136 On the Emphyment of Plat'ma 



talned by washing the earth. When the largest grains of 

 gold have been picked from the mixed mass of gold and 

 platina. the remaining gold is extracted by amalgamation ; 

 by means of which qpcfation the platina is left behind in 

 the form of flat plates or scales. 



The deceptions formerly practised by mixing gold with 

 platina have induced the Spanish government to prevent the 

 Exportation ot it, and to give orders to all their servants in 

 that countrv to keep the platina bv them, and to wash it 

 in water from time to time. But as means have been found 

 to detect easily and in a certain manner the adulteration of 

 gold with platina, and also to employ it for valuable pur- 

 poses, it is lo be hoped that the Spanish government wil} 

 hot persist in cau.sine a prohibition so injurious to the arts 

 and to its own finances to be executed with the former se- 

 verity. 



Mv object at present is not to enlarge on the chemical 

 and physical properties of platina, but only to offer a few 

 observations on tlie naps in the arts to which it has hitherto 

 been applied ; and then to give an account of the result of 

 an experiment \\hlch I made in regard to a new application 

 of this metal to objects of manufacture. 



Tiie apparent iiifusibility of platina by itself, formerly 

 considered as an insuperable obstacle, was sufficient to pre- 

 vent the employment of it except in combination with other 

 metals, as experience showed that it was capable of uniting 

 with the greater part of them by fusion. Of such mixtures, 

 that arising from a combination of brass ^nd platina was. 

 found to be exceedingly proper for the specula of retiecting 

 telescopes, as this alloy was susceptible of a beautiful poli>h 

 not subject to be injured by the prejudicial influence of the 

 atmosphere and of moisture. At first, however, the em- 

 ployment of platina was not extended further until the ex- 

 periments made known by Morveau, Sace, and other che- 

 mists, and afterwards prosecuted on ^ larger scale by count 

 Von Sickingen, formed as it v/ere an epoch in the history 

 of this metal, and showed in what manner phitii>a might 

 be freed from its foreign particles, be welded, h^nnnered, 

 and drawn out into wire, so as to be applicable to a variety 

 of purposes. 



It was, however, not yet possible to employ it in cases 

 which reqihi'cd an actual fusion for the purpose of casting 

 it; because this metal, in its purified state, was always by 

 itself infusible in a common furnace, ft was therefore 

 a discovery of great importance to find that platina mav be 

 Tendered fusible by arsenic j and that when roi.xcd with this 



substa,ncc. 



