In soldering lead, the fluxes used are sometimes mischievous, concealing minute fractures and faults, where the solder has not bitten or fused into the lead. <Callout type="warning" title="Safety Hazard">The gas consumed in lead burning is a mixture of common air and pure hydrogen.</Callout> The hydrogen is specially made in the generator, and provides its own pressure, while the air has to be pumped by hand or foot, and delivered under an artificial pressure to the burner jet. Blocks or cuttings of zinc are indifferently used, with diluted sulphuric acid — about six parts of water to one of acid — to generate the hydrogen gas. The gas generator is made of lead, and all brass and copper parts are protected from the acid. The generator consists of two closed chambers, A and B. The lower chamber, b, is fitted on top with an opening closed by a screw stopper, c. Through this opening pieces of zinc are introduced until the lower chamber, b, is nearly filled, and the stopper is screwed down. The upper chamber, a, has a loose cover, D, on top, which lifts off freely, and also a fixed cover, E, or diaphragm, under the loose one, in which a large hole is made and hollowed downwards, and a small diaphragm, F, attached below the hole in the centre of the fixed cover. A tube, G, is connected from the bottom of the upper chamber, a, down through the top of the lower chamber, b, to within a short distance of the bottom, where also a diaphragm, or false bottom, is fixed, into which the tube is connected. The upper end of this tube is closed by a stopper, H, having a wire handle, and the upper chamber is then filled with the diluted sulphuric acid, until it just covers the small diaphragm, f, below the hole, leaving the space above the diaphragm as a reserve to prevent overflow of the acid. <Callout type="important" title="Critical Rule">The acid has not been allowed to come in contact with the zinc in the lower chamber.</Callout> This is now effected by removing the plug from the tube in the upper chamber. A plug, T, for the removal of exhausted acid is arranged under the false bottom of the lower chamber. <Callout type="risk" title="Explosion Risk">A box, or safety-chamber, s, is constructed between the upper and lower chambers, forming the chief support of the upper chamber.</Callout> An aperture closed with a plug, is made in the side of the chamber, three inches above the bottom, and water is poured in to form a water-seal or trap, into which a tube, K, is dipped two or three inches. This tube, K, is fixed vertically in the top of the lower chamber and fitted with a stop-cock, M; and before it reaches the bottom of the upper chamber it is turned into the top of the safety-box and down into the water-seal. The pipe by which the gas passes from the generator to the flame-burner is taken from the top side of the safety-box; the possibility of any return of flame is absolutely prevented by this means. It is well to know that if air was mingled with the gas in the lower chamber, and that a flame came back from the burner, or was carelessly brought into contact with the mixture, a dangerous explosion would take place. <Callout type="tip" title="Pro Technique">The explosive nature of hydrogen gas mixed with air in contact with flame should be fully known.</Callout> We now proceed: the stopper in upper chamber being removed and the cover replaced, the acid solution flows down through the tube, G, and comes in contact with the zinc in lower chamber. The stop-cock m is left open as well as the stop-cock L, which is fitted on the end of a flexible tube, o, leading from the safety-box, s; and as the solution continues to fill the lower chamber it expels the air through the safety-box and flexible tube to the burner, and the hydrogen gas, commencing to form immediately, follows the air, which will be found escaping in a jet under pressure at the burner, E, and, being tested by a flame, will act first as a blow-pipe until all air is expelled, when the hydrogen gas following will ignite, and is kept burning until all appearance of air mixture has disappeared, and experience tells that the pure hydrogen is forming in the chamber. The stop-cocks L and N are now closed, and the generation of hydrogen in the lower chamber proceeds rapidly, instantly raising the temperature of the chamber, so that the hand cannot remain in contact with it. <Callout type="important" title="Temperature Warning">The hand cannot remain in contact with the heated chamber.</Callout> As we have finished with the generation of hydrogen, we can let it stand a moment while we examine and prepare the other portions of our apparatus. A pressure of common air is required in the process, and this may be supplied by any convenient means which will give a gentle, constant, and even pressure — a pair of double bellows worked by the assistant, or, in case of necessity, by the lead-burner himself; and a weight is arranged on the bellows to maintain a steady pressure of air, which is conveyed to the worker through a flexible tube any convenient length, similar to the tube conveying the hydrogen gas. Both tubes are united to a brass connection having two stop-cocks, L and N, one for the gas and one for the air. From this brass connection (which may be fixed or loose) a flexible tube is extended to the burner-jet, which the workman holds in his hand; these jets require to be well made to give a true pointed flame, and they may be kept in various sizes to suit the character of the work in hand. The flexible tube from the stop-cocks to the burner need not be very long, as the workman requires to handle it easily, and also to be within reach of the stop-cocks, to alter or regulate pressure at will. As soon as work commences and gas is consumed, its place is at once supplied in the generator by the descent of the solution upon the zinc again, generating more gas, until the accumulation of pressure again drives the acid solution back; and so it goes on for three or four days, after which time in constant use the liquid becomes changed into sulphate of zinc, which is then drawn off at the vent, T, and the machine recharged as before. Experience and practice alone can teach a worker how to regulate his flame to the proper point to suit his work, and the same remark applies to the work itself; but there is no difficulty about lead-burning work which any good neat workman cannot overcome by practice in a month's time. Nothing but actual practice of the work can teach it practically. The lead to be joined by burning must be steadily secured in its place, either edge to edge or lapped over jointing, and must have the parts to be united scraped bright and the jet of flame regulated and applied, a thin strip of pure lead being held in hand to supply any deficiencies observed during the progress of the burning.
Key Takeaways
- Use zinc and diluted sulphuric acid to generate hydrogen gas for lead burning.
- Ensure proper ventilation and safety measures to prevent explosions.
- Practice is essential for mastering the lead-burning technique.
Practical Tips
- Always wear protective gloves and goggles when handling acids and gases during the lead-burning process.
- Regularly check the generator's temperature to avoid burns or overheating.
- Use a flexible tube with stop-cocks to regulate gas and air pressure effectively.
Warnings & Risks
- Be cautious of mixing hydrogen with air, as it can cause dangerous explosions.
- Avoid touching the heated chamber to prevent burns.
- Ensure proper ventilation to avoid inhaling harmful fumes during acid generation.
Modern Application
While modern plumbing techniques have advanced significantly, understanding historical methods like lead burning is crucial for emergency situations where traditional tools and materials are necessary. This knowledge can help in repairing or maintaining old infrastructure, ensuring safety and functionality.
Frequently Asked Questions
Q: What safety measures should be taken during the lead-burning process?
Safety measures include wearing protective gloves and goggles to avoid burns and chemical exposure, ensuring proper ventilation to prevent inhaling harmful fumes, and being cautious of mixing hydrogen with air as it can cause dangerous explosions.
Q: How does the generator work in lead burning?
The generator works by using zinc and diluted sulphuric acid to produce hydrogen gas. The solution flows down through a tube into the lower chamber, where it comes into contact with zinc, generating hydrogen that is then expelled under pressure to the burner.
Q: What are the key steps in preparing for lead burning?
Key steps include setting up the generator by introducing zinc and acid, ensuring proper ventilation, and preparing a flexible tube connected to the burner jet. The process requires careful regulation of gas and air pressure to maintain a safe and effective flame.