DEPOSITION OF VARIOUS METALS. 



containing 1000 litres of a solution of caustic soda concentrated 

 at 3 Baume ; 100 grammes of stannic chloride and 300 grammes 

 of potassic cyanide. He uses anodes of pure tin which are 

 dissolved during the operation. 



The cast-iron objects, well pickled, are immersed during 

 24 hours in this bath, and kept in communication with a large 

 surface Daniell cell. 



This experimenter heats the tinned objects to the tem- 

 perature of fusion of tin, which gives them an exceptional 

 appearance and solidity. 



Tinned zinc heated under these conditions becomes more ex- 

 tensible and more easy to laminate and solder than ordinary zinc. 



BIRGHAM'S PROCESS. Mr. Birgham tins all the metals by 

 dissolving merchantable tin in hydrochloric acid, precipitating 

 the solution by means of a lixivium of potash and mixing it 

 with a second solution of caustic potash and potassic cyanide. 



OBTAINING CRYSTALS OF TIN BY MEANS OF ELECTROLYSIS. 



The crystallisation of tin offers a remarkable phenomenon 

 when a solution of stannous chloride is electrolysed. The 

 crystals of tin formed upon the cathode increase so rapidly in 

 length as to grow across the solution and touch the anode in a 

 few minutes. If the solution is concentrated, the current 

 strong and the cathode small, the mass of crystals rapidly fills 

 the whole vat, converging towards the anode. If the anode is 

 taken further apart the crystals are seen to follow it. 



In order to obtain large size crystals a platinum cup is 

 covered externally with a layer of wax leaving the bottom 

 exposed; this cup is placed on a sheet of amalgamated zinc 

 contained in a porcelain vessel. The cup is afterwards en- 

 tirely filled with a dilute solution, not too much acid, of stannic 

 chloride, and the external vessel is filled with hydrochloric 

 acid diluted with nineteen volumes of water up to the height 

 at which the two liquids come into contact. The energetic 

 current generated reduces the tin salt ; in a few days' time the 

 crystals are much developed. They must be washed in large 

 volumes of water and quickly dried. 



