540 Platina. — Cdalt. — D<coii:pofitioiis of Soap. 



a difengagement of caloric from the vital air * ? This niuft be determined by new experi- 

 niciiu> wliich I have good reafon to cxpcft from the illullrious philofophcr to whom 1 have 

 the honour to addrefs myfclf. I fublimcd the oxided powder of mercury in a fmall glafs re- 

 tort. It afForded metallic mercury, and the muriate of mercury. The fubllancc which 

 remained at the bottom of the retort was friable, light, and of a colour inclining to a deep 

 grey yellow. The fmall quantity of the powder of amalgam which I fubjecflcd to experiment 

 was not fulBcient to admit of an examination of this refidue. 1 (hall not fail to repeat the 

 experiment more at large, and acquaint you with the refults. In the mean time I requeft 

 that the contents of this letter may ferve as a fupplement to the hiftory of platina, and beg 

 that you will give it a place in your Annals under that title. 



III. Conceriihig Cobalt. 



^\T TH regard to the experiments 1 have made on cobalt, I mud fufpend my informa- 

 tion until I (liall have been able to procure the regulus of cabalt in a quantity fomewhat 

 conlidcrable, for the purpofe of repeating my experiments in the large way. Thofc which 

 I have already made h,ive afforded feveral intcrefting phenomena, particularly with regard 

 to the eficifls of cold as a chemical agent. At prefent, I fhall only remark, that the oxides 

 oi cobalt, which have hitherto been fuppofed, after the methods of the belt chemifts, to be 

 abfolutely pure, arc neverthelefs contaminated with much foreign matters. 



IV. On the Aiitivwniat Soap. 

 PROFESSOR RUDOLPH has made an antimonial foap, after my method of preparing 

 the mercurial foap. He finds it very active. 



\'. On the Deeomfcjiticn of Soaps by the Acid Extracls of Colouring Matters. 



1 II.'WE obferved, in dccompofingfoaps, that the acid extradsof colouring matter, fuch, 

 for example, as that of Brazil wood by the diluted acetous acid, perfe£tly decompofe foaps, 

 whether made with oil or wax. The oleo-colorant or cero-colorant compounds thus ob- 

 tained are abfolutely infoluble in water, and afford extremely brilliant colours, which may 

 perhaps be advantageoufly ufedin painting, particularly encaullic f. It would be likewife 



interefling 



' Tiit Hjilior tlimks, aiiJ niili reafon, that the oxygcne united to the platina is far from being fufficient to 

 oxide fu large a quantity of mercuty ; but he has not perhaps fuflicicmly attended to the facility with which the 

 ffafl oxidibic metals pafs to the Kaicof oiidc, when they arc rendered fluid, and their parts difcngagtd bytlicir 

 iffir.ity witli mcrcur)-. This has long been obfcr^'cd with regard to the amalgim of guld, which foon becomes 

 cove;cd with a purple ojide by mere cx|)ofure to the air. Citizen Guy ton, in a memoir on certain properties of 

 platina, read to the N.itional Inftitute the lirft McflTidor, in the year 4, has exhibited a new proof of tliis prin- 

 ciple in the oxidation of an amalgam of plaiina, obtained by the di reft combination of the two metals, by means 

 of an elevated temperature, and by the fimple ctTcft of the affinity which was .announced by the rank which 

 platina occupies in the fcale of adhefions to mercury. Vtic of tbc EJilon cf ibe Aiinala.' 



i Citizen ChaufTicr has already communicattd, in his IcQbns to the Polytechnic School, feveral cxpcnmcntt 

 uf this kind, whie'.i have pcrfcift'y fuccccded. The foap of copper afforded a very brilliant green, which it is 



prefttme 



