NEWS which are taken from Sir Walter Scott's tale of the Chemical Technology, or Chemistry in its "Monastery." It has been skilfully arranged by one of the Directors, Dr. Croft, who takes a lively interest in, and devotes much time to, the interests of the Polytechnic. London International Exhibition, 1873.-The second meeting of the Committee on Surgical Instruments and Appliances was held on the 23rd December, 1872, at 3 o'clock, in the offices, Gore Lodge, South Kensington. Among those present were Mr. Cæsar H. Hawkins, F.R.S., in the chair, Sir William Fergusson, Bart., F.R.S., Dr. P. Allen, Mr. W. Bowman, F.R.S., Mr. B. Brudenell Carter, Mr. W. White Cooper, Dr. W. T. Domville, R.N., Dr. Arthur Farre, F.R.S., Dr. G. T. Gream, Mr. Prescott G. Hewett, Mr. J. Hilton, F.R.S., Mr. J. Hinton, Professor J. Marshall, F.R.S., Mr. T. W. Nunn, Dr. W. S. Playfair, Mr. R. Quain, F.R.S., and Mr. Edwin Saunders. Letters received from the Royal College of Surgeons, and the Royal Medico-Chirurgical Society were read, and it was stated that many of the leading surgical instrument makers in London, Dublin, Paris, and other capitals had signified their intention to contribute. It was suggested that the Exhibition should be brought before the notice of the British Medical Association at its meeting in August, 1873. The committee resolved to recommend the Royal Commissioners to invite corresponding members in foreign countries, and after the transaction of general business adjourned till Monday, the 20th January, 1873. Vol. XXVI. of the CHEMICAL NEWS, containing a copious index, is now ready, price 11s. 4d., by post, 12s., handsomely bound in cloth, gold lettered. The cases for binding may be obtained at our office, price 1s. 6d. Subscribers may have their copies bound for 2s. 6d. if sent to our office, or, if accompanied by a cloth case, for s. 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The CHEMICAL and TOXICOLOGICAL CLASS on Monday and Thursday evenings at 8 p.m., commencing October 1st. The LATIN CLASS on Tuesdays and Fridays at 8 p.m., commencing October 2nd. The MATERIA MEDICA and BOTANICAL CLASS, every Wednesday and Saturday at 8 p.m., commencing October 3rd. The BOTANICAL GARDEN affords to Students desirous of acquiring a Practical Knowledge of Botany every facility for doing so. During the Season BOTANICAL EXCURSIONS are made every Saturday at 10 a.m. Fee to either of the above Classes Half-a-Guinea per Month Pupils can enter at any period to either Classes or Laboratory. All Fees must be paid in advance. PRIVATE TUITION for the usual Examinations of the Society, the Modified Examination, &c. Letters of inquiry should be accompanied with a stamped envelope. Address-54, KENTISH TOWN ROAD, N.W. a hard wedgwood mortar, and after thorough mixing a quantity was reduced to an impalpable powder in the same mortar. Two determinations of the sulphur and sand in the portion gave the following results:-Sulphur, 45'08 per cent; sand, 8.92 per cent; and sulphur, 45'01 per cent; sand, 8.88 per cent. 2. Another portion of the sifted sample was similarly reduced in a wedgwood mortar, which had been in use for some considerable time previously (this mortar was perceptibly softer than that used in the preceding experiment). Two determinations of sulphur and sand gave By NICHOLAS GLENDINNING and ALFRED J. M. EDGER. Sulphur, 43'56 per cent; sand, 1152 per cent; and THE great consumption of pyrites in industrial chemistry renders the accurate determination of the sulphur it contains a matter of great commercial importance. Judging however, from the serious discrepancies which so frequently occur in the results obtained by different chemists when operating upon the same sample, it would appear that the estimation of sulphur is either surrounded by great difficulty or performed under very defective manipulation. sulphur, 43'44 per cent; sand, 11.50 per cent. in an agate mortar, gave in two determinations :-Sulphur, 3. Another portion of the same sifted sample, reduced 45 28 per cent; sand, 6.2 per cent; and sulphur, 46.15 per cent; sand, 6·24 per cent. 4. A duplicate sample of the same ore, instead of being ground in a wedgwood was reduced in a steel mortar, and a portion brought to an impalpable powder in the agate, two determinations giving :-Sulphur, 46.25 per cent; sand, 611 per cent; and sulphur, 46.36 per cent; sand, 6.13 per cent. The following is an arrangement of the results in a tabular form : Average Average Sulphur per cent. Sand per cent. Sulphur per cent. Sand per cent. 1. Wedgwood mortar alone 2. It will be quite within the recollection of the members of this society that their attention was drawn by a late president (Mr. Glover) to the differences observable in the results obtained by different experimenters. This gentleman explained that in seven samples, each tested by two professional chemists, there was a maximum difference of 19, a minimum of 14, and an average of 16 per cent of sulphur, but differences still greater have come under our own observation. This subject was afterwards noticed by Messrs. Teschemacher and Smith in their article "On the Estimation of Sulphur by Barium," published in the CHEMICAL NEWS, vol. xxiv., 3. p. 61. They were of opinion that the observed differences might be traceable to different methods of testing, and adduced a number of results by way of proof that 4. the method then in general use was not reliable. Shortly after the appearance of their article we published results in support of that method (see CHEMICAL News, vol. xxiv., p. 140), and we now beg to draw your attention to a source of error which precedes the analytical process, and precludes the possibility of correct results being obtained,. We allude to the use of the wedgwood mortar in the preparation of the portion for analysis, and are persuaded that its use obtains very generally in both professional and private laboratories. a In the midst of all the contention respecting the differ; ences between results, it does not seem to have occurred to the experimenters that the cause of difference might be introduced in the preparation of the sample; and yet it must have been observed that, to whatever use wedgwood mortar has been applied, a very perceptible wearing is effected in course of time. A few years ago we devoted some attention to the differences which were causing so much annoyance; and from the circumstance of mortars becoming somewhat worn, we inferred that this might be the solution of the problem, and subsequent experiments proved the accuracy of this conclusion. We prepared a sample by passing it through a sieve of 529 meshes to the inch to ensure uniformity of composition, and then reduced portions to an impalpable powder for analysis; and then estimated in the several portions the sulphur and sand. The sulphur results were found to differ to an extent in some cases of upwards of 2 per cent, and this was accounted for by the amount of sand found in their respective portions. We at orce saw that the wedgwood mortar was quite unsuited to the purpose, and have since prepared samples in a different way. We will now proceed to lay before you some results obtained quite recently from samples prepared in various ways. 1. A sample of pyrites was passed through a sieve of the above description, the coarser particles being reduced in Read before the Newcastle-on-Tyne Chemical Society, Dec. 19, 1872. It will be observed that the difference between the results of Nos. and 2 is, sulphur 2.80, and sand 5'39 per cent; and between Nos. and I, sulphur 124, and sand 278 per cent; whilst between Nos. 4 and 3 there is only the slight difference of sulphur o'09, and sand o 10 per cent. Duplicate samples of another pyrites were tested by a chemist, and ourselves, with the following results :— metropolitan professional chemist, a local professional Sulphur per cent 43.8 45'5 46.84 46.8 Sand per cent 8.3 8.1 5'60 5'5 We may mention that A represents the results of the metropolitan chemist, and B those of the local chemist. Our sulphur results were obtained by the method described in our article in the CHEMICAL NEWS before mend as capable of giving concordant and reliable results. alluded to, which we can, with great confidence, recomWe may remark that the sulphur result of No. 2 is not sufficiently high by 0.3 per cent if the difference between its sand and that of No. 4 be taken as the full extent of the contamination. We have, however, so repeatedly found this to occur that we assume that some portion of the detached mortar is soluble in the acids employedprobably not the wedgwood itself, but matter which the mortar may have absorbed during its use, It is obvious from these results that by using the wedgwood mortar very serious differences may arise, their extent varying of course with circumstances, e.g., the hardness of the sample, the hardness of the mortar and its condition, and the industry of the operator. In conclusion, we hope we are justified in assuming that the results we have had the pleasure of laying before you afford sufficient proof that the use of the wedgwood mortar involves a more or less serious depreciation of the sample, and that under these circumstances the proba- | remains in solution, and this quantity does not vitiate the bility of the attainment of a result representing the true results. In order to obviate the washing of the precipitate, value of the sample as it reached the assayer's laboratory I dilute the previously-cooled fluid to 500 c.c. I next is of a most remote character, and an occurrence which filter it through a dry filter, and take 250 c.c. of the filtrate, can only be due to an error in analysis. equal to 0.55 grm. of the quantity of the material originally taken, and in these 250 c.c. I estimate the manganese. When the manganese is intended to be precipitated by a further addition of acetate and bromine, and the quantity of dioxide of manganese then acidimetrically determined, we again meet with the difficulties occasioned by the ready decomposition of the acetate of manganese, and the capability of the dioxide of entering into combination with the lower oxides of manganese, and consequently the protoxide. These difficulties are best met by the following method of operation:-10 grms. of sodic acetate are dissolved in 150 c.c. of water, 50 c.c. of bromine-water are added, and, at intervals of half an hour, 50 c.c. of the manganese solution, care being taken that at the third half-hour 50 c.c. of bromine-water be again added to the fluid, to which heat should not be applied. NOTE. Since reading the above paper, we have made experiments substituting the porcelain in lieu of the weedgwood mortar in the preparation of the test sample, and the results obtained show that it also contaminates the sample to a serious extent, as will be seen from the following results :-A sample of the same pyrites as was used in the preceding experiments (and which gave by the steel and agate mortars in two determinations-Sulphur, 46 25 per cent; sand, 6'11 per cent; and sulphur, 46 36 per cent; sand, 613 per cent) gave when the porcelain mortar was used-Sulphur, 45'3 per cent: sand, 8.21 per cent; and sulphur, 45:36 per cent; sand, 8:23 per cent. Or, comparing their averages, the results of the porcelain mortar show an excess of 2.1 per cent of siliceous matter, and a deficiency of 0.97 per cent of sulphur. ON THE ESTIMATION OF MANGANESE IN PIG-IRON, As, in these days, iron which contains more or less manganese is considered to be more or less valuable, it occurred to me to try to devise a method whereby the estimation of manganese in the above-named materials might be rendered more expeditious and less liable to the errors ordinarily inherent in that estimation. At a future period I intend to publish an exhaustive account of my researches; I therefore now communicate only what is of direct practical utility. When a hydrochloric acid solution of perchloride of iron is neutralised by means of carbonate of soda, so as to cause a permanent precipitate, and the latter is cautiously re-dissolved by the addition of some hydrochloric acid, a liquid is obtained which contains fourteen times its equivalent of ferric hydrate in solution, yet it is not precipitated by boiling. In order, therefore, to precipitate the iron by means of acetate of soda, aided by boiling heat, there is, theoretically, only as much acetate required as is sufficient to convert the chloride into acetate, viz., 3 molecules of acetate to 15 atoms of iron, or I part, by weight, of crystallised acetate of soda to 2 parts, by weight, of iron. It is, indeed, an easy matter to precipitate completely, by boiling, from previously carefully neutralised iron solutions, I'I grm. of iron upon 500 c.c. of fluid by means of I grm. of acetate of soda, even when, in order to prevent the possible decomposition of other acetates, I grm. of acetic acid had been added. Under these conditions, only very small portions of manganese are thrown down along with the iron--for instance, from 13 per cent only about o'02 to 0.05 per cent, and less when the quantity of manganese is smaller. From what has just been stated, it is quite evident that the loss often experienced in the estimation of manganese by the method just alluded to is mainly due to the fact that too large a quantity of acetate of soda is employed, in consequence of which a portion of the chloride of manganese is also converted into acetate, which salt is readily decomposed into protoxide and acid, a fact almost entirely overlooked. It is probable that my improved method may also be applied to the separation of iron from zinc, copper, nickel, and cobalt, Before I found out this method I used sulphate of soda, for decomposing the previously neutralised chloride of iron. Although this salt may even be used in excess without any manganese being precipitated, I found that 1 grm. of it is sufficient to separate 1'i grm. of iron; only a very small quantity of it In this manner, the manganese dioxide is thrown down from so dilute a solution that only from o'02 to 0'03 per cent of manganese out of 13 per cent are lost in the shape of protoxide. On the other hand, small, but, with the whole quantity, proportional, quantities of manganese remain, either in solution as permanganate, or are so fixed to the sides of the glass vessel in which the operation takes place, that it is necessary to re-dissolve it. After the free bromine has been driven off by heat, the precipitate is filtered off, washed with dilute solution of acetate of soda, and then treated, together with the filter, with from 5 to 15 c.c. of a solution of chloride of antimony (1 to 5) and 15 c.c. of concentrated hydrochloric acid, after which the fluid is diluted with 100 c.c. and titrated with decimal permanganate solution, I c.c. of which then equals o'5 per cent of manganese. When the quantity of manganese is less (below I per cent), all quantities are tripled, and 5-6ths of the filtrate from the iron precipitate, previously concentrated by evaporation, are treated for manganese, I c.c. of permanganate becoming in this case equal to o'1 per cent of Mn. The titre of the solution of permanganate is found, either by comparing it with a solution of potassic bichromate of known strength by means of chloride of antimony, or by investigating a known quantity of pure protoxide of manganese according to the method described above. By mixing pure solutions of manganese (I often used for this purpose solutions of permanganate of known strength, with solutions of iron, the manganese in which had been previously determined, in variable proportions), I made mixtures for testing, in which the quantity of manganese varied from o'1 to 13 per cent. As instances of at least four experiments, I quote the following: NEWS and cobalt, metals often present in iron in greater or less quantity, small quantities are thrown down along with the manganese precipitate, copper and nickel only as monoxides, but cobalt as sesquioxide; the latter, therefore, unless it be separately estimated, may bring on a slight error, so that the quantity of manganese would be found somewhat too large, viz., about half the quantity of the cobalt present.-Ber. d. Deutsch. Chem. Gesells. THE ESTIMATION OF SULPHUR IN PYRITES. By PHILIP HOLLAND. THE practical importance of providing a reliable method for estimating sulphur in pyrites has, I need hardly say, been fully realised by chemists who are called upon to make assays of this kind. The experiments detailed in the present communication, some of which have yielded but indifferent results, were made, not so much with a view of arriving at an entirely new scheme for valuing sulphur ores, but rather to supplement our present ways and means of conducting the operations now in vogue. For most purposes, I think it may be assumed that sulphur in mineral substances is usually, if not invariably, determined as sulphate of barium, and that there are four methods in general use for this purpose-three direct, and one somewhat indirect. The direct comprise a gravimetric and two volumetric processes. The indirect is also a volumetric one, and is known as Mohr's alkalimetric method, useful in many cases, but scarcely applicable to the valuation of pyrites, since the conditions of an assay are not usually such as readily to adapt themselves to it. I tried the following alkalimetric process, which I believe has been already described by Bohlig (Fresenius's Zeitschrift) for estimating sulphuric acid, with the intention of applying it to the valuation of pyrites. It was soon evident, however, that the experimental conditions of an assay are not such as to adapt themselves readily to it. If hydrate of barium be added to a neutral solution of a sulphate of an alkali, and the excess be removed by CO2, the amount of caustic alkali liberated will be equivalent to the sulphuric acid previously combined in the absence of phosphates and fluorides. The solution containing the soluble sulphate in the presence of free HCl is precisely neutralised whilst boiling with sodium carbonate free from sulphuric acid. Hydrate of barium is then added in slight excess, the whole boiled for a few minutes, and the excess removed by CO2. After filtration and thorough washing of the residue on the filter by boiling-water, the filtrate is neutralised by standard acid. The following experiments were made; the volume of fluid was in each about 250 c.c.: that in the first stage had there not been a loss of alkali. Some of the experiments were repeated, and similar results were obtained; the error was always one of deficiency when the sulphuric acid was about half a gramme. The low results are doubtless due to the fact that boiling water fails to remove all alkali from the mixed precipitates, which is not at variance with our present knowledge of the properties of barium precipitates generally. I did not continue this enquiry further, inasmuch as it did not seem probable that closer numbers would be obtained unless the process was inconveniently prolonged. The next method to which some attention was paid is the direct volumetric one of Wildenstein, which has lately been carefully studied by Messrs. Teschemacher and Denham Smith; I am able to confirm much that these chemists have said about it in several particulars. My own experiments satisfy me that it is desirable to conduct the titration in the presence of but little free HCl, in the entire absence of nitric acid, and to standardise the barium chloride by iron sulphate, as nearly as possible under the conditions which will prevail in a pyrites assay so far as the amount of free acid and volume of fluid are concerned. Some little difficulty is experienced in deciding what shall be considered the end-point of the titration, owing to the barium chloride or sulphuric acid produces a slight so-called neutral point in the fluid when a drop of either turbidity. I may just mention that up to a certain stage the testing for excess of barium can be done on a watch-glass. A drop of the partially clear solution is removed by means of from the burette is brought near, and the two fluids a narrow tube pipette. A drop of the barium solution allowed to run together. If the point of contact be careindicate sulphuric acid. The rapidity of the change and fully observed, the appearance of a faint opalescence will the depth of the opalescence serve to warn the operator of the approaching completion of his experiment. The absolute completion cannot be decided except on a filtered portion in a tube, and this can only be done under certain conditions, as the following observation testifies. Two pyrites assay were taken, and to each was added respecmeasured equal volumes (4 c.c.) of the solution in a tively and at the same time one drop less than o'r of a c.c. of the normal barium, and a like amount of normal sulphuric acid. In the tube to which the acid was added a slight turbidity appeared at the end of a minute and a half; in the other tube the fluid remained quite clear. To the latter four additional drops of barium were added, when a turbidity showed itself in a few seconds. I am not able to give an explanation of the phenomenon. Perhaps sulphate of barium is slightly soluble in a solution not containing too large an excess of BaCl2? Whatever may be the explanation, the reaction must be taken into account when verifying the strength of the barium chloride. In assaying pyrites for sulphur only by the fusion method, I have worked as follows and obtained good results. The process will no doubt be useful in laboratories which do not possess large platinum crucibles. A test-tube or piece of sealed combustion-tube, about six inches long and half an inch internal width, is fitted with a cork and delivery tube, the latter bent at a right angle and long enough to reach to the bottom of the flask in which it is intended to make the titration. The fusion mixture consists of equal parts of nitre and ignited acid carbonate of sodium, both free from sulphur, dry, and in fine powder. Nine to ten grammes is taken in an operation, together with one of pyrites, the latter must be in exceedingly fine powder; the two are mixed in a warm porcelain dish or agate mortar, and transferred to the tube without loss. The delivery tube is then inserted with its extremity dipping into the flask. A channel is made on the surface of the mixture, and the tube suitably supported is heated in small portions at a time with a Bunsen gas flame, commencing as usual with the anterior portion. When the operation is progressing favourably, the deflag ration proceeds for a few seconds after removing the flam There is no danger to be apprehended, and the tube does not crack or blow out with proper care. When the tube has been heated throughout, and the deflagration has ceased, it is then more strongly heated with a Herapath or powerful gas flame. It is a good plan at this stage to slip a coil of wire gauze over the tube, which helps to accumulate the heat. It is not, however, necessary that the contents should be fused a second time, at least this has not been done in experiments appended. The sulphur ores examined have yielded their sulphur readily. The gaseous products of the combustion which mechanically carry over with them small quantities of sulphates or sulphuric acid, being heavier than air, collect in the flask, and are washed by shaking with a little water, closing the flask with the palm of the hand. The delivery tube is also washed. That containing the fused mass is carefully broken and put in the flask, together with sufficient hydrochloric acid to dissolve nearly the whole of the iron oxide; then ammonia is added, until a precipitate of oxide reappears, and lastly as much free HCl and water as are necessary to bring the fluid to the conditions which obtained when the barium solution was standardised. I have used 2 c.c. of free acid, and the total volume of solution was 200 c.c. Experiments have been made on three samples of iron yrites. The one containing the most sulphur has a bright crystalline fracture, and appears to contain but little siliceous matter. I have not made a complete analysis of it, as I wish to reserve a specimen. It was given to me by the landlord of a small inn at Macugnaga in the Val-Anzasca, near which place a mining company has been established to work the vein. The mineral is said to contain gold. I am uncertain of the source of the other two specimens. In the following experiments I have compared the results obtained by the method of working just de scribed with those obtained by oxidising the sulphide with nitro-hydrochloric acid. In some laboratories both processes are used in valuing sulphur ores. The tables give the sulphur per cent on the dry sample. Mean 50:46 50'45 47°42 47'44 45.80 45'80 A single gravimetric determination was made on the Val-Anzasca specimen; the number obtained was 50'44. Nitro-hydrochloric acid was used to oxidise the sulphur, and the excess was removed by evaporation at 100° C. before adding the barium salt; the precipitation was made in the boiling solution, which was somewhat dilute. The chief cause of failure in conducting a fusion as above described is the possible incomplete oxidation of the sulphur. Such is rarely the case, provided the heat is sufficient and the mineral finely divided. To insure the latter condition it is desirable to sift the dry sample through muslin. I have not had an opportunity of extending the method to sulphur minerals generally, but there is little doubt that most, if not all, can be decomposed in this manner without loss of sulphur-that is to say, if ordinary precaution be taken. An anterior layer of fusion mixture may be dispensed with, and it is not necessary to rinse the dish; a camel-hair brush will remove any remaining particles both from it and the mouth of the tube. DETECTION AND ESTIMATION OF PARAFFINE IN STEARINE CANDLES. By M. HOCK. MAKERS of stearine candles mix paraffine with the fatty mass in quantities up to 20 per cent. Paraffine candle attribute valuable properties to such a mixture, so far as makers also mix stearic acid with their paraffine, and candle-making is concerned. The attempt to determine if paraffine be present, and if so, to get some approximate idea of the quantity, in a sample of stearine and point and specific gravity of such a mixture, is shown to vice versa, by means of the comparison of the meltingwhich the paraffine is obtained, as also in the case of the be useless, as these vary according to the source from stearic acid, since the pure commercial article is by no means a chemically pure article. acid in paraffine has been devised by R. Wagner, viz., by A good method for detecting the presence of stearic treating a boiling solution of the paraffine in alcohol with an alcoholic solution of neutral acetate of lead, when, if stearic acid be present, a dense floccular precipitate appears, but none if it be absent. method, and one which can be used quantitatively as well as qualitatively, is described as follows: The best Not less than 5 grms. of the candle are taken and treated with warm solution of hydrate of potash, which the stearic acid, whilst the paraffine is left unaltered. must not be too concentrated. A soap is formed with Salt is thrown into the solution, whereby the soap is separated out as a soda soap, and in precipitating takes down the paraffine with it. The soap obtained is thrown on the filter and washed with cold water or very dilute spirits of wine. Thus, firstly, the salt is washed out, and finally, the soap is brought into solution and likewise then dried at a temperature below 35° C., so as not to fuse washed through the filter, leaving the paraffine, which is and after repeated washing with this solvent, the ethereal it. The paraffine is then treated on the filter with ether, solution is carefully evaporated in a weighed porcelain crucible, in the water-bath, at a low temperature. The residue, consisting of the paraffine, is then weighed, and the stearic acid is estimated by difference. ON THE MEANS OF REGULATING GAS-FLAMES JEANNEL and Martensont have recently published descriptions of regulators of temperature, by means of which a constant temperature higher than that of the boilingpoint of mercury may be kept up. It is unnecessary to enter here into details of the construction of these apparatus; suffice it to say that air is applied in them as the expanding medium. While engaged in a series of experiments on the process of dissociation of oxide of mercury, I required a high, but constant and only slightly varying, temperature for a considerable length of time, and for that purpose constructed a modification of Schlösing's apparatus, in which, in lieu of a mercury-reservoir, an air-reservoir is used, consisting of four glass tubes placed side by side and tied to each other, each tube 15 centimetres long by 2 centimetres diameter, This apparatus was placed into an airbath, through a slit cut in the top of it, at the side where the door is placed, care being taken that the bath is air *Polyt. Journ., No. 204, p. 460; Chem. Centralbl., 1872, p. 497. + Pharm. Zeitschr. f. Russland, 1872, No. 11, p. 136; Chem. Centralbl., 1872, p. 513. |