where quately expressed by means of the following table of rational formulæ *, the non-essential constituents are separated from the essential constituents by a horizontal line : 2C1; H2O, 2H, C2; H2O2 2 2 H2 02 2C2; H2O: 2H; 20,0 2 20,; H2O, 2H; 20, 0, 20; H2O: 2H; 2C, O, So far as the author knows, the glycolic alcohol, which is the parent molecule of this family group, has not yet been obtained in a state of isolation. The ethylen-glycol might at first sight be taken for the missing alcohol, more particularly when we couple the decidedly biatomic character of their respective molecules with the other, and even more significant fact, that the whole of the glycolic heterologues may be produced by the simple oxidation of the ethylen-glycol. Nevertheless, and notwithstanding these striking points of resemblance, the author is inclined to believe that these two alcohols are only isomeric; and he grounds this belief upon the occurrence of a certain class of chemical compounds, among which the so-called diethyl-acetal is the most conspicuous and best investigated member. This diethyl-acetal is strictly isomeric with the diethyl-ether of the ethylenglycol, and it is no doubt the missing glycolic alcohol to which we are indebted for this curious and instructive case of isomerism. A cursory examination and comparison of the subjoined rational formulæ will suffice in order to prove the correctness of this view. 2 2H, C.; H2O,. 2H, C.; H2O2. 2 Ethylen-glycol differs from glycolic alcohol in two essential points :-First, in the former compound the two alcoholic constituents are represented as playing the coordinate part of principal alcoholic bases, while in the latter compound one of these alcoholic bases is represented as playing the subordinate part of adjunct to the other base. Secondly, the relative positions which the two alcoholic constituents occupy in ethylen-glycol are exactly reversed in the glycolic alcohol. A mere glance at the two formule which express the chemical constitution of the isomeric ether derivatives will enable the reader to complete the analysis of these hitherto obscure and unintelligible cases of isomerism. To the second member in the family of glycolic heterologues, which is likewise very little known, the author has applied the term "deglycolic alcohol," in order to record the fact that it is produced from the primary alcohol by the simple abstraction of two molecules of hydrogen from the methylen adjunct of the principal water-base. This secondary alcohol, like the majority of the alcohols which occupy the second place in the *The following are some of the typical symbols of molecular grouping used in these formulæ a dot connects the base with its acid, a semicolon the hydrocarbon adjunct with its principal, an inverted semicolon the halogen (acid, base, or salt) adjunct with its prin cipal, and a concave curve two principal bases with one another— H=2; C=12; 0,=16. family group of the heterologues of the fatty alcohols, seems, from its want of stability, very prone to merge into the isomeric and far more permanent modification of the glycolite of water. In this remarkable metamorphosis the double carbon adjunct of the principal water-base becomes first of all converted into an acid twin carbon-nucleus, which reunites under this new form with the old waterbase, whereupon, under the combined influence of base and acid, the remaining water-molecule becomes decomposed, so as to surrender its oxygen to the envelope of the acid twin carbon-nucleus, while the hydrogen connects itself with the same nucleus under the typical form of a hydrocarbon adjunct. It is worthy of note that in this singular and characteristic rearrangement of the constituent elements the organic molecule has, without loss of substance and without loss of saturating capacity, passed at one bound from the category of a true and genuine alcohol into the category of a true and genuine water-salt. As regards the two remaining heterologues of glycolate of water and oxyglycolate of water, you cannot but see that their formation is due to the successive absorption of two molecules of oxygen by the envelope of the glycolous acid constituent, and that they differ from each other in this respect only, that the former contains for its principal constituent formate of water, while the latter contains instead of it oxyformate of water. This oxyformate is a highly interesting isomeric modification of the neutral carbonate of water, which, on account of its excessive want of stability, cannot be obtained in a state of isolation. The compound before us differs from the isomeric neutral carbonate in being decidedly monobasic, while the latter is as decidedly bibasic. The cause of this apparent anomaly becomes now fully revealed; for it is plain that one of the two hydrogen-molecules, which in the ordinary carbonate of water are both of them readily displaceable by metals, has assumed the hydrocarbon form of grouping, in consequence of which it will cease to play the part of a basic nucleus; and although it may become eliminated or exchanged in obedience to other modes of substitution, it is certain that the ordinary process of double decomposition has no control over it. The Molecular arrangement of the Alloy of Silver and Copper employed for the British Silver Coinage. By WILLIAM CHANDLER ROBERTS, Chemist of the Mint. Experiments have demonstrated that when a molten alloy of silver and copper is allowed to cool, the composition of the resulting metal is not uniform, the cooling being attended with a remarkable molecular rearrangement, in virtue of which certain constituents of the molten alloy become segregated from the mass, the homogeneous character of which is thereby destroyed. Thus, to take an extreme case, an alloy containing 77:33 per cent. of silver and 22-67 per cent. of copper was cast in a cubical mould of 42 millimetres. A portion cut from the centre of the mass gave on assay 78-318 per cent. of silver, while a portion cut from one of the angles was found to contain only 77-015 per cent. of silver, showing a difference of 13.03 millièmes. Levol proved that the alloy containing 71.89 per cent. of silver is homogeneous, and in all alloys containing more silver than this amount the centre of the solidified mass is richer than the exterior; on the other hand, in alloys of fineness lower than 71.89, the centre contains less silver than the external portions. The alloy employed for the British silver coinage contains 925 parts of silver and 75 parts of copper in 1000 parts of alloy. The metals are melted together and cast into bars 18 inches long and 1 inch thick; these bars are subsequently rolled into strips or ribands, and from these ribands the disks of metal to form the coins are cut. Experiments conducted in the most careful manner proved that the centre of the riband contained more silver by two parts in the thousand than the external edges. The increase in richness from one edge of the riband to the centre, and the corresponding decrease in richness from the centre to the opposite edge, was extremely regular, as was shown by the curve or graphic representation of the results by which the paper was illustrated. · On the Retention of Organic Nitrogen by Charcoal. By E. C. C. STANFORD. Improvements in Chlorimetry. By JOHN SMYTH, Jun., A.M., M.I.C.E.I., F.M.S. The author showed that the use of the milky solution of bleaching-powder in chlorimetry is unsatisfactory, and was therefore glad to discover a method of securing a clear solution containing all the chlorine by dissolving the sample in an alkaline solution. This is conveniently done by adding, say, 10 grammes of bleachingpowder to 20 grammes of soda-crystals (Na, CO2+10H, O), filtering out the precipitated carbonate of lime, which is known to be washed when it no longer discharges the colour of dilute sulphate of indigo, and making up the filtrate by water to one litre of fluid. It is a clear colourless liquid of the sp. gr. 1.007, but if made of sp. gr. 1.233 it is slightly greenish, having a pleasant oily feeling between the fingers, contrasting favourably with the roughness of the decanted solution of the bleaching-powder, with which it gives a precipitate. Most satisfactory results are obtained from it by all the chlorimetrical methods; and it has the additional advantage of showing the amount of lime in the sample, a solution of known strength of carbonate of soda being added until a precipitate is no longer formed. It is manufactured and used in the north of Ireland for bleaching fine linens; and from the ease and accuracy with which the percentage of chlorine was obtained, the author was led to investigate the feasibility of converting bleaching-powder into it for chlorimetrical purposes, and obtained the above results. Contributions to the History of the Phosphorus Chlorides. I. On the Reduction of Phosphoryl Trichloride. The author has attempted, but without success, to prepare the phosphorus chlorides corresponding to the oxychlorides of vanadium discovered by Roscoe. He found that when phosphorus oxychloride was heated with metallic zinc in a sealed tube to a temperature above the boiling-point of mercury, the phosphorus trichloride (P Cl,) was produced. It appears, therefore, that the action of zinc at a high temperature on phosphoryl trichloride is sensibly different from the action of this metal on the corresponding vanadium compound; in the former case the reaction is attended with abstraction of oxygen, in the latter with abstraction of chlorine. II. On the Preparation of Phosphorus Sulphochloride. The author found that perfectly pure phosphorus sulphochloride may be easily prepared by a reaction analogous to that by which phosphoryl trichloride has long been obtained; that is, by simply substituting P, S, for P, O, according to the following reaction, P, S,+3 P CI1,5 PS Cl. 2 2 5 5 The materials mixed in this proportion were heated in a sealed tube to about 150° C.; in a few minutes combination was quietly effected, and the entire contents of the tube were transformed into colourless phosphorus sulphochloride, a mobile liquid boiling constantly at 126° at 770 millims barom. Its vapour is extremely irritating, but when diluted with air it has an aromatic odour, reminding one of that of the raspberry. On the Dissociation of Molecules by Heat. By C. R. C. TICHBORNE, F.C.S., M.R.I.A. The term dissociation is applied by the author to specify a certain class of phenomena somewhat distinct from ordinary decomposition. This latter term is generally applied to any case of molecular change which has been consummated, whilst dissociation is used to convey a passive but present phenomenon. If this latter is carried far enough, it ultimately results in a rupture, and thus the phenomena of decomposition and dissociation are so intimately connected, that they can hardly be investigated alone. 1871. 6 Compound molecules exist in the solid, liquid, and gaseous condition, providing that the temperature necessary to convert them into these physical modifications is not above the temperature at which their components are dissociated. Thus we can easily conceive that a substance A may be of sufficient structural stability to pass through all the increasing vibratory action of heat without dissociation of its component molecules, until it has passed through the solid, liquid, and far into the vaporous condition; whilst a substance B has what the author calls a thermanalytic point, or the point where the equilibrium is broken. If it lies below 100% C., we have dissociation in the liquid condition among compounds soluble in water. A well-known natural group of bases had been studied as regards these phenomena, viz. the trioxides, alumina, chromic and ferric oxides, and it has been found that all the compound molecules of these bases were more or less dissociated on heating their solutions. The ferric compounds are the most easily affected. The solutions of these compounds, if pure, are almost colourless; the usual slight tinge being in most cases produced by the basic action of the water. By the cautious addition of dilute acid, almost colourless solutions will be procured. On the application of heat this solution becomes gradually darker and darker, until it becomes a dark reddish-brown fluid. If the water bears any considerable proportion to the salt, a basic precipitate falls before it has reached the boiling-point. The relative amount of the water is of the utmost importance in these phenomena, because its basic action lowers the thermanalytic point. The result of the dissociative influence of heat when a precipitate is not produced, is the repartitioning of the elements by which a basic and an acid salt are produced in the same fluid simultaneously. If these experiments are carried on under pressure, or in the presence of a great excess of water, the dissociative influence is so great from the increased range of temperature, that anhydrous oxide of iron can be produced in the presence of water. The compounds of chromium are capable of dissociation in a similar manner, and the change of colour produced by heat upon these solutions is due to basic condition, and not to the state of hydration of the salt as generally stated. The aluminic molecules obey exactly the same rule; but as the thermanalytic point is much higher, and as there is no chromatic change to mark the dissociative influence of heat, it is difficult to discern the phenomenon. Under the influence of solutions boiling at an increased pressure of 11 or 12 atmospheres alumina was procured. The same results may be obtained by increasing the basic condition of the solution by a large volume of water. As the pressure raises the boiling-point of the water until we reach the thermanalytic point of the molecule, so the basic action of the water upon the stylous group lowers the thermanalytic point until we get it within the range of 100° C. If 500,000 to 600,000 times the weight of water is used to the amount of salt, a precipitate is produced at 100° C. This precipitate is best seen by passing a beam of electric light through the flask. Most of the precipitates may be observed by the eye, but not all; they redissolve on cooling. On the behaviour of Supersaturated Saline Solutions when exposed to the open air. By CHARLES TOMLINSON, F.R.S. It is known that when a vessel containing a supersaturated saline solution is opened in a room, it immediately crystallizes provided the temperature be not too high. Mr. Tomlinson shows that supersaturated solutions of Glauber's salt (and also of Epsom salts and of alum) may be exposed to the open air of the country for many hours, and even be taken out of the flasks in clean metal spoons, without crystallizing. From a large number of experiments conducted under various conditions, the following conclusions are drawn : 1. That a highly supersaturated solution of sodic sulphate may be exposed to the open air of the country in an uncovered flask, and in cloudy weather, for from twelve to twenty hours, without any formation of the ordinary tenwatered crystals. 2. That if the temperature fall to 40° Fahr. and under, the modified sevenwatered salt is formed at the bottom of the solution just as in covered vessels. 3. That if the exposed solution suddenly crystallize into a compact mass of needles, a nucleus may always be found in the form of an insect, a speck of soot, a black point of carbon, &c. 4. That if during the exposure rain come on, the solution generally crystallizes suddenly in consequence of an active nucleus being brought down; but if the flask be put out during heavy rain, when we may suppose all the solid nuclei to be brought down, the rain-drops, now quite clean, fall into the solution without any nuclear action. 5. That the young and newly sprouted leaves of trees, such as those of the gooseberry and currant, have no nuclear action. 6. That in clear cloudless weather, when the force of evaporation is strong, the solutions by exposure produce fine groups of crystals of the ten-atom salt, just as a saturated solution would do if left to evaporate slowly in an open dish. 7. That if the solution, after being exposed to the open air, be brought into a room, it crystallizes immediately under the action of aerial nuclei. On the Constitution of Salts. By J. A. WANKLYN, F.C.S. Recent Progress in Chemistry in the United States. By C. GILBERT WHEELER. On the Oxidation products of the Essential Oil of Orange-peel, known as "Essence de Portugal." By C. R. A. WRIGHT, D.Sc., Lecturer on Chemistry in St. Mary's Hospital Medical School, and CHARLES H. PIESSE, Assistant Analyst in St. Thomas's Hospital. Through the kindness of Messrs. Piesse and Lubin, we have had the opportunity of examining a specimen of pure oil of orange-peel. As stated by Soubeiran and Capitaine, and also by Dr. Gladstone, this oil consists mainly of a hydrocarbon of formula C10 He, boiling at 174° C., and termed Hesperidene. We find that the crude oil commences to boil at 175°, and that 97.2 per cent. comes over below 179°; on redistillation over sodium this portion all comes over between 175° and 177° (uncorrected). The remaining 2.8 per cent. is a soft resin, which does not harden on standing, and is perfectly fluid at 100°. It is not volatile without decomposition, and after complete volatilization of residual hesperidene is inodorous; in alcohol, even boiling, it is but sparingly soluble, readily soluble in ether, and insoluble in water, to which, however, it communicates the aromatic bitter taste of orange-peel. It contains no nitrogen, and on combustion gives numbers agreeing with the formula C20 H30 O3.. Hesperidene redistilled over sodium is attacked with violence by concentrated warm nitric acid; by dilution of the acid with its own bulk of water the action becomes less violent; after boiling some hours with an inverted condenser attached, the evolution of red fumes and of CO, almost ceases. At this stage the hydrocarbon has principally formed a brown resinous substance, becoming a very thick viscid liquid at 100°, but setting on cooling to a hard brittle mass. This contains much nitrogen and less hydrogen in proportion to the carbon than the original substance. Its examination is not yet completed, but the numbers obtained are consistent with the supposition that it is derived from the original hydrocarbon by addition of oxygen and replacement of hydrogen by NO. With strong nitric acid this brown resin is further acted on, producing a yellow resin not softening at 100°, and containing nitrogen and less carbon and hydrogen than the brown resin. Much oxalic acid is also produced, and probably also another acid containing nitrogen; for the snow-white oxalic acid got by precipitation as lead-salt, decomposition with hydric sulphide, and several recrystallizations from water, contained much nitrogen, and yielded (as well as its silver salt) numbers not agreeing with but approximating to those required by theory. On heating one part of hesperidene with a mixture of three parts potassium |