摘要:

T E E DETERMINATION OF CARBON AND SULPHUR I N STEEL. BY BERTRAM BLOUNT, F.I.C. (Read at the Meeting, March 7 , 1900.) EXISTING methods in corninon use for the determination of carbon and sulphur in steel are curiously roundabout. The obvious course is to oxidize the whole mass of metal, so that all its constituents-iron, carbon, sulphur, phosphorus, manganese, and minor impurities-are brought to their highest state of oxidation consonant with the conditions, and to collect and separate those products which are volatile-viz., the oxides of carbon and sulphur. This method has been propounded with many elaborations for carbon. As a rule, the analytical description begins by requiring that the steel shall be reduced to fine powder to aid its combustion, a proceeding hopelessly impracticable in the case of mild, tough metal used for structural purposes, and sufficiently difficult with any grade of steel.An alternative plan is to remove the iron by volatilization in a stream oi chlorine, which must be free from oxygen, and to burn the carbon thus disentangled from iron in oxygen. The difliiculty of insuring the freedom of the chlorine from oxygen is the chief obstacle to the wider use of this method.142 THE ANALYST. I have tried to work out a process for determining both carbon and sulphur by direct combustion of steel of all grades in oxygen. I n this endeavour I have encoun- tered certain difficulties which are not yet wholly overcome ; but the work has reached a stage at which it may be usefully recounted. The process employed was extremely simple.The steel was heated in a porcelain tube in a current of oxygen, and the gaseous products absorbed and estimated by the usual means. As the method was intended for use in ordinary practice, no attempt was made to divide the metal finely ; turnings or drillings, such as are commonly taken from a sample for analysis, were employed in all my experiments. 1. Determiizntioiz of Cadon.--Various experiments were carried out to determine the conditions necessary to be observed in order to oxidize completely fairly thick fragments of steel, such as ordinary turnings or drillings. As it was an obvious advantage to work at a moderate temperature, the attempt was made to oxidize the steel at the temperature attainable in a porcelain tube heated by a good Fletcher combustion furnace.The temperature which can be reached thus may be taken as between 700" C. and 800" C. I t was found that oxidation took place readily at first, but that the steel soon became coated with a layer of magnetic oxide so dense and adherent that the rate of oxidation rapidly fell off. This layer doubtless acts as a carrier of oxygen to the core of unoxidized metal; but the speed of translation of oxygen is so low that complete combustion cannot be effected in a reasonable time, and the process is impracticable. It is evident that the rate of oxidation would be greatly increased if the combustion could be effected in the presence of some flux which would slag off the iron oxide as fast as it was formed. A mere solvent flux such as boric acid would be useless, because the glass formed by it would protect the unoxidized metal even more effectually than the layer of magnetic oxide.The flux should be an oxidizing agent as well as a flux, and preferably one capable, not only of supplying, but of carrying, oxygen. Lead oxide fulfils these conditions; but, unfortunately, no ordinary material which can be used to make a boat will withstand the attack which it, or the lead reduced from it by the iron, may cause. Pending the construction of a boat of fused alumina or some similar material, the use of lead oxide as an oxidizing flux must be set aside. It was found that at a temperature of about 1,100* to 1,200" C. (well above the fusing-point of copper), such as can easily be attained in a small Fletcher lecture furnace, oxidation proceeded fairly fast, and for a quantity of 3 to 5 granimes of metal was usually complete in about one hour, reckoning from the time when the furnace becnine fully hot.The rate of oxidation was at first so rapid that the oxygen passing through the tube was almost completely absorbed; as soon as a crust of magnetic oxide had formed the rate naturally fell off. Occasionally there remained a slight core of metal, but analysis of this showed it ti, be free from carbon. The core had been decarburetted by a kind of reverse cementation. Ultimately the method arrived at was as follows : 3 to 5 grammes of steel in the form of drillings or turnings, which may be quite thick,* are placed in a porcelain boat, and heated in a porcelain tube for at least one hour at a temperature of 1,100" Oxidation of the steel at a higher temperature was then tried.' Evidently, if thin turnings are available, they will present the advantage of oxidizing more rapidly.THE ANALYST. 143 to 1,200" C.-Le., to about as high a temperature as a good porcelain tube will bear. [The process of oxidation may be watched through a glazed spyhole by the use of the little device described in a paper of mine on '' The Determination of Oxygen in Copper," ANALYST, xxi., 571. The oxygen before it enters is purified by the usual train of absorption tubes, and the gases as they leave the porcelain tube pass through a glass tube kept at a dull red heat, and containing a column of copper oxide and one of lead chromate. This is necessary to insure the oxidation of small quantities of CO which might arise from a momentary defect of oxygen, and also to stop sulphur, which is the only element other than carbon in the steel yielding a gaseous oxide.Direct experinient has proved that no sulphur escapes from this tube into the absorption bulbs. The purified CO, is dried, absorbed, and weighed in the usual manner. Now, although the advantages of this direct method over the usual lengthy process of dissolution in potassium cupric chloride, filtration and combustion of the residue are so manifest that their discussion would be tedious, yet there are certain difficulties and defects which arise, chiefly from the high temperature needed for oxidation. The life of the porcelain tubes is unduly short, and there is some risk of cracking in the course of an experinient.I arn inclined to think that tubes-and, in fact, porcelain generally from the Royal Berlin porcelain factory-is now somewhat inferior to that which was made some years since ; I have noticed many small signs of a lowering of quality. The necessarily high temperature of the air in the neigh- bourhood of a small but vigorous injector furnace makes the task of the absorption tubes uuusually difficult, unless they are elaborately screened from radiation or kept at a distance ; in the latter case the connections are inconveniently long. Lastly, it is almost a necessity for practical work that the blast of air should be obtained by power ; the use of a foot-blower is too laborious, and the risk of unduly rapid heating is too great to allow of the ordinary bellows being conveniently employed.In my own case I use a Root's blower driven by a gas-engine for all such operations. On account of these difficulties, which sometimes cause errors, I cannot recommend the method as being in its present state capable of replacing generally the older process; it is, however, useful as a completely independent method of checking a result which may appear to be in doubt. What is needed in order t o make it generally applicable is some modification that will allow of the complete oxidation of the metal at a temperature not exceeding a moderate red heat-say, 800" C. 2. lletemziimtioiz of SdplLur.--This is the only other element commonly present in steel which, on the complete oxidation of the metal, yields a gaseous oxide.I t seemed reasonable to suppose from general considerations that a fragment of steel heated in oxygen until fully oxidized would yield the whole of its sulphur as SO, (or partly as SO,). Granting this, the estimation of the sulphur would be extremely simple, consisting merely in combustion of the steel in oxygen and reception of the products of combustion in any suitable absorbent. In my experiments I used apparatus similar to that employed for carbon, The steel, in the forin of drillings, was heated in a porcelain tube to nearly 1,200" C. and a current of oxygen passed over i t ; the products of combustion were at once led into baryta-water. After the operation, the baryta-water, containing barium carbonate, sulphate, and sulphite in suspension, was144 THE ANALYST.made acid with hydrochloric acid, saturated with bromine, and the resulting barium sulphate estimated in the usual way. It was found easy to catch and estimate all the sulphur which was evolved as oxides, but quite impracticable to expel the last trace from the magnetic oxide left in the boat. As much as 20 per cent. of the total sulphur in the steel might thus remain; in what form it can be fixed is by no means clear. I t would probably be feasible to expel this residua1 sulphur by fusion of the magnetic oxide with an acid oxide such as silica or boric anhydride but the proceeding would need an operation successive to and distinct from the combustion proper, and would so complicate the method as to destroy its chief ground for consideration.Moreover, it was found that any small fragment of unoxidized metal (which is harmless in the determination of carbon) means serious loss of sulphur, that element being segregated and gradually driven in towards the centre as combustion proceeds. The core, though small, may therefore contain a sensible proportion of the total content of sulphur. These facts are well illustrated by the figures obtained in the following experiment : A mild steel containing 0.064 per cent. of sulphur was used ; 10 gramines of this were oxidized ; the sulphur passing into the absorption bulbs, that remaining in the crust of magnetic oxide and that remaining in the small metallic core (weighing 0.4075 grammes), were severally determined. But an unexpected difficulty arose.The results are appended : Per Cent. Sulphur volatilized ... ... 0.006 I Sulphur from magnetic oxide . . . 0.041 Calculated on the original steel. Sulphur from metallic core ... 0.017 Total sulphur.. . .". ... 0.064 This particular experiment was stopped at a point when there was still a sensible weight of unoxidized core. Had it been proceeded with until oxidation was complete and the whole mass of magnetic oxide had been strongly heated for some hours, no doubt the bulk of the sulphur would have appeared in the absorption bulbs. Even then, however, an appreciable fraction would have remained with the magnetic oxide. The large quantity of sulphur left in the core becomes more evident mhen it is calculated on the weight of the core itself ; in this instance it amounts to 0-4 per cent.These facts go to show that, whereas the method which I have indicated may prove useful and, with some modification, convenient for the determination of carbon in steel, the corresponding method for sulphur is not likely to he found practically available. DISCUSSION. Xr. ALLEN said that the greater number of the steels with which he had to deal contained chromium and nickel, constituents which were not taken into account in the author's investigation, but which probably would not interfere with the success of the method proposed. As a check upon the usual method of dissolving the metal in ammonio-cupric chloride and burning the carbonaceous residue, a method based on direct combustion of the steel itself would have many advantages.The chlorine method was a good one, but, as had been pointed out by the author, the chlorine must be free from oxygen, and dry, which constituted the great difficulty of theTHE ANALYST. 145 method. He once tried to avoid this difficulty by using bromine, which could easily be obtained dry and free from oxygen. He understood that Mr. Archbutt had successfully used chromic acid for oxidizing the carbon, but; he (Mr. Allen) had not been able to get sufficiently good results with this process. The method of dissolving the iron in cupric chloride was perhaps the one most suited for practical work, and if a simple direct combustion process could be satisfactorily turned to account for checking purposes, it would be of considerable value. Mr. ARCHBUTT said that he had tried the method of direct combustion at a red heat, but had abandoned it as being too cumbrous.The chief difficulty of Mr. Blount’s method, he imagined, was to find apparatus that wocld stand the very high tempera- ture. E e had long ago abandoned the chromic acid method because it also was too tedious, although it was sufficiently accurate if proper precautions were observed. His present method was to dissolve the steel with the double chloride of copper and potassium, burning the residue in oxygen. Results were obtained rapidly, and duplicates were very close; but it was desirable to have an alternative method based on a different principle, by which the results could be checked. The only really reliable method of determining sulphur in steel was by oxidizing the steel with aqua regia, and precipitating the sulphur with barium chloride.Mr. ALLEN said that his difficulty with the chromic acid method had not been that it was too tedious, but that the sulphuric acid used for dissolving the chromic acid was liable to dissolve carbon dioxide. Nr. BEVAN suggested that a correction might be obtained for this once for all by determining the quantity of carbon dioxide dissolved by the sulphuric acid in a blank experiment. Plilr. ARCHBUTT said that as, when the carbonaceous matter was placed in a flask with chroinic acid, a much larger quantity of oxygen was evolved than was necessary for oxidizing the carbon, he would have expected all the carbon dioxide to be driven off. Besides, it was customary to aspirate air through the flask and tubes after the combustion was complete.Mr. ALLEN said that he had been anxious to measure the carbon dioxide in the nitrorneter instead of weighing it. I t was not possible to blow air through, but the chromic acid mixture was heated until oxygen was evolved, and the carbonic acid wa8 absorbed. The difficulty, however, caused by the solubility of the carbon dioxide in sulphuric acid prevented the satisfactory working of the process in this way. Xr. JENI~IXS observed that in such a method of determining carbon, if the com- bustion were carried out at a lower temperature, the core of metallic iron remaining mould presumably still retain some carbon : and the difficulty would be to insure, in the case of any iiietallic core left after combustion, that it no longer contained any carbon. The PRESIDEXT suggested that the sulphur collected in the core might perhaps be obtained by cracking the core and picking out the middle, somewhat in the same way in which the nodules of sulphide of copper were extracted from burnt pyrites.Mr. BLOUNT said that the segregation of the sulphur in the manner described was a phenomenon of quite general occurrence ; as the crust of oxide was brittle, it146 TEE ANALYST. was of course possible to separate the core mechanically, and to oxidize it separately, but the process would cease to be a simple one, and there would still remain the obstacle that the sulphur lurked to a comparatively enormous extent in the crust, which was a fully oxidized product. If a core were left in the carbon process, there would of course always be room for some doubt, though it did not follow necessarily that carbon was left behind. But he did not propose so to limit the process that any core remained ; properly there should be no core. He would have thought that the simplicity of the use of bromine mentioned by Mr. Allen would have balanced any disadvantages which might have attended it. Mr. ALLEN said that the experiments with bromine had been made a good many years ago, when the question of rapidity of working wit8 not of so much consequence as at present ; but as a volatilizing agent, which could be easily insured to be dry and free from air, bromine would certainly seem to be worth considering. Mr. BLOUNT, continuing, said that 1,200" C., although appreciably above the melting-point of copper, was by no means an impracticable temperature. A good porcelain tube would certainly stand it, and the only serious diflficulty was that porcelain tubes had lately been of indifferent qualit,y and liable to crack. He was quite of Mr. Archbutt's opinion that the aqua regia method was the only one of any practical utility for determining sulphur in steel.

ISSN:0003-2654    

DOI:10.1039/AN900250141b

出版商:RSC    

年代:1900

数据来源: RSC

摘要:

146 TEE ANALYST. MAIZE OIL. BY ROWLAND WILLIBNS, F.I.C. (Read at the Meetiytg, H’adL 7, 1900.) THIS oil has attracted a considerable amount of attention during the last few years, and its properties have been investigated by several well-known chemists. Among others, Archbutt has published an interesting paper on the subject (Jam. SOC. Chenz. I d , vol. xviii., p. 346’). Maize oil is, I understand, largely used in the manufacture of soap, especially of soft-soap, and I am informed that it is also employed in the United States for making paints and varnishes. It was, indeed, as a possible drying oil that maize oil was first brought under my notice, and during the last two or three years I have examined a good many samples of the oil, both analytically in the laboratory and also practically on a larger scale, with a view to determine whether its drying properties are sufficiently marked to enable it to be used, either partially or entirely, as a substitute for linseed and other drying oils.According to Lewkowitsch (“ Oils, Fats, and Waxes,” p. 372), ‘‘ Naize oil is, not- withstanding its high iodine value, almost devoid of drying powers. No decided drying properties are imparted to it by subjecting it to the process of ‘ boiling,’ or by addition of lead oxide. If, however, a current of air is passed through it at 150” C. [?for how long], it will, on addition of manganese borate, acquire to a small extent drying properties, and a thin film on lead dries in ten to twenty hours, but not com- pletely.” My own experiments have led me to the conclusion that, although maizeTHE ANALYST.147 oil does possess drying properties to a certain degree, which may be increased by suitable treatment, it is not at all likely to take the place of linseed and similar oils in the manufacture of paints and varnishes. One advantage claimed for maize oil is the comparative paleness of a film of the oil when dry, in consequence of which it is said to be more suitable than linseed oil for mixing with white and delicate pigments in general; but I have not found its slight superiority in this respect to counterbalance its undoubted disadvantage as regards sloxness of drying. I find that a thin layer of maize oil (about 3 gramrne), when heated on a watch- glass to 100" C. for some considerable time, gradually increases in weight for perhaps twenty-four hours, after which it usually begins to lose slowly, until at the end of three or four days the weight is generally less than that originally taken.The maximum increase in weight does not, as a rule, exceed 1.5 per cent., whereas good linseed oil under similar conditions will generally gain at least 4 per cent. On heating in the way described above maize oil thickens slowly, and eventually becomes solid if the oil is of good quality and the heating is continued long enough (usually two or three days); but the film thus obtained is inferior in many respects to a linseed-oil film. In the following table I have recorded some of the figures obtained in the exainination of several samples of maize oil. These were procured from most reliable commercial sources, and I have no reason to doubt their genuine character : No. 1 No.2 :::I No. 3 ..., No. 5 NO. 6 ...I No. 4 ...I .'*I No. No. 8 .-.I .../ 9252 -926s -9244 -9256 -9284 -92.16 -9262 -9248 .~ 1 18.88 ~ 19.07 ' 18-96 1 18-62 19-00 18-79 18-74 , 18.81 ______ - 3-50 ' 3.18 3.64 2 -39 1-53 1.50 2.27 ' 3.02 -- . 23.7 24.4 25.3 23.4 23.3 23.3 23.2 23.5 123.97 127.27 122.57 j 127.36 125-56 ~ 121.99 1 123.98 1 120.85 j 124-74 127.48 123.54 128.02 122.21 136.62 122.68 125.05 - 1.66 I t will be observed that the iodine value was determined by Wijs' as well as by 8Hiibl's solution, with essentially the same results, The bromine value of three of the samples was also determined by the bromine absorption method dgscribed by McIlhiney (Jozw. Anzer.Clzem. Xoc., December, 1899). The figures obtained were about 2 per cent. lower than the theoretical bromine values calculated from the iodine values. DISCUSSIOK. The PRESIDENT having invited discussion, Dr. LEWKOWITSCH said that he was not altogether responsible for the passage which the author had quoted. I t was, in fact, itself a quotation from the original paper of Smith. It would have been interesting to ask the author whether he had examined the unsaponifiable matter. Recently, by American chemists, the unsaponi-148 THE ANALYST. fiable matter of niaize oil had been variously stated to consist of cholesterol and of phytosterol, but, as a matter of fact, the unsaponifiable matter of vegetable oils had been shown invariably to consist of phytosterol, and that of the animal fats and oils to consist of cholesterol. To admit, therefore, the presence of cholesterol in maize oil would be to upset a classification which was well founded on observations. Accord- ing to his experience, such an admission would be erroneous. Mr. ALLEN observed that the percentages of unsaponifiable matter were very high as compared with those of most vegetable oils. Dr. LEWKOWITSCH said that a high percentage of unsaponifiable matter was one of the special characteristics of maize oil. Mr. ARCHBUTT said that the question of whether maize oil was capable of being satisfactorily blown had recently been tested for him on a, practical manufacturing scale, and the result was to show that it yielded an excellent blown oil without any difficulty what ever.

ISSN:0003-2654    

DOI:10.1039/AN9002500146

出版商:RSC    

年代:1900

数据来源: RSC

摘要:

148 THE ANALYST. ON THE ASSAY OF CREOSOTE. BY A. D. HALL, b1.A. (Read nt the H e e t i n g , March 7 , 1900.) BEIKG not infrequently called upon for advice as to the most suitable kind of creosote for the preserving of hop-poles and other kinds of timber used agriculturally, I was led to examine a nuniber of different samples of creosote in commerce. The authorized method for the examination of creosote, introduced, I believe, by Dr. Tidy, seemed to afford considerable scope for improvement, and, after some experiment, I have adopted the following method as more rapid in execution and less liable to errors of manipulation : 1. The creosote in bulk is warmed, and well mixed till all crystals of naphthalene, etc., are dissolved. 2. A portion is dipped out into a measuring glass marked at 100 c.c., and thence transferred to the distilling flask.The glass is rinsed out with 5 C.C. of benzene, which is added to the flask. For the distillation I prefer to use a nickel flask, holding about 500 c.c., as a glass flask can rarely be used a second time. 3. To the flask is connected by a cork a straight glass tube of 4 inch bore about 2 feet long, which serves as a condenser. A thermometer reading to 350” also passes through the cork. 4. The condensing tube passes into the receiver, a cylindrical separator of about 300 C.C. capacity, stoppered at the top and terminating in a tap at the bottom. The cylinder is graduated from the tap upwards. 5. The distillation is begun gently, then pushed till a temperature of 325” C. (600” F,) is reached, and maintained till no further distillate passes over.It may be necessary from time to time to warm the condensing tube to prevent it blocking with naphthalene. 6. When no more conies over, the volume of distillate is read off in the receiver, 5 C.C. is deducted for the benzene used, and so the percentage of “residue non- volatile at 600” F.” is obtained.THE ANALYST. 149 7. To the receiver 100 C.C. of caustic soda solution are now added (alkali of specific gravity 1.2 is specified in the old method, but there is no objection to the use of the alkali of specific gravity 1.3, commonly used for ammonia distillations). The mixture is well shaken and put in a water-oven for an hour at least, being well shaken from time to time. Finally, it is allowed to stand till cool, the volume read, and the greater part of the caustic soda solution is drawn off by the tap.There will be more than 100 c.c., owing to the phenols absorbed. 8. The caustic soda solution is boiled for a few minutes, to expel any traces of hydrocarbon, etc., it may retain, and allowed to cool. When cold, 10 C.C. are with- drawn by a pipette, and run into the bottle of a Leffmann-Beam centrifugal milk apparatus; dilute sulphuric acid is added carefully till the alkali is neutralized and the so-called “ tar acids )) are liberated, then the bottle is whirled for a few minutes in the machine, allowed to cool, and the quantity of “ t a r acids” in the neck of the bottle read off. A preliminary calibration of the divisions on the neck of the bottle is, of course, necessary to obtain their value in C.C.From these data the percentage of ‘‘ tar-acids ” in the original creosote is calculated. 9. To the contents of the receiver 100 C.C. of dilute sulphuric acid (1 : 5 ) is now added, and the heating and shaking of 6 is repeated. The contents of the receiver are allowed to cool, and the volume of the acid extract is read off (it is greater than 100 c.c., because some of the caustic soda solution was not drawn off). Ten C.C. of this are pipetted off into a Leffmann-Beam bottle, the “ tar bases liberated by alkali, and their volume measured after whirling, just as in the last operation. After correct- ing for the volume of the acid solution, the proportion of ‘( tar bases ’) in the original creosote is calculated. The “ tar bases ” sometimes solidify, making it difficult to read their volume with accuracy.The disadvantages inherent in the old process are the necessity of complete separation of the oil from the caustic soda solution and of the ‘‘ tar acids ’) after acidifying, and the filtration of the latter through asbestos. By taking an aliquot part of the soda solution, the losses inevitable in the attempt to collect the whole of the “tar acids ’) are avoided, while the use of the small bottle and the centrifugal method enables the “ tar acids” to be separated and measured with accuracy and speed. The ease of the method also enables the ‘( tar bases ” to be estimated, which is desirable, because of their preservative power. In the old method the distillate, etc., has to be transferred from vessel to vessel four times before it is actually measured as ‘( tar acids”; in the method suggested there is no such transference of a liquid that has to be finally measured.Exn?lzpl c. Readings : Distillate ... ... ... ... Volume of soda solution ... ... ‘‘ Tar acids” in bottle ... ... . . . Volume of acid solution . . . ... ‘‘ Tar bases” in bottle ... ... ... Residue non-volatile at 600” 17. “ Tar acids )’ . . . ... ... . . . “ Tar bases ” . . . ... ... ... Calculated : ... ... 66 C.C. 67.5 C.C. ... 110 ) ) 110 I ! ... 47 ,) 47 > > . .. 103 ,, 100 9 , ... 15 ,, 10 2 , . . . 39 per cent. 37.5 per cent. ... 9.3 ), 9.3 , , ... 3-8 ,, 1 , 3 .>150 THE ANALYST. I t may not be out of place here to give a brief account of some experiments instituted to ascertain in which constituent of the creosote its preservative power mainly resides, as no sound information seems to be available on the point.The “ t a r acids” are always referred to in creosote specifications, and they have been supposed to act by combining with albuminoids in the wood ; others, again, lay stress on the injection of the heavy oils into the pores of the wood, thus mechanically pre- venting the entry of water, and’ therefore of decay ; while, again, I find many users of hop-poles prefer “ creosote salts,” which consist practically of naphthalene. I t was decided to institute some experiments to throw light on the relative pre- servative powers of the various constituents of ordinary creosote, and the first trial was carried out by Mr.H. H. Cousins, M.A., of the South-Eastern Agricultural College at Wye, upon a good sample of hemp-string, which had an average breaking strain when fresh of 33 pounds. Lengths of this string were soaked in various extracts from creosote and other pure materials, as set out below, at a water-bath temperature ; the string was partly buried for two months in ordinarygarden soil, dug up, and its strength redetermined. The results set out in Table II. gave a low value either to pure phenols or the homologous phenols extracted from commercial creosote by alkali ; naphthalene was little better ; while the non-volatile portion of tho creosote, the ‘‘ tar bases” extracted from it by acid, and the bone oil, which is rich in similar bases, had pre- served the string.I t does not, however, follow that string will behave in the same way as wood, and other experiments were begun upon wood. I n one set sinall blocks of wood, sawn transversely to the grain, were soaked for half an hour in 5 per cent. solutions in benzene of the constit’uents to be tested, the solutions poured off, and the blocks dried. One of my colleagues, Professor J. Percival, then seeded each block with a pure culture of penicillium and also with fragments of rotting waod ; the blocks were kept in a moist chamber in the dark. The experiment, however, did not succeed ; most of the substances entirely inhibited the growth of penicillium, etc.: though the wood was repeatedly seeded, and even streaked over first with a nutrient medium. In the other trial a series of small rods of deal were carefully selected; they were 8 inches long by inch square, and were soaked in the various materials for one and a half hours at a temperature of 90” C.They were then buried in about three-quarters of their length for ten months in ordinary garden soil, taken up, washed and slowly dried, and then broken transversely under similar conditions, with the result set out in Table III. The results show that the creosote itself, and particularly the non-volatile con- stituents, had considerable preservative power, as also had the bone oil; the tar ‘‘ acids ” and “ bases ” had a real but smaller preservative power ; but pure cresol had Iittle or none. As far as the experiments go, they seem to show that the preservative action of creosote lies in its power t o fill the cells of the wood with a fixed moisture-resisting material rather than in any chemical antiseptic action ; the preservative qualities of cresol and naphthalene are small, for thin pieces of wood at any rate, because the one evaporates and the other dissolves, leaving the wood open to attack.It alsoTHE ANALYST. 151 seems desirable in the commercial examination of creosote to estimate the pyridine “ tar bases ” and rate them as of equal preservative value to the ‘‘ tar acids.” Further experiments on large pieces of wood are in progress, which I hope to lay before the Society at some future time. TABLE 11. Rrenkiizg Stmirz of Xtriizg uftes’ Two Montlzs’ Exposwe (original Breukilzg Straiiz, 33 Poumls). Breaking Po1mds. Treatnient. C‘ondi tioii.Strain, ... ... 0 Untreated ... ... ... ... ... Rotten . . . ... ... 0 With ‘‘ tar acids ” ... ... ... ... Rotten ... ,, volatile distillate from creosote ... Rotten ... ... ... 0 ... ... 0 ,) phenol ... ... ... ... Rotten ... ... ... 0 ,) cresol ... ... ... ... ... Rotten ... ... ... ... 3 ,, naphthalene ... ... ... Partly rotten ), ‘‘ tar bases” ... ... I.. ... One in six rotten ... ... 16 ... ... ... ... 18 ,, bone oil ... ... ... Sound ) ) non-volatile residue from creosote Sound ... ... ... 16 ... .., ... 4 ,, creosote in the cold ... ... _- ... ... 13 ,, same creosote, hot ... ... __ Breaking Strain (trcuzsoerse) of Ileal Rods exposed Telz X o ~ ~ t J u (oi-igiiaal Brcaki?zg S t rain, 630 Po 21 d s ) . Bitaking Treatiiient. Coiidition. Stlain, 1’011 nds.Untreated ... ... ... ... ... &Inch decayed ... ... 300 I ‘ Tar acids ” ... ... ... ... X little decayed ... ... 430 ‘‘ Tar bases ’* ... ... ... ... Surface good ... ... 360 Naphthalene ... ... ... ... Surface decayed, sound within ... ... ... 410 Xon-volatile residue ... ... ... Sound ... ... ... 570 Animal oil ... ... ... ... Surface fair ... ... 440 Creosote ... . . . ... ... ... Sound ... ... .., -1-70 Cresol ... ... ... ... ... Xuch decayed ... ... 230 ... The PI:ESII)ENT having invited discussion, Dr. LEIYIIOXVITSCH said it seemed very probable indeed that the alkaline solution would contain some proportion of the bases, which it would be important to collect and duly take into account in the analysis. Mr. BLOUNT said that while the methods described in the paper were certainly illore refined than the older ones, nevertheless the latter, when properly worked, yielded equally satisfactory results.The practical experiments of the author seemed to indicate that one of the constituents which engineers were most careful to exclude from creosote-namely, the heavy oils-possessed considerable preservative value for wood. The Dr. DYER desired to join in thanking l l r . Hall for a very interesting paper.152 THE ANALYST. latter part of the paper confirmed the views held by the late Dr. Tidy, who used to maintain that a high percentage of tar acids was by no means a necessary index of the preservative properties of creosote. Specifications used to stipulate that not more than a certain proportion of non-volatile matter should be left after distillation at 600" C.; but Dr. Tidy exactly reversed this, maintaining that at least a certain proportion of non-volatile matter ought to be present. Tf7ith regard to the determina- tion of the tar acids, he (Dr. Dyer) would like to hear whether Mr. Hall had tried, after exhausting with a large quantity of alkali, subsequently exhausting with repeated small quantities. The usual process was to exhaust with repeated small quantities of alkali, probably for the reason that, although carbolic acid (or phenol proper) dissolved in alkali of any strength, yet the higher acids-cresols, etc.-were singularly capricious, being liable, while dissolving in a certain volume of alkaline solution to separate out if the volume of solution were increased.Mr. ALLEN said that cresol, the immediate higher homologue of phenol, dis- solved readily in a solution of sodium cresylate, so that, if there was sufficient alkali to form sodium cresylate, it would stand dilution without separation, while if there was an insufficient quantity of alkali, the cresol dissolved in it if it was strong, being thrown out of solution on dilution. If sufficient alkali were used, the various tar acids would all dissolve, but not with equal facility. It was a case of fractional neutrali- zation, the phenol going first, as the stronger acid. But if too much alkali were used, probably some of the hydrocarbons would go into solution as well. Creosote was very largely employed for the preservation of timber-piles, piers, etc., exposed under water, which in the tropics were destroyed very rapidly owing to the action of the teredo and other worms.A method was much to be desired for the determina- tion of acridine, which was probably the constituent most objectionable to such animal pests. Mr. CHAPMAN suggested that the use of cork in place of wood in laboratory experiments such as those which the author had made would probably lead to more conclusive results, owing to the greater readiness with which cork would be penetrated by fungoid growths. The difficulties experienced in determining phenols by extraction with alkaline solutions were also met with in the analysis of essential oils containing phenolic bodies. I n the case of clove oil, for instance, the determination of eugenol by treatment with caustic potash solution was vitiated owing to the sesquiterpene, caryophyllene, being also appreciably soluble in the alkaline liquid.With regard to the statement as to the non-occurrence of albuminoids in wood, it was, he thought, a very general belief that, but for the presence of those substances in the wood, the cellulose would undergo little or no change. Mr. ARCHBUTT said that the author's experiments confirmed the conclusions arrived at by Mr. Boulton, and embodied in a paper read by him before the Institu- tion of Civil Engineers in 1884. Mr. Boulton brought forward a good deal of evidence to show that the value of creosote oil for preserving timber lay in the higher and less volatile fractions, and especially in the tar bases, much of this evidence being based on the experiments of the late Dr.Tidy, That paper led to the abandonment of the late Dr. Letheby's specification, in which the phenol was regarded as the most important constituent, and the substitution for it of Dr. Tidy's specification, in whichTHE ANALYST. 153 a, certain proportion of less volatile constituents was required, the exact percentage of phenol being of less importance. Personally he had found no difficulty in using a glass retort over and over again, provided that the distillation was not carried to coking. The advantage of using very strong soda was that, when the soda was mixed with dilute sulphuric acid, a supersaturated solution of sodium sulphate was produced, in which the phenols became insoluble, so that the whole of the phenols were thrown out on adding excess of acid.For removing neutral oils and naphtha- lene dissolved in the soda, filtration through asbestos had been recommended by Dr. Tidy, but he (Mr. Archbutt) had found it simpler to shake the caustic soda solution with ether. In estimating the tar bases he had adopted the method of distilling a separate portion down to coking and shaking with dilute sulphuric acid. The acid liquid is then evaporated to a small voIume, and the bases are thrown up by adding pieces of solid stick soda or potash. Mr. HALL said that he had a good many times tried the effect of boiling the caustic soda solution, comparing the quantities of tar acids obtained with boiled and unhoiled solution ; but he had never found any notable difference, though it was possible that differences might occur in some samples, and therefore he had sug- gested the boiling of the solution as a precaution. He had occasionally tried, after removing everything possible by means of alkali, what could be obtained by means of acid. The effect of second and third extractions with alkali had been tried, but as far as his experience went a single treatment with alkali extracted all the phenolic substances. With regard to the question of the presence of alburninoids in wood, it was very hard to say that anything quite of the nature of an albuminoid existed in wood, but the analogy had been pressed strongly that the preservative power of creosote was due to the sort of antiseptic action which carbolic acid, for instance, had upon a substance like true albumen, namely, coagulation. There was nothing in wood exactly equivalent to true albumen, coagulable by phenol. It was the starch always that was affected. Decay was always quickest in fresh sap wood, where the cells contained a good deal of starch. He had been trying to ascertain how far the fungi penetrated the treated wood, but could not get the fungus to start into the wood except in one case, when it had been saturated with cresol, though where the other materials mentioned were present the growth was arrested at the surface.

ISSN:0003-2654    

DOI:10.1039/AN9002500148

出版商:RSC    

年代:1900

数据来源: RSC

摘要:

154 THE ANALYST. ABSTRACTS OF PAPERS PUBLISHED IN OTHER JOURNALS. FOODS AND DRUGS ANALYSIS. The Influence of Certain Alcohols, Acids, and Sugars on the Digestion of Proteids by Pepsin and Trypsin. E. Laborde. (Joemz. fwm. Chinz., 1899, x., 484-488.)-1n his comparative experiments on this subject the author digested a definite quantity of coagulated egg albumen with acid pepsin or alkaline trypsin in ths presence of 50 C.C. of a 20 per cent. and 5 per cent. solution of the given alcohol, and also as a check with the enzymes in 50 C.C. of water. The flasks were kept at a temperature of 40" C. for four hours in the pepsin digestions, and for three hours in the trypsin digestions, and at the end of those periods the amount of albunioses and peptones in the filtered liquids was determined by precipitating the former with ammonium sulphate and estimating the organic nitrogen in the solution before and after removal of the albumoses. I n the experiments with pepsin it was found that isobutyl alcohol, glycerol, and malic acid favoured the digestion when present in small quantity, whilst methyl alcohol appeared to have a very slight accelerating influence.On the other hand, the digestion was markedly retarded by the presence of ethyl and propyl alcohols, by lactic and tartaric acids, and by mannitol and glucose. In the case of trypsin the activity of the enzyme was accelerated by methyl and isobutyl alcohols, by glycerol, and by glucose, and retarded by ethyl and propyl alcohols, by lactic, malic, and tartaric acids, and by mannitol. c.A. ng. The Ratio bstween Proteids and Fat in milk. H. Timpe. (Chenz. &&., 1899, sxiii., 1040.)-In Table I. (p. 158) are given the analytical results obtained on examining milk derived from cows of different breeds and different localities, the samples being placed in order according to the amount of fat they contain. These figures bring to light various relationships between the several constituents in the normal secretion which are apt to be overlooked when the milk of only one descrip- tion of cattle is tested, since the composition of the liquid produced by each heed is too uniform to show these ratios distinctly. Calculated per I00 parts of total solids, it, will be seen that the sugar varies inversely with the fat, so that within certain limits the proportion of sugar plus fat is constant.The ash (calculated on the solids) also decreases as the €at rises, so that, with five exceptions, the value sugar divided by ash is always between 6.04 and 6-84 On the other hand, the amount of proteids (calculated on the solids) is remarkably uniform : the largest difference among the fats is 27.43 per cent. ; among the sugars, 82.92 per cent. ; but among the proteids it is only 2.88 per cent., and even the ash varies within wider limits. Therefore per 100 parts of total solids the amount of fat, sugar, and ash together is essentially constant. This fall in sugar and ash as the fat rises, when calculated on the solids, finds a simple explanation if the two former ingredients remain practically the same, however the fat varies, when the calculation is made upon the original milk.The table shows signsTHE ANALYST. 155 of this : the fat in No. 21 is 520 per cent. of that in No. 1 ; the greatest increase in sugar is only 13 per cert., and that in ash 26 per cent. of their lowest proportions respectively. In contradistinction to the fat, therefore, it may be said that the amount of sugar and ash in milk is roughly constant. If these were constant in amount in the milk itself, they should fall, like the sugar and ash, as the fat rises when calculated on the solids. I t appears, however, that they are remarkably con- stant in the total solids; therefore they must increase (calculated on the milk), though on a far smaller ratio, with increases in the fat. Although there is no ratio between the percentage of proteid and of fat in the milks, there is a distinct ratio Matters are different in the case of the proteids.between their several variations; for it will be observed that when the latter rises 5.36 per cent., the former rise 1.S9 per cent., which is roughly 3 : 1; and this ratio obtains not only between the extreme samples, but also practically throughout them all. I t is evident, therefore, that the ratio may be expressed by the formula P = CL + bF, where P is proteid, I? fat, and a and b two constants. From Table I. CL is shown to equal 2, I, t o equal 0.35; and the formula thus becomes : P = 2 + 3.35F. The figures in column S record the amount of proteid calculated froin the fat by this formula, and column 9 gives the differences between the theoretical and analytical results.The coincidence is brought out more clearly in the accompanying diagram, where the thick line marlis the theoretical value of P. The maximum difference is =tO.12 per cent. ; only in three cases does it exceed =tO*OS per cent. I t niay also be imagined tbat the proteids are divisible into two classes, u and p. The P-proteid perhaps is lorined from the same original substance which yields the fat, and the ratio P-proteid : fat equals 0.35 : 1. The a-proteid is produced iudepen- dently of the fat, and is present constantly in the proportion of 2 per cent. Thus, it may be said generally that ash, sugar, and u-proteid are approximately constant in normal milk; P-proteid and fat vary in the ratio mentioned. These observations apply only to the milk of healthy cows fed with normal food ;156 THE ANALYST.illness and exceptional feeding lead to different results. I n Table 11. (p. 159) are collected various more or less abnormal milks. Nos. 1 to 3 are from stall-fed cattle ; Nos. 4 to 8 from experimentally-fed cows; No. 9 is not described; Nos. 10 to 12 represent the milk of a cow suffering from foot-and-mouth disease; No. 13 onwards record the history of a Simmenthal cow ill, and recovering, from a severe attack of gastric cztarrh (“ Magenkatarrh ”). [The ash figures are omitted ; they appear un- affected except in Nos. 10 to 12, where they stand at 1.01, 0.88, and 0.90 per cent. respectively.] With the exception of No. 9, special feeding has caused the amount of proteids to be less than the theoretical-that is to say, has produced an excess of fat, which is the more noticeable seeing that the fat and one portion of the proteids have a conimon origin.This increase of fat must therefore be regarded as abnormal, if not pathological-a view which is strengthened by the phenomena of foot-and-mouth disease and gastric catarrh in its acute stages (Nos. 10 to 16). The sudden change from a deficiency to an excess of proteids on the fourth day of the latter ailment may be explained by the complete alteration in character of the milk during disease, which causes the ordinary ratios to be no longer valid ; by November 6, when the catarrh had disappeared and only the animal’s body-weight was still reduced, the secretion may be said to have become normal again.It should be noticed that, with five exceptions, even when the cows were ill, the amount of sugar remained within its proper limits of 4.4 to 5 per cent. This matter is of great importance in the valuation of milk samples. To show that the ratio of fat to proteids is a constant, and is affected only by disease or by sudden changes in the conditions of life, but not by the influence of the food itself, some experiments made by Landbeck may be quoted. Three cows were fed specially during four periods of twenty days with a diet rich in proteid and fat. The proportions of the latter in the food were higher during the second period than during the first, higher during the third than during the second ; during the fourth they were the same as at first.Each period was divided into a preliminary and a second stage of ten days each (the food being the same in both stages of the same period). One of the cows remained practically constant in weight throughout the whole experiment, having so good a constitution as not to be deranged by the sudden alterations in diet. The analyses of its milk were as follows : Proteids. Period I., first stage ... . second stage Yeriod II., first stage ... second stage Period III., first stage ... second stage Period IV., first stage ... second stage Pat. ... ... 4.20 *.. ... 4-10 ... ... 4.29 ... ... 4.15 ... ... 4-59 ... ... 4.29 ... ... 4.35 ... ... 4-39 Fbund. 3-13 3-40 3.33 3.44 3.49 3.51 3.43 3.45 Calciilated. Difference. 3.44 - 0.04 3.50 - 0.17 3.45 - 0-01 3.58 - 0,09 3.50 - 0.01 3.52 - 0.09 3.51 - 0.06 3.47 - 0.34 It will be evident that it was the sudden changes in food, and not the food itself, which affected the ratios, for otherwise the ‘‘ differences ” which rose at each alteration would have remained of the same dimensions during the second stage of each period.The other two cows gained in body weight during the investigation, and their milk was constantly abnormal.TEE ANALYST. 157 Inasmuch as commercial milk is always a mixed product derived from a large number of cows, the disturbing influence on the ratio of proteids to fat which is produced by the stall-feeding of a few individuals is practically eliminated ; and it may be said that the diEerence (D) between the proteids obtained by analysis and by calculation (calculated amount deducted from that recovered by analysis) in such mixed milk will scarcely ever exceed k0.06 per cent.The factor thus becomes of great value in judging the quality of ordinary milk samples; and the effect of the various methods of sophistication may consequently be studied. Renzorcd of Crecwz.--If cream has been removed from a milk, D becomes positive, while sugar and ash remain normal. %'hen, for example, milk No. 11, Table I., was skimmed till it contained only 3-02 per cent. of fat, it gave on analysis 11.74 per cent. of total solids, 4-63 per cent. of sugar, 0.74 per cent. of ash, and 3.35 per cent. of proteids. The theoretical proteids were 3.01 per cent., therefore D equalled + 0.34. From the amount of proteids found, the original proportion of fat (or the degree of fat removal) could be calculated by the formula F= and gave 3.85 per cent.-- an error of 0.13 per cent.Addition of Water.-When the proportion of fat falls through natural causes, the P-proteids are reduced correspondingly, while the a-proteids remain unaltered ; but if water is added, all the constants are lowered, and their ratios one to another are the same as in whole milk. Addition of water thus causes D to be negative. A negative D, however, by itself does not prove addition of water ; it is necessary to consider the proportion of sugar and ash. By adding fat to a skimmed milk, a negative D is produced, the fat and sugar remaining normal ; dilution with water would diminish the percentage of the latter bodies as well. On mixing 100 C.C.of milk No. 11 with 20 C.C. of water, the following figures were obtained : 10.37 per cent. of total solids, 3.13 per cent. of fat, 3.84 per cent. of sugar, 0.63 per cent. of ash, 2.77 per cent. of proteids by analysis, 3-10 per cent. by calculation, D being accord- ingly -0.33. By usiqg the formula -D ~ ~ __ loo the amount of added water could be P - 0.35 F' deduced, and gave 19.7 C.C. Removal of Cmam and Addition of Water.-Detection of this method of sophistication is more difficult, but in the majority of cases it can be effected with certainty. As the former process yields a positive D and the latter a negative one, if the exact amount of water is added which compensates for the removal of fat, D remains at its proper value ; but as the quantity of fat removed cannot be ascer- tained except by analysis, it is impossible for a milk-dealer to know how much water to add, and probably D will be either too high or too low.If, however, the two processes were carried out successfully, so that D gave no sign, the deficiency in ash and sugar would be apparent. Only if the degree of dilution were so small that the percentage of sugar remained above the minimum would detection be impossible ; but if the analytical results are recalculated to a basis of an average sugar-content, the figures for fat and proteids so obtained will show the removal of cream. For example, Milk No. 11 was skimmed and mixed with one-sixth its volume of water. On analysis it showed 10.36 per cent. of total solids, 2.93 per cent. of fat, 3.93 per cent.of sugar, 0.64 per cent. of ash, 2.86 per cent. of proteids (found), 3.03 per cent. - 0%'158 THE ANALYST. by calculation. D was equal to - 0-17, for too much water had been used, the presence of which was also indicated by the lowness of the sugar. Recalculating to a basis of 4.7 per cent. of sugar, the fat was 3.50 per cent,, and the proteids 3-42 per cent. Calculating the proteids from the 3.50 per cent. of fat gave 3.23 per cent., D being +0.19. By the formuh given above, the added water was represented to be 19-6 (instead of 16.7) c.c., and the original proportion of fat to be 4.05 (instead of 3-72) per cent. Therefore the falsification can not only be detected, but even estimated with some degree of accuracy-at any rate, more safely and conveniently than by 6 L an appeal to the cow." In practice the following cases have to be considered : (1) Sugar and ashnormal. If D is less than ztO.06, manipulation cannot be detected.If D exceeds +0*06, cream has been removed, theoriginal amount of fat being If D exceeds - 0.06, the milk has been loaded with cream. (2) Sugar and ash at or below the minimum. The amounts of fat and proteids are recalculated to the normal basis of 4.7 per cent. of sugar, in order to yield their respective proportions before addition of water. If then the recalculated D is approximately correct, only water has been added ; if 1) is positive, cream has been removed as well, and the magnitude of the sophistication can be ascertained as above. [Judged solely on these rules, the average normal morning milk quoted by Richmond (ANALYST, 1899, xxiv., 199) would appear as though it had been partly skimmed, €or it gives D = + 0.226 ; the evening milk gives D = + 0.025, and accord- ingly would be regarded as genuine.Even if the morning and evening figures are combined, I> = + 0.125, and the mixed milk would be regarded as skimmed.-Ass. J This proved the removal of cream. P-2 0-35 ' + 0.01 i- 0 '01 - 0.12 - 0.01 - 0.11 - 0-01 - 0 '01 -t 0.01 4- 0 .os - 0'01 - 0'01 -i- 0'03 - 0.07 f 0.08 + 0.0"159 1 Proteids. Total Fat. Solids. Differ- ence. i Siigar. ~ I Found. 4-25 3.04 4.69 2.98 4-52 3-10 4.66 3.03 4.58 2.89 4.36 3-19 , ~~ Calco- lateti. 3.27 3-30 3.36 3.16 3-31 3.44 3.04 3-58 3.86 4-21 3.90 3.04 2.65 5.07 -~ ~ ~~~ 11-63 3.62 12.06 i 3.71 12.15 3-88 ll.G(i 3.30 11.91 3.73 1 2 4 4-10 13-46 4-50 15-69 ' 6.30 11-75 2.96 __ - - - ..1 Stall-fed, . . ... . . . ... 2 1 7 7 -.. 3 7 7 ..- 4 I:sperirnental feeding . . . . . .._ ... ... ... ... K - 0 9 3 - 0.26 - 0.13 - 0.42 - 0.25 - 0.54 - 0.35 + 0.86 - 2.42 - 2.51 - 2.69 - 0.99 - 0.53 - 0.19 - 0.20 + 0.15 + 0.19 + 0.72 -+ 0-31 + 0.37 1- 0.21 + 0-47 + 0.21 + 0.23 - 0.03 - 0.25 - 0.08 - 0.05 + 0-08 + 0.05 + 0.02 - 0.13 - 0.27 + 0.05 + 0.03 + 0.23 + 0.15 + 0.36 + 0.27 - 0.32 ,J G 8 9 10 11 1 2 13 r 7 7 9 7 7 7 > 7 Foot and 0;;. 31. 1 7 7 7 7 9 7 7 7 7 ... ... ... ... ... . . . ... . . . ? lllouth Disease . . . 7 7 7 7 l l 7 7 . . . . . . Cow suffering fram 5.11 4 -80 4.15 5.35 19.81 20.61 15.32 13.71 12 60 13.0b 12.11 12.57 12.46 12.50 12.82 12-85 19-34 12-33 12.22 12.22 12.78 9.18 10.00 7.29 5.20 4.05 4-45 3.41 3.87 3-15 3.64 3.65 3-03 3.29 3.72 3.52 3.88 4.15 3.95 3-69 7-06 2.70 6.90 2.81 3.80 , 3.56 1 4-16 I 3.29 4.61 ~ 2.23 4-52 3.36 5-21 5.50 4-5.5 3.82 3.42 3.56 3-19 3.36 3-10 3.27 3 28 3-37 3-15 3-30 3.23 3.36 3-45 3.38 3-29 3.22 ... ... ... ... ... ... ... ... ... ... ... . . . ... ... ... 1.2 7 7 15 Nov. 1. 9 7 Kov. 3. KO\-. 3. wov. 4. Nov. 5. I ? 9 ) 7 7 I 16 17 18 19 20 21 22 23 4.68 4 4 3 4.75 4-54 4.79 4-58 4.64 4.37 4.54 4.30 4.66 4-86 4.96 4.85 4.73 4 -80 4.75 4.45 4.63 4.78 4.95 5-06 4 -64 3.35 3.55 3.82 3.58 3.65 3.58 3-62 3.51 3.46 3.33 3.20 3.30 3.24 3.30 24 9 ) 25 ' Nov. 6. 26 7 7 27 Nov. 7 . 28 7 7 29 Xov. 8. 30 9 7 31 1 Nov. 9. 32 7 7 33 ' Nov. 10. . . . , 12.78 I 12-61 ... . . . ... . . . ... ... ... ... ... ... ... ... 19-29 3.47 12-42 ~ 3-69 12.52 3.73 12.53 1 3.80 12.50 ~ 4-18 12.44 I 3.72 3.34 3.29 3.33 , 3-31 3.19 3.33 3.19 I 3.46 3.35 1 3.38 3.46 3.43 34 35 36 37 38 39 40 _- 7 9 Nov. 11. Nd;. 14. Nov. 18. 9 7 7 9 4.09 3.60 3.76 3.20 3.28 12.95 12.72 12.98 12 -04 12.15 3.49 3.47 3.48 3-26 3.32 3.12 3.15

ISSN:0003-2654    

DOI:10.1039/AN9002500154

出版商:RSC    

年代:1900

数据来源: RSC

摘要:

160 THE ANALYST. ORGANIC ANALYSIS. Iodometric Determination of Small Quantities of Carbon Monoxide. L. P. Kinnicut and G. R. Sanford. (JOZLT~. Ainer. Chew. Soc., vol. xxii., pp. 14-18.) -The apparatus used is a modification of that employed by Nicloux. Twenty-five grammes of purified iodine pentoxide are placed in a sniall U-tube, supported in an oil-bath at 150" C., and connected to a Wolff blood-absorption tube containing 0.5 gramme of potassium iodide in 5 C.C. of water. The air to be examined is freed from unsaturated hydrocarbons, hydrogen sulphide, sulphur dioxide, and similar reducing gases by passing it through U-tubes containing sulphuric acid and solid caustic potash respectively, and is then passed through the iodine pentoxide tube, the liberated iodine being retained in the Wolff tube and estimated by :oi, K sodium thiosulphate.The rate of flow of the air-current is regulated by dry mercurj to about 3 litre per hour. The method will Zetect as little as 0.0025 per cent. by volume of carbonmonoxide in air. c. s. The Separation of Formic, Acetic, Propionic, and Butyric Acids by Haber- land's Method. J. Schutz. (Zcit. anal. C'he?u., 1900, xxxix., 17, 1s.)-The method of separation proposed by Haberland (Zcit. nml. C?LCTTZ., 1S99, 217) consisted in liberating the acids by means of phosphoric acid, distilling them in a current of steam, and evaporating the distillate to dryness with an excess of lead oxide. The basic lead propionate, being insoluble in water, was removed ; the filtrate, after removal of the lead, was evaporated to dryness with zinc oxide and the zinc acetate, and butyrate separated from the zinc formate in virtue of their different solubilities in alcohol.In examining this method, the author has made experiments with the three acids separately by evaporating on the water-bath titrated amounts with 2n excess of zinc oxide and a small quantity of zinc sulphate, liberating and distilling the acids from the residue, and again titrating. The loss increased with the molecular weight of the acids, and amounted to 10.5 per cent. with the formic acid, 73.9 per cent. with the acetic acid, and 82.3 per cent. with the butyric acid. Similar, though somewhat more favourable, results were obtained in the case of the lead salts of these acids, and the author therefore concludes that these bases are not suitable for the estiinat.ion of these acids by the method described by Haberland.c. A. If. - The Composition of Geranium Oils of Different Origin. Jeancard and Satie. (Bzill. SOC. Chinz., 1900, xxiii., 37-39.)-The samples examined by the authors were selected from oils distilled in 1898 and 1899, and were known to be pure. A direct determination of the esters by the ordinary method gave the following results, calculatecl as C,,H200, : Cannes oil, 19.11 ; Spanish oil, 23-03 ; Corsican oil, 21.07 ; African oil, 23-03 ; Bourbon oil, 25-95 ; and Indian oil, 15.05 per cent.- figures in substantial agreement with those of Charabot, Dupont, and Pillet (Cf. ,\NALYST, XXii., 193).THE ANALYST. 161 Taking into account the fact that geranium oil invariably contains free acids, the authors determined the degree of acidity in the following manner : Three grammes of the oil were mixed with 10 C.C.of 96 per cent. alcohol and 10 C.C. of semi-normal potassium hydroxide solution. After two minutes the oil was precipitated by the addition of water, and the excess of alkali titrated with standard sulphuric acid. It is essential not to prolong the contact of the alkali with the oil beyond the two minutes, since otherwise a partial saponification takes place. Under the con- ditions given above the author considers that there is hardly any saponification, and that the figure obtained in milligrarnmes of potassium hydroxide per grainme o oil is equal, or but slightly higher than that corresponding to the free acids actually present.I n the case of a sample of African geranium oil the results thus obtained were : After two minutes, 42.93; after five minutes, 43.06; ten minutes, 43.S6; twenty minutes, 45.73; forty minutes, 48.53; one hour, 49.35; two hours, 49.93; and by hot saponification, 65.80 milligrammes. By this method of cold saponification the authors have found that geranium oil becomes oxidised on contact with the air. Thus, a sample of Bourbon oil with a cold saponification value of 56.00 gave a value of 66-73 after being left for two months in a partially filled flask. On the other hand, a Cannes oil became oxidised much less readily, the figures only varying in a year from 26.6 to 29.66. In the subjoined table of the characteristics of the different varieties of geranium oil the esters were calculated as C,,H,002 (allowance being made for the free acids) and the alcohols as Clu13~s0 : Dellsity at & o t a t o ~ I'omr SaIionificattioii V:Llue, Esters, Alcohols, cl;id.per Cent. per Cenr;. a t 15" c'. Oil of t ;eraiiium. "5' '* in 100 111ni. tube. H>t. Cannes ... 0.8972 - 9.40 54.60 26.60 9-80 61-31 1 Spanish ... 0.9073 - 7.30 65.80 43.40 7-54 66.23 Corsican . . . 0.9012 - s.00 60.20 40.13 '7.00 68.55 ,4frican ... 0.9006 - 8.06 65.80 42.93 8-05 63.19 Bourbon ... 0.8905 - 8.20 '74.00 56.00 6.65 71.3s Indian ... 0.8960 - 0.48 43.00 9.60 11.30 8-1-62 The solubility of the different oils in dilute alcohol was practically the same, volume of oil dissolving in 0.9 to 1 volume of 80 per cent, alcohol, or in 2 to 2.3 volumes of 70 per cent'.alcohol at 15" C. The authors consider that it may be possible to base a method of distinguishing between oils from different sources on the fact that those containing much free acid undergo oxidation inore rapidly than oils containing a smaller amount, such as palmarosa oil (Cannes oil), c. A. &I. Detec5on ol Io:ion=: in Violet-scented Preparations ; and Scprra5im of the TWQ Varieties thereaf. R. Schmidt. (.%its. aizgczo. Clzenz., 1900, 189.)-If the original substance is an alcoholic solution, it is poured into twenty times its volume of water, and extracted twice with ten volumes of ether; the ether is washed two or three times with water, filtered through a double paper, and distilled off. If the162 THE ANALYST. substance is a solid, it may be thoroughly distilled in a current of superheated steam as long as any volatile matter passes over, extracting the distillate with ether.Pomades may be treated with warm 80 per cent. alcohol two or three times, separating the fat by solidification, then distilling the alcoholic extract (after removal of the solvent) as before. The crude material thus obtained is ready for quantitative analysis, or it can be purified for qualitative purposes only by a distillation at a pressure of 1 2 millimetres, collecting the liquid which comes over between 125" and 135" C. Melting-point Detc7.mi7zutio7z.-0.5 granime of the oil is mixed with a cold solution of 0.5 gramme of parabroruophenylhydrazine in 2.5 grammes of glacial acetic acid. According to the amount of ionone present, the mass either solidifies directly, after an hour or two, or after the addition of drop of water; the crystals are dried on a porous tile.The melting-point of the parabromophenylhydrazone of crude p-ionone lies between 110" and 115" ; the presence of a-ionone may raise the observed tempera- ture t o 140". By repeated recrystallization from hot alcohol or light petroleum the a-ionone derivative may be isolated, and will give the proper melting-point of 142" to 143". Contamination of the ionones with other ketones or aldehydes will either greatly lower the melting-point, or prevent the formation of crystals. Separation of the Ketones f y o m other Siibstaizces (Von Baqer's Process).-Fifty grammes of the oil are agitated mechanically for ten hours with 83 gramrnes of p-hydrazobenzene sodium sulphonatc dissolved in 500 C.C.of water, and 2 grammes of strong sulphuric acid diluted with 50 C.C. of water. The mass is made alkaline with 3 grainmes of anhydrous sodium carbonate, and mixed with enough ammonium sulphate (200 or 250 grammes) to cause the liquid to separate into three layers when treated with ether. The whole is extracted twenty times with ether, and the two aqueous layers are distilled with 150 gramiiies of phthalic anhydride in steam, taking up the volatile oil in ether. The solvent is boiled off under reduced pressure, and the residue is fractioned at 12 millimetres pressure, retaining the distillate between 125" and 135*, which contains the ionone. Separatiou and I&mti$cntion of u- c u d P-Ioiione.-This method is the one described in G ~ Y .Pat., 106, 512 [cf. E I Z ~ . Pat., 1944, 1899 ; .J. S'oc. Chcm. Iizd., 1900, 69-ABS.]. If only a qualitative identification of the two ketones he desired, the operation may be conducted on the crude oil recovered as above ; but if a quantitative separation be necessary, the product of Von Baeyer's process must be used. Seventy-five grammes of commercial bisulphite solution are warmed on the water-bath, neutralized with 10 per cent. soda solution (about 25 grammes), and acidified again with 10 or 12 grammes of bisulphite. This mixture is boiled under an inverted condenser with 15 grammes of alcohol and 95 grammes of ionone for ten to twenty-five hours, according to the purity of the ketone, until a small sample of the liquid gives only a faint turbidity with water.I t is then diluted with 2 volumes of water, the undissolved ionone extracted by three agitations with ether, and the aqueous portion distilled in a current of steam as long as oily drops pass over, and until the contents of the retort begin to froth. The p-ionone in the distillate is collected with ether; t o the retort are added 30 grammes of sodium hydroxide, and the a-ionone recovered by distillation as before. To identify the a-ionone, its parabromophenylhydrazone is This process is not quantitative.THE ANALYST. 163 prepared, which melts before purification at 138" to 140°, after recrystallization from hot alcohol at 143" or, if heated fast, sometimes at 145" C. It crystallizes from petroleum in hexagonal plates, from alcohol in rhomboids, The /I-ionone is identified by means of its seinicarbazone, which, from alcohol, gives firm white crystals, becoming yellowish in air, and melting at 148".The compound is readily broken up by warming with dilute hydrochloric acid, and the p-ionone may be converted into its parabromophenylhydrazone, which crystallizes in large rhombs from alcohol, and melts at 118" C. If the mixed ketones consist mainly of p-ionone, as will be shown by the first melting-point test coming out between 110" and 116", a qualitative separation may be effected more rapidly its follows : 10 graiiimes of the original oil fraction are mixed with a, solution of 7 grammes of semicarbazide hydrochloride and 10 grammes of sodium acetate in 40 C.C.of water, and sufficient alcohol to insure dissolution; and the whole is allowed to rest twelve or fifteen hours. I t is then precipitated with water, the semicarbazone collected, washed with water, and dissolved in about 50 grammes of spirit. After a time the bulk of the /I-ionone derivative crystallizes out, and much of the remainder can be recovered by stirring with a rod, starting the crystallization again with a crystal from the first yield. This P-ionone-semicarbazone is filtered off, washed with weak alcohol, and recrystallized; it melts at 148" C. The alcoholic mother liquors containing the a-ionone are warmed for two minutes on the water-bath with a little dilute sulphuric acid, poured into water, and the oil collected by means of ether. From this the parabromophenylhydrazone of a-ionone may be prepared, and recognised by its appearance.F. H. I;. Volumetric Estimation of Tannin. L. Specht and F. Lorenz. (Chenz. &it., 1900, xxiv., 170,)-This process depends on the precipitation of safraniiie as a tannin- antimony lake, using an excess of dye, and determining that excess by titration with a standardized hydrosulphite. The reagent is prepared by suspending 50 grammes of zinc dust in 100 C.C. of water, and adding, at a temperature not exceeding 36" C., 600 C.C. of a 20" Beaume solution of ammonium bisulphite previously neutralized with ammonia. When the precipitate has settled, 75 C.C. of the clear supernatant liquor are diluted to 2 litres, and the solution is again clarified by subsidence. To standardize the hydrosulphite, it is titrated against (1) a weak aqueous solution of safranine '' T extra," of the badische Anilin Fabrik, twice recrystallized from alcohol, and (2) against the same volume of water just tinted pink with the dye solution.From the iigures so obtained are calculated the value of the hydrosulphite in terms of safranine, and the amount of reagent destroyed by the oxygen dissolved in the water. To carry out the analysis, about 0-16 gramme of tannin, 0.2 gramme of tartar emetic, and 0.33 gramme of safranine are dissolved separately, mixed together, diluted to 2 litres, and allowed to stand for five or six hours, with occasional agitation. A portion of the clear liquid is finally titrated with the hydrosulphite till the colour disappears. Deducting from the volume of reagent used the quantity decomposed by the oxygen dissolved in the water, the remainder indicates the amount of safrenine unprecipitated; and thus the weight of dye in the lake, or the value of the tannin, may be deduced,164 THE ANALYST.I n order to express the latter in figures, parallel experiments with a pure tannin, or with a tannin of known degree of purity, must be conducted simultaneously. The titration should be done in a beaker under a layer of oil, the jet of the burette entering the aqueous liquid ; and the hydrosulphite should be stored in a reservoir, connected as usual to the base of the burette, and also covered with oil. The reagent thus retains its strength practically unchanged for twelve hours. All the water employed should be thoroughly boiled.When using pure tannin as the standard, the substance should be air-dried merely, the proportion of moisture in it being determined in a separate portion. F. H. L. Estimation of Uric Acid by Precipitation as Ammonium Urate. E. W6rner. (Zeits. physioL Clzem., xxix., 70 ; through Zeits. a?zgc~i*. Chem., 1900, 141.)-This process depends on Fischer's statement ( B e y . , 1899, xxxii., 3266) that uric acid can be heated with dilute caustic soda without losing ammonia. 150 C.C. of urine are warmed to 40" or 45" C., and 30 grammes of ammonium chloride are dissolved in it. After standing for about an hour the precipitated arnmonium urate is filtered off and washed with a 10 per cent. solution of ammonium sulphate till it no longer gives a chlorine reaction. The residue is dissolved in hot 1 or 2 per cent. caustic soda, and the paper is washed with hot water. The filtrate is then heated on the water- bath until all free ammonia has disappeared, and finally kjeldahled with 15 C.C. of strong sulphuric acid and a little copper sulphate. One C.C. of decinormal sulphuric acid corresponds to 0.0042 gramme of uric acid. It seems improbable that other substances should be thrown down from the urine by this treatment. Small amounts of albumin are without effect; larger quantities are objectionable. Urines containing urate or phosphate deposits can be used directly. F. 13. L.

ISSN:0003-2654    

DOI:10.1039/AN9002500160

出版商:RSC    

年代:1900

数据来源: RSC

摘要:

164 THE ANALYST. I N O R G A N I C A N A L Y S I S . Lead Assay. J. Flath. (Chem Zeit., 1900, xxiv., 263.)-The author states that the process of determining lead in ores, residues, etc., by reduction under fluxes in a wrought-iron crucible is more accurate tha,n is often imagined. He quotes results obtained with fourteen products found to contain by wet analysis from 1-25 to 76.15 per cent. of lead, which shorn a maximum deficiency of 1.48 (mean - 0.79) per cent. in the yield calculated on the samples when treated by the fusion method. The best composition of the flux either for an acid or a basic material is sodium carbonate, 70 parts ; borax, 28 parts ; and potassium bitartrate, 2 parts ; but the proportions need not be maintained exactly. F. H. L. Determination of Thallium as Normal or Acid Sulphate.P. E. Browning. (Zeits. anorg. Chem , 1900, xxiii., 155.) -Thallium can be determined as acid sulphate by heating its chloride with sulphuric acid to a temperature between 220" and 240" C., or as normal sulphate by igniting it similarly at a, dull-red heat. Both processes are perfectly satisfactory. F. H. L.THE ANALYST. 165 The Rapid Evaluation of Metallic Tungsten Powders. F. Ibbotson and H. Brearley. (Chemical News, vol. lxxx., pp. 294, 295.)-The following method is more rapid than the usual one, and gives as near an approximation to the truth ; Three grammes of the substance are weighed in a tared platinum dish, then ignited to tungsten trioxide and weighed (A). After treating the mass with hydrogen fluoride it is re-weighed (B), the loss indicating silica.To the residue is added water and pure sodium hydroxide, and the whole is diluted to 200 to 300 c.c., boiled, filtered through paper pulp, ignited, and weighed (C), then treated with a little hydrochloric acid, diluted, filtered, and the precipitated trioxide ignited, and weighed (D). B =tungsten trioxide and its iron and manganese compounds, which in turn are represented by C - D ; therefore B - C + D = the amount of tungsten trioxide. The residue D and the filtrate from the sodium hydroxide treatment contain the whole of the tungsten, which may be estimated direct if required; and the filtrate obtained previous to the final weighing (D) contains the iron and manganese. S Z ~ ~ ~ Z Z U , if not removed during the hydrochloric acid treatment or in roasting, makes the results too high.It should not, however, be present in tungsten powders used for steel-making. Cc~rbon may be estimated by roasting in a current of oxygen, or by combustion with lead oxide. c. s. The Action of Ammonia upon Magnesium Salts. W. Schieber. (Oeste7.1". Chem. Zcit., 1900, iii. , 83.)-According to the text-books, magnesium salts are not quantitatively precipitated by ammonia, while if sufficient ammonium salts are present no precipitate is formed at all. These phenomena are explained by the pro- duction of a double compound of the typical formula (MgClJ(NH&, which is not decomposed by ammonium hydroxide. It is noticeable that the authorities say nothing about the influence of temperature; these statements refer only to cold solutions; in hot liquids, even in presence of 4 molecules of an ammonium salt per 1 molecule of magnesium, sufficient ammonia will cause a turbidity, if not a precipitate.The matter is important in water analysis, where alumina is thrown down by boiling with ammonia, for the deposit may also contain magnesia, which is scarcely capable of re-solution under the working conditions. From a special series of experiments the author finds that to insure all magnesium remaining in solution in such separa- tion it is necessary to have an excess of ammonium chloride, and to use as little ammonia as possible. Employing normal solutions of magnesium sulphate, ammonia, and ammonium chloride, the following ratios show the maximum proportion of ammonia and the minimum proportion of ammonium chloride which will allow the mixtures to be raised safely to the boiling-point : ' MgSO, K H, lSH,Cl 1 2 1 1 10 2 F.H. L. Composition of Ammonium Magnesium Arsenate. M. Austin. (Zeits. anorg. Chem., 1900, xxiii., 146.)-This precipitate will be obtained of theoretical compo-166 THE ANALYST. sition provided a faintly acid solution of arsenic acid, free from ammonium salts, is treated with 30 C.C. of ammoniacal magnesia mixture more than is necessary to throw down the arsenic, the total volume of liquid not being allowed to exceed 200 C.C. If the precipitate is filtered off and washed with 25 C.C. of ammoniacal water, no arsenic will remain in solution. Ammonium chloride has a slight solvent action upon the double arsenate ; and although this effect can be overcome by employing a larger excess of magnesia mixture, the chloride also has a tendency to cause the displacement of part of the magnesium by ammonium in the original precipitate.The author’s magnesia mixture contains 110 grammes of crystalline magnesium chloride and 58 grammes of ammonium chloride in 2 litres of water, to which are added 10 C.C. of 6‘ ammonia.” IF. H. 1;. Phosphotungstic Acid as a Test for Potassium. E. Worner. (D. Pharm. (78s. Bey., 1900, x., 4 ; through Chenz. Zeit. Be]>., 1900, 48.)-A 10 per cent. solution of ordinary crystalline phosphotungstic acid forms a more sensitive reagent for potassium than either platinic chloride or tartaric acid. From acid solutions the potassium salt falls in coarse crystals, from a neutral solution it separates in a very fine state of subdivision, rendering the liquid milky.Barium, strontium, calcium, and magnesium are not thrown down by the reagent ; sodium chloride is only pre- cipitated from a saturated solution, and the deposit dissolves immediately on dilution. .hmonium compounds must be previously removed. F. H. L. Estimation of Iodic Acid in Sodium Nitrate. R. Aueenat. (Il/loonit. Scieizt., 1900, xiv., 72 ; through G‘hem. Zeit. Bep., 1900, 48.)-Six similar test-tubes, 18 centimetres tall and 25 millimetres in diameter, each provided with a mark at the 50 C.C. point, are placed side by side in a stand in front of a white background. In the first are put 10 C.C. of a solution of potassium iodate (1 gramme per litre) ; in the second 30 c.c., in the third 35 C.C.. . . in the sixth 50 C.C. of a solution of the nitrate under examination (33 grammes per litre). The tubes are then filled up to the mark with water, and 2 C.C. of 10 per cent. potassiuni iodide and 5 drops of glacial acetic acid are quickly added to each. After shaking gently and standing for ten minutes the colours are compared with the standard tube (No. 1); but if none of them is a satisfactory match, the whole test is repeated with a different quantity of potassium iodate. Coinmercial sodium nitrate generally contains iodic acid equivalent t o 1 or 2 per cent. of sodium iodate. F. H. L. Determination of Phosphoric Acid as Phospho-Molybdic Anhydride. J. Isanamann. (Zeits. Zundiu. Versz~chszu. Ocstcrr., 1900, iii. , 53 ; through C7~e.m.Zeit. Rep., 1900, 72.)-The author strongly advocates the direct method of estimating phosphoric acid indicated by the above title. He employs the Wagner-Stutzer reagent : 150 grammes of ammonium molybdate and 400 grammes of ammonium nitrate dissolved in two Zitres of water and poured into 1 litre of 1.19 nitric acid. Twenty-five C.C. of the phosphate solution are mixed with 50 C.C. of the reagent,THE ANALYST. 167 warmed very slowly up to 40" C., and stirred for ten minutes ; the precipitate is washed with acid ammonium nitrate, then with alcohol, and dried, ignited, and weighed. His factor for the conversion into P20s is 0.03946. F. H. L. This ignition must be done uniformly, avoiding too great heat. Erdmann's Reagent [Ami3onaph%hol-K-Sulphonic Acid] for B itrites in Water. H. Mennickc. ( Z e i t s . C L ~ Z ~ C Z U . Chem., I900,235.)-The present author agrees that Erdmann's new reagent (this vol., p. 81) is most useful. Its indications are perfectly certain. They are not affected by the presence of ferric chloride, nitric acid, or other oxidizing agents ; a large excess of the latter bodies only causes the colour to be more wine-red. The limit of sensitiveness for a sharp eye in daylight is 1 part of sodium nitrite per 300 million--i.c., it is about 300 times inore delicate than starch and potassium iodide. The colour attains its maximum intensity in half an hour. Mennicke quotes analyses of several town and waste waters which fully bear out his statements. F. H. L. ~

ISSN:0003-2654    

DOI:10.1039/AN9002500164

出版商:RSC    

年代:1900

数据来源: RSC

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THE ANALYST. 167 APPARATUS. New Form of Water-bath Regulator. H. S . Hatfield. (Chenzical News, vol. lxxxi., p. GEi.)-To obviate the stoppage of the supply by accumulations of air in the ordinary syphon- tube regulator, the author employs the form illustrated in the drawing. The supply-tube is bifurcated, one limb dipping under the liquid of the bath, and the other being open to the air at A. The water in the bath will rise only slightly above the level of A, the excess being due to the force necessary to divert the stream. All the tubes must be full of water; any air-bubbles formed are swept away by the current, which must be strong enough for this purpose. The water must leave the sides of the glass at A. c. s. Apparatus for the Analysis of Illuminating and Fuel Gases. G.E. Thomas. (Jozmz. Anzcr. Chenz. Soc., vol. xxi. [la], pp. 1108-1112.)-The apparatus measures 16 inches long by 15 inches high. The burette, 1, is graduated to 100 c.c., 40 of which (the bulb, 3) are in whole divisions, and the rest in 0-2 C.C. I t is fitted with platinum terminals, 4, 5, and filled with water acidified with sulphuric acid to decrease the solubility of the carbon dioxide. The absorption bottles, 15,16, 17, and the storage bottle, 18, are connected with the burette by a capillary tube, c , and the T tubes shown, these latter being provided with rubber connections. Nos. 15 to 17 are fitted with stop-cocks, Z), c, d. Bottle 15 is filled with caustic potash solution, the surface being increased by the use of glass tubes ; No. 16 contains bromine water, and No.17 (protected from light) phosphorus under water. The burette and capillary tube, 10, being filled with water by raising the levelling168 THE ANALYST. tube, 7, the tap, a is closed, 10 is connected with the gas supply, and 100 C.C. of gas are drawn into the burette by lowering 7 and reopening a. The gas is then forced into bottle 15, the operation being thrice repeated, and the loss (carbon dioxide) in volume measured after draining. The illuminants and oxygen are then measured by absorp- tion in bottles 16 and 17 respectively, care being taken to absorb the bromine vapours in the gas bybottle 15 before measuring the residual gas. The unabsorbed remainder is collected in 18 for explosion tests. For these latter about 80 C.C. of air are drawn into the burette through 10, followed by about 15 C.C.of gas from 18, water being drawn through the capillary as far 3s a from bottle 17. The mixed volume having 5 34 ‘ 2 been carefully measured, mixing is completed by passing the air and gas into 15 and back again. The tap, a, is closed and the pressure reduced by lowering 7 ; and a water-seal is formed by bending the rubber tube and securing it in a slit in the frame. The spark is then passed, the explosion being very mild owing t o the peculiar con- struction of the burette; and, when cooled down, the contraction in the volume, the amount of carbon dioxide, and the excess of oxygen are determined successively, the water from the burette being finally forced through the capillary system into 17, to insure complete absorption. The final volume contains only the nitrogen in the air plus that in the gas. For fuel-gas analysis 17 and 18 are charged with cuprous chloride solution, air being excluded by a seal of petroleum in the funnels. A lubricant is necessary to insure success, vaseline being suitable for the bromine bottle. c. s.

ISSN:0003-2654    

DOI:10.1039/AN9002500167

出版商:RSC    

年代:1900

数据来源: RSC