XCriON OF PLATJNA ANDMERCURY. l^T - 



in order not to obftrud the pafiage of caloric. A c)ljndflca{— ;3 fmall cylln- 

 piece of wood, as a pencil, was then forced into the t^<^»lf*5 0^j„^a^ei"thc^ ^^ 

 the thick inafs of lamp-black at the bottom, and the djanieteflower partof ths 

 of tills rod was determined by (he. quanlily of metal to be'^"''^^* 

 fufed, or varied according to other circumftances at pleafure. 

 In general the axis of the cylindrical hole was about three or 

 four limes the diameter of the bafis. After withdrawing the 

 rod the crucible was about half filled with borax. Upon this— *^|ic metal oc- 

 was placed the metal to be fufed j and if it had been before ^j^^^ J- ^ ^afs of 

 melted into a cylindrical form, the axis of the metallic cylinder borax that filled 

 was placed horizontally, and was of courfe perpendicular toJJJ'^^^g^g^V ^ 

 the axis of the cylindrical excavation at the bottom of the 

 crucible. More borax was then added to cover the piece of 

 metal, and another quantity of lamp-black was pr^fled hard \ 



over the whole in order to keep it tight together. An earlheri 

 cover was finally luted to the crucible, and in this ftate it \V¥is 

 expofed to lieat in a forge, in which upon another occafion, 1 

 had, in the prefence of JVIefii Hatchett, Howard, Davy, and 

 others, completely melted a Hetfian crucible lined and pre- 

 pared in the fame manner. The fuel which I ufed was the-— ftrong heat 

 patent coak of MefF. Davey and Sawyer. In the prefent ex*^^^^^^^ » 

 periments I moderated the heat fo as not materially to injure 

 the crucible, and upon taking it out of the fire, the lining was 

 generally found fo compact and fo firm that it remained in a 

 Iblid mafs after the crucible was jbroken. When the metallic — ^^^ when the 

 cylinder occupied the fpace at the bottom, it w^s natural to ^''^^' 1?^ f ^ ^^ 



•' ■ ' dimenlions ana 



fuppofe that it had been fufed; becaufe in no other fiale but occupied the cy, 



that of liquidity could it have run into the mould. In order ''"'^"^^l"^'*^^* 

 1 n . • o- T1 , . . fc. itmufthavf 



however to prevent all objections I had the precautjon'tb make been fufcd. 



the hole of a different diaiucler from the metallic cylinder, 



and to obferve whether the neceflary change in the (liape of 



the latter enfued. If alter fuch a teli, repeated as often ^ 



required, I perceived that the metal did not vary in its fpecific 



gravity, I thought myfelf authorifed to conclude that it was 



exempt from air. 



M. Richter fays that he had hoped to have put hirafelf inM. Richter^ 



potTelTion of a confiderable piece of palladium by repeating J"^^"!'^;^"^, 



wiih inimile accuracy the procefs which I had recommended 



as the betl. He precipitated a mixed folution of platina and 



mercury by a folution of green fulphate of iron; and after 



varv ing the fubfequent operations, to which he fubmitted the 



product 



