NEWS A FEW interesting, and, to a certain extent, novel results, have recently been developed in our laboratory, which I venture to present in their present incomplete form, since the pressure of other duties will postpone, for a few months, further investigations in this direction. Up to the present time the larger number of our experiments have been made upon the behaviour of tempered bars under a transverse stress, although a few qualitative trials have been made upon changes in electric conductivity and coefficients of expansion. I. The modulus of elasticity decreases as the hardness of the steel increases; in other words, the harder the bar the greater the deflection produced by a given weight. Many manuals of practical mechanics give a higher modulus for tempered than for untempered steel. Reuleaux, in "Der Constructeur" (p. 4), states that it may be increased 50 per cent by hardening. Coulomb and Tredgold state that hardening has no influence whatever, while Styffe finds that the modulus is diminished. For our first experiment, five pieces of good tool-steel, each 13" long, were cut from a half-inch square bar. These were carefully annealed, squared, and polished. No. I was laid aside, and the others were hardened in cold water in the usual manner; No 2 was "drawn" on a hot plate to a dark blue; No. 3 to a purple; No. 4 to a straw-colour; No, 5 was left hard. The modulus of elasticity was then determined by measuring the deflection produced by a weight applied at the middle of the bar. The probable error of the experiments did not exceed onefifth of 1 per cent. The experiment was varied in many ways; several qualities of steel and bars of different dimensions were employed with uniform results. In some grades of steel a difference of more than 10 per cent has been found between the modulus of the hardened and that of the annealed bar. II. The increase of deflection in a given time is greater the harder the steel. It is well known that the deflection of a bar left under stress will increase for a long time. I am not aware, however, that comparative tests of the rate of increase in steel of different tempers have previously been made. III. The immediate set increases with the hardness of the steel. In the experiments each bar was of course loaded with the same weight, which was allowed to act for the same number of minutes. IV. A bar recovers from a temporary set with greater rapidity the harder it is. The remarkable fluctuations in the line of the bar ob served by Prof. Norton (Amer. Journ. of Science and Arts, April, 1876) became more marked and had a wider range as the hardness of the bar increased. In none of the experiments referred to was a permanent set produced, though in some cases forty-eight hours had elapsed before the bar recovered its original line. In a few experiments an attempt was made to determine the approximate hardness of the bars by grinding. The results obtained, however, could not be considered very reliable. A more satisfactory method was found in the determination of the temperatures employed in hardening and drawing, by the specific heat of platinum, or by the use of the pyrometer. I am indebted to Mr. F. C. Blake for the accuracy with which the experiments referred to in this note have been conducted.-American Journal of Science and Arts, CORRESPONdence. ON THE PRESENCE OF ARSENIC IN THE VAPOURS OF BONE-MANURE. To the Editor of the Chemical News. SIR,-In the CHEMICAL NEWS (vol. xxxiv., p. 68) you criticise a book bearing the above title. In the course of your remarks you say: "Miasms or organic poisons could scarcely meet with a more efficient corrective than chloride of arsenic, fluorine, and other of the volatile compounds said to be given off. On the other hand, sulphuretted hydrogen and sulphide of ammonium are admirably calculated to purge the atmosphere of arsenical fumes." I wish, as this opportunity presents itself, to lay before contradict the suggestion that sulphuretted hydrogen you a fact repeatedly observed, which seems calculated to would form a purge for an atmosphere contaminated with arsenical fumes. The same fact would throw some doubt on the other suggestion, viz., that trichloride of arsenic is a corrective for miasms and other organic poisons. While making some experiments on the purification of hydrochloric acid from arsenic, the late Mr. Henry Deacon suggested to mix the arsenical hydrochloric acid in the gaseous state with gaseous sulphuretted hydrogen. Accordingly, some gaseous hydrogen chloride was mixed with arsentrichloride and sulphuretted hydrogen, in one case in as dry a condition as the use of concentrated sulphuric acid will permit, in another case saturated with aqueous vapour. In the one case, when the gaseous mixture was dry, no trace of sulphide of arsenic had deposited on the side of the glass vessel containing the mixture; in the other case, in which some liquid hydrochloric acid was introduced into the vessel, so that its sides were wet, a little chloride of arsenic had been decomposed and deposited as sulphide. In both instances, however, large quantities of sulphide of arsenic were formed when the gaseous mixture was driven through a wash-bottle containing water. The experiments were repeated constantly with the same result. The conclusion is that gaseous arsentrichloride does not react upon gaseous sulphuretted hydrogen. You will readily admit that sulphuretted hydrogen will form no purge for an atmosphere contaminated with arsenical fumes, and you will doubt with me, seeing that chloride of arsenic will not act in the gaseous state upon sulphuretted hydrogen, whether arsentrichloride will, under those conditions, correct the noxious miasms or organic poisons.—I am, &c,, DR. FERD. HURTER. Laboratory of Messrs. Gaskell, Deacon, and Co., Widnes, August 19, 1876. glass or porcelain tubes, and was enabled to perform com- | nitrogen, Berzelius adds "Il semblerait, d'après cela, bustion after combustion with the greatest ease." Before applying the platinum tube to the direct combustion of iron or steel, "an experiment was tried with pure sugar to ascertain whether a stream of oxygen, in conjunction with a layer of only 4 inches of cupric oxide would be sufficient to convert all the carbon into carbonic anhydride. The result was perfectly satisfactory, an amount of carbonic anhydride being obtained equal to 42.086 per cent of carbon instead of 42.105, showing a loss of only o'019 per cent upon the theoretical amount." To prove that a platinum tube is equally applicable in the case of small quantities, I give the results of duplicate estimations of carbon in steel by direct combustion :— que le degagement d'oxygene dans ces animaux est du à traction du soleil sur la chlorophylle qu'ils contiennent," a singularly sagacious conclusion, and one that ought to induce those interested in water-supply to have this matter thoroughly investigated by competent individuals, for it is quite possible that the growing of water-cresses, for instance, and the purification of water are more nearly related to each other than directors of water companies imagine. That chlorophyll performs important duties in both the vegetable and animal economy seems certain, though its powers as yet are undefined and but little understood. Still, however, we can notice that it invariably exists on the surface of the living leaves of plants, also in the bile, and sometimes in the blood of animals; and within the last two years it has been discovered that the spots and colouring found upon the eggs of birds is chlorophyll; and, in some cases, as in the egg of the hedge-sparrow, this chlorophyll is blue (which seems, indeed, to be the colour of pure chlorophyll, as will be explained on a subsequent occasion, when speaking of the composition of bile, a matter now under examination). For the present we may remark that room enough exists to warrant energetic interference on the part of our Metropolitan water directors with the closely-allied subjects of water-purity and water-jobbery; because it may so be that Nature's THE PRESENCE OF NITRITES IN THE WATER remedy is staring them in the face whilst they are blindly OF THE THAMES. hunting by expensive methods to perform a really inexpensive operation, and thus uselessly sinking an immense capital that will have to be paid for hereafter, and therefore in all time to come limit the use of Heaven's greatest boon throughout the largest metropolis in the world. We have already seen something of this kind brought about in the case of coal-gas, the price of which in London at the present moment would not have been more than two shillings per 1000 cubic feet had matters been left to the wholesome action of common sense and honest competition. But all the benefits arising from improvements and economies in gas-making during the last twenty years has been swallowed up by expensive Acts of Parliament and engineering jobbery, so that the price remains almost unchanged, and is, perhaps, unchangeable. LEWIS THOMPSON. To the Editor of the Chemical News. SIR,-The following experiments were made with a view to ascertain whether nitrites of any kind existed in Thames water; but although the process employed was one capable of detecting the ten-thousandth part of a grain of any nitrite whatever, yet it totally failed in this instance to indicate even a trace. The first experiment was made upon Thames water which had been purposely allowed to concentrate in a steam-boiler until 400 cubic feet of it had been reduced to 8 cubic feet, and of this concentrated water I gallon was evaporated down to the bulk of 100 grains, when it was tested in this manner:-One drop of the water in question being placed on a clean white por--I am, &c., celain slab, à corresponding drop of a solution of the protochloride of iron was put close to it, and then the two drops were made to unite by means of a platinum wire, but no visible effect was produced in consequence of the admixture. The water in this case had been obtained about 1 mile below London Bridge, and a precisely similar negative result was derived from water taken near Vauxhall Bridge, although the amount of concentration was then six times greater than in the first instance; consequently we cannot regard the existence of nitrites in Thames wate as an established fact: and here, perhaps, it may be as well to remark technically that the nitrites in general, but particularly the nitrite of soda, possesses many advantages over the bisulphite of soda for what is called an "antichlore." It is more easily made, it is cheaper, and after being used it may be recovered by evaporation in the form of nitrate, and again converted into nitrite for repeated use. Moreover, it does not by its employment lead to the production of an acidulously destructive compound like bisulphate of soda, because the nitrite of soda, when used as an antichlore, is merely converted into a neutral nitrate, after having arrested the injurious influence of two atoms of chlorine. Whilst upon the subject of Thames water, it is interesting to review an observation made by Berzelius, which may be found at page 686 of the fifth volume of his "Chemistry," translated into French by Valerius. After quoting numerous experiments made by Wohler, Ehrenberg, and Morren, which prove that the effect of infusorial animals in water is to oxidise the water, and generate an air contatning 51 per cent of oxygen and 49 per cent of CHEMICAL NOTICES FROM FOREIGN NOTE.-All degrees of temperature are Centigrade, unless otherwise expressed. Comptes Rendus Hebdomadaires des Seances, de l'Academie NEWS having excited it by the action of diffused light to observe, the extinction of phosphorescence produced by this part of the spectrum. This extinction causes unequally active parts to appear, i.e., spaces corresponding to the black rays or bands of the spectrum. Paraldol, an Isomeric Modification of Aldol.-M. A. Wurtz.-This compound softens at 80°, and is melted at 90°. It dissolves readily in water and alcohol, from which latter it is obtained in fine anorthic prisms. Reply of M. Hirn to the Criticism of M. Ledieu in "Comptes Rendus," July 10, 1876.-M. Hirn complains that M. Ledieu ascribes to him the very views which he is attempting to refute. Production of the Electric Effluve.-M. A. Boillot. -The author, in experimenting upon the chemical action of the effluve, makes use of the following arrongement :Two narrow tubes, filled with graphite in powder and calcined, and are parallel to and near each other. They are inserted with their whole length in a test-tube about 18 centimetres in length, and they terminate each with a platinum wire communicating with the carbon. The wire from one of these tubes traverses the test-tube to its upper part; the other is bent back in a downward direction. Two other tubes enter the test-tube; the one ends at the summit, and the other penetrates to 2 or 3 centimetres of the orifice. The first is destined to introduce the gases, and the second to collect them. The effluve is produced in the space between the two carbon conductors. Photometric Researches on Coloured Flames.M. Gouy. Not suitable for abstraction. Note on the Radiometer.-M. A. Gaiffe.-The author has made a modification, which he considers proves that the actinic and thermic rays act upon this instrument. It is a radiometer of the ordinary form, the discs being coloured a dead blue on one surface and a dead red on the other. It may be made to revolve in either direction by using alternately suitable sources of heat and light. If, e.g., we expose this instrument to the sunlight, the blue surfaces acquire a predominant action, and after some moments hesitation the mill begins to turn from the left to the right. If it is exposed to the flame of a common gas-jet, or of a Bunsen burner, or to the radiations of a plate of hot iron the rotation takes place in an inverse direction. Radiometers composed of Laminæ of Different Materials. MM. Alvergniat Freres.-The following observations have been made with radiometers with discs of different materials. No. I is a radiometer with discs of silver and transparent mica. In the light the radiometer turns with the mica in front and the silver repelled; in obscure heat, with the radiometer plunged in water at 30° or 40°, the rotation is in the opposite direction. In ice it turns as if exposed to light. No. 2 is composed of aluminium and blackened mica. In the light this radiometer turns with the metal first, and the blackened surface repelled. Obscure heat and light, however intense, do not modify the direction of the rotation. If plunged in ice it turns in the opposite direction. No 3 is formed of aluminium and mica not blackened. In light this radiometer turns with the mica first. In ice the rotation is in the same direction as in light. Dark heat niakes it turn in the opposite direction, with the metal first. With this radiometer M. Jamin made the following experiment:-He directed a small light upon one point of the radiometer while in motion, so as to heat only a single point of the globe. This threw the discs into such a state of equilibrium, that instead of rotation there ensued oscillations like those of a pendulum. The two surfaces of the discs, the metal and the mica, are both repelled: if the distance of the flame is varied one of the two lamina is repelled more or less. No. 5 is a radiometer with discs of silver and aluminium. This radiometer has been heated to 440°, distilling sulphur, and continuing to make a vacuum with the aid of the mercurial pump. The instrument was ren dered insensible, though it turned very quickly if a vacuum was made without heating in the ordinary manner. But if the discs, instead of being made of two metals, were made half of metal and half of mica the instrument could not be rendered insensible. The glass case was pierced by an electric discharge, when the radiometer began to turn with great speed, and continued for an hour. The aperture was so small that its diameter could be approximately estimated only by the aid of a powerful microscope. It was found practicable to re-form a vacuam in this instrument up to 100 m.m., even though perforated; rotation then took place in the ordinary manner. Nos. 6, 7, and 8, are radiometers with discs of mica and varnished copper, green, blue, red, and yellow; the colours, in these conditions, have no effect on the radiation. Cause of the Motion of the Radometer.-M. G. Salet. According to all the experiments made, the cause of movement in the various apparatus resembling the radiometer of Crookes is a difference in the temperature of the surfaces of the discs. The theory of Tait appears the best. A disc, compound or simple, whose surfaces have actually two different temperatures, and which is plunged into a highly rarefied atmosphere, begins to move, the hottest surface recoiling. Whilst the difference of temperature exists the movement continues. There is no occasion to bring forward the possible action of gases condensed on the surfaces. Wherever two thermometers, isolated in a vacuum, and constructed of two different substances, A and B, would indicate different temperatures, a radiometer disc composed of adjacent laminæ, the one of the substance A and the other of B, will begin to move, of the difference of temperature. In the circle of lights and the movement will show the direction and the degree the discrepancy between the indications of two thermofor an indefinite time; it is the same with the movement meters, the one with its bulb blackened maintained itself of the radiometer. Not content with repeating the exper-ment of Mr. Crookes and M. Fizeau, by placing the radiometer in the centre of a sphere of opal glass so as to equalise the light and avoid currents of air, the author has made an experiment which he considers absolutely demonstrative. He has fixed upon the mill of a radiometer the needle of a compass: the discs were composed of two laminæ of burnt mica, one of them blackened. Under the influence of an adjacent flame the needle deviated to a certain angle, and variations in the lustre or in the distance of the flame were shown very distinctly by a corresponding change in the deviation. The source of light having remained constant for four days the needle kept its position invariable for the whole of the time. The action of condensed gases cannot be invoked here. Decomposition of Alkaline Bicarbonates, Moist or Dry, under the Influence of Heat and of a Vacuum. -M. A. Gautier.-Perfectly pure and dry bicarbonate of soda is not sensibly decomposed in a vacuum at 20° to 25°. bicarbonate of soda in water set to evaporate in a vacuum At 100° it is rapidly decomposed in dry air. Solutions of are decomposed at 20° to 25°, and this the more rapidly The bicarbonate of the greater the quantity of the water. potassa is decomposed much less rapidly at elevated temperatures than the corresponding soda salt. Geological Age of Certain Metallic Veins, and, in particular, of Mercury.-M. Virlet d'Aoust.-The author concludes that in the Asturias, as in Mexico and France, mercury is of very modern origin. Les Mondes, Revue Hebdomadaire des Sciences, Occurrence of the Germs of the Tape-worm in Meat.-An article taken from the Abeille Medicale points out the danger of eating meat in the half-raw condition, called by some persons "rare," as the ova of the tapeworm are only killed by thorough cooking. Those whose dered into a condition capable of being dissolved In water. Or instead of employing any of the before-mentioned alkaline compounds or pro tastes lead them to select meat in this condition are recommended to eat the flesh of the horse, which is less in- ducts, I submit the phosphate of alumina by preference in a finelyfected by the Tania than the ox, sheep, or pig. divided condition in conjunction with sulphate of soda, coal, or other carbonaceous matter to the action of heat in order that the phosphoric acid, together with the alumina, shall be converted into a soluble condition. Improvements in dyeing. E. T. Hughes, Chancery Lane, London. (A communication from G. C. F. Bartels and E. F. Freise, Goetlingen, Hanover, Germany.) May 11, 1875.-No. 1764. This consists in chemical combination of mercaptane, which has great affinity to both vegetable and animal fibres, whereby instead of using several baths for the different kinds of fibres as heretofore, but one bath is required, and tissues of mixed fibres may be dyed with one bath. Improvements in the treatment of animal blood, also of fibrous mate rials, and in the manufacture of manures therefrom. G. F. Snelling, Edith Terrace, Victoria Road, Upton Lane, Essex. May 19, 1876.No. 1844. This relates (1) to the treatment of animal blood in special manner. (2) To the treatment of shoddy and woollen and cotton rags in a special manner. (3) To the manufacture of manures from the above ingredients, separately or combined with other ingredients, such manures containing large fertilising properties, which free themselves by or in contact with moisture alter application to or upon the soil. Improvements in the treatment of sewage. M. F. Anderson, Priory Road, Coventry, Warwick. May 19, 1875.-No. 1845. This Provisional Specification describes drying sewage sludge by adding to it coprolite and sulphuric acid. Improvements in deodorising blood to enable it to be used for Middlesex. May 20, 1875.-No. 1855. This consists in mixing blood manuring and other purposes. J. Smith, Cattle Market, London, with suitable proportions of phosphate of lime or ground coprolites, calcic oxide, and sulphuric acid (cr by preference ammonia lignine saturated with sulphuric acid), the mixture being well stirred as the different ingredients are added. Improvements in and relating to the obtainment of phosphorus and phosphides. J. Townsend, Glasgow, Lanark, N.B. May 21, 1875.No. 1862. This invention consists in the utilisation, as a source of the phosphorus and phosphides, of phosphate of alumina; and the kind known as Rodonda phosphate answers quite well, although other varieties will do so also. Improvements in photometers. W. Morgan-Brown, Southampton Buildings, London. (A communication from O. Shuette, Rue Gallion, Paris.) May 21, 1875.-No. 1865. This invention consists in measuring light by interposing one or several thicknesses of slightly opaque substances, as paper, carrying increasing numbers, by which figures the relative intensity of the light is measured. 19. "A New Form of Plaster of Cantharides." Mr. A. Greek-J. G. Greenwood, LL.D., Fell. Univ. Coll., Lond. W. Gerrard. Latin; Comparative Philology-A. S. Wilkins, M.A., Fell. Univ. Coll. Lond. English Literature; Ancient and Modern History-A. W. Ward, M.A., Fell. St. Peter's Coll., Camb. 20. "A Proposed Solution of Citrate of Iron and Quinine." Mr. J. F. Brown. Preliminary Report on the Chemistry of Ivy." R. H. Davies, F.C.S. 22. "Supplementary Note on Phosphate Syrups." W. L. Howie, F.C.S. 23. "On Filtering Papers." Thomas Greenish, F.C.S. PATENTS. ABRIDGMENTS OF PROVISIONAL AND COMPLETE SPECIFICATIONS. Improvements in the manufacture of alkaline sulphates. J. C. Stevenson, South Shields, Durham. May 8, 1875.-No. 1723. This invention relates to the preparation of common salt to be used in the process patented by Messrs. Hargreaves and Robinson for the manufacture of sulphate of soda by exposing common salt to the action of sulphurous acid. Improvements in the treatment of natural substances containing phosphates of alumina. M. Prentice, Stowmarket, Suffolk. May 11, 1875. No. 1758. This invention relates to the treatment of natural products containing phosphoric acid and alumina, and consists in subjecting such natural phosphates to the action of an alkali or alkaline carbonate, such, for example, as caustic soda, or carbonate of soda, or soda-ash, or to what is known as black-ash liquor, or to other alkaline products, such, for example, as the waste alkaline liquors from paper works, in order that the phosphoric acid and the alumina contained in the natural phosphates may be separated therefrom by being thus ren English Language-T. Northcote Toller, M.A., late Fell. Christ's Coll., Camb. Mathematics-Thomas Barker, M.A., late Fell. Trin. Coll., Camb. Jurisprudence and Law-Alfred Hopkinson, M.A., B.C.L., Stowell Chemistry and Metallurgy-H. E. Roscoe, B.A., Ph.D., F.R.S. Animal Physiology and Zoology; Vegetable Physiology and Botany Physiology and Histology-Arthur Gamgee, M.D., F.R.S. Oriental Languages; German-T. Theodores. French Language and Literature-J. F. H. Lallemand, B. ès Sc. Harmony and Musical Composition-Edward Hecht. With Assistant Lecturers in all the Principal Departments. The NEXT SESSION will COMMENCE on the 3rd of OCTOBER. Candidates for Admission must not be under fourteen years of age, and those under sixteen will be required to pass a Preliminary Examination in English, Arithmetic, and the Elements of Latin. Prospectuses of the several Departments of Arts, Science and Law, Medicine, the Evening Classes, and of Scholarships and Entrance Exhibitions, will be forwarded on application. J. HOLME NICHOLSON, Registrar. NEWS THE CHEMICAL bismuth or 2 of subnitrate with 7 parts of crystalline NEWS. hyposulphite. In spite of the improvements in the estimation of potassa introduced by Peligot and Schloesing, its exact determination in a somewhat complex substance remains one of the most delicate operations in analytical chemistry. We have, further, no reagent sensitive enough to detect its presence in small quantities. The new reaction of the salts of potassa in presence of hyposulphite of soda and a salt of bismuth in a solution mixed with alcohol solves both these difficulties. We dissolve in a few drops of hydrochloric acid 1 part of the subnitrate of bismuth-say half a grm.-and, on the other hand, about 2 parts (1 grm. to 1) of crystallised hyposulphite of soda in a few c.c. of water. The second solution is then poured into the first, and concentrated alcohol is added in large excess. This mixture is the reagent. + If brought in contact with a few drops of the solution of a potash-salt it at once gives a yellow precipitate. With an undissolved potassic salt it produces a decidedly yellow colouration, easily recognised. All potassic salts with mineral acids are equally susceptible of this reaction, sulphates and phosphates as well as nitrates, carbonates, chlorides, &c. It is also very sensitive with the organic salts, tartrates, citrates, &c. The reaction is not interfered with by the presence of other bases with which nothing analogous is produced. The character is, therefore, perfectly distinct. Baryta and strontia alone may occasion some difficulty, by reason of the white precipitates of double hyposulphites which they form with the same reagent; but it is very rare to meet them along with potassa, and they are very easily detected and removed. The solution of the potassic salt is placed in a small flask, the bismuth solution is added, then the hyposulphite, the whole is mixed rapidly, and 200 to 250 c.c. of concentrated alcohol are added. The whole is agitated for a few moments, and left to settle. The yellow precipitate collects at the bottom of the flask, and may be filtered after a quarter of an hour, and carefully washed with alcohol. The precipitate cannot be weighed; it is dissolved upon the filter in excess of water; the bismuth is thrown down as sulphide by sulphydrate of ammonia, washed by decantation, collected on a tared filter, dried at 100°, and weighed. The weight obtained may be corrected by separating from the filter a part of the dried precipitate, and heating it again to 150 to 200° in a small platinum crucible, weighing before and after, and correcting the total weight of the sulphide accordingly. The weight of the potassa is found on multiplying the weight of the sulphide of bismuth found by If we have a solution containing merely a few milligrms. ot potassa, it is reduced by evaporation to a very small volume, or even to dryness, when the characteristic reaction readily appears. Or slips of filter-paper may be repeatedly saturated with the dilute solution, and after drying be steeped in the alcoholic reagent, when the yellow colour will appear, especially on the margins of the paper. The author's quantitative experiments refer chiefly to nitrates, chlorides, and mixtures of the two salts. With some special precautions the method may probably be applied directly to sulphates, though these are easily converted into chlorides by chloride of barium, removing the excess of baryta with sodic or ammonic carbonate. The hyposulphite of commerce is sufficiently pure for use; the crystals are dissolved in a small quantity of water at the moment of the experiment. 3 KO Bi2S3 =0'549 The method has been found accurate in presence of soda, lithia, ammonia, lime, magnesia, alumina, and iron. -Comptes Rendus. The chloride of bismuth is prepared by treating the pulverised metal with a few drops of nitric acid, evaporating to dryness, and then heating with a very small quantity of hydrochloric acid. The lead possibly present in the bismuth is got rid of by adding to the cold solution concentrated alcohol, which causes chloride of lead to be deposited. Or subnitrate of bismuth may be dissolved in a few drops of hydrochloric acid. The liquid in which the potassa is to be determined should not exceed 10 to 15 c.c. in bulk, so that the entire volume of the aqueous solutions may not exceed 20 to 25 c.c. For I part of supposed potassa we take 2 parts of distillation- According to Mr. Lowe the volatile oil possesses all the characters of that of copaiva, and the hard resin, which he regards as pure copaivic acid, free from the soft resin, which, according to him, exists in the most part of commercial copaivas, seemed to him to indicate a superior quality as a medicine. I avow that I scarcely understand this conclusion, and that I am so much the less convinced of the identity of the hard resin with copaivic acid as Mr. Lowe has observed in the new resinous balsam the singular property of solidifying when exposed, in a closed vessel, to a temperature of 230° F.; copaiva presents nothing similar. Í find further this difference, that the new balsam distilled with an addition of a little quantity of an oxidising body as chlorine, hypochlorite of lime, or bichromate of potash, furnishes an essence of a beautiful blue colour, whilst common copaiva with soft resin scarcely furnishes any coloured essence. The notice concludes with a mention of a falsification which appeared to me at once ill-founded and little to be feared; it is that cold sulphuric acid produces with copaiva a purple colouration like that obtained with cod-liver oil, to such an extent that dishonest persons might sell a mixture of olive oil or any other fatty oil with a little quantity of copaiva for cod-liver oil. Mr. D. Hanbury tells us in his notice that oil of wood is extracted from Dipterocarpus turbinatus by quite a peculiar process, which I shall describe in a few words, in order to make the nature of the product better known. To obtain it a large incision is made in the trunk of the tree, about 30 inches from the ground, upon |