68 PYROMETALLURGY. [ HI, 



Peruvian Grold Alloy. — According to How (Journ. Pract. 

 Chem. xliii.), the Peruvian gold alloy consists of gold 38.93, 

 silver 54.828, copper 5.80. 



11. — A few operations on the metals, connected with the 

 preceding subject, are here thrown together. 



Metal Pipes and Tubes. — An improvement consists in the em- 

 ployment of machinery for ramming the moulds and cores, and 

 a measured quantity of sand being pressed into each portion 

 of the flask and between the converging sides of the divided 

 core-box, and for forming a core by enveloping a metal rod in 

 a coil of wire upon which the sand is compressed. (Lond- 

 Journ. xxxviii. Aug.) 



Cleaning Metal Castings. — To cleanse metal castings, they 

 are usually thrown into water acidulated by sulphuric or mu- 

 riatic acid ; but as some metal is removed and the surface left 

 rough, the process is objectionable. Thomas and Delisse 

 found by their experiments that if several organic substances 

 were added to the acid water, the scale of dirt and oxide was 

 removed, but the surface of the metal unattacked. Eisner 

 found that tar added to the acid water completely cleansed an 

 iron casting, while another piece of casting in the usual acid 

 water was nearly dissolved. (Technologiste. See also Journ. 

 Fr. Inst. (3) xviii. 49.) 



Enameled Iron. — After cleaning the surface to be enameled, 

 the enamel is laid on as a paste and burned in under a muffle. 

 F. Walton (Lond. Journ. Arts, 1847) uses three successive 

 layers, which are as often heated in the muffle. The first coat 

 is made by fritting 6 pts. pounded flint-glass, 3 pts. borax, 1 

 pt. red lead, and 1 pt. oxide of tin. One part of this frit, 

 mixed with 2 pts. calcined and ground bones, is ground fine 

 with water, spread over the metallic surface as a thick paste, 

 dried, and then heated to redness in the muffle. The second 

 coat is made of 32 pts. calcined and ground bones, 16 pts. 

 kaolin, 14 pts. Cornish granite, and 8 pts. potash in solution : 

 the paste thus made is fritted for 2-3 hours in a reverberatory 

 and then powdered. Of this frit 5| pts. are mixed with 16 

 pts. coarsely-powdered flint-glass, 5| pts. calcined and ground 



