126 On the manujactiir'ingf an a lars^c Scale, 



Being desirous to ascertain \vhetl>erthc air and light alone 

 nii^ht produce a similar effect on this sulphurated oxide, 

 JSI. Pavsse put a hundred parts of the same substance, in 

 powder, into a vessel of the same kind, and exposed them 

 to the action of a strong liiiht for more than a month. He 

 took care, as before, to renew the surfaces vefv frequently 

 by stirring the matter, in order to multiply the points of 

 contact of the sulphurated oxide with the air which served 

 it as an atmosphere ; but instead of acquiring a more agree- 

 able red, it assumed a brick colour inclining to brow a. After 

 this experiment, there can be no doubt that light has a sen- 

 sible influence on this substance, and tends to reduce the 

 sulphurated oxide of mercury bv taking from it a portion 

 of oxygen, as it does from most matters of this kind exposed 

 to iuiuiediate contact. 



Red Oxide of Mercury lij Nitric Acid (Red Precipitate). 



This oxide, so generally known in commerce by its bril- 

 liancy and its beautiful colour, was also one of the prepara- 

 tions which M. Pavsse had the curiosity to see made in 

 Holland, in order that he might learn the means employed 

 by the manufacturers to obtaui always a brilliant red of a 

 crystalline appearance, similar to that manufactured in Ger- 

 many, and which comes to us in particular from Nurem- 

 berg, Franconia, Bale in Swisserland, and i'rom Trieste. 



Every work on chemistry gives a process for preparing 

 this oxide ; but few of them agree in regard to tlie means 

 of obtaining a beautiful, lively, and brilliant red. Some, 

 after dissolving tlie mercury in nitric acid, evaporate the 

 liquor and expose the matter to a pretty violent heat for 

 some hours, in order to decompose the nitrate of mercury 

 and convert it into red oxide: others pour a certain quantity 

 of nitric acid over the first solution when dried and distilled. 

 By repeating this operation several times M. Chaptal ob- 

 tained red precipitate very beautiful and crystallized*. 

 Some also, after having dried the nitrate of mercury, in- 

 corporate with it a new quantity of liuid mercury ; and ex- 

 pose the mixture, when well formed, to a brisk heat of a dark 

 red colour, between two crucibles luted together. Van 

 Mons asserts, that in this manner he obtained, with great 

 case, red oxide of mercury perfectly crystallized f- 



All tliese processes, though exactly described, are not 



• Elcmens de Chimie, art. Merctrr. 



\ Journal jIc I'iivsique ct de Chimie t'.e Van Mons; Memoires de M. 

 pisclicr ct Lichtenberg, 15 I'luviose, an 10, p. 'JU ; et 15 Uruniaire, an 12, 

 p. 178. 



sufficient 



