not necessarily slang, but period usage..

5. [Cf. PURE v. 1b.] Tanning. Dogs' dung or other substance used as an alkaline lye for steeping hides. Also in Comb. as pure-collector, -finder, -finding. (Also spelt pewer, puer.)
1845 G. DODD Brit. Manuf. V. ix. 189 A solution called the ‘pure’ or the ‘pewer’ is prepared in a large vessel, and into this the skins are immersed. 1851 MAYHEW Lond. Labour II. 142 Dogs'-dung is called ‘Pure’, from its cleansing and purifying properties. Ibid., The name of ‘Pure-finders’..has been applied to the men engaged in collecting dogs'-dung from the..streets. Ibid., There are about 30 tanyards..and these all have their regular Pure collectors. 1858 SIMMONDS Dict. Trade, Puer, a tanner's name for dogs' dung. Ibid., Pure, Pewer. 1946 Thorpe's Dict. Appl. Chem. (ed. 4) VII. 264/2 Modern artificial bates have replaced almost completely the older ‘dung bate’ or puer, an infusion of dog- or, less often, pigeon-dung. -OED2

Last edited by tsuwm; 02/11/2007 8:07 PM.