NEWS OBITUARY. SIR WILLIAM HUGGINS. THE news of the death on Thursday, May 12th, of Sir William Huggins will be received with universal regret. The scientific world has suffered the loss of a distinguished worker who was still engaged in active research, and was adding to the sum of the knowledge of the universe possessed by mankind. Sir William Huggins was born in London in February, 1824. He was educated at the City of London School, and subsequently studied under private tutors, devoting himself from the first to the natural sciences. He laid a thorough foundation in physics and chemistry for his later work, and was, moreover, at one time much attracted by physiology, then a young and rapidly-growing science. Astronomy, however, early claimed his attention, and in 1856 he built himself an observatory at Tulse Hill, where he perfected his knowledge of the fixed stars and planets by following the then usual lines of astronomical research. When, however, Kirchoff's great discovery concerning the composition of the solar atmosphere was announced he turned more particularly to the study of spectroscopic astronomy, which was thereafter recognised as a special and important branch of astronomy, and one to which the rest of his life was devoted. At first the experimental difficulties connected with the spectroscopic examination of the light emitted by the fixed stars appeared almost insurmountable, but Sir William Huggins's unconquerable energy and skill finally overcame the last of them, and then began a period of the most fruitful research, an account of which was given in a note communicated to the Royal Society in 1863, "On the Lines of some of the Fixed Stars.' In 1864 Sir William Huggins published an account of the results of his investigations of the true nature of the nebulæ, then almost universally supposed to be composed of galaxies of innumerable stars. To use the great astronomer's own words, "I was fortunate in the early autumn of 1864 to begin some observations in a region hitherto unexplored, and which to this day remains associated in my memory with the profound awe which I felt on looking for the first time at that which no eye of man had seen, and which even the scientific imagination could not foreshow." The results of the spectroscopic examination were startling. The light of the nebula first examined-a planetary nebular in Draco-was found to be monochromatic, and "the riddle of the nebula was solved." They consist not of an aggregate of stars but of a luminous gas. Further observations confirmed this view, and thenceforward it was regarded as firmly established that the nebulæ are evidences of the evolution of the heavenly hosts, different nebulæ representing different stages in the condensation of the original nebular matter. Sir William Huggins's next great achievement was the measurement of the velocity of approach and recession of the stars with reference to the earth. By the application of Doppler's principle relating to the alteration of frequency of the light emitted by radiating bodies moving towards or from the observer, to the case of the displace ment of the lines of the ordinary spectra of the fixed stars, Huggins was enabled to calculate the velocity of motion of the stars in the line of sight of terrestrial observers. More exact measurements have since been made with the aid of photography. The years 1866, 1867, and 1868 were devoted to the study of the spectra of comets, and the outcome of the observations made during this period was the proof that their principal constituent is vapour of carbon. Subsequently, when the use of the photographic plate had become possible, the presence of nitrogen and hydrogen was also detected. In 1871 the Royal Society placed at Sir William Huggins's disposal a far more powerful telescope than he had hitherto possessed, and with its aid he was enabled to add to his discoveries, and his work was much facilitated and extended by the use of the photographic plate, the recently perfected dry plates with gelatin films being of invaluable assistance. The work of the following twentyfive years was the mapping of the star spectra, and in 1899 Sir William and Lady Huggins published a magnificent "Atlas of Representative Stellar Spectra," in which some of the changes which the stars have undergone in their gradual evolution are depicted from the least condensed condition to the final stage in which the spectrum is indistinguishable from that of the sun. The magnitude of Sir Willlam Huggins's work was fully recognised in his lifetime, and he was the recipient of many honours. The Royal Society bestowed upon him a Royal, Copley, and Rumford Medal, and he became the President of the Society in 1900. He was the President of the Royal Astronomical Society from 1876 to 1878, and received two medals from it in addition to several prizes given by the Académie de France. He was created K.C.B. in 1897, and was selected as one of the original members of the Order of Merit in 1902. PROFESSOR STANISLAO CANNIZZARO. IT is with much regret that we announce that the veteran Italian chemist Stanislao Cannizzaro has recently passed away at Rome at the age of eighty-four years. Born in Sicily, Prof. Cannizzaro studied medicine and natural science at Palermo, and finally devoted himself entirely to chemistry at the University of Pisa. He held the posts of Professor of Chemistry at the Universities of Genoa and Palermo successively, and was appointed to the Chair of Chemistry at Rome in 1871. He was also a Senator, and held high office on the Board of Public Education at Rome. en When Cannizzaro became Professor of Chemistry at Palermo chemical theory was in a state which can only be described as chaotic. Kekulé and Couper were deavouring to lay the foundations of the "structural theory," and the first structural formulæ for alcohol, acetic acid, &c., had been suggested. It was beginning to be realised that in order to arrive at the true constitution of chemical compounds the atomicity or valency of the elements must be accurately known, but no clear distinction was drawn between the atomic weight and the equivalent of an element, with the result that frequently different chemists would give quite different formulæ for the same substance, while in the text-books the same formulæ might be used to denote different substances. Thus water was indiscriminately written as H2O, HO or H2O2, and C4H404 meant sometimes acetic and sometimes maleic acid." This uncertainty was greatly affecting organic chemistry, for by many chemists the atomic weight of carbon was correctly taken to be 12, while that of oxygen was supposed to be identical with the equivalent, viz., 8. Such was the state of confusion that it was recognised that it was imperative for the development of the science that the matter should be cleared up, and in 1860 a meeting of chemists was called at Karlsruhe by Welzien, Wurtz, and Kekulé. At this meeting, which was attended by more than a hundred of the foremost chemists of the day, a paper was read by Cannizzaro, entitled "Outlines of a Course of Chemical Philosophy." It was virtually a reprint of an article which he had published two years before in an Italian journal, but which had attracted but little attention except perhaps among his immediate circle of students. In this paper Cannizzaro advanced the now universally accepted idea that the true atomic weights of the elements can be ascertained only by the determination of the vapour densities of their gaseous compounds. He also showed to what extent it was admissible to deduce the atomic weights of elements which had no gaseous compounds by the appli Their formula The action of solutions of different strength on polarised light increases with the concentration, thus: 5 10 = Solution containing 2 grms. per 100 cc., [a|D= +24°12° [a]D = +45.89° [a]D +58.50° This variation appears to be due to dissociation. The substance is soluble in water and in alcohol. cation of the specific heat law of Dulong and Petit. | pale yellow or pink crystals are deposited. of the science. Although it will always be for his work in chemical philosophy that Cannizzaro's name is known and revered throughout the scientific world, he was a skilled experimenter and an acute observer. His researches lay mostly in the region of organic chemistry, which he enriched by the discovery of benzyl alcohol, afterwards subjecting its properties to a thorough investigation; he also studied santonin and other naphthalene derivatives, and was the first chemist to prepare the useful organic compound cyanamide. CnH2n+1.OH+H2SO4 = H2O+SO4H.CnH2n+1 With metallic oxides a similar intermediate product is 2(CnH2n+1.OH) +ThO2 = H2O +ThO (OCnH2n+1)2. At a moderate temperature the following reaction occurs :ThO (OCnH2n+1)2 = ThO2 + (CnH2n+1)20, while if the temperature is raised above 300° the thorianate decomposes as follows:-ThO(OCnH2n+1)2 = ThO2 + H2O +2CnH2n. Detection of Methyl Alcohol, especially in Presence of Ethyl Alcohol.-G. Denigès.-5 cc. of 1 per cent KMnO4 and 0.2 cc. of pure sulphuric acid are added to O'I cc. of the alcohol to be tested. The liquids are well mixed, and after two or three minutes o'r cc. of an 8 per cent solution of oxalic acid is added. When the liquid has become pale yellow I cc. of pure sulphuric acid is added, and then 5 cc. of fuchsine bisulphite. A violet coloration is produced if methyl alcohol is present. The presence of ethyl alcohol does not interfere with this reaction, in fact it is an advantage rather than otherwise. To detect methyl ethers they must first be saponified, while methyl glucosides can be hydrolysed by dilute acids or suitable diastases. Arsenic and Aniline Emetic.-P. Yvon.-Arsenic MISCELLANEOUS. Chemical Society. - Owing to the death of his Majesty King Edward VII., the Banquet to the Past-Presidents who have completed their Jubilee as Fellows has been postponed from May 26th to the Autumn. International Congress of Radiology and Electricity, Brussels, September 13, 14, and 15, 1910. -Communications relating to the Physical Sections of this Congress should be addressed to Prof. Rutherford or the undersigned, and communications relating to the Biological Section to Dr. W. Deane Butcher, Holyrood, Ealing, London, W. Intending members should, however, communicate directly with the General Secretary, Dr. J. Daniel, Rue de la Prévôté, Brussels.-W. MAKOWER, Physical Laboratory, the University, Manchester. MEETINGS FOR THE WEEK. SATURDAY, 21st.-Royal Institution, 3. "Johnson without Boswell," TUESDAY, 24th.-Royal Institution, 3. "Earth Tides," by Prof. A. E. H. WEDNESDAY, 25th.-Royal Society of Arts, 8. "Persia, and the Re FRIDAY, 27th.-Royal Institution, 3. "The World of Plants before INSTRUCTION IN PURE CULTIVATION OF YEAST. Courses for Beginners, as well as for Advanced Students, in Physiology and Technology of Fermentations. Biological Analysis of Yeast. The Laboratory possesses a numerous collection of Yeasts (Brewers', Distillers', Wine, Disease Yeasts), Moulds, and Bacteria. Manuals: ALFRED JÖRGENSEN, "Micro-organisms and Fermentation" (London) and "The Practical Management of Pure Yeast" (London, "The Brewing Trade Review"). The Laboratory supplies for direct use Pure Cultures of Yeast and aniline emetic can be prepared by allowing one molecule CHEMICAL APPARATUS (secondhand) of aniline acid tartrate to act in aqueous solution on half a molecule of arsenious acid. On evaporating colourless and Reagent Bottles for general Quantitative Analysis; also Voltmeter and Ammeter. Must be cheap.-List and price to H. HAMILTON, 25, Gilbert Road, Redfield, Bristol. B. A solution of 85 grms. ammonium nitrate in 250 cc. of water. C. 25 per cent nitric acid (68 cc. concentrated, sp. gr. 1'4, made up to 250 cc. with water). D. As washing liquid a solution of 25 grms. ammonium nitrate and 80 cc. nitric acid (concentrated) made up to litre with water. E. An 8 per cent solution of ammonia (23 cc. o.880 made up to 100 cc. with water). The above quantities are sufficient for about four estimations. Some of the phosphate, containing at the most o'i grm. of P205, is weighed out, and introduced into a 500 cc. beaker. It is dissolved in the smallest possible quantity of nitric acid, diluted to about 50 cc., and ammonia is added till the solution is only just acid. Thirty cc. of Solution B and 10 to 20 cc.* of Solution C are added, and it is heated till bubbles begin to rise; 120 cc. of Solution A are heated to boiling, and transferred to a separating funnel. The beaker containing the phosphate is rapidly rotated, while Solution A is run into the middle of it from the separating funnel; the rotation is continued for one minute more, then the beaker is allowed to stand for fifteen minutes. The clear liquid is poured through a filter, and the precipitate is washed by decantation with 50 cc. of Solution D, the washings being poured through the same filter. As much precipitate as possible is washed off the filter into the beaker, and then 10 cc. of Solution E are poured through the filter into this beaker. The liquid is stirred till all the precipitate is dissolved. 20 cc. of Solution B, 2 cc. of Solution A, and 20 cc. of water are poured through the same filter into the beaker, which is then heated as before till bubbles begin to rise. The phosphate is then re-precipitated by the addition from a separating funnel of 20 cc. of hot Solution C, the beaker being rotated as before. The liquid is allowed to stand ten minutes, and is then filtered through a Gooch crucible and the precipitate washed. This crucible is introduced into a nickel crucible on the bottom of which about in. of asbestos has been placed. The crucible is now very gently heated, and the temperature is raised till the bottom of the nickel crucible is at a red heat. This is maintained for a short time after the precipitate has assumed a uniform bluish black colour. The ignition takes about twenty minutes. The crucible is then allowed to cool, and is weighed. No organic matter or chlorides should be present, but no other substances appear to influence the result. To determine the accuracy of this method, some calcium phosphate, containing 00495 grm. P2O5, was analysed by this method, and the following results were obtained :0'04955 grm., 004942 grm. Also the percentage of P2O5 in pure re-crystallised sodium phosphate (which contains 19.845 per cent P2O5) was determined by this method; the. results were 19.79 and 19.73. The results appear to be slightly lower than those obtained by weighing the phosphorus as magnesium pyrophosphate, but besides occupying only about half the time, the method described appears to be more accurate (this has also been found by other chemists). In view of its greater rapidity and accuracy, it would be interesting to know whether it is much used by analysts. METHODS FOR THE ANALYSIS OF WATERS." (Continued from p. 235). MINERAL WATERS. until all sediment has settled. Remove from 100 to 250 CC., cool, and weigh. litres of water to which has been added hydrochloric acid, Iron and Aluminium.—Treat an aliquot portion of the silica filtrate with ammonium chloride (to keep magnesia in solution) and heat to boiling. Add ammonium hydroxide, off from the solution. Boil the solution until the smell of a drop at a time, until it can be very faintly smelled coming ammonia has practically disappeared, filter, wash with hot water, dry, burn, and weigh as ferric oxide (Fe2O3) and alumina (Al2O3). Use the filtrate for the determination of calcium and magnesium. Iron.-Treat an aliquot portion of the silica filtrate with 2 or 3 cc. of concentrated sulphuric acid, and evaporate to a syrupy consistency. Take up with water, reduce with hydrogen by the addition of zinc, filter, and determine the If less than o'r grm. of P2O5 is present, the following quantities of iron in the filtrate with standard potassium permanganate. solutions should be used: Manganese-Treat an aliquot portion of the silica fil- | trate just as described above for iron and aluminium, so as to eliminate these two elements, and treat the ammoniacal filtrate resulting with more ammonium hydroxide and a few drops of bromine, stir, and boil. Remove from the source of heat, cool slightly, and add a little more ammonium hydroxide and bromine. Repeat this process once or twice, precipitating all the manganese as the oxide. Make the solution slightly acid with acetic acid, filter, and wash with hot water. Transfer the filter and contents to a crucible, ignite, and weigh as manganese tetroxide (Mn304). Calcium and Magnesium.-(Not applicable in the presence of weighable amounts of phosphoric acid). Treat the filtrate from the iron and aluminium determination with ammonium hydroxide and ammonium oxalate, and allow to stand over night. Filter off the liquid, wash twice with hot water by decantation, dissolve the precipitate in hydrochloric acid, and re-precipitate with ammonium hydroxide and a little more ammonium oxalate. Allow to stand over night, and filter and wash on the same paper previously used. Dry the precipitate and transfer to a crucible, ignite and blast in the ordinary way, and finally weigh as calcium oxide. Evaporate the combined filtrates to dryness in platinum, and drive off the major part of the ammonium salts by heating. Dissolve the residue in dilute hydrochloric acid, and filter. Make the filtrate slightly ammoniacal, add enough sodium phosphate solution, a drop at a time, to precipitate all magnesium, and 10 cc. of concentrated ammonium hydroxide, drop by drop. Cover the beaker, and allow to stand over night, filter, wash with 25 per cent of ammonium hydroxide until free from chlorides, dry, blast, and weigh as magnesium pyrophosphate. (The method given under "Waters for Technical Purposes," see prox., may be used). Sulphuric Acid, Potassium, Sodium, and Lithium.Treat another portion of the silica filtrate while boiling with hot dilute barium chloride, and, after standing, filter and wash the precipitated barium sulphate, dry, burn, and finally weigh in the usual manner. Evaporate the filtrate to dryness, and take up with water. Precipitate with a solution of barium hydrate or milk of lime, and filter off the insoluble magnesium hydrate. Wash thoroughly with hot water the magnesium hydrate precipitate, and combine the filtrate and washings. Treat with ammonia, ammonium carbonate, and a little ammonium oxalate to precipitate calcium and barium. Allow to stand over night, filter, and wash thoroughly. Evaporate the filtrate and washings to dryness, dry in the oven, and finally drive off the ammonium salts by a gentle heat. Take up the residue with water, filter through a small filter, using as little wash-water as possible; evaporate to a small volume, and finally again precipitate with a drop of ammonium hydroxide, and two or three drops of ammonium carbonate and oxalate. If any precipitate appears, which is not usually the case, filter and repeat the same process. In any case, filter the solution from the magnesium hydrate that is precipitated on concentrating the solution. Evaporate the filtrate to dryness and drive off all ammonium salts by heating in platinum to a little below redness. Take up the residue with a little water and run through a small filter, using as little wash-water as possible, and again heat in platinum to a point slightly below red-heat. By this time all of the magnesia should be removed. Take up the residue with a little water, filter into a weighed platinum dish, add a few drops of hydrochloric acid, and evaporate to dryness. Dry in an oven, heat to a little below redness, cool in a desiccator, and finally weigh the combined chlorides of potassium, sodium, and lithium. The determination of lithium is then made according to he method of Gooch (Am. Chem. Journ., 1887, ix., 23). Dissolve the combined chlorides in water and transfer to a small beaker, and again evaporate practically to dryness. Add about 30 cc. of dehydrated amyl alcohol boiling-point 130° C.), and boil till the temperature rises approximately to the boiling-point of the amyl alcohol, The weight of the sodium chloride is found by subtracting the combined weights of the lithium chloride and the potassium chloride (corrected) from the total weight of the three chlorides. If the amyl alcohol in the determination of lithium is not evaporated to exactly 15 cc. the corrections will differ from those mentioned. (For the discussion of this point see original article by Gooch, loc. cit.). Phosphoric Acid.-Treat another portion of the silica filtrate with about 10 cc. of concentrated nitric acid, and evaporate in a porcelain dish nearly to dryness to drive off hydrochloric acid. Take up the residue with water and, if necessary, filter. Add ammonium hydroxide to alkalinity and then just enough nitric acid to restore acidity. Add some ammonium nitrate, and heat in the water-bath from 45° to 50° C. Add molybdate solution, and keep at a temperature of 45° to 50° C. for half-an-hour. The yellow precipitate formed at this point appears generally only in traces; if more than traces are present filter and wash with cold water until entirely free from nitric and molybdic acids. Transfer the precipitate and filter to a beaker, add a little water, and heat the paper and contents to a pulp. Dissolve the yellow precipitate by the addition of a small amount of standard potassium hydroxide solution (1 cc. I mgrm. of PO4); add phenolphthalein and titrate with standard acid of exactly the same strength as the alkali solution. From the data so obtained calculate the phosphoric acid ions in the water to parts per million (U.S. Dept. Agr., Bureau of Chemistry, Bull. 107, Revised, p. 4). Barium and Strontium (Gooch and Whitford, U.S. Geological Survey, Bull. 47).-The washed residue remaining after evaporating a large quantity of the water with sodium carbonate and filtering is used for this determination. (For an explanation of how this residue is obtained see method of preparing solution for determinations of barium, iodine, arsenic, and boric acid). Dry the filter and contents and transfer the residue to a large platinum dish, burn the filter and add the ash to the platinum dish. Treat the residue thus obtained twice with sulphuric and hydrofluoric acids to remove silica, and drive off the excess of these substances each time by heating with the full flame of a Bunsen burner. Fuse the residue with sodium carbonate (care being taken that the entire residue is acted upon), treat with water and a few drops of alcohol to dissolve the excess of sodium carbonate and sodium sulphate formed, filter and carefully wash until all traces of sulphates disappear from the washwater. Digest the contents of the filter with hot dilute acetic acid to dissolve barium, strontium, magnesium, and calcium carbonates. It sometimes happens at this point that undissolved iron comes through the filter and can not be washed out. If so, add ammonium hydroxide to the filtrate to alkalinity; then heat to coagulate the iron, filter, and wash. Make the filtrate very slightly acid with acetic acid, and add about fifty times the weight of the combined sulphates supposed to be present in ammonium sulphate which is dissolved in four times its weight of water. Heat on the steam-bath until the sulphates of barium and strontium settle out, and allow to stand over night. Filter the precipitated sulphates and wash with a concentrated solution of ammonium sulphate until no more calcium is present in the wash-water. Ignite the filter to a white ash, then treat with a few drops of sulphuric acid, ignite again, and weigh. The residue thus obtained consists of barium and strontium sulphates. Digest this residue for twenty-four hours (with frequent stirring) with ammonium carbonate solution to change the strontium sulphate to strontium carbonate. Transfer the residue remaining to a filter, wash, and dissolve the strontium carbonate with dilute hydrochloric acid. Wash the residue, ignite as before, and weigh the barium sulphate. The difference between the last weight and the total weight gives strontium sulphate. (To determine absolutely that the strontium has been dissolved out and not calcium, evaporate the small amount of hydrochloric acid extract to a small volume, and test with the spectroscope. It occasionally happens that a very minute residue is weighable and yet consists of calcium only, which has not been completely washed out). Bromine, Iodine, Arsenic, and Boron.-Evaporate large quantities of water to dryness, after the addition of small amounts of sodium carbonate. Boil the residue thus obtained with distilled water, transfer to a filter, and thoroughly wash with hot water. Make the alkaline filtrate up to a definite volume, and determine the constituents specified in aliquot portions. Iodine and Bromine.-Qualitative Method.-The qualitative tests for the presence of iodine and bromine are very much the same as those given by Fresenius. Evaporate an aliquot portion of the alkaline filtrate to dryness on the steam-bath. Add 2 or 3 cc. of water to dissolve the residue, and enough absolute alcohol to make the percentage of alcohol about go. Boil and filter, and repeat the treatment of the residue with 90 per cent alcohol once or twice. Add 2 or 3 drops of sodium hydrate solution to the filtrate and evaporate to dryness. Repeat the process of extracting with 90 per cent alcohol on the new residue, and filter the extract from the undissolved portion. Add a drop of sodium hydroxide to the filtrate, and evaporate to dryness. Treat the residue with a little distilled water, add dilute sulphuric acid to acid reaction, transfer the liquid to a test-tube, add a little carbon bisulphide, and 3 or 4 drops of 2 per cent potassium nitrite solution, and vigorously shake the test-tube. The presence of iodine is shown by a pink colour in the carbon bisulphide. Add chlorine water until the pink colour due to the iodine has disappeared, and then a little more chlorine water. The presence of bromine is shown by an orange colour in the carbon bisulphide. In most cases the above qualitative examination is sufficient, since iodine and bromine are usually not present, or only as traces. If qualitative examination shows a large amount of bromine, the following method, devised by Gooch and Whitfield (U.S. Geological Survey, Bull. 47), is used: Gravimetric Method.-Evaporate an aliquot portion of the alkaline filtrate to dryness and extract with 90 per cent alcohol, as in the qualitative examination just described. Evaporate the alcoholic extract to dryness, acidulate with dilute sulphuric acid, mix with a ferric sulphate solution, and distil from a retort which is joined to a condenser, sealed by a U-tube filled with water and carbon bisulphide. If iodine is present it colours the carbon bisulphide, and is titrated with standard sodium thiosulphate. After the distillation has been continued long enough to be sure that all iodine has been volatilised, add crystals of potassium permanganate, and continue the distillation as before, except that the U-tube, acting as a seal, is now filled with water and chloroform. Treat the contents of the tube with sodium hydroxide and zinc in a beaker and acidify the chloride and bromide solution so formed with nitric acid and precipitate with silver nitrate. Dry the precipitate and weigh. Dissolve in potassium cyanide, and precipitate the silver by electrolysis (Whitfield, Am. Chem. Fourn., 1886, viii., 421). From the combined weight of the silver chloride and bromide and the deter. mined silver the necessary data are obtained for the calculation of the bromine. Chlorimetric Method.-(U.S. Dept. Agr., Bureau of Chemistry, Bull. 91, Mineral Waters of the United States). Evaporate an aliquot portion of the alkaline filtrate (see above) to dryness, and extract with 90 per cent alcohol as in the qualitative examination just described. Dissolve the residue in a little water, acidify with sulphuric acid (1 to 5), using 3 or 4 drops in excess, and transfer to a small flask. Add 4 drops of 2 per cent potassium nitrite solution and about 5 cc. of carbon bisulphide freshly purified by distillation. Shake until all iodine is extracted. Filter off the acid solution from the carbon bisulphide. Wash the flask, filter, and contents with cold distilled water, and transfer the carbon bisulphide (containing the iodine in solution) to a 12 cc. Nessler-tube by means of about 5 cc. of pure carbon bisulphide (this tube was made from the ordinary 10 cc. Nessler-tube by re-marking it at the 12 cc. level). Make the contents of the tube up to the mark, and match the colour with that of other 12 cc. tubes containing known amounts of iodine dissolved in carbon bisulphide. Prepare the standard tubes by taking measured quantities of a solution of known potassium iodide content, acidifying with sulphuric acid (1 to 5), adding 3 or 4 drops of potassium nitrite, and extracting with carbon bisulphide just as in the actual determination. Use the filtrate from the carbon bisulphide for determining bromine. Add to the filtrates from the iodine standards, different measured quantities of a potassium bromide solution of known strength, the standards being run with the actual determination and conducted in exactly the same way. Transfer the filtrates, both from the actual determination and from the standards, to small flasks and add freshly prepared chlorine water. Usually from 2 to 8 cc. of a saturated solution of chlorine is suffi cient. Care must be taken not to add too much chlorine in excess of that necessary to set the bromine free, since a bromo-chloride may be formed with an excess of the reagent, thus spoiling the colour reaction. The best results are obtained by adding approximately the same excess of chlorine to the standards as to the actual determination. This may be accomplished by adding the chlorine water I cc. at a time, and shaking between additions. After a little practice one can approximately determine when the chlorine ceases to set bromine free. After all bromine has been thus set free, add 5 cc. of freshly purified carbon bisulphide to each of the flasks, and shake thoroughly. Filter off the water solution from the carbon bisulphide through a moistened filter, wash the contents of the filter two or three times with water, and then transfer to a 12 cc. Nessler-tube by means of about I cc. of carbon bisulphide. Repeat this extraction of the filtrate twice, using 3 cc. of carbon bisulphide each time. The combined carbon bisulphide extracts usually amount to from 11.5 to 12 cc. If they do not quite reach the 12 cc. mark, add enough carbon bisulphide to each tube to bring them to the required volume, and compare the sample with the standards. In some cases when working with the |