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SEPTEMBER 1931. Vol. LVI. No. 666, Carbon Monoxide Poisoning : Its Detection and the Determination of Percentage Saturation in Blood by Means of the Hartridge Reversion Spectroscope. BY ROBERT C. FREDERICK A.I.C. INTRODUCTION.-~O much has been heard in recent years of carbon monoxide poisoning that there is a tendency to regard casualties from this cause as being peculiar to the age. Though cases are now apparently more numerous the number has always been large and Lewinl goes so far as to state that carbon monoxide is now and has been since the first discovery of fire the most widespread poison connected with human life and activity. The vehicle in which the poison is conveyed has however certainly changed with the times. In the literature nearly a century ago there is discussion regarding the many fatalities occurring in France (a large proportion of which were suicidal) due to the use of braziers.French writers of fiction in their works frequently introduced 56 562 FREDERICK CARBON MONOXIDE POISONING situations where death took place by this means and one Zola himself met his death accidentally in this way. The use of fire fumes was a method of suicide employed by the Romans. At the present time in this country the most common cause of carbon monoxide poisoning is the public gas supply and history is repeating itself for the majority of these cases are suicidal. The extremely poisonous character of the gas is due to the carbon monoxide content being increased by admixture with water-gas and similar products. The Report of the Departmental Committee appointed to consider the increase in the number of deaths ascribed to poisoning by coal gas supplied for domestic purposes2 reveals that such as were suicidal increased from 193 in 1918 to 1191 in 1928; the figures for those considered officially as due to accident were 102 and 168 respectively.Apart from the question of gas escape poisoning may occur when the gas is burning if the flame is striking a cold conducting material; hence the menace of geysers and other types of hot water heaters when fitted without adequate flues. The advent of the petrol engine has brought in its train numerous cases of poisoning not all accidental due to the carbon monoxide in the exhaust gases. A certain number of cases of poisoning by carbon monoxide have occurred with men seeking warmth and falling asleep by the slow-burning heaps of town and ironworks refuse.Poisoning by carbon monoxide is an occupational hazard in many industries amongst which are water gas producer gas and coal gas manu-facture; blast furnace and coke oven operatim; lime and charcoal burning; and coal mining. The physiological response of the individual to various concentrations of carbon monoxide has been studied by Henderson Haggard Teague Prince and W~nderlich,~ and their findings have been summarised by the two first-named in the following table#* :-Concentration. Carbon monoxide. Per Cent. Allowable for an exposure of several hours . . 0.0 1 Can be inhaled for one hour without appreciable effect . . . . O-OPO-05 Causing a just appreciable effect after one hour's exposure .. . . 0*06-0*07 Causing unpleasant but not dangerous symptoms after one hour's Fatal in exposure of less than one hour . . 0.4 and above exposure . . . . 0.1 -0.12 Dangerous for exposure of one hour . . . . 0.15-0*20 The poisonous effect of carbon monoxide is exercised through the blood owing to the great affinity of the gas for haemoglobin (some 300 times that of oxygen) which results in the formation of carboxyhaemoglobin. The carboxy-haemoglobin is entirely incapable of carrying oxygen to the tissues and according to the amount of haemoglobin thus inactivated (or percentage saturation) so the individual exhibits illness of proportionate severity; if the percentage satura-tion becomes sufficiently high death ensues.The average physiological effects * Modified to show figures in terms of percentage instead of parts per million FREDERICK CARBON MONOXIDE POISONING 663 caused by varying percentage saturations of the blood with carbon monoxide have been succinctly set out by Henderson and Haggard in the following table6:-Haemoglobin in combination with carbon monoxide. Per Cent. 10 20 30 40-50 60-70 80 Over 80 Physiological effect. No appreciable effect except shortness of breath on vigorous muscular No appreciable effect in most cases except short wind even on Decided headache ; imtation ; ready fatigue ; disturbance of judgment. Headache confusion collapse and fainting on exertion. Unconsciousness ; respiratory failure and death if exposure is long continued.Rapidly fatal. Immediately fatal. exertion. moderate exertion; slight headache in some cases. Some of the differences between normal blood and blood containing carbon monoxide are readily evident such as the colour (which is invariably but rather unhappily described as cherry-red) whilst others are revealed only by the spectro-scope. The colour of the blood at least in the cadaver is not specific as is so generally supposed and it is essential in the absence of other positive evidence that spectroscopic examination should be made before arriving at a conclusion. Normal blood shows two absorption bands between the D and E lines and blood containing carbon monoxide will appear to exhibit identical features unless an instrument of precision is employed when especially if the percentage saturation of the blood is high and the spectrum of a normal blood is viewed simultaneously, careful observation will reveal that the bands of carboxyhaemoglobin are very slightly nearer the violet end of the spectrum.The spectroscopic difference is too slight to be diagnostic unless the Hartridge Reversion Spectroscope is employed. A chemical method of differentiation is available by observing the effect of the addition of a reducing agent such as ammonium sulphide when in theory, with a normal blood the two bands of oxyhaemoglobin merge into the one broad band of haemoglobin and in blood containing carbon monoxide the bands of carboxyhaemoglobin remain unchanged. This chemical method of differentiating the bands has been transcribed from one text-book to another and the accounts nearly all give the same impression of a process without difficulties or limitations.I n practice in my hands this test has frequently yielded results which were open t o doubt except with blood almost saturated with carbon monoxide even when carried out with simultaneous treatment and observation of a normal blood control. This is only to be expected for in the presence of a reducing agent the stable absorption bands of carboxyhaemoglobin are masked to a less or greater extent by the broad band of haemoglobin from reduction of oxyhaemoglobin according to the percentage saturation of the blood. With the Hartridge Reversion Spectroscope it is possible in a few minutes not only to detect carbon monoxide in blood with certainty even in small amount but also to determine the percentage saturation and therefore to express an opinio 664 FREDERICK CARBON MONOXIDE POISONING whether this was the cause of illness or death.In life the gas is rapidly eliminated as soon as the person is removed from the poisonous atmosphere but specimens of blood taken from an individual will retain the carbon monoxide for weeks if these are stored under suitable conditions. THE HARTRIDGE REVERSION SPECTROSCOPE Fig. 1. THE HARTRIDGE REVERSION SPECTROSCOPE.-The spectroscope is shown in Fig. 1; it is quite a small instrument measuring at the longest diagonal of the base only about 14 cm. A source of light must be provided at the collimating lens (seen prcjecting behind the micrometer screw).The lighting Enit (which may be obtained with the instrument) is conveniently a 60 C.P. electric lamp housed in one box arrangement superimposed on another which contains an adjustable mirror and has one side (facing the spectroscope) made of ground glass. I had this re-constructed and the complete apparatus with the spectroscope adjustable in position mounted on a miniature table 35 cm. high. Interposed between the source of light and the spectroscope is a holder for the cell containing the blood under examination. The cells used are 40 mm. square at the face and are of the type made by cutting a U-shaped piece from a solid piece of glass. Those made for me are 5 mm. thick; the depression is a true semi-circle (17 mm. in diameter at the bottom) and has an extreme height of 30 mm.The diameter is just sufficient to cover completely the collimating lens and enables an examination to be made if necessary with the absolute minimum quantity of sample-a single drop of blood. The principle of the instrument is the utilisation of the fact already referred to that in blood containing carbon monoxide the absorption bands are situate FREDERICK CARBON MONOXIDE POISONING 565 slightly nearer the violet end of the spectrum and in addition that the extent of this difference in wave-length is related to the percentage saturation. To enable this difference to be measured more accurately the effect is doubled by the simple and ingenious expedient of employing two spectra in reverse directions. With the instrument at zero the field of the spectroscope in observation of a normal blood is shown (Fig.2) in a and with blood containing carbon monoxide in b. By turning the micrometer screw the bands in either case may be brought into the basal position shown in c and a record obtained directly in Angstrom Units of the difference in wave-length between a normal blood and a blood sample containing carbon monoxide. should be used in a dark-room. The mirror of the lighting unit and the spectro-scope having been adjusted to give the essential uniform illumination of the spectra the reading for a normal blood is first obtained. The normal blood should be human and from an individual who is not a heavy smoker; Hartridge6 has found that blood from such subjects may be saturated with carbon monoxide to the extent of 6 per cent.Animal blood is to be avoided, as the intestinal gases of herbivora are stated to contain carbon monoxide; Hartridge’ has found carbon monoxide in sheep’s blood. The blood is diluted with distilled water* to such a degree that trial observations show the bands to be visible distinctly and the distance between them to be about the same as the width of the alpha band. For this purpose the small quantity of diluted blood required is pipetted (using a drawn-out glass tube with rubber teat attached) into or from a cell which is of course interposed between the instrument and the source of light. It will be necessary probably to focus; this is done by adjustment of the milled screw on the collimating lens. Once the position of this has been found it must not be moved again before examination of the suspected sample.Observation is made at the eyepiece seen on the extreme left of Fig. 1; it is fitted with a shield not shown. While these trial observations are being made the micro-meter screw (seen on the extreme right of the illustration) should be at zero. The knife edge in the centre foreground is a coarse adjustment but this is not used; it is placed exactly at 3 and is thereafter ignored except to see that it remains in that position. These preliminaries having been completed the reading for normal blood is now determined by turning the micrometer screw until the two alpha bands are in line (Fig. 2 C) and then when this position has been attained noting the figure on the screw.It is necessary to take the average of ten readings; a certain degree of variation will be found between the separate figures but the average of a series should be within one or two digits of another series of observations on the same blood. The most concordant results are obtained by making the adjustment quickly and without hesitation. The screw is graduated into 100 divisions each * The effect of adding distilled water is to burst the envelopes of the red blood corpuscles (hence the turbidity produced) and to cause the contained haemoglobin to pass into solution; this phenomenon is known as ‘ I laking.” This difference Hartridge terms the “ span.’’ THE DETERMINATION OF THE SPAN OF A BLOOD SAMPLE.-The instrumen 566 FREDERICK CARBON MONOXIDE POISONING representing one hgstrom Unit; these are marked at each tenth with the single numerals 0 to 9.If the adjustment of the bands entails the screw being turned away from the operator the graduations have to be read backwards e.g. a complete turn and the screw at 81 would be a reading of lOO+(lOO-81)=119. The suspected sample is now examined in precisely the same manner; it is a useful precaution thereafter to confirm the normal blood reading with a repeat series of observations. It is to be noted that the glass containers must not be sealed by fusion as carbon monoxide may be absorbed from the heating agent. The samples should not be exposed unduly to daylight as this may cause a loss of carbon monoxide. If the sample gives a reading appreciably greater than that of the normal blood i.e.the span is a definite figure the presence of carbon monoxide to the extent of a certain percentage saturation is revealed. Blood saturated with the gas gives a span of about 65 Angstrom Units. To determine the percentage satura-tion indicated by a span it is necessary to construct a calibration curve for the particular instrument employed as the figures are not in direct proportion FREDERICK CARBON MONOXIDE POISONING 567 PREPARATION OF CALIBRATION CURVE.-For the preparation of the curve it is necessary to establish four points the span of blood saturated with carbon monoxide to the extent of (i) 25 (ii) 50 (iii) 75 and (iv) 100 per cent. with carbon monoxide. Stock quantities of diluted normal blood (N) and blood saturated with carbon monoxide (S) must first be prepared.For N a small quantity of blood is placed in a stoppered bottle and distilled water is added to this until observation of a portion shows the degree of dilution to be such as has been specified in the foregoing. For S coal gas is passed through a similar quantity of blood in another stoppered bottle which is shaken from time to time; this blood is then diluted as requisite and afterwards again treated with coal gas to make certain of complete saturation. The reading for normal blood, which has to be deducted from each reading of blood containing carbon monoxide, is obtained by filling one cell with dilution N and the other with distilled water and taking the average of a series as already described. (i) Span for 25 Per Cent. Saturation.-In a test tube are placed 7.5 C.C.of dilution N and 2.5 C.C. of distilled water; in another 2-5 C.C. of dilution S and 7.5 C.C. of distilled water. Both dilutions are mixed in their separate tubes and a quantity from one is pipetted into one cell and from the other into another cell. With the two cells face to face as before the average of a series of readings is obtained, and this less that for the normal blood is the figure required. The other figures are determined by the same procedure except that the preparation of the test tube dilutions is varied as noted below. (ii) Span for 50 Per Cent. Satwation.-Five C.C. of dilution N and 5 C.C. of distilled water in one; 5 C.C. of dilution S and 5 C.C. of distilled water in the other. Two 5 mm. cells are employed face to face.(iii) Span for 75 Per Cent. Saturation.-The dilution N (2.5 c.c.) and 7.5 C.C. of distilled water in one; 7.5 C.C. of dilution S and 2-5 C.C. distilled water in the other. (iv) Span for 100 Per Cent. Saturatzout.-Distilled water aione in one; ciiiution S alone in the other. On plotting out the span figures a smooth curve should be obtained and this is extended to the zero point. The calibration curve once constructed is available permanently for immediate conversion of the span of a blood sample into terms of percent age saturation. NOTE ON THE PRESENCE OF NITRIC OXIDE HAEMoGLOBIN.-The possibility of NO-haemoglobin formed after death being mistaken for CO-haemoglobin in the examination of blood has been discussed by Banham Haldane and Savage,s following a case where the individual had not been exposed to carbon monoxide, yet the blood of whom post-mortem responded to certain of the usual tests for CO-haemoglobin ; the spectroscopic examination it is important to note was not carried out though they considered that had this been done it would have con-firmed the apparent presence of carbon monoxide.The opinion was expresse 568 FREDERICK CARBON MONOXIDE POISONING that the actual cause of death was broncho-pneumonia due to an infecting organism which produced nitrite. These authors state that the double-banded spectrum of NO-haemoglobin is similar to that of CO-haemoglobin and oxyhaemoglobin except that the bands are much less sharply defined than those of oxyhaemoglobin and somewhat less sharply than those of CO-haemoglobin ; the NO-haemoglobin band in the yellow extends also to a slight distance on the red side of the D line.The positions of the alpha and beta bands of the three haemoglobin compounds under discussion have been determined by Hartridge,’ and the wave-lengths of these are given below. Alpha band. Beta band. A.U. A. u. Oxyhaemoglobin . . 5768 5398 CO-haemoglobin . . . 5714 5360 NO-haemoglobin . . 5785 5418 Examination of these figures shows that there is no reason why NO-haemog,Jbin should be mistaken for CO-haemoglobin if the reversion spectroscope is employed, for if NO-haemoglobin is present the span will be a minus instead of a plus figure. 1. 2. 3. 4. 6. 6. 7. 8. 9. REFERENCES. Lewin L. Die Kohlenoxydvergi~~ung.Berlin Julius Springer 1920. Review by Alice H.M. Stationery Office 1930. Henderson Yandell; Haggard Howard W.; Teague Merwyn C.; Prince Alexander L.; and Wunderlich Ruth M. Henderson Yandell; and Haggard Howard W. New York Chemical Catalog Co. 1927 p. 110. Ibid. p. 108. Hartridge H. Hartridge H. Lancet 1928 214 1137. (ANALYST 1928 53 395.) Banham H. A. L.; Haldane J. S.; and Savage T. Hartridge H. Hamilton. J. Ind. Hyg. 1921 3 No. 2. Summary Brit. Med. J. 1930 1 No. 3607. J. Ind. Hyg. 1921 3 Nos. 3 and 4. Noxious Gases. Proc. Physiol. Soc. January 31 1920. Brit. Med. J. 1925,2 No. 3370 187. J. Physiol. 1920 54 No. 4; 1922 57 47 (ANALYST 1923 48 341); (ANALYST; 1925 50 520.) PYOC. Roy. Soc. 1923 A 102 575 (ANALYST 1923 48 351). NoTE.-A valuable summary of the literature on carbon monoxide poisoning (with a bibliography of 195 references) is given by R.R. Sayers and Sara J. Davenport in Review of Carbon Monoxide Poisoning Public Health Bulletin No. 195 Washington, D.C. United States Government Printing Office 1930. ROYAL NAVAL MEDICAL SCHOOL, ROYAL NAVAL COLLEGE GREENWICH S.E. 10. * DISCUSSION. Dr. ROCHE LYNCH said that he was very glad that Mr. Frederick had brought this instrument to the notice of the Society as he thought it was not at all well known. Most analysts had to examine blood at times and there was no doubt that this instrument provided the most suitable method of analysis. In his experience it was capable of much greater accuracy than the Haldane method. With the Hartridge instrument one could work with low percentages and deal with even 4 or 5 per cent.of carbon monoxide; this would be useful in cases of chroni FREDERICK CARBON MONOXIDE POISONING 569 carbon monoxide poisoning. There was a great deal of this about although it was not generally recognised. In many households there were gas jets gas rings, geysers etc. constantly alight and having no flues and these were all giving off carbon monoxide into rooms where people spent a great deal of time. He believed a considerable number of minor ailments were due to people inhaling carbon monoxide in this way. Mr. Frederick had pointed out that 80 per cent. saturation would cause death for certain and he (Dr. Roche Lynch) was inclined to think that probably 60 to 65 per cent.could cause death. However it must be remembered that if the patient were taken out in a moribund condition and lived for a few hours it was surprising how quickly the percentage in the blood fell and very possibly only about 15 per cent. would be found. Also, there were cases of carbon monoxide poisoning where the patient lived for two or three days and then died. Here two factors had to be considered-the factor of the percentage in the blood and the factor of the damage done to the tissues as a result of exposure to the deoxygenated blood. Regarding the figures for suicide from coal gas he remarked that this was a very easy way of terminating life and, although one would like to see an even greater tightening of the Poisons Act, the narcotic poisons available to the public were really very few and consequently coal gas helped to bring up the suicide figures considerably.Sir BERNARD SPILSBURY thanked Mr. Frederick for his observations on nitric oxide haemoglobin which tended to confirm his own opinion. He must plead guilty to having used the Haldane method. Dr. Haldane claimed to read to within 3 per cent. and he (Sir Bernard) thought that he could read to within 5 per cent. which of course was satisfactory where large amounts were con-cerned. He admitted that the test certainly required delicacy of judgment in matching the sample under examination with the standard. His investigations had always been made upon the bodies of persons found dead. In these cases the blood was difficult to examine owing to its coagulation after death and he wondered if the same difficulty were likely to arise with the Hartridge reversion spectroscope.The figures given by Henderson for a fatal result seemed to be unreasonably high. Of course here again one had to take into consideration th'e difference in the results obtained by the two methods but he himself generally found the fatal figure to be about 60 per cent.; it had reached 70 but never ap-proached 80 per c a t . The figures given werej presumably for normal people. whereas people not in normal health succumbed more rapidly. He agreed that the Hartridge reversion spectroscope was a great improvement for lower satura-tions of the blood and was very useful in cases of chronic carbon monoxide poison-ing. Quite recently a medical friend had asked him to investigate certain illness, the cause of which he could not discover.Children were always ill when living in the house although quite well when away. On examining the premises Sir Bernard had found in a basement kitchen a destructor used for getting rid of household refuse. It was a coke furnace standing near the kitchen stove with a flue from the top of the furnace to the top of the chimney. However there =as a loose-fitting lid covering the hole into which the rubbish was put and gases could very easily escape from this into the room. A mouse was placed on the kitchen mantelpiece and in three days it died death being proved to be due t o carbon monoxide poisoning. Such instances must be fairly common in ordinary house-holds and in these days of almost universal motoring also in many badly venti-lated garages.For these cases the Hartridge method of investigation would be of very great advantage. Mr. W. J. A. BUTTERFIELD said that it was very interesting to hear an account of this instrument although he had no experience of its use. The figures for th 570 FREDERICK CARBON MONOXIDE POISONING number of deaths from coal gas poisoning during 1918 and 1928 were probably fairly comparable as regards suicides but he was quite sure from a study of the statistics which he made some years ago for the purpose of a report to the Board of Trade published in 1924 that it was very misleading to take a single year’s accidents and compare them with any other single year ten years later. They varied very much from-year to year and to get a fair comparison he was sure that three consecutive years at least should be taken.For instance comparison of 1917 1918 and 1919 with 1927 1928 and 1929 would be much fairer. One got an enormous difference by picking out individual years ten years apart; if one took the next year in each case one got entirely different figures. It had been suggested that the increased number of accidents was due to the increase of the proportion of carbon monoxide in the gas. As regards 1918 and 1928 the carbon monoxide in gas in this country was much higher in 1918 than in 1928 owing to the emergency emeasures adopted during the war years to produce gas to keep up the supply. During some of these years the carbon monoxide was much higher than it had ever been since.How misleading comparisons of single years could be might be appreciated from the facts that the mean proportion of carbon monoxide in all the gas supplied in Great Britain was 15.2 per cent. in 1921 when the number of accidental deaths was 126 and 14.4 per cent. in 1922 when the accidental deaths rose to 203. Regarding the susceptibility to small proportions of carbon monoxide in the air breathed any reference to headaches resulting therefrom must be referred to the previous experience of the individual; otherwise one might be misled very much. People living in an atmosphere free from carbon monoxide were more susceptible to small doses. He gave one illustration-the drivers and stokers of the engines on the old Metropolitan Railway in the time of the steam trains were in the tunnels a considerable time inhaling carbon monoxide which (between King’s Cross and Edgware Road) incapacitated anyone who tried to walk through the tunnel quite apart from the sulphur dioxide.These men felt quite well and examination of their sick-club books showed them to be a very healthy set. The same thing was experienced in gas works and in garages. Mr. Butterfield added that he had mentioned this paper to Dr. Haldane but as the title suggested that it was simply a description of the instrument Dr. Haldane had thought it unnecessary to postpone a visit to the North in order to be present at the meeting. With regard to the treatment with carbon dioxide mixed with oxygen which was clainied to be of Arliericaii intl-oductim he did not think Prof.Henderson claimed it as originating in America. The actual origin was due to observations in war time in Europe and the theory was certainly known in this country before the practice was developed and brought into general use in America. Mr. W. PARTRIDGE said that treatment with oxygen mixed with carbon dioxide was claimed to hasten respiration. Speaking from memory he was under the impression that about ten years ago an American committee dealing with the proportioii of zarboii riioiioxidz iii t h e streets had f ~ u n d that t h e additim of carbon dioxide reduced the toxicity of carbon monoxide. The years 1918 and 1928 were bad ones to be taken for accidental deaths because the peak year was about 1922 or 1923 and at the later date he believed the companies were using drawn pipes and not seamed tubing for gas.Dr. Roche Lynch had mentioned that fewer poisons were available in 1928 than in 1918. He (Mr. Partridge) did not think that many of the additional poisons scheduled as dangerous in the ten years mentioned were generally available to the public. Mr. FREDERICK replying said that there was little he need say in reply, since the remarks made were not so much in the nature of criticism as valuable . FREDERICK CARBON MONOXIDE POISONING 57 1 contributions to our knowledge of the subject of the paper. In any discussion of poisoning by carbon monoxide there was a tendency for undue importance to be attached to the question of suicide by this means; suicide statistics were influenced by so many factors that he preferred not to pursue this aspect of the subject.He was sorry that Dr. Haldane had not been present as his authoritative remarks would have added still further to the interest of the discussion. With regard to the treatment of carbon monoxide poisoning by a mixture of oxygen and carbon dioxide this was really outside the scope of the paper and had only been mentioned as a matter of general interest. Communications on the foregoing paper :-THE INVESTIGATION OF CARBON MONOXIDE POISONING. By J. S. HALDANE C.H. F.R.S. As Mr. Frederick's paper conveys the impression that in the examination of blood from suspected cases of carbon monoxide poisoning the use of spectroscopic methods and particularly of the Hartridge reversion spectroscope is essential, I should like to point out that this is not the case.The colorimetric method as applied to diluted blood requires no special apparatus,' can be made with a single drop of the blood and when it is made quantitative gives very exact information as to the percentage saturation of the haemoglobin with carbon monoxide. I do not think that an analyst requires to use a more complicated method; it is this simple method which I have used exclusively in the numerous investigations which I have made of carbon monoxide poisoning or in which carbon monoxide was used as a physiological reagent. In cases of suspected nitrite poisoning the colorimetric method gives information at once if the blood sample is taken during life when much methaemoglobin is present; and after death the presence of nitric oxide haemoglobin is a t once revealed by the colour of the clot formed on boiling.THE PREPARATION OF NITRIC OXIDE HAEMOGLOBIN. By H. HARTRIDGE M.D. F.R.S. Nitric oxide haemoglobin was prepared by Gamgee by passing nitric oxide gas through blood or a solution of haemoglobin. Since nitric oxide reacts with oxygen to form nitrogen peroxide and since this reacts with water to form nitric acid which would change the haemoglobin to acid haematin oxygen must be excluded during the reaction of the nitric oxide with the blood or haemoglobin, or alkali must be added previous to the reaction so as to neutralise the nitric acid which will be formed. In order to exclude oxygen a stream of neutral gas such as nitrogen or hydrogen may be passed through the apparatus in which the nitric oxide is to be generated and through the blood which is to react with it.If this neutral gas is oxygen-free the oxygen in combination with the haemoglobin may be dissociated from it by warming and shaking the haemoglobin during the passage of the neutral gas. Hufner prepared nitric oxide haemoglobin by first passing pure carbon monoxide gas through the apparatus and the blood. This gas displaced the oxygen both from the apparatus and the blood with the formation of carbon monoxide haemoglobin. This compound on passing the nitric oxide gas was then decomposed into nitric oxide haemoglobin with the liberation of the carbon monoxide Nitric oxide haemoglobin can be more readily obtained by addin 572 FREDERICK CARBON MONOXIDE POISONING to blood a solution of a nitrite of an alkali metal and a suitable reducing agent.Dilute solutions of sodium nitrite and ammonium sulphide are commonly used. THE PROPERTIES O F NITRIC OXIDE HAEMOGLOB1N.-It iS a red crystalline compound (Hermann). Its solutions are less orange than those of oxyhaemoglobin, but are more orange than those of carbon monoxide haemoglobin. Two absorption bands are present in the visible spectrum which superficially resemble the oxy-haemoglobin bands in position but are more diffuse. A comparison of the position of its absorption bands with those of oxyhaemoglobin and carbon monoxide haemoglobin with the reversion spectroscope shows that they are on the long wave-length side of those of oxyhaemoglobin; that is on the opposite side to those of carbon monoxide haemoglobin (see Table at the end of Mr. Frederick's paper). Experiments on the stability of nitric oxide haemoglobin show that whereas nitric oxide can displace carbon monoxide from its combination with haemoglobin the compound thus produced is not so stable but tends to change spontaneously into methaemoglobin. On heating a ' solution of carbon monoxide haemoglobin, coagulation commences at about 65" C. whereas on heating a solution of nitric oxide haemoglobin to 50" C. it spontaneously changes to alkaline methaemoglobin, which then coagulates

ISSN:0003-2654    

DOI:10.1039/AN9315600561

出版商:RSC    

年代:1931

数据来源: RSC

摘要:

572 FREDERICK CARBON MONOXIDE POISONING The “Rope” Spore Content of Flour and its Significance. BY A. J. AMOS B.Sc. A.I.C. AND D. W. KENT- JONES PH.D. B.Sc. F.I.C. (Read at the Meeting M a y 6th 1931.) INTRODUCTION.-There are only two diseases other than mould infections, to which wheaten bread is known to be liable and fortunately neither of them is of frequent occurrence. The disease giving rise to the so-called “bleeding bread” GCCU~S so rarely that it hzs never occasioned an exhaixtive investigation. whereas the “rope” disease although by no means common has been extensively studied by a large number of workers. It has been definitely established that the bacteria responsible for the pro-duction of “ropiness” in bread are members of the mesentericus group. B. mesentericus vulgatus (Fliigge) has been isolated from “ropy ” bread by Kratschmer and Niemilowicz (1889) Uffelmann (1890) Watkins (1906) and Kent- Jones and Amos (1930) ; B.mesentericus fuscus by Watkins (1906) and Kent- Jones and Amos (1930); B. mesentericus niger by Biel (1896) and Lloyd Clark and McCrea (1921); B. mesentericus ruber by Kent-Jones and Amos (1930). Other organisms that have been isolated are B. panificans by Laurent (1884) B. Ziodermos by Uffelmann (1890) and B. mesentericus panis viscosus I and I1 by Vogel (1897) although it is probable that some of these organisms are identical with some of those given above. Lloyd Clark and McCrea (1921) isolated five different types which they labelled A to E but from the table of cultural characteristics which they give it seems extremely probable that their type B was B.mesentericus vuZgatus whils AMOS AND KENT-JONES “ROPE” SPORE CONTENT OF FLOUR 573 their type A was possibly identical with the B. mesentericus ruber reported by Kent-Jones and Amos (1930). It is remarkable however in view of the large amount of published literature on the subject of “ropyJ’ bread that so little attention has been paid to the extent to which flours are contaminated with these causative bacteria. I t seemed to us that a knowledge of such contamination might not only throw more light on the development of the disease but might also be of importance in outbreaks of “ rope ” in deciding to what extent the blame rested with the miller or the baker. Lloyd Clark and McCrea in the paper cited above describe a method for the enumeration of heat-resistant spores in flour and give a number of results obtained by applying the method to various samples of wheat and flour.The American Association of Cereal Chemistry (1928) in their book of standard methods, describe a method for the determination of the bacterial spores in flour which is essentially the same as the above. In our opinion however these methods are open to serious criticism and we were unable to obtain consistent results with them. The only other method known to us for determining quantitatively the con-tamination of flours with rope organisms was one personally communicated to us by Dr. Hoffman of New York and briefly reported upon in our previous paper (Kent-Jones and Amos ANALYST 1930 55 248).We have now examined this method more critically and in our view it does not yield sufficiently satisfactory results. However we preferred it to those mentioned above and hence have used it as the basis for our technique. EXPERIMENTAL.-A~~ the three methods referred to are dependent upon the fact that the members of the mesentericus group are characterised by the formation of spores which are extremely resistant to heat. Lloyd Clark and McCrea shake 100 grms. of flour with 300 C.C. of sterile water in a plugged flask and then add 1 C.C. of the resulting suspension to each of four tubes of melted nutrient agar. The tubes are heated in boiling water for 20 minutes and the contents are then poured into sterile Petri dishes. Our own experiments lead us to conclude that this method suffers from the following serious faults: (1) The method of shaking (viz.in a plugged flask where violent shaking is im-possible) especially with a water to flour ratio as small as 3 to 1 does not lend itself to the complete detachment and uniform distribution of the bacteria. (2) The heating at 100” C. often results in the formation of agglomerates due to the gelatinisation of the starch because the viscosity of the melted agar does not allow thorough mixing of this medium and the added suspension. These agglomerates tend to entrap organisms and thus cause low counts. (3) In pouring the plates even if this is performed a t 100” C. a certain amount of both the flour and the agar is left in the tube 574 AMOS AND KENT-JONES “ROPE’ SPORE CONTENT OF FLOUR These remarks apply also to the method of the American Association of Cereal Chemists which only differs in that 500 C.C.of water are used instead of 300 C.C. In Hoffman’s method the primary suspension is prepared by shaking 2 grms. of the flour with 94.6 C.C. of sterile water and 5 grms. of sterile sea sand. Volumes of this suspension varying from 4.8 C.C. to 0.192 C.C. and corresponding with weights of flour varying from 1/10 to 1/250 grm. are added to 10 C.C. tubes of standard nutrient broth and the tubes then heated for 30 minutes in an Arnold steriliser. The tubes are incubated at 37.5” C. for 48 hours and at the end of this time are reported as positive or negative according to whether they show a pellicle or not. The number of rope spores per grm.of flour is taken as being equal to the reciprocal of the highest dilution giving a positive result. As previously mentioned we were unable to obtain sufficiently consistent results by the use of this method; in some cases where duplicate suspensions were pre-pared the set of tubes from one suspension were all negative whilst the other set indicated the presence of as many as 40 spores per grm. As the quantity of flour used (2 grms.) was very small the effect of increasing this to 10 grms. was investigated. There was some improvement in the results,. but the agreement was still not sufficiently good. During incubation the added flour lies at the bottom of the tubes of course,. and it seemed possible that this sediment in some cases might be sufficient to entrap organisms and prevent them from forming a pellicle.Some tubes which were negative at the end of 48 hours were accordingly well shaken and replaced in the incubator; at the end of 16 hours a number of them were positive. This result indicated the further necessity of thoroughly shaking each tube immediately before it was placed in the steriliser as otherwise especially with the tubes containing 1/10 and 1/20 grm. of flour the gelatinisation of the starch resulted in the formation of a tenacious mass which could not be disintegrated and distributed throughout the liquid by subsequent shaking. On thoroughly shaking the tubes immediately before placing them in the steriliser the gelatinised particles were of very small size and subsequent shaking produced a uniform mixture.Some tubes contained 14 C.C. of liquid (10 C.C. of broth and 4 C.C. of added suspension) and it was found to be almost impossible to mix thoroughiy the contents of such tubes without wetting the plugs. In several cases where this had occurred the tube gave a negative result but on the under side of the wetted plug was a slight growth of rope organisms. It was thought to obviate this source of error by the employment of wider tubes (1 inch diameter instead of 5/8 inch) but this modification caused the results to be less consistent. The explanation probably is that in the narrower tubes the film receives artificial support by adherence to the walls of the tube at an earlier stage of its formation; in the wider tubes the frail pellicle before reaching the walls may become dislodged and sink to the bottom.This shaking of the tubes introduced another source of error AMOS AND KENT-JONES “ROPE” SPORE CONTENT OF FLOUR 575 The necessity for retaining the narrower tubes meant that a smaller quantity of broth would have to be used but in order to prevent undue dilution through the addition of comparatively large amounts of suspension it became necessary to increase its strength. The only other modifications introduced consisted in increasing the quantity of both the flour and the sand to 20 grms. and shaking them in 400 C.C. of sterile 0-5 per cent. sodium chloride solution instead of in 100 C.C. of water. One point of great importance that emerged from these investigations was that, for the results to be reliable the positive tubes when finished with must be cleaned by a special method (such as that given later) before being used again.We found that heating the positive tubes in a steam steriliser for 30 minutes cleaning out the contents with hot water and a brush plugging and heating at 150°C. for one hour and a half and then filling with fresh broth and sterilising for 10 minutes on three successive days did not in some cases result in the death of all the contaminating rope spores; after several days’ storage a number of the tubes so treated showed a pellicle. METHoD.-The details of the method finally adopted are as follows :-The bottles pipettes and measuring cylinder are sterilised by heating at 150” C. for two hours. The 0.5 per cent. sodium chloride solution is sterilised by boiling in a plugged flask for one hour.Four hundred C.C. of the sodium chloride solution are measured into a sterile 16-oz. glass-stoppered bottle and 100 C.C. into a sterile 8-oz. glass-stoppered bottle. Twenty grms. of purified silver sand are heated to redness in a platinum capsule for some minutes and then poured while hot, into the liquid in the 16-02. bottle. Twenty grms. of the flour are weighed out on a sterile watch-glass and transferred by means of sterile paper to the 16-OZ. bottle. Volumes of 2 C.C. and 1 c.c. respectively of the suspension are then added immediately by means of a sterile 1 C.C. pipette to 5 C.C. tubes of the broth (for preparation of the broth see later). The bottle is re-shaken once or twice and by means of a sterile pipette, 20 C.C.of the suspension are added at once to the liquid in the 8-02. bottle and this bottle then well shaken. By means of a fresh sterile 1 C.C. pipette volumes of 4 c.c. 3 c.c. 2.5 c.c. 2 c.c. 1.7 c.c. 1.5 c.c. 1.3 c.c. 1.2 C.C. and 1 C.C. respectively of this dilution are then added to 5 C.C. tubes of the broth. The bottle is shaken once or twice before the withdrawal of each of the above quantities. Each tube is taken individualiy the contents thoroughiy mixed and the tube at once placed in a bath of boiling water so that the level of the water is above the level of the liquid in the tube. The tubes are allowed to remain in the bath for 20 minutes, and during this time the water is kept boiling. On removal of the tubes from the bath their contents are thoroughly mixed and they are then placed in an incubator kept at 37” C.The contents of the tubes are well mixed three or four times d,uring the first 24 hours’ incubation. At the end of 48 hours’ incubation the tube is re-ported as positive or negative according to whether the contained broth shows a ~ellicle or not. The number of rope spores per grm. is taken as the reciprocal of the This bottle is then shaken vigorously for two minutes 576 AMOS AND KENT-JONES "ROPE" SPORE CONTENT OF FLOUR smallest fraction of a grm. of flour giving a positive result. If as sometimes happens a negative result is obtained with a quantity of flour greater than the smallest amount giving a positive result then the number of spores per grm. is taken as the reciprocal of the quantity next greater than the smallest amount giving a positive result.The quantity of flour corresponding with the various volumes used is as under: 2 C.C. of primary suspension = 1/10grm. flour 1 C.C. , ,> , = 1/20 9 ,, 4 C.C. of 20 100 dilution = 1/30 9 ,, 3 C.C. 9 , , , = 1/40 9 ,, 2.5 C.C. , , , , 1/48 J ) J ) c.c' 9 J J J J , = 1/60 , Y , c'c* > > J > J , = 1/70 9 J J 1.5 C.C. 9 Y ,# J J = 1/80 ,> 9 , 1.3 C.C. , , , 3 = 1/92 1 ) 2 , le2 c*c* > Y > J 9 ) 2 f 1/100 , ,, 1 c-c. 9 , Y Y = lj120 , ,, If the flour contains more than 120 spores per grm. a further dilution is made. Cleaning of Used Tubes.-The tubes are heated in a steam steriliser for at least 30 minutes. The plugs are then removed the contents discarded and the tubes well washed out with hot water a test-tube brush being employed.The tubes are then placed in a bath of mercuric chloride solution (1 1000) and allowed to remain there for some hours. On removal from this bath the tubes are washed out ten times with water drained plugged and heated at 150" C. for one hour and a half.* Preparation of Nutrient Broth.-Ten grms. of B.D.H. bacteriological peptone, 5.4 grms. of "Difco" beef extract and 9 grms. of A.R. sodium chloride are dis-solved in a litre of distilled water and the +H adjusted to 7.2 to 7.3. The solution is boiled and filtered and the filtrate made up to one litre. The medium is dis-tributed in 5 C.C. quantities in sterile test-tubes of 5/8 inch diameter and sterilised for ten minutes on three successive days in a steam steriliser.In order to make certain of the complete absence of rope spores in the sterilised tubes of broth they are placed in a blood-heat incubator for 48 hours; any of the tubes that show pellicle formation are discarded. It is not to be expected of course that attempts to enumerate living or-ganisms in a substance will furnish results as consistent as those obtained in the * Since the reading of this paper it has been suggested to us that the use of mercuric chloride as a disinfectant may result in the inhibition of growth when the tubes are again employed, owing to the imperfect removal of this substance. Whenever a negative result was obtained in the above experiments however we inoculated the broth with a pure culture of B. mesentericus vulgatus and in every case a pellicle was sub-sequently formed.This showed that the non-formation of a pellicle in the test was not due to the bactericidal action of traces of mercuric chloride. The cleaned tubes can also be tested by filling them with litmus-lactose-peptone water, inoculating the medium with B. coli and then incubating the tubes a t 37" C. for 48 hours. The production of acid indicates that the disinfectant has been successfully removed LOAVES INFECTED WITH “ ROPINESS. AMOS AND KENT-JONES “ROPE” SPORE CONTENT OF FLOUR 577 determination of definite chemical compounds. When as in the case under consideration the organisms to be enumerated are normally present in small numbers and the substance itself is particularly difficult to deal with then the variation in results to be expected is still greater.For these reasons we consider it advisable always to prepare duplicate sets of tubes from the suspension. Often, of course the two sets do not yield the same figure but we consider that the results obtained under these conditions are in view of the nature of the problem, satisfactorily consistent. As examples we give the following typical results : TABLE I. Reference. Tubes. A 1st series 2nd ,, A (same lstseries sample 2nd ,, week later) B lit series C 1st series D 1st series E 1st series F 1st series G 1st series H 1st series J 1st series 2nd ,, 2nd ,, 2nd 9 , 2nd J 9 2nd ,, 2Ild ,, 2nd 1 , 2nd J J Quantity of sample in Grms. Spores 7 Per 1/10 1/20 1/30 1/40 1/48 1/60 1/70 1/80 1/92 1/100 1/120 grm.A + + + + - - 0 0 0 0 + + + - - 0 0 0 0 + + + + - - o O O O O } 4 0 + + - + - 0 0 o 0 } 3 O 0 0 0 o o o o + + - -o o o o + + - -- - - - 0 0 0 0 0 0 0 0 0 o } 6o - - - - 0 0 0 0 0 0 o } <lo } 100 0 0 0 0 o”} 2o + + + + 0 + + + - - ~ } 7 0 - 8 0 + + + + o - + + - -0 o o + + + o -o o o + - + o + o + + + - + - - + + - - -0 + + a t least 0 0 0 0 ( l o + + + - + + -+ + - + - + - - 0 0 0 0 o + + - + - - - : + + + - + - - - 0 0 o } 40-50 0 = tube omitted from series. B. subiiiiis is another organism which someiiriies occurs iii flour and if present, will form a pellicle on the broth. Since experiments we have performed have shown that this organism does not turn bread ropy it may be advisable when the spore count is high to determine whether the pellicles are due to this or-ganism and not to those of the mesentericus group.A quick way of doing this is to prepare agar slant cultures from the pellicles; the form of the resulting growth will indicate which bacteria are present. B. mesentericus vulgatus forms a greyish-white growth which is a t first moist and “blister”-like in appearance but later becomes drier and finely wrinkled. B. subtilis gives a whitish spreading growth 578 AMOS AND KENT-JONES “ROPE” SPORE CONTENT OF FLOUR the edges of which viewed under a low power appear as an interwoven mass of fine hairs. THE SIGNIFICANCE OF THE “ ROPE ” SPORE CONTENT OF FLouR.-Having established a satisfactory method of determining the rope spore content of flours, we decided to investigate the connection existing between this factor and the development of the ‘‘ rope ” disease in bread.Watkins (1906) considered that the number of rope organisms in the flour was of primary importance and Hoffman in the private communication cited above, also concludes that this is the most important single factor. He states further, that 40 spores per grm. is a reasonable limit but that counts beyond this figure are unsafe. In our preliminary experiments we made loaves from flours of different spore contents and stored these loaves in a warm moist atmosphere. We confirmed that, generally speaking the greater the spore content of the flour the more rapidly did rope develop in the loaf provided as will be emphasised later that all the other conditions were equal.We then made an appeal through trade journals for any baker who had an outbreak of rope to send us samples of the bread and of the flour from which the bread was made. These samples and others which were causing no complaints, we examined by our method and the results obtained are given in Fig. 2. Reference. PC1 PC2 WT WTR WTF WTM F1 F2 B1 B2 cs1 cs2 A TABLE 11. Type of flour. Complaint. Wheatmeal Bread badly ropy ,J None J J Bread badly ropy Bakers’ grade J J J J J J J l J J J 9 J J J J J J J J . J J J J J J J I J J ) J J J J J J ,> J J J J 1 J J J J J J J J J 9 J J I J J J J J J J J J J J J None ,J ,J J Number of spores per grm. 60 (40 30 30 < 10 (10 30 (20 30 30 120 160 80 These results are surprising in that they appear to be contrary to the indica-tions given by our preliminary experiments with regard to the influence of the spore content of the flour upon the incidence of the disease in the final bread.With one exception all the bread in which the disease had developed had been made from flours which did not contain more than 30 spores per grm.; in two cases the number of spores per grm. was less than 10. On the other hand two flours which contained over 100 spores per grm. had caused no complaints although they had been sent out to a number of commercial bakeries during the summer months AMOS AND KENT-JONES “ROPE” SPORE CONTENT OF FLOUR 579 These facts make it evident that in the case of commercial bread the number of rope spores in the original flour is not the most important factor in the development of the disease.In our own baking tests all the flours had been subjected to exactly the same procedure during fermentation and baking (see Modern Cereal Chemistry 2nd Edn., p. 174) and the final loaves had all been stored under identical conditions. Thus, of all the factors liable to affect the incidence of the disease the only one that varied was the spore content of the flour. In commercial practice however the systems of fermentation times and temperatures of baking and conditions of bread cooling and storage which prevail are as varied as the spore contents of the flours employed. We concluded therefore that whether bread becomes ropy or not under commercial conditions does not depend so much upon the number of rope spores in the original flour but is governed almost entirely by those factors which ac-celerate or retard the development of the organisms in the final bread.That is, a flour may have a low spore content and yet yield ropy bread because either the bread itself or the conditions of cooling and storage or both are particularly suitable for the development of the disease. On the other hand a flour may contain a large number of spores and yet furnish satisfactory bread because these spores are unable to develop sufficiently on account of the non-suitability of the bread or the cooling and storage conditions or both. It is realised of course that a flour of high spore content will produce ropy bread more readily than a flour of low spore content if both are subjected to exactly the same treatment during fermentation and baking of the dough and cooling and storage of the bread.It is only under such conditions however that the magnitude of the spore content becomes of first importance. As the initial spore content of the flour is not the main factor external con-tamination oi doughs with spores from dirty troughs and benches although dangerous is not likely to have a great influence except in extreme cases. None of the cases we have investigated has been due to this cause. Our experiments on commercial lines have convinced us that with the ordinary run of flours the important factor is the rate of development of the bacteria in the final bread and this depends upon:-(1) The fermentation of the dough; (2) the baking of the dough; (3) the cooling of the bread; (4) the storage of the bread.The fourth factor was extensively studied by Watkins (1906) who confirmed the general opinion that the trouble occurs mainly in summer time Le. when climatic conditions are favourable to the development of the disease. Our work was intended to indicate those factors most helpful in retarding the spread of the disease in bread subjected to such favourable condition of storage. Hence we decided to confine ourselves to an investigation of the first three factors. In this section of the investigation we were not concerned with the academic side of the question but hoped to obtain some definite data which would be helpful The explanation of the apparent discrepancy is as follows 580 AMOS AND KENT-JONES “ROPE” SPORE CONTENT OF FLOUR to the baking trade.In view of this we did not base our decisions as to the degree of ropiness of the different loaves upon the results of sugar estimations (Lloyd and McCrea 1918) or upon the changes in the catalytic activity (Bunzell and Forbes 1930) but upon the intensity of those symptoms which commercial bakers know to be indicators of rope. These symptoms are the peculiar and distinctive odour (this is the earliest of these symptoms) patches of greyish to brown dis-coloration in the crumb and stickiness of these discoloured patches and often of the rest of the crumb. In all the following experiments the final loaves were stored in a moist at-mosphere at 27” C.for several days to assist the development of the disease but the same conditions existed for all loaves. (1) FERMENTATION OF THE DouGH.-There are many commercial methods of bakery practice and therefore it was thought best to study the following main factors :-(G) Duration of fermentation; (b) initial temperature of the dough; (c) per-centage of yeast incorporated in the dough; (d) percentage of water used for doughing. All the following baking tests were performed in a well-designed and equipped bakery by an expert and experienced test baker. It should be re-membered that in small test bakes a greater percentage of yeast must be used than in commercial practice with large doughs. This of course does not interfere with the comparative value of the tests. (a) Duration of Fermentation.-It was noticed quite early in these investigations that loaves made from a flour of high spore content on a short system ( 3 i hours to oven) showed only a mild development of the disease after several days’ storage in a warm moist atmosphere i.e.under conditions favourable to its development. As a much stronger development was expected it appeared that a short fer-mentation tended to inhibit rope development. To confirm this point two series of 2-lb. tin loaves were made from the same flour but one series was made by a 3&-h01ii system and the other series by a ?i-hour s j r s t e ~ . After appropriate storage the loaves were cut into halves. As expected from the method of storage all the loaves were ropy but those made on the short system were less affected than the others.The long-system loaves had the stronger odour and the stickier crumb which was discoloured; the crumb of the short system loaves showed no discoloration. This experiment was repeated on several occasions, and each time the long-system loaves became decidedly more ropy than those made en t h e short “Y cxrsterr?. Both the haves in Fig 1 were made from the same flour and were stored under identical conditions but a 3i-hour system was used for loaf A whilst loaf B was made by a 74-hour system. It is seen that loaf B is considerably more ropy than loaf A. In the shorter system about 1.8 per cent. of yeast was employed and about 1.1 per cent. in the longer system. As stated previously such large quantities of yeast could not be used in commercial practice, but the relative proportions would not be dissimilar.As it is known that acidity will inhibit rope it was thought that the advantage of one system over another might primarily be due to a greater alteration in th AMOS AND KENT-JONES "ROPE" SPORE CONTENT OF FLOUR 581 hydrogen ion concentration. On investigation very little difference in the acidities was found and this could not therefore account for the differences in the develop-ment of the disease. It may be that the gradual conditioning of the gluten during the longer fermentation results in the formation of nitrogenous bodies which are easily assimilated by the organisms whereas in short vigorous fermentations such compounds may not be formed to the same extent. (b) Initial Temperatwe of the Dough.-Three 2-lb.tin loaves were made from a commercial flour on a 7i-hour system. The temperature of the doughing water was varied for each dough but otherwise they all received exactly the same treatment throughout the test. The initial temperatures of the doughs were 70" F. 80" F. and 88" F. respectively; under the conditions of the test 80" F. was the normal initial temperature. Fig. 2 shows the appearance of the cut loaves after several days' storage under conditions favourable to the growth of the organisms. The letters A B and C correspond with the initial temperatures 70" F. 80"F. and 88"F. respectively. Loaf A was decidedly the worst of the three. It had a stronger smell than the other two and the middle of the crumb was very soft and sticky and badly discoloured.There was not a great deal of difference between loaves B and C but loaf C was slightly more ropy than the other. Other similar tests have confirmed the fact that a low initial temperature in the dough aids the development of the disease in the final bread. On reflection this is not unexpected as naturally in such instances the fermen-tation would not be so vigorous although no differences in the +H of the loaves when made were observed. (c) Percentage of Yeast Incorporated in the Dough.-A series of loaves was made from a commercial flour on a 74-hour system and except that they contained different amounts of yeasts all the doughs were similar and received exactly the same treatment. The amcunts of yeast employed were 0.5 0.8 1.1 3-4 and 1-7 per cent.respectively; the normal quantity for a test bake under these con-ditions is 1.1 per cent. After the usual several days' storage under conditions favourable t o the growth of the organisms the loaves were cut and they showed marked differences in the degree of development of the disease. The loaves containing the normal quantity of yeast (1.1 per cent.) had a decided smell and a somewhat sticky but only faintly discoloured crumb. The loaves containing the larger proportions of yeast were appreciably less affected (particularly those with 1-7 per cent. of yeast) while the loaves with the smaller than normal quantity of yeast were decidedly the worst. Fig. 3 shows the difference in the ropiness of three of these loaves; loaf A contained 0-5 per cent.of yeast loaf B 1.1 per cent. (the normal quantity) and loaf C 1.7 per cent. Again further experiments con-firmed these results. The various loaves of the series did not show any appreciable differences in pH value. (d) Percentage of Water used in Doughing.-For this investigation a series of loaves was made and all the doughs were similar except in their water content 582 AMOS AND KENT-JONES "ROPE" SPORE CONTENT OF FLOUR The amounts of water used in making the doughs were 52 55.5 58 62 and 64 per cent. respectively; the correct quantity for this flour was 58 per cent. Those loaves which had been made with less than the correct amount of water did not differ very much in degree of ropiness from the loaves with the normal quantj ty, but if anything the disease seemed slightly less pronounced in the former loaves.Those loaves made with more than the correct amount of water were more ropy than those with the normal quantity and in the case of those loaves with 64 per cent. of water the disease was very marked. These points are illustrated in Fig. 4, where loaves A B and C were made with 52 58 and 64 per cent. of water respec-tively. Slacker doughs therefore appear to assist in the development of the disease. (2) BAKING OF THE DOUGH.-A large dough was made on a 'Ii-hour system, and subsequently scaled off into 2-lb. pieces. After these had been moulded and proved they were placed in the oven but instead of their all receiving a normal baking of 45 minutes they were taken from the oven in batches after 25 45 and 65 minutes' baking respectively.When the loaves were eventually cut after severe storage those that had received a normal baking (45 minutes) possessed a ropy odour and exhibited a few discoloured patches; those that had been baked for only 25 minutes had a very soft sticky and discoloured crumb and smelt very strongly; those that had been baked for 65 minutes exhibited no symptoms of the disease save for a very faint ropy odour. Loaves A B and C in Fig. 5 had received 25 45 and 65 minutes' baking respectively. This confirms the general view in the baking trade that in times of doubt the bread should be well baked. COOLING OF THE BREAD.-It is well known that both warmth and moisture exert a positive influence upon the development of ropiness. Obviously, therefore any conditions which tend to retard the cooling of hot bread will hasten the appearance of the disease.On several occasions half the loaves from a batch of bread were allowed to cool slowly in the bakehouse (temperature 24" C. approximately) overnight while the others were cooled rapidly outside (temperature 12" C. approximately) for an hour and then placed in the bakehouse. Subsequently all the loaves were placed in a warm moist atmosphere in accordance with our usual procedure. After several days' storage those loaves which had been rapidly cooled were appreciably less ropy than the others. A large loaf cools more slowly than a smaller one and hence it is to be expected that under identical storage conditions large loaves will become more ropy than small ones.To test this point a number of both 2-lb. tin and 4-lb. tin loaves were made from the same dough and were cooled and stored together. In every case the loaves of quartern size were more ropy than the 2-lb. loaves after our usual incubation. The cooling of bread is considerably retarded if the loaves are wrapped soon after leaving the oven. A series of loaves was made from a large dough and soon after they had left the oven a number of them were wrapped. The loaves wrapped (3) The rate of cooling of a loaf is affected by its size. AMOS AND KENT-JONES “ROPE” SPORE CONTENT OF FLOUR 583 and unwrapped were stored for several days and then cut. The wrapped loaves always showed a more marked development of the disease than did the unwrapped loaves. Of course if the loaf is well cooled before wrapping the trouble is not aggravated.The pairs of ropy loaves obtained in the various tests described in this section were very similar in appearance to the two loaves of Fig. 1 and were therefore, not reproduced. CoNcLuSIoNS.-The rope spore content of flour unless particularly high is of little significance in outbreaks of rope in commercial practice. While it is helpful that flour of low spore content or at least of not very high spore content should be supplied by the miller of far greater importance are the systems of fermen-tation baking and bread cooling employed by the baker. That the technique employed in the bakehouse can influence the incidence of the disease in the bread is known to the trade but whether the importance of this factor has been sufficiently recognised is doubtful.Further opinions differ as to the manner in which variations in bakery practice affect the development of ropiness. Thus Wihlfahrt ( A Treatise on Baking 1927) states that when rope appears, the doughs should be made stiffer and at a relatively low temperature whereas Bennion (Breadmaking 1929) advises the use of freer doughs and a suitably high temperature. Our own experiments have convinced us that when this trouble occurs the following rules should be observed in fermenting the dough (1) Avoid a long system of fermentation; (2) use a liberal quantity of yeast; (3) avoid low temperature in the dough; (4) avoid slack doughs. It is possible that attention to this and the following advice might permit the eradication of the trouble without the use of acid additions such as vinegar and acid calcium phosphate although this latter practice can usually be easily carried out and is effective.Care should be taken that the dough is well baked since an underbaked loaf is a medium particularly favourable to the growth of the organisms. The bread should be cooled as rapidly as possible in a well-ventilated space and, if the loaves are to be wrapped this operation should not be performed until they have been well cooled. In connection with the cooling of the bread it is as well to remember the effect of the size of the loaves. i t is advisabie when trouble is threatened to make no loaves larger than the 2-lb. size. Quartern loaves especially if they are banked together will only tend to increase the trouble.As a matter of fact we found that one of the firms who responded to our appeal was experiencing bad trouble at a large institution solely from this cause. All the bread was made in quartern tin loaves which were banked together so that the cooling was unduly prolonged. Our findings do not mean that a knowledge of the spore contents of flours is of no value. To a miller such information will indicate whether his flour is mor 584 AMOS AND KENT-JONES “ROPE ” SPORE CONTENT OF FLOUR than usually liable to produce ropy bread and whether it is advisable to modify his wheat-cleaning procedure; to a baker it will indicate whether any trouble experienced is the result of his own baking procedure or whether he is handicapped by the possession of an abnormal flour.What our results do prove however is that it is quite impossible to fix a universal safety limit for the number of rope spores in flour; the safety line depends entirely upon the methods used for making baking cooling and storage of the bread. It should be remembered that rope is encountered in warm countries far more than in England as for instance in South Africa where one of us saw several instances recently. Under such climatic conditions all bread will become ropy very rapidly and were it not for the fact that bread is consumed quickly the trouble would be even more prevalent. I t is true that such flours are often inclined to have fairly high spore contents but after our investigations we should like to re-emphasise the findings of Lloyd Clark and McCrea (1921) in this respect namely that the higher the extraction of the flour the better medium it is for the growth of B.mesentericus. Rope is often more severe with long extraction flours or wholemeals. Finally it is hoped that this work may be of value in settling many contro-versies in the baking trade. We have made the investigation as wide as possible, so that our findings may be of practical value to millers and bakers also especially those working under difficult climatic conditions. We have drawn upon a fairly wide experience of both trades and have endeavoured to perform the work in a judicial spirit. We must admit that the trend of our conclusions is surprising, but we are confident of them after the systematic and careful investigation we have made.SUMMARY.-A method of determining the number of rope spmes in fi~ilr is described which gives satisfactorily consistent results. The rope spore contents of various flours some of which were producing ropy bread under commercial conditions are reported. These results indicate that the rope spore content of a flour is of less importance in the development of rope in commercial bread than the technique adopted in the bakery. Experiments are described which show that the following conditions tend to aggravate rope trouble in bread which has been stored in conditions favourable to the development of the disease :-Long systems of fermentation; low tem-peratures in the doughs; sparing use of the yeast; slack doughs; insufficient baking; conditions causing slow cooling of the bread such as wrapping the bread while warm making quartern loaves banking loaves together.Our thanks are due to many millers and bakers who have assisted us in this work and also to Mr. G. Austin who has carried out the various baking tests AMOS AND KENT-JONES “ROPE, SPORE CONTENT OF FLOUR 585 LITERATURE CITED. American Association of Cereal Chemists. Bennion E. B. Breadmaking. 1929. Oxford University Press. Biel. Bunzell H. H. and Forbes M. Fliigge. Die Micro-Organismen 3rd Ed. 1896 2 198. Kent- Jones D. W. Modern Cereal Chemistry. 1927. Northern Publishing Co. Kent-Jones D. W. and Amos A. J. Kratschmer and Niemilowicz. Vierteljahrschr. Nahr.-u. Genussm. 1889 305. Laurent E. Bull. de Z’Acad. Science de Belgique 1885 [3] 10 765.Lloyd D. J. Clark A. B. and McCrea E. D. Lloyd D. J. and McCrea E. D. Uffelmann. Vogel. Watkins E. J. Wihlfahrt J. E. A Treatise on Baking. 1927. The Fleischmann Co. N.Y. Methods for the Analysis of Cereals and Cereal Products. 1928. Lancaster Press Inc. Cent. Bakt. 1896 Zte Abt. 11 137. Cer. Chern. 1930 7 5 465. ANALYST 1930 55 248. J . Hyg. 1921 19 4. 380. Re$ort to the Food (War) Committee of the Royal Society, 1917 No. 48. Cent. Bakt. 1890 8 481. 2. f. Hyg. 1897 26 398. J . SOC. Chern. Ind. 1906 25 350. DISCUSSION. Dr. KENT- JONES said that he would like to emphasise the fact that “ropiness” was a matter of some importance to the milling and baking trade and that they were always having to face the difficulty of having to deal with infuriated bakers (whose bread had gone “ropy”) who blamed the millers or with millers who wanted to know if their flour really was the cause of “ropiness.” At the outset they had thought that it must be something to do with the number of spores.‘ Other conditions being equal the number of spores actually was the deciding factor but in ordinary commercial circumstances other conditions were not equal, and fermentation baking etc.affected it. It had been shown that flour with quite a high spore content could be baked in such a way that it would give no trouble. Therefore they had thought they would be doing a service to the baking trade if they could ascertain the type of fermentation which made the trouble develop. Of course in hot countries bread was more inclined to go “ropy” than in England.On a visit to South Africa he had been surprised to see how much bread actually became “ ropy” ; practically all the bread would become ‘ ‘ ~ o p y ! ~ ~ but for the fact that it was eaten before the trouble arose. They had tried in this paper t o point out the conditiclns which woiilcl help thosc Fcople who en-countered the trouble. The loaves used in the tests had been purposely allowed to become “ropy ” ; they had been used as a standard to see what type made the trouble worse and what type retarded “ropiness.” Mr. R. L. COLLETT asked whether the authors had been able to produce “ropiness” artificially by inoculating flour or dough from a pure culture. Mr. MCLACHLAN asked in connection with the authors’ statement that the spores could not be killed by heat whether they had tried steam pressure.Often when dry heat failed to kill sieam succeeded. Also since r d t extract was being increasingly added to bread he asked whether bread containing malt extract tended to become more “ropy” than ordinary bread. Mr. D. M. FREELAND enquired whether “ropiness ” was liable to occur in cake. Mr. AMOS replying said they had actually reproduced “rope ” with pure cultures. They had inoculated doughs in marked positions with Bacillus mesen-tericus vulgatus and “ rope ” had developed in those marked positions long before it had anywhere else. They had also sterilised tubes of bread and inoculated these. It was rather difficult to say whether Scotch bread would be more or less liable to “ropiness.” The fermentation was slower which would tend to mak 586 AMOS AND KENT-JONES “ROPE” SPORE CONTENT OF FLOUR the trouble worse but on the other hand Scotch bread was decidedly more acid than English bread and he thought that would tend to retard development. He had never yet met with a case of “rope” in cake. He believed it had been mentioned in the literature that a certain amount of acid developing from the fruit tended to inhibit “rope.” He thought it quite probable that if one could sterilise long enough dry heat would eventually kill the spores but they had found it too long a process to use in their tests. They had made experiments on the effect of malt extract and in some cases the trouble became worse whilst in others it was not so bad. It seemed to depend on the quality and properties of the malt extract used. Dr. KENT-JONES said that he had been asked a question as to the difference in this respect between white bread and brown bread. The spore contents of both white flours and wholemeals were recorded in the paper. The nature of the proteins etc. in brown bread assisted the development of the disease

ISSN:0003-2654    

DOI:10.1039/AN9315600572

出版商:RSC    

年代:1931

数据来源: RSC

摘要:

294 EVERS: THE DETECTION OF SMALL QUANTITIES OF CALCIUM Adding 5 mgrms. of calcium. Added salts. Result. No added salt. Immediate pptn. Sodium chloride, 1 grm. Borax, 1 grm. Sodium potassium tartrate, 1 grm. Potassium citrate, 1 grm. Variations in the concentration of the reagents did not appreciably improve matters. It was found that even 0.25 grm. of potassium citrate in 60 C.C. of solution prevented the precipitation of 2 mgrms. of calcium. Further complications would be introduced if magnesium were also present in the salt as an impurity. CALCIUM OLEATE TEsT.-The formation of an opalescence on the addition of sodium oleate solution to a solution is an extremely delicate test for calcium. Under the best conditions 0.01 mgrm. of calcium in 50 C.C. of solution, or 0.00002 per cent., can just be detected.The test is also, of course, a test for magnesium, but is much less sensitive, 0-6 mgrm. in 50 C.C. of solution, or 0-0012 per cent., being the minimum quantity which can be detected. Further, within certain limits of concentration the pre- cipitation of magnesium is entirely suppressed in the presence of potassium citrate, whilst the sensitiveness of the calcium test is actually increased. The best conditions for the detection of calcium were found to be as follows: Take 50 C.C. of the solution containing calcium, which should be neutral or slightly alkaline. Dissolve in it 2 grms. of potassium citrate, and add 0-3 C.C. of a solution prepared by dissolving 10 grms. of oleic acid in 200 C.C. of 1 per cent. sodium hydroxide. A certain excess of alkali is desirable for the best results.The test is only satisfactory between certain limits of calcium concentration. With quantities exceeding 1 mgrm. in 60 C.C. the opalescence is actually reduced. Under the above conditions quantities of mag- nesium up to 15 mgrms. give no opalescence. Summarising the results, the oleate test is excellent for quantities of calcium varying from 0-01 mgrm. up to 1 mgrm. in the absence of more than 10 mgrms. of magnesium, and within these limits in the absence of other salts the opalescence appears proportional to the calcium present. Further experiments showed, however, that, in spite of its delicacy, the oleate test is not suitable for the purpose in view. Possibly, if the test could be carried out, using standards containing the same concentration of the same salt, it would be satisfactory, but this is hardly practicable.The addition of other salts, even in the absence of potassium citrate, caused the results to be erratic. This was partly due to their “salting out ” effect on the soap, which sometimes caused flocculation, but this was not the whole explanation. Almost immediate pptn. Slight ppt. after 30 minutes. Slight ppt. after 30 minutes. No ppt. This line of investigation was therefore abandoned. Mix and allow the mixture to stand. An excess of the reagent gives less opalescence.294 EVERS: THE DETECTION OF SMALL QUANTITIES OF CALCIUM Adding 5 mgrms. of calcium. Added salts. Result. No added salt. Immediate pptn. Sodium chloride, 1 grm. Borax, 1 grm. Sodium potassium tartrate, 1 grm.Potassium citrate, 1 grm. Variations in the concentration of the reagents did not appreciably improve matters. It was found that even 0.25 grm. of potassium citrate in 60 C.C. of solution prevented the precipitation of 2 mgrms. of calcium. Further complications would be introduced if magnesium were also present in the salt as an impurity. CALCIUM OLEATE TEsT.-The formation of an opalescence on the addition of sodium oleate solution to a solution is an extremely delicate test for calcium. Under the best conditions 0.01 mgrm. of calcium in 50 C.C. of solution, or 0.00002 per cent., can just be detected. The test is also, of course, a test for magnesium, but is much less sensitive, 0-6 mgrm. in 50 C.C. of solution, or 0-0012 per cent., being the minimum quantity which can be detected.Further, within certain limits of concentration the pre- cipitation of magnesium is entirely suppressed in the presence of potassium citrate, whilst the sensitiveness of the calcium test is actually increased. The best conditions for the detection of calcium were found to be as follows: Take 50 C.C. of the solution containing calcium, which should be neutral or slightly alkaline. Dissolve in it 2 grms. of potassium citrate, and add 0-3 C.C. of a solution prepared by dissolving 10 grms. of oleic acid in 200 C.C. of 1 per cent. sodium hydroxide. A certain excess of alkali is desirable for the best results. The test is only satisfactory between certain limits of calcium concentration. With quantities exceeding 1 mgrm.in 60 C.C. the opalescence is actually reduced. Under the above conditions quantities of mag- nesium up to 15 mgrms. give no opalescence. Summarising the results, the oleate test is excellent for quantities of calcium varying from 0-01 mgrm. up to 1 mgrm. in the absence of more than 10 mgrms. of magnesium, and within these limits in the absence of other salts the opalescence appears proportional to the calcium present. Further experiments showed, however, that, in spite of its delicacy, the oleate test is not suitable for the purpose in view. Possibly, if the test could be carried out, using standards containing the same concentration of the same salt, it would be satisfactory, but this is hardly practicable. The addition of other salts, even in the absence of potassium citrate, caused the results to be erratic.This was partly due to their “salting out ” effect on the soap, which sometimes caused flocculation, but this was not the whole explanation. Almost immediate pptn. Slight ppt. after 30 minutes. Slight ppt. after 30 minutes. No ppt. This line of investigation was therefore abandoned. Mix and allow the mixture to stand. An excess of the reagent gives less opalescence.294 EVERS: THE DETECTION OF SMALL QUANTITIES OF CALCIUM Adding 5 mgrms. of calcium. Added salts. Result. No added salt. Immediate pptn. Sodium chloride, 1 grm. Borax, 1 grm. Sodium potassium tartrate, 1 grm. Potassium citrate, 1 grm. Variations in the concentration of the reagents did not appreciably improve matters. It was found that even 0.25 grm.of potassium citrate in 60 C.C. of solution prevented the precipitation of 2 mgrms. of calcium. Further complications would be introduced if magnesium were also present in the salt as an impurity. CALCIUM OLEATE TEsT.-The formation of an opalescence on the addition of sodium oleate solution to a solution is an extremely delicate test for calcium. Under the best conditions 0.01 mgrm. of calcium in 50 C.C. of solution, or 0.00002 per cent., can just be detected. The test is also, of course, a test for magnesium, but is much less sensitive, 0-6 mgrm. in 50 C.C. of solution, or 0-0012 per cent., being the minimum quantity which can be detected. Further, within certain limits of concentration the pre- cipitation of magnesium is entirely suppressed in the presence of potassium citrate, whilst the sensitiveness of the calcium test is actually increased.The best conditions for the detection of calcium were found to be as follows: Take 50 C.C. of the solution containing calcium, which should be neutral or slightly alkaline. Dissolve in it 2 grms. of potassium citrate, and add 0-3 C.C. of a solution prepared by dissolving 10 grms. of oleic acid in 200 C.C. of 1 per cent. sodium hydroxide. A certain excess of alkali is desirable for the best results. The test is only satisfactory between certain limits of calcium concentration. With quantities exceeding 1 mgrm. in 60 C.C. the opalescence is actually reduced. Under the above conditions quantities of mag- nesium up to 15 mgrms. give no opalescence. Summarising the results, the oleate test is excellent for quantities of calcium varying from 0-01 mgrm.up to 1 mgrm. in the absence of more than 10 mgrms. of magnesium, and within these limits in the absence of other salts the opalescence appears proportional to the calcium present. Further experiments showed, however, that, in spite of its delicacy, the oleate test is not suitable for the purpose in view. Possibly, if the test could be carried out, using standards containing the same concentration of the same salt, it would be satisfactory, but this is hardly practicable. The addition of other salts, even in the absence of potassium citrate, caused the results to be erratic. This was partly due to their “salting out ” effect on the soap, which sometimes caused flocculation, but this was not the whole explanation.Almost immediate pptn. Slight ppt. after 30 minutes. Slight ppt. after 30 minutes. No ppt. This line of investigation was therefore abandoned. Mix and allow the mixture to stand. An excess of the reagent gives less opalescence.294 EVERS: THE DETECTION OF SMALL QUANTITIES OF CALCIUM Adding 5 mgrms. of calcium. Added salts. Result. No added salt. Immediate pptn. Sodium chloride, 1 grm. Borax, 1 grm. Sodium potassium tartrate, 1 grm. Potassium citrate, 1 grm. Variations in the concentration of the reagents did not appreciably improve matters. It was found that even 0.25 grm. of potassium citrate in 60 C.C. of solution prevented the precipitation of 2 mgrms. of calcium. Further complications would be introduced if magnesium were also present in the salt as an impurity.CALCIUM OLEATE TEsT.-The formation of an opalescence on the addition of sodium oleate solution to a solution is an extremely delicate test for calcium. Under the best conditions 0.01 mgrm. of calcium in 50 C.C. of solution, or 0.00002 per cent., can just be detected. The test is also, of course, a test for magnesium, but is much less sensitive, 0-6 mgrm. in 50 C.C. of solution, or 0-0012 per cent., being the minimum quantity which can be detected. Further, within certain limits of concentration the pre- cipitation of magnesium is entirely suppressed in the presence of potassium citrate, whilst the sensitiveness of the calcium test is actually increased. The best conditions for the detection of calcium were found to be as follows: Take 50 C.C.of the solution containing calcium, which should be neutral or slightly alkaline. Dissolve in it 2 grms. of potassium citrate, and add 0-3 C.C. of a solution prepared by dissolving 10 grms. of oleic acid in 200 C.C. of 1 per cent. sodium hydroxide. A certain excess of alkali is desirable for the best results. The test is only satisfactory between certain limits of calcium concentration. With quantities exceeding 1 mgrm. in 60 C.C. the opalescence is actually reduced. Under the above conditions quantities of mag- nesium up to 15 mgrms. give no opalescence. Summarising the results, the oleate test is excellent for quantities of calcium varying from 0-01 mgrm. up to 1 mgrm. in the absence of more than 10 mgrms. of magnesium, and within these limits in the absence of other salts the opalescence appears proportional to the calcium present. Further experiments showed, however, that, in spite of its delicacy, the oleate test is not suitable for the purpose in view. Possibly, if the test could be carried out, using standards containing the same concentration of the same salt, it would be satisfactory, but this is hardly practicable. The addition of other salts, even in the absence of potassium citrate, caused the results to be erratic. This was partly due to their “salting out ” effect on the soap, which sometimes caused flocculation, but this was not the whole explanation. Almost immediate pptn. Slight ppt. after 30 minutes. Slight ppt. after 30 minutes. No ppt. This line of investigation was therefore abandoned. Mix and allow the mixture to stand. An excess of the reagent gives less opalescence.

ISSN:0003-2654    

DOI:10.1039/AN9315600586

出版商:RSC    

年代:1931

数据来源: RSC

摘要:

294 EVERS: THE DETECTION OF SMALL QUANTITIES OF CALCIUM Adding 5 mgrms. of calcium. Added salts. Result. No added salt. Immediate pptn. Sodium chloride, 1 grm. Borax, 1 grm. Sodium potassium tartrate, 1 grm. Potassium citrate, 1 grm. Variations in the concentration of the reagents did not appreciably improve matters. It was found that even 0.25 grm. of potassium citrate in 60 C.C. of solution prevented the precipitation of 2 mgrms. of calcium. Further complications would be introduced if magnesium were also present in the salt as an impurity. CALCIUM OLEATE TEsT.-The formation of an opalescence on the addition of sodium oleate solution to a solution is an extremely delicate test for calcium. Under the best conditions 0.01 mgrm. of calcium in 50 C.C. of solution, or 0.00002 per cent., can just be detected.The test is also, of course, a test for magnesium, but is much less sensitive, 0-6 mgrm. in 50 C.C. of solution, or 0-0012 per cent., being the minimum quantity which can be detected. Further, within certain limits of concentration the pre- cipitation of magnesium is entirely suppressed in the presence of potassium citrate, whilst the sensitiveness of the calcium test is actually increased. The best conditions for the detection of calcium were found to be as follows: Take 50 C.C. of the solution containing calcium, which should be neutral or slightly alkaline. Dissolve in it 2 grms. of potassium citrate, and add 0-3 C.C. of a solution prepared by dissolving 10 grms. of oleic acid in 200 C.C. of 1 per cent. sodium hydroxide. A certain excess of alkali is desirable for the best results.The test is only satisfactory between certain limits of calcium concentration. With quantities exceeding 1 mgrm. in 60 C.C. the opalescence is actually reduced. Under the above conditions quantities of mag- nesium up to 15 mgrms. give no opalescence. Summarising the results, the oleate test is excellent for quantities of calcium varying from 0-01 mgrm. up to 1 mgrm. in the absence of more than 10 mgrms. of magnesium, and within these limits in the absence of other salts the opalescence appears proportional to the calcium present. Further experiments showed, however, that, in spite of its delicacy, the oleate test is not suitable for the purpose in view. Possibly, if the test could be carried out, using standards containing the same concentration of the same salt, it would be satisfactory, but this is hardly practicable.The addition of other salts, even in the absence of potassium citrate, caused the results to be erratic. This was partly due to their “salting out ” effect on the soap, which sometimes caused flocculation, but this was not the whole explanation. Almost immediate pptn. Slight ppt. after 30 minutes. Slight ppt. after 30 minutes. No ppt. This line of investigation was therefore abandoned. Mix and allow the mixture to stand. An excess of the reagent gives less opalescence.294 EVERS: THE DETECTION OF SMALL QUANTITIES OF CALCIUM Adding 5 mgrms. of calcium. Added salts. Result. No added salt. Immediate pptn. Sodium chloride, 1 grm. Borax, 1 grm. Sodium potassium tartrate, 1 grm.Potassium citrate, 1 grm. Variations in the concentration of the reagents did not appreciably improve matters. It was found that even 0.25 grm. of potassium citrate in 60 C.C. of solution prevented the precipitation of 2 mgrms. of calcium. Further complications would be introduced if magnesium were also present in the salt as an impurity. CALCIUM OLEATE TEsT.-The formation of an opalescence on the addition of sodium oleate solution to a solution is an extremely delicate test for calcium. Under the best conditions 0.01 mgrm. of calcium in 50 C.C. of solution, or 0.00002 per cent., can just be detected. The test is also, of course, a test for magnesium, but is much less sensitive, 0-6 mgrm. in 50 C.C. of solution, or 0-0012 per cent., being the minimum quantity which can be detected.Further, within certain limits of concentration the pre- cipitation of magnesium is entirely suppressed in the presence of potassium citrate, whilst the sensitiveness of the calcium test is actually increased. The best conditions for the detection of calcium were found to be as follows: Take 50 C.C. of the solution containing calcium, which should be neutral or slightly alkaline. Dissolve in it 2 grms. of potassium citrate, and add 0-3 C.C. of a solution prepared by dissolving 10 grms. of oleic acid in 200 C.C. of 1 per cent. sodium hydroxide. A certain excess of alkali is desirable for the best results. The test is only satisfactory between certain limits of calcium concentration. With quantities exceeding 1 mgrm.in 60 C.C. the opalescence is actually reduced. Under the above conditions quantities of mag- nesium up to 15 mgrms. give no opalescence. Summarising the results, the oleate test is excellent for quantities of calcium varying from 0-01 mgrm. up to 1 mgrm. in the absence of more than 10 mgrms. of magnesium, and within these limits in the absence of other salts the opalescence appears proportional to the calcium present. Further experiments showed, however, that, in spite of its delicacy, the oleate test is not suitable for the purpose in view. Possibly, if the test could be carried out, using standards containing the same concentration of the same salt, it would be satisfactory, but this is hardly practicable. The addition of other salts, even in the absence of potassium citrate, caused the results to be erratic.This was partly due to their “salting out ” effect on the soap, which sometimes caused flocculation, but this was not the whole explanation. Almost immediate pptn. Slight ppt. after 30 minutes. Slight ppt. after 30 minutes. No ppt. This line of investigation was therefore abandoned. Mix and allow the mixture to stand. An excess of the reagent gives less opalescence.294 EVERS: THE DETECTION OF SMALL QUANTITIES OF CALCIUM Adding 5 mgrms. of calcium. Added salts. Result. No added salt. Immediate pptn. Sodium chloride, 1 grm. Borax, 1 grm. Sodium potassium tartrate, 1 grm. Potassium citrate, 1 grm. Variations in the concentration of the reagents did not appreciably improve matters. It was found that even 0.25 grm.of potassium citrate in 60 C.C. of solution prevented the precipitation of 2 mgrms. of calcium. Further complications would be introduced if magnesium were also present in the salt as an impurity. CALCIUM OLEATE TEsT.-The formation of an opalescence on the addition of sodium oleate solution to a solution is an extremely delicate test for calcium. Under the best conditions 0.01 mgrm. of calcium in 50 C.C. of solution, or 0.00002 per cent., can just be detected. The test is also, of course, a test for magnesium, but is much less sensitive, 0-6 mgrm. in 50 C.C. of solution, or 0-0012 per cent., being the minimum quantity which can be detected. Further, within certain limits of concentration the pre- cipitation of magnesium is entirely suppressed in the presence of potassium citrate, whilst the sensitiveness of the calcium test is actually increased.The best conditions for the detection of calcium were found to be as follows: Take 50 C.C. of the solution containing calcium, which should be neutral or slightly alkaline. Dissolve in it 2 grms. of potassium citrate, and add 0-3 C.C. of a solution prepared by dissolving 10 grms. of oleic acid in 200 C.C. of 1 per cent. sodium hydroxide. A certain excess of alkali is desirable for the best results. The test is only satisfactory between certain limits of calcium concentration. With quantities exceeding 1 mgrm. in 60 C.C. the opalescence is actually reduced. Under the above conditions quantities of mag- nesium up to 15 mgrms. give no opalescence. Summarising the results, the oleate test is excellent for quantities of calcium varying from 0-01 mgrm.up to 1 mgrm. in the absence of more than 10 mgrms. of magnesium, and within these limits in the absence of other salts the opalescence appears proportional to the calcium present. Further experiments showed, however, that, in spite of its delicacy, the oleate test is not suitable for the purpose in view. Possibly, if the test could be carried out, using standards containing the same concentration of the same salt, it would be satisfactory, but this is hardly practicable. The addition of other salts, even in the absence of potassium citrate, caused the results to be erratic. This was partly due to their “salting out ” effect on the soap, which sometimes caused flocculation, but this was not the whole explanation.Almost immediate pptn. Slight ppt. after 30 minutes. Slight ppt. after 30 minutes. No ppt. This line of investigation was therefore abandoned. Mix and allow the mixture to stand. An excess of the reagent gives less opalescence.294 EVERS: THE DETECTION OF SMALL QUANTITIES OF CALCIUM Adding 5 mgrms. of calcium. Added salts. Result. No added salt. Immediate pptn. Sodium chloride, 1 grm. Borax, 1 grm. Sodium potassium tartrate, 1 grm. Potassium citrate, 1 grm. Variations in the concentration of the reagents did not appreciably improve matters. It was found that even 0.25 grm. of potassium citrate in 60 C.C. of solution prevented the precipitation of 2 mgrms. of calcium. Further complications would be introduced if magnesium were also present in the salt as an impurity.CALCIUM OLEATE TEsT.-The formation of an opalescence on the addition of sodium oleate solution to a solution is an extremely delicate test for calcium. Under the best conditions 0.01 mgrm. of calcium in 50 C.C. of solution, or 0.00002 per cent., can just be detected. The test is also, of course, a test for magnesium, but is much less sensitive, 0-6 mgrm. in 50 C.C. of solution, or 0-0012 per cent., being the minimum quantity which can be detected. Further, within certain limits of concentration the pre- cipitation of magnesium is entirely suppressed in the presence of potassium citrate, whilst the sensitiveness of the calcium test is actually increased. The best conditions for the detection of calcium were found to be as follows: Take 50 C.C.of the solution containing calcium, which should be neutral or slightly alkaline. Dissolve in it 2 grms. of potassium citrate, and add 0-3 C.C. of a solution prepared by dissolving 10 grms. of oleic acid in 200 C.C. of 1 per cent. sodium hydroxide. A certain excess of alkali is desirable for the best results. The test is only satisfactory between certain limits of calcium concentration. With quantities exceeding 1 mgrm. in 60 C.C. the opalescence is actually reduced. Under the above conditions quantities of mag- nesium up to 15 mgrms. give no opalescence. Summarising the results, the oleate test is excellent for quantities of calcium varying from 0-01 mgrm. up to 1 mgrm. in the absence of more than 10 mgrms. of magnesium, and within these limits in the absence of other salts the opalescence appears proportional to the calcium present. Further experiments showed, however, that, in spite of its delicacy, the oleate test is not suitable for the purpose in view. Possibly, if the test could be carried out, using standards containing the same concentration of the same salt, it would be satisfactory, but this is hardly practicable. The addition of other salts, even in the absence of potassium citrate, caused the results to be erratic. This was partly due to their “salting out ” effect on the soap, which sometimes caused flocculation, but this was not the whole explanation. Almost immediate pptn. Slight ppt. after 30 minutes. Slight ppt. after 30 minutes. No ppt. This line of investigation was therefore abandoned. Mix and allow the mixture to stand. An excess of the reagent gives less opalescence.

ISSN:0003-2654    

DOI:10.1039/AN9315600590

出版商:RSC    

年代:1931

数据来源: RSC

摘要:

294 EVERS: THE DETECTION OF SMALL QUANTITIES OF CALCIUM Adding 5 mgrms. of calcium. Added salts. Result. No added salt. Immediate pptn. Sodium chloride, 1 grm. Borax, 1 grm. Sodium potassium tartrate, 1 grm. Potassium citrate, 1 grm. Variations in the concentration of the reagents did not appreciably improve matters. It was found that even 0.25 grm. of potassium citrate in 60 C.C. of solution prevented the precipitation of 2 mgrms. of calcium. Further complications would be introduced if magnesium were also present in the salt as an impurity. CALCIUM OLEATE TEsT.-The formation of an opalescence on the addition of sodium oleate solution to a solution is an extremely delicate test for calcium. Under the best conditions 0.01 mgrm. of calcium in 50 C.C. of solution, or 0.00002 per cent., can just be detected.The test is also, of course, a test for magnesium, but is much less sensitive, 0-6 mgrm. in 50 C.C. of solution, or 0-0012 per cent., being the minimum quantity which can be detected. Further, within certain limits of concentration the pre- cipitation of magnesium is entirely suppressed in the presence of potassium citrate, whilst the sensitiveness of the calcium test is actually increased. The best conditions for the detection of calcium were found to be as follows: Take 50 C.C. of the solution containing calcium, which should be neutral or slightly alkaline. Dissolve in it 2 grms. of potassium citrate, and add 0-3 C.C. of a solution prepared by dissolving 10 grms. of oleic acid in 200 C.C. of 1 per cent. sodium hydroxide. A certain excess of alkali is desirable for the best results.The test is only satisfactory between certain limits of calcium concentration. With quantities exceeding 1 mgrm. in 60 C.C. the opalescence is actually reduced. Under the above conditions quantities of mag- nesium up to 15 mgrms. give no opalescence. Summarising the results, the oleate test is excellent for quantities of calcium varying from 0-01 mgrm. up to 1 mgrm. in the absence of more than 10 mgrms. of magnesium, and within these limits in the absence of other salts the opalescence appears proportional to the calcium present. Further experiments showed, however, that, in spite of its delicacy, the oleate test is not suitable for the purpose in view. Possibly, if the test could be carried out, using standards containing the same concentration of the same salt, it would be satisfactory, but this is hardly practicable.The addition of other salts, even in the absence of potassium citrate, caused the results to be erratic. This was partly due to their “salting out ” effect on the soap, which sometimes caused flocculation, but this was not the whole explanation. Almost immediate pptn. Slight ppt. after 30 minutes. Slight ppt. after 30 minutes. No ppt. This line of investigation was therefore abandoned. Mix and allow the mixture to stand. An excess of the reagent gives less opalescence.294 EVERS: THE DETECTION OF SMALL QUANTITIES OF CALCIUM Adding 5 mgrms. of calcium. Added salts. Result. No added salt. Immediate pptn. Sodium chloride, 1 grm. Borax, 1 grm. Sodium potassium tartrate, 1 grm.Potassium citrate, 1 grm. Variations in the concentration of the reagents did not appreciably improve matters. It was found that even 0.25 grm. of potassium citrate in 60 C.C. of solution prevented the precipitation of 2 mgrms. of calcium. Further complications would be introduced if magnesium were also present in the salt as an impurity. CALCIUM OLEATE TEsT.-The formation of an opalescence on the addition of sodium oleate solution to a solution is an extremely delicate test for calcium. Under the best conditions 0.01 mgrm. of calcium in 50 C.C. of solution, or 0.00002 per cent., can just be detected. The test is also, of course, a test for magnesium, but is much less sensitive, 0-6 mgrm. in 50 C.C. of solution, or 0-0012 per cent., being the minimum quantity which can be detected.Further, within certain limits of concentration the pre- cipitation of magnesium is entirely suppressed in the presence of potassium citrate, whilst the sensitiveness of the calcium test is actually increased. The best conditions for the detection of calcium were found to be as follows: Take 50 C.C. of the solution containing calcium, which should be neutral or slightly alkaline. Dissolve in it 2 grms. of potassium citrate, and add 0-3 C.C. of a solution prepared by dissolving 10 grms. of oleic acid in 200 C.C. of 1 per cent. sodium hydroxide. A certain excess of alkali is desirable for the best results. The test is only satisfactory between certain limits of calcium concentration. With quantities exceeding 1 mgrm.in 60 C.C. the opalescence is actually reduced. Under the above conditions quantities of mag- nesium up to 15 mgrms. give no opalescence. Summarising the results, the oleate test is excellent for quantities of calcium varying from 0-01 mgrm. up to 1 mgrm. in the absence of more than 10 mgrms. of magnesium, and within these limits in the absence of other salts the opalescence appears proportional to the calcium present. Further experiments showed, however, that, in spite of its delicacy, the oleate test is not suitable for the purpose in view. Possibly, if the test could be carried out, using standards containing the same concentration of the same salt, it would be satisfactory, but this is hardly practicable. The addition of other salts, even in the absence of potassium citrate, caused the results to be erratic. This was partly due to their “salting out ” effect on the soap, which sometimes caused flocculation, but this was not the whole explanation. Almost immediate pptn. Slight ppt. after 30 minutes. Slight ppt. after 30 minutes. No ppt. This line of investigation was therefore abandoned. Mix and allow the mixture to stand. An excess of the reagent gives less opalescence.

ISSN:0003-2654    

DOI:10.1039/AN9315600594

出版商:RSC    

年代:1931

数据来源: RSC

摘要:

294 EVERS: THE DETECTION OF SMALL QUANTITIES OF CALCIUM Adding 5 mgrms. of calcium. Added salts. Result. No added salt. Immediate pptn. Sodium chloride, 1 grm. Borax, 1 grm. Sodium potassium tartrate, 1 grm. Potassium citrate, 1 grm. Variations in the concentration of the reagents did not appreciably improve matters. It was found that even 0.25 grm. of potassium citrate in 60 C.C. of solution prevented the precipitation of 2 mgrms. of calcium. Further complications would be introduced if magnesium were also present in the salt as an impurity. CALCIUM OLEATE TEsT.-The formation of an opalescence on the addition of sodium oleate solution to a solution is an extremely delicate test for calcium. Under the best conditions 0.01 mgrm. of calcium in 50 C.C. of solution, or 0.00002 per cent., can just be detected.The test is also, of course, a test for magnesium, but is much less sensitive, 0-6 mgrm. in 50 C.C. of solution, or 0-0012 per cent., being the minimum quantity which can be detected. Further, within certain limits of concentration the pre- cipitation of magnesium is entirely suppressed in the presence of potassium citrate, whilst the sensitiveness of the calcium test is actually increased. The best conditions for the detection of calcium were found to be as follows: Take 50 C.C. of the solution containing calcium, which should be neutral or slightly alkaline. Dissolve in it 2 grms. of potassium citrate, and add 0-3 C.C. of a solution prepared by dissolving 10 grms. of oleic acid in 200 C.C. of 1 per cent. sodium hydroxide. A certain excess of alkali is desirable for the best results.The test is only satisfactory between certain limits of calcium concentration. With quantities exceeding 1 mgrm. in 60 C.C. the opalescence is actually reduced. Under the above conditions quantities of mag- nesium up to 15 mgrms. give no opalescence. Summarising the results, the oleate test is excellent for quantities of calcium varying from 0-01 mgrm. up to 1 mgrm. in the absence of more than 10 mgrms. of magnesium, and within these limits in the absence of other salts the opalescence appears proportional to the calcium present. Further experiments showed, however, that, in spite of its delicacy, the oleate test is not suitable for the purpose in view. Possibly, if the test could be carried out, using standards containing the same concentration of the same salt, it would be satisfactory, but this is hardly practicable.The addition of other salts, even in the absence of potassium citrate, caused the results to be erratic. This was partly due to their “salting out ” effect on the soap, which sometimes caused flocculation, but this was not the whole explanation. Almost immediate pptn. Slight ppt. after 30 minutes. Slight ppt. after 30 minutes. No ppt. This line of investigation was therefore abandoned. Mix and allow the mixture to stand. An excess of the reagent gives less opalescence.294 EVERS: THE DETECTION OF SMALL QUANTITIES OF CALCIUM Adding 5 mgrms. of calcium. Added salts. Result. No added salt. Immediate pptn. Sodium chloride, 1 grm. Borax, 1 grm. Sodium potassium tartrate, 1 grm.Potassium citrate, 1 grm. Variations in the concentration of the reagents did not appreciably improve matters. It was found that even 0.25 grm. of potassium citrate in 60 C.C. of solution prevented the precipitation of 2 mgrms. of calcium. Further complications would be introduced if magnesium were also present in the salt as an impurity. CALCIUM OLEATE TEsT.-The formation of an opalescence on the addition of sodium oleate solution to a solution is an extremely delicate test for calcium. Under the best conditions 0.01 mgrm. of calcium in 50 C.C. of solution, or 0.00002 per cent., can just be detected. The test is also, of course, a test for magnesium, but is much less sensitive, 0-6 mgrm. in 50 C.C. of solution, or 0-0012 per cent., being the minimum quantity which can be detected.Further, within certain limits of concentration the pre- cipitation of magnesium is entirely suppressed in the presence of potassium citrate, whilst the sensitiveness of the calcium test is actually increased. The best conditions for the detection of calcium were found to be as follows: Take 50 C.C. of the solution containing calcium, which should be neutral or slightly alkaline. Dissolve in it 2 grms. of potassium citrate, and add 0-3 C.C. of a solution prepared by dissolving 10 grms. of oleic acid in 200 C.C. of 1 per cent. sodium hydroxide. A certain excess of alkali is desirable for the best results. The test is only satisfactory between certain limits of calcium concentration. With quantities exceeding 1 mgrm.in 60 C.C. the opalescence is actually reduced. Under the above conditions quantities of mag- nesium up to 15 mgrms. give no opalescence. Summarising the results, the oleate test is excellent for quantities of calcium varying from 0-01 mgrm. up to 1 mgrm. in the absence of more than 10 mgrms. of magnesium, and within these limits in the absence of other salts the opalescence appears proportional to the calcium present. Further experiments showed, however, that, in spite of its delicacy, the oleate test is not suitable for the purpose in view. Possibly, if the test could be carried out, using standards containing the same concentration of the same salt, it would be satisfactory, but this is hardly practicable. The addition of other salts, even in the absence of potassium citrate, caused the results to be erratic.This was partly due to their “salting out ” effect on the soap, which sometimes caused flocculation, but this was not the whole explanation. Almost immediate pptn. Slight ppt. after 30 minutes. Slight ppt. after 30 minutes. No ppt. This line of investigation was therefore abandoned. Mix and allow the mixture to stand. An excess of the reagent gives less opalescence.294 EVERS: THE DETECTION OF SMALL QUANTITIES OF CALCIUM Adding 5 mgrms. of calcium. Added salts. Result. No added salt. Immediate pptn. Sodium chloride, 1 grm. Borax, 1 grm. Sodium potassium tartrate, 1 grm. Potassium citrate, 1 grm. Variations in the concentration of the reagents did not appreciably improve matters. It was found that even 0.25 grm.of potassium citrate in 60 C.C. of solution prevented the precipitation of 2 mgrms. of calcium. Further complications would be introduced if magnesium were also present in the salt as an impurity. CALCIUM OLEATE TEsT.-The formation of an opalescence on the addition of sodium oleate solution to a solution is an extremely delicate test for calcium. Under the best conditions 0.01 mgrm. of calcium in 50 C.C. of solution, or 0.00002 per cent., can just be detected. The test is also, of course, a test for magnesium, but is much less sensitive, 0-6 mgrm. in 50 C.C. of solution, or 0-0012 per cent., being the minimum quantity which can be detected. Further, within certain limits of concentration the pre- cipitation of magnesium is entirely suppressed in the presence of potassium citrate, whilst the sensitiveness of the calcium test is actually increased.The best conditions for the detection of calcium were found to be as follows: Take 50 C.C. of the solution containing calcium, which should be neutral or slightly alkaline. Dissolve in it 2 grms. of potassium citrate, and add 0-3 C.C. of a solution prepared by dissolving 10 grms. of oleic acid in 200 C.C. of 1 per cent. sodium hydroxide. A certain excess of alkali is desirable for the best results. The test is only satisfactory between certain limits of calcium concentration. With quantities exceeding 1 mgrm. in 60 C.C. the opalescence is actually reduced. Under the above conditions quantities of mag- nesium up to 15 mgrms. give no opalescence. Summarising the results, the oleate test is excellent for quantities of calcium varying from 0-01 mgrm.up to 1 mgrm. in the absence of more than 10 mgrms. of magnesium, and within these limits in the absence of other salts the opalescence appears proportional to the calcium present. Further experiments showed, however, that, in spite of its delicacy, the oleate test is not suitable for the purpose in view. Possibly, if the test could be carried out, using standards containing the same concentration of the same salt, it would be satisfactory, but this is hardly practicable. The addition of other salts, even in the absence of potassium citrate, caused the results to be erratic. This was partly due to their “salting out ” effect on the soap, which sometimes caused flocculation, but this was not the whole explanation.Almost immediate pptn. Slight ppt. after 30 minutes. Slight ppt. after 30 minutes. No ppt. This line of investigation was therefore abandoned. Mix and allow the mixture to stand. An excess of the reagent gives less opalescence.294 EVERS: THE DETECTION OF SMALL QUANTITIES OF CALCIUM Adding 5 mgrms. of calcium. Added salts. Result. No added salt. Immediate pptn. Sodium chloride, 1 grm. Borax, 1 grm. Sodium potassium tartrate, 1 grm. Potassium citrate, 1 grm. Variations in the concentration of the reagents did not appreciably improve matters. It was found that even 0.25 grm. of potassium citrate in 60 C.C. of solution prevented the precipitation of 2 mgrms. of calcium. Further complications would be introduced if magnesium were also present in the salt as an impurity.CALCIUM OLEATE TEsT.-The formation of an opalescence on the addition of sodium oleate solution to a solution is an extremely delicate test for calcium. Under the best conditions 0.01 mgrm. of calcium in 50 C.C. of solution, or 0.00002 per cent., can just be detected. The test is also, of course, a test for magnesium, but is much less sensitive, 0-6 mgrm. in 50 C.C. of solution, or 0-0012 per cent., being the minimum quantity which can be detected. Further, within certain limits of concentration the pre- cipitation of magnesium is entirely suppressed in the presence of potassium citrate, whilst the sensitiveness of the calcium test is actually increased. The best conditions for the detection of calcium were found to be as follows: Take 50 C.C.of the solution containing calcium, which should be neutral or slightly alkaline. Dissolve in it 2 grms. of potassium citrate, and add 0-3 C.C. of a solution prepared by dissolving 10 grms. of oleic acid in 200 C.C. of 1 per cent. sodium hydroxide. A certain excess of alkali is desirable for the best results. The test is only satisfactory between certain limits of calcium concentration. With quantities exceeding 1 mgrm. in 60 C.C. the opalescence is actually reduced. Under the above conditions quantities of mag- nesium up to 15 mgrms. give no opalescence. Summarising the results, the oleate test is excellent for quantities of calcium varying from 0-01 mgrm. up to 1 mgrm. in the absence of more than 10 mgrms. of magnesium, and within these limits in the absence of other salts the opalescence appears proportional to the calcium present. Further experiments showed, however, that, in spite of its delicacy, the oleate test is not suitable for the purpose in view. Possibly, if the test could be carried out, using standards containing the same concentration of the same salt, it would be satisfactory, but this is hardly practicable. The addition of other salts, even in the absence of potassium citrate, caused the results to be erratic. This was partly due to their “salting out ” effect on the soap, which sometimes caused flocculation, but this was not the whole explanation. Almost immediate pptn. Slight ppt. after 30 minutes. Slight ppt. after 30 minutes. No ppt. This line of investigation was therefore abandoned. Mix and allow the mixture to stand. An excess of the reagent gives less opalescence.

ISSN:0003-2654    

DOI:10.1039/AN9315600595

出版商:RSC    

年代:1931

数据来源: RSC

摘要:

294 EVERS: THE DETECTION OF SMALL QUANTITIES OF CALCIUM Adding 5 mgrms. of calcium. Added salts. Result. No added salt. Immediate pptn. Sodium chloride, 1 grm. Borax, 1 grm. Sodium potassium tartrate, 1 grm. Potassium citrate, 1 grm. Variations in the concentration of the reagents did not appreciably improve matters. It was found that even 0.25 grm. of potassium citrate in 60 C.C. of solution prevented the precipitation of 2 mgrms. of calcium. Further complications would be introduced if magnesium were also present in the salt as an impurity. CALCIUM OLEATE TEsT.-The formation of an opalescence on the addition of sodium oleate solution to a solution is an extremely delicate test for calcium. Under the best conditions 0.01 mgrm. of calcium in 50 C.C. of solution, or 0.00002 per cent., can just be detected.The test is also, of course, a test for magnesium, but is much less sensitive, 0-6 mgrm. in 50 C.C. of solution, or 0-0012 per cent., being the minimum quantity which can be detected. Further, within certain limits of concentration the pre- cipitation of magnesium is entirely suppressed in the presence of potassium citrate, whilst the sensitiveness of the calcium test is actually increased. The best conditions for the detection of calcium were found to be as follows: Take 50 C.C. of the solution containing calcium, which should be neutral or slightly alkaline. Dissolve in it 2 grms. of potassium citrate, and add 0-3 C.C. of a solution prepared by dissolving 10 grms. of oleic acid in 200 C.C. of 1 per cent. sodium hydroxide. A certain excess of alkali is desirable for the best results.The test is only satisfactory between certain limits of calcium concentration. With quantities exceeding 1 mgrm. in 60 C.C. the opalescence is actually reduced. Under the above conditions quantities of mag- nesium up to 15 mgrms. give no opalescence. Summarising the results, the oleate test is excellent for quantities of calcium varying from 0-01 mgrm. up to 1 mgrm. in the absence of more than 10 mgrms. of magnesium, and within these limits in the absence of other salts the opalescence appears proportional to the calcium present. Further experiments showed, however, that, in spite of its delicacy, the oleate test is not suitable for the purpose in view. Possibly, if the test could be carried out, using standards containing the same concentration of the same salt, it would be satisfactory, but this is hardly practicable.The addition of other salts, even in the absence of potassium citrate, caused the results to be erratic. This was partly due to their “salting out ” effect on the soap, which sometimes caused flocculation, but this was not the whole explanation. Almost immediate pptn. Slight ppt. after 30 minutes. Slight ppt. after 30 minutes. No ppt. This line of investigation was therefore abandoned. Mix and allow the mixture to stand. An excess of the reagent gives less opalescence.294 EVERS: THE DETECTION OF SMALL QUANTITIES OF CALCIUM Adding 5 mgrms. of calcium. Added salts. Result. No added salt. Immediate pptn. Sodium chloride, 1 grm. Borax, 1 grm. Sodium potassium tartrate, 1 grm.Potassium citrate, 1 grm. Variations in the concentration of the reagents did not appreciably improve matters. It was found that even 0.25 grm. of potassium citrate in 60 C.C. of solution prevented the precipitation of 2 mgrms. of calcium. Further complications would be introduced if magnesium were also present in the salt as an impurity. CALCIUM OLEATE TEsT.-The formation of an opalescence on the addition of sodium oleate solution to a solution is an extremely delicate test for calcium. Under the best conditions 0.01 mgrm. of calcium in 50 C.C. of solution, or 0.00002 per cent., can just be detected. The test is also, of course, a test for magnesium, but is much less sensitive, 0-6 mgrm. in 50 C.C. of solution, or 0-0012 per cent., being the minimum quantity which can be detected.Further, within certain limits of concentration the pre- cipitation of magnesium is entirely suppressed in the presence of potassium citrate, whilst the sensitiveness of the calcium test is actually increased. The best conditions for the detection of calcium were found to be as follows: Take 50 C.C. of the solution containing calcium, which should be neutral or slightly alkaline. Dissolve in it 2 grms. of potassium citrate, and add 0-3 C.C. of a solution prepared by dissolving 10 grms. of oleic acid in 200 C.C. of 1 per cent. sodium hydroxide. A certain excess of alkali is desirable for the best results. The test is only satisfactory between certain limits of calcium concentration. With quantities exceeding 1 mgrm.in 60 C.C. the opalescence is actually reduced. Under the above conditions quantities of mag- nesium up to 15 mgrms. give no opalescence. Summarising the results, the oleate test is excellent for quantities of calcium varying from 0-01 mgrm. up to 1 mgrm. in the absence of more than 10 mgrms. of magnesium, and within these limits in the absence of other salts the opalescence appears proportional to the calcium present. Further experiments showed, however, that, in spite of its delicacy, the oleate test is not suitable for the purpose in view. Possibly, if the test could be carried out, using standards containing the same concentration of the same salt, it would be satisfactory, but this is hardly practicable. The addition of other salts, even in the absence of potassium citrate, caused the results to be erratic.This was partly due to their “salting out ” effect on the soap, which sometimes caused flocculation, but this was not the whole explanation. Almost immediate pptn. Slight ppt. after 30 minutes. Slight ppt. after 30 minutes. No ppt. This line of investigation was therefore abandoned. Mix and allow the mixture to stand. An excess of the reagent gives less opalescence.294 EVERS: THE DETECTION OF SMALL QUANTITIES OF CALCIUM Adding 5 mgrms. of calcium. Added salts. Result. No added salt. Immediate pptn. Sodium chloride, 1 grm. Borax, 1 grm. Sodium potassium tartrate, 1 grm. Potassium citrate, 1 grm. Variations in the concentration of the reagents did not appreciably improve matters. It was found that even 0.25 grm.of potassium citrate in 60 C.C. of solution prevented the precipitation of 2 mgrms. of calcium. Further complications would be introduced if magnesium were also present in the salt as an impurity. CALCIUM OLEATE TEsT.-The formation of an opalescence on the addition of sodium oleate solution to a solution is an extremely delicate test for calcium. Under the best conditions 0.01 mgrm. of calcium in 50 C.C. of solution, or 0.00002 per cent., can just be detected. The test is also, of course, a test for magnesium, but is much less sensitive, 0-6 mgrm. in 50 C.C. of solution, or 0-0012 per cent., being the minimum quantity which can be detected. Further, within certain limits of concentration the pre- cipitation of magnesium is entirely suppressed in the presence of potassium citrate, whilst the sensitiveness of the calcium test is actually increased.The best conditions for the detection of calcium were found to be as follows: Take 50 C.C. of the solution containing calcium, which should be neutral or slightly alkaline. Dissolve in it 2 grms. of potassium citrate, and add 0-3 C.C. of a solution prepared by dissolving 10 grms. of oleic acid in 200 C.C. of 1 per cent. sodium hydroxide. A certain excess of alkali is desirable for the best results. The test is only satisfactory between certain limits of calcium concentration. With quantities exceeding 1 mgrm. in 60 C.C. the opalescence is actually reduced. Under the above conditions quantities of mag- nesium up to 15 mgrms. give no opalescence. Summarising the results, the oleate test is excellent for quantities of calcium varying from 0-01 mgrm.up to 1 mgrm. in the absence of more than 10 mgrms. of magnesium, and within these limits in the absence of other salts the opalescence appears proportional to the calcium present. Further experiments showed, however, that, in spite of its delicacy, the oleate test is not suitable for the purpose in view. Possibly, if the test could be carried out, using standards containing the same concentration of the same salt, it would be satisfactory, but this is hardly practicable. The addition of other salts, even in the absence of potassium citrate, caused the results to be erratic. This was partly due to their “salting out ” effect on the soap, which sometimes caused flocculation, but this was not the whole explanation.Almost immediate pptn. Slight ppt. after 30 minutes. Slight ppt. after 30 minutes. No ppt. This line of investigation was therefore abandoned. Mix and allow the mixture to stand. An excess of the reagent gives less opalescence.294 EVERS: THE DETECTION OF SMALL QUANTITIES OF CALCIUM Adding 5 mgrms. of calcium. Added salts. Result. No added salt. Immediate pptn. Sodium chloride, 1 grm. Borax, 1 grm. Sodium potassium tartrate, 1 grm. Potassium citrate, 1 grm. Variations in the concentration of the reagents did not appreciably improve matters. It was found that even 0.25 grm. of potassium citrate in 60 C.C. of solution prevented the precipitation of 2 mgrms. of calcium. Further complications would be introduced if magnesium were also present in the salt as an impurity.CALCIUM OLEATE TEsT.-The formation of an opalescence on the addition of sodium oleate solution to a solution is an extremely delicate test for calcium. Under the best conditions 0.01 mgrm. of calcium in 50 C.C. of solution, or 0.00002 per cent., can just be detected. The test is also, of course, a test for magnesium, but is much less sensitive, 0-6 mgrm. in 50 C.C. of solution, or 0-0012 per cent., being the minimum quantity which can be detected. Further, within certain limits of concentration the pre- cipitation of magnesium is entirely suppressed in the presence of potassium citrate, whilst the sensitiveness of the calcium test is actually increased. The best conditions for the detection of calcium were found to be as follows: Take 50 C.C.of the solution containing calcium, which should be neutral or slightly alkaline. Dissolve in it 2 grms. of potassium citrate, and add 0-3 C.C. of a solution prepared by dissolving 10 grms. of oleic acid in 200 C.C. of 1 per cent. sodium hydroxide. A certain excess of alkali is desirable for the best results. The test is only satisfactory between certain limits of calcium concentration. With quantities exceeding 1 mgrm. in 60 C.C. the opalescence is actually reduced. Under the above conditions quantities of mag- nesium up to 15 mgrms. give no opalescence. Summarising the results, the oleate test is excellent for quantities of calcium varying from 0-01 mgrm. up to 1 mgrm. in the absence of more than 10 mgrms. of magnesium, and within these limits in the absence of other salts the opalescence appears proportional to the calcium present. Further experiments showed, however, that, in spite of its delicacy, the oleate test is not suitable for the purpose in view. Possibly, if the test could be carried out, using standards containing the same concentration of the same salt, it would be satisfactory, but this is hardly practicable. The addition of other salts, even in the absence of potassium citrate, caused the results to be erratic. This was partly due to their “salting out ” effect on the soap, which sometimes caused flocculation, but this was not the whole explanation. Almost immediate pptn. Slight ppt. after 30 minutes. Slight ppt. after 30 minutes. No ppt. This line of investigation was therefore abandoned. Mix and allow the mixture to stand. An excess of the reagent gives less opalescence.

ISSN:0003-2654    

DOI:10.1039/AN9315600598

出版商:RSC    

年代:1931

数据来源: RSC

摘要:

294 EVERS: THE DETECTION OF SMALL QUANTITIES OF CALCIUM Adding 5 mgrms. of calcium. Added salts. Result. No added salt. Immediate pptn. Sodium chloride, 1 grm. Borax, 1 grm. Sodium potassium tartrate, 1 grm. Potassium citrate, 1 grm. Variations in the concentration of the reagents did not appreciably improve matters. It was found that even 0.25 grm. of potassium citrate in 60 C.C. of solution prevented the precipitation of 2 mgrms. of calcium. Further complications would be introduced if magnesium were also present in the salt as an impurity. CALCIUM OLEATE TEsT.-The formation of an opalescence on the addition of sodium oleate solution to a solution is an extremely delicate test for calcium. Under the best conditions 0.01 mgrm. of calcium in 50 C.C. of solution, or 0.00002 per cent., can just be detected.The test is also, of course, a test for magnesium, but is much less sensitive, 0-6 mgrm. in 50 C.C. of solution, or 0-0012 per cent., being the minimum quantity which can be detected. Further, within certain limits of concentration the pre- cipitation of magnesium is entirely suppressed in the presence of potassium citrate, whilst the sensitiveness of the calcium test is actually increased. The best conditions for the detection of calcium were found to be as follows: Take 50 C.C. of the solution containing calcium, which should be neutral or slightly alkaline. Dissolve in it 2 grms. of potassium citrate, and add 0-3 C.C. of a solution prepared by dissolving 10 grms. of oleic acid in 200 C.C. of 1 per cent. sodium hydroxide. A certain excess of alkali is desirable for the best results.The test is only satisfactory between certain limits of calcium concentration. With quantities exceeding 1 mgrm. in 60 C.C. the opalescence is actually reduced. Under the above conditions quantities of mag- nesium up to 15 mgrms. give no opalescence. Summarising the results, the oleate test is excellent for quantities of calcium varying from 0-01 mgrm. up to 1 mgrm. in the absence of more than 10 mgrms. of magnesium, and within these limits in the absence of other salts the opalescence appears proportional to the calcium present. Further experiments showed, however, that, in spite of its delicacy, the oleate test is not suitable for the purpose in view. Possibly, if the test could be carried out, using standards containing the same concentration of the same salt, it would be satisfactory, but this is hardly practicable. The addition of other salts, even in the absence of potassium citrate, caused the results to be erratic. This was partly due to their “salting out ” effect on the soap, which sometimes caused flocculation, but this was not the whole explanation. Almost immediate pptn. Slight ppt. after 30 minutes. Slight ppt. after 30 minutes. No ppt. This line of investigation was therefore abandoned. Mix and allow the mixture to stand. An excess of the reagent gives less opalescence.

ISSN:0003-2654    

DOI:10.1039/AN9315600601

出版商:RSC    

年代:1931

数据来源: RSC

摘要:

294 EVERS: THE DETECTION OF SMALL QUANTITIES OF CALCIUM Adding 5 mgrms. of calcium. Added salts. Result. No added salt. Immediate pptn. Sodium chloride, 1 grm. Borax, 1 grm. Sodium potassium tartrate, 1 grm. Potassium citrate, 1 grm. Variations in the concentration of the reagents did not appreciably improve matters. It was found that even 0.25 grm. of potassium citrate in 60 C.C. of solution prevented the precipitation of 2 mgrms. of calcium. Further complications would be introduced if magnesium were also present in the salt as an impurity. CALCIUM OLEATE TEsT.-The formation of an opalescence on the addition of sodium oleate solution to a solution is an extremely delicate test for calcium. Under the best conditions 0.01 mgrm. of calcium in 50 C.C. of solution, or 0.00002 per cent., can just be detected.The test is also, of course, a test for magnesium, but is much less sensitive, 0-6 mgrm. in 50 C.C. of solution, or 0-0012 per cent., being the minimum quantity which can be detected. Further, within certain limits of concentration the pre- cipitation of magnesium is entirely suppressed in the presence of potassium citrate, whilst the sensitiveness of the calcium test is actually increased. The best conditions for the detection of calcium were found to be as follows: Take 50 C.C. of the solution containing calcium, which should be neutral or slightly alkaline. Dissolve in it 2 grms. of potassium citrate, and add 0-3 C.C. of a solution prepared by dissolving 10 grms. of oleic acid in 200 C.C. of 1 per cent. sodium hydroxide. A certain excess of alkali is desirable for the best results.The test is only satisfactory between certain limits of calcium concentration. With quantities exceeding 1 mgrm. in 60 C.C. the opalescence is actually reduced. Under the above conditions quantities of mag- nesium up to 15 mgrms. give no opalescence. Summarising the results, the oleate test is excellent for quantities of calcium varying from 0-01 mgrm. up to 1 mgrm. in the absence of more than 10 mgrms. of magnesium, and within these limits in the absence of other salts the opalescence appears proportional to the calcium present. Further experiments showed, however, that, in spite of its delicacy, the oleate test is not suitable for the purpose in view. Possibly, if the test could be carried out, using standards containing the same concentration of the same salt, it would be satisfactory, but this is hardly practicable.The addition of other salts, even in the absence of potassium citrate, caused the results to be erratic. This was partly due to their “salting out ” effect on the soap, which sometimes caused flocculation, but this was not the whole explanation. Almost immediate pptn. Slight ppt. after 30 minutes. Slight ppt. after 30 minutes. No ppt. This line of investigation was therefore abandoned. Mix and allow the mixture to stand. An excess of the reagent gives less opalescence.294 EVERS: THE DETECTION OF SMALL QUANTITIES OF CALCIUM Adding 5 mgrms. of calcium. Added salts. Result. No added salt. Immediate pptn. Sodium chloride, 1 grm. Borax, 1 grm. Sodium potassium tartrate, 1 grm.Potassium citrate, 1 grm. Variations in the concentration of the reagents did not appreciably improve matters. It was found that even 0.25 grm. of potassium citrate in 60 C.C. of solution prevented the precipitation of 2 mgrms. of calcium. Further complications would be introduced if magnesium were also present in the salt as an impurity. CALCIUM OLEATE TEsT.-The formation of an opalescence on the addition of sodium oleate solution to a solution is an extremely delicate test for calcium. Under the best conditions 0.01 mgrm. of calcium in 50 C.C. of solution, or 0.00002 per cent., can just be detected. The test is also, of course, a test for magnesium, but is much less sensitive, 0-6 mgrm. in 50 C.C. of solution, or 0-0012 per cent., being the minimum quantity which can be detected.Further, within certain limits of concentration the pre- cipitation of magnesium is entirely suppressed in the presence of potassium citrate, whilst the sensitiveness of the calcium test is actually increased. The best conditions for the detection of calcium were found to be as follows: Take 50 C.C. of the solution containing calcium, which should be neutral or slightly alkaline. Dissolve in it 2 grms. of potassium citrate, and add 0-3 C.C. of a solution prepared by dissolving 10 grms. of oleic acid in 200 C.C. of 1 per cent. sodium hydroxide. A certain excess of alkali is desirable for the best results. The test is only satisfactory between certain limits of calcium concentration. With quantities exceeding 1 mgrm.in 60 C.C. the opalescence is actually reduced. Under the above conditions quantities of mag- nesium up to 15 mgrms. give no opalescence. Summarising the results, the oleate test is excellent for quantities of calcium varying from 0-01 mgrm. up to 1 mgrm. in the absence of more than 10 mgrms. of magnesium, and within these limits in the absence of other salts the opalescence appears proportional to the calcium present. Further experiments showed, however, that, in spite of its delicacy, the oleate test is not suitable for the purpose in view. Possibly, if the test could be carried out, using standards containing the same concentration of the same salt, it would be satisfactory, but this is hardly practicable. The addition of other salts, even in the absence of potassium citrate, caused the results to be erratic.This was partly due to their “salting out ” effect on the soap, which sometimes caused flocculation, but this was not the whole explanation. Almost immediate pptn. Slight ppt. after 30 minutes. Slight ppt. after 30 minutes. No ppt. This line of investigation was therefore abandoned. Mix and allow the mixture to stand. An excess of the reagent gives less opalescence.294 EVERS: THE DETECTION OF SMALL QUANTITIES OF CALCIUM Adding 5 mgrms. of calcium. Added salts. Result. No added salt. Immediate pptn. Sodium chloride, 1 grm. Borax, 1 grm. Sodium potassium tartrate, 1 grm. Potassium citrate, 1 grm. Variations in the concentration of the reagents did not appreciably improve matters. It was found that even 0.25 grm.of potassium citrate in 60 C.C. of solution prevented the precipitation of 2 mgrms. of calcium. Further complications would be introduced if magnesium were also present in the salt as an impurity. CALCIUM OLEATE TEsT.-The formation of an opalescence on the addition of sodium oleate solution to a solution is an extremely delicate test for calcium. Under the best conditions 0.01 mgrm. of calcium in 50 C.C. of solution, or 0.00002 per cent., can just be detected. The test is also, of course, a test for magnesium, but is much less sensitive, 0-6 mgrm. in 50 C.C. of solution, or 0-0012 per cent., being the minimum quantity which can be detected. Further, within certain limits of concentration the pre- cipitation of magnesium is entirely suppressed in the presence of potassium citrate, whilst the sensitiveness of the calcium test is actually increased.The best conditions for the detection of calcium were found to be as follows: Take 50 C.C. of the solution containing calcium, which should be neutral or slightly alkaline. Dissolve in it 2 grms. of potassium citrate, and add 0-3 C.C. of a solution prepared by dissolving 10 grms. of oleic acid in 200 C.C. of 1 per cent. sodium hydroxide. A certain excess of alkali is desirable for the best results. The test is only satisfactory between certain limits of calcium concentration. With quantities exceeding 1 mgrm. in 60 C.C. the opalescence is actually reduced. Under the above conditions quantities of mag- nesium up to 15 mgrms. give no opalescence. Summarising the results, the oleate test is excellent for quantities of calcium varying from 0-01 mgrm.up to 1 mgrm. in the absence of more than 10 mgrms. of magnesium, and within these limits in the absence of other salts the opalescence appears proportional to the calcium present. Further experiments showed, however, that, in spite of its delicacy, the oleate test is not suitable for the purpose in view. Possibly, if the test could be carried out, using standards containing the same concentration of the same salt, it would be satisfactory, but this is hardly practicable. The addition of other salts, even in the absence of potassium citrate, caused the results to be erratic. This was partly due to their “salting out ” effect on the soap, which sometimes caused flocculation, but this was not the whole explanation.Almost immediate pptn. Slight ppt. after 30 minutes. Slight ppt. after 30 minutes. No ppt. This line of investigation was therefore abandoned. Mix and allow the mixture to stand. An excess of the reagent gives less opalescence.294 EVERS: THE DETECTION OF SMALL QUANTITIES OF CALCIUM Adding 5 mgrms. of calcium. Added salts. Result. No added salt. Immediate pptn. Sodium chloride, 1 grm. Borax, 1 grm. Sodium potassium tartrate, 1 grm. Potassium citrate, 1 grm. Variations in the concentration of the reagents did not appreciably improve matters. It was found that even 0.25 grm. of potassium citrate in 60 C.C. of solution prevented the precipitation of 2 mgrms. of calcium. Further complications would be introduced if magnesium were also present in the salt as an impurity.CALCIUM OLEATE TEsT.-The formation of an opalescence on the addition of sodium oleate solution to a solution is an extremely delicate test for calcium. Under the best conditions 0.01 mgrm. of calcium in 50 C.C. of solution, or 0.00002 per cent., can just be detected. The test is also, of course, a test for magnesium, but is much less sensitive, 0-6 mgrm. in 50 C.C. of solution, or 0-0012 per cent., being the minimum quantity which can be detected. Further, within certain limits of concentration the pre- cipitation of magnesium is entirely suppressed in the presence of potassium citrate, whilst the sensitiveness of the calcium test is actually increased. The best conditions for the detection of calcium were found to be as follows: Take 50 C.C.of the solution containing calcium, which should be neutral or slightly alkaline. Dissolve in it 2 grms. of potassium citrate, and add 0-3 C.C. of a solution prepared by dissolving 10 grms. of oleic acid in 200 C.C. of 1 per cent. sodium hydroxide. A certain excess of alkali is desirable for the best results. The test is only satisfactory between certain limits of calcium concentration. With quantities exceeding 1 mgrm. in 60 C.C. the opalescence is actually reduced. Under the above conditions quantities of mag- nesium up to 15 mgrms. give no opalescence. Summarising the results, the oleate test is excellent for quantities of calcium varying from 0-01 mgrm. up to 1 mgrm. in the absence of more than 10 mgrms. of magnesium, and within these limits in the absence of other salts the opalescence appears proportional to the calcium present. Further experiments showed, however, that, in spite of its delicacy, the oleate test is not suitable for the purpose in view.Possibly, if the test could be carried out, using standards containing the same concentration of the same salt, it would be satisfactory, but this is hardly practicable. The addition of other salts, even in the absence of potassium citrate, caused the results to be erratic. This was partly due to their “salting out ” effect on the soap, which sometimes caused flocculation, but this was not the whole explanation. Almost immediate pptn. Slight ppt. after 30 minutes. Slight ppt. after 30 minutes. No ppt. This line of investigation was therefore abandoned.Mix and allow the mixture to stand. An excess of the reagent gives less opalescence.294 EVERS: THE DETECTION OF SMALL QUANTITIES OF CALCIUM Adding 5 mgrms. of calcium. Added salts. Result. No added salt. Immediate pptn. Sodium chloride, 1 grm. Borax, 1 grm. Sodium potassium tartrate, 1 grm. Potassium citrate, 1 grm. Variations in the concentration of the reagents did not appreciably improve matters. It was found that even 0.25 grm. of potassium citrate in 60 C.C. of solution prevented the precipitation of 2 mgrms. of calcium. Further complications would be introduced if magnesium were also present in the salt as an impurity. CALCIUM OLEATE TEsT.-The formation of an opalescence on the addition of sodium oleate solution to a solution is an extremely delicate test for calcium.Under the best conditions 0.01 mgrm. of calcium in 50 C.C. of solution, or 0.00002 per cent., can just be detected. The test is also, of course, a test for magnesium, but is much less sensitive, 0-6 mgrm. in 50 C.C. of solution, or 0-0012 per cent., being the minimum quantity which can be detected. Further, within certain limits of concentration the pre- cipitation of magnesium is entirely suppressed in the presence of potassium citrate, whilst the sensitiveness of the calcium test is actually increased. The best conditions for the detection of calcium were found to be as follows: Take 50 C.C. of the solution containing calcium, which should be neutral or slightly alkaline. Dissolve in it 2 grms. of potassium citrate, and add 0-3 C.C. of a solution prepared by dissolving 10 grms.of oleic acid in 200 C.C. of 1 per cent. sodium hydroxide. A certain excess of alkali is desirable for the best results. The test is only satisfactory between certain limits of calcium concentration. With quantities exceeding 1 mgrm. in 60 C.C. the opalescence is actually reduced. Under the above conditions quantities of mag- nesium up to 15 mgrms. give no opalescence. Summarising the results, the oleate test is excellent for quantities of calcium varying from 0-01 mgrm. up to 1 mgrm. in the absence of more than 10 mgrms. of magnesium, and within these limits in the absence of other salts the opalescence appears proportional to the calcium present. Further experiments showed, however, that, in spite of its delicacy, the oleate test is not suitable for the purpose in view.Possibly, if the test could be carried out, using standards containing the same concentration of the same salt, it would be satisfactory, but this is hardly practicable. The addition of other salts, even in the absence of potassium citrate, caused the results to be erratic. This was partly due to their “salting out ” effect on the soap, which sometimes caused flocculation, but this was not the whole explanation. Almost immediate pptn. Slight ppt. after 30 minutes. Slight ppt. after 30 minutes. No ppt. This line of investigation was therefore abandoned. Mix and allow the mixture to stand. An excess of the reagent gives less opalescence.294 EVERS: THE DETECTION OF SMALL QUANTITIES OF CALCIUM Adding 5 mgrms. of calcium.Added salts. Result. No added salt. Immediate pptn. Sodium chloride, 1 grm. Borax, 1 grm. Sodium potassium tartrate, 1 grm. Potassium citrate, 1 grm. Variations in the concentration of the reagents did not appreciably improve matters. It was found that even 0.25 grm. of potassium citrate in 60 C.C. of solution prevented the precipitation of 2 mgrms. of calcium. Further complications would be introduced if magnesium were also present in the salt as an impurity. CALCIUM OLEATE TEsT.-The formation of an opalescence on the addition of sodium oleate solution to a solution is an extremely delicate test for calcium. Under the best conditions 0.01 mgrm. of calcium in 50 C.C. of solution, or 0.00002 per cent., can just be detected. The test is also, of course, a test for magnesium, but is much less sensitive, 0-6 mgrm. in 50 C.C.of solution, or 0-0012 per cent., being the minimum quantity which can be detected. Further, within certain limits of concentration the pre- cipitation of magnesium is entirely suppressed in the presence of potassium citrate, whilst the sensitiveness of the calcium test is actually increased. The best conditions for the detection of calcium were found to be as follows: Take 50 C.C. of the solution containing calcium, which should be neutral or slightly alkaline. Dissolve in it 2 grms. of potassium citrate, and add 0-3 C.C. of a solution prepared by dissolving 10 grms. of oleic acid in 200 C.C. of 1 per cent. sodium hydroxide. A certain excess of alkali is desirable for the best results. The test is only satisfactory between certain limits of calcium concentration. With quantities exceeding 1 mgrm.in 60 C.C. the opalescence is actually reduced. Under the above conditions quantities of mag- nesium up to 15 mgrms. give no opalescence. Summarising the results, the oleate test is excellent for quantities of calcium varying from 0-01 mgrm. up to 1 mgrm. in the absence of more than 10 mgrms. of magnesium, and within these limits in the absence of other salts the opalescence appears proportional to the calcium present. Further experiments showed, however, that, in spite of its delicacy, the oleate test is not suitable for the purpose in view. Possibly, if the test could be carried out, using standards containing the same concentration of the same salt, it would be satisfactory, but this is hardly practicable.The addition of other salts, even in the absence of potassium citrate, caused the results to be erratic. This was partly due to their “salting out ” effect on the soap, which sometimes caused flocculation, but this was not the whole explanation. Almost immediate pptn. Slight ppt. after 30 minutes. Slight ppt. after 30 minutes. No ppt. This line of investigation was therefore abandoned. Mix and allow the mixture to stand. An excess of the reagent gives less opalescence.294 EVERS: THE DETECTION OF SMALL QUANTITIES OF CALCIUM Adding 5 mgrms. of calcium. Added salts. Result. No added salt. Immediate pptn. Sodium chloride, 1 grm. Borax, 1 grm. Sodium potassium tartrate, 1 grm. Potassium citrate, 1 grm. Variations in the concentration of the reagents did not appreciably improve matters. It was found that even 0.25 grm.of potassium citrate in 60 C.C. of solution prevented the precipitation of 2 mgrms. of calcium. Further complications would be introduced if magnesium were also present in the salt as an impurity. CALCIUM OLEATE TEsT.-The formation of an opalescence on the addition of sodium oleate solution to a solution is an extremely delicate test for calcium. Under the best conditions 0.01 mgrm. of calcium in 50 C.C. of solution, or 0.00002 per cent., can just be detected. The test is also, of course, a test for magnesium, but is much less sensitive, 0-6 mgrm. in 50 C.C. of solution, or 0-0012 per cent., being the minimum quantity which can be detected. Further, within certain limits of concentration the pre- cipitation of magnesium is entirely suppressed in the presence of potassium citrate, whilst the sensitiveness of the calcium test is actually increased.The best conditions for the detection of calcium were found to be as follows: Take 50 C.C. of the solution containing calcium, which should be neutral or slightly alkaline. Dissolve in it 2 grms. of potassium citrate, and add 0-3 C.C. of a solution prepared by dissolving 10 grms. of oleic acid in 200 C.C. of 1 per cent. sodium hydroxide. A certain excess of alkali is desirable for the best results. The test is only satisfactory between certain limits of calcium concentration. With quantities exceeding 1 mgrm. in 60 C.C. the opalescence is actually reduced. Under the above conditions quantities of mag- nesium up to 15 mgrms. give no opalescence. Summarising the results, the oleate test is excellent for quantities of calcium varying from 0-01 mgrm. up to 1 mgrm. in the absence of more than 10 mgrms. of magnesium, and within these limits in the absence of other salts the opalescence appears proportional to the calcium present. Further experiments showed, however, that, in spite of its delicacy, the oleate test is not suitable for the purpose in view. Possibly, if the test could be carried out, using standards containing the same concentration of the same salt, it would be satisfactory, but this is hardly practicable. The addition of other salts, even in the absence of potassium citrate, caused the results to be erratic. This was partly due to their “salting out ” effect on the soap, which sometimes caused flocculation, but this was not the whole explanation. Almost immediate pptn. Slight ppt. after 30 minutes. Slight ppt. after 30 minutes. No ppt. This line of investigation was therefore abandoned. Mix and allow the mixture to stand. An excess of the reagent gives less opalescence.

ISSN:0003-2654    

DOI:10.1039/AN931560602b

出版商:RSC    

年代:1931

数据来源: RSC

摘要:

294 EVERS: THE DETECTION OF SMALL QUANTITIES OF CALCIUM Adding 5 mgrms. of calcium. Added salts. Result. No added salt. Immediate pptn. Sodium chloride, 1 grm. Borax, 1 grm. Sodium potassium tartrate, 1 grm. Potassium citrate, 1 grm. Variations in the concentration of the reagents did not appreciably improve matters. It was found that even 0.25 grm. of potassium citrate in 60 C.C. of solution prevented the precipitation of 2 mgrms. of calcium. Further complications would be introduced if magnesium were also present in the salt as an impurity. CALCIUM OLEATE TEsT.-The formation of an opalescence on the addition of sodium oleate solution to a solution is an extremely delicate test for calcium. Under the best conditions 0.01 mgrm. of calcium in 50 C.C. of solution, or 0.00002 per cent., can just be detected.The test is also, of course, a test for magnesium, but is much less sensitive, 0-6 mgrm. in 50 C.C. of solution, or 0-0012 per cent., being the minimum quantity which can be detected. Further, within certain limits of concentration the pre- cipitation of magnesium is entirely suppressed in the presence of potassium citrate, whilst the sensitiveness of the calcium test is actually increased. The best conditions for the detection of calcium were found to be as follows: Take 50 C.C. of the solution containing calcium, which should be neutral or slightly alkaline. Dissolve in it 2 grms. of potassium citrate, and add 0-3 C.C. of a solution prepared by dissolving 10 grms. of oleic acid in 200 C.C. of 1 per cent. sodium hydroxide. A certain excess of alkali is desirable for the best results.The test is only satisfactory between certain limits of calcium concentration. With quantities exceeding 1 mgrm. in 60 C.C. the opalescence is actually reduced. Under the above conditions quantities of mag- nesium up to 15 mgrms. give no opalescence. Summarising the results, the oleate test is excellent for quantities of calcium varying from 0-01 mgrm. up to 1 mgrm. in the absence of more than 10 mgrms. of magnesium, and within these limits in the absence of other salts the opalescence appears proportional to the calcium present. Further experiments showed, however, that, in spite of its delicacy, the oleate test is not suitable for the purpose in view. Possibly, if the test could be carried out, using standards containing the same concentration of the same salt, it would be satisfactory, but this is hardly practicable.The addition of other salts, even in the absence of potassium citrate, caused the results to be erratic. This was partly due to their “salting out ” effect on the soap, which sometimes caused flocculation, but this was not the whole explanation. Almost immediate pptn. Slight ppt. after 30 minutes. Slight ppt. after 30 minutes. No ppt. This line of investigation was therefore abandoned. Mix and allow the mixture to stand. An excess of the reagent gives less opalescence.294 EVERS: THE DETECTION OF SMALL QUANTITIES OF CALCIUM Adding 5 mgrms. of calcium. Added salts. Result. No added salt. Immediate pptn. Sodium chloride, 1 grm. Borax, 1 grm. Sodium potassium tartrate, 1 grm.Potassium citrate, 1 grm. Variations in the concentration of the reagents did not appreciably improve matters. It was found that even 0.25 grm. of potassium citrate in 60 C.C. of solution prevented the precipitation of 2 mgrms. of calcium. Further complications would be introduced if magnesium were also present in the salt as an impurity. CALCIUM OLEATE TEsT.-The formation of an opalescence on the addition of sodium oleate solution to a solution is an extremely delicate test for calcium. Under the best conditions 0.01 mgrm. of calcium in 50 C.C. of solution, or 0.00002 per cent., can just be detected. The test is also, of course, a test for magnesium, but is much less sensitive, 0-6 mgrm. in 50 C.C. of solution, or 0-0012 per cent., being the minimum quantity which can be detected.Further, within certain limits of concentration the pre- cipitation of magnesium is entirely suppressed in the presence of potassium citrate, whilst the sensitiveness of the calcium test is actually increased. The best conditions for the detection of calcium were found to be as follows: Take 50 C.C. of the solution containing calcium, which should be neutral or slightly alkaline. Dissolve in it 2 grms. of potassium citrate, and add 0-3 C.C. of a solution prepared by dissolving 10 grms. of oleic acid in 200 C.C. of 1 per cent. sodium hydroxide. A certain excess of alkali is desirable for the best results. The test is only satisfactory between certain limits of calcium concentration. With quantities exceeding 1 mgrm.in 60 C.C. the opalescence is actually reduced. Under the above conditions quantities of mag- nesium up to 15 mgrms. give no opalescence. Summarising the results, the oleate test is excellent for quantities of calcium varying from 0-01 mgrm. up to 1 mgrm. in the absence of more than 10 mgrms. of magnesium, and within these limits in the absence of other salts the opalescence appears proportional to the calcium present. Further experiments showed, however, that, in spite of its delicacy, the oleate test is not suitable for the purpose in view. Possibly, if the test could be carried out, using standards containing the same concentration of the same salt, it would be satisfactory, but this is hardly practicable. The addition of other salts, even in the absence of potassium citrate, caused the results to be erratic.This was partly due to their “salting out ” effect on the soap, which sometimes caused flocculation, but this was not the whole explanation. Almost immediate pptn. Slight ppt. after 30 minutes. Slight ppt. after 30 minutes. No ppt. This line of investigation was therefore abandoned. Mix and allow the mixture to stand. An excess of the reagent gives less opalescence.294 EVERS: THE DETECTION OF SMALL QUANTITIES OF CALCIUM Adding 5 mgrms. of calcium. Added salts. Result. No added salt. Immediate pptn. Sodium chloride, 1 grm. Borax, 1 grm. Sodium potassium tartrate, 1 grm. Potassium citrate, 1 grm. Variations in the concentration of the reagents did not appreciably improve matters. It was found that even 0.25 grm.of potassium citrate in 60 C.C. of solution prevented the precipitation of 2 mgrms. of calcium. Further complications would be introduced if magnesium were also present in the salt as an impurity. CALCIUM OLEATE TEsT.-The formation of an opalescence on the addition of sodium oleate solution to a solution is an extremely delicate test for calcium. Under the best conditions 0.01 mgrm. of calcium in 50 C.C. of solution, or 0.00002 per cent., can just be detected. The test is also, of course, a test for magnesium, but is much less sensitive, 0-6 mgrm. in 50 C.C. of solution, or 0-0012 per cent., being the minimum quantity which can be detected. Further, within certain limits of concentration the pre- cipitation of magnesium is entirely suppressed in the presence of potassium citrate, whilst the sensitiveness of the calcium test is actually increased.The best conditions for the detection of calcium were found to be as follows: Take 50 C.C. of the solution containing calcium, which should be neutral or slightly alkaline. Dissolve in it 2 grms. of potassium citrate, and add 0-3 C.C. of a solution prepared by dissolving 10 grms. of oleic acid in 200 C.C. of 1 per cent. sodium hydroxide. A certain excess of alkali is desirable for the best results. The test is only satisfactory between certain limits of calcium concentration. With quantities exceeding 1 mgrm. in 60 C.C. the opalescence is actually reduced. Under the above conditions quantities of mag- nesium up to 15 mgrms. give no opalescence. Summarising the results, the oleate test is excellent for quantities of calcium varying from 0-01 mgrm. up to 1 mgrm. in the absence of more than 10 mgrms. of magnesium, and within these limits in the absence of other salts the opalescence appears proportional to the calcium present. Further experiments showed, however, that, in spite of its delicacy, the oleate test is not suitable for the purpose in view. Possibly, if the test could be carried out, using standards containing the same concentration of the same salt, it would be satisfactory, but this is hardly practicable. The addition of other salts, even in the absence of potassium citrate, caused the results to be erratic. This was partly due to their “salting out ” effect on the soap, which sometimes caused flocculation, but this was not the whole explanation. Almost immediate pptn. Slight ppt. after 30 minutes. Slight ppt. after 30 minutes. No ppt. This line of investigation was therefore abandoned. Mix and allow the mixture to stand. An excess of the reagent gives less opalescence.

ISSN:0003-2654    

DOI:10.1039/AN9315600608

出版商:RSC    

年代:1931

数据来源: RSC