A very ingenious mode of casting lead pipe of any by a continuous process, was invented by Mr. John Hague, and patented by him in 1822, which we ought not to omit noticing in this place. A rectangular cut-iron vessel, containing the lead, was placed over a suitable furnace, to melt and preserve it in a fluid state ; through this vessel, in a horizontal direction, was passed a very stout cast-iron cylinder, each end of which came to the outside of the vessel, at a short distance from which they were each connected to a small reservoir of water to keep them cool. A hole about half an inch in diameter was made in the upper side of the cylinder through which the latter was charged with the fluid metal, and the hole was then stopped by a plug screwed down from above. The internal diameter of this cylinder was about six inches, and throughout its length of two feet its surface was cut into a screw thread ; and into this a solid screw plunger worked from one extremity, which by its revolution gradually forced the metallic fluid through a mould and core fixed at the end, where the pipe was constantly drawn off as it solidified (by the cooling influence of one of the before-mentioned reservoirs of water) on to a drum, loaded with a weight upon its axis, which caused the drum to turn round with just sufficient force to wind the pipe upon it as it was formed.
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 Ilvmklia Journal, with reference to the subjoined cut, which represents a vertical section of the essential parts of the apparatus. A A is a hollow cylin der 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 11. 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 taper ing, 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 ft 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 con nected 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 pres sure upon the surface of the lead, and thus to produce the same effect. The pipe, as it is forced o0 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 oxydated ; and though the water has no direct action on the lead itself, it has on this oxide ; it dissolves aportion 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 sub stitute 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 Leen 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 pre viously 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 y 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 pipeswere drawn of pure tin, and rendered at a price lower than the tin cased pipe could be afforded.