Lead and articles thereof Note. 1.- In this Chapter the following expressions have the meanings hereby assigned to them : (a) Bars and rods Rolled, extruded, drawn or forged products, not in coils, which have a uniform solid cross-section along their whole length in the shape of circles, ovals, rectangles (including s uares), equilatertl trim les or regular convex polygons (includin " flattened c~rcles'' and " molified rectan les of w ich two opposite sides are convex arcs, tfe other two sides being straight, of equal and parallel). Products with a rectangular (including s uare), triangular or poly onal cross-sectlon may have corners rounded along the~rwhole length. ~ i th~ckness e of such pro ucts which have a rectangular (including " modified rectangular ") cross-section exceeds one-tenth of the width. The expression also covers cast or sintered products, of the same forms and dimensions, which have been subsequently worked after production (otherwise than by simple trimming or de-scaling), rovided that they have not thereby assumed the character of articles or products of other Eeadings. f fad (b) Profiles Rolled, extruded, drawn, forged or formed products, coiled ox not, of a uniform cross-section along their whole length, which do not conform to any of the definitions of bars, rods, wire, plates, sheets, strip, foil, tubes or ipes. The expression also covers cast or sintered products, of the same forms, which have been sugsequently worked after production (otherwise than by simple trimming or de-scaling), provided that they have not thereby assumed the character of articles or products of other headings. (c) Wire (d) Plates, sheets, strip and foil Flat-surfaced products (other than the unwrought products of heading 78-01), coiled or not, of solid rectangular other than s uare) cross-section with or without rounded corners (including " rnodifie rectan les " o? wh~chtwo opposite sides are convex arcs, the other two sldes being straight, of equal?ength and parallel) of a uniform thickmess, which are : - of rectangular (including square) shape with a thickness not exceeding one-tenth of the width, - of a shape other than rectangular or square, of any size, provided that they do not assume the character of articles or products of other headings. Heading 78.04 applies, inter alia, to plates, sheets, strip and foil with atterns (for example, ! have been perforated, grooves, ribs, chequers, tears, buttons, lozenges) and to such products whicI corrugated, polished or coated, provided that they do not thereby assume the character of articles or products of other headings. (e) Tubes and pipes Hollow products, coiled or not, which have a uniform cross-section with only one enclosed void along their whole length in the shape of circles, ovals, rectangles (including squares), equilateraI triangles or regular convex polygons, and which have a uniform wall thickness. Products with a rectangular (including square), equilateral triangular or regular convex polygonal cross-sechon, which may have comers rounded along their whole length, are also to be considered as tubes and pipes provided the inner and outer cross-sections are concentric and have the same form and onentation. Tubes and ipes of the fore oing cross-sections may be dished, coated, bent, threaded, drilled, waiste , expanded, cone-s aped or fitted with flanges, co lars or rings. 'I' !' Subheading Note. 1.- In this Chapter the expression " refined lead "means Metal containing by weight at least 99.9 % of lead, rovided that the content by weight of any other element does not exceed the limit spec~fiedin the folbwing table : TABLE - Other elements Element Limiting content % by weight Ag Silver 0.02 As Arsenic 0.005 Bi Bismuth 0.05 Ca Calcium 0.002 Cd Cadmium 0.002 Cu Copper 0.08 Fe Iron 0.002 S Sulphur 0.002 Sb Antimony 0.005 Sn Tin 0.005 %n Zinc 0.002 Other (for example Te), each 0.001 GENERAL This Chapter covers lead and its alloys, and certain articles thereof. Lead is main1 extracted from alena, a natural lead sulpbide ore often containing silver. The crushed ore, a er concentration y flotation, is generally roasted or sintered, and is then reduced by smelting. During the roasting or sinterin process, the sulphide is largely converted into oxide; in the smelting qrocess, the oxide is re uced to lead by means of coke and a flux. In this manner " bullion lead ' or " work lead " is obtained; this contains a number of impurities, frequent1 including silver. It is therefore generally further refined to produce almost completely pure lead' Lead is also obtained by remelting lead waste and scrap. Lead is a heavy, bluish- ey metal; it is very malleable, easily melted and very soft (it can be marked easily with the t umb nail). It resists the action of most acids (e.g., sulphuric acid or hydrogen chloride) and is therefore used in the construction of chemical plant. f Because of its low melting point lead is easily alloyed with other elements. The principal lead alloys which may fall in this Cha ter under the provisions of Note 5 to Section XV (see the General Explanatory Note to that ection), are the following : d (1) Lead-tin alloys used, for example, in lead-based soft solders, in terne-plate and in foil fox the packing of tea. (2) Lead-antimony-tin alloys used for printing type and in anti-fiction bearings. (3) Lead-arsenic alloys used for lead shot. (4) Lead-antimony alloys (hard lead), used for bullets, accumulator plates, etc. (5) Lead-calcium, lead-antimony-cadmium,lead-tellurium alloys. The Chapter covers : (A) Unwrought lead and waste and scrap (headings 78.0 1 and 78.02). (B) Products generally obtained by rollin or extruding the unwrought lead of heading 78.01 f (headings 78.04 and 78.06); lead pow ers and flakes (heading 78.04). (C) Tubes, pi es and fittings and the other articles of the residual heading 78.06 which covers all other ead articles other than those covered by Note 1 to Section XV or included in Chapter 82 or 83 or those more specifically covered elsewhere in the Nomenclature. l' Products and articles of lead may be subjected to various treatments to improve the properties or a pearance of the metal, etc. These treatments are general1 those referred to at the end of the &enera1 Explanatory Note to Chapter 72, and do not affect e classification of the goods. X The classification of composite articles is explained in the General Explanatory Note to Section XV.