produced ly Heat in coloured Bodies. 433 



snbslances can furnish. When exposed to heat It is at 

 first orange, and afterwards takes the red colour of the oxide 

 of iron. 



Experiment 1 2. — Turliih Mineral. 

 Its colour is of a very fine yellow resembling the ranun- 

 culus j when heated it becomes of a brick-red colour. 



Experiment 13. — Chromnte of Lead. 

 When cold, it is of a very fine yellow mixed with a lit- 

 tle orange. Upon heating it, it pas«es to the orange, but 

 does not become so brilliant as might be expected. 



Experiment 14. — Miniate of Iron at the Maximum. 

 lis natural colour when it is concentrated is o[ a fine 

 yellow, but when applied in a thin layer its colour is that 

 of broom flowers a little sullied. On raising ihe tempera- 

 ture it assumes a chcsnut colour. Red therefore has been 

 added to its primitive colour. 



Experiment 15. — Green Oxide of Chrome. 



When projected upon a piece of earthen ware almost 

 red hot, it becomes of an olive colour, as if we had mixed 

 a little colcolhar with this oxide. 



Experiment 1(3. — Liquid Muriate of Copper. 



This salt was of a greenish blue similar to what is callt d 

 water-green. Wlien heated, but not so as to evaporate its 

 water, it becomes Of a fine green, as if it luid l)een made 

 brighter with gamboge : when cold it resumes its primitive 

 colour. If we concentrate it more it retains, when cold, a 

 fine green colour, containing however less yi^H'^w than 

 when it is warm. On evaporating it again, it becomes of a 

 dirty ochrey yellow. We may obtain This colour by mixing 

 a little oiaiige colour with the fine green colour which it 

 had formerly. 

 Experiment 1 7. — Highly concentrated Nitrate of Copper. 



When cold it is of a pure blue, and docs not appear to 

 contain any green. Wlicn heated it becomes "of a blueish 

 green, as if a little gamboge had been added to the solution. 

 Experiment 18, — Azure. 



When exposed to a heat of 400" it is altered to gray, as 

 if a litlle rjraugc colour had been added to it. 



Experiment IQ. — Protoxide of Cupper. 



When cold it has a grayish tint mixed with brownish 

 red, which makes a dirty violet with gray. With heat it 



Vol.41. No. 182. Jung 1813. E e becomes 



