some extent even in strong alcohol. In forming this salt, if platinum solution containing acids of nitrogen be used, chlorplatinate of ammonium is obtained. In using platinum black, dark-coloured products are formed, which partly remain with the platinum, and interfere with the process. The author has tried all the other forms of platinum, and they all act more or less; but finds that platinized charcoal is the best. He prefers cocoanut-shell charcoal, because of its greater absorptive power; but ordinary charcoal, containing the same proportion of platinum, 5 per cent., answers very well.

Hydrogen from dilute sulphuric acid and zinc is passed through a wash-bottle, then through a cyanogen-bottle (giving off cyanogen from the mixture mentioned above). The mixed gases pass then through a wash-bottle containing water, then through an empty bottle, then through a long calcium-chloride tube to dry them thoroughly. They then pass over the heated charcoal placed in a flask or in a tube bent into a convenient form, and heated in an air-bath to 190° to 200° C., according to the rapidity of the current of the gases.

When this apparatus is working, dense white fumes are seen in the Liebig's bulb containing dilute hydrochloric acid, through which the gases finally pass. With a sufficient excess of hydrogen, little cyanogen escapes unacted on; and the charcoal remains as efficient after some days' use as at first.

This platinized charcoal also serves well for the hydrogenation of hydrocyanic acid. Ordinary charcoal possesses in some degree the property of causing the gases to combine at a temperature of 210° C.

III. Cyanogen Hydriodate.-This substance is obtained by bringing the two dry gases into contact-more conveniently by passing cyanogen into dry ether, and then saturating it with dry hydriodic acid gas. It crystallizes out during the process. It has a reddish-yellow colour and onion-like smell, and stains the skin, paper, &c. dark brown. It absorbs moisture from the air with avidity, and is decomposed by water and by alcohol. From the aqueous solution the iodine is entirely precipitated by argentic nitrate. It is dried and freed from ether by passing over it a current of dry hydrogen while the flask containing it is placed on the water-bath. Heated above 100° C. it decomposes, giving off free iodine. Analyses give percentages agreeing well with the formula C, N, H2 I.

2

A compound containing more II I than the above exists, but is exceedingly unstable, continually losing hydriodic acid at ordinary temperatures.

These substances were obtained while experimenting on the hydrogenation of cyanogen by the action of metals on cyanogen and excess of hydriodic acid in etherial solutions.

Note on the Distillation of Sulphuric Acid. By THOMAS FAIRLEY, F.C.S. In an attempt to obtain sulphuric anhydride by distilling sodium anhydrosulphate with strong sulphuric acid, the author observed the great facility with which sulphuric acid boils and distils in the presence of alkaline sulphates. By heating sulphuric acid and some alkaline sulphate over an ordinary Bunsen rose-burner, in a glass retort sheltered simply from draughts of cold air, quantities of pure sulphuric acid may be readily obtained. If the sulphuric acid contains acids of nitrogen, as it should do when an acid free from arsenic is required, these come over first, along with any water that may be present. Lead sulphate crystallizes out during the process, but does not interfere till it has accumulated from repeated operations.

On the Purification of Sankey Brook. By ALFRED E. FLETCHER, F.C.S. The Sankey Brook flows through St. Helens, in Lancashire. Its chief impurities are free acid and sulphide of hydrogen.

The author proposes to allow the water to flow over beds of the old alkali waste, which is to be found in immense quantities in the neighbourhood.

This, containing hyposulphite of calcium, would give off sulphurous acid when dissolved in the acid water of the brook, and thus destroy the sulphide of hydrogen, the two gases forming together sulphur and water; at the same time the lime would neutralize the free acid.

Air-pollution from Chemical Works. By ALFRED E. FLETCHER, F.C.S.

On the Utilization of Sewage, with special reference to the Phosphate Process. By DAVID FORBES, F.R.S.

It was stated that sewage irrigation was the only process which had as yet utilized the entire liquid as well as the solid contents of the sewage. As, however, there are many cases in which sewage irrigation is neither applicable nor advantageous, it is desirable that some chemical process should be sought for by which the sewage could be so far purified by precipitation that the supernatant water could be allowed to run off directly into rivers without danger to health or animal life, whilst the precipitate should be of so high a value as manure as to pay for its transport to a distance for the use of the agriculturists. The experiments made already on the London sewage by the phosphate process, and on the present occasion successfully repeated on a small scale before the audience with Liverpool sewage, appear to fulfil in a great measure these conditions. This process, brought forward by the author in conjunction with Dr. A. Price, is based upon the fact that certain mineral phosphates, when in a freshly precipitated state, eagerly combine with both organic matter and ammonia in sewage. The process required nothing beyond a reservoir containing the sewage, to which the phosphates (in major part of alumina) are added, preferably in the state of solution in hydrochloric or sulphuric acid, from which, by the addition of a little milk of lime (just sufficient to neutralize the acid which holds them in solution), they are at once precipitated, along with the organic matter and part of the ammonia in the sewage. The deposit subsides rapidly, and leaves the water clear and colourless, even if tinctorial substances of great power are present: in the experiments shown, ink was added to the Liverpool sewage, but the colouring-matter was instantly removed along with the precipitate. The effluent water obtained by this process is, of course, not any thing like so pure as water ordinarily supplied for drinkingpurposes; still the water from the London sewage at Barking Creek, so purified, could, as was shown, be drunk without repugnance, fishes could live in it, and it had remained free from offensive smell for months, during the entire hot summer of last year, without any tendency to putrefy or emit any disagreeable odour. With regard to the value of the precipitated manure, it was admitted that no known chemical substances could precipitate from sewage the whole amount of substances valuable for agriculture; and it was only claimed that so much of them had been extracted as to leave the effluent water innoxious, whilst one of the most important features of the process, in which it differs from all the others, is, that all the substances employed in the purification augment the agricultural value of the precipitated manure, and thus render it of such value as to enable it to bear the cost of transport to a distance.

On the Action of Sulphurous Acid, in Aqueous Solution, on Phosphates and other Compounds. By Dr. B. W. GERLAND.

Sulphurous acid in aqueous solution dissolves various phosphates without decomposing them, even when the oxide forms with sulphurous acid an insoluble compound. In this respect the tribasic phosphate of lime is particularly interesting. By means of sulphurous acid a solution of 13 sp. gr. can be obtained. This keeps very well in the cold; but a rise of the temperature to 19° determines the gradual precipitation of sulphite of lime. If the solution is quickly heated, a compound corresponding to the formula 3CO, PO,, SO,, 2HO is formed, which separates as a white crystalline powder, and is characterized by great stability. It is a powerful disinfectant and an active manure. The solution gives dibasic phosphate of lime by boiling under reduced pressure, by standing in vacuum, and by mixing with alcohol.

The dibasic phosphate of lime is also easily dissolved by sulphurous acid. The solution again deposits the original phosphate when the sulphurous acid is removed. The phosphates of manganese and magnesia form strong solutions with sulphurous acid, from which the original phosphate can be again obtained. The phos

phate-of-magnesia solution shows a great tendency to precipitate the dibasic phosphate, even if the tribasic salt is in solution. Phosphate of magnesia-ammonia is decomposed when used in excess, so that dibasic phosphate of magnesia is left

in the residue.

The phosphate of copper is less soluble. The solution spontaneously deposits ruby-coloured crystals, Cu, O SO,+CuO SO2+2HO; but when rapidly heated to the boiling-point, pure phosphate of copper is again formed.

Phosphate of uranium is sparingly soluble in water charged with sulphurous acid; and when the solution is heated the phosphate is again precipitated, with its original composition.

The crystals of tribasic phosphate of soda, 3NaO, PO,+24HO, absorb a current of SO, with great energy, heat is liberated, and the phosphate melts. After cooling, acid sulphite of soda crystallizes; and the remaining oily liquor is separated, by mixing with alcohol, into two layers, the lower being principally an aqueous solution of acid phosphate of soda, and the upper one an alcoholic solution of acid sulphite of soda. If the crystals of the phosphate are mixed with a little water and then saturated hot with SO2, the clear solution separates, after standing, into two distinct layers, which unite again by shaking.

The phosphates of baryta, lead, and silver are decomposed by sulphurous acid into insoluble metallic sulphites and phosphoric acid, which is dissolved.

No other compound of sulphurous acid with a phosphate like the lime compound has been obtained.

The phosphates of stannic oxide, metastannic oxide, and bismuthic oxide are not acted on by sulphurous acid.

Arsenite of lime, prepared by precipitating ammoniacal solutions of arsenious acid and chloride of calcium, treated, when suspended in water, with sulphurous acid, gives a solution containing 3 eq. CaO and 1 eq. AsO,, and arsenious acid is left undissolved. By boiling, the solution is decomposed into sulphite of lime, and arsenious acid remains in solution.

Vanadiate of copper forms a solution with water and sulphurous acid, which, when boiled, forms beautiful yellow metallic scales, containing copper, a lower oxide of vanadium, and sulphurous acid. They tarnish rapidly when exposed to the air.

Oxalate of lime is very sparingly soluble in water charged with sulphurous acid, and is deposited unchanged when the latter is driven out by heat.

Note on the Occurrence of Vanadium. By Dr. B. W. GERLAND. The author's friend, Mr. Jon. Donn, discovered a large deposit of a sandstone, the chemical analysis of which proved it to contain vanadiate of lead and copper, beside a great number of other metals, also thallium in appreciable quantity. The manufacture of vanadic acid from this ore is not difficult. The author has prepared 5 lbs. of pure vanadic acid from 1 cwt. of picked pieces of the sandstone. Vanadic acid is likely to prove useful by its oxidizing property in both neutral and acid solutions. As the lower oxide of vanadium formed in this process is apt to take up oxygen from the air, the vanadic acid can play in solution the part of nitrous acid in the vitriol-chambers. For instance, a solution of 30 grms. of aniline in hydrochloric acid, mixed with 2 grms. ammonium vanadiate and much water, deposited, after some time, a deep-blue substance, which increased in quantity until all aniline had disappeared. The vanadiate was left in solution.

On Reciprocal Decomposition viewed with reference to Time.
By JOHN H. GLADSTONE, F.R.S., F.C.S.

When solutions of two salts are mixed together, it has been found that they at once begin to decompose one another; but if the new compounds are themselves soluble in water, the decomposition is never complete, but the four salts remain together in solution in certain proportions, dependent on the strength of affinity of each base for each salt-radical, and on the actual amount of each. If, however, one of the new compounds is insoluble in water, it removes itself from the field of

action, and a redistribution of the constituents takes place, until the whole of the insoluble salt that can be formed is formed and precipitates. If one of the new compounds is so sparingly soluble that it crystallizes out, it is inferred that a further redistribution must also take place till the amount that the water holds in solution is sufficient to balance what remains of the original compounds. This is what has been termed "reciprocal decomposition."

In most cases that have been examined, this action takes place rapidly, the balance being attained apparently as soon as the salts are thoroughly mixed; in other cases, however, the action will go on for minutes, hours, or even days. Quantitative experiments had been made on the rate of formation of ferric meconate, ferric ferrocyanide in oxalic acid, potassio-iodide of platinum, the sulphates of barium, strontium, and calcium, oxalate of magnesium, and acid tartrate of potassium. It was found that where all four compounds remain in solution, the amount of new salt produced in equal periods of time becomes gradually less and less till the limit is very slowly attained; but where one of the new compounds crystallizes out, the maximum of chemical change is not at the commencement of the action but after a certain quantity of crystals have been already deposited. In this latter case many circumstances of a mechanical nature affect the rate, which do not influence the decomposition when all the compounds continue in solution; but a rise of temperature was found in both cases greatly to accelerate the chemical action.

On the Soda Manufacture. By W. GOSSAGE.

This contribution was a supplement to a paper on the same subject read at Manchester in 1861, noticing various improvements connected with the processes of manufacturing soda during the lapse of nine years since that period, and giving also some details of the increase which has taken place in the extent of this important manufacture during that time. One of the most important events has been the passing of "The Alkali Act, 1863," rendering it imperative that manufacturers decomposing common salt for the production of sulphate of soda, should condense not less than 95 per cent. of the hydrochloric acid gas evolved by such decomposition. In the former paper, the means the author had devised and carried into successful operation in the year 1836, for effecting such condensation, were described, these means being now adopted universally, and so successfully that, in many instances, this condensation exceeds 99 per cent. The most important use for the hydrochloric acid obtained by such condensation is the manufacture of hypochlorite of lime, or bleaching powder, the demand for which has taken an extraordinary development since the introduction of straw, Esparto grass, and some other substances than rags for the manufacture of paper. At the date of the previous paper, the chlorine was obtained by the action of hydrochloric acid on peroxide of manganese. Recently Mr. Walter Weldon, of London, has perfected a process by which peroxide of manganese is obtained from the chloride of manganese produced by the action of hydrochloric acid on peroxide of manganese; and this process has been successfully carried into practice in this district, also in that of Newcastle, and it has already been adopted by some of the largest manufacturers in both localities. Allusion was then made to Mr. Deacon's very scientific process for the manufacture of chlorine without the use of manganese. Mr. James Hargreaves, of Widnes, has also devised means for producing chlorine without the use of oxide of manganese. The iron slag is treated with hydrochloric acid, and thereby protochloride of iron in solution is obtained as a by-product, which is evaporated, producing dry protochloride; and this, by slow application of heat with access of atmospheric air, becomes perchloride, which undergoes decomposition, yielding chlorine and peroxide of iron. In the former paper it was remarked that nearly all the sulphur used in this manufacture, the cost of which is about equal to two fifths of the total cost of materials required, was reobtained in combination with calcium, forming what is expressively designated as "alkaliwaste;" and it was noticed, also, that this presented a problem worthy of attention for its solution. Mr. L. Mond has made a near approximation to the solution of this problem. His process consists in causing atmospheric air to be brought into intimate contact with the alkali-waste as this is left in the lixiviating vats after

treatment with water. A very pure sulphur, almost absolutely free from arsenic, is obtained by this mode of working, which has been carried out successfully by various manufacturers; but the quantity of sulphur obtained is far short of that contained in the waste, and the author considered the problem still remained as an exercise for ingenuity and perseverance. The former mode of obtaining copper and silver from the burnt residua of coppery pyrites which had been used for yielding sulphur to manufacture sulphuric acid, has been superseded by a process devised by Mr. Henderson, which consists in mixing a small proportion of salt with burnt pyrites, previously ground to a fine powder, exposing this mixture to a low red heat, and passing through it a current of air. By these means the small portion of sulphur which has escaped being consumed in the burnt pyrites becomes oxidized, producing sulphate of iron, which decomposes common salt, yielding chloride of copper and sulphate of soda, which are obtained in solution on lixiviating the product with water. The copper is then precipitated from the solution by means of iron, and is obtained in the metallic state. A large quantity of oxide of iron is obtained as a residuum from the lixiviation. This is sold to the iron-smelters for the production of iron. These operations are carried out very extensively by the Tharsis Metal Company at Glasgow, Newcastle, and Widnes; and at the Widnes Metal Company, Mr. J. A. Phillips has carried out successfully a process invented by Mr. Claudet, of London, for extracting gold, silver, and lead from the burnt residua of coppery pyrites. In the year 1861, during the negotiation of the French Treaty of Commerce, it was estimated that the total quantity of salt decomposed in Great Britain for the production of soda was 260,000 tons per annum. Of this quantity 125,000 tons were decomposed in what is called the Newcastle district, and 135,000 tons in the Lancashire district. According to the returns of the AlkaliManufacturers' Association for the year 1869, the total quantity of salt decomposed for the manufacture of soda was 326,000 tons, thus showing an increase of 66,000 tons, or 25 per cent. on the total. Of this quantity the decomposition in the Newcastle district in 1869 was 142,000 tons, which, being compared with 125,000 tons in 1861, shows an increase of 17,000 tons, or 13.6 per cent. The decomposition in the Lancashire district is returned as 184,000 in 1869, against 135,000 tons in 1861, showing an increase of 49,000 tons, or 36 per cent. Thus the Lancashire district in 1869 exceeds by 30 per cent. the total quantity decomposed in the Newcastle district during the same year. One of the most important applications of soda to other manufactures is that of the production of soap. In the year 1852, when the excise duty was finally abolished, the total production in Great Britain was equal to 1600 tons per week, less than one half of which was produced in the Lancashire district. The present production in the Lancashire district is fully equal to the total production in 1852. Regarding the immense number of manufactories at work in Lancashire for the production of chemical substances to be used in bleaching, dyeing, calico-printing, &c., the conclusion was arrived at that Lancashire is the largest seat of chemical manufactures in this country.

On a Method for the Determination of Sulphur in Coal-gas.
By A. VERNON HARCOURT, F.R.S.

This paper gave a description of a piece of apparatus, which was exhibited in action, and an account of the results obtained with it. The apparatus consisted of a small Bunsen burner, whose nozzle passed into a glass cylinder, closed at both ends, through which air was drawn by an aspirator. The products of combustion were washed with an ammoniacal solution of copper during their passage through a system of bulbs. A Woulfe's bottle, filled with fragments of pumice steeped in ammoniacal solution of copper, served to purify the air at its entrance, and also to charge it with ammonia.

The apparatus had been tested by passing through it carbonic acid mixed with a known amount of sulphurous acid, and also by washing a second time the gases leaving it. Satisfactory results had been obtained. Moreover two or more analyses of the same sample of gas gave numbers which were closely concordant.