The following Papers and Reports were read:— 1. A New View of the Genesis of Dalton's Atomic Theory, derived from Original Manuscripts. By Sir H. E. RoscoE, F.R.S., and ARTHUR HARDEN. A number of previously unknown manuscript volumes in Dalton's writing have been found in the library of the Manchester Literary and Philosophical Society. These consist of laboratory note-books containing the record of Dalton's practical work from the year 1802 onwards, and the notes used by him for some of the lectures delivered at the Royal Institution, London, in 1810. The examination of these volumes has cast an unexpected light on the genesis of the atomic theory, and the relation in which that theory stands to the law of combination in multiple proportions. Neither in Dalton's published papers, nor in the New System,' was any satisfactory account to be found of the genesis of his theories, and hence the question as to whether the atomic theory was founded on an experimental knowledge of the law of combination, or whether Dalton arrived at this law as a necessary consequence of the atomic theory of matter, was not to be gathered from his own writings. The balance of evidence derived from these newly discovered documents is strongly in favour of the statement made in London by Dalton himself, in 1810, that he was led to adopt the atomic theory of chemistry in the first instance by purely physical considerations, in opposition to the view, hitherto held by chemists, that the discovery by Dalton of the fact of combination in multiple proportions led him to devise the atomic theory as an explanation. 2. Report on the Teaching of Science in Elementary Schools. 3. The Action of Nitric Oxide on some Metallic Salts. The experiments here recorded are part of a systematic investigation into the conditions of stability of the oxides of nitrogen. They are by no means complete, but the results so far obtained appear to be of sufficient interest to warrant a preliminary notice. The reactions of nitric oxide have so far alone been studied. The gas was prepared by Emich's method-viz., the interaction of sodium nitrite, strong sulphuric acid, and mercury. The mixture was kept in continual agitation by a specially contrived stirrer, worked by a turbine. In this way a regular stream of gas is obtained, which analysis showed to be of a high state of purity. In order to study the action of nitric oxide upon the salts selected a weighed amount of the salt was placed in a boat contained in a Lothar Meyer constant temperature furnace. By means of a thermostat, also devised by Lothar Meyer, the temperature can be kept constant to within one degree. Temperatures above the range of an ordinary instrument were measured by means of a high temperature thermometer, constructed by Max Kaehler and Martini, of Berlin, which would give accurate readings to over 400°. The salt was heated gradually in a stream of nitric oxide, and the phenomena noted as the temperature rose. The salt was weighed at different intervals of temperature and time. Thus it was possible to tell at what temperature reaction began, and at what point it attained a maximum velocity. So far oxy-salts have been chiefly studied. It was thought that by comparing their behaviour under the above conditions some light might be thrown on their stability, and thence on their constitution. One or two oxides were first examined, the results agreeing with those of Sabatier and Senderens; e.g., PbO, forms a basic nitrate of lead: when heated in nitric oxide the action begins at 15°, but does not attain its maximum till over 130°. MnO, behaves similarly, but the change is not so rapid. It attains a maximum at 216°. In neither case is any but a trace of a nitrite formed. Silver oxide, if containing traces of moisture, yields a mixture of almost equivalent parts of silver nitrite and metallic silver at the ordinary temperature. At higher temperatures, with the dry oxide, nitrate and metallic silver are formed almost entirely. Silver permanganate behaves, when treated with nitric oxide, very much as a compound of oxide of silver and a higher oxide of manganese might be supposed to do. It begins to be attached at the ordinary temperature, and at 80° the alteration is very rapid. The residue was found to consist of metallic silver, silver oxide, silver nitrate, and manganese dioxide. Very little, if any, manganese nitrate was formed. Potassium permanganate is much more stable than the silver salt. It is not appreciably attacked till a temperature of over 100° is reached, and the increase in weight becomes rapid at 190°. The residue on moistening was not alkaline, and no manganese could be dissolved out. The potassium is converted into nitrate, and the manganese into oxide. Interesting differences were noted in the behaviour of other silver and potassium salts, notably, the chlorate and iodate. Potassium chlorate is attacked by nitric oxide at the ordinary temperature, chlorine being evolved in considerable quantity, and nitric peroxide being formed. The gaseous product was condensed in a tube immersed in a freezing mixture, and the percentage of chlorine in the brown liquid obtained was determined. It was found to be much in defect of that required to form nitrosyl or nitroxyl chloride. So that the reaction does not consist simply in the formation of an oxychloride of nitrogen. On analysis of the residue in the boat, no chloride of potassium was found to be present. Nitrate was formed. and also a trace of perchlorate. This seems to be direct proof that in potassium chlorate the potassium and chlorine are separated. With barium chlorate a similar reaction takes places. With silver chlorate (prepared according to Stas's method from silver oxide) chlorine was given off, but a considerable amount of silver chloride was also formed, nearly one-third of the silver present being found as chloride. This may be due to a difference in constitution between the chlorates of silver and of potassium, or to a difference in the stability of the salts and the products of reaction. That some difference of constitution exists between the silver and potassium salts appears to derive confirmation from the behaviour of their iodates when treated with nitric oxide. Potassium iodate heated to 80° in nitric oxide begins to give off iodine, and the reaction becomes rapid at 110°, crystals of iodine condensing on the cool portion of the tube; no trace of iodide, however, is formed, as is shown by there being no liberation of iodine on acidifying a solution of the residue after adding some potassium iodate. The residue is not alkaline, the potassium being converted into nitrate, recognised by the evolution of ammonia when the residue is warmed with zinc dust and caustic soda. Silver iodate, on the other hand, is stable up to a rather higher temperature than the potassium salt, and when heated above this temperature, about 110°, no trace of iodine is given off, but all the silver is converted into iodide, none being dissolved out by water, and the yellow residue being insoluble in dilute nitric acid. The perchlorates and periodates which have been examined show themselves more stable than the corresponding chlorates and iodates. Of the salts so far examined the chromates have shown themselves the most stable, being analogous in this respect to the sulphates. Lead chromate was unaltered at temperatures exceeding 400°. 1895. UU Silver chromate did not suffer appreciable change till above 300°. Metallic silver was found to be present in the residue as well as silver nitrate. The chromium was all converted into the sesquioxide. Some amount of nitrite of silver was also formed. Silver sulphate is only attacked at the highest temperature of the furnace. It was found in certain cases-e.g., with lead nitrate-that the intermixture of a decomposable oxide-e.g., PbO, or MnO2-with the salt, caused the latter to be attacked at a temperature below that at which action begins with either the salt or oxide taken separately. Experiments have also been in progress on the interaction of nitric oxide and various gases, but the results are not yet quite complete enough for publication. 4. On the Respirability of Air in which a Candle Flame has burnt until it is extinguished. By FRANK CLOWES, D.Sc. At the last meeting of the British Association the author stated the composition of artificial mixtures of nitrogen and carbon dioxide with air, which were just able to extinguish various flames. It was found that the flames of ordinary candles and lamps were extinguished by mixtures which contained on the average about 16.5 per cent. of oxygen and 83.5 per cent. of the extinctive gases. A flame of coal-gas, however, required for its extinction a mixture still poorer in oxygen, and containing 11.3 per cent. of oxygen and 88.7 per cent. of the extinctive gases. These results have since been confirmed by a different method. The method consisted in allowing the flames to burn in air enclosed over mercury until they were extinguished; the remaining extinctive atmosphere was then subjected to analysis, and its composition was found to be practically identical with that previously obtained from the artificial mixtures. An analysis of air expired from the lungs proved that it was also of the same composition as that which extinguished the flame of an ordinary candle or lamp. The average percentage composition of expired air and of air which extinguishes a candle flame is as follows:-oxygen 164, nitrogen 80.5, carbon dioxide, 3.1. Now an atmosphere of this composition is undoubtedly respirable. Physiologists state that air may be breathed until its oxygen is reduced to 10 per cent. The maximum amount of carbon dioxide which may be present is open to question, but it is undoubtedly considerably higher than 3 per cent. Dr. Haldane maintains that the above atmosphere is not only respirable, but would be breathed by a healthy person without inconvenience of any kind; he further states that no permanent injury would result from breathing such an atmosphere for some time. The conclusion to be drawn from these facts is that an atmosphere must not be considered to be dangerous and irrespirable because the flame of an ordinary candle or oil lamp is extinguished by it. The view is very generally advanced that a man must, on no account, venture into air which extinguishes the flame of a candle or of a bundle of shavings. It will be seen that this precaution may deter one from entering an atmosphere which is perfectly safe and respirable, and from doing duty of a humane or necessary character. An atmosphere which extinguishes a coalgas flame, however, appears to approach closely to the limit of respirability, as far as the proportion of oxygen which it contains is concerned. Hence the coal-gas flame appears to be a more trust worthy indicator of respirability than the flame of a candle or oil-lamp. Undoubtedly the candle and lamp flames should be discarded as tests of respirability of air. 5. The Action of Light upon the Soluble Metallic Iodides in presence of Cellulose. By Douglas J. P. BERRIDGE, B.A., Malvern College. It was shown by Cook, in 1894, that whilst potassium iodide, purified by ordinary methods, is decomposed by light, the salt is not thus affected if purified by either fusion with charcoal or crystallisation from absolute alcohol. Although this is so, the iodide is readily decomposed, even when perfectly pure, when exposed to light in the presence of cellulose, the most suitable form of this material being filter-paper, which has been extracted by hydrochloric and hydrofluoric acids. If a solution of the ordinary pure salt is sealed in a bulb and exposed to light, whilst in another bulb is placed an equal quantity of the same solution, together with pure cellulose, it is found that considerably more iodine is liberated in the latter than in the former: this difference in many cases amounting to 800 per cent. The solution not containing cellulose gives an alkaline reaction with phenolphthalein, whilst one sealed with sufficient cellulose is quite neutral: the action of the cellulose is therefore probably due to its combination with any potassium hydrate produced by the oxidation of the iodide in presence of light and moisture. If a sheet of note-paper containing starch is saturated with a solution of potassium iodide, and exposed to light in a printing frame under a negative, it will become printed in a period varying from ten minutes to four hours, the colour of the exposed paper being pink or chocolate; this changes, however, to blue when placed in water, the alteration being doubtless due to the formation of the so-called starch iodide, for the production of which the presence of an excess of water is necessary. It was found impossible to imitate this chocolate colour by any solution of iodine: if the solution was aqueous, a blue stain was produced, whilst, if anhydrous, a brown stain resulted. At last, however, the colour of the exposed paper was obtained by the action of a very concentrated solution of potassium iodide upon paper previously coloured blue by starch iodide. This appears to show that the colour is due to the formation of potassium triiodide, or some similar compound. The prints obtained in this manner were fixed by rapid washing in water, followed by treatment with a dilute solution of lead acetate; if subsequently sized and varnished, they appear to be quite stable. The iodides of sodium, calcium, strontium, barium, iron, and zinc, all behave like the potassium salt: the two latter, however, yield prints difficult to see, owing to the decomposition of the salt upon the portions of the paper unexposed to the light. Cadmium iodide differs from the other soluble metallic iodides in yielding a print which is blue, and not chocolate coloured; from which it appears that this element is alone unable to form a higher iodide. 6. Second Report on Quantitative Analysis by means of Electrolysis. See Reports, p. 235. 7. Report on Wave-length Tables of the Spectra of the Elements. FRIDAY, SEPTEMBER 13. Joint Meeting with Section A.-See p. 609. SATURDAY, SEPTEMBER 14. The Section did not meet. MONDAY, SEPTEMBER 16. A discussion was held in conjunction with Section K (Botany) on the Relation of Agriculture to Science. The discussion was opened by the following Papers:How shall Agriculture best obtain Help from Science? By Prof. R. WARINGTON, F.R.S. Ordered to be printed in extenso.-See Reports, p. 341. Agriculture and Science. By T. HENDRICK. The Application of Science to Agriculture. By M. R. J. DUNSTAN. The following Paper and Reports were read: 1. Work at the Agricultural Experimental Stations in Suffolk and Norfolk. By T. B. WOOD. Two stations were started in West Suffolk in 1893, one on the chalk at Higham, the other on a good deep loam at Lavenham-both typical soils in the county. Crops are grown at each station in rotation with various manures, and an annual report is printed and circulated among farmers of the county. Demonstrations are given on the plots on the action of manures, the methods and effects of potato spraying, &c. Expenses are borne by West Suffolk Technical Instruction Committee, and the management is under the Cambridge and Counties Agricultural Education Scheme. In Norfolk the arrangements are different. The experiments, started in 1886, are conducted by the Chamber of Agriculture; since 1888 they have received an annual grant from the Board of Agriculture, and since 1892 one from the Technical Education Committee of the Norfolk County Council. The experiments have included manurial experiments on all the ordinary crops in the usual course of farming; the comparison of many well-known varieties of wheat and barley; the value of residues of manures, and various sheep-feeding experiments to test the value of oil in cakes very rich in oil; the comparison of the values of many popular diets; the determination of the most economical rations, &c. Besides these experiments in the field a considerable amount of laboratory work has been done at both the county stations. 2. Report on the Preparation of Haloids from Pure Materials. 3. Interim Report of the Committee on the Bibliography of Spectroscopy. See Reports, p. 263. TUESDAY, SEPTEMBER 17. The following Papers and Reports were read: 1. Some Remarks on Orthochromatic Photography. By Dr. H. W. VOGEL. My first researches on orthochromatic photography were published twenty-three years ago. These investigations were confirmed by Becquerel and were first brought under the notice of the English public by Meldola in 1874. An account of the discussion is published, and is sold at the Office, price 3d. |