(a) The tin-clippings are put into a drum, consisting of stout copper-sheeting, and provided with holes 3/8 in. diameter and 2 in. apart. It holds about 1000 lb. of clippings. It is first made to rotate in an acid bath, in which the tin is separated from the iron: then, by means of a crane, it is lifted into a water-bath, thence into a potash chlorate bath, and, finally, once more into a water-bath. In the first bath the drum rotates, according to the quantity of free acid, 5-50 minutes; in the others, which are only intended to wash away the acid, 5 minutes in each. The work of filling and passing the drum through the four baths, and emptying it, takes 70 minutes, and as a drum holds 1000 lb., 4 1/2 tons of tin waste may easily be worked up in a working day of 10 hours.

In the acid bath about 5 per cent. of iron are dissolved beside the tin. This solution having been passed into suitable vessels, the lead is first separated, whereupon, by the insertion of zinc plates, pure tin is precipitated. The latter is obtained partly in well developed crystals, but mostly in a floc-culent state. After having been well washed in water, it can be melted in an iron vessel, and cast in blocks for sale. Since, by the precipitation of the tin, zinc is dissolved (one part of zinc precipitates about two parts of tin), there is finally obtained a solution of zinc and sulphate of iron, which may be used for preserving wood from rot, for disinfect-iug, or in the preparation of various paints. The waste freed from tin is packed into casks, and sent to ironworks/ All the work may be done by six men. The outlay for acids and zinc amounts to about 3l. 5s. per ton. The waste is sold at 8-12s. per ton. - (A. Otto.)

(6) It is not possible to obtain a complete separation of the iron and tin by proceeding according to the various methods which depend upon bringing the scrap to the melting-point of tin, which is then removed in the molten state by mechanical means, such as revolving the scrap in a drum with sand, or by use of a centrifugal machine. The iron which is left contains so much tin as to be of little value for working up in the furnace. The salts of tin obtained by treating the scrap with acid solvents are also too much contaminated with iron to render an acid extraction process advisable. Better results, however, should be obtained with Reinecker's process, which -depends upon the power which caustic alkali has of dissolving tin when an oxidising agent is present. According to this process, the scrap is cut up into small fragments, treated in revolving drums with caustic soda for the removal of grease, and thence transferred to other drums, to be acted .upon by a solution of lead oxide in caustic soda. The reaction which occurs may be expressed by the equation: Sn + 2NaOH + 2PbO = Na2SnO2 + 2Pb + H2O, and since, to a great extent, this is prevented from taking place by atmospheric carbonic acid, Reinecker has devised a suitable apparatus for the purpose.

The lye containing soda stan-nate is separated from the finely divided lead, the former to be worked up in the most convenient manner, the latter to be oxidised and employed in subsequent operations. - (Dr. Czimatis.)

(c) Owing to the vast accumulation of tin scrap in canister, button, and other manufactories where tinned iron plate is extensively employed, considerable attention has been devoted to the utilisation of the same, chiefly with a view to the recovery of the tin, either in the metallic form or that of one of the various salts of tin used in commerce.

It would be interesting and amusing, although not instructive to an equal degree, to glance at the various methods, patent or otherwise, which have been suggested from time to time to effect this purpose. The separate actions of acids, alkalies, and chlorine gas have been utilised; friction and fusion have been resorted to; and more recently electricity has been pressed into service.

Of these methods I am only aware of three which have been employed on any large scale, viz. dissolving in a mixture of hydrochloric and nitric acids, and subsequent precipitation of tin by metallic zinc; treatment with caustic soda and litharge, forming soda stannate; and the formation of tin tetrachloride by the action of dry chlorine gas.

The last-named process is worthy of special mention. It has been described by Prof. Lunge in his report of the chemical section of the Swiss National Exhibition, held in Zurich in 1883.

Some time ago I was requested to recommend some practical method for the utilisation of these tin cuttings, in a district where they could be collected in large quantities. After reading all the literature at my disposal relating to the subject, I was induced to make some experiments, and amongst, others, actuated by a knowledge of certain electrolytic processes employed for the precipitation of metals from their ores, I tried the effect of a current of electricity in passing through an acid solution in which, a quantity of cuttings were suspended forming the anode, a copper plate serving as cathode. These experiments proved that not only is tin dissolved at the anode, but that it is also deposited in a pure form at the cathode, very soon after the commencement of the action. After continuing these experiments, and making the necessary calculations, I came to the conclusion that this might form the basis of a practical method for the recovery of tin from tin scrap on a large scale.

I recommended that a trial should be made of this process; this was undertaken; the ceremony of obtaining a patent was duly observed, and I was intrusted with the supervision of the erection of the plant, an account of which, and of the results obtained therefrom, I now give in a brief form.

At least four English patents have been granted for the same object, effected by very similar means; still, as there are important differences in the process about to be described, and especially as, to the best of my knowledge, it was under my direction that the first plant was erected for the employment of an electrolytic method on any large scale, I venture to hope that the following details may be of interest. The cuttings with which we had to deal varied considerably in value. Some of the thicker ones contained little more than 3 per cent. of tin, while some of the thinner, kinds contained 8-9 per cent. I considered 5 per cent. as about an average. The quantity obtainable was calculated at about 6 tons per week, and the plant was designed to accommodate that quantity, charging twice a day. The iron was designed to be converted into sulphate, a large quantity of which could be disposed of at a high price; the remainder was to be converted into "iron mordant"; the tin was to be converted into stannous chloride, and other salts of tin employed as mordants, and largely used by the dyers of that neighbourhood.