Stnntiiii. Suits cf PLtiiia, jjy 



Several of the properties which they have defcribed !iad been before obltrved by MelVrs. 

 Klaproth, Hope, and Pellctier ; but feveral alfo are of tlieir own difcovery. We have not 

 here fpoken of fuch of the refults afforded by the two earths in their combinations, as were 

 perfectly fimilar to each other; it having been our principal objeiSl to point out thofe fpecific 

 charaflers by which they are to be diftinguilhed. 



It is clear that we may reafonably entertain a hope, that more extenfive experiments fli.ill 

 one day point out ufes both of barytes and (Irontian, as well as of their combinations, of greut 

 importance in refpe£l of the arts, when they fliall have been found more abundantly in na- 

 ture, and when the progrefa of fcience fliall have perfe£led the means of obtaining them in 

 a ftatc of purity. The extreme folidity which barytes alfumes when flaked, may lead us to 

 prefume that it may be of ufe for making very hard and durable cements, or perhaps even 

 mordants for the application of difterent matters on (lone, glafs, pottery and other fub- 

 flances of a like nature. 



III. 



ExtraB of a Letter from Count MusSIN PUSCHKIN, Vke-Pytfident of the Department of 

 Mines at Peterfburg. On the Salts, Precipitates, and Jlmalgam of Platina ,- on Col/alt ; on 

 jintimoiiial Soap ,• and on the Decompfition of Soap by the Acid EstraBs of Colouring Matters*. 



I. On the Salts and Precipitates of Platina. 



JL HE brick-coloured fait, which is obtained by pouring muriate of ammoniac into a fo- 

 lution of platina, is totally foluble in water, and depofus, when difiblved in boiling water, 

 a black matter, which M. Fourcroy believes to be iron ; but, in my opinion, it feems rather 

 to be plumbago, though I have not yet made the requifite experiments to afcertain this faft. 

 A fpecimen of this fubftance accompanies this letter. 



In order that the whole of the fait may diffolve, it is necetTary to boil it for a long time 

 with water ; and when it is perceived that no more of the fait is taken up, the water muft be 

 decanted, and frefh water poured into thevcflel. An ounce of the fait required upon the 

 whole between eight and nine pounds of water poured on and decanted at five different, 

 times. By this means the whole of the fait was not only dilTolvcd, but its colour imme- 

 diately became a beautiful orange ; and by thefe cryflallizations, by evaporation on the 

 wateir-bath and new folutions, after which the fluid was left to a very flow evaporation, the 

 orange-colour of the cryftals became converted into a mod brilliant topaz-colour, and by 

 new ebullitions was found no longer to depofit any black matter. I have not yet fucce^dcd 

 in obtaining larger cryftals than thofe which Werner calls very final I ; but, by the afliflance 

 of a good Englidi microfcope, all thofe which the topaz-coloured fait aflbrc'cd were ob- 

 ferved to be perfeflly tranfparent, and with fcarcely any exception afl'efted the form either 

 of an oflahedral pyramid, or that of a polyhedron compofed of fix perfefl liexagons united 

 together by eight ifofceles triangles. There were fome lefs regular cryft.iU, wliich pirtook 

 of the nature of both tlicfc figures. 



- Annales do Cliimie.X'XJV. so;. 



Vol. I.— MiRCH, 1798. 3Z Tin- 



