Account x)f certain 'Colours dug up at Pompela. -i i \ 



|>rcparing an apparatus for performing this experiment, 

 in a niaimer which, I hope, will lead to distinct conclu- 

 sions. 



LXT. Account of certahi Cohiira dug rtp at Fompeia. 

 Ecad to the National Insiiluic the Gih of March 180g. 

 By M. CuAi'TAL*. 



xJ-KR majesty the empress and queen did me the honour 

 to present me with seven speciiriens of colours fuund is the 

 shop of a colour merchant at Pompeia. 



No. 1. seems to have received no prcpr.ralion from hu- 

 man art ; it is a greenish and saponaceous ari^il, such as 

 nature exhibits in several parts of the globe ; itls analogous 

 with terra Veronica. 



No. 2. is an ochre of a fine yellow, which has been 

 cleansed by washing, as still practised, from all the prin- 

 ciples which might injure its fineness or purity. As this 

 substance becomes red when calcined in a moderate heat, 

 the yellow colour, which it has preserved without any alte- 

 ration, furnishes us with a new proof that the ashes which 

 covered Pompeia were not very hot. 



No. 3. is a reddish-brown of the same nature with what 

 is now used in commerce, and employed for the coarse 

 reddish paint applied to casks in sea ports, and on the 

 doors, windows, and railipgs, belonging to sonic houses. 

 This colour is produced by the calcination of the yeljovy 

 ochre already mentioned. 



No. 4. is a pumice-stone, very light and white; its tex- 

 ture is fine and serrated. 



The three remaining packets contained cbrapound co- 

 lours, which I was obliged to submit to analysis in order to 

 discover their constituent principles. 



The lirsl of these three, being No. 5, is a fins rich and 

 deep blue ; it is in small pieces similar in form. The ex- 

 terior of the i)icccs is paler than tiie interior, which ia 

 brighter than t!ie finest Saunders blue. 



The muriatic, nitric, aiid sulphuric acids make a slijiht 

 cfRrvescence with this colour; they seem (o brighteu^it, 

 even after a long ebullition : the oxygenized nmriatic acid 

 lias no action on it. 



This colour has therefore no connection with ultrama- 

 rine, which is destroyed by these acid?, as observed by 

 Messrs. Clement and Dcsormcs. 



• From /ImiuJei de Chimic, tonse lux. p. 'J J. 



Aminouia 



