摘要:

THE ANAL Y'S'I'. MARCH, 1896. THE DETERMINATION OF OXYGEN I N COMMERCIAL COPPER. BY BERTRAM BLOUNT, F.I.C. (Rend at the Meeting, February 5 , 1896.) THE only conventional method with which I an1 acquainted for the determination of oxygen in commercial copper consists in dissolving the metal in a solution of silver nitrate, and estimating the oxide of copper, which is supposed to be left as a basic nitrate, by solution in standard sulphuric acid and titration of the excess of acid by sodium carbonate. As commonly formulated, this method includes no precautions for ensuring regularity of action between the copper and silver nitrate, although, granting all other assumptions, such regularity is essential for the attainment of accuracy. I n a recent investigation on the atomic weight of copper, the conditions requisite for the regularity of the reaction in question have been laid down.The58 THE ANALYST. condition of most moment is that the solution shall be kept at a low temperature, preferably at 0" C., for otherwise a smooth exchange between copper and silver does not take place, but an oxidation of the copper at the expense of the NO, group occurs, with the result that the residue of silver left after the reaction has been brought to a close contains basic cupric nitrate, not owing its presence to oxygen existing in the copper under analysis, but due to the nitrate of silver used as a reagent. On observing the precaution of conducting the operation in a vessel buried in chips of ice, no difficulty arising from irregularity of interaction is experienced.Solution proceeds slowly, but eventually reaches the limit set by the relative quantities of the substances concerned. It is usual to employ a weight of copper somewhat greater than can be dissolved by the quantity of silver nitrate taken. A single strip of the metal is convenient, because the recovery and re-weighing of the undissolved portion is then an easy matter ; when several small pieces are used, one may be overlooked in the mass of spongy silver which is precipitated. An additional precaution may be taken by filling the flask in which the reaction is carried out with CO,, so as to avoid possible oxidation of the copper during solution, and, for the same reason, using boiled-out water. The conscientious operator having done all this and more, soon becomes aware that the method is entirely worthless.I n point of fact, the more carefully he excludes chance oxidation, the more erroneous are his results, for the method, when skilfully worked, fails to find any oxygen whatever in ordinary commercial copper, although that body is certainly present. The reason will be given in a later portion of this communication. Having purged the silver nitrate method from accidental errors with the incidental discovery that its indications depended wholly on their occurrence, I turned my attention to other methods that seemed feasible on u priori grounds. Thus copper, in the form of thin turnings, was heated in a glass combustion-tube in a stream of hydrogen ; the reduction was, however, only superficial.Next, copper, in the form of small bars, such as could be cut out of fire-box plate, was heated in an atmosphere of nitrogen, and sulphur vapour was then passed over it. Reaction readily occurred, and it was easy to convert the whole of the bar into a sulphide which approached the composition Cu,S when the temperature was fairly high, but always contained rather more sulphur than corresponded with this formula. In adapting this method to practical requirements, the copper was placed in a boat in a combustion-tube, and the sulphur (recently fused) in another boat a little behind that containing the copper. Nitrogen, prepared froin ammonium chloride and potassium nitrite, washed, dried, and purified by passage over red-hot copper, was caused to expel the air in the tube containing the boats in which were respectively the sulphur and the copper.When the displacement of air was complete, the portion of the tube in which was the boat containing the copperwas heated, and then that in which was the sulphur boat. Sulphur vapour was driven gently by the stream of nitrogen over the heated copper, which forthwith began to glow. Excess of sulphur was caught in a cool part of the tube beyond the copper boat, and any flowers of sulphur that might be formed were filtered oft' through an asbestos plug. The exit end of the combustion- tube was connected with an absorption apparatus containing ammonia and hydrogenTHE ANALYST. 59 peroxide. That portion of the sulphur which had been oxidized to SO, by the oxygen in the copper was caught in the absorption-tube, and finally estimated as barium sulphate.Owing to the ease with which the reaction between copper (even in pieces of large section) and sulphur takes place, a simplification of the above method was devised. A weighed rod of copper and an excess of sulphur (recently fused) were placed in a narrow piece of combustion-tube, closed at one end, which was then exhausted and s d e d . On heating this tube to a temperature just short of the softening-point of the glass, the copper and sulphur combined; on the completion of the reaction, the tube was allowed to cool, and any gas which it contained collected over mercury and anal ysed. Both methods yielded small and varying quantities of SO,, but as their working was improved and accidental presence of oxygen excluded, the quantity tended to a minimum.In short, much as in the silver nitrate method, the indications of the process disappeared when its errors were eliminated. The oxygen in commercial copper is generally assumed to exist as cuprous oxide dissolved in the metal. No doubt this is substantially true in ingot copper refined and containing no appreciable amount of impurity save oxygen, but not brought to tough-pitch. In copper intended for structural use, on the other hand, impurities other than oxygen, notably lead, are almost invariably present. There is no reason to suppose that the oxygen of such tough-pitch copper is present as cuprous oxide. Lead oxide or more complex bodies, such as lead arseniate, probably account for a considerable fraction.When copper containing oxygen in this form is dissolved in silver nitrate, the oxygen- bearing substances remain as a sludge with the spongy silver, and are substantially unattacked by the dilute standard sulphuric acid used to estimate the total basicity of the residue. The assumption on which the silver nitrate method is based is to the effect that all oxygen in the copper appears as basic cupric nitrate, a substance readily attacked by dilute sulphuric acid. Lead oxide or arseniate, on the other hand, in the refractory state which from their origin (in a mass of melted copper) they would naturally assume, would be but superficially attacked by weak sulphuric acid, and thus saturation of the acid in amount corresponding with the oxygen- contents of the copper could not occur.A similar influence appears to limit the reaction of copper containing oxygen in other forms than that of cuprous oxide when it is heated with sulphur. At the low temperature at which copper and cuprous oxide are attacked by sulphur, the more stable oxygen compounds-e.g., lead oxide- are but little affected, and the oxygen is not eliminated as SO,. Doubtless it would be possible to decompose such oxides by means of sulphur at a higher temperature, but the practical difficulty caused by the softening of combustion-tubing at such a temperature then intrudes, The method, after many trials, was abandoned, and a return made to the obvious and simple plan of reducing the copper in hydrogen. As mentioned above, only superficial reduction was obtained at any temperature below the softening-point of a glass combustion-tube.Fine division of the copper was thought undesirable, both from the risk of surface oxidation and from the difficulty of preparing filings or saw- A little reflection allows these facts to be grouped under one head.60 THE ANALYST. dust free from contamination. Recourse was had to the use of a temperature well above the melting-point of copper, the adoption of a porcelain tube set in a small injector furnace being therefore a necessity. Preliminary trials showed that it was not feasible to fuse copper in hydrogen and estimate the oxygen by loss of weight, for during the process the metal is spattered about with such violence that mechanical loss can hardly be avoided. It became necessary, therefore, to weigh the water produced by the action of hydrogen upon the melted copper, and the apparatus shown in the figure was finally adopted.The following are the principal parts : A hydrogen- generator containing zinc and sulphuric acid (not hydrochloric, lest vapours of that acid pass over with the hydrogen) is connected with a wash-bottle of copper sulphate solution followed by a sulphuric acid drying-tube. The oxygen of any air that may be entangled in the zinc or acid of the hydrogen-generator is eliminated by passing the gas through a, bulb-tube of platinized asbestos gently heated. Any water there formed is caught in a second sulphuric acid drying-tube, and the pure dry hydrogen (containing at worst a trace of nitrogen) enters a porcelain tube set horizontally in ti small furnace of the injector pattern driven by a blast from a Root’s blower (or bellows).The copper in which the oxygen is to be determined is cut in stout strips or bars to fit a small porcelain boat; 10 to 15 grammes may be conveniently taken. The porcelain tube, the boat, and all corks and connecting-tubes are thoroughly dried, and placed in position while so hot that they can scarcely be handled with comfort. The exit end of the porcelain tube is connected with a weighed sulphuric acid tube protected by a sulphuric acid guard-tube. (I have laid emphasis on the use of sulphuric acid tubes throughout ; they cannot be replaced by any less thorough means of drying ; calcium chloride, as always for exact work, is “useless, dangerous, and ought to be abolished.”) The inlet-tube is a I, with the right-hand horizontal limb dosed by fusion.The vertical limb is that entering the rubber cork of the porcelain tube. This little Error due to adhering moisture is thus avoided.THE ANALYST. 61 device makes it possible to look along the axis of the porcelain tube, and observe the behaviour of the copper during the process of reduction. The phenomena which occur are these : The copper suffers no visible change up to and including the time when it is at a bright red heat. No sensible action of the hydrogen upon the oxygen in the copper takes place up to this point, for no water appears in the exit tube. Just before fusion, when the metal is softening, small bubbles and excrescences appear on the surface of the copper, and evidently eject some gas.I t seems probable that hydrogen is occluded by the copper at a temperature just short of fusion, and that the bubbles are due to the escape of water-vapour from the action of this hydrogen upon’ the oxygen of the copper. However this may be, it is certain that the appearance of these bubbles is immediately followed by the formation of water, which partly condenses in the glass exit tube, and is swept on into the weighed absorption tube in the usual manner. The bubbles soon cease to form, and the copper remains in tranquil fusion with a brilliant surface. The whole reaction is over in a couple of minutes, and the furnace can be shut down. Hydrogen is passed for another five minutes, to ensure the displacement of any water which may have lodged in the exit tube.During cooling, the copper again passes through a volcanic period, and finally solidifies with a rugose surface. This second spitting (which in outward form resembles the ‘I sprouting ” of silver) is probably due to expulsion of absorbed hydrogen ; it is certainly not identical in nature with the first, for it is not attended by the forrnation of water. The violent motion of the melted copper during these two periods of disturbance causes a rain of tiny globules of copper, which coat the porcelain tube in the neighbourhood of the boat, and sometimes cause the two to adhere after cooling. This scattering of the copper is the effectual reason for the impracticableness of determining oxygen by loss of weight on heating in hydrogen.Nothing now remains but to displace the hydrogen in the weighed tube with air, and to allow it to cool for weighing. Hydrogen is supplied continuously to the porcelain tube while it cools, so that all copper therein is brilliantly clean when the tube is opened. By thus avoiding casual oxidation the tube can be kept corked indefinitely, and used on the next occasion without any precaution save a preliminary warming. every way. difficulty with which zinc oxide is reduced. I have had the method in use for a considerable time, and find it satisfactory in It is applicable to copper-tin alloys, but not to brass, on account of the DISCUSSION. Mr. BEVAN inquired what proportion of oxygen commercial copper usually contained. Mr. HEHNER asked if Mr. Blount could suggest any explanation of the difficulty in obtaining a cuprous sulphide of constant composition to which he had referred.In Rose’s well-known method for the determination of copper, which, as far as his experience went, always gave Ratisfactory results, pure Cu,S was readily obtained. Mr. BLOUNT said that the amount of oxygen present in commercial copper depended upon the proportion of other impurities. I n a high-class tough-pitch copper containing over 99 per cent. of Cu, with, say, 0.15 per cent. of arsenic and a62 THE ANALYST. similar quantity of lead, one might expect to find about per cent. of oxygen. In copper which was considerably under-poled, or in the condition in which it came direct from the refiners, the proportion of oxygen would be considerably greater. With regard to Mr. Hehner’s question, in the method which he (Mr. Blount) had described, the temperature wag considerably lower than that reached in Rose’s method ; although a very fair approximation to Cu,S could be obtained by carrying the heating as far as a combustion-tube would stand, the copper could not be said to be completely converted into Cu,S ; an excess of sulphur always remained. For the purposes of the method described in the paper, it was, however, not necessary to take any special precautions to get the copper to that point.

ISSN:0003-2654    

DOI:10.1039/AN896210057b

出版商:RSC    

年代:1896

数据来源: RSC

摘要:

62 THE ANALYST. A NEW FORM OF CARBONIC ACID APPARATUS. BY CECIL H. CRIBB, B.Sc. (LONDON). (Read at the Meeting, Febwury 5, 1896.) THE apparatus is intended for the estimation of carbonic acid by the ordinary loss of weight method, and is identical in principle with the numerous forms at present in use. Of course anyone with a small flask, a cork or two, and some glass tubing can construct an appliance for himself which will answer every practical purpose, but that there is a demand for a more elaborate and specialized form of apparatus is obvious from an inspection of the catalogues of the makers of chemical apparatus, and from a glance round the shelves of most laboratories. Quite apart from the merits or demerits of the method itself, which can only be regarded as one of moderate accuracy, most of the apparatus now in use suffer from more or less grave defects or inconveniences, and it is with a view of remedying some of these that The central tube the form represented in the diagram has been designed. I t consists of a wide-mouthed vessel, A, in which the substance to be analysed is placed, and an upper part composed of an absorption chamber, B, in which the carbonic anhydride is dried before escaping, together with a reservoir, C, for the acid used to decompose the carbonate.To prevent any of the acid in C from prematurely reaching the carbonate, owing to the expansion of the air in C during the pre- liminary handling of the apparatus, a little trapped tube, D, is attached by indiarubber. It also serves another purpose, which is mentioned later.The drying-chamber is charged by removing the stopcock, E, and dropping in the requisite quantity of sulphuric acid. Should too much be added, the excess may be poured out through G. may with advantage be filled with broken up pumice-stone, or ranulated calcium chloride may be used if preferred, as the desiccating agent. To fill C with acid, the stopcock at F is taken out, and the little tube D is bent kink ” in the indiarubber thus quite closing upwards parallel to the side of C, theTHE ANALYST. the passage through D. When the stopcock is replaced and turned off, and D is allowed to fall down into its norlnal position, no liquid will leave the chamber, C, as long as the tap remains closed. When thus prepared the apparatus is weighed, and the substance to be examined inserted through the wide mouth of A.It is then weighed again, and the decomposi- tion of the carbonate is commenced by turning on first the tap at E and then that at F. The following are the chief advantages of the apparatus : The substance to be analysed is introduced with the greatest ease, and the residue left after the analysis can be completely recovered and used for other deter- minations. The lower vessel can be cleaned out and wiped dry with a cloth, so that another analysis can be commenced in a few minutes, The drying-chamber allows of the use of solid or liquid absorbents ; and in the case of the latter the length of the central tube renders any loss of acid, owing to a sudden evolution of gas, practically impossible if the tube be filled with broken pumice.The comparatively large capacity of C, which holds over 25 c.c., enables a considerable weight of material to be operated upon. If desired, a measured quantity of standard acid could be employed, the residue in A being titrated back with standard alkali, thus giving a check on the gravimetric estimation without extra weighings. If the little trapped tube is used, and is long enough to reach the bottom of A, the action becomes automatic, like that of a Kipp’s apparatus, so that in com- mencing an analysis it is only necessary to turn on the taps at E and F, when the evolution of gas mill proceed quietly until decomposition is complete, provided, of course, that the pressure of the column of liquid in C and D is more than sufficient to overcome the resistance interposed by the drying-chamber to the exit of the gas through E. The two taps at E and F allow of a current of dry air being drawn through at the end of the analysis to remove residual carbonic anhydride, and alao serve to shut off the drying-chamber completely from the external air when the apparatus is not in use.The lower vessel, A, which is the part exposed to the greatest heat, is easily replaced in case of fracture. The apparatus was made for me by Messrs. C. E. Miiller and Co., of 148, High Holborn, from whom it can be obtained. The acid may then be poured in through F. DISCUSSION. Mr. HEHNEN said that, while he acknowledged the ingenuity of the apparatus devised by Mr. Cribb, his experience led him to think that the old double-flask arrangement of Fresenius and Will was in no way surpassed by the many modifica- tions of it, which seemed mainly designed to show the glass-blower’s skill.He had come to the conclusion that, in order to obtain a reliable result with any arrange- ment of the kind, in which the carbon dioxide was measured by the loss in weight, so many precautions had to be taken that it was in every way preferable to determine64 THE ANALYST. the carbon dioxide by absorption. Unless the evolution of the gas was very slow, and sulphuric acid tubes were joined to the apparatus both at the inlet and exit, correct results could only be obtained by chance. He did not think that it was worth while to bestow any thought upon the construction of new forms of the Schroetter device.Mr. ALLEN said he thought the determination of carbon dioxide was liable to be very erroneous in any apparatus in which it was requisite to dry the gas by a considerable quantity of sulphuric acid. The amount of gas absorbed by the acid was much larger than was commonly supposed, and in some cases sufficient seriously to affect the accuracy of the results. Mr. DIBDIN said that, from a somewhat extensive experience in the determination of carbonic acid in mortar, lime, etc., he had come to the conclusion that all methods of estimating this constituent by displacement were much to be mistrusted; and he preferred for exact determination to absorb it directly over mercury. The PRESIDENT said he quite agreed that carbonic acid could be really satis- factorily determined only by absorption, although the ingenuity of Mr. Cribb’s arrangement was certainly very praiseworthy. Mr. CRIRB disclaimed any special admiration for apparatus of this kind, and said that as a matter of fact this modification had been designed in a fit of irritation at the shortcomings of the existing forms. The point mentioned by Mr. Allen as to the absorbing power of sulphuric acid, was entirely new to him. He thought, how- ever, that it would hardly affect the results obtained by the method under discussion, inasmuch as the passage of a current of air through the acid would remove almost all the carbonic anhydride that had previously been absorbed. While not regarding the loss of weight method of estimation as one of great accuracy, he found it both convenient and rapid under certain circumstances, and thought that by the new form of apparatus both the speed and the accuracy of the process had been increased. Working wiihout any special precautions, he generally found that duplicate estima- tions did not differ by much more than 0.1 per cent.

ISSN:0003-2654    

DOI:10.1039/AN8962100062

出版商:RSC    

年代:1896

数据来源: RSC

摘要:

64 THE ANALYST. ABSTRACTS OF PAPERS PUBLISHED IN OTHER JOURNALS. FOOD ANALYSIS. Estimation of Boric Acid in Milk. R. T. Thomson. (Ghsgozu Cit!j ~ l ~ a l . SOC. Repts., 1895, p. 3 . ) - h e to two grammes of sodium hydrate are added to 100 C.C. of milk, and the whole evaporated to dryness in a platinum dish. The residue is thoroughly charred, heated with 20 C.C. of water, and hydrochloric acid added drop by drop until all but the carbon is dissolved. The whole is transferred to a 100 C.C. flask, the bulk not being allowed to get above 50 to 60 c.c., and 0.5 granlllle dry calcium chloride added. TO this mixture a few drops of phenolphthalein solution are added, then a 10 per cent. solution of caustic soda, till a permanent slight pink colour is perceptible, and finally 25 C.C.of lime-water. In this way allTHE ANALYST. 65 the phosphoric acid is precipitated as calcium phosphate. The mixture is made up to 100 c.c., thoroughly mixed and filtered through a dry filter. To 50 C.C. of the filtrate (equal to 50 grammes of the milk) normal sulphuric acid is added till the pink colour is gone, then methyl orange, and the addition of the acid continued until the yellow is just changed to pink. Fifth-normal caustic soda is now added till the liquid assumes the yellow tinge, excess of soda being avoided. At this stage all acids likely to be present exist as salts neutral to phenolphthalein, except boric acid, which, being neutral to methyl orange, exists in the free condition, and a little carbonic acid, which is expelled by boiling for a few minutes.The solution is cooled, a little phenolphthalein added, and as much glycerine as will give at least 30 per cent. of that substance in the titrated solution, and titrated with fifth-normal caustic soda till a distinct permanent pink colour is produced; each C.C. of fifth-normal soda is equal to 0.0124 gramme crystallized boric acid. A series of experiments with this process showed that no boric acid was precipitated along with the phosphate of calcium so long as the solution operated upon did not contain more than 0.2 per cent. of crystallized baric acid, but when stronger solutions were tested, irregular results were obtained. The charring of the milk is apt to drive off boric acid, but by carefully carrying the incineration only so far as is necessary to secure a residue which will yield a colourless solution, no appreciable loss occurs. W.J. S . Relative Efficiency of Various Preservatives in Milk. R. T. Thomson. (Glasyow City d i d . SOC. IZepts., 1895, p. &)--The author kept measured quantities of the same milk, to which the various preservatives were added, in stoppered bottles, under identical conditions, and examined them from time to time. The following table gives the result of the observations : Preservative used. (Pure milk) . . . Formic aldehyde (40 P.C.) I , 9 9 3 s I , Boric acid . . . . . . Boric acid + borax (calculated to boric acid) fjalicylic acid . . . Benzoic acid . . . Grains of Preserva- tive per ;al. of milk - 8-75 -0125 p c . 17.5 .0dt5 p.c. :z 6 .05 p.c. 35 .0*5 p.c. :3 5 17'5of ea.17.5 -025 p.c. :1: 5 -05 p.c. li*.i -025 p c . After standing 2 days. Distinctly turned Sweet Sweet Sweet Sweet Sweet Sweet Sweet Sweet After tanding 4 days. Slightly sour Sweet Sweet Sweet Sweet Sweet Sweet Sweet Sweet After tandinq 6 days. Sour Sweet Sweet Sweet Turned Sweet Sweet Sweet Slightly turned After standing i days. Sour and cnrdled Sweet Sweet Sweet Sour and curdled Sweet Turned Sweet Sour 4fter 8 days. Lactic Acid, per cent. - -68 Sweet -1 2 Sweet '10 Sweet -07 4 2 Sweet -10 Sour -26 Sweet -10 Sour '4 5 After 11 days. Lactic Acid, per cent. - -7 I ;our & curdled -43 Sweet -14 Sweet -10 -62 Sour -32 -42 Sour -33 '52 It will be seen that boric acid alone was not so effective as the mixture of boric acid and borax, the mixture being so made that each contributed 17.5 grains of66 TEE ANALYST.crystallized boric acid per gallon. Thirty-five grains of boric acid per gallon is the amount generally found in milks in which it is used. Formalin shows itself to be by far the most effective of the preservatives. The author concludes with a few reinarks on the physiological effects of the preservatives, in which he deprecates the practice of using them without having full proof that they are harmless, or without letting consumers know what they are getting. He quotes the following words of Dr. Leffmann : ‘‘ Processes of digestion are allied to processes of decomposition, in so far that the latter are frequently preceded by transformation under the influence of ferments. We may infer, there- - fore, that whatever prevents putrefaction must at least delay digestion.” W.J. S. Determination of the Dry Extract of Wine. L. Magnier de la Source. (Ann. de Chim. Analyt., i., 7.)-The present method is proposed as a substitute for the author’s process of evaporating the wine in vacim without the application of heat where the operator does not possess the necessary apparatus for the production of a vacuum. For the modified process only a few instruments are required-a balance capable of weighing to a milligramme, a bell-glass fitting on a glass plate, a, few cylindrical glasses 5 c.m. wide and 2 em. high, a pipette, and small quantities of sulphuric acid and phosphorus pentoxide, being sufficient to ensure results accurate enough for all practical purposes. The glass containing the wine is placed under the bell-glass, and left there for about three days in presence of concentrated sulphuric acid. At the end of this time, the sulphuric acid dish is removed and substituted by one containing a little phosphorus pentoxide; another couple of days sufficing to complete the desiccation without the necessity of exhausting the receiver, thus saving the double operation generally practised. To find the amount of the extract, the test-glass, previously tared, has then merely to be weighed, and the difference to be multiplied by 200 to express the result per litre. These agree fairly well with those from the vacuum process, and will be, Five C.C. of wine are taken. with a little care, exact to within a margin of 0-5 gramme. c. d.

ISSN:0003-2654    

DOI:10.1039/AN8962100064

出版商:RSC    

年代:1896

数据来源: RSC

摘要:

66 THE ANALYST. TOXl COLOGICA L AN A LYSIS. The Toxicity of Acetylene. L. Brociner. (Compt. Rend., 1895, cxxi., 773 ; through Chenz. Zeit. Rep., 1895, 416j.-Blood dissolves about 0.8 of its volume of acetylene, most of which it loses on exposure to air in the cold, the rest at 60" C., while the whole disappears when placed in a vacuum. Examined with the spectro- scope, the solution has no characteristic appearance, resembling rather normal oxygenated blood, and it is reduced by ammonium sulphide in a manner precisely similar to the latter. If there be any compound of acetylene and hznioglobin, it must be very unstable. Acetylene cannot be considered any more poisonous than other hydrocarbons, such its methane, etc., for animals can survive its action even for many hours, if sufficient oxygen is present, and the atmosphere is renewed at intervals. F. H. L. Purification of Sulphuretted Hydrogen bymeans of Iodine. Z. H. Skraup. (Zeits. ostew. Apotl~. Ver., 1896, xxxiv., 72 ; through Chern. Zeit. Rep., 1896, 22.)-THE ANALYST. 67 Jacobson and Brunn’s process for the removal of arsenic from this reagent, which consists in the employment of iodine, has been investigated by the present author, who finds that so long as not more than about 10 gramrnes of the gas are used in each test, the purification is sufficiently complete even for legal work. F. H. L.

ISSN:0003-2654    

DOI:10.1039/AN8962100066

出版商:RSC    

年代:1896

数据来源: RSC

摘要:

THE ANALYST. 67 ORGAN I C AN A LY S IS. Saponification in the Cold. R. Henriques. (Zeit. angew. Chem., 1895, pp. 721-724.)-The determination of the Kottstorfer and Reichert-Meissl numbers is in many ways simplified by carrying out the saponification in the cold, instead of by the usual process of boiling with alcoholic potash. From 3 to 4 grammes of the substance are dissolved in a flask with 25 C.C. of petroleum spirit, and treated with 25 C.C. of alcoholic soda of about normal strength. The saponification is complete in a few hours, but it is advisable to let the flask stand over-night, especially in the case of wool-fat and waxes. The titrating back of the excess of alkali is carried out in the usual manner. Where the soap has gelatinized, the flask should be gently warmed on the water-bath before titration, a little more alcohol being added if necessary.Since waxes are only sparingly soluble in cold petroleum spirit, a slight modifica- tion of the process is necessary in their case. The substance is dissolved in warm petroleum spirit of a higher boiling-point (100" to 150" C.), the alcoholic potash then added, and the whole allowed to stand for 24 hours in the cold. By using 3 to 4 grammes of the substance instead of the smaller amounts usually taken, the risk of errors introduced in measuring out and titration is considerably reduced. Another advantage of this over the old method is the avoidance of the alterations produced in strong alcoholic soda on continued boiling. The following are saponification numbers obtained by this method and in the old way : Oil, etc.Linseed Rape, I. Rape, 11. 7 , Y ) 9 , Castor, I. Castor, 11. 9 , I , 9 , Olive ... !, - - . 7 , - - . 9 7 - - . Cotton 7 ) ..- 7 , ... 9 ) * . - Cocoa-nut Cold Saponi- fication. ... 195.3 ... 195.0 ... 178.6 ... 176.4 ... 175.5 ... 176.4 ... 186-0 ... 186.3 ... 186-4 ... 185.8 ... 186.1 ... 196.3 ... 195.4 . . . . 196.2 ... 196.6 ... 198.7. ... 199 . .. 198.7 ... 198.7 ... 366.8 Warm Saponi fication. 195.0 193.5 178 175.6 176.8 185.9 186.6 185.8 186-1 196 196.6 196.6 199.2 200.0 201.6 266.4 - - - - Beef-margarine 201.3 201 7 , 201.2 202.2 Oil, etc. Cold Saponi- fication. Beef-margarine 201.5 Butter, I. ... 227.3 Butter, 11. .._ 221.3 Wool-fat ... 129.4 I ? ... 1285' Lanolin (anhy- drous) ... 90.4 Lanolin (anhy- drous) ...90.6 Yellow Bees- wax ... 96-6 Yellow Bees- wax ... 97-1 Yellow Bees- ~7ax ... 97.4 Acetic Ether 640 ?, ... 129.1 636-6 Ether . . . 700.5 Malo& Ethyl 9 , ,, 700.7 Theory. 636.4 700 Warm SaDo-68 THE ANALYST. I n adapting this method of saponification to the determination of the Reichert- MeissI number, the author gets rid of the objection that small quantities of the volatile acids remain in the form of their ethers and escape estimation. Five grammes of the fat are dissolved in 25 C.C. of petroleum spirit in a, covered porcelain dish, and allowed to stand over-night in contact with 25 C.C. of a 4 per cent. soda solution. Next morning the liquid is rapidly evaporated on the water-bath and the residue powdered. The author has never found that carbon dioxide was taken up during this process.The dry powder is then introduced into the distillation-flask, and the basin washed with the quantity of water requisite for the solution. The remainder of the process is as usual. REICHEXT-MEISSL NUMBERS. Cold Saponification, Old Method. A -- Bound. Mean. Found. Mean. ... 30-1 Berlin Butter, No. 1 ... 30.6 30.0 1 24.4 1 24.7 ... 25.1 1 1 I , ... ... 30.4 1 30.6 30.2 ) ... ... 30-9 Berlin gutter, g o . 2 ... ... 25.3 24-55 25.3 Y , ... ... 25.3 } 9 , 9 , ... ." ... 26.2 26.0 1 26.0 24.4 25.4 Konigsberg Buker ... ... 9 , I9 ... ... ... ? l I , 0 a93 Prime Margarine 1-20] ... ... ... 1.341 25.8 1 0.91 0.95 1-27 ... ... ... 8.65 ... ... ... ... 8-5 9.3 C. A. M. Butter-mixture prepared in labor- Butter-mixture prepared in labor- atory atory A New Reagent for Bromine and Iodine.J. H. Kastle. (A~IzcI'. clzem. Jounz., xvii., 1895, pp. 704-708.)-The use of chlorine water as a reagent in testing for bromine and iodine is open to several objections which do not apply in the case of a new compound made by the author. This is the di-chlor derivative of benzene sulphonamide. It is prepared by dissolving benzene sulphonamide in as little as possible of a 1 : 10 solution of caustic soda and passing in a rapid current of chlorine. The white precipitate, which contains a considerable amount of unchanged amide, is filtered off, and the filtrate treated with the gas again. The second precipitate, which is very nearly pure, is filtered off and washed with hot water. It melts at 70" C , is almost insoluble in hot water, and in many of its physical properties resembles an acid chloride.I t may be further purified by dissolving in alcohol and adding water which precipitates it in white lustrous plates. I t acts on metallic bromides and iodides forming metallic chlorides, and the corresponding bromine and iodine deriva- tives of the amide. When this reaction is carried out in the presence of chloro- form or carbon bisulphide, these solvents are coloured brown or violet, as in the ordinary test for bromide and iodine. In applying the test, the reagent may beTHE ANALYST. 69 added either in the solid state or in carbon bisulphide solution. The author's ex- periments, which are given in detail, show that the test is capable of detecting OB00O0127 gramme of iodine in the presence of 0.0400 gramme of bromine, or 0*00000635 gramme of iodine in the presence of 0-003 gramme of bromine. When testing for very minute quantities of iodine, correspondingly small quantities of the reagent must be added, since it reacts with the liberated iodine to form colour- less iodine trichloride.C. A. M. Spermaceti. Lyman F. Kebler. (Amer. Jozmz. Pharm., lxxviii., 7.) The author has examined a number of samples of spermaceti from various sources, and found their melting-points to vary from 42" to 47" C., their specific gravities to range from 0-905 to 0.945 at 15" C., their saponification number to vary from 125.8 to 134.6, while the acid numbers ranged from 0 to 5.17, varying with the age of the sample. A fresh sample, recrystallized twice from alcohol (the cetine of Chevreul) melted at 44" C., had a specific gravity of 0.942, a saponification number of 127.6, and contained no free acid.The author considers that the acid and saponification numbers are the most reliable constants for spermaceti, and that adulterations would have to be most cleverly adjusted to disturb these without destroying the peculiar crystalline structure of the substance. W. J. S. Detection of Benzene in Petroleum Spirit, and vice-versa. Holde. (Mittheil. K. Techn. Verszbchss., Berlin, 1895, xiii., 241 ; through Chenz. Zeit. Rep., 1895, 416.) -The usual method for detecting the presence of either of these substances in the other, which consists in the observation of the colour produced by dissolving iodine in the liquid, is only available when large additions of the adulterant are suspected.The colours also vary according to the concentration of the solutions prepared. A better process is based on the different solubility of asphaltum in the two liquids. The material is prepared for the test by washing its powder with petroleum spirit of the highest possible specific gravity, until it is so free froin soluble matter that when a little fresh petroleum spirit is shaken with the powder in a test-tube it is only faintly coloured yellow. A little of the asphaltum is then placed in a filter-paper, a few C.C. of the liquid to be tested poured on it, and the colour of the filtrate noted. The presence of 5 to 10 per cent. of benzene in light petroleum of specific gravity 0.64 to 0.70, or of 10 per cent.of benzene in petroleum ether boiling below 35" C., can be detected, and, conversely, any considerable addition of petroleum to benzene is recog- nisable by the tint of the solution. F. H. L. Scheme for the Identification of Acetanilide, Phenacetin, etc. F. S . Hyde. (Jozbm. Amer. Chem. Soc., xvii., 1895, pp. 933-935.)-0ne of the most important tests in this scheme is the '' Carbylamine reaction," or " isonitrile test," made by boiling the substance with caustic potash and chloroform. The reaction occurs with primary amines (R - NH,) in accordance with the equation : R-N@,'+'c~?Hc+~KoH . . , . . . . . . . . .. . . . . . . . . . __ - R - NE C + 3KC1+ 3H,O.70 ~~~~~ Acid. THE ANALYST. SCHEME. Bromine Water. Solution of Substance in Water. 3olour- less.3olubility in Water. White crys- tals ; para- brom-acet- anilide. Boiled with Excess KOH md a few drops of CHCls. 3loudy- yellow solution. Crystals of nitro com- pound. Ferric Chloride. No precipi- tate. Melting- point C. 113" Pure Substance. Acetanilide (phenyl acetamide) C6H,NH. COCH,. Soluble i n cold ; more so in hot. Ddour of isonitrile. Yellow solu- tion ; redon boiling. 3olour- less, To precipi- tate. Exalgin (methyl phenyl acet. C6H,N. CH,.COCH,. amide) : 101" 135" So m.p. HCl comp. 43" 118" Yellow solu- tion ; cloudy red on boil- ing. Yellow solu. tion ; blood- red on boil- ing. Yo odour oi isonitrile ; class of secondary amines. Odour of isonitrile. Odour of isonitrile. Not very soluble i n cold ; easi- ly soluble in hot. S o 1 u b 1 e with di0i.culty. Very soluble. S o l u b l e with diffi. culty. Easily soluble. Phenacetin (acetyl-para-amido phenetol) : C6H,.0C,H,.NH. COCH,. P henecoll hydrochloride (gly- cocoll-para-amido-phenetol) : C6H4<NH.COCH,,.KH,.HCl. OC,H, Yellow s o h . tion ; dark- ens and orange pre- cipitate on boiling. Salol (phenol salicylate) : C,H,.OH. coo. C6H,. No precipitate cold ; white pound on boiling. Yellowish cloudy corn- precipitate dissolving immediately. Colour- less. Yellow solution Yellow solu. tion ; blood. red on boil. ing. Dark - violet yellowish on adding dro1 of H,SO,. No odour ol isonitrile ; yellow sohi. tion. No odour oj isonitrile ; carmine-red solution. Resorcin (meta-diqxy-benzene) C,H,(OH),. Quinine sulphate : C,,H,,N,O,. H,SO,. ... Slightly soluble. Base precipi, tates and dissolves or heating.Yellow solu. tion. Colour- less, with bluish fluores- cence. Dry substance on porcelain with weak bromine water gives green colour 011 adding two or three drops NH,OH ; Thallieoquin test. Antipyrine (phenyl - dimethyl HOC,N,(CH,)yC,H,. pyrazolon) : 113" Soluble. Nothing. Blood -red ; disappears on adding drop of H,SOJ. Colour- less. Yellowish white pre- cipitate. Phenacetin gives the isonitrile reaction, and therefore cannot be distinguished in By boiling acetanilide with an alkaline solution of sodium this way from acetanilide.THE ANALYST. 71 hypobromite (NaBrO), or with alkaline permanganate, the same smell of isonitrile is produced. I n making the isonitrile test it is advisable to have the solution strongly alkaline, so as to ensure complete decomposition and a more perceptible odour.C. A. M. Determination of Nitrogen in the Compounds of Amines with Metallic Chlorides. W. von Dam. (Rec. trav. chim. des Pays-Bas, 1895, xiv., 217 ; through Chm. Zeit. Rep., 1895, 415.)--8s Delepine has already pointed out (ANALYST, xx., ill), Kjeldahl's process is useless in the case of platino-chlorides, owing to the production of free nitrogen. It works, however, perfectly with the compounds of gold and mercury chloride, although the reason of this peculiarity in the case of the gold salts is not apparent, By using a powerful reducing agent, such as 3 grammes of zinc-dust, well mixed with the amine platino-chloride before adding the sulphuric acid, the results are satisfactory ; while the employment of mercury, except in the case of ammonium platino-chloride, also enables the process to yield correct results.F. H. L. The Examination of Soaps. Ed. Spaeth. (Zeit. angezc. Chem., 1896, 5-9.)- The usual method of estimating the L L filling material " in a soap is to heat the dried soap with eight or ten times its volume of alcohol on the water-bath, filter through a tared filter, and weigh the residue. The principal objections to this are the solidi- fication of the soap during filtration, and the difficulty of detaching all the insoluble matter from the beaker. I n place of this, the author proposes extraction in a Soxhlet extractor with alcohol, the soap being contained in a narrow glass vessel similar to a weighing bottle, but with perforations at the bottom and in the lid (see description, Zeit.anyew. Chem., 1893, 513). The holes at the bottom are covered with ignited asbestos fibre, over which is a layer of filter-paper, and finally a glass disc with fine perforations. The bottle thus prepared is dried at 105" C. for an hour, and weighed. From 5 to 6 grammes of the soap cut in thin strips are weighed into the bottle. This is then heated at from 50" to 60" C. to melt the Hoap, then for two hours on the water-bath, dried at 105" C., and weighed. The loss in weight gives the amount of water in the soap. The bottle without the lid is then placed in the Soxhlet extractor, and its contents extracted with neutral alcohol for about six hours. After complete ex- traction, the bottle and its contents are dried at 105" C., and weighed, the result giving the amount of The determination of mineral substances, dextrin, gelatin, etc., in this is carried out in accordance with Benedikt's directions (Anal. der Fette., 209).Since the extraction is made with neutral alcohol, the amount of free fatty acids or alkalies in the alcoholic extract can be directly titrated with standard alkali or acid. As a rapid process for judging of the value of a soap, the author has found the following reliable: About 5 grammes are weighed into a dried tared flask with a filling material " in the soap.78 THE ANALYST. mark at 120 C.C. The soap is dissolved in 50 per cent. alcohol, and, when cold, the solution is made up to the mark with the same alcohol. For the estimation of the water, 60 C.C.are pipetted into a platinum basin containing a, known weight of ignited quartz sand, the alcohol gently evaporated, and the basin and its contents dried, first on the water-bath, with occasional stirring, and afterwards in the water- oven. The remainder of the contents of the flask are again made up to 120 C.C. with the 50 per cent. alcohol, then poured into a separating funnel, the flask being washed out twice with 5 C.C. of the alcohol. The soap solution is shaken up with 20 C.C. of normal sulphuric acid, and again after the addition of 100 C.C. of a petroleum spirit of low boiling-point. After standing for some time, the lower layer is run off, the liquid filtered, and the excess of acid determined in an aliquot portion of the filtrate. From this can be calculated the amount of alkali corresponding to the fatty acids left in the separating funnel.The amount of glycerin may be estimated in another portion. For the estimation of the fatty acids, 50 C.C. of the petroleum spirit solution left in the separating funnel are pipetted into a weighed flask, the petroleum spirit evaporated on the water-bath at 60" to 80' C., a current of hydrogen being meanwhile passed in. The flask is kept for ten minutes on the (boiling) water-bath, hydrogen being still introduced. The saponification equivalent of the fatty acids in the flask is determined in the usual manner. The comparative results of experiments tabulated .by the author show clearly that the introduction of hydrogen during the drying of the fatty acids makes the figures obtained much more reliable.I t is then left for an hour over sulphuric acid, and weighed. C. A. M. Quantitative Analysis of Soaps. W. Waltke and Co. (Chena Zeit., 1896, xx., 20 and 38.)-I. Estimation of Inorganic Constitzmts.-Benedikt has stated that soaps containing sodium silicate yield free alkali on treatment with alcohol, but the present authors deny the truth of this. Even when the samples contain as much as 15 per cent. of Na,Si,O,, the alcoholic solutions are perfectly neutral. From 5 to 10 grammes of the soap are extracted with boiling alcohol, the residue is dissolved in water, filtered, evaporated, and dried to constant weight. In the absence of borax, the silica is removed as usual, calculated into the above-mentioned silicate, and in the filtrate the total chlorine is determined volurnetrically after removing the free acid.The silicate, reckoned as chloride, is subtracted from the total chloride obtained, the remainder being the amount of carbonate (expressed as chloride) existing in the soap. I n the presence of borax, the carbon dioxide is estimated in one portion of the aqueous solution of the salts. I n the residue the silica and total sodium are found as before, when by deducting the carbonate and silicate (obtained from the yield of CO, and SiO, respectively), calculated as chloride, from the total sodium chloride, the remainder gives the amount of chloride corresponding to the borax in the original sample. The results quoted are satisfactory.THE ANALYST. 73 11. Estimation of Uncontbined Fat.-Ten grammes of the soap, dried till free from water, are reduced to fine powder, and shaken for some minutes with about 100 C.C.of dry petroleum spirit. The mixture is diluted to 200 c.c.: and allowed to stand till the supernatant liquid is perfectly clear. Fifty C.C. are then filtered through a double filter, run into a platinum basin, evaporated, dried at 110" C., and weighed. I t very seldom happens that any soap dissolves in the ether if everything is quite dry, but the solubility of the extracted fat should always be tested with a fresh portion of the solvent, and if there is any insoluble matter, the analysis should be repeated. F. H. L. On Some Californian Oils. W. C. Blasdale. (Jozw. Anzer. Chem. SOC., 1895, xvii., 935-941.)-This work was undertaken by the author mainly with the object of determining what were the limits of variation in the constants of Californian olive- oils.For the investigation of the olive-oils eleven samples were prepared in the laboratory from six standard varieties of olives, and ten samples of commercial salad-oil were pro- cured from different Californian makers. Of the latter three were found to be heavily adulterated with cotton-seed-oil, and one was very suspicious. The figures obtained with the pure olive-oils prepared in the laboratory were : Specific gravity, 0.9162- 0.9174 ; refractive index, 1-4710-14717 ; thermal degree, 45-0-47.0 ; viscosity, 573-655 ; melting-point of fatty acids, 21"-26" ; iodine absorption, 80.43-86.53 ; saponification number, 190.48-193-52 ; elaidin test, reaction in from 4 to 6 hours ; Milliau's test, no reaction.Most of these constants agree fairly well with those obtained for European olive-oils, but the iodine absorption is higher than the commonly-accepted standard. The thermal degree was obtained by noting the rise of temperature on mixing 15 C.C. of oil with 5 C.C. of concentrated sulphuric acid. The method of making the viscosity test was substantially that adopted by Babcock. Fifteen grammes of oil were saponified on the water-bath with exactly 74 grainmes of caustic potash and 10 C.C. of alcohol. The soap was washed into an evaporating dish, heated to expel alcohol, and made up to 500 C.C. The viscosity of this solution was then determined by means of a torsion viscometer, and the result expressed in the number of grammes of sugar it would be necessary to add to a litre of water in order to produce a solution of equal viscosity.This method promises to be of great value in detecting adultera- tion in olive-oils. Although the variation among them is considerable, it is not so great as between olive-oil and many other oils. The author obtained the following figures with some of these : Cotton-seed, 280 ; almond, 645 ; rape-seed, 670 ; poppy- seed, 95 ; sesame, 415 ; lard-oil, 250; earth-nut, 220. Of these the only ones approaching olive-oil are almond, rape, and sesame oils. The first is unlikely to be used as an adulterant, and the other two are readily detected by other tests. With regard to the elaidin test, the author is of the opinion that it is not as reliable as has been supposed.The three new oils examined were : 1. Oil extracted with petroleum spirit from the fruit of the oak (Qzierczbs agrzfolia). At the same time three new oils of vegetable origin were examined.74 THE ANALYST. Acorn-oil . . . Pine-nut-oil . . . Californian nut- meg-oil ... This was a deep brown fluorescent oil, solidifying at 10" C., and depositing waxy matter on long standing. A: brown, drying oil, of unpleasant smell and taste. 2. Oil from pine-nuts (probably Pinus monophyZZa). 3. Oil from the fruit of the Californian nutmeg (Tumion CaZifornicum). The results obtained with these were : 0.9162 0.9333 0.9072 1.4731 60.0 305 25" 1.4769 71-0 100 19" --r 1.4766 77.0 235 19" 100.66 101.3 94-71 C. A. M. Determination of Hydrochloric Acid in the Gastric Juice. W.von Moracewski. (D. med. I+-ochenschr., 1896, xxii., 24 ; through Chem. Xeit. Rep., 1896, 23.)-The sample is evaporated on the water-bath down to 1 c.c., brought into a 100 C.C. flask, and made up to the mark with a mixture of 25 C.C. of absolute alcohol and 75 C.C. of dry ether. All the chlorides are precipitated, and the free hydro- chloric acid in solution can, after neutralization, be determined by titration with silver, using potassium chromate as indicator. F. H. L. Analysis of Gutta-percha. J. A. Montpellier. ( L h z . de Chim. AnaZyt., i., 2.)-The durability of gutta-percha being in inverse ratio to the degree of oxidation or resinification, it becomes important to estimate the proportions of true gutta and the two resins (aZban and Jluvial) present ; and as, furthermore, the water always present in the finished product facilitates oxidation, this also, as well as any impurities-whether introduced by accident or design-have to be determined.To arrive at the amount of the pure gutta, 0.5 to 1 gramme of the substance is broken up into small pieces and placed in a tared filter, supported by a cone of platinum gauze. This is inserted in a flask containing absolute alcohol, so that the cone is immersed to half its height in the liquid. On surmounting the apparatus with a Soxhlet and a Liebig condenser, and heating on a sand-bath, the boiling alcohol extracts the resins, leaving the gutta behind. The last traces of the resins are removed by transferring the cone and its contents into the Soxhlet tube, where itl is surrounded by alcohol vapour.Each section of the process requires five or six hours' boiling to accomplish, and the apparatus is allowed to cool after each stage. The residue left on the filter must now be dried in a current of carbon dioxide at 100" C. To this end it is placed in a platinum or porcelain capsule, suspended in a tubulated balloon flask placed in an oil-bath. The carbon dioxide is generated in aTHE ANALYST. 75 Kipp apparatus, and, after being purified by passage through a bottle containing potassium bicarbonate solution and one containing sulphuric acid, as well as through a glass containing pumice and sulphuric acid, is led into the flask, and emerges therefrom through the lateral tubule, carrying with it the water-vapour.This latter is absorbed by pumice and sulphuric acid in two U-tubes, followed by a 5-bulb Liebig tube containing sulphuric acid. At the end of five or six hours the rubber is re-weighed, the total loss, as compared with the original weight, indicating the percentage of resins and water. The water can be determined by the same apparatus, on a fresh portion (1 gramme) of the sample in which case the drying should proceed for six or seven hours. The separation of the resins from each other is very difficult, and cannot be completely effected. An approximate determination can, however, be made by extracting 5 grammes of the gutta-percha in the manner already described, the alcoholic extract being then concentrated by evaporation at a gentle heat, until the limits of solubility of the alban are passed, whereupon this resin separates out on cooling, and leaves the other behind in the alcohol as a straw-coloured solution.Impurities are estimated by dissolving out the gutta and resins by pure chloro- form in the same apparatus as before, except that a constant level water-bath replaces the sand-bath. After washing, the residue, consisting of the impurities, is dried in a carbon dioxide oven. The ash-which never exceeds 0.5 per cent.-is determined by weighing the residue left after incinerating a known quantity of the substance in a platinurn O r porcelain capsule. c. s. Estimation of the Total Tartaric Acid in Crude Tartar and Wine Lees. D’H. de Rochefontaine. (Ann. d e Chinz. Aizalyt., i., 25.)-These substances are of somewhat complex constitution, consisting, in addition to the tartaric acid--present as acid tartrate of potassium and calcium tartrate-of calcium carbonate and sulphate, alumina, oxide of iron, silica, magnesia, chlorides, phosphates, organic and colouring matters, and particles of wood and sulphur.For the estimation of their chief constituent two processes are in general use -the Marseilles method and the Goldenberg method. The former is of a less scientific character than the latter, but is sufficiently accurate for technical purposes. Mcmeilles Mct1iod.-Place 50 grammes of powdered tartar or lees in a 300 C.C. porcelain capsule, and expose to the action of 100 C.C. of pure hydrochloric acid (goD Be.) for three hours. Then add 15 grammes of pure powdered calcium carbonate, agitating at intervals until solution, which takes a considerable time, is effected.Add 100 C.C. of water, transfer to a 400 C.C. flask, fill up to the mark, and pass through a filter of not less than 25 cm. in diameter. Transfer 191 C.C. of the filtered liquid into a conical glass, and neutralize with ammonia as exactly as possible ( i e . , until a violet tinge is imparted to red litmus- paper). The bulk of the calcium tartrate settles down immediately, but the whole must be left at rest for six hours, after which the clear liquid is decanted. This (the mother liquor) is allowed to stand for any further precipitate to come down while the principal precipitate is being treated.76 THE ANALYST. Add 200 C.C. of water to the mein precipitate, and leave to settle for a few minutes; then decant, reject the washings, and collect the precipitate on a tared filter 15 C.C.in diameter. Decant and reject the mother liquor, and join any pre- cipitate which may have formed in it to the one on the filter, and wash twice with water. Then dry at 100" C. in an oven, and weigh, continuing the drying until two consecutive weighings at an interval of half an hour differ by not more than 0.15 gramme. The final weight (less that of the filter) multiplied by 2.3 gives the percentage of tartaric acid in the original substance. The sources of error are the slight solubility of the calcium tartrate in water, especially in presence of a large excess of calcium chloride; the liability of iron and alumina to be precipitated by excess of ammonia ; and the inclusion of a little colour- ing matter in the precipitate. These errors, however, coiiipensate one another, and the method, if carried out strictly as prescribed, gives concordant results. Goldenberq Method-This well-known method is performed as follows : Place 3 grammes of the finely-powdered substance in a porcelain capsule, add 9 C.C. of pure hydrochloric acid of specific gravity 1.10, agitate, and leave to react for two hours ; then add a small quantity of water, pass through a small filter into a 200 C.C. flask, wash till perfectly neutral, and make up to the mark. Transfer 100 C.C. of the solution to a porcelain capsule, and add 3 grammes of potassium carbonate little by little. Boil for half an hour, filter and wash, join the filtrate and washings, and evaporate down to 5 or 6 C.C. Then add 2 C.C. of 50 per cent. glacial acetic acid, allow to cool, and pour in 100 C.C. of 95 per cent. alcohol; agitate briskly, and allow the mixture to stand for half an hour. Collect the precipitate on a filter, and wash with alcohol until the washings are neutral. The filter with its contents are placed in the beaker used for effecting the precipitation, distilled water added, and the whole titrated with normal potassium hydrate solution until a drop changes the colour of red litmus-paper to blue. Each C.C. of alkali solution corresponds to 1 per cent. of tartaric acid in the original substance. This method is more precise than the other, but the presence of colouring matter militates against accurate titration. It is advantageous to remove the filter before titrating. This is efYected by driving off the alcohol at 40" to 50", washing the filter with hot water (which dissolves the acid potassium tartrate), and titrat.ing the liquid in the originai precipitating glass. c. s.

ISSN:0003-2654    

DOI:10.1039/AN8962100067

出版商:RSC    

年代:1896

数据来源: RSC

摘要:

76 THE ANALYST. INORGANIC ANALYSIS. Estimation of Sulphur and Carbon in Zinc. Robert Funk. (Bed. Ber., xxviii., 3129.)-The author uses Fischer’s reaction for the estimation of sulphur, which depends upon the formation of methylene-blue when hydrogen sulphide is allowed to act on a solution of y.amido-dimethylaniline and ferric chloride. The zinc to be tested is placed in a flask holding about 200 c.c., having a tapped funnel ground into its neck. Pure hydrochloric acid is dropped upon the zinc, and the gas evolved passed through a Pettenkofer tube containing 25 C.C. of a mixture of equal volumes of it 2 per cent. solution of zinc sulphatc and of a half per cent. solu- tion of ammonia.THE ANALYST. 77 When the evolution of gas has ceased, the contents of the absorption tube are placed in a cylinder holding 40 c.c., the tube washed out with 2 C.C.of dilute hydro- chloric acid, and the whole fluid made up to 40 C.C. One C.C. of the p-amidodirnethyl- aniline solution (1 : 500) and one drop of a 10 per cent. ferric chloride solution are added. The blue colour produced is compared with that obtained under similar cir- cumstances from a known amount of H,S. The author finds that the purest zinc contains from 0 to 2-5 parts of sulphur in ten million parts of zinc. The carbon is determined as follows : A strong combustion-tube is closed at one end, and bent to an angle of about 140" at a distance of about 8 cm. from its closed end. The shorter arm of the tube is filled with pure potassiuni chlorate, previously freed from organic matter by fusion; an asbestos plug is then inserted, followed by a layer of pure copper oxide.The zinc to be analysed is then inserted in a porcelain boat, and in front of this another layer of copper oxide. ,4fter the tube has been exhausted by a Sprengel pump, the heating is carefully commenced. The moment the pressure inside the combustion-tube equals that of the external atmo- sphere, a Pettenkofer absorption-tube, containing a 2 per cent. basic lead acetate solution (first recommended by Duprk and Hake) is attached, and the heating continued. The author found that the sulphur and carbon are not dissolved in the zinc, but can be removed by melting the zinc and repeatedly filtering through an asbestos plug. 0. H. Nessler's Reaction as a Test for Mercury or Iodides.G. Deniges. (Clzenz. Zeit., 1896, xx., 70.)-The author remarks that the brown precipitate or coloration yielded by Nessler solution in presence of ammonia will serve equally well, iizutatzs maitaizdis, for the detection of mercury or for an iodide. For the former purpose, if the substance is already in solution, 2 C.C. of the fluid are taken ; if a solid, a small amount is boiled with aqua regia, and evaporated down to a few drops, taken up with 5 C.C. of water, filtered if necessary, 2 C.C. of ammonia, and the minimum amount of potassium iodide required to dissolve the precipitate added. After shaking, a precipi- tate may form. Should this be coloured, it must be removed; but if it be white, or the liquid remain clear, the characteristic reaction will be obtained on the addition of caustic alkali.I n the presence of copper, strong dilution is necessary. Excess of potassium iodide must be avoided. When examining solutions for iodine which contain metals precipitated by the reagent, the test should be carried out on the filtrate from the ammonium sulphide precipitate of these. This is acidified, boiled till free from sulphuretted hydrogen, and made alkaline with ammonia. Caustic soda, and afterwards a few drops of mercuric chloride, are added, when the formation of a more or less dark red pre- cipitate denotes the presence of iodine. F. H. L. The Volumetric Determination of Titanic Acid and Iron in Ores. H. I,. (JOZLT. LJnzer. Chem. soc., 1895, xvii., pp. 878-883.)--9 Wells and W. L. Mitchell.78 THE ANALYST.volumetric niethod of determining titanic acid was proposed by Pisani (Compt. Rend., lix., 289), but does not appear to have been found generally satisfactory. Marignac (Zeit. anal. Chem., vii., 112) applied Pisani’s method in the estimation of titanic acid in the presence of niobic acid, special conditions being adopted to avoid the reduction of the latter. The authors have modified Pisani’s process as improved by Marignac, and employ it for the determination of iron together with the titanic acid. Sulphuric acid solutions are used, and the liquid is protected from the air during cooling and titration by means of a current of carbon dioxide, The details of the operation are as follows : Five grammes of the pulverized ore are treated with 100 C.C. of concen- trated hydrochloric acid in a covered beaker, using a gradually increasing heat, and adding more acid if necessary. When there is no further action, 50 C.C.of a mixture of equal volumes of sulphuric acid and water are added, and the liquid evaporated until it fumeR strongly. After cooling, 200 C.C. of water are added, the whole heated until the sulphates dissolve, and the liquid filtered into a litre flask. If anything besides silicious matter is left on the filter-paper, it should be fused with potassium bisulphate, treated with concentrated sulphuric acid, and the sulphates dissolved in hot water and added to the main solution. The liquid in the flask is made up to the mark with water, and 4 portions of 200 C.C. each taken, 2 in Erlenmeyer flasks (500 c.c.), and the other 2 in ordinary 350 C.C.flasks. To determine the iron, sulphuretted hydrogen is passed into the solutions in the ordinary flasks to saturation, after which they are boiled until all the sulphuretted hydrogen has been removed, care being taken to avoid any contact of the solution with the air by covering the mouths of the flasks with crucible lids. The flasks are then quickly filled to the neck with cold recently-boiled water, rapidly cooled, trans- ferred to large beakers, and titrated with standard potassium permanganate. To the solutions in the Erlenmeyer flasks 25 C.C. of concentrated sulphuric acid are added and 3 or 4 rods of pure zinc, about 50 mm. long and 6 or 7 mm. in diameter, are suspended in the liquid by means of a platinum wire attached to the loop of a porcelain crucible lid, which is inverted over the mouth of the flask.The liquid is then gently boiled for 30 or 40 minutes. Then, without interrupting the boiling, a rapid current of carbon dioxide is introduced under the cover. The flask is now rapidly cooled, the zinc washed with a jet of water and removed, and the solution titrated with permanganate, while the current of carbon dioxide is still being passed in. The difference between the permanganate used in this case and that required for the iron alone, represents the amount corresponding to the titanic acid. The factor for metallic iron divided by 0.7 gives the factor for titanic acid (TiO,). The most convenient strength r’or the permanganate solution ie one of ‘7.9 grammes per litre, corresponding to about 0,014 gramme of metallic iron.In the determination of iron by reduction with sulphuretted hydrogen, no effect is produced on cold permanganate solution by the precipitated sulphur present, but precipitated sulphides, such as copper sulphide, should be filtered off before boiling. The results of test analyses of recrystallized potassium titanofluoride were as follows : Each of these represents 1 gramme of the ore.THE ANALYST. 79 K,TiF, taken. Titanium found. Titanium calculated. Error. Gramme. Gramme. Gramme. Gramma. 0.7638 0-1437 0.1527 0~0090 0.7778 0-1524 0-1555 0-0031 0-6359 0-1215 0.1271 0.0056 0-4634 0.0882 0.0926 0.0044 The results were invariably too low. This was probably due partly to impurities in the salt used, but chiefly to the air gaining access to the flask in spite of all precau- tions. The accuracy of the method would apparently be increased by adding or 2G to the amount of titanic acid found, but even without this correction it is likely to give more reliable results than those obtained by gravimetric determination. C.A. M. Quantitative Separation of Metals in Alkaline Solution by means of Hydro- gen Peroxide. P. Jannasch, E. von Cloedt and H. Kammerer. (Zeits. Anorgan. Chem., 1895, x., 405 and 408; through Chem. Zeit. Rep., 1896, 5.)-To separate chromium from iron, manganese, or aluminium, Jannasch and von Cloedt add the solution containing the metals with 50 C.C. of 6 per cent. hydrogen peroxide and 30 C.C. of strong ammonia, in a pressure flask fitted with a wired-in rubber cork, and a tube drawn out to a capillary and sealed.After standing for an hour cold, the flask is heated on the water-bath for one or two hours longer. The chromium will all be found in solution, while the other metals are precipitated. The same process is con- venient for the precipitation of manganese when mixed with zinc. To separate arsenic from iron and manganese, Jannasch and Kamnierer mix the liquid containing the latter metals together with arsenious acid with the alkaline peroxide, throwing down the resulting arseniate by magnesia mixture, Iron may also be separated from nickel, zinc and copper, by treating the chlorides, or, better still, the acetates, with the same reagent. The peroxide should be prepared by Wolffenstein’s process, i.e., by distillation in VCLCUO and extraction with ether.F. HI. L. Quantitative Separation of Chlorine and Bromine. S. Bugarski. (8ezts. Anorgan. Chem., 1895, x., 387 ; through Chem. Zeit. Eep., 1896, 5.)-The mixed chlorides and bromides are treated with 50 C.C. (or in presence of much of the latter 100 c.c.) of decinorrnal potassium di-iodate, 10 C.C. of 1 : 5 sulphuric acid, andenough water to bring the whole up to about 200 C.C. A little pumice is added, and the liquid boiled for 40 minutes, until the halogens are volatilized in the steam. The residue is made up to 100 c.c., some crystals of potassium iodide added, and the iodine det,er- mined in a portion of the liquid. From the amount of iodic acid used the bromine is calculated. The original liquid is titrated according to Volhard’s method to give the total amount of the halogens, when, by difference, the chlorine can be found.F. H. L. Estimation of Phosphorus in Phosphor-Bronze. F. Oetell. (Chem. Z e d , 1896, xx., 19.)-FreseniusY process (Quant. Anal., ii., 550j for this determination isSO THE ANALYST. very tedious, owing to the time taken up in filtering and washing, the tin oxide con- taining the phosphorus, and if it is decomposed by fusion with sulphur and soda, instead of by boiling with acid, the product is contaminated with silica. Classen has suggested dissolving the oxide in sodium sulphide, converting the latter into the ammonium salt by means of ammonium sulphate, precipitating the tin electro- lytically, and finally determining the phosphorus as usual. The large excess of ammonium salts, however, affects the accuracy of the method, and any arsenic in the bronze is estimated with the phosphorus.From 3 to 10 grammes of the alloy are treated with nitric acid, the tin oxide filtered off and washed slightly. I t is dried, ignited in a porcelain crucible, three times its weight of potassium cyanide added, and the mixture fused for some minutes. The tin is reduced, carrying with it any arsenic that may escape volatilization, while the phosphorus remains in the form of potassium salt. The mass is extracted with water, filtered, acidified with strong hydrochloric acid, boiled till free from hydro- cyanic acid, and a current of sulphuretted hydrogen passed to remove traces of copper and tin. After filtering, it is boiled, a little bromine added, made alkaline with ammonia, and the phosphorus thrown down with magnesia mixture as usual.The author remarks that the term “phosphor-bronze” applies rather to the process of manufacture than to the composition of the alloy, and that inany samples contain extremely little phosphorus ; while he considers that the amount present is of very little practical importance. F. H. L. New Reagents for Hydrogen Peroxide. L. I. von Nagy Ilosva. (Ber. 1895, xxviii., 2,029.)-Bach has described a new test for peroxide of hydrogen, con- sisting in a solution of aniline and potassium bichromate in presence of oxalic acid. The present author has found that a number of other aromatic amines, excepting diphenylamine and inethyldiphenylamine, are also available, and that, of those examined, dimethylaniline is the most sensitive and convenient.Five drops of the amine and 0.03 gramme of potassium bichroniate are dissolved in a litre of water, and, in testing, equal parts (5 c.c.) of the reagent and the liquid to be examined are -mixed together, with the addition of a drop of 5 per cent. oxalic acid. A blank test is carried out at the same time with 5 C.C. each of water and the solution of the dimethylaniline, as the colour of the latter constantly changes, although this does not interfere with the delicacy of the reaction. Even in dilutions of one part per five million the presence of the peroxide is shown by a yellow colour appearing after a few minutes, while in stronger solutions a violet (methyl violet) colour is produced.Very weak solutions, containing an equivalent quantity of nitrous acid, are not amenable to this treatment, owing to the decomposition of the peroxide; and care must be taken that the coloration be not in any case caused by the action of ozone. The author notes that hydrogen peroxide does not entirely vanish from solutions of less than 1 per 500,000 in three or four days, and that stronger solutions (1 per 50,000) yield a faint reaction after a week. F. H. L.THE ANALYST. 81 Estimation of Available Phosphoric Acid in Basic Slag. M. Gerlach and 16. Passon. (Chem. Zeit., 1896, xx., 87.)- Wagner's '' dilute citrate solution " (ANALYST, xx., 215) contains per litre 14 grammes of free citric acid and 46 grammes combined as ammonium citrate. It is the former constituent which gives the liquid its power as a solvent, and Wagner's view that some of the phosphoric acid, when dissolved, acts as a solvent on the remainder cannot be substantiated.The presence of the ammonium citrate is to a large extent unnecessary, for of eighty-four slags treated with a 1.4 per cent. citric acid solution, all excepting three gave values agreeing with those obtained by Wagner's process. These three samples, which yielded 9.96, 13.02, and 8-82 per cent. of available phosphoric acid, gave up 12.10, 13.72, and 9.63 per cent. respectively to the free citric acid. On treating them, how- ever, with a solution containing only one-tenth of the usual amount of citrate (18.6 grammes of crystallized citric acid and 1.17 grammes of ammonia per litre), perfectly concordant results were obtained ; and the authors advise that the solution should always be made according to this formula.They also state that the speed of the agitating apparatus and the time of extraction have little influence on the results, but the temperature must be maintained at 17.5" C. I t may be noted that by two or three successive extractions with fresh portions of the solvent the whole of the phosphoric acid present in the slag can be removed. F. H. L. An Improved Molybdate Solution. M. G. Meillere. (J. Pharm. Chim., 1896 [6], iii. 61.)-By mixing together 200 C.C. of a 15 per cent. solution of ammonium molybdate, 20 C.C. of 1 in 1 sulphuric acid, and 30 C.C. of pure nitric acid, a liquid is obtained which is permanent for several months, and may even be heated to 100" C.without decomposition. When determining phosphoric acid, it suffices to start the precipitation by slight warming, allowing it to continue in the cold. In the case of arsenic acid prolonged warming is necessary, which may induce the deposition of molybdic acid; but if in the subsequent precipitation with magnesia mixture sufficient alkaline citrate (not tartrate) be present, this is without injurious effect. F. H. L. Estimation of Potassium. P. Losche. (Chem. Zeit., 1896, xx., 38.)-This process is specially applicable to such substances as carnallite, crude potassium salts, etc., where the amount of alkali present is approximately known. Fifty grammes of the sample are boiled with 150 C.C. of water and 10 C.C. of strong hydrochloric acid, and when cold diluted to 200 C.C.Ten C.C. of the filtrate are then treated in a, small basin with about 14 times the theoretical amount of a solution of platinum chloride, containing 10 per cent. of the metal, necessary to effect complete precipitation. The whole is evaporated to dryness, broken up with a glass rod, and extracted with 96 per cent. alcohol. It is then placed on a filter, which has been dried a t 120"--130" C., and weighed, Some 10 per cent, ammonium chloride is warmed to 30" C., and the precipitate washed therewith until all the sulphates are removed, the double chloride being perfectly insoluble. A final rinse in alcohol is given to remove the ammonium chloride, and the paper with its contents82 THE ANALYST. dried again and weighed in the usual manner.A number of results obtained from different liquors containing potash, minerals, etc., are recorded, showing satisfactory agreement with the usual process of analysis, which involves the use of much larger quantities of platinum, beside the removal of the sulphuric acid. F. H. L. Standard Potassium Dichromate Solution. J. D. Dougall. (Glasgozo City Anal. SOC. Repts., 1895, p. 6.)-The author shows, by a series of experiments, that this solution may be made quite as, or even more, reliably by weighing the theoreti- cal amount of potassium dichromate, and making up to a definite bulk, as by the more tedious process of first analysing a sample of iron wire and then standardizing the dichromate against this. W. J. S. Estimation of Lead Colorirnetrically. Maurice Lucas.(Bull. SOC. Chim. (3) xv.-xvi., %.)-For the determination of small quantities of lead, such as occur in copper, bronze, brass, tinfoil, water passed through lead pipes, etc., ordinary chemical methods are inefficient, and in such cases a colorimetrical method may be resorted to with advantage. The sulphide is, however, the only lead salt suitable, the pre- cipitates of all the others-and it is only the insoluble salts that exhibit colour- settling down too rapidly to admit of examination in this way. The presence of salts or alkalis affects the colour, alkalis imparting a brown, and neutral salts a grayish tinge, the latter being heightened by carbonates or bicarbonates ; and as the collection of the precipitate is hastened in direct proportion to the quantity of salt or alkali and degree of concentration of the solution, their addition-with the exception of a slight quantity of alkali to prevent oxidation of the sulphide--is inadvisable.The sulphide, moreover, is six times, and twenty times, as sensitive as the chromate and iodide re- spectively, and permits the detection of as little as 0.00001 gramme-in fact, it is only surpassed in qualitative delicacy by microchemical methods. The strength of the solution most convenient for testing is between 1 and 20 mg. per litre. In the analysis of bronze, which is given as a typical case, the nitric acid solution of 1 gramme of metal, freed from tin and antimony, is treated with 1 C.C. of sulphuric acid, evaporated down to a bulk of 7 or 8 c.c., taken up again with water and electrolyzed in a Riche apparatus with a constant current of 2 volts and 0.3 ampere for about twelve hours, after which the liquid is syphoned off and tested, to see that all the copper has been deposited; this also indicates the deposition of the lead.The copper and lead adhering to the negative and positive poles respectively are washed while the current is still passing, and are weighed after drying quickly. The lead oxide multiplied by 0.865 will give the approximate amount of lead, and afford a guide to the dilution necessary: if over 5 mg. the lead should be weighed as sulphate without filtering. Solutions of neutral lead nitrate (1 gramme), sodium hydrate (300 grammes), and sodium nitrate (640 grammes, per litre), having been prepared in advance, the lead oxide is redissolved in 1 C.C.of nitroso-nitric acid obtained by electrolyzing nitric acid. The crucible being washed with a little boiling water, and the solution neutral- ized by sodium hydrate from a Mohr burette, the volume is made up to 50 C.C. for each mg. of lead, and 5 drops of ammonium sulphide are mixed in.THE ANALYST. 83 The standard solutions for comparison must contain a quantity of sodium nitrate equal to the sodium hydrate added to the test solution, be of equal volume with the latter, and have 5 drops of ammonium sulphide added. When the solution is very dilute, it is better to divide it into two parts, and test one first. A number of standard solutions, graduated to twentieths above and below the shade observed, are then employed for comparison with the second half; this obviates the variation occurring in the shade on standing.Between 0.0001 and 0.004 gramme the results are exact to within 10 per cent., and agree with sufficient precision. The method is more reliable than an estimation as sulphate, even if 10 grammes of substance are employed. c. s. Analysis of Aluminium and its Alloys. H. Moissan. (Conzptes Rendzls, 1895, p. 851.)-A preliminary examination for copper, by dissolving 2 grammes of the metal in dilute hydrochloric acid and passing a current of hydrogen sulphide, is necessary. If the amount of copper be very small, the liquid must be kept warm for several hours. I n the absence of copper, silicon is estimated by dissolving 3 grarnmes of the metal in dilute (1:lO) HCl, any grayish residue left being fused with sodium carbonate in a platinum crucible, taken up with water and added to the main solution.After evaporation in a porcelain basin on the water-bath, the HC1 is driven off by exposing the basin to a temperature of 125" for twelve hours. The sides of the basin are scraped at intervals with a platinum spatula, and the granular mass broken down by an agate pestle. The mass is then taken up with warm distilled water containing a little HCI, the solution boiled for a few moments, and the silica collected, ignited, and weighed. For the estimation of aluminium and iron, the liquid from the preceding stage is made up to 500 c.c.; 25 C.C. (equal to about 0.15 gramme of metal) are then neutralized by ammonia in the cold, and precipitated by ammoniutn sulphide. After digesting for an hour the precipitate is collected, washed, dried, ignited, and weighed ; this gives the total amount of oxide of iron and alumina. The iron is determined in 250 C.C.of the primary solution concentrated to 100 c.c., and treated with suficient potassium hydrate (free from silica) to redissolve the alumina. After keeping the whole near boiling heat for ten minutes, the precipitate is washed five or six times, dissolved with diluted hydrochloric acid, re-precipitated by potash, mashed and again dissolved, and the iron thrown down by ammonia. On filtering off and weighing the oxide of iron after ignition, the resulting weight deducted from that of the two oxides gives the amount of alumina. As aluminium nitrate decomposes at a lower temperature than the corresponding sodium salt, the latter metal may be estimated by dissolving at a gentle heat 5 grammes of aluminium in nitric acid, diluted with an equal volume of water, the vessel being covered by an inverted funnel to prevent loss of the liquid.The solution is concentrated and evaporated to dryness, and the residue, after being powdered with an agate pestle, is maintained at a temperature below the fusing-point of sodium nitrate until the evolution of nitrous funies ceases, whereupon a little boiling water is added and the alumina washed several times by decantation, the washings being then acidified with a few drops of nitric acid and evaporated to dryness. After taking up84 TBE ANALYST. several times with boiling water, to successively eliminate portions of the alumina mixed with the alkali nitrate, pure hydrochloric acid is added to the filtrate, and the liquid evaporated to dryness. The nitric acid is driven off at 300", the sodium chloride re-dissolved, its chlorine determined as silver chloride , from which the weight of sodium can be deduced. Carbon is estimated by triturating 2 grammes of metal with 10 to 15 grammes of powdered mercuric chloride and a little water. The mixture, after evaporation, is placed in a porcelain boat, inserted in a Bohemian glass tube, which is heated to redness, and through which a current of oxygen (free from CO,) is passed. The effluent gas is absorbed by KHO, and the carbon calculated from the increase in weight of the potash tubes. In alloys of copper and aluminium, the weight of the former metal is ascertained by dissolving 0.5 gramme in nitric acid free from chlorine, diluting the solution to 50 c.c., and passing a current of 0.1 ampkre for six hours at 60", or twenty-four hours in the cold, the copper being washed, dried, and weighed as metal. The remaining components are, after throwing down the copper by hydrogen sulphide, estimated as already described. The following is an analysis of Pittsburg aluminium : A1 ... ... ... . 4 . 98-82 Fe ... ... ... ... 0.27 Si ... ... ... ... 0.15 c u ... ... ... ... 0-35 Na ... ... ... ... 0.10 C ... ... ... ... 0.41 N ... ... ... ... traces. Ti ... ... ... traces. S ... ... ... ... nil. ... 100*10 c. s.

ISSN:0003-2654    

DOI:10.1039/AN8962100076

出版商:RSC    

年代:1896

数据来源: RSC

摘要:

84 TEE ANALYST. APPARATUS. G. W. A. Kahlbaum. (Bed. Ber., xxix., 69.)-The con- denser bearing Liebig’s name was invented by Christian Ehrenfried Weigel, and described by him in his dissertation of March 25, 1771. (hiebig was born in 1803.) Weigel’s condenser was described in Goettling’s “ Manual of Chemistry,” 1794, and Liebig, when he first described the use of this condenser, mentioned the source from which he had obtained the description of the apparatus. Liebig Condenser. 0. H. An Improved Gas-measuring Vessel. F. Cochius. (Chewz. Zed., 1896, xx., 89.)-This is an ordinary gas burette, which may have its upper portion expanded or not. The top of the tube terminates in a neck, into which is ground a perforated stopper, which may either carry a funnel, a sniall connecting-tube, or a three-way tap. To the under side of this stopper a thermometer is attached in such a position that the latter is entirely within the measuring-tube. With this device the tempera- ture of the gas can be read off at once, without having to wait for some time until it has fallen to the temperature of the outside air. The contrivance is especially useful for the collection of warm gases. F. H. L.

ISSN:0003-2654    

DOI:10.1039/AN8962100084

出版商:RSC    

年代:1896

数据来源: RSC