摘要:

JUNE 1909. Vol. XXXIV. No. 399. THE ANALYSIS OF AIR. BY W. J. ATKINSON BUTTERPIELD M A . F.I.C. (Read at the Meeting iVay 5 1909.) THE methods for the analysis of air which are about to be described have for the most part been extant for some years past but information relating to them is scattered in various Blue Books technical and scientific periodicals and textbooks which are not ordinarily found in the library of the analytical chemist. Certain modifications having for their object greater ease and certainty of inanipulation of the apparatus used and the attainment of a higher degree of accuracy in the analysis, have moreover been introduced since the original descriptions of the methods appeared. The results of the extended experience which has now been gained of the working of most of the methods can also be put on record with advantage 258 THE ANALYST.The methods about to be described deal only with the estimation of moisture, carbon dioxide methane (fire-damp) or other combustible gas oxygen and by difference nitrogen (including argon) in air. The estimation of any one of these constituents to a high degree of accuracy is now required of the analyst for the purpose of controlling the efficiency of the ventilation of factories schoolrooms, public buildings tunnels mines and submarines etc. as well as the effect on the composition of the air of rooms of different modes of lighting heating or artificially varying the degree of humidity The estimation of other constituents such as argon, of minor importance from the technical standpoint will not be dealt with in this paper.The methods have been speaking broadly devised or perfected either in-dependently or with the aid of collaborators by J. s. Haldane M.D. F.R.S., whose attention was first turned to the analysis of air in the course of numerous physiological investigations for which methods of analysis combining extreme sensitiveness with rapidity of execution were absolutely essential. The general principles and procedure involved in these methods have proved of very wide applicability and of great utility in air and gas analysis. The constituents of air under consideration may with the exception of moisture, all be estimated in the laboratory on a comparatively small sample of air which may be taken by anyone capable of following a few simple directions.(The estimation of moisture necessarily involves the use of apparatus on the spot and in so far as the chemical or direct methods of estimation are concerned involves the attendance there of someone more or less skilled in the manipulation of analytical apparatus.) The method of sampling is as follows : A narrow-mouthed bottle of about 2 ounces capacity with well-fitting glass stopper is washed and dried. The stopper is greased with vaseline to insure an air-tight tit. A sample of air is taken thus The bottle is held in one hand and a piece of rubber tubing about &-inch bore and 2 feet long is taken in the other and one end put in the mouth. The bottle is held at arm's length the stopper is removed and held by the forefinger and thumb of the other hand while the free end of the rubber tubing is passed through the mouth of the bottle to the bottom.A full inspiration of air is taken by the mouth through the rubber tube thus drawing the air of the room into the bottle and displacing that already there. As a man on the average draws about 500 c.c. or 18 ounces of air into the lungs at one normal inspiration it will be seen that the air contained in the sample bottle is displaced nine times-or many more with a deep inspiration-by this operation. When the inspiration is nearly finished the rubber tube is removed from the bottle and the stopper is inserted and turned round in the neck of the bottle to distribute the vaseline evenly in the joint. A stout rubber band is passed over the head of the stopper and the bottom of the bottle and is secured in place by affixing a gummed label round the bottle.The stopper should have a square head to reduce the risk of the band slipping off it. If the bottle containing the sample has to be transmitted to a distant laboratory, it may be safely sent by post in a wooden box lined with corrugated paper. Boxes divided into lined compartments for six sample bottles have been freely used fo THE ANALYST. 259 some years by the Factory Department of the Home Ofice and also by other Government Departments for the transmission of air samples by post. The risk of breakage and consequent loss of the sample is small of the last 2,000 samples which have come into the author’s hands after transmission by post (letter post as a rule) from various places in Great Britain and Ireland four bottles only have been broken and four cracked so slightly that it was doubtful if there had been any leakage of the contents.One of the travelling boxes with the lid partially opened, displaying two bottles in position is shown in Fig. 1 (incidentally in use as a stand for the mercury trough referred to later). In front of the box is one of the sample bottles with rubber band and label in position after a sample of air has been taken in it, In regard to the method of sampling it might be contended that unskilled persons might unintentionally pass expired air directly into the bottle instead of only drawing the air for inspiration through it. Such an accident would however be readily detected on analysis of the sample as expired air contains about 4 per cent.of carbon dioxide or say 20 to 100 times as much as would ordinarily be found in the air of occupied rooms. Out of some 9,000 samples taken by a large number of different people of both sexes which have come into the author’s hands there have only been two cases in which the sampling appeared to be faulty-viz. one batch of six samples with which results of about 2& per cent. of carbon dioxide indicated clearly that the samples were substantially expired air and a single sample in which also the proportion of carbon dioxide was otherwise inexplicably high. The trustworthiness of the method has been proved time after time by concordant results having been obtained from samples taken in duplicate at the shme time and spot.The samples undergo no change through lapse of time provided the containing bottles are dry and clean. If the bottles are wet but clean carbon dioxide is liable to be absorbed from the sample ; if they are wet and contain dust carbon dioxide is liable to be formed by bacterial action. I n the ordinary course of the author’s work the bottles after use are thoroughly washed and then dried at a high temperature on a hot plate and as soon as they are cool the greased stoppers are inserted. Thus the bottles supplied for sampling are not only dry and clean but to all intents and purposes sterilised also. The Estimation of Moisture and Carbon Dioxide Gravimetrica1ly.-Provided momentary changes in the composition of the air at a given spot are not in question, the gravimetric method carried out in the manner about to be described is the most accurate and satisfactory of all chemical or physical methods of determining the proportion of moisture and carbon dioxide in air.It however requires the attend-ance on the spot of a trained analytical chemist and hence it is used only to check the accuracy of other and more generally convenient methods or in special cases where extreme precision is desired. On occasion also it is for another reason, practically indispensable in that the air of a hall theatre church or debating chamber in which the presence and operations of an analyst are undesirable at the time can by its employment be sampled and the carbon dioxide determined unknown to the occupants Composition gaspipe of small diameter is previously run from a suitable point or points in the hall to the analytical apparatus placed i 260 THE ANALYST.an adjacent room and thereby at any desired time during the occupation of the hall air may be aspirated through the pipe by the chemist in charge of the apparatus. This plan was followed by the author in 1902 when the air was drawn from five different points of the debating chamber of the House of Commons during sittings of the House (vide Journal of Hygiene 1903 3 486; and the Blue Book “Report, House of Commons Ventilation,” 227 of 1903). In this case the historic rule against the admission of strangers to the floor of the House during its sittings practically precluded the use of any other method of sampling and analysis but it is obvious that in many other cases it may be considered that the operations of an analyst in a hall etc.would disturb the occupants. The gravimetric method of determining moisture in air was recognised by Regnault in 1853 as superior in accuracy to any other but he found it too troublesome and tedious for frequent use (Anmles de China. et de Phys. 1845 15 152 and 1883 37 257). Shaw in 1888 made an investigation by which he found that a U-tube filled with pumice and sulphuric acid only absorbed moisture completely from air when the rate of aspiration did not exceed 8 to 10 litres per hour while the tube varied considerably in weight from hour to hour more or less unaccountably. As a determination required about one hour’s aspiration there was considerable uncertainty as to the accuracy of the results obtained (Phil.Tyans. 1888 A p. 73). Haldane and Pembrey in 1890 described improvements which they had made in the method (Phil. Mag. 1890 306). They reduced the accidental variations in the weight of the absorption tubes and at the same time increased the efficiency of the latter (thereby rendering a more rapid rate of aspiration possible) by altering their form and weighing them against a counterpoise consisting of a tube similar in shape size, and contents. The absorption tubes originally used by them were 4 inches deep, and 1 inch in diameter made of thin glass fitted with a doubly-bored cork through which an inlet pipe extended nearly to the bottom of the tube and an outlet pipe to just below the cork. The tubes were made up in pairs the outlet pipe of one and the inlet pipe of the other being formed of one piece of glass by bending at the top.The insertion of the long iulet pipe in the tube after it had been charged with the absorptive material was rather troublesome and the doubly-perforated cork increased the risk of leakage. To overcome these defects absorption tubes were later blown in pairs with the inlet and the outlet tubes blown into the walls about 2- inch below the top. Thus after charging only well-fitting shallow plain corks had to be inserted. The corks about 8 inch deep were soaked in melted paraffin wax and pressed into the cleaned and warmed mouths of the tubes until they were a little below the tops. A layer of paraffin was was then spread over the cork to the level of the top of the tube.Before each time of use each tube was tested for soundness by connecting its inlet to one limb of a U-shaped water-gauge slightly exhausting through and then closing its outlet and observing whether the water in the gauge remained at the same level for about half an hour. When not in use the tubes were closed by stoppers of about 2 inch of rubber tubing closed at one end by a short piece of glass rod. The counterpoise served of course for any number of absorption tubes in use at the same time. The stoppers were removed simultaneously from all the tubes and the counterpoise before weighing and replaced simultaneously whe THE ANALYST. 2 61 all the tubes had been weighed. This form of double absorption tube .has been largely used by the author and has given very satisfactory results.I t was obvious, however that ground-glass stoppers would be superior to the corks but it was not forthwith apparent how they could be fitted without interfering with the principle involved in the design of the tubes. Ultimately however a stoppered form of this type of absorption tube was evolved in B. Blount’s laboratory (about 1904) and this, with a slightly wider stopper is now being used by the author. (An illustration to scale of this tube with however the inconveniently narrow stopper has been given in vol. i. of the third and fourth editions of the author’s “Handbook on Gas Manufacture. ’’1 The reasons for the adoption of the Haldane and Pembrey type of absorption tube and for weighing it against a similar counterpoise may be briefly enunciated.The amount of moisture on the outer surface of such tubes varies from time to time; it is difficult absolutely to exclude penetration of moisture to the inside and variations of temperature and barometric pressure may affect the weighings. These variations which in the aggregate may cause a tube to vary more than 2 mgm. in weight are rendered of no effect by the practice of weighing the tube against a similar tube which has been throughout exposed to the same conditions. The form of tube is chosen with a view to securing weight for weight great absorptive efficiency. Owing to the great width of the tube the air passes upward through the absorptive material at a comparatively low rate of flow thus affording time for absorption.The sulphuric acid on the pumice is gradually diluted by the moisture absorbed from the air and ultimately dilute acid collects in the bottom of the first of the pair of tubes and continues to do preliminary absorptive work on the air without impairing the strength of the overlying pumice in the same tube or of the pumice in the second tube. In the ordinary U-tube on the other hand the diluted acid would spread throughout the first limb and the bend and only the pumice in the second limb would retain its full strength for any length of time. One double absorption tube charged with sulphuric acid pumice weighs 70 to 80 grams and will continue to absorb moisture completely from air even after 12 grams of moisture have already been absorbed-that is to say after 2,000 litres or more of air have been aspirated through it.The rate of aspiration may be as high as 7 litres per minute and as 5 to 10 litres is a convenient quantity for one determination it will be seen that the moisture in air may if required be accurately determined gravi-metrically over as short a period as two minutes. The method thus becomes invaluable as a check on the readings of wet and dry bulb hygrometers or other psychrometers with which instantaneous readings are made. The author proposes to deal in a subsequent communication with the comparative results afforded by certain of these instruments as well as by a volumetric absorption apparatus somewhat re-sembling one described by S. Rideal last year (Journ. Royal Sanitary Inst. 1908,39,87). The advantages of the Haldane-Pembrey type of double absorption tube are even more marked when it is applied to the absorption of carbon dioxide.The first of the paired tubes is then filled with uniformly granulated soda-lime (granules 1 to 2 mm. in diameter) free from dust and the second with pumice saturated with strong sulphuric acid. The soda-lime absorbs carbon dioxide from air aspirate 262 THE ANALYST. through the tube while the moisture thereby displaced from the soda-lime is retaimd by the sulphuric acid The net increase in weight of the double tube therefore, gives forthwith the amount of carbon dioxide absorbed. It is of course necessary that the air entering the soda-lime should be free from moisture and consequently a double absorption tube containing sulphuric acid pumice is placed before it and the moisture in the air may thereby incidentally be determined simultaneously with the carbon dioxide.As the absorption of carbon dioxide by soda-lime is less vigorous than that of moisture by sulphuric acid it becomes necessary however to aspirate at a somewhat lower rate and it is desirable to have a double guard tube charged with soda-lime and sulphuric acid pumice to detect any failure on the part of the first soda-lime tube to absorb the whole of the carbon dioxide. The train of apparatus is therefore set up in the following order starting at the air intake (1) A double absorption tube charged throughout with sulphuric acid pumice for the absorption (and determination if desired) of the moisture. (2) A double absorption tube the first tube of which is charged with soda-lime and the second tube with sulphuric acid pumice.This tube ordinarily absorbs all the carbon dioxide from the air. (3) A double absorption tube similar to the last acting merely as a guard tube. And (4) an aspirator of 10 to 50 litres capacity, The rate of aspiration should not on the average greatly exceed 1 litre per minute. At 2 litres per minute a trace of carbon dioxide will usuallyreach the guard tube. For outside air as much as 20 litres should if possible be aspirated as the increase in weight of the absorption tube would with that quantity of air be only about 12 mgm. The absorption tubes are of course weighed against a similar tube as a counterpoise. It will thus be seen that a determination ordinarily covers a, period of about twenty minutes but for vitiated air ten minutes will suffice.On the other hand the time may be extended so that the determination gives the average amount of carbon dioxide in the air over a period of say one hour. The prolongation of the test is limited practically only by the capacity of the aspirator which may of course be of a double vessel reversible type. The author has used carboys suitably fitted with a cork and siphon-tube as aspirators up to a capacity of about 55 litres. The capacity of the aspirator from a mark on the neck to which it is filled to a mark near the bottom should be accurately determined; and if it is desired to stop a test before the latter mark is reached it is easy afterwards to measure the quantity of water remaining down to that mark.It is often convenient to adjust the lower mark to the position for a given round number of litres and so reduce trouble in calcula-tions. An approximate scale of litres on the side of the aspirator is an aid in adjusting the rate of aspiration. In all cases a thermometer must be fixed in the aspirator and read when the aspirator is stopped and the height of the barometric column at the time of the test must be noted so that the volume of air collected in the aspirator may be corrected for deviation from its volume under normal temperature and pressure. Unless the room in which the aspirator is used varies little in temperature and the water is at the temperature of the room it is advisable to jacket the aspirator-with felt for instance.It must also be remembered that the volume measured by the aspirator is sir saturated with moisture but deprived of carbon dioxide. The amount of the latter absorbed by the soda-lime must be added to th THE ANALYST. 263 aspirated volume of air in calculating the exact proportion of carbon dioxide in the air examined. The moisture correction must be similarly made if it is desired to refer the results to dry air or to air of the degree of humidity of that examined. Simultaneous determinations by the gravimetric method as here described will always give results agreeing as to moisture well within 1 per cent. if only 6 litres of air are taken and as to carbon dioxide within 2 per cent. if only 20 litres of air are taken. The mean error is considerably lower-viz.about 0.1 per cent.-and as the unavoidable differences in weighings are chiefly responsible for any want of con-cordance in analyses made in duplicate it is obvious that by increasing the volume of air aspirated the degree of accuracy of the results may be enhanced to almost any desired limit. That is to say if the air of a room contained exactly 5 volumes of carbon dioxide per 10,000 volumes of air determinations could be made by this method of which the extreme results would be 5.1 and 4.9 volumes. If the air contained exactly 20 volumes of carbon dioxide per 10,000 more than 20.1 or less than 19.9 volumes should not be found by this method. Ordinarily with reasonable care in working the deviation would be considerably less as the mean error of a carefully made determination is only about +O-01 volume of either moisture or carbon dioxide per 10,000 volumes of air.The Estimation of Carbon Dioxide Vo1z~rnetrically.-The author thinks it necessary on this occasion only to refer to the volumetric method introduced by J. S. Haldane about 1900 (vide Journ. of Hygiene 1901 1 109 ; and the Blue Book, First Report of the Committee on the Ventilation of Factories and Workshops, Cd. 1302 of 1902). It is tolerably well known so that only a brief description need be given and certain modifications of the apparatus used which the author has found convenient referred to. I t depends on the absorption of the carbon dioxide in a measured volume of gas by solution of caustic potash. The apparatus used com-prises a burette of about 20 C.C.capacity of which the stem represents a little over 0.2 c.c. and the bulb the remainder. The stem is graduated in 100 divisions, each representing of the capacity of the burette from the bottom (zero mark) division on the stem to the tap above the bulb. One division is about 0.04 inch or 1 mm. in length and it is possible therefore to read the height of the column of mercury in the stem to one-fifth of a division or to 0.2 part per 10,000 with fair precision. The changes of volume of the portion of air enclosed in the burette, resulting from variations of temperature and barometric pressure would frequently be greater than the reduction of volume due to the absorption of the carbon dioxide, and would thus ordinarily prevent this reduction being directly observed.A change of temperature of one-tenth of a degree Fahrenheit represents approximately the total change of volumo due to the absorption of the proportion of carbon dioxide ordinarily present in outside air. It would thus be practically impossible to make readings of temperature with sufficient accuracy for correcting the volume of air in the burette to normal. Fortunately this trouble may be avoided and a higher degree of accuracy attained by the employment of a control tube of the same size and shape as the burette placed alongside the latter in a water-jacket. The stem of the control tube is filled with water so that the air within the tube is saturated with moisture and a trace of water in the burette serves similarly to saturate the sample of air enclosed therei 264 THE ANALYST.Referring to the illustration of a modified form of this apparatus in Fig. 1, it will be seen that the burette A and control tube B communicate by means of independent connections of about the same capacity with separate limbs of what is in effect a lJ-tube or differential pressure gauge C charged with solution of caustic potash. The limb in communication with the burette is enlarged below the normal surface-level of the solution to a bulb D of about 20 C.C. capacity and a tubulure at the base of the U-tube communicates by flexible tubing E with a glass bulb F, which may be raised or lowered over a limited range by sliding its stem in the spring-FIG. 1.-APPARATUS FOR THE DETERMINATION OF CARBON DIOXIDE IN AIR. clip which supports it.The lower end of the stem of the burette communicates by means of flexible tubing with a reservoir G containing mercury. This reservoir i s carried by a rack H which is raised and lowered by turning a milled head J attached to the spindle of the pinion on which the rack travels. By means of three-way taps, K and L on the connections both the burette and the control tube may be put out of communication with the U-tube and into communication with the outer air. The pressure in both may thus be equalised with that of the outer air. After this equalisation if they are shut off from the outer air and put in communication with the potash solution in the U-tube the solution will stand at approximately the sam THE ANALYST. 265 level in both limbs of the tube. If now the water in the water-jacket is agitated by blowing through the tube M from time to time to preserve uniformity of temperature throughout it and consequently uniformity of temperature of the burette and control tube the level of the potash solution in the two limbs of the U-tube will be affected equally by changes of volume of the air contained in the equal-sized burette and control tube arising from variations of temperature or atmospheric pressure.Hence so long as the potash solution in the two limbs of the U-tube is kept at the same level any observed alteration of volume of the air contained in the burette is due to an alteration of mass and not to mere expansion or contraction of the original mass of air. The means is thus obtained of measuring accurately the amount of any constituent of the air which is removed therefrom by the action of any absorbent.The carbon dioxide in air is thus estimated by passing the measured volume of air to and fro between the burette A and the caustic potash solution in the bulb D in the one limb of the U-tube. The mercury reservoir G is raised and lowered to effect this transference. The volume of air is measured again with the levels of the potash solution balanced in the two limbs and the reduction in volume since the first measurement shows the volume of carbon dioxide absorbed from the known volume of air. As the volume of air taken for an estimation in the apparatus in question is always about 10,000 times that contained between two adjacent graduations on the stem of the burette readings of the level of the mercury in the latter made in the conditions indicated before and after passing the contained air to and from the potash solution twice or thrice show directly by difference the volumes of carbon dioxide per 10,000 volumes of the air represented by the sample.The expression ‘‘ U-tube ” has been used in the foregoing explanation of the function of the control tube because its purpose is that of a U-gauge by which any difference between the pressures prevailing in the two limbs may be at once detected. As the limbs of the gauge are in contact with confined volumes of air an alteration of one volume independently of an alteration of the other may be readily observed and measured. As a fact the actual form given, for other reasons to the parts here referred to as a U-tube does not at once suggest that they form a U-pattern differential pressure gauge.The use of a control tube in gas analysis was described by Williamson and Russell in 1868. They however used with it a mercury gauge which of course was far less sensitive than the gauge described above in which the liquid is a 10 per cent. aqueous solution of caustic potash.“ Pettersson subsequently used a drop of oil in a horizontal tube as a gauge to indicate difference of pressure between a burette and a control tube. The introduction of the simple gauge containing solution of caustic potash which serves both as a gauge liquor and as an absorbent for carbon dioxide, is due entirely to J. S. Haldane. It is applied with advantage as will be seen later, in apparatus for the estimation of other constituents in air and is naturally also applicable to many estimations of constituents of industrial gases.The use of the control tube and differential gauge containing an aqueous liquid has led to a degree of precision combined with rapidity of work in air analysis that otherwise is quite unattainable. * F. R. Japp in 1891 used a control or “ regulator ” tube with a mercury differential gauge in his “gravivolumeter” (uide S. Rideal [inf~a] and Jam. Chem. Soc. 1891 69 894) 266 THE ANALYST. The Haldane apparatus for the volumetric estimation of carbon dioxide in air is in its original portable form perfectly convenient for estimations carried out iiz situ. For use in the laboratory when the sample of air for analysis is drawn from a bottle inverted over mercury in a trough the author has tried modifications with a view to rendering the burette more readily accessible for cleaning and the three-way tap at the top of the burette less liable to obstruction by a globule or plug of mercury (or even of water).Such a globule sometimes interferes with free communication between the potash solution and the burette and so with the proper action of the differential pressure gauge. The author now prefers a tap N (Fig. l) with two parallel ways by one of which the sample is drawn into the burette from the bottle 0 inverted in the mercury trough P and by the other of which the burette is put in communication with the potash solution. Mercury need then never enter the latter way through the plug of the tap so that there is no risk of obstruction of this way.A three-way tap K is placed in the connection between this tap and the potash solution so that either the latter or the burette may be readily put into communica-tion with the outer air. The apparatus may still be in a portable cabinet as shown in the figure but as at times it is more convenient to work with the light in front of, instead of behind the observer a flap R has been arranged in the back of the cabinet, through the opening of which light may reach the stem of the burette and the levelling marks S S on the differential gauge. The flexible rubber connection between the differential gauge and the potash reservoir F may when new and if it contains much sulphur form a sulphur compound with the solution of potash which then absorbs some oxygen as well as carbon dioxide.This action of the potash on the rubber soon ceases and gives no trouble after the potash solution has been twice renewed after standing in the apparatus for about a week each time. Consecutive estimations of carbon dioxide by the Haldane volumetric apparatus should give results always agreeing within 1 volume in 10,000. The normal deviation from the mean is however only about * 092 volume which is about the limit of accuracy of readings with the naked eye of the graduations of the stem of the burette ; that is to say a sample of air containing exactly 20 volumes of carbon dioxide per 10,000 would by this apparatus with careful manipulation not appear to contain more than 20.2 or less than 19.8 volumes.The 2-ounce bottles used for samples contain sufficient air for three estimations and it is the author’s practice always to make two estimations and if the results differ appreciably to make a third. When large numbers of samples of air are dealt with it is convenient to have a mercury trough of as limited capacity as is consistent with comfortable manipulations. The author uses wooden troughs (P Fig. 1 and A Fig. 3) with the reservoir narrowing towards the base and provided with a raised flange to hinder overflow of the mercury when the fingers are plunged in for removing the stopper of the bottle. A cover B (Fig. 3) serves to keep out dust when the trough is not in use and also to prevent the mercury being splashed over by slight jars to which its stand C (Fig.3) may accidentally be subjected. The light wooden arm T (Fig. l) lightly clamped by the screw U serves to hold the bottle after inversion and removal of the stopper steady in the trough. The Estimation of Methane (Fire-Damp) and Oxygen VolumetricaIly.-Th THE ANALYST. 267 estimation of methane (fire-damp) in the air of mines or of small proportions of a combustible gas in air generally is best carried out by the combustion of the methane or other combustible gas by means of the oxygen contained in the sample of air. The combustion is effected by passing the air containing the combustible gas to and fro over an electrically-heated spiral of fine platinum wire. This method of effecting the complete combustion of small quantities of methane was first proposed by Coquillion (Conzptes Rend.1877 84 458). I t avoids any need for the addition of hydrogen detonating gas or neat oxygen to the air under analysis which addition is necessary when explosion by a spark is relied upon for the combustion. By its use complete combustion may be absolutely insured. If the proportion of methane exceeds about 8 or 9 per cent. [the precise proportion depending on the amount of black damp (carbon dioxide plus nitrogen) also present] an addition of a measured volume of pure air only will be necessary to effect the complete combustion of the methane. No neat oxygen is required even with such an abnormal sample of mine air. The platinum spiral is fixed in a suitablyshaped pipette D (Figs. 2 and 3), in a manner admitting of its being readily replaced in case it is fused by too strong a current.I n ths apparatus used by the author it requires from 2 to 4 volts to raise it to incandescence and this is readily supplied from an accumulator E (Fig. 3), through a variable resistance F by means of which the wire may be gradually brought to the desired degree of incandescence. The contraction due to the com-bustion of the methane is measured and then the carbon dioxide produced is absorbed in the caustic potash solution in the pipette G and its volume ascertained by difference. If the volume of carbon dioxide is other than half the contraction, the combustible gas is not wholly methane. If methane and only one other com-bustible gas such as carbon monoxide are present the amounts of methane and carbon monoxide may be calculated from the ratio of the contraction to the carbon dioxide resulting from the combustion.In samples of air from coal-mines however, the combustible gas present is almost always pure methane and the carbon dioxide produced tallies accordingly with the contraction on combustion over the incandescent platinum spiral. I t is necesssary of course that the carbon dioxide in the sample of air should have been absorbed by the caustic potash solution in the pipette G prior to the combustion of the methane. After combustion of the methane the residual oxygen in the sample is absorbed by means of the alkaline solution of pyrogallol contained in the pipette H. Oxygen equivalent to double the volume of methane found must also have been present and consumed in the combustion of the methane.This must be added to the volume of oxygen absorbed by the pyrogallol solution in order to obtain the total volume of oxygen in the sample. As a check on the working a second portion of the sample may be afterwards taken and after absorp-tion of the carbon dioxide by caustic potash solution the total oxygen may be at once absorbed by the pyrogallol solution. The proportion of oxygen thus found should tally with that already computed by adding the volume of oxygen used for the com-bustion of the methane to the volume of residual oxygen found after that combustion. A check on the whole analytical work is thus readily obtained. The pyrogallol solution for the absorption of oxygen is prepared by adding 100 C.C. of a completely saturated solution of caustic potash to 10 grams o 268 THE ANALYST.pyrogallic acid contained in a stoppered bottle. After shaking and allowing a little time for the pyrogallic acid to dissolve a sufficient quantity of the solution to fill the absorption pipette H is transferred to the latter by means of an ordinary measuring pipette. The outer bulbs J of the double ab-sorption pipette are then charged with strong solution of caustic potash to prevent the oxygen and moisture of the atmosphere gaining access to the pyrogallol solution. An absorp-tion pipette thus charged should absorb oxygen rapidly and certainly for 150 to 200 analyses of air. The absorption is rapid and complete, and no trace of carbon monoxide is formed. Proof of the latter statement is easily obtained by passing the residual gas together with a fresh proportion of air over the heated platinum spiral.No contraction or formation of carbon dioxide will be detected. If however the solu-tion of pyrogallol has been prepared with a weak solution of caustic potash the absorption of oxygen is attended by the formation of carbon monoxide. The burette used for the estimation of methane and oxygen has a stem of rather more than three-tenths of the total capacity. The stern is graduated in divisions each & (Fig. 3) or .&(Fig. 2) of the total capacity and it is possible to read to one-tenth of a division with-out the use of a telescope. Thus estimations of methane and oxygen may be made with certainty within 0.01 volume per 100 volumes of air.Careful calibration of the burette used i s essential in all cases. A determination of the oxygen in pure country air will disclose any error of moment in the burettes described and if the result differs from 20.93 per cent. by more than k 0.01 other analytical results should be corrected accordingly. But if careful calibra-FIG. 2.-LABORATOlLY Arp,lr,aTus FOP. THE tion of the burette with mercury shows that DETERMISATIOS OF Cancos DIOXIDE the stem is ‘irregularly divided the burette should be discarded as corrections in such a AND OXYGEN IN THE AIR. case are very troublesome and uncertain. This apparatus is shown in two sizes one being in a cabinet (Fig. 3) and readily portable the other (Fig. 2) having a larger and longer burette being METHAXE (OIL OTHER COBIliUbl’IIILE GAS THE ANALYST.269 suitable only for laboratory use. The larger apparatus has a somewhat lower limit of error than the smaller but the latter can be used with careful manipulation to the degree of accuracy already stated. With the portable apparatus the capacity of the burette is about 10 c.c ; with the larger about 20 C.C. The large number of analyses of samples of mine air made gome by the author and some by Mr. E. B. Whalley for the Royal Commission on Mines of which the results are recorded in the recently issued Blue Book (Cd. 4551) containing reports on ‘‘ The Ventilation of Coal-Mines and the Methods of Examining for Fire-Damp,” by FIG. 3.-POnTABLE APPARATUS FOR THE DETERMINATION OF CAltBON DIOXIDE bfETHAXE (OR OTHER COMUUSTIELE GAS) AKD OXYGEN IK AIL Professor John Cadman and Mr.Whalley were made with these two types of apparatus. The smaller apparatus was originally described by J. S. Haldane (Journal of Hygiene 1901,6 74) and the larger in the textbook on (‘ The Investigation of Mine Air,” by Sir.C. Le Neve Foster and J. S. Haldane but some small modi-fications have been introduced in the apparatus as now illustrated. It will be observed that the differential pressure gauge containing 10 per cent. solution of caustic potash is embodied in both (K Figs. 2 and 3) as well as the control tube M immersed alongside the burette in a water-jacket. I t is necessary before corn 270 THE ANALYST. mencing an analysis that the connections between the burette and the absorption pipettes should contain only nitrogen.This is the residue naturally remaining after a complete analysis of a sample of air; consequently analyses may be made one after another without intermediate delay. When however the apparatus has been put aside for twenty-four hours or longer a certain amount of oxygen may have. found its way into the connections by tranefusion through the rubber joints and this must be absorbed in the pyrogallol pipette before an analysis is started. If before the apparatus is put aside after use the residual nitrogen in the burette i s transferred to the pyrogallol pipette and enclosed in the latter by turning the tap, this nitrogen may be employed when the apparatus is next brought into use to displace air which may have found its way into the connections.As a fact if stout-walled rubber tubing of good quality is used for making the joints and it i s lightly greased inside with vaseline very little oxygen finds its way into the connec-tions even after prolonged disuse. The time required for the determination of carbon dioxide and either methane or oxygen is about fifteen minutes or for all three constituents half an hour. The limit to the employment of this type of apparatus for the analysis of more complex mixtures of gases is fixed in practice by the number of pipettes required since each connection previously used in the course of the analysis must have its gaseous contents displaced at each stage in order that each constituent may be absorbed from the whole of the volume of original gas taken for analysis.Four pipettes may be used with advantage for certain gaseous mixtures but if more than four are required the process of analysis becomes very tedious with this type o€ apparatus, I t is often possible however by a judicious disposition of the taps and connections, and by omitting the determination of some one constituent having no significance for the work in hand or by determining two constituents together to render the type of apparatus described applicable to the analysis of relatively complex technical gaseous mixtures. Advantage may thus be taken generally of the high degree of accuracy which is attainable with it. DISCUSSION. The CHAIRMAN ( A h . Blount) said that one of the many interesting and important points brought out in this paper was that the old cumbrous methods of determining the constituents of a gas were dead.NowadayF if the constituents of a gas were known generally it could be readily analysed in a rapid and very accurate manner. No doubt in the case of a perfectly new gas or a new kind of mixture the methods of Bunsen and Frankland would have to be resorted t o ; but with some knowledge of the probable composition of the gas much simpler and more precise methods could be used. Another point was that compen-sation for variations in temperature and pressure had been applied in both the gravimetric and the volumetric forms of this process thus eliminating errors which otherwise were liable to become hopelessly large having regard to the limits of accuracy which it was necessary to attain.I n saying this he was not speaking merely academically for through the kindness of Dr. Haldane and Mr. Butterfield, he had been greatly helped when on some occasions he had had to analyse the ai THE ANALYST 271 of halls and theatres; and the small contribution which he had been able to make in designing with the help of his colleagues a tube suitable for the absorption of carbon dioxide was but a trifling return for the benefit he had obtained from that help. He had been much struck by the way in which while complying with all requirements as to precision the apparatus and the method of collecting samplee had been simplified and he thought that Mr. Butterfield and his coadjutors were to be heartily congratulated on the perfection they had attained in this important branch of analysis.Mr. A. E. PARKES asked if any steps were taken to exclude dust and carbon dioxide in the moisture determination or whether the influence of these was negligible; and also whether when the samples were taken in an adjacent chamber, after the air had been drawn through metal piping there would not be some risk, if the air was fairly saturated of moisture being condensed in the pipe. He thought, it would be interesting if Mr. Butterfield would describe a little more fully the method of transferring the samples from the small bottles to the apparatus. At the time when the tunnel under the Thames from Stepney to Rotherhithe was being made he (Mr. Parkes) had had to analyse samples of the air from the point where the men were at work in compressed air in the chamber behind the shield.That air of course was in a somewhat abnormal condition. The samples were taken in the old-fashioned way in bottles of about 3 litres capacity and Pettenkofer’s method of estimating the carbon dioxide was used. The proportions of carbon dioxide found varied considerably-from about 4 parts per 1,000 down to as little as 0.4 to 0.5 part. The higher figures were obtained in winter and the lower in Summer this being probably due to the fact that in winter free ventilation was objected to by the men on account of the cold. Mr. W. T. BURGESS suggested that it would be readily possible to design a simple but effective valve which would at any rate prevent blowing into the bottle. With regard to physical methods of determining moisture in air he had recently had occasion to examine some wet and dry bulb thermometers and had come to the conclusion that in the instruments usually sold the arrangement for keeping the wet bulb wet was not as good as it might be.Properly speaking the wet bulb should be covered with very fine muslin tied tightly round it and instead of the usual large wick,” there should be two or three threads of cotton leading from the muslin into a vessel of water some 3 or 4 inches away. Mr. G. N. HUNTLY said they were indebted to the author for calling attention to the utility of the Haldane apparatus which hitherto had been hardly known to more than a few. Some sixteen years ago he first used the compensation method, and he thought that the use of a compensating sir-tube was first suggested by Pettersson; but the original device was by no means practical and he believed Dr.Haldane was the first to work out the ingenious arrangement described in the present paper. He (Mr. Huntly) had used the small range apparatus for some time, and had found it capable of a degree of accuracy of about 1 in 20,000 but it was possible to work as closely as 1 in 50,000 under favourable conditions. In the larger apparatus the difficulty lay in the graduation of the tubes. He had found a varia-tion in the graduated portion only of as much as 3 per cent. by volume (3 per cent 272 THE ANALYST. of 6 C.C. = 0.18 c.c.) and many of these badly graduated tubes were to be met with. Tubes with such small divisions (0.01 c.c.) were difficult to calibrate and the use of the tube wet caused variations in the shape of the meniscus so that it was not possible to read accurately to a tenth of a division and an accuracy of 1 in 10,000 Wa8 as much as could be really relied upon.The method of calibration described in Haldane and Foster’s book on Mine Air was scarcely good enough for accurate work, as the meniscus which could not be allowed for amounted to about half a division. The only satisfactory way was to fuse on a three-way capillary tap and run the mercury up from the bottom running the whole of it out each time ; but this was a very tedious operation. For a single determination such as that of carbon dioxide, the method was an ideal one but the addition of further pipettes for other deter-minations made its working less convenient.At the end of the operation all these added spaces ought in theory to be full of nitrogen but in practice it was difficult to insure this so that with every additional determination the accuracy fell off. Con-siderable difficulty arose with regard to the combustion of traces of methane. He very much doubted whether the last traces of combustible gas were completely burnt, at any rate when the original quantity was small. Complete combustion could be insured by adding some hydrogen but the introduction of another gas was objectionable. Dr. RIDEAL said that a compensating “ gravivolumeter,” as it was called was described by Japp some years ago ( J . Chenz. SOC. 1891 894) which seemed to be the forerunner of the CO apparatus shown. He (Dr.Rideal) had had some experience with the small portable form of the apparatus described by Mr. Butter-field and had found that as Mr. Huntly had mentioned it had some disadvantages, from which however the larger form seemed to be free. Mr. BEVAN said that in some analyses which he had once had to make of carbon filaments for electric lamps he had found that variations in temperature and pressure caused large errors which would be eliminated by the compensating device now described. He should like to hear if Mr. Butterfield had tried the use of silica tubes and could say whether the quantity of moisture condensed on these was less or greater than with glass. Dr. LESSING said that in determining the proportion of nickel in nickel carbonyl gases (by decomposing the nickel carbonyl by heating to about 200” C.which resulted in an increase in volume of 4 to I) he had observed that whenever air was added to the gas or when air leaked into the tube there was always a contraction in volume. This had not been explained but might be due to oxidation by some nickel present in the tube. This contraction was a parallel to the abnormal expansion of methane when insufficient air was present for complete combustion. Mr. BUTTERFIELD in reply said that this gravimetric mode of analysis was often used in conjunction with a bacteriological examination of the air and in that case a tube containing sterilised cotton-wool was attached to the free end of the tube through which the air was drawn so that the air was filtered at any rate through that.As to condensation of moisture in the metal pipe that was liable tooccur if there were appreciable differences of temperature and he did not advocate the drawing of samples through a long tube when the moisture wa8 to be determine THE ANALYST 273 exactly though there was not much fault to be found with this plan in regard to the determination of carbon dioxide. As to the transference of the sample to the apparatus the neck of the bottle was inserted in the mercury trough the stopper taken out beneath the mercury and the free end of a bent tube (already filled with mercury and connected to the burette) inserted through the mouth of the bottle, which was then clamped down and the sample drawn over. In examining a number of samples in succession it was sufficient to leave a plug of mercury in the open end of the tube drawing over the air contained between that plug and the apparatus into the burette and expelling it into the open air and then drawing in the sample; but the orthodox way was to fill the tube first with mercury.I n examining air under pressure all sorts of difficulties might arise and the quantity of carbon dioxide found in compressed air workings sometimes varied more or less unaccountably. One point of importance when samples were taken under considerable pressure (as for instance, at the bottom of deep mines) was that a very stout band should be placed over the stopper otherwise under the lower barometric pressure at the surface the stopper might be blown out. He had recently been using this type of apparatus with satiefac tory results at considerably reduced pressures and also at pressures! con-siderably higher than the normal.He had hoped to deal with the subject of wet and dry bulb thermometers or psychrometers but the paper had already become too long. He showed however a specimen of the form of wet and dry bulb thermometer now generally accepted by German physicists and known as the Assmann psychrometer, The ordinary form-i.e. Mason’s hygrometer-was perfectly satisfactory when used outdoors with currents of air passing over the wet bulb ; but when it was indoors the damping arrangement created round the bulbs a local humidified atmosphere which remained unchanged and consequently the true humidity of the room was not shown the air in the neighbourhood of the reservoir being saturated to a greater extent than the air of the rest of the room.The German instrument had a clockwork fan which drew the air over the bulbs so that there was no stagnation and there was an arrangement for moistening the wet bulb every ten minutes-the period of the fan’s running. This was now considered to be the best physical means of determining the humidity of the air and in a future paper he hoped to compare the results yielded by this and by the gravimetric method. I t might be mentioned that some years ago Dr. Pembrey had proved ihat the ordinary Mason’s hygrometer was perfectly reliable outdoors. Dr. Pembrey’s determinations extended over several months this gravimetric method for which he was partly responsible being used in the comparisons.As Mr. Huntly had remarked the gravimetric method as here shown for the determination of carbon dioxide was not very widely known which was one of the reasons for the writing of the present paper. The accuracy as apart from the consistency of the results obtained with the small apparatus had been amply checked by comparison with the results of gravimetric determinations. The Pettenkofer method was of course a very good one but a larger sample was required, and in order to be sure of the results it was necessary always to make a control test on outside air. The results merely showed the degree of divergence from the outside air. This of course was generally what was really wanted but there was an error of uncertain magnitude and generally of uncertain origin.Mr. Huntly had remarke 274 THE ANALYST. that in the application of the apparatus to gas analysis the necessity for using several pipettes made an analysis a long proceeding because of the necessity for clearing the gas out of the connections each time. This was quite true but with only three determinations there was not very much difficulty it being possible to make complete and exact determinations of carbon dioxide methane and oxygen in half an hour once the apparatus had been prepared for use. At the outset as was mentioned in the paper the connections had to be filled with nitrogen which was easily done by two or three times passing air through them and into the pyrogallol pipette and drawing it out again. On each subsequent occasion nothing but nitrogen from the last analysis was left in the connections and the next analysis could be proceeded with at once. I t did not therefore pay to make only one analysis a day because in the course of the twenty-four hours diffusion through the rubber took place but half a dozen samples could be analysed one after another at the rate of something like half an hour per sample for the three constituents He agreed that sodium hyposulphite was quite satisfactory but it did not last so long as the pyrogallol solution one pipetteful of which would serve for 150 to 200 determinations. As to the combustion of methane he had not been able to detect any trace that could not be burnt and certainly as little as 0.01 per cent. of methane could with care be detected

ISSN:0003-2654    

DOI:10.1039/AN909340257b

出版商:RSC    

年代:1909

数据来源: RSC

摘要:

274 THE ANALYST. ABSTRACTS OF PAPERS PUBLISHED IN OTHER JOURNALS. FOODS AND DRUGS ANALYSIS. Note on the Periodide Test for Alkaloids. A. H. Clark. (Anzcr. JO26YlZ. Pharm., 1909, 81, 176-177).-The author has observed that water saturated with ether gives on acidification a reddish-brown precipitate of kdinc on adding a solution of iodine in aqueous potassium iodide, and this precipitate resembles in appearance that formed by an alkaloid with the same reagent. Water containing ether without acidification does not cause such a precipitate, n9r does acidulated water, nor acid alone, with the iodine reagent. I n order to guard against this source of error in testing for traces of alkaloids in extraction work, it is only necessary to add an equal volume of water, when the precipitate of iodine will dissolve, while that due to an alkaloidal iodide will be unaffected.A. R. T. The Distillation of Butter-Fat, Cocoanut Oil, and their Fatty Acids. By K. S. Caldwell and W. H. Hurtley. (Proc. Chem. Soc., 1909, 25, 73.)-The authors are of opinion that fats and fatty acids have no boiling-points in the vacuum of the cathode light, but that for any particular substance a temperature can be selected at which evaporation occurs at a speed convenient for fractional distillation. Butter-fat, cocoanut oil, and their fatty acida were distilled in the vacuum ofTHE ANALYST. 275 the cathode light. The lowest fraction obtained from butter-fat distilled with the bath temperature at 250" to 270' C. and inner thermometer at 187" to 210' C. Tributyrin distils rapidly with the bath temperature at 127" and inner thermometer at 107' C. For this and other reasons it is concluded that butter does not contain tributyrin. The iodine numbers yielded by the various fractions seem to indicate that there is little or no triolein in butter-fat.Lauric acid forms at least 60 per cent. of the fatty acids in cocoanut oil, whilst it could not be detected in butter. This method of distillation enabled the authors to detect with ease the presence of 10 per cent. of cocoanut oil in butter. The presence of palmitic acid in cocoanut oil has been questioned by Ulzer (Chenz. Revue, 1899, 203), but the authors isolated several grams of this acid from cocoanut oil. Estimation of Quinine in Quinine Tannate and Ferro-Citrate. E. Rupp and W.Callies. (Apoth. Zeit., 1909, 24, 159; Pharnz. Jozwn., 1909, 82, 584.)-1.2 grams of quinine tannate is thoroughly shaken with 10 grams of a solution of potassium carbonate of 1.334 specific gravity until a uniform mixture results, when exactly 30 grams of ether are added, and the whole well shaken for some minutes. Half a gram of tragacanth is next added, the shaking repeated, and the mixture set aside for five minutes. Exactly 25.3 grams of the clear ethereal layer (= 1 gram of the tannate) is removed, the ether evaporated, and the residual quinine, which should not be less than 0.3 grams, weighed. Similarly, 1.2 grams of quinine ferro- citrate is dissolved in 5 grams of water, the alkaloid liberated with 5 grams of caustic soda solution, 0.5 gram of tragacanth added, and the whole shaken with 31 grams of ether, and 25.1 grams of the ethereal solution evaporated.A. R. T. Composition of Infant and Invalid Foods. (The Connecticut Agric. Exp. Stat. Report, 1908, Part 9, 599-606.)-This paper contains a number of analyses of proprietary foods. The Estimation of Certain Organic Acids occurring in Fruits. G. Jorgensen. (Zeit. Untersuch. Nahr. Genussnz., 1909, 17, 396-412.)-As the result of further experimental work, the author suggests certain modifications in the process described previously for the separation and estimation of certain organic acids (ANALYST, 1907, 32, 169). The residue of succinic acid obtained should be re-dissolved in 9 C.C. of water, the solution acidified with 1 C.C. of dilute hydrochloric acid, and again shaken out five times with ether; the ethereal solution is then evaporated, and the quantity of succinic acid estimated as described.The strength of the alcohol. employed for the separation of the barium citrate from the barium malate should be 26 per cent. by volume; in cases where the precipitate of barium citrate is large, the precipitation must be repeated in order to separate all the barium malat e. A sample of sloe fruit (Przmus cornmzmis) examined contained about 3 per cent, of malic acid and a very small quantity of another acid, which was possibly succinic acid ; tartaric and citric acids could not be detected in the fruit, w. P. s.276 THE ANALYST, The Chemical Examination of Isinglass. K. Dieterich. (Clzem. Zeit., 1909, 33, 357-358; 367-368.)-The following method of analysis has been devised by the author, the material in each case being first cut into fragments of 0.5 square em.in size.--Moistzwe: About 5 grams are dried at 100" to 105" C. Ash and potcissium carbonate in the ash are estimated in the usual way. Substances soluble in boililzg water: Ten grams are mixed with about 500 C.C. of cold water in an enamelled vessel, which is allowed to stand on a water-bath until most of the isinglass rises to the surface. The liquid is then boiled over a naked flame until violent frothing has ceased, after which it is evaporated to 300 or 400 c.c., any adherent particles being meanwhile detached from the sides of the vessel with a glass rod. The vessel is again transferred to a water-bath, and as soon as the insoluble matter has settled, the supernatant liquid is decanted as completely as possible into a graduated litre flask.The residue is treated with 800 C.C. of boiling water, and the liquid evaporated over a free flame to 200 c.c., and decanted as before. This process is repeated three or four times until the flask is nearly filled, and finally the residue itself is washed into the flask. The contents of the latter are cooled to 15" C., made up to the mark, and filtered, 50 to 100 C.C. of the opalescent filtrate evaporated, and the residue dried at 100" to 105" C. Absorption value and gelatinising power (Quellungs- xahl) : Ten grams of the sample are mixed with 800 grams of hot water in a tared enamelled vessel, and the liquid evaporated on the water-bath with constant stirring to about 510 grams.If no gelatinisation takes place on cooling, another 50 to 100 C.C. of water are evaporated, and the liquid again cooled. The weight at which gelatinisation occurs gives the required values. Thus, e.g., if the weight was 370 grams, the gelatinising power is 1 : 36, or the absorption value is 36. Fat: Ten grams are extracted for three hours with ether in a Soxhlet apparatus. Collagene is taken as the difference between the fat and soluble plus insoluble substances. Crude glutin : Ths dry residue from the estimation of the fat is completely exhausted with boiling water in the manner described above, and 500 C.C. of the filtrate (= 5 grams of the fat-free isinglass) evaporated to about 50 grams i n a tared beaker, and treated, little by little, while still hot, with 200 to 300 C.C.of absolute alcohol. The precipitate is allowed to subside for at least twelve hours, and the supernatant liquid decanted through a small tared filter which is washed with alcohol. The weight of the residue in the filter and beaker, dried at 100" C., gives the amount of glutin. Acid value: This is determined by heating 2 grams of the isinglass for three hours on the water-bath, with 100 to 150 C.C. of water, filtering the solution, and titrating an aliquot portion of the filtrate. Iodine watue: Fifty C.C. of the aqueous filtrate (=0*5 gram of isinglass) are shaken with 20 C.C. of a -& potassium iodide solution of iodine, and the unabsorbed iodine titrated with sodium thiosulphate after standing for twenty-four hours.Szilphur : The isinglass is fused with potassium nitrate and sodium carbonate, and the aqueous solution of the residue tested for sulphuric acid. This test is of importance, since isinglass bleached with sulphurous acid is of less value than products not artificially bleached. Starch is also tested for in the aqueous solution. Optical rotation of the gZutiiz solution; The aqueous solution of the glutin should be levo-rotatory. The Artificial products may give a positive reaction.THE ANALYST. 277 following results were thus obtained in the analysis of twenty samples of genuine isinglass, and of a Russian sample adulterated with gelatin : Moisture ... ... Ash ... ... Potassium carbon- ate in ash ... Soluble substances I n s o l u b l e s u b - stances... ... Absorption value.. . Fat Collagene. . . ... Crude glutin ... Acid value ... Iodine value . . . Ash in glutin ... Optical rotation of ... ... glutin ... ... Sulphur . . . ... Price, per kilo. ... Russian Saliansky , Beluga, Samovy). Per Cent. 13-20 0.5-1-7 8-3 3 65-81 1-19 0-49 0-1-1.2 79-85 66-82 0-6.0 19-45 0.4-0-7 laevo-rotatory present 4-18 marks Chinese. Per Cent, 11-17 0.9-2.3 32-53 68-86 2-15 14-25 0.1-1*2 81-88 69-74 0 39-46 0.67 Iwo-rotatory present 2-11 marks American (Brazilian, Vene- zuela, Maracaibo, and refuse). Per Cent. 13-18 1-3.7 6-37 59-75 9-25 16-55 0.1-0.8 80-87 66-75 0-2.76 30-47 0-4-0.7 lmo-rotatory present 1-4.50 marks Saliansky adulterated with Gelatin. Per Cent. 16 0.6 72 a2 1.5 0.3 25 83 82 37 3.8 0.4-0.7 laevo-ro t story present - A good sample should contain as little ash as possible, and a high percentage of soluble substances and collagene, whilst the latter should contain a large amount of glutin, though approximate agreement between the values for collagene and glutin does not occur in genuine products.The presence of gelatin is indicated by the ratio between these two substances, by the proportion of potassium carbonate in the ash, and by the absorption and acid values. Thus, a sample of Saliansky isinglass contained 0.358 per cent. of potassium carbonate; a sample of gelatin, 0.695 per cent. ; and a sample of isinglass adulterated with gelatin, 0.422 per cent. A high acid value in pure isinglass indicates decomposition, and good samples are practically neutral. Gelatin has an acid value of over 11, and the adulterated sample in the above table therefore has an acid value of nearly 4.C. A. M. The Composition of Kirsch Liqueurs. X. Rocques and L. Levy. ( A m . de Chim AiznZ. Appl., 1909, 14, 138-140.)-Comparative distillations were made with a solution of hydrocyanic acid in 50 per cent. alcohol, and with samples of new and old Kirsch liqueurs both before and after saponification with sodium hydroxide. In each case nine fractions of 100 C.C. each were collected, and the hydrocyanic acid in them titrated with standard silver nitrate solution in the presence of ammonia, and potassium iodide. The saponified samples were rendered slightly acid with phosphoric acid before distillation. The amounts of hydrocyanic acid formed by direct distillation corresponded to 3.5995 and 22.0 C.C.of silver nitrate solution278 THE ANALYST. respectively in the case of two recently prepared samples, and ranged from 8.45 to 17.25 c,c. in the case of five samples two or three years old. After saponification the two recent samples gave distillates requiring 17-45 and 19.85 C.C. respectively, and the other samples distillates requiring from 6.75 to 17.50 c.c., the greatest increase being 2-75 C.C. I n the distillation of the alcoholic solution of hydrocyanic acid the whole of that acid passed over in the first five fractions, the curve being a continuous one. The curve for the amounts of hydrocyanic acid in the different fractions distilled from recently prepared Kirsch liqueurs differed from that of the hydrocyanic acid solution and from that of old liqueurs.In the latter it fell as far as the fifth fraction, then rose to a maximum in the seventh fraction, to fall again to the ninth fraction. After saponification the curve approximated that of a hydrocyanic acid solution. The last fractions of the distillation, corresponding to the maxima of the curves, had a characteristic odour, resembling that of linseed-meal warmed with water. This odour was not perceptible after saponification, but the distillates at the corresponding points then contained fatty matter. From these results the authors conclude that only part of the hydrocyanic acid in Kirsch liqueurs two or three years old is in the free state, and that a considerable proportion of that acid is in combina- tion with fatty substances. C .A. M. Estimation of Malic Acid in Wine. C. von der Heide and H. Sieiner. (Zed. Uiztersuclz. Nahr. G ~ I Z U S S ~ . , 1909, 17, 307-315.)-The various steps involved in the method proposed are : (1) Removal of the tartaric acid as potassium hydrogen tartrate; (2) removal of the acetic and lactic acids as their alcohol-soluble barium salts; (3) extraction of the succinic and malic acids by means of ether; and (4) estimation of the malic and succinic acids from the alkalinity of the ash of their alkali salts. Fifty C.C. of wine are treated with 1 C.C. of glacial acetic acid, 0.25 C.C. of 20 per cent. potassium acetate solution, 7.5 grams of powdered potassium chloride, and 7.5 C.C. of 95 per cent. alcohol. After the lapse of fifteen hours the precipitate is collected on a filter, washed with a mixture consisting of 15 grams of potassium chloride, 20 C.C.of 95 per cent. alcohol, and 100 C.C. of water, not more than 10 c.c of the solution being used for the washing. Ths filtrate and washings are evaporated to a volume of a few c.c., the residue is dissolved in a little water, and the solution neutralised with powdered barium hydroxide after theaddition of 5 C.C. of 10 per cent. barium chloride solution. The excess of barium hydroxide added is removed by treatment with carbon dioxide, the whole solution is brought to a volume of exactly 20 c.c., and 85 C.C. of 96 per cent. alcohol are added with constant stirring. At the end of two hours the precipitate is collected on a filter, washed with 80 per cent.alcohol, then rinsed with water back again into the basin and evaporated almost to dryness. The residue is treated with 3 C.C. of 40 per cent. sulphuric acid, and suflicient powdered anhydrous sodium sulphate is added to form the whole into a dry mass. This is extracted with ether in a Soxhlet apparatus for six hours, the ethereal extract is diluted with a little water, and, after the ether has been evaporated, the solution is treated with 3 grams of animal charcoal, the mixture being placed on the water-bath for one hour. The charcoal is now removed by filtration, washed with hot water, and the filtrate, thus freed from tannin is neutralised, evaporated toTHE ANALYST. 279 dryness, the residue is carefully ignited, and the alkalinity of the ash is titrated.From the alkalinity (carbonate) found, the amounts of succinic acid and rnalic acid present may be calculated; or the succinic acid may be estimated separately by the process described in the following abstract and the amount found deducted from the sum of the two acids. Results of experiments are given which show that from 96.3 to 100.6 per cent. of the quantities of malic acid added to wine (about 0.3 gram of the acid to 100 C.C. of wine) may be found by the method. w. P. s. Estimation of Succinie Acid in Wine. C. von der Heide and H. Steiner. @it. Untersmh. Nalw. Genussm., 1909, 17, 291-307.)-The authors have subjected the method described by Kunz (ANALYST, 1903, 28, 314) to a critical examination, and find that, whilst the process as a whole is the best of many methods which have been proposed for the estimation of succinic acid, certain modifications in the method of procedure are necessary to obtain accurate results.The process as modified is as follows : Fifty C.C. of the wine are evaporated in a basin of about 200 C.C. capacity until the alcohol has been removed; after the addition of 1 C.C. of 10 per cent. barium chloride solution and a little phenolphthalein, the residual solution is treated with powdered barium hydroxide until all the acidity has been neutralised. Excess of barium hydroxide is removed by treating the mixture with carbon dioxide, and 85 C.C. of 96 per cent. alcohol are then added to the mixture, with constant stirring. After the lapse of at least two hours, the precipitate consisting of barium succinate, tartrate, and malate, together with other barium salts, is collected on a filter, washed with a small quantity of 80 per cent.alcohol, and then washed back again into the basin by the aid of a jet of boiling water. The contents of the basin are now heated until all alcohol has been removed, and 5 per cent. potassium permanganate solution is then added in quantities of about 3 C.C. at a time until the red coloration does not disappear after the mixture has stood for five minutes. A further 5 C.C. of permanganate solution are then added, and the mixture is heated on the water-bath for fifteen minutes. The excess of permanganate is destroyed by the addition of sulphurous acid, and, after the mixture has been acidified with sulphuric acid, more sulphurous acid is added until all the manganese dioxide has been redissolved.The mixture is then evaporated to a volume of about 30 c.c., and extracted with ether for twelve hours in a percolating apparatus, after the addition of so much 40 per cent. sulphuric acid that the solution contains about 10 per cent. of free sulphuric acid. The ethereal extract is diluted with water, the ether is evaporated, and the residual solution, after neutralisation, is transferred to a 100 C.C. flask, 20 C.C. of & silver nitrate solution are added, and the whole is diluted to the mark and filtered. The excess of silver is then titrated in 50 C.C. of the filtrate, Volhard's method being used for the purpose. Data are given showing that the method is trustworthy. w. P. s. A Method of Estimating the Volatile Acids in Wine. P. Malvezin. (Bull. Xoc. Chim., 1909 [iv.], 5, 332-335.)-The following rapid method is based on the author's observations that 72 per cent. of the volatile acids in wines are dissolved by ether, whilst tartaric acid is insoluble and succinic acid only sparingly soluble280 THE ANALYST. under the conditions of the estimation. Ten C.C. of the wine and 10 C.C. of ether are shaken vigorously together for one or two minutes in a tube 20 cm. in length by 20 mm. in internal diameter. The tube is now closed by a cork through which passes a, thermometer, and is allowed to stand for ten minutes in a water-bath at 15’ C . Five C.C. of the supernatant ether are then drawn off with a pipette, and mixed with 5 C.C. of 90 per cent. alcohol, and the liquid titrated with & sodium hydroxide solution, with phenoJphthalein as indicator. The volatile acidity in parts per 1,000 of sulphuric acid is found by means of the following formula in which A represents the number of C.C. of alkali used- (2A - 0.2) x 25 x 1-63 ti The results thus obtained with twenty samples of wine of different kinds and origin were almost identical with those given by DUCI&UX’S method. C . A. M.

ISSN:0003-2654    

DOI:10.1039/AN9093400274

出版商:RSC    

年代:1909

数据来源: RSC

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280 THE ANALYST. BACTERIOLOGICAL, PHYSIOLOGICAL, ETC. Polarimetric Method of Identifying Chitin. J. C. Irvine. (Jozwn. Chem. SOC., 1909, 95, 564-570.)-The author has determined the specific rotatory power of chitin prepared and purified in the usual manner from the shells of various inverte- brate animals. For this purpose, the chitin was dissolved in concentrated hydro- chloric acid with special precautions. All the metal parts of the polarimeter tube were coated with a thin layer of vaseline; the readings were taken at 20" C., with solutions at a concentration of about 1.75 per cent. The sample of chitin is finely powdered and dried at 110" C. until constant in weight; it is then dissolved in concentrated hydrochloric acid as rapidly as possible, since the rotation changes appreciably when the solution is allowed to stand at the ordinary temperature. Solutions of the concentration mentioned above may, however, be readily prepared without change.Under these conditions the specific rotatory power of chitin, calculated on the original weight of substance, in solution in hydrochloric acid of specific gravity 1.160, is [aID= -14.1'. On standing, the chitin in solution is gradually converted into glucosamine hydrochloride, and its specific rotatory power changes until it reaches the value [ u ] ~ ~ ~ = + 56", calculated on the original chitin. This change may be accelerated by heating at 40" to 45" C., and is then complete in eight to ten hours. The polarisation test for chitin therefore includes the determina- tion, not only of its direct specific rotation, but of its rotatory power after hydrolysis.A still further confirmation may be obtained by treating the hydrolysed solution with nitrous acid, which effects its conversion into the monosaccharide chitose. For this purpose, 15 C.C. of the hydrolysed solution are withdrawn and treated with 10 C.C. of a 5 per cent. solution of potassium nitrite added drop by drop. The liquid is gently warmed until all nitrous fumes are expelled, and then diluted to 30 C.C. The rotations observed after this treatment are not so uniform as those obtained in the previous stages of the test, but it is sufficient to note that the specific rotatory power of the hydrolysed chitin is approximately halved. These relationships afford a reliable means for the identification of quite small quantities of chitin, without the necessity of calculating the specific rotations.The test specimen is dissolved in the minimum quantity of hydrochloric acid necessary to fill the 100 mm. tube, the direct polarisa-THE ANALYST. 281 tion, a,, is observed; the liquid is then heated at 45" C. in a stoppered flask and the hydrolysed solution is polarised, giving ub ; finally the solution is treated with nitrous acid and the corrected reading a, is obtained. Then, if the substance is chitin, the following relationships should hold : a, : a, : ac= - 1 : + 4 : + g. J. F, B. Estimation of Several Sugars when present together in Diabetic Urine. H. C. Geelmuyden. (Zeit. anal. Chem., 1909, 48, 137-163.)-By polarisation and titration before and after inversion, it is possible to estimate four sugars in presence of each other, provided that not more than two of them are monosaccharides and that no sugar is destroyed by the inversion process.The principal sugars to be estimated in diabetic urines are dextrose, lwulose, and maltose ; sucrose is sometimes present after large quantities of that sugar have been ingested. The author has never encountered more than mere traces of pentoses and glycuronic acid in diabetic wines. The hydrolysis of maltose is best effected by heating equal volumes of urine and 6 per cent. sulphuric acid in soda-water bottles with patent stoppers, the bottles being immersed in a boiling water-bath for three to four hours and allowed to cool in the bath. If maltose has to be hydrolysed, both sucrose and lwulose must be absent, since appreciable quantities of these sugars are decomposed by the treatment.The author prefers to use Knapp's solution instead of Fehling's for the titration of reducing sugars. Given a mixture of maltose and dextrose, or maltose and laevulose, the two constituents are best determined in the usual manner from the direct polarisation and reducing value of the mixture ; for mixtures of maltose and dextrose, the polarisation before and after inversion also gives sufficiently accurate results ; the titration method before and after inversion is not so accurate. Although the estimation of sucrose does not come into practical account in urines containing maltose, it is frequently necessary to determine the three sugars-maltose, dextrose, and laevulose-in presence of each other.For this purpose, fermentation by means of a selective yeast is necessary. Fermentation by a yeast which will remove all the sugars is also necessary in order to correct for the optical rotation (generally lmo) of the normal constituents of the urine, For the latter purpose, the author prefers Logos " yeast as being rapid and complete in its action. S. thermantitomm appears to be equally suitable. Yeasts do not grow well indefinitely in aaccharine urines, and the pure cultures should be made in wort media, From these, a saccharine urine medium containing a little magnesium sulphate should be inoculated, and the crop of yeast developed in this after three to four days at 24" to 25' C. should be drained off on a porous sterilised filter and used for the fermentation.For the selective fermentation of monosaccharides the author recommends yeast No. 583 of the Berlin Versuchs-und-Lehranstalt fur Brauerei. Unless special precautions be taken, this yeast tends to remove appreciable quantities of maltose. In the first place the urine appears to contain an inverting enzyme, the action of which is sensible in the period necessary for fermentation. The urine must therefore be sterilised by heating at 100' C. before fermentation; if it be neutral or very faintly acid, neither the maltose nor the dextrose is injured by this treatment. Next, after the monosaccharides have disappeared, the yeast gradually attacks the maltose ; the fermentation should therefore not be prolonged beyond five days.For fhe estimation282 THE ANALYST. of maltoee, dextrose, and IEvulose, with the aid of yeast No. 583, the author has determined empirical corrections, which are +Om019 to be added to the observed percentage of the maltose, -0.066 for the dextrose and +0*004 for the l~evulose, provided that the polarisation readings are correct within 0.01 per cent. and are taken on the same solutions as are used for titration; provided also that duplicate titrations with Knapp’s solution are concordant to 0.1 C.C. on solutions equivalent to about 1 per cent. concentration of dextrose, and lastly, that the yeast is cultivated in the manner described above and the fermentation is conducted for five days. J. F. B. Determination of Urea in Urine. C. G. L. Wolf and E.Osterberg. (Jounz. Amer. Chcm. SOC., 1909, 31, 421-428).-I.n a recent paper by Benedict and Gephart (ANALYST, 1909, 27), a method was proposed for the estimation of urea in urine by effecting its hydrolysis into carbon dioxide and ammonia by heating in the autoclave with hydrochloric acid. This method appeared to be a distinct improve- ment on Folin’s method of distillation with magnesium chloride, but it always yielded higher results than the latter method. The authors have investigated the matter, testing the new method on urea itself and on uric acid and creatinine, which normally accompany urea in urine. They find, however, that the treatment with hydrochloric acid invariably effects the hydrolysis of appreciable quantities of uric acid and creatinine, and that the high results were due to this circumstance. Benedict and Gephart’s method, therefore, is not available as a substitute for Folin’s method, in spite of the undoubted convenience of their procedure. The magnesium chloride in Folin’s method has the advantage of automatically regulating the temperature at the most favourable point and of providing a hydrolysing agent which, while only imparting a slight acid reaction, is able, by reason of the shifting equilibrium, to furnish more than sufficient acid for any neutralisation or hydrolysis that may be needed. J. F. B.

ISSN:0003-2654    

DOI:10.1039/AN9093400280

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年代:1909

数据来源: RSC

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282 THE ANALYST. ORGANIC ANALYSIS. Determination of Carbon in Aliphatic Hydroxyl Compounds by Moist Combustion [Estimation of Cellulose in Cuprammonium Solutions]. E. Berl and A. G. Innes. ( B e y . deut. Chem. Ges., 1909, 42, 1305-1309.)-The authors describe the procedure they have adopted for the moist combustion of organic hydroxylated compounds of the aliphatic series, chiefly carbohydrates and salts of organic acids. They find that phosphoric acid is preferable to sulphuric acid as a dehydrating agent, the latter tending to give high results owing to the production of sulphur dioxide. The substance is heated with a mixture of chromic acid and phosphoric acid in highly concentrated solution, and the carbon dioxide evolved by the combustion is collected in a Bunte burette and measured by absorption with sodium hydroxide.I n certain cases when the substance is not readily oxidised, the addition of a couple of drops of mercury to the mixture in the reaction flask suffices to induce combustion. The reaction flask has a capacity of about 30 c.c., and isTHE ANALYST. 283 provided with a ground-in stopper carrying a gas-evolution tube which is connected with the upper tube of the Bunte burette. A tapped funnel is fused with a bend into the side of the neck of the flask. When the substance has been weighed into the flask and the latter connected with the burette, the whole apparatus is evacuated as completely as possible. The quantityof substance taken is such that a diminished pressure will still exist in the apparatus after the combustion is finished.Five to six C.C. of a saturated solution of chromic acid are admitted through the funnel, and when the reaction (if any) has subsided, 5 to 6 C.C. of a very concentrated solution of phosphoric acid, prepared from pure phosphorus pentoxide, are introduced. The combustion is completed by heating for five to ten minutes, and the gas is then expelled from the flask by the admission of hot water through the funnel until it reaches the upper cock of the burette. After cooling, the volume of gas is measured over saturated brine, the carbon dioxide is absorbed by a strong solution of sodium hydroxide, and its volume is ascertained after removing the alkali and returning the brine. The results should be controlled by means of blank determinations, and examples quoted by the authors show that in the case of substances for which the method is applicable, the results are as accurate as those obtained by dry combus- tion; compounds of the aromatic series show carbon values which are far too low.The method was specially devised for the estimation of cellulose in cuprammonium solutions. For this purpose the solution to be analysed is weighed out from a pipette into the reaction-flask, and the ammonia is expelled by gentle heat. Phosphoric acid is then added and the gases which are liberated from carbonates and other by- products are removed by warming in vacuo. Finally the apparatus is connected up and the combustion is made in the manner described. J. I?. B. On the Simultaneous Estimation of Carbon Monoxide, Hydrogen, and Methane by Combustion.V. Nesmjelow. (Zeit. anal. Chem., 1909,48, 232-272.) -Whilst carbon monoxide is oxidised completely by passing it repeatedly through silver oxide at a temperature of 1'7.5" C., and hydrogen only reacts with silver oxide at tempeieatures above 30" C., the method of oxidation cannot be put to practical use for the separation of carbon monoxide, hydrogen, and methane, as a part of the carbon monoxide formed combines with the silver oxide to form silver carbonate, and it is difficult to avoid some action of the hydrogen on the silver oxide. Carbon monoxide may, however, be estimated in a mixture of these three gases by passing the mixture over palladium-asbestos, provided that the current of gas is at the rate of not more than 1 litre per hour.I t is not necessary to heat the palladium-asbestos previously. If the gaseous mixture be passed through the tube containing the palladium-asbestos at such a rate that the temperature becomes high, methane is also oxidised, and the results become inaccurate, h better method for the estimation of the carbon monoxide consists in passing the mixed gases over copper oxide heated to a tempera- ture of 250" C. The methane is not attacked, and the velocity of the current of gas through the tube may be varied within wide limits without affecting the results obtained. w. P. s.284 THE ANALYST, Estimation of Diphenylamine. W. Dreger. (Zeit. gcs. Schiess zcizd Sprengstofzo., 1909,4, 123 ; Chem. Z e i t . R e p . , 1909, 33,2l0.)-Commercial diphenyl- amine is dissolved in alcohol and an excess of bromine added.The solution is diluted with twice its volume of water and boiled down to about half the volume, with constant stirring, until alcohol and excess of bromine have been volatilised. The precipitated tetrabromdiphenylamine is filtered on a Gooch crucible, dried at 98" to 100" C. and weighed. The weight, multiplied by 0.34872, gives the quantity of diphenylamine originally present. The tetrabrom compound is insoluble in water, difficultly soluble in alcohol, and easily soluble in benzene, chloroform, and acetic ether. From gelatinised gun-cottons diphenylamine is liberated by boiling with sodium hydroxide and distilling ; the distillate is extracted with ether after adding sodium chloride, the ethereal solution evaporated, the residue dissolved in alcohol, and diphenylamine then estimated as above.,4. G. L. Examination of Explosives Prescribed by the German Railway Administration. (Zeit. ges. Schiess und Sprengstofzo., 1909, 4, 175.) A . Blasthzg Agents.-These comprise ammonium nitrate explosives, organic nitro- compounds, and mixtures containing them, nitrated chlorhydring, nitrocelluloses, chlorate and perchlorate explosives, black powder and similar mixtures, dynamite and similar explosives. I n each class an explosive, the composition of which is given, is set up as a standard, to which an explosive in that class must conform. The explosive is examined for certain of the following points, according to its class : Chemical analysis, identification. (melting-point, etc.), uniformity of composition, behaviour to litmus paper, behaviour under prolonged heating, resistance to separation of constituents under prolonged shaking, resistance to ignition, and to shocks, blows, and friction, behaviour on moistening (separation of nitroglycerine), solubility in water and tendency to form salts, nitrogen content by Schulze Tiernann (Schlosing) or Lunge method, flash-point, water or alcohol ccntent, percentage of any other admixtures, stability at 145" C., and behaviour in moist and dry air.B. PropeZZants.-The constituents of smokeless gelatinised nitrocellulose and nitro- glycerine powders are tested separately, as well as the finished powders. The nitrocellulose is tested for disengagement of nitrogen peroxide at 132" C., and for flash-point, the nitroglycerine for acidity.The finished powders must be gelatinised, and are tested for flash-point, stability under heating, and expansion in the Trauzl block. C. Other Explosive Siibstaizces.--Tn the dry state these must show a resistance to shocks, blows, and friction, and to ignition, at least equal to that of pure picric acid solidifying at or above 120" C. For details of the tests the original must be consulted. No scheme of testing for black powder propellants is issued. 0. E. M. Spurious Gum Tragacanth. W. L. Scoville. (Pharnz. Jozwn., 1909, 82, 493.)-This gum is largely adulterated with, or substituted by, ( ' Indian gum," under which name two similar gums are known, (1) from Sterculia w e n s (" Karai "), (2) from Cochlospernzzm gossypizm (" Hindu tragacanth ").These gums may beTHE ANALYST. 285 distinguiHhed from tragacanth by the following tests, working on a 2 per cent. solution : Appearance of solution ... Reaction to litmus . , . Solution of iodine ... ... Equal volume of 5 per cent, KOH ... ... Basic lead acetate ... Mercuric nitrate . . . ... ... 1 Ferric chloride ... ... Tannic acid ... ... ... Pjcric acid . . . .. . ... Alcohol (equal volume) . , . Alcohol (two volumes) Heated with 2 per cent. HCi Fehling’s solution after HCl Borax test (2 per cent. cold aqueous solution treated with 2 grams of powdered borax until dissolved and allowed to stand twenty- four to thirty-six hours). Gum Tragacanth. Opaque, slimy, semi-fluid. Neutral. Blue colour. CoZd, froths on shaking. Hot, yellow solution.Gelatinises. Precipitates in mass. Precipitates ; deep red solution. No reaction. No reaction. Precipitates slowly. Precipitates immediately. slight darkening ; liquefies gradually. Reduced. Darkens slowly ; no change in consistency in two to three days. Indian Gum. Transparent, non-adhesive jelly. Acid ; sometimes neutral. No blue colour. No froth on shaking. Very slightly brownish. Slight hardening. Precipitates in clots. Precipitates ; deep red solution. No reaction. No reaction. Clear mixture. Precipitates slowly. Reddish - brown ; limpid solution, does not again gelatinise. Reduced. Darkens slowly ; becomes slimy a n d t a c k y . ‘‘ Strings ” markedly on pouring (5 per cent. in tragacanth can be thus detected). A. R. T. The Analysis of Commercial Metol.A. Nicolle. (Mon. Scientif., 1909, 23, 173; Chem. Zeit. Rep., 1909, 33, 192.)-The photographic developer rnetol (methyl-pamidophenol sulphonate) ought not to contain any p-amidophenol sulphonate, sihce solutions prepared from it then readily undergo decomposition. As a test of its purity 1 gram of the sample is treated with 2 to 3 C.C. of concentrated hydrochloric acid, and should dissolve completely. The other compound is insoluble in hydrochloric acid. C. A. M. Colour Reactions of Sesame Oil with Aromatic Aldehydes. C. Fleig. (Ann. de Chim. anal. AppZ., 1909, 14, 132-138.)-1n a previous communication (ANALYST, 1908, 33, 480) the author showed that colorations were produced by many aromatic aldehydes with sesame oil. Those giving the most characteristic reactions are parahydroxybenzaldehyde (intense gooseberry red) ; protocatechuic aldehyde and vanillin (peach colour, changing to gooseberry red or deep violet) ; anisic aldehyde (gooseberry red) ; piperonal (bluish-violet or bluish-green) ; and cinnamic aldehyde (cherry red).Some of these reagents are capable of detecting from 1 to 5 per cent.286 THE ANALYST. of sesame oil in admixture with other oils. Salicylic aldehyde, benzaldehyde, orthonitrobenzaldehyde, and paradimethylaminobenzaldehyde also give pronounced colorations, but are less sensitive than the preceding reagents, whilst metanitrobenz- aldehyde, cinnamic aldehyde, and paranitrobenzaldehyde are still less sensitive. The test is best applied by adding 0 - 2 to 0.4 C.C. of a 2 to 4 per cent. solution of the aldehyde in 90 to 95 per cent.alcohol, to 10 C.C. of the oil and 10 C.C. of hydro- chloric acid (21O to 22O Be.), shaking the tube vigorously for about a minute, and noting the colour of the lower layer that separates on standing. Distinctive colorations may also be obtained by applying the test to an extract obtained by shaking sesame oil with its own volume of strong alcohol. Sulphuric acid may take the place of hydrochloric acid in the test, but the colorations are in some cases less intense. The colorations obtained with an alcoholic extract of sesame oil are more stable than those given by the oil itself, and might probably be made the basis of colorimetric method of estimating sesame oil in mixtures. C. A. M. On Schulz's Colour Reaction for Mineral Oils.C. Krauz. (Chem. Zeit., 1209, 33, 409.)-The author shows that the red colour given with mineral oils by a, solution of commercial picric acid in benzene is due, not to any impurity in the picric acid, as stated by Schulz, but to the picric acid itself. The same reaction is, however, also obtained with the other nitro-phenols. The author also points out that the picramine and potassium cyanide reactions, usually regarded as characterising picric acid, are also given by the other nitro-phenols. A. G. L. The Colorimetric Estimation of Pitch in Fuel Briquettes. K. Leo. (Chem. Zeit., 1909, 33, 359-360.)-A rapid colorimetric method is based upon the fact that benzene dissolves the bitumen in pitch, forming a brown solution, t h s intensity of the colour of which is proportional to the amount of bitumen.A standard 5 per cent. solution of pitch for the comparison is prepared by mixing together 0.05 gram of pitch and 0-95 gram of finely powdered cod, and boiling the mixture with 200 C.C. of colourless benzene for exactly thirty minutes under a, reflux condenser. The liquid is then cooled and rapidly filtered, and 50 C.C. of the filtrate kept in a stoppered flask. One gram of the finely powdered briquette sample is treated in the same way, and the colour of the two filtrates matched in a colorirneter by the addition of measured quantities of benzene to the darker liquid. The accuracy of the method is shown by test experiments in which two samples containing 7 per cent. of pitch were found to contain 6.9 and 7.0 per cent.respectively. C. A. M. The Composition of African Balsam Oil. H. von Soden. (Chem. Zeit., 1909, 33, 428.)-A sample of African balsam yielded on distillation with steam about 45 per cent. of a colourless oil with a, slight odour. It had a, specific gravity of 0.9215, a rotation of [aID= +2l0, boiled at 266" to 270" C., and apparently con- sisted in the main of sesquiterpenes (CI5H2J. Another sample of the balsam yielded an oil with similar characteristics : Specific gravity, 0.920; [uID = + 16" 50' ; ester value, 5.6 ; and acetyl value, 10. From the results obtained by partial saponificationTHE ANALYST. 287 with 5 per cent. alcoholic alkali and distillation with steam, this oil appears to consist chiefly of dextro-rotatory cadinene. Thus the main fraction, obtained by fractional distillation in vacuo, boiled at 269" C.under ordinary pressure, and had a epecific gravity of 0.9225 and an optical rotation of [a], = + 55". It yielded a hydro- chloride melting at 116" to 119" C., which in 10 per cent. benzene solution had a rotation of [u],, = about - 3O. The hydrocarbon recovered from the hydrochloride by boiling with glacial acetic acid and sodium acetate and distillation with steam had a specific gravity of 0.930, an optical rotation of [a],= -97" 30', and a boiling- point 274" to 275" C. In this reaction of the hydrochloride with sodium acetate an ester of acetic acid appears to be formed as the primary product, and then to be decomposed into acetic acid and a sesquiterpene (Lcadinene). This was confirmed by saponifying the crude sesquiterpene and distilling the product with steam, the product having the following characteristics, in close agreement with those of I-cadinene : Specific gravity, 0.928 ; - 94' ; and boiling-point at 743 mm., 274.5" to 276' C.C. A. M. A Colour Reaction of Colophony. J. Sans. (Ann. de Chim. Anal. AppZ., 1909,14, 140-141.)-When colophony, or a substance such as soap containing it, is gently heated with a little methyl sulphate, a coloration changing from rose to deep violet is obtained. If the temperature of the liquid be now increased, the colour fades to a light brown tint. This reaction, which is given by substances containing only a trace of colophony, is more characteristic than Liebermann's reaction, and more simple than Halphen's test (ANALYST, 1909, 108).Ethyl sulphate may take the place of methyl sulphate in the test, the reaction apparently being brought about by the action of the traces of free sulphuric acid in these compounds upon the organic matter. Conversely, the reaction may be used as a test of the degree of purity of methyl or ethyl sulphate. C. A. M. Caucasian Copal. E. Pyhala. (Chem. Rev. Fett- QL. Ham-Id., 1909, 16, 72.) -In 1907 deposits of fossil resin were discovered near Schuscha in South Caucasus, and samples of this resin examined by the author were found to contain copal resin, either in the form of small, round, transparent fragments, or of large irregular opaque pieces ranging from yellow to dark brown in colour. The copal was very hard, and had a specific gravity of 1.0574 at 18OC.It burned with a somewhat hissing flame, and then emitted an aromatic odour, although in the cold it was odourless and tasteless. I t showed signs of melting at 200" C., but was not com- pletely fluid below 250" C. At about 180" to 200" C. it became elastic, but was brittle again after cooling. On dry distillation the transparent modification yielded 25 per cent. of a light yellow distillate at 240" to 250' C.; 27.14 per cent. of a brownish-yellow distillate at 270"to 280" C., and 10 per cent, of a red-brown distillate at 300° to 330" C. The residual coke was 18.0 per cent., and water and loss were 19-86 per cent. The opaque modification yielded 58-75 per cent. of distillate, 26.25 per cent. of coke, and 15 per cent. of water (and loss). All the distillates had an aromatic odour.The resin was insoluble in petroleum spirit, methyl, and ethyl alcohols, sparingly soluble in turpentine oil, but readily soluble in chloroform. The288 THE ANALYST. distillates from the dry distillation were only slightly soluble in 95 per cent. alcohol, but dissolved readily in petroleum spirit, benzene, turpentine oil, and chloroform. C. A. M. Detection and Estimation of Dammar Resin in Kauri Resin. S. Stewart. (J. SOC. Chent. Ind., 1909, 28, 348-351.) - The ethereal or chloroform solution of kauri resin is not precipitated by alcohol, whereas that of dammar resin yields a curdy white precipitate, and this difference in their action to solvents forms the basis of the proposed method. Qualitatively, the method is carried out by treating 0.5 gram of the finely-ground sample with chloroform, filtering the solution, and adding absolute alcohol.The liquid remains clear if kauri only be present, but a cloudiness or precipitate indicates dammar resin. A fairly accurate estimation of small quantities of this admixture may be made by preparing a standard mixture containing 1 per cent, of the “white substance,” and treating the mixture as described, comparing the amount of white precipitate obtained in the sample with the standard. For the more accurate estimation of larger quantities of dammar resin in kauri resin, the author extracts 2.5 grams of the carefully sampled and finely-ground resin in a Soxhlet apparatus with absolute alcohol for several hours. I n the case of pure kauri resin only vegetable fibre and mineral matters are left insoluble, the percentage of pure resin being obtained by difference.In the case of dammar resin, or a mixture containing it, the residue will contain also a white substance, which is readily dissolved by chloroform ; the solvent is then distilled off, and the residue weighed after moistening with absolute alcohol, and drying at 100” C. Dammar resin contains about 50 per cent. of the white substame obtained by the above method, and this figure may be taken as a basis for calculating the approximate amount of adulterant (dammar resin). Where possible it is preferable to pick out a few lumps of the suspected resin, rub them separately on a glass plate with a drop of chloroform, and add a drop of absolute alcohol, when the white precipitate will be obtained in the case of any lump consisting of dammar resin.With lumps so isolated, the amount of white substance in the specimen of dammar present is determined by the foregoing method, and also the amount of this substance in the whole sample, from which data the proportion of dammar resin in the mixture can be calculated. The following results were obtained : Kauri Dammar Resin. Resin. Soluble in absolute alcohol ... ... 91.56 ... 58-28 Insoluble in alcohol, soluble in chloroform None ... 36.40 Vegetable matters.. . ... ... ... 3.28 ... 3.24 Mineral matters ... ... ... ... 5.16 ... 2.08 100~00 100~00 Dammar per cent. (calculated) ... ... ... ... Mixture, 80 per Cent. Kauri, and 20 per Cent. Dammar. ... 85.82 ... 7.30 ... 2.38 ...4-50 100-00 20.05 A. R. T. -THE ANALYST. 289 Shellac Analysis. H. Endemann. (Zeit. angew. Chem., 1909, 22, 676-677.) -The author makes a few supplementary remarks on the method of analysis described by him in a previous paper (ANALYST, 1907, 32, 425). The direction to dry the shellac, after dehydration by means of hydrochloric acid, by heating for two hours st 100” to 1 0 2 O C., must be strictly observed ; the temperature of s water-bath is not sufficient. Insufficient heating is recognised by the evaporated residue from the alcoholic solution not being clearly resoluble in alcohol, even after the addition of a drop of hydrochloric acid. I n such cases the drying must be repeated with a further quantity of acid, after powdering the residue as finely as possible.The test for rosin, described Zoc. cit. by means of sulphuric acid and sugar, is meant to be carried out on this alcoholic extract, not on the original sample. In the latter case the colouring matter inhibits the test, unless it be previously destroyed. Further experience has confirmed the author’s observation that all pure and genuine shellacs show very little deviation from the prescribed (‘ normal ” of 8 per cent. soluble in alcohol. Seed-lacs, however, are exceptional, and sometimes contain as much as 16 per cent., because seed-lacs contain impurities, such as fat and salts, which increase the alcoholic extract. When shellac is prepared from seed-lac the impurities are strained off, and the residue is sold as shellac refuse,” containing about 70 per cent.of shellac and fat. This refuse, when powdered, looks like good shellac, and is only recognisable either by analysis or microscopic examination. J. F. B. The Commercial Control of Tannery Lime Liquors. H. G. Bennett. (J. SOC. Chem. I d , 1909, 28, 292-293.)-The author proposes a method for esti- mating the weakly basic substances, such as peptones, calcium salts of amino acids and other weak acids, amines, and a certain quantity of ammonia, which are formed in the lime liquors employed for the depilation of hides and skins. These weak bases, resulting from the decomposition of the protein matter of the skin, are proportional to ‘‘ the dissolved hide substance,” and to the bacterial activity and ‘‘ mellowness ” of the lime liquor. The process consists in titrating 25 C.C.of liquor with ;c hydro- chloric acid in the presence of phenolphthalein until the pink colour just disappears; methyl-orange is then added, and the titration continued until the indicator first distinctly changes to red. The difference between the two titrations represents the amount of weak bases present. The following results were obtained with a series of lime liquors, using the above method, and also by estimating the nitrogen by Kjeldahl’s method and by the formaldehyde method (see following abstract). The figures express C.C. of & solution. 1. Titration difference 2. Ammonia by 3. Formaldehyde Ratio of Column 3 for 25 C.C. of Liquor. Kjeldahl Process. Method. to Column 1. 4.10 2.80 2.80 0.68 5-37 3.50 3-55 0.68 11-00 7.45 7-50 0.68 11.75 8.05 8.10 0.68 13.50 9.05 9.10 0.67 These results show that 1 C.C.titration difference corresponds with 0.0053 gram of dissolved hide substance. In the case of liquors containing large quantities of sodium sulphide, the most useful figure will be the total alkalinity to methyl-orange. w. P. s.290 THE ANALYST. Method for the Estimation of Nitrogen in Organic Substances, and in particular for the Estimation of Hide-Substance in Leathers and of Dissolved Hide-Substance in the Soak Liquors and Lime Liquors of the Leather Factory. H. G. Bennett. (J. SOC. Chem. Ind., 1909, 28, 291-292.)--In the method proposed the substance under examination is digested with sulphuric acid as in the ordinary Kjeldahl process, and the quantity of ammonia formed is then estimated by the use of formaldehyde as described by Ronchese (ANALYST, 1907, 32, 303).The procedure is as follows : A weighed quantity of the sample is heated with sulphuric acid until a clear solution is obtained, and the excess of sulphuric acid is neutralised by the addition of sodium hydroxide solution, using phenolphthalein as indicator. Neutral formaldehyde solution is now added, and the sulphuric acid, liberated from the ammonium sulphate owing to the formation of hexawethylene- tetramine, is titrated with & alkali solution. The reaction between the aldehyde and the ammonium sulphate proceeds according to the equation : S(NH,),SO, + 6H.CHO = 2H,SO, + N(CH,.N:CH,), + 6H,O. The quantity of nitrogen present in the sample is calculated from the quantity of alkali required for the titration. The results obtained by the method in the case of leather agree within 0.04 per cent. with the figures given by the ordinary Kjeldahl process. w. P. s. Detection of Sulphite-Cellulose Liquors in Tanning Extracts. H. R. Procter and S. Hirst. ( J . SOC. Chem. Ind., 1909, 28, 293-294.)-Waste calcium bisulphite liquor, which has been used to remove the ligneous constituents of coniferous woods in the manufacture of paper pulp, may be concentrated under reduced pressure, and then yields an extract very similar in appearance to that of oakwood. Such an extract has been put on the market under the name of “ Pinewood ” or “ Fichtenholz,” and contains about 25 per cent. of tanning matter or substance absorbed by hide. The extract is, however, an unsatisfactory tanning material, especially when used alone, and the following test is given for detecting the presence of sulphite extract in ordinary tanning extracts : Five C.C. of the extract solution under examination are shaken with 0.5 C.C. of aniline, and 2 C.C. of concen- trated hydrochloric acid are added to the mixture. With all ordinary extracts this has the effect of immediately clearing the turbidity caused by the aniline ; but where pinewood (sulphite) extract is present even in comparatively small quantity, a precipitate is rapidly produced which rises gradually to the top of the liquid. Any precipitate which forms after a time is to be ignored. w. P. s.

ISSN:0003-2654    

DOI:10.1039/AN9093400282

出版商:RSC    

年代:1909

数据来源: RSC

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290 THE ANALYST. INORGANIC ANALYSIS. Estimation of Aeids in Hydrogen Peroxide. H. Endemann. (Zed. angew. Chem., 1909, 22, 673-674.)-Hydrogen peroxide nearly always contains appreciable quantities of acid, added for the purpose of increasing its stability. The quantity of acid present in pharmaceutical preparations should be as small as possible, and is generally estimated by titration with sodium hydroxide in presence of phenol-THE ANALYST, 291 phthalein. The author has observed, however, that decomposed samples of hydrogen peroxide apparently contain far more acid than the same samples in the fresh condition. If the estimation be effected by adding excess of alkali and titrating back, the same result is obtained as by direct titration. This value only corresponds to one-half of the true amount of free acid present.I n order to determine the whole of the acid, it is necessary to add excess of standard sodium hydroxide, heat the liquid in a platinum dish until the hydrogen peroxide is completely decomposed, and titrate back with acid in presence of phenolphthalein. Glass vessels are not suitable unless a piece of platinum wire be present to eifect the catalytic decomposition of the peroxide. For technical purposes it is sufficient to multiply the acidity, found by direct titration in the cold, by 2. The explanation of the anomaly observed by the author in the titration of the acids in hydrogen peroxide is found in researches of Tafel. When sodium hydroxide is added to hydrogen peroxide, sodium peroxide is formed, which immediately splits up into a perhydroxide and ordinary hydroxide, thus : Na202 + H,O = NaOOEI + NaOH.The latter, of course, has an alkaline reaction towards phenolphthalein, but the perhydroxide is neutral. The latter reacts with concentrated hydrochloric acid in alcoholic solution, giving a sodium oxychloride, NaOCl, which is not identical with sodium hypochlorite. J. F. B. Direet Volumetric Method for the Estimation of Alumina. W. H. Seamon. (Western Chemist and Metall., February, 1909 ; Chem. Engineer, 1909, 9, 116.)-The precipitate of alumina, and iron oxide, obtained as usual, is dissolved in the smallest possible quantity of concentrated hydrochloric acid. To this solution 2 to 5 grams of sodium peroxide are added, so as to yield it strongly alkaline solution containing aluminium as aluminate.The solution is filtered from ferric hydroxide, and exactly neutralised with hydrochloric or sulphuric acid, after the addition of phenolphthalein. The liquid is then heated slmost to boiling, methyl orange is added, and then standard sulphuric acid, until the aluminium hydroxide previously precipitated is entirely redissolved, and a permanent acid reaction is obtained. The quantity of standard acid used corresponds to the alumina present. The method is inapplicable in the presence of lead or zinc. Sodium peroxide is used to make the solution alkaline, instead of sodium hydroxide, on account of its greater purity. A. G. L. Separation of Antimony from Tin. G. Panajotow. (Ber. deut. Chem. Ges., 1909, 42, 1296-1299.)-The quantitative separation of antimony and tin is one of the most difficult in analytical practice.Of the methods hitherto proposed, that of Vortniann and Metzl (ANALYST, 1905, 30, 281) is the simplest, and gives useful results. The author, however, has found that a ready means for the separation of the sulphides of these two metals may be based on their different solubilities in hydrochloric acid of different concentrations. Antimony sulphide, though soluble in hot concentrated hydrochloric wid, is insoluble in the 15 per cent. acid, whilst tin292 THE ANALYST. sulphide is completely soluble. When both metals are present in an acid solution of such concentration, saturation with hydrogen sulphide at the ordinary tempera- ture throws out a little of the tin sulphide in association with the antimony, but this may be avoided by performing the precipitation at a temperature of 50" to 60" C.A mixture of antimony and stannic salts is treated with strong hydrochloric acid sufficient to give a concentration of 15 per cent. of the acid. The beaker containing the solution is then placed in a water-bath, and the temperature is maintained at 50° to 60' C.; a strong current of hydrogen sulphide is then passed through the liquid for thirty minutes, and the antimony sulphide separates readily as a scarlet precipitate. The liquid is then cooled below 30" C., and a moderate stream of hydrogen sulphide is passed for ten minutes. The clear liquid is decanted off through a Gooch crucible, previously dried at 110' C. and tared. The precipitate is rapidly collected, washed with 50 C.C.of 15 per cent. hydrochloric acid saturated with hydrogen sulphide, then with water and hydrogen sulphide, and then in succession with alcohol, a mixture of alcohol and carbon bisulphide, carbon bi- sulphide, again with alcohol, and finally with ether. I t is dried at l l O o C. and weighed. The tin remains in the filtrate, which is partially neutralised with ammonia, diluted with water, warmed and saturated with hydrogen sulphide. The results are exact, and are independent of the relative quantities of the two metals. The method is applicable in all cases where antimony is present in the form of a solution of the trioxide. J. F. B. Volumetric Estimation of Small Quantities of Arsenic. L. W. Andrews and H. V. Farr. (Zeit.anorg. Chem., 1909, 62, 122-128.)-The method proposed is an application of Bettendorff's reaction (Zeit. aaal. Chem., 1869,9,105), and consists in precipitating the arsenic in the metallic state by means of stannous chloride; the arsenic is then titrated with iodine and thiosulphate solution. The process is suitable for estimating quantities of arsenic ranging from 0.1 to 100 mgm. The method of operating is as follows : The arsenical solution under examination is neutralised, evrllporated to a volume of about 15 c.c., and transferred to a flask of about 100 C.C. capacity. To the solution is added 2.5 times its volume of stannous chloride solution, prepared by dissolving 20 grams of crystallised stannous chloride and 40 grams of tartaric acid in 1 litre of concentrated hydrochloric acid (containing 40 per cent. HCI) ; the flask is then closed securely, and its contents are kept at a temperature of about 40° C.until the precipitated arsenic has settled down, leaving the supernatant liquid quite clear. This usually takes about three hours. The precipitate is then brought on to an asbestos filter by the aid of small quantities of concentrated hydrochloric acid (free from chlorine), and the flask, precipitate, and filter are next washed completely with water. Air should be excluded as far as possible from the precipitate during the filtration. An excess of about 100 per cent. of the quantity of & iodine solution required for combination with the arsenic, as shown by the equation : As + 51 + 7NaHC0, = Na,HAs04 + 5NaI + 7C0, + 3H,O, is added to the flask, and the filter and precipitate are then introduced.Sufficient 5 per cent, sodium hydrogen carbonate solution is added to keep the mixture neutralTHE ANALYST. 293 during the reaction, but an undue excess is to be avoided. The mixture is thoroughly shaken, and the excess of iodine is then titrated back with + thiosulphate solution, using starch solution as indicator. For quantities of arsenic of less than 0-5 mgm., & iodine and thiosulphate solutions may be used, but a correction should in this case be made for the amount of the iodine solution required to give a reaction with the starch solution. iodine solution is equivalent to 0.15 mgm. of arsenic. Results of estimations, in which quantities of arsenic varying from 0.375 to 75.0 mgm.were taken for the experiment,lshow that the accuracy of the method lies Each C.C. of within limits of kO.8 per cent. w. P. s. An Acidimetric Method of Estimating Alkali Iodides. E. Rupp and F. Pfenning. (Arch. Pharm., 1909, 247, 108-110.)-Mercuric cyanide is readily decomposed by potassium iodide with the formation of a compound iodo-cyanide, in which the alkali cyanide component may be titrated with acid. The following reactions take place : 2Eg(CN), + 2KI = Hg(CN),.Hg12.2KCN. Hg(CN),.Hg12.2KCN + 2HCl= Hg(CN), + HgI, + 2KC1+ SHCN. In making an estimation, the precipitation of the mercuric iodide prevents the recognition of the end-point, and it is therefore necessary to add an excess of acid and to titrate back an aliquot portion of the filtrate with normal alkali solution.Leaving out of consideration the mercuric cyanide in the triple salt, the reaction taking place may be represented by the formula : Hg(CN), + 2KI + 2HC1= HgI, + SHCN + 2KC1. From 1 to 2 grams of mercuric cyanide are dissolved in 50 C.C. of water, and 10 C.C. of a 10 per cent. potassium iodide solution added. Any crystals of the triple salt that separate are dissolved by the addition of more water, and the liquid mixed with 20 C.C. of Fifty C.C. of the filtrate are titrated with The results thus obtained with a solution of known strength ranged from 99.8 to 100 per cent. of the theoretical amount. The presence of chlorides does not interfere with the results ; on the contrary, a small addition of potassium chloride accelerates the filtration.Bromides, however, have a disturbing influence, and must be removed beforehand. C . A. M. hydrochloric acid, made up to 100 c.c., and filtered. alkali solution with methyl orange as indicator. Volumetric Estimation of Mercuric Salts. L. W. Andrews. (Zeit. anorg. Chem., 1909, 62, 171-172.)-1t is pointed out that the process described by Morawitz (ANALYST, 1909, 73) consists essentially in titrating the acidity of the solution with potassium cyanide solution, whilst in the process described by the author (ibid., 1903, 28, 323) sodium hydroxide is employed for the titration. The author sees no advantage in the modification proposed by Morawitz, as the older process is known to give trustworthy results. The end-point of the reaction is sharply defined, and it is difficult to underetand how the addition of 10 drope of TT hydrochloric acid to the mercuric chloride solution, as recommended bg294 THE ANALYST.Morawitz, can have any favourable effect on the reaction or the titration, seeing that hydrochloric acid is liberated in considerable quantity in the solution as the result of the reaction. w. P. s. Comparison of the Electrolytic, Brunck, and Grassmann Methods for the Estimation of Nickel in Steel. Prettner. (Chem. Zeit., 1909, 33, 396 and 411-412.)-According to the author, the electrolytic estimation of nickel is $00 tedious for use in steel analysis. He removes iron by extraction with ether before eleotrolysis, electrolyses in ammoniacal solution for twenty-four hours, filters off the manganese hydrate, again electrolyses the filtrate with a clean cathode to recover the last traces of nickel, and examines the deposits for the small quantities (0.1 to 0.2 per cent.) of manganese they contain.Estimation by means of dicyandiamidine or dimethylglyoxime is much simpler. With the first reagent, to which a little hydrazine sulphate should be added to reduce manganese, precipitation is absolutely complete only after forty-eight hours’ standing ; the second reagent gives com- mercially useful results after one hour’s standing, and exact results after twenty-four hours’ standing. Since the volumetric potassium cyanide method yields accurate results much more quickly, these methods will be used in Ateel and ore analysis chiefly il cobalt is also present. A. G. L. The Estimation of Nitrogen in Nitrates by Means of Stannous Chloride and Iron Filings.A. Kleiber. (Chem. Zeit., 1909, 33, 479.) -Ten grams of substance are dissolved in water and made up to 150 C.C. To 7.5 C.C. of the solution in a 700 to 1,000 C.C. distilling-flask are added 5 grams solid commercial stannous chloride, 15 C.C. concentrated hydrochloric acid, and 4 to 5 grams iron filings; the mixture is heated for fifteen minutes on a water-bat%, or on a wire gauze over a small flame. 90 to 100 C.C. water, a piece of paraffin wax, if necessary, as large as a pea, and about 40 C.C. of concentrated caustic soda solution, are added, and distillation effected with a large flame from the beginning, so that it is complete in half an hour. Twenty C.C. of seminormal sulphuric acid are placed in the receiver. The ammonia left behind in the distilling-flask is found to be constant in amount, and may be allowed for by deducting 0.2 from the number of cubic centimetres of baryta solution used in titrating back.The results are satisfactory. 0. E. M. The Reduction and Estimation of Perchlorates. V. Rothmund. (Zeit. anorg. Chem., 1909,62,108-113.)-Whilst perchlorates are not attacked by the usual reducing agents, such as sulphur dioxide, iron, zinc, sodium amalgam, etc., they are reduced comparatively quickly by titanous salts, and the following method, based on this fact, is described for their estimation : A solution of the perchlorate is mixed with an excess of titanous sulphate solution containing sulphuric acid, 4 C.C. of concentrated sulphuric acid are added, and the mixture is boiled under a reflux condenser for one hour, carbon dioxide being passed through the flask during the whole time.After cooling, the excess of titanous chloride is oxidised by the addition of potassium permanganate, and the chlorine is then estimated by Volhard‘s method. The reduction may be effected by the use of standardised titanous sulphate solution,THE ANALYST. 295 and the excess ti trated back with standardised ferrous ammonium sulphate solution, but in this case the greatest care must be taken to exclude sir from the apparatus during the whole operation. Vanadium and molybdenum salts also reduce prchlorates, tungsten salts act similarly but much more slowly, whilst chromium salts have no reducing action. w. P.s. The Quantitative Separation of Sulphates and Fluorides. R. Ehrenfeld and A. Indra. (Chem. Zeit., 1909, 33, 375-376.)-1n the presence of fluorides sulphates are estimated by mixing the sample with ten to twenty times its weight of zinc-dust in a Rose crucible, covering the whole with a layer of zinc-dust, and igniting over a Teclu or blast-lamp for thirty minutes in a current of hydrogen or coal-gas washed with lead acetate solution. After cooling in the reducing atmosphere, the contents of the crucible are transferred to a flask in which the sulphide formed is decomposed by dilute sulphuric acid, the evolved hydrogen sulphide being absorbed by standard iodine solution. A current of carbon dioxide is led through the flask during the whole operation. To diminish the attack on the glass by the hydrogen fluoride formed, several grams of a mixture of equal parts of precipitated silica and finely divided alumina are placed in the flask.The standard iodine solution used must be neutral; if it is alkaline, high results are obtained. The results obtained are accurate to about 0.4 per cent. on the sulphate present. A. G. L. The Electrolytic Estimation of Thallium. G. Gallo and G. Cenni. ( G a m Chim. Ital., 1909, 39, 285-296.)-The electrolytic estimation of thallium presents difficulties, owing to the fact that thallium has a tendency to separate from solutions of its salts partly in the form of the metal on the cathode, and partly as an oxide upop the anode. In the following method it is deposited completely as an oxide upon the anode.The solution of the thallium salt (sulphate), containing about 0.3 to 0.6 gram i n 100 c.c., is acidified with about 0.1 gram of oxalic acid, and electrolysed at the ordinary temperature in a Classen's dish, in which a disc of platinum is made to rotate as the negative electrode. If the speed be kept at about 800 revolutions per minute, any deposition of thallium upon the cathode is prevented. A current of from 3 to 4 volts and 0.15 to 0.20 ampere is used for the electrolysis. After about an hour the deposition of the thallium oxide begins, and it is advisable t9 continue the electrolysis overnight. The black deposit is washed by decantation with water, with alcohol, and with ether, and then dried in the dish, until constant in weight, in a well-closed air-oven maintained at a temperature of 160" C., and in the lower part of which is a uniform layer of soda-lime.From a series of experiments, the authors conclude that the deposit consists of a new oxide of thallium, T1,0,, which contains 88.48 per cent, of thallium. Applying this factor to the varying quantities of the deposit obtained as described above, the amounts of thallium found in eight test estimations in no case differed by more that 0.0005 gram from the theoretical quantities. C. A. M. Estimation of Tungsten. M. Tschilikin. (Ber. deut. Chem. Ges., 1909, 42 1302-1304.)-Knorre (Ber. deut. Chem. Ges., 1905, 38, 783) described a method for the296 THE ANALYST. estimation of tungsten by means of benzidine hydrochloride ; the author has found that a-naphthylamine is equally suitable for the purpose.The reaction takes place at the ordinary temperature, and gives quite satisfactory results. The benzidine salt should be recrystalliaed from water, and the a-naphthylamine from light petroleum Sodium tungstate, Na2W0, + 2H20, was employed for the tests. The composition of the benzidine compound corresponds with the formula 2(C,,H,,N2).5W0,.5H20. The combination with a-napthylamine has the composition 2(C,,H,N).5W0,.3H20~ For the precipitation of the tungsten, a solution of 25 grams of the amine and 1.5 grams molecular weight of hydrochloric acid are dissolved in water and diluted to 1 litre. To 100 C.C. of this reagent, 25 C.C. of a 2 per cent. solution of sodium tungstate are added at the ordinary temperature. The mixture is allowed to stand for three hours, the precipitate is filtered off and washed with the amine solution diluted with five times its volume of water.The moist filter is then incinerated, and the residue weighed as tungstic anhydride. J. F. B. Test for Nitrites in Potable Waters. A. Rochaix. (L’Union Pharm-, 1909, 50, 62; Pharm. J., 1909, 82, 494.)-Neutral red (toluol red, or symmetric dimethyl-diamino-toluol-phenszine hydrochloride) gives, with a minute quantity of nitrous acid, a blue colour, and may be employed for the detection of this acid in waters. A 0.02 per cent. solution of neutral red is used, 20 C.C. being added to 10 CA. of the water, together with 1 to 3 C.C. of 20 per cent. sulphuric acid. The colour changes from violet to bright blue on shaking, if nitrous acid be present.Strong sulphuric acid will itself give the blue colour with the reagent. If the water be alkaline, a yellow colour may first be seen, but this does not interfere. 0.05 mgm. of nitrous acid per litre of water may be detected by this test. A. R. T. Analytical Examination of Metallic Zirconium. E. Wedekind and S. J. Lewis. (Zeit. nngew. Chew., 1909, 22, 725-729.)-To estimate metallic zirconium in samples of commercial zirconium, 0.5 gram of the sample is placed in a boat in a combustion-tube, and first thoroughly dried, either in a stream of pure hydrogen, or else by evacuating the tube; the moisture may amount to 3.5 per cent. Without admitting even a trace of air, pure chlorine, made from hydrochloric acid and permanganate, and dried by means of sulphuric acid, is then led into the tube, the boat part of which is gradually heated to a red heat, the volatilised zirconium tetrachloride being partly collected in the cooler parts of the tube, and partly in 8, remiver containing dilute hydrochloric acid, and cooled by ice.The boat is then withdrawn from the tube, and the contents of the latter dissolved in water and filtered, together with the solution in the receiver, to free them from any traces of oxide mechanically carried out of the boat. The oxide left in the boat is also thoroughly washed on the same filter to remove traces of chloride left behind ; it is then ignited and weighed, representing the oxide originally present in the sample. The zirconium in the solution is precipitated by adding a considerable excess of strong ammonia and a little ammonium chloride ; the hydroxide obtained is ignited to oxide and weighed. It represents zirconium originally present as metal and as nitride.THE ANALYST. 297 Carbon is estimated by igniting another portion of the sample in oxygen, and weighing the carbon dioxide as usual. On account of the violence of the reaction, the combustion is commenced under highly reduced pressure, oxygen then beiug gradually admitted until the interior of the combustion-tube is again under normal pressure, when the operation is finished as usual. Hydrogen is estimated in the same manner as carbon. Nitrogen is detected as ammonia on fusing the sample with pure sodium hydroxide, or after dissolving it in boiling sulphuric acid. Nitrogen is estimated quantitatively by dissolving in boiling sulphuric acid to which a little hydrofluoric acid or persulphate is added, as solution in pure sulphuric acid requires several days ; the ammonia formed is distilled as usual. The samples examined contained 25 to 84 per cent. of metallic zirconium, besides 12 to 54 per cent. of combined zirconium, 4 to 19 per cent. of oxygen, and nil to 2 per cent. and more of nitrogen. One sample, made by a magnesium process, contained also 0.074 per cent. of carbon and 0.28 per cent. of magnesium. In two samples the hydrogen amounted to about 0-2 per cent. A. G. L.

ISSN:0003-2654    

DOI:10.1039/AN9093400290

出版商:RSC    

年代:1909

数据来源: RSC

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THE ANALYST. 297 APPARATUS, ETC. New Apparatus for the Estimation of Carbon. A. Kleine. (Clz,enz. Zeit., 1909, 33, 376.)-The wet combustion apparatus shown in the first figure is characterised by the fact that the condenser carries both air- entry and gas-exit tubes. The air-inlet tube is provided with an opening through which air can enter the flask even when the bend of the tube is stopped up by chromic acid. The basket carrying the sample is suspended from EL projection on the same tube in such a way that it remains suspended by its longer wire after it has been inverted by inclining the flask. The soda-lime phosphoric anhydride tube shown in the second figure is provided with a glass disc in one of its limbs, as shown. Through this glass disc go three short tubes, on which is placed an asbestos plug, and above this phosphoric pentoxide, the remainder of the tube being filled with soda-lime.The tube can still be used even after the asbestos has become moist with phosphoric acid, as the glass disc prevents contact with the soda-lime. A. G. L. FIG. 1. W FIG. 2. The Emerson Fuel Calorimeter. C. J. Emerson. (The Chem. Eyi?zeer, 1909, 9, 113-114.)-The calorimeter is of the bomb type, and differs from existing intruments in being made in two cup-shaped pieces, held together by a large nut at298 THE ANALYST, the centre. The lower part carries the capsule, and is shaped so as to fit into a special holder without screwing, The calorimeter vessel is tapered to fit the lower part of the bomb, less water being required, aad a greater rise in temperature being obtained thereby.The pipe con- veying oxygen to the bomb is made of a short rigid piece of metal instead of the usual flexible tubing. It is stated that these modifications make the bomb more suitable for use by an inexperienced operator without impairing its accuracy. The lining is of porcelain or metal, as before. A. G. L. The Munroe Crucible. W. 0. Snelling. (J. Amer. Chem. Soc., 1909, 31, 456- 461.)-It is pointed out that C. E. Munroe was the first to describe a crucible of the Gooch type containing platinum sponge as the filtering medium (Chem. News, 1888, 58, 101). Such crucibles are prepared by precipitating a concentrated solution of chloroplatinic acid with a slight excess of ammonium chloride, washing the preci- pitate first with water and then with alcohol, and pouring it, to a height of 0-25 to 0.5 cm., into a platinum crucible with perforated bottom held firmly on a pad of several layers of filter-paper.As soon as the excess of alcohol has been absorbed by the filter-paper, the crucible is dried in a water-oven; cap and cover are then put on, and the crucible is cautiously heated to dull redness. 8hould the sponge so obtained show any cracks, it may be pressed together, or patched by adding fresh chloroplatinic acid and igniting. A firmer mat is obtained if a disc of fine platinum gauze is first placed in the bottom of the crucible ; a second similar disc may also be placed on top if the crucible is used for precipitates requiring mechanical removal. By gently rubbing the mat with a hard object a smooth polished surface is obtained, which sometimes is an advantage, but makes filtration slower.Platinum filters are generally much quicker than asbestos filters. A. G. L. Determination of the Specific Gravity of Small Quantities of Liquids. H. von Wartenberg. (Ber. deut. Chem. Ges., 1909, 42, 1126-1131.)-1t is some- times desirable to ascertain the specific gravity of a liquid of which only very small quantities are available. The author has applied to this purpose the ‘( micro- balance” of Nernst. After numerous attempts, he has succeeded in obtaining reasonably accurate results by the use of small capillary pipettes weighing, when empty, from 0.009 to 0.035 gram, and containing from 0.4 to 2 C.C. of liquid. The pipettes are of the usual shape, and are filled by inserting the bulb, by means of the forceps, in a rubber collar fixed in the end of a tube provided with a stopcock, and sucking the liquid up into the bulb. When the bulb is full, the stem of the pipette fills itself by capillary attraction. The pipette is then suspended on the micro- balance in a horizontal position by means of a wire support, and the deflection of the balance is observed. The determination is made more accurate by calibrating the balance with liquids of known specific gravities, within certain convenient limits, so that the pipette when filled with the lightest liquid stands at zero on the balance- scale, and shows the maximum deviation when it is filled with the heaviest liquid of the series.The smaller the range of the series selected, the greater is the accuracy of the determination, and the values of the scale readings, with the zero andTHE ANALYST.299 maximum points fixed by any given liquids, are plotted in the form of curves for reference. The error8 of working are caused, on the one hand, by volatilisation during weighing, since no caps can be carried on the pipette, and, on the other hand, by the presence of traces of liquid on the outside of the point of the pipette, The former error is only sensible in the case of liquids which are more volatile than water ; the latter error may be reduced in the case of aqueous liquids by drawing the point of the pipette between two slightlygreasy fingers. After a series of determina- tions, the zero point should again be checked by means of the lightest standard liquid of the scale, in order to see that the adjustment of the balance has not altered, With volatile liquids, such as ether and chloroform, the average error amounts to about +O-005 in the specific gravity.With aqueous liquids, a pipette of the maximum dimensions mentioned above, and a smaller range between the zero and the maximum points (1.0 to 1*5), the error can be reduced to about k0.00025. No special means are available for ascertaining the temperature of the liquid in the pipette, so that it is necessary to fill and weigh this at a constant temperature. J. F. B. A Compressed-Air Wash-Bottle. E. Dowzard. (Amer. J. Plzarm., 1909, 81, 174-176.)-This apparatus will be found useful where compressed air is available.A flask of 2 or 3 litres capacity is provided with a two-holed rubber stopper, as shown in the figure. A limb of the T-piece A passes through one perforation of this stopper ; this T-piece should have a horizontal tube twice the diameter of the vertical tube. The tube B nearly touches the bottom of the flask, its other end passing through the horizontal limb of the T-piece C, and being held in position by the stopper D The vertical limb of C is con- nected with A by the rubber tubing E. To the end of the tube B in the T-piece C any desired length of narrow rubber- tubing is attached (say about 2 feet), and a glass jet, F, is joined on the end. A piece E of rubber-tubing about twice the diameter of the narrow tube is passed over the latter and joined to the T-piece C at G. The other end is attached to the glass- tube H, which has a perforation, 6 mm. in diameter, at the side. The glass jet is fixed in this tube as shown by means of the stopper I. By means of hooked copper wire, this tube can be attached to the neck of the flask. The end of the T-piece A is connected with the compressed-air main by rubber tubing. When the air is300 THE ANALYST. turned on it passes out at H, but if H be closed by the finger, it passes into the flask and forces water out through the jet F, the force being regulated by allowing some air to escape at H if necessary. A. R. T.

ISSN:0003-2654    

DOI:10.1039/AN9093400297

出版商:RSC    

年代:1909

数据来源: RSC

摘要:

300 THE ANALYST. REVIEW. A COMPENDIUM OF FOOD MICROSCOPY. By E. G. CLAYTON. London: Bailliire, This work is stated to have been compiled largely from the works of the late Dr. A. H. Hassall, and constitutes a tribute to the memory of one to whom food analysts are more deeply indebted than they sometimes realise. The preparation of the book has evidently been a, labour of love, and the author has given a, brief summary of the life-work of Hassall, which will be read with interest by many. Whilst the microscopical portion of Hassall’s published works on the adulteration of food constitutes the basis of Mr. Clayton’s book, very numerous additions have, of course, been made, and the whole has been submitted to a thorough revision. The ground covered is very considerable, and there are very few substances likely to come into the hands of the Public Analyst which are not described in the 300 drawings with which the text is illustrated. The word ‘ 4 drawing” is used advisedly, since the author is of opinion that for the purposes of the food- microscopist careful drawings made with the aid of a camera lucida are much more useful than photo-micrographic reproductions. I n this there is a great deal of truth, since the observer can emphasise structures which are characteristic, and hence of diagnostic value, whereas the photo-micrograph is in a sense undiscriminating.But the observer who essays to guide us must be highly trained, discriminating, and accurate. On the whole, the illustrations afford abundant evidence of the possession by their authors of these high qualifications, and the book is one which cannot fail to be of great usefulness to every analyst who is called upon to pronounce an opinion on the purity of articles of food and drugs.There is also a section dealing with the -microscopical examination of water, which is well written, and which will be of u ~ e to many. The text is commendably free from typographical mistakes, and is clear and to the point. The wisdom of including a section in which certain proprietary foods are referred to by name may be questioned, since at the best these are of passing interest, and at the worst their inclusion may be thought to savour of advertisement. A few of the illustrations, notably some representing certain starches, are not really ( 6 convincing,’’ and it is not correct, in‘connection with Fig. 121, to speak of torulz as the spores of a fungus.” These, however, are small matters, and the book is one which may be safely commended to all who are interested in the microscopy of foods and drugs. A glossary of scientific terms and a bibliography are included, and there is an adequate index. A. CHASTON CHAPMAN, Tindall and Cox. 418 pp. Demy 8vo. 1909. Price 10s. 6d.

ISSN:0003-2654    

DOI:10.1039/AN9093400300

出版商:RSC    

年代:1909

数据来源: RSC