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JANUARY 1926. Vol. LI. No. 598, THE ANALYST PROCEEDINGS OF THE SOClETY OF PUBLIC ANALYSTS AND OTHER ANALYTICAL CHEMISTS. AN Ordinary Meetint of the Society was held a t the Chemical Society’s Rooms, Burlington House on Wednesday 2nd December 1925. Mr. S. F. Burford, F.I.C. Vice-president was in the chair. Certificates were read for the first time in favour of Messrs. Guy Chignell, K. Saito and Hugh Gower Watts. Certificates were read for the second time in favour of Messrs. John Douglas Barrett B.Sc. A.I.C. ; Arthur Frank Lerrigo B.Sc. F.I.C. Oscar Adolf Mendel-sohn B.Sc. Harold Edward Monk B.Sc. A.I.C. and Eric Voelcker A.R.C.Sc., -4. I. c . The following were elected Members of the Society :-Messrs. Alexander Bruce B.Sc. F.I.C. Sydney George Clarke B.Sc. A.I.C.Felix John Theodore Grigg M.Sc. A.I.C. John Hanley F.I.C. Arthur John Jones A.I.C. Henry William Lawrence F.I.C. Fred Mattingley B .Sc. A.I.C. Clive Newcomb I .M.S., M.D. F.I.C. Bartle Frere Sawbridge M.A. F.I.C. Harold Jacob Stem B.Sc., Ph.D. A.I.C. The following papers were read and discussed :-“ Measuring the Smoke Pollution of City Air,” by J. S. Owens M.D. A.M.I.C.E.; 2:4-Dinitrophenyl-hydrazine as a Reagent for the Detection of Aldehydes and Ketones,” by Oscar L. Brady D.Sc. F.I.C. and Gladys V. Elsmie; “The Determination of Phosphoric Acid as Magnesium Ammonium Phosphate ” by Gunner Jorgensen ; and “On the Effect of ‘Blowing’ on the Composition of Certain Fatty Oils,” by C. H. Thomson. NORTH OF ENGLAND SECTION. A MEETING of the Section was held at Leeds on November 21st 1925. The fol-lowing notes were read:-(1) “The Use of Jena Sintered-Glass Crucibles; (2) “The Reichert-Polenske-Kirschner Values of the Fat of Canned Milk and Cream,” by G. D. Elsdon B.Sc. F.I.C. Dr. J. T. Dunn initiated a discussion on the misdescription of foodstuffs.

ISSN:0003-2654    

DOI:10.1039/AN9265100001

出版商:RSC    

年代:1926

数据来源: RSC

摘要:

2 OWENS MEASURING THE SMOKE POLLUTION OF CITY AIR Measuring the Smoke Pollution of City Air. BY J. S. OWENS M.D. A.M.I.C.E. (Advisory Committee on Atmospheric Pollution.) (Read at the Meeting December 2 1925.) THE question is often asked What is the use of measuring the amount of smoke in the air? As this aspect of the problem appears to have much weight with the public it may be as well to specify clearly what we expect to gain by measurement. Broadly speaking in any investigation unless we can reduce the data to a quantitative value we do not get very far. It is also true that in few researches can the whole bearing or importance of the work be seen at ihe start and indeed, there would be very little original research work carried out if we waited to know the full bearing before doing anything.This necessarily follows from the fact that it is chiefly during the process of such research work that the practical bearings suggest themselves. To return to the measurement of smoke pollution It is necessary to bring out the extent of the evil and its incidence at different places but until the work of measurement had been placed on a reasonably sound basis we had no means of comparing cities with each other nor could we say if things were getting worse or improving. When efforts are made to purify the air it is advisable that we should be in a position to ascertain what degree of success attends these efforts. The demand for clean air in our cities will never be sufficiently imperative unless the public realise that there is a need for purifying the air similar to and just as important as that for providing pure water and food for human consumption.In the present paper the author does not propose to deal with the problem of measuring smoke from individual chimneys this is a problem in itself and one which urgently requires solution. Attention will be confined to methods of estimating the degree of smoke pollution of the air itself due to the combined effect of all the chimneys and other sources of pollution in a city. The methods hitherto adopted have been very numerous but we may divide them into two groups:-(1) Those aiming at measuring the deposit of impurity from the air; (2) Those which deal with the impurity while suspended in the air. DEPOSITED MATTER.-Attempts to measure deposit were made in 1902 in Manchester by Mr.W. Irwin (J. SOC. Chem. Ind. 1902,21 533) by estimating the amount of deposited matter contained in snow. He inferred that in ten days about 3.05 tons of soot fell per square mile or 30 tons per day on 100 square miles, with Manchester as centre. In 1906 Mr. F. W. Harris collected the deposit in Glasgow by exposing boxes during the winter. He calculated in this way that there was a soot fall of 896 tons per square mile per annum in Glasgow OWENS MEASURING THE SMOKE POLLUTION OF CITY AIR 3 Cohen (Smoke; A Study of Town Air Arnold 1912) measured the deposit in Leeds in 1907-08 in funnels 12 inches diameter obtaining 539 tons per square mile in the industrial district. Preliminary experiments were made by Des Voeux and the author (“Sootfall of London,” Lancet January 6th 1912) in 1910-11 in searching for a suitable method of measurement.The sootfall obtained in that year for different parts of London was 500 to 650 tons per square mile. SUSPENDED MATTER.-These attempts to measure the deposit from the air could not if successful tell the whole story as the very finely divided particles, of the order of 1 micron diameter settle so slowly through the air that the measure-ment of deposit could only deal with part of the impurity; there would remain the suspended matter kept up by turbulent air motion. Many efforts have been made in the past to devise methods of measuring this. These lend themselves to con-sideration under different headings :-IMPACT.-h most methods attempting to utfiise impact a stream of dusty air is forcibly directed against a surface specially prepared with some sticky material such as glycerin oil and so on.All such depend primarily upon the greater density of the particles causing them to be centrifuged out when the air is made to change its direction rapidly. An example of such is the Kotze koni-meter in which a jet of air is caused to strike a glass slide smeared with vaseline (Final Report of Miner’s Phthisis Prevention Committee Union of South Africa, 1919) and the dust spot so obtained is examined microscopically. As impact methods depend upon the superior density of the suspended par-ticles and the centrifugal force developed when these are caused to bend round a small radius the efficiency of such methods must be a function of the velocity .of the jet.When a particle of weight W moves in a path of radius R with a linear velocity V the centrifugal force developed is equal to:- WV2 gR The force projecting the particles against the glass therefore varies with the square of their velocity but if the jet velocity is sufficiently high to make the method efficient any adhesive used is blown away from the point of impact or pitted. This is the fundamental objection to the use of adhesives in such methods, and is the reason why in the author’s instrument described later the use of such .adhesives has been abandoned. Again when particles of dust are embedded in a liquid or semi-liquid some of them may dissolve while others become invisible if their refractive indices are the same as the liquid.A final objection is the difficulty of accurately counting such records since a low-power microscope must be used. FILTRATION.-Many attempts have been made to filter the suspended matter from the air and often with success. The use of soluble filters such as sugar, permits the subsequent solution of the filter in water and a dust count may be made from a sample of this. Of course all particles soluble in the medium are thus neglected. Filtration through paper or cotton wool or indeed any medium In actual use the efficiency of the method is low 4 OWENS MEASURING THE SMOKE POLLUTION OF CITY AIR of suitable structure might be used and many forms of such filters have been tried such as extraction thimbles (Brady and Touzlain J . Ind. Eng. Chm.1911). Collodion wool and cloths of various kinds have also been used. There is however, a difficulty in connection with filtration methods:-If the material trapped is to be weighed as is usually attempted then the time required to get a weighable quantity is usually a matter of some hours. When it is realised that the winter air in London and other large cities rarely contains more than a milligramme of dust per cubic metre excluding days of dense smoke haze when there is an abnormal pollution it will be seen that a very large volume of air must be filtered to get a weighable quantity. If we wish to know the impurity present at a particular time it is not much use using a method which requires to be run for some hours to give a measurable result. Hence gravimetric methods are hardly applicable, except for getting averages over long periods.This consideration drives one to seek for some other method of estimation and the method adopted in the author’s recorder to be described later is to compare the discoloration on a filter paper with a calibrated scale of shades. AGITATION WITH WATER.-Attempts have been made to wash out the sus-pended matter from air by passing the air through fine sprays or bubbling it through liquid. In Palmer’s apparatus (Amer. J . Pub. Health 1916) air is drawn at high velocity through 40 C.C. of water in a special vessel so as to produce great disturbance and spraying; the loss from evaporation is made good and a 1 C.C. sample of the liquid counted in a cell after settlement. This apparatus has not proved very efficient and takes account of insoluble dust only.In this connection it is well to remember that the dust particles in air are not always easily wetted; in fact one might expect that tarry soot particles would not. In attempts t o trap such by bubbling through water and other liquids it has been found that most of the suspended matter passes through the liquid unaffected. This is not very surprising when we picture a particle of under one micron diameter floating inside a bubble one or two thousand times that diameter; it may by a lucky chance come in contact with the walls but if so it is unlikely that it should adhere. CONDENSATION.-The well-known Aitken dust counter (Collected Scienti$c Papers of J . Aitken Cambridge 1923) aims at causing condensation of atmospheric moisture upon the dust particles and the number of drops thus formed which settle from a known volume are subsequently counted.Aitken himself realised that condensation did not occur on all the dust particles but only upon those having an affinity for water. Hence his definition of dust limited the word to particles which serve as nuclei of condensation. Unfortunately the use in this specialised sense of a word which had a colloquial meaning has given rise to misunderstanding. The Aitken dust counter is known now to deal only with the hygroscopic nuclei, taking no account of the insoluble non-hygroscopic dust. ELECTRICAL PRECIPITATION.-The method of electrical precipitation has been used successfully for measuring suspended dust. Its application is described b OWENS MEASURING THE SMOKE POLLUTION OF CITY AIR 5 Sir Oliver Lodge (Electrical Precipitation Physics in Industry Series Vol.3) Cottrell (Proc. Amer. Inst. Elec. Eng. 1915) and recently by Drinker and Thomson ( J . Indus. Hyg. Vol. 7 No. 6 1925). The last describe a convenient method of using electrical precipitation for obtaining dust counts from the air. It is however, obvious that all such methods require a source of electricity and usually a high voltage. Drinker and Thomson using a voltage of from 10,000 to 20,000 pre-cipitated the dust upon thin celluloid foil roued up and pushed inside a glass tube, upon the outside of which was metal foil and in its axis a precipitating electrode inside a small glass tube. The celluloid could be withdrawn and pieces cut and mounted for microscopic examination.Professor Drinker has recently informed the author that he is successfully using this method combined with the author’s dust counter in examining dust in alveolar air. ULTRA MIcRoscoPE.-Attempts to count the suspended dust by means of the ultra microscope have been made with varying degrees of success. Two main difficulties affect this method :-First the Brownian agitation of small particles makes the use of high magnification impossible as the velocity of movement is magnified at the same time as the particle. Again the visibility of the particle depends upon the intensity of illumination. Attempts made by the author to count dust particles in this way gave lower counts than given by the jet dust counter to be described presently.In one for example the dust counter gave 21,760 particles per cubic centimetre the ultra microscope 18,750. Another great objection to the method is that one is forced to use a very small volume of air which may not be representative. SETTLEMENT.-AttemptS to measure dust by settlement can hardly be said to give more than very rough comparative values unless special precautions are used and indeed a special instrument such as the settlement dust counter (Tevzth Annual Report of Advisory Committee on Atmospheric Pollution ; cf. ANALYST, 1925 50 452). The rate of settlement depends upon the temperature the degree of disturbance of the air the size the shape and the density of the particles so that unless a fixed volume is enclosed and all the dust allowed to settle these methods give little useful information.Turning now to the methods adopted by the Advisory Committee; these are of three types:-(1) The deposit gauge; (2) The automatic filter or recorder; (3) The dust counter. The results obtained by these methods are embodied in the Annual Reports of the Committee (cf. ANALYST 1922 47 256; 1924 49 34 340; 1925 50 452), and a general review of the whole subject will be found in The Smoke Problem of Great Cities by Sir Napier Shaw F.R.S. and the author to be published shortly. MEASUREMENT OF DEPosIT.-The standard deposit gauge consists of an open-topped funnel connected below with bottles. The rain and deposited matter falling into this are collected in the bottles underneath and removed monthly for analysis.There are fifty-eight such gauges now in operation in different parts of the country. While there are two different types of gauge the fundamenta 6 OWENS MEASURING THE SMOKE POLLUTION OF CITY AIR STONEWARE DEPOSIT CAUCE. GAUGE VESSEL THE STANOARO SlUHEWARE GAUGE CONSISTS OF A hLVARlSE0 IRON STAN0 SU-RTING A CIRCULAR ENAMELLEO STONEWARE VESSEL hOJECTlNG AEOM THE GAUGE VEssEL IS A WIRE SCREEN OPEN AT THE TOP INTENMD TO PREVENT BIRD5 FROM SETTLING ON THE EOGE OF THE VESSEL THE VESSEL 6 CONICAL AT W E BOTTOM AN0 COMMUNICATES BY MEANS OF A GLASS TUBE AN0 RUBBER CONNEXION WITH ONE OR MORE BOTTLES OESIGNCO TO HOLO ONE M O N T H 5 RAINFALL THE RAIN A N 0 MFOSITEO MATTER FAUltiG ON THE GAUGE ARE COLLECTEO IN M E 8OlTLES AN0 REMOVED ONCE A MONTH FOR ANALVSIS Fig.1 OWENS MEASURING THE SMOKE POLLUTION OF CITY AIR 7 principle is the same in each. The larger gauge consists of a circular enamelled cast iron funnel about 70 cm. in diameter whilst the other has a glazed stoneware funnel of 30 cm. diameter (Fig. 1). The large size of these is necessary to provide sufficient deposit for analysis. The inside of the gauges is washed down monthly with some of the collected water before the latter is removed for analysis. The deposited matter is divided into soluble and insoluble and a partial analysis made of each showing the tarry carbonaceous or sooty and the insoluble mineral matter; the soluble part is divided into combustible or volatile matter and mineral matter. A further analysis of the soluble part is made into sulphates chlorides and ammonia.I t was felt that such a division gave the main constituents of the deposit which would be of interest whilst a more complete analysis would have involved too much work and therefore limited the scope of the enquiry. The authorities co-operating with the Committee make their own analyses and return to the Committee a monthly form as shown herewith in which the deposit is shown as grammes per cent. of total solids and metric tons per square kilometre. The form has lately been modified to include also English tons per square mile. The nature of the deposit collected is shown in the accompanying table which is taken from The Smoke ProbZem of Great Cities above referred to and this serves to show the great variation in different places.Another point of great interest is the curious relation which the deposit of sulphates bears to that of total solids. In all cases it will be seen that as the total deposit goes up the percentage of sulphates falls. From the figures for deposit collected over several years it appears that the mean monthly deposit in London has fallen from 40.86 tons per square mile in 1916 to 24-14 in 1924. In Glasgow the deposit has fallen in the same period from 46.28 tons per square mile to 30.77. These figures show the marked improvement in the air of these two cities of recent years and illustrate one of the uses of measurement. The method of measuring deposit in this way has been criticised as giving results depending upon rainfall rather than upon quantity of impurity.The figures collected by the Committee indicate that the deposit of insoluble matter bears no relation to the rainfall whilst a relation is observable between the deposit of soluble matter and the amount of rainfall. This is of interest as indicating the part played by the soluble impurities as nuclei of condensation. In setting up these gauges great care has to be taken in the selection of suitable sites and efforts are made to observe certain rules:-The gauge is set up in an open position well removed from any special source of impurity. It must not be sheltered in any way and should be a distance from any obstacles in its neigh-bourhood such as walls or buildings equal to twice the height of the obstacle. The gauge is set up when possible upon the ground level but the stand supporting the funnel raises the edge of the latter about 4 feet above the ground.AUTOMATIC FILTER OR RECORDER.-The conditions which an instrument for measuring suspended impurity should fulfil may be summarised as follows :-The record should be either continuous or taken at short intervals of not more than fifteen minutes. This is essential since it has been found that the variatio 8 OWENS MEASURING THE SMOKE POLLUTION OF CITY AIR Grammes. FORM 4761. No. of Report METEOROLOGICAL OFFICE AIR MINISTRY LONDON. Metric tons per square K ilom e t re. :( of Total Solids. ADVISORY COMMITTEE ON ATMOSPHERIC POLLUTION. REPORT OF OBSERVATIONS FOR MONTH ENDING 192 Gauge No. Factor " F '' for gauge i Centre Collector .Volume of Water Collected litres = Millimetres of rainfall Total Solids dissolved grammes 1 . ried @ 100" C. Total Insoluble matter J - yo yo yo --Total Solids Collected grammes =tons per sq. Kilometre. . COMPOSITION OF UNDISSOLVED MATTER:-Soluble in CS (tarry matter) Combustible matter insoluble in CS Ash - - yo .yo -Total undissolved matter COMPOSITION OF DISSOLVED MATTER:-Loss on ignition Ash - - yo yo yo --Total dissolved matter Sulphate as SO Chlorine as C1. Ammonia as NH REMARKS :-Signed Date . OWENS MEASURING THE SMOKE POLLUTION OF CITY AIR 9 in the density of the suspended matter is very rapid. A dense smoke haze in London has been known to clear practically completely in fifteen minutes.The instrument should be automatic otherwise there will be too few observations to be of much value. It should be simple and reasonably reliable otherwise skilled operators will be required. It is also preferable that the record given should be permanent. The automatic filter devised for the Advisory Committee appears to fulfil these conditions fairly well. In operation it depends upon the automatic filtration of two litres of air through a disc of white filter paper at short intervals. The disc through which the air is drawn is 1/8th in. in diameter and a discoloration depending in depth upon the quantity of smoke present is made upon the surface of the paper. The instrument has been already described in detail in the Fourth Annual Report of the Advisory Committee 0% Atmospheric Pollution so that a very short description will be sufficient here:-The air to be filtered is measured and aspirated by the filling and emptying of a cylindrical vessel of water.The operation is automatic and controlled by a siphon; at each downward stroke two litres of air are drawn in to the vessel and a per-forated plug is pressed upon a disc of filter paper so as to isolate a 1/8th in. diameter spot through which all the air is forced to pass on its way to the vessel. The pres-sure of this fdter plug is given through the medium of a flexible diaphragm acted on by the air pressure outside the vessel. To bring this diaphragm into operation a system of balance weights controlled by the water through the medium of a surface tension valve is used.The filtering disc is mounted on a turn-table the rotation of which is controlled by a clock the hour hand of which the turn-table It is illustrated in Fig. 2 COMPOSITION OF DEPOSIT AT FIVE REPRESENTATIVE STATIONS GIVEN AS ( a ) ENGLISH TONS PER OF TOTAL DEPOSIT. BOTH ( a ) AND ( b ) BASED ON MEAN MONTHLY DEPOSIT Mineral Combustible Mineral Carbonaceous matter or volatile matter Tarry or sooty insoluble in matter sol- soluble in Total Sulphates - 7- 7’7- Y- - Tons Tons Tons Tons Tons Tons Tons persq. Per persq. Per persq. Per persq. Per persq. Per persq. Per persq. mile. Cent. mile. Cent. mile. Cent. mile. Cent. mile. Cent. mile. Cent. mile. Station. matter. matter. water uble in water. water. Solids. Oldham 0.56 0.71 16.39 20.08 41-85 53.20 6.16 7-80 13.81 17-50 78-77 100 6.53 1915-16 Sheffield, Attercliffe 0.72 1.31 9.61 17.60 23-71 43.50 4.58 8.40 15.93 29-30 54-56 100 7.25 1914-15 London, averageof 8 0.20 0-76 5.89 15-60 13.65 36.20 5.07 13.40 12.89 34-10 37.79 100 5.48 stations 1915-16, Manchester, averageof 5 0.13 0.41 4.30 13.57 12.13 38.27 3-38 10.66 11.76 37.09 31.69 100 4.79 stations 19 15-1 6, Malvern, 19 15- 16 0 0 0.38 8.26 0.67 14.30 1.25 26.90 2.33 50.00 4.65 100 1.0 OWENS MEASURING THE SMOKE POLLUTION OF CITY AIR 11 follows round being itself actuated by a weight and string.Thus the filtering disc is free to stop when the filter plug is pressed upon it and to overtake the clock when the pressure is released. Record discs are obtained such as shown in Fig. 3 and the value of each shade is read by inserting the disc under a scale so Fig.3. that the discoloured spot is seen through a 1/8th in. hole in the centre of each shade, thus permitting a good match to be obtained. The scale itself is calibrated by weighing the process having been carried out for London air by a somewhat elaborate experiment in which a filter disc 24 ins. in diameter was used so as to get a sufficient deposit for weighing. Briefly the value of the unit shade thus obtained was 0.32 milligrammes per cubic metre and each succeeding shade is a multiple of the unit; Shade 2 indicates twice the impurity of Shade 1 and so on. The records can thus be interpreted either in terms of shade or weight of impurity OWENS MEASURING THE SMOKE POLLUTION OF CITY AIR 12 nl \ C w OWENS MEASURING THE SMOKE POLLUTION OF CITY AIR 13 and curves of variation over any desired period may be prepared.Such curves are shown in Fig. 4 for Blackburn London and Stoke-on-Trent and it will be seen that there is evidence of great variation in the conditions a t different places. The relation of the growth and fading of the impurity to human activities is very evident; even the delay of the maximum on Sundays owing to later rising is brought oiit in many of the curves. The history of a London smoke haze or smoke fog as it is often called is written on the records of this instrument and it is curious to observe how often a day of thick smoke haze is preceded by the failure of the air to clear as it normally does between midnight and 5 or 6 a.m.DUST COuNTER.-The third method of investigation used is the jet dust counter devised by the author. I t will be evident that the automatic filter depends for its indication upon the colour of the impurity and gives no information as to its nature; hence something else was required and the jet dust counter was evolved. In this instrument described in the Proceedings of the Royal Society (Vol. A 101 1922; ANALYST 1922 47 322; 1921 49 35) an impact method is used; great precautions are taken to get the highest possible efficiency. For example the jet of air which is caused to impinge is made excessively thin and flat like a ribbon. In the standard instrument it is 1 centimetre wide and 0.1 millimetre thick. I t is caused to strike a microscope cover glass at such a high velocity that the adiabatic expansion and cooling of the air brings about con-densation of water upon the dust or at least upon many of the dust particles, and the line of impact of the jet upon the cover glass is wetted in this way, causing the dust to adhere.When the jet impinges it is deflected laterally in two very thin films of air which are so shallow owing to the thinness of the jet that the high velocity enables the dust particles to penetrate to the bed of the air stream and to strike the cover glass. The instrument is illustrated in Fig. 5 . I t will be seen that it consists of a head containing the slot for forming the jet an air pump to draw the air through the jet and a damping chamber through which the air must enter and where it may pick up sufficient water to act as an adhesive.When taking a record the screwed plug C is removed and the damping chamber filled with the air to be tested by making a few strokes of the pump; a thoroughly clean cover glass is placed in the cell R the plug C screwed home and the handle of the pump withdrawn as rapidly as possible. I t is useless to draw the air through slowly as the velocity will not be sufficient to give high efficiency. The pump piston is therefore withdrawn as instantaneously as possible so that the air will enter at its maximum velocity which is about that of sound and impinge upon the cover glass where it deposits its dust. The apparatus has been tested for efficiency in several ways :-An instrument was prepared having two cells one above the other and two slots in series but staggered so that the air drawn through the first slot impinged upon the roof of its cell and passed on to the next slot impinging upon the roof of the second cell.The floors and roofs of these cells were made of glass so that the process could be watched under the microscope, and an indication of the efficiency was given by the number of particles trappe 14 OWENS MEASURING THE SMOKE POLLUTION OF CITY AIR T A N # C N N A f 2 IE N B I I i Fig. 5 OWENS MEASURING THE SMOKE POLLUTION OF CITY AIR 15 upon the roof of the second cell. Obviously if all were caught in the first cell none would appear in the second. Tested in this way with the damping chamber in position practically all the particles were found to be trapped in the first cell.Without the damping chamber in dry weather the efficiency is not nearly so high. Again air which had passed through the jet was subsequently drawn through a paper filter known to trap all the dust but such air did not produce a discoloration. The record obtained in this instrument is a linear trace of dust 1 centimetre long across the cover glass. I t is mounted record downwards over a metal or paper ring upon a microscope slide and is then ready for examination. The linear form of the record permits it to be easily found by using a low power such as a 2/3rd in. objective and dark ground illumination. The record having been found the high power is moved into position and the dust particles can. then be examined under a 1/12th in. oil immersion objective.I t will be understood that, although the particles are not embedded in a medium they are in contact with the under surface of the cover glass and that therefore there is no air gap to spoil the resolution of the oil immersion objective. The particles can be counted by means of a net-ruled micrometer examined and measured if desired. In this way it is found that the air of London on an ordinary winter’s day contains from 5000 to 10,000 particles per cubic centimetre but that during a dense smoke haze the number rises to 60,000 or 80,000. The dust particles are mostly small, averaging about 0.7 to 0.8 microns and rarely exceeding 2 microns and always scattered amongst the irregular black particles are a certain number of spherical transparent balls of a diameter up to 14 microns or 2 microns sometimes colourless and sometimes yellow or ruby These are doubtless particles.of fused ash from fires.During dense smoke haze the average size of the particles is greater. A second method of using the instrument may be of interest:-It will be understood that the adhesion of the particles depends upon the condensation of water and this water if there is not enough in the air is supplied from the damping chamber. A volume of 50 C.C. is found to provide a record nicely scattered and suitable for counting in London air. If a larger volume say 1000 c.c. be drawn through the particles are piled one on top of the other and if at the same time, the damping chamber be held in the hand so as to warm it slightly enough water is condensed on the record to be blown out sideways in definite streams.In the heads of these streams which dry up immediately are found crystals of the soluble salts present in the dust. The examination of these crystals provides a means of identifying the salt present. Another method of examination is to take a very dense record on the cover glass and support a second cover glass about 1 millimetre above it the record being enclosed between the two. A drop of water placed on the top cover glass keeps it cool while the lower one with its record is heated. Treated in this way it is found that often over the line of dust on the lower glass a line of oil drops is de-posited on the upper one. Such drops from London records are soluble in xylol but not in water and no doubt are derived from tar in the soot 16 OWENS MEASURING THE SMOKE POLLUTION OF CITY AIR Still another method of utilising the instrument is to take records upon prepared cover glasses on which a dilute solution of methyl orange has been allowed to evaporate covering the glass with small crystals.The dust impinging upon the prepared surface and being wetted a t the same time acts upon the methyl orange forming crystals characteristic of the acid or alkaline salt. For example, during a dense London fog on January 22nd 1922 the dust examined in this way was definitely acid whereas a few days previously a definitely alkaline reaction was obtained. A modification of this method has been tried in which two half-discs of filter paper have been fixed upon a thin ring so as to fit in the instrument instead of a cover glass.One half disc was coloured with methyl orange or congo red made slightly acid and the other with the same indicator slightly alkaline, but both as nearly neutral as possible consistent with distinct coloration. The record was then taken across the junction of the half discs and the colour change on the paper observed. In the examination of the soluble salts found in these records there is con-siderable difficulty since the crystals obtained are very small. The author has sometimes obtained records consisting of practically nothing but crystalline matter; one group of such records was obtained during a warni sunny day with a bluish haze on the sea coast in the south of Portugal. All the particles of the haze were obviously common salt or at least sea salt.Another remarkable record of a similar type was obtained in the Gulf of St. Lawrence. Here there was a white haze and brilliant sunshine and the record also consisted entirely of soluble crystalline matter. These crystals are too small to give characteristic effects under polarised light as they can hardly be regarded as transparent. Methods of microchemical examination of such have been attempted but not with very great success. For example a reagent was sprayed into the air and when the spray had practically all disappeared a cover glass was held under it and a few minute drops were found to have settled on this. This cover glass was then mounted in a special instrument drops downwards and over but separated from a second cover glass with the crystals to be examined.On breathing towards the crystals being hygroscopic they collected water and dissolved. Keeping them under obser-vation under the microscope the drops of reagent and solution were brought into contact. The test was on such an excessively small scale that although some-times characteristic reactions were obtained this was not always so. A method is now being experimented on by the author and promises more accurate results but this has not been sufficiently advanced to be described. Some idea of the scale of the operations and the sort of difficulties encountered may be formed when it is realised that the total weight of a 50 C.C. of dust record from London air on an average winter day would be about 1/2O,OM)th of a milli-gramme.Such a record would have scattered over it about 600,000 dust particles. The weight of the individual particle or crystal it is desired to examine may thus be such that 12,000 million of these go to make one milligramme OWENS MEASURING THE SMOKE POLLUTION OF CITY AIR 17 DISCUSSION. Mr. WM. PARTRIDGE having remarked upon the benefit to the country of such a paper referred to the filtration methods of obtaining the dirt on soluble filters such a6 sugar and said that he had always found insoluble particles in both cane and beet varieties when a qnantity of thirty grammes was dissolved in water. He remembered that W. Chattaway and F. M. Wharton had about 1901 demon-strated before the Society the use of liquefied gelatin for removing bacteria from air and he wondered if it could be applied to dirt.As January was generally the coldest month of the year it was difficult to understand why one obtained the maximum deposit in November. Mr. R. C. FREDERICK said that theoretically both the dust counter and the recorder would be liable to give results appreciably erroneous but that Dr. Owens had rather disarmed criticism by showing the chart in which duplicate deter-minations by these two methods were in close agreement. With regard to the deposit gauge however much care was exercised in selecting the site it was im-possible to obtain on such a small superficial area the average conditions pre-vailing over a square mile or more and therefore the calculation of results to the second place of decimals was not justified.As one engaged both in the teaching and practice of hygiene he would be the last to belittle the importance of a pure atmosphere but he felt that the expression of the results in tons per square mile, while useful for propaganda purposes gave from the scientific point of view an altogether exaggerated impression of the condition of affairs. He concluded by drawing attention to the large amount of work on this subject which had been carried out recently in America. Mr. H. E. BURGESS described a form of disc he had invented to determine the amount of dirt in public buildings. He had collected dirt before and after theatrical performances in London and had estimated it on the Lovibond tinto-meter. He had also burnt a known quantity of benzine in a room which was ventilated by a fan; unfortunately he had not been able to bring this method to any satisfactory mathematical conclusion but at the same time he thought that the measurement of dirt by such a method might be possible.Dr. GEOFFREY MARTIN referred to coal-grinding apparatus the fine particles of coal dust from which penetrate right through clothing. From experiments on grinding he had found that the number increased as the diameter decreased according to the compound interest law. He added that on the seashore there was a constant grinding action among the pebbles which caused them to increase in number as the diameter decreased in the same way and he enquired if there was any similar relationship between the fineness and the number of particles floating in the atmosphere.Mr. E. HINKS referred to the fluid obtained from the gauge and said he had found some difficulties in carrying out the methods laid down for its examination. The deposit itself was difficult to dry to constant weight and he had found asbestos more satisfactory than pulped filter paper; the weight of “ tarry matter’’ obtained by evaporating the carbon bisulphide extract was generally considerably higher than that obtained by diff erence-the method prescribed; in titrating the chloride difficulty was experienced in obtaining a good end-point unless a greater amount of chromate indicator than was usually required were added. Dr. R. S. EVANS remarked that he had noticed that where the maximum was given in the curves it was always preceded by a sharp minimum 18 OWENS MEASURING THE SMOKE POLLUTION OF CITY AIR Mr.C. C. ROBERTS remarked that among the figures given for London there were none for any place east of London Bridge which in his opinion was mis-leading; or was London getting a better character for cleanliness than hitherto? The CHAIRMAN (Mr. S. F. Burford) remarked that meteorology was a science of variables. Notwithstanding differences in volume of rainfall and differences in deposits a mean of a long period would give reliable information for a given locality. He wondered there was nothing said about the use of permanganate as a reagent; what about the sulphur in the air acting as a bactericide? A good deal of sulphur must be present in the air; Did such a place as Rochdale have a higher death rate than other places with less air pollution? Dr.OWENS replying said that he could not agree with the suggestion that by passing air through liquid gelatin all the dust would be trapped; his experience of trapping dust by bubbling through liquid did not suggest that the method would be much use. With regard to the reference to a maximum deposit in November: the maximum was not always in November but varied from year to year. It was doubtless influenced by the nature of the weather and wind experienced in any particular month. Regarding Mr. Frederick’s and Mr. Burford’s remarks, he was afraid it was impossible to get great accuracy in measuring atmospheric impurity but some method giving the closest practical approximation to accuracy had to be used. He did not think it wrong to return results in tons per square mile a form which was acceptable to non-technical people.The same objection applied to expressing rainfall in tons per acre or per square mile but it was a useful and correct way to express it sometimes. He agreed with the speaker who referred to the work being done in America; the Americans were very go-ahead and were now using the instrument he had described. In replying to the criticism as to the use of a second place of decimals, it was difficult to get rid of the second place sometimes but what they now aimed a t was really to provide two significant figures. As to the suggestion that the residue from evaporation of carbon bisulphide should be taken as a measure of tar rather than the loss due to washing he thought that this would probably be more correct as the loss of the tar doubtless made the part left more hygroscopic and would therefore account for a difference in the result obtained by the two methods.Dr. Evans suggested that a maximum was always preceded by a mini-mum in the deposit figures but he did not attach much importance to this. The curves for deposit for the different months were all parts of the same deposit and tended more or less to vary together. Individual years did not show the tendency to a low minimum preceding a maximum. As to the deposit gauges in London not extending far east he thought they were in reasonably representative positions. I t was not every place that could be utilised for a deposit gauge; in fact it was always difficult to find suitable and representative positions.One had to remember that wind direction governed the source from which the impurity was derived so that a gauge in a particular locality did not necessarily get the impurity produced in the immediate neighbourhood although this applied more to the fine suspended matter recorded by the automatic filter than to the matter which was deposited in the gauges

ISSN:0003-2654    

DOI:10.1039/AN9265100002

出版商:RSC    

年代:1926

数据来源: RSC

摘要:

NEWCOMB THE DETERMINATION OF ALCOHOL ETC. I N CHLOROFORM 19 The Determination of Alcohol and Ethyl Chloride in Chloroform. BY CLIVE NEWCOMB M.D. F.I.C. Major I.M.S. (Read at the Meeting November 4 1925.) ANAESTHETIC chloroform is commonly said to be a mixture of chloroform and alcohol with in some cases ethyl chloride added. I t also contains some water. It was thought of interest to try to devise methods of determining these substances in chloroform and of removing them so that the physical constants of the resulting chloroform could be used for determining its purity. So long as it is known that only these four substances are present this is not difficult. The addition of anhydrous potassium carbonate will remove the water. Washing the chloroform with water in the way described below will remove all the alcohol and none (or only a very small trace which can be allowed for) of the ethyl chloride.The difference in density before and after washing will give a measure of the amount of alcohol and the difference in density of the washed chloroform from the density of pure chloroform will give a measure of the amount of ethyl chloride. Further-more boiling the mixture of chloroform and ethyl chloride with potassium hydroxide solution and then washing it will remove the ethyl chloride and leave pure chloro-form saturated with water. This water can then be removed if necessary by dehydrating agents. If however it is not known or assumed that only these four substances-chloroform alcohol ethyl chloride and water-are or may be, present the problem is more difficult.There are many other substances which might be present and in small quantities escape detection by the B.P. tests, especially if the analyst’s sense of smell were not particularly keen. A few of these possible impurities have been considered in this paper. I t is plainly an endless task to try to deal with every possible impurity. The values obtained by the method outlined above are however in any case maximum values for the amounts of alcohol and ethyl chloride present and if a liquid with the right density for pure chloroform is obtained after their removal the presence of many of the other possible impurities is unlikely. In the experiments described below 27” C. has been adopted as the standard temperature because this is about the average temperature of this laboratory in the cold weather.When working a t other average laboratory temperatures the corrections for the rate of change of density of chloroform with the temperature (given below) can be applied without grave error. All the densities given are absolute densities i.e. the weight in grms. of one millilitre as weighed in VUECUO. All percentages are weight percentages. The word “impurity” is used both for desirable and undesirable extraneous substances in chloroform 20 NEWCOMB THE DETERMINATION OF ALCOHOL AND THE DETERMINATION OF THE T)ENSITY.-The determination of the density of chloroform is not such a simple matter as it would seem one of the chief diffi-culties being the fixing of the temperature. An error of a tenth of a degree in the temperature will produce an error of about 0-0002 in the density and chloroform will cool itself by evaporation a degree or more even in being poured from m e vessel to another.The most accurate densities can no doubt be obtained by using a specific gravity bottle and a thermostat but strange as it may seem for such a very volatile liquid a much more convenient apparatus is a Westphal balance. This is the apparatus which has been used in the following experiments. A preliminary calibration of the balance is essential to get even the third place of the density right. This can be done by checking the weights of the riders against a standard set of weights and then working out the exact volume and expansion with temperature of the plummet from the observed density of distilled water a t different temperatures.In using the balance it is first carefully levelled with no riders on in air. It seems perhaps unnecessary to mention this but a series of the earlier experiments was vitiated by the neglect of this precaution and by assuming that the table on which the balance stood was level. A thermometer, also calibrated and a stirrer are put in the cylinder holding the chloroform. The riders are then adjusted as nearly as possible to the right places the chloroform is vigorously stirred and the oscillations of the balance checked with a small camel hair brush. If necessary an adjustment of the smallest rider is made to get the balance exactly even and then the temperature is read to the nearest tenth of a degree.The process is repeated a t least six times giving a series of temperatures and corresponding densities extending over perhaps as much as two degrees. The corrections both for the balance and the thermometer are then applied the results plotted-the density against the temperature- and the best line of the right slope for the known change in density with temperature drawn through them. As a check on the consistency of the observations the densities of ten different chloroforms were determined six observations for each of them (60 in all) being taken. The maximum deviation of any observation from the mean was 4 in the fourth place and this only occurred once. The mean deviation of the whole 60 was 1.3 and the standard deviation 1.6 in the fourth place. A further test of the consistency of the method was the checking from time to time of the density of mixtures in measured proportions of chloroforms of which the densities had been determined.In no case in four such experiments was the difference between the observed and the calculated density more than 1 in the fourth place. As a check on the absolute accuracy of the method the density of distilled water at the labora-tory temperature was determined from time to time and the result was always within 2 in the fourth place of the density given in Castell Evans’s tables (Vol. II., p. 1225). The density of a chloroform was also determined both by means of the bottle with all possible precautions and by means of the balance and the results were the same within 5 in the fifth place.The following density determinations are therefore probably to be relied on as accurate to within 2 in the fourth place The whole process takes ten or fifteen minutes. (& 0*0002) ETHYL CHLORIDE I N CHLOROFORM 21 THE RATE OF CHANGE I N DENSITY WITH TEMPERATURE.-For the reduction of the densities of chloroform as found by the balance to some common temperature, one needs to know the rate of change in density with temperature. This-or what comes to the same thing the expansion of chloroform by heat,-has been determined by Thorpe for pure chloroform ( J . Chem. SOC. 1880 196) and his results work out to :-dD/dt = - 0.00188 a t 0°C. - 0*00189 10°C. - 0~00190 20°C. - 0.00192 30°C. From experiments made in this laboratory the following results were obtained:-For pure chloroform the average rate of change in density per degree centigrade between 5" and 25" C.:-- 0.00189 1 in two experiments, - 0~00190 For chloroform containing 1 per cent. by weight of alcohol:-- o*oo188 } in two experiments. - 0*00189 For chlbroform containing 5 per cent. by weight of alcohol:-- 0*00180 in one experiment. In this last case special care had to be taken to prevent the chloroform from absorbing water from the air as with so much alcohol it does so very rapidly. In view or the agreement of the first two with Thorpe's figures these are probably correct to within one in the last place. A less reliable determination was made for chloroform containing 1 per cent. of ethyl chloride and this worked out to:-dD/dt = - 040188 per degree between 20" and 30" C.The difficulty with this was that the solution tended to lose ethyl chloride while its density was beipg determined. It is however sufficient to indicate that the presence of a small proportion of ethyl chloride does not greatly alter the rate of change of density with temperature. WASHIKG CHLOROFORX.I.-Ch~orOform can be washed free from alcohol by shaking it five or six times with an equal volume of water in a separating funnel, A much more efficient convenient and economical method is by the use of the apparatus shown in the figure. The tube by which the distilled watw cntt-rs is drawn out to a fine point which is arranged so as to come about 2 inch above the stopcock. The opening at the poilit must be of such a size that with a head of about two feet of water it will give iii the air a The vesscl is a separating iunnel of about 300 to 400 C.C.capacity 22 NEWCOMB THE DETERMINATION OF ALCOHOL AND very fine jet and not a series of single drops. The tube by which the wash water is drawn off can be adjusted to different levels by pushing it a longer or shorter way through the cork. The rate of flow of water is regulated by the vacuum pump and must be fast enough to give clouds of very fine bubbles of water in k the chloroform but the vacuum must not be enough to make the chloroform boil. With the apparatus in use in this laboratory this means that between 10 and 20 C.C. of water run through per minute. Using this apparatus with 140 C.C. of a chloroform containing about 1 per cent.of alcohol it was found that after 100 C.C. of water had run through (ti minutes) 9’7 per cent. of the alcohol had been removed and after 200 C.C. of water (12 minutes) the whole of the alcohol. As a general rule as the rate of running is variable, 20 minutes’ washing is recommended. After the chloro-form bas been washed it is full of very small bubbles of water which take a long time to rise but which can be removed by filtering through a dry (fat-free) paper. I t is convenient to arrange another large separating funnel a t a higher level than the washing vessel as a reservoir for the distilled water. This affords an easy means of seeing that the water is running through a t a proper rate and of avoiding the possibility of any chloroform being sucked back when the vacuum is released.In deducing the amount of alcohol in a chloroform from the density before and after washing one needs to know:-(1) the effect of washing on other substances which may be present; (2) the effect of the water present on the density both before and after washing; (3) the effect of different proportions of alcohol on the density of chloroform. THE EFFECT OF WASHING ON VARIOUS SUBSTANCES IN CHLOROFORM.-Among the substances possibly present in chloroform on which the effect of washing has been tried are:-(1) Acetone.-This substance has never been found in any of the commercial chloroforms tested for it. This is rather surprising in view of the common use of acetone in the manufacture of chloroform and of the delicacy of the Scott-Wilson test (Folin Lab.Manual p. 189). I t may be noted in passing that this test can be applied direct to chloroform or to a watery extract of it by dropping a drop of the liquid to be tested into a C.C. or two of the reagent. An immediate white precipitate indicates the presence of acetone. A grey precipitate developing on standing means nothing and is due to the chloroform itself. If acetone is present it is removed by washing though not so rapidly as alcohol. In on ETHYL CHLORIDE IN CHLOROFORM 23 experiment with a chloroform containing about 1 per cent. of acetone the amount present was reduced to less than 1 in 100,000 by 40 minutes' washing. (2) Ethyl chloride.-If ethyl chloride is present in comparatively large amounts, washing as indeed any manipulation or even standing in a not too well stoppered bottle removes some of it.In one experiment in which a chloroform containing 2.3 per cent. of ethyl chloride was washed-not in the washer described but by shaking with six successive lots of water-the change in density corresponded to a reduction of 1-9 per cent. Keeping this chloroform for ten days (with five density determinations over that time) further reduced the amount of ethyl chloride in it to 1.46 per cent. If however ethyl chloride is present only in such amounts as are likely to be found in anaesthetic chloroform washing removes very little of it. The following experiments show this:-Density Time of Density Difference Per Cent. of before washing after in fourth ethyl chloride. 0.50 0.34 0.22 0-21 0.18 0.11 0.07 0.07 0-03 washing at 27" C.1 -4703 1.4716 1 -4726 1.4727 1 -4730 1 94735 1 04740 1 04740 1 04744 in minutes. 30 36 20 25 20 40 35 30 30 washing place of a t 27" C. decimals. 1 *4703 0 1-4717 1 1 *4729 3 1.4729 2 1 -4731 1 1 -4737 2 1 -4744 4 1-47 2 2 1 *4744 0 Average difference 1-7 Although all these differences are within what is thought to be the experimental error of the observations they are all in the direction of an .increase of density with washing so that it is probable that washing in these concentrations causes a slight loss of ethyl chloride amounting to about 0.0002 in the density i.e. to about 0.02 per cent. of ethyl chloride. These experiments are not sufficiently accurate to show it but one would suppose the loss to be greater the higher the concentration.One might take 0.0002 in the density as the average loss for concentrations from 0.05 per cent. to 0.50 per cent. (3) Ethyl Carbonate.-This substance in small concentrations is not removed by washing. In one experiment a chloroform containing 1-30 per cent. of it had the same density (1.4573 at 31" C.) before and after washing for 20 minutes. The ethyl carbonate used for mixing with the chloroform in this experiment was probably not pure as its density was 0.9662 at 31" C. against the density extra-polated from the recorded figures (Beilstein III. 8) of 0.9636 at 31" C. It did, however presumably consist largely of ethyl carbonate and none of it was removed. Ethyl carbonate is of course the substance said to be formed when the phosgene generated by the oxidation of chloroform reacts with the alcohol present 24 YEWCOMB THE DETERMINATION OF ALCOIIOL AND (4) Carbort Tetrachloride.-This seems to be a possible impurity.It is not removed by washing as the following experiments show:-Per Cent. of carbon tetra-chloride. Density Time of before washing washing in at 27" C. minutes. 5.56 1.4797 21 5-58 1.4797 25 4.50 1.4786 20 2.06 1 -4767 20 Density after washing at 27" C. 1.4797 1 -4800 1.4786 1 *4665 Difference in fourth place of decimals. 0 +3 0 -2 All the above densities were taken with the chloroform saturated with water. THE EFFECT OF WATER ON THE DENSITY OF CHLOROFORM.-Although the chloroform after washing with water can be dried before taking its density it is obviously a great saving of time and trouble to take the density with the chloroform wet and to determine and allow for the effect of the water.The following ex-periments show the effect on the density of drying the chloroform by letting it stand over anhydrous potassium carbonate :-Sample. D E F G Density Density Density Time of after after wet at drying drying Differ- wetting 27O c. in days. at 27" C. ence. again. 1 -4746 3 1 *4752 6 14 1 *4750 4 1.4746 1.4746 1 1.4753 7 2 1.4753 7 3 1.4751 5 1.4747 1 04746 1 1.4750 4 2 1.4750 4 1 a4747 1 1 -4752 5 4 1 *4752 ti Average difference 5.2 --According to these experiments the addition of 5 to the fourth place of the density of a wet chloroform gives the density of the same chloroform dry.It goes without saying that these results only apply to chloroforms which have no alcohol in them. When alcohol is present the mixture dissolves much more water. THE EFFECT OF ALCOHOL ON THE DENSITY OF CHLOROFORM.-The difficulty in estimating the effect of alcohol on.the density of chloroform is that it is im-practicable to attempt to add absolutely anhydrous alcohol. To get over this difficulty various quantities of from 92 to 98 per cent. alcohols have been added to chloroform and from the effects of the various percentages of alcohol and water together on the density an attempt has been made to calculate the effects of each alone. The following experiments were made : ETHYL CHLORIDE I N CHLOROFORM 25 1 2 3 4 5 G 7 Per Cent.Per Cent. of of alcohol water -(by weight) .-0.323 0.027 0.395 0*008 0-648 0.054 0.792 0.016 0.970 0.030 0.977 0.082 1 -046 0*008 1 0308 0.110 1.718 0.035 Lowering in fourth place of decimals in density a t 27" C. 46 56 93 109 134 136 140 178 230 Lowering calcula-ted for no change in total volume. 43 51 85 103 126 128 135 171 220 Differ-ence 4-3. 3 5 8 6 8 8 5 7 10 Lowering due to , water. 2 1 4 1 2 6 1 8 3 1 alcohol 3-6. 44 55 89 108 132 130 139 170 227 The figures in column 4 are the calculated lowerings on the assumption that no change in total volume takes place when chloroform alcohol and water are mixed.?'he differences between the observed lowerings (column 3) and the calculated lowerings (column 4) are not so even as could be wished but they are all positive, and show in general an increase as the proportion of alcohol increases. This indicates that there is a small increase in volume on mixing. The rather arbitrary assumption-but one which seems to fit the figures-that the whole of this increase in volume is due to the alcohol gives columns 6 and 7. Plotting the results in column 7 and taking the best line through them gives the effect of alcohol alone. The mean result of all the observations is that 1 per cent. of alcohol (by weight) lowers the density of chloroform by 134 (Le. by 0.0134). Other percentages up to 1-5 per cent.lower the density in proportion e.g. 0.792 per cent. lowers it by 0.792 x 134 = 106. THE EFFECT OF WASHING ON VARIOUS CIILOROFORMS.-The effect of washing on various commercial anaesthetic chloroforms is shown in the following table :-Per Cent. Density Time of Density of water-Brand before washing after soluble and was hi ng in washing Differ- substances sample. a t 27" C. minutes. a t 27" C. ence. as alcohol. Brand A. Sample 1 1.4635 35 80 2 1.4627 38 68 3 1.4610 45 4 1 *4688 30 60 0 1 -4633 30 6 1 04642 30 -1 *4740 1 -4744 1 -4743 1 04745 1.4741 1 *4744 1 -4744 1.4743 1 ~4742 09 0.85 18 0.92 31 1.01 56 0.46 10 0-86 00 0.78 7 1 -4629 30 1.4744 115 0.90 8 1 -4640 30 1 -4740 60 1 -4742 102 0-80 9 1 -4547 21 1 -4747 200 1-53 10 1 *4637 20 194747 110 0.86 (Continzced 011 next page) 26 NEWCOMB THE DETERMINATION OF ALCOHOL AND Brand and sample.Brand B. Sample 1 2 3 Brand C. Brand D. Density before washing a t 27” C. 1 -4620 1.4618 1 *4622 1.461 8 1.4610 Time of washing in minutes. 20 40 20 20 20 20 Density after washing Differ-a t 27” C. ence. 1 -4730 1 -4731 111 1 -4728 110 1 94730 108 1 a4750 132 1 -4746 136 Per Cent. of water-soluble substances as alcohol. 0*85* 0-84” 0 83* 1 -02 1 005 * An allowance has been made for loss of ethyl chloride vide supra. With the exception of the density in some cases all the above chloroforms passed the B.P. tests. Brand A is made in some cases if not in all from mixtures of other brands by redistillation.The amount of alcohol added to it is very variable, and the variations in density after washing undoubtedly represent variations in composition and are not experimental errors. Brand B is a chloroform to which the makers state some ethyl chloride is added. Brands C and D are well known brands. THE REMOVAL OF ETHYL CHLORIDE FROM CHLOROFORM.-A good many methods for the removal of ethyl chloride from chloroform were tried. These included (1) “refluxing,” with the condenser water at a temperature (32” to 35” C.) well above the boiling point of ethyl chloride (12-5” C.)-a method which sounds most hopeful but which does not work ; (2) “ refluxing ” with alcoholic silver nitrate solution; (3) treatment with ammonia and subsequent washing and some others.The only method which under certain conditions removed the whole of the ethyl chloride was that of boiling with potassium hydroxide. This method also destroys the chloroform itself and experiments were made to find the conditions which gave the maximum destruction of the ethyl chloride and the minimum destruction of the chloroform. The method finally evolved was that of “refluxing,” and adding a solution of potassium hydroxide (100 grms. of sticks per litre of water) slowly and continuously throughout the whole time of “refluxing.” In this way the vapour condensing in the condenser which is richer in ethyl chloride than the bulk of the liquid comes in contact with the fresh potassium hydroxide first. The amount of potassium hydroxide solution used is equal to the bulk of the chloro-form “ refluxed,” and the time about 19 hours-though perhaps two hours would be safer.At the end of that time the chloroform is separated from the aqueous layer washed for 20 minutes in the washer filtered and its density taken. This process will not remove either ethyl carbonate or carbon tetrachloride. The following experiments show this : ETHYL CHLORIDE I N CHLOROFORM 27 Nature and concentra-tion of solute. Per Cent. Ethyl chloride. 0.0 0.04 0.04 0-16 0.17 0.78 0-80 Density before reflux wet a t 27OC. 1.4747 1 04743 1 -4743 1.4733 1.4734 1 -4675 1 4-673 Ethyl carbonate. Carbon tetrachloride. 1.3 1 *4649 4.5 1 *4786 Time of reflux in hours.1.5 1.5 1.5 1 *25 1 -42 1.5 2.0 3.0 1 1 025 Density after reflux wet at 27” c. 1 04748 1 94747 1 -4747 1 -4747 1 -4746 1 -4745 1 04740 1 04747 1 -4646 1 04786 Differ-ence. 1 4 4 14 12 70 74 --3 0 Potassium hydroxide used. C.C. 157 84 132 147 153 161 I 93* 139 90 * In this experiment the amount of potassium hydroxide used was presumably insufficient. THE EFFECT OF ETHYL CHLORIDE ON THE DENSITY OF CHLOROFORM.-In these experiments the density of a chloroform was determined a quantity of it weighed out in a bottle and a weighed tube of ethyl chloride put in. The whole was then cooled in ice to be below the boiling point of ethyl chloride and the tube broken by violently shaking the bottle.The density of the resulting solution was then determined as soon as the mixture had again nearly reached the tem-perature of the laboratory. The broken pieces of the tube were then collected, dried and weighed. The ethyl chloride used was Burroughs and Wellcome’s “pure for anaesthesia.’’ Three experiments were made :-Lowering in the density a t 27” C. Per Cent. of ethyl chloride. 0.841 0.976 2.257 0.0077 0.0088 0.0212 The mean result of the above experiments is that one per cent. by weight of ethyl chloride lowers the density of chloroform by 0.0092 and other concentrations up to 2 per cent. in proportion. Another experiment was made to see if the effect of alcohol and ethyl chloride together was the sum of their effects singly.A mixture was made containing:-Chloroform 97.76 Calc. lowering Ethyl chlor. 0.50 46 Alcohol 1-71 229 Water 0.03 2 Total 277 28 NEWCOMB THE DETERMINATION OF ALCOHOL AND The original density of the chloroform wet at 27” C. was 1-4748 and after the addition of these substances it was 1.4473 (difference 0*0275) so that within the experimental error the lowering calculated is the same as that observed. THE DENSITY OF PURE CHLOROFORM.-The values for the density of pure chloroform given in various books when reduced to a common temperature are found to show the most surprising variations. Two of them however giving its density at 0” C. agree very closely viz. Thorpe ( J . Chem. Soc. 1880 p. 196) 162637, and Timmermanns etc. (Compt. Rend. 1922 174 365-367) 1.52635.Calculating from this value using the figures given by Thorpe (Zoc. cit.) for the expansion by heat the density at 27” C. works out to 1.4752. For wet chloroform this should be reduced to 1.4747 (vide suj5ra). and this is the usual figure obtained when alcohol and ethyl chloride are removed from commercial chloroforms. For a sample prepared in this laboratory from chloral hydrate and subsequently purified and redistilled the middle portion of the distillate being taken the density dry a t 27” C. was 1.4751 which is within the experimental error of Thorpe’s figue. The figure adopted in this laboratory for pure chloroform wet at 27” C. is 1.4747. following experiments were made :-THE EFFECT OF OTHER SUBSTANCES ON THE DENSITY OF CHLOROFORM.-The Observed change Calculated change in final decimals on assumption of in the density no change in total Nature and concentration of solute.a t 27” C. volume. 5.7 per cent. + 50 +56 Carbon tetrachloride 2.1 per cent. +21 +21 Ethyl carbonate 1-30 per cent. - 98 -98 The figure “50” for the 5.7 per cent. of carbon tetrachloride is probably wrong, and the effect of these substances can be calculated on the no-volume-change assumption. The amounts detectable by the density of the residual chloroform after removal of alcohol and ethyl chloride are 0-3 per cent. upwards for carbon tetrachloride and 0-03 per cent. upwards for ethyl carbonate. SUGGESTED ROUTINE.-The above data are by no means so complete as could be desired but they form a basis. It is suggested that the following routine might usefully supplement the tests given in the B.P.for the examination of anaesthetic chloroforms. It is washed for 20 minutes in the washer described filtered and its density again taken wet. It is then “refluxed” for two hours an amount of 10 per cent. potassium hydroxide solution about equal to the volume of the chloroform being gradually and continuously added over the whole time of reflux the chloroform then separated washed for 20 minutes, filtered and its density taken wet for the third time. The difference between the first two densities plus 0*0005 for the water dissolved and minus 0*0002 if from 0.05 to 0-50 per cent. of ethyl chloride is present gives a measure of the water-soluble subs t ances-mos tly alcohol-and conveniently called “ wat er-soluble substances reckoned as alcohol.” This figure will include any water present in The density of the chloroform is taken ETHYL CHLORIDE IN CHLOROFORM 29 the original chloroform but will not include any ethyl chloride ethyl carbonate or carbon tetrachloride.The difference between the second and third densities, plus 0*0002 when from 0-05 to 0.50 per cent. of ethyl chloride is found gives a measure of the amount of ethyl chloride. The density of the residual chloroform should be within 0.0002 of 1-4747 at 27” C. (for other temperatures vide supra), and if this figure is found it is an indication that no other impurities are present. If more than 0.03 per cent. of ethyl carbonate or more than 0.3 per cent. of carbon tetrachloride is present it will show in this last density except in the unlikely case of their being present in equivalent amounts.As an example of the method:-A chloroform has an original density of 1.4620 a t 27” C. After reflux its density wet was 1.4747. The difference between the first and second densities is 04110. To this add 0.0005 for wetness and subtract 0.0002 for loss of ethyl chloride making 0.0113. This corresponds to 113/134 = 0.84 per cent. of alcohol. The difference between the second and third densities is 0.0017. To this add 0.0002 for loss of ethyl chloride making 0.0019 which corresponds to 19/92 =0*21 per cent. of ethyl chloride. The final density of 1.4747 is correct for pure chloro-form. After washing its density wet was 1.4730. 1 his chloroform thereiore contains :-Water-soluble substances reckoned as alcohol No evidence of other impurities.0.84 per cent. Ethyl chloride . . . . . 0.21 ,, In the preparation of this paper a good many references have been found to literature which is not available in Madras. If any of the experiments duplicate those of others and no acknowledgments have been made the author tenders his apologies and hopes that at any rate he many not be suspected of intentional plagiarism. CHEMICAL EXAMINER’S LABORATORY, MADRAS. DISCUSSION. Mr. C. E. SAGE said that he wished to criticise the paper from the point of view of the bulk of the chloroform used for the tests. It was customary to put up anaesthetic chloroform in small bottles and if the whole of one of these were used for testing the result was no guarantee that all the other bottles were of the same composition.He asked what could it matter if there were more than 0 - 5 per cent. of alcohol in a sample if it were pure seeing that it was customary to employ chloroform containing more than that proportion of alcohol. The British Pharmacopoeia specified 2 per cent. and the frequently employed anaes-thetic “A.C.E.” was a mixture of absolute alcohol one part chloroform two parts and ether three parts. Mr. G. N. HUNTLY commented on the absence from the paper of any mention of the work of Dr. Wade on the subject of alcohol chloroform and acetone chloro-form. Dr. Wade had proved that acetone chloroform was pure and that ethyl chloride was present in alcohol chloroform; eventually he had found a means of isolating the ethyl chloride and his work had been taken up by manufacturers and used extensively during the War 30 ELSDON JENA SINTERED GLASS CRUCIBLES Mr. WILLIAM PARTRIDGE said that chloroform for anaesthetic purposes was not always provided in 4-02. bottles but often in 2-lb. bottles. He thought that the climatic conditions in India as compared with England might make a great difference in the figures obtained; more especially he disliked the idea of relying on the specific gravity of chloroform taken by Westphal’s balance when fifteen minutes were taken over the determination. Mr. RAYMOND Ross referred to the types of specific gravity bottles used and advocated a type having a tall stopper with a graduated capillary bore; readings for the volume of this bottle filled to various graduations were obtained and recorded once for all and the bottle filled with the substance to be tested to any given mark was compared with its content when filled to the same mark with water

ISSN:0003-2654    

DOI:10.1039/AN9265100019

出版商:RSC    

年代:1926

数据来源: RSC

摘要:

142 ABSTRACTS OF CHEMICAL PAPERS milk-solids-not-fat and 3.25 per cent. of milk fat, and in the reductase test (see Section 42) shall require at least 4 hours to decolorise the methylene blue solution. Cream must contain at least 40 per cent. of milk fat. (46) Butter.-Butter shall contain at least 80 per cent. of milk fat, and not more than 16 per cent. of water or 20 grains per lb. boron preservative (calculated as boric acid).(47) Cheese.-Cheese shall contain not less than 50 per cent. of milk fat on the dry substance, and skim-milk cheese not less than 10 per cent. (48) Tea.-Tea shall yield between 4 and 7 per cent. of ash (at least one half of which is water-soluble) and at least 30 per cent. of extract, which shall be determined by boiling 2 grms. of tea in 200 C.C. of distilled water under a reflux condenser for 1 hour, filtering hot, cooling and evaporating an aliquot portion to constant weight.Tea dust shall not yield over 5 per cent. of ash insoluble in water. Cofee.-Coffee shall contain not less than 10 per cent. of fat, and more than 1 per cent. of saccharine matter, and shall yield not more than 6 per cent. of ash, of which not less than 75 per cent.shall be soluble in water. Co$ee essence shall contain not less than 0.5 per cent. of caffeine. Cocoa.-Cocoa paste, mass or slab, is the solid or semi-solid mass pro- duced by grinding cocoa nibs, and shall contain not less than 45 per cent. of cocoa fat. The dry fat-free residue shall not contain more than 19 per cent. of natural cocoa starch, 6-33 per cent.of crude fibre, 8 per cent. of total ash, 5-5 per cent. of insoluble ash, and 0.4 per cent. of ferric oxide. Soluble cocoa or cocoa essence must not exceed a maximum of 3 per cent. of added alkali (as K,CO,) , and prepared cocoa must contain at least 20 per cent. of fat-free cocoa. Chocolate $ash, coatings, +owder and confectioners’ chocolate shall contain at least 16 per cent.of fat-free cocoa. No cocoa husks, weighting substance, paraffin wax, or foreign fat may be added to cocoa or to any preparation thereof. (49) (50) D. G. H.142 ABSTRACTS OF CHEMICAL PAPERS milk-solids-not-fat and 3.25 per cent. of milk fat, and in the reductase test (see Section 42) shall require at least 4 hours to decolorise the methylene blue solution. Cream must contain at least 40 per cent.of milk fat. (46) Butter.-Butter shall contain at least 80 per cent. of milk fat, and not more than 16 per cent. of water or 20 grains per lb. boron preservative (calculated as boric acid). (47) Cheese.-Cheese shall contain not less than 50 per cent. of milk fat on the dry substance, and skim-milk cheese not less than 10 per cent. (48) Tea.-Tea shall yield between 4 and 7 per cent.of ash (at least one half of which is water-soluble) and at least 30 per cent. of extract, which shall be determined by boiling 2 grms. of tea in 200 C.C. of distilled water under a reflux condenser for 1 hour, filtering hot, cooling and evaporating an aliquot portion to constant weight. Tea dust shall not yield over 5 per cent. of ash insoluble in water.Cofee.-Coffee shall contain not less than 10 per cent. of fat, and more than 1 per cent. of saccharine matter, and shall yield not more than 6 per cent. of ash, of which not less than 75 per cent. shall be soluble in water. Co$ee essence shall contain not less than 0.5 per cent. of caffeine. Cocoa.-Cocoa paste, mass or slab, is the solid or semi-solid mass pro- duced by grinding cocoa nibs, and shall contain not less than 45 per cent. of cocoa fat.The dry fat-free residue shall not contain more than 19 per cent. of natural cocoa starch, 6-33 per cent. of crude fibre, 8 per cent. of total ash, 5-5 per cent. of insoluble ash, and 0.4 per cent. of ferric oxide. Soluble cocoa or cocoa essence must not exceed a maximum of 3 per cent. of added alkali (as K,CO,) , and prepared cocoa must contain at least 20 per cent. of fat-free cocoa. Chocolate $ash, coatings, +owder and confectioners’ chocolate shall contain at least 16 per cent. of fat-free cocoa. No cocoa husks, weighting substance, paraffin wax, or foreign fat may be added to cocoa or to any preparation thereof. (49) (50) D. G. H.

ISSN:0003-2654    

DOI:10.1039/AN9265100030

出版商:RSC    

年代:1926

数据来源: RSC

摘要:

142 ABSTRACTS OF CHEMICAL PAPERS milk-solids-not-fat and 3.25 per cent. of milk fat, and in the reductase test (see Section 42) shall require at least 4 hours to decolorise the methylene blue solution. Cream must contain at least 40 per cent. of milk fat. (46) Butter.-Butter shall contain at least 80 per cent. of milk fat, and not more than 16 per cent. of water or 20 grains per lb. boron preservative (calculated as boric acid).(47) Cheese.-Cheese shall contain not less than 50 per cent. of milk fat on the dry substance, and skim-milk cheese not less than 10 per cent. (48) Tea.-Tea shall yield between 4 and 7 per cent. of ash (at least one half of which is water-soluble) and at least 30 per cent. of extract, which shall be determined by boiling 2 grms. of tea in 200 C.C. of distilled water under a reflux condenser for 1 hour, filtering hot, cooling and evaporating an aliquot portion to constant weight.Tea dust shall not yield over 5 per cent. of ash insoluble in water. Cofee.-Coffee shall contain not less than 10 per cent. of fat, and more than 1 per cent. of saccharine matter, and shall yield not more than 6 per cent. of ash, of which not less than 75 per cent.shall be soluble in water. Co$ee essence shall contain not less than 0.5 per cent. of caffeine. Cocoa.-Cocoa paste, mass or slab, is the solid or semi-solid mass pro- duced by grinding cocoa nibs, and shall contain not less than 45 per cent. of cocoa fat. The dry fat-free residue shall not contain more than 19 per cent. of natural cocoa starch, 6-33 per cent. of crude fibre, 8 per cent. of total ash, 5-5 per cent. of insoluble ash, and 0.4 per cent. of ferric oxide. Soluble cocoa or cocoa essence must not exceed a maximum of 3 per cent. of added alkali (as K,CO,) , and prepared cocoa must contain at least 20 per cent. of fat-free cocoa. Chocolate $ash, coatings, +owder and confectioners’ chocolate shall contain at least 16 per cent. of fat-free cocoa. No cocoa husks, weighting substance, paraffin wax, or foreign fat may be added to cocoa or to any preparation thereof. (49) (50) D. G. H.

ISSN:0003-2654    

DOI:10.1039/AN9265100031

出版商:RSC    

年代:1926

数据来源: RSC

摘要:

142 ABSTRACTS OF CHEMICAL PAPERS milk-solids-not-fat and 3.25 per cent. of milk fat, and in the reductase test (see Section 42) shall require at least 4 hours to decolorise the methylene blue solution. Cream must contain at least 40 per cent. of milk fat. (46) Butter.-Butter shall contain at least 80 per cent. of milk fat, and not more than 16 per cent. of water or 20 grains per lb. boron preservative (calculated as boric acid).(47) Cheese.-Cheese shall contain not less than 50 per cent. of milk fat on the dry substance, and skim-milk cheese not less than 10 per cent. (48) Tea.-Tea shall yield between 4 and 7 per cent. of ash (at least one half of which is water-soluble) and at least 30 per cent. of extract, which shall be determined by boiling 2 grms. of tea in 200 C.C. of distilled water under a reflux condenser for 1 hour, filtering hot, cooling and evaporating an aliquot portion to constant weight.Tea dust shall not yield over 5 per cent. of ash insoluble in water. Cofee.-Coffee shall contain not less than 10 per cent. of fat, and more than 1 per cent. of saccharine matter, and shall yield not more than 6 per cent. of ash, of which not less than 75 per cent.shall be soluble in water. Co$ee essence shall contain not less than 0.5 per cent. of caffeine. Cocoa.-Cocoa paste, mass or slab, is the solid or semi-solid mass pro- duced by grinding cocoa nibs, and shall contain not less than 45 per cent. of cocoa fat. The dry fat-free residue shall not contain more than 19 per cent. of natural cocoa starch, 6-33 per cent.of crude fibre, 8 per cent. of total ash, 5-5 per cent. of insoluble ash, and 0.4 per cent. of ferric oxide. Soluble cocoa or cocoa essence must not exceed a maximum of 3 per cent. of added alkali (as K,CO,) , and prepared cocoa must contain at least 20 per cent. of fat-free cocoa. Chocolate $ash, coatings, +owder and confectioners’ chocolate shall contain at least 16 per cent.of fat-free cocoa. No cocoa husks, weighting substance, paraffin wax, or foreign fat may be added to cocoa or to any preparation thereof. (49) (50) D. G. H.142 ABSTRACTS OF CHEMICAL PAPERS milk-solids-not-fat and 3.25 per cent. of milk fat, and in the reductase test (see Section 42) shall require at least 4 hours to decolorise the methylene blue solution. Cream must contain at least 40 per cent.of milk fat. (46) Butter.-Butter shall contain at least 80 per cent. of milk fat, and not more than 16 per cent. of water or 20 grains per lb. boron preservative (calculated as boric acid). (47) Cheese.-Cheese shall contain not less than 50 per cent. of milk fat on the dry substance, and skim-milk cheese not less than 10 per cent. (48) Tea.-Tea shall yield between 4 and 7 per cent.of ash (at least one half of which is water-soluble) and at least 30 per cent. of extract, which shall be determined by boiling 2 grms. of tea in 200 C.C. of distilled water under a reflux condenser for 1 hour, filtering hot, cooling and evaporating an aliquot portion to constant weight. Tea dust shall not yield over 5 per cent. of ash insoluble in water.Cofee.-Coffee shall contain not less than 10 per cent. of fat, and more than 1 per cent. of saccharine matter, and shall yield not more than 6 per cent. of ash, of which not less than 75 per cent. shall be soluble in water. Co$ee essence shall contain not less than 0.5 per cent. of caffeine. Cocoa.-Cocoa paste, mass or slab, is the solid or semi-solid mass pro- duced by grinding cocoa nibs, and shall contain not less than 45 per cent. of cocoa fat.The dry fat-free residue shall not contain more than 19 per cent. of natural cocoa starch, 6-33 per cent. of crude fibre, 8 per cent. of total ash, 5-5 per cent. of insoluble ash, and 0.4 per cent. of ferric oxide. Soluble cocoa or cocoa essence must not exceed a maximum of 3 per cent. of added alkali (as K,CO,) , and prepared cocoa must contain at least 20 per cent.of fat-free cocoa. Chocolate $ash, coatings, +owder and confectioners’ chocolate shall contain at least 16 per cent. of fat-free cocoa. No cocoa husks, weighting substance, paraffin wax, or foreign fat may be added to cocoa or to any preparation thereof. (49) (50) D. G. H.142 ABSTRACTS OF CHEMICAL PAPERS milk-solids-not-fat and 3.25 per cent.of milk fat, and in the reductase test (see Section 42) shall require at least 4 hours to decolorise the methylene blue solution. Cream must contain at least 40 per cent. of milk fat. (46) Butter.-Butter shall contain at least 80 per cent. of milk fat, and not more than 16 per cent. of water or 20 grains per lb. boron preservative (calculated as boric acid).(47) Cheese.-Cheese shall contain not less than 50 per cent. of milk fat on the dry substance, and skim-milk cheese not less than 10 per cent. (48) Tea.-Tea shall yield between 4 and 7 per cent. of ash (at least one half of which is water-soluble) and at least 30 per cent. of extract, which shall be determined by boiling 2 grms. of tea in 200 C.C. of distilled water under a reflux condenser for 1 hour, filtering hot, cooling and evaporating an aliquot portion to constant weight.Tea dust shall not yield over 5 per cent. of ash insoluble in water. Cofee.-Coffee shall contain not less than 10 per cent. of fat, and more than 1 per cent. of saccharine matter, and shall yield not more than 6 per cent. of ash, of which not less than 75 per cent. shall be soluble in water. Co$ee essence shall contain not less than 0.5 per cent.of caffeine. Cocoa.-Cocoa paste, mass or slab, is the solid or semi-solid mass pro- duced by grinding cocoa nibs, and shall contain not less than 45 per cent. of cocoa fat. The dry fat-free residue shall not contain more than 19 per cent. of natural cocoa starch, 6-33 per cent. of crude fibre, 8 per cent. of total ash, 5-5 per cent. of insoluble ash, and 0.4 per cent. of ferric oxide. Soluble cocoa or cocoa essence must not exceed a maximum of 3 per cent. of added alkali (as K,CO,) , and prepared cocoa must contain at least 20 per cent. of fat-free cocoa. Chocolate $ash, coatings, +owder and confectioners’ chocolate shall contain at least 16 per cent. of fat-free cocoa. No cocoa husks, weighting substance, paraffin wax, or foreign fat may be added to cocoa or to any preparation thereof. (49) (50) D. G. H.

ISSN:0003-2654    

DOI:10.1039/AN926510032b

出版商:RSC    

年代:1926

数据来源: RSC

摘要:

142 ABSTRACTS OF CHEMICAL PAPERS milk-solids-not-fat and 3.25 per cent. of milk fat, and in the reductase test (see Section 42) shall require at least 4 hours to decolorise the methylene blue solution. Cream must contain at least 40 per cent. of milk fat. (46) Butter.-Butter shall contain at least 80 per cent. of milk fat, and not more than 16 per cent. of water or 20 grains per lb. boron preservative (calculated as boric acid).(47) Cheese.-Cheese shall contain not less than 50 per cent. of milk fat on the dry substance, and skim-milk cheese not less than 10 per cent. (48) Tea.-Tea shall yield between 4 and 7 per cent. of ash (at least one half of which is water-soluble) and at least 30 per cent. of extract, which shall be determined by boiling 2 grms. of tea in 200 C.C. of distilled water under a reflux condenser for 1 hour, filtering hot, cooling and evaporating an aliquot portion to constant weight.Tea dust shall not yield over 5 per cent. of ash insoluble in water. Cofee.-Coffee shall contain not less than 10 per cent. of fat, and more than 1 per cent. of saccharine matter, and shall yield not more than 6 per cent. of ash, of which not less than 75 per cent.shall be soluble in water. Co$ee essence shall contain not less than 0.5 per cent. of caffeine. Cocoa.-Cocoa paste, mass or slab, is the solid or semi-solid mass pro- duced by grinding cocoa nibs, and shall contain not less than 45 per cent. of cocoa fat. The dry fat-free residue shall not contain more than 19 per cent. of natural cocoa starch, 6-33 per cent.of crude fibre, 8 per cent. of total ash, 5-5 per cent. of insoluble ash, and 0.4 per cent. of ferric oxide. Soluble cocoa or cocoa essence must not exceed a maximum of 3 per cent. of added alkali (as K,CO,) , and prepared cocoa must contain at least 20 per cent. of fat-free cocoa. Chocolate $ash, coatings, +owder and confectioners’ chocolate shall contain at least 16 per cent.of fat-free cocoa. No cocoa husks, weighting substance, paraffin wax, or foreign fat may be added to cocoa or to any preparation thereof. (49) (50) D. G. H.142 ABSTRACTS OF CHEMICAL PAPERS milk-solids-not-fat and 3.25 per cent. of milk fat, and in the reductase test (see Section 42) shall require at least 4 hours to decolorise the methylene blue solution. Cream must contain at least 40 per cent.of milk fat. (46) Butter.-Butter shall contain at least 80 per cent. of milk fat, and not more than 16 per cent. of water or 20 grains per lb. boron preservative (calculated as boric acid). (47) Cheese.-Cheese shall contain not less than 50 per cent. of milk fat on the dry substance, and skim-milk cheese not less than 10 per cent. (48) Tea.-Tea shall yield between 4 and 7 per cent.of ash (at least one half of which is water-soluble) and at least 30 per cent. of extract, which shall be determined by boiling 2 grms. of tea in 200 C.C. of distilled water under a reflux condenser for 1 hour, filtering hot, cooling and evaporating an aliquot portion to constant weight. Tea dust shall not yield over 5 per cent. of ash insoluble in water.Cofee.-Coffee shall contain not less than 10 per cent. of fat, and more than 1 per cent. of saccharine matter, and shall yield not more than 6 per cent. of ash, of which not less than 75 per cent. shall be soluble in water. Co$ee essence shall contain not less than 0.5 per cent. of caffeine. Cocoa.-Cocoa paste, mass or slab, is the solid or semi-solid mass pro- duced by grinding cocoa nibs, and shall contain not less than 45 per cent. of cocoa fat.The dry fat-free residue shall not contain more than 19 per cent. of natural cocoa starch, 6-33 per cent. of crude fibre, 8 per cent. of total ash, 5-5 per cent. of insoluble ash, and 0.4 per cent. of ferric oxide. Soluble cocoa or cocoa essence must not exceed a maximum of 3 per cent. of added alkali (as K,CO,) , and prepared cocoa must contain at least 20 per cent. of fat-free cocoa. Chocolate $ash, coatings, +owder and confectioners’ chocolate shall contain at least 16 per cent. of fat-free cocoa. No cocoa husks, weighting substance, paraffin wax, or foreign fat may be added to cocoa or to any preparation thereof. (49) (50) D. G. H.

ISSN:0003-2654    

DOI:10.1039/AN9265100035

出版商:RSC    

年代:1926

数据来源: RSC

摘要:

142 ABSTRACTS OF CHEMICAL PAPERS milk-solids-not-fat and 3.25 per cent. of milk fat, and in the reductase test (see Section 42) shall require at least 4 hours to decolorise the methylene blue solution. Cream must contain at least 40 per cent. of milk fat. (46) Butter.-Butter shall contain at least 80 per cent. of milk fat, and not more than 16 per cent. of water or 20 grains per lb. boron preservative (calculated as boric acid).(47) Cheese.-Cheese shall contain not less than 50 per cent. of milk fat on the dry substance, and skim-milk cheese not less than 10 per cent. (48) Tea.-Tea shall yield between 4 and 7 per cent. of ash (at least one half of which is water-soluble) and at least 30 per cent. of extract, which shall be determined by boiling 2 grms. of tea in 200 C.C. of distilled water under a reflux condenser for 1 hour, filtering hot, cooling and evaporating an aliquot portion to constant weight.Tea dust shall not yield over 5 per cent. of ash insoluble in water. Cofee.-Coffee shall contain not less than 10 per cent. of fat, and more than 1 per cent. of saccharine matter, and shall yield not more than 6 per cent. of ash, of which not less than 75 per cent.shall be soluble in water. Co$ee essence shall contain not less than 0.5 per cent. of caffeine. Cocoa.-Cocoa paste, mass or slab, is the solid or semi-solid mass pro- duced by grinding cocoa nibs, and shall contain not less than 45 per cent. of cocoa fat. The dry fat-free residue shall not contain more than 19 per cent. of natural cocoa starch, 6-33 per cent.of crude fibre, 8 per cent. of total ash, 5-5 per cent. of insoluble ash, and 0.4 per cent. of ferric oxide. Soluble cocoa or cocoa essence must not exceed a maximum of 3 per cent. of added alkali (as K,CO,) , and prepared cocoa must contain at least 20 per cent. of fat-free cocoa. Chocolate $ash, coatings, +owder and confectioners’ chocolate shall contain at least 16 per cent.of fat-free cocoa. No cocoa husks, weighting substance, paraffin wax, or foreign fat may be added to cocoa or to any preparation thereof. (49) (50) D. G. H.142 ABSTRACTS OF CHEMICAL PAPERS milk-solids-not-fat and 3.25 per cent. of milk fat, and in the reductase test (see Section 42) shall require at least 4 hours to decolorise the methylene blue solution. Cream must contain at least 40 per cent.of milk fat. (46) Butter.-Butter shall contain at least 80 per cent. of milk fat, and not more than 16 per cent. of water or 20 grains per lb. boron preservative (calculated as boric acid). (47) Cheese.-Cheese shall contain not less than 50 per cent. of milk fat on the dry substance, and skim-milk cheese not less than 10 per cent. (48) Tea.-Tea shall yield between 4 and 7 per cent.of ash (at least one half of which is water-soluble) and at least 30 per cent. of extract, which shall be determined by boiling 2 grms. of tea in 200 C.C. of distilled water under a reflux condenser for 1 hour, filtering hot, cooling and evaporating an aliquot portion to constant weight. Tea dust shall not yield over 5 per cent. of ash insoluble in water.Cofee.-Coffee shall contain not less than 10 per cent. of fat, and more than 1 per cent. of saccharine matter, and shall yield not more than 6 per cent. of ash, of which not less than 75 per cent. shall be soluble in water. Co$ee essence shall contain not less than 0.5 per cent. of caffeine. Cocoa.-Cocoa paste, mass or slab, is the solid or semi-solid mass pro- duced by grinding cocoa nibs, and shall contain not less than 45 per cent. of cocoa fat.The dry fat-free residue shall not contain more than 19 per cent. of natural cocoa starch, 6-33 per cent. of crude fibre, 8 per cent. of total ash, 5-5 per cent. of insoluble ash, and 0.4 per cent. of ferric oxide. Soluble cocoa or cocoa essence must not exceed a maximum of 3 per cent. of added alkali (as K,CO,) , and prepared cocoa must contain at least 20 per cent. of fat-free cocoa. Chocolate $ash, coatings, +owder and confectioners’ chocolate shall contain at least 16 per cent. of fat-free cocoa. No cocoa husks, weighting substance, paraffin wax, or foreign fat may be added to cocoa or to any preparation thereof. (49) (50) D. G. H.

ISSN:0003-2654    

DOI:10.1039/AN9265100036

出版商:RSC    

年代:1926

数据来源: RSC

摘要:

142 ABSTRACTS OF CHEMICAL PAPERS milk-solids-not-fat and 3.25 per cent. of milk fat, and in the reductase test (see Section 42) shall require at least 4 hours to decolorise the methylene blue solution. Cream must contain at least 40 per cent. of milk fat. (46) Butter.-Butter shall contain at least 80 per cent. of milk fat, and not more than 16 per cent. of water or 20 grains per lb. boron preservative (calculated as boric acid).(47) Cheese.-Cheese shall contain not less than 50 per cent. of milk fat on the dry substance, and skim-milk cheese not less than 10 per cent. (48) Tea.-Tea shall yield between 4 and 7 per cent. of ash (at least one half of which is water-soluble) and at least 30 per cent. of extract, which shall be determined by boiling 2 grms. of tea in 200 C.C. of distilled water under a reflux condenser for 1 hour, filtering hot, cooling and evaporating an aliquot portion to constant weight.Tea dust shall not yield over 5 per cent. of ash insoluble in water. Cofee.-Coffee shall contain not less than 10 per cent. of fat, and more than 1 per cent. of saccharine matter, and shall yield not more than 6 per cent. of ash, of which not less than 75 per cent.shall be soluble in water. Co$ee essence shall contain not less than 0.5 per cent. of caffeine. Cocoa.-Cocoa paste, mass or slab, is the solid or semi-solid mass pro- duced by grinding cocoa nibs, and shall contain not less than 45 per cent. of cocoa fat. The dry fat-free residue shall not contain more than 19 per cent. of natural cocoa starch, 6-33 per cent.of crude fibre, 8 per cent. of total ash, 5-5 per cent. of insoluble ash, and 0.4 per cent. of ferric oxide. Soluble cocoa or cocoa essence must not exceed a maximum of 3 per cent. of added alkali (as K,CO,) , and prepared cocoa must contain at least 20 per cent. of fat-free cocoa. Chocolate $ash, coatings, +owder and confectioners’ chocolate shall contain at least 16 per cent.of fat-free cocoa. No cocoa husks, weighting substance, paraffin wax, or foreign fat may be added to cocoa or to any preparation thereof. (49) (50) D. G. H.142 ABSTRACTS OF CHEMICAL PAPERS milk-solids-not-fat and 3.25 per cent. of milk fat, and in the reductase test (see Section 42) shall require at least 4 hours to decolorise the methylene blue solution. Cream must contain at least 40 per cent.of milk fat. (46) Butter.-Butter shall contain at least 80 per cent. of milk fat, and not more than 16 per cent. of water or 20 grains per lb. boron preservative (calculated as boric acid). (47) Cheese.-Cheese shall contain not less than 50 per cent. of milk fat on the dry substance, and skim-milk cheese not less than 10 per cent. (48) Tea.-Tea shall yield between 4 and 7 per cent.of ash (at least one half of which is water-soluble) and at least 30 per cent. of extract, which shall be determined by boiling 2 grms. of tea in 200 C.C. of distilled water under a reflux condenser for 1 hour, filtering hot, cooling and evaporating an aliquot portion to constant weight. Tea dust shall not yield over 5 per cent. of ash insoluble in water.Cofee.-Coffee shall contain not less than 10 per cent. of fat, and more than 1 per cent. of saccharine matter, and shall yield not more than 6 per cent. of ash, of which not less than 75 per cent. shall be soluble in water. Co$ee essence shall contain not less than 0.5 per cent. of caffeine. Cocoa.-Cocoa paste, mass or slab, is the solid or semi-solid mass pro- duced by grinding cocoa nibs, and shall contain not less than 45 per cent. of cocoa fat.The dry fat-free residue shall not contain more than 19 per cent. of natural cocoa starch, 6-33 per cent. of crude fibre, 8 per cent. of total ash, 5-5 per cent. of insoluble ash, and 0.4 per cent. of ferric oxide. Soluble cocoa or cocoa essence must not exceed a maximum of 3 per cent. of added alkali (as K,CO,) , and prepared cocoa must contain at least 20 per cent.of fat-free cocoa. Chocolate $ash, coatings, +owder and confectioners’ chocolate shall contain at least 16 per cent. of fat-free cocoa. No cocoa husks, weighting substance, paraffin wax, or foreign fat may be added to cocoa or to any preparation thereof. (49) (50) D. G. H.142 ABSTRACTS OF CHEMICAL PAPERS milk-solids-not-fat and 3.25 per cent.of milk fat, and in the reductase test (see Section 42) shall require at least 4 hours to decolorise the methylene blue solution. Cream must contain at least 40 per cent. of milk fat. (46) Butter.-Butter shall contain at least 80 per cent. of milk fat, and not more than 16 per cent. of water or 20 grains per lb. boron preservative (calculated as boric acid).(47) Cheese.-Cheese shall contain not less than 50 per cent. of milk fat on the dry substance, and skim-milk cheese not less than 10 per cent. (48) Tea.-Tea shall yield between 4 and 7 per cent. of ash (at least one half of which is water-soluble) and at least 30 per cent. of extract, which shall be determined by boiling 2 grms. of tea in 200 C.C. of distilled water under a reflux condenser for 1 hour, filtering hot, cooling and evaporating an aliquot portion to constant weight.Tea dust shall not yield over 5 per cent. of ash insoluble in water. Cofee.-Coffee shall contain not less than 10 per cent. of fat, and more than 1 per cent. of saccharine matter, and shall yield not more than 6 per cent. of ash, of which not less than 75 per cent. shall be soluble in water. Co$ee essence shall contain not less than 0.5 per cent.of caffeine. Cocoa.-Cocoa paste, mass or slab, is the solid or semi-solid mass pro- duced by grinding cocoa nibs, and shall contain not less than 45 per cent. of cocoa fat. The dry fat-free residue shall not contain more than 19 per cent. of natural cocoa starch, 6-33 per cent. of crude fibre, 8 per cent. of total ash, 5-5 per cent.of insoluble ash, and 0.4 per cent. of ferric oxide. Soluble cocoa or cocoa essence must not exceed a maximum of 3 per cent. of added alkali (as K,CO,) , and prepared cocoa must contain at least 20 per cent. of fat-free cocoa. Chocolate $ash, coatings, +owder and confectioners’ chocolate shall contain at least 16 per cent. of fat-free cocoa. No cocoa husks, weighting substance, paraffin wax, or foreign fat may be added to cocoa or to any preparation thereof. (49) (50) D.G. H.142 ABSTRACTS OF CHEMICAL PAPERS milk-solids-not-fat and 3.25 per cent. of milk fat, and in the reductase test (see Section 42) shall require at least 4 hours to decolorise the methylene blue solution. Cream must contain at least 40 per cent. of milk fat.(46) Butter.-Butter shall contain at least 80 per cent. of milk fat, and not more than 16 per cent. of water or 20 grains per lb. boron preservative (calculated as boric acid). (47) Cheese.-Cheese shall contain not less than 50 per cent. of milk fat on the dry substance, and skim-milk cheese not less than 10 per cent. (48) Tea.-Tea shall yield between 4 and 7 per cent. of ash (at least one half of which is water-soluble) and at least 30 per cent.of extract, which shall be determined by boiling 2 grms. of tea in 200 C.C. of distilled water under a reflux condenser for 1 hour, filtering hot, cooling and evaporating an aliquot portion to constant weight. Tea dust shall not yield over 5 per cent. of ash insoluble in water. Cofee.-Coffee shall contain not less than 10 per cent.of fat, and more than 1 per cent. of saccharine matter, and shall yield not more than 6 per cent. of ash, of which not less than 75 per cent. shall be soluble in water. Co$ee essence shall contain not less than 0.5 per cent. of caffeine. Cocoa.-Cocoa paste, mass or slab, is the solid or semi-solid mass pro- duced by grinding cocoa nibs, and shall contain not less than 45 per cent.of cocoa fat. The dry fat-free residue shall not contain more than 19 per cent. of natural cocoa starch, 6-33 per cent. of crude fibre, 8 per cent. of total ash, 5-5 per cent. of insoluble ash, and 0.4 per cent. of ferric oxide. Soluble cocoa or cocoa essence must not exceed a maximum of 3 per cent. of added alkali (as K,CO,) , and prepared cocoa must contain at least 20 per cent.of fat-free cocoa. Chocolate $ash, coatings, +owder and confectioners’ chocolate shall contain at least 16 per cent. of fat-free cocoa. No cocoa husks, weighting substance, paraffin wax, or foreign fat may be added to cocoa or to any preparation thereof. (49) (50) D. G. H.142 ABSTRACTS OF CHEMICAL PAPERS milk-solids-not-fat and 3.25 per cent. of milk fat, and in the reductase test (see Section 42) shall require at least 4 hours to decolorise the methylene blue solution.Cream must contain at least 40 per cent. of milk fat. (46) Butter.-Butter shall contain at least 80 per cent. of milk fat, and not more than 16 per cent. of water or 20 grains per lb. boron preservative (calculated as boric acid). (47) Cheese.-Cheese shall contain not less than 50 per cent.of milk fat on the dry substance, and skim-milk cheese not less than 10 per cent. (48) Tea.-Tea shall yield between 4 and 7 per cent. of ash (at least one half of which is water-soluble) and at least 30 per cent. of extract, which shall be determined by boiling 2 grms. of tea in 200 C.C. of distilled water under a reflux condenser for 1 hour, filtering hot, cooling and evaporating an aliquot portion to constant weight.Tea dust shall not yield over 5 per cent. of ash insoluble in water. Cofee.-Coffee shall contain not less than 10 per cent. of fat, and more than 1 per cent. of saccharine matter, and shall yield not more than 6 per cent. of ash, of which not less than 75 per cent. shall be soluble in water. Co$ee essence shall contain not less than 0.5 per cent.of caffeine. Cocoa.-Cocoa paste, mass or slab, is the solid or semi-solid mass pro- duced by grinding cocoa nibs, and shall contain not less than 45 per cent. of cocoa fat. The dry fat-free residue shall not contain more than 19 per cent. of natural cocoa starch, 6-33 per cent. of crude fibre, 8 per cent. of total ash, 5-5 per cent. of insoluble ash, and 0.4 per cent.of ferric oxide. Soluble cocoa or cocoa essence must not exceed a maximum of 3 per cent. of added alkali (as K,CO,) , and prepared cocoa must contain at least 20 per cent. of fat-free cocoa. Chocolate $ash, coatings, +owder and confectioners’ chocolate shall contain at least 16 per cent. of fat-free cocoa. No cocoa husks, weighting substance, paraffin wax, or foreign fat may be added to cocoa or to any preparation thereof.(49) (50) D. G. H.142 ABSTRACTS OF CHEMICAL PAPERS milk-solids-not-fat and 3.25 per cent. of milk fat, and in the reductase test (see Section 42) shall require at least 4 hours to decolorise the methylene blue solution. Cream must contain at least 40 per cent. of milk fat. (46) Butter.-Butter shall contain at least 80 per cent.of milk fat, and not more than 16 per cent. of water or 20 grains per lb. boron preservative (calculated as boric acid). (47) Cheese.-Cheese shall contain not less than 50 per cent. of milk fat on the dry substance, and skim-milk cheese not less than 10 per cent. (48) Tea.-Tea shall yield between 4 and 7 per cent. of ash (at least one half of which is water-soluble) and at least 30 per cent.of extract, which shall be determined by boiling 2 grms. of tea in 200 C.C. of distilled water under a reflux condenser for 1 hour, filtering hot, cooling and evaporating an aliquot portion to constant weight. Tea dust shall not yield over 5 per cent. of ash insoluble in water. Cofee.-Coffee shall contain not less than 10 per cent. of fat, and more than 1 per cent.of saccharine matter, and shall yield not more than 6 per cent. of ash, of which not less than 75 per cent. shall be soluble in water. Co$ee essence shall contain not less than 0.5 per cent. of caffeine. Cocoa.-Cocoa paste, mass or slab, is the solid or semi-solid mass pro- duced by grinding cocoa nibs, and shall contain not less than 45 per cent. of cocoa fat. The dry fat-free residue shall not contain more than 19 per cent. of natural cocoa starch, 6-33 per cent. of crude fibre, 8 per cent. of total ash, 5-5 per cent. of insoluble ash, and 0.4 per cent. of ferric oxide. Soluble cocoa or cocoa essence must not exceed a maximum of 3 per cent. of added alkali (as K,CO,) , and prepared cocoa must contain at least 20 per cent. of fat-free cocoa. Chocolate $ash, coatings, +owder and confectioners’ chocolate shall contain at least 16 per cent. of fat-free cocoa. No cocoa husks, weighting substance, paraffin wax, or foreign fat may be added to cocoa or to any preparation thereof. (49) (50) D. G. H.

ISSN:0003-2654    

DOI:10.1039/AN926510038b

出版商:RSC    

年代:1926

数据来源: RSC

摘要:

142 ABSTRACTS OF CHEMICAL PAPERS milk-solids-not-fat and 3.25 per cent. of milk fat, and in the reductase test (see Section 42) shall require at least 4 hours to decolorise the methylene blue solution. Cream must contain at least 40 per cent. of milk fat. (46) Butter.-Butter shall contain at least 80 per cent. of milk fat, and not more than 16 per cent. of water or 20 grains per lb. boron preservative (calculated as boric acid).(47) Cheese.-Cheese shall contain not less than 50 per cent. of milk fat on the dry substance, and skim-milk cheese not less than 10 per cent. (48) Tea.-Tea shall yield between 4 and 7 per cent. of ash (at least one half of which is water-soluble) and at least 30 per cent. of extract, which shall be determined by boiling 2 grms. of tea in 200 C.C. of distilled water under a reflux condenser for 1 hour, filtering hot, cooling and evaporating an aliquot portion to constant weight.Tea dust shall not yield over 5 per cent. of ash insoluble in water. Cofee.-Coffee shall contain not less than 10 per cent. of fat, and more than 1 per cent. of saccharine matter, and shall yield not more than 6 per cent. of ash, of which not less than 75 per cent.shall be soluble in water. Co$ee essence shall contain not less than 0.5 per cent. of caffeine. Cocoa.-Cocoa paste, mass or slab, is the solid or semi-solid mass pro- duced by grinding cocoa nibs, and shall contain not less than 45 per cent. of cocoa fat. The dry fat-free residue shall not contain more than 19 per cent. of natural cocoa starch, 6-33 per cent.of crude fibre, 8 per cent. of total ash, 5-5 per cent. of insoluble ash, and 0.4 per cent. of ferric oxide. Soluble cocoa or cocoa essence must not exceed a maximum of 3 per cent. of added alkali (as K,CO,) , and prepared cocoa must contain at least 20 per cent. of fat-free cocoa. Chocolate $ash, coatings, +owder and confectioners’ chocolate shall contain at least 16 per cent.of fat-free cocoa. No cocoa husks, weighting substance, paraffin wax, or foreign fat may be added to cocoa or to any preparation thereof. (49) (50) D. G. H.142 ABSTRACTS OF CHEMICAL PAPERS milk-solids-not-fat and 3.25 per cent. of milk fat, and in the reductase test (see Section 42) shall require at least 4 hours to decolorise the methylene blue solution. Cream must contain at least 40 per cent.of milk fat. (46) Butter.-Butter shall contain at least 80 per cent. of milk fat, and not more than 16 per cent. of water or 20 grains per lb. boron preservative (calculated as boric acid). (47) Cheese.-Cheese shall contain not less than 50 per cent. of milk fat on the dry substance, and skim-milk cheese not less than 10 per cent. (48) Tea.-Tea shall yield between 4 and 7 per cent.of ash (at least one half of which is water-soluble) and at least 30 per cent. of extract, which shall be determined by boiling 2 grms. of tea in 200 C.C. of distilled water under a reflux condenser for 1 hour, filtering hot, cooling and evaporating an aliquot portion to constant weight. Tea dust shall not yield over 5 per cent. of ash insoluble in water.Cofee.-Coffee shall contain not less than 10 per cent. of fat, and more than 1 per cent. of saccharine matter, and shall yield not more than 6 per cent. of ash, of which not less than 75 per cent. shall be soluble in water. Co$ee essence shall contain not less than 0.5 per cent. of caffeine. Cocoa.-Cocoa paste, mass or slab, is the solid or semi-solid mass pro- duced by grinding cocoa nibs, and shall contain not less than 45 per cent. of cocoa fat.The dry fat-free residue shall not contain more than 19 per cent. of natural cocoa starch, 6-33 per cent. of crude fibre, 8 per cent. of total ash, 5-5 per cent. of insoluble ash, and 0.4 per cent. of ferric oxide. Soluble cocoa or cocoa essence must not exceed a maximum of 3 per cent. of added alkali (as K,CO,) , and prepared cocoa must contain at least 20 per cent.of fat-free cocoa. Chocolate $ash, coatings, +owder and confectioners’ chocolate shall contain at least 16 per cent. of fat-free cocoa. No cocoa husks, weighting substance, paraffin wax, or foreign fat may be added to cocoa or to any preparation thereof. (49) (50) D. G. H.142 ABSTRACTS OF CHEMICAL PAPERS milk-solids-not-fat and 3.25 per cent.of milk fat, and in the reductase test (see Section 42) shall require at least 4 hours to decolorise the methylene blue solution. Cream must contain at least 40 per cent. of milk fat. (46) Butter.-Butter shall contain at least 80 per cent. of milk fat, and not more than 16 per cent. of water or 20 grains per lb. boron preservative (calculated as boric acid).(47) Cheese.-Cheese shall contain not less than 50 per cent. of milk fat on the dry substance, and skim-milk cheese not less than 10 per cent. (48) Tea.-Tea shall yield between 4 and 7 per cent. of ash (at least one half of which is water-soluble) and at least 30 per cent. of extract, which shall be determined by boiling 2 grms. of tea in 200 C.C. of distilled water under a reflux condenser for 1 hour, filtering hot, cooling and evaporating an aliquot portion to constant weight.Tea dust shall not yield over 5 per cent. of ash insoluble in water. Cofee.-Coffee shall contain not less than 10 per cent. of fat, and more than 1 per cent. of saccharine matter, and shall yield not more than 6 per cent. of ash, of which not less than 75 per cent. shall be soluble in water. Co$ee essence shall contain not less than 0.5 per cent.of caffeine. Cocoa.-Cocoa paste, mass or slab, is the solid or semi-solid mass pro- duced by grinding cocoa nibs, and shall contain not less than 45 per cent. of cocoa fat. The dry fat-free residue shall not contain more than 19 per cent. of natural cocoa starch, 6-33 per cent. of crude fibre, 8 per cent. of total ash, 5-5 per cent. of insoluble ash, and 0.4 per cent. of ferric oxide. Soluble cocoa or cocoa essence must not exceed a maximum of 3 per cent. of added alkali (as K,CO,) , and prepared cocoa must contain at least 20 per cent. of fat-free cocoa. Chocolate $ash, coatings, +owder and confectioners’ chocolate shall contain at least 16 per cent. of fat-free cocoa. No cocoa husks, weighting substance, paraffin wax, or foreign fat may be added to cocoa or to any preparation thereof. (49) (50) D. G. H.

ISSN:0003-2654    

DOI:10.1039/AN9265100044

出版商:RSC    

年代:1926

数据来源: RSC