摘要:

JUNE, 1908. Vol. XXXIII., No. 387. STUDIES IN STEAM DISTILLATION. BY H. DROOP RICHMOND, F.I.C. (Read at the Meeting, A p d 1, 1908.) PART THEORETICAL. THE vapour given off by a saturated aqueous solution at the boiling-point must be saturated--that is, the ratio of the number of molecules of the substance to those of steam will be the s&me as the ratios of the vapour pressures at the temperature of ebullition measured in the same molecular state of association. The ratio df the molecular composition of the vapour to that of the solution will be the rate of distillation of the substance relative to that of water. Unfortunately, as both water and many other substances are associated, it is but rarely that the rate of distillation of any substance, even in dilute solution, can be deduced from the vapour pressuresTHE ANALYST.and maximum solubility. I t is clear, however, that of two substances having vapour pressures of the same order, the less soluble will distil the faster. If the conditions be such that the molecular state of association does not change, the rate of distillation will remain constant ; the rate of distillation of a substance in dilute solution appreciably, though not absolutely, conforms to this law. Expressed mathematically, calling the number of molecules of substance y, and of water x7 the ratio of the molecules of substance to those of water in the vapour at any moment d?l will be dz, and the relation of this ratio to the ratio in solution will be expressed by & Y the equation = a - -. dx x If the volume is kept constaut, as is practically the case in an ordinary steam distillation, x becomes a constant, and may be taken as 1 ; as we must in this case consider the relation of the quantity of water removed to the quantity of substance left behind, the equation must then be written - "' =ay.Integrating, we get the equation -- log y = ax + C ; or, as the integration constant disappears on evaluating for zero, y = e-'lX (9 = amount of substance left in solution, original amount being taken as 1, when x=aiiiount of water distilled, the original amount of water being taken as 1). If, however, we do not keep the volume constant, but make no addition what- ever to the liquid, as is the case when a solution is distilled, the equation is dx k a Y . and integrating we get log y = a log x, or y = x ( ~ (?j = amount of substance dx x' left in solution, and x = the amount of water remaining in the solution, the original amounts being taken as 1).For dilute solutions .c may be taken as the total amount of solution remaining without appreciable error. As in an ordinary distillation condensation always occurs, it will be well to consider the eflfect of this. Let us suppose that a fraction b of the aqueous vapour condenses, and the fraction of the vapour of the substance that condenses will be n x b ; the equation for The above equations suppose that no condensation takes place. dy - abdg = c1 ,y -+ nbdy d.x - Dtl.ra .?:+ bdx ' but as &j and ( 7 . ~ are equilibrium at any moment will be 1 - h y infinitesimally small in relation to y arid L, the equation becomes t7!1=.a x (In: 1 - ab ..I' -that is, the efl'ect of condensation will be to increase the rate of distillation if cd is greater than 1, and to decrease it if less. If the amount of condensation is known, or is kept constant, the apparent rate of distillation can be determined ; but it is rare that either of these conditions obtains. In many methods depending on differences of the rate of distillation, attempts are made to obtain constancy of condensation by prescribing dimensions of various kinds ; but the important points, such as external temperature and conductivity of the still head, are usually ignored. I t is quite tt simple matter to eliminate condensation in the still by providing it with a steam- jacket. If a, greater quantity of substance is present in the still than can dissolve in theTHE ANALYST, 211 water, the composition of the vapour will remain constant provided that the rate of solution is as rapid as the rate of removal by distillation.The condition which tends to ensure this is that the substance shall be intimately distributed throughout the liquid, which can be attained by agitation. If, as is often the case, a non-volatile substance is present in which the substance is soluble, the distillation will follow a simple law provided that the rate of diffusion of the substance from the non-volatile solvent to the water is as rapid as the rate of removal. For equilibrium between the water and the solvent we have the equation , (y’= the amount of substance in the water, and s the volume of the solvent); then y’= y.Substituting this in the equation 2 = a $, we get %!= ac -!’ and integrating the equation becomes log y = a log (s +cx)+ C. dx s + CJ-’ Evaluating the constant for y = 1, .I: = 1, we get log y = n log (s + cx) - a log (s + c), or ; thiEi equation shows that it is impossible to distil all the substance If the volume of water is kept constant, and the differential equation This condition requires intimate admixture. _ _ ?/I - c Y - ! / I z CX s+cx s + c.c ( I I/ = (S + C ) when all the water has passed over. - = &?J’ is used, this becomes - - ?/, and integrating we get d,?’ - nc (1J tlx s+a This equation is much simpler than the former, and lends itself more readily to experimental verification; it shows that it is an advantage to keep the volume constant by passing steam into the still, and there is the further advantage that, agitation is thereby secured.If we have two or more substances in solution, so long as the quantity of each is suficiently small not to affect the molecular state of association of the others or of the water, the ratios (ijtf : ayii ~ ~ 1 1 ‘ . . . . ( I . ~ ( I l ! j ’ I L L ~ ~ y ~ t : c ~ l l p l l ~ . . . . : will hold; in other words, each substance in dilute solution retains its rate of dis- tillation in the presence o€ others. If we have one substance in greater amount than will dissolve in the water, and another substance which is soluble in both water and in the first subetance, we get the equation as above for the second substance Y’ ,I‘ - -’ - ,s ” ; if the substance not wholly dissolved can rapidly go into solution, and replace that which has distilled, we get the equation -.const., or s = kx ; and substituting this we get ”= ak * ‘- which will hold until the whole of the substance has passed into solution. The agitation of the solution must be very thorough for the experimental verification of this equation. ax: - dx k + c 2 ’212 THE ANALYST, PART II.--THE RECOVERY OF AMYL ALCOHOL FROM THE ACID LIQUORS OHTAINED IN THE GERBER METHOD. The recovery of amyl alcohol entails so little labour and expense that a distinct economy is effected in laboratories where many determinations of the fat in milk by the Gerber method are made. The working out of the process has proved an interesting study in distillation, and the results obtained have incidentally proved that no appreciable amount of amyl alcohol is contained in the layer of fat which is separated and read off for the determination of the percentage of fat in milk.Early in 1905, J. A. Goodson, working in my laboratory, observed that by a simple steam distillation of the acid liquors a large proportion (upwards of 70 per cent.) of the amyl alcohol came over when about 50 C.C. of water had distilled per litre of liquor ; considerable blackening occurred, and a good deal of sulphurous acid passed over. Repetition of Goodson's experiments showed that if the acid liquors were allowed to cool to room temperature before being placed in the distillation vessel, and heated solely by steam, the dilution caused by the condensation of the steam was sufficient to prevent almost entirely the blackening, and to suppress completely the evolution of sulphurous acid, while the yield of recovered amyl alcohol W;LS increased. A number of quantitative estimations were made, which it is not necessary t o give in full.The following is the result of one which is typical: The acid liquors from 306 fat determinations were placed in a stoneware jar, and 500 C.C. of the water condensed in a previous distillation added; steam was passed in till the vapours passed over, and at this point it was estimated that the total volume would have been 8,060 C.C. if measured at 15" C. Fractions were collected as under : 1 ... 2 ... 3 ... 4 ... 5 ... 6 ... 7 ... 8 ... C'twdc Ariiyl Alcoliol.c. v. ... 78 ... 59 ... 48 ... 32 ... 45 . . . 0 ... 21 ... 7 Aqueous Layer. 50 47 50 51 100 5 0 152 153 c. c. Ae was to be expected, the ainyl alcohol contained water, and the water amyl alcohol, both probably being saturated, or nearly so. By distilling 500 C.C. of crude amyl alcohol till no more water passed over, separating the amyl alcohol which had distilled, fractionating this, and repeating this process three times, 37 C.C. of water (saturated with amyl alcohol) were separated. This, corrected for the amyl alcohol in the water, corresponds with 7.12 per cent. by volume.THE ANALYST. 213 Five hundred C.C. of condensed water were distilled, and the following fractions collected : Airiyl Alcoliol Total. c. c. 1 ... ... 8.0 2 . . . ._. 10.5 3 ... .. . 12.5 4 ... ... 14.0 5 ... ... 15.5 G ... . . . 16.5 Water TO tit I . (’. C . 7-0 9.5 12.5 16.0 19.5 93.5 Amy1 Alcohol Total. c. c. 7 .. . . . 17.0 8 . . ... 17.0 9 ... ... 17.2 10 ... ... 17.2 11 ... ... 17.3 Water Total. c. c. 28.0 33.0 37.8 42.8 50.0 By extrapolation of the results after correction for the water in the amyl alcohol, it was estimated that the dry amyl alcohol in the water was 3.63 per cent. by volume. The experiments aff‘ord data for deducing the rate of distillation of amyl alcohol relative to that of water both from aqueous and acid solutions. There are certain facts which slightly vitiate the deductions, but not to any serious extent. First it was observed, as recorded by Balbiano (BCY., 1876, 9, 1437), that the aqueous solution of amyl alcohol, though quite clear when cold, became turbid on warming, and a slight separation of globules on the surface took place when near the boiling- point ; this means that the strength of the amyl alcohol solution at the boiling-point was not accurately known.The second point is that the continued small con- densation of steam in the jar from which the acid liquors were distilled prevents the volume from being accurately known at any moment ; it was assumed to be constant fhroughout, and the error thus introduced is not very important, For the deductions it was assumed that the ratio between the amyl alcohol and water in the vapour at any moment bore a constant relation to the ratio between amyl alcohol and water in the liquid; this is practically Henry’s law.Calling the amyl alcohol y in the distilling vessel, and the water x, this relation is expressed mathematically as - t7‘’- cLy or, as the water is assumed to be constant in the dx- x ’ experiment with acid liquors, and its value 1, -- ‘ly = 09. (The niinus sign is due to the fact that the water measured is removed from the liquid.) Integrating this gives the simple formula: log y = -ax (:c being the quantity of water distilled, and y the quantity of amyl alcohol remaining). I n the distillation of the aqueous portion, the volume of water is constantly decreasing; it is convenient to let y and x represent the quantities of smyl alcohol and water remaining in the flask. rlx Integrating the first expression, the formula in this case is log y = a log x. Correcting in each case the amyl alcohol for dissolved water, and water for dissolved arnyl alcohol, also in the first experiment making a, correction of 2.5 per cent.of amyl alcohol used in the 306 determinations for mechanical loss (a near214 THE ANALYST. approximation), and adding on the amyl alcohol dissolved in the 500 C.C. of water added, we get the following values : y (total=l). 0.764 0.590 0.442 0.342 0.198 0.165 0.085 0.048 - 0.2G9 - 0.528 - 0.816 - 1.073 -- 1.620 - 1.802 - 2.465 - 3.037 and for the aqueous solution : y (total=l). 0.576 0.450 0.340 0.257 0.174 0.108 0.080 0 so69 0.047 0.030 0.020 log y, - 0.552 - 0.798 - 1.079 - 1.359 - 1.749 - 2.226 - 2.523 - 2.674 - 3.058 - 3.507 - 3.912 log 5 0.0069 0.0133 0-0200 0.0266 0.0395 0.0458 0.0650 0.9841 - 0.0152 - 0.0209 - 0.0269 - 0.0347 - 0.0424 - 0.0511 - 0.0605 - 0.0712 - 8.0810 - 0.0921 - 0.1069 0.0151 0,0207 0.0265 0.0341 0.0415 0.0498 0.0587 0.OG87 0-0782 0.0880 0.1014 39.0 Mean, 40.4 39.3, 39.3 36.1 1 2 (total= 1).i4j 39.2 i;:; From curve 43.1. 41.7 i 37% 38.0 36-8 The values were plotted out as curves, and the mean value of a read from the curves. I n the case of the distillation of water saturated with ainyl alcohol, it was evident both from the results and the curve that there was a disturbing influence a t the commencement of distillation, which was alniost certainly the separation of a. portion of the amyl alcohol as oily drops before mentioned; it wag therefore thought advisable to read a from the curve. I t is probable that this result is low, as it is seen that the value drops towards the end of the experiment, and a very slight alteration in the extrapolated value for the total dissolved amyl alcohol would not only correct this, but would slightly raise all the values.There is another method for deducing the value of a ; from Henry's law i t follows that a saturated solution should be in equilibrium with a saturated vapour. Assuming that the amyl alcohol is pure iso-amyl alcohol, which is of course not the case, but which assumption will not lead to great error, and that a saturated solutionTHE ANALYST. 215 at 100" C. is equal to one that contains at 15" C. 3.5 per cent. by volume of amyl alcohol, we find that the molecular ratio of amyl alcohol to water in a saturated vapour at 100' C. will be the vapour-pressure of water at 100" C.divided by the vapour-pressure of amyl alcohol at 100" C. = - - , the molecular ratio of a saturated solution will be = - which is n figure of the same order as that deduced from the distillation values. (mean), 3S.2 (from curve), and 40.2 (mean) and 40.1 (from curve). are the values of a, and the percentage by volume of sulphuric acid : 230 760 3.5 x 0.82 i 88 96.5 x 1+18 230 3-5 x 0.82 i 88 , and the value of a will equal 760t -gs15 xi 18 - = 49 8, Other distillation experiments from acid solutions gave the values of a 38.2 The three acid solutions had not quite the same concentration; the following Percc~ntage by Volume of' a Sulphiiric Acid. 38.2 ... ... ... ... ... 39.4 39.3 ... ... ... ... ... ... 37.9 40.1 ... ... ... ... ...... 36.3 Now, by the law of mass action, C A ~ H S ~ ~ = KCAm~H.CH2s04 (C = molesular con- centration) and the total molecular concentration of the amyl alcohol is proportional to y = C t i r n ~ ~ S ~ , + C A r l l ~ ~ ~ = (1 + KC/II,SO~) CA~~OEI, and we may write our fundamental (a'= the relation of the ratio of amyl differential equation as - alcohol to water in the vapour to the ratio of amyl alcohol as AmOH to water in the solution). d?/ a', Y d.c x( 1 + KCHI,SO,) a' 1 -I- KCrrS;.l' Therefore, n = The accuracy of the figures is not suflicient to render the calculation of K (the dissociation co-efficient) of any real value, but it is seen that the values of a vary inversely as the concentration of the sulphuric acid. I t is also seen that the dissociation of AmEISO, is large.From the values of cc given above, it is calculated that to distil 95 per cent. of the amyl alcohol it is necessary to distil- P.(*. of \Vatu per 10 0.c. Sulphuric Acid. Pc~r Cent. of Rater. 7.77 ... ... ... ... ... ... 2.00 7.64 ... ... ... ... ... .. 2.02 7.49 ... ... ... ... ... ... 2-06 Dilution of the acid liquid is seen to be such a slight disadvantage with regard to the quantity distilled that it practically is immaterial; as, however, approxi- mately 2% of the amyl alcohol distilled is in solution in the water, it is a real advantage to save this, and add it to the next distillation. I t was found from the mean of a large number of distillations that the volume of crude axnyl alcohol recovered was equal to 97.8 per cent. of the amyl alcohol used.The recovered product had always a slight brownish colour, and a smell which differed from that of the original.216 THE ANALYST. Trials were made to ascertain whether the crude amyl alcohol could be used for the Gerber process, but it was found that the results for fat were always high, averaging 0.12 per cent. in excess. A fractionation was carried out, and it was found that boiling commenced at 34" C., and the boiling-point rose steadily to about 85" C. before water began to come over ; the temperature then rose slowly to 92' C., at which it remained for a long time, this being the temperature which previous experiments with purer alcohol showed was the boiling-point of amyl alcohol saturated with water ; the temperature then rose slowly to 123" C., when all the water appeared to have distilled.As noted previously, the portion of the amyl alcohol distilling below 123' C. was three times refractionated, and 7.12 per cent. of water separated; 8 per cent. boiled below 123" C., a fraction boiling between 123" and 131" C. was distilled amounting to HO per cent., and a residue of 4 per cent. remained, which was very dark in colour. The fractions were used for testing milk, and gave the results below : Below 123" C. reading showed ... ... 0.8 excess 123" to 131' C. reading showed (about) ... . . , 0.05 ,, Residue reading showed ... ... v . . ... 0.8 ,, An attempt was made to dehydrate the crude product by adding 30 grams of caustio soda to 400 c.c., but although an aqueous layer separated, the alcohol still contained 1.5 per cent.of water, and so much soda dissolved that the distillation could not be carried very far, only 66 per cent. of the fraction 123" to 131" C. being obtained. The addition of 10 per cent. of anhydrous sodium sulphate and 10 per cent. of lime respectively only had a slight effect in dehydrating, and caused 10 and 16 per cent. of mechanical loss respectively, the fractions obtained being 65 per cent. and 68 per cent. respectively. All these also gave an excess reading of about 0.05 per cent. when used for fat estimation. These were refractionated, and small portions hoiling below 126' C. and above 131" C. were rejected, which both gave readings about 0.2 per cent. in excess. The mixed fractions, 126" to 131" C., were then refractionated, and the following fractions obtained : Fraction. 92" to 126" C. 126" to 128" C. 128" to 128.5" C. 128.5' to 129' C. 129" to 130' C. 130" to 130.3' C. 130.3' to 131" C. Residue Percentage. 5.3 (trace of water) 13.8 12.6 6.3 21.2 527.6 9.9 3.2 - 6.9 25.2 12.6 21.2 92.0 14.1 -THE ANALYST. 21 7 Except the residue, which gave an excow reading of 0.2 per cent., all the frac- tions gave excess readings of about 0.05 per cent. These results indicate that the chief constituents are a substance boiling a little above 128" C. (active amyl alcohol) and a substance boiling a little above 130" C. (iso- amyl alcohol), and that it is impossible to separate any substance that gives the excess reading of 0.05 by fractionation. I t wag deduced from the results of distillation, and from the excess readings in the Gerber tests, that the crude aniyl alcohol recovered by steam distillation had the following composition : Water . . . ... ... ... ... ... ... 7.1 per cent. Substance of high boiling-point (above 131" C.) ... 0.4 ,, &4myl alcohol (giving excess readings of 0.05 per cent.) ,, Substance of low boiling-point (34" C. ?) . . . ... 0.9 y j 91.7 By fractional distillation of several litres of the recovered amyl alcohol (after the addition of small quantities of lime to neutralise the acid) 87-5 per cent. of amyl alcohol was recovered from the crude product.

ISSN:0003-2654    

DOI:10.1039/AN908330209b

出版商:RSC    

年代:1908

数据来源: RSC

摘要:

THE ANALYST. 21 7 A RAPID METHOD FOR THE ESTIMATION OF MERCURIC SALTS IN AQUEOUS SOLUTION. BY S. G. LIVERSEDGE, A.I.C. (Iiead at tlic X e c t i n y , April 1, 1908.) FROM time to time I receive samples of ‘‘ liquor hydrargyri perchloridi ” for analysis, and as the amount of the salt required in this preparation is only 0.114 gram per 100 c.c., it is necessary to employ an accurate method of analysis in order to determine whether the solution is in accord or otherwise with the B.P. standard, I have used the sulphide method, recommended by Fresenius as giving “very satisfactory ” results, but there is always a possibility of the precipitate containing a little sulphur. Even if sulphur be absent, the operation of drying the precipitate takes several hours, and time in a technical laboratory is of some consideration.I t occurred to me that the estimation of the chloride of mercury might be effected by utilising the solubility of iodide of mercury in ether; thus, mercuric iodide is soluble in ether to the extent of 1 in 70, whereas in water it is almost insoluble. By conversion of the chloride into the iodide by the addition of iodide of potassium and subsequent extraction with ether the mercury may be readily estimated; but, in order that the method may be reliable, it is necessary to reduce the solvent action of excess of potassium iodide to a minimum, and this I found to be effected by the addition of a small quantity of phosphoric or citric acid. Nitric218 THE ANALYST. acid has a solvent action on mercuric iodide, so that the results obtained by its use were low.A known volume of the solution--e.g., 25 c.c.-is pipetted into a, double-bulb glass sepaxator, and, if necessary, diluted a little. The mercury is precipitated by carefully adding a dilute solution of potassium iodide ( 5 per cent.) drop by drop until no further precipitate is produced; a large excess should be avoided. Next, a few drops of phosphoric acid (specific gravity 1.750) are added, followed by 50 C.C. of ether. After shaking vigorously to dissolve out the iodide, the solvent is allowed to separate, and the lower aqueous layer withdrawn and again shaken with the same quantity of ether. This operation having been repeated three times, the mixed ethereal extracts are washed three times with small quantities of distilled water, and finally transferred to a tared Erlenmeyer flask and the ether distilled off. The residue, consisting of mercuric iodide, is dried in a steam oven, evaporation of the moisture being assisted by passing into the flask from time to time a stream of filtered air, and in this way it is possible to dry it completely within an hour.The weight of iodide obtained, multiplied by 0.597, equals the amount of mercuric chloride in the solution taken. If the iodide be left in the oven for five hours or so, it volatilises to the extent of some 4 mgms. I t is Cecessary, perhaps, to point out the importance of using a large amount of ether proportionate to the mercury present and the volume of the liquid taken, but this is no drawback, since most of it is recovered by distillation. The process which I have adopted is as follows : The following are some results obtained by this method : Aniount of Mercuric Chloride taken per 100 C.C.Amount Obtained. Amount of Mercuric Cliloridc taken per 100 C.C. Aniount Obtained 0-1290 0.8936 0.2485 0-1 140 0.1296 0.8736 0.2445 0~1000 2.9450 0*1000 1~0000 0-0320 2.9208 0.1008 1*0010 0.0309 In the case of “Donovan’s Solutioii,” which consists of 1 gram of both the iodides of mercury and arsenic per 100 C.C. of water, it is only necessary to add to a known volume 10 to 20 drops of the phosphoric acid--no visible change is produced in the solution-and to proceed with the ether extraction as detailed above. The ether dissolves out a small quantity of free iodine, but as the latter is readily volatilised at the temperature of the steam oven, this fact does not affect the accuracy of the method. I n conclusion, I desire to thank hIr. R. 0. Carty, A.R.C.Sc., for his assistance in the experimental part of the work. The PKESIDENT said that the real difficulty was in dealing, not with large quantities of mercuric compounds, but with small quantities such as were present inTHE ANALYST. 919 medicines. He had recently had a liquid to deal with containing corrosive sublimate in medicinal quantity, with iodide of potassium, and had had to resort to precipitation of the mercury on copper after the m9th0d of 12einsch, the mercury being afterwards sublimed,

ISSN:0003-2654    

DOI:10.1039/AN9083300217

出版商:RSC    

年代:1908

数据来源: RSC

摘要:

THE ANALYST. THE EXAMINATION OF TURPENTINE AND TURPENTINE SUBSTITUTES. BY J. H. COSTE, F.I.C. (12end at the Meeting, May 6, 1908.) Preliminary. IT is generally known that the various species of coniferous trees yield, when bled,” more or less considerable quantities of oleoresin, from which by suitable means a volatile spirit or oil of turpentine can be distilled. Of all these varieties, American turpentine, principally obtained from the Georgia and loblolly pines-Piitus ilzLstraZis and Pims tmh-is the best known, and commands the highest price, its principal use being a diluent or solvent material for paints and varnishes. This material is usually distinctly destro-rotatory, and has a strong and not disagreeable odour. I t is completely volatile at ordinary temperatures, or at most leaves mere traces of osidised products.Its principal constituent is dextro-pinene. American turpentine also contains dipentine and various oxidation products. Furfural appears to be usually present in traces. Much of the American turpentine sold to-day does not conform to the foregoing description. I t is of an unpleasant acrid colour, at times lcevo-rotatory, and, judging from its behaviour on distillation, contains but little of either dextro- or lzvo-pinene. This alteration in character which has occurred of late years is shown in Table II., and is due to one or both of the following causes : (1) The forests of Georgia and Carolina, having been worked in a very reckless manner, are now exhausted, and, consequently, new districts towards Florida have been opened up, the turpentine from which is of a diflerent character.(2) The methods of distillation have been varied, and not only is the volatile (‘ spirit ” distilled from the oleoresin in the old-fashioned manner, but the wood and stumps of the pines themselves are submitted to a process of distillation, which yields a crude turpentine, known locally as “ stump spirit ” or Whichever cause is at work-and it appears most probable that both are contributory--there is no doubt that much of the turpentine shipped to Europe from the United States is of a very different character from that which a few years ago was recognised as typical American turpentine. I t is certain that wood turpentine as such can only be obtained with difficulty in London, although much of it is distilled in America.Some is doubtless used in the States for varnish-making und painting, but it appears very probable that a great deal is shipped to Europe wood turpentine.”220 THE ANALYST. either as a substitute for (' box " turpentine or mixed with it as an adulterant. That this is a very general opiniou amongst analyst8 may be gathered' from the various methods suggested for its detection. Adulteration of American turpentine with the more volatile fractions of petroleum appears to be less frequent than was the case before "wood turpentine" was available for the purpose. Occasionally, however, cases of such adulteration come under one's notice, more particularly, perhaps, in the case of varnishes than in turpentine supplied as such under contract.Russian and Swedish turpentine from Pinus SyZvestyis and P. ledebo?wdii are now refined, with the object of removing the unpleasant persistent odour which is so characteristic, and sold for painters' use under various names. They have a some- what higher specific gravity, boiling-point, and refractive index than American turpentine, and are strongly dextro-rotatory. Their principal constituent is sylwestrene. One drop of sylvestrene dissolved in a little acetic anhydride gives an intense blue colour with one drop of concentrated sulphuric acid (Russian turpentine itself appears not to give this colour). German turpentine is of very similar character, as also is much of that from Finland. French turpentine, from P. pinastey, is similar to American, but lmo-rotatory, owing to Imo-pinene being its principal constituent.According to Long (Jozwn. Amer. Chenz. Soc., 1894,16, 844-847), spruce turpentine, from P. gtabra, is strongly lawo-rotatory-from 63.1" to 70.3" in a, 200-mm. tube. In other respects it appears to be like ordinary American turpentine. Various turpentine substitutes, sold under names more or less similar to turpentine, are mostly petroleum products mixed with small quantities of Russian turpentine, or waste terpenes from other industries, in order to give an odour of turpentine. The boiling-point has a very wide range, and the refractive index is low. These materials mill be considered in detail later. The specific gravity is usually between 0.78 and 0.82. Methods of Examination. Many processes have been suggested for the examination of turpentine.The following are mentioned, not as being novel, but as having been found useful, during a long experience, in aiding one to form an opinion as to the nature and quality of samples of this material. Speci$c Gyavity (D ~ """ C.).-This varies between from 0.8G and 0.871, A 15-5" lower value may be due to petroleum or shale oil, a higher to resin spirit, Russian turpentine, or old oxidised turpentine. Refyactive Index (n,20) varies from, say, 1.4690 to 1.4720, and is influenced similarly to specific gravity. This can be very conveniently determined by means of either the hbb6 or the Zeiss refractoineter. Temperature correction -f 1" C. T .00037. Optical rotation affords no very direct information as to quality, but is frequently useful in forming an opinion as to the nature of turpentine wheu considered in con- nection with other figures. I t is now geneyaZZy much lower than mas the case ten years ago.Temperature correction +_ lo C. T -00066.THE ANALYST. 221 Initial boiling-point 157" and 160" C. ... ? ) ,, 160" and 165" C. ... 1 Y ,, 165" and 170" C. ... ' 9 ,) 170" and 175" C. ... #, ,, 175" and 180" C. ... FrnctionaZ DistiZZution.-The following table will give some idea of the relative amount of separation obtained by distillation of 100 C.C. from (1) a three-bulb Laden- burg flask, (2) EL round-bottomed flask with a plain, Wurtz tube about 6 inches long, and (3) a Young's rod and disc " column : 44 C.C. 14.5 C.C. 45 C.C. SO ,, 54.5 ), 31 7 ) 9.5 ,, 14 > Y 8.5 Y ? 4 ,, 5 9 , 3.5 Y 7 3 ,) 3 9 ) 3.0 Y9 TABLE I.-100 C.C.AMERICAN TURPENTINE (ROTATION IN A 1 -DECIMETRE TUBE +16" 35' n1)?O0 1.4686). A rn oun t of' Dis- t ill:t te. L'einpcra. ture "C. 159 159-3 159.6 160 160.8 161.5 164.0 168.0 180 1. Rotation 1-Ueci- metre Tube. 111 iL 20" 8' 20" 0 19" 45' 19" 34' 18" 57' 18" 12' 17" 22' 15" 28' 11" 29' 12D2"O. 1.4662 1.4663 1.4666 1-4666 1 *4668 1.4674 1.4680 1.4683 1.4704 l'empera ture "C. 159.6 160.3 160.7 161.3 162.1 164.7 165.2 168.9 180.6 2. Rotatioii i n a 1- Decimetre Tube. 19" 40' 19" 41' 19" 35' 19" 7' 18'35' 18'7' 17" 1' 15" 34' 11" 43' Distillate between 1.4660 1.4663 1.4667 1.4668 1.4671 1.4673 1-4677 1.4684 1 -4 704 Tempera ture "C. 158.1 158.6 159.0 159.5 160-1 161.2 162.6 166.4 180.6 3. Rotation in a 1-Deci- metre Tube.20" 58' 20" 39' 20" 21' 19" 51' 19" 40' 19" 2' 17" 57' 15" 54' 10' 30' 1.4656 1.4660 1.4661 1.4664 3.4668 1.4671 1.4675 1,4679 1.4702 ..* 1 90.5 ,, Total ... ... ... The Ladenburg flask is very convenient, and the separation is not very different from that effected by the "rod and disc" column. A three-bulb Ladenburg flask of 180 C.C. capacity to the bottom of the neck is adopted by the author as a standard flask for this and similar distillation tests, using 100 C.C. of liquid. The time of dis- tillation is about twenty minutes. A No. 4 Anschutz thermometer is of convenient size and range. I t should be standardised with brombenzene (boiling-point 155" C.) and aniline (boilingpoint 184.1" C.), and should be carefully matched to see that any mercury condensed on the upper part of the tubeis united to the main volume before using.222 THE ANALYST.The normal constituents of American turpentine are stated to be : tl-pinene . . . ... ... Cymene* ... ... ... Dipentine (i-limonene) . . . Resinous matters . . . ... E. P. 155-6" 178.0" 175-6' - n ,,20° 1.4652 1.4731 1.4926 (at 13.7") Very high 15.5" 15.5 D -u c. 0.861 0.848 0.8722 (at 0') Very high Rotation in a l-Dcm. Tube. 40" 0" 0" - Of these pinene is the principal and characteristic constituent, dipentine being the result of overheating in the process of distillation, and cymene and the resinous matter the products of oxidation due to keeping. A pure, carefully prepared, and fresh turpentine, therefore, should clearly yield on distillation no constituent having a lower boiling-point than 155" C.; the greater portions should distil at tempera- tures very close to 155' C., and all, with the exception of a very small residue, should distil below 180' C.None of the distillate should have a lower refractive index than that of pinene, and the first portions should have the lowest refractive index and the highest optical rotation, as the optically active constituent (pinene) is also the constituent of lowest boiling-point. This view is confirmed hy the detailed results in Table I. I t is usually desirable to note the initial boiIing-point, and if below 155" C., to collect separately the fraction which is distilled up to that temperature. If it contains any water, this should be tested for acetic and formic acids, the presence of which would be evidence of old turpentine.The oily portion is, if necessary, dried, and its refractive index and optical rotation determined. If the refractive index is below that of pinene, and the optical rotation is lower than that of the original sample or of the next fraction, adulteration with an optically inactive liquid of low refractive power-e.g., light petroleum-is indicated. Confirmation of this may be obtained by Armstrong's method (vide infra). I n any case, the first 5 or 10 per cent. of distillate from 155" C. upwards are collected apart, and the refractive index and optical rotation determined. These should conform to the above statie- ment. The amounts of distillate obtained at each 5" from 155" to 180" C. are noted, and it is useful also to observe the temperature at which each 10 C.C.from 10 to 90 C.C. comes over. A good American box turpentine should, in the opinion of the author, comply with the following specification : 100 c.c., on distillation in a three-bulb Ladenburg flask of 180 C.C. capacity to neck, shall yield no distillate before the temperature reaches 155' C., and not less than 70 C.C. between that temperature and 160" C., and a total distillate of not less than 95 C.C. up to a, temperature of 180" C. The amount of * A sample prepared by t h e anthor from camphor by t h e action of 1'205 had ?in'LO"=l -4896, the correction for +_1" bring T.0004, and boiled from 174.5" t o 177" C. D 1 ~ ' ~ " o . 8 6 ~ ~ . 1d.d"THE ANALYST. 263 distillate up to 180" C. is really higher than that sbserved by about 1 per cent.(varying with the length, etc., of the condenser), when allowance is made for wetting the condenser and for the flaskful of vapour left behind. Free dcitZ.-It is advisable to titrate 10 C.C. diluted with alcohol, and to note the volume of :c alkali required to neutralise the free acids-acetic, formic, and probably abietic-using phenolphthalein as indicator. Steam distillation occasionally gives useful results, but generally fractional distillation will impart as much information with less trouble. For the direct determination and separation of petroleum spirit in turpentine che author is of opinion that the process of polymerisation and sulphonation pro- posed by Armstrong (Joz~rn. SOC. Chmn. Ind., 1882, 1, 480) is in every way preferable 80 the various drastic and even pyrotechnic processes suggested by later workers. Briefly, the method is to polymerise, carefully avoiding rise of temperature, with diluted sulphuric acid (2 volumes acid; 1 volume water).Any petroleum spirit or unaltered oil of turpentine is separated from the less volatile polyterpenes by steam dinhillation. The distillate is then treated with stronger acid (4 volumes acid; 1 volume water), and the portion volatile in steam collected. If this does not exceed 5 per cent. of the original volume of turpentine, it is probably cymene which is normally present in old turpentine, and is formed to a small extent by the action of sulphuric acid. This can, if desired, be identified by its properties : - D 13'70 C. 0.8619, B.P.175-6" C., nJ3.7 1,4926, optically inactive. 4" I t is also completely sulphonated by treatment at 50" to 60" C. with diluted Nord- hausen acid. Any excess over 5 per cent. of unpolymerised residue would he petroleum, which, after removal of cymene by sulphonation, can be detected by its low specific gravity, wide range of boiling-point, low refractive index, and its behaviour to sulphuric and nitric acids. The amount obtained in this process represents the minimum of adulteration with mineral oil; shale oil is too much acted on by sulphuric acid to be detected in this manner. As small a quantity as 100 C.C. of turpentine will with care give reliable results by this method. A qualitative test for wood tziipentiite, recommended by Conradson ( J o ~ L ~ . SOC.CI~enz. I n d . , 1897, 16, 519), Flath (ANALYST, 1908, 27), and others, is agitation with an equal volume of a saturated solution of sulphurous acid. Wood turpentine assumes a yellow colour, and Russian and Swedish turpentines a yellow-greenish cobur. This test certainly more often gives a yellow coloration with the newer type of turpentine than with the older more volatile kind. Turpentine should not leave a stain on paper which has been coated with it. The paper should take ink freely after hanging up to dry. The comparative volatility of samples can be determined by exposure of 0.5 or 1.0 c.e. of each in similar flat dishes to the air of the laboratory, noting: from time to time the loss in weight which occurs. If time and loss are plotted a curve is obtained, which does not begin t o flatten until nearly all the liquid is volatilised.The various substitutes show 8 falling off in the rate of volatilisation much sooner than genuine turpentine. American or French turpentine remains white. All wood oils are said to give this yellow or green colour.224 THE ANALYST. The detailed results of the examination of a few selected samples examined during the period beginning in 1899 are given in the following table : TARLE II.-RESULTS OF THE EXAMINATION OF SAMPLES OF TURPENTINE SUPPLIED AS GENUINE AMERICAN TURPENTINE. DiHtillation of 100 C.C. Properties of First 10 C.C. of Distillate. u; 0 co H 0 4 0 t- u' 3 s 0 0 +l d 0 L- H 0 +a 0 (0 m 1. 2. 3. 4. 5. 6 . 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 1s. 19. 20. 21. 22. 23. 24.25. 26. 27. 28. 29. 30. - 0.8dSe 0.8611 0.8677 0.8688 0'8670 0.8650 0.8685 0.8697 0'8504 0.8693 0-8680 0.8715 0.8706 0'9141 0-8670 0.8682 0.8712 0'8668 0.8662 0.8676 0.8670 0.8659 0.8707 0'8701 0.8677 D.8700 3 8655 1.8658 1.8664 1.8670 80 -0 47'0 i8.O 72.0 85.0 93.0 92.0 76'0 42.0 83.0 20.5 63-0 30.0 25.0 81.0 51 *o 13.0 57.0 18.0 92'0 i 5 . 0 10.0 30.0 i 9 . 0 70.0 18.0 j2.0 17'0 38-0 ZO.0 - 13.0 26'0 16.0 16.0 7.0 4.0 3.5 18.0 25.0 10'0 32 *o 125.0 35.0 30.0 11.0 39 -0 18'0 19.0 33.0 66'0 4'0 15.0 72.0 58.0 13.5 23.0 42 .O 30.5 68.0 6.5 2.0 9.0 1.0 3.0 1.0 1 * 5 5% 9 *o 2.0 35 '0 5 . 0 9.0 9.0 3.0 4.5 3.0 2.0 4-0 5 '5 1 *5 4'0 6.0 4.0 2.5 3.0 4.5 2.5 7.0 1 .o - 1 -0 4.0 1'0 2.0 2'0 - - - 6 -0 - 7'*0 2.0 8.0 4.0 1.0 1.0 2 -0 2.0 1 -0 3.5 1.5 2'0 2.5 1 '0 0 '5 1 *5 1 *5 2.0 1 -0 - 97.0 89.0 97.0 94-0 96.0 97.0 97.0 99-6 85.0 95.0 96.5 96.0 85.0 71.0 97.0 97.0 94 '5 97.0 95-0 94.0 97-5 96.0 33.0 36.0 36.5 37.5 36.0 )6..5 36.0 16.5 - - +2" 6' $24" 50' - - - - - - - - - - -1-6" 50' i-3" 57' +7" 59' -0" 44' +11" 19' +5" 8' +lo 39' + 4 9' -29" 44' +2" 4' t-2" 10' f 30 0' t 6 " 15' t 2" 45' t 4" 0' -0" 10' - - - __ - - - - - - - - - Helow 155.0" 154.0" 155 -0' 155.0" 1 5;-0" 165.5" 154.5" 159.0" 158.0" 157.0" 158.5" 158.5" 157.5" 158.8" 156 5" - - - - - - - - - -_ - - - - - - 1.4689 1.4686 1 '4686 1'4694 1.4683 1.4682 1.4680 1.4699 1.4685 1.4686 1.4681 First 1 -4680 2.4680 1.4699 1.4674 1.4676 .. - -_ - - - _._ - - - - _ _ - 4-9" 0' +5" 55' +11° 20' +I0 45' +14c 0' +7O 2' - 33" 11 ' +4" 15' i per cent. + 5 O 30' +go 5' +5O 0' +i" 0 + 2" 50.- - - - - - - -_ - - - - - - - - 1 *4709 1.4713 1 '471 4 1'4710 1.4703 1'4714 1 *4699 1.4693 1'4715 1.4707 1-4702 1.4699 1.4699 :4704 . -4703 . *4700 Some few samples call for special remark : No. 2 : The low specific gravity and small amount of total distillate point to the presence of petroleum. After polymerisation and sulphonation, 8.6 per cent. of a 15.5" liquid was left, with D ~ 0 . 8 1 6 3 , and range of B.P. 150" to 220° C. ; it was evidently petroleum. No. 9 : -4gain, the specific gravity and result of distillation point to adulteration with petroleum. The residue, after treated by Armstrong'sTHE ANALYST. 225 15*53 method, was 15 per cent. by volume, and had D 1m 0.7879. No. 13 : On further distillation, 10.5 per cent. by volume was obtained up to 225" C .The original liquid contained at least 12 per cent. of a liquid unattacked by either sulphuric or nitric acids, with D 15'5" 0.8376, and range of B.P. 160" to 210". No. 1 4 : The high 15.5" specific gravity and small amount of distillate indicated the presence of resin oil or old turpentine, which was confirmed by the high acidity figure. The residue in the 15.5" distillation flask was of D 1m 1.0048, and required 2.8 per cent. of KOH to saponify. Having regard to the fact that 7 C.C. distilled below 155" C . , it is fairly certain that this was old turpentine containing acetic and formic acids. No. 15 : This, after polymerisation (not sulphonation also), left a residue of 2.2 per cent., with n,20° 1.4822. This was cymene frorn genuine turpentine.Nos. 18 and 30 : The change of sign of the rotation is remarkable as indicating the presence of two active constituents, one dextro and the other l w o , of different boiling-points. This, like all the other samples in the above table, was sold as American turpen- iine. The free acid in the above samples was on the average equal to about 0.3 per cent. of abietic acid, corresponding to 0.8 to 1.0 C.C. & KOH for 10 C.C. of turpentine. The author is of opinion that only those samples in the above table which comply with the specification previously mentioned can be considered as satisfactory. The results of the examination of a few samples of Russian turpentine will suffice to indicate the general character of this material and its marked difference from American turpentine.I t is worthy of note that the rubefacient properties of Russian turpentine are mom marked than those of American turpentine, so much so as to render it an unpleasant material to handle for cleaning or polishing purposes." No. 23 I t is probably either French or spruce turpentine. No. 1. No. 2. ... ... ... ... ... 0.8662 ... 0.8837 D -To n 20' ... ... ... ... ... 1.4740 ... 1.4750 15.5" 15 5 Optical rotation (1-dcm. tube) ... ... + 14" 29' ... + 16" 20' Percentage distillates from Ladenburg flask between 145" and 160" C. ... ... 4 (157Oand 16OOC.) 2 160" and 165" C. ... ... 12 16 165" and 170" C . ... ... 43 36 170" and 175" C. ... ... 20 18 175' and 180" C . ... ... 11 7 180" and 185" C. ... ... 3 4 185" and 190" C. ... ... 2 2 No. 1, on polymerisation by Armstrong's method, yielded 14.3 per cent.(volume) 15.5" of unaltered matter with D 15.30. 0.8496 and ~ Z D ~ O ' 1.4778. Distillates : 146" to * This property of Riissiaii tiirpentiiie was indicated to a niarked and painfiil degree in coniparative .r?xpcrinients made, under the i i i ~ t h o ~ ' ~ supervision, by q)plyiiig Rnssiaii and Anierican turpentine :LR poultices to the wrists, with i l view of investigibtillg i i con'iplaint from workinen using Russian twpciitinr.296 THE ANALYST. 160" C., 2-5 per cent. ; 160" to 165" C., 3.7 per cent. ; 165" to 170" C., 11.2 per cent. ; 170" to 175" C., 56.2 per cent. ; 175" to 180" C., 20 per cent. ; 180" to 185"C., 2-5 per cent. ; total, 96.1 per cent. On sulphonation of this with Nordhausen acid, a volume corresponding to 4.3 of the original turpentine was obtained, having a refractive index 1.4528.Evidently the residue of the polymerisation was principally cymene, which is said to be largely present in Russian turpentine, with about 5 per cent. of petroleum. Such adulteration with petroleum has frequently been noticed by the author in Russian turpentine. When turpentine is exposed to the air in vessels sufficiently closed to prevent evaporation, oxygen is absorbed and ozone (or hydrogen peroxide)" formed. This causes the bleaching of the cork often observed in such cases. Considerable oxida- tion also occurs; aoetic and formic acids are formed, with cymene and resinous products. The physical changes occurring are indicated by the following figures : TABLE III.-AMERICAN TURPENTINE.15.5" D 15rpC. ..- Distillates : 160" C. 160" to 165" C: 165" to 170" C. 170" to 175" C. 175" to 180" C. Total ... Rotation in a l-dcm. tube Refractive index ... Viscosity (Red- wood's visco- meter) ... Free acid (c.c. per- 100 C.C. liquid) . . . October, 1903. 0.8686 92.5 3.0 - - - I. October, 1904. 0.9040 29 29 11 5 3 November, 1906. 0.9540 7.0 12.0 23 8 4.5 54.5 - - - - February, 1905. 0.8717 51 37 6 1 1 96 4" 4' - - 0.5 11. October, 1906. 0.9091 14 36 10 10 - 70 5" 1' - - - March, 1908. 0.9270 18 24 14 6 6 68 5" 0' 1.4802 46 sec. (Fresh turpen- tine, about 30 seconds) ; soluble acids, 8.4 ; insol- uble, 134. * Iiingzett has shown that hydrogen peroxide, and not ozone, is formed by the atmospheric This certainly appears to be the case, although the contrary statement has oxidation of turpentine.been made on good anthority.THE ANALYST. 227 Old turpentine leaves a, greasy stain on paper. The residue after distillation of 11. had a specific gravity of more than 1.0, and refractive index 1-5077, and resembled resin spirit,. If kept in a well-corked bottle, turpentine is not altered appreciably on keeping for a year. I t will be noticed that the refractive index and boiling-point of the first fractions obtained on distillation of turpentine, as shown in Tables I. and II., do not agree closely with those of pinene, but one or other of these figures is always higher than one would expect if the mixture distilled contained constituents boiling between 155°C. (pinene) and 175" C. (cymene).The existence of at least one other normal constituent of turpentine appears to have been firat presumed by v. Bayer (Ber., 1896, 29, 1923), who obtained from the products of oxidation of French turpentine, by means of a neutral solution of permanganate of potash, as indicated by Tiemann and Semmler (Ber., 1896,29, 529), an acid which he called B-pznonic acid, to distinguish it from the pinonic acid obtained by those authors, and another acid to which he gave the name nopic acid, isomeric with pinonic acid, but difTering from it in not containing the keto-group. Pure pinene did not yield nopic acid on oxidation. The acid was, therefore, presumed to be the oxidation product of another terpene, to which the name nopinene or p-pinene was given. Recently Wallach (Annulen, 1907, 357, 49-71) has, by suitable means, prepared from nopinone, a derivative of nopic acid, a, terpene possessing the following properties : Boiling-point 158" C.D20" 0.8630 [.ID + 15*93", n,20° 1.4699. This is apparently not the /3-pinene of French and American turpentine, but is closely allied to it. The existence of a turpentine possessing properties very similar to this P-pinene or its laavo-isomer is certainly indicated by the properties of the distillates from American turpentine. Year. 1899 I.. 1900 ... 1901 ... 1902 ... 1903 ... 1904 ... 1905 .._ 1906 ... 1907 I . . NO. Examined. 2 18 14 13 20 26 54 78 35 CONTKACT 1. TABLE IV. CONTRACT 2 (and Casual Samples). Percentage Passing Specification. (a) 100 67 93 92 100 8 11 10 37 NO. Examincd. 26 24 35 38 39 63 61 52 59 Percentage Passing Specitication. ( a ) 54 83 97 97 85 11 20 31 15 The terpenes are a, class of bodies very liable to change in structure, and it must be borne in mind that the methods of distillation, even when the oleoresin itself is distilled, are such as to yield not merely the volatile hydrocarbons of the turpentine,228 THE ANALYST. but secondary products of the nature of dipentine, cymene, etc.Probably, if distilla- tion with low-pressure saturated steam or distillation under reduced pressure were adopted, much more uniform results would be obtained. When pine-wood is distilled more or less destructively either alone or with superheated steam, more complex products must be expected. The general alteration in character of turpentine examined by the author during the last nine years is indicated in the following summary, &owing the extent to which turpentine supplied under two different contracts, and some casual samples (usually of superior quality to those supplied under contract), complied with the specification mentioned previously-Le., to yield 70 per cent.distillate between 1 5 5 O and 160" C. and 95 per cent. up to 180' C. (column a, Table IV.), and also the percentage in each year yielding 60 per cent. up to 160" C., and a total of 95 per cent. (column b). I t will be seen that in both cases the year 1904 marks the change which has been indicated by the great decrease in the amount distilling between 155' and 160' C., and a corresponding increase in the next fraction, 160' to 165" C.If the somewhat strongly expressed belief in the sulphurous acid colour-test is well founded, a great deal of wood turpentine must find its way to the United Kingdom; but in the author's opinion such tests are not very reliable unless the chemistry of the process, which in this case appears to depend on the presence of aldehydes and ketones, is well understood. Under the circumstances, it appears very difficult to state more of a sample than whether (1) it is adulterated with petroleum or hydrocarbons other than the terpenes and their allies; (2) it is fresh and in good condition, or old and badly kept ; (3) its general properties are such as to establish the presumption that it is freshly distilled American (or French) box turpentine, or a second-rate but simiIar product ; (4) it is Russian turpentine, or a similar mixture of terpenes ; or (5), what- ever its nature, whether its volatility at ordinary temperatures is such that it is probably sufficiently good for use as a diluent for paints and varnishes.This last point lertds to the question of turpentine substitutes. Turpentine Substitutes. The general character of these materials has already been indicated ; as to their utility, much diversity of opinion exists. The volatility of the best of them at ordinary temperatures is inferior to that of American turpentine, a very marked flattening of the curve being noticed. This volatility is probably, however, in the better kinds suficient for most purposes, and the materials are much cheaper than turpentine. I t is sometimes said that turpentine leaves a residue possessing some occult properties of a highly satisfactory nature.This residue cannot be very different from ordinary colophony, which is not a particularly good material in paint w varnish, and which, if it were so, eould easily be added to the substitutes. Turpentine may, by its power of forming ozone or hydrogen peroxide on evaporation, aid the oxidation of linseed oil, and in this respect be superior. Good turpentine has a more steady rate of evaporation than the best substitutes,THE ANALYST.. 2222 and it is also not of so persistent an odour. I t is dificult to obtain definite facts from trade sources. Some makers of high-class varnish point out thah with a cheaper solvent they can for the same price give better gums in a varnish, and maintain that no differenee in working exists between turpentine varnishes and those with good substitutes.Others say that for high-class work nothing is equal to American turpentine. The substitutes are certainly much used in varnishes, and appear to be quite satisfactory so far as the appearance of the coat is concerned. This might be expected, when one considers that in both paints and varnishes the solvent is only added to make the material workable, and is not a permanent constituent of the film applied to the surface to be protected or decorated. For wax-polishing of floors substitutes are found to be quite satisfactory, I t is certain that American turpen- tine will not be entirely ousted from the field until the various substitutes are made of a more uniform character.The results obtained in the examination of several samples of substitutes am given in the following table : TABLE V. d 7, 1 2 3 4 5 6 7 8 9 10 11 12 13 1 4 0 0 2 1::;: - I P n 0.8210 0.8816 0'8204 0'8088 0.7981 0.8073 0'8011 0-8030 0.7977 0'7896 0'8004 0'8144 0'8079 0 *7 9 8 4 1'4504 1.4.5 10 1'4493 1'4493 1.441s 1.4488 1.4454 1.4457 1'4426 1 -4394 1.4447 1.451% 1'4492 - ci 0 9 3 0 Y 3 7 3 3.0 * 2.0 1.0 14.0 13.5 12.5 11.5 14.0 11.0 24'0 2.0 1'5 2.0 Distillation of 100 C.O. 3.3 * L 1.2 11.5 11'5 7 . 5 9.0 S *5 12.0 1s.o 14.0 3 .O 13'0 5.7 12.0 10'0 1% 11.6 9.0 6.5 7 -5 9.5 11.5 11.6 11.0 5 . 5 5.0 -.- d m (0 3 0 + 0 0 9 4 4.0 6 . 5 - 4.7 9.0 s *5 7.0 3.5 8.0 9.0 9'0 12.0 5.0 9.0 5.0 2.0 6-0 9'5 8.0 7.0 5.5 2.5 9.0 i . 5 S.5 4.0 9.0 r r 1 . 3 9.0 T ' O 11.0 20 '0 5-0 6.0 3.5 5.0 7.5 5-0 4'5 11'5 4.5 s.5 8'0 10'5 9-0 30.0 7.0 '7.0 8.0 10'0 7.5 7.0 5'0 10'0 5.5 9.0 - m c 35.0 38.0 39.0 68.0 75.0 74.0 53.5 65.0 64'0 75.5 92.5 69 *o 30.0 57.5 Of these materials, Nos. 1, 2, 3, 4, 5 , and 11 appeared to be suitable for use in the preparation of oil paint. That marked No. 11 is a particularly satisfactory material, and is of very uniform character. I t will almost invariably pass the following specification: The specific gravity to be 0.790 to 00810 at 15.5" C. ; 100 C.C. on distillation in a, three-bulb Ladenburg flask of 180 C.C. capacity to neck shall yield not more than 2 C.C. of distillate below 140" C., nor less than 85 C.C. between 140° C. and 180" C. The somewhat low flashpoint does not appear to * Amount not noted.230 THE ANALYST. introduce any real element of danger. This material is largely used for wax floor- polishes and for high-class varnishes.::: I t will be seen from the properties of these materials that any considerable proportion could not be mixed with turpentine without being detected by the lowered specific gravity and refractive index. None of these materials left any stain on paper. CHEMICAL DEPARTMEST, LONJIOS COCSTY COUSCIL.

ISSN:0003-2654    

DOI:10.1039/AN9083300219

出版商:RSC    

年代:1908

数据来源: RSC

摘要:

230 THE ANALYST. ADDENDUM. A sample of '' synthetic turpentine " examined recently by the author gave the following results : 15'5" '' 0.8832 ; ND 20", 1-5023 ; rotation in 1-dcm. tube, + 1" 30'. = 15.50, On distillation of 100 C.C. the following fractions were obtained : Up to 140" C., 0.7 C.C. ; 140" to 145" C., 2.8 C.C. ; 145" to 150" C., 8.5 C.C. ; 150" to 155" C., 8.0 C.C. ; 155" to 160" C., 12.0 C.C. ; 160" to 165" C., 11.0 C.C. ; 165" to 170" C., 9-0 C.C. ; 170" to 175" C., 9.0 c.c.; 175" to 180" C., 11.0 C.C. The first 5 per cent. of distillate had the following properties : N ~ 2 0 " 14927, rotation +lo 30'. The residue left in the flask after distillation had a refractive index at 20" C., 1.522 ; this liquid gave a yellow colour with sulphurous acid, and a mauve colour after standing with Schiffs reagent.The ( ( synthetic turpentine " is unlike either turpentine or the usual sub- stitutes. The high density and refractive index led the author to believe that he was dealing with a mixture of coal-tar naphtha, containing higher homologues of benzene, and turpentine. Thie view appeared to be confirmed by its behaviour with fuming nitric acid, as a heavy nitration product was obtained. The progress of the distillation points to a mixture of constituents of widely differing boiling-points. I t appears, however, from the discussion following the paper, that this is a product obtained in the manufacture of artificial camphor, and might reasonably be expected to be a mixture of terpenes. Its general behaviour certainly does not support this view.Such a material could not be added in any amount to American turpentine without being detected.+ Total, 72.0 C.C. DISCUSSION. Mr. L. M. NASH said that Russian turpentine was now so manufactured that, if judged merely by its smell in the bottle, it might be considered suitable for use. But during the drying of the paint it gave off an objectionable odour, and on this account painters would not use it, even though it was cheap. For many years American * This affords a good example of Lhe point raised by Xr. Hchner during the discussion of this paper -viz., that the materials which distil within the narrowest limits are the most satisfactory. The evaporation curve of this substitute is practically a straight line up t o 99 per cent. (five hours).The curves for Nos. 13 and 14 flatten badly a t 54 per cent. (scveii hours) and 76 per cent. (six hours) respectively, showing that the range of boiling-point for such similar materials affords some criterion of the vapour pressure a t lower temperatures. t The volatility curve of this suLlstancc is similar to that of turpentine, and closely approaches a straight line.THE ANALYST. 231 wood turpentine had, without doubt, been finding its way into this country-not much was sold as such, but was blended with ordinary turpentine. The sulphurous acid test for wood turpentine was a fairly satisfactory one. He was not sure that it was capable of indicating the presence of less than about 20 per cent., but that quantity could be detected by this test, while it would not be indicated by the specific gravity or the range of boiling-point, in which features wood turpentine, if properly refined, closely approached American turpentine.He considered, from experiments he had made, that properly prepared petroleum spirit was just as good in paints as American turpentine. The residue left by evaporation of turpentine was not hard like colophony, but was softer and more sticky, and had a lower acid value, and he thought the view that its presence was helpful was a mistaken one. The mineral spirit, however, had the same disadvantage as Russian turpentine for inside painting -namely, that it gave the paint an unpleasant odour during drying. Russian turpentine as it came into this country was crude, varying from light yellow to dark brown in colour.Among the many samples he had examined, in only one instance was its specific gravity higher than that of Smerican turpentine, and after rectification fhis would become normal. A method which had been recoinmended for the separation of petroleum spirit from turpentine waB that of shaking one volume of the sample with three volumes of aniline oil for five minutes. The aniline oil dissolved the turpentine, and the petroleum spirit rose to the top, its volume being read in a graduated tube. He should like to hear the author’s opinion of it. A useful little qualitative test for the presence of petroleum spirit was to shake the sample vigorously. As little as 5 per cent. of petroleum spirit in turpentine caused a great deal of frothing, whereas the large bubbles formed in genuine turpentine disappeared immediately.I t was thus possible, without removing the cork from the bottle, to decide in a few moments whether the sample was adulterated. Mr. BODRIEH, asked whether the author attached any value to the British Pharmacopaeia test of solubility in glacial acetic acid. He (Mr. Bodmer) had examined several sariiples of turpentine, and found only one that complied with that test. The method to which the author had alluded of oxidation with fuming nitric acid, although it seemed capable of giving good results when successfully applied, was extremely dangerous, and not a method to be generally recommended. On two occasions a violent explosion occurred when he tried this method. Mr. ARCHBUTT said that he was somewhat surprised that, the author had made no reference to the iodine value, which in his (Mr.Archbutt’s) opinion was a very useful guide. The true iodine absorption was not obtained, and the test, as applied t o turpentine, was a purely empirical one; but if rigid conditions were adhered to, fhe results would differentiate turpentine very sharply from the cheaper substitutes. His practice was to act on EI certain quantity of turpentine with Wijs’s solution for exactly twenty minutes, under such conditions that a t the end of that time the quantity of unabsorbed iodine was at least equal to, and not more than 5 per cent. greater than, that which had been absorbed. Under these conditions genuine American turpentine absorbed from 300 to 320 per cent. of iodine. In the distillation of turpentine he had never found it necessary to use more than an ordinary retort with the thermometer bulb immersed in the turpentine.This had the advantage232 ANALYST. of being very simple, and the figures obtained with genuine turpentine were practically tbe same as those obtained by the author with a fractionating bulb. He wondered whether wood turpentine was in any way inferior to genuine turpentine as a vehicle for paints and varnishes, and also how the prices of the two compared. He thought it very desirable that a definite decision should be come to with regard to substitutes, since these were now so largely used. The main thing was to ascertain whether the substitutes evaporated as rapidly as genuine turpentine and without leaving an oily residue.If they did, he did not see why they should not give as good results as turpentine. With many of them, however, the flashpoint was dangerously low, and this must be carefully watched. His experience was that the specific gravity of American turpentine was usually from 0.865 to 0.866. If ib was higher than this, there wm usually a fraction which distilled at a higher temperature than the normal, and the turpentine was probably old. Some time ago, with the idea of keeping a standard sample, he had filled a Winchester quart bottle with genuine American turpentine and kept it in the dark. At the end of fourteen months the turpentine had undergone s chwge which could not have been due to oxidation, but must have been a polymerisation change, which had considerably raised the specific gravity, and caused an oily residue to be left, whereas the original turpentine had volatilised completely under the same conditions.Steam distillation did not improve it, but by distilling from caustic soda and collecting only 80 per cent. of the distillate, the turpentine was obtained in its original condition. He could quite confirm Mr. Bodmer’s remark as to the danger of the nitric acid test. He thought that the only satisfactory method of separating the petroleum hydrocarbons was by polymerisation with sulphuric acid, as the author had stated. Mr. J. H. B. JENKINS said that in his experience the aniline test was a, rough one, giving low results, especially if the impurity present in the turpentine was of a highly volatile nature.In confirmation of the author’s remark as to the blistering properties of Russian turpentine, he might mention that at the railway works with which he was connected an outbreak of eczema occurred, and was attributed to the use of Russian turpentine instead of American for cleaning engines. He thought that those who had to test turpentine must find difficulty sometimes in distinguishing the origin, owing to the fact that Russian turpentine seemed to be getting more and more highly purified, whilst at the same time American turpen- tine appeared to be degenerating in quality; and he should like to hear what method the author would finally adopb for distinguishing between the degenerate American turpentine and the highly refined Russian turpentine. Mr. HEHNER said that the sulphurous acid method, although it gave as it at present stood more or less indefinite results, must depend upon some aldehyde or ketone reaction, and it might perhaps be worth while to see whether a definite quantitative addition oould be brought about.He should be interested to hear whether the author had met with the turpentine brought into the market through the manufacture of artificial camphor from oil of turpentine by conversion of the solid hydrochloride into camphene. The liquid portion of the hydrochloride, which waO useless for this purpose, was reconverted into turpentine, and sold as such. As to the relative value of turpeptine and other solvents, he thought it should not be tooTHE ANALYST. 233 lightly assumed that, because a material was as good a solvent as turpentine, it was, therefore, a good substitute. I n connection with ship's paints made with naphthas, it WBS found that, albhough these hydrocarbons were excellent solvents, they were unreliable and unsatisfactory if their distilling temperatures ranged in the same sample over a wide scale.The advantage of pure oil of turpentine was that it distilled and dried within a very narrow range of temperature. This was no doubt the reason why many turpentine substitutes, consisting of mixtures of turpentine with lighter or heavier hydrocarbons, were never satisfactory, although each hydro- carbon by itself might be satisfactory. With regard to the question of physiological action, it had been experienced in the manufacture of leather-cloth in which linseed oil and varnishes were mixed with certain hydrocarbons, that some of the hydro- carbons gave off very injurious vapours, whilst other kinds were physiologically inert.Mr. CHAPMAN asked if any attempt had ever been made to detect the presence of shale oil in turpentine by determining the proportion of sulphur. Even highly refined shale oil usually contained some sulphur. Mr. COSTE, in reply, said that he agreed with what had been said as to the objectionable odour of Rusgian turpentine on drying. He thought that Russian turpentine was frequently adulterated with tar oil or similar products. Small fractions were frequently obtained distilling below 155' C., and with a low refractive index. He had had no experience of the aniline oil test, but must say that soh- bility tests of that kind did not appeal to hirn.He had never taken the British Pharmacopceia test seriously, but if glacial acetic acid of proper strength were more readily obtained, it might be possible to rely more on the test. The fuming nitric ac'id test was too dangerous for the ordinary experienced analyst to attempt. He agreed with Mr. Archbutt that the iodine value was a very empirical test. Tilden for a long time thought that he had obtained tetrabrompinene, but probably it was a dibrompinene with substitution products. I t was very difficult to regulate the admission of the halogen. The Ladenburg flask was a very simple apparatus with three bulbs in the neck, and was no more difficult to use than a retort. As to the value of substitutes, he was going to have some tests made on a practical scale.The flashpoint of many of them was certainly low. He thought that there was a very definite distinction between Bussian and American turpentine in the refractive index, which was distinctly higher in the former. In polymerising with sulphuric acid he had first tried shaking in a bottle in accordance with Armstrong's original directions, but the bottles broke. He had since learned that Armstrong had taken to using flasks, and he (the speaker) had found that, provided the flasks were thin and kept very cool, they were perfectly satisfactory. As regards the possibility of making the sulphurous acid test quantitative, he was having some experiments made with sulphurous acid and with Schiffs reagent, but, 80 far as he could see at present, the results did not entirely agree. Only that day he had had brought before hirn a sample of the synthetic turpentine referred to by Mr. Hehner. It was very different indeed in its physical properties from ordinary turpentine, and he did not think there would be any difficulty in detecting its presence in considerable quantity. I n connection with substitutes, the vapour- tension at ordinary temperatures W ~ B more important than the boiling-point. Of234 THE ANALYST. course, a, short range of boiling-point did not necessarily mean that the vapour- tension at ordinary temperatures was fairly constant. He had never made use of the estimation of sulphur for the detection of shale oil, but should think it would be worth while. good thing to shake up with lead oxide in alkaline solution, and see whether the presence of sulphur was indicated by the formation of lead sulphide. If so, the material Would, of course, be unsuitable for use with white lead. Certainly with substitutes containing petroleum it was

ISSN:0003-2654    

DOI:10.1039/AN9083300230

出版商:RSC    

年代:1908

数据来源: RSC

摘要:

234 THE ANALYST. ABSTRACTS OF PAPERS PUBLISHED IN OTHER JOURNALS. FOODS AND DRUGS ANALYSIS. The Detection of Boric Acid in Foods. C. Mannich and H. Priess. (Chem. Zeit., 1908, 32, 314-315.)-The following method of applying the flame test enables 0.1 mgrm. of boric acid to be detected with certainty: A Beckmann’s “ chemical distributor ” is fitted over the tube of a small Bunsen burner, as shown in the figure. When a trace of boric acid dissolved in 2 C.C. of concentrated sulpburic acid is introduced into the distributor, and 5 or 6 C.C. of methyl alcohol subsequently added, the vapours are’ drawn into the burner, and give a green-coloured flame, which is visible for at least twenty seconds. The presence of copper or barium does not interfere .with the test, but the sensitiveness of the reaction largely depends upon the ratio of 2 C.C.of sulphurjc acid to 4 C.C. of methyl alcohol being maintained. When ash con- taining boric acid is tested, the yellow sodium flame appears first, but gives place in a few seconds to the characteristic green flame. In examining, e.g., meat preparations, 5 grams of the finely divided sample are triturated with 0-25 C.C. of 20 per cent. sulphuric acid, and extracted with small portions of 90 per cent. alcohol, until the united extracts amount to 50 C.C. The liquid is then filtered, the filtrate mixed with 0.5 C.C. of 15 per cent. sodium hydroxide solution, evaporated to dryness, the residue ignited, and the ash tested as above described. As little as 0.005 per cent. of boric acid may thus be detected.c. A. i\r. Estimation of Benzoic Acid in Ketchup. C. H. Lawall and H. A. Bradshaw. (,4mcr. Journ. PhaLnn., 1908, 80, 171-172.)-A mixture of 20 grams of the ketchup, 2 gram8 of sodium chloride, 5 C.C. of concentrated hydrochloric acid, and 25 C.C. of a saturated solution of common salt, is thoroughly shaken for five minutes and filtered, and the residue washed with a saturated solution of salt until 100 C.C. of filtrate are obtained. The benzoic acid is extracted from this solution byTHE ANALYST. 235 shaking with quantities of 25 c.c., 15 c.c., and 10 C.C. of chloroform, which is then allowed to evaporate at room temperature, the residue dried over sulphuric acid, and weighed. If t h e residue be impure, it should be dissolved in 10 C.C. of a weak solution of ammonia, and the filtered liquid acidulated and re-extracted with chloroform.The benzoic acid may be titrated in alcoholic solution with 2G potassium hydroxide and phenolphthalein as the indicator, and calculated to sodium benzoate, in which form it is usually added. Saccharin, salicylic and cinnamic acids are extracted by the above process. The last mentioned may be detected by means of a solution of manganous sulphate, which gives a precipitate with cinnamic acid, but not with benzoic acid (cf. ANALYST, 1908, 48). A. R. T. The Variation in Activity of Commercial Crude Drugs. F. H. Carr and W. C. Reynolds. I t is shown from the results recorded, and from the published statements of other observers, that climate, soil, time of harvesting, and method of drying, all affect the activity of drugs, and since these variations cannot be foretold by a physical examination of the drugs, the importance of submitting them to a chemical or physiological assay is demonstrated.The following table gives the lowest and highest percentages of active ingredients found in a number of drugs which had previously been selected as of apparently good quality : (Pharm. Journ., 1908, 80, 542-544.) Drug. Aloes Curacjoa ... ... Atropa belladowan root Broom-tops . . . ... Calabar beans ... ... Cinchona succirubya ... Coca leaves ... ... ,, ,, dried he;b 9 , 9 , ... Colchicum seed ... ... Hgdrastis Canadensis root Hyoscyamus iziger leaves . . . Pomegranate root bark 9 9 9 , 7 9 Pilocuyp. Jaborandi ... Pilocarp. microphyl. ... Ipecacuanha root ...9 , ,, (Rio) ... Jalap ... ... ... Soammony root ... ... . . . 9 9 ... 9 , 9 , Nux vomica beans ... Podophyllum peltutuin . . . Lowest per Cent. 12.60 0.29 0.23 0.07 0.04 1.06 2.70 0.02 0.12 1-14 2.23 0.06 trace trace 0.12 1.76 0.98 0.48 5.10 0.81 3.80 7.75 Highest per Cent. 27.90 0.55 1-08 1.06 0.37 4.64 8.30 0.79 0.57 3.17 5.80 0.21 0.05 0.99 0.29 2-77 1.83 1-29 15.80 2.00 6.65 10.80 Active Principle Estimated. Aloin Total alkaloid Sparteine sulphate Eserine Quinine and cinchonidine Total alkaloid Alkaloid soluble in petro- leum spirit Colchicine Hydras tine Berberine sulphate Total alkaloid Pilocarpine nitrate Total ilkaloid ” Emetine Cephaeline Resin Strychnine Resin Resin 9 , 9 , 9 , 9 1 w. P. s.236 THE ANALYST. Detection of Cocoanut Oil in Butter by Means of the “Silver Value.” C. Barthel.(Zeit. Untersuch. Nahr. Genussnt., 1908, 15, 487-488.)-The author has applied the method described by Wijsman and Reijst (ANALYST, 1906, 31, 158) t o a number of pure butters and to mixtures of butter and cocoanut oil. Whilst at firsb results were obtained which tended to show that the method was useful for detecthg the presence of cocoanut oil in butter, later experiments with pure butters demon- strated the unreliability of the method. In the case of butter yielded by cows fed on sour beetroot slices, the second ‘( silver value ” was considerably higher than the first. w. P. s. The Precipitation Method for the Estimation of Oils in Flavouring Extracts and Pharmaceutical Preparations. C. D. Howard. (Jozdrn. Amel-. Chem.Soc., 1908, 30, 608-611.)-Trustworthy results may be obtained if the oil be precipitated with dilute acid in the presence of a small quantity of chloroform. On submitting the mixture to centrifugal action the oil and chloroform separate, and the chloroform is evaporated after the aqueous portion has been removed. The details of the method are : 10 C.C. of the extract are placed in an ordinary Babcock milk bottle, and 25 c.e: of water, 1 C.C. of hydrochloric acid (specific gravity 1.2), and 0.5 C.C. of chloroform, are added. The contents of the bottle are well mixed, then submitted to centrifugal action for two minutes; the clear supernatant liquid is siphoned off as completely as possible, and 1 C.C. of ether is added to the residue in the bottle. After thorough mixing, the bottle is immersed in boiling water for exactly one minute, the bottle being held at a slight angle and rotated gently during this time.The ether serves the purpose of steadily and rapidly sweeping out every trace of chloroform, but there is no loss of oil. The contents of the bottle are then cooled, and water is added so that the layer of oil is brought into the neck of bhe bottle; after centrifuging for about half a minute, the reading is taken at the highest point of the meniscus. If desired, bottles with a narrower neck may be employed, but with the ordinary Babcock bottle there is no dificulty in obtaining results correct to within 0.1 per cent. Mod$cat.ion for the Heavier Oils.-In order to obtain a compact readable column of oil, it .is best to fill the bottle with dilute sulphuric acid (1 : 2). Oils of wintergreen, cloves, and cinnamon can thus be estimated, and there is no danger of the sulphuric acid decomposing the two latter oils if agitation be avoided and care be taken that the temperature of the acid does not exceed 25” C.In the case of essence of almond, it is necessary to use a bottle having a graduated neck holding 2 c.c., and to employ double the quantities of chloroform and ether mentioned above. A correction is not necessary for the oil retained in solution, as the chloroform, while saturating the water, apparently displaces any appreciable trace of oil The reading multiplied by 2 gives the percentage of oil. remaining in the water-alcohol mixture. w. P. s. Detection of Formic Acid in Foods.A. G. Woodmann and A. L. Burwell. (Chenz. Zeit., 1908,32, 409.)-The method depends on the dry distillation of calcium formate. Fifty grams of the sample are mixed with 20 C.C. of 20per cent. phosphoricTHE ANALYST. 237 acid and distilled with steam. Two C.C. of 30 per cent. aeetic acid, free from forinic acid, and about 20 C.C. of a 10 per cent. milk of lime, are added to the distillate. The solution is evaporated to dryness, at first over a flame, and later on a water-bath. The dry residue is placed in a test-tube, provided with a cork and a bent delivery- tube, and submitted to dry distillation. To the distillate are added 3 C.C. of the ordinary magenta reagent for aldehydes; the mixture is allowed to remain for exactly five niinutes, and then compared with a colour standard.The magenta reagent is prepared by dissolving 0.2 gram of rosaniline in 10 C.C. of a freshly pre- pared saturated solution of sulphurous acid, allowing the liquid to stand until it acquires a pale straw colour, and diluting with 200 C.C. of water. J. F. B, Determinations of the Gravity of Malt Extracts during Summer. G. C, Jones. (Jozmz. Inst. Brewing, 1908, 14, 9-12.)-The author draws attention to the different coefficients of expansion with rise of temperature of malt extracts and water, When the temperature of observation is sensibly above the standard temperature of 60" F., it is not sufficient to determine the weights of malt extract and water contained by the pyknometer at the same temperature. The results so obtained must be corrected for the difference in the coefficients of expansion.The following corrections are to be added to the brewers' extracts (in the neighbourhood of 94 pounds) determined at different temperatures : At 61" F., 0.0 ; at 62' to 63" F., 0.1 ; at 64" to 65" F., 0.2; at 66" to 67" F., 0.3; at 68" to 69" F., 0.4; at 70" to 71" F., 0.5 ; at 72" F., 0-6 ; at 73" to 74' F., 0.7 ; at 75" F., 0.8. J. F. B. A Reaction Distinguishing between Raw and Boiled Milk. L. Gaucher. (Ann. do Chinz. Anal. AppZ., 1908, 13, 146-147.)-0n adding 20 drops of a freshly prepared 1 per cent. solution of hEmatin to 20 C.C. of milk and shaking the mixture the liquid is decolorised in a few seconds in the case of boiled milk, whilst with raw milk the rose colour lasts for twenty-four hours, or longer, until bacterial action destroys the colouring matter.The reaction is obtained with milk which has been boiled a long time (e.g., twenty-four hours) previously. The speed of decolorisation of the reagent depends upon the temperature to which the milk has been heated. Thus, in the case of milk heated in f t ; l open vessel for fifteen minutes at 70" C. (pasteurised milk) the colour becomes faint at once, but does not completely disappear until after about ten minutes ; whilst with milk heated to 80" C. the decolorisation is practically instantaneous. If the milk has been heated in a closed vessel for thirty minutes at 100" C. instead of in contact with the air, the colour becomes appreciably fainter, but is not destroyed. I t also persists in the case of milk sterilised at 110' C,, although the colour sometimes changes to pale yellowish-brown. C.A. 15. Use of Methylene Blue in the Hygienic Examination of Milk-Supplies. C. Barthel. (Zezt. Untersuch. Nahr. Genussnz., 1908, 15, 385-403.)-A test is proposed for ascertaining the purity of milk from a bacteriological point of view which is based on the fact that milk bacteria are capable of decolorising a solution of methylene blue (cf. ANALYST, 1903, 28, 32), the time required for the decolorisation238 THE ANALYST. being inversely proportional to the number of bacteria present. The test is carried out as follows: Ten C.C. of the milk under examination are placed in a test-tube, 0-5 C.C. of methylene blue solution (prepared by diluting 5 C.C. of a saturated alcoholic solution of methylene blue with water to a vcluiae of 200 c.c.) are added, a few C.C.of liquid paraffin are poured over the surface of the mixture, and the test-tube is immersed in water at a temperbture of 40° to 45" C. If the colour is discharged within a few minutes, the milk undoubtedly contains 100,000,000, or more, bacteria per C.C. A solution of methylene blue containing formaldehyde (ibid.) may be used, but the decolorisation is more rapid and less under control. w. P. s. Composition of the Portion of Meat Extract which is not Precipitated by Zinc Sulphate, etc. (Zeit. Untersuch. Nalcr. GenzLssm., 1908, 15, 449-462.)-By precipitating a solution of meat extract with zinc sulphate, and treating the filtrate successively with ammoniacal alcohol, alcohol, concentrated hydrochloric acid, phosphotungstic acid, and alcohol containing hydrochloric acid, a syrup remains, after rejecting the precipitates produced by these reagents, which on hydrolysis yields a product consisting principally of amino acids.Of these, glycocoll and glutamic acid predominate, alanin, leucin, and aspartic acid also being present, whilst prolin and phenylalanin were not detected. The absence of the two latter substances, as well as the negative behaviour of the syrup towards the usual reagents for proteins, indicates that the syrup contains a body which is not a true albuminoid ; it is probably a peptide. Certain of the amino acids, alanin and glutamic acid, are actually present in small quantity in meat extract, whilst the others mentioned may have resulted from the hydrolysis of proteins.Taurin was w. P. s. K. Micko. found to be present, as such, in meat extract. Detection of Yeast Extract in Extract of Meat. C. M. W. Grieb. (Pharm. Journ., 1908, 80, 441-442.)-The author points out the necessity for using a clear, boiling solution of Searl's modified Fehling reagent (ANALYST, 1903, 28, 360). If the reagent becomes turbid on heating, it must be filtered before use. Twenty-five C.C. of this clear, boiling solution are then added to a boiling solution of the sample (0.5 gram or more dissolved in 60 C.C. of water), and the boiling continued for not longer than one and a half to two minutes. The liquid becomesviolet-black in colour, and in the absence of yeast extract remains clear; but the presence of yeast extract causes the precipitation of large flocculent masses of a yellowish-grey colour.If the test be carried out on the alcohol-insoluble portion of the sample, as recom- mended by Searl, less than 1 per cent. of a yeast product in meat extract may be detected. A. R. T. Characteristics of Some Japanese Vegetable Oils. M. Tsujimoto. (Journ. Coll. Eitqaneerilzg, Imp. University, Tokyo, 1908, 4, 75-88.)-Tsubaki oil from the seeds of the Tsubaki-tree (Thea japonica), as found in commerce, is a pale yellow to reddish-yellow oil. I t is chiefly used as a hair oil, and for lubricating delicate machinery, and to a less extent as food. I t consists chiefly of olein, and closely resembles olive oil in its general properties. It is largely adulterated withTHE ANALYST.239 cheaper oils, notably rape, cotton-seed, bean, and arachis oil. Bieber's reagent (a mixture in equal parts by weight of water, fuming nitric acid, and concentrated sulphuric acid) affords a test of its purity. On adding 7 C.C. of the reagent to 2 C.C. of the oil, a green zone is obtained, the colour changing to bluish-green on shaking, then to yellow, and finally to greeniRh-yellow. I n the case of adulterated oil the green coloration lacks the blue shade, and on standing a reddish tint is produced. It is distinguished from olive oil by its low solidification-point ( - 15" C.). Sasanqzca oil, from Thea sasanqua, closely resembles tsubaki oil, for which it is used as a substitute. I t solidifies at higher temperature, however (-9" C.), and may be distinguished by giving a yellowish-green colour, changing, after twenty-four hours, to orange-yellow with Bieber's reagent.Kaya oiZ, from the seeds of Torreya nucqera, is a yellow liquid with faint odour and mild taste. I t yields an elastic film when heated for three hours at 100" C., and dries at the ordinary temperature after boiling with manganese resinate. The fatty acids yield a tetrabromide, but give no deposit in the hexabromide test. The oil is used as food, for burning, as an insecticide, and in the manufacture of oil-papers, etc. It is a light yellow liquid, which does not solidify at - 15" C. It dries in four hours when heated at 100" C. Kzcsu oil is contained in the fruit of the camphor-yielding tree, Cinnamomum Campiwra Nees (Lauracee). It resembles cocoanut oil in general characteristics, but its chief constituent appears to be laurin.Inzdcusu oil, from the fruit of Machilus Thunbergii, is a brownish-yellow oil which forms crystalline deposits at low temperatures. It resembles kusu oil, but its lower saponification value and higher iodine value indicate the presence of glycerides of higher unsaturated fatty acids. I t does not become turbid at - 20" C. Inzckaya oil is obtained from the seeds of inukaya (Cephalotoxus drupacea). Oil. Tsulwki .. . ... Sasaiiqua . , . . . . liaya .., ... Iiiukaye ... ... Kusn ... ... Inuknsu ... ... Specific Gravity a 1 5 5 O C. 0.9159- 0.9164 0.9188 0 -923 3 - 0-9244 0.9250 0'9267 (a 09347 (a 25" C,) 0.91 63- 25" C.) Acid Value. 1.63-8.84 0-36-6 -73 1'48-12'66 - 4.7 19-31 3aponifica- Lion Value. 189.89- 192.58 193.3- 193.9 197.9- 188.4 188'5 283'7 241 '4 Iodine Value (Wijs). 80.21- 81-32 81 -67- 82.31 133.4- 142'2 130.3 4 *49 66-08 Refractive Index at 20Q c. 1 '4679- 1'4691 1'4691 1'4757- 1.4770 1.4760 1'4517 (at 25" C.) 1'4646 (at 25" C.) Hehncr Value. 95.6 96.35 95.7 - - Re i c h e r t- Metssl Value. 0 5 3 1.17 0.93 - 0.53 2 *05 Melting- Point. C. A. M. The Constituents of Simaruba Bark. C. Gilling. (Pharm. Jozcrn., 1908, 80, 510-513.)-The author has identified the following constituents of the bark of Simaruba amara: (1) A tasteless fixed oil, from which a solid separates on long standing; (2) an acid resin; (3) 0.05 to 0.10 per cent. of a crystalline bitter240 THE ANALYST. principle C,,H,,09, soluble in methyl and ethyl alcohols and acetone, moderately soluble in chloroform, but insoluble i n ether, and giving a violet coloration with strong sulphuric acid. I t melts at 229" to 230" C. with decomposition, has a specific rotation of + 67.6' in a chloroform, and + 58.0' in an alcoholic, solution, and apparently contains no methoxy or carbonyl groups ; (4) a non-bitter substance, crystallising in feathery needles melting at 240" to 241" C., and nearly insoluble in chloroform ; and (5) traces of a, fluorescent body which was not isolated. A. R. T.

ISSN:0003-2654    

DOI:10.1039/AN9083300234

出版商:RSC    

年代:1908

数据来源: RSC

摘要:

240 THE ANALYST. BACTERIOLOGICAL, PHYSIOLOGICAL, ETC. Determination of Diastatic Power of Malt by Lintner's Method. G. C. Jones. (Jounz. Inst. Brewing, 1908, 14, 12-32.)-The author deals with some of the factors which tend to produce discordant results in the estimation of diastatic powers when carried out by different operators, even when working on the standard system approved by the Committee of the Institute of Brewing. In the first place, the reaction of the soluble starch employed, whether acid or basic, has a considerable influence on the results, and the Committee's specification '6 neutral to litmus " is not sufficiently precise. The author finds alizarin paste (1 gram in 200 c.c.) a satisfactory indicator for the purpose; when the starch is neutral, 2 drops of this indicator, when added to 200 C.C.of a boiling 2 per cent. solution, give a clean yellow colour, which is changed to an incipient purple by 1 drop of The maximum diastatic action is obtained when 0.1 C.C. of =& acid is added to 200 C.C. of a neutral solution of starch. The reaction of the starch should always be determined and adjusted before it is taken into use. According to the author's experience, the use of water distilled in glass vessels from alkaline permanganate for preparing the starch solution is a superfluous refinement. The temperature at which the diastatic digestion is carried out has a very great influence on the results, and the prescribed temperature of 70" F. must be rigidly maintained; the specified quantity of 3 C.C. of malt infusion must also be adhered to, I n the preparation of soluble starch by digestion with hydrochloric acid, the viscosity and cupric reducing power of the product may vary greatly according to the temperature of the room in which the digestion is carried out.I t is probable that the different viscosities are not of practical importance owing to the rapid liquefying action of the malt, but the different reducing powers may affect the results to the extent of 0.5". One of the most serious and obscure causes of dis- crepancies between the results of different chemists is the manner of filtering the malt ; i t would appear that the later portions of the filtrate sometimes have a higher diastatic power than the early and less brilliant portions. The author describes the procedure he adopts in the following terms : 25 grams of malt are extracted in a beaker with 500 C.C.,of water for three hours, and the well-stirred mixture is transferred to a 24-cm. filter, so that from the start a fair proportion of the grains go forward. The filter holds about half the quantity ; more is added as filtration proceeds, until the whole contents of the beaker have been transierred to the funnel. A clean 200-C.C. beaker is used to collect the next 20 C.C. or so of filtrate, which is used to rinse out the 200-C.C. beaker in which the next 100 C.C. of filtrate are collected for the test. To ensure a maximum alkali.THE ANALYST. 241 result it would be necessary to pass a portion of the filtrate B second time through the filter. I t is to be noted that if a strong infusion of malt be diluted so as to represent a 5 per cent.extract, higher results are obtained than if a 5 per cent. infusion be prepared direct. J. F. B. The Examination of Commercial Preparations of Rennet. A. Burr and F. M. Berberich. (Chem. Zeit., 1908, 32, 313-314.)-Commercial samples of the fluid preparations and of rennet powder gave analytical results of which those shown in the following table are typical. All the samples had an acid reaction, that of the liquid preparations being much more pronounced, The ash consisted largely of sodium chloride, due to the brine used in the original extraction. The ash of five liquid preparations gave only a weak boric acid reaction, whilst the solid preparations were free from that acid. The strength was determined at 35" C. upon mixed fresh milk derived from several large herds, the values representing the number of C.C.coagulated in forty minutes; but as the same rennet may vary with different milks as widely as 1 : 200,000 and 1 : 300,000, they must only be regarded as approximate values. Liquid Prepara- tions : 1 ... ... 2 ... ... 3 ... ... Rennet Powders : 1 ... ... 2 ... ... 3 ... ... 4 ... ... Acid Value. 100 C.C. 01 .OO Gram Neutral- ised by & NaOH C.C. 95.0 95'0 - 26 '0 40.0 37 -5 25.0 Dry Sub- stance. 'er Cent. 16.21 13.82 11 *oo 99.93 99.60 99.80 99.90 Ash. 'er Cent. 12-17 9 *48 6 . 8 i 92.93 93.00 92.96 97 *50 Sodium Xiloride. 'er Cent. - 8.6s 4.18 8s-34 S3.07 84.24 95'94 Organic Sub- stances. 'er Cent 4 *04 4'34 4.13 7.00 6 -60 6 *84 2'40 Nitro- gen.'er Cent. 0.56 0.66 0 *38 0.82 0.80 0.75 0 *35 Vitrogei in Organic stances Sub- 'er Oeni 13.86 13'06 9-32 11.7 12.2 11.0 14.6 Strength. paration in Milk at 350, C. AC. COitgU lated. 15,584 14,285 19,753 237,624 186,040 120,040 88,889 in Milk at 55O C. C.C. coagu- latcd. 385,742 329,149 475,281 4394,625 !,81S,T87 . ,764,386 I, 705,708 Acid Value of the Milk used. 6.8 s.0 7.1 7.0 7.2 '7.2 6.2 C. A. RI. The Hydrolytic Enzyme in the Resting Seeds of Some Gramineae. Y. Tanaka. (Journ. Coll. Engineering, Imp. University, Tokyo, 19013, 4, 39-52.)- The diastase of glutinous millet (Setayia italica) and of common millet (Panicurn miliaceum) has a higher optimum temperature of hydrolysis (50" to 55" C.) than that of barley diastase investigated by J. L. Baker (Trans. Chem. SOL, 1902, 1177). It rapidly liquefies starch paste, and hydrolyses the soluble starch through successive dextrins to achroo-dextrin, with the simultaneous formation of only a relatively small amount of maltose. Owing to its strong liquefying, but weak saccharitying power, equal amounts of maltose are formed by it from starch paste and soluble starch at242 THE ANALYST. equal intervals. The dextrins formed as intermediate products in the hydrolysis consist of erythrodextrin and a-erythrodextrin. The latter, which is probably more complex than erythrodextrin, gives a red coloration with iodine, and is very slowly saccharified by millet diastase. The starch paste of glutinous millet and other varieties of glutinous starch are liquefied more rapidly, but saccharified more slowly than ordinary starch paste by millet diastase. A greater yield of maltose is produced from starch paste by the combined action of barley and millet diastase than by the action of either diastase by itself. C. A. 1%.

ISSN:0003-2654    

DOI:10.1039/AN9083300240

出版商:RSC    

年代:1908

数据来源: RSC

摘要:

242 THE ANALYST. ORGANIC ANALYSIS. The Detection and Estimation of Small Amounts of Benzene in Alcohol. D. Holde and G. Winterfeld. (Chem. Zeit., 1908, 32, 313.)-The method is based Apon the fact that on distillation the whole of the benzene passes over in the first 10 per cent. of the distillate, and appears as an oily layer floating on the surface. One hundred C.C. of the alcohol under examination are diluted with sufficient water to bring the alcoholie strength to 24.7 per cent. by weight, the mixture distilled, and the first 10 C.C. of the distillate collected in a flask cooled in ice-water. On diluting this distillate with 18 to 20 C.C. of water, and transferring it to a measuring cylinder or a burette, the proportion of separated benzene may be read directly. The amount of benzene remaining dissolved in the turbid lower layer amounts to about 0.3 per cent.by volume, and remains practically constant whether the original quantity of benzene be 0.5 or 5 per cent. C. A. 11. Estimation of the Degree of Bleaching of Cellulose. C. G. Schwalbe. (FtirbeY-Zcit., 1908, 19, 33 ; Chem. Zeit. B e p , 1908, 32, 204.)-A normally bleaehed cotton should show no reducing action when boiled with Fehling's solution ; but faulty or excessive treatment with the bleaching chemicals may give rise to the production of oxycellulose or hydrocellulose, both of which reduce Fehling's solution. For the estimation of the cupric reducing power of any cellulose, two portions of 3 grams each of the sample are weighed out. One serves for the estimation of the moisture by drying at 100" to 105" C.for four hours, whilst the other is suitably disintegrated and moistened with 150 C.C. of boiling water. One hundred C.C. of Fehling's solution are heated to boiling and added to the moist cellulose, the vessel being rinsed with 50 C.C. of hot water. The mixture is heated under a reflux condenser for exactly fifteen minutes after full ebullition is reached. The mass is then drained on a, filter by means of a pump, and washed with boiling water until no more copper is dissolved. The cake of cellulose is then heated with about 30 C.C. of 6.5 per cent. nitric acid, and sufficient water to make a paste. The liquid is filtered off, and the residue washed with boiling water ; the filtrate is evaporated to a, small bulk, and the copper is determined electrolytically.Tht? weight of the metallic copper, expressed as per cent. of the cellulose dry substance, is called the '' copper value '' of the sample. Since mercerised cotton absorbs cupric oxide, a correction must be made for the copper deposited in this form. This is determined by a,THE ANALYST. 243 separate treatment with Fehling's solution, the cupric oxide being extracted with acetic acid instead of nitric acid. J. F. B. Manila and Pontianak Copals. C. Cofllgnier. (Bull. SOC. Chim., 1908 [4], 3, 453-459.)-The following results were obtained in the examination of commercial samples : Specific gravity . . . Melting-point . . . Acid value ... Saponification value Insoluble in boiling : Ethyl alcohol ... Methyl alcohol ... Amyl alcohol .... Ether ... ... Chloroform . . . Benzene ... ... Acetone ... ... Turpentine oil . . . Benzaldehyde . . . Aniline ... ... Amyl acetate Carbon tetrachloyide ... ... ... ... ... ... ... ... ... ... ... . . . ... ... ... ..I Manila (Hard). 1.065 at 17' C. 190" c. (soft at 80" C.) 72-80 87.0 Per Cent. 55.90 64.60 Soluble 58.50 36.70 63.90 52.0 73-20 1-10 Soluble 69% Manila (Soft). 1-060 at 1 7 O C. 120" c. (soft at 45O C.) 145.2 185.1 Per Cent. Soluble 7-30 Soluble 28-70 52-40 57.90 Soluble 64.10 1.70 Soluble Pon tiaiiak. 1.037 at 16" C. 135' C. (soft at 55" C.) 134.3 186.5 Per Cent. Soluble 13.50 Soluble 46.0 50.3 63.0 Soluble 66.40 Soluble Pontianak copal, which is a product of Borneo, has only been in use a few years. I t has an aromatic odour, recalling that of eleniic resin, and varies in colour from pale yellow to reddish-brown.I t closely resembles soft Manila copal in its general physical and chemical characteristics. C. A. M. Chrysalis Oil. M. Tsujimoto. (Jozinz. CoZZ. Eizgiizeering, Imp University, Tokyo, 1908, 4, 63-74.)-Chrysalis waste is now extensively used as a, source of oil for soap-making in the silk-producing districts of Japan. A sample of the material examined by the author contained 5-48 per cent. of moisture, 26.26 per cent. of oil, and 3-77 per cent. of mineral matter. The oil was a yellowish-red liquid, of un- pleasant odour. It solidified at 0" C., and gave the following analytical values: Specific gravity at 15.5" C., 0,9280 ; acid value, 18.68 ; saponification value, 194.12 ; iodine value (Wijs), 131-96 ; Hehner value, 94.5 ; Reichert-Meissl value, 3.38 ; true rtcetyl value, 19.72 ; refractive index at 20" C., 1-4757.Fatty Acids .- Specific gravity at 100°/15*50 C., 0.8513 ; melting-point, 36.5" C. ; solidification point, 27" to 289 C. ; neutralisation value, 199.34; mean molecular weight, 28143 ; iodine value, 135.83; unsaturated acids (with iodine value, 178.73)) 75 per cent.; and melting-point of saturated acids, 57" C. (cf. Lewkowitsch, ANALYST, 1907, 32, 53).244 THE ANALYST. The oil contained 9.42 per cent. of glycerin, and 1.63 per cent. of unsaponifiable matter, consisting principally of phytosterol (melting-point, 143.5' C.), and not cholesterol, as in the sample examined by Lewkowitsch (Zoc. c2.t.). The fatty acids yielded hexabromide corresponding to 4.38 per cent, of linolenic acid.No linolic tetrabromide was obtained, but isomerides of linolic acid were apparently present. The solid fatty acids contained palmitic acid, but no stearic acid was found. c. -4. &I. The Japanese Dyewood '' Doss." E. Ito. (Joimt. CoZZ. Eizgineeriiig, Imp. Univeysity, Tokyo, 1908, 4, 57-62 )-The bark and extract of the evergreen tree " d o s ~ ~ ~ (Ilcz Merteizsii, Naxim) is used as a substitute for myrica bark in dyeing. The author has isolated from it a new dyestuff, dossetiit, C15HyOj, which crystallises in yellow needles, and melts at 271" to 272" C. With alumina mordant it gives a dull yellow colour, with tin a bright yellow, and with iron an olive colour. C. A. M. Japanese Lacquer. K. Miyama. (Jour?b.CoZZ. Engineering, Imp. Uizi- versity, Tokpo, 1908, 4, 89-110.)-The milky juice (umshi) .frob the Japanese lacquer-tree, Rhus vernicifera, turns brown when heated or exposed to light, and is then mixed with pigments, oils, etc., to form the lacquer. The crude liquid contains as its main constituent a polyhydric phenol, C3+Hj004, termed urushiol by the author. I n very dilute solution this gives a green coloration with ferric chloride, changing to red on the addition of sodium carbonate. I t yields a green precipitate with barium hydroxide, and gives a silver mirror in the cold with tlmmoniacal silver nitrate solution. The quality of a lacquer depends largely upon the proportion of urushiol it contains, whilst the greater the quantity of gum the poorer the quality.Samples drawn from the same tree at different periods varied greatly in composition-e.g. , moisture, 17.81 to 27.62; urushiol, 64.14 to 77.63 ; gum, 2.62 to 7-57; and nitro- genous substances, 1.78 to 2.47 per cent. Lacquers imported from China and India, contained more moisture, less urushiol (36-88 per cent. in inferior Chinese, and 26.39 per cent. in medium Indian), and more gum (23.5 and 37.78 per cent. reapectively). The presence of an enzyme causes the lacquer to dry at low tempera- tures. At 70" to 80" C. the drying process is suspended, but at temperatures above 100" C. drying takes place without enzymic action, and the urushiol itself, which does not dry at the ordinary temperature, then also dries readily. I n the valuation of a lacquer, the durability, transparency, lustre, and smoothness of its dried film, and the duration of drying and viscosity of the substance itself, are taken into account, whilst for the chemical examination the following method is recommended.: Moisture is estimated by heating 1 gram of the raw or 2 grams of the finished lacquer upon the water-bath until transparent, and then in the hot-water oven for thirty minutes.Umshiol: The dried lacquer is treated with 10 (or 20) C.C. of absolute alcohol, and left for thirty minutes (or one hour), after which the liquid is filtered through a tared filter, and the residue washed with absolute alcohol. The filtrate and washings are divided into two portions, one of which is used for the estimation of the substances soluble in alcohol. The other is titrated with N-bariumTHE ANALYST 245 hydroxide solution, with phenolphthalein as indicator, the barium urushiolate formed uhder these conditions approximating closely to the salt formed in the equation- C,,H,,O, + 2Ba(OH), = C,,H,,O,Ba, + 4H,O, 1 gram of the urushiol thus corresponding to 6-14 C.C.Oils are obtained by deducting the urushiol from the substances soluble in alcohol, whilst gz~m arabic is estimated by extracting the residue on the filter with boiling water, and evaporating the extract, and the final insoluble residue on the filter gives the amount of nitro- geizozis substances. In the case of black finished lacquer the solution of substances soluble in alcohol is assisted by the addition of one or two drops of hydrochloric acid. The dissolved substances left on evaporation are then successively washed with hot water, hot sodium carbonate solution, and hot water, and redissolved in alcohol. C.A. M. Test for Mineral Oil. F. Schulz-Kolin. (Chem. Zeit., 1908, 32, 345.)-A solution of commercial picric acid in benzene gives a red coloration with mineral oils. The reaction depends on some impurity in, the crude picric acid (probably lower nitration products or higher homologues), since the pure acid gives no coloration. Rosin oil shows the same coloration as mineral oils, and the test may be regarded as a general one for the detection of the hydro-aromatic hydrocarbons and their oxidised derivatives. Since the pure animal and vegetable fatty oils show no change in colour with picric acid, this is a very convenient reagent for the detection of their adulteration.The presence of 1 per cent. of vaseline in a dark yellow coloured rape oil showed a distinct reddening on testing with picric acid ; the test may also be used with linseed oil varnishes. J. F. B. The Iodine Values of the Phenols. E. Wake and H. Ingle. (Jouwt. SOC. Che?n,. Iizd., 1908, 27, 315-31G.)-From the figures given it is seen that the meta- phenols and P-naphthol have iodine (Wijs) values which correspond with 6, 4, or 2 atoms of iodine per molecule, the values found being : Phenol, 267 ; carvacrol, 177 ; yhloroglucinol, 478 ; resorcinol, 690 ; and @naphthol, 178. A determination of the iodine value could thus be used for ascertaining their purity. The experiments with the phenols gave ample evidence of the reducing action of potassium iodide on iodochlorides.From a-naphthol, which by Hiibl’s method gives an iodine value of 264, by Wijs’ method adding potassium iodide first, iodine values from 195 to 200 were obtained; whilst when water was added to the test so as to precipitate the iodochlorides in the chloroform solution before adding t h i potassium iodide, an iodine value of 262 (31 = 265) was obtained. I n the case of phenol the iodine value found was 623 when water was added before the potassium iodide, whilst when the iodide was added first the value obtained was 267. I t was found that, while the ortho and para poly-phenols liberated iodine from Wijs’ solution, the meta derivatives did not do so. This test may be used to determine whether the hydroxyl groups are in the meta or in the ortho or p a m positions, and also to distinguish a- from @-naphthol, the former liberating iodine246 THE ANALYST.from Wijs’ solution. The best may be carried out as follows: The substance is dissolved in a small quantity of chloroform, and a quantity of freshly prepared Wijs’ solution is added. If any darkening of the solution takes place, the substance under examination contains ortho or para phenols or a-naphthol. Rosin also liberates iodine from the reagent, and its presenee in shellac may be detected by this means. The behaviour of the esters of the phenols is interesting, for whilst the free phenols absorb iodine, such is not the case with the esters (benzoates). W. P. S. New Method for the Estimation of Tannin.G. Metzges. (Cl~cm. Zeit., 1908, 32, 345.)-The author describes a method for the precipitation of tannin under the action of the electric current; the unreliable precipitation by means of hide powder is thus avoided, but all the other operations remain the same as in the old process. The solution containing tannin is subjected to the action of a simple long- phase alternating current between aluminium electrodes ; the precipitation of the tannin takes place gradually, and the end of the reaction is ascertained by drop-tests. The current may be obtained from an ordinary continuous current main at 110volts ; this is passed through a resistance of four 16-candle-power lamps arranged in parallel. The current is transformed by a rotating commutator operated by a small turbine or motor. An aluminium dish 100 mm. in diameter, of a capacity of 250 c.c., consti- tutes one electrode, and the other consists of a perforated aluminium disc of 60 mm. diameter. The solution, prepared by the standard method, is placed in the dish, and the disc electrode is adjusted at a depth of 1 cm., the volume of the liquid being 100 to 120 C.C. During the passage of the current the contents of the dish are frequently stirred. The precipitation of the tannin is complete a€ter about thirty minutes, a few drops of the solution being filtered off and tested with iron or gelatin. The precipitate is then removed by means of a dry filter, and 50 C.C. of the filtrate are taken for the estimation of the non-tannin in the usual way. The results are said to agree well with those obtained by the official hide-powder method. J. F. B.

ISSN:0003-2654    

DOI:10.1039/AN9083300242

出版商:RSC    

年代:1908

数据来源: RSC

摘要:

246 THE ANALYST. INORGANIC ANALYSIS. The Electrolytic Estimation of Bismuth. F. J. Metzger and H. T. Beans. { Jozcm. Anzer. Chem. Soc., 1908, 30, 589-593.)-Bismuth can be coiupletely pre- cipitated on a rotating cathode in an adherent form from a solution of the nitrate if fhe latter is first made alkaline to phenolphthalein with sodium hydroxide, and then acid again with sufficient acetic acid to give a practically clear solution. The further addition of boric acid yields a still better deposit. The conditions used were : Acetic acid, 20 C.C. of 50 per cent. acid; boric acid, 2 grams; dilution, 250 c.c.; current, N.D.,, = 0.2 to 0.16 amp6re a t 1.8 to 2-8 volts ; temperature, 63' to 78" C. ; bismuth, 0.1 grain ; time, one and a quarter hours. For 0.4 gram bismuth, 30 C.C.of acetic acid were used, and the time required was two and a quarter hours with the same cathode, which was shortened to one and a half hours when a cathode with a surface of 100 sy. cm. was employed. The cathode made 700 revolutions per minute, A. G. L.THE ANALYST. 247 The Analysis of Nearly Pure Gases. H. Franzen. (Zeits. hzorg. Clzem., 1908, 57, 395-397.) -Considerable quantities of impurities present in nearly pure and difficultly absorbable gases (c.g., com- pressed oxygen) are conveniently collected by means of the apparatus shown in the figure. I t consists of a 150 C.C. gas-sample tube provided with two taps, and a mark at 50 c.c., reckoned from the lower tap, and a Drechsel wash-bottle containing water. The sample tube is first filled with water.Gas is next passed through the wash-bottle until all air has been expelled, whan the sample tube is connected with the wash- bottle by means of a rubber tube, as shown. Both taps being opened, gas is passed into the sample tube to the mark. Both taps are then shut, a reservoir containing water is connected to the lower tap, which is then opened, and the residual 50 C.C. of water are sucked out. A small quantity of an absorbing reagent (e.g., sodium hyposulphite in the case of oxygen) is then introduced into the sample tube from below as usual, after which the lower tap is shut, the upper one opened, and gas allowed to flow into the sample tube, which is meanwhile vigorously shaken. When no more gas is absorbed, a fresh quantity of reagent is introduced, and this procedure repeated until the sample tube is completely filled with the unabsorbable impurities. A.G. L. A Separation of Iron from Manganese. R. B. Moore and I. Miller. (Jouriz. ilmer. Chem. SOC., 1908, 30, 593-594.)-A good separation of iron from manganese can be effected by adding to a fiolution of the chlorides containing a little free hydrochloric acid a sinall excess (0.5 c.c.) of pyridine. The solution may be gently warmed; the precipitate should be filtered off at once, and washed with pyridine water (1 : 500). The manganese in the filtrate cannot be precipitated with bromine and ammonia; it may be recovered by means of potassium carbonate or hydroxide. I n separating about 0.1 gram iron from its own or twice its weight of manganese, the error amounted to 0.5 mgm.at the most after a single separation. A. G. L. Methods for the Detection of Lead Dust and Fumes i n Works. Heim and Herbert. (Zeits. Gezoerbe-Hyg., 190 8, 15, 82-85 ; through Chem. .&it. Rep., 1908, 32, 193.)-Of the usual methods €or the detection of lead, the sulphide reaction is the most delicate, a reaction being obtained with 0.1 to 0.2 mgm. of lead, provided a layer of liquid 10 cin. deep be viewed from above. This method is, of course, inapplicable in the presence of other heavy metals. Trillat therefore propose3 t o248 THE ANALYST. utilise the colour developed by the action of peroxides on tetramethyldiamidodiphenyl- methane, the corresponding carbinol [C,H,N( CH,),],CH-OH being produced. The reagent is prepared by warming together for one hour 30 grams of dimethylaniline, 10 grams of formaldehyde, and 200 C.C.of water, acidified with 10 grams of sulphuric acid. An excess of soda is then added, and the unchanged dimethylaniline romoved by steam distillation. On cooling, the reagent crystallises out ; it is recrystallised from alcohol and dissolved in nitric acid (5 grams per 100 c.c.). The solution should be kept in the dark. In testing for lead, the substance is treated with sodium hypochlorite, the chlorine removed, and the reagent added. The air is led through cotton-wool and then through d p h u r i c acid. The cotton-wool is ashed after moistening with sulphuric acid, the sulphuric acid is evaporated to dryness, and both residue$ are tested as above. The method is stated to be exceedingly delicate.A, G. L. Purification of Mercury. W. Bettel. (Chenz. News, 1908, 97, 158.)-The author finds that gold and the base metals present as impurities in metallic mercury may readily be removed by a weak cyanide solution, the purification being hastened by the addition of sodium peroxide to oxidise the base metals. I n one experiment 7 kilogms. of impure mercury were treated in a shallow, flat-bottomed receptacle with 1,500 C.C. of a 3 per cent. solution of potassium cyanide, 20 grams of sodium peroxide being added at intervals and the solution occasionally agitated. During the first four days the base metals were dissolved and the gold contents remained practically stationary, but on the fifth day the amount of gold dropped from 150 to 90 mgms. per kilogm.of mercury. On the sixth day, 12 mgms. ; seventh, 6 mgms. ; eighth day, 5 mgms. of gold per kilogm. were found. The cyanide solution was then removed, and replaced by a fresh 0.2 per cent. solution. On the fourteenth day of treatment the gold remaining in the mercury was less than mgm. per kilogm., and the metal thus purified was superior to the vacuum-distilled product. As there is practically no loss of mercury, the cost of the operation is very small. A. R. T. The Detection of Nickel in Ores and Nickel Steel. H. Grossmann. (Chenz. Zeit., 1908, 32, 315-316.)---The author criticises the method of Pozzi-Escot (ANALYST, 1907, 32, 432; 1908, 106), which he regards as unsuitable for the estimation of nickel in New Caledonian ores. For its detection in ores and nickel steel he gives the following modification of his dicyandiamidine method (ANALYST, 1907, 32, 273, 394).The filtrate from the metals of the hydrogen sulphide group is concentrated to a small volume, freed from too large an excess of mineral acids, and treated with Rochelle salt in the proportion of at least 4 grams to 1 gram of the mineral or alloy, The solution is then rendered strongly alkaline with ammonia, and treated with about 1 gram of dicyandiamidine sulphate and with potassium hydroxide. The nickel separates immediately, or, if present only in sinall quantity, after a short time. If R large amount of manganese is present, it is best to treat the liquid with hydrazine sulphate, which prevents the oxidation of the amrnoniacal tartrate solution and separation of higher manganese oxides.C. A. M.THE ANALYSTo 249 The Gravimetric Estimation of Tellurium. V. Lenher and A. W. Hom- berger. (Jozmn. Anzer. Chem. SOC., 1908, 30, 387-391.)-The authors find that tellurium can be quickly and accurately estimated by heating a fairly concentrated solution of either oxide, containing 10 per cent. of hydrochloric acid, to boiling, adding 15 C.C. of a saturated solution of sulphur dioxide, then 10 C.C. of a 15 per cent. solution of hydrazine hydrochloride, and then another 25 C.C. of the solution of sulphur dioxide, The solution is boiled until the precipitate settles in a form suitable for washing, which should take about five minutes. The precipitate is then filtered off on a Gooch crucible, washed first with hot water, then with alcohol, dried at 105" C., and weighed.A. G. L. Quantitative Separation of Thallium from Silver. J. F. Spencer and Margaret Le Pla. (Proc. Chem. Suc., 1908, 24, 75.)-A quantitative separation of the salts of silver and thallium is effected by treating the mixture with a stream of chlorine, whereby the thallium is converted into the very soluble thaliic chloride and the .silver is precipitated as silver chloride. After removing the latter, the solution is concentrated, and reduced by means of sulphur dioxide (either liquid or gaseous). The excess of sulphur dioxide is removed by boiling, and the thallium precipitated as thallous iodide, filtered, washed, and dried at 104". The results are quantitative, and are obtained very quickly. Thallous chloride was found to be more soluble in potassium carbonate than in water, for, whereas water dissolves 3-86 grams per litre at 25", a 5 N-solution of potassium carbonate dissolves 21.84 grams per litre at the same temperature.Volumetric Estimation of Titanium. H. D. Newton. (Zeits. Anoiy. CJzeiiz., 1908,57,278-280.)-The titanium solution, containing about 10 per cent. of sulphuric acid, is reduced by warming with zinc in a 100-c.c. flask, closed by a stopper carrying an inlet-tube and a small separating funnel. During the reduction and subsequent cooling a current of hydrogen is led through the flask. An excess of a solution of ferric sulphate is then added, the flask is completely filled with cold water, and its contents are transferred to a larger flask in which the ferrous iron produced is titrated with potassium permangmate solution.The zinc used must be free from iron, or else contain a known amount of this metal. The test results quoted are very good. A. G. L. Notes on Wijs' Solution. H. Ingle. ( J o z L ~ . SOC. Chenz. ITzd., 1908, 27, 314.)-In reply to Harvey's objections (ANALYST, 1903, 28, 41) to the method of procedure proposed by the author, the latter states that no advantage is t o be gained by adding water to the blank test before the potassium iodide! as there are no iodochloridea of unsaturated compounds present. Iodine chloride being soluble in both chloroform and water, it is not removed from the sphere of action of either water or potassium iodide. The loss of titre which takes place in this case is due to the decomposition of the hypoiodous acid formed by the action of the water on the iodine chloride.(1) IC1+ H,O = HI0 + HCI, and (2) 4HIO = 2H20 + 21, + 0,. The reactions which take place may be represented thus :250 THE ANALYST. The first is a reversible reaction. If the amount of hydrochloric acid present in the solution is increased less hypoiodous acid is formed, and consequently there is less tendency for the second reaction to take place. If Wijs’ solution and water be mixed in equal volumes, the solution gradually becomes redder in colour, owing to the separation of iodine, and bubbles of gas rise to the surface. Harvey’s contention that the reduction in the titre in the blank test may be due to substitution in the acetic acid by the action of the free iodine and iodic acid does not appear to the author to be sound, for it is impossible for iodic acid to exist in the presence of hydrochloric or hydriodic acid.w. P. s. The Preparation of Conduetivity Water. H. Hartley, N. P. Campbell, and R. H. Poole. (Trans. Chenz. Soc., 1908, 93, 428-431.)-With the still described below, the authors have found no difficulty in preparing 2.5 litres of water with a specific conductivity not greater than 0.75 gemmho (1 gemmho = 1.0 x 1 0 - 6 reciprocal ohms), and 3 more litres of fairly good water of 1.5 gemmhos, in a, single distilla- C - -71 -T A tion, without any special precautions for keeping the air of the laboratory free from impurities. The boiling vessel ( A ) is of copper or tinned iron, holding about 10 litres. This is filled with ordinary distilled water (of approximately 5 gem- mhos).From A the steam passes through the glass trap (B), where any dust is stopped by the glass wool (W), and any con- densed water escapes at P. The steam then passes into the condensing vessel (C), which is made of the best tinned iron. The con- denser tube ( T ) is made of block tin and is soldered through the lid. I t is cooled internally by a stream of tap water. P represents baffle plates. Water condenses on T, and the small tin cover prevents any water, except that con- densed on the block tin surface, from dropping into the tin funnel and delivery tube (E). The waste water runs away through R. A fine capillary tube is attached to both D and 12, to prevent steam blowing off. The water is collected in a steamed-out Jena flask,THE ANALYST.251 holding 3 litres. The tin delivery tube passes through a piece of Jena tubing in the rubber stopper of the flask, a small piece of rubber tubing making an air-tight joint. The water is drawn off through a siphon of Jena glass tubing, and connection between the flask and the air is made through the soda-lime tube (8). The small flask ( K ) contains nioist glass wool, to prevent any soda-lime dust from being carried over into the large flask. For the first half-hour after boiling begins the water collected is impure, and is rejected. The flask ( F ) is then attached to the delivery tube, and the water is collected for two hours. The two litres obtained serve to wash out the flask, and are then run off, and during the next three hours the best water collects.This usually amounts to about 2.5 litres, having K,, = 0.75 gemmho. The flask is then removed, the small tube is quickly closed with a rubber plug, and the water may be kept ready for use without its conductivity increasing to any extent. By putting another flask under the delivery tube at this stage, another litre may be obtained with Kls= 1 gemmho. w. P. s. Volumetric Estimation of Zinc. W. H. Keen. (JOZ~Y~Z. Amer. Clzem. Soc., 1908, 30, 225233.) -In titrating zinc by potassium ferrocysnide the author standardises the latter solution on varying quantities of zinc, since a slightly different factor is obtained according to the amount of zinc present. A " blank " experiment should also be made with the ferrocyanide solution, about 0.20 C.C.being generally consumed. All titrations are carried out on a, volume of about 150 C.C. of solution at a temperature of 85' C. Zinc in Ores.-After the removal of lead, silica, copper, and iron, the titration of the zinc may be carried out directly in the absence of manganese and nickel. If manganese be present, it may be got rid of (together with the iron if in small quantity only) by adding to the acid filtrate from the hydrogen sulphide separation, after evaporation, 5 grams of potassium or sodium bromide, rendering the liquid strongly ammoniacal, and stirring for one hour, or allowing to stand overnight. The precipitate should be washed with ammonia, and the manganese determined by dissolving the precipitate in sulphurous acid solution, adding nitric acid and expelling any nitrous fumes, and the estimation completed by the bismuthate process.If manganese be present in the ore in considerable quantity, or if nickel be present, the best plan is first to precipitate the zinc as sulphide. The precipitate is dissolved in hydrochloric acid, and hydrogen sulphide passed through the solution to ensure the removal of all the copper, Any occluded iron is removed from the filtrate, which is then neutralised, and 3 C.C. of hydrochloric acid added in excess, and titrated with ferrocyanide as usual. Analysis of Brasses. --After the removal of tin, copper, and lead, the evaporated filtrate is taken up in hydrochloric acid, the iron removed, and the zinc in the filtrate titrated with ferrocyanide. [In the case of manganese bronzes a similar method may be followed, but the manganese must be separated by the alkali-metal bromide process, vide supra.] Alternatively, after the removal of tin, copper, and lead, the filtrate is rendered ammoniacal, colourless ammonium sulphide added, and the liquid kept hot for an hour. The zinc sulphide is then redissolved in hydrochloric252 THE ANALYST. acid, any copper present removed by hydrogen sulphide, and, after precipitating the iron from the filtrate, the ferrocyanide titration is proceeded with. .Zinc in Alzhminium Alloys.-In the absence of iron the titration may be m d e directly, since aluminium does not interfere. Iron is, however, generally present in considerable quantities, in which case 1 gram of the sample is dissolved in nitric or hydrochloric acid, a little citric acid added, followed by ammonia and then ammonium sulphide to the boiling liquid. The precipitate is allowed to settle, the liquid filtered, the last traces of citric acid being carefully washed out with a wash- water containing a little ammonium sulphide. The precipitate, which contains the zinc and any copper and iron originally present, is treated as described under “Brasses.” Or the metal may be dissolved in hydrochloric acid, and the zinc precipitated from a slightly acid solution, as directed in the separation from nickel in ores. A. R. T.

ISSN:0003-2654    

DOI:10.1039/AN9083300246

出版商:RSC    

年代:1908

数据来源: RSC

摘要:

252 THE ANALYST. APPARATUS, ETC. Receiver for Fractional Distillation under Reduced Pressure. H. Vigreux. (BUZZ. SOC. Chinz., 1908 [4], 3, 479-481.)-The receiver for fractional distillation under \! maintains a, constant vacuum reduced pressure (see figure) is combined in one piece with the condenser, which consists of a, vertical cylinder cooled internally by a stream of water, which enters and leaves the apparatus at the places in- dicated by the arrows. The tap A connects the re- ceiver bulb with the condensing portion of the apparatus, the tap B serves to discharge the dig- tillate, and the tap C admits air for the same purpose. The tap D leads to the vacuum pump, the apparatus being arranged to work either with one pump attached to F-in which case E and G are joined together by a piece of rubber tubing-or with two pumps attached to F and G. In working with one pump, when it is desired to withdraw a fraction the taps A and D are closed, the vacuum is still main- tained in the distillation flask by way of the tube c0nnecting.G and E, and the second fraction collects in the condensing cylinder.The first fraction is withdrawn by opening 13 and C, and the second fraction may then be let down into the bulb. By attaching a flask to the tube at B, three fractions limy be collected without breaking the vacuum in the bulb. When comparatively large quantities of liquid have to be distilled without interruption, it is neces- sary to have two pumps; the pump attached to G in the distillation flask, whilst the pump attached to F serves to evacuate the bulb after the withdrawal of each fraction before connecting it with the cylinder.J. 3’. B.THE ANALYST. 253 Standard Light for Estimating Colour in Malt Extracts and Beer. J. W. Lovibond. (Jot~rn. Iizst. Brewing, 1908, 14, 2-5.)-1n using Lovibond's tintometer for estimating the colour values of worts and beers, in cases where a good north light is not obtainable, the author recommends the light of the standard candle adopted by the gas referees. The illuminating surface is a complex screen large enough to fill both apertures of the instrument with an even light. The screen is made up of one red absorbent of 0.5 unit value and two diapersers, each of 0.5 unit north light dispersive value. The intensity of the light at the recommended distance of 1 inch from the end of the optical instrument is 36 units; the dispersive side of the screen should be towards the light.Under these conditions the author found that a wide range of measurements, without exception, gave readings in accord with those of north daylight. In studying the influence of daylight at various distances from the window of a room-k, with lights of different intensities and qualities (CJ J. L. Baker and H. F. Hulton, Jozmt. Inst. Brewing, 1906, 12, 302)-the author found that, when using a screen of tissue paper fixed to the window, the results were constant at all distances up to 10 feet, with light-intensities ranging from 24 to 18 units. But when the light was obtained from the opal reflector attached to the box of the instrument, considerable divergences were observed as the instrument waa moved further back into the room, and were quite unreliable when the light-intensity fell below 14 cnits.J. F. B. Modified Spectroscopie Apparatus. Go P. Baxter. (Jounz. Amer. C h m , SOC., 1908, 30, 577-578.)-A form of container for the solution to be examined i s shown in Fig. 1. The light passes lengthwise through the tube, B, and is focussed upon the slit, S, by the solution in the part of the tube, A, which acts as a cylindrical lens. If the tube, B, is long, the length of the path of the outside and middle rays of the beam is essentially the same. so that the absorption is nearly the same in all parts of the beam. A convenient form of fulgurator is shown in Fig. 2. The two glass tubes, AA, are fused togsther in a nearly parallel position by means of a short piece of glass rod, B. One of the wires at the bottom of the tubes is bent in the form of a U, so that the end is directly below and parallel with the wire in the other tube. The end of the lower wire may be covered with a glass capillary, C, in the usual way. The tubes can be readily transferred from one solution to another, and are easily cleaned or rinsed. If a ---" I L u- figrre E g v r e 2 rod be used to join the tubes together, the tubes may be brought so near without danger of short-circuiting that the apparatus is narrow enough to be inserted in a wide test-tube. If the tubes are joined by means of a tube, there is some difficulty from this source. w. P. s.

ISSN:0003-2654    

DOI:10.1039/AN9083300252

出版商:RSC    

年代:1908

数据来源: RSC

摘要:

254 THE ANALYST. REPORT OF THE COMMITTEE OF THE NATIONAL PHYSICAL LABORATORY. THE members constituting this Committee were the Right Hon. G. Balfour (Chair- man) ; Sir Acdrew Noble, Bart., K.C.B., F.R.S. ; Sir J. Wolfe Barry, K.C.B., F.R. S. ; Mr. W. J. Crossley, M.P. ; and Mr. R. Chalmers, C.B. ; and a comprehensive abstract of their Report has already appeared in the April number of the ANALYST. Our readers will doubtless remember that the Committee appointed by the Treasury t o consider the desirability of establishing a National Physical Laboratory reported in 1898 that in their opinion ‘( a public institution should be founded for standard- ishg and verifying instruments, for testing materials, and for the determination of physical constants.” The Report was a tolerably long one, and dealt in some detail with the nature of the work with which it was thought that the new Laboratory might rightfully and usefully deal. I n order that there might be no misunderstand- ing as to the meaning which the Committee attached to the words “testing of materials,” the point was discussed at some length in the body of the Report.In paragraph 9 it is stated that “There is much evidence that further facilities are needed by the public for the standardising and verifying of instruments both for scientific and commercial use ; and also that it would be of great benefit to trade if means were provided for the public testing of the quality of certain classes of materials.” The paragraph then gives espression to the following important opinion : “ I t would neither be necessary nor desirable to compete with or interfere with the testing of materials of various kinds as now carried out in private or other labora- tories, but there are many special and important tests and investigations into the Btrength and behaviour of materials which might be conducted with great advantage st a Laboratory such as is contemplated in the reference.” After giving instances of several kinds of investigations which might most usefully be conducted at a National Physical Laboratory, the Report continues : We could give other instances of the same nature, and have merely referred to the above subjects as examples of such matters as would, in our opinion, be proper for investigation at a public institution, as distinguished froin the ordinary testing of materials used in commerce or in construction and machinery, which can be, and is, now efficiently conducted at private establishments.” From this it is abundantly clear that the Treasury Committee foresaw the possibility of competition springing up between the new National Laboratory and private institutions, and desired to place on record a clear statement of their opinion as to the proper functions of the former for the guidance of the future Director and.Executive Committee. It may perhaps be pointed out in passing, that of the five members of the recent Treasury Committee no fewer than three (Sir Andrew Noble, Sir J. Wolfe Barry, and Mr. R. Chalmers) were members of the original Committee, and sub- scribed to the above views as to the restriction of competition.The Laboratory was opened in 1902, and in 1903 a case came t o light which showed that the staff of the Laboratory were not averse to undertaking ordinary testing work in corn-THE ANALYST. 255 petition with private chemical practitioners. Into the details of the case, which was concerned with the chemical examination of a sample of cod-liver oil taken under the Sale of Food and Drugs Acts, it is not necessary to go. I t is sufficient to say that the certificate given by the Nationd Physical Laboratory brought that institu- tion into collision with Dr. Thorpe, and was instrumental in raising the question as to whether the Laboratory authorities had not exceeded their proper functions in undertaking such work. Other evidence of a similar character was forthcoming, and it was felt that, unless some steps were promptly taken, the existenceof the National Physical Laboratory would prove a serious menace to the interests of independent professional men.Protests were therefore addressed to the Chairman of the Executive Committee by the Society of Public Analysts, the Institute of Chemistry, and the Society of Chemical Industry. A good deal of correspondence ensued, and ultimately the matter was referred to His Majesty’s Treasury, who in 1906 appointed the Com- mittee referred to at the commencement of this article. This Committee was requested to inquire generally into the work now performed at the National Physical Laboratory, with special reference to- 1. The character of the mechanical, physical, and chemical tests undertaken 2.The possibility of these interfering unduly with the business of other 3. The desirability of publishing the results of such testing work, and to (1) Whether, having regard to the industrial interests of the country generally and to those of private agencies, any change is desirable in the scope of the work of the Laboratory; and (2) On what lines any further developments of its business should proceed. The above brief outline of the circumstances attending the foundation of the National Physical Laboratory, and of the events which led up to the appointment of the recent Treasury Committee, has been given in order that those of our readers who are not intimately acquainted with the details of the matter may be in a better position to appreciate t,he true character of the Committee’s Report.A considerable amount of evidence was given by witnesses representing the interests of professional analysts and others. From the point of view of analysts and testing engineers, the point of chief importance was whether the National Physical Laboratory had shown a tendency to ignore the principle clearly embodied in paragraph 9 of the Report of the original Committee, in reference to the undesirability of interfering in the testing of materials such as is now being carried out in private or other laboratories. This matter is, of course, dealt with somewhat fully in the Report under review, but in a manner which can scarcely be considered satisfactory to the professional men, who rightly considered that their interests had been threatened, The Committee arrive at the conclusion that the language in the original Report was so ambiguous as to render profitless any inquiry a~ to its there.agencies. report-256 THE ANALYST, correct interpretation, and they therefore consider it better to attempt to re-define the policy which they think should guide the National Physical Laboratory in the future. I t is pointed out, in extenuation, that the number of cases in which routine or commercial tests of materials have been undertaken has been in the past exceed- ingly small, but analysts can scarcely be blamed if they have considered it better to attack a practice at its birth than to wait until it had assumed serious proportions. That their fears were not without foundation is shown by the statement of the Committee that, if the Laboratory has hitherto done little in the way of ordinary testing of materials, this is due not mainly to a recognition of the restrictions referred to in the Report of the original Committee, but rather to want of adequate equipment and to the situation of the Laboratory itself.I n addition to this, there is Lord Rayleigh’s significant admission that the Treasury had urged upon the Laboratory authorities the necessity of increasing their income as far as possible by means of fees, and that this had induced them to undertake work which they might otherwise have refused, and which presumably did not properly come within the sphere of their activities. The Committee, while expressing the opinion that the fears of professional analysts and other practitioners are exaggerated, is neverthe- less compelled to admit that these fears had some reasonable foundation, and, while suggesting that the testing of materials should continue to be carried out by the Laboratory under proper restrictions, it yet states that a more precise formulation of the testing work proper to be undertaken is desirable, in order that public and private interests may as far as possible be harmonised.The Committee in their Report differentiate ‘‘ commercial testing ” into two branches-viz., ‘( contractual testing ” and ‘( investigatory testing.” The first of these ernbraces all cases of ordinary testing of materials for the purpose of ascertaining whether their quality and behaviour are in accordance with the contracts.The second branch comprises systematic investigation of various substances for commercial pur- poses where no question of contract arises-for example, the examination of copper for conductivity, of insulating materials such as gutta-percha, balata, or india-rubber, the systematic experimental work necessary to ascertain the value of various specimens of concrete, stone, or mortar required for harbour-building, and other examinations of this character. So far as ‘‘ investigatory testing ” is concerned, the Committee is of opinion that the Laboratory should have an absolutely free hand, but it recommends that, as a general rule, ‘‘ contractual testing” should not be undertaken. Not only is this recommendation-qualified by the words ‘‘ as a general rule,” but it is subject to certain exceptions, one of these being that, in the case of “any electrical, thermal, optical, and other physical tests, which cannot be carried out adequately, if at all, in any existing private establishment,” the Laboratory should not be debarred from undertaking the work merely on the ground that the tests are intended to ascertain whether certain materials comply with the requirements of a contract. There is, however, no mention in the Report of the person who is to decide the important point as to whether the special work referred to can or cannot be adequately carried out in a private establishment.This is only one example ofTHE ANALYST. 257 a want of definiteness in the Committee’s Report which may possibly conduce to unfortunate misunderstandings in the future between the Executive of the National Physical Laboratory on the one hand, and analysts and testing engineers on the other.I t will be obvious that no sharp line can be drawn between ‘‘ contractual ” and “investigatory” testing; and, to use the words of the Report, “ i t is not a question of the kind of testing applied to any particular substance or material, but of the nature and objects of the investigation to be undertaken, which differentiate ‘ contractual ’ and ‘ investigatory ’ testing.” I t is clear therefore that, as the National Physical Laboratory is to have a free hand in respect of the latter, divergences of opinion between the Executive Committee and analysts in private practice are not unlikely to occur in the future.I t is noteworthy that two members of the Committee-Sir Andrew Noble and Sir J. Wolfe Barry-go even farther than their colleagues, and, in a note appended to the Report, suggest that the debarring clause relating to ‘‘ contractual ” testing shall only hold for a period of ten years, leaving the Laboratory absolutely free after that time to undertake any kind of work that may present itself. Special reference is made in the Report to the question of fees, and the Committee express the opinion that, as an additional safeguard against injurious competition with private enterprise, the fees charged by the Laboratory should be at least as high as those ordinarily charged by independent practitioners. While it is satisfactory to note that the National Physical Laboratory have no desire to undercut in the matter of fees, the presence of this paragraph in the Report clearly indicates the possibility of future competition; and it must not be lost sight of that, even if the fees charged by the National Physical Laboratory were appreciably higher than those normally current, many manufacturers and others would prefer a report emanating from a public institution to one given by a private individual, and, as one of the professional witnesses put it, would be willing to pay more for the cachet. To sum up, the Report is one that can only be regarded with feelings of dissatisfaction and disappointment by the analytical profession, since, as has been indicated above, it suggests no adequate means for the safeguarding of private interests, the interpretation to be placed upon the somewhat vague expressions employed being apparently left to the Executive Committee itself.Quite apart from the impropriety of State-aided institutions entering into direct competition with individuals, it seem a pity that any of the energies of the Laboratory sliould I)e expended in the direction of routine testing (much of which, it should be said, can be far better done in existing private laboratories) when so nisny problems of national importance await solution-problems with which a, National Laboratory alone can deal in an efficient and satisfactory manner. A. C. C. P. A. E. R.

ISSN:0003-2654    

DOI:10.1039/AN9083300254

出版商:RSC    

年代:1908

数据来源: RSC