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XXVIII. A new Process fur rendering Plathia malleablt;, 

 - Bij Alexander Tilloch. Read before the Askesian 

 Society in the Session 1804-3. 



J. HE methods hitherto employed for bringing this metal 

 into a malleable state, may be comprehended under one or 

 other of the three following processes. 



1. To dissolve the crude platina in nitro-mm*iatic acid, 

 precipitate by muriate of ammonia, wash and dry the preci- 

 pitate, and tlieu expose it, mixed with arsenic, to such a 

 degree of heat as may volatilize the latter, leaving the pia- 

 tina in a spungy form ; which, by gentle hammering, and 

 repeated exposures to a high degree of heat, is at length 

 rendered solid and malleable. 



2. To mix the pure precipitate with twice its weight of 

 mercury, and bring ihe whole into the state of an amatgam, 

 which is then moulded into the form of bars, and bv ex- 

 posure to heat freed from the mercury, and then ham- 

 mered, gently at first, into a solid form. 



3. To expose the precipitate pe7- se in a crucible to such 

 a heat as may agglutinate the particles, which are thea 

 brought into closer union by gently pressing, and at last 

 hammering the mass. 



I purposely avoid a more minute detail of these pro- 

 cesses, as they must be well known to all the members of 

 this siociety ; and will be in a great measure superseded bv 

 my new process, which is as follows. 



Dissolve, precipitate, and wash the platina in the usual 

 manner ; and then, instead of mixing it with a volatile me- 

 tal, or exposing it per se to heat in an earthen crucible, en- 

 velope the precipitate (previously heated to drive ott'the ad- 

 hering ammonia) m a piece of platina, already malleable, and 

 spread out by means of a flattiiig-nnll. Nothing more is then 

 necessary,but to expose repeatedly the mal leable pla tina,and i ts 

 contents, to a sufiicient temperaturc,andliammering between 

 each exposure, till the whole is brought into a compact state. 



The best way to inclose the, precipitate in the malleable 

 plaiina is, by rolling up-lhe latter into the form of a tube, 

 filling this with the precipitate, well rammed in, and then 

 closing the ends, by hammering them in, before exposurc- 

 to ilie tire. 



When a sufficient heat is obtained, apply the hammer at 

 fjr:it only on the side where the malleable platina overlaps. 

 not all round the tube. By this means its capacity is les- 

 sened, and the contents are soon welded, and brouirht into 

 uniou with the tube, after which it may be worked into 

 the form of a bar, or any other shape wanted. 



XXIX. Dr- 



