Instead of directly agitating the colourless solution with air, it may be first neutralised or rendered very slightly acid with hydrochloric acid, cooled, and then rendered alkaline with ammonia. If this solution be now agitated, in the manner before described, it becomes filled with minute green needles of amido-diimido-orcin. Although the first method gives the best results, when carefully conducted, it requires considerable experience to stop the oxidation at the precise point when the whole of the triamido-orcin is oxidised to amido-diimido-orcin, and before the latter becomes destroyed. With the ammoniacal solution there is far less danger of over-oxidation. Trinitro-orcin is also reduced by treatment with tin and hydrochloric acid, or zinc and hydrochloric or sulphuric acid. One part of trinitro-orcin and four parts of granulated tin are heated in a capacious flask with eight measures of concentrated hydochloric acid diluted with sixteen measures of water. In a short time a powerful reaction takes place, so that it is advisable to remove the flask from the source of heat in order to prevent the contents from boiling over. When the action has become somewhat moderate, the solution is boiled until it is colourless, then diluted with water, and the tin precipitated by hydrosulphuric acid. The clear solution acquires a purple tint on standing, and deposits large dark-coloured prisms of amido-diimido-orcin hydrochlorate, or the amido-diimido-orcin may be obtained directly by adding a slight excess of ammonia to the filtrate from the tin sulphide and oxidising by agitation in the presence of air, when the base immediately separates in minute green needles. Trinitro-orcin and granulated zinc are boiled in a flask with twenty or thirty parts of water, and hydrochloric acid added in small quantities at a time until the solution becomes almost colourless. The clear liquid, poured from the excess of zinc and allowed to cool, is rendered slightly alkaline by ammonia and exposed to the air. As soon as the triamido-orcin is oxidised, which may be known by the brown colour of the product, an excess of hydrochloric acid is added to dissolve the zinc oxide and precipitate the amido-diimido-orcin as hydrochloride. The yield is, however, considerably less than when sodium-amalgam is employed as the reducing agent. The amido-diimido-orcin sulphate or hydrochlorate obtained by any of the above processes is readily decomposed by treatment with a slight excess of dilute ammonia, leaving the free base in an impure state. This should then be dissolved in warm dilute acetic acid, filtered, and precipitated by a slight excess of ammonia. Two or three solutions and re-precipitations are sufficient to render it pure. Pure amido-diimido-orcin crystallises in small needles, which have a dark green metallic lustre by reflected light. They are insoluble in alcohol, ether, and benzol, and almost insoluble in water and dilute ammonia. Strong ammonia only dissolves the base in small quantity, yielding a pale blue solution, but it is readily soluble in a solution of sodic hydrate, with a fine deep blue colour; the solution, however, when boiled, loses its colour, ammonia being at the same time evolved. The base gives off ammonia when heated, and leaves a carbonaceous residue very difficult of combustion. As might be expected, when amido-diimido-orcin is treated with sodiumamalgam, it is re-converted into triamido-orcin. Analysis of Amido-diimido-orcin.-0'290 grm. substance, dried in vacuo, lost o'025 grm. when dried at 100°, equivalent to 8.62 per cent. I. 0140 grm. substance, dried at 100°, gave o 234 grm. carbonic anhydride and o'075 grm. water. II. o 290 grm. substance, dried at 100°, gave 0.487 grm. carbonic anhydride and o'152 grm. water. Theory. I. = 84 = 45'40 22.70 185 C7 N3 = = 100'00 II. Mean. 45'59 45'77 45.68 It will be seen that the results of the analyses agree with the formula C,(CH3) (NH2) (NH)2(HO)2+H2O for the substance dried at 100°, and the formula for the substance dried in vacuo is probably— C6(CH3) (NH2(NH)2(HO)2+2H2O, as it requires 8.87 per cent water. Triamido-orcin.-The colourless solution obtained by the reduction of trinitro-orcin with tin and hydrochloric acid, after removal of the tin by sulphydric acid, appears to contain triamido-orcin hydrochloride along with excess of hydrochloric acid. On concentrating the solution at 100°, much of the triamido-orcin is decomposed and a considerable amount of ammonium chloride formed; whilst, although long needles of triamido-orcin hydrochloride are obtained by evaporating it in a vacuum, yet owing to their great solubility, and the readiness with which they absorb water and deliquesce, the salt has not yet been obtained in a state fit for analysis. On moistening the crystals of this hydrochloride with ammonia they become almost instantaneously converted into the metallic-green needles of the amido-diimido-orcin. If a current of sulphuretted hydrogen be passed through a solution of ammonium sulphydrate in which amidodiimido-orcin is suspended, the latter rapidly loses its colour, and becomes converted into a sandy deposit consisting of colourless crystals. These are apparently triamido-orcin, and may be washed by decantation with a dilute solution of aramonium sulphydrate, in which they are but slightly soluble. These crystals rapidly acquire the metallic-green lustre of amido-diimido-orcin when exposed to the air, and are readily soluble in dilute acids. The hydrochloric acid solution behaves in a manner precisely similar to that obtained by the reduction of trinitroorcin with tin and hydrochloric acid, becoming deep red, and depositing crystals of amido-diimido-orcin hydrochloride when exposed to the air. Amido-diimido-orcin Hydrochloride.-The hydrochloride obtained in the preparation of amido-diimido-orcin, as described in the earlier part of this communication, may be purified by crystallisation from hot water; but as heat decomposes solutions of the salts of this base, it is better to precipitate a cold solution of the acetate by a slight excess of hydrochloric acid, in which the hydrochloride is but slightly soluble: the precipitate should be thoroughly washed with alcohol, pressed, and dried. Pure amido-diimido-orcin hydrochloride crystallises in different ways, according to the circumstances under which the crystals are formed. As produced directly by adding hydrochloric acid to the blue solution of the base in caustic soda obtained from trinitro-orcin by sodiumamalgam, it forms long silky needles of a brownish-red colour; an aqueous solution of the acetate or hydrochloride precipitated by an excess of hydrochloric acid yields a mixture of these needles with rhomboidal plates; the latter are purple by reflected light, and of an olivegreen colour by transmitted light. The slow oxidation of the hydrochloric acid solution of triamido-orcin obtained by means of tin and hydrochloric acid yields dark-coloured, short, thick prisms. The hydrochloride is insoluble in alcohol and ether, moderately soluble in cold water, and readily in boiling water, although the latter causes partial decomposition. Its aqueous solution is precipitated almost entirely on acidulating it with hydrochloric acid; but the salt is soluble in concentrated hydrochloric acid, especially when warm, forming a purple solution. On boiling this the salt is rapidly decomposed, and the colour changes to a dirty green. Analysis of Amido-diimido-orcin Hydrochloride.-0428 grm. substance, dried in vacuo, lost 0.035 grm. when heated to 100°, corresponding to 841 per cent water. I. 0 255 grm. substance, dried at 100°, gave o 180 grm. argentic chloride. II. 0232 grm. substance, dried at 100°, gave 0·164 grm. argentic chloride. III. 0 344 grm. substance, dried at 100°, gave o*242 grm. argentic chloride. ON ULTRAMARINE.* By C. UNGER. Mean. 20.69 468 100'00 The formula of this salt would therefore appear to be[C6(CH3)(NH2) (NH)2(HO)2]2SO4+H2O. Amido-diimido-orcin Nitrate is prepared, like the sulphate, by adding a slight excess of nitric acid to a moderately strong solution of the acetate, and washing the precipitate with alcohol. It closely resembles the sulphate in appearance, but is much more soluble in water. When heated with excess of nitric acid it is decomposed, yielding a yellow solution, which, on being evaporated, leaves a mixture of oxalic acid and an amorphous yellow substance. Amido-diimido-orcin Acetate. - Amido-diimido-orcin dissolves readily in acetic acid, and on carefully evaporating the solution, at a low temperature, the acetate is obtained in ill-defined crystalline plates having a purple iridescence. It is readily soluble in cold water, but only slightly soluble in glacial acetic acid. Amido-diimido-orcin Oxalate.-Very slightly soluble purple scales obtained by precipitating a solution of the acetate with oxalic acid. Amido-diimido-orcin Picrate.-On adding a solution of picric acid to a dilute solution of amido-diimido-orcin acetate, and washing the precipitate with alcohol, the picrate is obtained in iridescent green needles and plates. It is insoluble in alcohol, and but slightly soluble in water. I cannot conclude this paper without acknowledging the very efficient aid I have received from my assistant, Mr. Charles Edward Groves, in conducting this investigation. ALTHOUGH ultramarine has been frequently the subject of research, its chemical nature has not hitherto been well elucidated, and the supposition that it contains sulphuret of aluminium or sulphuret of sodium, or a polythionate of soda, becomes a dubious matter, seeing that ultramarine is not decomposed by fused chlorate of potassa, while it (the ultramarine) resists, for some length of time, fusion with alkalies and nitrates. Ultramarine, when ignited with A criticism of this Article appeared in our last number. soda-lime, yields only a trace of ammonia; but, when ignited with phosphor salt, or with an alkaline bisulphate, nitrogen is largely given off. This reminds me of an old observation made by the late Berzelius, who states, in his treatise on the blowpipe, that, when lapis lazuli is treated with phosphor salt, the mineral is dissolved with a continuous effervescence yielding a colourless bead. Nothing is said as regards the nature of the gas alluded to; it is probable, however, that even then it may have been known that lapis lazuli contains nitrogen. When I analysed a sample of artificially-made ultramarine, free from sulphuret of sodium, as well as from any acid of sulphur, I found that sample to contain-deductions being made for some kaolin which had escaped the process of conversion, and for some soda separated by treating the residue left after my operations with chloride of ammonium-upon 126 per cent of sulphur, 5.5 per cent of nitrogen, or equal atoms of each of these elements, and further Sodium Silicium Oxygen found by loss Nearly, if not quite, all the oxygen contained in this ultramarine is evidently combined with sodium, aluminium, and silicium, forming soda, alumina, and silica, which are colourless compounds. On the other hand, the elements which form the blue-coloured compound ought to be present in atomistical proportions; and upon I atom of sulphur or nitrogen there must be at least I atom of sodium or aluminium, silicium or oxygen, supposing there is an excess of these. Now it is well known that ultramarine gelatinises when treated with acids, thereby proving that the silica is really combined with bases. The blue-coloured body must contain, for I atom of nitrogen, I double atom of aluminium and I atom of silicium, but no sodium, otherwise there would not be left a sufficient quantity of basis for the silica of the colourless body, without which (soda) the gelatinising by the action of acids cannot take place. The supposition of the presence of only I double atom of aluminium in the blue-coloured body is based upon the fact that the quantity of aluminium found by analysis is not sufficiently large to admit of the presence of 2 double atoms of that element; while, as regards silicium, there can only be 1 atom, since the second atom must of necessity be combined with oxygen, which would otherwise be present in free state, and in order to find elements to combine with the oxygen present, it is evident that it (the O) is to be divided between the sodium, aluminium, and silicium; there remains then, however, a residual quantity of oxygen, which must belong to the blue body, since it is ascertained that that O is not a constituent of an acid of the sulphur or of the nitrogen. Consequently the analysed sample of ultramarine contained 55'7 per cent of silicates of soda and alumina, with a relation of the oxygen in the acids and bases = 2:1 and 443 per cent of the blue body, AlSiS2N2O3; this formula is based upon the following data: I first investigated which of the salts present in the wellknown mixture employed in the making of ultramarine during the calcination process form, with kaolin, ultramarine blue. I found that neither sulphur, sulphite of soda, hyposulphite of soda, nor mono- or poly-sulphuret of sodium have this effect; but I ascertained that hyposulphite of soda does so when mixed with either carbonate or caustic soda. I equivalent of carbonate and 2 equivalents of hyposulphite of soda react upon each other, but the deepest blue is formed when equal equivalents of silica and alumina are applied. The result I obtained by a large number of calcinations with differently made up mixtures proved that the blue body is most copiously formed when the mass to be calcined is compounded according to the following formula:AIO3+SiO2+4 Na2S2O3+2Na2O or 2Na2CO3. Per cent. 14 I 14'4 20'4 33'0 Since, however, the two soda salts are, while being ignited, decomposed in such a manner that half of the sulphur forms sulphate of soda; and since this decomposition begins early in the calcination process, while silicates of soda and alumina are also formed, it is only a relatively small portion of the soda salts which, with the earths, forms blue ultramarine. The following reasoning convinced me that the formula quoted above for blue ultramarine is correct. Artificially-made ultramarine contains a silicate and a residue AIO,SiS2N2O3; while, among all the bodies containing sulphur, there is only one which yields, with the aid of carbonate of soda, blue ultramarine, and this of the finest quality and largest quantity, when the mass to be calcined consists of When this washed and dried mass, which is some what bluish-green colour, is ignited with chloride of ammonium, the result is the formation of corn-flower (Carduus benedictus), blue-coloured ultramarine. The hydrogen of the chloride of ammonium partly forms water and is partly eliminated as gas; the chlorine is found combined with sodium; while the nitrogen combines with the blue-coloured body. AlO3+SiO2+4Na2S2O3+2Na2O or 2Na2CO3. I find that there is then formed 4Na2SO4.* (Some acces- When this calcined, washed, and dried mass is ignited in contact with vapour of sulphur, the original faint bluish-green colour of the calcined mass is retained until it is ignited in contact with air. Again, if the once calcined mass is fused with chlorate of potassa, previous to being ignited with sulphur, the mass retains, after ignition with the last-named substance, its original colour, and only turns blue (becomes ultramarine) when ignited in contact with air. Consequently, in each case a deoxidation precedes the addition of nitrogen. On comparing the composition of the hardly-coloured body with that of the ultramarine formed from it, or when it is tried to determine the change of weight which the first-named body undergoes by its conversion into the second, the quantity of the fire-proof (feuerfesten) materials and the sulphur contained in both is found to be the same. As, therefore, a difference of weight cannot be ascertained with certainty (at least, not at all in preparations which contain about 15 per cent of the blue compound), there only remains the supposition that the oxygen eliminated by reduction weighs nearly as much as the nitrogen taken up, or that an equal number of atoms of the oxygen are exchanged for an equal number of atoms of nitrogen. Although the nitrogen has not been estimated in the sample of ultramarine which I prepared on the small scale, I have no doubt that the bluecoloured body owes its colour as much to nitrogen, as is the case with the ultramarine made on the large scale, a sample of which was analysed by me. The following formulæ exhibit, beginning with that of the mixture of the dry materials to be made, by calcination, into ultramarine, the various reactions of the process : A1O3+SiO2+4Na2S2O3+2Na2CO3= Dry mixture to be calcined. =AISO2+SiSO+2Na2S+4Na2SO4+2CO2. Sulphobasic oxysulphuret, which is removed. AlSiS203 + SO2. Oxysulphuret. Which is removed. Addition to it of 2N from the air- THE ACTION OF PHOSPHORUS UPON By A. OPPENHEIM. IT is my intention briefly to record here what was viva voce communicated to the Society in the earlier part of this year (1872), respecting the researches made by me for the purpose of preparing phosphorus metals (phosphurets) by a new method. There obtain such a method, not only because it will enable us can be no doubt that it is of great importance to thus to prepare new organic phosphines, but, also, because we shall become better acquainted with the metallic phosphines (phosphurets). In the older systems of, and works on, chemistry, the phosphurets are classified Lavoisier's "Traité de Chimie," and in Berzelius's exwith the oxides and sulphurets, as may be seen in haustive work on chemistry. Up to the present day very and agreeing with our present views of valence (valenz) few metallic phosphines exhibiting a well-defined character have been obtained. Only rarely and with rather dubious preparation of the phosphurets, most of which have been results has the reduction of phosphates been tried for the prepared, either by the melting together of the elements, or by heating the metals in the vapour of phosphorus. Dr. Schrötter applied the last-named method, and thus obtained a series of incomplete (unvolkommen) or non-crystalline compounds, but it was difficult to say whether they really were chemical combinations. Hooslef employed the same method, and also the plan of reducing, by means of charcoal, the oxides of the metals previously mixed with phosphoric acid. He obtained some partly crystalline bodies, the composition of which curiously jars, with one exception, with our views on the trivalence of phosphorus; the formulæ are the following: Fe"P, Fe3"P, Cu2"P, Cu3"P, Zn"P2, and Zn3"P2 (the only one agreeing with the trivalence of phosphorus). It is clear that by the use of the methods just alluded to there is a danger of mixtures of several different combinations, or so-called alloys, being obtained.. The most ready way to obtain phosphurets-the precipitation of metallic solutions by phosphuretted hydrogen-is of no use, because the precipitation either fails altogether, or is incomplete. It is true that the salts of the noble metals are precipitated, but, as proved by H. Rose, not as phosphurets, but as reduced metals in finely divided state. It might be suggested that, instead of using the hydrogen of the phosphuretted hydrogen as a reducing agent, the phosphorus • Found in three calcined mixtures, 49'5, 53'4, 46'7 per cent of itself might be so applied; that is to say, whether it would sulphur, due to the total quantity of hyposulphites, on an average 49.8 per cent. not be possible to obtain phosphurets by heating metallic solutions with phosphorus. Of course there is a risk, to be avoided as much as possible, of getting with the phosphurets other compounds, such as, for instance, insoluble phosphates, or phosphites and hypophosphites. On this account I operated with metals in alkaline solution, so that any of the phosphorus acids which might happen to be formed should combine with the alkali and not with the metal. I have thus operated with oxide of copper dissolved in ammonia, protoxide of nickel dissolved in ammonia, oxide of lead in potassa, oxide of silver in ammonia, oxide of cadmium in potassa, protoxide of tin in potassa, and oxide of zinc in ammonia. Excepting the two last named, which, even when strongly heated with the phosphorus in sealed tubes, were not acted upon at all, the solutions were heated with phosphorus in excess, and benzol for the purpose of dissolving the phosphorus. The vapours were re-conducted to the flask, in which the operation took place, by means of a condenser vertically connected therewith; while, by frequent agitation, the contact between the phosphorus and metallic solutions was promoted. I, moreover, took care to occasionally add more ammonia to the solutions containing that liquid. The tin solution yielded only a white-coloured slimy mass, similar to that which the acids of the phosphorus yield with the oxides of tin, and therefore I did not further investigate these substances. The solutions of copper, nickel, lead, silver, and cadmium yielded dark-coloured precipitates, which were first washed with water and alcohol, and next with sulphide of carbon, for the purpose of eliminating any excess of phosphorus, after which the substances were dried in vacuo. The deep brown-coloured precipitate obtained from the copper solution was found to be mixed with specks of metallic copper, and yielded by analysis only a small quantity of phosphorus; the bulk of the mass was metallic copper and protoxide of copper. The nickel solution gave a black-coloured precipitate, the composition of which was found to vary in the different samples I prepared. I found for instance This substance was evidently a mixture of phosphuret of nickel, and the salt of a phosphorus acid akin to that which Dr. Rammelsberg lately obtained while igniting hypophosphite of nickel (See Ber. d. Deutsch. Chem. Gesells., vol. v., p. 495. 1872). The lead solution also yielded a black-coloured precipitate, which was found to contain from 98 to 99 per cent of metallic lead, and about from 04 to o per cent phosphorus not chemically combined, but only mechanically mixed with the lead, which on being heated in a current of hydrogen did not, while melting, yield any phosphuretted hydrogen. The silver, also, had been precipitated, yielding finely divided grey-coloured metallic silver, which, on being heated in a current of hydrogen, became white coloured (frosty), similar in every respect to the silver obtained by Rose while treating a solution of that metal with phosphuretted hydrogen. I found the samples prepared by me to contain on analysis from 97.39 to 99 per cent of silver. The cadmium solution yielded a light brown-coloured pulverulent precipitate, which, after having been purified as above described, evolved when treated with hydrochloric acid a large quantity of phosphuretted hydrogen; while when treated with nitric acid it exploded with simultaneous combustion, bursting into flame of the gas which was liberated. I had, therefore, in this instance to deal with a phosphuret of cadmium, but not pure, since the results of the analysis varied greatly in different samples: for instance THE determination of sulphur in organic substances by many of the methods in use is not only a difficult and tedious operation, but the amount of fixed reagents often employed greatly increases the liability to error. In the process here described, substances are burned in oxygen, and the sulphur is condensed from the gaseous products in the form of sulphuric acid. Experiments made by passing the products of combustion of sulphur compounds through nitric acid failed to give satisfactory results. A variable loss was due to a dense white fume containing sulphuric acid, which was not completely absorbed by water or by caustic alkalies. The apparatus here described was designed for making the combustions in a confined volume of gas, to avoid this source of error. The bottle, a (see figure), has a capacity of from 4 to 10 litres, according to the amount of oxygen required. The neck should be large enough for a stopper 35 to 40 m.m. in diameter. The condenser, b, is made of rather thin tubing, 14 m.m. in diameter; at the upper end it is expanded to a bulb, in order to admit some motion to the tube cd. Below the bulb it is surrounded by a waterjacket 22 c.m. high; from the point where it enters the stopper of the bottle it is narrowed somewhat for convenience of fitting. The combustion-tube cd is made of hard glass of 12 to 15 m.m. internal diameter; the portion c is 18 c.m. from curve to curve, and is protected by a sheetiron trough lined with asbestos; the part d is from 35 to 45 c.m. in length. The wire attached at I is to sustain c in case d breaks; c is joined to b by a collar of black rubber. The U-tube e is connected with d by a rubber collar drawn over the latter at k; this U-tube is slightly inclined, that no liquid may run against the rubber connectors. The tube f connects a with e; it is narrowed at both ends to 10 m.m. diameter. Near the upper end it is jointed by a piece of black rubber tubing in order that the apparatus may be easily disconnected at k. The ends of f extend 2 c.m. or more beyond the stoppers. Through the rubber stopper, i, a small glass tube passes beyond the end of f, where it is narrowed to an opening of 1 m.m. The double-bulb tube, j, is to accomodate variations of pressure, and to admit air as the original volume of gas diminishes during the combustion. The tubes b, c, d, and f should at no point have an internal diameter less than 8 m.m.-10 m.m. is preferable-and the narrowed ends should be cut obliquely that drops of water may not obstruct the circulation. The rubber stoppers and connections should be freed from adhering sulphur by heating in a solution of sodium hydrate. . The joints of the apparatus are sufficiently tight when water will stand in one limb of the safety-tube. The bottle, a, is filled over water with oxygen, and, if necessary, rinsed with distilled water a few drops of bromine are poured in, the tubes adjusted, and a slow | being connected at k, slow volatilisation of the liquid is stream of water made to flow through the water-jacket. The assay, if not volatile, is introduced into the tube d in a platinum tray,* which should not fill more than half the bore of d, leaving space enough for the free circulation of the oxygen. The part c is gradually heated, and kept hot during the combustion. This hot inclined tube acts as a chimney; the heated gases rise in it, pass into the cold tube b, and fall, thus causing a constant stream of gas to pass over the assay. It is important to ignite the assay without distilling off any considerable portion. To do this a small splinter of wood may be placed in contact with that part of the substance nearest 1, or that end of the tray may hold a thin layer of the assay, which is heated as rapidly as safety allows by a lamp held in the hand. To ensure a full supply of gas in the tube d at the commencement of the combustion, oxygen is passed from a gasometer through the tube i till the white fume which appears in the condenser, b, passes into a. The products of combustion, being denser, fall to the bottom of the bottle, and for a while displace the oxygen, thus increasing the circulation. After the substance is ignited, the fire passes to the other end of the tray. The part of the tube about the tray is heated by a lamp which is required to keep a up the combustion. At the end of the operation the heat is increased. If drops of liquid collect in c, and are liable to run down to the hotter parts of the tube, they should be driven off by heat. If carbonic acid be the principal product of the combustion, there is little change in the volume of gases in the apparatus; but if water and sulphuric acid are formed in much quantity, the volume is diminished, and air enters through the safety-tube. Most solid substances heated alone in the open tray yield volatile products too rapidly for entire combustion, but if mixed with sand in suitable proportion they burn slowly and completely. Liquids should be enclosed in narrow tubes sealed at one end and drawn out at the other to a capillary bore for 2 or 3 inches of length. Upon the point of the tube a bit of platinum sponge is fixed to assist the oxidation. The liquid should not fill more than twothirds of the wider part of the tube. effected by cautiously applying a flame under the empty portion of the tube containing the substance, so as to maintain the platinum-sponge in a steady glow. As soon as a cloud of combustion-products appears in the vessel, a, oxygen is shut off from i. When all the liquid has distilled from the interior tube, the tube cd is cooled slowly, and the apparatus is left for two hours, or until the fume has entirely subsided. If no odour of bromine be perceptible when the apparatus is disconnected at k to remove the tray or tube, a few drops of it should be poured through a funnel-tube put in the place of j, and the whole allowed to stand some time, to ensure complete oxidation of the sulphur compounds and deposition of the sulphuric acid. The tubes d and e are then rinsed into a beaker; this water is poured into b, which is then thoroughly washed by the aid of the wash-bottle. The large rubber stopper is lifted from the bottle, and the lower part of brinsed; without removing the tube ƒ from the stopper, it is rinsed into a beaker, and, finally, the bottle is carefully washed. The solution obtained, which need not exceed 500 c.c., is evaporated to a small volume, filtered, if necessary, and the sulphuric acid precipitated by barium chloride. The barium sulphate washes easily, as the solution contains no nitrates or fixed salts; its purity is ascertained by treatment with water and a few drops of chlorhydric acid, warming some time, filtering, and re-weighing. In case the substance leaves an ash or residue in the tray, this must be dissolved in aqua regia, the nitric acid removed by evaporation with strong chlorhydric acid, and any sulphuric acid it may contain separated in the usual manner. In the use of this apparatus there is no danger from explosions, if care be taken to have the combustiontube hot enough to ignite combustible vapour. Before attempting to burn a substance in the apparatus, it is best to try it in a large inclined tube open at both ends, or with oxygen supplied at the lower end. Such a preliminary trial will usually indicate the precautions necessary in burning the substance in the apparatus. The writer found that when oxygen prepared from a mixture of potassium chlorate and manganese dioxide, or from the chlorate alone (no rubber stoppers or connections being employed), stood some time in a bottle containing a few drops of bromine and a little water, the water gave a slight turbidity with barium chloride. Neither the bromine nor the solution of the chlorate gave reactions for sulphuric acid; the manganese dioxide contained, however, a trace of sulphur. Combustions of alcohol and of sugarcharcoal, made by the method here described, yielded with barium chloride a precipitate apparently no greater than that obtained from the oxygen alone, and too slight to influence ordinary results. This shows that, with suitable care, rubber stoppers are not objectionable. The following results, obtained in the order they are given, show the applicability of the method, while some of the details mentioned may help to explain the use of the apparatus: 9. Bituminous coal Before introducing very volatile substances, the 10 c.m. IO. of the combustion-tube ld should be heated to dull red11. Wool".. ness. Oxygen is passed in at i, the tubes are disjointed 12. at k, and the tube holding the assay is then pushed in till 13. Tobacco the platinum just reaches the heated zone. The apparatus 14. * A platinum tray which answers well may be made 10 to 20 c.m. long, 10 m.m. wide, and 7 to 10 m.m. deep, by bending thin foil over a glass tube. The ends may be roughly bent together or left open. Weight Per cent Found. 9 litres of oxygen were used in Nos. 1, 2, 13, and 14 and 4 litres in each of the other analyses. |