Action of Light upon Dyed Colours. CHEMICAL NEWS, Oct. 21, 1898. neither soda molybdate nor lead acetate is present in other than negligible quantities. As the solution is passed and repassed through the same filter until the end is reached, there is no loss through the absorption of the paper. And, finally, it is always open, if desired, to complete the gravimetric operation. This process is shorter than the gravimetric one, and on pure solutions it is equally accurate. We have not observed the interference of large amounts of metallic salts. 205 Our bacteriological examinations of the 297 samples have been quite satisfactory. The extraordinary deficiency in the rainfall in the Thames Valley, which now amounts to 44'5 per cent from the 1st of January, as our tables show, has had no effect in causing deterioration in the water supply of the Metropolis. We are, Sir, Your obedient Servants, THE WILLIAM CROOKES. The test proposed as a supplement to Schindler's is a very delicate one. In a faintly but decidedly acid (acetic) solution, measuring 400 c.c., a distinct cloudiness is formed by lead acetate when only o'ooo1 grm. of Mo is present, that is, one part in four million parts of solu- ACTION OF LIGHT UPON DYED COLOURS.* tion, a degree of accuracy not to be surpassed by the most fastidious working of the gravimetric process. To MAJOR-GENERAL A. DE COURCY SCOTT, R. E., Water Examiner, Metropolis Water Act, 1871. London, October 10th, 1898. SIR, We submit herewith, at the request of the Directors, the results of our analyses of the 182 samples of water collected by us during the past month, at the several places and on the several days indicated, from the mains of the London Water Companies taking their supply from the Thames and Lea. In Table I. we have recorded the analyses in detail of samples, one taken daily, from Sept. 1st to Sept. 30th inclusive. The purity of the water, in respect to organic matter, has been determined by the Oxygen and Combustion processes; and the results of our analyses by these methods are stated in Columns XIV. to XVIII. We have recorded in Table II. the tint of the several samples of water, as determined by the colour-meter described in previous reports. In Table III. we have recorded the oxygen required to oxidise the organic matter in all the samples submitted to analysis. Of the 182 samples examined by us during the month all were found to be clear, bright, and well filtered. The serious deficiency in the rainfall still continues. Rain fell at Oxford on six days only during September, The thirty years' the total fall being only 0.38 inch. average is 2'43 inches; we thus have a deficiency of 2.05 inches, bringing the total deficiency for the year up to 8.22 inches. Our bacteriological examinations of 258 samples have given the results recorded in the following table; we have also examined 39 other samples, from special wells, stand. pipes, &c., making a total of 297 samples in all :— Microbes per c.c. 485 12 2957 32 highest 3378 River Lea, unfiltered (mean of 26 samples) River Lea, from the East London Company's clear water well (mean of 26 samples). (Continued from p. 193). BLACK COLOURING MATters. CLASS I. VERY FUGITIVE COLOURS. (WOOL). Wool Book XIV. Acid Colours. Azo Colours. 4. Violet Black. From p-phenylene-diamine, with anaphthylamine and a-naphthol-sulphonic acid NW. S. and J. III. 502. Direct Cotton Colours.- From p-phenylene-diamine-azoa-naphthylamine and amido-naphthol-sulphonic acid y. 2. Tabora Black R. Constitution not published. NOTES.-During the first "fading period " Violet Black changes to a dull vinous red colour. CLASS II.-FUGITIVE COLOURS. (WOOL). Wool Book XIV. Acid Colours. 6. Azo Nigrine R. From phenol-disulphonic-acid-azoa-naphthylamine and ẞ-naphthol. 12. Wool Black. From amido-azo-benzene-disulphonic 13. Jet Black G. Constitution not published. 206 Transformation of Chemical Energy into Electric Energy. *3. Diamine Black ROO. From benzidine and B-amido. 5. Diazo Black H. Constitution not published. De De *8. Diamine Black BO. From ethoxy-benzidine and amido-naphthol-sulphonic acid y. Developed with Fast Blue Developer AD. S. and J. III. 229. Oxazine Colours. THE original construction of the Borchers cell presented a series of defects which became more and more marked after prolonged use. We cannot here go into the details of the research which Borchers undertook in the endeavour to eliminate these defects, however useful they may have been to future workers on the subject. The greatest diffi culty was to succeed in getting as perfect a contact as possible between the gas, the electrolyte, and the electrode, without allowing the solutions charged with the two gases to become mixed. The best results were obtained by stopping the continued current of air and by using an oxidising material which would be periodically regenerated by the atmospheric air. As an oxidising material Borchers took Weldon mud (manganite of lime mixed with a solution of chloride of lime). This mud is placed in an iron or lead box, which at the same time serves as an electrode; a flattened cell of refractory clay kept away from the air is plunged into the mud. This cell contains a horizontal plate of carbon which also serves as an electrode, and an acid solution of chloride of copper, through which a current of carbonic oxide is passed. The battery lasts until all the binoxide of manganese is reduced to the state of oxide. This can then be easily regenerated by blowing in more air. If we take precautions to maintain the solution of the chloride of copper, acid, and that of the manganite alkaline, the working of the cell will be very regular, and its electromotive force o'6 volt with an external resistance of about 50 ohms. Borchers himself is far from wishing to attribute any commercial value to his cell, such as it is described. The question as to how far the oxidation of the carbonic oxide can be pushed in such a cell has not yet been decided. But it may be permissible to regard Borcher's process as a method for the preparation of oxalic acid, starting from carbonic oxide, a method which at the same time produces electric energy, and which therefore may some day lead to the solution of the problem. The researches of Borchers took place in the laboratory of Prof. Nernst at Gottingen, and in that of the Elberfelder Farben. fabriken. A comparison of Borcher's experiments with those of * Moniteur Scientifique, Series 4, vol. xii., July, 1898. CHEMICAL NEWS, Oct. 21, 1898. Reed (Zeit. f. Elect., iii., p. 87) will show us what different lines have been followed in the endeavour to construct a commercial galvanic battery. Reed based his research on the following fact. Sulphurous acid reacts on sulphuretted hydrogen, giving rise to the formation of water and sul. phur. This reaction is followed by a disengagement of electric energy when carried out in a suitable apparatus constructed on the principle of a gas cell. As for the two gases they are obtained in the following manner. Sulphur is burnt in a retort to produce sulphurous acid, which is passed into the cell; the heat given off by this combustion is sufficient to vapourise the sulphur and make the carbons which are in the retort red-hot. The vapour of the sulphur gives sulphide of carbon, which is mixed while hot with steam, giving rise to the following decomposition:-CS2+2H2O=2H2S+CO2. The sulphuretted hydrogen and the carbonic acid pass into the other compartment of the cell, where the electric current is generated by the reaction-2H2S+SO2=3S+2H2O. We thus see that the three atoms of sulphur which were necessary to produce one molecule of sulphuretted hydrogen and one molecule of sulphurous acid are regenerated, and that the final result of all these operations is the transformation of the carbon into carbonic acid by the intermediary of sulphide of carbon. As the transformation of carbon into carbonic acid gives off 97,000 calories, and as the reaction between the sulphuretted hydrogen and the sulphurous acid gives off 25,000 calories, we see that 61 per cent of the heat of combustion is disposable for being transformed into electric energy. From the above data Reed estimates the electromotive force of his cell at o'63 volt. His apparatus, however, only gave him o'36 volt. This disagreement may be partly explained by the fact that calculations of electric energy based on thermochemical data are never very exact. According to Reed the importance of his process consists less in its practical value than in its principle. He believes that the true method of obtaining the electric energy of carbon will be to employ an intermediary material which, like sulphur, would serve to make the oxidation of the carbon indirect. But in the presence of the results he obtained this assertion would appear to be a little pretentious. We can see that the problem of making a carbon battery is still far from being solved. But it is possible that the solution of the more general problem of the commercial transformation of chemical into electric energy may be elucidated by the aid of other chemical reactions besides the combustion of the carbon. Several interesting researches have already been made in this direction. We know that a cell with carbon electrodes, one of which is placed in a solution of chloride of protoxide of copper and the other in chloride of cupric oxide, gives an electric current when we pass chlorine gas through the cupric chloride; the current lasts as long as any unoxidised chloride of the protoxide remains. If this can be continu. ally reproduced by means of a reducing gas we should get a practically continuous galvanic cell. Andrews found (Zeit. f. Elect., iii., p. 88) that sulphurous acid (but not carbonic oxide) can be used for this purpose. The sulphurous acid is transformed into sulphuric acid, and it is evident that it is the oxidation of the sulphurous acid which causes the electric energy of the cell. No doubt it is now impossible to commercially isolate the sulphuric acid which is formed in this process; but we can do away with the copper salts if instead we use carbon tubes plunged into dilute sulphuric acid, and if by means of these tubes we introduce chlorine and sulphurous acid under high pressure. The following reaction here serves for the production of electric energy SO2+2H2O+Cl2 = H2SO4+2HC), and we obtain an electromotive force of o'5 volt when the circuit is closed through a resistance of 1 ohm. It now remains to find a means of replacing the chlorine by the CHEMICAL NEWS, Iodometric Determination of Molybdenum. Oct. 21, 1898. oxygen in the air, so as to produce simultaneously pure, sulphuric acid as well as electric energy. As far as we can judge at the present day the formation of hydrochloric acid from its elements would still be the easiest reaction to employ for the production of electric The more the electrolytic energy by chemical means. manufacture of the alkalis progresses the more important becomes the question of the utilisation of the chlorine set at liberty in these electric processes. While in the old Leblanc process the chlorine was considered as a valuable secondary product which could be produced in large quantities, it becomes in the electrolytic processes an encumbrance if we cannot find new applications for it. In the earlier times there was generally produced one ton of chloride of lime for each two or three tons of caustic soda, while the chlorine given off in the manufacture of the same quantity of soda by the electrolytic process gives nearly five tons of chloride. It is probable that a corresponding increase in the consumption of chloride of lime for bleaching purposes, disinfection, &c., is very unlikely. On the other hand, the electrolysis of the alkaline chlorides gives at the cathodes equivalent quantities of hydrogen, the utilisation of which is yet an interesting problem. The idea of combining the chlorine and the hydrogen naturally presents itself for the purpose of obtaining hydrochloric acid, of which the Leblanc process is at present the principal source. The preparation of hydrochloric acid from chlorine and hydrogen has already been the subject of many patents, all of which point to the direct union of the two gases one with the other; but it is evident that we thus lose chemical energy which might be transformed into electricity if we could but construct a suitable apparatus in which the two gases could be combined indirectly. The energy that could be collected in this manner is fairly considerable, since the galvanic combination, Cl, CIH, H, gives with a great external resistance an electromotive force of 1'37 volts. If we could only succeed in making a commercial battery of this type the future of electrolytic processes for the manufacture of soda would be assured, even in face of the Solvay process. Thus by retransforming a part of the gas given off as hydrochloric acid we should obtain the The remainder electric current as a secondary product. of the chlorine would be converted into chloride of lime, while the corresponding quantity of hydrogen could, if advisable, be compressed. These considerations naturally give many points for elucidation, but they show that the problem of the transformation of chemical into electrical energy can be attacked from more than one side. A PROCESS for the iodometric determination of molybdic acid, which consists in treating a soluble molybdate in a Bunsen distillation-apparatus with potassium iodide and hydrochloric acid, has been advocated by Friedheim and Euler (Ber. d. D. Chem. Gesell., xxviii., 2066). According to this process the molybdate, containing from o'z grm. to 0'3 grm. of molybdenum trioxide, is treated with from 0'5 grm. to 0.75 grm. of potassium iodide, and enough hydrochloric acid, of sp. gr. 1'12, to fill two-thirds of the flask of the apparatus. The liquid is warmed until heavy vapours of iodine fill the flask, and then boiled until iodine vapour is no longer visible and the colour of the liquid residue is a clear green. The iodine liberated is collected in the distillate and titrated with sodium thiosulphate, every atom of iodine found indicating presumably * Contributions from the Kent Chemical Laboratory of Yale University. From the American Journal of Science, vol. vi., 1898. 207 the reduction of a molecule of molybdic acid to the condition of the pentoxide Mo2O5, It was pointed out in a former article from this laboratory (Gooch and Fairbanks, Amer. Journ. Sci., IV., ii., 156), that greater precaution than was taken by Friedheim and Euler is necessary in order that the reduction may proceed according to theory, and that the iodine collected may serve as a reliable measure of the molybdic acid. It was found that the green colour of the liquid comes gradually, and that it may develop distinctly before the molybdic acid is fully reduced. It was found, also, that since even a trace of oxygen liberates iodine from the hot mixture of potassium iodide and hydrochloric acid of the strength employed, it is not sufficient to rely upon the volatilisation of iodine to expel the air originally in the apparatus, but that it is essential to conduct the distillation in an atmosphere devoid of oxygen. The suggestion was made, therefore, that the operation should be carried on in a current of carbon dioxide, and that the mixture, constituted definitely, should be boiled between stated limits of concentration which were determined by experi ment. It was found that when amounts of a soluble molybdate containing less than 0.3 grm. of molybdenum trioxide are treated with potassium iodide, not exceeding the theoretical proportion by more than o'5 grm., and 40 c.m.3 of a mixture of the strongest hydrochloric acid and water in equal parts, the reduction proceeds with a fair degree of regularity, and is practically complete when the volume has diminished to 25 c.m. If the operation is properly conducted in an atmosphere of carbon dioxide, it was shown that the iodine in the distillate may be trusted to indicate the molybdic acid within reasonable limits of accuracy. It appeared, however, that too great an excess of potassium iodide tends to induce excessive reduction, and that the same tendency shows when the liquid is concentrated to too low a limit. To this criticism Friedheim took exception (Ber. d. D. Chem. Gesell., xxix., 2981), and contrasted, to their disadvantage, our results by the modified method with those of Friedheim and Euler by the original method. It became necessary, therefore, to point out (Gooch, Amer. Journ. Sci., IV., iii., 237) the fact that of the results published by Friedheim and Euler, upon which reliance was placed to prove the liability of their method, five out of seven in one series and one out of five in another series had been calculated incorrectly from data given. Another series of six determinations was, however, apparently faultless in this respect. More recently (Zeit. f. Anorg. Chem., xv., 454) Euler has explained that the errors were not really arithmetical. Two of them may be presumed, inferentially, to be due to careless copying or proofreading; and four, we are told by Euler, were introduced into the series by mistake, and actually represent (as Prof. Friedheim kindly informs him) the analysis of a sample of ammonium molybdate of undetermined constitution, that is to say, the figures now given by Euler represent the original percentages of molybdenum trioxide which had been changed by some unconscious process from— 80.62 per cent to 81.85 per cent. 80'71 81.69 Curiously enough Euler's corrected figures, as given here, are still affected by trifling arithmetical errors of from one to four units in the second decimal place. The agreement of these results among themselves is no proof of the correctness of the process of analysis. The great variation between the average percentage of molybdenum trioxide in ammonium molybdate as found by Euler in a molybdate of known constitution, and the percentage of the trioxide as found by Friedheim (if we understand Euler aright), may be due conceivably to either or both of two causes, viz., the change of material analysed and the change of operator or conduct of the operation. We shall show in 208 Iodometric Determination of Molybdenum. the following account of our work that the exact control of the conditions of treatment, along the lines laid down formerly, is actually essential to the reduction of molybdic acid according to the theory of the process. Our experiments were made with ammonium molybdate twice re-crystallised from the presumably pure salt. The constitution of the preparation was determined by careful ignition per se, and, for greater security, with sodium tungstate free from carbonate. It contained 81-83 per cent of molybdenum trioxide. The potassium iodide which we used was prepared by acting with re-sublimed iodine upon iron wire, and precip tating by potassium carbonate-the proportions of iodine and iron having been adjusted to secure the formation of the hydrous magnetic oxide of iron. The filtrate from the iron hydroxide gave on evaporation and crytallisation potassium iodide which was free from iodate. The hydrochloric acid was taken of sp. gr. 1'12, because this is the strength used by Friedheim and Euler. CHAMICAL NEWS, as shown in the figure and carbon dioxide was passed freely through the whole apparatus for some minutes. The stop-cock d, between the bulb of the funnel A and the flask B, was closed and hydrochloric acid (40 c.m.3, sp. gr. 1'12) was poured into the funnel; the air above the liquid in the funnel was displaced by carbon dioxide through the space between the neck of the funnel and the loosely adjusted stopper carrying the inlet tube; the connection between the funnel and inlet tube was tightened, the stop-cock opened, and the acid, under the pressure of carbon dioxide, was permitted to flow into the flask. In this way the acid, iodide, and molybdate were made to interact with little danger of the presence of oxygen. The flask was heated by the Bunsen burner and the iodine evolved, passing over quietly in the slow current of carbon dioxide, collected in the receiver. The liquid was boiled until fumes of iodine were no longer visible above the liquid in the flask and connecting tubes backed by a ground of white, and then a full minute more. At this stage, the green colour of the liquid having developed fully, the apparatus was permitted to cool, the current of carbon dioxide was increased, the cap of the receiver was loosened at f, the contents of the trap were washed back into the receiver, the rest of the apparatus was lifted bodily from the receiver, the liquid adhering to the inlet tube was dipped immediately into a solution of potassium iodide. The constant flow of carbon dioxide prevented reflux of air during the transfer, and as soon as the end of the tube had been submerged in the solution of potas sium iodide (which was employed not only as a water-seal, but to catch any iodine still carried in the gas), it was possible to reduce the rapidity of the current. The sodium thiosulphate employed was taken in nearly decinormal solution, and was standardised by running it into an approximately decinormal solution of iodine which had been determined by comparison with decinormal arsenious acid made from carefully re-sublimed arsenious oxide. We chose this method of standardising -the introduction of the thiosulphate into the iodine-tube was washed off into the receiver, and the end of the rather than the reverse operation, in order that the conditions of the actual analysis might be followed in the standardisation. The distillation apparatus was constructed with sealed or ground joints of glass wherever contact with iodine was a possibility. It was made by sealing together a separating funnel A, a 100 c.m. Voit flask B, a Drexel wash-bottle c, and a bulbed trap g, as shown in the figure. Upon the side of the distillation-flask B was pasted a graduated scale by means of which the volume of the liquid within the flask might be known at any time. Carbon dioxide, generated in a Kipp apparatus by the action of dilute hydrochloric acid (carrying in solution cuprous chloride to take up free oxygen) upon marble previously boiled in water, was passed through the apparatus before and during the operation, so that it was possible to interrupt the process of boiling at any point of concentration, to remove the receiver by easy manipu lation, to replace the receiver, and to continue the distillation without danger of admitting air to the distillation flask. After titrating the iodine in the distillate the receiver was again placed in the train and the process of distillation was resumed under the former conditions and continued until the volume of the liquid, as indicated upon the scale, had diminished to 25 c.m., when the distillation was interrupted. The apparatus was manipulated as before to prevent access of air, and the iodine evolved in the second treatment determined. A third period of distillation served to show the iodine liberated during the concentration of the liquid from 25 c.m. to 10 c.m. (To be continued). MISCELLANEOUS. Salts of Pertungstic and Permolybdic Acids.-P. Melikoff and L. Pissarjewsky. - To prepare these salts solutions of sodium and potassium hypotungstates and hypomolybdates are cooled to -2°, and added to the calculated quantity of H2O2; on addition of alcohol cooled kept for some time at -12°, and then filtered and washed to -12°, precipitation takes place. The precipitate is with alcohol. It can then be dried on a porous tile and analysed. The salts prepared by this method have the following compositions : Na2O2.WO4.H2O2+(Na2O2)2W04+7H2O Na2O2.WO4.H2O2 All these salts are very unstable, and are decomposed by water, with evolution of oxygen. To analyse the salts a weighed quantity of the salt is decomposed by dilute H2SO4 at -6°, and the liberated oxygen titrated with permanganate solution.-Ber. der Deutsch. Chem. Gesell., 1898, No. 6. In experiments to be described (1) to (5) of the table -the proportions of potassium iodide and molybdic acid, and the strength of the hydrochloric acid recommended by Friedheim and Euler were retained. The essential change of condition is the removal of atmospheric air from the distillation flask before the acid is admitted to contact with the other reagents. Potassium iodide (3 grm.) and water (200 c.m.) were put into the receiver c, and a FRIDAY, little of this solution was allowed to flow into the trap g. Ammonium molybdate carefully weighed (0'3 grm.) and potassium iodide (o'5 grm. to o'75 grm.) were introduced into the distillation-flask B, the apparatus was connected MEETINGS FOR THE WEEK. 28th.-Physical, 5. "An Influence Machine," by W. R. Pidgeon, M.A. "The Repetition of an Experiment on the Magneto-optic Phenomenon Discovered by Righi," by Prof. Silvanas P. Thompson, F.R.S. "The Magnetic Fluxes in Meters and other Electrical Instruments," by Albert Campbell, B.A. THE NEW YO CHEMICAL NEWS,} Interaction of Sodium Arsenate and Sodium Thiosulphate. LIC LIBRARY 1898. NOTE ON THE INTERACTION OF SODIUM ARSENITE AND SODIUM THIOSULPHATE.* By L. W. McCAY. IN the CHEMICAL NEWS for March 25th, 1898 (vol. lxxvii., p. 131), there is a note by Dr. Leonard Dobbin in which he calls attention to a new and interesting reaction which takes place when concentrated aqueous solutions of a cyanide and a thiosulphate are mixed and allowed to stand. The products formed are a thiocyanate and a sulphite : KCN+K2S2O3=CNSK+K2SO3. This reaction of Dr. Dobbin is in some respects similar to one I discovered in the summer of 1897. By means of my reaction I have been able to prepare the tertiary sodium salt of orthomonothioxyarsenic acid in large amounts and in beautiful well-defined crystals. I simply rub up in a mortar, with a sufficient quantity of caustic soda solution to form a thick paste, the calculated amounts of sodium arsenite and sodium thiosulphate. The reaction proceeds as follows: Na3A8O3+ Na2S2O3 Na3AsO3S+ Na2SO3. = It may be well to state, however, that I am not in the habit of making use of this reaction for preparing the orthomonothioxyarseniates. The sodium compound is most easily and rapidly obtained by rubbing up in a mortar, with enough water to form a paste, the stöchiometrical amounts of sulphur, caustic soda, and arsenious oxide, dissolving the resulting mass in water, filtering the solution, concentrating it, and allowing the salt to crystallise out. A few c.c. of absolute alcohol added to the contents of the mortar serve to accelerate the reaction in a very marked manner. It will be seen that this latter method is but a modification of that of Weinland and Rumpf. It is, however, simpler and quicker than their original method, and, as far as yield is concerned, leaves nothing to be desired. It was this method for preparing Na3AsO3S+12H2O which suggested to me the use of sodium thiosulphate. As is well known, Na2S2O3 yields sulphur very readily, especially when used for fusion purposes. The mechanism of the reaction is undoubtedly complicated. The simplest interpretation would be this: *Received August 2, 1898. ACTION OF WATER ON METALLIC COPPER AND LEAD. By ROBERT MELDRUM, F.C.S. Action on Copper. THE results obtained are expressed in parts per 100,000. The experiments were made in large test-tubes, each containing 100 c.c. of water and 7 feet bright copper wire 1/16" diameter. The metal dissolved was estimated by the potassium ferrocyanide colorimetric method. 1. Lake water containing 26 06 total solids; 0.0056 free NH3; 00126 albumenoid NH3; 1756 Cl; in 24 hours dissolved o‘099 Cu. 2. Water containing 27.66 total solids; no free NH3; o'oor albumenoid NH3; 1′22 Cl; dissolved in 24 hours 0023 Cu. 3. Town water supply, 2177 total solids; o'55 SiO2; 003 Al2O3 P203; 4'70 CaSO4; 10'50 CaCO3; 0'92 MgCO3; 2'07 NaCl; 30 organic matter; after 94 hours contact dissolved o'0825 Cu. 4. Free NH3 water, and, therefore, free CO2, after 115 hours contact contained o 1925 Cu. By this time the water had absorbed both NH3 and CO2. 5. Distilled water in five months dissolved o'055 Cu. 6. The following is the analysis of a sludge from a water tube boiler after being in use for some years. It is interesting as indicating a constant solvent action of the water on the copper and brass fittings :-H2O, 13'12 per cent; SiO2, 2'4 per cent; Fe2O3 Al2O3, 2.30 per cent; CaCO3, 81 90 per cent; copper, o'006 per cent. Action on Lead. These experiments were made with six different lengths of new lead piping, 2' long x " bore, cut from the same coil and closed at one end, each of which is distinguished by a number placed before the lead determination. These were treated by frequently filling and agitating with their respective waters during 24 hours, so as to corrode the |