Pure Grades of Lead

The commercial grades of pure lead (Table 3.1-273) are used in chemical plants, sound attenuation, roof- 

For applications requiring corrosion protection and formability, as per ASTM B29-92 As per ASTM B29-92 As per ASTM 749-85 (re-approved 1991) 

Coefficients of internal friction of relevance to acoustic damping are given in Table 3.1-275 [1.299, 302]. As lead is used in sound attentuation applications, acoustic transmission data of selected single-skin and double-skin partitions with and without lead are given in Table 3.1-276 [1.299]. The sound reduction versus frequency is given in [1.299,304]. 

Corrosion rates of lead in H2SO4 and HF acids are presented in Figs. 3.1-351 and 3.1-352 [1.301]. Corrosion behavior of chemical lead in some common environments is presented in Table 3.1-277 [1.301]. Corrosion rates of the different lead grades normally fall in the same category. 

As lead is extensively used in radiation shielding, the gamma-ray mass-absorption data for lead are presented in Fig. 3.1-353 [1.299,305]. 

Single-crystal line lead Single-crystal Pb-0.033 wt% Sn Single-crystal Pb-0.035 wt%Bi Single-crystal Pb-0.0092 wt% Cd Single-crystal Pb-0.0022 wt% In 

---

Surgical Implant Alloys Cemented Carbides 277 277 3.1.11 Lead and Lead Alloys 3.1.11.1 Pure Grades of Lead A07 A07... 

Table3.1-274 Mechanical properties of pure grades of lead [1.299-301]...

The leachaint is then filtered to remove the cement. The efficiency of this process is good enough to produce a pure electrolyte that ensures a four-nines lead final product. Of course, the concentration of impurities in the electrolyte does not translate directly to the concentration of impurities in the lead because of competitive electrodeposition. The metallic lead content of the cement is above 90%. The cement is re-melted and absorbed into secondary alloyed or other commercial grades of lead in the factory. 

There are four common grades of lead pure lead, common lead, chemical lead, and acid-copper lead. These grades are covered by ASTM B 29-92, Standard Specification for Refined Lead. Pure lead and chemical lead contain 99.94 % minimum lead, while the latter two contain 99.9 % rninimum. Typical impurities include Bi, Cu, Ag, Fe, Zn, Ni, Sn, and Sb [4]. Higher purity is also available in commercial quantities, like low bismuth low silver pure lead with 99.995 % minimum lead. However, because lead does not possess the level of required mechanical strength for material of construction, and in many cases, it is unable to support its own weight, alloys have been developed to improve its physical and mechanical properties, especially mechanical rigidity. 

Cadmium pigments require to be made from pure grades of chemicals, especially as many common metal sulfides such as iron, nickel, copper and lead are darkly colored and would inhibit pigment brightness and acceptability. 

One can replace the oxygen atoms by other atoms, for example, by silicon itself. This leads to pure silicon, which cannot be neglected in the field of microelectronics. The significance of very pure grade silicon is so important for the entire electronic industry, especially for computers, etc. that we could say we are living in a "Silicon Age" in comparison to the "Ceramic Age or the "Bronze Age" of the past. 

Electrolytic refining of lead bullion is commonly employed in many modern plants to obtain high purity grade metal. Various separation processes for removal of individual metals are not required. In such refining (Betts process), a solution of lead fluosilicate is used as an electrolyte, while the anode consists of impure lead bullion and the cathode constitutes a thin sheet of pure lead. Lead deposits on to the cathode during electrolysis. Impurity metals remain undissolved and attached to the anode, forming a slime which may be removed after electrolysis and treated for recovery of these metals. 

Pure lead azide may be produced in the same equipment, but instead of lead nitrate and dextrin lead acetate is employed. The precipitation temperature is lower than in the manufacture of technical-grade lead azide (having a purity of less than 95%). All other operations are the same as already described. 

Cyanamide pigments are produced from industrial-grade calcium cyanamide which is first dissolved. Sulfide and phosphide impurities are precipitated as iron or lead salts [5.127]—[5.132] or oxidized [5.133] [5.135] and filtered off together with graphite impurities. The pure calcium cyanamide is reacted in an aqueous medium with soluble lead or zinc salts or with a slurry of lead oxide or zinc oxide [5.127], [5.129], [5.133], [5.136]—[5.138]. The pigments are filtered, washed, dried, and ground. Zinc cyanamide [5.139] and pure lead cyanamide are not explosive. An explosion reported during the production of lead cyanamide was caused by contamination with small amounts of acid or nitrates [5.140],... 

This allows one to prepare just double the amount of material in the same sized flask. The product obtained in this way, however, is slightly yellower than that obtained when more alcohol is used, but upon recrystallization it gives just as pure a product as that obtained by recrystallization of crude material made in the presence of more solvent. The results of many experiments lead to the conclusion that if large amounts of benzoin are to be prepared, the method described above is the better one. If, however, only a small amount is needed and a good grade of crude material is satisfactory, the larger amount of solvent is perhaps more desirable. 

Reagent grade hydrochloric acid contains up to O.03 ppm of lead (S5). Solution of anhydrous hydrogen chloride gas In purified water Is the usual method of obtaining the pure acid (C0). Scrubbing the gas twice In a bubble tower with triply distilled water before dissolution reduces the lead concentration to O.06 ppb (t6). Very pure hydrochloric acid can also be obtained by Isothermal distillation, e.g., by placing a dish of concentrated hydrochloric acid and a dish of pure water (in platinum, silica, or polyethylene) side by side In an empty desiccator and allowing to stand for a day or so (S5). 

Up to 0.01-0.03 ppm of lead la commonly encountered In reagent grade concentrated add (S5). Redlstillatlon of the azeotrope (655 HNO -HgO) Is generally used for purification. Redlstillatlon In a boroslllcate-glass still gives adequate purification for many purposes (Al). If an extremely pure produce Is required (< 1 ppb) the use of a fused silica.condenser has been proposed (Fill) but significant quantities of lead (at this level... 

---