摘要:

THE ANALYST. JUNE, 1896. THE BACTERIOLOGICAL EXAMINATION OF WATER FOR THB TYPHOID BACILLUS. BY T. H. PEARMAIN AND C. G. MOOR, M.A. (Rend at the Meeting, April I, 1896.) (Coucluded from p . 122.) THE ISOLATION OF THE TYPHOID BACILLUS FROM WATEE. IN waters that have been very copiously contaminated with sewage there is no great difficulty in detecting the typhoid or colon bacillus if present, but it is necessary to bear in mind that usually when drinking-water has suffered sewage pollution the quantity of the polluting matter is relatively very minute when compared with the great bulk of the water-supply. The contamination of water by sewage is, moreover, in the majority of cases of an intermittent nature. When such waters are examined, as large a quantity as 1 cubic centimetre or more of the water may be “plate cultured,” and even then it is easy to miss the colon bacillus, not to speak of the typhoid bacillus.In order to isolate the B. tz~p7zosz~s suspected to be present in a sample of water,142 THE ANALYST. it is necessary to submit a large volume of the water to examination. This object is attained by concentrating the bacterial contents of the water by passing 1,000 to 3,000 C.C. or more of the sample through a small sterile Pasteur-Chamberland, or, better for practical purposes, a small Berkefeld filter. By this treatment all the bacteria in the water are retained on the outer surface of the filter. The particulate matter thus retained is then brushed off the outer coating of the filter with a sterile brush into about 20 C.C. of sterile distilled water.One C.C. of this, containing the particulate matter from 50 to 150 C.C. of the original water, is then immediately submitted to plate-culture by one of the undermentioned methods to isolate the colon bacillus and also the typhoid bacillus if present. (1) Iizhibitioit by Means qf PlmuoZ. The B. typhosiis and the B. coli C O ~ ~ L ~ L Z L I Z ~ S are among the limited number of micro-organisms which will grow in the presence of small quantities of phenol, which addition retards, or inhibits the common water bacteria, such as the B. JIZLOTESCC~ZS Iiquefcicieits, Proteus udgai-is, B. iiiesciite&us, etc., the presence of which would liquefy the gelatin, and by their rapid growth would annihilate the B. typhosus if present. The presence of a small quantity of phenol does not in any way interfere with the growth of the B.typhosus or the B. coli, but exhibits a marked inhibitory effect upon the corxiinon water bacteria, and, by the retardation and suppression of these, the colonies of the 5'. t y p l m z u and the B. coli have time and opportunity to appear. Phenol appears to have been first used for this purpose by Chantemesse and JVidal,* who employed nutrient gelatin containing 0-25 per cent. of phenol. Thoinot,f a little later, inhibited the growth of organisms, other than the typhoid and colon bacillus, by adding 0.25 per cent. of phenol to the water under examination, which was then incubated at blood-heat and the water afterwards plate-cultured. L4s pointed out by IIolz, and confirmed by Dunbar, the above authors use a per- centage of phenol which altogether prevents the growth of the B.typlzosus. Dunbar states that 0-12 per cent. of phenol greatly interferes with the growth of the typhoid bacillus, while in the preeence of 0.14 per cent. it will not develop at all. He further states that in the presence of small quantities of phenol the colon bacillus presents stronger resemblances to the typhoid bacillus than usual. To ascertain if the resisting power of cultures of the B. typlzoszis to phenol differed, we tried the following series of experiments on different cultures of the organism, using varying percentages of phenol, with the following results : Percentage of Phenol. I 0.05. n. typlLosus ( a ) ... ... ... !) (4 1 , (4 9 , (4 ...... ... . . . ... ... ... Iz. coli coii~iizzmis . . . ... ... 3. + + + + 0.20. 0.30. - + Thus, it is seen that the resisting power of the B. typhosz~s to phenol varies The sample marked (a), which was freshly isolated from the with different cultures. * Gazette des HGpitanx, 1887, p. 203. f Ibid., 1887, p. 348.THE ANALYST. 143 dejecta from a typhoid case, had less resisting power than other samples which had been sub-cultured through many generations. Parietti proposed the use of broth containing both phenol and hydrochloric acid to eliminate the common water organisms. He takes advantage of the fact that the typhoid and colon bacillus will grow in a slightly acid medium, whereas the majority of other organisms will not. Parietti’s method is as follows : The following solution is prepared : Five grammes of phenol and 4 grammes of pure hydrochloric acid are added to 100 C.C.of distilled water. From 0.1 to 0.3 C.C. of this solution is added to a series of test-tubes con- taining 10 C.C. of sterile nutrient broth (=Om05 to 0.15 per cent. of phenol). The tubes are then incubated at blood-heat for twenty-four hours, to destroy any stray organisms that may have gained access to the tubes, From 0.1 to 0.5 of a C.C. of the water under examination is then added to the tubes, the contents well mixed, and the tubes again returned to the incubator. If, after twenty-four hours’ incubating at blood-heat, any of the tubes appear to be turbid, they are submitted to ordinary plate-cultivation and the resulting colonies carefully examined in sub-cultures.Frankland states that when only a few typhoid bacilli are present, the incubation must be prolonged for forty-eight or even seventy-two hours. We have found the above method to be a very reliable one, although somewhat tedious. I n practice, however, we prefer to use simple carbolized gelatin containing 0.05 per cent. of phenol. This quantity is quite sufficient to restrain the growth of liquefying organisms, and, moreover, with this quantity there is no danger of losing the typhoid bacillus if it is present. (2) E71swr’s Alctlzod. Dr. Elsner, of Berlin, has recently published* the results of an investigation made to ascertain the possibility of an early recognition of enteric fever by the bac- teriological examination of the stools. He has been able to recognise the Eberth- Gaffky bacillus in some cases in as short a time as forty-eight hours.Dr. Elsner went over the existing methods for the separation of the B. typhosus and coli, with no better results than have previously been obtained. In all cases but one he found that either persistent organisms other than those sought to be isolated would grow to a sufficient extent to spoil the plate (e.g., B. proteus or 1*awzosus), or else the B. coli would develop to an extent capable of preventing the recognition of the typhoid bacillus. The exception was slightly acid potato-gelatin, containing 1 per cent. of iodide of potassium. The process recommended is to boil potato-decoction (500 grammes to 1 litre of water) with 10 per cent. of gelatin. Sufficient of a 2 per cent.solution of sodium hydrate is added till only a faint acidity remains, litmus being used as indicator. Elsner found that the B. yrotcw and rcmosus, which always grow on carbolized gelatin, either never occurred on this medium, or were rapidly overgrown by the colon bacillus. The B. coli grew in twenty-four hours, presenting the usual appear- ance of that organism on acid media; the B. typhosus was scarcely visible in twenty-four hours, but in forty-eight hours appeared in small, shining, very finely- * Zeitschr. f. Hyg., xxi. 1.144 THE ANALYST. granulated colonies like little drops of water, which contrasted strongly with the larger coarsely-granulated, brownish colonies of the colon bacillus. The B. coli only acquired the appearance of the typhoid colonies when a great number of the organ- isins were present, and many, therefore, grew without finding room for their proper development.In plates made with weaker inoculations, it is impossible to mistake one bacillus for the other. We have used this method with sa,tisfactory results. The colonies of the B. typhosus appear more quickly on this medium than on carbol-gelatin, but otherwise this appears to be the only advantage it possesses. A number of other methods for the isolation of the B. typhosus and coZi have been proposed by different investigators. Uffelmann has suggested the addition of 0.1 per cent. of citric acid to the nutrient gelatin, to restrain the growth of the liquefying organisms. Dunbar has found, however, that the amount of citric acid prescribed by Uffelmann is in excess of what the typhoid bacilli are capable of withstanding.He found that in many cases, whilst the colon bacillus developed, the growth of the B. typhosus was restrained. Holz has used faintly acid potato-juice, thickened with 10 per cent. of gelatin, with or without the addition of 0.05 per cent. of phenol, with satisfactory results. This method is practically the same as Elsner's, except that the potassium iodide is replaced by phenol. Gasser, Holz, Lyonnet, and others have suggested the use of various media tinted with fuchsine and other aniline dyes. The typhoid and colon bacilli are stated to decolorize, or to cause other changes, in such media where the growth of the coIonies occurs, whereas other organisms do not possess this property.We find that but little reliance is to be placed on these appearances, as we have found other organisms give the same characteristics as the typhoid and colon bacilli. After a considerable experience in the use of the above methods, we find that the best and most reliable processes to be employed for the isolation of the typhoid bacillus from water are the use of carbolized gelatin (0.05 per cent.), Elsner's method, and Parietti's acid carbolized broth. As soon as the colonies which develop on the carbolized or potato-gelatin become sufficiently advanced they are examined with a lens, and any suspicious colonies are carefully sub-cultured into faintly alkaline sterile milk-tubes, which are then incubated at 37" C. for thirty-six hours. The milk-tubes are then examined, and any that have become coagulated are rejected, as certainly not typhoid.From the tubes that have not coagulated the following sub-cultures are pre- pared : (a) Gelatin (' streak " culture ; ( b ) gelatin " shake " culture ; (c) broth culture. The gelatin cultures are kept for three days at a temperature of from 18" to 20" C. The broth-tubes are incubated at blood-heat for the same length of time, and then tested by the indol reaction. With reference to the general question of the bacteriological examination of drinking-water, much information as to the character of a water is gained by in- cubating a small quantity of the sample at blood-heat for twenty-four hours. The number of organisms is then ascertained by an ordinary gelatin plate culture. TheTHE ANALYST.145 Approximate nurnber of organisms per C.C. in the original water, as determined by a gelatin plate culture ... ... Number of organisms per C.C. appear- ing on an agar-agar plate colony, after incubahing at blood-heat for Approximate number of organisms per c.c., after incubating the water being determined by an agar-agar ... ... twenty-four hours ... ... ... at blood-heat, the organisms then plate.. . ... ... ... ... number of organisms so found is compared with the number of organisms found by a direct gelatin plate culture which is made on the water immediately upon the receipt of the sample. If a sample of water is polluted with sewage, a great increase in the number of the organisms will be found to have taken place as the result of the incubation.All the organisms normally prese.nt in faeces grow and multiply vigorously at blood-heat, whereas this temperature is fatal to the mijority of the cominon water bacteria ; therefore a corresponding decrease in the nurnber of the organisms will be found to have taken place in a pure water. A more convenient plan is to prepare an agar-agar plate culture with a fraction of a, cubic centimetre of the water. The resulting-plate is incubated at blood-heat for thirty-six hours. This method is the most satisfactory, as it has the advantage that the actual number of the micro-organisms that will grow at blood-heat is ascertained. The following examples show the value of these two methods : (4 1 800 I )- 220 ‘a Polluted Surface-well Waters.(W 1,050 180 uncount - able. (4 1,400 350 uncount- able. Waters of Average Quality. (4 180 10 - (4 270 5 - The majority of the organisms from a polluted water which grow at blood-heat will be found on sub-culturing to be the colon bacillus. The presence of the B. coli co?iammis in small numbers can hardly be considered as good evidence of sewage- pollution, but when it is found in large numbers it is fair to conclude this to be the case. The colon bacillus is spoken of by Klein* ‘‘ as a certain index of faecal pollution.” The recent researches of Dr. A. A. Kanthack, however, show that the Bacillus coli is much more widely distributed than was formerly supposed, being found by him in pure water, saliva, dust, etc., so that the generally prevailing idea that its presence necessarily signifies excretal pollution is erroneous.The widespread dis- tribution of the B. coli c o ~ ~ z ~ ~ ~ z c ~ z i s has, however, long been known to bacteriologists, and it is comparatively rare to find it absent from waters of high degree of purity that have been exposed to the air. * The 23rd Aiiiii~nl Report of the Local Government Board.-Supplement containing the Medical Officer’s Report, p. 6’7.146 THE ANALYST. As pointed out by Dr. Thresh* in a recent paper before this Society, all surface- waters contain large numbers of micro-organisms, and waters from deep-seated springs are almost sterile. When such pure waters are allowed to stand for a few days, however, the number of organisms increase enormously. Frankland states that a pure water containing, say, five organisms per cubic centimetre when freshly drawn, may, even if kept in a sterile flask free from aerial contamination, contain after a few days, perhaps, 500,000 in the same volunie-or, in other words, as many as are found in slightly-diluted sewage.He also points out, however, that whilst in sewage the number of organisms only gradually diminishes, in these pure waters “after the rapid increase in numbers follows a correspondingly rapid decline, so that the numbers again fall below those found in impure surface-waters.” The above facts must be constantly before one when interpreting the results yielded by the bacterio- logical examination of a sample of water. Messrs. Laws and Andrewest failed, after a most prolonged investigation, to find the typhoid bacillus in the London sewage from the Barking and Crossness outfalls, but they found it present, as would be expected, in the sewage from the Homerton Fever Hospital.With respect to the question of the detection of the typhoid bacillus in water, we are satisfied that the Eberth-Gaffky bacillus can be, and has actually been, detected and isolated from water, though some of the cases in which it has been reported may rest upon insuficient evidence. We would, however, consider that the discovery of any of the pseudo-typhoid organisms, such as have been already mentioned, should lead to as decided a condemnation of the water as though an organism possessing the precise inorphological and cultural characters of the Eberth- Gaffky bacillus were isolated.While we would not agree with those who would regard the bacteriological examination as useless, we still further dissent from the view-if, indeed, it is seriously held by any-that the biological examination can in the smallest, degree supplant the chemical analysis of water, which, on account of the valuable data it yields, niust always remain an integral part of the examination of potable water. The most enthusiastic bacteriologist cannot deny that the specific organism may have been present in a given water-supply a week ago, and at the time of examination have disappeared. The incubation period of enteric fever is about fourteen days; so that if a sample of drinking-water were sent for examination when the disease declared itself, it might easily be three weeks since the conveyance of the infection, and during this time the Eberth-Gaffky bacillus may have been annihilated by the common water bacteria.Therefore, to say that a given water was safe because no specific organism was demonstrable, and to ignore the information that a chemical analysis might yield, would be entirely illogical. DISCUSSION. Mr. JOSEPH LUNT, B.Sc., said he had listened to the paper with very great The matter was a most difficult one, and one to which he thought Public * ANALYST, 1896, p. 99. + Report on the H e s d l a of the Iiaceutigatioiw on the Micro-Or!jani.sms of Sewage, presented t o the interest. London County Council, December, 1891.THE ANALYST. 147 Analysts ought to pay a great deal of attention. He would have liked to hear the middle portion of the paper, which dealt with the methods used for separating the typhoid bacillus from water in presence of the Bacillus coli communis.It was very important to distinguish between the typhoid bacillus and the pseudo-typhoid bacilli, which were apt to occur in water. He would not like to go so far as the authors of the paper, in saying that all waters ought to be condemned which contain these pseudo forms resembling typhoid, because he was afraid that if such a course were followed, there would be condemned a great many good waters which were in constant use without harmful results. Only a few days ago he had had a sample of water for examination in the Water Laboratory of the British Institute of Pre- ventive Medicine, which gave a bacillus which resembled the typhoid bacillus most closely, but which was not identical with it, although other indications seemed to show that the water should not be condemned.I t seemed to him that such points as this required a very great deal of investigation before a satisfactory conclusion could be come to. To condemn all waters which contained typhoid-like organisms would, he was afraid, be going rather too far. Dr. HEWLETT said that he had not had so much experience in this direction as Mr. Lunt. Certainly the question of organisms resembling the typhoid bacillus-the so-called '( pseudo-typhoid bacilli "--made the matter extremely difficult to deal with, and perhaps there might be some danger in anyone taking up the bacteriological examination of water, unless he had spent a considerable amount of time in studying the methods and in differentiating these organisms.In some cases the differentiation might be very difficult, and might require a larger amount of time than most Public Analysts would be likely to have at their disposal. He quite agreed with the authors that the chemical and biological examinations of water should go hand-in-hand. He did not think anyone, in the present state of lrnowledge, would rely upon bacterio- logical examination alone. A point had been raised with regard to theidentity of the Bncillm coli conznzzmis and of the typhoid bacillus from the resemblance of the action of their metabolic products. He did not think this was a matter of great importance, because many organisms which were totally different would protect against other organisms.The Bacillus prodigioszu, for example, would protect against the cholera bacillus, two organisms which could not be mistaken for each other in any way. What he would have liked to have heard was of some method for separating the BaciZZzis coli covznmzis when this and typhoid were present together. The PRESIDEKT said he had listened with great interest to this paper, much of which was perhaps foreign to the ordinary work of the Public Analyst, viz., the very interesting ~ d s z i r n b which had beengiven of what had been done with regard to ascer- taining the pathogenic or other characteristics of the typhoid and other organisms. What was perhaps most specially interesting to Public Analysts was the differentiation between the true typhoid bacillus and the Bncilhs coli and other typhoid-like organisms. The subject was one in which he himself had taken a great interest during the past year in connection with the investigations with regard to the water- supply of London. The great difficulty arose after the organisms had been reduced by cultivation at high temperatures to, say, typhoid and coli. The difficulty was not so great when there were large numbers of typhoid organisms present, or reason to148 THE ANALYST. suspect them ; but when search had to be made for the typhoid organism in very small numerical proportions, in the presence of large numbers of BaciLZzbs coli, the difficulty became very great. From his own experience, one could not rely upon one single indication without confirmation by several well-known tests, and this, if he had understood the paper aright, was the conclusion which the authors had come to.

ISSN:0003-2654    

DOI:10.1039/AN896210141b

出版商:RSC    

年代:1896

数据来源: RSC

摘要:

148 THE ANALYST. NOTE ON THE ESTIMATION OF FORMIC ALDEHYDE. BY HARRY &I. SMITH. (Read at the Meeting, ApriL 1, 1896.) ACTING on the suggestion of Dr. Stevenson, I have made experiments as to the conditions aflecting the oxidation of formic aldehyde into formic acid, with the follo\v- ing results : When formic aldehyde is treated with excess of an alkaline solution of potassium perrnanganate in the cold, it is completely oxidized into formic acid. The absence of formic aldehyde after oxidation is proved by filtering, removing the excess of permanganate by means of oxalic acid in the presence of sulphuric acid, and treating the slightly acid solution with Schiff's reagent. The presence of formic acid is proved by its reducing action on amnioniacal silver nitrate and on mercuric chloride.If, however, formic aldehyde is boiled with excess of an alkaline solution of potassium pernianganate, it is oxidized to carbon dioxide and water. The oxidation, therefore, takes place in two stages, thus : 1st stage : In the cold- 2nd stage : On boiling- HCOH + 0 = HCOOH. HCOOH + 0 = GO, + H,O. By careful attention to temperature these reactions can be made strictly The reagents required are : 1. A standard solution of potassium permangnnnte. 5.260 grammes potassium permanganate in 1,000 C.C. of water. alkaline solutions, quantitative. This is prepared by dissolving When used in 1 C.C. = 0.00080 gramme oxygen. 1 C.C. = 0.00115 ,, formic acid (boiling). 1 C.C. = 0-00075 ,, formic aldehyde (boiling). 1 C.C. = 0.00150 ,, formic aldehyde (cold).3. A solution of potassium hydroxide. This is prepared by dissolving 50 grarnmes of stick potash in water and making the solution up to 100 C.C. As a preliniinary step, a measured quantity of the sample of formic aldehyde is placed in a porcelain dish, and potassium hydroxide solution added, so that the solu- tion shall contain at least 10 per cent. of alkali. The permanganate solution is then run in slowly from a burette. At first a fine green coloration is obtained from the formation of potassium manganate, but this rapidly turns to a reddish -brown,THE ANALYST. 149 especially if the solution is gently warmed. The addition of permanganate is con- tinued, with constant stirring, preferably with a small thermometer, until the green colour disappears rather slowly.The solution is then warmed to 30" C., as this temperature aids the separation of the precipitate of hydrated manganese peroxide, and the colour of the supernatant liquid can then be observed. The addition of permanganate is continued, 0.5 C.C. at a time, until an olive-green colora- tion, permanent for about fifteen to twenty seconds, is obtained, this being about the time necessary for the precipitate to subside. This is the end of the first stage of the reaction, which may be represented by the following equation : K,Mn,O, + KOH + 3HCOH = 2MnO(OH), + 3HCOOK. I t should be noted that the addition of permanganate in slight escess will not increase the colour of the supernatant liquid, but the precipitate appears much darker for a time. The quantity of permanganate used should be noted, and a further quantity equal to the first less 2 C.C.is at once run in, and the solution raised to the boil. The heating is stopped, and the precipitate allowed to settle. There should be no green coloration, but on the further addition of permanganate solution, four or five drops at a time, raising to the boil between each addition, an emerald-green colour, per- inanent for at least ten minutes, is finally obtained. This indicates the end of the second stage, the equation being : K,Mn,O, + KOH + 3HCOO.K = 2MnO(OH), + 3K,CO:,. Having obtained from this experiment a rough estimate of the dilution required, which should be such that the colour of the supernatant liquid can be easily observed, a, second experiment should be made, in which nearly the whole of the permanganate solution required for the completion of the first stage of the reaction should be run in at once.The solution is then heated to a temperature not exceed- ing 30" C., and the reaction completed as quicklyas possible in the manner described above. If the temperature be raised above 50" C., or if time is lost in determining the end point of the reaction, as indicated by the green colour of the supernatant liquid, oxidation of the formic acid occurs. The second stage of the reaction is completed as described in the first experiment, and requires no special precautions. I t must be remembered, however, that solutions of alkaline manganates are gradually decomposed by carbonic acid, and therefore prolonged heating must be avoided.The presence of not less than 10 per cent. of alkali is advisable in order that the green colour of the niangmate may be suficiently pronounced to admit of a, delicate end point. The acidity of the sample of formic aldehyde should be ascertained, and a deduction made, if necessary, for the formic acid present. But the largest amount of formic acid likely to be present in a sample of commercial formalin is so small that its influence on $he results obtained by the method described is inappreciable, I t is evident that the second stage of this metbod of. analysis may be applied to the estimation of fmmic acid.150 2. G~~~~~ of ~~~~i~ Aldehyde present. THE ANALYST. 3. 4. Gramme of Formic Aldehyde found. 1st Stage. 2nd Stage. A , \ H. C. Jones (Anzay. Chenz.Jow., 1895, xvii.) describes a somewhat similar process to this for the estimation of formic acid (see abstract, ANALYST, xx., 205). The following table gives the results of analyses, by the permanganate process, of dilute solutions of a sample of formalin. The figures in the second column are based on an analysis of the sample by the ordinary method, depending on the conversion of formic aldehyde by the action of ammonia into hexamethylene tetramine : ANALYSES OF SOLUTIONS OF FORMALIN. 1. C.C. of Dilute Solution taken. 1 4 10 10 20 30 20 !j 0 25 0.024 0.024 0.032 0.034 0.080 0.087 0.055 0.058 0.009 0.010 0-003 Not de t errninable 0-0009 ,, J , 0.0045 $ 9 ?, 0-0022 9 , 9 9 0-025 0-034 Not determined 0.058 0.009 0.002 0-0006 0-0028 0.0015 The experiments hitherto described apply only to aqueous solutions of formic aldehyde, but I am making experiments with a view to the application of the method to the estimation of formalin in milk and other articles of food. The results of these experiments I hope to lay before the Society on some future occasion, but it may be useful to state here that I have found that the difficulty met with in the distillation of milk may be entirely obviated by passing a current of steam through the liquid instead of heating it directly.In conclusion, I have to thank Dr. Stevenson, and also my friend Mr. Norman Leonard, for kind assistance given me in the work described in this paper. DISCUSSION. Mr. HEHNEH. remarked that if a sample of milk containing formalin were distilled and tested for formaldehyde, it would not be possible to get the same depth of reaction as would be obtained with a sampleof water containing the samequantity of formalin.Further, if this test were applied to any substance which had under- gone fermentation, and in which traces of alcohol had consequently been formed such traces of alcohol would also cause a reaction, and would be included as for- maldehyde in the result. Dr. RIDEAL said it seemed to him that the small quantity of formalin which had to be dealt with when it was used as a, preservative would not lend itself to exact estimation by means of titration with permanganate. Mr. CASSAL said it was certainly very doubtful that formalin estimated in the distillate from milk could be taken as approximately representing that which was originally added to the milk.The action of formalin upon the constituents of milk- upon the ‘‘ casein,” in fact, as upon fibrin, albumin, and so forth-was evidently of aTHB ANALYST. 151 very decided character, and the formalin originally added could hardly be recovered by a distillation process. Mr. BEVAN said he did not think there was any doubt at all about the first point to which Mr. Hehner had referred. The amount of formalin recovered was by no means representative of the amount added, a fact which he believed to have been shown long before he himself read some notes on the action of formalin on milk. The fact that the weight of the total solids could be increased almost in proportion to the amount of formalin added was evidence that there was a combination, and it was clearly not possible to get back all the formaldehyde by distillation.Mr. CASSAL said that the increase in the weight of the total solids was presum- ably due to the permanent effect produced by formalin on milk, but he did not know if Mr. Bevan had carried his experiments further, and had dried the total solids to constant weight. If formalin was present, it was necessary to dry for a very long time, but it was possible to get B very near approach to the actual total solids. Dr. RIDEAL thought there might be some doubt as to whether the increase of the weight of the total solids was due to an addition of formaldehyde to the milk solids which remained after drying. It was conceivable that the formalin caused a combination of water with the milk-solids, and that the increase was not due to a direct combination with the formaldehyde. He believed that some of these com- pounds dissociated at boiling-point, the formaldehyde coming off again. It was, however, perfectly true that the distillate from milk containing formaldehyde would not give so much coloration as a water solution containing the same proportion of formaldehyde. Mr. SMITH, referring to Mr. Hehner’s remarks, said it was quite true that alcohol and many other organic substances, if present, would interfere with the titration, but that the oxidation of the aldehyde in the cold was so instantaneous that it might be possible to make an estimation in the presence of less easily oxidizable substances. With regard to the distillation of milk, he had found that with, say, 100 C.C. of milk containing a certain amount of formaldehyde, distilled in a current of steam, about 300 C.C. of distillate might be collected, with the aldehyde still coming over. The aldehyde, in fact, distils over very slowly, and this is also the case with aqueous solutions.

ISSN:0003-2654    

DOI:10.1039/AN8962100148

出版商:RSC    

年代:1896

数据来源: RSC

摘要:

THB ANALYST. 151 OFFICIAL METHODS FOR THE ANALYSIS O F FERTILIZERSl ISSUED BY THE GERMAN MANURE MANUFACTURERS’ ASSOCIATION, HARZBURG, MAY 28, 1895. CONTHIBUTED BY H. H. B. SHEPHERD, F.I.C., ANGLO-CONTINENTAL GUANO WORKS, LONDON. (colLtilzuea from p . 132.) B. DetermiiLntioia of the Citratc-soluble Phosphoric Acid by Wagner’s Method (Clzein. Zeit., No. 63, 1895).-I. Preparation of the &7h6tiOl&S.-(1) Concentmted dmmonizm Citrate Solutioiz. -This solution must contain 150 grammes of pure crystallized citric acid and 23 grarnmes of ammoniacal nitrogen (27.93 grammes NH,)152 THE ANALYST. per litre. The citric acid can be added by weight and the ammonia adjusted by analysis. We have prepared, for example, 10 litres of this solution as follows: 1,500 grarnmes of citric acid were dissolved in about 2 litras of water, with the addition of 3,500 C.C.o€ an 8 per cent. ammonia solution. After cooling, the solution was made up to exactly 8 litres with water, and 25 C.C. of this solution were taken and diluted to 250 C.C. Twenty-five C.C. of this diluted solution were then used for an ammonia determination. Two hundred C.C. of water and 3 grammes of calcined magnesia were added, and the ammonia distilled over into 40 C.C. sulphuric acid. The ammoniacal nitrogen found corresponded to 20.0 C.C. 2 soda solution ; consequently the 8 litres of concentrated citrate solution contained 20" )'0035 x 8000 = 224.0 grainmes 2 -5 ammoniacal nitrogen. In order, therefore, to produce 10 litres of solution containing 1,500 grammes citric acid and 230 grammes aminoniacal nitrogen, it was necessary to add to the 8 litres a further 2 litres containing 230 - 224 = 6 grarnmes ammoniacal nitrogen, or 7.3 grammes ammonia, or 91 grammes of 8 per cent.ammonia, or 94 C.C. ammonia of 0.967 specific gravity. (2) Dilzited Anznzoiiizin~ Citrntc Solution.-Two volumes of concentrated arn- inonium citrate solution are diluted with three volumes of distilled water. (3) MoZybde7zunz SoZz~tion.-This solution may be prepared in either of the following ways : (a) One hundred and twenty-five grammes of molybdic acid are placed in a litre flask, and dissolved by the addition of about 300 C.C. of an 8 per cent. solution of ammonia. Four hundred grainmes of ammonium nitrate are then added, and the solution made up to the mark with water. This is then mixed with 1 litre of nitric acid of 1.19 specific gravity, allowed to stand for twenty-four hours at about 35" C., and filtered.( b ) One hundred and fifty grammes of ammonium molybdate are dissolved in water in a litre flask, 400 grammes ammonium nitrate added, the solution inade up to the mark with water, mixed with 1 litre of nitric acid of 1.19 specific gravity, allowed to stand for twenty-hours at about 35" C., and filtered, (4) Ma,gnesia Mixture.-One hundred and ten grammes of pure crystallized mag- nesium chloride and 140 grainmes of ammonium chloride are dissolved in 1,300 C.C. of water, with the addition of 700 C.C. of 8 per cent. ammonia. The solution is allowed to stand for several days before filtering. 11. Directions for Working.-Five grammes of Thomas phosphate powder (in the condition as received) are placed in a half-litre flask, which is then filled up to the mark with diluted ammonium citrate solution at 17.5" C.The flask is closed with an indiarubber stopper, and at once placed in a rotating machine making thirty to forty revolutions per minute. The solution is kept agitated by the machine for thirty minutes, and is then promptly filtered off. Fifty C.C. of the filtrate are introduced into a beaker, together with 100 C.C. of molybdenum solution; the beaker is placed in a water-bath heated to 80" to 95" C., allowed to remain in the bath from ten to fifteen minutes, taken out, the solution cooled to the temperature of the room, and filtered. The yellow precipitate is then washed with a 1 per cent.nitricTHE ANALYST. 153 acid solution, and dissolved in about 100 C.C. of a 2 per cent. ammonia solution (cold). The phosphoric acid is precipitated in this by 15 C.C. magnesia mixture added drop by drop with constant stirring. After standing for about two hours, the ammonium magnesium phosphate is collected upon a filter (unless the Gooch crucible is used), washed with a 2 per cent. ammonia solution, dried and ignited. For igniting the precipitate, a Bunsen burner is used until the filter is completely consumed (thirty to forty minutes), and afterwards a Rossler gas crucible furnace (for about two minutes). III. Reinayks upon the above Method.-(I) It is self-evident that the citrate solution niust contain as nearly as possible the prescribed amount of citric acid and ammoniacal nitrogen.Deviations from the proper quantity have considerable effecb upon the results. (2) The citrate solution should be as nearly as possible of the ordinary mean temperature of the laboratory (17.5" C.). Fluctuations in temperature occasion serious mistakes. If the rotating machine be in a separate room, its temperature should be the same as that of the laboratory, so that the citrate solution shall undergo no change of temperature during the half-hour it is in the machine. (3) The use of shaking machines instead of rotating machines has been proved to be inadmissible. Being of varied construction, they have not all the same power, and analyses made by the use of different machines have varied considerably. The machine made by the firm of Ehrhardt and Metzger of Darmstadt should be used.(4) The machine should make not less than thirty and not more than forty revolutions per minute, and care should be taken that the half-hour is accurately timed. It is also important that the filtration should be commenced directly the vessel is taken from the rotating machine, as, if allowed to stand for any time before filtering, deviations either way in the results may take place. ( 5 ) The filtration should be conducted as quickly as possible. Should the filtrate be at all turbid, it should be passed through the filter again, until quite clear. Too frequent filtration, however, should be avoided on account of prolonging the time. (6) The phosphoric acid must be determined by the molybdate method; direct precipitation by magnesia gives high results when the percentage of silicic acid rises above a certain limit. (7) No other molybdenum solution but the one described (containing ammonium nitrate) is to be used for precipitating the phosphoric acid.(8) If the beaker is plunged deep into the water-bath, the phosphoric acid is completely precipitated in five minutes, though it is better to allow ten to fifteen. If, however, the digestion be continued as long as fifty minutes, incorrect results are obtained, in consequence of the precipitate becoming too much contaminated with silicic acid. (9) The yellow precipitate should dissolve quickly and completely in the 2 per cent. ammonia solution, without warming. If the solution only becomes clear after long standing, it should be rejected, and the determination be recommenced in a fresh sample.c. Determination of the Percentage of Fine Meal.-Fifty grammes of Thomas It is constructed of metal and driven by a hot-air motor.THE ANALYST. powder are to be shaken for fifteen minutes in a No. 100 sieve, to be obtained from Amandus Kahl, Hamburg. The shaking may be done by hand or by means of a machine constructed for the purpose. IV. Determination of Potash in Potash Salts.* - A. Analysis of Concentrated Potash Salts.-(1) Muriate of Potash.-(a) Determination of the Potassium Chloride. -An aqueous solution is made by dissolving 7.6405 grammes of the finely prepared sample in 500 C.C. With salts containing more than 0-5 per cent. SO,, it is neces- sary first to convert the sulphates into chlorides by precipitation with solution of barium chloride, acidified with hydrochloric acid.Twenty C.C. of the solution = 0.3056 gramme of the salt, are placed in a flat porcelain basin of about 10 c.m. diameter, 5 C.C. of platinic chloride added, and the solution evaporated on the water- bath, until, when allowed to cool, the syrupy fluid quickly solidifies in fine crystals. The basin should be lifted off the bath frequently during the evaporation, and the fluid mixed by imparting to it a circular motion. The dry residue is then rubbed up quite fine with a glass rod, about 20 C.C. alcohol added, again stirred and filtered through a weighed filter. The filter should be previously washed with alcohol, and dried at 120" to 130" C., and it should be weighed warm.In filtering, care should be taken that the liquid first poured on does not touch the edge of the filter. The filtration can be expedited by the aid of a moderately powerful aspirating apparatus, and the double salt can be easily washed quite clean on the filter itself. The filter with the precipitate, after removal of as much as possible of the alcohol, by suction and pressing between blotting-paper, is dried at 120" to 130" C. until it ceases to lose weight. The drying occupies, as a rule, about twenty minutes. 0.001 gramme of potassium platinum chloride corresponds to 0.1 per cent. KC1. ( b ) Determination of the Sodium Chloride.-l2-5 grammes of the sample are dissolved in 25 C.C. of water, by boiling in a quarter-litre flask, after the addition of a little potassium carbonate to convert the magnesium and calcium compounds into carbonates, and the solution is then made up to the mark with absolute alcohol.It is now filtered, and 100 C.C. of the filtrate = 5 grammes substance, introduced into a platinum or porcelain basin, a few drops of concentrated hydrochloric acid added to convert any potassium carbonate into chloride, and the liquid evaporated to dryness ; the residue is then gently ignited and weighed. I n this mixture of potassium chloride and sodium chloride, either the potassium chloride is determined by means of platinic chloride in the usilal way, and the sodium chloride taken by difference, or the mixed chlorides are titrated with a ( c ) Determination of the Magnesaum Chloride.- Twenty-five grainmes are dis- solved in water in a half-litre flask, 10 c .~ . normal potash solution added, end the flask made up to the mark. The liquid is then filtered, and 50 C.C. of the filtrate titrated with a Calcium compounds remaining in the solution have no influence upon the result. (2) Determination of Potassium Szdphate in Sulphate of Potash or Sulphate of' Potash and Magnesia.--8.9235 grammes of the finely prepared sample are dissolved in about 350 C.C. of water, with the addition of 25 C.C. concentrated hydrochloric *. Methods used in the Stassfurt potash works, and communicated by the syndicate. It is to be weighed warm. silver solution. sulphuric acid solution.THE ANALYST. 155 acid by boiling in a half-litre flask. The sulphuric acid is then precipitated by the addition of barium chloride drop by drop to the boiling solution from a burette, its complete precipitation being indicated by a crystal of barium chloride producing no turbidity in the clear liquid, after the precipitate has settled out.Any excess of barium chloride must be gob rid of by the addition of sulphuric acid. The solution is cooled, made up to the mark, and filtered, and to 20 C.C. of the filtrate=0-357 gramme of substance, 5 C.C. of platinic chloride are added, and the determination continued in the usual way. One milligram K,PtCl, corresponds to 0.1 per cent. K,SO,. I n testing samples of sulphate of potash,.0.3 per cent. is to be added to the percentage of potassium sulphate found, but with sulphate of potash and magnesia no correction is required.(3) Detennination of Potassium Chloride or Sulphate iiz Calcined Potash Salts used as Fertilizcrs.-15-281 grammes (for KCl) or 17.847 grammes (for K,SO,) are dissolved in water in a half-litre flask, with the addition of 10 C.C. concentrated hydrochloric acid, the solution made up to the mark, and filtered. Two hundred and fifty C.C. of the filtrate (corresponding to 7.6405 grammes or 8.9235 grammes, as the case may be) are transferred to a half-litre flask and further treated, by addition of barium chloride, as directed for the determinatlion of potassium sulphate. B. Deternaination of Mugnesium Szdphate in Kieserite. -Ten grammes of the finely prepared sample are placed in a half-litre flask about two-thirds filled with water, and boiled for not less than an hour.The solution is then cooled, 50 to 60 C.C. of potash solution of double normal strength and 26 C.C. of a solution of neutral potas- sium oxalate (1 in 10) added, made up to the mark, allowed to stand a quarter of an hour, and filtered. Five hundred C.C. of the filtrate are then titrated back with a & sulphuric acid solution. To the percentage of magnesium sulphate found 0.2 per cent. is to be added. c . Netliods jbr the Exa.naincLtion of JIineral Potash Sults (Carnallite, Kainite, Sylvinite, and ~l~ZL?atain-Kieserite) .- (1) Preparation of the Sample.--In order to avoid differences arising through imperfect grinding, a large sample-if possible, at least half a kilo in weight-should be ground in a niill or mortar. (2) Deternaiizatio.rz of Potash by the Precipitation Method.- 35-70 granimes of kainite or sylvinite, or 30.56 grammes of carnallite or mountain-kieserite, are dis- solved in 350 C.C. of water, with the addition of 10 C.C. of hydrochloric acid, by boiling in a half-litre flask. The solution is cooled, made up to the mark, and 50 C.C. precipitated with barium chloride in a 200 C.C. flask. Twenty C.C. of the filtrate (corresponding to 0.3570 gramme or 0,3056 gramme, as the case may be) are then evaporated with 5 C.C. of platinio chloride solution, and further treated in the usual way. (3) Complete Analysis of' iWineral Potash Salts. - One hundred grammes are dissolved by boiling in about 500 C.C. of water, filtered, the residue washed, and the filtrate and washings made up to 1 litre.A portion of this solution is used for making a gravimetric determination of sulphuric acid by precipitation with barium chloride, and another portion for the determination of the lime and magnesia. The alkaline chlorides are determined as follows : One hundred C.C. of the above solution, corresponding to 10 grainmes of substance, are acidified with hydrochloric acid,156 THE ANALYST. raised to the boil, the sulphuric acid precipitated by barium chloride (taking care not to use an excess), and the filtrate made up to a half-litre. Fifty C.C. of this, corresponding to 1 gramme of substance, are evaporated to dryness to expel hydro- chloric acid, and the magnesium chlorides separated by ignition with oxalic acid. The residue, after ignition, must be moistened with a little ammonium carbonate to convert the caustic lime into carbonate. The alkaline chlorides, being completely freed from lime and magnesia, are now weighed, and then the potassium chloride determined in them by means of platinic chloride, using 10 C.C. The sodium chloride is taken by difference. I n the case of kainite and sylvinite, the results are put together in the following manner : From the total soluble sulphuric acid found, that present as calcium sulphate is deducted ; the soluble sulphuric acid then remaining is combined with the potash and magnesia in such a way as to form the two sulphates in molecular proportions, these salts being associated in this way in kainite and schiinite; any remaining potassium or magnesium is then reckoned as chloride. In this way, the potassium present as kainite (K,SO,,MgSO,,MgCl, + 6H,O) or schiinite (K,SO,, MgSO, + GH,O), and that present as chloride, are separately shown. The sodium is stated as chloride. I n the analysis of carnallite and mountain-kieserite, the results are put together as follows : The lime is first com- bined with its proper proportion of sulphuric acid to form calcium sulphate, and the remainder of the sulphuric acid is then combined with magnesia ; lastly, the magnesium not combined with sulphuric acid is reckoned as magnesium chloride. (To be continued.)

ISSN:0003-2654    

DOI:10.1039/AN8962100151

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年代:1896

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156 THE ANALYST. NOTE ON THE USE OF THE WESTPHAL BALANCE. BY A. MCGILL. IS using the Westphal balance on cylinder oils, I have had occasion to note the much greater sensitiveness of a particular instrument made by Westphal than of another made by Oertling. The former has a plummet weighing 4.3 grammes, and displacing 1.02 grainrnes water at 15" C. ; the latter a plummet weighing 15.0 grammes, and displacing 6.5 grammes water. The specific gravities of these plummets are, therefore, approximately 4 and 2 respectively. In attempting to explain the undoubted fact of greater sensitiveness in the first of these, I argue as follows : A B C If AC represents the beam of a Westphal balance with fulcrum at B and plummet at D, let a =weight of short arm, acting at its centre of gravity. ,) b = ,, c = ,, plummet in air.,, c' = ,, volume of liquid displaced by D. ,, longer arm, with suspended weights, acting at the centre of gravity of the system.THE ANALYST. 157 The condition of equilibrium is : a= b + (c- c’) ; and in order that motion may take place downwards at the plummet end, an addi- tional weight (zu) must be given, the magnitude of which will diminish with the viscosity of the liquid in which D is immersed, and inversely with the delicacy of the adjustments, friction of knife-edges, etc. While the system is a rigid one-ie., so long as the wire suspending the plummet is tense-motion is produced by a force whose measure is the difference between a and b + (c - c’) + w. But once this motion begins, the system may separate into two parts (owing to the flexibility of the wire suspending D, and to inertia); namely, into that part which moves in air, and the remainder of the system moving in the liquid in which D is immersed The first part will have a tendency to move in a reversed direction under a force whose magnitude is a - ( b + w), while the plummet sinks under a force of magnitude ( c - c’) ; whose value changes with the density of the plummet and that of the liquid, as well as with the absolute weight of the former.I am convinced that the best results will be obtained by employing plummets of different weight and density, according to the different specific characters (viscosity, etc.) of the liquids operated on, and am well assured of the fact that for viscous oils the value of the ratio c : c’ should approximate 4 rather than 2. I have no doubt that the absolute value of c should bear some relation to 20, and probably also to the density and viscosity of the liquid worked on. So far as this relation to w is con- cerned, it will evidently vary with each balance; but the relation to the liquid might be determined experimentally once for all. Ottaza, M w r h 31, 1896. LABORATORY OY THE INLAXI) REVENUE DEPARTMENT,

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DOI:10.1039/AN8962100156

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年代:1896

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THE ANALYST. 157 NOTE ON HEHNER’S TEST FOR FORMIC ALDEHYDE. BY NORMAN LEONARD, B.Sc., F.I.C. IN trying Hehner’s test for formic aldehyde in milk, which consists in the produc- tion of a blue or violet colour when formalized milk is poured on to the surface of strong sulphuric acid, it was found that the reaction could be easily obtained with commercial sulphuric acid, but quite failed when the pure redistilled acid was used. I n order to identify the impurity present in commercial sulphuric acid, to which Hehner’s reaction is due, the effect of adding common impurities to the redistilled acid was ascertained. Nitric acid, nitrous acid, hydrochloric acid, arsenious acid, and lead sulphate were found to have no effect, but the addition of a trace of ferric chloride at once conferred upon the pure acid the power of giving the violet colour with formalized milk.Platinic chloride answered equally well, while mercuric chloride, bromine, and potassium permanganate were less effectual. No reaction could be obtained by the use of sodium hypochlorite, of ferrous sulphate, or of potassium bichromate. The commercial acid was found to give distinct reactions with potassium ferrocyanide and with ammonium sulphocyanide, whereas no trace of iron could be detected in the pure redistilled acid,158 THE ANALYST. I t would therefore appear that the presence of a feeble oxidizing agent, such as a metallic perchloride, is necessary for the production of Hehner’s reaction. The test is not improved by the addition of any considerable amount of ferric chloride, but rather the reverse. A trace only is necessary and sufficient. NoTE.-Mr. Hehner informs us that he used ‘‘ pure ” or (‘ redistilled ” sulphuric acid in all his tests, but he now finds that a trace of ferric chloride renders the re- action far more distinct.--EDITOR.

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DOI:10.1039/AN8962100157

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年代:1896

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158 THE ANALYST. ABSTRACTS OF PAPERS PUBLISHED IN OTHER JOURNALS. FOOD ANALYSIS. Estimation of the Volatile Acids in Wine. L. Magnier de la Source. ( A m . dc Chinzia AizaZyt., i., 65-68.)-The following modification of the illuller method is recommended by the author, as giving very exact results with less trouble and attention than are required in the original process. It is also quicker than the author's evaporation in vacuo process, proposed as a modification of the Muller method. To compensate for the somewhat slower rate of evaporation in air compared with that in a vacuum, the exposed surface of the liquid is increased. To this end two evaporating dishes of about 4 centimetres radius and 2 centimetres in depth are employed, in each of which 5 C.C. of the wine, previously freed from carbonic acid, is placed.One of them is then put into a desiccator containing both concen- trated sulphuric acid and caustic potash, and the other, after the addition of five drops of alcoholic phenol-phthalein solution (0.5 gramme per 100 c.c.), is neutralized with baryta water, 1 C.C. of which corresponds exactly to 0.004 gramme of sulphuric acid. The colour of the wine turns directly, and as soon as it passes into violet the reaction is complete, the number of C.C. of baryta used indicating the total acidity in terms of sulphuric acid. The wine in the desiccator is left to evaporate for two days at a temperature of about 15" C., by whichtime the extract will have become practically dry. It is then taken up with 2 C.C. of warm water, and left to re-evaporate for another two days.The acidity being determined as in the other case, the difference in the amount of baryta used expresses (as sulphuric acid) the acidity due to the volatile acids. The volatilization of the acetic acid is so complete, that a wine partially transformed into vinegar, and having a total acidity of 29-80 grammes per litre (as H,SO,), left behind after this treatment only 1.60 grammes of fixed acid. The method is also applicable, with a certain amount of modification, to wines whose acidity has been partly masked by the addition of an alkali or a neutral tartrate. I n such cases, instead of operating direct on the wine, about 2 C.C. of a freshly-prepared solution of tartaric acid, containing some 25 grammes per litre, are first added to each basin, care being taken that the two volumes of added acid are exactly equal. This allows the displacement of the volatile acids, and their amount can be determined by difference as before.This will always represent the original acidity of the wine before it was doctored.THE ANALYST. 159 Whether the wine has been neutralized or not, the proportion of volatile acids will come out higher under this last mode of treatment-an effect that may be due to several causes, such as partial displacement of the acid radical in the potassium chloride by the added tartaric acid, or by a disturbing of the equilibrium which exists between the last traces of acetic acid and the natural tartrates in the wine ; but in all cases where neutralization has been effected the results will be so decided as to be unmistakable, as is shown by the following examples : NATURAL WINES.Degree of Acidity due to Volatile Acids. - ~~ r ~~~ By Direct Determination in the Wine. Determined after the addition of Tartaric Acid in Excess. Gironde wine.. . ... 0.52 gramme per litre ... ... 0.67 Sour ... ... 2-56 ,, 9 s ... ... 2-64 1, - . - ... 2.32 ,, ,, ... ... 2-60 Tunis wine, unsound 2.58 ,, Y 9 ... ... 2.88 Algerian wine ... 1.56 ,, 2 , ... ... 1.76 I ? 9 , 1 , ... 1-72 ... 1-47 ,, ... WINES PARTLY NEUTRALIZED. By Seignette salt ... 0.68 ,, 9 2 ... ... 1.40 tartrate ... ... 2-40 ,, 9 , ... .," 3.33 By ammonia.. . ... 2.0 7 , 7 , ... ... 2.72 By neutral potassium c. s. Notes on Lard, etc. C. Fresenius. (Clienz. Zeit., 1896, xx., 129.)-The present author agrees with Goske that the iodine test is not of inuch use for detecting adulteration in lard when the added oils and fats are of fair purity.Becchi's test is fairly reliable, and the wine-colour that often appears must not be ignored; for even after a thorough washing in dilute acetic acid, a lard containing cotton-oil gives some reaction, and only in the presence of very small quantities of oil does the liquid remain colourless. An examination of the crystalline form is strongly to be recom- mended. Mixed fats should not be tested as such for their melting and solidification points ; but the fatty acids should be prepared. The author prefers the following process : The sample is introduced into a test- tube 2-5 c.m. wide and 10 c.m. long placed in a beaker filled with cotton-wool. The temperature of the laboratory should be 17 to 20" C., the fat heated to 40" C.and allowed to cool at the rate of 1" per ten minutes. The point to which the ther- mometer first falls is called the " critical point." The time during which it remains constant is noted, and also the point to which it again rises. If more than 15 per cent. of oil alone is added to lard, no period of constant temperature is noticed; while in the case of adulterated samples, if the critical point is above 26" C., tallow, with or without oil, has been added ; and if below 24" C . , oil only has been employed, The annexed table shows the results obtained on a number of products, the period of rest" indicating the time in minutes of constant temperature as shown by the thermometer in the fat :160 THE ANALYST.Butcher's lard ... ... 1 , ,, ... ... ... ... American steam lard.. . ... ' 7 1 7 ' 1 1 ' ... ... ... ... 95% 90 90 90 85 82 80 77.5 70 62.5 67 60 10 s5 3 , 9 9 ... ... lard, 5% oil ... . 1 . ... tallow ... oil, 2% tallow 8 1 5 1' ' 7 t3 7 3 7 ' 10 2 , ' 1 7.5 ' 1 7 7 10 YY 7 9 12.5 ' 1 tallow ... beef tallow . . . oil and tallow cocoanut - oil, tallow, etc. . . Critical point. 27-6 27.4 26.6 25-5 25.2 24.6 24.4 23.9 23.3 31.1 24-0 28.3 29.6 31.7 30-6 30.3 30.0 38.0 31.0 36-5 26.0 Period )f rest. 2 2 2 3 2 3 2 2 3 3 7 5 2 4 2 4 4 10 10 5 10 First rise to. 29.4 28.3 29.3 26-3 25.9 25-5 24.9 34-1 23-7 - - - - 31.9 31.0 30-5 30.5 38.9 37.4 - - Period if rest. 2 10 2 3 3 3 3 3 2 - - - - 3 2 2 2 3 5 - - Second fall to.Period D f rest. Second rise to. Period of rest. F. H. L. TOXl COLOGICAL ANALYSIS. Detection of Hydrocyanic Acid in Cases of Poisoning. F. Filsinger. (Chem. Zeit., 1896, xx., 305.)-A case of supposed poisoning by potassium cyanide has recently occurred in Dresden, in which it was necessary to examine the stomach, etc., of the corpse ten days after death. After proving the absence of inert cyanides, ferro- and ferri-cyanides by means of the iron and copper tests, the different articles were distilled, according to Dragendorff's process, on the water-bath in presence of tartaric acid. The distillates were examined for the formation of Prussian blue, ferric thiocyanate, and by Schonbein's reaction. In the stomach and its contents hydrocyanic acid was readily detected by all three tests ; in fact, it would have been possible to conduct the operation quantitatively. The smaller intestines and the blood reacted strongly with Schonbein's test, giving a powerful blue colour, but the other reactions were uncertain. A small brpwnish, alkaline deposit found in a tumbler that had evidently contained the wine in which the potassium cyanide was dissolved also gave Schonbein's test very plainly; so that this process, in spite of recent statements to the contrary, seems to be the best to adopt in similar cases. F. H. I;.

ISSN:0003-2654    

DOI:10.1039/AN8962100158

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年代:1896

数据来源: RSC

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THE ANALYST. 161 ORGANIC ANALYSIS. The Oil of the Egg. P. Paladin0 and D. Toso. (Gior. di Ph.arrn. di Chem. ; through Jour. de Pharnt. cmd Chim., 1896, 247-249.) -This oil, which is used in ointments, is extracted from the dried yellow of the egg either by pressure or b!, solvents. The normal composition of eggs is 60 per cent. of white and 40 per cent. of yolk, the latter containing from 25 to 35 per cent. of oil. I n preparing it the authors separated the yolks (900 grammes) of sixty-eight hard-boiled eggs, heated them rapidly in a porcelain dish, and extracted the oil by pressure. As thus obtained the oil was perfectly limpid and of a yellow colour. On cooling, it became viscous, and deposited a crystalline sediment. I t readily became rancid and lost its colour on exposure to air and light.Its physical constants were : Density ... ... ... ... ... ... 0.9156 at 20" C. Solidifying-point ... ... I . . ... ... 8-10" c.c Melting-point ... ... ... ... ... 22-22-5" c. Fatty acids (melting-point) ... ... ... 34.5-35" c. Saponification number ... ... ... ... 185.2 to 186-7. Iodine number ... ... ... ... ... 81-21 to 81-6. The melting was often incompletd, owing to the presence of crystals melting at 145O, which probably consisted of cholesterin. C. A. M. Technical Analysis of Asphaltum. No. 2. Laura A. Linton. (Jour. dmer. Chcnt. SOC., 1896, xviii., 275-283.)-1n this paper Miss Linton gives an account of further work on this subject (ANALYST, xx., 41), which has led her to modify her methods in some respects. She finds that the old method of determining moisture does not give correct results, since not only water but also portions of petrolene volatile below 100" C.are expelled. This may be obviated by drying at 50" C., experiments proving that all the moisture may be driven off at that temperature. At the same time it is urged that, since the moisture is of hygroscopic origin and varies with the atmospheric conditions, it should never be estimated as a constituent part of the asphaltum. To obtain comparative results it is advisable to air-dry all samples to constant weight, and thus entirely exclude water from their percentage composition. A mechanical improvement consists in the use of weighed filter-paper instead of an Erlenmeyer flask, the digestions being carried out in separLtting funnels.The only precaution necessary is to see that the solution in the funnel is not too concen- trated before running from the tap, since this causes precipitation of petrolene. This is readily obviated by frequently changing the petroleum spirit at first, until the greater part of the petrolene is removed, when it is safe to leave it for longer periods. By fractionation of the asphaltene into the portion soluble in boiling turpentine and that soluble only in chloroform, Miss Linton considers that figures are obtained which probably indicate the relative altering or '' ageing " of different varieties of asphaltum. The process, which is very tedious, often taking from one to four weeks,162 THE ANALYST. Asphal- tene. is as follows : After complete removal of petrolene, the filter is digested with boiling turpentine until the filtrate is colourless, the contents of the filter being then washed in alcohol and dried at 100” C.The dried residue should be a loose brown powder without coherence. If otherwise, the extraction with turpentine must be repeated possibly several times. The part of the asphaltene soluble in boiling turpentine is a black viscid semi-liquid substance resembling tar and melting at or below 100” C. The percentage results in the following table show that not only do the “aged” varieties of asphaltum contain a larger percentage of asphaltene, but that the turpentine fraction becomes a smaller proportion of the total bitumen, while the chloroform fraction becomes larger : Total Bitumen Variety. Organic Matter not Bitumen.1. Average land asphal- tum, Trinidad . . . 2. Altered or “aged” (iron pitch) land, Trinidad 3. ‘‘ Aged,” land, ,, 4. Average, lake, ,, 5. &‘Aged,” lake, ,, 6- 9 7 9 , 9 , 7. “Aged” (iron pitch), lake, Trinidad ... 8. Asphaltum, Texas ... 9. Turrellite, ,, ... 10. Asphaltum, I n d i a n Territory . . . ... 11. Graphamite, W. Va. ... 12. Scyssel asphaltic rock, France ... ... Mineral Matter. Petrolene 33.73 33,574 21.362 35.40 26.925 19.25 22.25 7.538 8.786 9,503 49.959 7.486 18.849 23.327 30.312 17.58’7 25.3 33.312 22.325 1.601 3.267 0.9CJO 50.041 4.316 Turpen- tine Fraction 52.579 56.901 51.674 53.987 52.225 52.562 44.575 9.139 12.053 10.493 100.00 11.802 15.67 13.7 15.2 12.30 18.613 22.35 9.785 1.601 3.267 0.990 17-458 3.945 L1.528 8.414 9.85 10.962 11-237 9,562 8.937 - - - - - Chloro- form Fraction.35.886 34.684 38.375 36.100 36.537 37.875 46462 90.861 87.947 89.506 - 88.198 3.179 9.627 15.112 5.287 6.687 10.962 12.54 trace trace trace 32-583 0.371 Ratio Fraction to total Bitumen, CHC13 1 : 16 1 : 6 1 : 3 1 : 10 1:8 1 : 5 1 : 4 - - - 1 : 3 1 : 31 C. A. M. Estimation of Sulphur in Petroleum. R. Kissling. (Chenz. Zeit., 1896, xx., 199.)-This investigation was carried out without knowledge of Heusler’s work on the same subject (ANALYST, xx., 187), and is essentially but a modification of his process. The petroleum was burnt in a lamp fitted with a, chimney contracted and bent to an acute angle at the top, to which were connected a 200 milliinetre U-tube filled with glass beads, and also two of Will and Varrentrapp’s nitrogen bulbs. A 5 per cent.solution of perrnanganate was employed to absorb the sulphur, preliminary experiments having shown that a mixture of sodium carbonate and potassium nitrate was not efficient. The beads were moistened with 15 C.C. of the liquid, and 5 C.C. were placed in the bulbs. The lamp was so arranged that a current of 300 C.C. of air drawn through the apparatus per minute was sufficient to maintain perfect com- bustion. After boiling the resulting solution with HCl, it was found necessary toTHE ANALYST. 163 cool it well before filtration, to remove hydrocarbons ; formed, it proved advisable to repeat the test, although to dryness, and ignited in presence of an oxidizing lasted from eighteen to forty-six hours, and the oil and if much lamp-black had the liquid could be evaporated substance.The experiments burnt varied froin 26 to 107 grammes. No-special provision was made to remove sulphur compounds from the air admitted to the lamp, but care was taken to prevent alterations in the purity of the atmosphere. Some twenty-five samples were examined, and the results are summarized in the following table, the figures being the weight in graumes of the sulphur in 1,000 grammes of the oil burnt : Description of Sample. " Lima " petroleum ... ... ... Pennsylvanian petroleum ... ... (from another works) ... $ 9 '' Kaiseroel " ... ... ... ... " Safety oil '' (85" Abel), specially refined ... Alsatian oil ... Baku oil ... ... ... ... Galician oil _., ... ... ... " Kronenoel " froin Pennsylvania, specially refined 9 , ...... ... ... ... ... ... 9 , ,, (from another works) ... ... Sulphur. Per 1,000. ... ... 0.448 ... . . . 0.278 ... 0.271 . . . ... 0.105 ... ... 0.098 ... ... 0.193 ... ... 0.589 ... ... 0.297 ... ... 0.388 ... ... 0,233 ... ... 0.190 ... F. H. L. Molybdic Acid as a Test for Alcohol. E. Merck. (Clzem. Zed., 1896, xx., 328.)-The author proposes the following modification of Davy's test : Pure molybdic acid is dissolved in warm strong sulphuric acid, and the resulting solution poured through the liquid under exaininatiou in a test-tube, both being kept as nearly as possible at a temperature of 60" C. I n presence of alcohol, a distinct blue ring appears at the junction between the two liquids, which is the inore intense the larger the proportion of alcohol present.On shaking, the colour disappears, but by addition of a further quantity of the reagent it may be r?produced. The test is, of course, not characteristic of alcohol only, but it will detect even 0.02 per cent. of ethyl alcohol, and 0.2 per cent. of methyl alcohol in aqueous solution. F. H. L. Estimation of Morphine in Opium. G. LOOK (Apoth. Zed., 1896, ii., 192 ; through Chem. Zeit. Rep., 1896, 114.)-Five grammes of the sample in fine powder are rubbed down with 5 C.C. of water, dashed into a tared flask, and diluted to 44 grammes in (nett) weight. After shaking for fifteen minutes, 1 gramme of sodium salicylate is added, the whole shaken again and filtered. This treatment removes the substances which usually hinder the precipitation of the alkaloid.25.8 grammes of the filtrate (= 3 grammes of opium) are then treated with 3 grammes of ether and 1 of' ammonia. The mixture is agitated for ten minutes, the morphine collected on a small filter, the flask rinsed twice with 5 C.C. of water, and the precipitate washed therewith and dried. It is finally extracted with benzene, dried again, and weighed. F. H. L.164 THE ANALYST. Detection of Resin and Rosin Oil in Oils and Varnishes. F. Ulser. ( M i t t h i l . t e c h . Gezu. MZLS. Vienna, 1896, 91 ; through Chem. Zeit. Bep., 1896, 146.) -A very weak solution of pure linseed-oil varnish in acetic anhydride gives a, dark, reddish-brown colour on addition of sulphuric acid. I n certain cases it is better to shake up the sample with absolute alcohol, and after several hours to remove and evaporate the spirit, treating this residue with acetic anhydride and sulphuric acid.The Storch-Morawski (qf. ANALYST, xvi., 155) process is very useful in the examination of varnishes, and it is capable of showing the presence of even comparatively sinall amounts of resin, the reaction being particularly suited for detecting the addition of cheap resins such as rosin to copal and amber varnish. F. E. L. Estimation of Nitrogen in Guano. E. Franke. (Chem. Zezt., 1896, xx., 325.) -Haselhoff has lately thrown some doubt on the Jodlbauer method of conducting this analysis, and has suggested that the sample should be extracted with water on a filter, the nitrogen existing as ammonia and nitrates being determined in the soiution by Ulsch’s process, and the organic nitrogen in the residue according to Kjeldahl.It is at once evident that this modification is inexact, for the guano contains easily soluble organic nitrogen compounds which are not completely converted into ammonia by the action of caustic soda. The author has examined several samples of guano by the Ulsch-Kjeldahl process applied to the manure itself, and also by that of Jodlbauer, and has compared the figures obtained with those of Haselhoff’s modification, and finds the latter considerably too low. Experiments on guano to which sodium nitrate had been added, showed that the Jodlbauer process was exact up to a certain limit (9per cent.), but above that the phenol sulphonic acid treatment gave too low a yield : the Ulsch-Kjeldahl method Was always perfectly satisfactory. The author concludes that as guanos seldom contain more than 2 per cent. of nitrates, the former is perfectly reliable, that Hasel- hoff‘s suggestion is useless, and that in all doubtful cases recourse should be had to reduction by means of iron and sulphuric acid (Ulsch), followed by the Kjeldahl process. I?. H. L. A New Test for Dulcin. A. Jorissen. (Reprint from the J. Pharm. de Lidge ; through Chem. Zeit. Rep., 1896, 114.)-This substance is a, derivative of saccharin, and is already being used to sweeten various beverages. The sample is suspended in water in a test-tube, and 2 or 3 drops of a solution of mercuric nitrate, containing no free acid, and preferably made from the freshly-precipitated oxide, added. The tube is plunged into boiling water for five or ten minutes, when a faint violet tint should appear. On introducing a small quantity of lead peroxide, a fine violet colour is momentarily produced. The reaction is capable of detecting 0.001 gramme of dulcin. F. H. L.

ISSN:0003-2654    

DOI:10.1039/AN8962100161

出版商:RSC    

年代:1896

数据来源: RSC

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THE ANALYST. 165 INORGANIC ANALYSIS. An Electrolytic Method for the Determination of Mercury in Cinnabar. W. Rising and V. Lenher. ( J o z L ~ . Arrizc~. Ch??n. SOC., xviii., 1896, pp. 96-98.)-To avoid the objections to the employment of aqua regia as a solvent for cinnabar, the author proposes the use of hydrobromic acid. This is made by treating potassium bromide with sulphuric acid of 56" Baumb (s.g. 1.364), and conducting the gas into water. The solution of cinnabar is nearly neutralized with caustic potash, pure potassium cyanide added, and electrolysed in a, weak current (0.025 amperes per square centi- metre), when the mercury is deposited on a platinum dish used as a negative electrode. The results quoted are concordant, and agree well with those obtained with aqua regia as the solvent.As thus prepared the hydrobromic acid contains no free bromine. C. A. M. Estimation of Mercury with Sodium Peroxide. M. C. Schuyten. (Cheiib. Zeit., 1896, xx., 239.)-This process has been tried on both the chlorides, the sulphate, nitrate, and red oxide of mercury. I t is also available for organic compounds, but cinnabar is not attacked. The substance is weighed out into a porcelain basin, covered with water, and an inverted funnel with a neck bent at right angles placed over the vessel. The peroxide is then added by degrees until no further precipitate is formed. The whole is warmed gently, cooled, and the metallic mercury filtered off. During drying, the desiccator must be kept in the dark at a low temperature, and the funnel should be covered with paper.Three tests on recrystallized mercuric chloride gave a, mean of 73-52 per cent. of Hg (theory, 73-92 per cent.). If the filtrate is neutralized, the halogen it contains can be titrated direct, according to Volhard's method. F. H. L. Detection of Mercuric Cyanide. D. Vitali. (Boll. Chim. $'am., 1896, xxxiv., 737 ; through Chenz. Zeit. Rep., 1896, 72.)-On warming a solution of mercuric cyanide with magnesium (ribbon), hydrogen is evolved, which soon begins to smell of hydrocyanic acid. If the action is only allowed to proceed for a short time, a mixture of mercury and mercurous oxide is produced ; but if it is continued as long as any gas is set free, the mercury will be found only in the metallic state, while much magnesium cyanide can be detected in the liquid.I n cases of supposed poisoning, the material is inixed with magnesium powder, and introduced into a tubulated retort fitted with a safety-tube and a well-cooled condensing arrangement containing caustic soda. The retort is heated over a sand- bath as long as gas is given off; but before the inass becomes dry, acetic acid is gradually added to decompose the magnesium cyanide. The whole of the hydro- cyanic acid distils over, and the mercury can easily be detected in the residue. F. H. L.166 THE ANALYST. Influence of Magnesia Mixture on Glass. L. L. de Koninck. (Chem. Zed., 1896, xx., 129.)-The author has repeated his earlier experiments on the action of magnesia mixture on glass, using a new Erlenmeyer flask of Jena glass 135 milli- metres high, with a superficial area of 1,625 square centimetres.On allowing an old and perfectly clear solution to remain for thirteen months in the vessel, it was found considerably attacked, the magnesium silicate removed weighing, after ignition, 0.1525 gramme (=On2168 of air-dried silicate), and corresponding to a loss of 1.5 niilligrammes per square centimetre. With Stas's glass this was proved less than 1 milligramme per square centimetre in seventeen months. I n Ostwald's laboratory it is the custom to treat all glass apparatus that is to be employed for exact work with steam. This appears to alter the nature of the surface of the material so that it is no longer attacked by reagents; in fact, after fifteen months a flask so treated was practically untouched by the magnesia mixture. I t should be observed that if the first layer of silicate be removed, and an ordinary flask submitted to the action of the liquid for a second time, it is attacked even more rapidly than before.F. H. L. The Quantitative Estimation of Arsenic in Crude Concentrated Sulphuric Acid. (Zeit. aizgczo. Chcm., 1896, 130-131.) -The usual method of making this estimation is to dilute the sulphuric acid, to filter off the precipitated lead sulphate, and to precipitate the arsenic in the filtrate. But this is tedious, and, according to the author, inaccurat'e for small amounts of arsenic. The following method is based on the fact observed by Neher (Zeit. anal. CIzc,~n., xxxii., 45) that arsenic is completely precipitated from strong hydrochloric acid solution by sulphuretted hydrogen : 500 C.C.of the strong acid (of specific gravity, say, 1-815 at 22' C. j are diluted with 500 C.C. of water, the mixture having a gravity of 1-46 at 15" C. After cooling, 500 C.C. of this are mixed with 500 C.C. of dilute hydrochloric acid (1 : 2), which is sufficient to prevent the precipitation of the lead as sulphate, and subse- quently as sulphide. Sulphuretted hydrogen is then passed in for about one hour, the precipitate which is in the form of arsenic pentasulphide filtered off, and the arsenic determined as sulphide, or, after oxidation, as arsenic acid. The author found the precipitate quite free from lead, although in one case the amount of lead present in the acid was ten times that of the arsenic. The filter-paper is not attacked by the acid when diluted to the above-mentioned degree.G. Hattensauer. C. A. M. Action of Ammonium Citrate on Basic Slag. 0. Foerster. (Che?n. Z c k , 1896, xx., 131.)-The explanation of the abnormal behaviour of the three slags quoted by Gerlach and Passon (ANALYST, xxi., Sl), in giving up more phosphoric acid to free citric acid than to ammonium citrate, is explained by the fact that the former is a much more energetic solvent of all phosphates than the latter. The difference is only likely to be observed in analysis when the samples examined contain diffi- cultly soluble phosphates, such as the tricalcium salt or the compound (Ca,P,O,),CaO, that yield up more phosphoric acid to free citric acid than to ammonium citrate. Most slags, however, do not contain these substances ; their I ' unavailable " portionTHE ANALYST.167 consisting of iron or aluminium phosphates, which not only are much less soluble, but behave more similarly to both reagents. F. H. L. Estimation of Copper by the Cyanide Process. G. Denigks. (Bull. s'oc. PJ~arm., Bo7decmx, 1896, p. 18, through Ann. de Clai?nia Analyt., i., 70, 71.)-The Parkes method may be improved by operating in an ammoniacal solution kept at boiling temperature throughout, the reaction being thereby rendered more regular and less dependent on the medium, without affecting the accuracy of the result. Ten C.C. of the copper solution are placed in a porcelain capsule, along with an equal bulk of ammonia and made up to 40 C.C. with water. When the boiling-point is attained, a solution of cyauide of potassium, standardized on a one-tenth normal solution of argentic nitrate, is added quickly, drop by drop, until the blue tint has become very weak. Thenceforward an interval of three or four seconds should elapse between the drops until the decolorixation is complete, care being taken that the ebullition is uninterrupted and brisk throughout. Doubling the volume of ammonia, or the presence of ammoniacal salts up to 1 or 1.5 gramnie, does not affect the result. One C.C. of the standardized cyanide of potassium corresponds to oiie ten- thousandth of a molecule of copper salt multiplied by 0-594 (the theoretical equiva- lent is 0.500). ( 1 2 -0.1) x 0.594 x 0.00635, 11 being the C.C. of cyanide solution used, and 0.1 C.C. a constaut arrived at by the The metallic copper can be determined by the calculation author, as corresponding to the accuracy of the results. c. s.

ISSN:0003-2654    

DOI:10.1039/AN8962100165

出版商:RSC    

年代:1896

数据来源: RSC

摘要:

THE ANALYST. 167 R E V I E W . PETEOLEUN. By BOVERTOX REDWOOD, assisted by G. T. HOLLOWAY. London : C. Griffin and Co., Limited. 2 vols. Price 2 2 2s. THIS treatise, as stated in its sub-title, deals with ‘‘ the geographical distribution and geological occurrence of petroleum and natural gas ; the physical and chemical pro- perties, production and refining of petroleum and ozokerite ; the characters and uses, testing, transport and storage of petroleum products ; and the legislative enactments relating thereto ; together with a description of the shale-oil and allied industries, ” . A scheme so cousiderable needs the aid of careful classification for its execution, and such classification has been successfully carried out. The book is divided into sections of moderate size, each section being confined as closely as is practicable to a single distinct subject.Reference is thus facilitated, and the book inade suitable for those needing speedy information on a specific point. Vol. I. is chiefly concerned with historical and geographical matter, with details of methods of winning petroleum, and with accounts of manufacturing processes for the refining of the crude material. I n the second volume occurs that part of the work which is of more immediate interest to the readers of the ANALYST. Nearly 130 pages are occupied with aTHE ANALYST. description of the testing of petroleum and its products, and a large amount of information has been collected. The evaluation of crude petroleum is somewhat briefly discussed, the impression (a correct one, be it said) left on the reader’s mind being that no standard method can be usefully laid down, and that the operator must use a modicum of brains. The section on methods and apparatus for deter- mining the flashing-point of mineral oil is full of detail concerning the many forms in which the test is applied.The determination of viscosity is also treated of at length, many forms of apparatus, some well- devised and useful, others sufficiently obscure and likely to remain so, being described and freely illus- trated. The section on mechanical tests of lubricating oils by the use of sundry frictional testing machines is similarly full, although the author concludes most justly that, save for special purposes, the utility of a frictional machine is small, and the method of choosing an oil by means of frictional results on a laboratory apparatus is altogether inferior to that of making selection by the aid of a knowledge of the viscosity of the lubricant.In the whole of the analytical part care has been taken to get together ample data; it is opinion rather than fact which is lacking. Of half a dozen apparatus or processes described, the expert knows well enough that only one or two are to be commended, but the non-specialist needs guidance. No one is better qualified than Mr. Redwood to state authoritatively what are, and what are not, useful methods, and this portion of the book would gain greatly in value were he to do so. Such uses of petroleum as the production of ‘‘ air-gas ” and of oil-gas, and as fuel for prime-movers, including the modern autocar, are dealt with in the later portion of the volume, which concludes with a reprint of the regulations in use in civilized countries for the safe handling of petroleum, and with a statistical section.The book, as a whole, is a storehouse of facts well classified and presented, but the reader must provide his own mental pepsin. B. B. CORRESPONDENCE. To the Editor8 of THE ANALYST. DEAR Sm,--In the April number of THE bNALYST I note that in Messrs. Droop Richmond and Boseley’s paper on “ The Detection of Formalin ” the authors have misquoted my figures published in THE ANdT,wr, xx., p. 157, as to the quantity of formalin present in milk samples. There are, however, two misprints in m y paper which I should like to correct. I state correctly that “ 5 ounces of formalin to 1 gallon, corresponding to 2 ounces formaldehyde in 160 ounces, is used for making the milk formalin solution ”; but the alternative, “ or I : 320,” should read, “ 1 : 80.’’ The second misprint is “ 8 pint,” which should read “ 1 gill or 5 ounces,” and I find that in my original MSS. the words “ one gill ”* were altered to ‘‘ 4 pint ” by your- self. The calculation deduced from the above data is correct, viz., 1 part of formaldehyde in 46,080 parts milk, assuming that a churn is 18 gallons as a maximum. Yours faithfully, SAMUEL RIDEAL. 28, VICTORIA &1.\SSIONS, \‘ESTJfINSTE:R, S.W. * A gill is a somewhat indefinite measure, since i t means half a pint in some parts of the country.-- ED rr o n.

ISSN:0003-2654    

DOI:10.1039/AN8962100167

出版商:RSC    

年代:1896

数据来源: RSC