French National InJl'ituU. 329 



portance in fait works. He difcovered the caufe of it in 

 the difengagement of caloric, which becomes a difaggrega- 

 tive power. Since chemifts have extended their refearches 

 to the matter of heat, it is well known that carbon is one of 

 the weakeft conductors of it. Pyrometrical experiments 

 have proved to Cit. Guyton, that a body enclofed in carbon 

 does not receive from the fame fire bur two thirds of the 

 heat received by a fimilar body placed in fdiceous fand. 

 The confequences to be drawn from this fa 61 will ferve to 

 improve the procefTes employed in reduction and fufion. 



Chemifts have hitherto been checked in many of their ex- 

 periments, by not being able to increafe the intenfity of fire. 

 The application of an hydraulic principle to the conftru6tion 

 of Macquer's furnace, furnifhed Cit. Guyton with the means 

 of increa'ing heat to fuch a degree, that a crucible of platina 

 began to melt ; a circumftance never before obferved. 



ProfefTor Klaproth, at Berlin, had announced that the 

 colouring matter of the emerald was iron; but the lail analyfes 

 of Cit. Vauquelin prove that the emerald is compofed of fili- 

 ceous alumine, a particular earth which has been called glu- 

 cine, and the calx or oxyde of chrome •, fo that the emerald 

 as well as the beryl or cigue- marine are two (tones perfectly 

 fimilar, and compofed of the fame principles, the colouring 

 matter excepted. (See p. 204.) 



By an accurate application of chemical knowledge to the 

 art of dyeing, Cit. Chaptal has difcovered a fimple and eaff 

 procefs for communicating to cotton a darker or lighter 

 chamoy yellow (janne chamoi-). JJy. uniting alumine to the 

 oxyde of iron, this chemift has been able above all to give to 

 his colours a foft and velvety appearance, which they caa 

 never acquire when that oxyde is employed alone. He has 

 .examined the different methods of combining that oxyde 

 with the red of madder, to form a violet colour, and has re- 

 duced to fimple principles, operations which were exceed- 

 ingly complicated. He has fhewn the rcafons why no other 

 aftringents, whatever be the dofe employed, can be fubfti- 

 tutcd for oail-nuts in dyeing cotton. 



9 To 



