a pavement; the spaces between the upper parts of the blocks are filled with asphalte, sand, &c.

The patentee does not claim the use of blocks of wood, or other material, with six sides, generally, but only when the sides are caused to incline in opposite directions, as shewn in the drawing, in order that each block may support and be supported by the surrounding blocks. He claims also combining a series of blocks, of the figure above described, for paving or covering, and making roads, ways, or other surfaces.—[Inrolled in the Inrolment Office, April, 1843.]

To JOHN MULLINS, of Battersea, in the county of Surrey, surgeon, for certain improvements in making oxides of metals, in separating silver and other metals from their compounds with other metals, and in making white-lead, sugar of lead, and other salts of lead, and salts of other metals.-[Sealed 27th October, 1842.]

THIS invention consists, Firstly,—in causing oxides to form on the surface of or in melted metals, heated to the temperature of their respective points of oxidation, by forcing gas or air, or allowing gas or air to pass through the body of the melted mass, either by a forcing or exhausting apparatus, and then skimming off, or otherwise removing from the surface of the melted metals, the said oxides, whereby the patentee is enabled, in the event of there being any admixture of metals, as in lead for instance, which contains a portion of silver, so to surcharge the melted mass with the foreign metal or matter, as to make a subsequent process of separation easy and valuable. Secondly,-in the manufacturing of white-lead, by exposing oxide of lead, so obtained, as aforesaid, to the vapour of vinegar, and of carbonic acid gas, as hereinafter described. Thirdly,-in the manufacturing of white-lead, by exposing a solution of acetate of lead, or other suitable salt of lead, made from oxide of lead, obtained as aforesaid, to an atmosphere of carbonic acid gas, as hereinafter described. Fourthly,—in

the use of common soot, as a deoxidating agent, in the reducing of the said oxides, so obtained, as aforesaid, and of other metals and ores, or the oxides. And Fifthly,-in the application of magnets, for separating iron from other metals, as hereinafter described.

In Plate XVI., a, a, a, fig. 1, is the brick-work of the furnace for heating the metal (which, in this case, is supposed to be lead) in the pan B, B, with the elongated lip c, c: the flame from the fire, in the furnace-grate, passing along and under the lip c, c, is carried off by the flue D. Into the pan B, B, is immersed a tube of iron, porcelain, or other suitable material a, fig. 2, which is in connection with the iron vessel b. Into this vessel is condensed, by means of the pump c, air or gas, or a mixture of air and gas, the which, when the stop-cock i, is opened, passes through the tube a, into the metal, and rises to the surface, oxidizing the metal through which it passes. The oxide, being of less specific gravity than the metal from which it is formed, floats on the surface of the metal, and is continually in the course of removal, by means of the skimming-plates K, K, (fig. 1,) attached to the endless flexible chain E, E, which works round the toothed wheels F, F. These skimmingplates, being kept in constant but slow motion, remove the oxide as it is made, thereby preventing the admixture of unoxidized metal with the oxide; and this is further effected by means of the inclined plane G, G, up which it is drawn. This inclined plane is formed of round bars, which are placed a short distance apart, as shewn in the plan, fig. 3, at G, G; these bars being kept hot, by reason of the body of heated metal below them, if any unoxidized metal remain in that portion of the oxide which is removed by the skimming-plates, it runs through into the lip c, c, of the pan B, B. When the oxide reaches the summit of the inclined plane, it is delivered, by means of the spout I, into the receiver I. The flexible tube f, fig. 2, is for the purpose of enabling the operator to raise, or lower, or otherwise shift the air-tube, as may seem most convenient. g, g, are safety-valves; d, a mercury-gauge, to ascertain the pressure of air or gas in the vessel b; this is necessary to

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enable the operator to know when there is sufficient pressure to overcome the resistance offered by the column of metal through which it has to pass, and to keep up a constant current. The pipe h, is for the purpose of forming a connection between the pump c, with a gasometer or other reservoir of gas, when gas is employed instead of atmospheric air. When atmospheric air is used, this pipe may be disconnected at the union-joint k. The piston of the pump c, is worked by the vibrating stirrup-rod c, 1.

At fig. 9, is shewn an apparatus, for the more effectual prevention of the admixture of unoxidized metal with the oxide. The plate A, A, made of iron or other material, is attached to the air-pipe B, a little above the diffuser c. When the current of air leaves the diffuser, it strikes against the plate A, and passes onwards to the edge, as shewn at F. By this means, any agitation on the surface of the metal, where the oxide is collected, is prevented, the air having a tendency to blow away the oxide from the place where it makes its exit. When this plate is used, the skimming apparatus must be accommodated to it.

At fig. 10, is shewn another method of oxidizing metals; in this case the oxygen is generated below the surface of the metal. Into the pan or pot A, is put black oxide of manganese or other material, from which oxygen may be obtained. The holes F, are drilled in the bottom of the iron pot A, for the purpose of allowing the heated metal, (supposed in this case also to be lead,) to enter. E, is the top or cover, having some fine holes drilled therein; it is retained in its place by the cross-bar D. When the pot is immersed in the metal, the metal enters at the bottom holes, shewn at F, and fills up the unoccupied space, and the manganese or other material, when sufficiently heated, gives off gas, which will combine with the metal and form an oxide.

The oxides, thus formed, if desirable, may then be treated by grinding, sifting, washing, or heating, to produce the various oxides of commerce, as the yellow pigment massicot, red-lead, and litharge, or for the manufacture of salts of the respective metals, as the operator may desire.

The metal or metals, when so oxidizing, as aforesaid, should all be melted and heated to the temperature of their respective points of oxidation.

By the mode of oxidation, herein described, if the metal used, be lead or other metal, and should contain any silver or other metal, the latter, being less oxidizable than the former, will remain unoxidized in the pan B, B, and will be continually accumulating therein; and when the operator judges necessary, such silver or other metal can be drawn off through the pipe м, fig. 4, by withdrawing the valveplug N, and it will then pass away into any vessel placed for its reception below the outlet o, to be further purified or separated. The pipe м, can be heated, if necessary, by the small furnace R, beneath.

The oxide of lead, formed by the herein described process, (attention being paid to the heat of the metal in the pan B, B,) is neither vitrified nor semi-vitrified, as is the litharge and some of the oxides of lead of commerce; and, for this reason, is far more readily acted upon by chemical agents, and, consequently, is preferable for the manufacture of the acetate, carbonate, nitrate, and other salts of lead, because of its more quickly combining with the several acids.

In manufacturing white-lead or ceruse, the patentee uses the oxide so formed, having first carefully washed and elutriated it in the usual manner. Into chambers, made of any suitable material, (as wood, lined or not with sheet lead,) and of any suitable size or shape, and having moveable air-tight lids or covers, are placed, horizontally, several trays, supported, one above the other, with spaces between, which trays may be made of wood, and lined with sheet lead, or made of slate, or other suitable material. On these trays the oxide of lead, made and prepared, in the manner herein described, (the litharge and vitrified massicot of commerce not answering,) slightly moistened with distilled water, is placed about one inch deep. These trays are introduced into the chambers, and the lid or cover secured down; and then the vapour of vinegar, together with carbonic acid gas,

is made to enter the said chambers through suitable pipes. The vinegar, or acetic acid of commerce, is put into a vessel, in effect similar to the common distilling apparatus, and heat applied, in the usual way, and the vapour thereof is directed, through a pipe or pipes, into the said chambers; and at the same time, by means of another pipe, communication is made with a gas-holder or reservoir, containing carbonic acid gas, (made after any of the usual methods,) which gas is made to enter freely into the chambers. The room, where the chambers are placed, is kept at a temperature of about 1000 or 120° Fahrenheit; and the vapour generators, and the gas-holder, are erected in an adjoining apartment. When the lids or covers of the chambers are about to be taken off, the vapour of vinegar and the gas must be turned off, by means of stop-cocks in the pipes, or by other means. By this arrangement, which is exemplified at fig. 5, the oxide of lead becomes, in due season, converted into ceruse or white-lead.

Another method of manufacturing ceruse or white-lead is shewn at fig. 6. In chambers, or large jars of earthenware or other material, are suspended several large sponges or other like substances. These sponges are supported in the jars by strings of worsted or other like substance, or by other means, so as not to touch the sides of the jars, or one another. Having made a saturated, filtered, and neutral solution of acetate of lead, or of other suitable salt of lead, from the oxide obtained as aforesaid, and placed this solution in a vessel above the top of the jars, as on an adjoining shelf, and having moistened slightly the sponges with the solution, and also the worsted strings suspending them, the strings are then made to dip into the solution contained in the vessel above the jars, and by the power of capilliary attraction the sponges are kept constantly moist by a supply of the solution descending down the worsted strings; and the supply can be regulated at pleasure, by the size of the strings or otherwise. Evaporation is continually going on, and crops of salts of lead are formed on the surface of the sponges. The jars are made to communicate with a gas-holder, or other