Slfiguhr Pfiemmetia of the Amalgam of Platlm. 53^' 



In a few minutes the fait loft its colour, becoming at firft brown, and aftcrwarcb greenifh- 

 brown s the matter was reduced to a very fine powder. Another dram of mercury was 

 then added and the trituration continued, when the powder became grey ; a third dram of 

 mercury began to form an amalgam, and when the quantity amounted to Hx drams the 

 amalgam was perfeft. The whole operation fcarcely employed twenty minutes. I added 

 mercury to the quantity of nine limes the weight of the fait, notwithftanding wTiich the 

 amalgam was very tenacious ; a faft which is indeed furprifing, when it Is confidered that 

 the fait contains no more than about 40 parts of platina in the hundred. In my Experi- 

 me;it therefore 24 grains 6f platina were fufficient to give confiftence to 540 grains of mer- 

 cury. This amalgam was eafdy fpread out under the peftle ; it perfedly well received 

 the impreffions of the molt delicate feals ; its grain was very clofe and brilliant, and in no 

 refpea inferioV to that of the beft amalgam of tin. 



Though the fight of a perfeft amalgam of platina made in a few minutes, the produc- 

 tion of which had coft Lewis feveral weeks, and Sickingen feveral days, gave me pleafurc, 

 I had not lefs fatisfadion in obferving the lingular phenomenon I fliall proceed to defcribe : 



Being defirous of clearing my amalgam of its faline parts by watliing, I triturated it in 

 •water in a glafs mortar, and had fcarcely given a few ftrokes of the peftle before I obferved 

 the furface of the amalgam to be covered with a black powder, mixed with fome yellow 

 particles. In lefs than ten minutes the whole of the amalgam difappeared, inftead of 

 which I had this black powder. Tlie yellow matter, which conf.fted of undecompofed fait 

 of platma, having likewife difappeared by trituration ; the black powder was feen, upon de- 

 canting the water, in extremely brilliant malTes {parcelles), which probably were platina. 

 The mercury had therefore paiTed with the greateft facility to the ftate of black oxide, 

 nearly approaching the metallic ftate. A portion of running mercury was found beneath] 

 in the quantity of about two drams. Having taken a portion of the amalgam in the palm 

 of my hand, and rubbed it with my finger, the fame decompofition took place in a few in- 

 ftants, and left a black powder interfperfed with brilliant particles. On the fuppofition that 

 this oxide would eafdy pafs to the ftate of cinnabar in the humid way, I poured the fulphate 

 of ammoniac (Beguin's volatile liver of fulphur) upon it, and in lefs than 24 hours the powder 

 became of a dull red, intermixed with metallic particles, which were evidently platina. I 

 afcertained afterwards by fome experiments, that various metallic fubftances, and all the 

 animal matters which I tried, decompofe this amalgam by fimple contaa. For thefc 

 leafons it is abfolutely neceffary to ufe a glafs or filiceous peftle and mOrtar in the compo- 

 fition of the amalgam. 



In what manner arc we to explain the fpeedy reduaion of the platina without oxidation 

 of the mercury during the formation of the amalgam, as well as the much more fpeedy oxi- 

 dation of the mercury when brought into contaa with water, or metallic or animal mat- 

 ters? This appears to me to be a very difficult qucftion, of which I expea the folutioii 

 from more enlightened chemifts. For the fmall quantity of oxygcne in the fait of platina 

 is furely infulhcient to deprive fo large a portion of mercury of its metallic ftate ; befules 

 which, in the dry trituration, fuch as that which is made in the hollow of the hand, the 

 acid is not diffolvcd. Is it likely that there may be a decompofition of atmofphcric air, and 



3 Z 2 a dif- 



