activity. From these data, two equations can be constructed, and a solution of the simultaneous equations gives the values of each. In this procedure, however, errors are magniiied, and the procedure is not so accurate as the determination of reducing power before and after oxidation. It appears that oxidation with bromine may be of use in the technical analysis of honey, syrups, jams, and other articles containing these sugars, especially as it affords an easy method of detecting the presence of dextrose in abnormal quantities. TRINITY COLLEQE, DUBLIN.

ISSN:0003-2654    

DOI:10.1039/AN9174200012

出版商:RSC    

年代:1917

数据来源: RSC

摘要:

AND OTHER SUBSTAXCES CONTAINING LLEVUJIQSE 13 ABSTRACTS OF PAPERS PUBLISHED IN OTHER JOURNALS. FOOD AND DRUGS ANALYSIS. Vitamines and Lipoids in Butter and Margarine. J. de Ruiter. ( J . Id. and Eng. Ghem., 1916, 8, 1020-1021.)-A method of estimating lipoid substances in oils in fats was based on their solubility in concentrated acids, and precipita- tion on dilution with water. Results were most rapidly obtained by means of hydrochloric acid of sp.gr. 1.19, the lipoid being subsequently separated by the addition of water, washed on a filter, dried a t 100” C., and weighed. In this way the following results in grms. per 100 C.C. of fat were obtained: Sesame oil, 0.10; arachis oil, trace; olive oil, trace; cod-liver oil, trace; refmed coconut oil, trace; filtered butter fat, trace ; butter, 0.40 ; vegetable margarine (“ Klappa ”), 0.75 ; vegetable margarine (“ Planta ”), 0.475; margarine, 0-975; and “bran butter,” 1.125. These results indicate that the lipoids in butter are not in the fat, but in the casein, and that they represent only a part of the total lipoid content of milk (0.75 per cent.).The vegetable margarine and the margarine proper derived their lipoids mainly from the skimmed milk with which they were churned, while egg yolk in addition to skimmed milk may have caused the high result given by the margarine.It is suggested that albumin containing vegetable seeds may be used to increase the Lipoids in margarine, as was done in the case of the “ bran butter,’’ which was pre- pared from arachis oil and coconut oil incorporated with a liquid obtained by steeping wheat bran in lime water and separating it from the deposit of starch.C. A. M.14 ABSTRACTS OF CHEMICAL PAPERS Detection of Excess of Shell in Cacao Powder. (Chem. Zeit., 1916,40,969- WO.)-ThefoUowing official (German) methods are given for the detection of an excess of cacao shell in cacao powder. If a preliminary microscopical examination of the cacao shows indications of an excessive proportion of shell particles in the ssmple, an estimation of the amount of crude fibre is made.In some cases, however, owing to the fineness to which the shell has been ground, the microscopical examination does not indicate plainly that excess of husk is present, and the insoluble phosphatee must be estimated in addition to the crude fibre. Estimations of the moisture and fat are esaential, since the results for crude fibre are expressed in terms of the dry, fat-free substance.Es€imution of Moisture.-l?ive grms. of the sample are mixed with 20 grms. of ignibed sand, and the mixture is dried at 105" C., until practically constant in weight, but the heating should in no case be prolonged for more than four hours.E8t~mzt~on of Fd.-Five grms. of the cacao are placed in a tube 4 cm. in diameter and containing a small layer of asbestos supported on a, porcelain plate having holes about 1 mm. in diameter; this filter tube is attached to a filter ffask, and 10 C.C. of ether are poured on the surface of the layer of cacao. As soon rn the ether begins to drop into the flaek, suction is applied, and further quantities of 10 C.C.of ether are added, successively, until about 100 C.C. of ethereal solution have been collected. This solution is then evaporated and the residue of fat weighed. Ei3timution of Crude Fibre.-The residue of cacao remaining in the filter tube ia freed from ether, and, together with the asbestos (the asbestos used in this and the succeeding filters should have been boiled with dilute sulphuric acid, then with dilute potassium hydroxide solution, washed, dried, and ignited), is transferred to a flask and boiled for one hour under a reflux condenser with 200 C.C.of 1.25 per cent. sulphuric mid. The mixture is then filtered through an asbestos ater, waahed with hot water, and the filter and its contents are returned to the flask and boiled for one hour with 200 C.C.of 1.25 per cent. pota.ssium hydroxide solution. The mws is again collected on an asbestos filter and washed, and the treatment with sulphuric acid and alkali solution repeated. The washed mixture of asbestos and crude fibre obtained finally is transferred to a platinum basin, dried a t 105" C., and weighed, then ignited, and again weighed.The dserence between the two weights gives the quantity of crude fibre present. The fat-free, dry cacao should not contain more than 6 per cent. of crude fibre; if this limit is exceeded, the cacao contains an amount of shell in excess of that which is present in well-manufactured cacao powder. Bstimation ofPb~phates.-Twenty grms.of the cmao are ignited at a low temperature, the carbonised mass is collected on a filter, washed with hot water, and the filter and its contents are ignited in $I platinum basin fo a white ash; the filtrate is now added to the basin and evaporated to dryness.The residue thus obtained is gently ignitecl, again evaporated with the addition of a few drops of hydrogen peroxide aolution and 10 c:c. of 25 per cent.hydrochloric acid, the residue is taken up with hydrochloric acid and hot water, the solution is filtered, the filtrate nearly neutralked With sodium hydroxide solution, using methyl orange as indicator, then heated on a water-bath for five minutes, and treated with a further small quantity of alkali, so that the solution still remains slightly acid in reaction. The precipitated iron and aluminium phosphates are now collected on a filter and washed.The filtrateFOOD AND DRUGS ANALYSIS 15 is diluted to 100 C.C. The soluble phosphates are estimated by treating 10 C.C. of this solution with 30 C.C. of neutral calcium chloride solution, adding a, few drops of phenolphthalein solution, titrating the mixture with & sodium hydroxide solu- tion until a distinct red coloration is obtained, then keeping the mixture at 15” C.for two hours, and titrating the slight excess of alkali added. Under these con- ditions 1 C.C. of & alkali solution is equivalent to 4.75 mgrms. of PO4. To estimate the insoluble phosphates, the filter containing the precipitated iron and aluminium phosphates is transferred to a flask containing 30 C.C.of trisodium citrate solution (200 grms. of the salt dissolved in 300 C.C. of water) which have been previously cooled in ice-water and neutralised, using phenolphthale’in as the indicator. The contents of the flask are heated on a water-bath for twenty minutes, then cooled in ice-water, and titrated with =& sodium hydroxide solution. Each C.C. of -& alkali solution is equivalent to 9.5 mgrms.of POa. The results of both estimations are expressed as percentages of the cacao powder; in the case of a cacao free from an excessive quantity of shell, the proportion of insoluble PO4 will not exceed 4 per cent. of the total PO4. w. P. s. Fermented Milk Products: the ‘‘ Laben Raieb ” of Egypt and the c 4 Mieiu- ratu” of Sardinia. A. Sanna. (Stax. sperim.agrar. ital., 1914, 49, 773-788; through Int. Rev. of the Science and Practice of Agriculture, 1916, 7 , 878-880.)- “ Miciuratu ” is prepared by boiling milk (cow’s, ewe’s or goat’s, or a, mixture of the three) for about six minutes, then cooling it to 37” C., and introducing the ferment diluted with milk; after seven hours the milk forms a doughy mass and is ready for consumption.The sugar, fah, and proteins undergo changes during the preparation, the sugar being converted into lactic acid; the acidity increases gradually up to the end of three days, after which time the product is unfit for use owing to butyric fermentation. Ethyl alcohol is also formed, the three-day-old product containing about 2 per cent. of this alcohol, and traces of acetaldehyde are present.The casein and albumin are parfially peptonised and the fat is hydrolysn,d to a slight extent, traces of glycerol appearing in the product. “ Laben raieb ” is prepared in a similar manner, but the milk is evaporated at 80” C. until its volume is reduced by one- third before the ferment is introduced; the ferment in this case consists of a mixture of milk (also concentrsted by one-third) and “ laben raieb ” prepared the day before.Allowing for the difference in concentration, its composition is similar to that of ‘‘ miciurat~.~.” w. P. s. Detection of Resoreinol. F. C. Krauskopf and G. Ritter. (J. Amer. Chem. Xoc., 1916’38, 2182-2187.)-When as little as 1 mgrm. of resorcinol dissolved in 50 C.C. of water is treated with 1 C.C. of a dilute solution of cobalt chloride (0.4 grm.cobalt per litre), 0.25 C.C. of concentrated ammonia, and 3 C.C. of 95 per cent. alcohol, a dark green colour is developed. Phenol under similar conditions does not produce any’ colour, whilst cateohol, quinol, and pyrogallol, when present in sufficient quantity, develop a brown colour. Nevertheless, the solution is green without a perceptible trace of brown if as much as 10 mgrms.of resorcinol are present in 50 C.C. of a solution containing 0.2 grm. of quinol or of pyrogdlol. As little as 5 mgrms. of resorcinol16 ABSTRACTS OF CHEMICAL PAPERS can be readily detmted in presence of 0.2 grrn. of catechol. Although phenol does not itself produce an interfering colour, it reduces the sensitiveness of the test for resorcinol to about 5 mgrms.in 50 C.C. of solution containing 0-3 grm. of phenol. G. C. J. Estimation of Salol and Acetanilide, or of Salol and Phenacetin, in their Mixtures. B. Salkover. (Amer. J. Pharm., 1916, 88, 484-485.)--The method depends on the relative insolubility of acetanilide or phenacetin in petroleum spirit, and on the solubility of salol in this solvent. A weighed quantity of the mixture under examimtion is shaken for thirty minutes in a closed flask with a measured volume of chloroform; an aliquot portion of the solution is then filtered into weighed flask, the chloroform is evaporated, the residue dried a t 60" C., and weighed.This estimation gives the combined amount of salol and acetanilide, or of salol and phenacetin, which may be present.Another portion of the sample is then extracted in a similar way with petroleum spirit; the residue obtained is dried a t 50" C., and weighed. In this case the residue consists of salol alone, but its weight must be corrected for the slight solubility of acetanilide or phenacetin, depending on which of these is present in the mixture. One hundred C.C. of petroleum spirit (b.-pt.40" to 45" C.) dissolve 0.015 grm. of phenacetin or 0-022 gm. of acetanilide. The accuracy of the method is not affected by the presence of talc, starch, acacia or tragacanfh. w. P. s. Estimation of Sugar in Meat Products, particularly Extracts. W. B. Smith (J. I d . and Eng. Chem., 1916, 8, 1024-1027.)-Five grms. of meat extract in about 25 C.C. of water (or the aqueous decoction from 50 grms.of the finely divided meat product) are treated with an excess (4 to 6 grms.) of solid picric acid and an excess (40 to 60 c.c.) of a 20 per cent. aqueous solution of phosphotungatic acid, and made up to 100 C.C. and filtered. An aliquot portion (60 c.c.) of the filtrate is treated with 3 C.C. (or more if necessary) of hydrochloric acid, made up to 66 c.c., and filtered rapidly, and the reducing sugar estimated without delay by means of Fehling's solution.In the presence of cane sugar the results will be accurate within 0.1 or 0-2 per cent., provided that the hydrochloric acid in the filtrate is neutralised a t once; otherwise slow inversion will continue. Another portion of the filtrate is inverted with hydrochloric acid and the invert sugar estimated.@. A. M. Estimation of Strychnine in Ntcx Vmndca. H. R. Jensen. (Pham. J . , 1916997, 458-461.)-The unnecesaary manipulation and the hot (50" C . ) nitration method prescribed in the British Pharmacopceia, 1914, for the separation of brucine from Strychnine is unreliable, and gives results for strychnine which are from 5 to 11 per cent. too low. Nitration at 20" C.with " active " nitric or with nitric acid which has been " activated " with sodium nitrite is more trustworthy. Attention is drawn to the fact that when the nitrated mixture is treated with sodium hydroxide strychnine nitrate is liable to "salt out" before it is decomposed by the alkali; this strychnine nitrate is very slightly soluble in chloroform, but to an extent suffi- cient to influence the results.In a number of experiments the average contaminationFOOD AND DRUGS ANALYSIS 17 of the alkaloid by strychnine nitrate was 843 per cent., and in each case the nitrate gradually crystallised from the chloroform extract. The alkaloid may also be contaminated by igomeric strychnine compounds formed during the nitration. It is recommended, therefore, that the residue of strychnine should be weighed, then dissolved and titrated, using cochineal as the indicator.The actual quantity of strychnine present is then found by calculation from the gravimetric and voh- metric results obtained. w. P. s. Estimation of Vanillin in Vanilla Extract. A. W. Dox and G. P. Plaisanee. (Amer. J. Pharm., 1916,@, 481-484.)-The vanillin is precipitated by thiobatrbituric acid in hydrochloric acid solutioh; the precipitate formed is the condensation pro- duct, 3-methoxy-d-hydroxybenzaImalonylthiourea. Twenty-five C.C.of the ex- tract are evaporated to remove alcohol, and are then diluted t o 50 G.C. with lead acetate solution; after standing for several hours a t 37" C., the mixture is filtered, 40 C.C. of the filtrate are treated with concentrated hydrochloric acid in quantity sufficient to make the volume up to 50 C.C.and the acidity 12 per cent., the lead chloride formed is separated by filtration, and 40 C.C. of this filtrate are mixed with thiobarbituric acid in 12 per cent. hydrochloric acid solution. After about eighteel1 hours, the orange-coloured precipitate is collected on a filter, washed with 50 C.C. of 12 per cent. hydrochloric acid, then with 20 C.C. of water, dried at 98" C., and weighed. A correction of 2-6 mgrms. is added to the weight of precipitate found, this being the allowance for the slight solubility of the compound. The method cannot be applied to artificial extracts coloured with caramel, sime this contains furfuraldehydic derivatives, and thiobarbituric acid is a precipitant for all aromatic aldehydes. The presence of caramel is denoted by the brown colour of the filtrate obtained after the treatment with lead acetate ; this filtrate is straw-coloured in the absence of caramel. The latter may also be detected by the formation of a brown precipitate when the acidified filtrate is treated with phloroglucinol. W. P. s.

ISSN:0003-2654    

DOI:10.1039/AN9174200013

出版商:RSC    

年代:1917

数据来源: RSC

摘要:

FOOD AND DRUGS ANALYSIS 17 BACTERIOLOGICAL, PHYSIOLOGICAL, ETC. Comparative Study of the Proteins of the Colostrum and milk of the Cow and their Relations to Serum Proteins. C. Crowther and H. Raistriek. (Biochem. J., 1916, 10, 434-451 .)-The chief proteins of cow’s colostrum and cow’s milk were isolated, and ctnalysed by the method of van Slyke, with the following results : Caseinogen, total lactoglobulin, and lactalbumin are sharply differentiated and distinct proteins, and have respectively the same composition whether prepared from colostrum or from normal milk.The presence in milk of a globulin in small quantities (0.03 per cent isolated) was proved. Eulactoglobulin and pseudolacto- globulin are identical as far as the protein part; of their molecules is concerned. Lactoglobulin from either colostrum or milk is very closely allied to, and is probably identical with, serum globulin from ox-blood.Lactalburnin from either colostrum or milk is very different in composition from serum albumin from ox-blood. H. F. E. H.18 AB8TRACTB OF CHEMICAL PAPER8 Reactions of Peroxidase purified by Ultrafiltration. A. Bach. (Arch. 8ci. p h p .nat., 1916, [iv.], 42, 56-61; through J. Ckm. Soc., 1916,110, i., 682-683.) w h i l s t phenol, guaiacol, quinol, and pyropllol were found to give the same colour reactions with an extract of horse-radi& and when the same extract was aubjected t o ultrafiltration in presence of hydrogen peroxide, very different results were obfained with orcinol, aniline, dimethyl- and diethyl-aniline, benzidine, and p-phenylenediamine.When o-cresol and saligenin are treated with a mixture of purified peroxidme and hydrogen peroxide, a yellow colour is produced in both cases, which changes fo brown and then to reddish-brown. Salicylaldehyde only reacts when the solution is made slightly alkaline with hydrogen-potassium phosphate. Salicyljc acid gives no reaction. Ii the oxidation of 0-cresol and saligenin, formic wid is produced, but no appreciable amount of carbon dioxide can be detected.Ethyl alcohol is not attacked. It is considered more probable that ethyl alcohol is oxidised by a mixture than by a specific “ alcoholoxidase.” Examination of Certain Methods for the Study of Proteolytic Action. H. C. Sherman and D. E. Neun. ( J . Amer. Chem.Soc., 1916, 38, 2199-2216.)- The experiments recorded were all carried out with preparations of commercial pepsin and trypsin, the following methods being employed: (1) The Mett method; (2) the estimation of total nitrogen of digestion products ; (3) the measurement of increase of amino nitrogen by the Van Slyke method ; (4) the titration of the acidity of acid cleavage products (Volhard Lohlein method) ; (5) the increase of electrical conductivity; (6) the polarimetric method; (7) the biuret reaction; (8) the triketo- hydrindene hydrate (Ninhydrin) method.In every case, with the exception of the Mett method, a casein substrate was used. In general terms it was found that the quantitative estimation of the total nitrogen (2), or of the amino nitrogen of the digestion products (3), or both, were more delicate methods of detecting profeolysis than either the biuret or the Ninhydrin reactions, and also more generally applicable as a means for its measurement than any of the other methods.All the results emphasised the importance in quantitative comparisons of so limiting the amount of enzyme preparation and the time of its action as to keep within the region in which the velocity of hydrolysis is directly proportional to the enzyme concentration.As regards the popular Mett method, it wa8 found to be quite unreliable for trypsin a t all concentrations, owing to the action of the a b l i upon the albumin, while with pepein the action is only approximately proportional to the quantity of pepsin employed a t the very lowest concentrations at which the length of column digested is too short for accurate measurement.With the second method described above it was found that the amount of digested nitrogen increamd in direct proportion to the amount of enzyme used to about 20 to 25 mgrms. of nitrogen in the case of pepsin, or 40 to 60 mgrms. in the case of trypsin, quantities large enough to be determined by the Kjeldahl method with 8r high degree of accuracy. The nitrogen is estimated in the filtrate after precipitating the undigested casein by aodium sulphate and hydrochloric acid.For the estimations by the Van Slyke method the “ micro ” apparatus, using the new 3 C.C. gas burette, was employed. The pohrimetric method was found to afford a delicate means of detecting the action of very small amounts of proteolytic enzyme, but the fact that the change in rotationI I39 0 V L a 0 9 L 0 U 138 137 136 135 134 t33 132 131 130 I29 '12 8 127 126 125 12 4 123 122 121 120 i 19 118 8'17 112 1 1 1 110 109 108 106 105 I04 103 102 r 01 100 99 98 97 36 95 194 '93 '92 92 9 0 89 ' 8 8 87 8 6 85 8 q '8 3 82 81 Boiling Point o f Last 5 0 c.c.Boilmq Point o f Last 50 C.C.0 1 rn L t i," 0 L 01 tj 0 <I- 0BACTERIOLOGICAL, PHYSIOLOGICAL, ETC. 19 does not proceed progressively with the amount of enzyme or its time of action neoessarily renders its use for quantitative work of little or no value. Neither the biuret nor the Ninhydrin reaction ist susceptible of yielding more than rough com- parisons of proteolytic power within the range covered by the colour changes, even when the greatly enhanced delicacy obtained by the Herzfeld modification of the latter is taken advantage of (Biochem. Zeitsch., 1914, 59,249; J .Biochem., 1915,20, 217; 1916, !&, 503. See also Long and Barton, ~ A L Y S T , 1914, 39,551). H. F. E. H. General Method of Estimating the Relative Turbidity or Opacity of Fluid Suspensions including Bacterial Emulsions.G. Dreyer and A. D. Gardner. (Biochem. J . , 1916,10,399-407.)- The procedure adopted embodies the main features of the method employed by Dreyer and Hansen in an investigation dealing with the effect of light on enzymes (Cmpt. rend., 1907, 145, 564). The method is of general application for all chemical and biological measurements of turbidity, and, as described in the present paper, is concerned specially with the standardisation of agglutinable cultures.A. graduated series of dilutions of each fluid is made in miniature test-tubes of uniform bore, clean and free from scratches. By artificial light against a black background the turbiditjes of a number of tubes of one series are matched against a succesr;ion of tubes of the other series. Each reading pro- vides figures from which the relative turbidities can be calculated, and by taking the average of a number of readings, an accurate ratio is obtainable. Special details are given of the method of cdculation, and the method is shown to be capable of great accuracy in the estimation of silver in high dilutions when precipitated as silver chloride, as well as for the comparison of bacterial growths in broth, etc. H. F. E. H.

ISSN:0003-2654    

DOI:10.1039/AN9174200017

出版商:RSC    

年代:1917

数据来源: RSC

摘要:

BACTERIOLOGICAL, PHYSIOLOGICAL, ETC. 19 ORGANIC ANALYSIS. Methods for the Estimation of Mixtures of Four or More Carbohydrates involving Oxidation with Bromine. E. G. Wilson and W. R. G. Atkins. (Biochem. J . , 1916, 10, 504-521 .)-The five carbohydrates usually found in foliage leaves are starch, cane-sugar, dextrose, Iawulose, and maltose, with, in addition, sometimes small quantities of pentoses.For the estimation of starch, see Davis and Daish (ANALYST, 1914,39, 312) ; and for pentoses, Davis and Sawyer (ibid., 1915, 40,128) and Daish (ibid., 1914,39,555). The present work deals only‘with the four remaining sugars. Since all methods involving the use of Fehling’s solution for the quantitative estimation of reducing sugars are liable to error, owing to the solvent action of the hot sodium hydroxide on cuprous oxide, it was decided to employ Kendall’s method (ANALYST, 1912,37, 205).It was found that dextrose and mal- tose are quantitatively oxidised by bromine at room temperature when allowed to stand in a saturated solution; the liquid, however, still retains a small amount of its original reducing power towards albline copper solutions.Lzevulose is not oxidised at a11 by bromine under these conditions, or only to a, very small extent, while in the presence of -& sulphuric acid there is a slight loss of laevulose in sixty-six hours at room temperature .20 ABSTRACTS OF CHEMICAL PAPERS A mixture of cane-sugar, maltose, dextrose, and lzevulose may be a n a l y d as follows: (a) The amount of cane-sugar is determined by polarisation and reduc- tion before and after treatment with invertase.(6) The resulting mixture of re- ducing sugars is treated with bromine under standard conditions of acidity and temperature for a given time. The aldehydic sugars, dextrose (including the p r - tion derived from cane-sugar) and maltose, are oxidised, and the 'ketonic sugar kmdose, (including the portion derived from cane-sugar), remains behind.ma reducing power of the solution may then be taken as due to the lsvulose only. (c) The rotations due to the lzevulose and cane-sugar are then allowed for in the initially determined rotation. This gives the rotation due to dextrose and maltose- ( d ) The reduction due to laevulose is subtracted from tho initial reduction. This gives the reduction due to dextrose and maltose.From these data two equations may be constructed, which, when solved, give the amounts of the two remaining sugars. When only dextrose and lsvulose are present, the bromine method enables the latter to be estimated directly. The addition of dilute alkali (z or 2N sodium hydroxide) to a solution of dex- trose, laevulose, or maltose was found to produce a large temporary increase in its reducing power.From a study of the electrical conductivity of a mixture of sodium hydroxide and dextrose some indication was obtained of the formation of a com- pound between these two substances. An attempt to modify Barfoed's solution (cupric acetate and acetic acid) for quantitative work, by reducing the reaction to the first order instead of the fifth, was found unsuccessful (Bunzel, Amer.J . Phy8iol., 1908, 21, 23). H. F. E. H. Modification of the Pratt Method for Estimation of Citric Acid. J. J. Willaman. ( J . Amer. Ohem. Soc., 1916,38,2193-2199.)-Pectins are precipitated by adding twice the volume of 50 per cent. alcohol to the aqueous solution. The solution is filtered through paper on a Buchner funnel, and the precipitate washed with 65 per cent. alcohol.The filtrate is diluted until approximately of 30 per cent. alcoholic strength, and 5 C.C. of a 10 per cent. solution of barium acetate in 30 per cent. alcohol are then added. The barium citrate is filtered off on a Gooch crucible, washed once with 30 per cent. alcohol, dried, and dissolved in hot 6 per cent. phosphoric acid (60 c.c.), followed by about 40 C.C.hot water. The solution is transferred to a dia- Wing flask, the side tube of which is connected to a condenser, whilst the cork in the neck carries a tap funnel or other arrangement for running in a 0-05 per cent. solution of permanganate. Precautions must be taken against bumping. The adapter of the condenser dips into 40 C.C. of Denigh' mercuric reagent for acetone, made by heating 50 grms.of mercuric oxide with 500 C.C. water and 200 C.C. sulphuric acid, making up to 1,000 c.c., and filtering. The citric acid solution is heated to boiling, and permanganate is run in at the rate of about 5 C.C. a minute, the distillation pro- ceeding at a somewhat faster rate. When 'a deep pink colour has persisted for two minutes, the reaction is complete.The distillate is made up to 300 c.c., and if more bulky than this, 15 C.C. of Denigds' reagent are added for each additional 100 C.C. It is then boiled under a reflux condenser for forty-five minutes, after which the precipitate is filtered off and washed twice with hot water. The precipitate adheringORGANIC ANALYSIS 21 to the flask is dissolved in a small quantity of hot 5 per cent.hydrochloric acid, which is then used to dissolve the precipitate on the filter. The flask and filter are thoroughly washed with hot water, the solution nearly neutralised with 10 per cent. sodium hydroxide, made up to 100 c.c., and transferred to a burette. It is then titrated against a measured quantity of potassium iodide solution containing 28.02 grms.per litre, 1 C.C. of which equals 2 mgrms. of citric acid under the conditions of the experiment. G . C. J. Errors in the Estimation of Acid Values of Boiled Oils and Varnishes. E. E. Ware and R. E. Chrisfman. ( J . I d . and Eng. Chem., 1916,8, 996-997.)- The presence of metallic linoleates and resinates in a boiled oil or varnish will cam= the acid value t o appear too high, since the potassium hydroxide will not only neutralise the free fatty acids of the soap, but also hydrolyse the metallic soaps.In test experiments the linseed oil soaps of lead, manganese, cobalt, calcium, and zinc were prepared, dried in vacuo, dissolved in alcohol-ether, and their " acid values " estimated in the usual way, the molecular equivalent of the acid radicle being taken its 280.The values obtained differed by only a few tenths from the calculated values, except in the case of the calcium soap, the hydrolysis of which had only been partial, so that the value was 79.5 instead of 1864. In like manner the resin- ates of the same metals were partially hydrolysed in the test, the difference between the observed and calculated " acid values " indicating that from 81.3 to 94.0 per cent.were hydrolysed (calcium resinate, 49-1 per cent.). A sample of linseed oil with an acid value of 3.05 was heated with lead linoleat,e until a cloudy solution was obtained, and then contained 1.15 per cent. of ash and had an acid value of 10.20. The same oil heated alone under parallel conditions showed an acid value of 2.31 and contained 0.18 per cent.of ash, the decrease in the acid value being attributable to volatilisation of fatty acids. The difference between the amounts of ash indicated the presence of about 1 per cent. of lead oxide in solution, and this would cause an apparent acid value in the oil of 7.1, assuming that hydrolysis occurred to the same extent as in the experiments. C . A.M. Some Fatty Oils. S. Uchida ( J . SOC. Chem. Ind., 1916, 35, lQ89-1093.)- Paru rubber tree seed (Hevea braziliensis) yielded on expression 32.88 per cent. of a pale yellow oil with .weak drying properties. Shiromoji seed oil, from Lindera triloba (yield from kernels, 45.26 per cent.), is a pale yellow non-drying oil, with a, higher saponification value than any other known vegetable oil.Calophyllum Oil, from Calophyllum inophyllurn (yield from kernels, 33-83 per cent.), is a dark green, viscous, semi-drying oil, the high acid value of which is due to the presence of resin. H e r n d i a seed oil, from Hernandia peltata (yield from kernels, 33-89 per cent.), is a reddish-brown oil, which dries to a soft brittle film when heated for six hours at 100" C. It is suitable for soaps and rubber substitutes and as a, lamp oil.Hakuunboku seed oiE, from Styrax obussia (yield from kernels, 30-51 per cent.), is a semi-drying oil, containing a c6nsiderable amount of volatile fatty acids (butyrio acid). Akebi seed oil, from the Japanese shrub AEebia quinuta (yield frdm kernels, 17.69 per cent.), is a yellowish-brown non-drying oil, with an extremely high Reichert-Oil from OIL.Para rubber tree seed . . .. FATTY ACJDS. Shiromoji seed . . .. .. Calophyllum seed .. .. Hernandia seed . . .. .. Hakuunboku seed .. .. Akebi seed .. .. .. Kuromoji seed . , .. .. e Aburwhan seed . . .. .. Magnolia whole fruit . . .. ,) fruit flesh . . .. 9 ) 9 ) .. .. Tea seed .. .. .. Sp. Or. at 15' C. 0 *9239 0.9361 0 *9452 0.9380 0.9610 0 *9340 009401 0 a9348 0.9315 0 *9239 0.9288 0.9126 at 30"/30" C.: (3Oo/3O0 C.) - Refractive Index.La4720 (27.5" C.) 1.4732 (27.3" C.) 1.47925 (26.8" 0.1 1.47735 (27.2" C.] 1.48925 (27.5" C.: 1.46145 (27.5" C.: 1.4680 (27" C.) 1*4550 (27" C.) 1.4739 (26.8" C.) 1.4693 (27" C.) 1.4754 (27" C.) 1.4669 (27.6" C . ) 4.21 191.9 0.30'95*37 130.8 - 0.63 282.0 2-03 85-72 11.68 - 6-91 194.1 0.389341 95.49 37 7-39 195.7 1-77 93.17 126.1 - I 1.73 1814 16*45'92*94 115.4 - 25.45 246.4 39-76 85.80 18.78 255.6 2.53 86-22 66.29 - 2.60 2734 1.39 89.21 20.53 - 13-43 224.4 4-93 93-11 109.2 36- 35.5 13.59 205-0 4.67 91.83 89.53 36.5 78-38 3&3( 6.69 207.4 0.1719864 1246 - I 4-12 193.8 0*10(95*76 86-2 - I I---- ----I -- 27-0 185.0 1164 303.3 ti I4 14.0 287.1 12*19105-4 28-29 190.1 95.4 295.1 12-13 185-7 130.0 302-1 3 0~ c) 14-136 1664 114.7 337.8 31 191.7 77.8 292-7 P 9-5 262.0 37-0 214-1 ' td 134 277.2 18*282024 t4 28-284 201.9 99-662774 32-324 205-1 86-16 273.6 17.5-17-0 193.7 125.5 289.6 26.5 190.5 80.79 294.5 "!--.---- -3 IORGANIC ANALYSIS 23 Meissl value.It can be used for edible purposes and for the manufacture of soap and Turkey-red oil.Kuromoji seed oil, from Lindera serica (yield from kernels, 58.02 per cent.), has an aromatic odour. It is best suited for soap-making. Abura- chan seed oil, from Lindera prmox (yield from kernels, 18.17 per cent.), is a dark brown non-drying oil. Nagnolia fruit oil, from Magnolia hypoleuca (yield from seed and flesh, 31-51 per cent.), is a semi-drying oil suitable for burning and soap- making.The flesh alone yielded 35.34 per cent, of oil, and the seeds 7-74 per cent., but it would not be profita'ble to press them separately. Tea seed oil (Thea Chinemis) is a pale brown non-drying oil suitable for soap-making, lubrication, and burning. With strong sulphuric acid it gives an indigo-blue coloration, changing to greenish- brown on stirring. The following analytical values were obtained with these oils : (see p.22). C. A. M. Rapid Volumetric Estimation of Indigo. S. M. Jones and W. Spaans. ( J . Ind. a d Eng. Chern., 1916, 8, 1001-1002.)-This method, like that of Mtiller, is based on the reduction of indigo to indigo white. Instead, however, of working in presence of coal-gas, the authors use a current of hydrogen, which is found to be a great improvement.Formaldehyde sodium sulphoxylate also re- places the unstable sodium hydrosulphite as reducing agent; but as its action is slow, sodium bisulphite is added to set free sodium sulphoxylate and so accelerate the reaction. The sample (1 grm. of powder, proportionately more of paste) is mixed to an even paste with 15 C.C. sulphuric acid, a further 15 C.C.of acid is added, and the mixture heated to 55" to 60" C. for threehours, when sulphonation should be com- plete. The cooled mixture is diluted to 300 c.c., again cooled, diluted to exactly 1,000 c.c., and filtered. One grrn. of pure indigo is similarly treated to produce a standard for comparison. Fifty C.C. of the standard solution and 50 C.C. of 35 per cent. sodium bisulphite solution are mixed in a flask of 300 C.C.capacity, and the flask is closed with a rubber stopper with four holes. Through one of these a thermometer dips into the liquid, two provide for the admission and exit of hydrogen, whilst the fourth accommodates the tip of a burette. The air is displaced by hydrogen, and the mixture heated t o 75" C. Standard sodium formaldehyde sulphoxylate is then r m in from the burette until the blue colour disappears.This solution is made by dissolving 1 grm. of the solid reagent in 1,000 C.C. of water. The sample to be analysed is treated in a, similar manner. G. C. J. Estimation of Free and Combined Galactose. A. W. Van der Haar. (Chem. Weekblad, 1916, 13, 1204-L213.)-This method, which is a modification of that of Creydt (Dissert., Erlangen, 1888), is based on the oxidation of galactose to mucic acid by means of nitric acid.In the case of free d-galactose, from 0-25 to 1 grm. is heated with occasional agitation with 60 C.C. of nitric acid (sp. gr. 1.15 a t 15" C.) in a beaker 12 cm. in height and 60 mm. in diameter, which is placed in a boiling- water bath. When the contents of the beaker have been reduced to less than24 ABSTRACTS OF CHEMICAL PAPERS 20 grms., the mixture is cooled, made up to 20 grms.with water, and after the addi- tion of 0-5 grm. of pure dry mucic acid (purified by recrystallisation from alcohol), the beaker is allowed to stand for forty-eight hours a t a temperature of 15" C. The deposit of muck acid is then collected on an asbestos filter in a Gooch crucible,.washed with 5 C.C. of water, and dried in the water-oven until constant in weight, and the 0.5 grm. of mucic acid which w&s added to promote the crystallisation is deducted from the result. In the case of combined galactose 0-25 to 1 grm. of the anhydrous glucoside or polysaccharide is hydrolysed with 25 C.C. of 2 to 5 per cent. sulphuric acid. When insoluble products are formed they are filtered off, after twenty-f our hours, and the filtrate and washings concentrated.The resulting solution of galactose is rendered slightly alkaline with sodium hydroxide solution,. made up to 30 c.c., and after the addition of 30 C.C. of 50 per cent. nitric acid, and as much cane-sugar as corresponds to the non-sugar portion of the glucoside (e.g., sapongenins), the mixture is dxidised as described above.The following tables give- the quantities of galactose corresponding to the weights of mucic acid obtained: I. GALACTOSE ALONE. Muck Acid. Mgrms. -4 + 0-8 5.6 10.4 15.2 20 27 34 41 45 55 64 73 82 91 100 108.4 116.8 125.2 133-6 149.8 157.2 16443 172-4 180 142 Galac- tose. Mgrms. 0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200 210 220 230 240 250 Mucic Acid.Rlgr m s. 187 194 201 208 215 223.1 231-2 239.3 247 *4 255-5 263-6 27 1-7 279.8 287.9 296 303 3 10 317 324 331 338 345 352 359 366 374.9 Galactose. Mgrms . 260 270 280 290 300 310 320 330 340 350 360 370 380 390 400 410 420 430 440 450 460 470 480 490 500 510 Mucic Acid. Mgrms. 383.8 392.7 401.6 410.5 419.4 428.3 437.2 446.1 455 462 469 476 483 490 497 504 51 1 518 525 534 543 552 561 570 579 588 Galactose.Mgrms . 520 530 540 550 560 570 580 590 600 610 620 630 640 650 660 670 680 690 700 710 720 730 740 750 760 770 Mucic Acid. Mgrms . 597 606 615 623 631 639 647 655 663 671 679 688 695 703.5 712 720-5 729 73795 746 754.5 763 771.5 780 Galactose. Mgrms . 780 790 800 810 820 830 840 850 860 870 880 890 900 910 9201 930 940 930 960 970 980 990 1 ,(@oMuck Acid.Mgrms. - 4 + 2.4 8.8 15.2 21.6 28 34.9 41 43 48.7 55.6 62.5 70 7745 85 92.5 100 106.6 113.2 119.8 126.4 133 139.4 14543 152.2 158.6 165 I s;I%ms* i 181 i 189 ORGANIC ANALYSI8 25 II.-GALACTOSE MADE UP TO 1 GRM. WITH SACCHAROSE. Mgrms. 260 270 280 Mgrm s. 0 10 20 30 I 197 290 40 50 60 70 80 100 110 205 212 219 226 233 240 248-8 257.6 2664 275.2 292.2 3004 3084 316.8 284 325 332 339 346 I j ; j I 1 j i 300 310 320 330 340 350 360 370 380 390 400 410 420 430 440 450 460 470 480 140 150 160 170 180 353 490 360 500 368 510 1 1 , I Mgrms.376 384 392 400 408 416 424 432 440 447 454 461 468 475 483 491 499 507 515 523 531 539 547 555 564 573 Mgrms. 520 530 540 550 560 570 580 590 600 610 620 630 640 650 660 670 680 690 700 710 720 730 740 750 760 770 Mgrms.582 591 600 609 618 627 636 645 654 663 672 681 690 699 708 717 726 735 744 753 762 17 1 780 Galactose . Mgrms. 780 790 800 810 820 830 840 850 860 870 880 890 900 910 920 930 940 950 960 970 980 990 1,000 C. A. M. Extraction of Lactic Acid for its Estimation. E. Ohlsson. (Skand. Arch. Phydiol., 1916, 33, 231-234; through J.Chern. Soc., 1916, 1.10, ii., 542-543.)- In the estimtion of lactic acid according to Von Furth-Charnass, as modified by Embden, the extrwtion with ether is a troublesome and lengthy process. For the isolation in a pure state the author finds ethyl acetate a better solvent, and when the acid is merely to be estimated, amyl alcohol is much better. The liquid con- taining lactic acid is saturated with ammonium sulphate, filtered after twelve hours, and mixed with & volume of 50 per cent.sulphuric acid. It is then shaken with 2 volumes of amyl alcohol, which are then freed from the acid by shaking with sodium carbonate, and used similarly for four more successive extractions of the fluid, Traces of amyl alcohol are removed from the sodium carbonate extracts by three extractions with benzene, and the estimation is then carried out in the usual way.26 ABSTRACTS OF CHEMICAL PAPERS Differentiation of the Two Naphthols by Means of Titanic Acid dissolved in Sulphuric Acid. G. Denigis. (Ann.. Chim. anal., 1916, 21, 216-217.)-A solution of titanic acid in sulphuric acid (cf. ANALYST, 1916, 41, 343) gives a bright green coloration when mixed with a small quantity of a-naphthol, whilst a blood- red coloration is obtained with ,&naphthol. If the mixtures are diluted with wetic acid, the green coloration given by a-naphthol changes to red-violet, but in the ome of @naphthol the blood-red colour remains unchanged. The reaction may be applied as 8 ring test, the naphthol being dissolved previously in acetic acid. The esters of the two naphthols yield similar distinctive reactions with the reagent. W. P. S.

ISSN:0003-2654    

DOI:10.1039/AN9174200019

出版商:RSC    

年代:1917

数据来源: RSC

摘要:

26 ABSTRACTS OF CHEMICAL PAPERS INORGANIC ANALYSIS. Estimation of Calcium in Ash of Forage Plants and Animal Carcases. S. B. Kuzirian. ( J . Amer. Chem. SOC., 1916, 38, 1996-2000.)-Phosphorus is re- moved from the acid solution of the ash as ammonium phosphomolybdate. Calcium is precipitated as oxalate, t-he solution containing the precipitate is boiled for half an hour, the oxalate filtered off on a Gooch crucible, and ignited to render molyb- denum compounds insoluble. The ignited precipitate is treated with dilute hych- chloric acid, the solution filtered, iron and alumina separated as hydroxides, and the calcium in the filtrate finally precipitated as oxalate.0. C. J. mciency of Calcium Chloride, Sodium Hydroxide, and Potassium Hydroxide as Drying Agents. G.P. Baxter and H. W. Starkweather. ( J . Amer. Ckm. Sm., 1916, 38, 2038-2041.)-Experiments are described which show that potassium hydroxide a t 25" C. is as efficient a, desiccating agent as sulphuric acid, the vapour pressure of the lowest hydrate being about 0.002 mm. That of sodium hydroxide is 0.15 mm., and of calcium chloride 0-34 mm. a t 25" C. The temperature co- efficients are high, the vapour pressure of sodium hydroxide being 0.04 mm.at 0" and 1.15 rnm. at 50°, and that of calcium chloride 0.07 mm. at 0" and 1-34 mm at 50" That of potassium hydroxide at 0" was unmeasurable by the methods used; at 50" it is 0.007 mm. G. C. J. Estimation of Hydrogen Sulphide in Water. L. W. Winkler. (Zeitsch. anqew. Chem., 1916, 29, 383-384.)-The water is collected in a 500 C.C.stoppered bottle containing about 20 grms. of marble free from any trace of sulphide, and the bottle should be filled completely with the water. The stopper of the bottle is removed and replaced by a rubber stopper carrying the stem of a bulb tube which is provided with a side tube; a tapped funnel containing hydrochloric acid is attached to the top of the bulb tube, and the side tube is connected with a U-tube contahing cotton wool, and then with an absorption vessel containing acid-free bromine water.The hydrochloric acid is admitted gradually into the bottle, and the liberated carbon dioxide passes over into. the absorption vessel, carrying with it the hydrogen sul- phide conbined in the water. The contents of the absorption vessel are then evaporated until all free bromine and hydrobromic acid have been expelled, and the residual solution is titrated with & borax solution, using methyl orangeINORGANIC AKALYSTS 27 as the indicator.The oxidation of the hydrogen sulphide proceeds according t o the equation: H,S+4Brs+4H,0=H,S0,+8HBr, and each C.C. of & borax solution is equivalent to 04705 mgrm. of hydrogen sulphide.Alternatively, the free bromine alone m y be expelled by boilirg, and the hydrobromic and sulphuric acids then titrated with & borax solution; in this case 1 C.C. of & borax solution (19.11 grms. of the crystallised salt per litre) corresponds to 0-341 mgrm. of hydrogen sulphide. Hydrogen sulphide in relatively strong aqueous solution may be estimated as follows: A stoppered flask containing 100 C.C. of & permanganate solution and 1 grm.of pure sodium hydroxide is weighed; a few C.C. of the hydrogen sulphide solution are now introduced, and the flask is again weighed. After one hour the mixture in the flask Is acidified with aulphuric acid, potassium iodide is added, and the liberated iodine titrated with & thiosulphate solution.Each C.C. of & permanganate soh- tion is equivalent to 0.4263 mgrm. of hydrogen sulphide. w. P. s. Method of Extraction as affecting the Estimation of Phosphoric Acid in Soils. H. Hale and W. L. Hartley. ( J . Id. and Eng. Chem., 1916,8,1028-1029.) -Experiments are recorded which show that two hours’ digestion with 2N nitric acid extracts as much phosphoric acid as ten hours’ digestion with hydrochloric acid of sp.gr. 1.115. It is also shown that the ten hours’ digestion with hydro- chloric acid brings down m.uch more interfering substances than the shorter digestion with nitric acid. G. C. J. Reagents for Use in Gas Analysis. V.-Relative Advantages of Sodium and Potassium Hydroxides in Preparation of Alkaline Pyrogallol. R. P. Anderson. ( J .In& and Eng. Chem., 1916,8, 999-1001.)-A criticism of the con- clusions of Shipley (AXALYST, 1916, 41, 349), who advocated the use of sodium hydroxide. It is agreed that when the best practicable solutions of sodium and potassium pyrogallate are eompared, the specific absorption of the sodium reagent is the higher, and the cost of the sod-urn reagent is less, even in normal times.But the author does not agree that the use of sodium hydroxide effects any real economy, even a t present prices of potassium compounds, as the loss of time when using the sodium reagent much more than counterbalances its lower cost. He gives figures showing that, a saving of three shillings in cost of chemicals involves the expenditure of some thirty addj tional hours in manipulation, each analysis with sodium pyrogallate taking about two and a half minutes longer than would be the case were potassium hydroxide substituted for sodium hydroxide.G . C. J. Solution of Red Lead. G. Torossian. ( J . Id. and Eng. Chem., 1916, 8, 1076.)-Dilute (1 : 5) nitric acid containing 0.5 per cent. of tartaric acid is an excellent solvent for red lead. Th.e hot mixture dissolves red lead instantly.Stronger soh- tions are sometimes convenient, but do not keep well. G . C. J.28 ABSTRACTS OF CHEMJCAL PAPERS Volumetric Estimation of Tin. R. L. Hallett. (J. Soc. Chem. Id., 1916, 35, 1087-1089.)-The following modification of the method of Pearce and LOW (Low, Technid Metho&s of Ore Analysis, p. 208) gives results accurate to within 0.1 per cent.in about one and a, half hours. It is based on the oxidation of stannous chloride to stannic chIoride by means of iodine in the presence of cold hydrochloric acid. Sulphuric acid in small amount does not interfere with the titration, but nitric acid or nitrates must not be present When tin is dissolved in hydrochloric acid it will require complete reduction to the stannous condition before titration. The final solution should contain between 25 and 40 per cent.of strong hydrochloric wid, and during the reduction and titration a current of carbon dioxide should be passed through the flask. From 0.5 to 2 grms. of the sample are dissolved in about 50 C.C. of hydrochloric acid, and the solution is diluted to 200 C.C. with water, and gently boiled for thirty minutes in a flan9k in which is suspended a nickel coil made by rolling 6 sq.inches of heavy sheet nickel into a loose roll, while the mouth of the flask is covered with a watch-glass. The reduc$ion is indicated by the change in the colour of the liquid from yellow to pale green, and the Aask is then left to cool, after the introduction of two small cubes of crystalline marble to produce an atmosphere of carbon dioxide.The nickel coil is withdrawn and washed with dilute hydrochloric acid (1 : 3) during its withdrawal, and the solution is a t once titrated with standard iodine solution, with starch as indicator. A convenient strength for the iodine solution is 10.7 grms. in 1,OOO C.C. of water containing 20 grms. of potassium iodide (1 c.c.=I per cent.of tin). Nickel, cobalt, manganese, molybdenum, uranium, chromium, aluminium, zinc, lead, calcium, magnesium, sulphates, phosphates, bromides, iodides, and fluorides, have no effect on the results, unless present in sufficient quantity to mask the colour of the indicator. Arsenious and antimonious acids have also no influence in the presence of hydrochloric acid of the strength used in this estimation.Precipitation of metallic antimony by the nickel coil may be prevented by the addition of an extra 25 C.C. of strong hydrochloric acid. Traces of copper do not influence the results, but if more than 0.05 grm. be present it should be removed beforehand by treatment with nitric acid, as in the case of titanium (infra). Bismuth is precipitated in metaIlic form in the reduction process, but the precipitate does not materially affect .the titration.Tungsten is also precipi- tated as a, bIue oxide. In small quantities the effect of this is negligible, but, if necessary, the solution may be filtered, and again reduced before the titration. Titanium is best removed by converting the tin into oxide by evaporation with nitric acid, fusing the residue for five minutes with potwsium acid sulphate, dis- solving the melt in dilute sulphuric acid, and filtering the solution.Any tungsten present may then be separated from the tin by treatment with ammonium car- bonate solution, in which the tin is insoluble. Ferrous chloride is not oxidised during the titration, unless a large amount of iodine is added and allowed to stand for some time.C. A. M.APPARATUS, ETC. 29 APPARATUS, ETC. Melting-Point of Fats. (Giorn. di Parrn. e di Chirn., 1916,4,151-153; through Chem. Eng. and Manufac., 1916, H, 188.)-To the thermometer employed is attached a platinum wire of a thickness of 0.3 to 0.4 mm., the free end of which is formed into a loop of 8 to 9 mm. diameter. The wire is attached in such a manner that the loop assumes a, vertical position immediately in front of, but not touching, the mercury bulb. The fat to be examined is melted at a; gentle heat, and when it is almost cool enough to solidify, the platinum loop is dipped parallel to the surface into the liquid and quickly withdrawn, leaving a thin film of fat, completely filling the loop. This is allowed to cool for an hour, the wire attached to the thermometer, which is:then immersed in a wide-necked glass flask of about 250 mm. capacity filled with distilled water, which is slowly heated on an asbestos card, until the film of fat in the platinum loop becomes completely transparent just before breaking up. The temperature of complete transparency is the melting-point of the fat. H. I?. E. H.

ISSN:0003-2654    

DOI:10.1039/AN9174200026

出版商:RSC    

年代:1917

数据来源: RSC

摘要:

30 REVIEW REVIEW. ELEMENTARY QUALITATIVE ANALYSIS. By BENTON DALES, Ph.D., and OSCAR LEONARD BARNEBEY, Ph.D. Pp. viii+205. John Wiley and Sons, New York; Chapman and Hall, Ltd., London. 1916. Price 5s. 6d. net. The authors state in their preface that this boob is intended to act as a guide in qualitative analysis for students who have previously carried out a year's course of work in general chemistry.The book, as its title implies, deals with the subject in quite an elementary manner, but with some innovations that would seem to have little to recommend them. For instance, it is difficult to see anything but disadvantage in fhe arrange- ment of the special reactions €or bases, not under the names of the latter, but in paragraphs 'headed with the formulae of the reagents giving characteristic precipitates.The authors also suggest that the acids present in a mixture should be defected before the bases; and although occasionally such a procedure may be found de- sirable, this is not. usually the case. The descriptions of the various reactions and tests are given concisely and clearly, but the detection tables are rather lacking in this respect, and, together with the general arrangement referred to above, this fact will probably militate against the general use of this book in teaching laboratories in this country. P. A. E. RICHARDS.

ISSN:0003-2654    

DOI:10.1039/AN9174200030

出版商:RSC    

年代:1917

数据来源: RSC