72 Miscellaneous-Answers to Correspondents. approximate to those procured by experiment, as closely as can be expected in such cases. I also freely admit that some of the relations above pointed out are more apparent than real; others, I trust, will prove of a more durable and satisfactory description. Chemical Notices from Foreign Sources. I. MINERAL CHEMISTRY. Action of Chloride of Phosphorus on some Metallic Sulphides.-M. Baudrimont sums up the results of his experiments as follows (Comptes-Rendus, t. lv., p. 378) :—1. Protochloride of phosphorus easily attacks metallic sulphides at a red-heat. With those of barium, calcium, &c., it produces a splendid incandescence, and gives immediately the phosphorous sulphide PS3, and the corresponding metallic chlorides. With the sulphides of antimony, lead, mercury, &c., it furnishes at first sulphophosphides by the union of the sulphide of phosphorus with the metals; these are afterwards destroyed by an excess of PC, and are completely changed into PS3. 2. Perchloride of phosphorus reacts twice on sulphide of hydrogen, producing at first chloro-sulphide of phosphorus, and afterwards, at a higher temperature, phosphoric sulphide, PCl5. 3. It behaves in the same way towards earthy and alkaline sulphides. 4. With the sulphides of antimony, tin, lead, mercury, &c., it produces the same results in the end, but forms intermediary sulphophosphides corresponding to PS, rather than PS. 5. The action of perchloride of phosphorus on sulphide of antimony is the basis of an easy method for the preparation of chloro-sulphide of phosphorus-(see CHEMICAL NEWS, vol. v., p. 41). 6. Chloro-sulphide of phosphorus attacks metallic sulphides exactly as it does PCl5. 7. The sulphophosphide of mercury obtained either by the reaction PC1, or PC1, on cinnabar, has for its formula PS, 3 (HgS), and appears to be the type of a group of sulpho-salts different from those described by Berzelius. Compounds of Perchloride of Phosphorus with other Chlorides -M. Baudrimont has also devoted a long series of experiments to the study of these compounds (Comptes-Rendus, t. lv., p. 361). He finds that PCI, combines with the chlorides of selenium (SeCl), of iodine (ICI), of aluminium (Al,Cl), of iron (FeCl3), of tin (SnCl2), of mercury (HgCl), and of platinum (PtCl). All these compounds may be obtained either by acting on the simple bodies with PC, or by combining the latter directly with the chlorides. The excess of PCI, can always be driven off by careful and prolonged heating to 160° or 180° C. At a higher temperature the double chloride sublimes. All these compounds are solid, volatile, and in some cases partly decomposed by heat. They fume in the air, are changed by moisture, and decomposed by water. The author describes the compounds formed with the chlorides named above, noticing particularly the platinum compound as being the only volatile salt of that metal known, and the iodine compound as being unequalled in causticity. II. ORGANIC CHEMISTRY. An Isomer of Amylic Alcohol.-Würtz (ComptesRendus, t. lv., p. 370) has compared the compound formed by the direct combination of hydriodic acid with amylene, and the iodide of amyl formed with amylic alcohol, and has been led to regard the two compounds, not as identical, but as isomeric. The bodies act very differently on moist oxide of silver, iodide of amyl having no action at the common temperature, while hydriodate of amylene acts energetically even at o°, the principal product being an organic hydrate, which Würtz regards as an isomer of amyl alcohol. With iodide of amyl and acetate of silver the author obtained an acetate of amyl, with its characteristic odour; but with the hydriodate of CHEMICAL NEWS, Feb. 7, 1863. amylene a body having very nearly the composition of acetate of amyl, but possessed of a very different odour. The author points out the relations which exist between the compounds of amyl and of amylene; and expresses his belief that hydrates, homologous with the hydrate of amylene, and isomeric with ordinary alcohols, may be obtained in a similar way from hydrocarbons near to amylene, such as caproylene, cnanthylene, and caprylene. Transformation of Urea into Sulpho-cyanide Ammonium.—M. Fleury effected this change (Comptes-Rendus, t. lv., p. 519) by heating urea with an excess of bisulphide of carbon according to the equation C2H4N2O2+ CS2 = CO2 + NH.C2NS. He has not perfectly succeeded in changing sulpho-cyanide of ammonium into urea. of MISCELLANEOUS. Simpson and Others v. Wilson and Another.— This cause is set down for trial on Monday, the 9th. If any new feature be introduced in the course of the trial we shall report it. Royal Institution.-On Monday, February 2, a General Monthly Meeting was held, William Pole, Esq., M.A., F.R.S., Treasurer and Vice-President, in the Chair. The Earl of Clanwilliam, Edward W. Cox, Esq., Sir William Augustus Fraser, Bart., General Charles H. Hamilton, C.B., and Peter Vanderbyl, Esq., were elected Members of the Royal Institution. The Secretary reported that the executors of the late James Walker, Esq., F.R.S., M.R.I., had bequeathed to the Institution a marble bust of Professor Faraday, by Mr. Matthew Noble, M.R.I. The thanks of the members were returned to Professor Tyndall, and to his Eminence Cardinal Wiseman, for their dis. courses on the evening meetings on Fridays, January 23 and 30. The presents received since the last meeting were laid on the table, and the thanks of the members returned for the same. The following lectures will be delivered :Tuesday, February 10, at 3 o'clock, Professor Marshall, "On Animal Mechanics." Thursday, Feburary 12, at 3 o'clock, Dr. E. Frankland, "On Chemical Affinity.' Friday, February 13, at 8 o'clock, Dr. E. Frankland, "On Saturday, February 14, at 3 Artificial Illumination." "On Life and Death." o'clock, W. S. Savory, Esq., Carbonic Acid as an Anæsthetic.-M. Ozanam has given a mixture of three parts carbonic acid with one part of atmospheric air with success as an anaesthetic. After breathing it for ten minutes the patient became insensible, and an operation was performed without his evincing any sign of pain. ANSWERS TO CORRESPONDENTS. All Editorial Communications are to be addressed to the EDITOR; and Advertisements and Business Communications to the PUBLISHER, at the Office, 1, Wine Office Court, Fleet Street, London, E.C. Vol. VI. of the CHEMICAL NEWS, containing a copious Index, is now ready, price 10s. 8d., by post, 118. 2d., handsomely bound in cloth, gold-lettered. The cases for binding may be obtained at our Office, price 18. 6. Subscribers may have their copies bound for 2s. if sent to our Office, or, if accompanied by a cloth case, for 6d. Vols. I. and II. are out of print. All the others are kept in stock. Vol. VII. commenced on January 3, 1863, and will be complete in 26 numbers. circumstances compelled the alteration. R. H.-We regret the change as much as our correspondent, but Juvenis.-Noad's lectures, or the volume of Lardner's Handbook of Natural Philosophy containing "Electricity." Dialyser. We do not know where the substance can be procured. It is obtained from a sea-weed. J. A. M. and Co.-Apply to Mr. Wilson, of Price's Patent Candle Company. council or secretary of the society. A Subscriber to the Cavendish Society should address a letter to the THE CHEMICAL NEWS. VOL. VII. No. 167.-February 14, 1863. IN a former Number of the CHEMICAL NEWS (vol. iv., p. 39) we gave incidentally a description of the method employed by Dr. Letheby for estimating sulphur in coal gas, by burning the gas in an atmosphere of ammonia. We are now, by the kindness of Mr. Sugg, enabled to give a cut, representing the apparatus in use, in illustration of which we again briefly describe the process. After passing the meter, the gas goes through a bottle filled with pebbles moistened with dilute sulphuric acid, for the purpose of estimating any ammonia the gas may contain. The inlet pipe to this bottle is allowed to pass only one inch through the cork; the outlet pipe passes to the bottom of the bottle. The gas is thus forced through the pebbles from the top, which prevents any accumulation of salt about the inlet pipe. In place of this bottle, a tube, about six inches long, an inch and ahalf in diameter, and drawn out at each end, may be used. It is filled, of course, with pebbles, moistened with sulphuric acid like the bottle, and may be placed horizontally. The gas thus purified from ammonia is consumed at the rate of about half a foot per hour in a Leslie's burner, which is placed under the long funnelshaped tube, as represented in the engraving. This tube is connected to one end of a large glass condenser, the other end of which is furnished with a piece of glass tube, about four feet long, joined in such a manner that any products of combustion condensed in it will flow back into the large receiver. In our former notice of this process we described two cylindrical receivers as being used, but experience has shown that when a large one is employed a second is unnecessary. The means by which ammonia is supplied to the Researches on the Platinum Metals,* by WOLCOTT GIBBS, M.D. (Continued from page 63.) Rhodium. When nitrite of potash is added to a solution containing the sesquichloride of rhodium, no change is at first produced, but, on heating, the solution becomes yellow, and on boiling or evaporation to dryness, part of the rhodium is precipitated in the form of a bright yellow or orange-yellow crystalline powder, which is extremely insoluble in hot or cold water, but which dissolves readily in hot chlorhydric acid. Another portion of the rhodium usually remains in the form of a yellow salt soluble in water, but insoluble in alcohol. The solutions of these two salts are decomposed with great difficulty by boiling with strong acids: alkaline sulphides give a dark brown precipitate of sulphide of rhodium soluble in a large excess of the precipitant, and completely precipitated from the solutions by the addition *From the American Journal of Science, vol. xxxiv., page 341. 74 Researches on the Platinum Metals. of an excess of chlorhydric acid. Nitrite of soda also gives a soluble and an insoluble salt with solutions of rhodium, but only the soluble salt is formed when the rhodium solution is boiled for a short time with an excess of the alkaline nitrite. : The application of these facts to the separation of the several metals of the group is as follows:Platinum from Iridium.-The separation of platinum from iridium, for the purpose of obtaining the two metals in a state of chemical purity, may be effected by either of the following processes :-The iridium is, in | the first place, to be brought into the form of bichloride by means of a current of chlorine or by nitric acid, and the two metals are then to be precipitated together as PtCl2,KCl and IrCl2,KCl, by the addition of a concentrated solution of chloride of potassium. The colour of the mixed salts varies from orange to almost black, according to the quantity of iridium present. The mass of crystals is to be rubbed fine in an unglazed porcelain mortar, and boiling water added in the proportion of three volumes of water to one of salt. A dilute solution of nitrite of potash is then to be added, until the liquid becomes deep olive-green, carbonate of potash being thrown in from time to time in quantity sufficient to prevent the solution from becoming strongly acid. The iridium is instantly reduced to sesquichloride, while the platinum salt remains as a reddish orange powder. The deep olive-green solution is to be poured off, and the undissolved mass treated a second time with hot water and nitrite. This process must be repeated as long as the liquid remains olive-green. The mixed solutions on cooling, or after evaporation, deposit a beautiful mass of crystals of the double chloride of potassium and iridium, Ir Cl3,3 KCl+6HO. By re-solution and repeated crystallisation, the iridium salt may be obtained perfectly free from platinum. Instead of nitrite of potash, nitrite of soda may be employed in the above-mentioned process; the iridium and sodium salt has the formula Ir2Cl2, 3 NaCl +24HO, and crystallises well. The undissolved mass and the mother-liquors from the iridium salt contain a large quantity of platinum, with a comparatively small quantity of iridium. When the absolute quantity of platinum salt is not very large, it may be dissolved in boiling water, a small quantity of an alkaline nitrite added, and the solution allowed to crystallise; the resulting chlorplatinate of potassium contains only a trace of iridium. The process just mentioned gives satisfactory results when carefully executed, but requires attention to two points. In the first place, the alkaline nitrite must be added in quantity just sufficient to reduce the iridium from bichloride to sesquichloride, but not so as to produce further chemical changes by the formation of the double nitrites of iridium and potassium or sodium. With a very little experience this is easily managed. In consequence of the facility with which the double nitrite of iridium and sodium is decomposed by boiling with chlorhydric acid into the double chloride IrCl2,NaCl, it is better to use nitrite of soda in the above process, because, in case an excess of nitrite is used, the mixed solution of double chloride and double nitrite can easily be brought to the form of double chloride, Ir,Cl2,3 NaCl, by boiling with chlorhydric acid, neutralising with carbonate of soda, and then reducing the iridium to sesquichloride by cautiously adding a very dilute solution of nitrite of soda. In the second place, it may happen, as in working with crude platinum solutions obtained, not from osmiridium, but from platinum ores, that the quantity of CHEMICAL NEWS, platinum is very large when compared with that of iridium. The process applies equally well to this case so far as the iridium is concerned, but it is difficult and troublesome to re-crystallise large quantities of a salt so insoluble as the chlorplatinate of potassium, PtCl2,KCI, and small quantities of the corresponding iridium salt are difficult to remove. A method of obtaining platinum in a state of chemical purity will be given further on. The above process is capable of giving chemically pure iridium when platinum is the only other metal present. This is rarely the case, and the following method is usually more advantageous:-The greater part of the platinum is first to be separated in the manner above pointed out. The solution of double chloride of iridium and sodium, Ir,Cl,,3NaCl, is then to be filtered, an excess of nitrite of soda added, and the solution boiled until it assumes a clear orange-yellow colour. To the boiling solution sulphide of sodium is to be added, drop by drop, as long as this produces a cloudiness, and until a small quantity of the precipitated sulphide of platinum, PtS2, is re-dissolved. Dilute chlorhydric acid is then to be added cautiously until the liquid, previously allowed to become cold, is distinctly, though faintly, acid, when it is to be filtered, and the sulphide of platinum on the filter washed continuously with hot water. The filtrate is then to be boiled with chlorhydric acid in excess, and the resulting chloro-iridate of sodium evaporated, preThis salt, on cipitated by a cold and strong solution of chloride of ammonium, and washed with the same. ignition, yields pure iridium, if the operation has been well conducted. It is in all cases, however, well, after separating the sulphide of platinum by filtration, to neutralise the filtrate with carbonate of soda, boil a second time with a little additional nitrite of soda, and then add sulphide of sodium, and proceed as before. In this manner every trace of platinum is removed, and the resulting iridium salt is chemically pure. Platinum from Ruthenium.-Ruthenium in the form of bichloride may be approximately separated from platinum by precipitating the two metals together in the form of PtCl2,KCÍ, and RuCl„KCl, and washing out the ruthenium salt with cold water, in which it is readily soluble. The mixed solutions should be evaporated to dryness with an excess of the alkaline chloride, and the dry mass rubbed to fine powder in a mortar, after which, almost the whole of the ruthenium may be washed out with water or with a cold and moderately strong solution of chloride of potassium. The undissolved platinum salt may then be purified by crystallisation, but usually retains traces of ruthenium. The rosered solution of the ruthenium salt contains a small quantity of platinum, from which it cannot be wholly freed by the difference in solubility of the two salts. Chloride of ammonium may be employed in this process in place of chloride of potassium. To obtain a complete separation, the following process may be followed with advantage :-The chloro-ruthenate of potassium, separated as far as possible from the platinum salt, is to be heated with a solution of nitrite of potash in quantity sufficient to convert the whole of the ruthenium into the soluble yellow double nitrite of ruthenium and potassium, carbonate of potash being added in small quantities so as to keep the solution neutral or alkaline. The yellow or orange solution is to be evaporated to dryness in a water bath, the dry mass reduced to powder and boiled with absolute alcohol until the ruthenium salt is completely dissolved. This is best effected in a flask furnished with a condensing tube bent upwards, so that the alcohol vapours may be condensed CHEMICAL NEWS, Feb. 14, 1863. Researches on the Platinum Metals, and flow back into the flask. The boiling need not be continued for a very long time, as the ruthenium salt is readily soluble in alcohol. The solution is then to be filtered off from the undissolved salts, and these are to be washed with absolute alcohol until the washings are colourless, or until they no longer give the characteristic ruthenium reaction with sulphide of ammonium. The filtrate and washings may then be distilled, to separate and save the alcohol, water being first added in small quantity. The residue in the retort or flask is then to be evaporated with chlorhydric acid, which readily decomposes the double nitrite, and yields a fine deep rosered solution of the chloro-ruthenate of potassium, containing at most only a trace of platinum. The mass of salts undissolved by the alcohol contains nearly all the platinum in the form of chlorplatinate of potassium, which is easily separated. The solution of chlororuthenate of potassium is now so pure that it gives the reactions of a chemically pure salt. To obtain the ruthenium in a state of absolute purity, the solution is to be evaporated to dryness with a saturated solution of sal-ammoniac in excess, re-dissolved, again evaporated, and the dry mass washed with a little cold water to remove the alkaline chlorides. The chloro-ruthenate of potassium is in this manner, for the most part at least, converted into chloro-ruthenate of ammonium. This salt is then to be dissolved in hot water, a solution of ammonia added, and the liquid boiled until it assumes a clear yellow or orange-yellow colour, after which it is to be evaporated to dryness upon a water bath. In this manner the ruthenium is converted into the chloride of ruthen-diamin, 2NH3,RuCl + 3HO, discovered by Claus. The yellow mass is to be dissolved in boiling water, and a solution of chloride of mercury added. A beautiful yellow crystalline double salt is precipitated, and the mother-liquor, when cold, contains only traces of ruthenium and platinum. The double chloride of mercury and ruthen-diamin has the formula 2NH3,RuCl + HgCl; it is almost insoluble in cold water, but is soluble in boiling water, and is easily rendered absolutely pure by re-crystallisation. On ignition, this salt yields chemically pure metallic ruthenium as a silver-white porous mass. When, in a mixture of solutions of ruthenium and platinum, the ruthenium is present either partly or wholly as sesquichloride, the liquid is to be boiled with nitrite and carbonate of potash as above, evaporated to dryness, boiled with excess of chlorhydric acid to convert the double nitrite of ruthenium and potassium into chlororuthenate of potassium, RuCl,,KCl, and the resulting solution treated by the process already described. Platinum from Rhodium.-The separation of these metals may be approximately effected by bringing the platinum into the form of PtCl2,KCl, or PtCl2,NH.Cl, and the rhodium into that of RhCl,,3KCl, or Rh2Cl3,3NH,Cl, and then carefully washing out the rhodium salt by small successive portions of cold water, or, better, of a moderately concentrated solution of chloride of potassium or ammonium. This is the method usually employed. By re-crystallising the platinum and rhodium salts respectively, they may be obtained in a state of purity, since they are not isomorphous. To obtain rhodium absolutely free from platinum, it is best to convert the two metals into the ammonium double salts, separate the rhodium salt as completely as possible by washing with a solution of sal-ammoniac, and then evaporate the double chloride of rhodium and ammonium with a solution of ammonia. In this manner the rhodium is converted into the chloride of the ammoniarhodium base discovered by Claus, 5NH,,Rh2Cl3, while 75 the platinum forms no well defined or crystallisable compound. The chloride of Claus's base may then be purified by repeated crystallisation. Iridium from Ruthenium.-The separation of these metals cannot be effected by igniting them with a mixture of saltpetre and caustic potash. Under these circumstances, the ruthenium is oxidised to ruthenate of potash, but a portion of the iridium also becomes soluble in the alkali, though in what state of oxydation it is difficult to ascertain. Moreover, the complete oxydation of a mixture of the two metals, even when in a finely divided state, can hardly be effected by a single fusion. Claus has given no general method for the separation of iridium and ruthenium in the wet way. In his method of treating the Siberian ores, the greater part of the ruthenium is separated as ruthenate of potash by the primary fusion with saltpetre and caustic potash, but a portion always remains with the iridium, and is difficult to remove, especially as, after solution in chlorhydric acid, salts of both sesquichloride and bichloride of ruthenium are invariably present. No part of the present investigation has cost more labour than the complete separation of iridium and ruthenium, the properties of mixtures of the salts of these metals having sometimes almost led to a conviction of the existence of new metallic elements in the osmiridium. A perfect separation of ruthenium from iridium may be easily effected by the following process, which is applicable to all cases, without reference to the state of oxydation in which either metal may exist. To the solution containing the two metals nitrite of soda is to be added in excess, together with a sufficient quantity of carbonate of soda to keep the liquid neutral or alkaline. The whole is to be boiled until the solution assumes a clear orange-yellow or orange colour. If a green tint should be perceptible, more nitrite of soda must be added, and the solution again boiled. Both ruthenium and iridium are converted into soluble double nitrites. A solution of sulphide of sodium is then to be added, in small quantities at a time, until a little of the precipitated sulphide of ruthenium is dissolved in the excess of alkaline sulphide. The first addition of the sulphide gives the characteristic crimson tint due to the presence of ruthenium, but this quickly disappears and gives place to a bright chocolate-coloured precipitate. The solution is then to be boiled for a few minutes, allowed to become perfectly cold, and then dilute chlorhydric acid added cautiously until the dissolved sulphide of ruthenium is precipitated, and the reaction is just perceptibly acid. The solution is then to be filtered through a double filter, and the sulphide of ruthenium washed continuously and thoroughly with boiling water. The filtrate is perfectly free from ruthenium: it is to be evaporated with chlorhydric acid, and treated with salammoniac in the manner already pointed out in speaking of the separation of iridium from platinum. The washed sulphide of ruthenium is to be treated, together with the filter, with strong chlorhydric acid and chloride of ammonia added in quantity sufficient to form chlororuthenate of ammonium. Nitric acid is to be added from time to time, in small quantities, until, with the aid of heat, the whole of the sulphide of ruthenium is oxidised and dissolved. The liquid is then to be filtered, the filter well washed, and the filtrate and washings evaporated to dryness on a water bath, when, after washing out the soluble salt with a strong solution of chloride of ammonium, the salt, RuCl,,NH.Cl, remains almost chemically pure. It is to be dissolved and converted into the compound of chloride of mercury and ruthen 76 The Indian Madar Plant, and its Useful Applications. diamin, 2NH,RuCl + HgCl, by the process already described. From this salt chemically pure ruthenium may be obtained by ignition, which is best effected in an atmosphere of hydrogen, as the reduced metal is easily oxidised in the air. It may happen that the precipitated sulphide of ruthenium contains traces of iridium. This can only arise from imperfect washing or want of proper care in precipitating with sulphide of sodium. In this case, the washings from the chloro-ruthenate of ammonium are yellow, and contain sulphate of iridium, probably Ir2O3,3SO3. The quantity of iridium in such cases is too small to be worth the trouble of separate treatment. When a solution contains iridium and ruthenium in the form of bichlorides, the ruthenium may be easily and completely separated by boiling the solution with nitrite of potash in excess, adding, at the same time, enough carbonate of potash to give an alkaline reaction, evaporating to dryness, and dissolving out the double nitrite of ruthenium and potassium by means of absolute alcohol, in the manner recommended for the separation of ruthenium from platinum. The undissolved mass in this case contains the two double nitrites of iridium and potassium. By adding a strong solution of chloride of ammonium, evaporating to dryness, igniting the dry mass in a porcelain crucible, and dissolving out the soluble salts, metallic iridium remains in a state of purity. This method may be used for the quantitative separation of iridium from ruthenium, but when the object is simply to prepare both metals in a state of chemical purity, I prefer the separation by means of sulphide of sodium. (To be continued.) On the Presence of Arsenic in the So-called Pure Com- According to M. Glénard, the presence of arsenic in hydrochloric acid may prove very injurious in the preparation of certain pharmaceutical products. It is, then, important that pharmaceutists should be aware of this fact, and abstain from employing hydrochloric acid which they have not previously tested carefully. The examination is attended, fortunately, with no difficulty. It is only necessary to mix the acid to be tested with its volume of a solution of hydrosulphuric acid, or to pass into it, during a few minutes, a current of this gas; or, better still, to throw into it a few morsels of artificial sulphide of iron. Under these three conditions, the acid, if it contains arsenic, will become troubled, owing to the separation of the yellow sulphide of arsenic. But how to obtain pure hydrochloric acid? M. Glénard proposes 1. The direct preparation of this acid. 2. The purification of commercial acid. In the direct preparation, the first step is to ascertain that the sulphuric acid is free from arsenic; otherwise, the arsenic, transformed during the preparation of the hydrochloric acid into very volatile chloride of arsenic, will escape with the acid, and with it become condensed in the water. The first thing to do is to eliminate the CHEMICAL NEWS, arsenic from the sulphuric acid. To effect this, the acid is diluted with half its weight of water, and to it is added a little hydrochloric acid, and then a current of hydrosulphuric acid gas is passed into it. The arsenie soon separates in the form of sulphide. It is next filtered through a funnel packed with amianthus, then heated in a capsule, to expel the excess of sulphuretted hydrogen, and to bring it to 60° of Baumé's areometer. The sulphuric acid thus purified is employed in the ordinary way, and furnishes perfectly pure hydrochloric acid. After describing the simple and ingenious process which consists in disengaging, by means of concentrated sulphuric acid, the hydrochloric gas contained in commercial acid, and in condensing this gas in distilled water, M. Glénard proposes the following method :Into the crude acid to be purified a current of hydrosulphuric acid is passed until all the arsenic is precipitated. : The sulphide of arsenic is separated either by letting the acid stand or by filtering it through a funnel packed with amianthus. Should the filtered liquid contain excess of sulphuretted hydrogen, some grammes of a concentrated solution of perchloride of iron are added, which destroys the hydrosulphuric acid, becoming reduced to protochloride. As the hydrochloric acid would then contain only fixed matters, it could then be rectified. Hydrochloric acid gas is displaced by means of sulphuric acid freed from arsenic.-Journal de Pharmacie et de Chimie. TECHNICAL CHEMISTRY. The Indian Madar Plant, and its Useful Applications, NUMEROUS applications having been made for further information on the above subject, in consequence of the article given in vol. vi., p. 59, we are induced to print the following extract from Major Drury's "Useful Plants of India," a work which is little known in England: Calotrophis gigantea. Natural order, Asclepiadace. English name, "Gigantic Swallow-wort." Hindostanee name, "Muddar," "Ack." Tamil name, "Yercum." Description: Shrub, 6 to 10 feet; leaves stem-clasping, decussate, oblong-ovate, wedge-shaped, bearded on the upper side at the base, smooth on the upper surface, clothed with woolly down on the under side; segments of corolla reflexed with revolute edges, stamineous corona five leaved, shorter than the gynostegium; leaflets keelformed, circinnately recurved at the base; incurved and subtridendate at the apex; umbels sometimes compound, surrounded by involucral scales; follicles ventricose, smooth; seeds comose; flowers rose colour and purple mixed. Uses Of late years the plant has attracted much notice from the many and important uses to which its several properties can be applied. The silky floss which surrounds the seeds has been woven into shawls and handkerchiefs, and even paper, besides a soft kind of thread, by the natives. In addition to its medicinal qualities, this plant is valuable from the fine strong fibres with which it abounds. To procure them, the straightest branches are cut, and exposed for at least twenty-four hours to wither. On the second and third day they are slightly beaten. The skin is then peeled, and the stringy substance between the bark and the wood taken out. They are then dried in the sun. This |