Solder in cans

So many industrial and commercial uses have been found for Pb that it is difficult to list them all. The main uses of Pb which are most relevant to environmental contamination and human exposure are lead-based indoor paints, lead water pipes, lead solder in cans for storing food, and leaded gasoline additives these have either since been banned or are in the process of being banned. Action is also being taken with respect to lead glazes on pottery and ceramics, lead in... 

The lead content of different foodstuffs varies widely, plant-based foods being the major source. Total diet studies in industrialized countries indicate a lead intake of the order of 200-300 jUg per day, although values ranging from less than 100 to more than 400 fig/day have been quoted (MAFF, 1982). Lead solder in cans, and the ingestion of dust by young children, make significant contributions to the daily lead intake, as does lead plumbing in areas with soft-water supplies. 

Federal regulation and similar actions have resulted in substantial progress in reducing blood lead levels in the entire U.S. population. For example, in the last two decades, the virtual elimination of lead from gasoline has resulted in reduced blood lead levels in children and adults. Lead levels in food have also decreased since most manufacturers stopped using leaded solder in cans and since atmospheric deposition of lead on food crops declined with the reductions of lead in gasoline. In 1978, the Consumer Product Safety Commission banned the addition of lead to new residential paint. 

Smaller amounts of phosphoms, or elemental phosphoms-containing materials, are also shipped in 115-L (30-gal) dmms that are DOT regulated (U.S. DOT lAl or 1A2 classification) and have thick shells and special gaskets and fittings for protection. Quantities up to 0.5 kg (1 lb) are allowed for shipping in two hermetically sealed (soldered), nested cans inside a wooden box where the empty space is filled with vermiculite (U.S. DOT 4C1, 4C2, 4D, or 4F classification). AH air transportation of elemental P, both U.S. and international, was prohibited beginning in 1992. 

The same general procedures of heating and cooling are foUowed in the case of soldering in a furnace, except that a piece of solder can be laid on the junction prior to insertion in the furnace. The solder melts and flows if the upper furnace temperature is properly set. The temperature should be set at ca 14—28°C (25—50°F) above the Hquidus temperature of the solder or at the manufacturer s recommended soldering temperature. 

Automated soldering operations can subject the mol ding to considerable heating, and adequate heat deflection characteristics ate an important property of the plastics that ate used. Flame retardants (qv) also ate often incorporated as additives. When service is to be in a humid environment, it is important that plastics having low moisture absorbance be used. Mol ding precision and dimensional stabiUty, which requites low linear coefficients of thermal expansion and high modulus values, ate key parameters in high density fine-pitch interconnect devices. 

Tin. Apphcation of tin on strip steel for can stock has decreased. Nevertheless, tin plating is still done in large volume, and tin plate for can stock was estimated at 11,750 t in 1990 (11). Additionally, 603 t of tin anodes were used for electroplating in electronic apphcations in the United States in 1990. The use of tin in solder manufacture is reported to exceed that used in can stock (12). The cost of tin in early 1993 was 7.50/kg (see Tin and tin alloys). 

Between 1979 and 1989 there was a virtual elimination of the use of lead-soldered food cans, with a concomitant drop in lead levels in food. Average daily intakes of lead for adults, based on an analysis of 27 market basket samples taken nationwide for a 1980-1982 Total Diet Study, were as follows (Gartrell etal. 1986b) ... 

Lead was as important in the Roman Empire as it was in the twentieth century and its use almost equally as disastrous. In the Roman Empire, lead s malleability and low melting point made it ideal for plumbing, not unlike its use in solder in plumbing, centuries later, that can be found in many households. The Romans also added lead to wine as a sweetener and preservative. In the twentieth century, lead was commonly added to paint, sometimes as much as 50%, which in fact created... 

Lower the same copper wire for one minute into the mother liquor from which the zinc chloride crystallohydrate crystallized and repeat the above experiment. Did the wires become soldered in this case What underlies the use of a concentrated zinc chloride solution when metals are soldered What else can be used to purify a metal ... 

The other major route of lead absorption is the gastrointestinal tract. Dietary intake of lead reached average peak values of almost 0.5 mg per person per day in the U.S. around the 1940s. Much of this lead came from lead solder used in cans employed for canned goods and beverages. Currently, daily intake of dietary lead in the U.S. is probably only around 20 pg per person per... 

The most common design is the bead type, which is usually glass-coated. However, thermistors can also be made into washes, disks, or rods. They can also be encapsulated in plastic, cemented, soldered in bolts, encased in glass... 

Lead (from gasoline, plumbing, solder in tin cans)... 

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