NOTES AND QUERIES. Our Notes and Queries column was opened for the purpose of giving and obtaining information likely to be of use to our readers generally. We cannot undertake to let this column be the means of transmitting merely private information, or such trade notices as should legitimately come in the advertising columns. Cleaning Engravings.-Will you be good enough to tell me, through the medium of the CHEMICAL NEWS, how I can best remove stains from engravings? I have tried a solution of chloride of lime, and succeeded in removing the stains, but could not get rid of the lime. Though I washed the print for six hours there remained, upon drying, a crystalline deposit on the face of the print. If I use a second bath of hyposulphite of soda as an anti-chlor will it not be as difficult to remove it from the fibre of the paper as it is to remove the lime? and would not the crystallisation of the hypo in the body of the paper be just as destructive as that of the lime would be?-PERPLEXED. Royal Institution, 3. "On the Classification of the WEDNESDAY, 2nd.-Society of Arts, 8. Geological, 8. "Evidence of a Carnivorous Reptile (Cynodrakon major, Ow.) about the size of a Lion, with Remarks thereon," by Prof. Owen, C.B., F.R.S., F.G.S. "On the Occurrence of the Genus Astrocrinites (Austin) in the Scotch Carboniferous Limestone Series, with the Description of a New Species (A.? Bennici), and Remarks on the Genus," by R. Etheridge, jun., F.G.S. "On the Genus Merycochærus (Fam. Oreodontidae), with Descriptions of Two New Species," by G. T. Bettany, B.A., B.Sc. Microscopical, 8. (Anniversary). Pharmaceutical, 8. THURSDAY, 3rd.-Royal, 8.30. = Royal Institution, 3. "On the Chemistry of the Non-Metallic Elements," by Prof. Gladstone. Royal Society Club, 8.30. Chemical, 8. "On the Formation of the Hydrocarbons of the CnH2n and CnH-2 Series and their Combination with the Haloid Acids and other Compounds," by H. E. Armstrong. "Note on the Formation of Anthrapurpurin," by W. H. Perkin. "On High Melting-Points. with special reference to Metallic Salts," by T. Carnelley. "On Metachromism, or Colour Changes," by W. Ackroyd. FRIDAY, 4th.-Royal Institution, 9. "Applications of Electricity to Silicates of Soda and Potash in the state of Protect Life on Railways," by Mr. Preece. Mineralogical (7, Savile Row), 12. "On the Scottish Rhombohedral Carbonates," by Prof. M. Forster Heddle, M.D., F.G.S.E. Geologist's Asociation. (Anniversary.) SATURDAY, 5th.-Royal Institution, 3. "On Excavations in Asia Minor," by R. P. Pullan. Manchester: PALMER & HOWE, 1, 3, and 5, Bond Street. London: SIMPKIN, MARSHALL, & Co. Soluble glass, or in CONCENTRATED SOLUTION of first quality, suited for the manufacture of Soap and other purposes, supplied on best terms by W GOSSAGE and Sons, Soap Works Widnes, Lancashire. London Agents, CLARKE and COSTE, 19 and 20, Water Lane, Tower Street, E.C., who hold stock ready for delivery. MINERALOGY & GEOLOGY. COLLECTIONS and SPECIMENS, also CABINETS, BOOKS, and every necessary for the study of the above, may be obtained as usual of JAMES R. GREGORY, at his New and Extensive Showrooms, No. 88, Charlotte Street, Fitzroy Square. Minerals for Chemical Research, -&c. TO LECTURERS, SCIENTIFIC TEACHERS, AND OTHERS. MR. J. C. STEVENS has received Instruc tions from CHARLES HEISCH, Esq., F.C.S., to offer for Sale by Auction (without reserve), at his Great Rooms, 38, King Street, Covent Garden, on Friday, February 4th, at hall-past 12 precisely, the Contents of his late Chemical Laboratory in the Middlesex Hospital Medical College, consisting of Chemical and Physical Apparatus,, Microscopes, Electrical Apparatus, Chemical Sets, Glass Bottles, &c., and a quantity of Photographic Apparatus, &c. On View the Morning of Sale, and Catalogues had. MR. VACHER will retire from the Chemical F. W. HART, Manufacturer and Dealer in LABORATORY, 20, Great Marlborough Street, W., on Lady Day next. The Fittings and Apparatus will be sold. Apparatus and Chemicals for Scientific Pursuits. Labora tory Fitter and Furnisher. Photographic Apparatus and Materials. 8, KINGSLAND GREEN (WEST SIDE), LONDON. CAST-IRON COILS. EXPANSION AND CONTRACTION UNLIMITED. 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Raw Materials for Manure Manufacturers. 78 & 80, ST. ANDREW STREET: LIVERPOOL. NEWS As is well known to those who frequently have occasion to determine the amount of manganese in speigeleisen, the usual methods are tedious and require great care on the part of the analyst. If sodium acetate is used to separate the iron, the oxide of manganese retains a considerable quantity of soda, which is extremely difficult to get rid of; and, on the other hand, if ammonium acetate is used, the precipitation of the manganese is very slow or it requires a large excess of bromine. ex Although the above methods have been in use for a long time no attempt seems to have been made to get a more expeditious one, or at all events none have been successful until Mr. Parry showed that a definite oxide of manganese could be got which enabled him to determine the manganese very accurately and peditiously. His method is simply to dissolve a weighed quantity of the speigeleisen in nitric acid (sp. gr. 1.20) in a small pear-shaped flask, evaporate to dryness, and heat pretty strongly over a Bunsen burner or spirit-lamp for about ten minutes. He then treats the contents of the flask exactly as a manganese ore, heating with sodium oxalate and hydrochloric acid, and measuring the resulting carbonic acid. The apparatus he uses (which was devised for the purpose) is, he states, a modification of Schiebler's, but as a matter of fact has many advantages over that apparatus, excellent as it is. One very decided advantage is that it admits of heating the solution, and altogether it would be very valuable in a laboratory, where the accurate estimation of carbonates or the measurement of gases are frequently required. As everyone, however, has not got the apparatus, I thought it would be advisable to show that the manganese could be determined some other way. The then heat with rather dilute hydrochloric acid. contents of the flask very soon dissolves, but it is well to keep shaking the solution while it is being heated to prevent loss of chlorine. It only remains now to determine the iron left unoxidised in order to arrive at the quantity of manganese, which can be done of course with potassium bichromate solution. If it is feared that the ferrous solution may get oxidised by exposure to the air, a small piece of marble put into the flask, which can also be fitted with a cork and tube, will readily prevent that. In four successive experiments I obtained the following results: No. Fe Oxidised. Equal to By Manganese p. c. Parry's Method. 23.88 No. 2 gave by the acetate of ammonium method 20:55 per cent, which was done with great care. repetition of No. 3. No. 4 is a If it is admitted that Mn2O3 can be easily formed, a number of methods immediately suggest themselves as being likely to give the amount of manganese, prominent among which is the well-known method of treating with hydrochloric acid, and passing the resulting chlorine through a solution of iodide of potassium, the liberated iodine being titrated with sodium hyposulphite. ("Fresenius," fifth edition, p. 135). Accordingly I tried that method, but although I took every care, and returned to it again and again I completely failed to obtain accurate or even constant results. This seems strange (I may say that Mr. Parry had previously tried and failed also), and at first I attributed my failure to the fact that I was not getting Mn2O3, but was afterwards convinced that it is much easier to get that oxide than at first sight it appears. I can scarcely avoid coming to the conclusion that there is something wrong with this method of determining free chlorine. It is evident of course that there is nothing original or new in the above method, but it contrasts very favourably with the usual methods of separating the iron with sodium or ammonium acetate, and precipitating the manganese from the filtrate with bromine. It is not at all troublesome, does not take long, and has the advantage that the only chemicals and apparatus required are those which are necessary for the assay of iron ores. The next method I tried proved in every way successful. I proceed exactly as Mr. Parry does (and find no difficulty in getting Mn2O3). 1 grm. of the speigeleisen is dissolved in nitric acid (sp. gr. 120) in a small round-bottomed flask, and evaporated to dryness. When dry the flame, which may be either a spirit-lamp or a Bunsen burner, is turned so that the bottom of the flask is cherry-red, for ten minutes. It is then allowed to cool very gradually. Ebbw Vale, Mon. ON SOME NEWLY OBSERVED PROPERTIES POSSESSED BY CERTAIN SALTS OF FULMINIC ACID.* At this point instead of forming carbonic acid, I simply put into the flask a weighed quantity of ammonio-ferrous sulphate or ferrous sulphate of a knowp strength, and By EDMUND W. DAVY, M.A., M.D. Professor of Forensic Medicine, Royal College of Surgeons, Ireland THE salts of fulminic acid, or the fulminates, have not received the attention which the interest arising from their extraordinary properties would lead us to expect. This highly explosive and consequently dangerous compounds, is, no doubt, due in a great measure to their being such which have already occasioned several serious and even fatal accidents to individuals whilst making them objects of research: they are, therefore, considering the amount perties, not very inviting subjects of inquiry, and necessiof personal danger attendant on a study of their protate the exercise of much caution on the part of those engaged in their investigation. The compound which is known to chemists under the pirical formula H2C2N2O2, though it has never yet been name of fulminic acid, and which is expressed by the emisolated or obtained in the free state, is capable, as is well salts, which are endowed with more or less explosive proknown, of forming a number of simple and compound perties. Of those salts, by far the most important is the fulminate of mercury, which constitutes, as is well known, detonating matters which are used to fire the charges in the active constituent of the percussion caps, and of the our guns and pieces of ordnance; and for those purposes it is now manufactured in large quantities, and forms a very important instrument of modern warfare, since by its rude means of firing small and large guns have been quite employment the use of flint and steel, matches, and other abandoned, at least among all civilised nations. Whilst making some experiments on the fulminate of cyanide of potassium, both in aqueous solution, are gently mercury, I observed that when that salt and the ferroheated together, the mixture at first acquires a faint reddeep purple colour, without the separation apparently, at dish yellow tint, which quickly passes into a port-wine or * A Paper read before the Royal Irish Academy. 48 Properties Possessed by Certain Salts of Fulminic Acid. least at first, of any gas or solid matter. The development, On prosecuting this inquiry, I further ascertained that when the purple compound was fully developed, if the heat was continued for some time, or more quickly if the temperature was raised to and maintained at the boilingpoint, the purple colour gradually disappeared, the liquid acquiring a light yellow tint, whilst more and more of a reddish brown solid matter (which was ascertained to be the peroxide of iron) was produced; these changes being accompanied by the evolution of more or less of ammonia, and by the mixture, which was at first quite neutral, acquiring a strong alkaline reaction. The solution being filtered, and concentrated by evaporation, was found to yield small prismatic crystals of a colourless or very light yellow salt, which appears to be a double cyanide of potassium and mercury. Considering that the principal feature of interest in the reaction of the fulminate on the ferrocyanide was the formation of the purple compound, my attention was chiefly directed to its investigation. But I soon ascertained that this compound was a substance of a very unstable character, and that it presented great difficulties in the way of its separation from the matters with which it was associated, as procured in the reaction referred to; and not being able to obtain it in a pure or suitable state to submit it to actual analysis, I was for a considerable time unable to obtain any clue as to its real nature, further than it was some organic compound of iron, in which cyanogen, or at least its elements, were constituents. At last it occurred to me that the colouration observed might be in some measure connected with the formation of the fulminate of iron; and on making some of that salt, and comparing its reactions with those of the compound referred to, many points of agreement between them were at once perceptible. I may observe that the fulminate of iron is readily obtained by the action of metallic iron on the fulminate of mercury suspended in water. Thus if about equal bulks of the fulminate and of fine iron filings are placed in a small stoppered bottle, which is then filled with distilled water, and being closed is occasionally agitated, the liquid in a short time acquires a yellowish tint, which gradually deepens in colour, whilst the filings become tarnished, and more or less of mercury, in the form of minute globules, make their appearance. After a few hours the decomposition of the fulminate of mercury will be more or less complete, and on filtering the mixture a dull yellow liquid is obtained, which holds the fulminate of iron in solution. This fulminate, as so obtained, was described by my late father amongst several other compounds of fulminic acid, which he was, I believe, the first 10 discover, during his elaborate researches on that acid. This salt was observed by him to produce, when treated with diluted acids, a fine red or purple colour, which disappeared after some time, evolving hydrocyanic acid amongst other products. He also found that a somewhat similar colour, rapidly changing to a bluish black, with a precipitate of that colour, was developed on heating this fulminate. But this development of colour only occurs in the case of the freshly prepared fulminate of iron, for the salt, being one of very great instability, commences almost immediately after its formation to undergo spontaneous changes, which are attended by the separation of a dark brown substance, even when the solution is kept excluded from the air in a well stoppered bottle: and after such changes have taken place it ceases to develop, either by the action of acids or by heat, the colouration just stated. My father also observed that alkalies produced in freshly prepared fulminate of iron a dull green precipitate, quickly changing to a brown colour, which is obviously due to the CHEMICAL NEWS, separation of iron as an oxide from the fulminate of iron As to the singular development of colour when the ful- acid again develops the purple colour by the re-formation 2FeC2N2O2+2KHO=FeK2(C2N2O)2+FeO+H20; and this double fulminate develops, as before observed, the purple colouration when treated with a diluted acid, and again becomes colourless, or very nearly so, on adding an excess of alkali, especially after the application of heat, and the colour can be again restored by acidifying the mixture, and these changes may be produced many times in succession. For the production of the acid fulminate of iron the NEWS double neutral salt is much preferable to that of the simple neutral fulminate of that metal, as in the latter case there will be produced, as before shown, a proto-salt of iron, which reacts on the acid fulminate, occasioning its more or less rapid decomposition. I may further observe that on heating the double fulminate just described there will be developed the red or purple colouration, unless there is present too great an excess of alkali. This remark, however, does not apply to the case of ammonia, the excess of which being expelled by heat does not interfere with its production. This development of the acid fulminate by heat is not so easily accounted for as where it has been due to the action of acids; it may, however, depend on the circumstance that the simple neutral and double fulminate of iron, are both easily resolvable by heat under certain conditions into the acid fulminate. I shall now point out how the explanation I have given of the production of the purple colouration in the case of the fulminate of iron may likewise serve to account for the similar development of colour, which I have myself observed, in the reaction of the ferrocyanide of potassium on fulminate of mercury. My experiments would seem to show, that when those compounds react on each other, there is at first formed, amongst other products, the double fulminate of iron and potassium, which, like that salt prepared directly, as already described, from the fulminate of iron, passes into the purple acid fulminate of that metal, on being heated or treated with diluted acids; the following formula and equation explaining the production of the double salt, accompanied, as it is in this case, by the cyanide of mercury and potassium : 2HgC2N2O2+K FeCy6=FeK2(C2Ñ2O2)2+ +2HgCy2+2KCy. Amongst other facts which might be mentioned in support of the foregoing statement is the following one that I have observed, that when the ferrocyanide of potassium and the fulminate of mercury, along with water, react on each other at the ordinary temperature, the mixture after a short time acquires a yellowish tint, which gradually passes into that of a reddish shade; and if a portion of the mixture in this early stage of reaction be treated with a drop or two of any dilute acid, or is heated, the deep purple colouration which results when the double fulminate is similarly acted on will at once be developed. I shall now briefly notice some of the more characteristic properties of the acid fulminate of iron as obtained by the action of the ferrocyanide of potassium on the fulminate of mercury, most of my experiments having been made on that salt as so procured. When that compound is dissolved in water it appears to possess, at the ordinary temperature, considerable stability, for it has been exposed to the air and even light in an open vessel for several weeks without its appearing to undergo any change of colour; but when the solution is allowed, even spontaneously, to evaporate to dryness, the dark purple residue very soon passes to a brown colour, from the decomposition of this salt, and the separation of its iron in the form of peroxide; and this proneness to decompose in the dry condition may account for the residue not exploding on the application of a strong heat, the salt having quietly decomposed before reaching the temperature necessary to explode it or other fulminates; and I may further observe, that even in aqueous solution it soon decomposes if the temperature is raised to the boiling-point, its decomposition being attended with the separation of peroxide of iron and ammonia. It does not appear to be soluble in ether, chloroform, bisulphide of carbon, or in benzol, though it is readily dissolved by alcohol. It is quickly decomposed by strong acids, with the evolution of hydrocyanic acid and the development of Prussian blue, and even in their diluted condition the same occurs, but more slowly. The caustic alkalies, at the ordinary temperature, slowly decolourise its solution; with the assistance, however, of heat that effect is quickly produced. It appears to possess but little, if any, disposition to assume a crystalline form, for as yet all my attempts to obtain it separately in such a condition have been unsuccessful. Several experiments were made as to the effects of dif ferent metallic salts on this compound, but no very characteristic results were observable, except in the case of the nitrate of silver, which produced a dull bluish precipitate, leaving the liquid colourless if sufficient of the silver salt be added. This precipitate, however, is one of great instability, for it very soon loses its blue colour (even when lying at the bottom of the stratum of liquid from which it has been precipitated), and becomes of a white or yellowish white appearance. If, however, while it still retains its blue colour, it is treated with diluted hydrochloric acid, or with an alkaline chloride, the solution regains its original purple colour, whilst the chloride of silver precipitates; but if the addition of the acid or chloride be delayed till after the precipitate has become white, then both fail to reproduce the purple colouration, owing to the previous decomposition of the silver compound. This red or purple combination appearing to be but little affected by many of the metallic salts seems to strengthen the view I have taken as to its nature, for had it been a peculiar cyanogen compound, such as we have in the case of the ferro-, ferri-, and nitro-ferricyanogen, as well as in other compound salt radicals of that substance, we should have expected that it would have produced very characteristic effects with different metallic salts. I may further observe that the same compound is formed when the ferricyanide of potassium (or as it is better known under the name of red prussiate of potash), instead of the ferrocyanide of potassium (the yellow prussiate), in aqueous solution is heated along with the fulminate of mercury, and that it, as well as the ferrocyanide, even without the application of heat, give rise to, but more slowly, the formation of the red or purple combination, the ferricyanide acting, however, in this respect more readily than the ferrocyanide. Lastly, I may add that I found that a similar purple compound was produced when the fulminate of silver was substituted for the mercurial salt in the reactions referred to, and that it is probable that some at least of the other fulminates would give rise to like effects. I regret that the results which I have brought before the Academy are not, in some respects, of a more definite character; but all who have experimented on the fulminates have experienced the great difficulties of such enquiries, arising from their instability and complexity of constitution; but I hope before long to be able to investigate more fully the subjects of this communication, as well as other matters bearing on them. I trust, however, that the results of the observations which I have already made may not be considered as devoid of interest, as any facts which may extend our knowledge of fulminic acid (a compound regarding the true nature of which chemists are not yet agreed) must possess more or less interest in a scientific point of view; and it is well known that many facts and observations, which at first have been regarded as mere matters of interest to men of science, have afterwards proved of much practical utility. Verification of Instruments.-The Kew Committee of the Royal Society give notice that in order to afford to the public greater facilities for the verification of instruments at Kew than have hitherto existed, they are prepared to undertake the transport of instruments, &c., from London to Kew and back, free of charge. With this object they have made arrangements for Mr. R. Strachan, of the Meteorological Office, 116, Victoria Street, to receive at that office any instruments intended for verification. As soon as the instruments have been verified and are returned to London, notice will be sent from Kew to the parties concerned. |