A different method of casting lead pipe continuously, has lately been patented in the United States of America by a Mr. Titus, which is thus described in the Franklin Journal, with reference to the subjoined cut, which represents a vertical section of the essential parts of the apparatus. A A is a hollow cylinder of metal, bored out, so that its inner diameter shall be equal to that of the pipes intended to be cast. Its length, for a pipe of l 1/4 inch may be about 8 inches. It has a flanch a a at its lower end. This tube gives the form to the outside of the tube to be cast. B is a plug or core, adapted to the inside of the pipe, and made of iron or other suitable metal; it must be perfectly smooth and slightly tapering, being smallest at top. It has a flanch b b adapted to the flanch a a; this flanch is perforated with a number of holes, to allow the fluid metal to pass up into the mould. C C is a basin to contain water standing up to the dotted line ff. D D is a tube by which the melted metal is to be conveyed from the melting-pot F into the mould. A stop-cock regulates the flow of the metal The tube D D is furnished with a flanch c, by which it is connected with the mould.
The melting, pot may be placed so high up, that the pressure of the melted metal will be sufficient to force the pipe from the mould, with a regular motion, as it is cooled by the water; this force being regulated by the quantity admitted by the stop-cock. The pipe D D must descend through a flue kept sufficiently heated to keep the lead in a fluid state, and heat must also be applied at its junction with the mould. Instead of elevating the melting-pot, an arrangement may be made for making a mechanical pressure upon the surface of the lead, and thus to produce the same effect. The pipe, as it is forced off", may be received upon a reel or drum placed above the mould. Under proper modifications, which experience alone must suggest, the principle described in this and Mr. Hague's process may be advantageously applied to the accomplishment of the object proposed.
In the application of lead pipes as conduits for beer, wine, vinegar, and other acid liquors, serious objections have been made by many scientific writers, on the ground that poisonous solutions of the metal are thereby formed. The editor of The Chemist, observes in Vol. I. p. 227, that "wherever water kept in leaden vessels is allowed to come into contact with air, the lead becomes oxvdated; and though the water has no direct action on the lead itself, it has on this oxide; it dissolves a portion of it, and becomes poisonous;" and Mr. S. F. Gray, author of several pharmaceutical works, says in his Operative Chemist, p. 392, ' the use of lead for cisterns, or even pipes, ought to be discontinued." Mr. John Warner informs us, that soon after the introduction of the convenient hydraulic apparatus employed by publicans, called beer engines, it was found that that portion of the beer which filled the leaden conducting pipes from the casks in the cellar, and had remained therein during the night, or for several hours during the day, had obtained a flat, bad taste, and was highly deleterious, owing to the lead it had dissolved during that time. This alarming discovery nearly caused the abandonment of beer engines.
Attempts were made to substitute pipes made of other metals or alloys, but without success; for leaden pipes still continue to be used, but with the necessary precaution on the part of the publican, or other vendor, to draw off and waste the beer contained in the pipes, amounting to several pints or quarts every morning; and this precaution is sometimes resorted to during the day.
To obviate the disadvantages attending the use of lead pipes, the skill and attention of many ingenious men have been exercised. The first, we believe, were Messrs. John and George Alderson, who contrived to put an interior case of tin to lead pipe; but they did not succeed in making a firm junction between the two concentric pipes. Alderson's method was, however, improved upon by Thomas Dobbs, of Birmingham, who took out a patent in December 1820, for the process, which is entitled a "new mode of uniting together or plating tin upon lead." The patent includes the tinning or plating of ingots and sheets of lead, besides that of pipes; the process with respect to the latter is thus described in the specification:-"First, in order to unite tin with lead-pipes, or to coat, cover, or plate them with tin, I take the pipe hot from the mould in which it has been cast, and lay it horizontally upon a bed of hurds. rags, or tow, which has been previously prepared or impregnated with turpentine, or other resinous substance, a small quantity of melted tin having been also previously put on the said bed of hurds, rags, or tow. prepared or impregnated as aforesaid with turpentine, or other resinous material, until the surface of the pipe is completely tinned.
I then attach to the end of a rod or wire a bunch of hurds, rags, or tow, prepared or impregnated as aforesaid with turpentine, and introduce it within the pipe, together with a little melted tin, and work the bunch up and down, in manner of the piston of a pump, until the inside is also tinned. I then place or fix the pipe in a larger pair of moulds, so as to leave a vacancy also between the pipe and the mould; and I also introduce and fix a small core into the centre of the lead pipe, leaving a vacancy also between the pipe and the core. I then take melted tin out of a furnace, and with a ladle I pour the tin down the two vacancies before-mentioned, by which means the two bodies are perfectly and soundly united, and the lead pipe is united or plated both inside and outside with a thick coating of tin. In this state it is then ready for drawing or rolling, whichever may be the most convenient It is not necessary that the tin should be quite pure to be united to lead by this mode, but it may be alloyed with other metals.
The moulds and cores I use are the same as those generally employed by lead-pipe makers, excepting that I prefer them made of copper or brass, instead of wrought and cast iron." Tin being a much harder and less ductile metal than lead, considerable difficulty was found in drawing them together, so as to get them sound in every part; frequent cracks and flaws being discovered in the tin, which would not so readily yield as the lead to the forcible extension they underwent. From this circumstance, and the greater rigidity of the tin, they could not be made to sustain the bending to which lead pipe is necessarily subjected by the plumber; they were not therefore successfully brought into use. About the same period also pipes were drawn of pure tin, and rendered at a price lower than the tin cased pipe could be afforded.
There being, however, no other known metal which possesses the same degree of flexibility and durability as lead, it was still deemed a most important desideratum to give a perfect coating of tin or other innocuous metal to lead pipe, without impairing the flexile or other valuable properties of the latter: and this we are happy to add has been supplied by a new process very recently patented by Mr. John Warner, jun.; the specification of which describes that process to be as follows: - A bath of melted tin is prepared in a vessel of a suitable form and size, which may vary according to the size of the pipe to be tinned, (or the size and shape of any other leaden article to he tinned.) The heat of the bath is to be so regulated that the metal shall continue-in a fused state, but not at a higher temperature than is necessary for that purpose, lest the lead when immersed should be melted thereby; the heat may be ascertained by the use of a thermometer, or a pyrometer; likewise by testing it by such alloys of tin and lead as will melt at certain given temperatures, between the melting point of tin (or such alloy of tin as may be used as a substitute for the pure metal,) and that of lead, when placed under the influence of a bath of melted tin.
This, the reader will observe, is a very nice point, and can only be practised by great skill and attention on the part of the workmen; for although tin melts at about 440° and lead at 612° of Fahrenheit's thermometer, yet, when they come together, an alloy is produced at the immediate points or surfaces in contact, whose fusibility is much lower than even that of tin; so that when, by mismanagement, the heat is raised a few degrees too high, a quantity of the lead in the form of an alloy runs off the pipe into the bath; and if, on the contrary, the heat be suffered to fall a few degrees too low, the tin is not sufficiently fluid, and deposits itself upon the lead in a thick and uneven coat When the pipes are to be tinned all over, the external surfaces are sprinkled with powdered resin, and the same material is blown up the pipes so as to cover their internal surfaces with it; a mixture of oil and resin boiled together is, however, preferred to the resin alone. The said mixture is to be spread over the surfaces of the lead pipes by an)' convenient means, and when they have been so prepared, they are to be passed through, or immersed in the bath of melted tin, which should be covered with fat, oil, or resin, to prevent the oxidation of the fluid metal, and to aid in the tinning.
But when the pipes are to be tinned on one side only, or partially, those parts which are not to be tinned are covered with a mixture of lamp-black and size, or with any other matter that will prevent the action of the tin upon the lead; and those parts that are to be tinned are to receive the powdered resin, or the mixture of oil and resin, as before mentioned. The pipes thus prepared are then to be passed through, or immersed in the bath of liquid tin, by which process they will be tinned only in the parts required. When the pieces of pipe to be tinned are of a small size they may be easily managed by hand; but when they are of considerable weight or length, a rope and pulley is resorted to, to draw them through the bath of melted tin: the form of the bath is that of a segment of a cylinder having two flat sides; the chord of the segment being the top or open part of the vessel, where it forms a parallelogram of about six inches wide and two feet long. Tl»is form, it will be perceived, accommodates the bended form of the pipes, to dip in at one end of the vessel, and curving round the bottom, to come out at the other end; the tin thus flowing in at one extremity of the pipe, and running out at the other.
This process, as we have had occasion to notice, gives a perfect coating of tin, and fills up any minute fissures or holes that there may be in the pipe, besides enabling the manufacturer to give the pipe any required thickness of coating, by drawing it any number of limes through the bath. But an extremely minute quantity of tin covers the surface effectually, and by not impairing the flexibility of lead, adapts it to every purpose to which both lead pipes and tin pipes are used, and at the most trifling cost above that of lead.